456 J. B. WOODWORTH — GLACIAL PLEISTOCENE IN GAY HEAT) CLIFFS 



the deposit and its geological position have an important bearing on the 



extension of the first ice invasion to New England, the facts are here 

 stated. 



Contents of the Deposit 



The significant fact in the contents of the boulder-bed is the occur- 

 rence in it of large and small fragments of rock borne from known ter- 

 ranes constituting the mainland on the north. A small boulder of 

 peridotite very clearl}' traveled from Iron Mine hill, in Cumberland, 

 Rhode Island, a distance of 59 miles, approximately along lines of trans- 

 portation of drift in the last ice invasion, though farther to the east than 

 any fragments of this rock seen by the writer in the till of the last ice- 

 sheet. Boulders of granite, gneiss, and diorite are present from the region 

 about Westport, Massachusetts. Some of these fragments are angular. 

 One boulder has already been described as having an approximate weight 

 of 8 tons. 



In addition to these materials which have been carried to and de- 

 posited on this disturbed section of coastal plain formations, the boulder 

 bed contains fragments of the strata in the old coast plain, showing that 

 the agency or agencies of transportation were capable of eroding ma- 

 terials quite down to the end of the journey — a feature possessed only by 

 ice moving over the land or the shallow deposits of the sea. Floating 

 ice could hardly have effected the transportation of blocks from Cum- 

 berland, at an elevation of 400 feet above the present sealevel, and also 

 from the edge of the coast plain as it then existed, for one or the other 

 of these areas would' have been above or below the zone of inclosing 

 debris for flotation, unless it be admitted that the land has been uplifted 

 with reference to the two localities b}' a tilt as great as 10 feet to the 

 mile, of which there is no evidence whatever. 



Structure of the Deposit 



The larger patches of the boulder bed exhibit an arrangement of the 

 pebbles and cobbles which is indicative of water action. The smaller 

 patches of larger boulders are less clearly stratified, and one patch, ex- 

 cept for the absence of fine materials, might well be termed till. The 

 frequently angular blocks of rock found in the deposits, particularly 

 near the base, show that water action was feeble, or of short duration if 

 strong. The same conclusion must be drawn from the occurrence of 

 glaciated pebbles yet to be described. The pell-mell order of certain 

 portions of the boulder bed can not be much relied on, for the reason 



