Papers by Wolfgang Schlager
Papers in the Earth and Atmospheric Sciences ... James A. Austin Jr., University of Texas at Aust... more Papers in the Earth and Atmospheric Sciences ... James A. Austin Jr., University of Texas at Austin Wolfgang Schlager, Vrije Universiteit, Instituut v. Aardwetenschap-pen Amanda A. Palmer, Texas A & M University - College Station Paul A. Comet, Core Labs Singapore ...
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Sedimentary Geology, 2005
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Sedimentology, 1999
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Geological Society of America Bulletin, 1976
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Basin Research, Mar 1, 1993
In the Sella platform of the Dolomite Alps, the horizontal beds of the Raibl Formation directly o... more In the Sella platform of the Dolomite Alps, the horizontal beds of the Raibl Formation directly overlie the Upper Schlern Dolomite (Cassian Dolomite of some authors). The Schlern Dolomite comprises steep clinoforms, together with a few tens of metres of horizontal topset beds in the platform interior.
Two-dimensional seismic modelling techniques were used to determine the seismic-response of this interesting situation. To perform this, two different lithological models were constructed based on outcrops of the Sella south face. The first model is that of a rapidly prograding platform with slow aggradation in the platform interior. The second model shows clinoforms toplapping against the topset beds of the platform interior.
P-wave velocities and bulk densities were assigned to the lithostratigraphical units in accordance with values from a similar study, involving the same formations. The vertical-incidence method was used to construct perfectly migrated time sections and depth sections of reflectivity. These were convolved with zero-phase Ricker wavelets of different peak frequencies to produce the final synthetic seismic sections.
Using conventional, low frequencies (e.g. 25 Hz), the seismic response of the two models is almost identical. The topset beds and the Schlern-Raibl contact appear as one event. In a real seismic survey, both sections would be interpreted as toplap of Schlern clinoforms against the Raibl Formation. At higher frequencies (75 Hz), however, differences are revealed. The angle of progradation in the progradation & aggradation model becomes visible, as opposed to the horizontal surface in the progradation & toplap model. Topset beds are resolved separate from the Raibl Formation, but still appear to form a single dipping pseudo-toplap surface.
Another modelling technique, simulating unmigrated sections, shows few differences between the two models even at high frequencies. In addition, the clinoforms are disturbed by the refraction of rays. This study demonstrates that, even under ideal acquisition and processing conditions, the seismic tool can introduce a pseudo-toplap. This implies that toplap in a seismic section is not necessarily toplap in outcrop.
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Rivista Italiana di Paleontologia e Stratigrafia
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Offshore Technology Conference, 3 May-6 May 1993, Houston, Texas, May 3, 1993
Understanding the nature and formation of unconformities allows for better interpretations of the... more Understanding the nature and formation of unconformities allows for better interpretations of the sediment architecture within a basin and, hence, a more accurate play and reservoir evaluation. Sequence stratigraphy assumes that 1) relative sea-level controls the generation of sequences and unconformities to the exclusion of all other mechanisms, and 2) all unconformities on seismic profiles are unconformities in the rock record.
Studies of the geometry of carbonate and siliciclastic shelves from seismic profiles showed that unconformities can form as the result/t of changes in the geometry of sediment dispersal systems and may be independent of sea-level. In addition, unconformities on seismic records may represent rapid transitions when studied in outcrop. Seismic modeling of carbonate platforms showed that, when using typical/ industrial/ frequencies, there are apparent truncations of the margin and significant basin ward shifts in the point of on/sp. The low resolution of the seismic tool also results in apparent pinch outs and pseudo-unconformities.
Unconformities on seismic profiles need not correspond to unconformities in the Iithological record. The seismic modeling of outcrops ultimately provides a means for evacuating the accuracy of unconformity interpretations based solely on seismic response. New constraints in the interpretation of unconformity geometry will/ lead not only to more accurate p/ay evacuations but possibly also to revision of the "Vail" sea-level curve which is based largely on the interpretation of unconformity geometries from industrial seismic profiles.
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Papers by Wolfgang Schlager
Two-dimensional seismic modelling techniques were used to determine the seismic-response of this interesting situation. To perform this, two different lithological models were constructed based on outcrops of the Sella south face. The first model is that of a rapidly prograding platform with slow aggradation in the platform interior. The second model shows clinoforms toplapping against the topset beds of the platform interior.
