Coiling direction in Globigerina bulloides of Middle Miocene age

Abstract

Abstract. Detailed analysis of the early evolutionary stage of Globigerina bulloides in Middle Miocene calcareous nannoplankton zones NN5 and NN6 shows no preference for sinistral or dextral coiling patterns despite seawater temperature variations (as inferred from stable isotope analyses of foraminifer shells). Accordingly, coiling direction was proportional or biased to sinistral.