Subantarctic Pacific hiatuses as clues to periods of enhanced oceanic circulation during the late Neogene

New stable isotope records from cores MV0502-4JC (50°20’S, 148°08’W, 4286m), ELT 25-11 (50°02’S, 127°31’W, 3969m), and ELT 20-11 (49°00’S, 144°50’W, 4517 m) obtained in close proximity to the Subantarctic Front in the southeast Pacific show a consistent pattern of hiatuses that could be related to late Neogene changes in the strength of the Antarctic Circumpolar Current (ACC). These subantarctic Pacific records show three hiatuses that we have dated to 1) the early Pliocene-early late Pliocene, 2) ~1.57-0.68 Ma, and 3) ~0.53-0.19 Ma. These hiatuses correspond well with the timing of the Pliocene Warm Period and the climatic transitions of the Mid-Pleistocene Revolution and the Mid-Brunhes, as well as with periods of reduced or non-deposition on the Maurice Ewing Bank, also located in the path of the ACC (Ciesielski, 1982). Interestingly, sediment cores recovered from regions outside of the ACC that experience significant bottom water flow (e.g. fracture zones and the western margins of continents), including the Vema Channel (Ledbetter et al., 1978), the South Australia Basin (Ledbetter, 1981), and the continental margin of Northwest Africa (Stein et al., 1986), also show intervals of reduced or non-deposition that correlate well with the timing of hiatuses in the subantarctic Pacific. This correlation could indicate that the Pliocene Warm Period and the climatic transitions of the Mid-Pleistocene Revolution and Mid-Brunhes were characterized not only by a more vigourous ACC but also by a stronger and more globally-distributed overturning circulation than the present day.