Ramil C. Wright

Alaskan Upper Miocene Marine Glacial Deposits and the Turborotalia pachyderma Datum Plane.

ln southeastern Alaska the first marine evidence of widespread glaciation occurs in Miocene sections near the base of the Yakataga Formation. An associated temperature decrease of about 10�C is indicated by the influx of an upper Miocene cold-water planktontic foraminifer, Turborotalia pachyderma, an event that occurred about 13 million years ago.

Late Neogene and Recent Bathyal Foraminifera of Mediterranean: ABSTRACT

Multivariate statistical analyses of recent deep-water benthic foraminifera of the Mediterranean reveal a bathymetric and geographic distribution that can be ascribed to water-mass distribution and bottom topography. Three bathyal zones were detected: upper (500 to 1,300 m), intermediate (1,300 to 2,800 m), and lower (> 2,800 m). The eastern Mediterranean (Ionian and Levantine Basins) displays significantly fewer species, fewer individuals, and shows lower species equitability than does the western Mediterranean. The Holocene foraminiferal distribution patterns provide a framework against which late Miocene and Pliocene foraminiferal dynamics were evaluated. The late Miocene (Messinian) salinity crises eliminated bathyal faunas from the Mediterranean. Pliocene foraminifera which repopulated the Mediterranean (1) are remarkably similar to pre-Messinian faunas of the middle upper Miocene Mediterranean sediments; (2) appear in the sedimentary record very soon after initiation of Pliocene sedimentation and attain population stability within 0.5 million years; (3) were derived predominantly from the Atlantic Ocean; and (4) migrated across the Mediterranean from the west to east. Population differences between the eastern and western Mediterranean faunas suggest the presence of Pliocene sills, especially in the Sicilian area. The geographic differences between Pliocene population structures were less significant than they are today. This phenom non can be explained by Pleistocene tectonism which further restricted water circulation. End_of_Article - Last_Page 1009------------

Revision of Tampa Formation, West-Central Florida: ABSTRACT

The Tampa Formation of west-central Florida historically has been defined primarily from biostratigraphic and geochronologic criteria. Formation definitions based on these criteria are not in accordance with the American Code of Stratigraphic Nomenclature. Furthermore, a type section of the Tampa has never been established. Currently, the Tampa Formation is recognized by ill-defined and conflicting criteria with boundaries that are vague. At the originally described localities on Tampa Bay, there is an interval of rocks that is mappable, has recognizable boundaries, and is capable of being defined in accordance with the code. It is proposed that this unit be designated the Tampa Formation. The unit is generally a quartz sandy limestone, having at least 10% quartz sand and less than 1% phosphate. The boundary with the units above the Tampa is defined by phosphate-bearing (5 to 50%) dolomites, clays, and quartz sands. The lower boundary is marked by a relatively pure carbonate unit containing only trace phosphates or quartz sands. The Tampa has been indirectly correlated with the Oligocene Chickasawhay Stage of the Gulf Coast. A type section for the Tampa is established in the Ballast Point core held by the Florida Bureau of Geology. The core was taken at Tampa Bay, Florida. End_of_Article - Last_Page 1605------------

Subsurface Neogene Stratigraphy of Bay County, Florida: ABSTRACT

The Neogene of Bay County, Florida, contains three subsurface units, the Bruce Creek, St. Joe, and Intracoastal Formations which make up the Coastal Group and range in age from middle Miocene to Pliocene. They are overlain by a blanket of Pliocene-Pleistocene sands. The Bruce Creek Formation is the oldest of the three units (middle Miocene) and rests upon the Suwannee Limestone which is generally considered Oligocene in age. The Bruce Creek, St. Joe, and Intracoastal units thicken southward down the paleoslope and pinch out toward the north. The Coastal Group extends laterally across Bay County and into neighboring counties to the east and west. Their full lateral extent is not known. The St. Joe and Bruce Creek are fairly fossiliferous micrites which contain some quartz sand. The Intracoastal changes from a micrite in the west to a sandy clay in the east. The Intracoastal contains a large percentage of planktonic and benthic Foraminifera. Biostratigraphic analysis of the Neogene of Bay County based on planktonic Foraminifera shows the Intracoastal Limestone to be Pliocene in the western part of the county (Globorotalia margaritae Zone) whereas it is significantly older in the east (G. fohsi fohsi Zone). The Bay County planktonic Foraminifera assemblages are somewhat unusual in that the presence of biostratigraphically useful planktonic Foraminifera assemblages in the nearshore Neogene sediments of the Gulf Coast is rare. The zonation schemes of Blow and Bolli which were developed in tropical sediments can be used only with difficulty in the temperate water sediments of the Florida Panhandle. End_of_Article - Last_Page 1599------------

Identification of Catapsydrax stainforthi Zone in Upper Part of Lower Saucesian Stage, California: ABSTRACT

Samples from the upper part of the lower Saucesian Stage represented in Reliz Canyon, California, reveal populations of Catapsydrax stainforthi Bolli, Loeblich, and Tappan together with specimens of Turborotalia opima nana (Bolli) and Globorotalia scitula praescitula Blow. The concurrence of these planktonic foraminiferal indices suggests a correlation of the upper part of the lower Saucesian of Reliz Canyon with the Catapsydrax stainforthi Zone of tropical areas and with the fossil fauna exposed on Erben Guyot, Pacific Ocean. Associated planktonic species include Globigerina angustiumbilicata Bolli, Globigerina woodi woodi Jenkins, Globigerina praebulloides Blow, Turborotalia mayeri (Cushman and Ellisor), and Turborotalia opima continuosa (Blow). Critical benthonic speci s include Planulina appressa Kleinpell and Rectuvigerina kleinpelli (Cushman). Equation of the Catapsydrax stainforthi Zone with the upper part of the lower Saucesian indicates that the underlying Catapsydrax dissimilis Zone of the tropics probably is equivalent in large part to the lowermost Saucesian; the superjacent Globigerinatella insueta Zone of the tropics is equivalent to the upper Saucesian and perhaps to the lowermost part of the Relizian Stage of California. End_of_Article - Last_Page 705------------

Function of Test in Foraminifera: ABSTRACT

Although the tests of foraminifers are used extensively by paleontologists as paleoecologic indicators, very little is known of the ecology of modern foraminifers, and virtually nothing is known of the function of the test. Investigation of test-protoplasm relations have been hampered by lack of suitable techniques for making meaningful observations. Now the scanning electron microscope provides a means of examination of the test on a scale which permits understanding of spatial relations of the test and the living organism. Coupled with experiments and observations on specimens in laboratory culture, the information yielded by studies of test structure and of fixed, frozen and dried protoplasm suggests a general theory of test function. 1. The most primitive tests are constructed of arenaceous material to provide weight to counteract bouyancy of the protoplasm. The simplest arenaceous tests seem to serve only this function. 2. The test upon elaboration into a long tube or series of chambers separated by narrow openings, serves as an effective barrier to retard the effects of unfavorable changes in environmental chemistry. 3. Further specialization may adapt the test for growth under special physical conditions, such as a certain substrate, or for particular symbiotic conditions, such as the greenhouse function of the test of Elphidium. The role of the test as a protective device against predation is not understood, but may account for some specialized forms. The great variety of test form in the foraminifers suggests that many taxa are particularly well adapted for specialized ecologic niches. The fact that the foraminifers are among the hardiest of marine protozoa and almost unique in their ability to withstand changes in the environment indicates that they have developed a highly efficient means of controlling their immediate environment without encystment or metamorphosis; that means is the test. End_of_Article - Last_Page 2040------------