PROVENANCE OF THE POTSDAM SANDSTONE FROM LASER ABLATION U-PB AGES OF DETRITAL ZIRCONS

The Upper Cambrian Potsdam Sandstone is a quartz arentite that forms the basal unit of Paleozoic cover representing the initiation of a major marine transgression as part of the Sauk sequence (Sloss, 1963). In western upstate NY, the Potsdam sandstone unconformably overlies Precambrian (Grenville) basement, separated by a 600 million year gap in the sedimentary record.

An important aspect of understanding the tectonic and depositional history of this sequence is the provenance of the sediment itself. Previous studies of the Potsdam (Montario and Garver, 2009) and its stratigraphic equivalent, the Poughquag quartzite (E. NY, McClennan et al., 2001) suggests a Grenville source. Earlier work, however, interpreted sources from both the Grenville and Superior Provinces (Gaudette et al., 1981). Here, we present laser ablation ICP-MS U-Pb ages of zircons from the Potsdam at Alexandria Bay, NY. We analyzed 385 individual zircons, and of these 209 yielded concordant ages of two populations: 1100 Ma and 2500 Ma.

References: Gaudette et al., (1981). EPSL 54, 248-260; McLennan et al., (2001). J. Sed. Res. 71, 305-317; Montario and Garver (2009). J. Geology, 117, 595-614; Sloss, L. (1963). GSA Bulletin 74, 93-113