georefid:2011-038853SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-07-06T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1130/G31726.1<gco:CharacterString>Two-stepping into the icehouse; east Antarctic weathering during progressive ice-sheet expansion at the Eocene-Oligocene transition</gco:CharacterString>2011-01-01publicationgeorefid:2011-038853doi:10.1130/G31726.1Scher, Howie D.University of California, Santa Cruz, Ocean Sciences Department, Santa Cruz, CA, United StatesauthorBohaty, Steven M.authorZachos, James C.authorDelaney, Margaret L.authorGeological Society of America (GSA), Boulder, CO, United StatespublisherdocumentHardcopyGeology (Boulder)39 (4)383-386In conjunction with increasing benthic foraminiferal delta (super 18) O values at the Eocene-Oligocene transition (EOT; ca. 34 Ma), coarse-grained ice-rafted debris (IRD; >425 mu m) appears abruptly alongside fossil fish teeth with continentally derived neodymium (Nd) isotope ratios (epsilon (sub Nd) ) in Kerguelen Plateau (Southern Ocean) sediments. Increased Antarctic weathering flux, as inferred from two steps to less radiogenic epsilon (sub Nd) values, coincides with two steps in benthic foraminiferal delta (super 18) O values. These results indicate that two distinct surges of weathering were generated by East Antarctic ice growth during the EOT. Weathering by ice sheets during a precursor glaciation at 33.9 Ma did not produce significant IRD accumulation during the first epsilon (sub Nd) shift. Glacial weathering was sustained during a terrace interval between the two steps, probably by small high-elevation ice sheets. A large increase in weathering signals the rapid coalescence of small ice sheets into an ice sheet of continental proportions ca. 33.7 Ma. Rapid ice sheet expansion resulted in a suppression of weathering due to less exposed area and colder conditions. Parallel changes in Antarctic weathering flux and deep-sea carbonate accumulation suggest that ice-sheet expansion during the EOT had a direct impact on the global carbon cycle; possible mechanisms include associated changes in silicate weathering on the East Antarctic craton and enhanced fertilization of Southern Ocean waters, both of which warrant further investigation.completedStratigraphyAntarcticabenthic taxabiochemistrybiostratigraphycarboncarbon cycleCenozoicclimate changecouplingdebrisEast AntarcticaEoceneForaminiferageochemical cycleglacial extentglacial geologyice movementice raftingice sheetsicehouse effectInvertebrataisotope ratiosisotopesKerguelen PlateauLeg 119lower Oligocenemarine sedimentsmicrofossilsmodelsO-18/O-16Ocean Drilling ProgramODP Site 738OligoceneoxygenpaleoclimatologyPaleogeneProtistasedimentsSouthern Oceanstable isotopesteethTertiarytransition zonesupper Eoceneweatheringurn:org.iodp:exp:119urnlargerWorkCitationcampaignurn:org.iodp:exp:119:site:738urnlargerWorkCitationstudyurn:org.iodp:exp:119urnlargerWorkCitationcampaignEnglishgeoscientificInformation82.471482.4715-62.4233-62.4232With GSA Data Repository Item 2011123