AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Evaluating the Role of Sediment Supply and Tectonics in Sediment Partitioning and Reservoir Distribution in the Cordilleran Foreland Basin: A Basin-Scale Analysis of the Lower Mesaverde Group, Utah and Colorado
(1) Geology and Geological Engineering, Colorado School of Mines, Golden, CO.
Previous work defined a strongly progradational, low-accommodation clastic wedge in the UT-CO segment of the Cordilleran Foreland basin (CFB). The wedge spans from the top of the Castlegate S.s. to the top of the Bluecastle Tongue, and is thought to have developed due to reduced accommodation during overlapping thin and thick-skinned tectonic styles. However, the role of sediment supply in the development of the wedge is poorly constrained. This study presents new isopach maps, sediment volumes, and sedimentation rates for high-frequency sequences within the wedge in the Uinta basin. These new data and preliminary analyses provide insight into the role of sediment supply in the development of the wedge, and sediment partitioning and reservoir distribution in the CFB during the Sevier-Laramide transition. A database of 50 well logs and 45 stratigraphic profiles were used to create isopach maps of both the entire wedge and high-resolution sequences within the wedge. Sediment volumes were calculated from the isopachs and combined with age-control to calculate sediment flux. Isopach maps show the wedge thickens towards the northeast, and thins against the Sevier thrust belt and San Rafael Swell (SRS). Analysis of high-frequency sequences within the wedge highlights this pattern, but also shows initiation and development of the northern Uinta basin depocenter and thinning toward the Uinta Uplift. The forced regressive to lowstand sequence set (top Castlegate S.s. to base Neslen Fm.) within the wedge thickens towards the northeast, and thins towards the thrust belt, the SRS, and the Uinta Uplift. The transgressive sequence set (Neslen Fm.) thickens to the east, highlighting an eastward shift in the depocenter. The Bluecastle Tongue shows a distinct thickening to the north into the E-W trending depocenter south of the Uinta Uplift. Calculated sediment volumes for the Neslen and Bluecastle Tongue were 853 km3 and 687 km3 respectively. Stratal thickness patterns suggest (1) the Uinta Uplift was active in the latest Campanian, earlier than previously thought, (2) the Sevier thrust-belt and SRS were active in the latest Campanian, and (3) sediment flux did not fluctuate greatly throughout the wedge’s development. This study shows both thick and thin-skinned tectonics contemporaneously affected deposition in the CFB during the Campanian. Further work should integrate data from the Piceance basin, so that a more complete transect of the CFB can be analyzed.