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The ultimate objective of this research program is to obtain a predictive understanding of the physical and biological processes responsible for the formation, alteration and preservation of sedimentary strata on continental margins. The general approach is to use focused field measurements to develop and test hypotheses., The original document contains color images.

The ultimate objective of this research program is to obtain a predictive understanding of the physical and biological processes that control the microtopography of the sediment-covered seafloor. Our primary means to address this topic is to make focused field measurements that extend and test conceptual frameworks, The original document contains color images.

The ultimate objective of this research program is to obtain a predictive understanding of the physical and biological processes responsible for the formation, alteration and preservation of marine sedimentary deposits. The general approach of this research program is the development and testing of theory mainly through field observations and measurements. This is a proposal, within the STRATAFORM Shelf Program, to study the formation, post-depositional alteration and preservation of flood deposits on the Pacific Northwest continental margin. Five related activities are being pursued: (1) continuation of time series measurements of the areal distribution and small-scale properties of the 1995 and 1997 flood deposits, (2) statistical analysis of the small-scale spatial variability of flood bed thickness and geometry at stations K60 and S60, (3) x-radiographic examination of piston cores for past flood deposits, (4) testing of simple conceptual ideas of event layer alteration and preservation using the above data sets, and (5) examination of patterns of sediment accumulation and event layer preservation offshore of other Pacific Northwest rivers.

A state-of-the-art digital x-radiography system was assembled to assist in the quantitative analysis of marine sediments. The system comprises a constant potential x-ray source, an amorphous silicon digital x-ray detector, a high-end computer workstation and lead shielding. System performance is excellent with no loss of resolution compared to film. To date, the system has been used on two research cruises funded by ONR. Future plans call for intensive use.

The ultimate objective of this research program is to identify and obtain a predictive understanding of the physical and biological processes responsible for variations in the subsurface bulk density field of marine sediments. To achieve this goal it is necessary to study formative processes occurring on the sediment surface (e.g., biogenic mound formation, ripple development), as well as processes occurring within the seabed (e.g., bioturbation and compaction). The approach to these areas of interest is predominantly field-oriented, with a secondary emphasis on model development.

The ultimate objective of this research program is to identify and obtain a predictive understanding of the physical and biological processes responsible for the formation and maintenance of the microtopography (decimeter to millimeter) of the sea floor. To achieve this goal, it is necessary to study formative processes occurring on the sediment surface (e.g., biogenic mound formation, ripple development), as well as processes occurring within the seabed (e.g., bioturbation, compaction) which generally lessen microtopography. The approach to this area of interest is predominantly fieldoriented, with a secondary emphasis on model development.

The ultimate goals of this research are to determine the dominant mechanisms whereby and the rates a which fine particles (0.05 mm) are incorporated into marine sediments. Particular focus is on developing a mechanistic understanding of the role that deposit- and suspension-feeding benthic invertebrates play in particle deposition and burial relative to the abiotic case. The objectives of this project are to manipulate and test various combinations of hydrodynamic, sedimentological and biological parameters to determine the magnitude of: (1) net accumulation of fine particles in sandy and reworked (mixed grain size) sediments relative to muddy sediments, (2) biodeposition by suspension feeders relative to deposit feeders, and (3) vertical transport modes and rates of sediment transport within the bed by deposit feeders., See also ADM002252. Prepared in cooperation with Oregon State Univ., Corvallis, OR.

The ultimate objective of this research program is to identify and obtain a predictive understanding of the physical and biological processes responsible for the formation and maintenance of the microtopography (decimeter to millimeter) of the sea floor. To achieve this goal, it is necessary to study formative processes occurring on the sediment surface (e.g., biogenic mound formation, ripple development), as well as processes occurring within the seabed (e.g., bioturbation, compaction) which generally lessen microtopography. The approach to this area of interest is predominantly field oriented, with a secondary emphasis on model development. The primary goal of this project, which is part of the Coastal Benthic Optical Properties (CoBOP) DRI, is the quantification of bottom roughness along transects extending from open sand flats to coral reefs near Lee Stocking Island (LSI), Bahamas. Specific questions include: (1) What is the sediment bottom roughness? (2) Does sediment bottom roughness vary spatially in a predictable manner (e.g., away from the coral reef)?, (3) Does sediment bottom roughness vary significantly in time?, and (4) What is the relationship between sediment bottom roughness and bioturbation intensity?, See also ADM002252.

