Recent Studies Help Extend the Ultra-High-Resolution Global Climate Record from Santa Barbara Basin Back to Pliocene Time

C. Nicholson¹, J. P. Kennett¹, R. J. Behl², C. C. Sorlien¹, and the R/V Melville SBCore Team
¹University of California, Santa Barbara, CA, [email protected], [email protected], [email protected]
²California State University, Long Beach, CA, [email protected]

Santa Barbara Basin provides one of the highest-resolution marine climate records of the late Quaternary ever recovered. 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 and uniform (~1 m/kyr over time spans of 1 yr to 1 Myr), and unaffected by orbital through millennial climatic oscillations. Unfortunately, ODP Site 893 drilled in 1992 to 200 mbsf only extends to ~160 ka. Detailed mapping of multichannel seismic (MCS) reflection and chirp data and stratigraphic correlation with existing well data indicate that continuous Quaternary strata 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, 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. Four glacial termination records were also obtained. In November 2008, a 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 Transition (~800 ka to 1.2 Ma). Results confirm the viability of proposed deeper coring by the Integrated Ocean Drilling Program to recover a continuous, complete ultra-high-resolution global climate record back to at least ~2 Ma.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009