Carolina Gomez, PhD Candidate
Contact Information:
Department of Geological Sciences, UT-Austin
Office: 6.120; No Phone
E-mail: cgomez@mail.utexas.edu
Current Research Summary:
Sediment Budget Distribution in a Source-to-Sink Transect (Late Campanian Western Interior Basin, SW Wyoming and N Colorado)
The problem of how sand and mud is distributed within sedimentary systems or how the total sediment budget is differentially stored and by-passed along source-to-sink time slices is currently a research topic of significant interest in the Sedimentary Geology community. The topic is important from a purely academic viewpoint (budget partitioning) as well as from an applied one.
This research project will dig into the problem of sediment partitioning along a regional transect in the Cretaceous Western Interior Basin. In order to quantify the amounts of sediment differentially sequestered during one complete cycle of relative sea level fall & rise, at both 4th and 3rd order time scales, a working hypothesis will be used. This hypothesis predicts that during early and main stages of relative sea level fall, erosion and sediment bypass occur throughout the upstream or fluvial part of the system, whereas widespread progradation and deposition occurs from the shoreline out into the basin. During sea level rise and transgression, however, almost the opposite happens, i.e., there is transgressive erosion and minimal deposition across the new marine shelf but significant sediment sequestering in the most proximal parts of the system, i.e. in the estuarine/coastal plain and fluvial areas.
The falling-stage, however, is controversial and other models anticipate less widespread erosion and partial filling of incised valleys during falling relative sea level, so that the sediment budget is partitioned both proximally and distally during regression.
Another problem related with the sediment budget partitioning is the establishment of the role of local tectonics and regional tectonics in the development of the sequences of various orders described above. In this respect, I will investigate the Laramide tectonics in the proximal parts of the system, to elucidate whether it has a 3rd order or 4th order time scale impact.
The rock succession that will be used to test these ideas corresponds to a 3rd order regressive-transgressive clastic wedge that was deposited in the Cretaceous Western Interior Seaway, located in south Wyoming and north Colorado. This wedge spans the time slice between ammonite zones Baculites perplexus complex to Exiteloceras jenneyi
In the proximal parts of the system this project will analyze the Campanian Trail and Rusty members of the Ericson Sandstone, in southwest Wyoming. Moving to the southeast, the intermediate (shoreline) reaches will be studied using the coeval Iles Wedge in the Sand Wash Basin. Finally, the distal zone of the system will be monitored in the time-equivalent Muddy Buttes-Hygiene-Carter and Hygiene-Terry Sandstones in the Middle Park and Denver Basins.
The ca. 3 m.y. stratigraphic time slice above will be studied using outcrop and subsurface data, and this information will be integrated to create a regional 400 km transect running from southwest Wyoming to north-central Colorado. This transect will be used to assess the 2-D sediment partitioning along the regressive and transgressive segments of the system.
In order to estimate the impact of Laramide (local) and Sevier (regional) tectonics in the deposition of these rocks, isopach and facies maps of the proximal reaches of the system (Trail, Rusty, and Trail plus Rusty members will be constructed. Furthermore, the geometry and lateral thickness changes of component 4th order cycles will be assessed.
Field Photos:
Past Research:
***All photos and content COPYRIGHT by C. Gomez; please e-mail for permission to use***