1. Sequence Stratigraphy of the South Texas Oligocene: Understanding the Relationship Between Shale Tectonism and Lowstand Deposition R. Treviño, L.F. Brown, R. Loucks, and U. Hammes Bureau of Economic Geology Jackson School of Geosciences The University of Texas at Austin

2. A New Depositional Model for the Frio / Vicksburg

3. Overview Location South Texas Growth-Faulted Subbasins Stratigraphy – Structure Interplay Dynamic Model Exploration Potential

4. Location Map

5. Seismic Line in Corpus Christi Bay

6. Schematic representation - successive growth-faulted intraslope subbasins

7. Organization of sands (after Mitchum and Van Wagoner, 1991)

8. Related to the interaction of: Origin of Growth-Faulted Subbasins - gravity tectonics, - relative sea-level changes, - and sediment supply.

9. Wireline-log sequence stratigraphy Basin-floor fans

10. Wireline-log sequence stratigraphy Slope fans

11. Wireline-log sequence stratigraphy Lowstand prograding wedge

12. Wireline-log sequence stratigraphy Lowstand prograding wedge

13. Organization of sands

14. Lowstand systems tract Incised-valleys Incised valleys commonly erode at fault intersections Slope upper - lower Pelagic deposition LST Prograding Wedges ~20 to 40 miles Early Lowstand Systems Tract Depositional systems after Galloway et al., 1982

15. Schematic representation of successive growth- faulted intraslope subbasins

16. Dynamic Depositional Model

17. Offshelf Lowstands overload slope Growth-faulted subbasins younger basinward Similar log facies, different subbasins = different time Deep Potential Conclusions

18. Acknowledgements Western Geco – Seismic Sabco IBC (now Boss Exploration)

19. STARR PROGRAM State of Texas Advanced Resource Recovery

22. Organization of sands (after Mitchum, 1991)

23. Organization: Seismic view Anahuac HST

24. Schematic representation of successive growth- faulted intraslope subbasins Organization

25. Regional dip cross section using S 5 logs Paleo control

26. Isochron map of lowstand prograding wedges Sediment input (incised valleys) axes

27. Isopach map of lowstand prograding wedges Incised valley feeder systems

28. Isopach map of lowstand incised-valley fills

29. Cross section of incised-valley fills (lowstand)

30. Wireline-log sequence stratigraphy Lowstand incised-valley fill, transgressive, and highstand systems tracts

31. Wireline-log sequence stratigraphy Lowstand incised- valley fill, transgressive, and highstand systems tracts

32. Red Fish Bay S 5 -Benchmark Chart

33. Section of Red Fish Bay S 5 -Benchmark Charts

34. Regional correlations of sands So, how do you correlate between subbasins?

35. Regional dip cross section using S 5 logs

36. Site-Specific Sequence-Stratigraphic Section Benchmark Charts (S 5 Benchmark Charts) Composite logs with Sequence stratigraphy additional data summarize subbasin geology Promote accurate correlations

37. Stage in development and filling of growth-faulted intraslope subbasins: Stage 1 Shelf edge ~3000-4000 ft +/-1000 ft

38. Stage in development and filling of growth-faulted intraslope subbasins: Stage 2 Turbidity flow

39. Stage in development and filling of growth-faulted intraslope subbasins: Stage 3 Turbidity flow

40. Stage in development and filling of growth-faulted intraslope subbasins: Stage 4 Turbidity flow Mobilized basinal shales forming incipient shale ridge

41. Stage in development and filling of growth-faulted intraslope subbasins: Stage 5 Incised valleys Termination of slope fan deposition

42. Stage in development and filling of growth-faulted intraslope subbasins: Stage 6 ivf

43. Stage in development and filling of growth-faulted intraslope subbasins: Stage 7

44. Schematic representation of successive shifting LST depocenters