Fluvial response in a sequence stratigraphic framework: Example from the Montserrat fan delta, Spain
- Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology and Geophysics
- Univ. de Barcelona (Spain)
- Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Geology and Geophysics
Exceptional exposure of the Montserrat fan-delta system (Eocene) in northeastern Spain provides an excellent framework to evaluate the alluvial response to sea-level changes over two different time scales. The alluvial system contains multiple fifth-order cycles ({approximately}10{sup 4} yr) and eight fourth-order cycles ({approximately}10{sup 4} yr). Fifth-order cycles are characterized by long-distance shoreline migrations and, occasionally, by incised basal scour surfaces but not by changes in fluvial style, lithofacies, or channel stacking pattern. Fourth-order cycles are composed of stacked fifth-order cycles and have non-erosional basal boundaries. Changes in the alluvial system during fourth-order cycles are most pronounced adjacent to shoreline and die away upstream over just a few kilometers--indicating that the base-level signal decays away over the distance of a few backwater lengths. Higher-frequency (fifth-order) changes in relative sea level appear to produce the largest shoreline migrations, but lower-frequency (fourth-order) changes have more impact on the channel stacking architecture of the alluvial systems. Observed changes in alluvial stacking pattern may be most commonly found in tectonically active, rapidly subsiding, foreland basins because of their back-tilted geometry. The authors propose a model in which sediment is trapped in the proximal basin during times of rapid tectonic subsidence and attendant relative sea-level rise. Progradation occurs as erosion rates in the mountain belt increase, and rates of subsidence and relative sea-level rise diminish. Changes in alluvial architecture reflect an increase in sediment flux towards the shoreline as less sediment is trapped upstream. Hence, changes in channel-stacking pattern coincident with transgressions and regressions likely reflect the interplay between subsidence and sediment supply in the proximal part of the basin and are not necessarily driven by eustatic sea-level changes.
- Sponsoring Organization:
- American Chemical Society, Washington, DC (United States); National Science Foundation, Washington, DC (United States); Commission of the European Communities, Brussels (Belgium); DGICyT (Spain)
- OSTI ID:
- 460586
- Journal Information:
- Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes, Vol. 67, Issue 2; Other Information: PBD: Mar 1997
- Country of Publication:
- United States
- Language:
- English
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