RECONSTRUCTING LATE PLEISTOCENE PALEOGEOGRAPHY AND SEDIMENTARY ENVIRONMENTS IN NORTHEASTERN NEW YORK USING GEOGRAPHIC INFORMATION SYSTEMS

Paleogeographic reconstructions of recessional glacial environments in northeastern New York are based upon correlation of ice-marginal and proglacial lake or marine deposits that are documented in existing literature and unpublished field data. Correlation of ice-marginal deposits was determined by an iterative process of projecting model-derived ice margin profiles from well-documented deposits in one valley into adjacent valleys. The projected ice margins were adjusted using available field evidence and the process was repeated until further readjustment produced only minor changes in the ice-margin position. Proglacial lake shorelines were recreated by fitting a topographic trend surface to the surface elevations of shoreline deposits and intersecting those surfaces with a 10-meter digital elevation model (DEM) for northeastern New York region. Similarly, the up-valley extent of fluvial-deltaic sandplains in major tributaries to the St. Lawrence and Champlain valleys were determined using an isostatic-rebound-corrected trend surface that projected up-valley at a gradient of 2 to 4 m/km. These procedures generally produced results that correspond well to interpretations presented in previous investigations in the region or provided reasonable alternative explanations. The resulting paleogeographic maps represent an integrated interpretation of deglacial environments in northeastern New York and provide a new baseline for inter-regional correlation of glacial deposits.

Geographic Information Systems (GIS) software and databases are effective tools for interbasinal correlation of sequences of glacial, proglacial lacustrine and marine deposits and reconstruction of late Pleistocene glacial environments in northeastern New York. GIS allows the user to work effectively at different spatial scales and facilitates application of simple mathematical models to account for ice-margin profiles of valley glacier margins, isostatic uplift of shoreline deposits and depositional slopes on fluvial-deltaic sandplains. Furthermore, the northeastern New York GIS databases are comprehensive archives for existing geospatial data and are easily updated as new information becomes available.