The ultimate objective of this research program is to obtain a predictive understanding of the physical and biological processes responsible for the formation, alteration and preservation of marine sedimentary deposits. While present focus is on the biological alteration of sedimentary event layers, the physical processes leading to the deposition and erosion of marine sediment remains an area of interest. The general approach of this research program is the development and testing of theory mainly through field observations and measurements., See also ADM002252.

The ultimate objective of this research program is to identify and obtain a predictive understanding of the physical and biological processes responsible for variations in the subsurface bulk density field of marine sediments. To achieve this goal, it is necessary to study formative processes occurring on the sediment surface (e.g., biogenic mound formation, ripple development), as well as processes occurring within the seabed (e.g., bioturbation and compaction). The approach to these areas of interest is predominantly field-oriented, with a secondary emphasis on model development., See also ADM002252.

The long-term goal of this research was to determine the dominant mechanisms whereby and the rates at which fine particles (<50 micronmeter) are incorporated into marine sediments. Flume and still-water experiments were conducted to quantify specific effects of deposit-feeding benthic invertebrates on the transport of fine suspended particulates from the water column to the bottom, and the retention of such particulates within the seabed. Experiments were conducted on (1) the effects of biogenic roughness (fecal mounds) on sand transport, (2) the potential effects of worm-tube arrays on fine-particle deposition, (3) fine-particle subduction by a surface deposit-feeding worm, and (4) density-dependent bioturbation by a head-down deposit-feeding worm. We also studied particle trapping by the viscous sublayer. These studies demonstrate ways in which deposit feeders can enhance fine-article deposition and retention within sandy marine sediments.

The objective of this proposal was to develop and apply computer-based, digital image processing techniques to the measurement of high-resolution (millimeter to decimeter) seafloor topography. Stereophotographs were collected as part of the 1990-1991 STRESS (Sediment TRansport Events of Shelves and Slopes) field program. A free-vehicle stereocamera tripod was deployed in mid-November 1990 at the 90-m STRESS site and successfully recovered in mid-March 1991. Results of the automatic image fusion research were disappointing, hence STRESS stereophotographs were analyzed manually using an analytical stereocomparator. During the deployment, five qualitatively different bed configurations were observed. In order of decreasing frequency these were: (1) biogenically reworked bed, (2) smoothed to scoured bed, (3) current-rippled bed, (4) scour-pitted bed, and (5) wave-rippled beds. Total vertical bed relief within the field of view was found to be typically less than 6 cm and the r-m-s vertical relief was of order 1 cm. Maximal relief occurred when the bed was current rippled (heights average 2 cm and lengths are about 15 cm) and was minimal following scour events. This study demonstrated that seafloor relief can change rapidly over short time scales.

In the general study of benthic processes an important set of unknown exists concerning interactions between the bed and the flow field. The local geometry of the bed in part controls the structure of the bottom boundary layer, but the bed geometry itself is also in part controlled by the flow. Benthic organisms complicate the problem further. Our long range research objectives are to understand the various interactions between sediments, flow and organisms in sufficient detail to permit predictions regarding the relative importance of various processes in different environments. Our approach is an iterative one between theory and field measurements. The proximate objectives of this research are to: (1) document the temporal variation in microtopography of a silt-bottom (90 m STRESS site, northern California shelf) that is most often influenced solely by biological processes, but is episodically modified by physical sediment transport events, (2) determine the recovery time required for biological reworking to erase physically generated bedforms, (3) measure absolute erosion and deposition amounts following sediment transport events, and (4) compare measured time-series of biological and physical roughness to predictions based on combined wave-current bottom boundary models that are forced using current velocity profiles and wave data.