Coiling Ratios of Neogloboquadrina Pachyderma (Ehrenberg): Variations in Different Size Fractions

Research Article| September 01, 1974 Coiling Ratios of Neogloboquadrina Pachyderma (Ehrenberg): Variations in Different Size Fractions PAUL VELLA PAUL VELLA 1Department of Geology, Victoria University of Wellington, Private Bag, Wellington, New Zealand Search for other works by this author on: GSW Google Scholar Author and Article Information PAUL VELLA 1Department of Geology, Victoria University of Wellington, Private Bag, Wellington, New Zealand Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1974) 85 (9): 1421–1424. https://doi.org/10.1130/0016-7606(1974)85<1421:CRONPE>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation PAUL VELLA; Coiling Ratios of Neogloboquadrina Pachyderma (Ehrenberg): Variations in Different Size Fractions. GSA Bulletin 1974;; 85 (9): 1421–1424. doi: https://doi.org/10.1130/0016-7606(1974)85<1421:CRONPE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract In surface sediments of the subantarctic and cooler subtropical areas of the southeastern Indian Ocean, coiling ratios of Neogloboquadrina pachyderma are more dextral in coarser size fractions than in finer size fractions. A sample from near lat 45°S. contained 14 percent (95 percent confidence limits 8 to 22 percent) dextral tests in the 0.124 to 0.175-mm fraction, and 67 percent (57 to 76 percent) in the size fraction >0.175 mm. The difference decreases toward the north where dextral coiling eventually becomes dominant in all size fractions, and toward the south where sinistral coiling becomes dominant in all size fractions. This phenomenon is thought to be due to the existence of at least two races or taxa in the range of forms usually classed as N. pachyderma. To these, the names N. pachyderma pachyderma (Ehrenberg) and N. pachyderma incompta (Cifelli) are applied provisionally.Whether the taxonomic interpretation is correct or not, the empirically determined differences in coiling ratios of the different size fractions provide a previously unsuspected latitude-dependent variable in planktonic foraminiferal faunas. When applied to the analysis of fossil samples, they enhance the value of coiling ratios as paleotemperature indices and can be used to detect north-south movements of ocean surface hydrologic features. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.