Mr.Lyell on the Tertiary Strata of Martha's Vineyard. 187 



Palcconiscus. In the sandstone between the fish-beds he discovered an 

 Ornithoidicnite, and observed numerous slabs exhibiting impressions 

 of rain-drops and ripple-marks. The rain-marks appear as if the rain 

 had been driven by a strong wind, and the direction of the impressions 

 indicated that the wind blew from the west, a quarter from which 

 violent squalls or thundergusts are still prevalent in these latitudes. 



5. On the Tertiary Strata of the Island of Martha's Vineyard in 

 Massachusetts. By Charles Lyell, Esq., V.P.G.S., &c* 



The most northern limit to which the tertiary strata bordering 

 the Atlantic have been traced in the United States is in Massachu- 

 setts in Martha's Vineyard, lat. 41° 20' north, an island about 

 twenty miles in length from east to west, and about ten from north 

 to south, and rising to the height of between 200 and 300 feet above 

 the sea. The tertiary strata of this island are, for the most part, 

 deeply buried beneath a mass of drift, in which lie huge erratic blocks 

 of granite and other rocks which appear to have come from the 

 north, probably from the mountains of New Hampshire. The ter- 

 tiary strata consist of white and green sands, a conglomerate, white, 

 blue, yellow, and blood-red clays and black layers of lignite, all in- 

 clined at a high angle to the north-east, and in some of their curves 

 quite vertical. They are finely exposed near Chilmark on the south- 

 west side of the island, and in the promontory of Gay Head at its 

 south-western extremity, where there is a vertical section of more 

 than 200 feet in height. 



Attention was first called to this formation by Prof. Hitchcock in 

 1823, who appears to be the only American geologist who has ex- 

 amined them personally. He compared the beds at Gay Head to 

 the plastic and London clays of Alum Bay in the Isle of Wight, to 

 which, lithologically, they bear a striking resemblance, consisting in 

 both cases of variously and brightly coloured clays and sands with 

 lignite, all incoherent and highly inclined. Various opinions, how- 

 ever, have been put forth as to the relative age of the Martha's Vine- 

 yard strata, which were assigned by Prof. Hitchcock, at a time when 

 the tertiary formations of the United States were less known, to the 

 Eocene period, while Dr. Morton supposed them to be in part only 

 tertiary, and that they rested on greensand of the cretaceous period. 



The section at Gay Head is continuous for four-fifths of a mile, 

 the beds dip to the north-east generally at an angle of from thirty- 

 five to fifty degrees, though in some places at seventy degrees. The 

 clays predominate over the sands. In one place Mr. Lyell found a 

 great fold in the beds, in which the same osseous conglomerate and 

 associated beds of white sand, on the whole fifty feet thick, were so 

 bent as to have twice a north-easterly and once a south-westerly dip. 

 In the yellowish and dark brown clay near the uppermost part of the 

 section at Gay Head, and in the greensand immediately resting upon 

 it+, Mr. Lyell found the teeth of a shark, that of a seal, vertebrae of 



* Read Feb. 1, 1843. See Mr. Murchison's notice of the contents of 

 this paper, p. 551 of our preceding volume, 

 f Nos. 5 and 6 of Prof. Hitchcock's section. 



