MAGNETITE IRON DEPOSITS OF SOUTHEASTERN NEW YORK 35 
Hudson river, crosses the river diagonally to Tompkins Cove, and 
passes southwestwardly through New York and into New Jersey, 
where the escarpment established by the displacement forms the 
southern boundary of the Highlands and sharply delimits the Pre- 
cambrian crystallines from the Triassic sediments. Occasional 
cross faults of small displacement, striking nearly east-west, are 
related to this period also. 
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Fig. 1 Cross-section showing the Precambrian complex of the Highlands 
overthrust on the Cambro-Ordovician sediments. Northern margin of 
the Highlands, near Beacon. 
The isolated hills of gneiss previously mentioned are frequently 
bounded on the northwest sides by thrust faults of the Appalachian 
type and on their southeast sides by Triassic gravity faults, thus 
owing their isolation to these movements and to the erosion fol- 
lowing; the “stranded fault blocks” of Berkey,*’ previously 
referred to (p. 32). The failure of earlier geologists to observe 
that blocks of Cambro-Ordovician sediments were down faulted into 
the Precambrian crystallines led to the confusion of these younger, 
infaulted sediments with the older group, and to the conclusion that 
the crystalline schists and limestones of Precambrian age (particu- 
larly the Manhattan schist and the Inwood limestone) were the 
metamorphosed equivalents of the Hudson River slate and Wap- 
pinger limestone of Cambro-Ordovician time. 
87 Berkey, C. P., & Holzwasser, Florrie. Geology of the Newburgh Quad- 
rangle. N. Y. State Mus. Bul. (Prepared) 
Ruedemann (N. Y. State Mus. Bul. 133, p. 164-03) classifies such struc- 
tures as “inliers caused by diastrophism”; he mentions the inliers of gneiss 
in the neighborhood of Newburgh and along the north side of the Schune- 
munk mountains and states that “faulting may, to some extent, have 
influenced the production of some of these inliers.” (p. 181) 
SE 
