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CAPE COD GEOLOGY 



these deposits is the plain at Eastham, which filled in what may have been a 

 depression between the moraine at Orleans and the ' 'table-lands of Eastham," 

 in Wellfleet, before the ice began its retreat. 



This plain is separated from the Falmouth moraine on the south by a narrow 

 belt of kames that extend across the Cape. The knobs and basins of this plain 

 are well shown about the hamlet of Eastham Centre and along the coast just 

 north of Nauset Beach lighthouse. 1 The kames in this plain were deposited 

 in the presence of ice and were originally probably an extension of the creased 

 plain on the north. Grabau first and Wilson later presented the view that 

 the Eastham plain was built from an ice mass lying east of the present coast of 

 Cape Cod by streams flowing westward, just after most of the ice had melted 

 away from the site of the moraine at Orleans. 



The Eastham plain (also called the "table land of Nauset") presents a 

 relatively even crest to the Atlantic waves at its cliffed edge. From an elevation 

 of about 70 feet at its eastern margin the plain slopes westward and merges on 

 the south and southwest into a field of kames and ends rather abruptly on the 

 bay side in deeply indented knobs of sand and gravel. Its surface is traversed 

 by creases made by running water. The plain lies north of the bouldery moraine 

 about Orleans and south of the broken higher plain in Wellfleet, so that its 

 position and its slope toward the continent and away from the sea excludes the 

 supposition that it was modeled by the action of the sea. 



The gravel and sand in the eastern bluff have been stratified by the action 

 of water except at the south end of the bluff, near the Coast Guard station, 

 where there is a bed of what appears to be till containing small pebbles and 

 subangular stones. 



Grabau and, later, Wilson appear to have assumed that this deposit of sand 

 and gravel was laid down later than that found on the high plain farther north. 

 Although the section along the cliffs was not entirely free from talus at the 

 critical place at the time of my visit, it seemed that the beds on the seaward side 

 of the Eastham plain may extend northward in continuity with the beds of the 

 high plain in Wellfleet. If the beds of the Eastham plain were laid down later 

 an unconformable contact should occur at the junction of the two plains where 

 the surface of the ground changes its level. The somewhat similar plain that 

 forms Pilgrim Head, at the north end of the Cape, is obviously a plane of erosion, 



1 The two lighthouses shown on the topographic map of 1887 are gone. On October 23, 1910, the north 

 light stood 16 feet back from the summit of the cliff and on August 7, 1916, the lighthouse tower, whose 

 base was about 15 feet in diameter, had fallen into the sea and the cliff was about 10 feet farther back 

 than the site of the tower. A new light stands somewhat back from the present cliff. 



