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BTChronostratigraphic Units
 .Phanerozoic
 ..Cenozoic
 ...Neogene
 ....Pliocene
 .....Yorktown Formation
RTSouth Carolina
 Virginia
 North Carolina
 Maryland
 Chesapeake Group
SNIn Chesapeake Group. Divisible into 2 major zones. Zone 1 (at base) corresponds to beds exposed at Raysor Bridge, South Carolina; Zone 2 (upper) includes: Uppermost Yorktown beds at Suffolk, Virginia, the beds at Yorktown, Virginia, and the Chama-bearing