Bartek, Louis1, Robert Wellner2, Jeff D. Warren1
(1) University of North Carolina, Chapel Hill, Chapel Hill, NC
(2) ExxonMobil Upstream Research Company, Houston 77252-2189, TX
ABSTRACT: Climate Change and Shelf Physiography -- Their Role in Shaping Sequence Architecture: An Example from the East China Sea
Nearly 3,000 km of high resolution seismic reflection data and approximately 3,500 km of chirp sonar data were acquired on the East China Sea (ECS) continental margin as part of an investigation of how variation of sediment supply and physiography alter the facies and stratigraphic architecture of depositional sequences. Eustatic change is a primary driver of stratigraphic sequence development, but climate change, in the region, plays an important role in altering river discharge and therefore the flux of sediment to the fluvial and marginal marine environments. An example of the key role of climate in shaping the incised valley architecture is from the ECS where the most extensive interval of valley incision occurs late in the lowstand and early in the transgression of the sea level cycle, when climatic conditions were at their wettest and fluvial discharge was greatest. This contrasts sharply with the timing of incision development driven primarily by eustasy, in which case, the maximum incision occurs in the interval when eustasy is falling at the highest rate. This point shows how climate change, rather than eustatic change, can govern the timing for the onset of incised valley development. A key point is that climate related processes can occur with a timing that is not in synch with the eustatic changes and may therefore enhance or negate the impact of the eustatic change in shaping the architecture. Physiography of margins governs sequence architecture development as well. Low gradient shelves and deep shelf slope breaks often lack the extent of lowstand incised valley fill as that associated with shallow shelf/slope breaks. Other examples with be presented in the paper.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.