The evolution of early diagenetic processes at the Mozambique margin during the last glacial-interglacial transition

Type Article
Date 2021-05
Language English
Author(s) Zindorf Mark Sebastian1, Rooze Jurjen2, Meile Christof2, März Christian3, Jouet GwenaelORCID4, Newton Robert3, Brandily Christophe1, Pastor Lucie1
Affiliation(s) 1 : Laboratoire Environnement Profond, Ifremer - Centre de Bretagne, 29280 Plouzané, France
2 : Department of Marine Sciences, The University of Georgia, Athens, GA 30602, USA
3 : School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
4 : Unité Géosciences Marines, Ifremer - Centre de Bretagne, 29280 Plouzané, France
Source Geochimica Et Cosmochimica Acta (0016-7037) (Elsevier BV), 2021-05 , Vol. 300 , P. 79-94
DOI 10.1016/j.gca.2021.02.024
WOS© Times Cited 3
Keyword(s) Mozambique margin, Reactive transport modeling, Sulfate-methane transition zone, Non-steady state early diagenesis, Authigenic pyrite
Abstract

The Mozambique continental margin experienced large variations in sedimentation rates, primarily due to re-routing of sediment deposition from the Zambezi River during the last glacial-Holocene transition. As changes in sediment accumulation and organic matter deposition impose a strong control on the formation of authigenic minerals in the sediment, the distribution of these minerals may reflect the regional paleoenvironmental and paleoclimatic evolution. Combining geochemical analyses of porewaters and sediments with a reactive transport modeling approach, we reconstruct the depositional history and its effect on pyrite formation and other biogeochemical transformations at a site on the Mozambique margin over the past 27 kyr. Fitting the model to match the observed geochemical patterns, most importantly authigenic pyrite, allowed for the reconstruction of past sulfate-methane transition zone depth, which migrated in response to changes in the sediment accumulation and organic matter deposition. Changes in sediment deposition quickly affected organoclastic sulfate reduction and associated pyrite formation, but the effect on anaerobic methane oxidation and subsequent pyrite formation occurred with a lag on the order of thousands of years. Model results reveal a transition from high diagenetic reaction rates representative of near-shore depositional environments during the late glacial maximum, to a setting typical of offshore sediments with low reaction rates at the present day. Notably, the remnants of methane and dissolved iron pools produced in the past still shape the diagenetic processes at and below the sulfate-methane transition zone today. Since deglacial shelf-flooding and corresponding changes in sediment deposition occurred along continental margins worldwide, our analysis highlights the important role of non-steady state diagenesis in continental margin sediments and its relevance for paleoceanographic interpretation of sediment cores experiencing strong variations in sediment input.

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Zindorf Mark Sebastian, Rooze Jurjen, Meile Christof, März Christian, Jouet Gwenael, Newton Robert, Brandily Christophe, Pastor Lucie (2021). The evolution of early diagenetic processes at the Mozambique margin during the last glacial-interglacial transition. Geochimica Et Cosmochimica Acta, 300, 79-94. Publisher's official version : https://doi.org/10.1016/j.gca.2021.02.024 , Open Access version : https://archimer.ifremer.fr/doc/00682/79360/