Boron, Gallium, Rubidium, and Vanadium as Geochemical Indicators of Marine and Freshwater Depositional Environments: Hamilton Group (Middle Devonian), Southeastern New York: ABSTRACT

Abstract

Listen

Translate article

Thirty-two shale-mudstone samples collected from the Hamilton Group and previously classified on the basis of paleoenvironmental studies using geologic criteria as being of marine, brackish, or freshwater origin were analyzed for the environmental-discriminant trace elements B, Cr, Ga, Li, Ni, Rb, and V by atomic absorption spectrophotometry. The most efficient trace element discriminator used to differentiate geochemical partition of Hamilton marine from freshwater argillaceous samples was based on B vs. V, but use of other trace-element partition variables produced nearly similar results. Considering marine and freshwater samples together, 69% of those designated on the basis of geologic criteria as either freshwater or marine were correctly classified according to the three best geochemical partition methods (B vs. V, B vs. Ga, and B vs. Ga vs. Rb). For those designated by geologic criteria as marine, partition plots of B vs. V, and B vs. Ga correctly classified 90%, and B vs. Ga vs. Rb correctly classified 95% of the samples. Only 14% of those samples geologically defined as being of freshwater origin were correctly classified based on these geochemical partition methods. The overall paleosalinity signature for the Hamilton based on geochemical partition methods is marine. The source area mountains (Acadian) at that time thus were still probably of low relief. The Ha ilton probably represents a degradational delta in part with many reentrant transgressive bays, and in part a sluggishly prograding mud-dominated shoreline. End_of_Article - Last_Page 1169------------