Abstract: Hybrid Log Displays Aid the Recognition of Maximum Flooding Surfaces: The Key To Sequence Stratigraphic Interpretation

Ted Pierce, Patrick Talamas, Norman Vallette

The maximum flooding surface is one of the key surfaces in sequence stratigraphic interpretation. This surface represents a time of maximum marine flooding of the shelf, and a time of minimal coarse clastic deposition to the outer shelf, slope and basin. The fine grained pelagic sediment associated with this surface, indicates very slow deposition, and is called the condensed section. Shales associated with this surface typically exhibit low resistivity and high gamma ray due to the high percentage of clay minerals. Pelagic faunal abundance and high faunal diversity are also commonly associated with the condensed section. We selected in excess of 30 well logs from the OCS Gulf of Mexico. The wells range from South Marsh Island Area to Grand Isle Area and were selected for the microfos il abundance curves which had been generated by Paleo-Data Inc. The wells represent Plio-Pleistocene to Miocene section which should contain 21 sequence boundaries based on coastal onlap curves. We created various hybrid logs by mathematically manipulating the resistivity, conductivity, gamma-ray, sonic, and density logs. These manipulations were directed toward exaggerating the physical

properties of the condensed sections which were indicated by Paleo-Data's abundance curves such that they stood out in comparison to the overall log. In addition to the creation of hybrid logs, we also compiled the physical property measurements of the identified condensed sections and compared them by trend, depth and age.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994