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
A New Depositional Model for the Frio / Vicksburg
Overview Location South Texas Growth-Faulted Subbasins Stratigraphy – Structure Interplay Dynamic Model Exploration Potential
Location Map
Seismic Line in Corpus Christi Bay
Schematic representation - successive growth-faulted intraslope subbasins
Organization of sands (after Mitchum and Van Wagoner, 1991)
Related to the interaction of: Origin of Growth-Faulted Subbasins - gravity tectonics, - relative sea-level changes, - and sediment supply.
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
Organization of sands
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
Schematic representation of successive growth- faulted intraslope subbasins
Dynamic Depositional Model
Offshelf Lowstands overload slope Growth-faulted subbasins younger basinward Similar log facies, different subbasins = different time Deep Potential Conclusions
Acknowledgements Western Geco – Seismic Sabco IBC (now Boss Exploration)
STARR PROGRAM State of Texas Advanced Resource Recovery
Organization of sands (after Mitchum, 1991)
Organization: Seismic view Anahuac HST
Schematic representation of successive growth- faulted intraslope subbasins Organization
Regional dip cross section using S 5 logs Paleo control
Isochron map of lowstand prograding wedges Sediment input (incised valleys) axes
Isopach map of lowstand prograding wedges Incised valley feeder systems
Isopach map of lowstand incised-valley fills
Cross section of incised-valley fills (lowstand)
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 S 5 -Benchmark Chart
Section of Red Fish Bay S 5 -Benchmark Charts
Regional correlations of sands So, how do you correlate between subbasins?
Regional dip cross section using S 5 logs
Site-Specific Sequence-Stratigraphic Section Benchmark Charts (S 5 Benchmark Charts) Composite logs with Sequence stratigraphy additional data summarize subbasin geology Promote accurate correlations
Stage in development and filling of growth-faulted intraslope subbasins: Stage 1 Shelf edge ~ ft +/-1000 ft
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
Stage in development and filling of growth-faulted intraslope subbasins: Stage 4 Turbidity flow Mobilized basinal shales forming incipient shale ridge
Stage in development and filling of growth-faulted intraslope subbasins: Stage 5 Incised valleys Termination of slope fan deposition
Stage in development and filling of growth-faulted intraslope subbasins: Stage 6 ivf
Stage in development and filling of growth-faulted intraslope subbasins: Stage 7
Schematic representation of successive shifting LST depocenters