Outcrop 12. Tres Pasos Formation Mass Transport Deposit Topography, Sierra Contreras
D.A. Armitage, B.W. Romans, J.A. Covault, S.A. Graham, 2009. "Outcrop 12. Tres Pasos Formation Mass Transport Deposit Topography, Sierra Contreras", Stratigraphic Evolution of Deep-Water Architecture: Examples of controls and depositional styles from the Magallanes Basin, southern Chile, Andrea Fildani, Stephen M. Hubbard, Brian W. Romans, J.A. Covault, W.H. Crane, A. Bernhardt, Z.R. Jobe, D.A. Armitage, J.C. Fosdick, M.R. Shultz, J. Clark, D.R. Lowe, S.A. Graham
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Outcrop accessibility: difficult Outcrop Coordinates: 50.8859°S, 72.6545°W Refer to outcrop 12 on location map
At Sierra Contreras, deep-water slope depositional relationships between fine-grained mass transport deposits (MTDs) and overlying turbiditic sandstones can be assessed. The lateral continuity of sandstone-rich reservoir-scale bodies was dominantly controlled by original seafloor topography, related to the morphology of underlying MTDs. Overlying sandstone beds pinch-out and lap onto the relative topographic highs of the MTDs. Turbidite architecture evolves to more laterally continuous, sheet-like deposits as a result of depositional smoothing of MTD relief and diminished confinement (Shultz et al., 2005; Armitage et al., in press).
Small-scale MTD topography, characterized by several meters of vertical relief, was associated with local pockets of accommodation where sands were ponded. These small-scale surface irregularities are inferred to have been associated with the rugose tops of viscous MTDs. Meso-scale MTD topography (10 to several 10s of meters relief) was created by coherent rafted sandstone blocks resting on top of, or within the upper portion of MTD deposits; it is onlapped by overlying sandstone beds. This topography can laterally compartmentalize significant packages of sandstone. The largest scale of topography identified (several hundred meters horizontally and vertically) resulted from individual mass-wasting events (e.g., outsized block emplacement) creating topographic relief at the time of deposition. Topographic features at this scale can laterally divide large-scale sediment gravity flow pathways, leading to significant compartmentalization of sandstone bodies.
The size and abundance of rafted blocks in MTDs increases vertically in the outcrop suggesting
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Stratigraphic Evolution of Deep-Water Architecture: Examples of controls and depositional styles from the Magallanes Basin, southern Chile
This large format (11 × 17 inch) all color outcrop atlas and field guide was produced for the SEPM Research Conference held in Chile in February, 2009. It contains a wealth of information on the world class deep water outcrops of the Cretaceous of the Magallanes Basin in the Ultima Esperanza District, Chilean Patagonia. This book covers the significant outcrops in the region the Punta Barrosa Formation, CerroToro Fm., and the Tres Pasos Fm.