Sedimentology of Bahía Sebastián Vizcaíno, Baja California, México.

Abstract

SEDIMENTOLOGY OF BAHÍA SEBASTIÁN VIZCAÍNO, BAJA CALIFORNIA, MÉXICO With support from the Oceanographic Ships H05 “Altair” and H03 “Alexander von Humboldt” of the Mexican Navy, 37 samples were collected using a Van Veen sediment dredge in Ranger Bank, Sebastian Vizcaino Bay, and around Punta Canoas of Cedros Island, on the west coast of Baja California. The distribution of sediments, grain size, composition of organic carbon and carbonate content, and phosphates were determined. Two major areas of sedimentation were identified: (a) the Ranger Bank, where oxidative and dynamical processes occur within a limestone dominated environment, and coal with high concentrations of organic matter with medium size sand (Ф = 1.0 to 2.1); b) the northeast portion of Sebastian Vizcaino Bay where the size of the sediments range from very fine to coarse grain (Ф = 0.2 to 3.7); there a high concen- tration of phosphates (maximum 22.3 %) occurs, with biogenic material consisting mainly of organic detritus, such as diatomaceous material, phosphorite from fish and other organisms. This can be considered a zone where incipient formation of phophoritic material is generated and formation of future marine phosphorite occurs. The prevailing material in Keller Canal, located between Cedros and Nativity islands consists of coarse grains because of the strong currents that remove the fine material, whereas in the central-western portion of the bay abundant and very fine sand and mud occur, which are associated with low speed near the center of rotation of an anticyclonic semipermanent flow that characterizes water movement in the Bay.