Pliocene and Pleistocene Diatom Datum levels from the Equatorial Pacific

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Abstract
Eight diatom and two silicoflagellate datum levels from the Pliocene and Pleistocene of the equatorial Pacific are ranked and related to the paleomagnetic reversal record, calcium carbonate fluctuations, and the oxygen isotope record. The datum levels and their position with respect to the paleomagnetic reversal record are as follows: (1) last occurrence ofThalassiosira convexamidway between the top of the Gauss and the base of the Olduvai; (2) transition fromRhizosolenia praebergoniitoRhizosolenia praebergoniivar. A just below the base of the Olduvai; (3) first appearance ofPseudoeunotia doliolusin the lower part of the Olduvai; (4) last occurrence ofRhizosolenia praebergoniijust above the Olduvai; (5) first appearance ofAsteromphalus hiltonianusmidway between the top of the Olduvai and the base of the Jaramillo; (6) first appearance ofMesocena ellipticajust below the base of the Jaramillo; (7) last occurrence ofMesocena ellipticamidway between the top of the Olduvai and the base of the Brunhes; (8) upward increase in abundance ofThalassiosira oestrupiijust below the base of the Olduvai; (9) last occurrence ofNitzschia reinholdiijust above the base of the Olduvai; (10) peak occurrence ofRoperia tesselatavar.ovatajust above Datum Level 9. By second-order correlation it is possible to relate these datum levels to the oxygen isotope record. Such a correlation suggests that some datum levels may be climate related.