PRE-WISCONSINAN GLACIATIONS OF NEW JERSEY

The easternmost outcrop belts of pre-Wisconsinan glacial deposits in North America are in New Jersey. Two pre-Wisconsinan glaciations are recognized: an older advance of early Pleistocene age and a later advance of probable Illinoian age. The early Pleistocene glaciation (former Jerseyan) is recorded by deeply weathered till (Port Murray Till), and a few fluvial and lacustrine stratified deposits. Clasts of weatherable rock types like gneiss and sandstone are fully saprolitized to depths of >5 m, or have thick (>1 cm) weathering rinds. Clasts of resistant rock types like quartzite and chert have surface staining or thin (<2 mm) weathering rinds. The deposits are preserved on gently sloping divides and interfluves, with modern valleys incised into bedrock 30-50 m below the former land surface. Weathered fluvial sand and lacustrine clay at several locations yield a mix of normal and reversed polarity, indicating deposition and weathering before 775 ka, followed by continued weathering after 775 ka. Pollen from basal sediments in Budd Lake, an upland lake first dammed during this glaciation, include frost-intolerant taxa that become regionally extinct with the onset of glacial climate in the Pleistocene. The topographic position, weathering characteristics, and pollen content are similar to that of a Pliocene fluvial deposit in the New Jersey Coastal Plain. These features suggest that this glaciation may be the earliest Laurentide advance between 2-2.5 Ma.

The later glaciation is recorded by till (Flanders and Bergen tills) and fluvial and lacustrine deposits. The till is eroded from steep slopes but remains on gentle to moderate slopes and forms subdued moraine ridges in several valleys. The stratified deposits fill modern valley bottoms, forming plains, terraces, and deltas, and are preserved in valley fills beneath late Wisconsinan deposits. Weatherable clasts have rinds <5 mm thick. In places, soils with red Bt horizons are developed on the deposits, indicating exposure through a full interglacial. Peat overlying lacustrine sand of this glaciation, and in turn overlain by colluvium, in an upland valley near Dover, NJ, dates to 36,070±280 yr BP (41 cal ka), proving at least a pre-late Wisconsinan age. These features suggest an Illinoian age.