Methodology for dissolution of sediment and calcareous deposits for paleontological specimen collection and identification

Abstract

The Lance Creek Formation (Late Cretaceous) is significant in the study of late dinosaurs and is a diverse formation containing both terrestrial and aquatic macrofossils. To study this important ecosystem, all of the fossils present must be uncovered and examined from Lance Creek sedimentary rocks, which exhibit variable degrees of lithification. In order to liberate the fossils, a dissolution methodology was designed to determine which solution was most effective at uncovering specimens and dissolving/disaggregating sediment. Different solutions were tested including water, a 50% Calgon© solution, and a 5% acetic acid solution. The control was a sedimentary rock sample not subjected to any solutions prior to rinsing and sieving. A small-scale dissolution (10 g of loose sediment) was performed using each solution and examined for fossils. Acetic acid was deemed the most effective solution for the dissolution of dense sandstones, and indurated sediment from the Lance Creek Formation. Large-scale disaggregation (800 g of consolidated sedimentary rock) yielded abundant terrestrial, fluvial, and marine macrofossils. Macrofossil disaggregation using these methods has the potential to yield a more diverse assemblage of contemporaneous fossils than macrofossils alone, and can therefore provide substantial insight into ecological reconstructions.•A small-scale study was done to determine which solution was the most efficient at dissolution of sediment. Acetic acid was deemed the most effective.•A large-scale experiment was done on dense sandstones using 5% acetic acid and a shaking incubator.•A large-scale experiment of indurated sediment was performed using 5% acetic acid.