Geology of the passive margin of New England

Rifting between northeastern North America and Morocco during the Middle-Late Triassic produced a complex series of horsts and grabens in Precambrian/Paleozoic crust. Intra-rift sediments consist of clastics, evaporites, and volcanics. Continental separation occurred and sea-floor spreading began 195-190 my B.P. The boundary between normal continental crust and crust radically altered by fracturing and intrusion may be represented by a pronounced basement hingezone. Prior to margin subsidence, extensive sub-aerial erosion carved a break-up uncomformity reflector K which truncated pre-existing rift structures and which must be approximately the same age as the oldest oceanic crust. Within the overlying drift sediments, six acoustic horizons have been regionally traced and correlated with strata samples by a well drilled on the western Scotian Shelf. The total sediment thickness of both rift and drift sequences beneath Georges Bank may be 13 km, of which more than 80% is Jurassic in age.