Globorotalia truncatulinoides as a Paleo-oceanographic Index

Abstract

In Recent surface sediments of the ocean floor Globorotalia truncatulinoides (d'Orbigny) grades from highly conical forms in tropical areas to rather compressed forms in cold-water areas. An interdependence exists between temperature of the surface water and form ratios as defined by mean ratio of width to height and mean ratio of width to the height from keel to ventral extremity. Values of these ratios serve to identify various water masses and thus constitute a potentially useful method in determining paleo-temperatures in Quaternary marine sediments. Subpolar populations, as end members of the cline, are found only in the Southern Hemisphere.