Paleogene sequence stratigraphy of the Transverse Ranges, southern California

Integration of satellite data, high-altitude photos, well log correlation and field observations has been used to develop a sequence stratigraphic framework for Tertiary strata in the Transverse Ranges. The framework is based on tracing sequence boundaries or unconformities in the field, and on the ability to recognize these surfaces on well log data. Identification of parasequence stacking patterns that are typical of transgressive, highstand, and lowstand systems tracts was significant in building this framework. Systematic development of these stacking patterns was considered unlikely where local random events alone influenced deposition. Biostratigraphic data was tied to eustatic cycle charts to relate these sequences to global events. Key boundaries that were identified include the 49.5-, 48.5-, 44-, 39.5-, 36-, and 30-m.y. sequence boundaries. For example, the 49.5- and 48.5-m.y. sequence boundaries are located within the Matilija Formation. These sequences locally exhibit truncation and development of highstand, lowstand, and transgressive system tracts; lowstand and transgressive system tracts are best developed. The 39.5-m.y. sequence boundary is located between the Sacate and Gaviota formations in the western Transverse Ranges. This boundary exhibits tectonic enhancement on satellite photos with truncation of middle Eocene folds below the unconformity. Previously, abrupt lithologic changes across this unconformity were regardedmore » as facies changes. Sequences within the Transverse Ranges exhibit variability in terms of systems tract preservation degree of truncation, and depositional setting. Identification of stratigraphic surfaces, unconformities and flooding surfaces, and repetitive stacking arrangement of strata is essential to development of a sequence framework. The ability to put a framework together in the Transverse Ranges indicates that both tectonic and eustatic events can be recognized.« less