^%, o^ \t IMAGE EVALUATION TEST TARGET (MT-3) 1.0 LI 1.25 IIIM 1112 liM 1.4 M IIIM 12.0 1.6 V2 <^ /i % 'a V' / o 7 w Photographic Sciences Corpomtion 23 WEST WAIN STREET WEBSTER, NY MS80 (716) 872-4503 »l LoBed fossils, on which this idontitication had been founded, were not really such, (this Journal, II, v, 116). Future explorers may, it is hoped, be more successful, and yet discover among thu strata of tlio White Mountains evidences of organic life, probably of primordial Silurian age. T. is. Hunt on the Geology of Eastern New England. 85 When, however, further investigation showed that the great and progreasive thickening which takes place in the paleozoic formations from the west, eastward, is not confined to the aug- mentations of existing subdivisions, but includes the intercala- tion of new ones ; when the few hundred feet of typical Pots- dam sandstone in New York are represented in Vermont, Quebec and Newfoundland, by thousands of feet of strata lithologically very unlike the type ; while the Quebec group, not less in volume, appears representing the beds of passage between the Calciferous and Chazy divisions of New York, we begin to conceive that conditions of sedimentation, very unlike anything hitherto suspected in the west, prevailed to the east- ward. When, moreover, we find widely separated areas of Labradorian and Huronian rocks, — remaining fragments of great series, — resting upon the Laurentian, from Lake Iluron to New- foundland, we get evidences of a process of denudation in past ages, not less remarkable than the sedimentation. My observations of last year have led me to a conclusion, whicn had previously been taking shape in my mind, that there exists above the Laurentian, a great series of crystalline schists, including mica-slates, staurolite and chiastolite-schists, with quartzose and homblendic rocks, and some limestones, the whole associated with great masses of fine-grained gneisses, the <30-called granites of many parts of New England, The lii*st suggestions of this were given me by the observation of Dr. Bigsby, confirmed by specimens since received from the region, that there exists to tne northwest of Lake Superior, an extended series of crystalline schists, unlike the Laurentian, and resem- bling those of the White Mountains. I have already called attention to this resemblance in a review of the progress of American Geology, in 1861 (this Jour., II, xxxi, 395). It was contrary to my notions of the geological history of the continent to suppose that rocks of Devonian age could, in that region, have assumed such lithological characters, and 1 was therefore led to compare these rocks with a great series of crystalline schists, abounding in mica-slates and micaceous limestones, which occupy considerable areas in the Laurentian region in Hastings county, to the north of Lake Ontario. The distribu- tion of this series has been traced out by Mi. Ycnnor, who, in 18B9, was able to show that, although much contorted, it rests unconformably upon the old Laurentian gneisses, while it is, at the same time, overlaid by the horizontal limestones of the Trenton group. This intermediate series, which attains a thick- ness of several thousand feet, is terminated by calcareo-mica- ceous schists, in which Eozoon (hruidense ha«. been found, both in Madoc and in Tudor. In these localities, as shown by Daw- son and Carpenter (this Jour., U, xliv, 367), the calcareous 89 T. S. Bunt on the Oeohgy of Eastern New England. skeleton of the Eozoon, instead of being injected by serpentine or another silicate, is simply filled with impure calcareous and carbonaceous matter. The presence of this fossil serves to con- nect these rocks with the Laurentian system, with which they had provisionally been classed, although their lithological dis- similarity had long been noticed, and in 1866 Sir William Logan had remarked their resemblance to the mica-slate series found near the sources of the Connecticut River (Report Geol Survey, 186G, p. 93). Mr. Alex. Murray's report of his explorations in Newfound- land, published in 1866, throws much light on the history of the rocks immediately succeeding the Laurentian in that region. He found in the great northern peninsula, about the Cloud Mountains and Canada Bay, not less than 5400 feet of strata, referred by him to the Potsdam group. Of these the lower 2500 feet consist of bluish-gray slates, holding near the summit, beds which become conglomerate from the presence of quartz peb- bles, and are followed by a mass of purplish amygdaloidal dio- rite, holding epidote and jaspery red iron ora Then follow 2000 feet of argillaceous and somewhat micaceous slates, with beds of quartzite and of limestone, generally impure. These contain, oesides numerous fucoidal markings, the remains of a Lingula, and of Olenellus Vermontamis^ a fossil characteristic of the Potsdam group. To this second division succeeds a third, consisting of about 900 feet additional of limestones and slates. Somewhat farther southward, at Great and Little Coney Arms, the lower half of the above series is not observed, but a succes- sion of strata, supposed to represent the upper portion of the Potsdam, is more particularly described. It consists, at the base, of 300 feet of pale bluish-gray