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Abstract:
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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 . A tremendous effort has been made in the last few years to characterize and better understand seafloor failures in numerous margins of the world . These mass failures have triggered the interests of geologists , particularly in the oil and gas industry , as they can form prominent seals and reservoirs . To increase our knowledge base of mass transport complexes (MTCs ) , the characteristics of 259 siliciclastic deposits worldwide , were analyzed in terms of their volume , area , length , thickness , lithology , and tectonic settings . In some instances , MTCs were geo -referenced and 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 mass transport deposits show a propensity to be short and thick . Muddy MTCs show a propensity to be longer and thinner . The highest number and largest volume of clastic mass transport deposits 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 less than 2000 km3 . Pre -Quaternary MTCs are systematically under -documented in literature , but known 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 . To date , 41 separate mass transport deposits composed dominantly of carbonate material have been identified in literature . The most extensive and voluminous (7000 km3 ) carbonate mass transport complexes occur in the Citronens Fjord , Offshore Greenland . They are 200m thick , Silurian -age mega -breccias that were deposited in a convergent margin setting . On comparison carbonate MTCs tend to show longer flows with coarser grain sizes , while clastics show coarser grained deposits to be of more limited length . The Mad Dog area , Gulf of Mexico is a region of active salt tectonics and mass transport processes . Consequently , it was selected to form a focus study area to test the relationships developed during this project . MTCs in this region were grouped into four main types based on their size , geomorphology and internal structure . Their geometries indicate they are comparable to MTCs found offshore Oregon and New Jersey and are most likely muddy in nature . |