THE TACONIC SYSTEM OF EMMONS, AND 
THE USE OF THE NAME TACONIC IN 
GEOLOGIC NOMENCLATURE. 
By Chas. D. Walcott, 
Of the U. S. Geological Survey. 
WITH PLATE III. [From the American Journal of Science, Vol. XXXV, March, 1888.j 
Art. XX.-The Taconic System of Emmons^ and the use of 
the name Taconic in Geologic nomenclature ; by Chas. D. 
Walcott, of the U. S. Geological Survey. With Plate III. 
The nomenclature employed in classifying geologic forma- 
tions and terranes should be based upon priority of definition 
and upon the accuracy of the original observations; the latter 
to be judged by the testimony of the formations within the 
areas where they were first made. If the original proposer of a 
name bases it upon such errors of observation and interpreta- 
tion that subsequent observers cannot verify his work, and the 
name can only be used by dropping a name proposed as the 
result of accurate observation and definition, the latter should 
be retained. 
There is another principle that has been frequently over- 
looked in discussions relating to the nomenclature to be applied 
to geologic formations and groups of formations forming ter- 
ranes. It is this: In the evolution of stratigraphic and his- 
toric geology, stratigraphic geology preceded paleontologic 
stratigraphy : that is, the succession of strata for a given geolo- 
gic province was first determined and then the succession of 
organic remains in the strata. This has been so far perfected 
that, in most instances, the known succession of life in a 
geologic terrane in one province can be compared with that in 
some other not geographically connected with it: also, different 
sections of strata in the same province may be compared with 
one another when the continuity of the strata is broken. 
From this it follows: First: that the unit of geologic nomen- 
clature is the formation as lithologically determined, and the 
combination of these units in any given section builds up the 
greater geologic divisions. Second: that the means of corre- 
lation of the formations and terranes of one province with 
those of another, is by the order of succession, as stratigraph- 
ically determined, of the contained organic remains of the 
respective formations and terranes. 
A paleontologist should rely largely upon the evidence of 
geologic age furnished by the fossils; but, at the same time, as 
a geologist, he should endeavor to obtain their stratigraphic 
position and order of succession in each geologic province. 
An example of the desirability of this is shown by the vertical 
distribution of the Devonian fauna in central Nevada, where 
several species of the Lower Devonian fauna of New York oc- 
cur at the Upper Devonian horizon, in the Eureka district. 
(Introduction to Monograph viii, IT. S. Geol. Survey). 
Am. Jour. Sci.-Third Series, Vol. XXXV, No. 207.-March, 1888. 
14 230 
C. D. Walcott-The Taconic System of Emmons. 
With the preceding statements in mind, I take up the ques- 
tion of the "Taconic System" in geology, as one that can only 
be intelligently understood and decided by the application of 
the principles contained in them. 
In pursuance of a general plan the subject matter is arranged 
under the following heads : 
1. The Taconic Area and geologic work within it. 
2. Geology of the Taconic Area as known at the present time. 
3. Geology of the Taconic Area, as known to Dr. Emmons. 
4. Comparison and discussion. 
o. Nomenclature. 
THE TACONIC AREA AND GEOLOGIC WORK WITHIN IT. 
The Taconic Area.-The Taconic area includes the Taconic 
range which trends north and south, nearly on the boundary 
line between the States of New York, Vermont, Massachusetts, 
and Connecticut, and the country immediately adjacent to the 
range, on the east and west. In this area Dr. Emmons first 
studied and elaborated the theory of the " Taconic System " of 
rocks. 
For the purpose of re investigation the counties of Wash- 
ington, and Rensselaer, N. Y., Bennington, Vt., and Berkshire, 
Mass., were taken as the typical Taconic area, as they contain 
sections of all the formations spoken of by Dr. Emmons and, 
also, nearly all the localities cited by him, where the facts sus- 
taining the theory which he proposed could be verified. 
Geologic work within the Taconic Area A-Quite early in 
the course of my study of the history of tlie investigation of the 
strata now referred to the Cambrian System in America I be- 
came acquainted with the voluminous literature of the Taconic 
controversy, and learned that two geologists only had studied the 
typical Taconic area with any considerable degree of thorough- 
ness. They were : Dr. Emmons, who founded the " Taconic 
System " as the result of his observations, and Professor James 
D. Dana, who studied the strata referred to the " Lower Ta 
conic " by Dr. Emmons. Before Dr. Emmons entered the 
* For an historical review of the field work and also of the opinions relating 
to the "Taconic System " the reader is referred to Dr. Emmons's memoir in the 
Agric. N. Y., vol. i, 1847, and to the review of the Taconic System in his Amer- 
ican Geology, pt. 2, 1856: also to the various publications of Prof. Jules Marcou 
on the Taconic System, especially " The Taconic System and its position in Strati- 
graphic Geology" (Proc. Amer. Acad. Sci. and Arts, vol. xii, 1885); to Dr. T. S. 
Hunt's memoir on " The Taconic Question in Geology " (Mineral Physiology and 
Physiography, pp. 516-686, 1886), also, "The Taconic Question Restated " (Amer. 
Nat. Feb., March and April, vol. xxi, 1887); Prof. Jas. D. Dana's paper on "The 
History of Taconic investigation previous to the work of Prof. Emmons '' (Amer. 
Jour. Sci., Ill, vol. xxxi, pp. 399-401, 1886), and many references in the series of 
papers on the results of original investigations in the Taconic area, published from 
1872 to 1887, by Prof. Dana. C. D. Walcott-The Taconic System of Emmons. 
231 
field Professors Dewey and Amos Eaton had studied more or 
less of the Taconic region, and the data obtained by them were 
of material aid to Dr. Emmons. 
Among others who have examined portions of the area 
studied by Dr. Emmons previous to 1844, are : Dr. W. W. 
Mather, of the geological survey of New York, who made a 
recoimoissance of the portion within New York State (Geol. 
N. Y., Rep. First Geol. Dist., 1842); Professor James Hall, who 
examined a section crossing from the Hudson River to the 
Green Mountains (Proc. Assoc. Am. Geol. and Nat., p. 68, 
1845), and the Professors W. B. and H. D. Rogers who 
studied a section extending from the Massachusetts side of the 
Taconic area td the Hudson River (loc. cit., p. 67 : also, Proc. 
Am. Phil. Soc., vol. ii, pp. 3 and 4, 1841). The Professors 
Edward and C. H. Hitchcock described and mapped the strata 
referred to the " Taconic System" in Vermont, and discussed 
the question of their geologic age (Geol. Vt., 1862). Subse- 
quently, Professor C. H. Hitchcock made a series of sections, 
crossing the " Taconic System " in Vermont (Bull. Am. Mus. 
Nat. Hist., vol. i, 1884). The observations made by Mr. S. W. 
Ford, from 1874 to 1886, in the counties of Rensselaer and 
Columbia, N. Y., have furnished important data on the forma- 
tions examined by him that will be referred to again. Some 
of the results obtained by the geologists mentioned will be 
spoken of under the head of " Comparison and Discussion." 
Dr. T. Sterry Hunt, Professor Jules Marcou and Professor 
N. H. Winchell have all written at length upon the " Taconic 
System," but I have been unable to discover that either of 
these gentlemen have made any field observations in the typical 
Taconic area * 
In searching for data to aid me in forming an opinion respect- 
ing the value of the name Taconic in American geologic nom- 
enclature, I found that there was such a wide divergence of 
opinion among the geologists who had studied the " Taconic 
System " in the field and those who had formed opinions upon 
it from partial observations in other areas, and the data given 
by Dr. Emmons and the Professors Hitchcock and Professor 
Dana, that there seemed to be no way to settle the questions 
at issue except by investigating the original Taconic area and 
identifying and mapping all the formations within it except 
the areas mapped by Professor Dana and the Professors Hitch- 
cock. The necessity of ascertaining the age of the different 
* Dr. Hunt's later opinionsappear to have been influenced by his geologic obser- 
vations in Pennsylvania, and by certain theoretic views founded on the lithologic 
characters of the " Lower Taconic " rocks. Professor Marcou examined the ex- 
tension of the "Upper Taconic" strata in Northern Vermont and Professor 
Winchell appears to have studied the publications of Messrs. Emmons, Marcou and 
Ford. 232 
C. D. Walcott-The Taconic System of Emmons. 
formations by paleontologic evidence, was also imperative, as 
their lithologic characters were of little comparative value out- 
side of the Taconic area owing to local differences in the orig- 
inal sedimentation and to the subsequent alteration of the strata 
by metamorphic agencies. 
With the assent of the Director of the Geological Survey I be- 
gan field work during the season of 1886 and continued it until 
the close of the field season of 1887. A few of the results of this 
work were given in a paper entitled " Geologic Age of the 
Lowest Formations of Emmons's Taconic System," and read 
before the Philosophical Society of Washington, January loth, 
1887, a brief abstract of which was published (this Journal, 
vol. xxxiii, p. 153, 1887). On the 22d of April, 1887, I 
read a paper before the National Academy of Sciences, at 
Washington, bearing the title: u The Taconic System of 
Emmons." In it were given the results of my studies up to 
that date; and I exhibited a geologic map, and a cross-section,- 
of the Taconic area. As I was soon to return to the field this 
last mentioned paper was not published.* 
Previous to studying the geology of the Taconic area I 
worked during portions of the field seasons of 1883-4 on the 
"Upper Taconic" strata of Northern Vermont and published 
a part of the results in the introduction to Bulletin Thirty "of 
the U. S. Geol. Survey, 1886. 
GEOLOGY OF THE TACONIC AREA AS KNOWN AT THE PRESENT 
TIME. 
The section (see map)f crossing the Taconic area shows the 
general position and relation of the strata, and their geographic 
distribution is given on the map. In a report on the geology 
of Washington County, N. Y., I shall describe the geologic 
section in detail. For the present purpose, however, the 
section and map. supplemented by notes on the geologic for- 
mations, will I think give the data required for a clear under- 
standing of the geologic terranes. Beginning on the east, the 
terranes will be mentioned in the order they are met with in 
passing westward from the pre-Cambrian crystalline gneisses of 
the Green Mountains to the Hudson River, and each will be 
given a number by which to identify it in subsequent referen- 
ces. 
One of the best localities to see the contact between the pre- 
Cambrian crystalline gneiss and the overlying, bedded quartzite 
* A short abstract of it was sent, June 8th, 1887, to Professor N. H. Winchell, 
reporter on the lower Paleozoic rocks to the American Committee of the Interna- 
tional Congress of Geologists, and was subsequently withdrawn owing to the 
field work of the season of 1887 having negatived and rendered obsolete several 
of the conclusions therein expressed. 
f To be inserted with the second part of this paper. C. D. Walcott-The Taconic System of Emmons. 
233 
is on the western crest of Clarksburg Mountain, northeast of 
Williamstown, Mass. It is one of Dr. Emmons's typical local- 
ities, and it has also been examined by Professor C. H. Hitch- 
cock, who, in speaking of the relations of the quartzite to the 
Green Mountain gneiss, says : 
" 3. Still more decisive is the fact that the lowest layer of 
the quartzite has been derived from the ruins of the gneiss. 
This stratum is a conglomerate, containing many pebbles of a 
peculiar blue quartz, and has been observed at Clarksburg, 
Mass., Sunderland, East Wallingford, Ripton, and in Lauzon 
conglomerate, at Bristol. (The Geology of Northern New Eng- 
land : royal 4to, p. 2, 1870). 
When making observations during the summer of 1887 on 
Clarksburg Mountain, I found the unconformity between the 
quartzite and gneiss to be well marked. The lower layers of the 
quartzite series contain shales and thin beds of conglomerate, 
and there are no passage beds between the quartzite series and 
the gneiss in the localities where the bedding of the gneiss and 
quartzite series appears to be conformable. In accordance with 
this, the unconformity has been represented in the section. 
The quartzite, including certain minor beds of schistose shale, 
conglomerate and limestone, I will call terrane number one. 
Terrane No. 1. -Professor James D. Dana, in describing 
the Quartzite series, in a paper on the Geology of Vermont 
and Berkshire, says " Associated with the limestone belt and 
following mainly its eastern border there is a quartzyte series, 
consisting in Vermont of quartzyte and crystalline slate or schist 
(hydromica slate, sometimes chlorite slate), and rising at inter- 
vals into mountain ridges. This quartzyte formation commences 
just abreast of the northern limit of the 'Eolian limestone' in 
Vermont: and it follows it southward through Massachusetts, 
and into Connecticut, being, throughout, its close attendant " 
(Amer. Jour. Sci., vol. xiii, p. 38, 1877). And on p. 204: "(4) 
The age of the Quartzyte formation, and its relation in position 
to the adjoining limestone.-The quartzyte formation includes, 
as has been explained, strata of quartzyte and schists-some- 
times one predominating, and sometimes the other. The special 
age of the formation is in doubt, equally with that of the eastern 
limestones. There may be quartzytes of different periods of 
the Lower Silurian : and so with the schists. The question of 
age can be positively answered only by the discovery of decisive 
fossils in the quartzyte of Vermont: and so many imperfect 
forms have already been brought to light (besides the unsatis- 
factory worm-burrows, and Fucoids or worm-tracks) that we feel 
sure the future will clear away the doubts." 
Professor Dana considers that the evidence proves the ex- 
istence of a limestone beneath the quartzite, in some sections, 234 
C. D. Walcott-The Taconic System of Emmons. 
but in Vermont Mr. Wing makes the limestone superjacent 
to the quartzite (loc. cit., p. 204). 
As all observers agree on the stratigraphic position of the 
quartzite series the paleontologic evidence of the age of the 
terrane, formed by that series, will be now considered. 
