GLACIAL FEATURES AND SEDIMENT TRANSPORT PROCESSES IN EASTERN LONG ISLAND AND WESTERN BLOCK ISLAND SOUNDS
The dominant glacial features in the study area are the northeast-trending Harbor Hill-Orient Point-Fishers Island moraine and another smaller, previously unknown, recessional moraine to the southeast. South-trending sinuous ridges and isolated bathymetric highs associated with the larger moraine are interpreted to be eskers and kames, respectively. Elevated lineations observed on exposed bedrock in the northwestern part of the study area, which trend 154o to 162o and parallel the striations and streamlined hills of onshore formations, show that the effects of glaciation on the bedrock continue offshore under LIS. Also, several irregular elevated lineations on the bedrock surface trend roughly 50o to 62o. These lineations parallel structural trends in the onshore Avalonian terrane and, therefore, may represent strike ridges.
Strong tidal currents have scoured and redistributed much of the glacial and younger sediment in easternmost LIS, and produced large bathymetric depressions adjacent to the Race that exceed 100 m in depth. Degradational processes that cause the scour depressions include seabed erosion and mass-wasting, and effects of both processes are visible in the imagery as erosional outliers and talus piles. Asymmetry of transverse sand waves, barchanoid dune orientation, and scour around isolated boulders and a shipwreck indicate that net transport is primarily toward the west and into LIS in the northern part of the study area, but primarily toward the east and out of the Sound in the southern part.