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A New Seismic Stratigraphy in the Indian-Atlantic Ocean Gateway Resembles Major Paleo-Oceanographic Changes of the Last 7 Ma

Gruetzner, Jens and Hines, S. K. V. (2019) A New Seismic Stratigraphy in the Indian-Atlantic Ocean Gateway Resembles Major Paleo-Oceanographic Changes of the Last 7 Ma. Geochemistry Geophysics Geosystems, 20 (1). pp. 339-358. ISSN 1525‐2027. http://resolver.caltech.edu/CaltechAUTHORS:20190307-080503704

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Abstract

The exchange of water masses between the Indian Ocean and the Atlantic constitutes an integral interocean link in the global thermohaline circulation. Long‐term changes in deep water flow have been studied using seismic reflection profiles but the seismic stratigraphy was poorly constrained and not resolved for the time period from the late Miocene onward. Here we present results from International Ocean Discovery Program Site U1475 (Agulhas Plateau) located over a sediment drift proximal to the entrance of North Atlantic Deep Water into the Southern Ocean and South Indian Ocean. Site U1475 comprises a complete carbonate‐rich stratigraphic section of the last ~7 Ma that provides an archive of climate‐induced variations in ocean circulation. Six marker reflectors occurring in the upper 300 m of the drift are identified here for the first time. The formation of these reflectors is mainly due to density changes that are mostly caused by changes in biogenic versus terrigenous sediment deposition. Synthetic seismograms allow age assignments for the horizons based on biostratigraphy and magnetostratigraphy. Prominent reflectors are related to late Pleistocene glacial/interglacial variability, the middle and early Pleistocene transitions, and the onset of the northern hemisphere glaciation. A peculiar early Pliocene interval (~5.3–4.0 Ma) bounded by two reflectors is characterized by fourfold elevated sedimentation rates (>10 cm/kyr) and the occurrence of sediment waves. We argue that this enhanced sediment transport to the Agulhas Plateau was caused by a reorganization of the bottom current circulation pattern due to maximized inflow of North Atlantic Deep Water.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2018GC007668DOIArticle
https://doi.org/10.1594/PANGAEA.896810DOIData
ORCID:
AuthorORCID
Gruetzner, Jens0000-0001-5445-2393
Hines, S. K. V.0000-0001-9357-6399
Additional Information:© 2018 American Geophysical Union. Received 7 MAY 2018; Accepted 14 DEC 2018; Accepted article online 21 DEC 2018; Published online 16 JAN 2019. We acknowledge the work of the crew, technicians, and scientific staff of IODP Expedition 361. This research used samples and data provided by the International Ocean Discovery Program (IODP). Funding was provided by the Deutsche Forschungsgemeinschaft (DFG) under contract Ue 49/17. Comments by Andrew Green and an anonymous reviewer greatly improved our manuscript. The data reported here are available through the Pangaea database (https://doi.org/10.1594/PANGAEA.896810).
Funders:
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)Ue 49/17
Subject Keywords:Agulhas Plateau; seismic reflection method; contourites; physical properties
Record Number:CaltechAUTHORS:20190307-080503704
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190307-080503704
Official Citation:Gruetzner, J., Jiménez Espejo, F. J., Lathika, N., Uenzelmann‐Neben, G., Hall, I. R., Hemming, S. R., et al. (2019). A new seismic stratigraphy in the Indian‐Atlantic Ocean gateway resembles major paleo‐oceanographic changes of the last 7 Ma. Geochemistry, Geophysics, Geosystems, 20, 339–358. https://doi.org/10.1029/2018GC007668
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:93608
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:07 Mar 2019 16:21
Last Modified:07 Mar 2019 16:21

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