Abstract
Large fossiliferous glacial erratics occur scattered within ground moraines throughout Passaic and Bergen Counties in the northern New Jersey Piedmont. The distinct lithology and fossil assemblages identified within these glacial erratics indicates that the source provenance resides in the Lower and Middle Devonian of the Lower Hudson Valley and Helderberg Mountain Regions of New York State. The glacial erratic assemblage is dominated by siliciclastic and impure carbonates that are physically and chemically resistant to glacial erosional processes. Diagnostic invertebrate fossils including: brachiopods, mollusks, corals, trilobites, crinoids, and tentaculites indicate that most formations occurring within the Helderberg Group, Tristates Group, Onondaga Formation, and Hamilton Group are represented. These fossiliferous piedmont glacial erratics provide a unique opportunity to reconstruct the travel path of the Hudson-Champlain Lobe of the Laurentide Ice Sheet. This travel path is due north to south and as much as 200 kilometers as delineated by Lower and Middle Devonian outcrop exposures and the recovered piedmont glacial erratics. Moreover, distribution of Lower and Middle Devonian erratics in the northern New Jersey Piedmont indicates that the Hudson-Champlain Lobe was channelized in topographic lows, between the Ramapo Mountains to the west and Watchung Mountains to the east, before ice melt and deposition.