318 On the Tertiary Strata of Martha's Vineyard. 
Arr. XII.—On the Tertiary Strata of the Island of Martha’s Vineyard 
in Massachusetts ; by Cuarntes Lye, Esq., V. P. G.S., &e.* 
Tue most northern limit to which the tertiary strata bordering the At- 
lantic have been traced in the United States, is in Massachusetts, 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 two and three hundred feet above the sea. 
The tertiary strata of this island are, for the most part, deeply buried bes _ 4 
neath 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 tertiary strata consist of white 
and green sands, a conglomerate, white, blue, yellow, and blood-red , 
clays, and black layers of lignite, all inclined at a high angle to the 
northeast, and in some of their curves quite vertical. They are finely 
exposed near Chilmark on the southwest side of the island, and in the 
promontory of Gay Head at its southwestern extremity, where there is 
a vertical section of more than two hundred 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 examin 
ed 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, lithologie- 
ally, they bear a striking resemblance, consisting in both cases of vari- 
ously and brightly colored clays and sands with lignite, all incoherent 
and highly inclined. Various opinions, however, have been put forth as 
to the relative age of the Martha’s Vineyard strata, which were assign- 
ed 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 green- 
sand of the cretaceous period. 
The section at Gay Head is continuous for four fifths of a mile; the 
* From the Proceedings of the London Geological Society, Vol. IV, No. 92. 
t Nos. 5 and 6 of Prof. Hitchcock’s section. 
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