FOSSILIFEROUS MARl^'E CLAYS 537 



a section over 100 yards long shows 8 feet of till resting on marine claj'. 

 The exposures can be seen in two brick-yards situated on either side of the 

 Boston and Maine railroad. The till consists of an unconsolidated deposit 

 of clay, gravel, and boulders, and is oxidized to a depth of 2 feet from the 

 top. The underlying clay is normally horizontal and contains some layers 

 of interstratified sand. Mr George C. Matson reports a fault in the sand 

 here and states that the strata are considerably contorted. In elevation 

 the clay rises about 100 or 120 feet above tide. Back from the clay 

 pits the till surface rises into a moraine-like deposit. Beneath the clay 

 another deposit of till, which appears to be Montauk, is found. The peb- 

 bles contained in it are, however, decomposed to an extent unusual in the 

 Montauk till. Similar conditions prevail in a pit of the same company 2 

 miles farther north. 



A condition similar to that at Exeter is found at jSTewburyport, Massa- 

 chusetts. The clay at that place is overlain by sand and gravel, which is 

 in turn overlain, east of the railroad, by till (see plate 60, figure 1). 



Section uf Drift at Newburyport, Massachusetts 



Material Feet 



4. (Top) Typical stony, clayey till, containing pebbles up to 3 inches in 



diameter 4 



3. White stratified sand, merging upward into till and downward into 



semi-stratifled sand containing some pebbles 2 



2. Below (3) is a reddish ferrnginons cnist one-halt inch to one inch in 



thickness. 

 ]. Much folded and faulted sand containing a few pebbles 5 -}- 



Total 11-1- 



The faulting in (1) indicates shoving from the north. 



The occurrence of till over clay at Danvers and Lynn, Massachusetts, 

 was first noted by Sears.* These deposits have been seen by the writer, 

 who agrees with Sears in his conclusions. The latter was the first person 

 to find fossils in these clays in Massachusetts. He believed that the over- 

 lying till formed the "toes" of near-by drumlins which were supposed to 

 rest on clay. What is considered by the present writer a more probable 

 condition is explained on page 550. At the Danvers locality 14 species 

 of fossils were found by Sears (column 8, pages 520-523). 



In 1866 Shaler described some fossiliferous clays and sands overlain 

 by till at Gloucester, Massachusetts,! and 37 3'ears later similar relations 

 in a neighboring cliff section were discovered by Tarr.J The fossil forms 

 found in this section are those noted in column 9 of the table. 



* J. H. Seai-s : Geology of Essex county, Massachusetts. Salem, 1905, pp. 357-373. 

 t Proc. Boston Soc. Nat. Hist., vol. xi, pp. 27-30. 

 t Bull. Harvard Coll. Mus. Comp. Zool., vol. xlii, 1903, pp. 181-191. 

 XLVII — Bull. Geol. Soc. Am., Vol. 18, 1906 



