Interplay of Mass-Transport and Turbidite-System Deposits in Different Active Tectonic and Passive Continental Margin Settings: External and Local Controlling Factors
Published:January 01, 2011
C. Hans Nelson, Carlota Escutia, John E. Damuth, David C. Twichell, Jr., 2011. "Interplay of Mass-Transport and Turbidite-System Deposits in Different Active Tectonic and Passive Continental Margin Settings: External and Local Controlling Factors", Mass-Transport Deposits in Deepwater Settings, R. Craig Shipp, Paul Weimer, Henry W. Posamentier
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The volume and interplay of mass-transport (MTD) and turbidite-system deposits varies on different continental margins depending on local and external controls such as active-margin or passive-margin tectonic setting and climatic and/or sea-level change. Erosion and breaching of local grabens at the shelf edge of the southern Bering Sea produce giant, gullied canyons and MTD sheets that dominate the basin-floor deposition and disrupt development of turbidite systems. In contrast, external controls of great earthquakes (> 8 M ) along the Pacific active tectonic continental margins of Cascadia and northern California cause seismic strengthening of the sediment, which results in minor MTDs compared to turbidite-system deposits. Messinian desiccation of the Mediterranean Sea caused a deeply eroded Ebro subaerial canyon and an unstable central segment with an MTD sheet, whereas other stable Ebro margin segments have only turbidite systems. In the northern Gulf of Mexico, the delta-fed Mississippi Fan and intraslope mini-basins contain MTDs and turbidites that are equally intermixed from the largest scales with MTD sheets hundreds of kilometers long to the smallest scales with beds centimeters thick. In the Antarctic Wilkes Land margin, global climate cooling caused a late Oligocene to middle Miocene time of temperate continental ice sheets that resulted in massive deposition of MTDs on the margin, whereas later polar ice sheets favored development of turbidite systems.
Our case studies provide the following new insights: (1) MTDs can dominate entire margins, dominate segments of a margin, be equally mixed with turbidites, or dominate a margin during some geologic times and not others; (2) on active tectonic margins with great earthquakes, the maximum run-out distances of MTD sheets across abyssal-basin floors are an order of magnitude less (~ 100 km) than on passive-margin settings (~ 1000 km), and the volumes of MTDs are limited on the abyssal sea floor along active margins; (3) where the most precise radiocarbon ages are available, major MTD episodes of deposition are correlated with the most rapid falls or rises of sea level; (4) gullied canyons feeding MTD sheets have irregular and steep axial gradients (5-9°), whereas canyons feeding turbidite systems have a regular graded profile and less steep gradients (1 to 5°). Our examples of MTD and turbidite systems provide analogues to help interpret ancient systems.
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Mass-Transport Deposits in Deepwater Settings
Historically, submarine-mass failures or mass-transport deposits have been a focus of increasingly intense investigation by academic institutions particularly during the last decade, though they received much less attention by geoscientists in the energy industry. With recent interest in expanding petroleum exploration and production into deeper water depths globally and more widespread availability of high-quality data sets, mass-transport deposits are now recognized as a major component of most deep-water settings. This recognition has lead to the realization that many aspects of these deposits are still unknown or poorly understood. This volume contains twenty-three papers that address a number of topics critical to further understanding mass-transport deposits. These topics include general overviews of these deposits, depositional settings on the seafloor and in the near-subsurface interval, geohazard concerns, descriptive outcrops, integrated outcrop and seismic data/seismic forward modeling, petroleum reservoirs, and case studies on several associated topics. This volume will appeal to a broad cross section of geoscientists and geotechnical engineers, who are interested in this rapidly expanding field. The selection of papers in this volume reflects a growing trend towards a more diverse blend of disciplines and topics, covered in the study of mass-transport deposits.