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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 49 (1965)

Issue: 10. (October)

First Page: 1760

Last Page: 1760

Title: Coiling Direction Ratios of Foraminifera Globigerina pachyderma (Ehrenberg) in Northeastern Pacific Surface Sediments: ABSTRACT

Author(s): Betty J. Enbysk

Article Type: Meeting abstract


Coiling direction ratios of Globigerina pachyderma (Ehrenberg) plotted for sediment surface samples from the northeastern Pacific north of 40°N. did not show the consistent relationship which would recommend them as reliable guides for deep-sea core analysis in this region. A generally increasing tendency for sinistral coiling toward the north was noted, from 13 per cent left reported by Parker (1962) from a nearshore sample (40°N.) to a consistent 95-100 per cent left in the northern Gulf of Alaska. Great irregularity in coiling ratios in seaward (east-west) traverses may be related to a nearshore area of warm-water intrusion (Fleming, 1958) affecting the type of plankton supplied to the substrate. Variations from 20-96 per cent left coiling were observed in th se traverses. Dextral coiling percentage usually was higher in samples containing many species and few individuals. The "recency" of the surface sample also affected the coiling ratios. The problem of distinguishing small Globoquadrina dutertrei (d'Orbigny)--predominantly right coiling--from Globigerina pachyderma (coiling in question) may qualify coiling ratios reported by various authors. Plankton tow samples off Oregon, Washington, and the Aleutian Islands had smaller percentages of G. pachyderma and higher dextral ratios than samples from the underlying sediment surface.

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