Print this pageSediment Budgeting of Arctic River Systems
Sediment budgeting is an important tool in understanding Arctic coastal stratigraphy. Sliding glaciers erode exceptionally large quantities of sediment from bedrock, while the short summer season causes high meltwater fluxes in brief periods that transport large volumes of sediment to lakes, sandurs and fjords. The fjordhead deltas of the Arctic coasts receive fresh-water and sediment influx through glaciers and fjords. Within the deglacial cycle, sandurs and fjords serve as transitional sediment storage basins, as the sediment is deposited, reworked and supplied towards the shelf by glacial and fluvial transport. The stratigraphic architecture in Arctic coastal basins is therefore the result of glacial, periglacial, fluvial and marine processes.
Field data was gathered in the Søndre Strømfjord, a Western Greenlandic fjord near the town of Kangerlussuaq. This field analogue serves as a verification tool for process modeling strategies and results. The sediment volumes and stratigraphy of the last glacial-deglacial cycle were surveyed using ground penetrating radar and onshore seismics. Sedimentary units were identified in the subsurface corresponding to ice contact deltas, proglacial lakes, moraine sequences, braided stream deposits and fjord-deltaic topsets. The depth of the Precambrian fjord basement rock was imaged using onshore seismics, in order to reconstruct total deposited sediment volumes. The onshore survey revealed over 5 km3 of sediment deposited during the last deglacial cycle (<18.000 yrs.) by a glacio-fluvial system with a small (~5000 km2) drainage area.
In order to predict stratigraphy in such regions, the sediment flux through a glacio-fluvial system is numerically simulated. Algorithms are devised to quantify sediment production from glacial erosion by ice dynamics, in order to link the GC2D glacier cover model to SEDFLUX, a sedimentary process model. Sediment supply to the basin and timing of the paraglacial sediment pulse are generated using glacial, fluvial and coastal process models. This strategy of coupling the glacial and periglacial domains is the first instance of a fully integrated source-to-sink sediment budget model for Arctic river systems originating from an ice sheet.
Simulated sediment volumes and stratigraphy can be used to quantify sedimentary architecture of glacial valley-fill reservoirs. Future applications include an upscaled regional study of the sediment budget for an extended section of the Arctic coast.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009