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The Kinematic Evolution of Stacked Strata on Experimental Shelf Margins

Abstract

Continental margin deposits provide the most complete record on Earth of paleo-landscapes, but their inherent complexity makes these records difficult to interpret. Mapped surfaces often present a static diachronous record of these landscapes through time. We present data that capture the dynamics of experimental shelf-margin landscapes at high-temporal resolution and define internal hierarchies within deposits from the shelf to the slope. Motivated by observations from acoustically–imaged continental margins offshore Brunei and in the Gulf of Mexico, we use physical experiments to quantify stratal patterns of sub-aqueous slope channels and lobes that are linked to delta-top channels. These experiments allow us to explore the kinematics of sea-scape evolution, as the up-dip delta approaches the shelf edge. The data presented here are from an experiment that was run for 26 hours of experimental run time. Overhead photographs and topographic scans provide a rich data-set to explore flow dynamics and surface evolution of the coupled terrestrial-submarine landscape. Currents rich in sediment built a delta that prograded to the shelf-edge. These currents were designed to plunge at the shoreline and travel as turbidity currents beyond the delta and onto the continental slope. Pseudo-subsidence was imposed by a slight base-level rise that generated accommodation space and promoted the construction of stratigraphy on the delta-top. Compensational stacking is a term that is frequently applied to deposits that tend to fill in topographic lows in channelized and weakly channelized systems. The compensation index, a metric used to quantify the strength of compensation, is used here to characterize deposits at different temporal scales on the experimental landscape. The compensation timescale is the characteristic time at which the accumulated deposits begins to match the shape of basin-wide subsidence rates (uniform for these experiments). We will use the compensation indices along strike transects across the delta, proximal slope and distal slope to evaluate the trends in the compensation time-scale, tied to: a) location within a mass extraction framework, b) changes in the sediment transport regime from primarily transport-limited on the delta to advection settling dominated on the continental slope, and c) the stacking of different topographic elements, from bedforms to sediment lobes.