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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.
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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
Overview • Location • South Texas Growth-Faulted Subbasins • Stratigraphy – Structure Interplay • Dynamic Model • Exploration Potential
Schematic representation - successive growth-faulted intraslope subbasins Organization Repetition
Organization of sands (after Mitchum and Van Wagoner, 1991)
Origin of Growth-Faulted Subbasins Related to the interaction of: - gravity tectonics, - relative sea-level changes, - and sediment supply. Feedback
Wireline-log sequence stratigraphy Basin-floor fans
Wireline-log sequence stratigraphy Slope fans
Wireline-log sequence stratigraphy Lowstand prograding wedge
Wireline-log sequence stratigraphy Lowstand prograding wedge
Early Lowstand Systems Tract Incised valleys commonly erode at fault intersections Lowstand systems tract Incised-valleys Slope upper - lower LST Prograding Wedges Pelagic deposition ~20 to 40 miles Depositional systems after Galloway et al., 1982
Schematic representation of successive growth-faulted intraslope subbasins
Conclusions • Offshelf Lowstands overload slope • Growth-faulted subbasins younger basinward • Similar log facies, different subbasins = different time • Deep Potential
Western Geco – Seismic Sabco IBC (now Boss Exploration) Acknowledgements
STARR PROGRAM State of Texas Advanced Resource Recovery
Organization of sands (after Mitchum, 1991)
A n a h u a c H S T Organization: Seismic view
Organization Schematic representation of successive growth-faulted intraslope subbasins
Regional dip cross section using S5 logs Paleo control
Isochron map of lowstand prograding wedges Sediment input (incised valleys) axes
Incised valley feeder systems Isopach map of lowstand prograding wedges
Wireline-log sequence stratigraphy Lowstand incised-valley fill, transgressive, and highstand systems tracts
Wireline-log sequence stratigraphy Lowstand incised-valley fill, transgressive, and highstand systems tracts
Red Fish Bay S5-Benchmark Chart
Regional correlations of sands So, how do you correlate between subbasins?
Site-Specific Sequence-Stratigraphic Section Benchmark Charts (S5 Benchmark Charts) • Composite logs with • Sequence stratigraphy • additional data • summarize subbasin geology • Promote accurate correlations
Shelf edge +/-1000ft ~3000-4000ft Stage in development and filling of growth-faulted intraslope subbasins: Stage 1
Turbidity flow Stage in development and filling of growth-faulted intraslope subbasins: Stage 2
Turbidity flow Stage in development and filling of growth-faulted intraslope subbasins: Stage 3
Turbidity flow Mobilized basinal shales forming incipient shale ridge Stage in development and filling of growth-faulted intraslope subbasins: Stage 4
Incised valleys Termination of slope fan deposition Stage in development and filling of growth-faulted intraslope subbasins: Stage 5
ivf Stage in development and filling of growth-faulted intraslope subbasins: Stage 6
Stage in development and filling of growth-faulted intraslope subbasins: Stage 7
Schematic representation of successive shifting LST depocenters
Schematic representation of successive shifting LST depocenters
Schematic representation of successive shifting LST depocenters
Schematic representation of successive shifting LST depocenters
Schematic representation of successive shifting LST depocenters