P-wave velocities and bulk densities were assigned to the lithostratigraphical units in accordance with values from a similar study, involving the same formations. The vertical-incidence method was used to construct perfectly migrated time sections and depth sections of reflectivity. These were convolved with zero-phase Ricker wavelets of different peak frequencies to produce the final synthetic seismic sections.
Using conventional, low frequencies (e.g. 25 Hz), the seismic response of the two models is almost identical. The topset beds and the Schlern-Raibl contact appear as one event. In a real seismic survey, both sections would be interpreted as toplap of Schlern clinoforms against the Raibl Formation. At higher frequencies (75 Hz), however, differences are revealed. The angle of progradation in the progradation & aggradation model becomes visible, as opposed to the horizontal surface in the progradation & toplap model. Topset beds are resolved separate from the Raibl Formation, but still appear to form a single dipping pseudo-toplap surface.
Another modelling technique, simulating unmigrated sections, shows few differences between the two models even at high frequencies. In addition, the clinoforms are disturbed by the refraction of rays. This study demonstrates that, even under ideal acquisition and processing conditions, the seismic tool can introduce a pseudo-toplap. This implies that toplap in a seismic section is not necessarily toplap in outcrop.
Studies of the geometry of carbonate and siliciclastic shelves from seismic profiles showed that unconformities can form as the result/t of changes in the geometry of sediment dispersal systems and may be independent of sea-level. In addition, unconformities on seismic records may represent rapid transitions when studied in outcrop. Seismic modeling of carbonate platforms showed that, when using typical/ industrial/ frequencies, there are apparent truncations of the margin and significant basin ward shifts in the point of on/sp. The low resolution of the seismic tool also results in apparent pinch outs and pseudo-unconformities.
Unconformities on seismic profiles need not correspond to unconformities in the Iithological record. The seismic modeling of outcrops ultimately provides a means for evacuating the accuracy of unconformity interpretations based solely on seismic response. New constraints in the interpretation of unconformity geometry will/ lead not only to more accurate p/ay evacuations but possibly also to revision of the "Vail" sea-level curve which is based largely on the interpretation of unconformity geometries from industrial seismic profiles.
Two-dimensional seismic modelling techniques were used to determine the seismic-response of this interesting situation. To perform this, two different lithological models were constructed based on outcrops of the Sella south face. The first model is that of a rapidly prograding platform with slow aggradation in the platform interior. The second model shows clinoforms toplapping against the topset beds of the platform interior.
P-wave velocities and bulk densities were assigned to the lithostratigraphical units in accordance with values from a similar study, involving the same formations. The vertical-incidence method was used to construct perfectly migrated time sections and depth sections of reflectivity. These were convolved with zero-phase Ricker wavelets of different peak frequencies to produce the final synthetic seismic sections.
Using conventional, low frequencies (e.g. 25 Hz), the seismic response of the two models is almost identical. The topset beds and the Schlern-Raibl contact appear as one event. In a real seismic survey, both sections would be interpreted as toplap of Schlern clinoforms against the Raibl Formation. At higher frequencies (75 Hz), however, differences are revealed. The angle of progradation in the progradation & aggradation model becomes visible, as opposed to the horizontal surface in the progradation & toplap model. Topset beds are resolved separate from the Raibl Formation, but still appear to form a single dipping pseudo-toplap surface.
Another modelling technique, simulating unmigrated sections, shows few differences between the two models even at high frequencies. In addition, the clinoforms are disturbed by the refraction of rays. This study demonstrates that, even under ideal acquisition and processing conditions, the seismic tool can introduce a pseudo-toplap. This implies that toplap in a seismic section is not necessarily toplap in outcrop.
Studies of the geometry of carbonate and siliciclastic shelves from seismic profiles showed that unconformities can form as the result/t of changes in the geometry of sediment dispersal systems and may be independent of sea-level. In addition, unconformities on seismic records may represent rapid transitions when studied in outcrop. Seismic modeling of carbonate platforms showed that, when using typical/ industrial/ frequencies, there are apparent truncations of the margin and significant basin ward shifts in the point of on/sp. The low resolution of the seismic tool also results in apparent pinch outs and pseudo-unconformities.
Unconformities on seismic profiles need not correspond to unconformities in the Iithological record. The seismic modeling of outcrops ultimately provides a means for evacuating the accuracy of unconformity interpretations based solely on seismic response. New constraints in the interpretation of unconformity geometry will/ lead not only to more accurate p/ay evacuations but possibly also to revision of the "Vail" sea-level curve which is based largely on the interpretation of unconformity geometries from industrial seismic profiles.