Application of REE geochemical signatures for Mesozoic sediment provenance to the Gettysburg Basin, Pennsylvania

Abstract

Rift basins adjacent to accreted terranes provide accommodation space for sediments eroded from these terranes. Despite similar depositional environments and geologic age, rocks of the Triassic Gettysburg Basin have approximately half the arsenic concentrations of the adjacent Newark Basin. Quartz-feldspar-lithics (QFL) diagrams and rare earth element (REE) geochemical signatures can inform sediment provenance. Here we investigate REE geochemical signatures of the sedimentary rocks in the Triassic Gettysburg rift basin, with the goal of distinguishing the main sources of siliciclastic sediment among the Appalachian foreland in the rift footwall from Piedmont arc and Iapetan continental margin rocks exposed in the hanging wall and ultimately understanding the geochemical cycling of arsenic to the Gettysburg Basin. Shale-normalized REE spider diagrams and Mann-Whitney tests on trace element ratios suggest that the Gettysburg Basin samples show patterns that most closely resemble those of the Iapetus Continental Slope Rise Iapetus Rift Volcanic, and Accretionary Complex deposits. Mann-Whitney Rank Sum analysis suggest that the Iapetus Continental Slope Rise terrane is the main source of sediments to the basin, which confirms results from prior QFL analysis and shows the utility of REE fingerprinting in provenance analysis. The main sources of sediment have smaller minimum and maximum arsenic concentrations than other terranes and the Newark Basin sediments, additionally suggesting the source of arsenic to the Gettysburg Basin is based upon specific terranes.