AN INTERPRETATION OF NEWLY DISCOVERED GLACIAL ADVANCE AND RETREAT FEATURES FROM THE SOUTHEAST CANADIAN CONTINENTAL SHELF BASED ON MULTIBEAM BATHYMETRY, GEOPHYSICAL SURVEYS AND SEABED SAMPLES

The recent collection, ground truthing and interpretation of multibeam bathymetry off Nova Scotia, Canada, has provided new insight into the characteristics of glacial marine features related to the advance and retreat of ice on the continental shelf. A series of retreat moraines termed the Scotian Shelf End Moraine Complex, formed by grounded glaciers with floating ice margins. The moraines are interbedded with ice proximal glaciomarine sediment in the form of till tongues. Multibeam bathymetry from northern Emerald Basin shows that the location of the moraines is controlled by local water depth and bedrock highs that anchored the glaciers. The moraines occur as lobate-shaped ridges convex seaward and most are covered with iceberg furrows. A sub-glacial drainage channel breaches the moraine with a distal grounding line fan. Areas between morainic ridges consist of broad regions of iceberg-furrowed ground moraine. Multibeam bathymetry from Browns Bank, western Scotian Shelf, shows a suite of preserved glacial features across the transgressed offshore bank. Terminal moraines are multi-lobate, up to 20 m high, and boulder covered. Other areas of the bank consist of low-relief gravel-covered terrain on which narrow and straight-curvilinear ridges occur and are interpreted as lateral moraines. On eastern Browns Bank areas of seabed appear as bouldery flutes that are interpreted to lie parallel to the direction of ice advance. Regions of small overlapping linear ridges are interpreted as eskers and iceberg furrows. Together these newly discovered seabed features indicate a complex history of ice advance and retreat and sea level change on the southeast Canadian continental shelf producing unique and unusual seabedscape geomorphic elements. Interpretation of these glacial features provides essential information for an understanding of continental shelf glaciation.