The nature, origin, and significance of the Carmanville ophiolitic mélange, northeastern Newfoundland

Abstract

The Carmanville ophiolitic mélange of northeastern Newfoundland forms an olistostrome within a thick succession of Middle to Upper Ordovician flyschoid shale, siltstone, and grey-wacke. The olistostrome consists of sedimentary, volcanic, and ultramafic olistoliths ranging in size from granules to several kilometres. The matrix appears to have been derived entirely by disaggregation and disintegration of hydroplastic and thixotropic sediments. The matrix was sufficiently fluid for turbulent motion to occur in the lower parts of the olistostrome, yet viscous enough to produce alignment of fragments and a pervasive cleavage, as well as drag folds in the surrounding hydroplastic sediments. The olistoliths have been drawn from a stratigraphic column hundreds, if not thousands, of metres thick, and an area many kilometres across. A small proportion of the olistoliths were deformed and metamorphosed prior to incorporation in the olistostrome.The Carmanville ophiolitic mélange is tentatively correlated with the Dunnage mélange to define the northern margin of a sheet of ocean floor and island arc obducted toward the southeast onto an accreting continental rise in Llanvirnian–Llandeilian time. Olistostrome formation within this unstable pile commenced in post-Arenigian time, and may have continued intermittently until Llandoverian time. The olistostrome and surrounding rocks were further deformed, metamorphosed, and intruded by granitoid plutons during Silurian and Devonian time.

Timing and spatial distribution of deformation in the Newfoundland Appalachians: a “multi-stage collision” history

“…Although thrusting was earlier reported from the Newfoundland Dunnage zone (Kay and Williams, 1963;Jacobi and Schweickert, 1976;Dean and Strong, 1977;Kidd, 1977;Blackwood, 1979;Pajari et al, 1979) it has recently become more widely recognized and better understood (Col-manSadd, 1980;Nelson, 1981;Thurlow, 1981;Blackwood, 1982;Karlstrom et al, 1982Karlstrom et al, . 1983Colman-Sadd and Swinden, 1984;Van der Pluijm, 1984a, 1986Kusky and Kidd, 1985).…”

“…The boundary between these two zones, locally, is a reverse fault (Pajari and Cnrrie, 1978;Blackwood, 1979Blackwood, , 1982Wilton, 1983). In the southeast, however, the contact is gradational (Currie et al, 1979;Pajari et al, 1979;Colman-Sadd, 1980;Blackwood, 1982;Colman-Sadd and Swinden, 1984). Pickerill et al (1978) and Blackwood (1982), therefore, suggested that Gander zone rocks are lateral correlatives of Dunnage zone rocks.…”

Provenance of tectonic history of the Gander Zone in the Caledonian/Appalachian Orogen: Implications for the origin and assembly of Avalon

“…1) is generally considered to represent part of the eastern passive margin of the Iapetus Ocean (Williams, 1979;Kennedy, 1975Kennedy, , 1976Pajari et al, 1979;Colman-Sadd, 1980). However, its provenance and relationship with respect to the adjacent peri-Gondwanan Avalon Zone (Williams, 1979) has remained unclear, hence its interpretation as a suspect terrane by Williams and Hatcher (1983).…”

Structural interpretation of the eastern Notre Dame Bay area, Newfoundland: regional post-Middle Silurian thrusting and asymmetrical folding: Discussion

“…Along the west and Silurian strata, and pointed out that the presence of side of Gander Bay where this contact is repeatedly an unconformity was supported by paleontological exposed by folding, Karlstrom et al agreed with the evidence. Cume et al (1980a) and PaJari et al (1979) earlier observations of cume et al (1980~) that the showed the Davidsville Group to be deep-water turbidites contact is stratigraphic rather than tectonic, and that the and contourites probably On large submarine fans, whereas the Indian Islands Group was interpreted 'paper by K. E. Karlstrom, B. A. van der Pluijm, and P, F. as stable-shelf, shallow-water sediments with a coralline Williams.…”