HR: 1400h
AN: OS23B-06    [Abstracts]
TI: Massive Rock Detachments from the Continental slope of the Balsas River Submarine Delta that occur due to Instability of Sediments which Produce Turbidity Currents and Tsunamis
AU: * Sandoval-Ochoa, J
EM: jhsandovalochoa@cancun.fi-a.unam.mx
AU: Aguayo-Camargo, J
EM: jaguayo@correodict.fi-a.unam.mx
AB: During the NOAA oceanographic delivery cruise of the US R/V "Roger Revelle" to the Scripps Institution of Oceanography at the University of California in San Diego, California USA, in July 1996; a well calibrated bathymetric equipment, the SeaBeam* 2012, was tested. Good resolutions in data allowed bathymetric mapping to visualize the sea floor relief. Detailed colorful chartographic images showed a portion of the continental slope between the Balsas River Delta and the Middle America Trench and between the Balsas Canyon and La Necesidad Canyon. The surveyed area covered more than 3 000 square kilometers. After the delivery cruise, one of the goals was to measure and analyze the Morphobathymetry of the uneven lower portion of the Balsas River Submarine Delta. So far some of the findings with the morphometric analyses consist of several isolated slump scars that each comprise more than 12 cubic kilometers in volume and a multiple slump scar with an evident steep hollow about 200 cubic kilometers absent of rock. These volumes of rock apparently underwent a remobilization from the slope during the Late Quaternary. The rock detachments occured in relatively small portions but in instantaneous massive displacements because of their instability as well as other identified factors in the region. Over time more and more authors have accepted that coastal cuts or submarine slump scars have been left by sudden movements of rock and fluids. The phenomena that occur in the region in general, are accompanied on one side by potential and kinetic energies like falling bodies, flows and gravity waves, and on the other side, by mass transfer of rock and fluid mobilization like turbidity currents, accumulations, sea wave surges or tsunamis. In some cases the phenomena is produced by another natural triggering forces or by an earthquake. We propose that events like these, i.e. massive detachments and their products such as accumulations, turbidity currents and depositional debrites or even modern turbidites in the troughs of the Middle America Trench and last but not least, tsunamis; have been occurring in the recent past in this portion of the continental margin of the East Pacific Ocean. In relation to this, no records or documentation at all of those features have been carried out in association with their mentioned products. In despite of this, phenomena will continue to occur in the future. In some towns in the low lands and shores, sea wave surges or tsunamis that have impacted along the coasts in southwestern Mexico have been observed, in particular near the Balsas River mouth, in Las Truchas - Lazaro Cardenas, State of Michoacan, where a Siderurgical Industrial Complex is located. However, no report or document on sea level oscillation, has been published in connection to any slump scar, seismic hypocenter or a trigger effect of another nature, v. gr. meteorological factors such as air pressure; hydrographic factors such as body waves; planets in line such as tidal waves; geological factors such as volcanoes; or others. In relation to other situations, new representative depositional models of modern debrites and turbidite sequences can help to understand and explain the content of favorable natural conditions to achieve a good ponderability of porosities and permeabilities in ancient turbidite systems in similar paleoenvironments for hydrocarbons and water reservoirs beneath the earth or submarine surfaces.
DE: 3070 Submarine landslides
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly