Geological Society of America

36 Marine Anoxia over Geologic Time—Where, When, Why, and Cause and Effect Relationships to the Evolving Biosphere I

Wednesday, 10 August 2005
9:00 AM - 12:00 PM

MID-CRETACEOUS CLIMATE AND ANOXIA IN THE OCEAN - DYNAMICS AND EFFECTS OF LAND-OCEAN INTERACTION DURING PERIODS OF EXTREM WARMTH

Paper number: 36-3
Program: THEME SESSIONS
Time: 10:00 AM – 10:20 AM

Authors

Thomas Wagner Presenting Author
University of Newcastle upon Tyne, Newcastle upon Tyne, N/A
Sascha Floegel
IFM-GEOMAR Leibniz Institute for Marine Sciences, Kiel, N/A
Peter Hofmann
University of Cologne, Cologne, N/A
Jaap S. Sinninghe Damsté
Netherlands Institute for Sea Rsch, Den Burg, Texel, N/A

Abstract

Continental margins are sensitive to climate change. As future global warming will affect human life and ecosystems specifically along coastal areas and continental margins with their associated sub-basins understanding the impact of climate change during greenhouse conditions is essential for all disciplines of the society. To improve our understanding it is indispensable to provide new high-resolution, multi-disciplinary records from past periods of extreme warmth. Recent research on the dynamics of the Mid-Cretaceous climate-ocean system emphasize the importance of processes associated with the Land-Ocean Interaction on the formation of organic carbon-rich sediments, i.e. marine black shale, and thus on the marine carbon cycle. The underlying causes and effects that operated during periods of black shale formation, commonly referred to as Oceanic Anoxic Events (OAE's), are still poorly constrained, especially for the impact of orbital forcing. This external control however essentially determined the temporal relationships of continental climate dynamics and the structure of ocean circulation.

High-resolution, geochemical, isotopic, and molecular records from the low-latitude Atlantic are presented that constrain the effects of orbital-driven fluctuations in African climate on ocean productivity and chemistry, and black shale formation along the continental margins of the evolving Equatorial Atlantic Gateway and NW-Africa. Marine records from ODP Sites and coastal outcrops in southern Morocco (Tarfaya) cover critical periods of Mid-Cretaceous extreme warmth and thus help to improve our understanding of regional and global controls on tropical African climate, hydrological cycling and continental run-off, and the associated response in the tropical Atlantic. Coupling of geological records with global climate modelling provide a substantial progress in assessing and understanding controls of rapid change during past extreme warmth and its possible impact on coastal areas and continental margins.