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Decoupling allogenic forcing from autogenic processes: Experimental geomorphology and stratigraphy

UTIG Seminars

Decoupling allogenic forcing from autogenic processes:
Experimental geomorphology and stratigraphy

Dr. Wonsuck Kim
UT Institute for Geophysics

When: Friday, April 22, 2011, 10:30 p.m. to 11:30 p.m.
Where: Seminar Conference Room, 10100 Burnet Road, Bldg 196-ROC, Austin, Texas 78758
Host: Charles Jackson, UTIG

Live Broadcast

image from Wonsuck's talk

At the heart of interpreting the evolution of the Earth's surface preserved in the sedimentary record is decoupling the preserved signal of environmental (allogenic) forcing from those of internally generated (autogenic) processes. A major stumbling block for distinguishing allogenic versus autogenic signatures in the stratigraphic record is a lack of quantitative understanding of autogenic processes and their interactions with allogenic forcing. Physical experiments with moving sediment and water construct topography with dynamic self-organized fluvial system, thus providing an opportunity to investigate autogenic processes under controlled boundary conditions (e.g., sediment supply and tectonics). This presentation reviews a set of tank experiments that are used to quantitatively examine 1) the autocyclic storage and release of sediment in the deltaic surface associated with river-pattern changes between channel and sheet flow, and 2) changes in fluvial autocyclic behavior driven by external forcing (e.g., sea-level change and tectonics). The time and event scales of the autogenic processes observed in the experiments conducted without external forcing provided the first-order quantitative understanding of the autogenic processes. Changes in the frequency of autogenic processes due to base-level change and lateral ground tilting provided a new view to the coupled allogenic and autogenic control on stratigraphic development. Coupled experiments that test the effect allogenic forcing on autogenic process are presented here: one conducted with constant external forcing and the other with cyclic changes in external controls. This review provides 1) quantitative measurements of fluvial autogenic processes and thorough comparisons of cyclic strata attributed to allogenic versus autogenic controls, and 2) suggestions of future directions on experimental study of fluvial autogenic processes that will enhance our ability to interpret the mixed signals of environmental variation and internal dynamics in the sedimentary record.