Hidden Cretaceous basins in Nova Scotia

Early Cretaceous unconsolidated quartz sand and kaolinitic clay deposits in the lowlands of Nova Scotia are preserved in narrow half-grabens obscured by glacial drift. The Chaswood Formation sediments can be subdivided into t hree members; upper and lower members dominated by cyclical sand-mud facies of fluvial origin and the middle member with lignitic clay of lacustrine o rigin. Ferruginous oxisols are common in the fine-grained facies of the upp er and lower members. Seismic data indicate that Chaswood Formation strata in the Elmsvale Basin are deformed into steeply dipping faults and fault-re lated folds (Rutherford Road fault zone). An Aptian-Albian age for this tec tonic event is inferred from synsedimentary deformation and from the angula r unconformity spanning the Late Cretaceous and Tertiary that truncates the Chaswood Formation. Exhumation of a thick cover of Mesozoic sediment (1-2 km) is needed to account for the preservation of Chaswood Formation outlier s after similar to 80 Ma of erosion. The half-grabens that host the Chaswoo d Formation were formed in the Mesozoic and were antecedent to the present- day structurally controlled lowlands.