Morphometric redefinition of the component chronospecies of the Globorotalia conoidea - G. inflata lineage in DSDP Hole 29-284


Phylo-zonations (or lineage-zonations) are based upon morphological changes within individual evolutionary lineages. These zonations, although potentially of use for stratigraphic subdivision and correlation, often suffer from a lack of quantitative exactness in the definitions of chronospecies. Thus exact reproducibility is hindered for stratigraphic determinations.The potential of morphometrically defined phylo-zonations is demonstrated on a temperate South Pacific Late Cenozoic lineage of planktonic foraminifera (Globorotalia conoidea through intermediate forms to Globorotalia inflata in DSDP Site 284) exhibiting phyletic gradualism. Our sampling interval is about 0.1 m.y. during the last 8 m.y. Changes in the number of chambers in the final whorl, test conicalness, percentage of keeled forms, and test roundness or inflatedness, are used to quantitatively define the following five chronospecies: G. conoidea (Late Miocene; 6.1->8.3 m.y.), G. conomiozea (latest Miocene ; 5.3-6.1 m.y.), G. puncticulata sphericomiozea (earliest Pliocene; 4.5-5.3 m.y.), G. puncticulata puncticulata (Early-Middle Pliocene; 2.9-4.5 m.y.), and G. inflata (Late Pliocene-Quaternary; 0-2.9 m.y.). This phylo-zonation is directly applicable to temperate cool subtropical Southern Hemisphere areas where the evolution took place (Kennett, 1967, 1973; Scott, 1979). It is still not known if the lineage occurs elsewhere; thus the applicability of the phylo-zonation over broader areas is still uncertain. Trends in general size and aperture shape seem to be climatically controlled, and thus may be only of local stratigraphic utility.The practical applications of morphometric phylo-zonation for stratigraphy is to a large extent dependent upon the amount of time and effort required to statistically define the trends. Experiments with large numbers of subsamples from this lineage demonstrate that accurate stratigraphic determinations are possible from measurements on only 15 specimens per sample, except for those very close to chronospecies boundaries.

Ages were interpolated from dated New Zealand sections (Loutit and Kennett, 1979), assuming constant sedimentation rates between age estimates: Miocene-Pliocene boundary, 5.3 m.y., Tongaporutuan-Kapitean boundary, 6.1 m.y., and the base of the sequence, 8.3 m.y

Supplement to: Malmgren, Bjorn; Kennett, James P (1982): The potential of morphometrically based phylo-zonation: application of a Late Cenozoic planktonic foraminiferal lineage. Marine Micropaleontology, 7(4), 285-296

Related Identifier
Metadata Access
Creator Malmgren, Bjorn; Kennett, James P
Publisher PANGAEA
Publication Year 1982
Rights Creative Commons Attribution 3.0 Unported;
OpenAccess true
Resource Type Supplementary Dataset; Dataset
Format text/tab-separated-values
Size 50 data points
Discipline Earth System Research
Spatial Coverage (167.680 LON, -40.508 LAT); Antarctic Ocean/Tasman Sea/PLATEAU