The Professors W. B., and H. D. Rogers, Edward, and C. II. 
Hitchcock, James Hall, Dr. W. W. Mather and Professor Jas. 
D. Dana have all held the opinion that the quartzite (Terr. 
No. 1) should be referred to the Potsdam horizon and, from 
its stratigraphic position, the tentative reference was in accord- 
ance with the facts known; but, as Professor Dana has said 
(ante), the question of age can only be answered by decisive 
fossils in the quartzites of Vermont. 
During the progress of the geological survey of Vermont, a 
few fossils were found in the quartzite. On page 356, of the 
Geological Report, vol. i, 1862,* it is stated : that besides Scol- 
ithus, a straight-chambered shell occurs in a hyaline quartz, on 
the west side of Lake Dunmore, and a species of Lingula in 
Starksboro, near Rockville ; and, on page 357 : " In the south- 
western part of Woodford there seem to be traces of organisms 
resembling bivalve shells, about the size of a three-cent piece. " 
I have, through the courtesy of Professor Dana, examined two of 
the specimens referred to, that are now in the collection of the 
Peabody Museum, at New Haven, and I find the " Modiolopsis- 
like shell" to be Nothozoe Vermontana, and the straight- 
chambered shell to be, to all appearances, a cast of Ilyolithes 
communis, a Middle Cambrian species. 
Professor B. K. Emerson kindly sent to me for examina- 
tion the specimens from the Amherst college collection men- 
tioned in the Geology of Vermont, and which were collected at 
Salisbury, Vt. I find one to be Nothozoe Vermontana and the 
other species to be a cast of Ilyolithes communis, or a closely 
allied species. In a small collection of fossils, received from 
Professor H. M. Seely, of Middlebury college, Vermont, who 
found them in quartzite bowlders on the west slope of Sunset 
Hill, near Lake Dunmore, there occurs the Nothozoe Vermon- 
tana described as " from the Potsdam sandstone,"f and, with 
it, heads of a species of Olenellus undistinguishable from O. 
Thompsoni of the Georgia formation in Franklin County, Ver- 
mont ; and in other specimens of the quartz rock, collected at 
the same locality and containing N. Vermontana and (J. 
Thompsoni, a species of Hyolithes occurs that is undistinguish- 
able from IL communis. 
An investigation of the reported localities of fossils, made by 
the writer in June and July, 1887, resulted in the discovery 
* Dated 1861, but issued in 1862. 
f Bull. Am. Mus. Nat. Hist., vol. i, p. 145, 1884. C. D. Walcott-The Taconic System of Emmons. 
235 
that only the Scolithus had been found in situ. Professor H. 
M. Seely had traced the Rockville " Lingula " to a bowlder, 
taken from a stone wall, and also the reported Lake Dunmore 
specimens to bowlders on Sunset Hill: no fossils being found 
in situ. In company with Professor Seely, I visited the Lake 
Dunmore locality, and found fossils in rounded quartz bowlders, 
but the quartz ledges gave no traces of them. The Woodford 
locality was too indefinitely described to be found; but as trans- 
ported bowlders afforded me Nothozoe and traces of trilobitic 
remains, similar bowlders were probably the source of the speci- 
mens mentioned. In Sunderland, east of Arlington, on Roaring 
Branch, Scolithus occurs abundantly in situ, in the quartzite; 
and angular blocks of quartzite were found, one mile up the 
ravine, that contained Ilyolithes and fragments of trilobites; 
but they were not traced to the beds from which they were de- 
rived. Two miles east of Bennington, however, success attended 
my search for fossils in situ. The section begins in the woods 
on the west slope of the mountain on the old Weeks farm north 
of the old Windham turnpike. 
Wooded slope, above pasture. 75 feet. 
1.-Light-gray, nearly white, compact, fine-grained 
massive-bedded quartzite, with alternating 
beds 'of hyaline quartz. Dip 0° to 5° S. E. ; 
strike, N. 35° E. (magnetic) 35 " 
2.-Light-colored, bedded quartzite, with brown 
spots ; showing grains of sand and fossils: 
the latter also in the compact rock. 
Fossils : Nothozoe, Hyolithes and Olenellus* 40 " 
3.-Alternating bands of layers of light-gray and 
hyaline quartzite, becoming more massive 
near the summit 325 a 
The dip increases from 5° to 10,° 15° and up to 
25° S. E., on the line of the section, and a lit- 
tle farther south, to 45° S. E. Strike, N. 45° 
E. (magnetic) 
400 feet. 
The quartzite was traced north into the valley of Roaring 
Branch, and it is a continuation of the deposit on the western 
slope of Bald Mountain ; to the south it extends along the west 
side of the ridge leading to Dome Mountain, in Pownal, north- 
east of Williamstown, Mass. It caps the latter and crosses the 
narrow valley on the south to the Clarksburg group of moun- 
tains, along the slopes of which it extends to a point opposite 
Williamstown, where it bends eastward along the south face of 
* I have shown elsewhere that the genus Olenelhis is characteristic of the Middle 
Cambrian horizon, over wide areas in North'America, and that it is a pre-Potsdam 
type. (Bull. U. S Geol Survey, No. 30, 1880.) 236 
C. D. Walcott-The Taconic System of Emmons. 
• ) 
the mountain, reaching into the valley north of North Adams- 
Mass. On the western summit of the mountain, toward Will 
iamstown, the quartzite series come in unconformable contact 
with the pre-Cambrian gneiss; and fragments of a trilobite, 
apparently the genus Olenellus, were found about one hundred 
feet above the contact. 
As a result of the discovery of fossils, in situ, in the quartz- 
ite east of Bennington, the fossiliferous bowlders are given a 
value, as they were undoubtedly derived from the quartzite for- 
mation, and were distributed in the valley to the west during Qua- 
ternary time and even at the present by floods occurring in the 
gorges and valleys that cut through the quartzite. It is now 
a question of search to trace the fossiliferous horizon in the 
quartzite from Starksboro, to Bennington, Vt. and to Dutchess 
County, N. Y., where Dr. Mather considered the " Quartzite " 
metamorphosed Potsdam sandstone, and he so called the com- 
pact sandstone of Stissing Mountain, in the northeastern part 
of Dutchess County, N. Y. (Geol. N. Y. ; First Geol. Dist., p. 
418, 1843). During the field season of 1886, I had the oppor- 
tunity of visiting the Stissing Mountain sandstone locality, in 
company with Professor W. B. Dwight, and we found Uyoli- 
thellus micans in the limestone layers, resting immediately on 
the sandstone; and the heads of Olenellus Thompsoni in the 
sandstone, fifty feet or more below the limestone. Ilyolithellus 
micans is known only in the Georgia terrane of New York, 
Vermont and Canada. A species of Triplesia is associated with 
the Olenellus at Stissing Mountain, but it has little value in 
the correlation of strata. 
If we now turn to the geologic map, we find that all the 
localities I have mentioned are on the line of outcrop of the 
quartzite (Terr. No. 1). 
Resume.-The stratigraphy shows the quartzite series (Teri'. 
No. 1) to be the oldest of the Paleozoic sediments known 
on the eastern side of the Taconic area, and the contained 
fauna correlates it with the middle division of the Cambrian, 
but not as low in position as the fauna of the lower strata of 
the Georgia Terrane. (See Terr. No. 5.) 
Terrane No. 2.-Dr. Emmons, when describing the sections 
of Graylock (Am. Geol., vol. i, pt. 2, p. 17, paragraph 16), 
states that the " rock overlying the quartzite is again talcose 
slate, siliceous at its base, but purely a talcose slate as a mass 
and which requires no further description. It is between 400 
and 500 feet thick and extends up the limestone which con- 
stitutes the seventh member of the Lower Taconic system." 
It is this belt of shales that I have numbered 2 on the sections : 
and it is assumed to represent, at this point, the Potsdam sand- 
stone of the western side of the Champlain basin. This ter C. D. Walcott-The Taconic System of Emmons. 
237 
rane is so much more extensively developed farther west, in 
the section, that I will omit its description until passing down 
the western side of the synclinal formed by terrane number 
three. (See Section on the map.) 
Terrane No. 3.-This is the limestone and marble belt that 
outcrops both on the eastern and western side of the Taconic 
range. Its distribution is shown on the map and in the sec- 
tion, and 1 think it unnecessary to restate the evidence given 
by Professor Dana to prove that this limestone belt is the rep- 
resentative of the limestones of the Trenton-Chazy-Calciferous 
series of the western side of the Champlain basin. His con- 
clusions are based on the stratigraphy, supported by paleonto- 
logic evidence,* discovered by Messrs. Wing, Dana and 
Dwight on the western side of the Taconic range, north and 
south of the typical area. The fossils have been referred, 
however, to the sparry limestone or "Upper Taconic" by 
those writers who favor the view of the pre-Cambrian age of 
the "Lower Taconic." Prior to August 5th, 1887, determin- 
able fossils had not been found in the limestone series east of 
the Taconic range. At that date, I found, in the eastern lime- 
stone, in the town of Pownal, Vt., about half a mile north of 
the Massachusetts line, a number of fossils that were weathered 
out in relief on the surface 
of a compact, clouded mar- 
ble. The collection gives 
Euomphalus ? (fig. 1); the 
lower whorl and aperture 
of a shell like Murchisonia 
loellicincta (fig. 2); two 
whorls of a form identical 
or closely allied to Mur chi- 
sonia Milleri (fig. 3). (fig. 
4 is a cast of Murchisonia 
Milleri^ from the Cincin- 
nati formation, for compar- 
ison with fig. 3): a cross- 
section and lower whorl of 
a Raphistoma-like shell, 
and a large, crushed gaste- 
ropod shell. The fauna 
belongs to the Trenton 
terrane, and, by it, we can correlate the Eastern with the 
Western limestone.f 
In September, 1887, I found fossils in the limestone on both 
* See Professor Dana's papers in Am. Jour. Sci., 1872 to 1887. 
f Paper read before the American Association for the Advancement of Science, 
August, 15th, 1887 : "Discovery of Fossils in the Lower Taconic of Emmons."- 
C. D. W. 238 
C. D. Walcott-The Taconic System of Emmons. 
the eastern and western side of Mt. Anthony, on the line of 
strike of the Taconic range. The strata of Mt. Anthony are 
conformable and form a southwardly-sloping synclinal of lime- 
stone and marble, carrying, above, a considerable thickness of 
shales. On the west side the limestones dip eastward and are 
well exposed one mile south of the Hoosic post office, N. Y. 
About 400 feet of limestone are shown in the section, and, near 
the upper part of it, shales appear which have a schistose 
structure. The shales are in thin beds alternating with the 
limestones at first, and then they increase until the interbedded 
limestone disappears and the typical Taconic " talcose slates" 
of Emmons are the prevailing rock. In the limestones, nearly 
200 feet below the shales, a stratum of limestone from two to 
four feet in thickness is crowded with shells of the genera 
Maclurea and Murchisonia. The limestone is compact and 
hard, so that sections only of the shells could be secured. To 
any one conversant w'ith the Trenton-Chazy limestones of 
Washington County, N. Y., both the lithology and 'fossils of 
the Mt. Anthony limestone, at this point, would prove the 
geologic horizon to be that of the Trenton-Chazy. Crossing 
the mountain to the eastern side, at a point three miles south 
of Bennington Centre, Vt., abundant fragments of crinoids 
occur in a dark bituminous limestone, above a band of clouded 
marble. In fig. 5, a few sections of a column 
is shown and also the calyx and portions of 
the arms of a crinoid, allied to llomocrinus 
gracilis of the Trenton limestone of New York. 
Above the dark shale and dipping westward 
with it, there is a band of arenaceous limestone 
upon which I noticed a fragment of an Orthoce- 
ras, an Euomphalus-like shell and sections of 
what appeared to be a Bhynchonella. This lime- 
stone is lithologically similar to that conformably 
overlying a bed of marble that dips toward and 
passes beneath Mt. Anthony at a quarry, two 
miles west of Bennington Centre. 
I next visited the limestone at the entrance of the Hopper 
on the north side of Graylock peak, a typical locality of Dr. 
Emmons's. The limestones and marbles are of the same litho- 
logic character as those of Mt. Anthony with the 
exception of the bituminous limestone, carrying the 
crinoids. Several traces of fossils were observed, 
but only one that could be recognized. It appears 
to be the inner whorl of a gasteropod related to 
Euomphalus or Maclurea (fig. 6). 
Having verified the stratigraphy as published by Dr. Em- 
mons and Professor Dana, and having found Trenton-Chazy 
fossils in the marble belt, I crossed the Taconic range to its C. D. Walcott-The Taconic System of Emmons. 
239 
western base, in the town of Berlin, N. Y. The schists of the 
range dip to the eastward, have a greenish color, feel talcose 
to the touch, and appear unlike the dark shales of the Hudson 
Terrane. Continuing on over the range and down the western 
slope, I found that the schistose character of the rock was 
gradually disappearing and that it was becoming more shaly. 
The greenish color continued, but, toward the western base 
of the range, a mile north of the village of Berlin, the color 
began to change, the green and dark shales appearing in the 
same stratum, and even in hand specimens, and soon the dark 
shale of the Hudson Terrane was the prevailing rock. A 
little lower down, the characteristic brown sandstones of the 
Hudson Terrane began to appear in the shales; and, just east 
of Berlin village, the limestones appeared from beneath the 
shales. In other words, it is a repetition of the Graylock and 
Mt. Anthony sections with the exception of less alteration in 
the lower part of the shales, and in the limestones. One mile 
south of South Berlin post office, on the eastern side of the 
valley, the limestones dip to the east and northeast. At the 
base of the section there is a considerable thickness of dark 
argillaceous shale, upon which the limestone rests conformably. 
