of stratigraphic units they are described for each mountain range or other area 
in which they occur.  Some Quaternary and Tertiary surficial deposits occur
throughout the State; consequently, no geographic area is designated.     
     The correlation diagrams show age ranges of map units; where a major 
unconformity separates individually described stratigraphic units that are 
combined in a single map unit, the age range is designated by a double-headed 
arrow.  A query (?) at one or both ends of the arrow indicates uncertainty as 
to extent of range.