Marine Geology of Sohm Basin, Canadian Atlantic Margin

摘要

Multichannel seismic reflection, seismic refraction, and magnetic anomaly data are used to interpret the Mesozoic sea-floor spreading history and subsequent sedimentary evolution of the Sohm basin southeast of Nova Scotia. Observed M-series (Mesozoic) magnetic anomalies show that oceanic crust in the Sohm basin was generated at very slow rates of sea-floor spreading (5-15 mm/yr half rates). The slow spreading created very rough crustal topography, but the crustal thickness and seismic-velocity structure are typical of 'normal' oceanic basement. Basement depths corrected for sediment loading fall below the predicted age/depth curve in the anomaly M25-M4 interval. These depth anomalies and an associated regional negative geoid anomaly suggest that the Sohm basin is underlain by asthenosphere denser and possibly colder than normal. Correlation of seismic reflection profiles in the basin to regional seismic stratigraphy, together with age constraints from reflection pinch-outs on dated oceanic crust, provides a chronology for interpreting the seismic sequences. Keywords: Abyssal ocean currents erosion. Sedimentation geologic age determination. Reprints. (EDC)