Palaeoenvironmental and stratigraphic significance of Pliocene rhodolith beds and coralline algal bioconstructions from the Carboneras Basin (SE Spain)

Geodiversitas

Julio Aguirre¹  Christian Betzler¹  Juan C. Braga¹  Jose M. Martín¹ 

关键词: Rhodolith beds;    coralline bioconstructions;    Pliocene;    coralligène;    Carboneras Basin;    SE Spain;    Couches à rhodolithes;    constructions à algues corallines;    Pliocène;    coralligène;    bassin de Carboneras;    Espagne;   

DOI  :  10.5252/g2012n1a7

学科分类：生物科学（综合）

来源: Museum National d Histoire Naturelle

【 摘 要 】

ThickrhodolithbedsoccurinthetransgressiveandhighstandsystemstractsoftheearlyPliocenesequenceintheCarbonerasBasininSESpain.Rhodolithbedsaccumulatedinmid-to-outerrampsettingsandintheleesideofaspitplatformduringthetransgressiveinterval,whereasrhodolithconcentrationsinthehighstanddepositsonlyformedinthemid-to-outerrampatthesouthernmarginofthebasin.Theelevationofrhodolithbedscomparedwithcoevalshoredepositssuggeststhatthebedsdevelopedatwaterdepthsofseveraltensofmetres(probablylessthan50m).Thispalaeodepthestimateisconsistentwiththecompositionofalgalassemblages,whicharedominatedbymelobesioidscommoninrelativelydeepplatformenvironmentsinthemodernMediterraneanSea.LithothamnionminervaeBasso,1995,L.philippiiFoslie,1909,andMesophyllumalternans(Foslie)Mendozaamp;Cabioch,1998withsubordinatePhymatolithoncalcareum(Pallas)Adeyamp;McKibbin,1970andM.macroblastum(Foslie)Adey,1970andlithophylloidsoftheLithophyllumincrustansPhilippi,1837-L.racemus(Lamarck)Foslie,1901complexarethemostcommonofatotalof21recordedspecies.Alltheidentifiedalgalspeciesarealsolivinginthepresent-dayMediterraneanexceptfortheextinctLithothamnionramosissimum(Reuss)Piller,1994andfortherecentSpongitesdecipiens(Foslie)Chamberlain,1993,whichhasbeenreportedintheIndo-PacificandSouthAdantic,butnotintheMediterranean.Moderateenergyandlowsedimentationratespromoteddevelopmentofrhodolithbedsinthetransgressivedeposits,buttheyarenotexclusivetothetransgressivesystemstractastheycontinuedtoaccumulateatthesouthernmarginduringthehighstand,beyondtheinfluxofsiliciclasticsthatreducedcarbonateproductionintherestofthebasin.Isolatedpillars(upto90cmhigh)orirregularpatches(upto2mhighand7mwide)ofcorallinealgal-bryozoan-bivalvebioconstructionsoccurinouterrampfine-grainedcalcarenites.Despitetheirsimilaritiestopillarsandlowreliefbuildupsconstructedbycorallinealgae(“coralligènedeplateau”)inthepresent-dayMediterraneanSea,thesebioconstructionsareuniqueasbryozoansarethemainbuildersandcorallinealgae(L.philippiiandM.lichenoides)playonlyasecondaryrole.IncontrastwithmodernMediterraneancorallinealgalbuildups,thelackofbioclasticdebrisderivedfromthebuild-upsinthesurroundingfine-grainedsedimentsandtheirgeneralmorphologysuggestthatthePliocenebioconstructionsintheCarbonerasBasindidnotcreatesignificantpositivereliefontheseafloor.

【 授权许可】

Unknown