SHALLOW MARINE CARBONATE MOUNDS OFF NORTHERN NOVA SCOTIA

Marine carbonate mounds occur 8km north of Bay St. Lawrence, Nova Scotia, on a 160 – 200m deep zone of the upper margin of the Laurentian Channel. The marine carbonate mounds occur subsurface of the Holocene siliciclastic sediments in an ancient fault zone. The <1m high mounds are porous to weakly solid with a smooth to bulbous surface and knobby popcorn-like clusters. Texturally, the overall aspect is a massive agglutinated mound of debris including bivalve shells, echinoid spines and silt to pebble sized siliciclastics with no internal lamination. The mound does has numerous thin (< 3mm diameter) vent tubes throughout. The microscopic texture of the carbonate matrix is vaguely peloidal and is silt sized or smaller. They have comparable characteristics with many deep-sea and cold-water carbonate formations, but the absence of an abundant biological component and the uncommon internal structure make these marine carbonate mounds unique. Formation of the marine carbonate mounds may originate from methane seepage along ancient faults and associated deep-sea biota, such as sponges and deep-sea corals.