Universität zu Köln

Hofmann, P. and Wagner, T. (2011). ITCZ controls on Late Cretaceous black shale sedimentation in the tropical Atlantic Ocean. Paleoceanography, 26. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 1944-9186

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Abstract

This study presents high resolution organic and inorganic proxy records for Coniacian to Santonian black shale on the Demerara Rise (ODP Site 1261) in the western tropical Atlantic off South America. We integrate these records with approximately time equivalent geochemical data from the eastern tropical Atlantic off tropical Africa (ODP Site 959) to extract the underlying relationships of Intertropical Convergence Zone (ITCZ) dynamics and black shale formation in the tropical Cretaceous Atlantic at orbital time scales. The geochemical records from the Demerara Rise show repetitive fluctuations in productivity, ocean redox conditions, and clastic sediment supply consistent with a dynamic paleo-upwelling regime off tropical South America. Upwelling intensity most likely was driven by shifts of the mean annual position of the ITCZ, which connects the large-scale precipitation and wind field patterns of the Hadley cells. Upwelling was strongest off South America and burial of oil-prone organic matter most pronounced when the ITCZ was in its southernmost position, which maximized the impact of NE trade winds on the inner, tropical part of the northern Hadley cell. Geochemical records from the Deep Ivorian Basin (equatorial Atlantic) suggest that source rock formation occurred in phase with regions north of the equator. Off tropical Africa, however, black shale formation was primarily driven by regional rainfall and nutrient export. The results of this study provide a conceptual framework that explains the formation, distribution and quality of petroleum source rocks below the tropical component of the Hadley cells on orbital time scales.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Hofmann, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wagner, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-483281
DOI:	10.1029/2011PA002154
Journal or Publication Title:	Paleoceanography
Volume:	26
Date:	2011
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	1944-9186
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language AFRICAN CLIMATE VARIABILITY; DEMERARA RISE; FORAMINIFERAL ASSEMBLAGES; ORGANIC-MATTER; TRACE-METALS; IVORY-COAST; RECORD; ACCUMULATION; TEMPERATURES; GLACIATION Multiple languages Geosciences, Multidisciplinary; Oceanography; Paleontology Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/48328