OffshoreLabrador

East Canada Offshore

Northern Baffin Bay

This tentative geological interpretation of a seismic line of Lady Anne geographic basin not only illustrates the Atlantic-type divergent margin of NW Baffin Bay but rift-type basins as well, which predate the breakup of the continental crust of the small Laurentia (paleocontinent, forming the base of North America and Greenland, also known as the North American Craton, in which the Canadian shield dated between 4000 2500 Ma, sis the oldest part of it). Take note that few rifting normal faults were reactivated as reverse by a Late Mesozoic compressional tectonic regime, creating uplifting and tectonic inversions as illustrated next.

Taking into account the erosional toplaps of the seismic reflectors visible, at sea floor, on southern part of this autotrace, it is evident that sediments were uplifted creating, locally, enhanced unconformities (angular unconformities), which change, northward, into cryptic unconformities, which are difficult to recognize, particularly landward of the basin edge and in deep-water. In fact, on seismic lines, the great majority of the unconformities are cryptic. The erosion, that characterizes them, is difficult to put in evidence. Landward of the basin edge, just the infilling of incised valley fills, can highlight the erosional surface accompanying the relative sea level fall, which characterize the unconformity. Seaward of the basin edge, the filling of submarine canyons or valleys are geological peculiarities that allow, also, the identification of unconformities, as it seems to be case on this tentative interpretation (southern boundaries of the sedimentary packages colored in green).

Slightly southward of the previous Canvas autotrace, near Scott inlet, this autotrace not only illustrates enhanced unconformities, but tectonic inversions as well, In other words, this autotrace corroborated the occurrence of compressional tectonic regimes in this offshore, not far from the coastline. The tectonic inversions observed in the rift-type basin sediments can just be the result of the reactivation of the rifting normal faults in reverse faults by a compressional tectonic regime. Similarly, the breakup unconformity is completely shortened. Also, the sediments of the Atlantic-type divergent margin are also shortened. As the unconformities are tectonically enhanced a recent compressional tectonic regime is conspicuous.