Giant Mass Transport Deposits of the Caribbean Margin and their Tsunamigenic Potential, Offshore Northern Colombia

Abstract:

Three large (170-290 m thick, >1000 km³) Mass Transport Deposits (MTDs) are recognized on seismic lines offshore northern Colombia covering a combined area of 27,000 km², an area the size of the state of Massachusetts. These deposits record a number of massive slope failure events along the Northern Colombian Margin proximal to the actively prograding delta and fan of the Magdalena River, the 26th largest river in the world by discharge volume . The largest MTD covers an area >15,000 km² outboard of the toe of the continental slope on the abyssal sea floor; the two smaller MTDs range from 5000 to 7000 km² in area. The volume of the largest deposited measured from >160 km of seismic reflection data ranges from 2000 and 5000 km³, comparable in size to the giant Storegga Slide offshore Norway (3500 km³) and the Nuuanu slide offshore the island of Oahu, Hawai’i (~3000 km³). The timing of the MTDs can be constrained from sparse wells and seismic data to be mid to late Miocene (15-5.3 Ma) through the Plio-Pleistocene (2.6 Ma). Likely causative factors for the MTDs include: 1) elevated pore pressure due to generation of biogenic gas in the sediment column of the continental slopes as observed on seismic reflection data; 2) rapid sedimentation related to the Magdalena delta that has produced oversteepened slopes since the late Miocene (7-10 Ma); and 3) tectonic uplift and infrequent large earthquakes related to shallow, southeastward subduction beneath the nearby Southern Caribbean Fold Belt. Preliminary models of inferred tsunamis and their projected run-ups around the Caribbean Sea are presented.