CO'2 TERTIARY SYSTEM. 



VIII. TERTIARY SYSTEM. 



§ 1. Tertiary and post-tertiary clays; albany and lake ciiamplain clays. 



This formation is the most recent in New-York, if we except the peat and marl beds, 

 which have usually been referred to the present era. I( apparently consists of three por- 

 tions : the lowest, a blue stiff clay ; the middle, a lighter colored clay ; and the uppermost, 

 a sand. The middle portion differs but little from the lower in composition. The diffe- 

 rence in color is partly owing to a longer exposure to the atmosphere, by which it becomes 

 lighter, and even a pale brown or drab. The sand appears between the layers, but only 

 in extremely thin beds : the great mass of sand is on the top of the formation; it is a ma- 

 rine deposit, a point which was determined at an early period of the New-York survey, 

 by the discovery of fossils, known as living inhabitants of the Atlantic ocean. 



The largest or most extensn e deposit occupies the Champlain and the St. Lawrence basins, 

 from which it extends into the Hudson valley. It is impossible to determine its real extent ; 

 for it differs in no respect from other clays, and can not be distinguished from them, unless 

 it is traced continuously to beds which are well known, or to those which contain fossils. 

 It is one hundred feet thick upon Lake Champlain; and what is worthy of special notice, 

 is that the deposit rests on the grooved surfaces of the Champlain rocks, or else upon beds 

 of drift. It exhibits all the characters of a deposit made during a period of perfect quietude. 

 We have to notice, however, that at the close of this period, one of some violence suc- 

 ceeded ; this is clearly indicated by the removal of large portions of the formation. The 

 sand, and part of the clay, has apparently been removed to distant points, leaving only the 

 lower portion, and even sometimes the whole mass down to the rock has been removed. 



§ 2. Fossils of the tertiary system. 



About twenty-two or twenty-five species of marine animals have been discovered 

 towards the upper part of the clay. The indurated clay, or claystones, in one or two 

 instances, have contained fossil fish. Besides these, a fossil jaw of a walrus was found by 

 Mr. Lyell in this formation in Maine. 



Of the conchifera belonging to this deposit, the Saxicava rugosa, and the Sanguiiiolaria, 

 have a wide distribution ; the remaining species are quite limited, and are confined to one 

 or two places on the borders of Lake Champlain and of the River St. Lawrence. At 

 Beauport, a village four miles from the city of Quebec, about fifteen species of fossils have 

 been found, all of them distributed throughout a single bank of clay and sand. Some of the 

 same species inhabit the northern seas ; and hence Mr. Lyell maintains, that during the era 

 of this deposit, the temperature of the part of the continent where these fossils are now found 

 was lower than it is at present. Doubts are thrown over the justness of this conclusion, 

 by the fact that some of the species are the present inhabitants of the Atlantic ocean on 

 the coast of Maine ; that marine animals have a wide distribution ; and as our waters have 



