Palisades Sill

rock unit, United States

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July 1, 2026

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The Palisades Sill is a geological formation composed of basaltic rock that forms the bluffs along the west side of the Hudson River in southeastern New York and northeastern New Jersey. These bluffs, ranging from 200 to 540 feet (60 to 165 meters) in height, were created by the slow cooling of molten material near the end of the Triassic Period, approximately 252 to 201 million years ago. The term "Palisades" itself is now commonly used to describe such columnar cliff formations. The area is overseen by the Palisades Interstate Park Commission, which manages park units and the Palisades Interstate Parkway.1

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Triassic Period
Igneous rocks
The well-known Palisades Sill of the Newark Supergroup was formerly regarded as Triassic in age, but this diabase intrusion, which is 300 metres (1,000 feet) thick, has yielded a potassium-argon age of 193 million years, indicating an Early Jurassic origin.
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The well-known Palisades Sill of the Newark Supergroup was formerly regarded as Triassic in age, but this diabase intrusion, which is 300 metres (1,000 feet) thick, has yielded a potassium-argon age of 193 million years, indicating an Early Jurassic origin.
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gabbro
; the Palisades, New Jersey; and many of the Karoo (Karroo) diabases in South Africa.
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; the Palisades, New Jersey; and many of the Karoo (Karroo) diabases in South Africa.
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