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AAPG Bulletin, V.
Seismic expressions of a Miocene prograding carbonate margin, Mut Basin, Turkey
1University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149; present address: Bureau of Economic Geology, University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924; [email protected]
2University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149
3University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149; present address: Bureau of Economic Geology, University of Texas at Austin, University Station Box X, Austin, Texas 78713-8924
4Institut Franais du Ptrole, Avenue de Bois-Prau, 92852 Rueil-Malmaison Cedex, France
5Total, CSTJF, Avenue Larribau, 64000 Pau, France
The detailed stratigraphic architecture of a Miocene intraplatform prograding carbonate margin, outcropping in Mut Basin, Turkey, was used to build two-dimensional synthetic seismograms by normal ray-tracing and finite-difference, exploding-reflector methods. The synthetic seismic models at various frequencies display the overall prograding architecture of the 1.5-km (0.95-mi) 250-m (820-ft) prograding margin, even at 40-Hz frequency; however, most of the complex stratigraphic architecture is below standard seismic resolution. Sigmoidal outcrop geometries create complex, shingled, seismic reflections that contain pseudodownlap, pseudotoplap, and various truncations at 40-Hz frequency. In addition, reflections that do not correspond to any impedance contrast are generated by a tuning effect within the clinoform. Interference patterns created by the complex impedance distribution create reflections that change phase laterally and cross stratigraphic timelines. Several high-impedance coral buildups at the slope break and on the platform top cause reflections to change phase and amplitude along the timeline. In addition, lateral-impedance variations generate mounded reflections that, in places, cross timelines and resemble seismic images for buildups or anticlinal structures.
Several of these resolution problems and interference patterns are reduced by an increase of the frequency. For example, at 80 Hz peak frequency, the sigmoidal geometries are better imaged. Improved resolution was also achieved on the synthetic seismic data simply by dividing trace spacing from 25 to 12.5 m (82 to 39 ft) but keeping the modeling frequency constant, indicating that for stratigraphic interpretation, horizontal seismic resolution is at least as important as vertical seismic resolution. This implies that adjusting the acquisition geometries would improve the seismic resolution without compromising depth by increased frequency. For seismic interpretation, this study shows how little of a complex stratigraphic architecture is truly imaged on seismic data and how complex impedance distribution can create false seismic reflection geometries that impede a correct seismic facies and sequence-stratigraphic interpretation.
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