Clastic wedge development and sediment budget in a source-to-sink transect (late Campanian Western Interior Basin, SW Wyoming and N Colorado) .

摘要

A 300 km (188 mi) sedimentary transect was reconstructed across the 500 m (1640 ft) thick, 3 my duration Iles Clastic Wedge in S Wyoming and N Colorado using well logs and stratigraphic columns. This wedge developed in mid-late Campanian times by progradation from the active Sevier fold-and-thrust belt and adjacent uplifted areas. Analysis of this transect allows the wedge and its component sequences to be better understood and permits a 2-D characterization of the sand-mud distribution. The Iles Wedge exhibits eleven, low-gradient, regressive-transgressive, high-frequency sequences that were correlated across several hundred kilometers.;Sediment partitioning analysis along the transect shows that: (1) Within the regressive limb of the Iles Wedge, the component higher order regressive compartments tend to thicken into the medial reaches of the wedge, whereas transgressive compartments thicken landwards. This geometry is driven by preferential erosion in proximal areas during regression, bypassing much sediment to the marine shorelines, and transgressive backfilling into proximal areas previously eroded more deeply. (2) The greatest concentration of sands tends to be located in the proximal fluvial and estuarine facies of the transgressive compartments and within the medial shoreline/deltaic facies of the regressive compartments. (3) As the high-frequency sequences develop, the effectiveness of basinward sand partitioning reaches a maximum value near the peak regression level of the wedge, apparently reflecting stronger erosion and sediment bypass during these times.