Continuing up the west slope of the mountain, more or less 
impure limestones are met with in which I found Solenopora 
compacta^ plates of crinoidal columns, Murchisonia gracilis t 
(fig. 7), and fragments of indeterminable gasteropods. The 
Lituites sp ? 
fossil-bearing limestone is subjacent to, and interbedded with, 
shales that are succeeded by arenaceous limestones which, in 
turn, are conformably subjacent to the shales and schists of the 
Taconic range. 
The next locality examined was one described by Dr. Em- 
mons as showing fossiliferous limestones of the Champlain 
series, resting unconformably upon the " Taconic " schists (Am. 240 
C. D. Walcott-The Taconic System of Emmons. 
Geol., pt. 2, pp. 73-77, 1856). He studied the section, 
where it is very much broken and disturbed, and found evi- 
dence that sustained his view. If he had gone a mile to the 
north, he might have discovered that the shales pass conform- 
ably beneath the limestone and, also, that shales occur con- 
formably above it. Fossils were abundant at a point one mile 
north, northwest of Hoosick Falls, and the following species 
were recognized: Solenopora comp acta, Maclurea sp.?, Litu- 
ites sp. ? (figs. 8 and 9), and Orthoceras sp. undet. 
On the map the localities, where fossils have been found in 
this terrane, are indicated by the letter F. 
Resume.-The stratigraphic and paleontologic evidence unite 
to prove that the limestones and marbles of Terrane No. 3 are 
the geologic equivalent of the Calciferous-Chazy-Trenton lime- 
stones of the Champlain and Hudson valleys, and belong to 
the system of strata characterized by the second fauna of 
Barrande. 
Terrane No. 4.-This terrane directly overlies and rests in 
synclinals of the limestones of Terrane No. 3, at Graylock and 
at other points; and there is no apparent reason to differ from 
Professor Dana in referring it to the Hudson Terrane. 
In regard to the graptolites found in it, near Hoosick, N. Y., 
I wish to state that I visited that locality and collected speci- 
mens of the flattened and distorted graptolites from the 
smooth shales. On comparing the specimens with those of 
Diplograptus pristis, from the Hudson Terrane, at Fort 
Edward, N. Y. and, also, from the Hudson Terrane in the 
western part of the township of Greenwich, Washington 
County, N. Y, I fully concur with the opinion given by Pro- 
fesssor James Hall, in 1847 (Pal. N. Y., vol. i, pp. 321, 322, 
pl. 72), that the Hoosick shale graptolite is identical with the 
Diplograptus pristis found in the Hudson Terrane, within the 
Hudson valley. 
Terrane No. 2.-In speaking of this terrane as the shale 
above the quartzite of Terrane No. 1 and beneath the lime- 
stone of Terrane No. 3, it was assumed that it represented the 
Potsdam horizon (ante); and we now have to search for 
the evidence of that horizon between the recognized Georgia 
horizon of Terrane No. 1, and the Chazy-Trenton horizon of 
Terrane No. 3. Unfortunately, on the east and west sides of 
the synclinal, on the line of the section, the shales beneath the 
limestones are unfossiliferous; but, from the data afforded by 
the Potsdam or Upper Cambrian strata of Saratoga, Dutchess 
and Washington counties, N. Y., we obtain a fairly satisfactory 
identification of the Potsdam horizon in the Taconic area. 
In Saratoga County a section occurs where a pure limestone, 
carrying a well-marked Potsdam fauna, rests directly on a mas- C. D. Walcott-The Taconic System of Emmons. 
241 
sive-bedded sandstone.* The sandstone is of Potsdam age, and 
contains typical fossils in its extension north in the valley of 
Lake Champlain: in Washington County I found, at Dewey's 
Bridge, south of Whitehall, fossils in the Potsdam sandstone, 
and at Whitehall, numerous Potsdam fossils in the limestone 
layers resting upon the sandstone and beneath the Calciferous 
formation. The Calciferous formation was subjacent to the 
Chazy limestone. 
In Dutchess County Professor Dwight found the Potsdam 
fauna in a limestone, three species of which are identical with 
those at the Saratoga and Washington County localities. This 
proves the presence of the Potsdam fauna in Dutchess County, 
not far distant from the sandstone and limestone carrying the 
Georgia fauna. Although no direct stratigraphic connection 
is yet known at this point between the limestone carrying the 
Potsdam fossils, and the limestone resting on the the sandstone 
carrying the Georgia fossils, there is little doubt, from the 
known succession of faunas elsewhere, that the Potsdam forma- 
tion was deposited in its usual position, between the Georgia 
and Calciferous formations, and that it has been displaced by 
the subsequent faulting of the strata. 
In Saratoga County, the Calciferous-Trenton terranes are 
superjacent to the Potsdam, and, also, in Dutchess and Wash- 
ington counties. In all the sections given in Bulletin 30, U. S. 
Geological Survey, the Potsdam is superjacent to the Georgia 
Terrane ; and I find that Terrane No. 5, beneath the 2,000 
feet of greenish schistose shales of Terrane No. 2, is character- 
ized by the Georgia or Middle Cambrian fauna. I think, then, 
that we may conclude that Terrane No. 2 represents the Pots- 
dam horizon : also, that the latter may be represented in part 
by sandstone or quartzite on the west side, near the limestones, 
or, if the same conditions prevail as in Dutchess County, the 
lower portion of the limestone; the shales and schists beneath 
the limestone all belong to the Middle Cambrian. To the 
east of the limestone, the Potsdam Terrane may be repre- 
sented in part by either (1) the upper part of the quartz- 
ite of Terrane No. 1, (2) the lower part of the limestone of 
Terrane No. 3, or (3) the hydromica shale between the quartz- 
ite and limestone, or Terrane No. 2, or by the combination of 
two or more of these parts. 
Terrane No. 5.-In my field work of 1886-'87, I studied 
with care the slates, shales and interbedded limestones and 
sandstones that form Terrane No. 5. On the map an inter- 
ruption is shown midway, by the presence of a broad belt of 
* Bull. U. S. Geol. Survey, No. 30, pp. 21, 22, 1886.-T found several species of 
this same fauna (Dicellocephalus, Ptychaspis, etc.) in sandstone in the upper beds 
of the Potsdam sandstone, in the vicinity of Chateaugay Chasm. Franklin County, 
N. Y.; also in a calciferous sandrock of the Potsdam Terrane, at Whitehall, N. Y. 242 
C. D. Walcott-The Taconic System of Emmons. 
the Hudson Terrane (No. 6), but 1 did not find that the two 
parts of Terrane No. 5 are a repetition of the same strata ex- 
cept possibly for a short distance, near the break between them. 
The upper or eastern portion is formed of green, purple and 
drab slates, with thin interbedded limestones, carrying charac- 
teristic Middle Cambrian fossils ; the lower and western part 
consists of dark and drab shales with interbedded sandstones, 
calcareous sandrock and limestones that contain Middle Cam- 
brian fossils. About 2,000 feet from the base, the fauna begins 
to show the presence of the Lower Cambrian or Paradoxides 
fauna, but not in sufficient force to overbalance the predomin- 
ating assemblage of Middle Cambrian species.-(See this Jour- 
nal, vol. xxxiv, p. 188,1887). Fossils occur more or less abun- 
dantly at over 100 localities as now known to me within the 
typical Taconic area, and they are distributed at various hori- 
zons throughout the 14,000 feet or more of strata referred to 
this Terrane. 
An examination of the sections and the faunas of Terrane 
No. 1 and Terrane No. 5, shows that the former is stratigraph- 
ically and faunally the equivalent of the upper or eastern part 
of Terrane No. 5, Terrane No. 1 being the sandy deposit of the 
shore line, and No. 5, the off-shore accumulation of finer sediment. 
Terrane No. 5, like No. 1, is referred to the Middle Division 
of the Cambrian. 
Terrane No. 6.-This is a belt of red, black and green slates, 
cherts and sandstones faulted in between the two parts of Ter- 
rane No. 5. The contained graptolites show it to be a portion 
of the Hudson Terrane. Its distribution and relation to the 
other terranes is shown on the map and in the section. 
Resume.-I have briefly noticed the strata included within 
the Taconic area with the exception of the beds west of the 
great fault line, separating Terrane No. 5 from the recognized 
strata of the Calciferous-Chazy-Trenton and Hudson terranes. 
Along the line of the fault, the strata of Terrane No. 5 are 
usually thrust against, and, sometimes, over and upon, the latter, 
but in no instance have I been able to find an unconformity by 
original deposition between the strata of Terrane No. 5 and the 
strata of any of the superjacent terranes. This will be more fully 
described later under the head of Comparison and Discussion. 
In the preceding pages, the strata of the Taconic area are 
grouped under six terranes and identified as follows . 
Terranes Nos. 1 and 5 = Middle Cambrian.* 
Terrane No. 2= Upper Cambrian.* 
Terrane No. 3 = Calciferous, Chazy and Trenton limestones. 
Terranes Nos. 4, and 6 = Hudson shales, sandstones, etc. 
[To be continued.] 
* For a description of the term Cambrian as used in this paper see this Journal, 
III, vol. xxxii, pp. 138-157, 1886. [From the American Journal of Science, Vol. XXXV, April, 1888.] 
Art. XXVI.-The Taconic System of Emmons, and the use of 
the name Taconic in ideologic nomenclature ; by Chas. D. 
Walcott, of the IT. S. Geological Survey. With Plate III. 
(Continued from page 242.) 
Geology of the Taconic Area as known to Dr. Emmons. 
(1). The strata referred to the " Taconic System (2). The 
stratigraphic position of the " Taconic System." 
Dr. Emmons began the study of the Taconic area in Berk- 
shire County, Mass., and from there extended his investiga- 
tions, to the north, into Bennington County, Vt., and to the west, 
into Washington and Rensselaer counties, N. Y.f In 18424 
* Ch. News, x, 263, 1864. Phil. Mag., IV, xxix, 475. 
f " My first business is to sketch a picture of the oldest of the sediments, as 
they are exhibited in a series which collectively constitute the Taconic System 
and as it is developed in the Taconic ranges of Berkshire and the adjacent 
country immediately north and south." (Am. Geol., pt. 2, p. 5, 1856). 
| Geol. N. Y., pt. 2, p. 144, 1842. 308 
C. D. Walcott-The Taconic System of Tmmons. 
he proposed the Taconic System, with the statement that it 
was composed of five different rocks, as follows: 
" 1. A coarse granular limestone of various colors which I 
have denominated Stockbridge limestone" etc. 
"2. Granular quartz rock, generally fine-grained, in firm, 
tough, crystalline masses of a brown color, but sometimes white, 
granular and friable." 
" 3. Slate, which for distinction I have denominated Magnesian 
slate" etc. 
" 4. Sparry limestone, generally known as the sparry lime- 
rock." 
" 5. A slate, which I have named Taconic Slate, and which is 
found at the western base of the Taconic range. It lies adjacent 
to the Lorraine or Hudson River shales, some varieties of which 
it resembles," etc. 
A section is given on page 145, fig. 46, to show -that the 
" Taconic System " embraced all the strata between the gneiss 
on the east and the " shales of the Champlain group " on the 
west. The latter are represented as unconformably superja- 
cent to the " Taconic slate." 
His second memoir appeared in 1844* as a pamphlet, pub- 
lished in advance of vol. i, of the Agriculture of New York, 
in which, in 1847, the subject matter was reprinted without 
change. The changes from the stratigraphic scheme of 1842 
consist in placing the granular quartz at the base of the 
system, with the Stockbridge limestone conformably resting 
upon it. A theoretical section^ is given to show the rela- 
tion of the various formations. The crystalline gneiss is rep- 
resented with (1), the Granular Quartz or brown sandstone 
resting upon it; then, in turn (2), the Stockbridge limestone; 
(3), Magnesian slate; (4), Sparry limestone; (5), Roofing 
slate ; (6), coarse brecciated bed ; (7), Taconic slate, and (8), 
Black slate. On the following page, the section shown by 
fig. 7 represents these beds as all having a high and uni- 
form dip to the eastward,^ and with the Hudson river 
shales (9), unconformably superjacent to the Taconic slate (8). 
When speaking of the lithologic characters of the system, 
Dr. Emmons says: " Taking one broad view of the whole sys- 
tem, it may be described as consisting of fine and coarse slates, 
* Agric. N. Y., vol. i, pp. 45-112, 1847. The pamphlet of 1844 is very rare, 
as few copies were issued, and I shall make all references to its contents as re- 
printed in the volume of 1847, combining the dates as 1844-47. 
f Loc. cit., p. 62, tig. 6. 
| This is corrected for the " Lower Taconic " rocks in the Section published 
in 1856 (Am. Geol., vol. i, pt. 2, p. 19), but all the strata of the "Upper Taconic" 
are considered superior to the Stockbridge limestone. C. D. Walcott-The Taconic System of Emmons. 
309 
with subordinate beds of chert, tine and coarse limestone, and 
gray, brown and white sandstone.* 
The geological map, prepared to accompany the memoir of 
1844-'47, bears the date of 1844 and is a reprint of the Geo- 
logical Map of New York, issued in 1842, with additional data 
on the geology east of the Hudson and Champlain valleys. 
The long, narrow range of the " Taconic System " is colored 
drab in its extension from Canada to Westchester County, 
N. Y. There is no reference to the " Taconic System " in the 
legend on the map, and the formations composing it are not 
distinguished by different colors, the reason for which is ex- 
plained in the description of the map, published on page 361 
of the Agriculture of New York, vol i, 1847.f 
In 18564 Dr. Emmons divided the " Taconic System " into 
an upper and a lower division: the upper division taking the 
formations 4 to 8 of the section of 1844-'47, and the lower 
division the formations 1 to 3 ; an arrangement that was re- 
peated in 1859 (Manual of Geology), when the name u Mag- 
nesian slate" was replaced by that of " Talcose slate." In the 
diagram, fig. 10, the formations are represented in the order 
of succession given in 1856 ; and, on the map, the geographic 
area is given within which the typical localities of the various 
formations occur and also the extension of the latter to the 
north and south. This is the stratigraphic scheme of the " Ta- 
conic System " as arranged by its author from the results of 
his latest field observations.^ 
" Gramular Quartz " (Terrane No. 1, of section on side of 
map and fig. 10).-Dr. Emmons calls the " Granular Quartz " 
the basal member of the " Taconic System," and, in his opin- 
ion, the base of the Paleozoic sediments on the North Ameri- 
can continent. He describes its occurrence in Vermont and 
follows it, with interruptions, across Massachusetts into the 
northeastern part of Dutchess County, N. Y., and also south 
into Putnam and Westchester counties. || The stratigraphic 
* Loc. cit., p. 61. 
f The copy I have of this map was purchased by me from a second-hand book 
dealer, in 1876. I have reason to state that 3000 copies were originally delivered 
to the Secretary of State, of the State of New York, by the printers, and I think 
that copies can still be obtained from the said Secretary's office, despite the pub- 
lished statement that the edition was stolen or destroyed. (See letter of Dr. 
Emmons to Prof. Jules Marcou: Am. Acad. Arts and Sci., vol. xii, p. 188, 1885, 
also copied by Dr. Hunt, Am. Nat., vol. xxi, p. 122, foot note 3, 1887). 
| The first part of this volume is dated 1855. The second part, containing the 
description of the '' Taconic System," was issued in 1856. 
§ I shall not comment on the so-called Taconic rocks, as identified by Dr. 
Emmons in Canada, Maine, Rhode Island, Michigan, and the southern Appala- 
chian region. All those determinations rested on lithologic characters ; and the 
strata referred by him to the " Taconic System " range from pre-Cambrian to the 
Niagara of the Silurian. 
F Agric. N. Y., vol. i, p. 86, 1847. 310 
C. D. Walcott-The Taconic System of Emmons. 
position was determined by its relation to the crystalline rocks 
beneath and the superjacent strata, as no fossils were known 
by him from the formation. A talcose conglomerate that is 
treated as a subordinate member of the " Granular Quartz se- 
ries" is described as occurring between the quartzite and 
Primary, in several localities. 
Fig. 10.-A tabular view of the strata as arranged by Dr. Emmons. 
The figures placed at the sides are equivalent to those used on the section on 
the side of the map. The dotted lines on the right side show the relation of the 
"Upper Taconic" to its geologic equivalent the "Granular Quartz." 
Conformably resting on the " Granular Quartz," on the 
north side of Graylock Peak, at the Hopper, he found a bed 
of "talcose slate," 400 to 500 feet thick, which is represented 
in the table (tig. 10) by number 2. It appears to be the ex- 
tension of a formation of more than 2,000 feet in thickness 
that occurs on the western side of the Taconic range. (See sec- 
tion on the map.) 
Stockbridge limestone (Terr. No. 3 of Section and fig. 10).- 
Upon the slates of Terrane No. 2 a series of limestones and 
marbles are conformably superimposed that are called by Dr. 
Emmons the " Stockbridge limestone." This includes all the 
limestones, " good and bad, in connection with the bed known 
as marble." A good description of this terrane is given in the 
memoir of 1844-'47, and again in 1856. It is assigned a thick- 
ness of 500 feet, in Saddle Mountain, Mass. C. D. Walcott-The Taconic System of Emmons. 
311 
Talcose Slates (Terr. No. 4 of Section and fig. 10). - 
These slates, which are called " Magnesian slates " in the re- 
ports of 1842-'44-'47, were given the name "Talcose slates" 
in 1856. A thickness of 2000 feet is assigned to them on the 
Taconic range and they are represented as conformably super- 
imposed upon the Stockbridge limestone. 
"Upper Taconic}'-In the scheme published in 1844-'47 
the Magnesian slate is succeeded by the Sparry limestone, 
Roofing slate, a coarse brecciated bed, Taconic slate, and Black 
slate, and on p. 13, Am. Geol., pt. 2, 1856, this succession is 
recognized. On page 49 (loc. cit.), however, the entire scheme 
is changed; the Black slate is placed at the bottom of the 
series and then, in succession, siliceous slates: slates and sand- 
stones, with thin-bedded blue limestones succeeded by thicker 
beds of sandstone ; blue, green, purple and red roofing slates, 
coarse sandstone and shale passing into conglomerates and brec- 
ciated conglomerates. " The latter terminate the series east- 
ward, and geographically near the Hoosick roofing slates. In 
the foregoing brief enumeration in the ascending order, the 
rocks follow each other in a conformable position, and begin- 
ning with the thin black slates, end in thick bedded sandstones 
and conglomerates," (loc. cit., p. 50). 
In this re-definition of the "Upper Taconic," the Sparry 
limestone is no longer considered as belonging to it, and I have 
failed to find it mentioned subsequently as a distinct formation 
of the " Upper Taconic." The sparry limestone spoken of in 
describing the "Upper Taconic " section crossing Washington 
County, refers to the thin interbedded sparry limestones, in 
which I have found Olenellus and other Middle Cambrian fos- 
sils. The sparry limestones west of Hoosick Falls are referred 
to the Lower Silurian and removed entirely from the " Taconic 
System." 
As is shown by Professor Dana, Dr. Emmons, in 1842, called 
the Sparry limestone the oldest of the Taconic limestones, and, 
in 1844, he placed it beneath the Taconic slate and above the 
Stockbridge limestone.* In 1856,f however, a section was 
published showing the Taconic Range by C and, at its western 
base, the limestone (2) is identified with the Stockbridge lime- 
stone (2), of B (Graylock Peak). What Dr. Emmons intended 
by this, and why he did not mention the charige in the text, is 
not explained by him. Professor Dana called my attention to 
it by letter, and says that he accepts the evident meaning given 
by the section, which is, that Dr. Emmons identified the Sparry 
and Stockbridge limestones as one formation. With our pres- 
ent knowledge, this explanation is the only one open to us. 
* This Journal, III, vol. xxxiii, pp. 415, 416, 1887. 
f Am. Geol., vol. i, pt. 11, p. 19, fig. 2. 312 
C. D. Walcott-The Taconic System of Emmons. 
In 1859 the section is republished,* but the numbers are 
omitted from all the formations except those of Graylock Peak. 
Whether the omission was by design or accident is unknown. 
In the black slates, at the summit of the " Taconic System " of 
1844-'47 and at the base of the "Upper Taconic" of 1856, 
Dr. Asa Fitch found a few fossils which he gave to Dr. Em- 
mons, who described two species in the memoir of 1844-47, 
under the names of Elliptocephala asaphoides and Atops tri- 
lineatus. In 1859 Dr. Emmons compared these fossils with the 
Primordial fauna of Barraude, and established their position in 
the stratigraphic series on paleontologic evidence.^ Their ref- 
erence to a pre-Potsdam horizon, in 1844-'47 and 1856, was on 
the supposed stratigraphic position of the beds in which they 
occurred. 
Resume.-It is not necessary to repeat the full and accurate 
lithologic descriptions of the five terranes (fig. 10) mentioned 
by Dr. Emmons in 1844-'47 and 1856. They are grouped in 
fig. 10 to represent his view of their succession within the 
" Taconic System." 
2. Stratigraphic position of the " Taconic Sy stem A-Dr. 
Emmons founded the " Taconic System " under the belief that 
it was composed of older formations than those of the New 
York Lower Silurian, the base of which was then the well- 
known Potsdam sandstone. In the memoir of 1812, he says: 
" But I have, at the head of this section, asserted that the 
slates and masses of the Taconic System are not related to, or 
connected with those of the Champlain group. By this I mean 
that they are not the same rocks in another condition." $ 
Again he says : " They are to be considered, however, as fur- 
nishing us with a knowledge of that state which immediately 
preceded the existence of organic beings." § After further field 
study his views became more positive in regard to the relation 
of the Taconic to the Lower Silurian rocks. He says: "I shall 
take the broad and distinct ground that the Taconic System oc- 
cupies a position inferior to the Champlain division of the 
New York system, or the Lower division of the Silurian system 
of Mr. Murchison." || 
" 1. Position.-It rests unconformably upon primary schists, 
and passes beneath the New York system, the oldest and infe- 
rior members of the latter being superimposed unconformably 
upon the Taconic slate."These views were sustained in his 
publications of 1856, 1859 and 1860. 
On the section, accompanying the memoir of 1844-'47, pl. 
18, Section I, the strata of the " Taconic System " all dip con- 
* Manual of Geology, p. 85, fig. 60. 
t Geol. N. Y., pt. 2, p. 138, 1842. 
|| Agric N. Y., vol. i, p. 55, 1847. 
f Manual of Geology, p. 87, 1859. 
§ Loc. cit., p. 164. 
Loc. cit., p. 108. C. D. Walcott-The Taconic System of Emmons. 
313 
formably to the eastward. On the east they rest unconforma- 
bly on the primary and, on the west, the Calciferous and Hud- 
son terranes are represented as unconformably superjacent to 
the Taconic slates. Dr. Emmons says: " This section may 
be regarded as one of the best for exhibiting and proving the 
entire independence of the Taconic System from the Primary 
below and the New York system above." * 
Two sections published in 1859 f may be taken as express- 
ing his latest views of the relations of the different parts 
of the " Taconic System," in its typical area, with the 
exception of the "Upper Taconic" and the Lower Silurian 
(Ordovician), on the western side. In these sections, the 
" Lower Taconic " forms a synclinal with the " Granular 
Quartz " at the base and then the Stockbridge limestone and 
Talcose slates, respectively superjacent, the " Upper Taconic" 
being entirely disconnected from the latter. He held the view, 
from the first, that the eastward dip of the greater part of 
the strata of the " Taconic System " resulted from successive 
uplifts, " which, in consequence of the confined position of the 
rocks, have often produced local foldings and plications of the 
strata." His view of the extent and character of the uplifts 
was subsequently changed, as is shown by his representation of 
the position of the sparry limestone in 1842,§ 1844§ and 1855. 
In the memoir of 1856 several sections were illustrated and 
described to show the unconformity between the Taconic slate 
and the Calciferous sandrock, and thus establish the inferior 
position of the " Taconic System " to the Lower Silurian (Or- 
dovician) strata. These sections will be spoken of again, under 
the head of " Discussion and Comparison." 
Dr. Emmons correlated the " Taconic System " with the 
Cambrian system of Sedgwick, in his first memoir of 1842, in 
the following words : || " The Taconic rocks appear to be equiv- 
alent to the Lower Cambrian of Prof. Sedgwick, and are alone 
entitled to the consideration of belonging to this system, the 
upper portion [of the Cambrian-C. D. W.] being the lower 
part of the Silurian System." 
Again, in the memoir of 1844-'47, he says, when speaking 
of the proposed abandonment of the Cambrian System by Eng- 
lish geologists:".... were it not for a single fact, the 
* Log. cit., p. 366. 
f Manual of Geology, p. 85, figs. 58 and 60. 
t Geol. N. Y., pt. 2, p. J 42, 1842. 
§ See Professor Dana, this Journal, 3d Ser., vol. xxxiii, p. 415. 
|| Geol. N. Y., pt. 1, p. 163, 1842. 
<Dr. T. S. Hunt (Am. Nat., vol.xxi, p. 124, 1887) interprets this passage to 
prove that Dr. Emmons in 1842 correlated the upper portion of the Taconic with 
the Lower Silurian of Murchison, but, as I read it, Dr. Emmons refers the Upper 
Cambrian, not his Taconic, to the Lower Silurian. 
Am. Jour Sci.-Third Series, Vol. XXXV, No. 208.-April, 1888. 
19 314 
C. D. Walcott-The Taconic System of Emmons. 
writer would freely acquiesce in the decision, so far as the 
British rocks are concerned. This fact is found in the exist- 
ence of peculiar fossils on both sides of the Atlantic, which, 
so far as discoveries have been made, are confined to the slates 
of the Cambrian and Taconic systems ; and now the great ob- 
ject of the writer is to show that the above question has not 
been settled right, or according to the facts; or, in other words 
that the Taconic rocks are not the Hudson River slates and 
shales in an altered state, or that all the Cambrian rocks are 
not Lower Silurian." * 
In the following pages observations and deductions there- 
from are given to support the above statement in relation to 
the " Taconic System," but nothing further is said of the fos- 
sils from the Cambrian system, and I am at a loss to know to 
what species the author referred. Reference is made to the 
Cambrian sections of Sedgwick, in 1856, to show that although 
the Cambrian slates are conformably beneath the Coniston 
limestone bearing Lower Silurian fossils, and hence may be re- 
ferred to the Silurian, the Taconic rocks are unconformably 
beneath the equivalent Calciferous sandrock of the New York 
series and cannot be included with the Lower Silurian.f 
Among the letters of Dr. Emmons, published by Prof. Jules 
Marcou4 is one, dated November 19, 1860, in which he says :§ 
" .... I do not think him [referring to Barrande] right in 
maintaining that his Primordial group is a part or parcel of 
the Silurian: . . . . the Lower Silurian is strictly unconform- 
able to every part of my Taconic series, and this series is 
. . . . separate and distinct from Silurian." 
