SYSTEM OF MEASUREMENT UNITS The investigations underlying this series of reports were made over a period of years, and distances and Stratigraphic measurements appear fairly uniformly in English units. Measurements of fossil specimens, on the other hand, follow the longstanding convention of appearing in metric units. Because of the dates of the investigations and the amount of resulting data, the English measurements have been retained. Con versions to metric units may be made by using the following conversion table: To convert English unit: To metric unit: Multiple by: Mile (mi) Kilometer (km) 1.61 Foot (ft) Meter (m) .305 Inch (in.
The Middle through lower Upper Ordovician Lexington Limestone and lower part of the Clays Ferry Formation contain an abundant and diversified ostracode fauna. More than 10,000 specimens belonging to 39 genera and 53 species have been found in 73 collections made by members of the U.
Silurian and Early Devonian ostracode associations in North America represent at least three ecotypes, a leperditicopid association, a large beyrichiacean association, a mixed association, and possibly a fourth, spinose podocopid association, or Thuringian ecotype. Comparison of the large beyrichiacean association and mixed association ecotypes indicates the presence of three informal ostracode provinces, the Appohimchi, Baltic-British and Cordilleran, which remained relatively constant in geographical position throughout the Silurian and Early Devonian. Plotting the provinces on palaeogeographic maps suggests that temperature was not an important factor in delimiting the provinces, and land barriers, or possibly deep-water troughs as barriers, were the cause of provincial development. Benthic ostracodes differed from other benthic invertebrates such as brachiopods and corals in developing provincialism in the late Llandovery and having it start to decline in the Pragian through the Emsian.
The subsurface sedimentary Paleozoic rocks beneath northern Florida and adjacent parts of Georgia and Alabama comprise a .sequence of quarlzitic sandstones and micaceous shales, dark-gray shales, and red and gray siltstones ranging in age from Early Ordovician to Middle Devonian. The Silurian-Devonian pelecypod faunas from four wells (three of which, the Ragland, Cone, and Tillis wells, are in Florida, and one of which, the Chandler, is in Georgia) are described and illustrated. Also described are Silurian pelecypods from one locality in Bolivia and one in Turkey. Biostratigraphically, the faunas from the American wells range in age from Wenlockian or Ludlovian (Silurian) to Middle Devonian; the Bolivian specimens are probably Ludlovian (Late Silurian); and the Turkish specimens are probably Wenlockian or Ludlovian (Silurian). Paleoecologically, the strata in the American wel1s represent shallowwater normal marine environments, and all pelecypods known from them belong to one of three life-habit groups-'byssally attached, burrowing, or reclining. The Bol,ivian and Turkish pelecypods likewise belong only to these three life-habit groups. Analysis of the geograpMc distribution of the Florida Paleozoic pelecypod genera shows that they are closest to the forms found in central Bohemia and Poland; elements of this fauna also occur in Nova Scotia, North Mrica, and South America.
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