Pick Type: top or base pickChoiceType extPickChoiceType refinedPickChoiceType refinedExtPickChoiceType POSC 1.0 top The top of the formation. This value may be refined by a stratigraphic or physical, if desired, or by another refinement. In general, the top is the first encounter of a formation for a vertical or nearly vertical wellbore. Variations may occur if the formations are steeply dipping or overturned, or if the well is significantly deviated. base The base of the formation. This value may be refined by a stratigraphic or physical, if desired, or by another refinement. In general, the base is where the borehole leaves the formation for a vertical or nearly vertical wellbore. Variations may occur if the formations are steeply dipping or overturned, or if the well is significantly deviated. unknown The type of pick cannot be determined.