HR: 1330h
AB: The "Correlation Length Experiment," an ONR STRATAFORM-sponsored box coring effort off Eureka, California in the summer of 1997, endeavored to characterize the lateral variability of near-surface shelf sediments over scales from meters to kilometers. Understanding such variability is critical for constraining models of sediment deposition, reworking and preservation. Coring focused on two sites, K60 and S60, separated by $\sim$15 km along the 60 m isobath. The sites are near the sand/mud transition, although K60 is sandier owing to its proximity to the Eel River mouth. Both dip and strike lines were collected with sample interval that increased with distance from each site (minimum interval $<$ 10 m, maximum $\sim$1 km). The strike lines merge along the 60 m isobath. 137 cores were collected with penetration depths typically ranging between 20 cm and 40 cm. Physical parameters examined included density, porosity, and grain size, which were measured to at least 1 cm depth accuracy within each core. Variograms were computed for the full strike line, for both strike and dip directions at each site, and for depth at each site. At scales $>$$\sim$8 km in the strike direction and $>$$\sim$1 km in the dip direction, the variograms are are clearly dominated by the sand/mud transition. At scales less than $\sim$8 km in the strike direction, variability differs markedly between the two sites. At K60 no coherent bedding is seen; the cores are fully uncorrelated at the smallest scales examined (a few meters), and horizontal variability up to $\sim$8 km scale is equal to the variability seen within cores. At S60, by contrast, there is considerable structure both down hole and laterally. Coherent bedding is observed at S60 related to the preservation of the 1995 flood deposit. Laterally, a correlatable structure is seen with a characteristic scale of $\sim$500 m. The source of this structure is not yet determined. It is suggested that the high variability at the shortest observed scales at K60 is a result of more intense bedform reworking of the seabed in the sandier environment.
AN: OS62A-13
TI: Variability of Shelf Sediments in the STRATAFORM Natural Laboratory, Northern California
AU: * Goff, J A
EM: goff@utig.ig.utexas.edu
AF: University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Wheatcroft, R A
EM: raw@oce.orst.edu
AF: Oceanic and Atmospheric Sciences, Oregon State University, Corvalis, OR 97331 United States
AU: Drake, D E
EM: DD4DMC@earthlink.net
AF: Drake Marine Consulting, 1711 Quail Hollow Rd., Ben Lomond, CA 95005 United States
AU: Swift, D J
EM: dswift@odu.edu
AF: Old Dominion University, Dept Ocean Earth & Atmospheric Sciences, Norfolk, VA 23529 United States
AU: Fan, S
EM: sjfan@ocean.odu.edu
AF: Old Dominion University, Dept Ocean Earth & Atmospheric Sciences, Norfolk, VA 23529 United States
AU: Lee, H J
EM: homa@octopus.wr.usgs.gov
AF: USGS, 345 Middlefield Road, Menlo Park, CA 94025 United States
DE: 3022 Marine sediments--processes and transport
DE: 3045 Seafloor morphology and bottom photography
DE: 4219 Continental shelf processes
SC: OS
MN: Fall Meeting 2000