Oxygen isotope composition of benthic and planktonic foraminifera from ODP Holes 146-893A and 167-1017B

The detailed structure and timing of the penultimate deglaciation are insufficiently defined yet critical for understanding mechanisms responsible for abrupt climate change. Here we present oxygen isotope records (from planktonic and benthic foraminifera) at unprecedented resolution encompassing late marine oxygen isotope stage (MIS) 6 and Termination II (ca. 150-120 ka) from the Santa Barbara Basin, supported by additional southern California margin records, a region highly sensitive to millennial-scale climate oscillations during the last deglaciation. These records reveal millennial- and centennial-scale climate variability throughout the interval, including an interstadial immediately preceding the deglaciation, a brief warm event near the beginning of Termination II, and a Bølling-Allerød-Younger Dryas-like climate oscillation midway through the deglaciation. Recognition of these events in an oxygen isotope record from a 230Th-dated stalagmite allows the adoption of this radiometric chronology for 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.

Corg, CaCO3, bulk densities, accumulation rates and ages of ODP Leg 167 sites and three piston cores, California margin

Sediments from five Leg 167 drill sites and three piston cores were analyzed for Corg and CaCO3. Oxygen isotope stratigraphy on benthic foraminifers was used to assign age models to these sedimentary records. We find that the northern and central California margin is characterized by k.y.-scale events that can be found in both the CaCO3 and Corg time series. We show that the CaCO3 events are caused by changes in CaCO3 production by plankton, not by dissolution. We also show that these CaCO3 events occur in marine isotope Stages (MIS) 2, 3, and 4 during Dansgaard/Oeschger interstadials. They occur most strongly, however, on the MIS 5/4 glaciation and MIS 2/1 deglaciation. We believe that the link between the northeastern Pacific Ocean and North Atlantic is primarily transmitted by the atmosphere, not the ocean. Highest CaCO3 production and burial occurs when the surface ocean is somewhat cooler than the modern ocean, and the surface mixed layer is somewhat more stable.