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 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
Event
When
Details
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
Grenvillian Orogeny
1.1 billion years ago
Formation of Iapetus
Ocean
660 million years ago
Rifting
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
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
Taconian Orogeny
Formation of Atlantic
Ocean
*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 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 – Avalon collides with North America
Details:
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
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 subducted
The collision of Gondwana and Laurentia is along a transform margin
Gondwana 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
Breakup
of
Pangaea
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)
From
United 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, geojbb@hofstra.edu
Department of Geology
114 Hofstra University, Hempstead, NY 11549