A CHAMPLAIN SEA PHOCID SEAL FOSSIL FROM THE CHAMPLAIN LOWLAND AT PLATTSBURGH, NEW YORK

A SUNY Plattsburgh environmental geotechnology class uncovered several bones, most likely from a harbor seal (Phoca vitulina), from exposures of Champlain Sea mud at the former Plattsburgh Air Force Base marina. The glacial section at the site contains a complete record of Late Wisconsinan deglaciation in the Champlain lowland. A 1.5 to 2.0 meter thick section of fresh water ostracode (Candona subtriangulata) bearing, thinly laminated proglacial lacustrine rhythmites overlie massive gray diamicton near the base of the section. The lacustrine rhythmites contain a 0.0 to 0.2 meter thick layer of medium sand that may record one or more breakout floods from the Ontario and St. Lawrence lowlands. The lacustrine rhythmites grade upward to thinly laminated transitional rhythmites that contain marine and fresh water microfaunal assemblages. Approximately 1.5 to 2.0 meters of thinly laminated to massive, fossiliferous marine mud overlies the transitional facies, which in turn grades upward to an approximately 7-meter thick section of horizontally bedded silt and sand. The seal bones came from massive marine mud just below the transition to silt and sand.

The accidental fossil find occurred as the class collected mud samples for a slope stability analysis of the bluffs along the present shoreline of Lake Champlain. The collection consists of the tibia and fibula from both legs, four vertebrae, four ribs, an astragalus, a tarsal bone, a phalange, a molar and half of the mandible with a canine tooth attached. Collagen extracted from a piece of fibula has been sent to the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) for radiocarbon dating. The find represents the second phocid fossil recovered from the Champlain lowland. The left tibial shaft from another harbor seal, originally misidentified as a hooded seal (Cystophora cristata), was found in Plattsburgh in 1901. Harbor seals on the east coast of North America presently range from the mid-Atlantic region to the Canadian Arctic.