Use of Multibeam Echo Sounder MBES Backscatter and Bathymetry Data to Reveal New Insights into the Campeche Escarpment

Abstract

Abstract The Campeche Escarpment is a prominent feature extending over 600 km along the northern flank of the Yucatan Peninsula with steep cliff faces of up to 80° and a relief of over 4000 m. Analysis of Multibeam Echo Sounder (MBES) backscatter and bathymetry data reveal new insights into the cliff-forming geologic units as well as largescale erosional processes on the Campeche shelf. In 2013, the R/V Falkor collected MBES bathymetry and backscatter data sonars in the area of the Campeche Escarpment using Kongsberg EM302 30 kHz and EM710 70 kHz MBES systems. We use Fledermaus GeoCoder to process backscatter data, and ArcGIS to create mosaic of all survey lines. Fledermaus is then used to create a 3D representation of the dataset. We delineate the escarpment into four geomorphic provinces based on submarine canyon density and morphology, as well as pronounced geomorphological differences formed in response to erosional processes along-strike of the Campeche Escarpment. Analysis of backscatter data reveals a high backscatter intensity unit comprising the steep cliff faces of the Campeche Escarpment. Due to the high backscatter intensity of the unit, we infer this to be a carbonate unit, which is also associated with the K-Pg boundary layer as previously reported by Paull et al. (2014) based on a steep bathymetric change and constrained by cores from DSDP Sites 86 and 94. Large-scale retrogressive-appearing erosion has left high-angle breaks where slabs of sediment have eroded the escarpment edge, thus giving the slope a terraced appearance. This erosion reveals higher backscatter intensity material overlain with remnants of lower backscatter intensity sediments within the slide scar. We infer the high backscatter intensity material to be carbonate layers on which erosion occurred. The stark contrast observed in MBES backscatter data between high intensity carbonate material and lower intensity sediments, refines and constrains the location of the K-Pg boundary layer exposed along the Campeche escarpment and provides new insights into the erosional styles of the Campeche escarpment. MBES backscatter analysis is a low cost method that yields a more detailed assessment of surface material than bathymetry alone. This proves to be a powerful tool; enabling further inferences about geomorphic features and geologic characteristics of a study area, and as an efficient means of locating seafloor hydrocarbon seeps.