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Late Pleistocene depositional and morphostratigraphic units designated in Mississippi, were correlated along the north Gulf between Texas and northwest Florida. Subsidence resulted in thick Pleistocene sequences in the north-northwest. Due to steady, inland-centered uplift, only a thin Late Pleistocene interval survived erosion on the northeast Gulf. Neogene siliciclastics define the base of the Pleistocene. The open marine-to-paralic Biloxi, alluvial Prairie, and Gulfport barrier formations were deposited during the Sangamonian Interglacial. In sharp contrast with the Atlantic south coast, only a single barrier shoreline is recognized. Two sets of paralic deposits, separated by weathering horizon and/or different consolidation state indicate Sangamonian shoreline fluctuations on the Texas coast. Evidence contradicts recent suggestions of coastwise surface aggradation and of a warm interval, associated with a major eustatic rise during Middle/Late Wisconsinan times.

A newly recognized transgressive formation of late Pleistocene (Sangamon) age, along and off the Mississippi-Alabama coast, contains rich foraminifer and molluscan faunas reflecting its dominantly shallow-nearshore and open-marine depositional conditions. In some areas brackish-estuarine-embayment facies prevailed. The formation is overlain by the regressive alluvial-fluvial Prairie and the mainland barrier-beach-dune Gulfport Formations. Correlative units were identified in southeastern and southwestern Louisiana and probably also may be present in appropriate stratigraphic positions along the rest of the north and northwestern Gulf Coast in units the ages of which have not been established with certainty. Drilling indicated that all pre-Biloxi Pleistocene marine units have been eroded in the Mississippi-Alabama coastal and nearshore zones. Similarly, no pre-Gulfport Pleistocene barrier ridges or other relict shoreline features could be established along the northern-northeastern Gulf Coast. Both facts point to Pleistocene regional uplifts in this coastal area, in sharp contrast to the tectonic style of the adjacent Mississippi River delta region.

Field investigations failed to confirm the presence of earlier (pre-Sangamon) Pleistocene or Citronelle (Pliocene) littoral ridges and marine deposits on the surface in coastal Mississippi, Alabama, and the Florida Panhandle. The contrast between the numerous marine surfaces on the Atlantic coastal plain and the single Sangamon interglacial barrier complex of the Gulf Coast may be explained by the different regional tectonic behavior of the 2 provinces. Only 1 Pleistocene coastwise alluvial depositional surface was found in Mississippi and southwestern Alabama in addition to the Prairie (Pamlico, Beaumont) alluvial coastal plain. Its age could not be exactly determined. In addition to the known Pearl and Pascagoula River valley locations, intermediate valley terrace fragments ("Deweyville"?) were found near the mouth of the Biloxi and Tchoutacabouffa Rivers. These surfaces indicate the latest higher sea level stage which probably existed during the early Wisconsin stage. End_of_Article - Last_Page 1901

The Upper Cambrian Potsdam Formation (orthoquartzitic sandstone and conglomerate) in eastern Ontario, southwestern Quebec, and northern New York State, was deposited during an early Paleozoic transgression over the Precambrian surface of the Canadian shield. Rock types and sedimentary structures indicate three distinct environments: (1) Terrestrial, talus sheet wash fan (quartzite breccia), Frontenac arch, Thousand Islands region; (2) marine and (or) fluvial channel (cross laminated sandstone), Ontario and northern New York; and (3) low-energy, littoral to nearshore (laminated sandstone and some siltstone) Quebec and New York State. Reference outcrops are cited; bibliography is comprehensive.