Improved correlation of the late neogene planktonic foraminiferal datums in the equatorial to cool subtropical DSDP Sites, Southwest Pacific: application of the graphic correlation method

Abstract

Sequential order of planktonic foraminiferal datums has been established for the Late Neogene of five DSDP sites examined in the southwest Pacific. A critical analysis of the chronologic succession of planktonic foraminiferal datums reveals many of the datums to be time transgressive and thus not useful for correlation. Therefore, to evaluate the reliability of the datums for cross-latitudinal correlation, Shaw's graphic correlation method has been applied. The results show that the datums can be broadly grouped undeT two categories, namely : First ordeT datums and second order datums. Former category includes the datums which are synchronous or nearly synchronous over a wide latitudinal range. These are : Globigerinoides fisluloius LAD, Dentoglobigerina ultispira LAD, Globigerinoides fistulosus FAD, Sphaeroidinellopsis LAD, Globorotalia repenthas margarilae LAD, Globorotalia inflata FAD, Globorotalia spkericomiozea FAD, Cloboratalia pliozea FAD and Globorotalia conomioxeaYAD, The second order datiuns include those which arediachronous over a wide latitudinal range. These are : Globorotalia tosaensis LAD, Globigerinoides obliquus LAD, Glebigeritttt repenthes LAD, Globorotalia crassajormis FAD, Sphaeroidinella dehiscens FAD, Globorotalia tumida tumida FAD, Pullenialina primalis FAD, Globorotalia repenthas, LAD, and Globorotalia punciiculata FAD. The first order datums are reliable for cross latitudinal correlation whereas the second order datums because of their diachroneity are not useful for correlation over wide latitudinal exlent.