A Centennial Record of Paleosalinity Change in the Tidal Reaches of the Potomac and Rappahannock Rivers, Tributaries to Chesapeake Bay

Authors

Neil E. Tibert, University of Mary WashingtonFollow
Lindsay J. Walker, University of Mary WashingtonFollow
William P. Patterson, University of SaskatchewanFollow
J. Bradford Hubeny, Salem State UniversityFollow
Emma Jones, University of Mary WashingtonFollow
Olivia R. Cooper, University of Mary WashingtonFollow

Document Type

Article

DOI

10.25778/8q18-ay59

Abstract

Gravity and push cores from the Potomac and Rappahannock Rivers (Virginia Tidewater) were collected from central and proximal estuarine zones with known seasonal salinity stratification. The lowermost microfossil associations in the cores comprise alternating ostracode populations of Cyprideis salebrosa and Cytheromorpha. This microfossil association gives way to an oligohaline association dominated by the freshwater ostracode Darwinula stevensoni. Stable oxygen isotope values (δ¹⁸O) of Rapphannock Cyprideis salebrosa are highly variable ranging between -6.6 to -3.2‰ VPDB. δ¹⁸O values for Potomac Cytheromorpha fuscata range from -8.2 to -3.2‰ VPDB. Positive excursions in δ¹⁸O values are synchronous with population peaks for both Cyprideis and Cytheromorpha indicative of increased marine influence and/or higher salinities. Microfossil paleoecology coupled with oxygen isotope values record a marked shift towards gradual freshening and deterioration of the salinity structure in the tidal tributaries during the mid-to late 19^th century. We attribute these trends to both decadal climate trends and aggressive land use practices in the Chesapeake Bay watershed during the late 19^th to middle 20^th centuries.

Recommended Citation

Tibert, N. E., L. J. Walker, W. P. Patterson, J. B. Hubeny, E. Jones and O. R. Cooper. 2012. A Centennial Record of Paleosalinity Change in the Tidal Reaches of the Potomac and Rappahannock Rivers, Tributaries to Chesapeake Bay. Virginia Journal of Science 63 (3): 111-128.