Timing and Paleoceanography of Early Cretaceous Oceanic Anoxic Events in the Pacific Ocean as Determined From Wireline Logs
Abstract
DSDP and ODP core recovery of Early Cretaceous pelagic sediments in the Pacific Ocean has been limited by the widespread occurrence of chert. Remarkably, Leg 198 of the Ocean Drilling Program (Shatsky Rise, north west Pacific) was very successful in recovering shales rich in organic-carbon, dated as being equivalent to the Early Aptian "Selli Level", thus confirming the truly global nature of Oceanic Anoxic Event 1a. However, recovery of contiguous deposits of late Aptian and Albian age was generally poor. Two of three sites at which OAE1a was recovered (1207 and 1213) were logged using standard downhole geophysical tools, which provide us with an alternative method for investigating the sedimentary and paleoceanographic history of these sites. Using the downhole logs we present an interpretation of the Aptian-Albian sedimentary history of Shatsky Rise and discuss the paleoceanographic implications of changing abundances of clay, carbonate and biosiliceous sediments. Plotting the geophysical logging data against time yields interesting information about the onset, duration and termination of organic-carbon burial. Comparison with logging and biostratigraphic data from other sites in the Pacific and Tethys allows us to assess whether OAE1a was truly synchronous and to evaluate differences in paleoceanography in different ocean basins during OAE1a.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFMPP41B0836R
- Keywords:
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- 4267 Paleoceanography;
- 5100 PHYSICAL PROPERTIES OF ROCKS;
- 9355 Pacific Ocean