Oceanus Magazine
Back to Woods Hole Oceanographic Institution's Homepage

Images: Continental Margin Particle Flux

Scientists aboard R/V Atlantis II during a 1990 cruise deploy a sediment trap mooring in Guaymas Basin.

Composite surface ocean pigment concentration map derived from all Nimbus-7 Coastal Zone Color Scanner data acquired between November 1978 and June 1986. The pigment-rich coastal waters reflect the high productivity occurring in these regions and contrast sharply with conditions in much of the open ocean. The author's group is currently measuring particle fluxes in the three basins identified.

Cross-sections of the Santa Barbara, Guaymas, and Cariaco Basins showing the configuration of the sediment trap moorings. The region of anoxic conditions in each basin is indicated by purple shading. It is beneath these oxygen-deficient zones that laminated sediments are preserved.

Biogenic opal (blue) and terrigenous material (green) flux records from Guaymas Basin for the period July 1990 through March 1997 reflect seasonal and interannual changes in climatic conditions. The high opal fluxes are generally associated with the late fall to early spring period of high primary productivity, while terrigenous fluxes are usually high during the summer rainy season.

Changes in the relative proportions of biogenic material and terrigenous material in the total sediment flux for Guaymas Basin. These seasonal changes in the composition of the sediment flux result in the deposition of laminae on the seafloor. The high flux of biogenic material from late fall through spring produces the light laminae. In contrast, dark laminae form during the summer when the sediment flux carries high concentrations of terrigenous material

A comparison of satellite measured sea surface temperatures for Guaymas Basin and temperatures estimated from the oxygen isotopic composition of two species of planktonic foraminifera, Globigerina bulloides and Globigerinoides ruber collected in sediment traps. The good agreement between the observed and estimated temperatures indicates that the oxygen isotopic composition of shells of these species of foraminifera preserved in the sediments can be used to estimate past sea surface temperatures in the Gulf of California.

Comparison of a Greenland ice core oxygen isotope record and a record of the thickness of light laminae in a Cariaco Basin sediment core for the period 13,600 to 12,600 years ago. The oxygen isotope record provides information on changes in atmospheric temperature over Greenland, while the light-lamina thickness is a function of changes in productivity along the Venezuelan continental margin. The pattern of change on both records is very similar, with high productivity (thicker light laminae) occurring during periods of climatic cooling (lower oxygen isotope values).