mica-slates, with iron stains, ** softer, more finely laminated, and more uniform both in color and in texture " than some micaceous strata described by Mr. Murray as occurring in the Laurentian in that region. To these succeeded 430 fbet of similar soft bluish-gray mica-slates, holding numerous thin seams of dark colored limestone, and followed by 1000 feet of impure limestones and slates, often micaceous and calcareous, among which are a few betls of white compact marbla No indications of fossils, save fucoidal markings, were met with in this section. At Coney-Arm Head there is seen a series of " whitish granitoid, very quartzose jnica-slates," which appear to have a tliickness of from 1500 to 2000 feet The same rock is found in White Bay, where it overlies what is sup- posed to be Laurentian gneiss. The relations of these whitish granitic mica-slates are still obscure, but Mr, Murray was inclined to regard them as occupying a position beneath the Potsdam group. The latter, in Canada Bay, is immediately followed by the unaltered fossiliferous limestones and shales of £ T. S. Hunt mi the Oeology of Eastern New England. 87 the Quebec group. From these investigations of Mr. Murray we learn that between the Luurentian and the Quebec group, there exists a series of several thousand feet of strata, including soft bluish-grey mica-slates and micaceous limestones, belong- ing to the Potsdam group ; besides a great mass of whitish granitoid mica-slates, whose relation to the Potsdam is still uncertain. To the whole of these we mav perhaps give the pro- visional name of the Terranovan series, in allusion to the name Newfoundland. Imperfect gneisses and micaceous schists are found in several parts of the province of New Brunswick, associated with what has been described as a great granitic belt These rocks have been examined by Prof. Hind, and by Mr. Robb, on the St John and Mirimichi rivers ; and the former of these observers some years since pointed out the indigenous character of the so-called granites. In the summer of 1869 1 had an opportunity of examining, with Prof L. W. Bailev, the region about St. Stephen, on the river St Croix, where he had already observed a series of ferruginous quartzites and imperfect gneisses, accom- panied by soft bluish mica-slates sometimes holding chiastolite, staurolite, and garnet These highly crystalline schists are not more than five miles removed from unaltered shales of the Gasp«5 series, containing fossils of Ut)per Silurian or Lower Devonian types, and rest unconformably upon older granitoid rocks, which Prof Bailey regards as probably Laurentian. We subsequently examined the crystalline schists of the St John, which are apparently identical with those of the St Croix, and these also overlie, unconformably, an older granitoid gneiss. More recently Prof Hind has pointed out, that some of the so-called granites of Nova Scotia are ancient gneisses, probably of Laurentian age, and have shown that between these and the gold-bearing slates of that province, there is found, near Wind- sor, and near Sherbrooke, a series of beds of no great thickness, consisting of imperfect gneisses, quartzites and micaceous schists, which rest unconformaliy on the Laurentian, and are sometimes wanting altogether, 'these include mica-schists with chiastolite and garnet and appear identical with those already observed by Dr. Dawson in other parts of Nova Scotia, which I had already recognized as the same with those of the White Mountains, and those of the St Croix, just noticed. Prof. Hind, in a late paper, has called these, from their position in Nova Scotia, Huronian ; but the Cambrian or Iluronian rocks recognized by Messrs. Matthew and Bailey in New Brunswick, where they are widely spread along the north side of the Bay of Fundy, consist of massive diorites and quartzose feldspar- porphyries, with occasional sandstones and conglomerates, and are very unlike the gneissic and micaceous rocks in question, ^ 88 T. S. Hunt on tlie Otologif of Eastern New England. which 1 believe to bolonpf, like those of the St. Croix and the St. John rivi*rs, to the great Terrsinovan series. Tlie mica- ceous and hornblendie schists, with interstratified fine grained whitish gneisses (locally known as granites) which I have seen in Hallowell, Augusta, Brunswick and Wcrftbrook, in Maine, appear to belong to the same series ; which will also probably include much of the gneiss and mica-schist of Kastem New R]ngland, If this uj)per series is to be identified with the crys- talline schists wliich, in Hastings County, Ontario, overlie, unconformably, the Laurentian, and yet contain Eozoon Cana- (lense^ the presence of this fossil can no longer serve to identify the Laurentian system. To this lower horizon however, I have referred a belt of gncissic rocks in Eastern Massachusetts, which are lithologically unlike the present series, and identical with the Laurentian of New York and Canada. To the upper series appear to belong the great endogenous granitic veins so well known to minerdogists as containing beryl, tourmaline and other fine crystallized minerala The fine-grained, white granitoid gneisses, often present an apparently bedded structure, which enables them to be removed in large plates or layers, lying at no