HR: 16:20h
AN: U12B-02    [PDF]
TI: The Faithful Record of Synchrony and Amplitude of Neogene Sea Level Variability in Carbonate Depositional Environments From ODP Legs 133, 166, And 194
AU: * Eberli, G P
EM: geberli@rsmas.miami.edu
AF: University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149 United States
AU: Isern, A R
EM: aisern@nsf.gov
AF: National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230 United States
AU: Anselmetti, F S
EM: flavio@erdw.ethz.ch
AF: ETH-Zuerich, Sonneggstr. 5, Zuerich, 8092 Switzerland
AB: Recognizing the importance of sea level change in shaping near shore and open ocean environments, the Ocean Drilling Program (ODP) devoted numerous legs to the study of eustatic sea level and to how these changes are recorded in sediments from various depositional settings. Three ODP legs (133, 166, 194) utilized a series of holes to examine the sedimentary records from carbonate platform-to-basin transects to gain a better understanding of Neogene sea level variations. Because carbonate platforms are constructed by organisms that are sensitive to changes in environmental conditions such as water depth (sea level), the dominant energy regime (wind or currents), nutrient content, and water temperature, the study of sediments shed from carbonate platforms provides fundamental information regarding past environmental change. Unconformities and varying depositional regimes between sea level high- and lowstands allow sea level changes to be imaged on seismic data by series of unconformity-bounded seismic sequences. A synthesis of sequence stratigraphic results from Legs 133, 166, and 194 clearly demonstrates chronostratigraphic significance of prominent unconformity surfaces that produce seismic sequence boundaries on the margins in both the Atlantic and Pacific Oceans. The timing of many of these unconformities is remarkably similar in both oceans, indicating a strong eustatic control on their development. The timing of these sequences also correlates well with major shifts in stable oxygen isotopes, which are primarily controlled by changes in ice volume and thus are an excellent proxy for eustatic sea level variability. Between the three locations studied, 15 (Leg 133), 17 (Leg 166), and 13 (Leg 194) Neogene sequences are identified. Their sequence boundaries dated by correlating them seismically to the conformable successions in drilling locations distal to the carbonate platform complexes, where more quiescent conditions and reduced diagenesis help maintain a continuous depositional history through time. 10 of the sequence boundaries display, within the seismic and biostratigraphic resolution, the same ages in all transects, documenting the synchrony of unconformities that are caused by relative sea level changes. In addition, stratigraphic relationships and biostratigraphic information from Leg 194 provide evidence that the magnitude of the late middle Miocene eustatic fall was 86ñ30 m. This data provides an important calibration point for the global sea level curve and is similar to those derived from other proxies, such as oxygen isotopes, yet is greater than the magnitudes estimated from sediment sequences of siliciclastic margins (e.g. ODP Leg 150).
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3022 Marine sediments--processes and transport
DE: 4215 Climate and interannual variability (3309)
DE: 4267 Paleoceanography
DE: 4556 Sea level variations
SC: U
MN: 2003 Fall Meeting