HR: 1400h
AN: PP43C-05    [Abstracts]
TI: Ostracode Paleoecology and Trace Element Shell Chemistry: A case study from Laguna Salada, Baja California, Mexico.
AU: * Romero-Mayen, V
EM: varomay@gmail.com
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Coyoacan, Mexico City, D.F 04510, Mexico
AU: Bernal, J
EM: jpbernal@geologia.unam.mx
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Coyoacan, Mexico City, D.F 04510, Mexico
AU: Palacios-Fest, M
EM: terra_nostra_mx@yahoo.com.mx
AF: Terra Nostra Earth Sciences Research, 6312 N Barcelona Lane # 606, Tucson, AZ 85704, United States
AU: Carreno, A
EM: anacar@servidor.unam.mx
AF: Instituto de Geologia, UNAM, Ciudad Universitaria, Coyoacan, Mexico City, D.F 04510, Mexico
AB: The Laguna Salada Basin in northeastern Baja California constitutes the southwestern limit of the Salton Trough and provides insights into the evolution of marine and non-marine sedimentary basins during the latest Neogene at the head of the Gulf of California. A 43 m long core (LS04-1) recovered from the Basin consisted of alternating clay, silt and sand beds with gypsum lenses. Three radiocarbon dates provided the age control: 41,520±790 cal years BP at 30.21 m, 25,590±320 cal years BP at 26.60 m and 15,150±70 cal years BP at 7.50 m. A total of 103 samples were analyzed for taxonomy, taphonomy and geochemistry. Eighteen marine and brackish- water ostracode species and nine benthic foraminifera species were identified. Faunal changes suggest variations in the water source with the opening of the basin to the Gulf of California. The Mg/Ca and Sr/Ca ratios of valves of two ostracode species (Limnocythere staplini and Cyprideis castus) were measured using ICPMS. Based on the Mg/Ca ratios, water paleotemperatures were estimated using a regression model. Shell chemistry shows mixed results. Some intervals fit an acceptable range, whereas other are unrealistic. Analysis of Sr/Ca ratios ostracode valves from the conflicting horizons show evidence of diagenetic effects. The fossil assemblages indicate two dry periods: prior to the 41,520 cal years BP and after the 15 ,150 cal years BP, with the maximum highstand of the basin between 25,590 and 15,150 cal years BP. Given the diagenetic effects at Laguna Salada, ostracode shell chemistry paleotemperature estimates may not be warranted in attempting to determine this parameter from the dry periods shown by faunal assemblages.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1635 Oceans (1616, 3305, 4215, 4513)
DE: 3309 Climatology (1616, 1620, 3305, 4215, 8408)
DE: 4215 Climate and interannual variability (1616, 1635, 3305, 3309, 4513)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly