GEOMORPHOLOGY, SHALLOW STRUCTURE AND FLUID VENTING AT THE SEAFLOOR OF THE CONTINENTAL SLOPE OFFSHORE OF MANZANILLO, MEXICO
Multibeam bathymetric data, seafloor backscatter data and sub-bottom seismic reflection data collected during the MORTIC07 and JGAP2013 campaigns conducted aboard the B.O. EL PUMA reveals an extensive fluid vent field on the seafloor located on the continental slope, 50 km SW of Manzanillo, Mexico. This vent field is located on top (at water depths shallower than 1 kilometer) of a large seafloor dome at water depths shallower than 1 kilometer. The apex of the dome is located at 18o44’N, 104o38’W, at a depth of approximately 600m. The dome has a surface relief of over 1 km and a radius of approximately 15 km.
Herein, we present the seafloor geomorphology of the dome and associated vent field, as well as the spatial distribution of the faults associated with and adjacent to the dome. Also presented is the nature of the uppermost sediments infilling a prominent mid-slope basin located landward of the dome.
Notable observations include:
1. Numerous radial faults are observed to extend away from the apex of the dome.
2. The western flank of the dome is down-dropped to the southwest producing a collapse ramp which has modified a pre-existing seafloor escarpment.
3. The vent field contains several large vents (up to 20 meters relief and 300 meters in diameter).
4. Several of these large vents have extensive sediment ponds surrounding the vents, indicating that a substantial amount of sediments are being expelled along with the vented fluids.
5. Thrust faults and folds disrupt the shallow sediments within the mid-slope basin landward of the dome.
Lastly, the geomorphologic and structural features are consistent with crustal deformation related to the collision and subsequent subduction of a large seamount.