114-2 Repeated Construction and Destruction of Submarine Landscapes near the Terminus of the Rio Grande System, Offshore USA

Session: Geomorphology and Surface Processes Across the Solar System (Poster)

Presenting Author:

Authors:

Abstract:

The Rio Grande flows from south-central Colorado to the gulf, dropping 3,700 meters in elevation over a horizontal distance of 3,000 kilometers. Along its course, the river system collects water and sediment from both the southern Rocky Mountains and the northern Sierra Madres. Most of this sediment is ultimately deposited in the marine extension of the transport system. This submarine component adds 350 kilometers to the length of the system and increases its overall relief by an additional 3,000 meters. Our study focuses on a distal section of the transport system that is positioned 110 to 215 kilometers downslope from the Rio Grande coastline, where water depths increase from 850 to 1,720 meters. We take advantage of the B-28-99 3D seismic survey that was recently released through the National Archive of Marine Seismic Surveys. This seismic volume images a 4,765 square kilometers portion of both the present-day seafloor and underlying sedimentary deposits, which preserve records of past submarine landscapes. Previous work, using nannofossil dating, determined that the modern seafloor surface was most recently active during the Wisconsin Glacial Episode or Tarantian Stage (126,000 to 11,700 years ago). This landscape was primarily constructed by turbidity currents that produced a tributary network of submarine channels with intervening overbank surfaces. Together they form a seaward-dipping ramp with a concave up profile and average slope of 0.003 (3 meter drop per kilometer). Evidence of submarine landsliding can be found on this surface, but its contribution to building the seafloor appears minor. Investigation of the subsurface reveals that the role of submarine landslides and their mass-transport deposits (MTDs) in reshaping this environment is greater than suggested by the present-day seafloor. Numerous MTDs can be mapped covering areas commonly ranging between 100 and 1,000 square kilometers. Segments of ancient channel networks are typically preserved directly beneath these deposits, suggesting the seafloor was rapidly buried by the MTDs. Our presentation will explore both MTD emplacement and the rebuilding of a submarine channel network following landslide burial that resets seafloor terrain. Our results should reveal how resilient these channels and channel networks are to major and repeated topographic perturbations. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9071

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