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Sequence Stratigraphic Architecture of the Lea Park and Foremost Formations, Western Canada Sedimentary Basin

Andrew Mumpy
University of Alberta, Department of Earth and Atmospheric Sciences
Edmonton, Alberta, Canada [email protected]

The Campanian Lea Park and Foremost Formations of the Western Canada Sedimentary Basin (WCSB) are widespread beneath the plains of Alberta and Saskatchewan where they form a complex, cyclic transition zone between marine (Lea Park) and paralic (Foremost) deposits. An extensive well log database supplemented by core and outcrop data allows for high resolution subsurface mapping of these units in 3-D. Integration of biostratigraphic and magnetostratigraphic data provides age control for correlations. The Lea Park-Foremost transition zone affords an excellent opportunity to decipher the sequence stratigraphic architecture of a regionally extensive second-order cyclothem, and to potentially link marine and nonmarine sequence stratigraphic methodologies in a foreland basin case study. In addition, the widespread nature of the Lea Park Formation, which constitutes a previously unstudied potential shale gas play, makes the unit ideal for the assessment of the relative contributions of tectonic subsidence mechanisms, which were the driving forces behind relative sea level (RSL) fluctuations in the WCSB during Campanian time. RSL fluctuations produced by flexural subsidence and uplift are an important control on the creation or destruction of accommodation space in foreland settings, and may control the thicknesses of depositional sequences to a large extent, however, simple calculations indicate that dynamic subsidence associated with sublithospheric loading is also an important contributor. Isopach mapping of high frequency sequences in the Lea Park-Foremost transition zone will yield insight into the relative contributions of these subsidence mechanisms, and may shed light on the causes for previously documented regional unconformities in this stratigraphic interval.

 

AAPG Search and Discovery Article #90070 © 2007 AAPG Foundation Grants in Aid