A Predictive Stratigraphic Model for the Development of Alluvial Strata

The development of a generic predictive stratigraphic model for continental strata is important for understanding controls on the terrestrial fossil record, deciphering climate through time and, the exploration for and exploitation of, aquifers and hydrocarbon reservoirs. Models concerned with stratigraphic architecture in continental strata have focussed largely on the influence of downstream base-level controls on fluvial architecture and geometry. Although more recently the recognition that upstream controls are also important and may potentially dominate alluvial architecture has been acknowledged. Many of these models focus on specific large-scale aspects of alluvial deposits such as the development of sequence boundaries, sandstone stacking patterns or the relationship between soil development and stacking patterns and do not always consider the relationship of these alluvial architectural elements to the smaller scale autocyclic processes that are commonly inferred from studies of fluvial strata such as channel migration or avulsion.

Here we present a predictive stratigraphic model for the development of alluvial strata that combines an understanding of alluvial response to changes in accommodation space/sediment supply with likely facies distributions based on observations from modern aggradational settings. We integrate observations of autocyclically-driven facies distribution (e.g. avulsion), with variations in paleosol maturity, sandstone body stacking patterns, and development of erosion surfaces at both local and regional scales. An important aspect is that the model is driven by upstream controls (e.g. climate change in the catchment or tectonic processes) and can be considered to be independent of any control by fluctuations in marine base-level. We discuss the controls on the development of alluvial architecture using a hierarchical approach that can be considered with the commonly used surface order terminology.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California