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Driving mechanisms of organic carbon burial in the Early Cretaceous South Atlantic Cape Basin (DSDP Site 361)

  • Extensive black shale deposits formed in the Early Cretaceous South Atlantic, supporting the notion that this emerging ocean basin was a globally important site of organic carbon burial. The magnitude of organic carbon burial in marine basins is known to be controlled by various tectonic, oceanographic, hydrological, and climatic processes acting on different temporal and spatial scales, the nature and relative importance of which are poorly understood for the young South Atlantic. Here we present new bulk and molecular geochemical data from an Aptian–Albian sediment record recovered from the deep Cape Basin at Deep Sea Drilling Project (DSDP) Site 361, which we combine with general circulation model results to identify driving mechanisms of organic carbon burial. A multimillion-year decrease (i.e., Early Aptian–Albian) in organic carbon burial, reflected in a lithological succession of black shale, gray shale, and red beds, was caused by increasing bottom water oxygenation due to abating hydrographic restriction via South Atlantic–Southern Ocean gateways. These results emphasize basin evolution and ocean gateway development as a decisive primary control on enhanced organic carbon preservation in the Cape Basin at geological timescales (> 1 Myr). The Early Aptian black shale sequence comprises alternations of shales with high (> 6 %) and relatively low (∼ 3.5 %) organic carbon content of marine sources, the former being deposited during the global Oceanic Anoxic Event (OAE) 1a, as well as during repetitive intervals before and after OAE 1a. In all cases, these short-term intervals of enhanced organic carbon burial coincided with strong influxes of sediments derived from the proximal African continent, indicating closely coupled climate–land–ocean interactions. Supported by our model results, we show that fluctuations in weathering-derived nutrient input from the southern African continent, linked to changes in orbitally driven humidity and aridity, were the underlying drivers of repetitive episodes of enhanced organic carbon burial in the deep Cape Basin. These results suggest that deep marine environments of emerging ocean basins responded sensitively and directly to short-term fluctuations in riverine nutrient fluxes. We explain this relationship using the lack of wide and mature continental shelf seas that could have acted as a barrier or filter for nutrient transfer from the continent into the deep ocean.
Metadaten
Author:Wolf DummannORCiDGND, Sebastian SteinigORCiDGND, Peter HofmannORCiD, Matthias LenzORCiDGND, Stephanie KuschORCiDGND, Sascha Flögel, Jens Olaf HerrleORCiDGND, Christian Hallmann, Janet Rethemeyer, Haino Uwe Kasper, Thomas Wagner
URN:urn:nbn:de:hebis:30:3-624225
DOI:https://doi.org/10.5194/cp-17-469-2021
ISSN:1814-9332
Parent Title (English):Climate of the past
Publisher:Copernicus
Place of publication:Katlenburg-Lindau
Document Type:Article
Language:English
Date of Publication (online):2021/02/19
Date of first Publication:2021/02/19
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2021/08/30
Volume:17
Issue:1
Page Number:22
First Page:469
Last Page:490
Note:
This research has been supported by the Deutsche Forschungsgemeinschaft (grant nos. HO2188/9 and HE3521/6).
HeBIS-PPN:489163742
Institutes:Geowissenschaften / Geographie / Geowissenschaften
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 4.0