AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Source-to-Sink Correlation and Facies Architecture of the Late Campanian Twenty-Mile and Trout Creek Clastic Wedges
(1) Jackson School of Geosciences, The University of Texas at Austin, Austin, TX.
The Cretaceous Western Interior Seaway (WIS), an epicontinental seaway that connected the Arctic Ocean with the Gulf of Mexico/Atlantic Ocean though the middle of the North American continent, was part of a retro-arc foreland basin on the east side of the Sevier thrust-and-fold belt.
The Twenty-Mile (TMCW) and Trout Creek (TCCW) are the final two 3rd-4th order clastic wedges shed from Sevier Belt into the WIS. The TMCW contains coastal plain Almond Formation of South Wyoming that passes basinward into a series of marine, regressive shorelines, the Twenty-Mile sandstone and transgressive coastal plain and shorelines of the Holderness Member of Northwest Colorado. The TCCW is formed by the fluvial Canyon Creek Member of the Ericson Formation of South Wyoming, the regressive shorelines of the Trout Creek and transgressive coastal plain and shorelines of the Mount Harris Member.
The Twentymile Sandstone is a > 40 meters-thick deltaic succession that prograded some 80 km across parts of N Colorado. It presents at least two delta lobes of contrasting process domination on US Hwy 40, a lower deltaic lobe clearly dominated by storm waves and an upper lobe of complex tide-river domination with some storm influence. The upper lobe also presents an important variability along strike, varying from tide-river domination to storm domination laterally. The Canyon Creek Member of the Ericson Formation is a multi-storey, multilateral complex fluvial deposit that sits unconformably over the previous deposits. Inside this member two internal unconformities can be observed.
The Almond Formation is composed of two units. The lower part is a very low net-to-gross coastal plain succession with meandering channels. The upper unit is composed of up to 5 different shoreline tongues in which there is important variability of process domination. Similar to this is the Holderness Member, having coastal plain deposits in the lower part and some transgressive shorelines in the top, but in this case they are thinner and only one or two tongues are present.
A 300km non-marine to marine transect is created through a combination of a well-log dataset with field observations and measured sections. This transect allows the examination of signals that the regressive-transgressive shoreline cycles implanted in the up-dip coastal plain, estuaries and fluvial feeders, as well as the evaluation of the possible controls that drove these cycles.