Open AccessSediment focusing in the central equatorial Pacific Ocean
Author(s) -
Marcantonio Franco,
Anderson Robert F.,
Higgins Sean,
Stute Martin,
Schlosser Peter,
Kubik Peter
Publication year - 2001
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2000pa000540
Subject(s) - geology , equator , oceanography , last glacial maximum , sediment , seawater , glacial period , sea level , extraterrestrial life , latitude , holocene , paleontology , physics , geodesy , astrobiology
At four sites in the central equatorial Pacific Ocean the flux of extraterrestrial ³He, determined using the excess 230 Th profiling method, is 8 × 10 −13 cm³ STP cm −2 ka −1 . This supply rate is constant to within 30%. At these same sites, however, the burial rate of ³He, determined using chronostratigraphic accumulation rates, varies by more than a factor of 3. The lowest burial rates, which occur north of the equator at 1°N, 139°W are lower than the global average rate of supply of extraterrestrial ³He by 20% and indicate that sediment winnowing may have occurred. The highest burial rates, which are recorded at the equator and at 2°S, are higher than the rate of supply of extraterrestrial ³He by 100%, and these provide evidence for sediment focusing. By analyzing several proxies measured in core PC72 sediments spanning the past 450 kyr we demonstrate that periods of maximum burial rates of 230 Th, ³He, 10 Be, Ti, and barite, with a maximum peak‐to‐trough amplitude of a factor of 6, take place systematically during glacial time. However, the ratio of any one proxy to another is constant to within 30% over the entire length of the records. Given that each proxy represents a different source ( 234 U decay in seawater, interplanetary dust, upper atmosphere, continental dust, or upper ocean), our preferred interpretation for the covariation is that the climate‐related changes in burial rates are driven by changes in sediment focusing.