220 



SCIENCE 



[N. S. Vol. XLI. No. 1049 



TILLITE IN NEW HAMPSHIRE 



In 1910 while spending the summer at Sugar 

 Hill, New Hampshire, I came across a forma- 

 tion which appeared to me to be tillite. The 

 Eev. S. S. Nickerson, of Sugar Hill, had a 

 glacial-boulder of conglomerate near his house 

 which looked as if made up of glacial pebbles. 

 Mr. Nickerson described an exposure of con- 

 glomerate which he had seen in Lyman, 12 

 miles west of Sugar HiU, several years before. 

 I visited this locality with Mr. ISTickerson. 

 The best outcrop found is about half a mile 

 north of Young's pond by the side of a little 

 schoolhouse, in the town of Lyman. I exam- 

 ined the formation and was immediately im- 

 pressed with its glacial appearance. There 

 was no stratification and the included rock 

 fragments of various kinds scattered through 

 an argillaceous matrix were of all sizes up to 

 6 feet in diameter. There were very few 

 rounded pebbles, most of the fragments being 

 angular and subangular. Here and there large 

 masses of slate, greatly contorted, were found. 

 One of them measured 6 feet long by 4 feet 

 wide on the two exposed dimensions. These 

 slate masses were so like the slate lumps found 

 by me in the Squantum tillite near Boston,^ 

 that I could not avoid the conclusion that this 

 formation might be tillite also. 



On account of the very great shearing and 

 distortion which these rocks have undergone 

 — much greater than the Squantum tillite has 

 been through — it will be impossible to hope 

 for any signs of striations. Even the concave 

 fractures so common on glaciated pebbles in 

 till, and in the Squantum tillite, have been 

 rendered unrecognizable. The general ap- 

 pearance of the rock and the distorted slate 

 fragments are the only criteria so far found 

 to determine the origin of this formation, 

 and the prospects are not very bright for find- 

 ing any very definite proof. To a glacial geol- 

 ogist, however, the appearance of the rock is 

 almost conclusively glacial. 



The thickness of this till-like section can 

 not be less than 100 feet and is probably much 



1 See Bulletin of the Museum of Comparative 

 Zoology, Vol. LVI., No. 2, "The Squantum TH- 

 lite, ' ' by Eobert "W. Sayles, pp. 148-155, 1914. 



greater. The eastern contact rock is an argil- 

 laceous schist with a northeast and southwest 

 strike and a thickness of over 1,000 feet. On 

 the west the contact rock is conglomerate, with 

 water-worn pebbles and some signs of stratifi- 

 cation. The thickness of this conglomerate is 

 uncertain, probably several hundred feet. 



A few days after the examination of this 

 section I found the " Geology of New Hamp- 

 shire," by Charles H. Hitchcock, in the small 

 library at Sugar Hill. On page 302, of Vol- 

 ume 2, the following description of this rock 

 is given: 



' ' There is a curious conglomerate west of Bev. C. 

 Coming's, in North Lyman, lying adjacent to the 

 Lyman group, and supposed formerly to consti- 

 tute a part of it. It resembles a mass of common 

 drift, because the pebbles are so numerous and 

 miscellaneously arranged. They consist of both 

 the white and green schists, and dip south 52° east. 

 The pebbles are mostly of large size, one measur- 

 ing 2 feet long and 5 inches wide. On the top of 

 IMormon Hill, nearly two niiles east of this ex- 

 posure I found a very coarse conglomerate with 

 strike N. 58° E. lying on the northwest side of clay 

 slates dipping N. 47° W. It is probable that these 

 two exposures belong to the same formation which 

 runs athwart the Lyman group, and may possibly 

 join a very coarse supposed Helderberg conglom- 

 erate in Littleton to be described presently. ' ' 



These words were written long before the 

 word " tillite " had been introduced by Pro- 

 fessor Penck, and before the idea of rocks 

 with a glacial origin had entered the minds of 

 American geologists. 



In the summer of 1911 I invited my friend, 

 Dr. F. H. Lahee, to investigate with me in 

 this region, for the purpose of finding out, if 

 possible, the age of the formation under dis- 

 cussion. He spent two summers making a 

 careful field study of all the formations. The 

 main results of his work, without a discussion 

 of the rock described in this paper, were pub- 

 lished by him in the American Journal of Sci- 

 ence, Vol. XXXVL, September, 1913, " Geol- 

 ogy of the New Fossiliferous Horizon and the 

 Underlying Eocks, in Littleton, New Hamp- 

 shire." The age of the supposed tillite is still 

 much in doubt, on account of faulting and 

 unconformity. Professor Lakee thinks the 



