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Tectonic History of Long Island Glenn Richard Stony Brook University Map from: http://people.hofstra.edu/J_B_Bennington/research/long_island/li.html
Tectonics: Greek for "builder", tekton - a geologic field of study that focuses on the structures, such as folds and faults, within the Earth's crust and the geologic phenomena that have created these structures by operating in specific regions.
New York State Geologic Map The geologic history of the region that includes Long Island is recorded in rocks throughout New York State and New England. Stony Brook Published by the University of the State of New York
Continued Major Geologic Eventsin New York State 1.1 Billion Years Ago – Grenvillian Orogeny Rodinia (supercontinent) 650 Million years Ago – Rifting of Rodinia Iapetus Ocean 480 Million years Ago – Taconian Orogeny 400 Million Years Ago – Acadian Orogeny 290 Million Years Ago – Alleghenian Orogeny Pangaea (supercontinent) 250 Million Years Ago – Rifting of Pangaea -> Atlantic Ocean 80 Million Years Ago – River delta -> Fossils now found on North Shore 1.6 Million Years Ago – Start of period of ice advances and retreats 20,750 Years Ago – Last ice sheet retreats
Tectonic Events along East Coast of what is now North America Tectonic* History of the Long Island Area *Relating to, causing, or resulting from structural deformation of the earth's crust.
Grenville Orogeny 1.1 Billion Years Ago Mount Haystack from Mount Marcy in the Adirondacks The Grenville Orogeny, 1.1 billion years ago, created a huge mountain range extending along what is now the east coast on North America down to Mexico, evidenced by rocks exposed in the Adirondacks and buried well below the surface of the remainder of New York State. This event also formed the Grenville Supercontinent.
Rifting of Rodinia 650 million years ago “North America” From http://www.scotese.com/precambr.htm
Diabase dike (650 mya) in western Adirondacks intruded during breakup of Grenville supercontinent.
500 Million Years Ago: A Warm Shallow Sea Ripple marks on Potsdam Sandstone (500 mya), Ausable Chasm display. Formed in warm shallow sea. Potsdam sandstone probably covered Adirondacks and was eroded from central portions after later uplift.
Taconian Orogeny 450 million years ago – Hartland Island arc collides with Laurentia “North America” Hartland Gneiss Details: Subduction zone forms in Iapetus OceanHartland volcanic island arc forms behind subduction zoneThe oceanic crust between the island arc and Laurentia subducts until the island arc collides with Laurentia
Acadian Orogeny 380 million years ago – Avalon collides with North America Details: Avalonia splits from Gondwana and becomes attached to BalticaBaltica included the land areas now bordering the Baltic SeaThe collision of Baltica with Laurentia in the Silurian is the Caledonian OrogenyCaledonian Orogeny progresses south and becomes the Acadian Orogeny
Alleghenian Orogeny 300 million years ago – Gondwana collides with Laurentia “North America” Diagram represents a time prior to the collision Details: Oceanic crust between Avalonia and Gondwana is subductedThe collision of Gondwana and Laurentia is along a transform marginGondwana rotates clockwise causing more intense uplift in southern Appalachians Diagram from: http://csmres.jmu.edu/geollab/vageol/vahist/Allegeve.html
Pangaea North America Europe, Asia Africa South America Australia Antarctica 300 million to 200 million years ago
Atlantic Ocean Rifting of Pangaea began about 200 million years ago
BreakupofPangaea 200 Million Years Ago – formation of the Atlantic Ocean Watchung Ridges Palisade Sill From http://3dparks.wr.usgs.gov/nyc/mesozoic/mesozoicbasins.htm
Late Cretaceous 94 million years ago By Late Cretaceous, extensive river deltas had formed along east coast of North America
Maximum Extent of the Most Recent Continental Ice Sheet(about 20,750 years ago) FromUnited States Geologic Survey Mashomack
Long Island: Digital Elevation Map Note lines of hills in central Long Island and along North Shore. A smaller, but similar, area of hills is present on Shelter Island. Harbor Hill Moraine Peconic Bay Moraine Ronkonkoma Moraine From: NEW OBSERVATIONS ON THE GLACIAL GEOMORPHOLOGY OF LONG ISLAND FROM A DIGITAL ELEVATION MODEL (DEM) Bennington, J Bret, email@example.com Department of Geology 114 Hofstra University, Hempstead, NY 11549