ABSTRACT: Isotope Chronostratigraphy: High-Resolution Stratigraphic Correlation of Exploration Wells within the South Galveston and East Breaks Areas, Gulf of Mexico

Dwight M. Trainor, D. F. Williams, J. Armentrout

Foraminiferal oxygen stable isotope records play an important role in regional stratigraphy of deep-water exploration areas of the Gulf of Mexico. Due to the fact that changes in ^dgr¹⁸O composition are linked to glacio-eustatic sea level fluctuations, ^dgr¹⁸O records are used to predict sea level highstands, lowstands, meltwater or freshwater discharge events, and relative transgression or regression sequences. Individual ^dgr¹⁸O records from exploration wells are calibrated to absolute time by using available biostratigraphy and previously established and published global ^dgr¹⁸O models.

This investigation uses exploration wells situated along a transect from South Galveston A3, South Galveston A70, East Breaks 160, and East Breaks 556. The isotope study is a part of a comprehensive integrated stratigraphy project involving Mobil Oil Corporation, Microstrat Inc., and Dow Geochemical. ^dgr¹⁸O records are produced from the planktonic special G. ruber and the benthic species Uvigenina spp. when they co-occur within a sample. The isotope chronostratigraphy provides a uniform time scale to compare and contrast the sedimentation rate changes of equivalent stratigraphic sections along the transect. The relationship of sea level to sediment type is determined by comparing the isotope records to the well logs. In particular, the occurrence of sand and the associated sea level height is documented along the transect. The resulting isotope chronostratigraphy will be integrated with high-resolution seismic stratigraphy, including interpreted seismic sequence facies, high-resolution biostratigraphy, and organic geochemistry of the Pleistocene to middle Miocene sections for the wells.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990