Print this pageThe Influence of Eustatic Sea-Level Variations from Shelf Morphology and Sediment Distribution in Source-to-Sink Systems
Tor O. Sømme1, William Helland-Hansen1, Ole J. Martinsen2, and John B. Thurmond2
1Department of Earth Science, University of Bergen, Bergen, Norway
2Norsk Hydro Research Centre, Bergen, Norway
During the Quaternary, high-frequency, high-amplitude eustatic sea-level changes have acted as the primary control on shelf morphology and accommodation, whereas tectonic uplift and subsidence have played a minor and secondary role. These fourth- to fifth-order variations reflect the growth and decay of polar ice sheets, and are known to have had a major influence on the timing and distribution of shallow- and deep-marine sediments in source-to-sink systems.
In this study, the role of eustatic sea level on sediment dispersal from the catchment to slope and basin floor fans is investigated for selected time periods, each characterized by different magnitudes and frequencies of eustatic sea-level change. This is achieved by the use of 3D stratigraphic modelling software which permits a direct comparison between the impact of eustatic sea level, shelf morphology and sediment partitioning. In three scenarios, a reference shelf is modelled for ~3 my with an imposed Quaternary sea-level curve, an Early Neogene curve reflecting the initiation of ice-sheet growth in the Antarctic, and a Late Cretaceous curve representing “greenhouse” conditions. A comparison between the three scenarios then allows for an estimation of shelf storage potential and sediment distribution patterns for the various time periods. Analysis of chronostratigraphic relationships also elucidates the timing of delta progradation and filling of shelf accommodation, suggesting that sediment delivery to the basin floor during highstand periods is determined by the magnitude and frequency of sea-level variations during deposition.
Finally, the principle of uniformitarianism in source-to-sink systems is challenged, implying that certain parameters describing shelf morphology and sediment distribution during modern conditions are not directly applicable to ancient systems controlled by other mechanisms.
AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas