The early Pliocene diatom biochronology in the Southern Ocean: evidence from Sites U1359 and U1361 off Wilkes Land margin, Antarctica

Excellent stratigraphic control is key to understanding the timing of paeoceanographic events through critical climate intervals such as warm Pliocene (cf. Bart and Iwai, 2012). We have applied the diatom age model of the Cody et al. (2008) during the Integrated Ocean Drilling Program Expedition 318 off Wilkes Land margin, Antarctica. However, systematic offset of diatom events and geomagnetic polarity in uppermost Miocene to lowermost Pliocene section have been observed at Site U1359 and U1361 (Escutia et al., 2011), similar to what it was recorded at Site 1095 along the pacific coast of Antarctic Peninsula (Iwai et al., 2002). Stratigraphic sequence is consistent between site to site, and the magnetostratigraphic correlation of U1359A in the interval of Chron C3r appears to be more robust than any of the other Antarctic sites cited for this interval (Tauxe et al., 2012). Therefore, the origin of the offset between biostratigraphic datum and magnetostratigraphic chron is most likely to result from the previous mismatched calibration. The direct calibration of biostratigraphy datum to high quality continuous magnetostratigraphic records at Site U1359 and U1361 will provide a reference section for Pliocene Southern Ocean biochronology.