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Anne Bernhardt, Zane R. Jobe Donald R. Lowe

The evolution of an elongate foreland basin: The deep- to shallow-marine filling of the Cretaceous Magallanes Basin, Chile. Anne Bernhardt, Zane R. Jobe Donald R. Lowe. ACKNOWLEDGMENTS. An industry affiliates program focused on the study of modern and ancient deepwater systems.

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Anne Bernhardt, Zane R. Jobe Donald R. Lowe

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  1. The evolution of an elongate foreland basin: The deep- to shallow-marine filling of the Cretaceous Magallanes Basin, Chile Anne Bernhardt, Zane R. Jobe Donald R. Lowe

  2. ACKNOWLEDGMENTS An industry affiliates program focused on the study of modern and ancient deepwater systems. Co-Directors: Don Lowe, Steve Graham (Stanford University) MEMBERS (2008) Aera Energy Hess Rohol-Aufsuchungs A.G. Anadarko Husky Reliance Industries (India) Chevron Marathon Repsol YPF ConocoPhillips Nexen Shell ENI Occidental ExxonMobil Petrobras

  3. Student Research in Magallanes Basin, Chile Michael Shultz (2004) Slope deposits-TP Andrea Fildani (2004) Basin evolution, slurry flows-PB Will Crane (2004) Conglomeratic basin-floor channels-CT Steve Hubbard (2006) Conglomeratic basin-floor channels-CT Brian Romans (2008) Upper Slope basins and channels-TP Dominic Armitage (2009) Slope mini-basins-TP Jake Covault (2009) Upper slope to delta plain transition Anne Bernhardt (in progress) Conglomeratic basin-floor channels-CT Zane Jobe (in progress) Conglomeratic basin-floor channels-CT Julie Fosdick (in progress) Structural evolution

  4. Research Objectives To develop an understanding of the facies, architecture, and controls on deepwater systems and of the processes by which they form Explore and develop analogs for subsurface deepwater systems Provide knowledge base for our affiliates to aid in understanding deepwater systems in general and in evaluating their individual prospects

  5. Key Observations There are no perfect analogs, but . . . Every outcropping deepwater system and every deepwater outcrop has analog value. One of the objectives in studying analogs must be to develop an understanding of deepwater deposits to the extent that we can consider applications of seemingly inappropriate analogs to understanding our own deepwater systems

  6. Stratigraphy Modified from Fildani et al., 2008

  7. Generalized Cross-section of the Magallanes Basin

  8. Map of study area Modified from Fosdick, ongoing PhD project

  9. Study area Fildani and Hessler, 2005

  10. It's a tough place to work but somebody's got to do it.

  11. Punta Barrosa Formation • Turbidites of the Punta Barrosa Formation record the onset of deep-water foreland basin sedimentation • Biostratigraphic assemblages indicate a paleo-water depth of 1000-2000 m • Paleocurrent measurements indicate a S-SE sediment dispersal pattern • Deposition within a narrow trough representing the axis of the early Magallanes foreland basin

  12. Lower Punta Barrosa Formation • The lower, shale-rich interval of the Punta Barrosa formation is incorporated into fold-and-thrust belt • Characterized by laterally extensive turbidite sandstone beds interbedded with mud-rich intervals, with mudstone making up at least 50%

  13. Upper Punta Barrosa Formation • The upper, sand-rich interval is less affected by tectonism. • Predominantly turbidites, some debris flows and sandy slurry flows Fildani and Hessler, 2005

  14. Upper Punta Barrosa Formation Sandy slurry flow deposits (sensu Lowe and Guy, 2000)

  15. Punta Barrosa Formation – Paleogeography • Deposition mainly on the more distal parts of a longitudinally-fed deepwater system. • Local sand bodies probably represent frontal splays to coarser, as-yet-unseen, perhaps more channelized upslope parts of the system

  16. Cerro Toro Formation – Lithofacies field book Flow Photo by Zane Jobe • Clast supported conglomerate • Avg. 1 m thick • Volcanic & meta-volcanic cobbles • Up to 40 cm boulders! • Normal grading • Cobble imbrication • Raft blocks uncommon • Emplaced by high-density • turbidity currents (R3)

  17. Cerro Toro Formation – Lithofacies • Thick bedded sandstone • Avg. 75 cm thick • Usually amalgamated • Massive (S3) • Dishes • Emplaced by high-density turbidity currents

  18. Cerro Toro Formation – Lithofacies • Muddy-matrix supported conglomerate • Avg. 7 m thick • Clast supported base • Muddy matrix supported top • Emplaced by transitional, turbulent slurry flows (Crane, 2004) 1.5 m

  19. Cerro Toro Formation – Lithofacies • Interbedded sandstone and mudstone • Flank channel margins • 5-50 cm sandstones • Distinct whitish color • Tb-c, bioturbated • Turbiditic mud • Sand filled burrows • Narrow levees & other • out-of-channel deposits

  20. Cerro Toro Formation – Stratigraphy Modified from Crane and Lowe, 2008

  21. Cerro Toro Formation - Silla Syncline Overview of the Silla Syncline looking south along the west limb. Park road in foreground.

  22. Cerro Toro Formation - Silla Syncline Modified from Crane, 2004

  23. Cerro Toro Formation - Silla Syncline Stratigraphic architecture of the Cerro Toro Formation along the west limb of the Silla Syncline. Modified from Crane, 2004

  24. Fining upward conglomerate, sandstone, and ss+mudstone channel fill of Pehoe A

  25. Stratigraphic relationships along the northern margin of the Paine C channel

  26. Generalized stratigraphic relationships and measured paleocurrent directions of major units in the Paine member of the Cerro Toro Formation along the west limb of the Silla Syncline

  27. Cerro Toro Formation - Silla Syncline Paine C- erosional surface

  28. Cerro Toro Formation - Silla Syncline Pehoe B Paine A cgl Pehoe A Paine C Paine A ss Paine B Modified from Crane, 2004

  29. Basin Models: (A) Silla Syncline area as the main axial zone of the Magallanes Basin. (B) Silla Syncline area as a structurally isolated slope basin lying west of the main axis of the Magallanes Basin.

  30. Cerro Toro Formation at Sierra del Toro 159°

  31. Cerro Toro Formation at Sierra del Toro

  32. Cerro Toro Formation at Sierra del Toro - Architecture

  33. Cerro Toro Fm at Sierra del Toro – Condor Margin from Jobe et al., in press

  34. Cerro Toro Fm at Sierra del Toro - Wildcat Axis Margin from Jobe et al., in press

  35. Cerro Toro Formation - Cordillera Manuel Señoret Cerro Castillo

  36. Cerro Toro Formation - Cordillera Manuel Señoret Cerro Mocho Modified from Hubbard et al., 2008

  37. Giant cross-sets in Cerro Toro Fm. conglomerate near Lago Sophia, Cordillera Manuel Señoret

  38. Cerro Toro Formation – Channel belt paleogeography Sierra del Toro Silla Syncline Cordillera Manuel Senoret

  39. E W (courtesy of De Ruig) Puchkirchen Formation, Upper Austria Hikurangi Trough, New Zealand N (Lewis and Pantin, 2002) N Cerro Toro Analogues? Peru-Chile Trench (Völker, 2004) 38o 37o

  40. Tres Pasos Formation Romans et al., 2008

  41. Tres Pasos Formation Modified from Romans et al., 2008

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