An integrated clinoform trajectory and sequence stratigraphic model for the Labrador margin, offshore eastern Canada

Abstract

The passive margin offshore Labrador began forming during rifting in the Early Cretaceous, with seafloor spreading starting in the Maastrichtian and ending near the Eocene–Oligocene boundary. A foundational understanding of the associated stratigraphy of this margin has been developed through previous studies of the lithostratigraphy, biostratigraphy, and seismic stratigraphy, but the significance of clinoforms, stratal boundaries, and transgressive and regressive events has never been fully explored. In this study, we identify a series of clinoform successions from the Late Cretaceous through Pleistocene and apply a second-order sequence stratigraphic model to refine the geological framework for the margin. We focus on the Hopedale Basin where there is sufficient well and reflection seismic data, with substantial new seismic data collected over the last decade. Seismic interpretation is combined with paleoenvironmental and biostratigraphic data from the wells to map clinothem packages along the margin including: seven shoreline, five subaqueous delta, one shelf-edge, and three shelf-edge deltas, with illustration of these on seismic profiles and paleogeographic maps representing several time slices. Trajectory analysis of these clinothems permits the delineation of eight second-order sequences, with systems tracts and sequence stratigraphic surfaces identified. Broader implications of our results include a revised lithostratigraphic column for the Labrador margin. We further demonstrate regional trends during rifting and opening in term of controlling factors on clinoform development through comparison with adjacent and conjugate margins. Tectonism dominated as a controlling factor in the Cretaceous and dwindled near the end of the Paleocene. Eustasy and climate also influenced clinoform development in the Late Cretaceous, but became major factors during the Cenozoic, enhancing relative sea level fall and sediment supply, with similarities to other clinoform successions developed during Greenhouse and Icehouse conditions. Impacts to petroleum prospectivity in the region are also discussed, and our overall seismic and stratigraphic framework provide a basis for future study.