HR: 0800h
AN: PP41C-0677    [Abstracts]
TI: Decadal to Million-Year Sedimentation Rates and the Ultra-High-Resolution Marine Record From Santa Barbara Basin
AU: * Behl, R J
EM: behl@csulb.edu
AF: Dept. of Geological Sciences, California State University 1250 Bellflower Blvd., Long Beach, CA 90840, United States
AU: Escobedo, D K
EM: dkescobe@gmail.com
AF: Dept. of Geological Sciences, California State University 1250 Bellflower Blvd., Long Beach, CA 90840, United States
AU: Kennett, J P
EM: kennett@geol.ucsb.edu
AF: Marine Science Institute, University of California, Santa Barbara, CA 93106, United States
AU: Nicholson, C
EM: nicholson@msi.ucsb.edu
AF: Marine Science Institute, University of California, Santa Barbara, CA 93106, United States
AU: Sorlien, C C
EM: chris@crustal.ucsb.edu
AF: Marine Science Institute, University of California, Santa Barbara, CA 93106, United States
AB: An inherent feature of the sedimentary record is that it is incomplete. Sadler (1981) showed that sediment accumulation rates are inversely related to the time-span of measurement for nearly all depositional environments - sediment accumulation rates decrease with larger time frames of interest because of the inclusion of more and larger undetected intervals of nondeposition or erosion. Nonetheless, investigation of the mechanisms and timing of climate change at high-resolution relies on the assumption of continuous, rapidly accumulating sedimentary successions. This creates a serious problem that is rarely addressed. Quaternary sedimentation in Santa Barbara basin (SBB) stands in marked contrast to this general trend by maintaining similar high rates of sediment accumulation spanning 5 orders of magnitude in time over the past million years. ODP Site 893 recovered the past ~160 kyr with 200 m of core. We have extended this record further in time by recovering more than thirty short piston cores from a breached anticline in the eastern SBB where older Quaternary strata have been uplifted and eroded. These cores demonstrate the persistence of alternating laminated and massive/bioturbated sediment in the older deposts similar to that observed at Site 893, as well as abundant microfossils suitable for ultra-high-resolution paleoclimate and paleoceanographic studies. Biostratigraphic and tephrachronologic age datums confirm that strata cropping out on the anticline extend back to 700 ka, an age previously unreachable by conventional deep coring methods. Linear sedimentation rates (LSR) estimated from varve-counts in laminated intervals are remarkably uniform across the entire age range sampled, and vary from about 80 to 130 cm/kyr, similar to the average LSR at Site 893 (120 cm/kyr) derived from radiocarbon dates and oxygen isotope stratigraphy. Correlated, dated, and depth-converted seismic stratigraphy indicates that such unusually high sedimentation rates are continuous for at least the last 1 m.y., with the average depth (bsf) to a dated 1-Ma horizon varying from 1.2 to 1.8 km (120 to 180 cm/kyr) over much of the deep SBB. These initial data suggest a remarkably uniform and rapid sedimentation process in spite of inclusion of evitable hiatuses or condensed sections. These older strata have already yielded paleoclimatic findings of similar resolution to ODP Site 893. Isotopic compositions of benthic and planktonic foraminifera reveal millennial and sub-millennial scale climate fluctuations in the climate record back as far as ~500 ka that include abrupt (decadal) climate jumps. SBB is thus quite capable of extending its usefulness as an ultra-high-resolution paleoceanographic record back further in time with continuous deeper drilling. Sadler, P.M., Sediment accumulation rates and the completeness of stratigraphic sections, Journal of Geology (September 1981), 89(5):569-584.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1861 Sedimentation (4863)
DE: 3022 Marine sediments: processes and transport
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4901 Abrupt/rapid climate change (1605)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting