Gah NEW YORK STATE MUSEUM 
were being eroded. The sediments derived from the erosion of | 
the young Appalachians were especially abundant because of the | 
vigorous wearing down of the young mountains. A thickness of | 
thousands of feet of nonmarine rocks, mostly red sandstones and 
shales, was finally accumulated in these basins, and is known as the 
Newark series. The great thickness of these rocks, from 10,000 to 
even possibly 15,000 feet, strongly argues for a gradual downwarp- 
ing of the basins as deposition of sediments went on. It is often 
stated that these strata were formed in estuaries, but at least in the 
northern area, from the Connecticut valley to Maryland, many of 
the layers show sun cracks, rain-drop pits, ripple marks, and re- 
mains and footprints of land reptiles. These features show that 
for the most part the beds were formed in very shallow water such 
fo 
eS 
s 
== 
are 
iS) 
EE IS REAM Coe 
ze 
es i 
3 
) 
Fic. 20 Detailed section running west-northwest through Pelhamville, 
Yonkers and the Palisades in southeastern New York, showing the intense 
folding of Taconic age, the granite dikes, and the relation of the Palisade 
lava to the other formations. Fg—= Fordham fineiss (Precambric) ; Pq = 
Poughquag quartzite (Cambric); Sd Stockbridge dolomite (Cambro- 
Ordovicic) ; Hs==Hudson schist (Ordovicic); Yg—=Yonkers gneiss; Gr 
—=eranite dike; Ns Newark sandstone (Jura-Trias) ; Pd — Palisade dia- 
base or lava (Triassic). 
Modified from New York City folio, U. S. G. 8. 
as flood plains or lakes where changing conditions frequently 
allowed the surface layers to lie exposed to the sun. 
During the time of the formation of the Newark beds there was 
considerable igneous activity as shown by the occurrence of sheets 
of igneous rocks within the mass of sediments. In some cases true 
lava flows, with cindery tops, were poured out on the surface and 
then became buried under later sediments, while in other cases the 
sheets of molten rock were forced up either between the strata or 
obliquely through them, thus proving their intrusive character. As 
a result of subsequent erosion, these lava intrusions often stand 
out conspicuously as topographic features. Perhaps the most note- 
worthy of these is the great igneous rock sheet, part of which out- 
crops to form the famous Palisades of the Hudson and which out- 
crops altogether for a distance of seventy miles.. As shown in 
