A seismic-stratigraphic study that used existing USGS high-resolution seismic-reflection profiles was made in the area of the TACTS coreholes. This report presents interpreted cross sections and isopach and structure-contour maps that resulted from that study and some preliminary conclusions. Structure contour maps showing depth below sea level to the upper Eocene, Oligocene, lower Miocene, middle Miocene, lower Pliocene, upper Pliocene, and Quaternary strata are presented. Maps that show the thickness of Oligocene, lower and middle Miocene, middle Miocene, lower Pliocene, upper Pliocene, and Quaternary strata and the total sediment thickness above the phosphatic middle Miocene strata are also shown.