CGS Monthly Meeting

Tuesday, March 16, 2010

 

High-Resolution Seismic Imaging, Basin Sedimentation and Paleoclimate Studies to Further Investigate the Remarkable Santa Barbara Basin Record

by

Craig Nicholson¹, Richard Behl², James Kennett¹, Christopher Sorlien¹, Sara Afshar², Courtney Marshall², Carlye Peterson², Lorraine Lisiecki³, Mike Barth⁴ and the SBCore Team

Abstract:  Santa Barbara Basin provides one of the highest-resolution paleoclimate records of the late Quaternary ever recovered from the world’s oceans. Its unique geologic, tectonic, and oceanographic setting has resulted in a small well-defined bathymetric basin that has proven highly sensitive for recording detailed changes in global climate and at a resolution similar to Greenland ice cores. Over much of the basin, sedimentation rates are remarkably high (>1 m/kyr), exhibit a relatively constant spatial pattern defined by local tectonics, and are largely unaffected by orbital through millennial-scale climatic oscillations. Multichannel seismic (MCS) reflection and industry well data indicate that, in several areas, continuous, late-Quaternary sediments deposited in the deep paleobathymetric basin were subsequently uplifted, folded, and in places eroded across various young, active fault-related fold structures. These older strata were mapped in 3D to seafloor outcrop, where they are now accessible to piston coring. In 2005, we were able to systematically recover substantial sections of these older sequences back to ~700 ka. Oxygen isotopic studies confirm the presence of millennial and sub-millennial-scale climatic oscillations similar to those that mark the latest Quaternary. This includes abrupt decadal-scale warming events (both onset and termination), climate flickering, and––in our ~700 ka core––a remarkably periodic (~1200 yr) millennial-scale climate oscillation never before observed owing to the previous lack of paleoclimate records of sufficient age and resolution. In several cores, sediment material properties, including acoustic impedance, density and total organic carbon exhibit a remarkable correlation with inferred paleoclimate oscillations. This correlation suggests that basin-scale variations in sediment composition and fabric produced by climatic forcing during deposition are surprisingly still well preserved, and that geophysical techniques like seismic profiling and core logs may provide valuable preliminary estimates of past climate behavior and the quality of the potential core record prior to conducting more extensive, labor-intensive isotopic analyses. In November 2008, a second, high-resolution MCS site survey and piston coring cruise was conducted to further extend this remarkable record and to test the basin’s continued sensitivity to global high-frequency climatic oscillations back through the Mid-Pleistocene Climate Transition (~800 ka to 1.2 Ma). Results confirm the viability of proposed deeper coring by the Integrated Ocean Drilling Program (IODP) to recover a continuous, complete ultra-high-resolution global climate record back to about 1.6 Ma.

 

¹ Marine Science Institute, UC Santa Barbara

² Department of Geological Sciences, CSU Long Beach

³ Department of Earth Sciences, UC Santa Barbara

⁴ Sub-Sea Systems, Inc., Ventura

 

Biography:  Craig Nicholson has degrees from Amherst College, St. Louis University and Columbia University.  His primary areas of research are earthquakes, active faulting and tectonics.  His current research involves mapping the distribution of active faults, folds and sedimentary basins offshore of southern California, and most recently, helping fellow geologists extend the high-resolution global climate record located in Santa Barbara Basin.  Craig is a Research Geophysicist with the Marine Science Institute and Adjunct Associate Professor with the Department of Earth Science at UCSB, where he has been since 1988.