SAYLES: THE SQUANTUM TILLITE. 145 



K. Tlie lower part of the till usually has a finer matrix and more 



striated pebbles than the upper part. 

 L. The materials in till showing that when deposited there was no 



evidence of v,^eathering or decomposition. 

 M. Materials in till usually composed of more local than foreign rocks. 

 N. Near the top of till, intercalated stratified beds may be found. 

 O. Included "nests" and layers often contorted. 



Description of localities. 



In descriptions of conglomerates the words "pebbles" and "boul- 

 ders" are used, as a rule, very indefinitely. In this paper I propose 

 to use the word pebble for sedinient from f of an inch up to 5 inches; 

 the word boulderet for rock fragments from about 6 inches up to 1 foot 

 in diameter; the word boulder for rock fragments over 1 foot in diame- 

 ter. 



Locality 1 . Hyde Park. At Hyde Park the sandstone and conglom- 

 erate beds just under the tillite, strike N 30° E, and dip 70° S. About 

 100 feet of the tillite is exposed. The matrix of the tillite is very fine, 

 originally of clay. So far as I have observed them the pebbles, 

 boulderets, and boulders are of granite, felsite, and quartzite, but 

 other varieties may be found later. The shapes of the rock fragments 

 indicate glaciation; angular and subangular for the most part, but 

 here and there rounded. Dr. La Forge found a well-striated pebble 

 embedded in the matrix, in the presence of Dr. Ellsworth Huntington 

 and the writer on July 11th, 1910. This pebble is shown in Plate 2. 

 I have since found two others from this outcrop. There is a large 

 boulder of granite in the matrix within a few feet of the place where 

 Dr. La Forge found his striated pebble, beyond the fence back of the 

 Becker Milling Machinery Company's storehouse. This boulder 

 measures somewhat over three feet in diameter, and is angular. This 

 spot is very near the bottom of the tillite, where it would be most 

 natural to find striated and well-glaciated pebbles. There are no 

 intercalated beds visible in the tillite of this outcrop, and absolutely 

 no stratification of any kind. No fragments of slate have been found, 

 and this is an important fact to be dwelt upon later. I have found 

 no melaphyre fragments or pebbles. Shearing is intense. See 

 Plate 1. 



Below the tillite there are some transition-beds of conglomerate and 

 sandstone about 100 feet thick. 



Criteria found (see page 144) : — A, B, C, D, E, F, G, H, J, K, L, M. 



