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The Great Unconformity exposed in the Grand Canyon. The Vishnu schist
below is ~1.7by overlain by the Tapeats Sandstone ~530my
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ATTRIBUTES OF GEOSYNCLINES
FROM P.B. KING
•
They form during sedimentation rather that afterwards. They are sedimentary
features as opposed to deformational features.
•
They from as a gradual process.
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They are NOT ordinary synclinal folds.
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They are sedimentary basins that formed under tectonic control.
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Subsidence is not a necessary consequence of sedimentation, but an
independent process. Sedimentation can cause some subsidence.
•
They commonly occur along the margins of Continental Platforms. There is
much variation in tectonic settings including:
1.
coastal interior, continental shelf, slope and rise
2.
deep sea trenches, island arcs, accretionary wedges and ocean floors
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Sediments of geosynclines are varied! No one suite is exclusively
Geosynclinal. Some have shallow water sediments and some have deep water
sediments. The term “Geocline” is often used.
•
Sediments often get deformed, metamorphosed and plutonized
Geocline
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Geocline
The Wilson Cycle
The cyclical opening and closing of ocean basins caused
by movement of the Earth's plates. The Wilson cycle
begins with a rising plume of magma and the thinning of
the overlying crust.
As the crust continues to thin due to extensional tectonic
forces, an ocean basin forms and sediments accumulate
along its margins.
Subsequently subduction is initiated on one of the ocean
basin's margins and the ocean basin closes up. When
the crust begins to thin again, another cycle begins.
The Wilson cycle is named after the Canadian
geophysicist J. Tuzo Wilson (1908-1993).
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• Klamath Mnts
(McCloud and
Tethyan Fauna)
• Paleozoic Rocks
in other
provinces:
• Coast Range
• Transverse
Range
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