On the same page, in a letter dated November 20th, 1860, 
he says: "On reading his [Barrande's] papers, I found that, 
after all, his Primordial group is only Lower Silurian. I con- 
ceive we have exactly his Primordial group in the band of 
slates containing the Paradoxides. But this band is only a 
very narrow belt of beds." 
In a letter dated December 28th, or 29th,|| he says, when 
speaking of the announcement of the Huronian System by 
Logan : " I claimed that the Huronian was the Taconic Sys- 
tem . • . Are you aware that most, if not all, of those beauti- 
ful graptolites Mr. Hall refers to the Hudson River group be- 
long to the Taconic System ?" 
Again, in a letter dated January 23d, 1861:T "The acknowl- 
edgment of the Primordial of Barrande in this country is 
really one of the finest and best facts in geology, making a coordi- 
nation of American and European rocks so complete and ha/r- 
moniousL 
* Agric. N. Y., vol. i, p. 49, 1847. SLoc. cit., p. 186. 
| Am. Geol., vol. i, pt. 2, p. 90, 1856, ||Loc. cit., p. 188. 
| Proc. Am. Acad. Arts and Sci., vol. xii, 1885, ^[Loc. cit., p. 190. C. D. Walcott-The Taconic System of Emmons. 
315 
In commenting upon Professor Marcou's reference of the 
Potsdam sandstone to the " Taconic System," he objects to 
such references on stratigraphic grounds, as is shown by his 
letter of January 28th, 1861. 
These later letters of Dr. Emmons prove that he considered 
the " Taconic System " to include the Huronian of Logan and 
the graptolite-bearing shales of the Hudson valley, from his 
letter of November 20th, 1860, he also included the Para- 
doxides beds of the "Upper Taconic" which equal the Pri- 
mordial group of Barrande, which- " is only Lower Silurian," 
and declared that " the Low'er Silurian is strictly unconform- 
able to every part of my Taconic series." 
Despite the statements made in the preceding paragraph, 
I think w7e may say that Dr. Emmons regarded the original 
" Taconic System " as stratigraphically unconformable and sub- 
jacent to the Potsdam sandstone of the Lower Silurian of the 
New York section and believed it to rest unconformably upon 
the crystalline gneiss at its base and to form a great system of 
sedimentary rocks between the gneiss and Potsdam sandstone. 
Comparison.-A comparison of the geology of the Taconic 
area as known at the present time with the geology of the 
same area as known to Dr. Emmons develops several points 
of agreement. His lithologic descriptions are usually easily 
verified; and the general dip and arrangement of the strata 
within the " Taconic System'' are the same with the exception 
of the relations of the strata referred to the " Lower " and 
" Upper Taconic." 
The points of disagreement are: the identification of the 
geologic age of the formations of the " Lower Taconicthe 
stratigraphic relations of the "Lower" and " Upper Taconic ;" 
the stratigraphic relations of the "Upper Taconic" and the 
superjacent Silurian formations, and the value of the strati- 
graphic and paleontologic identifications of the age of the 
" Upper Taconic" slates. 
1. Dr. Emmons considered the " Lower Taconic " to be 
composed of three non-fossiliferous pre-Silurian formations- 
" Granular quartz, Stockbridge limestone and Talcose slates" 
(see fig. 10) that were unconformably superjacent to the crystal- 
line gneisses beneath and conformably subjacent to a great 
series of slates, forming the " Upper Taconic," that, in turn, 
were unconformably subjacent to the lowest of the Lower 
Silurian formations, the Potsdam sandstone. 
We now know that the base of the " Taconic System," the 
" Granular Quartz," contains fossils that prove it to be the geo- 
logic equivalent of the greater portion of the " Upper Ta- 
Comparison and Discussion. 316 
C. D. Walcott-The Taconic System of Emmons. 
conic; also, that it is the arenaceous deposit that accumulated 
along the pre-Paleozoic shore while the siliceous, argillaceous 
and calcareous muds, now forming the " Upper Taconic," were 
being deposited to a greater depth off the immediate shore 
line. This entirely negatives the conclusion of Dr. Emmons, 
that the "Upper Taconic" slates were superjacent to the 
"Lower Taconic" rocks. 
2. The second formation, the " Stock- 
bridge limestone," has afforded fossils 
that-prove it to be the equivalent of the 
Trenton, Chazy and Calciferous lime- 
stones of the Lower Silurian of the New 
York section, and it is not, as claimed 
by Dr. Emmons, a peculiar pre-Silurian 
deposit of limestone. 
3. Conformably resting upon the 
"Stockbridge limestone" the "Talcose 
slates" (Terr. No. 4) occupy the strati- 
graphic position of the Hudson Terrane, 
in the New York section, and a species 
of graptolite, abundant in the Hudson 
Terrane, occurs in the " Talcose slates " 
near Hoosick, N. Y. 
We have next to consider the rela- 
tions of the " Upper Taconic" slates to 
the superjacent Silurian formations and 
the value of the stratigraphic and pale- 
ontologic identifications of the age of the 
" Upper Taconic." 
In the first published section* of the 
" Taconic System," the " Shales of the 
Champlain Group" are represented as 
resting unconformably against, and on, 
the Taconic slates. This is repeated in 
the section published in 1844-47. f 
These two sections are largely theoretic, 
but, on page 89 (loc. cit.), Dr. Emmons 
gives a section of Bald Mountain, in 
the town of Greenwich, Washington 
County, N. Y., which is here reproduced 
(fig; W- 
This section is intended to show the 
unconformity between the Taconic slates, 
6, b', 5", and the Calciferous formations, 
d, c and d', it being assumed by Dr. 
Emmons that the slates, J, 6' and 5", 
Fig. 11. 
* Geol. N. Y.; Rep. Second Geol. Dist., p. 145, fig. 46, 1842 
f Agric. N. Y., vol. i, p. 63, fig. 7, 1847. C. D. Walcott-The Taconic System of Emmons. 
317 
were identical, and that d' was a mass of the Calciferous 
sandrock of the New York section, and, also, the mass repre- 
sented by c. I began the investigation of this section, in 1887, 
by searching for fossils in the various formations, and then 
studied its stratigraphy. The result is given in the section 
represented by fig. 12. I found that the blue limestone, c, of 
figs. 11 and 12, extends beneath the shales and limestones cap- 
ping the mountain and that it is interbedded in the shales and 
considerably broken and displaced on the south edge of the 
mountain, toward the fault line, as shown in fig. 12. Leper- 
ditia fabulites was found in it, on both the west and south 
side of the mountain. The true Calciferous sandrock, of the 
New York section, is shown at E, interbedded in the shales, S 
and X. In the limestones, d, forming the summit of the 
mountain, in fig. 11, I found Lingulella ccdata, Linnarssonia 
Taconica, Obolella sp. undet., Hyolithellus micans, Microdis- 
cus speciosus and Olenellus Thompsoni: all of which are Mid- 
dle Cambrian species and characteristic of the slates, b", in fig. 
11, east of the mountain. Dr. Emmons identified this mass of 
strata, d', with the Calciferous sandrock on lithologic characters, 
overlooking the fact that a similar rock might occur in his 
Taconic series. Two miles to the north, on the farm of D. 
Walker Reid, this belt of calciferous rock is over 600 feet 
thick, it contains a characteristic Middle Cambrian fossil, Hyo- 
lithellus micans, and is conformably subjacent and superjacent 
to shales and limestones, containing over fifteen characteristic 
species of Middle Cambrian fossils. 
Figure 12.-Section of Bald Mountain from the south. The profile of the 
mountain and position of the Cambrian and Lower Silurian rocks are taken from 
a photograph. The " Upper Taconic "=Cambrian slate, sandrock and limestone 
are shown to the right of the fault, and c = Chazy limestone ; z = dark shales, 
interbedded between c and the Calciferous sandrock, E ; s=dark argillaceous 
shales beneath the Calciferous sandrock. 
The section of Bald Mountain proves that the strata of the 
" Upper Taconic" are there pushed over on to the Chazy Ter- 
rane, and that the " Upper Taconic" is not unconforrnably sub- 
jacent to the latter or to the Calciferous sandrock. 
To the north of Bald Mountain, about two miles, a somewhat 
similar mass of limestone to that of c is adjacent to the fault 318 
C. D. Walcott-The Taconic System of Emmons. 
line and contains: Orthis testudinaria, Strophodonta alter- 
nata, Maclurea and other gasteropods, Calymene senaria and 
fragments of Asaphus platycephalus. Details of all the ex- 
posures observed where the "Upper Taconic" shales and the 
rocks of the Lower Silurian come in contact will be given in a 
report on the geology of Washington and Rensselaer counties. 
Another section,* taken by Dr. Emmons just east of the 
village of Whitehall, is reproduced in fig. 13. The object of 
this is to show the presence of a mass of calcareous sandrock, 
d', resting unconformably upon the Taconic slate, which Dr. 
Emmons identified as the Calciferous formation of the Lower 
Silurian. I studied the section in 1886, also in 1887, and found 
Cambrian fossils, represented by the heads of the Olenellus 
and fragments of Ptychoparia, imbedded in the sandrock, d', 
and also found the strike and dip of the sandrock and shales to 
Figure 13, a, a.-Easterly prolongation of the mountain, which is surmounted 
by the Calciferous sandrock: b b, Tertiary clay; c, c, Taconic and black slate; 
d, d, Calciferous sandstone, unconformable to the Taconic slates, and dipping 
southeast at an angle of 40-45". (After Emmons.) 
be conformable. Another section on the same paget is en- 
tirely within the Champlain series on my map and west of the 
great fault line. It is 30 miles north of Bald Mountain and in 
the township of Whitehall. I found the Potsdam sandstone at 
its base, in the village of Whitehall, and then, superjacent to it, 
the Calciferous Terrane, with a band of dark argillaceous shale, 
lithologically similar to that of the Hudson Terrane, between 
it and the superjacent Chazy limestone. Resting on the Chazy 
limestone there is a second band of dark shales, 175 feet thick, 
that is subjacent to the Trenton limestone, and the latter is 
subjacent to the argillaceous and sandy shales of the Hudson 
Terrane. The strata of the entire section are conformable; 
and the limestones were identified by contained fossils. East 
of the shales of the Hudson Terrane, the existence of the great 
fault line is shown by the presence of strata, resting against, 
and on, the Hudson Terrane, that carry Middle Cambrian fos- 
sils. These interbedded shales, between the limestones, and, 
also, the Hudson shales, were considered, by Dr. Emmons, to 
be of Taconic age, and the limestone to lie unconformably 
above them.:}: 
* Agric. N. Y., vol i, p. 56. fig. 2, 1847. f Loc. cit., p. 56, fig. 3. 
t One fact, not recognized by Dr. Emmons at Bald Mountain or along the 
great fault line, is that in many localities belts of dark argillaceous shale occur 
between the Calciferous, Chazy and Trenton limestones; that, in others, one or 
more of these formations is entirely a shale formation, and that the Potsdam Ter- C. D. Walcott-The Taconic System of Emmons. 
319 
Another illustration of the supposed overlap of the Cham- 
plain upon the Taconic Terrane is given in the American 
Geology, pt. 2, p. 72, fig. 12. It is in the township of Green- 
bush, opposite Albany, N. Y, on Cantonment Hill. There 
a mass of the Trenton limestone is caught on the line of the 
great fault separating the Champlain and Cambrian strata, as 
at Bald Mountain and other places in Washington county, and, 
also, in Vermont. The strata of the Hudson and Trenton 
Terranes are broken and displaced, but there is no evidence 
that the Trenton was deposited upon the upturned edges of the 
Cambrian or "Upper Taconic" slate; and, on the line of the 
same fault, 20 miles to the south, in the township of Schodack, 
Mr. S. W. Ford discovered an unconformable contact between 
the dark-drab siliceous and micaceous shales of the Cambrian and 
the dark argillaceous shales of the Hudson Terrane.* Mr. Ford 
kindly took me to the locality which he has so well described, 
and I saw the "hade" of the fault, the slickensides on the op- 
posing surfaces, and broke out graptolites from the Hudson 
shales beneath, and within six inches of, the fault line. A 
short distance south the limestones interbedded in the dark- 
drab shales gave us an abundance of characteristic Middle Cam- 
brian fossils. For the details of this overthrust of the Cam- 
brian upon the Hudson Terrane, see Mr. Ford's paper. 
Dr. Emmons illustrates another sectionf that shows the same 
errors of observation as in the figure of the section at Can- 
tonment Hill. Again, in fig. 224 the section at Snake 
Mountain, in Vermont, the error made at Bald Mountain is 
repeated, for it is now well known that the supposed overlying 
Calciferous (?) sandrock (" Red sandrock ") is a stratum of the 
Cambrian pushed over on to the Lower Silurian Terrane,§ 
and not a Lower Silurian formation, unconformably superja- 
cent to the " Upper Taconic" strata. 
All the overlying limestones that he mentions as unconform- 
ably overlying the Taconic rocks, with the exceptions noted, 
where they contain Middle Cambrian fossils, are west of the 
rane, off shore, was originally deposited either as a calcareous or argillaceous mud. 
It was owing to this oversight that he frequently identified the shales of the 
Champlain series as those of the Taconic. Another phenomena not understood 
by him, was the creeping or protruding of shales from beneath heavy masses of 
limestone, on account of the pressure squeezing the shales out and turning them 
up. In this way many of his non-conformities of dip appear to have been erro- 
neously observed. In many instances he did not recognize the lithologic differ- 
ences between the great mass of his Taconic slate and that of the Hudson Terrane. 
The black shale (marked "Taconic," in the Bald Mountain section, &, b', fig. 11) 
is not similar to the shale containing the trilobites, east of the great fault, yet he 
identified them as lithologically the same formation. 
