Revision of Sequences Boundaries and Maximum Flooding Surfaces: Jurassic to Recent

Abstract

ABSTRACT The key to recognizing the third and fourth order depositional sequences is the maximum flooding surface. An age designation of this surface is extremely important in seismic sequence stratigraphic analysis. Therefore, the purpose of this paper is to recognize and date the Cenozoic, Cretaceous and Jurassic maximum flooding surfaces in Ma and to assign a specific numerical age and letter designation to each of these maximum flooding surfaces from the Jurassic to Recent. These designations can be used as a standard of reference for the maximum flooding surfaces worldwide. INTRODUCTION Seismic sequence stratigraphy is the integration of high resolution biostratigraphy (including age datable bioevents, paleobathymetry and fossil diversity and abundance histograms), well-log signatures and seismic profiles. Each of these three components are interdependent and incomplete by themselves and, therefore, they must be analyzed and integrated with each other using an iterative process in order to obtain accurate, reliable and reproducible results. The introduction of high resolution biostratigraphy and paleobathymetry into seismic sequence stratigraphy in 1987 (Lamb, 1986) provided the key data set that permitted Sequence Stratigraphy and Seismic Sequence Stratigraphy to become a practical reality in exploration and development. It permitted the explorationist to age date the maximum flooding surface within each sequence and help divide a stratigraphic section in a well and on a seismic section into a series of third order depositional sequences and systems tracts in a reasonable amount of time with a high degree of confidence. Maximum flooding surfaces can be age dated in millions of years before present (Ma) because of their association with important chronostratigraphic species within the maximum flooding surface condensed section. These maximum flooding surfaces, within one third order depositional sequence can be correlated with the Global Cycle Chart of Hardenbol et al., 1998. The (MFS) maximum flooding surfaces within a third order depositional sequence permits the recognition of the lowstand systems tract below the transgressive systems tract and highstand systems tracts above the maximum flooding surface. The maximum flooding surface is recognized by the bellshaped curve that is formed from the increase and decrease in fossil abundance in the maximum flooding surface condensed section, and the highest gamma and lowest resistivity peaks onthe well log. The depth of these peaks, converted to seismic time correlates with the regionally continuous, high amplitude seismic reflectors on seismic reflection profiles. The sample by sample paleobathymetric interpretation (Lamb et al., 1986)from fossils permits the recognition of maximum flooding surfaces (Lamb et al., 1987, Wornardt et al., 1990 and Shaffer,1990) at an increase in water depth and the sequence boundary at the decrease in water depth.