Quantifying Allogenic Forcing of Alluvial-Fan Stratigraphy by 3d Numerical Modeling and Comparison with Outcrop Examples

Sébastien Rohais¹, Dario Ventra², and Poppe L. de Boer^2
1Stratigraphy-Sedimentology, IFP, Rueil-Malmaison, France
²Earth Sciences, Utrecht University, Faculty of Geosciences, Utrecht, Netherlands

We explore a new methodology to solve questions about the effects of different and varying allogenic controls on deposition patterns and morphology of alluvial fans by performing a systematic series of numerical stratigraphic simulations of fan development using the DIONISOS program (IFP, France). Model output is compared to field examples of recent and ancient alluvial-fan systems.

Model runs span different time scales, from 10 ky, for comparison with abundant studies of late-Quaternary alluvial fans, to 500 ky, for comparison with ancient successions of long-lived systems preserved in the geological record. Models comprise a full spectrum of sensitivity tests. The effects of single factors, i.e., (variations in) tectonics, sediment supply, water discharge and sediment composition, as well as combinations of these, are tested under steady to unsteady forcing conditions, and with different time resolutions.

We compare our model output with a case study of a unique Miocene alluvial fan system in the Teruel Basin (central Spain). This fan system has aggraded in an astronomically forced, cyclically alternating paleoclimate with alternating relatively humid and arid periods. Comparison of the architecture of the alluvial-fan succession with the model output corroborates the approach used in the stratigraphic modeling.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas