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TECTONIC MAP EXPLANATION

Symbols

{short description of image}High-angle normal fault, hachures on downthrown side.

{short description of image}Low-angle thrust fault, barbs on overthrust block.

{short description of image}Boundary along which a terrane was welded to North America.

{short description of image}Clarendon-Linden monocline; draped over buried normal fault. Displacement is down to the west.

-500- On land, depth to basement in meters below sea level (not shown below 5000 m due to complexity of basement contours); offshore, depth of water in meters. Circle shows location of drill hole to basement.

UNDEFORMED ROCKS Listed in General Order from Oldest to Youngest

{short description of image}Sedimentary rocks of the North American platform, Late Proterozoic to Paleozoic in age. Deposited in shallow seas on the stable North American craton.

{short description of image}Tectonically passive. Rift basins of Late Triassic to Early Jurassic age, onshore and offshore, filled with non-marine sedimentary rocks as well as basaltic lava flows and their diabase feeders. Offshore basins are buried beneath younger marine sediments. Records a period of crustal stretching and rupture during opening of the Atlantic Ocean.

{short description of image}Mesozoic plutons, mainly granitic, of Jurassic and Cretaceous age. Includes the White Mountains in New Hampshire and the Monteregian Hills in southern Quebec. Plutons were intruded late in the crustal stretching related to opening of the Atlantic Ocean.

{short description of image}Marine and continental sediments of the Atlantic Coastal Plain, Cretaceous to Recent in age. Deposited near sea level as part of a passive continental margin on the east coast of North America. Offshore, submarine sediments and sedimentary rocks deposited since the North Atlantic Ocean began to open about 200 million years ago in the Jurassic Period. Passive continental margin.

DEFORMED ROCKS

Listed in Order of Deformation or Addition to North America

{short description of image}Archean volcanic and granitic rocks of the Superior Province, metamorphosed at low grade about 2.7 billion years ago. Lines show the trends of rock bodies.

{short description of image}Middle Proterozoic basement of the North American craton, last deformed and metamorphosed to high grade during the Grenville orogeny about 1 billion years ago. Exposed in the Grenville Province of the Canadian Shield and the Adirondack Mountains, elsewhere buried beneath sedimentary rocks of the platform.

{short description of image}Middle Proterozoic basement deformed at high metamorphic grade during the Grenville orogeny, and again, at medium grade, during the Taconian orogeny. Some areas also deformed during the Acadian and Alleghanian orogenies. Marine sedimentary rocks of an ancient continental shelf and slope, but also includes rift volcanic and rift sediments.

{short description of image}Late Proterozoic to Ordovician in age. Primarily deformed during the Taconian orogeny, with some areas deformed by the Acadian orogeny in New England, and the Alleghanian orogeny in the Mid-Atlantic Region. Low to high metamorphic grade. Toothed areas are remnants of Taconian thrust sheets that were transported westward onto the platform.

{short description of image} Early Paleozoic ultramafic rocks. Slivers of serpentinized oceanic crust welded onto North America as the Iapetus Ocean closed during the Taconian orogeny. Hachured areas show metamorphosed pre-Taconic mafic Baltimore Complex in Maryland, and undeformed post-Taconic Cortlandt Complex in southeastern New York.

{short description of image}Connecticut Valley Synclinorium. Metamorphosed volcanic and marine sedimentary rocks of Cambrian to Devonian age. Primarily deformed during the Acadian orogeny at medium metamorphic grade.

{short description of image} Bronson Hill Anticlinorium in New England, and the Charlotte and Carolina belts to the south. Metamorphosed volcanic island arc rocks, associated marine rocks, and exotic Proterozoic basement. Low to high metamorphic grade. This terrane was added to North America with the Taconian orogeny. Later deformed by the Acadian and Alleghanian orogenies.

{short description of image} Merrimack Synclinorium. Metamorphosed volcanic and marine sedimentary rocks of Cambrian to Devonian age. Deformed primarily during the Acadian orogeny at medium to high metamorphic grade.

{short description of image} Avalon Terrane. Granite and associated volcanic rock of Late Proterozoic age, overlain by metamorphosed marine and continental platform rocks of Late Proterozoic to Ordovician age. Low to medium metamorphic grade.The Avalon microcontinent was added to North America with the Acadian orogeny. Deformed by the Alleghanian orogeny. Small pieces of West Africa (not shown) remained attached to the Avalon terrane.

{short description of image} Igneous and metamorphosed granitic rocks. Mostly Devonian through Pennsylvanian in age and intruded during the Acadian and Alleghanian orogenies. Includes both strongly deformed and undeformed rock.

{short description of image}Mississippian and Pennsylvanian marine and terrestrial sedimentary rocks m deposited in basins that formed after attachment of the Avalon terrane to North America. The basins were created, filled, and deformed during a sideways-slip phase of the Alleghanian orogeny.

{short description of image}Valley and Ridge Fold Belt. (1) Anthracite grade rocks of Mississippian and Pennsylvanian age. (2) Platform rocks of Middle to Late Paleozoic age. (3) Platform rocks of Cambrian and Ordovician age. Deformed by compression during the Alleghanian orogeny.

{short description of image}Paleozoic sedimentary rocks of the North American Platform. Deformed into broad open folds during the Alleghanian orogeny. These folds gradually diminish into unfolded strata that glided northwestward on layers of salt. Compression has shortened the unfolded strata parallel to layering by 10 percent. --------------------------------------------------------------------------------

Overview of New York Geology Adapted From: EDUCATIONAL LEAFLET 33

By William B. Rogers, Yngvar W. Isachsen, Timothy D. Mock, and Richard E. Nyahay

http://gretchen.geo.rpi.edu/roecker/nys/nys_edu.pamphlet.html