A THEORETICAL FORELAND BASIN SUBSIDENCE-ACCOMMODATION-TIME- SERIES (SATS) MODEL WITH APPLICATION TO THE TACONIC SEQUENCE OF NORTHERN VIRGINIA

A theoretical subsidence-accommodation-time-series (SATS) diagram was developed which shows the relationships between a loading/subsidence curve and an accommodation curve that plots water depth and sediment volume changes through time. The model was tested against a model based on the actual Shenandoah Valley Taconic sequence with close correspondence between the two models.

We consider an ideal foreland basin to be tectonically loaded by a collisional thrust stack. Imagine a stratigraphic section containing the point of deepest subsidence of the basin. Subsidence driven by sediment loading initially creates accommodation space, slowly at first, then more rapidly as the tectonic load is applied, then followed by an exponentially decaying rate. Accommodation space fills with sediment at corresponding rates.

Because the basic SATS curve applies to the point of deepest basin subsidence, additional SATS diagrams are drawn for other parts of the basin. For example, as one moves toward the craton where rates and depths of subsidence diminish, the curves get shallower, although the basic shapes and their relationships remain.

The theoretical SATS is a predictive model of a foreland basin’s ideal history, and thus real-world deviations from the model act as an indicator that some other process may be affecting the evolution of the basin.

The theoretical SATS foreland basin model was initially developed for an undergraduate course that synthesizes stratigraphic, structural and tectonic principles to understand terrane evolution. It is used as an ideal foreland basin model against which actual ancient and modern foreland basins are compared, and tested, both in the classroom and in the field.