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

• Main Authors: Malmgren, Bjorn, Kennett, James P
• Format: Dataset
• Language: English
• Published: PANGAEA 1982
• Subjects: DEPTH, sediment/rock; AGE; Depth, top/min; Depth, bottom/max; Age, minimum/young; Age, maximum/old; Species; Chamber number; Angle; -; Roundness; Drilling/drill rig; Leg29; Glomar Challenger; Deep Sea Drilling Project DSDP; Planktonic foraminifera
• Online Access: https://dx.doi.org/10.1594/pangaea.684616; https://doi.pangaea.de/10.1594/PANGAEA.684616

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 ... : 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 ...