Extraordinary transport and mixing of sediment across Himalayan central Gondwana during the Cambrian–Ordovician
Paul M. Myrow1,*, Nigel C. Hughes2,†, John W. Goodge3, C. Mark Fanning4, Ian S. Williams4, Shanchi Peng5, Om N. Bhargava6, Suraj K. Parcha7 and Kevin R. Pogue8
-Author Affiliations
1Department of Geology, Colorado College, Colorado Springs, Colorado 80903, USA
2Department of Earth Sciences, University of California, Riverside, California 92521, USA
3Department of Geological Sciences, University of Minnesota–Duluth, Duluth, Minnesota 55812, USA
4Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
5State Key Laboratory on Paleobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Nanjing 210008, China
6103 Sector 7, Panchkula, Harayana 160020, India
7Wadia Institute of Himalayan Geology, Dehra Dun, Uttranchal 248001, India
8Department of Geology, Whitman College, Walla Walla, Washington 99362, USA
*E-mail: pmyrow@coloradocollege.edu
†E-mail: nigel.hughes@ucr.edu
Abstract
Detrital zircon samples from Cambrian and Lower to Middle Ordovician strata were taken across and along the strike of the Himalaya from Pakistan to Bhutan (∼2000 km). By sampling rocks from one time interval for nearly the entire length of an orogen, and by covering a range of lithotectonic units, we minimize time as a significant source of variance in detrital age spectra, and thus obtain direct assessment of the spatial variability in sediment provenance. This approach was applied to the Tethyan margin of the Himalaya, which during the Cambrian occupied a central depositional position between two major mountain belts that formed during the amalgamation of Gondwana, the internal East African orogen and the external Ross-Delamerian orogen of East Gondwana. Detrital age spectra from our Lesser and Tethyan Himalayan samples show that well-mixed sediment was dispersed across at least 2000 km of the northern Indian margin. The detrital zircon age spectra for our samples are consistent with sources for most grains from areas outside the Indian craton that record Pan-African events, such as the Ross-Delamerian orogen; East African orogen, including the juvenile Arabian-Nubian Shield; and Kuunga-Pinjarra orogen. The great distances of sediment transport and high degree of mixing of detrital zircon ages are extraordinary, and they may be attributed to a combination of widespread orogenesis associated with the assembly of Gondwana, the equatorial position of continents, potent chemical weathering, and sediment dispersal across a nonvegetated landscape.
Received 1 July 2009.
Revision received 4 November 2009.
Accepted 19 November 2009.
© 2010 Geological Society of America
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