* This Journal, vol. xxix, p. 16, 1885. 
t Am. GeoL, vol i, pt. 2, p. 79, fig. 14, 1856. 
i Loc. cit., p. 87. 
§ This Journal, III, vol. xiii, p. 413, 1877. 320 
C. D. Walcott-The Taconic System of Emmons. 
fault line separating the Cambrian and Silurian Terranes; and 
the shales west of the fault belong to the Silurian, not to the 
" Upper Taconic" Terrane. The line of outcrop of the Cam- 
brian Terrane is well marked, and I have endeavored to locate 
it accurately on the map. The great Appalachian fault sepa- 
rates the Potsdam and other Silurian rocks from the Cambrian ; 
and nowhere on the western side of the Cambrian Terrane, to 
my knowledge, either in New York or Vermont, is there a 
deposition contact, either conformable or unconformable, be- 
tween the rocks of the " Taconic System " and the Potsdam or 
other Silurian terranes. I have examined all the localities 
cited by Dr. Emmons and, later, by Professor Marcou and, in 
every case, the great fault separates the strata of the two sys- 
tems. In fact, the Taconic usually rests on the Silurian strata 
as the result of the overthrust from the east; and, as will be 
shown in my report on Washington County, N. Y., the strong- 
est proof of the presence of a fault line is shown by the me- 
chanical disturbance of the Cambrian strata, on the eastern 
side of the fault. 
That the Taconic slates are unconformably pre-Potsdam, is 
yet to be proven in any area known to Dr. Emmons, either in 
New York or Vermont. Where they pass beneath the shale 
representing the Potsdam horizon, beneath the Stockbridge 
limestone in the Taconic Range, they are conformably pre- 
Potsdam, but this fact was unknown to Dr. Emmons.* 
Resume.-As the result of these comparisons, we find that 
the " Lower Taconic " is essentially a repetition of the lower 
Silurian (Ordovician) section of the Champlain valley. It differs 
in lithologic details and in having a less abundant fauna in the 
typical Taconic area 
The "Upper Taconic" is found to be conformably subjacent 
to the " Stockbridge" limestone of the "Lower Taconic,'' and 
to include the Potsdam horizon at or near its upper portion. 
Its base is not unconformably subjacent to the Lower Silurian 
Terrane, as maintained by Dr. Emmons and Professor Marcou. 
The value of the paleontologic identification by Dr. Em- 
mons of the " Upper Taconic " slate as a pre-Potsdam forma- 
tion will now be considered. 
* Professor Henry D. Rogers, in his address before the meeting of the Asso- 
ciation of American Geologists and Naturalists, held at Washington, in May, 
1844. said, when speaking of the unconformity claimed by Dr. Emmons ^between 
the Champlain and Taconic rocks: "I must cake the liberty of expressing my 
disbelief of any such unconformity, and of observing that in the prolongation 
southwestward of this altered and plicated belt as far as the termination of the 
Blue Ridge in Georgia, a distance of 1000 miles, no interruption of the general 
conformity of strata has ever met the observation of my brother or myself."- 
(Amer. Jour. Sci., I, vol. xlvii, p. 152, 1844). C. D. Walcott-The Taconic System of Emmons. 
321 
On page 63, of the Agriculture of New York (vol. i), under 
the heading " Black Slate," Dr. Emmons says : " I shall de- 
scribe the rocks in the descending order: and by so doing, I 
commence with the mass of which there is some doubt whether 
it ought to be considered as a distinct rock or merely the 
upper portion of the Taconic slate; still I am disposed to re- 
gard it now as a separate and distinct rock, forming, so far 
as examinations have been made, the highest member of the 
Taconic system. Circumstances which have led to the separa- 
tion of this from the rock referred to are of an interesting 
character; interesting particularly as being connected with 
the discovery of crustaceans where they were least expected." 
Dr. Asa Eitch found the fossils from the " Black Slate," in 
1843, and gave them to Dr. Emmons, who described two spe- 
cies of trilobites under the names of Atops trilineatus and 
Elliptocepliala asaphoides', the first he thought to be an inter- 
mediate genus between the Calymene and Triarthrus ; of the 
second, Elliptocephala asaph oides. he compared parts with 
similar parts of the Asaphus tyrannus, of the Lower Silurian 
of England.* 
On page 68 of the same memoir, under the head-of " Fossils 
peculiar to the Taconic Slate," he describes two species of 
Annelid trails: one from the Green Taconic slate, and the 
other from the sandstone in Washington County. He follows 
this with a description of nine species of what appeared to be 
trails from the slates of Waterville, Maine. It appears from 
this that Dr. Emmons considered these various trails to be 
" fossils peculiar to the Taconic slate," and that the trilobites 
which he described he did not consider, at that time, as typi- 
ical of the " Taconic System," for he says (loc. cit., p. 64), in 
speaking of the " Black Slate "Assuming that its fossils are 
distinct from the fossils of this and other systems," etc. 
In his conclusions, he says :f "The Nereites and other fos- 
sils of the Taconic slate are unknown in any of the members 
of the Champlain group. In addition to which, it is impor- 
tant to bear in mind the fact that in this group the Mollusca 
of the New York system are also wanting." 
In 18564 he referred the Black slates to a position above the 
Talcose slates of the "Lower Taconic," thus making them the 
base of the "Upper Taconic" series. On page 98, loc. cit., 
the argument is made that the " Taconic System " is peculiar 
in its contained organisms, and that he has the right to con- 
sider the absence of certain Silurian fossils as evidence that 
the Taconic was not of Silurian age. As has been shown in 
the first part of this paper, the limestones of the " Lower Ta- 
* Loc. cit., pp. 64, 65. | Am. Geol., pt. 2, p. 49, 1856. 
f Loc. cit., p. 108. 322 
C. D. Walcott-The Taconic System of Emmons. 
conic " carry characteristic Lower Silurian (Ordovician) fossils, 
as, also, do the shales overlying the limestones. 
In 1859 (Manual of Geology, p. 87), Dr. Emmons for the 
first time compared his Elliptocephala asaphoides with the 
genus Paradoxides, of Barrande's Primordial Zone, stating 
that the Taconic Paradoxides is also Silurian, and hence it is 
shown that the Primordial Zone, in Bohemia, is in coordina- 
tion with the upper series of Taconic rocks. This statement 
is the first known to me upon which, either by paleontologic 
or stratigraphic evidence, Dr. Emmons could base his assertion 
that any portion of the " Taconic System " was of pre-Pots- 
dam age. 
The want of clearness in his views is well shown by the 
extract already quoted from his letter of Nov. 20, 1860, pub- 
lished by Prof. Marcou. " His [Barrande's] Primordial group 
is only Lower Silurian. I conceive we have exactly his 
Primordial group in the band of slates containing the Para- 
doxides."-What becomes of the stratigraphic break between 
the Lower Silurian and Taconic rocks if the " Black slates " 
are still retained in the " Taconic System," remains unex- 
plained. If removed the fossils go into the Lower Silurian 
with it. 
Dr. Emmons described several species of graptolites* from 
the " Taconic System," the majority of which are nowT known 
to also occur in the Hudson Terrane, in the valley of the 
Hudson. On the map, I have given the distribution of the 
Hudson Terrane in the Taconic area, as determined by strati- 
graphic and paleontologic evidence. It is in the central belt, 
carrying the red slates, that the graptolites occur which led 
Dr. Emmons to include, as a matter of necessity, if he put 
the red slates in the Taconic, the dark, argillaceous shales of 
Hudson Terrane at Troy, Albany, and Baker's Falls, in the 
Hudson Valley, for they contain the " beautiful graptolites 
referred to by him in 1860. At Albany, N. Y., however, the 
graptolite beds contain a characteristic Trenton-Hudson fauna.]: 
This removes a considerable portion of the " Upper Taconic " 
strata from the " Taconic System." 
* Am. GeoL, vol. i, pt. 2, pp. 104-111, 1856. 
f See letter to Prof. Jules Marcou; Proc. Am. Acad. Arts and Sci., vol. xii, p. 
188, 1885. 
| Mr. C. E. Beecher found three of the same species of graptolites (Climaco- 
graptus bicornis, Dicranograptus ramosus and Diplograptus mucronatus) as those 
found by me in the "Taconic Slates" of Washington and Rensselaer counties, 
associated with Brachiopoda, 5 species; Lamellibranchiata, 16 species; Ptero- 
poda, 2 species; Gasteropoda, 3 species; Cephalopoda, 2 species; Annelid, 1 spe- 
cies ; Crustacea, 1 species, and Trilobita, 2 species. For names of species, see 
Mr. Beecher's paper. (Thirty-sixth Ann. Rep. N. Y. State, Mus. Nat. Hist., p. 
78, 1884). C. D. Walcott-The Taconic System of Emmons. 
323 
(1.) The trilobites described in 1844-47, from the "Black 
Slate," were referred to the highest member of the " Taconic 
System," on stratigraphic evidence. 
(2.) The same trilobites were referred to the lowest member 
of the " Upper Taconic," on stratigraphic evidence, in 1856. 
(3.) In 1859 they were for the first time referred to a pre- 
Potsdam position by comparison with a fauna whose position 
had been stratigraphically determined in relation to the Silu- 
rian fauna. 
(4.) The Nereites and other trails with the exception of the 
two from Washington County, N. Y., described as typical of 
the " Taconic System," have not yet been stratigraphically 
located in the geologic series. 
(5.) The graptolites referred to the " Taconic System " form 
a portion of the fauna of the Hudson Terrane. 
Discussion.-There is not much opportunity for a discussion 
of the geologic age and position of the "Lower Taconic" 
rocks. The thorough work of Professor Dana practically set- 
tled those points before I began my investigation. Dr. T. S. 
Hunt opposed Professor Dana's conclusions, basing his dissent 
on the result of his own studies of the geology of southeastern 
Pennsylvania and, on his acceptance of certain theoretic views 
in regard to the lithology of the " Lower Taconic " rocks. He 
argued that the " Lower Taconic " was the typical Taconic Sys- 
tem and of Archean age,* and that Professor Dana's interpreta- 
tion of the stratigraphy was not sufficient, without the aid of fos- 
sils, in the typical Taconic region, to establish the Lower Silurian 
age of the Stockbridge limestone or the crystalline marbles of the 
Lower Taconic. With the facts presented in this paper, how- 
ever, I do not think that Dr. Hunt can claim support for his 
views without first substantiating them by researches in the 
Taconic area, a matter that he has apparently not given his 
attention, f heretofore. 
Resume of the Paleontologic Evidence. 
*(" Taconic Question in Geology;" Min. Physiology and Physiography, p. 
582, paragraph 92, 1886). " 92. Considering the pre-Cambrian age of the Lower 
Taconic to be established, as well as its distinctness alike from the older crystal- 
line rocks below and from the Cambrian series above, to which Emmons had 
given the name of Upper Taconic-it was proposed by the writer, in 1878, to 
restrict the term Taconic-for which the alternative name of Taconian was then 
suggested,-to the Lower Taconic of Emmons." For other views held by Dr. 
Hunt, see Am. Jour. Sci., 3d sen, vol. xxxiii, pp. 417, 418, 1887. 
fSome of Dr. Hunt's errors consist: 1. In relying upon a lithologic theory 
based upon observations made far distant from the Taconic area 2. His accept- 
ance of Dr. Emmons's theory of the stratigraphic position of the " Lower Taconic" 
strata without personal investigation when it was well known that all of Dr. 
Emmons's contemporary geologists opposed the " Taconic" theory. 3. His assum- 
ing that it was largely personal opposition to Dr. Emmons that led all geologists 
who investigated the Taconic area to decide against the " Taconic" theory. 4. 
His ignoring all stratigraphic and paleontologic evidence published by Professor 324 
C. D. Walcott-The laconic System of Emmons. 
Professor Dana was in accord with the opinion of Professors 
W. B. and H. D. Rogers, Edward and C. H. Hitchcock, W. 
W. Mather and Janies Hall, as well as with the results of his 
own field studies, when he called the " Granular Quartz" Pots- 
dam, the " Stockbridge limestones, Lower Silurian (Calciferous- 
Chazy-Trenton) and the overlying " Tai cose" shales the Hudson 
River formation. He held the opinion that the " Lower Ta- 
conic" was the typical " Taconic System," as first defined in 
1842, but as that was proven to be Lower Silurian in age the 
" Taconic System" could not longer be recognized. In opposi- 
tion to this Professors Marcou and Winchell argue that if the 
"Lower Taconic" was of Lower Silurian age the "Upper Ta- 
conic" contains Primordial fossils and is, therefore, equivalent 
to the Cambrian ; and, as the discovery of fossils in the 
" Upper Taconic" was made before typical Primordial fossils 
were published from Sedgwick's Cambrian System, the name 
Taconic had priority over that of Cambrian and should be used 
in place of it to designate the strata containing the First or 
Primordial fauna of Barrande. 
I was influenced by the statement made by Dr. Emmons 
that the slates of the " Upper Taconic" were unconformably 
beneath Lower Silurian strata, and, also, by the views of Pro- 
fessors Dana and Marcou when, in 1885, I wrote my observa- 
tions, " On the Use of the Name Taconic," in the introduc- 
tion to Bulletin 30, of the U. S. Geological Survey. I was 
satisfied from the evidence presented by Professor Dana, that 
the limestones of the "Lower Taconic" belonged to the CaL 
ciferous-Chazy-Trenton Terrane, and that the overlying schists 
were properly referred to the Hudson Terrane. The reference 
of the quartzite beneath the limestone to the Potsdam horizon, 
also appeared to be consistent with the data known to him. I 
was but partially convinced, however, from the evidence pre- 
sented by Dr. Emmons and Professor Marcou that the "Upper 
Taconic" slates were stratigraphically pre-Potsdam, or that 
there was a valid claim for the substitution of the name Taconic 
for that of Cambrian. 
