--> Abstract: Geometry and Nature of Modern and Ancient Mass Transport Deposits, by K. A. Singh, L. Wood, and L. G. Moscardelli; #90090 (2009).

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Geometry and Nature of Modern and Ancient Mass Transport Deposits

Singh, Kadira A.1; Wood, Lesli 1; Moscardelli, Lorena G.1
1 Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX.

Mass transport deposits form a significant portion of the rock record in both modern and ancient basins. Their geometry, composition, distribution and genesis are poorly understood, making it difficult to predict anything about these deposits in assessing subsurface basin stratigraphy or modern seafloor hazards.

To increase our knowledge base of MTCs, the characteristics of 253 deposits worldwide, were analyzed in terms of their volume, area, length, thickness, lithology, margin and tectonic settings. In some instances, MTCs were digitized into ArcGIS and their dimensions were calculated. These data reveal several interesting points and suggest a number of statistically significant predictive relationships. Sand-rich MTCs show a propensity to be short and thick. Muddy MTCs show a propensity to be longer and thinner. Gravel MTCs are both short and thin.

The highest number and largest volume clastic MTCs occur along passive margins. These mega-MTCs are typically muddy with lengths up to 800 km and volumes up to 5000 km3. Sandy and gravelly Quaternary-age MTCs show maximum lengths of less than 300 km and with volumes les than 2000 km3. Pre-Quaternary MTCs are systematically under-documented in literature, but documented occurrences are found in passive, active and convergent margins. The largest (30,000 to 40,000 sq km) occur along the older Tertiary margin of West Africa.

The most extensive and voluminous (7000 km3) carbonate mass transport complexes occur in the Citronens Fjord, Offshore Greenland. They are 200 m thick, Silurian-age mega-breccias that were deposited in a convergent margin setting. On comparison Carbonate MTC appear to have a larger length to area ratio than Clastic MTCs.

 

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