Authors : Elizabeth Keily, Arif M. Sikder, Joseph B. McGee Turner, Jonathan Suh, Daniel Boehling and S. Leigh McCallister
Abstract: The minor and trace inorganic elements may contribute to different colors of fossilized shells, depending on the environmental conditions of the sea water, differential fossilization process and diagenesis, even though the original color of the living biocalcifers’ shell is primarily developed by a variety of organic pigments. The sediments of the Piney Point Formation that crop up along the Pamunkey River are made up of blue glauconitic sand and clay with scattered, distributed enormous shell fossil fragments. Shattered fossil fragments of differing color from two exposures along the Pamunkey River were studied in terms of minor and trace element concentration to comprehend the relation between the color of fossil shells and paleoenvironments. The fossil fragments were grouped and sorted according to color independently of each of the other samples. Total 35 groups of fossil fragments resulted after sorting. The samples were organized by place in the stratigraphic column, then sorted into 5 similar color groups for analysis: Light, dark, gray, coated and black. Fossil fragment samples from the Piney Point Formation exhibited apparently lower concentrations of Barium than those in the Woodstock Member of the Nanjemoy Formation. Magnesium and strontium values were also higher in the Piney Point Formation. There was a higher level of strontium at the Piney Point-Old Church boundary, this could be due to an increased salinity in the Old Church Formation. Concentrations of sulfur and phosphorous in the partitioned fossil fragments were mostly anomalous, though the black and dark fossil fragments of Old Church Formation had significantly higher concentrations of sulfur. There were no linear and explicit relationships between the colors of the fossil shells fragments and trace metals concentration. Ba/Ca ratios tended to be higher in the fossil fragments of the Piney Point sediments. The higher Ba/Ca ratios in the Piney Point samples probably demonstrate an increase in biogenic activity. At the time of deposition of Piney Point sediments, the water probably had higher temperatures and the Piney Point-Old Church contact had an increased salinity condition.
Elizabeth Keily, Arif M. Sikder, Joseph B. McGee Turner, Jonathan Suh, Daniel Boehling and S. Leigh McCallister, 2014. Fossil Shell Color and Trace Element Concentration as Indicators of the Paleoenvironments of the Piney Point Formation at the Pamunkey River, Virginia Coastal Plain. Online Journal of Earth Sciences, 8: 1-12.