Professor Jules Marcou, although a persistent advocate for the 
use of the name Taconic, did not go to the typical Taconic area 
to study the " Taconic System," but studied the extension of 
the " Upper Taconic" slate and shales in northern Vermont, and 
identified the " Upper Taconic" as the true " Taconic System." 
I have carefully examined the localities where he describes the 
occurrence of a non-conformity between the Georgia slates and 
the superjacent so-called Potsdam sandstone and at none of them 
Dana and others within the past fifteen years on the ground that the writers were 
putting forth the " old metamorphic hypothesis" of Mather, Rogers, etc. (See 
Am. Nat., vol. xxi, pp. 114-320, 1887). C. D. Walcott-The Taconic System of Emmons. 
325 
could I find a trace of the Potsdam sandstone. The sandstone 
referred to the Potsdam is of Middle Cambrian age and, at 
Parker's farm contains two of the same species of fossils that 
occur in the slates conformably subjacent to the sandstone. 
The only non-conformity found is formed by the overthrust of 
the Georgia or Cambrian strata upon the Lower Silurian Ter- 
rane, just as at Bald Mountain in Washington County, N. Y., 
Snake Mountain in Vermont and all along the line of the great 
fault, wherever outcrops of the two systems occur. 
His extension* of the "Taconic System" to include the 
Potsdam sandstone is in opposition to all of Dr. Emmons's 
views of the relations of the Taconic and Potsdam strata, as 
Dr. Emmons founded the "Taconic System" largely on the 
belief that a great stratigraphic break existed between the 
Potsdam and Taconic, and that the fauna of the Taconic was 
unlike that of the " Champlain group," of which the Potsdam 
formed the base. 
Dr. Emmons's errors are nearly all traceable to his trust in 
the lithologic characters of the various formations within the 
Taconic area. He established the "Taconic System" in 1842, 
on the differences in the lithologic characters of the Taconic 
rocks and those of the New York ' Lower Silurian.' The un- 
conformity between the "Taconic System" and "Champlain" 
series, announced in 1844-'47, was primarily based on the sim- 
ilarity of the lithologic characters of the Calciferous sandrock 
of the Lower Silurian and the calciferous sandrock of what we 
now know to be, from its contained fossils, a part of his " Upper 
Taconic " series. Again, when the latter (calciferous sandrock 
of the Cambrian) was pushed over on to the dark shales of the 
' Lower Silurian,' on the line of the great fault, he identified 
the latter shales with the "Upper Taconic" shales, and thus 
obtained an unconformity, as at Bald Mountain, between the 
Lower Silurian and Taconic strata. He failed to recognize the 
fact, shown along an outcrop of a hundred miles or more, that 
the Potsdam and, frequently, the Calciferous Terranes were 
represented in the geologic sections by a shale undistinguishable 
from the shale of the Hudson Terrane; also, that the same con- 
ditions occur in the Champlain valley, in the towns of Fort 
Ann, Kingsbury, and Hartford, Washington County, N. Y., 
and that, in several localities, the Trenton limestone is replaced 
by shale. This explains much of the confusion in his stratigra- 
phy and, also, in that of Professor Jules Marcou, in northern 
Vermont, who was misled in the same manner. The shales 
containing the Primordial fauna are usually lithologically dis- 
similar from the dark argillaceous shales of the Lower Silurian, 
* Proc. Bost. Soc. Nat. Hist., vol vii, p. 371, 381, 1860. 326 
C. D. Walcott-The Taconic System of Emmons. 
but, as Dr. Emmons included the dark graptolitic-bearing shales 
of the Hudson Terrane, within the Taconic area, in the "Upper 
Taconic," he necessarily compared and identified the black 
shales of the Lower Silurian with the " Black Slate " of the 
" Upper Taconic." He could scarcely do otherwise, when the 
stratigraphy along the western side of the " Taconic System " 
supported his theory, if such an identification of the shale was 
made. 
The fact that the Potsdam sandstone, as a lithologic forma- 
tion, is a local deposit in the immediate vicinity of the Adiron- 
dack mountains and that the sediments being deposited at the 
other localities at the same time, embedding similar organic 
remains, were argillaceous, siliceous and calcareous muds, does 
not seem to have impressed him, although he devotes many 
pages of his various memoirs to the description and discussion 
of the lithology of the Taconic and Lower Silurian rocks. 
Dr. Emmons was not a collector of fossils, or he would have 
found them in nearly all the formations within the Taconic 
area; and I think that no student conversant with the faunas 
of the Lower Silurian and Cambrian terranes will long hesitate 
in concluding that he did not have sufficient critical knowledge 
of the faunas to which the fossils belonged that he did obtain, to 
identify the strata from which they came on paleontologic 
evidence otherwise he could not have so confused them.* 
When Dr. Fitch gave him the fossils that he had found in the 
" Black Slate," two miles north of Bald Mountain, in 1843, he 
at once referred them to a pre-Potsdam horizon, on stratigraphic 
evidence, without making any comparisons with a fauna which 
he knew to be pre-Potsdam at some other locality. In fact, no 
such data were at his command at that time, and the reference 
of the fossils to a pre-Potsdam horizon was based entirely upon 
the fact that they were in strata which he considered to be situ- 
ated unconformably beneath the Potsdam sandstone or, in its 
absence, the Calciferous sandrock. 
1 wish to mention here that, in 1847, Dr. Emmons did 
not consider the two species of trilobites as characteristic of the 
true Taconic slate, but of the overlying " Black Slate," which 
he considered to be pre-Potsdam, from the evidence of the 
Bald Mountain section. I also call attention, again, to the fact 
that there was no valid stratigraphic evidence of the pre-Pots- 
dam age of the " Black Slate;" moreover, as I have shown, the 
"Black Slate" is the lowest member of the " Taconic System " 
and not the highest, as stated by him, in 1847, or next above 
* It is not practicable for me, owing to want of space, to give a full analysis of 
the paleontologic work done by Dr. Emmons in connection with his argument for 
the Taconic system. This will appear in my report on the geology of Washington 
County, N. Y. C. D. Walcott-The Taconic System of Emmons. 
327 
the " Lower Taconic," as stated in the scheme of 1856. (See 
fig. 10.) 
The comparisons made by Dr. Emmons between the fossils 
of the " Black Slate " and the Primordial fauna of Barrande, in 
1859, came too late to anticipate the identification of the Prim* 
ordial fauna in the Cambrian of Sedgwick, for the Cambrian 
System, as used by me, was correctly identified, paleontolog- 
ically, by M. Barrande, in 1851.* 
As I liave repeatedly stated, Dr. Emmons assigned the two 
species of fossils described by him from the " Upper Taconic" 
slates to a pre-Potsdam horizon, on stratigraphic evidence that, 
on investigation, proves to have been based on errors of field ob- 
servation. Such being the case, there was no proof of the posi- 
tion of the fauna, as he had no means for comparison with a 
similar fauna that had been stratigraphieally located elsewhere in 
the geologic series. It was a fortunate happening that the " Up- 
per Taconic" fossils proved to be of pre-Potsdam age, and not 
a scientific induction based on accurate observations or compari- 
sons. 
M. Barrande visited England in 1851 and determined the 
age of the Primordial fauna found in the typical Cambrian 
area of Wales before he knew of the existence of the vestige of 
the Primordial fauna published by Dr. Emmons. Subse- 
quently, upon the evidence of Dr. Emmons's published strati- 
graphic sections, showing that he, Dr. Emmons, knew the 
fossils to be stratigraphieally pre-Potsdam, M. Barrande was 
misled into crediting him with a discovery (in 1859) that was 
based on errors of field observation, and I did the same thing 
in the introduction to Bulletin 30, U. S. Geological Survey, in 
1885. 
* January 20th, 1851, M. J. Barrande read a paper before the Geological So- 
ciety of France, upon the " Silurian Terrain of England." He presented a sketch 
of a section from Wales showing the Archean and, resting upon it, the stages 
corresponding to the stages 0 and D, of the Bohemian section, or the strata of the 
First or Primordial fauna and the Second or Lower Silurian fauna. Above the 
Lower Silurian the Upper Silurian is shown as resting unconformably upon the 
latter. In this paper the Lower Cambrian of Sedgwick is identified by organic 
remains, through comparison with the established succession of fossils in the 
Bohemian Basin. (Bull. Soc. Geol. de France, t. viii, pp. 207-212, 1851). 
[To be continued.] [From the American Journal of Science, Vol. XXXV, May, 1888.] 
Art. XXXIII.-The Taconic System of Emmons, and the use of 
the name Taconic in Geologic nomenclature: by Chas. D. 
Walcott, of the IT. S. Geological Survey. With Plate III. 
(Continued from page 327.) 
Nomenclature. 
I. Use of the name Taconic. II. Use of the name Cambrian. 
III. Classification of North American Cambrian rocks. 
Use of the name Taconic.-To the writer the evidence pre- 
sented and referred to in the preceding pages proves that the 
" Taconic System " was founded on errors of stratigraphy of 
such character and magnitude that the name Taconic has no 
claim upon the geologist for recognition in geologic nomenclat- 
ure. 
I endeavored to make, in 1886, an argument for the use of 
the name Taconic for the Middle division of the Cambrian 
System, but it failed in the light of later results of field work; 
and now I think that geologic nomenclature will be benefited 
by dropping the name entirely. Based on error and miscon- 
ception originally, and used in an erroneous manner since, it 
serves only to confuse the mind of the student, when applied 
to any formation or terrane. There are several reasons for the 
foregoing conclusions that perhaps it is best to here state : 
1st.-The name is not applicable. The Taconic range, from 
which the " Taconic System " was named, is not known to 
contain a fossil of the First fauna or a formation that contains 
one elsewhere. The " Upper Taconic " slates lie west of the 
range, and the " Granular Quartz " series east of it; and the 
range is formed of strata of the Trenton-Hudson Terrane. 
2d.-The "Taconic System" was considered pre-Potsdam, 
on two suppositions: (a) that the Calciferous sandrock of the 
Lower Silurian is unconformably superjacent to the Taconic 
slates, on the west; that the variation of the lithologic char- 
acters of the Lower Taconic rocks, from the New York Lower 
Silurian, indicates a distinct system of rocks. We find that 
the unconformity (a) was based on errors of field observation, 
and (6), that the " Lower Taconic " rocks are of Lower Silu- 
rian age, with the exception of the lower cpiartzite, which is 
Cambrian and conformably subjacent to the Lower Silurian. 
3d.-The claim of priority of discovery of the Primordial 
fauna is invalidated by the fact that the fossils found in the 
Taconic slate were referred to a pre-Potsdam horizon on an 
erroneous interpretation of the stratigraphy and not from com- 
parison with a known fauna that had been stratigraphically lo- 
cated in any clearly defined geologic section. 395 
C. D. Walcott-The Taconic System of Emmons. 
4th.-It is only a fortunate happening, and not a scientific 
induction based on accurate stratigraphic or paleontologic 
work, that any portion of the " Taconic System " is found to 
be where Dr. Emmons placed it. 
5th.-The application of the principles stated at the begin- 
ning of this paper rules out the name Taconic from geologic 
nomenclature. 
6th.-The term Cambrian antedates Taconic for a strati- 
graphic system and, also, as a correctly-defined faunal defini- 
tion. 
It was stated under " Discussion " that Professor Dana held 
the opinion that the " Lower Taconic " was the typical " Ta- 
conic System," as first defined in 1842, but as that was proven 
to be Lower Silurian in age, the " Taconic System " could not 
longer be recognized.* For a time I was inclined to disagree 
with this view, but as I approach the end of this investigation 
I am convinced, after a full consideration of all the circum- 
stances, that the position taken by Professor Dana is the cor- 
rect one. 
The first published section of the " Taconic System " gives 
all the rocks included within it in 1842. f The gneiss is rep- 
resented on the extreme east and the " Taconic slate " on the 
extreme west and the " shales of the Champlain group " as 
resting unconformably on the " Taconic slate." This section 
includes all the strata of the " Taconic System," as then known 
to Dr. Emmons, and agrees with the description, in the accom- 
panying text, of the rocks of the Systerti.j: 
Five additional sections are given on Plate XI, four of which 
are in the typical area and agree with the section in the text 
(loc. cit., p. 145, fig. 46). The latter section and the first four 
sections of Plate XI do not extend west of the area of Hudson 
slate on the line of Hoosick Falls in Rensselaer Co., N. Y. 
(see map). They all limit the " Taconic System " at this belt 
of the Hudson Terrane, and the accompanying text corrobo- 
rates the view expressed in the sections. A glance at the map 
shows that not one single outcrop of rock of the "Upper 
Taconic " was included in the " Taconic System," as originally 
proposed, with the exception to be noted of Section 5, Plate 
XI, and not until 1887 was it proven that any portion of the 
original Taconic System was older or subjacent to the horizon 
of the Potsdam sandstone. As is mentioned in the 1st reason 
given for rejecting the name Taconic, there is not a known 
stratum of rock in the Taconic range that is of the geologic 
* This Journal, III, vol. xxxi, pp. 241-244, 1886. 
f Geol. N. Y., pt. 2, p. 145, fig. 46, 1842. 
j Loc. cit., pp. 144, 145. C. D. Walcott-The Taconic System of Emmons. 
396 
age assigned to it by Dr. Emmons. In 1844 lie incorporated 
a great series of slates and shales belonging to another geologic 
system by extending his sections across the western belt of the 
Hudson Terrane, that limited the section of 1842, and on west 
to the next line of outcrop of Lower Silurian rocks. This 
addition gave the opportunity to separate off the " Upper 
Taconic " in 1856. I have shown that all his reasons for call- 
ing this series pre-Potsdam were based on errors of strati- 
graphy ; and that it was a fortunate happening that any por- 
tion of the " Upper Taconic" rocks occur where he placed 
them in his stratigraphic scheme. Even if there were no 
errors to vitiate Dr. Emmons's argument for the pre-Potsdam 
position of the "Upper Taconic," that portion of his system 
could not retain the name "Taconic;" for it belongs to a dif- 
ferent stratigraphic system from that to which the strata of 
the Taconic range belong and to which he gave the name 
" Taconic." 
Section V, of Plate XI, represents a section of strata a few 
miles south of Burlington, Vt., and includes, not the "Taconic 
System " of the first five sections and the text by Dr. Emmons 
in 1842, but strata entirely disconnected from the original 
Taconic, which, nineteen years later, was proven to belong in 
part to the "Upper Taconic." This section is not mentioned 
in the text, but it is evidently considered as exhibiting the 
same relative geologic section as the other sections, a view that 
is substantiated by the name " Taconic slate " being given to 
the strata referred to the "Taconic System." There is not any 
stratigraphic connection between the Vermont section (No. 5) 
and the sections in the Taconic area (see map), and until 1859 
there was not any paleontologic evidence that the slates of sec- 
tion 5 were or were not of the same geologic age as the " Ta- 
conic slates " of the five other sections and the text. In 1859 
the publication of the Olenellus fauna by Professor Hall, 
proved that Dr. Emmons was mistaken in referring the Ver- 
mont slates, of section 5, to his Taconic System of 1842. I do 
not think that we can admit as evidence in favor of the strata 
of the " Upper Taconic " having been described in the original 
work of 1842, such an erroneous identification of a section that 
had at the time no stratigraphic or paleontologic connection 
with the original Taconic System. 
It was not until the field work, in the fall of 1887, was con- 
cluded that I arrived at the above conclusions. Professor 
Dana reached it long before, and Dr. T. S. Hunt holds that the 
"Lower Taconic" is the typical Taconic. It matters not 
whether geologists agree to restrict the test of what the origi- 
nal Taconic was to the original Taconic of 1842 or hold that 
Dr. Emmons had the right to add the strata separated off into 397 
C. D. Walcott-The Taconic System of Emmons. 
the "Upper Taconic" in 1856, the name Taconic does not ap- 
pear to have any place in the geologic nomenclature of to-day. 
The following tabulation of the successive phases of the 
Taconic system viewed in the light of 'present facts is instruc- 
tive. It was proposed in a letter from Professor Dana to the 
writer: 
Phase I, 1842. 
"Taconic System". True order begins. 
6. Stockbridge limestone II. Lower Silurian limestone. 
$ j Magnesian slate of Graylock III. Hudson slate. 
* ' ( Granular quartz I. Cambrian. 
' 4. Limestone II. Lower Silurian limestone. 
3. Magnesian slate of Taconic mountains III. Hudson slates. 
2. Sparry limestone II. Lower Silurian limestone. 
1. Taconic slate III. Hudson slates. 
Phase II, 1844. 
5. a. Black slate. Fossiliferous I. Cambrian. 
b. Taconic slate " Mostly Hudson slate. 
4. Sparry limestone II. Lower Silurian limestone. 
3. Magnesian slates III. Hudson slates. 
2. Stockbridge limestone II. Lower Silurian limestone. 
1. Granular quartz I. Cambrian. 
Phase III, 1855. 
I. Upper Taconic. 
2. Black slate. I. Cambrian. 
1. Taconic slate III. Mostly Hudson slate. 
II. Lower Taconic. 
3. Magnesian slate III. Hudson slate. 
2. Stockbridge limestone and Sparry lime- 
stone II. Lower Silurian limestone. 
1. Granular quartz I. Cambria#. 
Use of the name Cambrian.-1There is no necessity for re- 
viewing the Silurian-Cambrian controversy. AH the facts, as 
understood by many writers, are accessible to the student of 
English geologic literature. It is my opinion that the name 
Cambrian should be used for the system of strata characterized 
by the " First Fauna." 
The Cambrian System was correctly established on a strati- 
graphic basis in 1835, and included the same relative geologic 
terranes as the " Taconic System," with the exception of going 
a little lower in the section containing the Primordial fauna 
Like the Taconic, it included the Lower Silurian (Ordovician) 
System, a fact noted and corrected by Dr. Emmons, for the 
Cambrian, in 1842. The Cambrian section stands intact to- 
day, and, on faunal evidence, separates into two great divisions, 
the lower of which is the Cambrian System, as used by many 
* Made equivalent to the lower unfossiliferous part of Sedgwick's Cambrian as 
known to Dr. Emmons at that time. C. D. Walcott-The Taconic System of Emmons. 
398 
writers for the system of strata characterized by the " First 
Fauna," and the upper the Champlain of Emmons, the Lower 
Silurian of Murchison, or the Ordovician of some more recent 
authors. 
Classification of North American Cambrian Rocks. 
In the classification of the fossiliferous sedimentary rocks of 
all countries it becomes more and more evident that the great 
systems-Cambrian, Silurian, Devonian, etc.-must rest on the 
broad zoologic characters of their included faunas and not on 
stratigraphic breaks between the systems, and that geologists 
will need to recognize the fact so well stated by Lapworth, that 
" we have no reliable chronological scale in geology but such as 
is afforded by the relative magnitude of zoological change-in 
other words, that the geological duration and importance of 
any system is in strict proportion to the comparative magnitude 
and distinctness of its collective fauna."* In pursuance of the 
above principle I have separated the Cambrian System in 
North America from the Lower Silurian. In the magnitude 
of sedimentation and extent of the fauna it ranks with the 
other great geologic systems, and we cannot unite it with the 
Lower Silurian except from reasons that, if followed out, will 
unite all the systems from the Cambrian to the Quaternary. 
In arranging the different strata composing the Cambrian 
System three primary divisions are distinguished by the pre- 
dominence in each of a fauna that, in assemblage of genera and 
species, may be separated from others whenever two or more 
of them occur in the same stratigraphic section. This extends 
to the identification of the relative geologic horizon by the 
fauna when its vertical or geographic connection with other 
faunas is not preserved. The three divisions of the table have 
been recognized to a greater or less extent in all the sections 
of Cambrian strata studied in North America, and all the ob- 
served Cambrian faunas come within their limits. 
The second column in the table gives local names that have 
been applied within certain geologic provinces, where the 
fauna and the sedimentation indicate a greater uniformity of 
conditions than existed throughout the larger areas outlined by 
the first three divisions. The right-hand column gives the 
names of local subdivisions where the conditions of sedimenta- 
tion and of life were still more restricted. 
The table is a correlation of the various sections described 
in the introduction to U. S. Geological Survey Bulletin No. 30, 
and hence is tentative. It is the expression of my present 
knowledge and opinion. All who use it in geologic work 
* Geol. Mag., vol. vi, p. 3, 1879. 399 
C. D. Walcott-The Taconic System of Emmons. 
should refer to the data given in that Bulletin, and decide indi 
vidually upon the value of the correlations made in the table. 
Lower 
Calciferous. 
Lower portion of the Calciferous formation of New 
York and Canada. Lower Magnesian of Wis- 
consin, Missouri, etc. 
Upper 
Cambrian. 
Potsdam. 
Knox. 
Tonto. 
Potsdam of New York, Canada, Wisconsin, Texas, 
Wyoming, Montana and Nevada; Tonto of Ari- 
zona ; Knox Shales of Tennessee, Georgia and 
Alabama. The Alabama section may extend 
down into the Middle Cambrian. 
Georgia. 
L'Anse au 
Loup. 
Prospect. 
Georgia and " Granular Quartz " formations of Ver- 
mont, Canada, New York and Massachusetts. 
Limestones of L'Anse au Loup, Labrador. 
Lower part of Cambrian section of Eureka and 
Highland Range. Nevada. Upper portion of 
Big Cottonwood Canon Cambrian section, Utah. 
Middle 
Cambrian. 
St. John. 
Braintree. 
Newfound- 
land. 
Uinta ? 
Paradoxides beds of Braintree, Mass., St. John, 
New Brunswick, St. John's area of Newfound- 
land ; Lower portion of Big Cottonwood Cafion 
Cambrian section, Utah. Uinta? (The Ocoee 
conglomerate and slates of East Tennessee are 
doubtfully included.) 
Lower 
Cambrian. 
Description of the Map and Section. 
The map shows the geographic distribution of the strata re- 
ferred to the "Taconic System" in eastern New York and 
western Vermont, Massachusetts and Connecticut. The data 
for it are taken from the Geological map of Vermont and New 
Hampshire, by Professor C. H. Hitchcock, 1877 (Geol. North- 
ern New England); the maps published by Professor Dana, 
on the geology of the region studied by him in western Massa- 
chusetts and Connecticut, and eastern New York; and the map 
of southwestern Vermont, published by Professor Dana on the 
result of Rev. A. Wing's field studies (Am. Jour. Sei., 3d 
ser., vol. xiii, 1877); and for Washington and Rensselaer 
Counties, N. Y., as mapped from field work done by myself 
in 1886-87. 
The line of contact of the Cambrian and pre-Cambrian rocks 
on the east, in Vermont, is tentative, as it is known to be in- 
correct in details; the data for correcting it have not been ob- 
tained. 
Certain changes in the identification of the strata, as com- 
pared with the older maps, have been rendered necessary by 
the correlations made in this paper; and the shales, in the 
vicinity of the limestones south of the Rensselaer county line, 
have not been colored, as it is yet undetermined whether they 
belong to the Hudson or Cambrian Terrane. The shales im- 
mediately beneath the limestone (3) are shown as a distinct C. D. Walcott-The Taconic System of Emmons. 
400 
terrane (2) in the section but on the map they are merged with 
the Georgia terrane (5). 
The exact localities of fossils within the typical Taconic area 
are shown by the letter F. Many localities to the north and 
south are not indicated. 
Section.-The geologic section crosses the Taconic area on 
the line marked A, B, on the map, which is very near the line 
of the original section published by Dr. Emmons in 1847 
(Geol. N. Y., pt. 1, pl. xviii, Sec. 1). On the line C, D fossils 
have been found more abundantly on the eastern side, and the 
structure is found as in Dr. Emmons's section of 1856. 
1. Cambrian quartzite-Terrane No. 1. 
2. Hydromica (Potsdam ?) shales-Terrane No. 2. 
3. Trenton, Chazy and other limestones of the Lower Silurian 
-Terrane No. 3. 
4. Hudson (hydromica) shales of the Taconic range and, in the 
Hudson valley, the Hudson terrane-Terrane No. 4. 
^a. A belt of strata of the Hudson terrane, faulted in between 
Cambrian rocks-Terrane No. 6 of text. 
5, 5a. Slates, with interbedded limestones and sandstones of 
the Georgia Terrane, of the Cambrian-Terrane No. 5. 
6. Pre-Cambrian (Agnotozoic) or Archean rocks, a, b, c, d, 
fault lines, known to the writer, in Washington County, 
N. Y. The hade of the Ball Mountain fault («) is ap- 
proximately correct (see fig. 12) while that of the other 
faults is probably much more oblique or inclined to hori- 
zontal than as represented. They are drawn to show where 
they occur and not to indicate the hade or angle of the 
faults. The minor undulations, faults and displacements 
that occur on the east side, between 3 and the gneiss are 
not represented. 
Comparing this with Dr. Emmons's sections, we find a dif- 
ference in the arrangement of the strata in the eastern half. 
The "Lower Taconic" embraced the strata from Terrane No. 
1, on the east, to Terrane No. 3, on the west side of the Ta- 
conic range, and included all the strata of the original " Taconic 
System " as knowm and defined by Dr. Emmons in 1842. The 
"Upper Taconic" included the strata of terranes Nos. 2,4, 
4«, 5, and 5a, west of the Taconic Range, which was added to 
the original "Taconic System" in 1844. 
I have not attempted to show that the quartzite contains 
interbedded limestones and schists in some localities, nor that 
the limestone series (3) is broken by interbedded schists or are- 
naceous beds; nor that, as at Gray lock, the quartzite (1) ex- 
tends completely beneath the synclinal of the limestone (3) and 
appears on the western side. It is only the illustration of the 401 
C. D. Walcott-The Taconic System of Emmons. 
general relations of the quartzite, limestone and schists to each 
other that is attempted. 
To the west of the Taconic Range the section passes down 
through the limestone (3) to the hydromica schists (2), and 
thence to the great development of slates and shales with their 
interbedded sparry limestones, calciferous and arenaceous strata, 
all of which contain more or less of the Olenellus or Middle 
Cambrian fauna.* 
No. 2 occupies the stratigraphic position of the Potsdam for- 
mation elsewhere; and 5 and 5a by contained fauna and strati- 
graphic relations, are correlated with the Granular Quartz 
series (1) and referred to the horizon of the Middle Cambrian, 
as the latter is defined in Bulletin 30, U. S. Geological Survey, 
and in the table of classification {ante). 
Between the limestone (3) and the slates (5) there are several 
displacements, but none to displace the strata sufficiently to 
bring rocks of other formations in sight, and so break the sec- 
tion that the general relations of 3, 2 and 5 can be interpreted 
by me in a different manner from that given in the section. 
* Thirty-five species in Washington County, N. Y„ as known to date. (See 
thios Journal fr September, 1887). PLATE III.