The age of the Roberts Arm Group, north-central Newfoundland: Discussion

Abstract

content over the entire stratigraphic limits of the Muncho-McConnell, Stone interval is a meaningless exercise within the context of this discussion -breccias do occur within sandy dolomite beds containing more than 30% by weight of quartz sand and it appears to us that special pleading is required if only the quartz sand-free beds are to be dissolved; (3) corrosion, solution, and resultant insoluble residue or deposits are not ruled out by a fracture mechanism, but the quantity of such lags is expected to be small (as is the case at Robb Lake) and not comparable in quantity, or areal extent with lag deposits associated with well-documented solution-collapse terranes such as those described by Sando (1974); (4) Figures 8 and 9 together with the accompanying discussion (Macqueen and Thompson 1978, pp. 1751-1752) demonstrate large scale geological relations that are not fully explained by a solution-collapse mechanism; (5) we did not make a direct comparison with the work of Phillips (1972) and we do not accept Sangster's (1979) contention that the geological relationships described by Phillips (1972) constitute the necessary and limiting conditions for a fracture mechanism to be operative; and (6) we suggested r? hydraulic fracturing mechanism as a pussihle alternative that meets the criteria set out on p. 1752 (Macqueen and Thompson 1978) as well as providing greater flexibility with regard to the timing of brecciation. We leave Si~ngster with the dilemma of timing: the occurrence of bitumen within the breccia matrix suggests breccia matrices may have been open long after deposition of the