4. Fluxes, Transport, and Deposition of Marine Sediments. Approximately 40% of 

 all sediments occupying the major global sedimentary reservoirs are found on the continental 

 slope and rise and in the deep ocean. These sediments reflect a wide variety of complex and often 

 interacting sources from continental erosion and pelagic productivity to volcanic eruptions and 

 deep sea hydrothermal activity. Transport, deposition, and, often, subsequent erosion of these 

 sediments are directly coupled to surface and deep ocean current systems and modified by the 

 long-term history of global seal evel. 



Recent research has concentrated on (1) developing geochemical tracers which allow 

 sedimentary components to be partitioned between source functions; (2) first-order studies of 

 sediment supply and alteration through use of sediment traps and surface sediment analyses; (3) 

 use of high resolution side-scan sonars and reflection profiling to study dynamic processes 

 which transport and erode sediments; and (4) use of the preserved record to model global 

 geochemical cycles of carbon, sulfur, and other elements. 



Although first-order models of many of these processes are available, a major limitation to 

 advancement is a lack of integrated field data sets incorporating comprehensive studies of 

 source, transport and flux, and depositional controls. Increased support for such studies on 

 continental margins are included as part of the Coastal Ocean Dynamics and Fluxes subinitiative. 

 Predictability of regional sedimentary sequences and their acoustic stratigraphy, the resistance 

 of sediment deposits to erosion or dissolution, slope stability along continental margins, and the 

 origin of microtopography are still poorly understood. 



Future emphasis will be on geochemical processes in the benthic boundary layer which modify 

 terrigenous and biogenic material before its incorporation into the geologic record. Such studies 

 will be coupled to ocean flux studies assessing production, transport, and dissolution of biogenic 

 and inorganic material in the water column. Funds are included in the Open Ocean Fluxes sub- 

 initiative for increased geochemical studies in this area. Efforts under the Land/Sea Interface 

 program in Biological Oceanography will similarly complement this activity. 



Additional emphasis at the current program level will be directed to effects of in situ reactions 

 within sediments and their influence on physical properties, pore fluids, and sediment layering 

 and chemistry. Enhanced support for a new Long Coring Facility is requested to improve 

 sampling quality and recovery for sedimentary analysis. 



5. Geologic and Climatic History of the Oceans. Paleoceanography has emerged as a 

 separate and important discipline. Study of microfossil assemblages, coupled with their 

 geochemical signatures, has provided a new tool for examining changes in global climate and 

 ocean circulation. Projects such as CLIMAP and SPECMAP have attacked the most recent portion 

 of the geologic record and uncovered the relation between orbital forcing and the Pleistocene ice 

 age. Samples from the Deep Sea Drilling Project have been used to document gradual decay of 

 global climate and resulting formation of ice sheets during the last 60 million years (e.g., the 

 CENOP project). 



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