GEOCHRONOLOGY OF QUATERNARY COASTAL-PLAIN DEPOSITS, SOUTHEASTERN VIRGINIA, USA

Three dusters of amino acid enantiomeric values (or aminozones) are de fined using molluscan fossils from the late Quaternary marine units ex posed in Gomez Pit, in the southeastern Virginia coastal plain. Mean a lloisoleucine/Isoleucine (A/I) values for two aminozones (IIa: 0.17 +/ - 0.02; Dc: 0.32 +/- 0.02) are superposed, show consistent relation to lithologic units, and are used to define local alloformations. A thir d aminozone (IId: A/I = 0.46 +/- 0.04) cannot be used to define a loca l alloformation because all IId mollusks appear to have been reworked into younger (IIc) lithologic units at the Gomez Pit site. LT-Th age e stimates on corals, and electron spin resonance (ESR) age estimates on fossil mollusks are used to calibrate aminozone IIa Combined U-Th, ES R, and amino acid enantiomeric data indicate a Stage 5 (80 to 130 ka) age for aminozone IIa. Age estimates for older aminozones Dc and lid a re calculated using aminozone IIa calibration applied to kinetic model s describing diagenetic racemization. Using this approach, age range e stimates for aminozone Dc (approximately 250 to 400 ka), and aminozone lid (approximately 500 to 800 ha) are proposed. Aminostratigraphic in terpretations are compared with other geomorphic and stratigraphic stu dies of the southern Chesapeake Bay region. Deposition of the ''IIa al loformation'' is correlative with parts of the Tabb Formation (Sedgefi eld Member), or parts of the Norfolk Formation, evolution of the Nassa wadox spit (lower Delmarva Peninsula), and filling of the Eastville pa leochannel of the ancestral Susquehanna River. The ''IIc alloformation '' is correlative with the Shirley Formation (on the York-James Penins ula) or Great Bridge Formation. Aminozone IId (in-place elsewhere in t he region) is correlative with the Shirley Formation (on the Rappahann ock River), evolution of the Omar-Accomack spit, and filling of the Ex more paleochannel of the ancestral Susquehanna River.