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Sedimentary and geochemical evolution of the Dras forearc basin, Indus Suture, Ladakh Himalaya, India

P. D. Clift, P. J. Degnan, R. Hannigan and J. Blusztajn
Sedimentary and geochemical evolution of the Dras forearc basin, Indus Suture, Ladakh Himalaya, India (in Special focus on the Himalaya, John W. Geissman (editor) and Allen F. Glazner (editor))
Geological Society of America Bulletin (March 2000) 112 (3): 450-466

Abstract

The Nindam Formation of the Indus suture zone represents the forearc basin to the Dras-Kohistan volcanic arc, which was generated in an intraoceanic setting during mid-Cretaceous time, and accreted to the margin of Eurasia during Late Cretaceous time. The Nindam Formation comprises volcaniclastic sediment and pelagic carbonate deposited in cyclic influxes of high-density, sheet-like turbidites, with locally well-defined channel morphologies. Debris-flow deposits as much as 5 m thick that rework older material are volumetrically <5% of the sequence. A fine-grained basal section is succeeded by several hundred meters of cyclic sandy turbidites, and finally a more shaley top. This large-scale variation may be linked to tectonic controls on arc activity, while individual sandy packages 50-100 m thick are inferred to have a glacioeustatic origin. Sedimentation mirrors similar patterns observed in the modern Mariana and Tonga forearcs. The lack of major unconformities and large-scale reworking suggests that the volcaniclastic sedimentary rocks should form a relatively complete record of geochemical change in the arc source. The sediment trace- and rare earth element (REE) signature is similar to that of the Dras and Chalt volcanic rocks erupted at the volcanic front during the intraoceanic phase of activity and is distinct from the Kardung Volcanic Group erupted during the continental arc phase, following collision with the Eurasian margin. Nd isotopes also support an intraoceanic origin. The sedimentary rocks show either no or slight light REE enrichment, similar to modern sediments from the Mariana arc, as well as the volcanic and intrusive core of the Dras-Kohistan Arc. The overall chemistry of the Dras-Kohistan Arc is thus more depleted in light REE than continental crust. Our data do not support models that propose continental crust being formed along intraoceanic active margins.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 112
Serial Issue: 3
Title: Sedimentary and geochemical evolution of the Dras forearc basin, Indus Suture, Ladakh Himalaya, India
Title: Special focus on the Himalaya
Author(s): Clift, P. D.Degnan, P. J.Hannigan, R.Blusztajn, J.
Author(s): Geissman, John W.editor
Author(s): Glazner, Allen F.editor
Affiliation: Woods Hole Oceanographic Institution, Woods Hole, MA, United States
Affiliation: University of New Mexico, Department of Earth and Planetary Sciences, Albuquerque, NM, United States
Pages: 450-466
Published: 200003
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 88
Accession Number: 2000-021922
Categories: Geochemistry of rocks, soils, and sedimentsSedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 200033; Woods Hole Oceanogr. Inst., Contrib. No. 9950
Illustration Description: illus. incl. sects., 2 tables, geol. sketch maps
N34°00'00" - N34°30'00", E76°15'00" - E77°15'00"
Secondary Affiliation: University of North Carolina, USA, United StatesUnited Kingdom Nirex, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200007
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