Bioturbational structures record environmental changes in the upwelling area off Vietnam (South China Sea) for the last 150,000years

Wetzel, Andreas, Tjallingii, Rik, Wiesner, Martin G. and Stattegger, Karl (2011) Bioturbational structures record environmental changes in the upwelling area off Vietnam (South China Sea) for the last 150,000years Palaeogeography, Palaeoclimatology, Palaeoecology, 311 (3-4). pp. 256-267. DOI 10.1016/j.palaeo.2011.09.003.

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Abstract

The sediments in the upwelling area off central Vietnam are totally bioturbated and display a low-diverse assemblage of bioturbational structures. During interglacial times (Marine Isotope Stage MIS 1, 5a, 5c, 5e), summer monsoon leads to pronounced upwelling and seasonally pulsed arrival of organic matter on the seafloor. These deposits are characterized by a 4-tier bioturbated zone with Zoophycos. Zoophycos producers used this seasonal food source and show a cache behavioral strategy. During glacial periods upwelling was weak and oxygenation of bottom water decreased as evidenced by bioturbational structures that show a decrease in size, penetration depth and diversity. Enlarged freshwater influx during glacial times fuelled primary production and led to estuarine circulation. The resultant oxygen minimum layer favored an increased deposition of organic matter that in turn affected sediment properties. During MIS 2 and 5b oxygenation was probably a little lower than today. During MIS 3 and 5d Chondrites-like burrows point to a stronger oxygen deficiency. During MIS 4 bottom water oxygenation was even lower and only biodeformational structures occur in soft sediment rich in benthic food. Based on these findings an ichnofabric model for food-rich, fairly soft deposits experiencing oxygen deficiency is suggested having biodeformational structures as low-oxygen end member.

Document Type: Article
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1016/j.palaeo.2011.09.003
ISSN: 00310182
Projects: Future Ocean
Date Deposited: 14 Apr 2017 11:33
Last Modified: 14 Apr 2017 11:33
URI: http://eprints.uni-kiel.de/id/eprint/37572

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