Nelson, C. Hans et al. (2011): Interplay of mass-transport and turbidite-system deposits in different active tectonic and passive continental margin settings; external and local controlling factors

ODP 155
ODP 155 936
ODP 155 941

Nelson, C. Hans
Universidad de Granada, Instituto Andaluz de Ciencias de la Tierra, Granada, Spain

Escutia, Carlota
University of Colorado at Boulder, United States

Damuth, John E.
Chevron Energy Technology, United States

Twichell, David C., Jr.
University of Texas at Arlington, United States

Interplay of mass-transport and turbidite-system deposits in different active tectonic and passive continental margin settings; external and local controlling factors
In: Shipp, R. Craig (editor), Weimer, Paul (editor), Posamentier, Henry W. (editor), Mass transport deposits in deep-water settings
Society for Sedimentary Geology (SEPM), Tulsa, OK, United States
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 Mw) 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 ( approximately 100 km) than on passive-margin settings ( approximately 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 degrees ), whereas canyons feeding turbidite systems have a regular graded profile and less steep gradients (1 to 5 degrees ). Our examples of MTD and turbidite systems provide analogues to help interpret ancient systems.
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Sedimentary petrology; Structural geology; abyssal plains; Amazon Fan; Antarctica; Atlantic Ocean; basin analysis; Bering Sea; California; Cascadia Basin; Cenozoic; clastic rocks; clastic sediments; continental margin; continental margin sedimentation; deep-water environment; deposition; depositional environment; earthquakes; East Pacific; Ebro Basin; Equatorial Atlantic; Europe; geophysical methods; geophysical surveys; Gulf of Mexico; Iberian Peninsula; Leg 155; marine environment; marine sedimentation; mass movements; Mississippi Delta; Mississippi Embayment; neotectonics; North Atlantic; North Pacific; Northeast Pacific; Ocean Drilling Program; ocean floors; ODP Site 936; ODP Site 941; offshore; Pacific Ocean; paleoclimatology; paleoenvironment; passive margins; petroleum; petroleum exploration; plate tectonics; sediment transport; sedimentary rocks; sedimentation; sedimentology; sediments; seismic methods; seismic stratigraphy; Southern Europe; Spain; submarine canyons; submarine fans; surveys; tectonics; Tertiary; transport; turbidite; United States; Wilkes Land;