Törnqvist, Torbjörn E.1
(1) University of Illinois at Chicago, Chicago, IL
ABSTRACT: The Role of Climate in a Sequence Stratigraphic Framework: Recent Progress and Future Challenges
The important role of upstream controls is increasingly recognized by investigators who seek to unravel the stratigraphic record in terms of allogenic forcing. The fluvial system is one of the components of the sediment-dispersal system that responds in a relatively direct fashion to climate change. Recent studies of late Quaternary, glacial-interglacial scale fluvial records unambiguously demonstrate that a large proportion of preservable fluvial strata accumulate during relative sea-level fall, due to climate-controlled high sediment supply from the hinterland. At present, no examples exist that point to the contrary. In addition, it has been shown that the response to rapid (millennium-scale) climate change can be remarkably complex, illustrated by spatially variable adjustments of the fluvial long profile following one simple perturbation. Strikingly similar insights have been generated by recent experimental studies.
Key questions that deserve future scrutiny include, but are not limited to (1) how rapidly do upstream forced changes propagate downdip through the sediment-dispersal system? (2) to what degree is the climate signal muted or overwhelmed by downstream controls? and (3) under which conditions are responses to upstream forcing likely to be nonlinear? Clearly, there is a particular need for a comprehensive, source-to-sink approach in order to resolve these issues.
The prospects of directly isolating the effects of climate change from ancient stratigraphic successions are presently dim. It is proposed here that a more viable approach would focus on gaining fundamental understanding from strata where independent climate and sea-level records are available and where numerical dating resolution is adequate. Experimental and mathematical models that pass the test of validation by means of high-resolution stratigraphic successions can subsequently be used to help interpreting the ancient rock record. Although this approach presents considerable challenges, model-data comparisons can at least constrain the degrees of freedom in the interpretation of ancient successions.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.