great angle, and appar- ently conformable to the present surface of the country. This structure, wliich I conceive to have been superinduced by super- ficial changes of temperature, is often quite independent of the bedding, as may be seen in the quarries near Augustti in Maine, and in the cuttings on the Grand-Trunk liailway near Berlin Falls, New Hampshire. It is also observed in exotic or intru- sive granites, like those of Biddeford, Maine. This is, in fact, the concoiitric lamination of granite, long since observed by Von Buch, and, I believe, correctly explained by Prof N. S. Shaler to be due to movements of contraction and expansion in the mass, caused by variation of temperature during the changes of the seasons, ite has not however observed this structure at greater depths than from three to five feet, while in some rocks I have found it penetrating probably twenty feet. (See Shaler's paper, read before the Boston Nat. History Society, Feb. 3, 1869, and published in the Proceedings of the Society, vol. xii, page 289). While however I admit the existence in the Dominion of Canada and in Eastern New England, of a great series of crys- talline schists, distinct Irom the Laurentian, and apparently the same with those found by Mr. Murray between the Laurentian and the Quebec group in Newfoundland, it is not less certain that we have in thesd^ regions rocks of Upper Silurian and Lower Devonian age, holding characteristic fossils. These strata in Maine and New Brunswick are generally but little altered. In the Connecticut valley at Beniardston, Massachu- T. S. Hunt mi Oie Otology of Eastern New England. 89 setts, near Lake Mempliremagog in Vermont, and further north- ward in tl>e province of Quebec, fossils of this horizon are found in rocks wliich, in some localities, ure more or less altered and crystalline. I believe however that much of the calcareous mica- slate of Eiustern Vermont will be found to belong to the Terra- novan series. The extent of these newer rocks, and the limits between them and the more ancient schists, of the ruins of which they are probably in part composed, remain problei ^ for farther investigation. i\>r the solution of these, Prof. C. 11. Plitchcock, by his labors in Vermont, is already well prc})ared, and it cannot be doubted that he, with his able assistants, will in the Survey of New Hampshire, now in progress, throw much light on New England geology. It is worthy of remark, that strata holding fossils of Lower llelderberg age, or therealM)uts, are not conlinea to the shores of Maine and New Brunswick, and the valleys of the Connecticut and St. John rivers, but are found beyonti the Green Mountains, in the valley of the St. Lawrence, near Mon- treal ; where, on the island ol St. Helen, they rest unconform- ably on the Utica slate, and at Belceil Mountain, near by, on intrusive diorites, which there break through the shales of the Hudson River group. The relations of this Terranovan series to the porphyries and diorite rocks which, in New Brunswick, have been called Cam- brian and Huronian by Mr. Matthew (first distinguished by him as the Coldbrook grou})), yet remains to be determinea. These rocks are found near to the city of St. John resting directly on what has been regarded as Laurentian, and are over- laid by the uncrystalline schists which contain the primordial fauna now so well known by the descriptions of Prof. Hartt Rocks which I regard as identical with ttiis same Coldbrook or Cambrian group, are found along the coast of New Brunswick, and constitute the diorites and porphyries of Eastport, Maine. They appear moreover to be the same with those met with near Newburyport, and at Salem, Lynn, and Marblciiead, Massachu- setts. Farther researches about Passamaquoddy Bay, where the mica-slates are found not fur removed from these porphyries, will probably enable us to determine their relations to each other. It will be remembered that Giimbel has found, in Bavaria, beneath the oldest fossiliferous clay -slates, a mica-schist (and horn- blende-schis^) series, reposing upon the Hercynian gneiss, which contains crystalline limestones, with graphite, serpentine and Eozoon Canadense, and which he has identified with the Lauren- tian of North America, lie distinguishes beneath this a great mass of red gneiss, apparently without limestones, to which he has given the name of the Bojian gneiss. It will however be remembered, that in his studies of the Laurentian system on the 80 T. & Hunt on the Geology of Sasiem New England. Ottawa, Sir WiUiam Logan has shown that this immense series (his Lower Lauren^ian), some 20,000 feet in thickness, includea lour great masses of peiss and quartzite, divided by three lime- stone tormations, and: that it is in the uppermost of these, which IS, m some parte, 1600 feet thick, that tlie Eozoon Canadense has been tound. Some of the lower gneisses of this vast system may very well represent the Bojian of Gumbel, who hi not recognized m Bavaria either the Labradorian (Upper Lauren- toan) or Huronian series. (See Gumbel on the Laurentian of ±iavana, translated and published in the Canadian Naturalist lor December, 1866). Comparative studies of this kind should not be neglected in the investigation of our American rocka Montreal, May 10, 1870.