HR: 11:20h
AN: PP32A-05    [Abstracts]
TI: Structure of the Penultimate Deglaciation Along the California Margin and Implications for Milankovitch Theory
AU: * Cannariato, K G
EM: cannaria@usc.edu
AF: Earth Sciences, University of Southern California, Los Angeles, CA 90089 United States
AU: Kennett, J P
EM: kennett@geol.usc.edu
AF: Geological Sciences, University of California, Santa Barbara, CA 93106 United States
AU: Stott, L D
EM: stott@usc.edu
AF: Earth Sciences, University of Southern California, Los Angeles, CA 90089 United States
AB: Several studies have suggested that the penultimate deglaciation occurred earlier than Milankovitch theory predicts therefore calling into question the orbital theory of ice ages. Furthermore, the detailed structure and timing of Termination II is insufficiently defined yet critical for understanding mechanisms responsible for abrupt regional and global climate change. High-resolution climate records and a means to accurately date them independent of orbital tuning are necessary to address these issues. Here we present planktonic and benthic foraminiferal oxygen isotope records at unprecedented resolution encompassing late MIS 6 and Termination II ($\sim$150 to 120 ka) from Santa Barbara Basin (ODP Site 893) supported by additional southern California margin records (Sites 1017 and 1014), a region highly sensitive to global millennial-scale climate oscillations during the last deglaciation. These records reveal millennial- and centennial-scale climate variability throughout the interval including a prominent interstadial immediately preceding the deglaciation, a brief warm event near the beginning of Termination II, and a B$\o$lling-$\AA$ller$\o$d/Younger Dryas-like climate oscillation midway through the deglaciation. Previous work suggests the presence of millennial-scale variability over broad regions during TII including climate instability during late MIS 6 and a pause or climate oscillation during TII. Low-resolution Mg/Ca- and alkenone-derived temperature records from these sites indicate the relative timing within the sequence of local salinity and global ice volume changes. Few options exist for dating marine records during Termination II. They are typically tuned to orbital insolation, which precludes testing deglacial mechanisms. However, the distinct millennial-scale features of TII documented by the California margin records represent several widespread climate events that potentially could be correlated with well-dated high-resolution records elsewhere. For example, the $^{230}$Th-dated stalagmite oxygen isotope record from Dongge Cave, China appears to exhibit the same millennial-scale climate events as the California margin records during late MIS 6 and Termination II. This allows the adoption of the stalagmite radiometric chronology to the California margin records. This chronology supports the Milankovitch theory of deglaciation. The suborbital history of climate variability during Termination II may account for records of early deglaciation.
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting