Surficial geology, coastal waters, Island of Newfoundland, Newfoundland and Labrador

Abstract

This bulletin is a synthesis of several decades of Geological Survey of Canada research into the surficial geology of the inner continental shelf around the Island of Newfoundland, and the geomorphology of adjacent coastlines. Based on analyses of data from multibeam-sonar surveys, other marine surveys, and from coastal mapping, the island is divided into fourteen regions, each with distinctive surficial geology and coastal geomorphology. The evidence of glaciation is dominant in all regions, and includes: 1) streamlined landforms formed in the onset areas of ice streams; 2) arcuate submarine moraines formed by glacial standstills at the mouths of west and south coast fiords; 3) transverse moraines formed by standstills within fiords; and 4) swarms of De Geer moraines formed during ice retreat. The seafloor of the inner shelf is imprinted by relict iceberg furrows and pits in all fourteen regions, but a modern population is recognized only off the east and northeast coasts. Evidence of lowered postglacial sea levels is found in submerged deltas and wave-cut platforms at various depths off the southwest and south coasts. The zone of modern sediment mobility is relatively wide on the shallow inner shelves off southwest and northeast Island of Newfoundland, and relatively narrow elsewhere. The multibeam-sonar imagery reveals a wide range of submarine landforms and processes, including active submarine fans in west coast fiords, an inner-shelf submarine canyon off the southwest coast, and large-scale erosion of the seafloor in Placentia Bay and off Bay of Islands. Anthropogenic modification of the seafloor is most intense near Corner Brook (Bay of Islands) and in parts of Placentia Bay, and includes submarine landslides triggered by port construction.