Sequence stratigraphy of a mixed siliciclastic-carbonate setting, Scotian Shelf, Canada

Abstract

During the Jurassic Period, a large-scale carbonate bank (Abenaki Formation) and a siliciclastic (Sable) delta coexisted in North America. Conventionally, carbonate systems (in situ) are separated from siliciclastic systems (transported) because of their contrasting origin. However, we developed a case study to show that the basic principles of sequence stratigraphy remain applicable. We integrated the results obtained from a regional 2D study and a detailed follow-up study using 3D seismic data of the Scotian Shelf, Canada. The results were integrated with the prepared Wheeler diagrams, and a unified sequence stratigraphic framework was proposed. We determined that two second-order sequences were developed on a larger scale during the Jurassic Period. The first sequence developed during the transition from a ramp to rimmed margin. The second sequence developed during the evolution from a rimmed to ramp margin. These sequences formed a distinct stratigraphic style throughout the Scotian Shelf. The siliciclastic supply varied from the northeast to the southwest depending on the studied site; however, the regions close to the siliciclastic supply contained well-defined clinoform patterns. The topsets of such clinoforms were mostly eroded. Their directions were also found to be different than the carbonate-related clinoform geometries. Most of the carbonates were developed; as such, they kept up and prograded toward a backreef margin during the rimming stages. The second-order sequences were further subdivided into four third-order sequences. These were studied using the 3D seismic data and were found to contain several barrier reefs that could have stratigraphic exploration potential in the Penobscot area.