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Potential Causal Mechanisms for MTC Generation from the Northwest African Shelf

Dunlap, Dallas B.1; Moscardelli, Lorena G.1; Hornbach, Matthew 2; Wood, Lesli 1
1 Bureau of Economic Geo, Univ of Texas at Austin, Austin, TX.
2 Institute of Geopyhsics, Univ of Texas at Austin, Austin, TX.

Recent detailed mapping in a 1,064 km2 3D seismic survey acquired in offshore Morocco has revealed the presence of at least three regional mass transport complexes (MTCs) within the Cretaceous interval of the Safi Haute Mer area, in addition to a number of smaller and younger MTCs. Their extent (projected up to 20,000 km2) and thickness (350 ms) is strongly influenced by surrounding structural features associated with regional tectonics and salt mobilization. The MTCs are characterized by chaotic, mounded seismic facies; however seismic attribute analysis has revealed some degree of internal organization including multiple kilometer-scale transported mega-blocks. Detailed analysis of the internal architecture of the mega-blocks has revealed the presence of discrete low sinuosity, single thread channels that are 90 m wide in average. The clear expression of stacked channel complexes within the mega-blocks indicates that they have preserved their original stratigraphy and were likely rafted from upslope, possible 100's of kms distance from their source area. Based on limited data, these deposits are suggested to be late Cretaceous or earliest Tertiary in age. Two working hypotheses address the issue of possible triggering mechanisms for these MTCs. The first one suggests that the causes of the mass failure are associated to the step relief along a narrow shelf and regional uplift associated with the initiation of the Alpine Orogeny.

However, the long-distance transport of kilometer-scale, well-lithified mega-blocks supports an alternative catastrophic model. The alternative hypothesis is that the failures were generated by mega-tsunamigenic forces associated with the K-T impact in the Yucatan Peninsula. Modeling of the potential tsunamigenic waves produced from both the failure of the Moroccan paleo shelf edge and from the Chicxulub impact are generated to support either of the two hypothesis.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009