HR: 1400h
AN: PP43B-06    [Abstracts]
TI: Climate and ocean variability recorded in laminated sediments from Carmen Basin, Gulf of California
AU: * Villagran-de-la-Cruz, E
EM: biani@oceano.umar.mx
AF: Universidad Nacional Autonoma de Mexico. Instituto de Geofisica, Ciudad Universitaria, Coyoacan, Mexico, DF 04510, Mexico
AU: Perez-Cruz, L
EM: perezcruz@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico. Instituto de Geofisica, Ciudad Universitaria, Coyoacan, Mexico, DF 04510, Mexico
AU: Vazquez, F
EM: felipe@mar.icmyl.unam.mx
AF: Universidad Nacional Autonoma de Mexico. Instituto de Ciencias del Mar y Limnologia, Ciudad Universitaria, Coyoacan, Mexico, DF 04510, Mexico
AU: Fucugauchi, J U
EM: juf@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico. Instituto de Geofisica, Ciudad Universitaria, Coyoacan, Mexico, DF 04510, Mexico
AB: We analyze a sedimentary laminated sequence; kasten core K58 (215 cm length), which was recovered in the western part of Carmen Basin at 720 m depth collected aboard of the UNAM R/V "El Puma". Core contains a high resolution record of paleoclimatic and paleoceanographic changes during the Holocene. Carmen Basin is one of a series of deep tectonically active basins developed in the Gulf of California, which are characterized by contrasting climatic, oceanographic and geologic conditions from the gulf mouth to the north. In order to provide a climate and ocean scenario during the late Holocene, radiolarian assemblages trace elements and magnetic properties are used as proxies of oceanographic and climatic variability. The record provides a tentative scenario for the last 4000 years. Analysis of the radiolarian polycystine were completed on samples spaced every 10 cm, whereas geochemical and magnetic properties analysis were completed in 30 light and dark laminae through out the core. Bulk ICP-MS geochemical analysis was performed on alternate laminae. The following elements were analyzed Al, V, Cl, Fe, Co, Ni, Cu, Zn, Ag, Cd, Ba, Pb and Hg and illustrate their variations in the sediment sequence. Radiolarians occurred through the entire core; they are diverse and show good preservation. Radiolarian assemblages were determined using Q-mode factor analysis of 22 samples of the core. For mineral magnetic analyses, low-field magnetic susceptibility was measured in 174 samples at low and high frequencies. Susceptibility displays its higher values at the top of the core, and a characteristic pattern of variations with depth. The remanent magnetization shows normal polarity, with downward inclinations around 60o. The magnetic hysteresis loops and IRM acquisition and back-field IRM demagnetization curves were measured in samples from the dark and light laminae, to investigate any differences in magnetic mineralogy, domain state and relative contents. Plots of hysteresis ratio parameters indicate that all samples fall within the PSD domain field, suggesting a mixture of SD and MD grains. Contribution of fine-grained SP material, which is also suggested from the frequency-dependent susceptibility measurements, is apparent from the data-point distribution above the mixing SD-MD curves.
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4944 Micropaleontology (0459, 3030)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly