Browsing by Subject "Experimental model"
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Item The effect of a pre-deposited mobile substrate on terminal fan evolution and channel organization : tank experiments(2016-05) Chatmas, Emily Sarah Jane; Kim, Wonsuck; Kocurek, Gary; Mohrig, DavidDepositional processes and interactions with a mobile substrate are seen in passive margins throughout the world. The interplay between brittle stratigraphic layers and a deformable substrate resulted in a complex stratigraphic record due to dynamic feedback influences. During the Late Jurassic, a fluvial-dump-wind-redistribute system deposited sediment on top of the pre-deposited Louann Salt layer in the eastern part of the early Gulf of Mexico basin. By using simplified, scaled-tank experiments we are able to investigate the evolution of a linked fan and terminal channel system in response to subsidence in a mobile substrate. A series of experiments were conducted with controlling variables including salt substrate thickness, sediment supply rate, and basin slope. Fan surface area and morphology, number of terminal channels, channel longevity, and geometry were measured along each experiment. Experimental results indicate: (1) an increase in substrate thickness resulted in increased subsidence around the fan that limited sediment transport to its terminal channels, (2) a higher sediment discharge rate on a thin substrate resulted in faster fan progradation coupled with less subsidence and more sediment transport to terminal channels, and (3) a higher-sloped experiment caused the largest amount of sediment transport downstream, while a decrease in basin slope resulted in a larger number of established channels along with a wider fan surface. An analysis of surface processes is also used to determine the expected stratigraphy between a linked fan and terminal channel system as it interacted with the mobile substrate. Furthermore, we utilize the experimental findings to improve the current depositional model for the Jurassic Norphlet Sandstone.Item Physical modeling of a prograding delta on a mobile substrate : dynamic interactions between progradation and deformation(2016-08) Jung, Eunsil; Kim, Wonsuck; Mohrig, David; Olariu, CornelThe subsurface architecture of a prograding delta on a mobile substrate (e.g., salt) is a product of the complex interplay between deposition and subsidence. Previous studies focused mainly on structural deformation of a salt layer in response to tectonic forcing, leaving the dynamic feedback between sedimentation and subsidence unexplored. We present results from physical experiments of delta progradation on a mobile substrate. Five carefully designed experiments were performed to understand the effects of delta progradation rate on the shape and dimension of salt deformation and associated delta deposition. All of the runs had constant sediment and water discharges, but the water depth and mobile substrate thickness varied from 1 cm to 3 cm and from 2 cm to 4 cm, respectively. The results showed that increasingly deeper water depths slowed the shoreline progradation rate, while increasingly thinner salt thickness accelerated delta progradation. The experimental results also provided a wide range of shoreline advance and subsidence rates that show changes in the shape and dimension of the salt deformation structure. Runs with fast shoreline progradation showed isolated salt domes developed internally on the delta plain and a rough platform pattern along the shoreline due to lobes built by channel flow between upwelled salt structures. However, runs with slow shoreline progradation developed long connected salt ridges around the toe of the delta, limiting sediment transport beyond the ridges. This overall pattern in salt structures is time dependent. As a delta surface grows larger and the shoreline progradational rate autogenically decreases with time, chances to develop isolated salt domes decrease but more connected long salt ridges occur. Physical modeling of a delta on a mobile substrate is important in predicting the mechanism for large-scale salt basin stratigraphy under a high sediment supply that interacts with the substrate.