Master of Science (MS)


Geology and Geophysics

Document Type



Pennsylvanian age Jackfork Group cores from the DeGray Lake Dam and outcrop from the east wall of the DeGray Lake Spillway, Arkansas, provide an opportunity for a detailed study on the transport and depositional characteristics of a fine-grained, deep-water depositional system. Two phases of resedimentation processes are responsible for deposition of the sediments in the cores and the outcrop. Primary resedimentation processes transport terrigenous sediments from the shelf or basin edge into the middle fan environment, while secondary resedimentation alter the sediments after they are initially deposited in the environment. Debris flows, slurry flows, and high and low density turbidity currents are all of the primary flows that can be identified in the cores and outcrop. It is likely that most of these flows (termed sediment gravity flows) were derived from slides and slumps that originated up-slope. Slides, slumps, creep, and debris flows have occurred on localized slopes on the sea floor, creating a secondary phase of deposition. Each of these events is recorded in rather small-scale intervals in the cores and outcrops, but their accumulated influence is significant. Core and outcrop can be placed into separate depositional packages based on changes in lithofacies characteristics. These packages are compared from core to outcrop, and those that are most similar are correlated. The cores and outcrop show bedding trends and other sedimentary characteristics that indicate they were deposited within the framework of a middle submarine fan. The middle fan is characteristic of thick-bedded channel axis sands, thick- to thin-bedded channel margin sands, thin-bedded levee/overbank sands and muds, and very thin-bedded distal overbank silty muds. In some cases, more than one subenvironment is suggested as an appropriate interpretation for a depositional package. This is due to the fact that the divisions between these subenvironments are gradual and many deposits may fall into a transitional realm. Core and closely spaced outcrops studied together offer several benefits over studying each separately. The cores provide new data from the subsurface that is applied to a well known outcrop. Fresh core faces show more fine-scale details that are hard to see in the spillway, which has many heavily weathered and covered sections. The spillway east outcrop, although tilted, provides more spatial variation, which can be correlated back to the cores. Bedding trends and contacts are better exposed in outcrop due to artificial breaks in the cores caused by drilling and recovery.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Arnold H. Bouma