Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Controls on Alluvial Architecture During Passive Salt Diapirism, Chinle Formation, Paradox Basin, Utah
(1) Geology & Petroleum Geology, University of Aberdeen, Aberdeen, United Kingdom.
An understanding of the control that salt movement has on alluvial architecture is important in predicting reservoir presence and quality adjacent to salt bodies in the subsurface. The quality of seismic reflection data adjacent to subvertical salt bodies means that reservoir presence is often difficult to determine, consequently studies of appropriate outcrop analogues can have a significant impact on subsurface understanding. A detailed outcrop study of the Upper Triassic Chinle Formation in the Moab area of the Paradox Basin has been undertaken. Previous work in this area suggests that individual lithostratigraphic units generated by specific fluvial planform types (either braided or meandering) can be traced across much of the region and that braided systems form sheet-like units developed during periods of relatively limited salt movement. Here we illustrate that lithostratigraphic correlation is not valid between adjacent salt mini-basins and that significant lithostratigraphic variations occurs even within mini-basins. Three examples are shown where vertical salt movement results in the periodic uplift and tilting of alluvial strata to produce a series of subtle, low angle unconformities/erosion surfaces. Amalgamation of sand bodies across these erosion surfaces produces laterally extensive sheet-like sand bodies that link the between the edges and centre of individual mini-basins. At a larger scale, reservoir presence is strongly influenced by the interaction between salt structures and alluvial drainage systems. Adjacent mini-basins can have a completely different stratigraphy dependent on whether they were isolated or open to an axial fluvial system.