Open AccessMiocene climate change recorded in the chemical and isotopic (Pb, Nd, Hf) signature of Southern Ocean sediments
Author(s) -
Vlastélic Ivan,
Carpentier Marion,
Lewin Éric
Publication year - 2005
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2004gc000819
Subject(s) - geology , antarctic ice sheet , weathering , carbonate , oceanography , circumpolar deep water , isotopic signature , trace element , paleontology , stable isotope ratio , geochemistry , north atlantic deep water , sea ice , thermohaline circulation , cryosphere , chemistry , physics , quantum mechanics , organic chemistry
The Middle Miocene transition from carbonate to biosilica sedimentation at DSDP site 266 (Australian‐Antarctic basin) reflects a global transition toward a colder climate. The 143 Nd/ 144 Nd, 176 Hf/ 177 Hf, and Al/Ti of bulk sediments display systematic, coupled variations through time, which have been attributed to a change of the detrital source. This change could correspond to a reduction of input from the Antarctic continent, an increase of input from the Kerguelen volcanic province, or both. Mixing models based on Nd isotopes and Al/Ti suggest a 30–40% reduction of Antarctic input and an equivalent increase of Kerguelen input during the Miocene. Reduction of Antarctic input may result from the formation of a stable East Antarctic ice sheet. Consistently, Pb isotopes and trace element systematics suggest a change of weathering style during the Miocene, with an increase in physical weathering, or a reduction of chemical weathering, after 15 Ma. Increase of Kerguelen input may reflect the initiation, or enhancement, of the Antarctic Circumpolar Current (ACC), thus raising the possibility of a simultaneous onset of North Atlantic Deep Water production and the ACC during the Middle Miocene. In addition, large geochemical oscillations occurred during the Pliocene, possibly reflecting fluctuation in strength of the ACC or, alternatively, periods of instability of the Antarctic ice sheet.