Print this pageAAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Sediment Volume and Facies Partitioning in Shelf-Margin Prisms
(1) Chevron, Houston, TX.
(2) Jackson School of Geosciences, The University of Texas, Austin, TX.
An understanding of how sediment budget volumes have been partitioned into differing compartments of source-to-sink fairways, as well as quantitative estimates of the relative amounts of sand and mud in these compartments, is of key importance to holistic studies of both modern and ancient large-scale sedimentary systems. We demonstrate how the early Maastrichtian Lewis-Fox Hills sediment budget was partitioned into the shelf, slope, and basin-floor fan compartments in the deep-water shelf margin prism of southern Wyoming. Basin-scale, budget-volume calculations for high-resolution (~100 ky) shelf-margin clinothems indicate that for mid-case scenarios the average ratios of volume partitioning are 1.1:1.1:1.0 for total sediment, 2.7:1.0:1.6 for sandstone, and 1:1.4:1.1 for shale. The partitioning of sandstone and mudstone mostly reflects the sandy composition of fluvial and shoreline systems on the shelf, and the efficiency of turbidity currents in bypassing sand through the slope to form large sand-prone basin-floor fans, while the same currents and other processes store much mud on the slope. Departures from these average ratios occur when the shelf-margin growth tends to be more aggradational or more progradational with a larger fraction of the sediment volume partitioned into the shelf or deep-water compartments respectively. As suggested by some data and observations, these ratios appear to be somewhat similar to ratios in other margins representing different tectonic settings, sediment supply and sea level regimes. Ratios of sediment volume partitioning are useful and fundamental in the description and analysis of source-to-sink sedimentary studies. They also enhance prediction and interpretation of the long term variables driving shelf-margin growth, basin infill, and overall source-to-sink evolution.