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. 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 EnergyHessRohol-Aufsuchungs A.G. AnadarkoHuskyReliance Industries (India) ChevronMarathonRepsol YPF ConocoPhillipsNexenShell ENIOccidental ExxonMobilPetrobras ACKNOWLEDGMENTS

3. 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 Student Research in Magallanes Basin, Chile

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

7. Stratigraphy Modified from Fildani et al., 2008

9. Generalized Cross-section of the Magallanes Basin

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

11. Study area Fildani and Hessler, 2005

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

14. 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 Punta Barrosa Formation

15. 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%

16. 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

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

18. 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

21. Cerro Toro Formation – Lithofacies 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) Photo by Zane Jobe field book Flow

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

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

24. 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 Cerro Toro Formation – Lithofacies

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

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

29. Modified from Crane, 2004

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

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

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

33. 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

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

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

36. 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.

38. Cerro Toro Formation at Sierra del Toro 159°

39. Cerro Toro Formation at Sierra del Toro

40. Cerro Toro Formation at Sierra del Toro - Architecture

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

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

44. Cerro Toro Formation - Cordillera Manuel Señoret Cerro Castillo

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

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

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

48. 38 o 37 o (Völker, 2004) N Peru-Chile Trench Hikurangi Trough, New Zealand N (Lewis and Pantin, 2002) Puchkirchen Formation, Upper Austria (courtesy of De Ruig) Cerro Toro Analogues? W E

49. Tres Pasos Formation Romans et al., 2008

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

51. Dorotea-Tres Pasos margin

52. Tres Pasos Fm at Cerro Divisadero 30 m Modified from Romans (2008)

53. NORTH SOUTH basal subunit thickens to the south Tres Pasos Formation at Cerro Divisadero red-brown layers = Miocene igneous sills Modified from Romans (2008)

54. Unit 1 Unit 2 Unit 3 Unit 4 Stratigraphic signature of the Tres Pasos prograding slope system meters lower slope to base-of-slope middle to upper slope Modified from Romans (2008)

55. Tres Pasos Formation Romans et al., 2008

56. Cerro Escondido Transition from Tres Pasos slope to Dorotea shelf-edge delta 2 sections (<300 m) at 10 cm-scale resolution Depositional-strike perspective basinward Modified from Covault, ongoing PhD project

57. Dorotea shelf-edge delta architecture 4 lithofacies associations 2 upward-shoaling lithofacies successions (<200 m thick) 1 2 Modified from Covault, ongoing PhD project

58. Dorotea shelf-edge delta architecture 4 lithofacies associations 2 upward-shoaling lithofacies successions (<200 m thick) –Thick, coarse-grained prodelta “sandwich” –Thick, wave-reworked shoreface sandstone –Thick subaqueous delta plain deposits 2 Delta front/shoreface Prodelta Subaqueous delta plain Modified from Covault, ongoing PhD project

59. Lithofacies association 2 Amalgamated, thick sandstone units and mudstone packages overlain by thinner sandstone units Processes: turbidity currents Paleoenvironment: prodelta Modified from Covault, ongoing PhD project

60. Lithofacies association 3 Hummocky, overlain by swaley, cross-stratified sandstone Processes: currents with wave reworking Paleoenvironment: delta-front/shoreface Modified from Covault, ongoing PhD project

61. Lithofacies association 4 Lenticular, trough cross-stratified sandstone bodies encased in carbonaceous mudstone Paleoenvironment: subaqueous delta plain Modified from Covault, ongoing PhD project

62. Tres Pasos Formation - Sierra Contreras Armitage et al., in review Next slide

63. Tres Pasos Fm - Sierra Contreras Dominated by a thick sequence of stacked mass transport deposits

64. Tres Pasos Formation - Sierra Contreras Armitage et al., in review Sand was deposited in lows on top of MTDs

65. Tres Pasos Formation - Paleogeography

66. Basin Evolution

67. THE END