Testing chemical weathering proxies in Miocene–Recent fluvial-derived sediments in the South China Sea

Author:

Hu Dengke1,Clift Peter D.2,Wan Shiming3,Böning Philipp4,Hannigan Robyn5,Hillier Stephen6,Blusztajn Jerzy7

Affiliation:

1. Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences, Guangzhou 510301, China

2. Department of Geology and Geophysics and Coastal Studies Institute, Louisiana State University, Baton Rouge, LA 70803, USA

3. Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China

4. Institute of Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, P.O. Box 2503, D-26111 Oldenburg, Germany

5. Department of Environmental, Earth and Ocean Sciences, University of Massachusetts-Boston, Boston, MA 02125, USA

6. The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK

7. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

Abstract

AbstractReconstructing variations in the intensity of chemical weathering in river basins is crucial if we are to understand how climate change impacts environment and whether there are feedbacks between climate and weathering processes. Quantifying chemical weathering is, however, a complicated process, involving a number of competing proxies. We compare weathering records from the Pearl River delta of southern China and Ocean Drilling Program (ODP) Sites 1144 and 1146 on the northeastern slope of the South China Sea in order to test which proxies are the most widely applicable and robust. Comparison with speleothem rainfall records indicates that K/Al tracks precipitation variations most closely and out-performs the widely used Chemical Index of Alteration (CIA). Correlation of K/Al and kaolinite/illite indicates that this clay ratio is also an effective proxy of weathering intensity across all sites and timescales. Kaolinite/smectite, and to a lesser extent smectite/(illite+chlorite), are also indicative of weathering intensity, but show more scatter between sites that may be linked to provenance effects. Mg/Al is relatively immune to grain-size effects, but does not correlate well with other proxies. K/Rb is a reasonably reliable indicator of chemical weathering intensity and may be more sensitive than CIA or K/Al to weathering changes over short timescales and when weathering is not too intense. 87Sr/86Sr can be useful but can be influenced by both grain size and provenance effects. In general marine archives of fluvial sediment may record variations in weathering linked to climate, but these are increasingly signals of reworking going further offshore.

Publisher

Geological Society of London

Subject

Geology,Ocean Engineering,Water Science and Technology

Reference69 articles.

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