GLACIAL FEATURES AND EOLIAN DUNES IN THE ST. LAWRENCE LOWLANDS

The history of the St. Lawrence Lowlands in Northern New York is complex with periods of glaciation, deglaciation, presence of proglacial lakes and their transition to modern landscapes. The area was covered by the Laurentide Ice Sheet during the Last Glacial Maximum and as the ice sheet melted, it formed a proglacial lake, Glacial Lake Iroquois (GLI). GLI retreated along with the ice sheet and eventually connected to Lake Champlain and the Atlantic Ocean through the St. Lawrence River. This caused an influx of ocean water and resulted in the Champlain Sea. When the Champlain Sea retreated in the early Holocene, it left behind unvegetated land and loose sediment. This paved the way for dune formation along the lowlands of the St. Lawrence River Valley. The exact age of dunes is unknown but can be narrowed down to the earliest retreat of the Champlain Sea to perhaps ~5-7 thousand years, the ages of possible related dunes in southern Quebec.

This study focused on dune interpretation over four quadrangles in northern St. Lawrence County (Morrisburg, Louisville, Waddington, Chase Mills, and Massena) using LiDAR hillshade models. Dunes were identified by overall morphology and components such as limbs and noses. The dunes in this area have been classified into six categories based on their morphology, including areas inferred to represent erosional remnants. It is believed that areas of low relief with closely-spaced crisscrossing pattern (resembling chicken feet) are indicative of eroded complex dune systems due to their locations around and behind dune fields. Over 550 dunes were classified along an approximately 20 km wide swath between Potsdam and the St. Lawrence River. Along with the identification of the dunes, other glacial features such as Rogen Moraines, flutes, and beach terraces were identified. Ground penetrating radar (GPR) data acquired across several dunes outside but not far from the field area (Brasher Falls State Forest, Clarkson University in Potsdam, Unionville) confirm the presence of sand dunes with southwest-inclined cross-beds overlying glacial deposits and sediments related to the retreat of the Champlain Sea. Future work is planned for acquiring GPR over for dunes within the field area as well as well as investigating the effect of land use and wetlands on dune preservation.