T41 The Next Generation—Sedimentary Geology Student Poster Session (Posters)

Sunday, 4 November 2012
9:00 AM - 6:30 PM
Hall B

FLUVIAL-DELTAIC PROCESSES DOMINATE LAND TO SEA SEDIMENT TRANSPORT EVEN IN A POLAR REGIME WITH LIMITED LIQUID WATER

Paper number: T41-14
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Explorers Cove (EC) at the mouth of the ice-free Taylor Valley, Antarctica is covered by multi-year sea ice that typically only melts in a narrow shoreline zone during the summer. We investigated how sediment is transported from the sediment-rich Taylor Valley to the seafloor given that water is frozen for at least 10 months each year, and year-round some years. Two observed mechanisms are: 1) wind transport of sediment from the Taylor Valley to the sea-ice surface and subsequent downward flow to the sea floor via cracks; and 2) delivery of sediment to a delta built a small ephemeral stream fed by glacial meltwater, followed by transport to the seafloor by deltaic processes after melting of the grounded sea ice at the shore. Analysis of sediment accumulated in sediment traps deployed for one year and grain size analysis of subaerial (moraine, delta, delta platform, and supra-sea ice) sediment and of seafloor sediment from cores taken by divers in water <30 m deep were used to infer the dominant process.

Sand-sized sediment on the sea ice analyzed by the Malvern Mastersizer is coarser than sediment on the seafloor (sea ice median=311.51µm, mode=318.35µm, n=69; seafloor median =233.07µm, mode=242.56µm, n=394). However, grain size of delta sand and delta-platform sand is similar to that of on the sea floor sand. Sediment accumulation rates in traps on the subaqueous delta from < 4 m depth to ~ 25 m depth range from 4.09 cm/yr to 0.02 cm/yr over a horizontal distance of less than 100 m. Grain size of sediment in traps also decreased away from the shore. Textural similarity of seafloor and deltaic sand and high observed rate of sedimentation on the delta documents the importance of fluvial deltaic transport, at least during years when grounded shoreline ice melts sufficiently to allow sub-ice water flow. Downward flow through cracks of surpra-ice aeolian does occur, but the textural disparity between sea ice and sea floor sediment suggests that it is of secondary importance.