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Sequence Stratigraphy of the South Texas Oligocene: Understanding the Relationship Between Shale Tectonismand Lowstand DepositionR. Trevio, L.F. Brown, R. Loucks, and U. Hammes
Bureau of Economic GeologyJackson School of GeosciencesThe University of Texas at Austin
A New Depositional Model for the Frio / Vicksburg
OverviewLocation
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 stratigraphyBasin-floor fans
Wireline-log sequence stratigraphySlope fans
Wireline-log sequence stratigraphyLowstand prograding wedge
Wireline-log sequence stratigraphyLowstand prograding wedge
Organization of sands
Early Lowstand Systems TractDepositional 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
AcknowledgementsWestern Geco Seismic
Sabco
IBC (now Boss Exploration)
STARR PROGRAMState of TexasAdvanced Resource Recovery
Organization of sands(after Mitchum, 1991)
Organization: Seismic view
Schematic representation of successive growth-faulted intraslope subbasins
Regional dip cross section using S5 logs Paleo control
Isochron map of lowstand prograding wedgesSediment input (incised valleys) axes
Isopach map of lowstand prograding wedges
Isopach map of lowstand incised-valley fills
Cross section of incised-valley fills (lowstand)
Wireline-log sequence stratigraphyLowstand incised-valley fill, transgressive, and highstand systems tracts
Wireline-log sequence stratigraphyLowstand incised-valley fill, transgressive, and highstand systems tracts
Red Fish BayS5-Benchmark Chart
Section of Red Fish Bay S5-Benchmark Charts
Regional correlations of sandsSo, how do you correlate between subbasins?
Regional dip cross section using S5 logs
Site-Specific Sequence-Stratigraphic Section Benchmark Charts (S5 Benchmark Charts)Composite logs with Sequence stratigraphyadditional data summarize subbasin geology
Promote accurate correlations
Stage in development and filling of growth-faulted intraslope subbasins: Stage 1
Stage in development and filling of growth-faulted intraslope subbasins: Stage 2
Stage in development and filling of growth-faulted intraslope subbasins: Stage 3
Stage in development and filling of growth-faulted intraslope subbasins: Stage 4
Stage in development and filling of growth-faulted intraslope subbasins: Stage 5
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
Thank colleauges, Bureau, Acknowledge STARR.
High falutin titlenow the real title
and their use for chronostratigraphic correlations in growth faulted basins.
A seismic line showing a typical growth fault and a growth-faulted subbasin on the downthrown side. From Mitchum & Van Wagoner paper in Sedimentary geologyDifference is the presence of the growth fault and the shale mass (in gray)All together they are called an off-shelf lowstand. Plan view of an early LST along S. Texas Oligocene coast. Note:Slope fans over-loading the slope w/ shale ridges formingIncised valleys funneling input to shelf edge (previously submerged in green)IVs often incise near juncture of adjacent older growth faults due to differential loading.Lets look at the development of a typical subbasin. And generate the growth faulted subbasinsAlmost intuitive, but has consequences for regional correlations because,Repetition of facies from one basin to the next (younger) one = nonetheless temporal distinctness. PW is just beginning to prograde over the SF complex.The next series of slides is intended to show the non-linear nature of the subbasins emplacement. The sequence model cross section is not intended to imply dip-alignment. Due to differential loading.