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Previous HitSeismicNext Hit Modeling of Depositional Sequences across a Carbonate Platform-to-Basin Transition: A Test for Previous HitSeismicNext Hit Sequence Stratigraphy


Previous HitSeismicNext Hit sequence analyses performed on synthetic Previous HitseismicNext Hit sections across a steep-sided carbonate platform margin (Montagna della Maiella, Italy) indicate that the record of Previous HitseismicNext Hit sequences is strongly dependent on the Previous HitseismicNext Hit acquisition parameters and the depositional morphology. In particular, variations in Previous HitseismicNext Hit frequency affect the Previous HitseismicNext Hit stratigraphic image in a way that the total number of Previous HitseismicNext Hit sequences increases with increasing frequency.

The lithologic content and the geometries of seven unconformity-bounded supersequences could be mapped on well-exposed, valley flank-sized outcrops of the Cretaceous to Tertiary platform-to-basin transition. Velocity and density measurements on approximately 200 outcrop samples revealed the petrophysical signature of all lithologies. These data, together with the geometries, provided the database to construct a layered impedance model which was convolved with a Previous HitseismicNext Hit wavelet using the normal incidence raytracing method and frequencies between 20 and 60 Hz. Previous HitSeismicNext Hit unconformities were traced on the synthetic Previous HitseismicNext Hit section allowing for a Previous HitseismicNext Hit sequence analyses at all chosen frequencies. Accurate sequence stratigraphic interpretation was complicated by the steep non-depositional escarpment that separates the Cretaceous platform deposits from the adjacent basinal sediments. The escarpment is seismically seen as one onlap surface, i.e. one sequence boundary, while in reality, time lines merge and eventually cross this surface. At low frequencies (20 Hz), only five of the seven depositional sequences can be resolved on the Previous HitseismicNext Hit section, because two of the six unconformities are not seismically recorded. A frequency increase to 40 and 60 Hz results in six and seven detected Previous HitseismicNext Hit sequences, respectively. The fact, that in this case a frequency of 60 Hz is needed to image all depositional sequences documents the pitfalls of using sequence analyses to make age correlations based solely on Previous HitseismicNext Hit data. Low Previous HitseismicTop frequency prevents thin depositional sequences and/or those with subtle geometric unconformities to be seismically detected. 

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.