NOAA/WDS Paleoclimatology - Diester-Haass 2004 Tasman Rise Neogene Paleoproductivity and Ice Rafting Data

Late Neogene sediments (11.3-1 Ma) at ODP Sites 1171 and1172 south of Tasmania are different in that (i) there is a hiatus at the more southerly Site 1171 covering the 5.23-8.7 Ma period, whereas Site 1172 shows a complete record during that interval, and (ii) coarse (up to 1000 um) sized clastic material and detrital glauconite occur at Site 1171, interpreted as ice rafted detritus from Antarctica, whereas at Site 1172 no glauconite has been found and clastic material is always smaller than 125 um, and is interpreted as eolian. Paleoproductivity as deduced from benthic foraminifers and carbonate dissolution was higher prior to 8.7 Ma than after the hiatus at Site 1171, related to the northward drift of the South Tasman Rise and increasing distance from the proto-polar front. Radiolarian opal concentrations anticorrelate with our paleoproductivity proxies. The depression in CaCO3 concentrations at 9.6-10 Ma and 10.6-11.2 Ma, and the strong dissolution, are tentatively regarded as an expression of the "carbonate crash event". The elevated productivity at Site 1171 at 5.23-4.5 Ma corresponds to a paleoproductivity maximum at Site 1172, where a sharp 3-5 fold productivity increase at 7-6.5 Ma points to the occurrence of the late Miocene "biogenic bloom event". Both these major late Miocene events, well known in the equatorial Indo-Pacific and SE Atlantic upwelling areas, have not be seen in the subantarctic before.