| Popis: |
The E-W to NE-SW trending Rockland Brook Fault (RBF) broadly parallels the late Paleozoic Cobequid Fault of mainland Nova Scotia, Canada. Because it separates multiply deformed Precambrian units to the south from previously undeformed Devono-Carboniferous intrusives which lie primarily to the north, the RBF has been cited as a Precambrian terrane boundary within the Avalon Terrane. In its E-W trending western and central portions, the RBF records intense, dextral ductile shear of late Paleozoic age. At its NE-trending eastern end, late Paleozoic strike- slip movement is minimal and the RBF is considered to represent a structural front separating cleaved Hadrynian volcano-sedimentary successions to the west from their upthrown, undeformed equivalents to the east. This earlier NE-trending segment (the ancestral RBF) is believed to have been rotated and reactivated as an E-W ductile shear zone with the arrival of the Meguma Terrane during the late Paleozoic. Later movement is considered to have produced a link to the Cobequid Fault, thus preserving the ancestral RBF while allowing for sufficient movement to produce the intense deformation seen along the E-W trending portion of the fault. The ancestral RBF is interpreted as a Precambrian thrust ramp but neither it nor the Paleozoic RBF are likely to have been a major terrane boundary. |
