Seismic Facies of Shelf, Slope, and Submarine Fan Environments of the Lewis Shale, Upper Cretaceous, Wyoming

Stratigraphic Cross Sections of the Lewis Shale in the Eastern Part of the Southwestern Wyoming Province, Wyoming and Colorado

“…In clinothems 1 to 6, the shelf edges have an aggradational/progradational stacking pattern, whereas clinothems 7 to 15, are strongly progradational. This stacking pattern has been demonstrated by McMillen and Winn (1991), Steel (2009), andOlariu andothers (2012), and is interpreted to reflect changes in sediment supply relative to sea-level and local subsidence.…”

“…3, cross section B-B') toward the Rock Springs uplift (fig. 1), recording the last major sealevel transgression in the area (McMillen and Winn, 1991).…”

“…The lower member of the Lewis is predominantly mudstone and has consistently higher GR values when compared to the rest of the Lewis. The lower member is interpreted as a third-order transgressive systems tract and may be an internal source of gas for sandstone accumulations within the Lewis (McMillen and Winn, 1991;Pyles and Slatt, 2000;Pasternack, 2007).…”

“…The Asquith marker is an organic-rich black shale that can be correlated in well logs throughout the study area and is the datum for all three cross sections. The Asquith marker is interpreted as a third-order condensed section that represents the maximum flooding surface of the Lewis Shale and records the turn-around from transgression to regression of the Cretaceous Western Interior Seaway (McMillen and Winn, 1991;Pyles and Slatt, 2000). The Asquith marker has been studied extensively in the Champlin 276 Amoco D-1 well (API number 4900720477), which cored the entire interval.…”

Defining the concept of stratigraphic grade and applying it to stratal (reservoir) architecture and evolution of the slope-to-basin profile: An outcrop perspective

“…The interval of strata below this datum records the transgressive (retrogradational) part of the third-order cycle, whereas the interval of strata above the datum records the regressive (progradational) part of the thirdorder cycle (Fig. 3) (McMillen and Winn, 1991;Pyles, 2000;Pyles and Slatt, 2000;Pyles and Slatt, 2007). The progradational part of the third-order stratigraphic cycle contains 15 fourth-order Pyles and Slatt, 2007).…”