PALEOCENE TO MIDDLE MIOCENE PLANKTIC FORAMINIFERA OF THE SOUTHWESTERNSALISBURY EMBAYMENT, VIRGINIA AND MARYLAND - BIOSTRATIGRAPHY, ALLOSTRATIGRAPHY, AND SEQUENCE STRATIGRAPHY

The Paleocene to Middle Miocene sedimentary fill of the southwestern S alisbury Embayment contains a fragmental depositional record, interrup ted by numerous local diastems and regional unconformities. Using plan ktic foraminiferal biostratigraphy, we have identified fifteen unconfo rmity-bounded depositional units, assigned to six formations and seven alloformations previously recognized in the embayment. The units corr elate with second- and third-order sequences of the Exxon sequence str atigraphy model, and include transgressive and high-stand systems trac ts. Alloformation, formation, and sequence boundaries are marked by ab rupt, scoured, burrowed, erosional surfaces, which display lag deposit s, biostratigraphic gaps, and intense reworking of microfossils above and below the boundaries. Paleocene deposits represent the upper parts of upper Paleocene Biochronozones P4 and P5, and rest unconformably o n Cretaceous sedimentary beds of various ages (Maastrichtian to Albian ). Lower Eocene deposits represent parts of Biochronozones P6 and P9. Middle Eocene strata represent mainly parts of Biochronozones P11, P12 , and P14. Upper Eocene sediments include parts of Biochronozones P15, P16, and P17. Oligocene deposits encompass parts of Biochronozone P18 -20 undifferentiated, P21a, and, perhaps, N4a. Lower Miocene deposits encompass parts of Biochronozones N4b to N7 undifferentiated. Middle M iocene strata represent mainly parts of Biochronozones NS, N9, and N10 . Nine plates of scanning electron micrographs illustrate the principa l planktic foraminifera used to establish the biostratigraphic framewo rk. Two new informal formae of Praetenuitella praegemma Li, 1987, are introduced.