CGS Monthly Meeting

Tuesday, September 16, 2008

Using Active Tectonics to Extend the Amazing Santa Barbara Basin Record a Million Years Further Back in Time

by:

Dr. Richard Behl
California State University Long Beach

Co-authors: Craig Nicholson, James Kennett, and Christopher Sorlien
(all UC Santa Barbara) 

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Abstract: Ocean Drilling Program (ODP) Site 893, located in Santa Barbara Basin, has provided one of the highest-resolution continuous climate records of the late Quaternary being studied from the world's oceans. Isotopic, microfossil and sedimentologic analyses of these sediments reveal a remarkable correlation of climate change between Santa Barbara Basin and the high-resolution Greenland ice cores since 70 ka, and extreme climate variability in coastal California. The Santa Barbara record indicates that the atmosphere and oceans respond both rapidly and dynamically to short-term climatic oscillations. ODP Site 893 also provides the highest resolution marine record in the world to date for the penultimate deglaciation and has contributed to new hypotheses about greenhouse amplification of climate change. The paleoclimate records from Santa Barbara Basin are so detailed because the basin’s unique geologic, tectonic, and oceanographic setting has resulted in a relatively small well-defined bathymetric basin that has proven highly sensitive to changes in global climate and ocean fluctuations.

Unfortunately, ODP Site 893 was only drilled to a depth of 200 meters below the seafloor, which goes back to ~160 ka.

Santa Barbara Basin is situated in the middle of a young, active fault-and-fold belt, and much of this deformation is <1 Ma. The global climate record produced and preserved in the basin is present in large part because of the basin’s unique location within this tectonically active region. Where most paleoceanographers avoid areas of tectonic disruption, we have embraced them. Detailed mapping of high-resolution multichannel seismic (MCS) reflection data and stratigraphic correlation with existing well data, indicate that continuous Quaternary strata originally deposited in the deep basin were subsequently uplifted, folded, and in places eroded across young, active fault-related fold structures in the eastern Santa Barbara Channel. These older strata are exposed at or near the seafloor, where they are now accessible to piston coring. In 2005, we were able to systematically recover substantial sections of many of these older late-Quaternary sedimentary sequences back to about 700 ka. We now intend to use this methodology to extend the spot record back to 1.2 Ma, to test the hypothesis that climatic sensitivity to high-frequency oscillations developed at the Mid-Pleistocene Transition (~800 ka) and to make the case for continuous coring by the new Integrated Ocean Drilling Project.

Biography: Dr. Richard J. (Rick) Behl is Professor of Geological Sciences at California State University Long Beach, where he is also on the faculty of the Environmental Sciences and Policy program, and a founding member of the Institute for Integrated Research in Materials, Environment, and Society (IIRMES), a teaching and research consortium of geologists, archaeologists, and biologists. Behl earned his Bachelors degree from UC San Diego, his PhD at UC Santa Cruz, and was a Post-Doctoral Fellow at UC Santa Barbara. He has participated in numerous international ocean coring expeditions, consults for the petroleum industry, and was an AAPG Distinguished Lecturer and President of the Pacific Section SEPM. His expertise is in sedimentary geology, particularly as it relates to the climatic, oceanographic, and tectonic evolution of the California margin and the Pacific Ocean. Behl’s research focuses on the Quaternary Santa Barbara Basin and the Miocene Monterey Formation.

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