Deep sea benthic foraminifera as proxies for palaeoclimatic fluctuations in the New Caledonia Basin, over the last 140,000years

Abstract

abstract Article history:Received 17 September 2012Received in revised form 19 June 2013Accepted 28 August 2013Available online 4 September 2013Keywords:New Caledonia BasinTasman SeaQuaternarySouthwest PacificOceanforaminiferapalaeoenvironment The New Caledonia Basin (NCB), SW Pacific, a deep bathyal to abyssal basin bordered by the Lord Howe Rise tothe west and the Norfolk Ridge to the east, has received little scrutiny with regard to the taxonomic diversityofbenthicorganismsinitsQuaternarytoRecentdeepseasediments.In2001,GravityCore4(GC4)wasextractedfrom the NCB and the uppermost 141 cm, representing approximately the last 140,000 years, was investigatedfor chemical isotopic, carbonate, non-carbonate and trace element signatures. In this study, subsamples of thesame uppermost 141 cm of GC4 were picked and sorted for all foraminiferal taxa. At selected intervals in GC4,allbenthicspecieswereidentifiedandcountedformeasuresofrelativeabundance.Atotalof161speciesofben-thic foraminifera were obtained from the core and 46 species occurred in sufficient numbers to investigatechangingpatternsandtrendsinbiodiversityandrelativeabundance.Changesfoundwithintheforaminiferaldis-tribution down the core can be related to some oceanic and palaeoclimatic fluctuations during the last~140,000 years. Within GC4, two distinct foraminiferal assemblages were detected using Bray–Curtis clusteranalysis and Multidimensional Scaling (MDS) analysis. Foraminiferal Assemblage 1 occurs in lower bathyal toabyssal depths and was largely influenced by high oxygen levels at the sediment–water interface throughoutMarine Isotopic Stage (MIS) 6–3 (approximately 128 –25 ka). Foraminiferal Assemblage 2 dominated theupper bathyal shelf during MIS 2 (approximately 25–10 ka), with surface waters characterised by high sea sur-faceproductivity(SSP)andeutrophicconditions.DuringthetimecoveredbyGC4,thereareinstanceswheretherelative abundanceofthe dominanttaxonEpistominella exigua(Brady)and other key taxadecreasesand oppor-tunistic species of Uvigerina, adapted to lower oxygen levels, increase in relative abundance, indicating a shift ofconditions at the sediment–water interface. Factors that influence the foraminiferal assemblages include envi-ronmentalsetting,SSP,oxygenlevelsatthesediment–waterinterfaceandtransportationbyoceaniccurrentsys-tems operating within the region.© 2013 Elsevier B.V. All rights reserved.