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Book Chapter

The northern suture in the Shigar valley, Baltistan, northern Pakistan

By
Carl R. Hanson
Carl R. Hanson
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Published:
January 01, 1989

The Shigar Valley is crossed by a large, southwest-verging reverse fault containing pods of serpentinized ultramafic rock; the fault is correlated with the Northern Suture, which separates Paleozoic shelf-type sedimentary rocks of the Asian plate from Cretaceous volcanic rocks of the Ladakh-Kohistan arc. In the Shigar valley, the Asian plate is represented by a series of folded schists and marbles (the Daltumbore Formation) that is faulted southward over metasedimentary rocks and volcaniclastics (the Bauma-Harel Formation) belonging to the volcanic arc. Cretaceous turritellid gastropod fossils were found in the Bauma-Harel Formation. Metamorphism on both sides of the suture occurred in a regime of high temperature but only low to moderate pressure. Metamorphic isograds are cut by the suture, so metamorphism must have occurred before faulting along the suture. Two main phases of igneous intrusion are exposed in the arc terrane: a pre-tectonic, possibly tholeiitic phase about 100 m.y. old, and a post-tectonic, calc-alkaline to subalkaline phase 40 to 60 m.y. old. The Northern Suture does not have the appearance of a major suture, but the Ladakh-Kohistan Arc seems to have been a separate plate from the Asian continent. The suture probably marks the closure of a small ocean basin in late Cretaceous to early Eocene time.

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GSA Special Papers

Tectonics of the western Himalayas

Lawrence L. Malinconico, Jr.
Lawrence L. Malinconico, Jr.
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Robert J. Lillie
Robert J. Lillie
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Geological Society of America
Volume
232
ISBN print:
9780813722320
Publication date:
January 01, 1989

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