JOURNAL OF PALEONTOLOGY V. 52, NO. 4, P. 916-920, 3 TEXT-FIGS., JULY 1978 ... A NEW LOWER ORDOVIC... more JOURNAL OF PALEONTOLOGY V. 52, NO. 4, P. 916-920, 3 TEXT-FIGS., JULY 1978 ... A NEW LOWER ORDOVICIAN (MIDDLE CANADIAN) DISPARID CRINOID FROM UTAH ... STUART M. KELLY AND WILLIAM I. AUSICH Indiana University, Bloomington 47401
Systematic revisions and revised stratigraphic occurrences are made toAorocrinus, Dorycrinus, Mac... more Systematic revisions and revised stratigraphic occurrences are made toAorocrinus, Dorycrinus, Macrocrinus, Paradichocrinus, Strotocrinus, andUperocrinusfrom the Osagean and Meramecian stratotype region in Iowa and Missouri. Systematic revisions include the assignment ofBatocrinus procerusMiller and Gurley as a junior synonym ofMacrocrinus mundulus. Batocrinus heteroclitusMiller and Gurley,B. vicinusMiller and Gurley, andB. stelliformisMiller and Gurley are assigned toUperocrinus heteroclitusn. comb. The concept ofAorocrinus spinosulus(Hall) did not match characteristics of the holotype. Consequently, the appropriate name for this concept isAorocrinus kelloggi(Worthen) n. comb., andA. spinosulusis assigned toDorycrinus mississippiensisas a junior synonym.Batocrinus strenuusis assigned toAorocrinus strenuusn. comb.?; andStrotocrinus glyptusis regarded as the valid name for the only species recognized in this genus.These systematic revisions result in the restriction ofStrotocrinus glyptusto the middle Osagean Burlington Limestone, and extension ofAorocrinus, Dorycrinus, Macrocrinus, andUperocrinusinto the Meramecian upper Warsaw Formation.
Distributional patterns of late Osagean (Mississippian) crinoids from the east-central United Sta... more Distributional patterns of late Osagean (Mississippian) crinoids from the east-central United States are examined using multivariate analysis of crinoid species diversity and species abundance data. We confirm previous hypotheses that three well-defined crinoid associations existed during the late Osagean. These associations were dominated, respectively, by 1) monobathrid camerates preserved in carbonate packstones; 2) poteriocrine inadunates in higher-energy siltstones and sandstones; and 3) disparid inadunates, cyathocrine inadunates, and flexibles in mudstones where neither monobathrids nor poteriocrines dominated. In conjunction with petrologic data on the enclosing sediments, the analyses suggest that these associations occurred along a spectrum of increasing current velocity at the seafloor. Camerates, poteriocrine inadunates, and flexibles are interpreted to display preferences for specific environmental conditions, whereas disparid and cyathocrine inadunates are inferred to be environmental generalists.The different environmental distributions of the major crinoid groups are interpreted to be a function of the mode or modes of aerosol filtration feeding used by each group. This inference is possible through functional morphologic and morphometric studies of crinoid arms, because the skeletal elements of the arms, which are commonly preserved, are directly involved in feeding.
ABSTRACT Diffusion studies of He in calcite suggest a potential to use carbonates as an alpha the... more ABSTRACT Diffusion studies of He in calcite suggest a potential to use carbonates as an alpha thermochronometer (Tc ~ 65°C). These results are all from coarse-grained calcite and dolomite but carbonate mud is a common constituent in many limestones. However, coarse calcite can usually be found in even the most micritic limestones in the form of biotic allochems. We have investigated the suitability of using crinoid columnals and shells of the bivalve Inoceramus for alpha thermochronolgy in limestones. After the death of a crinoid, the high-Mg calcite converts to low-Mg calcite with no loss of optical continuity, and the porosity is filled with syntaxial cement thus becoming permineralized. Bivalves undergo typical diagenesis where the high- Mg calcite converts to low-Mg calcite. Two of four crinoid samples yield reasonable alpha ages: A crinoid from the Thrifty Fm. (Pennsylvanian) in Texas gives an age of 120 Ma (0.7-4.0 ppm U) and one from the Edwardsville Fm. of the Borden Group (Lower Mississippian) in Indiana gives an age of 64 Ma (0.9 ppm U). Each of these results are consistent with the tectonic history of the regions. Crinoid pieces from the New Providence Shale Mbr. of the Borden Fm. (Lower Mississippian) in Kentucky have very low [U] (less than 90 ppb) and give Archean ages. Crinoids from the Hughes Creek Shale (Permian) in Kansas have seemingly robust amounts of U (0.7-2.1 ppm) but this sample also seems to be dominated by common He, yielding Proterozoic ages. Inoceramus from the Burditt Fm. of the Austin Gr. (Upper Cretaceous) in Texas gives an age of 0.5 Ma, suggesting that the closure temperature may be much lower than 65°C. Our preliminary conclusion is that crinoid columnals with more than 500 ppb U may be generally suitable for alpha thermochronology but that the closure temperature of He in Inoceramus shells may be too low for geologic application.
