Sediment Transport in the Western Interior Seaway of North America: Predictions from a Climate-Ocean-Sediment Model
Rudy Slingerland, Hmothy R. Keen, 1999. "Sediment Transport in the Western Interior Seaway of North America: Predictions from a Climate-Ocean-Sediment Model", Isolated Shallow Marine Sand Bodies: Sequence Stratigraphic Analysis and Sedimentologic Interpretation, Katherine M. Bergman, John W. Snedden
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Whether from the foreshore, shoreface, shelf, or incised esruarine valleys, sedimentary deposits along the western edge of the Western Interior seaway quite uniformly record southerly directed paleoflows. Cardium Formation shoreface gravels at Willesden Green, Alberta, decrease in clast size to the southeast. Isoliths outlining clastic wedges, such as the Chalk Creek, are recurved to the south. Large-scale cross-strata in rocks considered to be either shelf sand ridges or detached shorefaces, such as the Kakwa and Musreau Members of the Cardium Formation and the Straight Cliffs Formation of southwestern Utah, indicate southerly directed paleocurrents. Estuarine incised valley-fills trend south or southeast, reflecting a high-stand shelf topography inherited by rivers as they cut across the inner shelf in response to a high-order sea-level drop. To explain this uniformity we conducted two numerical experiments that predict circulation and sediment transport paths in the seaway in response to 1) mean annual atmospheric forcing and 2) the passage of a mid-latitude winter storm. The mean annual forcing for the early Turonian is computed by GENESIS, an NCAR global climate model; the cyclone is computed using an idealized hurricane model. For the mean annual experiment, circulation of the seaway is computed using a three-dimensional, turbulent flow, coastal ocean model under the following initial and boundary conditions: 1) paleobathymetry according to a new interpretation of the litho- and bio-stratigraphy for the early Turonian; 2) fresh water runoff and precipitation-evaporation magnitudes as computed by GENESIS; 3) temperatures and salinities of the Boreal and Tethys Oceans based on GENESIS atmospheric temperatures; and 4) mean annual and daily wind stresses computed by GENESIS. For the storm experiment, circulation is forced solely by wind stresses.
Results show that these boundary conditions combine to produce a basin-wide counterclockwise gyre that arises from Coriolis acceleration acting on runoff jets trapped along the coast, abetted by latitudinal temperature and salinity gradients and a north-south, wind shear-couple. Individual storm events reverse the general circulation locally, but summed over a storm's duration, the storm-driven fluid and sediment transport augments the mean-annual transport of the gyre. Thus, net sediment transport directions along the western margin of the seaway, both on the shelf and in the wave-driven littoral zone, were southerly because the mean annual wind field, latitudinal temperature gradient, and fresh water runoff from land created a background circulation consisting of southerly geostrophic flow there. In addition, counterclockwise rotating, mid-latitude cyclonic storms passing southeastward over the central seaway drove a net southerly littoral drift in the foreshore and shore-parallel geostrophic flows whose net sediment transport was southerly. Along the eastern margin the computed shelf and littoral transport was to the north.
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Isolated Shallow Marine Sand Bodies: Sequence Stratigraphic Analysis and Sedimentologic Interpretation
Isolated Shallow Marine Sand Bodies: Sequence Stratigraphic Analysis and Sedimentologic Interpretation - Isolated shallow marine sand bodies are significant hydrocarbon reservoirs and understanding sand body genesis and geometry is critical to successful exploration and exploitation of these deposits. Recent advances in sequence stratigraphy have rekindled and refocused the discussions surrounding these important reservoirs. This volume stems from a 1995 SEPM sponsored targeted research conference that brought together the proponents of the differing interpretations to discuss facts and principles as they relate to isolated shallow marine sand bodies, using the controversial Lower Campian Shannon Sandstone as the focus for discussion.