Collaborative Research: Flux and Fate of Sediment and Water from Small, Mountainous Rivers to the Continental Margin: The Gulf of Alaska Example

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Abstract ATM-9222405 Milliman, John D. The College of William and Mary Title: Flux and Fate of Sediment and Water from Small, Mountainous Rivers to the Continental Margin: The Gulf of Alaska Example Small rivers charging directly from mountains into the ocean carry greater sediment loads than commonly envisioned, a relatively great percentage of which may escape to deeper waters during high stands of sea level. This award supports a study of the flux of Holocene fluvial sediment into the Gulf of Alaska, whose generally small tributary rivers are collectively the largest supplier of sediment from North America. Alaskan rivers are relatively uninfluenced by human activities, although glacial activity has resulted in higher sediment yields than noted for other rivers with similar drainage areas. High-resolution seismic profiling, in conjunction with seismic data previously collected, will allow the identification of sediment accumulation and discharge patterns on the shelf and slope, as well as trace individual sediment layers derived from episodic (flood) events. Sedimentological data will help define the escape routes/processes, and a variety of radiometric datings will show frequency of occurrence and rates of accumulation. Facies will be defined by compositional and textural analyses, as will be sources (and fates) of terrigneous grains and organic matter in shelf sediments. Measurements of total organic carbon and total nitrogen, d13C, d15N, and lignin oxidation productions in sediment organic matter will be used to determine the amount and source of organic matter accumulating in the sediments. Contemporaneous oceanographic processes controlling strata formation will also be evaluated. This information should help in the interpretation of the older strata observed by seismic profiling and coring.