Isotopic evidence for the depth stratification of fossil and recent globigerinina: A review

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Abstract
Stable isotopic evidence for the depth stratification of the planktonic foraminifera is collected and reviewed. The aim is to establish the validity of the hypothesis that keeled (Globorotaliid‐like) forms have consistently lived deep in the water column relative to unkeeled (Globigerinid‐like) forms during the history of the Globigerinina. General trends in the distribution of δ18O and δ 13C across morphotypic spectra are clear, and suggest that keeled globorotaliids were the deep‐dwelling foraminiferal component of planktonic foraminiferal faunas only in the Pleistocene and Holocene. Earlier in the Neogene the deep water dweller was the globoquadrinid form Globoquadrina venezuelana while during the Oligocene the deep water forms were members of the genus Catapsydrax. In the earlier Palaeogene, members of the globorotaliid‐like genera Morozovella and Acarinina were surface dwelling forms while the deep water. dwellers were members of the genus Subbptina. The data available for the mid‐Cretaceous suggest a surface water dwelling habit for the globigerinid‐like genus Hedbergella while representatives of the keeled genus Rotalipora apparently lived deeper in the water cojumn.