--> Abstract: Impact of Variable Shoreline Trajectory from Facies Preservation During Marine Transgression, by Oliver Jordan, Sanjeev Gupta, Gary J. Hampson, and Howard D. Johnson; #90078 (2008)

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Impact of Variable Shoreline Trajectory from Facies Preservation During Marine Transgression

Oliver Jordan, Sanjeev Gupta, Gary J. Hampson, and Howard D. Johnson
Earth Science and Engineering, Imperial College, London, United Kingdom

Shoreline trajectory controls stratigraphic preservation potential in wave-dominated shoreline systems, because of shoreface erosion occurring during transgression (shoreface “razor”). Here we analyse net-transgressive successions showing variable shoreline trajectories to investigate variations in sandbody dimensions, distributions and architecture.

The Cretaceous Cliffhouse Sandstone exhibits a range of transgressive shoreline trajectories at outcrop in the San Juan Basin, southwestern US. Two detailed datasets have been collected, and facies architecture and sandbody distributions have been correlated within the net-transgressive sandstone complex over dip extents of c. 10 km in each dataset. The unit exhibits a complex arrangement of (1) stacked wave-dominated shoreface sandstones, (2) tide-dominated sheet and channel sandstones, (3) lagoonal sandstones, siltstones and mudstones, and (4) coastal plain sandstones and siltstones. These facies are separated into distinct stratal packages by a hierarchy of erosional bounding surfaces (wave and tidal ravinement surfaces) which control sandbody connectivity and may also act as barriers or baffles to flow. The wave and tidal ravinement surfaces are contemporaneous, and preservation of underlying strata is dependant on the relationship between the “step up” and the “step back” of the shoreline through time. Wave ravinement surfaces marked by large landward facies dislocations are associated with greater preservation potential, and near-complete regressive successions are preserved beneath them. Wave ravinement surfaces with smaller facies dislocations exhibit greater truncation of the underlying succession (e.g. foreshore and upper shoreface facies are absent). The geometry and distribution of these surfaces therefore determines reservoir thickness, dip extent, and degree of compartmentalisation by shale tongues.

 

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