Tectonic History of Long Island Glenn Richard Stony Brook University Map from:

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 Published by the University of the State of New York The geologic history of the region that includes Long Island is recorded in rocks throughout New York State and New England. Stony Brook

Continued Major Geologic Events in 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* History of the Long Island Area Tectonic Events along East Coast of what is now North America EventWhenDetails Grenvillian Orogeny1.1 billion years ago Magmatic arc Collision of Laurentia with Amazonia Supercontinent of Rodinia created High plateau like Tibet created Area affected extends to Mexico As bedrock eroded, plateau rose gradually due to isostasy In Adirondacks and Hudson Highlands, Grenville rocks at surface Grenville rocks below surface in much of eastern North America Formation of Iapetus Ocean 660 million years agoRifting Taconian Orogeny 450 million years ago Subduction zone forms in Iapetus Ocean Hartland volcanic island arc forms behind subduction zone The oceanic crust between the island arc and Laurentia subducts until the island arc collides with Laurentia Acadian Orogeny 380 million years ago Avalonia splits from Gondwana and becomes attached to Baltica Baltica included the land areas now bordering the Baltic Sea The collision of Baltica with Laurentia in the Silurian is the Caledonian Orogeny Caledonian Orogeny progresses south and becomes the Acadian Orogeny Alleghanian Orogeny 300 million years ago Oceanic crust between Avalonia and Gondwana is subducted The collision of Gondwana and Laurentia is along a transform margin Gondwana rotates clockwise causing more intense uplift in southern Appalachians Formation of Atlantic Ocean 200 million years ago Rifting initiates as a series of triple junctions In each case, one extension of the three halts, while the others continue Failed rifts: Newark Basin, Hartford Basin Atlantic Ocean continues to widen * Relating to, causing, or resulting from structural deformation of the earth's crust.

Grenville Orogeny 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. Mount Haystack from Mount Marcy in the Adirondacks 1.1 Billion Years Ago

Rifting of Rodinia 650 million years ago From “North America”

Diabase dike (650 mya) in western Adirondacks intruded during breakup of Grenville supercontinent.

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. 500 Million Years Ago: A Warm Shallow Sea

Taconian Orogeny Subduction zone forms in Iapetus Ocean Hartland volcanic island arc forms behind subduction zone The oceanic crust between the island arc and Laurentia subducts until the island arc collides with Laurentia Details: 450 million years ago – Hartland Island arc collides with Laurentia “North America” Hartland Gneiss

Acadian Orogeny 380 million years ago – Avalon collides with North America Avalonia splits from Gondwana and becomes attached to Baltica Baltica included the land areas now bordering the Baltic Sea The collision of Baltica with Laurentia in the Silurian is the Caledonian Orogeny Caledonian Orogeny progresses south and becomes the Acadian Orogeny Details:

Alleghenian Orogeny Oceanic crust between Avalonia and Gondwana is subducted The collision of Gondwana and Laurentia is along a transform margin Gondwana rotates clockwise causing more intense uplift in southern Appalachians 300 million years ago – Gondwana collides with Laurentia “North America” Details: Diagram from: Diagram represents a time prior to the collision

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

Breakup of Pangaea 200 Million Years Ago – formation of the Atlantic Ocean From Watchung Ridges Palisade Sill

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) From United States Geologic Survey Mashomack

Long Island: Digital Elevation Map From: NEW OBSERVATIONS ON THE GLACIAL GEOMORPHOLOGY OF LONG ISLAND FROM A DIGITAL ELEVATION MODEL (DEM) Bennington, J Bret, Department of Geology 114 Hofstra University, Hempstead, NY Note lines of hills in central Long Island and along North Shore. A smaller, but similar, area of hills is present on Shelter Island. Peconic Bay Moraine Ronkonkoma Moraine Harbor Hill Moraine