Brazos River Flood Sediment Deposition, Remobilization and Continental Shelf Pathways
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The Brazos River flows through central Texas and empties into the northwestern Gulf of Mexico. Brazos River discharge is highly variable and is controlled in part by the El Niño Southern Oscillation (ENSO). The Brazos River reached historic discharge levels in 2015 and 2016, including the second highest discharge event ever recorded, concurrent with a strong El Niño. Following these floods, several boxcore sampling cruises between February 2016 and September 2016 captured the temporal and spatial evolution of flood sediment deposited along the continental shelf near the mouth of the Brazos River. Additional boxcores and vibra-cores were collected farther downcoast in the Texas Mud Blanket (TMB), a continental shelf depocenter, in an attempt to determine preservation potential of Brazos River sediments. Brazos River flood sediments were identified in nearshore boxcores using ^7Be activities, grain size, porosity and x-radiograph data. Vibra-cores were analyzed using grain size, porosity, X-ray fluorescence (XRF),^ 210Pb geochronology, x-radiography and photography. Flood deposits are homogeneous, generally coarsen upwards, with relatively enriched ^7Be inventories. Flood deposit thicknesses ranged from 2.5 to 40 cm and thicken with increasing water depth and distance from the Brazos River mouth. TMB sedimentation rates range from 0.21 to 0.59 cm yr^−1 in the TMB, with evidence of Brazos River sourced sediment preservation and temporal variability of Brazos River sediment supply to the TMB. Flood deposits are reworked on an intra-annual, inter-flood timescale, with significant remobilization during fall and winter due to strong, westward currents, which likely play a role in sediment preservation within the TMB.
McGuffin, Andrew Brian (2018). Brazos River Flood Sediment Deposition, Remobilization and Continental Shelf Pathways. Master's thesis, Texas A & M University. Available electronically from