Chemical weathering and provenance evolution of Holocene–Recent sediments from the Western Indus Shelf, Northern Arabian Sea inferred from physical and mineralogical properties

Limmer, D. R., Köhler, C. M., Hillier, S., Moreton, S. G. , Tabrez, A. R. and Clift, P. D. (2012) Chemical weathering and provenance evolution of Holocene–Recent sediments from the Western Indus Shelf, Northern Arabian Sea inferred from physical and mineralogical properties. Marine Geology, 326-32, pp. 101-115. (doi: 10.1016/j.margeo.2012.07.009)

Abstract

We present a multi-proxy mineral record based on X-ray diffraction and diffuse reflectance spectrophotometry analysis for two cores from the western Indus Shelf in order to reconstruct changing weathering intensities, sediment transport, and provenance variations since 13 ka. Core Indus-10 is located northwest of the Indus Canyon and exhibits fluctuations in smectite/(illite + chlorite) ratios that correlate with monsoon intensity. Higher smectite/(illite + chlorite) and lower illite crystallinity, normally associated with stronger weathering, peaked during the Early–Mid Holocene, the period of maximum summer monsoon. Hematite/goethite and magnetic susceptibility do not show clear co-variation, although they both increase at Indus-10 after 10 ka, as the monsoon weakened. At Indus-23, located on a clinoform just west of the canyon, hematite/goethite increased during a period of monsoon strengthening from 10 to 8 ka, consistent with increased seasonality and/or reworking of sediment deposited prior to or during the glacial maximum. After 2 ka terrigenous sediment accumulation rates in both cores increased together with redness and hematite/goethite, which we attribute to widespread cultivation of the floodplain triggering reworking, especially after 200 years ago. Over Holocene timescales sediment composition and mineralogy in two localities on the high-energy shelf were controlled by varying degrees of reworking, as well as climatically modulated chemical weathering.

• Item Type: Articles
• Additional Information: The work was funded by a NERC studentship grant NE/G002029/1 for DL. The work was also supported by a grant from the International Association of Sedimentologists (IAS) for clay mineral analysis and a NERC facility grant for additional radiocarbon dates (NRCF allocation 1529.0311).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Moreton, Dr Steven
• Authors: Limmer, D. R., Köhler, C. M., Hillier, S., Moreton, S. G., Tabrez, A. R., and Clift, P. D.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Marine Geology
• Publisher: Elsevier
• ISSN: 0025-3227
• ISSN (Online): 1872-6151
• Published Online: 02 August 2012
• Copyright Holders: Copyright © 2012 Crown Copyright
• First Published: First published in Marine Geology 326-328:101-115
• Publisher Policy: Reproduced under a creative commons license