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Correlation of continental shelf-slope stratigraphy in Santa Monica Bay (southern California) with Ocean Drilling Program records for nearby slope-basin sites has illuminated the timing and scale of terrigenous sediment dispersal on margin since the Last Glacial Maximum (LGM). Marine flooding surfaces preserved in a transgressive sequence on the Santa Monica Shelf provide a key link between base-level elevation and sediment transport across shelf. Sediment-accumulation rates at slope-basin sites were maximal ca. 15-10 ka, well after the LGM, decreased during the 12-9 ka transition from fluvial-estuarine to fully marine conditions on the shelf, and decelerated throughout the Holocene to 30%-75% of their values at the LGM. The deceleration is interpreted to manifest a landward shift in the margin depocenter with the onset of transgressive sedimentation beginning when sea level surmounted the shelf edge ca. 13 ka, as predicted by sequence-stratigraphic models. However, the records make clear that factors other than base level modulated slope-basin accumulation rates during the deglaciation. [ABSTRACT FROM AUTHOR]

The sediments of Santa Barbara Basin, a valuable source of information about the history of the California Current, show cyclic deposition in three properties here investigated: varve thickness, total organic carbon (TOC) accumulation, and fish-scale abundance. We analyzed the record since A.D. 1350 for varves, A.D. 1120 for TOC, and A.D. 1200 for fish scales. Prominent periods are 169 yr, 93 yr, 51.4 yr, 17.7 yr (varve thickness), 124 yr, 56 yr, 37.4 yr (TOC flux), and 103 yr, 128 yr (fish-scale abundance). A surprising number of the varve and TOC cycles can be interpreted as deriving from the common tidal cycles, i.e., the 4.425 yr perigee period (describing the changing distance between Earth and Moon) and the 18.6 yr lunar nodal period (which pertains to the lineup of Earth, Moon, and Sun). We suggest that the record of the basin is partly a result of pulsed sedimentation aligned with tides. These findings support the hypothesis that a considerable portion of sediment destined for deposition in the center of the basin goes through a phase of shallow storage on the shelf where it can be remobilized through storms and tides. Mechanisms calling on tidally pulsed productivity or tidally influenced climate change are not excluded, but are considered less attractive than remobilization. Fish-scale cycles may reflect the influence of solar forcing. [ABSTRACT FROM AUTHOR]

Sediment cores were collected along floodplains in the Navarro River basin of coastal northern California to examine the controls on floodplain evolution in a tectonically active setting. Sedimentary strata were subsampled for organic content, bulk density, and grain size measurements. Organic samples were analysed for 14C age, which yielded net-averaged sedimentation rates for all cores. Overbank deposition rates decreased at all study sites through time and declined in the downstream direction. The ability of intermediary-order streams to store sediment in floodplains decreased the ability of highest-order streams to record sediment-pulse events. The effects of anthropogenic disturbance, primarily logging, on long-term overbank deposition rates were minimal. Climatic variability, by affecting sediment loading in the channel network, is the principal control on floodplain evolution through the Holocene. A hypothetical model is proposed to explain overbank deposition rates in the Navarro basin, which may be extrapolated to the northern-coastal California region during the late Pleistocene and Holocene. The complexities observed in sediment storage and routing in this study imply that caution should be made when extrapolating sediment-yield measurements obtained at river mouths or coastal shelves to geomorphic events within small, tectonically active basins. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]