JOURNAL OF PALEONTOLOGY V. 52, NO. 4, P. 916-920, 3 TEXT-FIGS., JULY 1978 ... A NEW LOWER ORDOVIC... more JOURNAL OF PALEONTOLOGY V. 52, NO. 4, P. 916-920, 3 TEXT-FIGS., JULY 1978 ... A NEW LOWER ORDOVICIAN (MIDDLE CANADIAN) DISPARID CRINOID FROM UTAH ... STUART M. KELLY AND WILLIAM I. AUSICH Indiana University, Bloomington 47401
Systematic revisions and revised stratigraphic occurrences are made toAorocrinus, Dorycrinus, Mac... more Systematic revisions and revised stratigraphic occurrences are made toAorocrinus, Dorycrinus, Macrocrinus, Paradichocrinus, Strotocrinus, andUperocrinusfrom the Osagean and Meramecian stratotype region in Iowa and Missouri. Systematic revisions include the assignment ofBatocrinus procerusMiller and Gurley as a junior synonym ofMacrocrinus mundulus. Batocrinus heteroclitusMiller and Gurley,B. vicinusMiller and Gurley, andB. stelliformisMiller and Gurley are assigned toUperocrinus heteroclitusn. comb. The concept ofAorocrinus spinosulus(Hall) did not match characteristics of the holotype. Consequently, the appropriate name for this concept isAorocrinus kelloggi(Worthen) n. comb., andA. spinosulusis assigned toDorycrinus mississippiensisas a junior synonym.Batocrinus strenuusis assigned toAorocrinus strenuusn. comb.?; andStrotocrinus glyptusis regarded as the valid name for the only species recognized in this genus.These systematic revisions result in the restriction ofStrotocrinus glyptusto the middle Osagean Burlington Limestone, and extension ofAorocrinus, Dorycrinus, Macrocrinus, andUperocrinusinto the Meramecian upper Warsaw Formation.
Distributional patterns of late Osagean (Mississippian) crinoids from the east-central United Sta... more Distributional patterns of late Osagean (Mississippian) crinoids from the east-central United States are examined using multivariate analysis of crinoid species diversity and species abundance data. We confirm previous hypotheses that three well-defined crinoid associations existed during the late Osagean. These associations were dominated, respectively, by 1) monobathrid camerates preserved in carbonate packstones; 2) poteriocrine inadunates in higher-energy siltstones and sandstones; and 3) disparid inadunates, cyathocrine inadunates, and flexibles in mudstones where neither monobathrids nor poteriocrines dominated. In conjunction with petrologic data on the enclosing sediments, the analyses suggest that these associations occurred along a spectrum of increasing current velocity at the seafloor. Camerates, poteriocrine inadunates, and flexibles are interpreted to display preferences for specific environmental conditions, whereas disparid and cyathocrine inadunates are inferred to be environmental generalists.The different environmental distributions of the major crinoid groups are interpreted to be a function of the mode or modes of aerosol filtration feeding used by each group. This inference is possible through functional morphologic and morphometric studies of crinoid arms, because the skeletal elements of the arms, which are commonly preserved, are directly involved in feeding.
ABSTRACT Diffusion studies of He in calcite suggest a potential to use carbonates as an alpha the... more ABSTRACT Diffusion studies of He in calcite suggest a potential to use carbonates as an alpha thermochronometer (Tc ~ 65°C). These results are all from coarse-grained calcite and dolomite but carbonate mud is a common constituent in many limestones. However, coarse calcite can usually be found in even the most micritic limestones in the form of biotic allochems. We have investigated the suitability of using crinoid columnals and shells of the bivalve Inoceramus for alpha thermochronolgy in limestones. After the death of a crinoid, the high-Mg calcite converts to low-Mg calcite with no loss of optical continuity, and the porosity is filled with syntaxial cement thus becoming permineralized. Bivalves undergo typical diagenesis where the high- Mg calcite converts to low-Mg calcite. Two of four crinoid samples yield reasonable alpha ages: A crinoid from the Thrifty Fm. (Pennsylvanian) in Texas gives an age of 120 Ma (0.7-4.0 ppm U) and one from the Edwardsville Fm. of the Borden Group (Lower Mississippian) in Indiana gives an age of 64 Ma (0.9 ppm U). Each of these results are consistent with the tectonic history of the regions. Crinoid pieces from the New Providence Shale Mbr. of the Borden Fm. (Lower Mississippian) in Kentucky have very low [U] (less than 90 ppb) and give Archean ages. Crinoids from the Hughes Creek Shale (Permian) in Kansas have seemingly robust amounts of U (0.7-2.1 ppm) but this sample also seems to be dominated by common He, yielding Proterozoic ages. Inoceramus from the Burditt Fm. of the Austin Gr. (Upper Cretaceous) in Texas gives an age of 0.5 Ma, suggesting that the closure temperature may be much lower than 65°C. Our preliminary conclusion is that crinoid columnals with more than 500 ppb U may be generally suitable for alpha thermochronology but that the closure temperature of He in Inoceramus shells may be too low for geologic application.
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