Associations of major and trace components in time-series settling particle samples from Cuenca Alfonso, SW Gulf of California

HR: 1340h
AN: OS33A-0991 [Abstracts]
TI: Associations of major and trace components in time-series settling particle samples from Cuenca Alfonso, SW Gulf of California
AU: Rodríguez-Castañeda, A P
EM: aprodri@ipn.mx
AF: Centro Interdisciplinario de Ciencias Marinas - Instituto Politecnico Nacional, Av. Instituto Politécnico Nacional s/n, Playa Palo Santa Rita, La Paz, BCS 23096, Mexico
AU: * Shumilin, E
EM: eshumili@ipn.mx
AF: Centro Interdisciplinario de Ciencias Marinas - Instituto Politecnico Nacional, Av. Instituto Politécnico Nacional s/n, Playa Palo Santa Rita, La Paz, BCS 23096, Mexico
AU: Silverberg, N
EM: silverb@ipn.mx
AF: Centro Interdisciplinario de Ciencias Marinas - Instituto Politecnico Nacional, Av. Instituto Politécnico Nacional s/n, Playa Palo Santa Rita, La Paz, BCS 23096, Mexico
AU: Morton-Bermea, O
EM: omorton@geofisica.unam.mx
AF: Instituto de Geofísica - Universidad Nacional Autonoma de Mexico, Coyoacan, Mexico, DF 04510, Mexico
AU: Hernandez-Alvarez, E
EM: aeliza@geofisica.unam.mx
AF: Instituto de Geofísica - Universidad Nacional Autonoma de Mexico, Coyoacan, Mexico, DF 04510, Mexico
AU: Aguirre-Bahena, F
EM: faguirre@ipn.mx
AF: Centro Interdisciplinario de Ciencias Marinas - Instituto Politecnico Nacional, Av. Instituto Politécnico Nacional s/n, Playa Palo Santa Rita, La Paz, BCS 23096, Mexico
AB: Cuenca Alfonso is a natural sedimentation basin in Bahía de La Paz, southern Baja California Peninsula, an arid subtropical region characterized by limited land runoff with a productive surface layer overlying a well-developed Oxygen Minimum Zone. A time-series sediment trap program was initiated in 2002 to help understand the processes controlling variations in the biogeochemistry of this environment. INAA, ICP-MS and ICP-OES analyses, as well as flame AAS were made for major and trace elements in 105 subsamples of material collected at 350 m depth during 2002-2005. Principal component analysis, including data for organic and inorganic carbon, biogenic silica and the lithogenic fraction, yielded four factors. Factor 1 (25% of the total variance) showed high eigenvalues for the classical terrigenous aluminosilicate elements: Al, Fe, Mn Sc. High loadings also occurred for the group of light to medium REEs (except for Eu). The latter are frequently associated with acid source rocks, such the granites and rhyolitic volcanics exposed on the margin of the bay. Factor 2 (18%) grouped mainly REEs, with high loading on the heavier members of the series that are more typical of basic rocks (thick sequences of andesitic volcanics occur to the NW), as well as Ni and Rb. Factor 3 (12%) appears to represent carbonate organism production, with high loadings for Cinorg, Ca and moderate levels for Corg and Cu, while %litho is moderately negative, as is biogenic silica. The fourth factor (9%) is characterized by high negative loadings for Cd, Co, Se and moderately negative values for Corg. Moderate positive loadings occur only for Sr and, at lower levels, for U, Sb and %lithogenic. This suggests that this grouping is related to particles that have been partially transformed within the Oxygen Minimum Zone. The results will be examined for distinctive periods within the time-series, such as the hurricane-influenced months of August-September 2003, the generally very low fluxes during 2005, and unusual peaks during winter 2002.
UR: http://www.CATS-baja.org
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0489 Trace element cycling (4875)
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 1051 Sedimentary geochemistry
DE: 1065 Major and trace element geochemistry
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting