ISOPACH CONTOUR MAP OF THE UPPER PALEOCENE AQUIA FORMATION AND STRUCTURE CONTOUR MAP OF THE PALEOCENE-EOCENE BOUNDARY IN THE SALISBURY EMBAYMENT OF MARYLAND AND VIRGINIA

Detailed information regarding the thickness and the spatial extent of formations across state boundaries enables more accurate documentation of the extent of regional aquifers, which is important for management of water resources. Data from more than 650 points of core and cutting descriptions and boreholes in the upper Paleocene Aquia Formation were obtained across the Salisbury Embayment of Maryland and Virginia. These points were used to produce an isopach thickness grid created with the Natural Neighbors interpolator in ArcGIS. A contour interval of 20 feet extracted from the resulting grid indicates a depocenter with large spatial extent. Values as thick as 76 meters (250 feet) are primarily centered in south-central and the upper eastern shore of Maryland. In Virginia, the greatest thickness values occur just south of the Potomac River with an average thickness of 9 meters (30 feet) across the coastal plain of southeast Virginia outside the region of the Chesapeake Bay impact crater. Additional work underway includes an isopach contour map of the lower Eocene Marlboro Clay and a structure contour map of the Paleocene-Eocene boundary to aid in defining the confining unit above the Aquia and for correlation of this important chronostratigraphic boundary.