The Double Mer Formation and the Lake Melville rift system, eastern Labrador

Abstract

The Double Mer Formation is a sequence of redbed arkosic sandstone, conglomerate, siltstone, and shale in the Grenville Province of eastern Labrador. The formation is closely associated with a rift system extending inland for at least 300 krn from the Labrador coast. Substantial thicknesses of strata of Double Mer Formation are confined to two basins, the Lake Melville graben and the Double Mer half graben. Strata correlated with the Double Mer Formation are found elsewhere in southeast Labrador; one isolated outcrop occurs within the Sandwich Bay graben, a separate, smaller basin 100 km to the southeast that trends parallel to the Lake Melville graben.The only definite age constraint on the Double Mer Formation is that it postdates Grenvillian deformation. Previously, the formation was assigned a latest Precambrian to Early Cambrian age based on lithological similarity with the Lower Cambrian Bradore Formation of the southeast coast of Labrador. On the basis of a structural model proposed here that suggests a link between graben configuration and latest Precambrian -Early Cambrian mafic dike trends, we concur with this viewpoint. The Double Mer Formation thus preserves the basin fill presumed to have accompanied graben formation, which, together with emplacement of mafic dikes and anorogenic plutons, documents latest Precambrian to Early Cambrian crustal extension that eventually led to the opening of the Iapetus Ocean.La formation Double Mer est une sCquence de couches rouges de grks arkosique, de conglomCrat, de silstone et de schiste argileux dans la province du Grenville du Labrador oriental. La formation est associCe de trks prks h un systkme de rift pCnCtrant h 19intCrieur des terres sur au moins 300 km h partir de la c6te du Labrador. Les strates de grandes Cpaisseurs de la formation Double Mer ne se retrouvent que dans deux bassins, le graben du lac Melville et le demi-graben Double Mer. D'autres strates mises en corrClation avec la formation Double Mer affleurent ailleurs dans la Labrador oriental; un affleurement is016 apparait dans le graben de la baie Sandwich, un petit bassin is016 situC h 100 km au sud-est et d'orientation parallkle au graben du lac Melville.La seule limite d'lge de la formation Double Merest celle qui post-date le dCformation grenvillienne. AntCrieurement, cette formation Ctait considCr6e comme d'lge entre le Pkcambrien fini-tardif et la Cambrien infkrieur, cette assignation Ctait fondCe sur les similitudes lithologiques avec la formation Bradore du Cambrien infkrieur de la c6te sud-est du Labrador. Ce point de vue est corrobork par le modkle structural proposC ici, lequel indique une relation entre le configuration du graben et les directions des dykes mafiques d'lge du PrCcambrien fini-tardif-Cambrien infkrieur. La formation Double Mar a donc empCchC 1'Crosion des matCriaux de remplissage du bassin lesquels vraisemblablement accompagnaient le dCveloppement du graben h 1'Cpoque de la mise en place des dykes mafiques et des plutons anorogCniques, ce qui fournit des enseignements s...

The influence of meltwater on the Labrador Current in Heinrich event 1 and the Younger Dryas

“…The lack of any increase in a* indicates this source was not in northern Newfoundland, which supplied red sediment at glacial maxima (Tripsanas and Piper, 2008a). A potential source area of the plume deposits is from the sandstones of the Double Mer Formation (Gower et al, 1986) in the Lake Melville region of southern Labrador. However, distal freshwater release farther north, such as from Greenland, cannot be excluded.…”

Generation and preservation of continental crust in the Grenville Orogeny

“…These were deposited during continental rifting associated with the breakup of Rodinia Cawood and Nemchin, 2001). Both of these formations have an assumed early Cambrian age, although the absence of Cambrian trace fossils in the Double Mer Formation might imply a late Neoproterozoic age (Gower et al, 1986;Williams and Hiscott, 1987). The Double Mer Formation consists of arkosic sandstone, conglomerate, siltstone, and shale and was deposited in a series of rift basins extending at least 300 km inland from the Labrador coast (Gower et al, 1986).…”

“…Both of these formations have an assumed early Cambrian age, although the absence of Cambrian trace fossils in the Double Mer Formation might imply a late Neoproterozoic age (Gower et al, 1986;Williams and Hiscott, 1987). The Double Mer Formation consists of arkosic sandstone, conglomerate, siltstone, and shale and was deposited in a series of rift basins extending at least 300 km inland from the Labrador coast (Gower et al, 1986). The Bradore Formation has a similar lithology to the Double Mer Formation and is dominated by arkosic sandstone, but it is only found within 30 km of the Labrador Coast (including Belle Isle) and on Newfoundland (Cumming, 1983;Williams and Smyth, 1983;Williams and Hiscott, 1987).…”