FORMATION OF PANGAEA

The Allegheny orogeny was the last Appalachian mountain-building episode. It featured the collision of the west African margin of the Gondwana continent with eastern Laurentia in the final stage of formation of the supercontinent Pangaea in the later Carboniferous (362-286 mya) and Permian (286-245 mya) periods. Unfortunately, Carboniferous rocks are limited and Permian rocks absent in New York State; thus local sedimentary rocks provide little data on this orogeny. The bedrock east of Syracuse provides indirect evidence of the Allegheny orogeny. Composition of the clay mineral illite and the baking of carbon of carbon-based biological remains to graphite in eastern New York indicate high burial temperatures. Because rocks get hotter with depth, the data indicate the Catskills were once buried by 4 miles (6 km) of rock. Deep burial “baked” all of the petroleum in eastern New York State to graphite and limited any hydrocarbons to natural gas. Future sources of petroleum will probably continue to be in Silurian-Devonian sandstones and carbonates in the western parts of the state, which have yielded oil since the late 1800s. Some features traditionally assigned to the older Acadian orogeny. For example, a major fault that trends north-northeast and south-southwest from Cornwall (Orange Co.) uplifted the Grenville rock of the Hudson Highlands against the Middle Devonian in southern Orange Co. and could be an effect of the Allegheny orogeny.

fig 45
Beginning of Alleghanian Orogeny

fig 46
Continued Alleghanian Oregeny - Formation of Supercontinent Pangea


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