Selective preservation of organic matter in marine environments; processes and impact on the sedimentary record
- 1Fachbereich 5 – Geowissenschaften, Postfach 330440, 27412 Bremen, Germany
- 2Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
- 3Woods Hole Oceanographic Institution, Fye 111, MS#4, Woods Hole, Ma. 02543, USA
- 4Zentrum für Meeres- und Klimaforschung, Universität Hamburg, Bundesstraße 55, 20146 Hamburg, Germany
- 5University of Washington, School of Oceanography, P.O. Box 355351, Seattle, WA 98195, USA
- 6Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790AB, Den Burg, The Netherlands
- 7Geochemistry, Faculty of Geosciences, Utrecht University P.O. Box 80.021, 3508 TA Utrecht, The Netherlands
- 8Institute of Environmental Biology, Faculty of Science, Utrecht University, The Netherlands
- 9Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology, P.O. Box 140, 4400 AC Yerseke, The Netherlands
- 10College of Oceanic and Atmospheric Sciences, COAS Administration Building 104, Oregon State University, Corvallis, OR 97331-5503, USA
- 11Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA
Abstract. The present paper is the result of a workshop sponsored by the DFG Research Center/Cluster of Excellence MARUM "The Ocean in the Earth System", the International Graduate College EUROPROX, and the Alfred Wegener Institute for Polar and Marine Research. The workshop brought together specialists on organic matter degradation and on proxy-based environmental reconstruction. The paper deals with the main theme of the workshop, understanding the impact of selective degradation/preservation of organic matter (OM) in marine sediments on the interpretation of the fossil record. Special attention is paid to (A) the influence of the molecular composition of OM in relation to the biological and physical depositional environment, including new methods for determining complex organic biomolecules, (B) the impact of selective OM preservation on the interpretation of proxies for marine palaeoceanographic and palaeoclimatic reconstruction, and (C) past marine productivity and selective preservation in sediments.
It appears that most of the factors influencing OM preservation have been identified, but many of the mechanisms by which they operate are partly, or even fragmentarily, understood. Some factors have not even been taken carefully into consideration. This incomplete understanding of OM breakdown hampers proper assessment of the present and past carbon cycle as well as the interpretation of OM based proxies and proxies affected by OM breakdown.
To arrive at better proxy-based reconstructions "deformation functions" are needed, taking into account the transport and diagenesis-related molecular and atomic modifications following proxy formation.
Some emerging proxies for OM degradation may shed light on such deformation functions. The use of palynomorph concentrations and selective changes in assemblage composition as models for production and preservation of OM may correct for bias due to selective degradation. Such quantitative assessment of OM degradation may lead to more accurate reconstruction of past productivity and bottom water oxygenation.
Given the cost and effort associated with programs to recover sediment cores for paleoclimatological studies, as well as with generating proxy records, it would seem wise to develop a detailed sedimentological and diagenetic context for interpretation of these records. With respect to the latter, parallel acquisition of data that inform on the fidelity of the proxy signatures and reveal potential diagenetic biases would be of clear value.