The contribution of calcareous green algae to the production of limestones: a review

Geodiversitas

Bruno Granier¹ 

关键词: Dasycladales;    Bryopsidales;    Halimeda;    bioherm;    euphotic zone;    phylloid;    aragonite;    calcite;    porosity;    epigenesis;    cementation;    Dasycladales;    Bryopsidales;    Halimeda;    bioherme;    zone euphotique;    phylloïde;    aragonite;    calcite;    porosité;    épigenèse;    cimentation;   

DOI  :  10.5252/g2012n1a3

学科分类：生物科学（综合）

来源: Museum National d Histoire Naturelle

【 摘 要 】

Calcareousgreenalgae(CGA)areanartificiallyunitedbuthighlyheterogeneousgroupoflargeunicellularbenthicalgaewithonecharacterincommon:allhavethecapabilityofsecretingacalcareouscoatingontheoutersideofthecytoplasmicenvelope.Today,theyareamajorcontributortocarbonatesedimentationatallscalesfromclay-sizedparticles(aragoniticneedles)tocoarsergrains(sandandgravel)andeventoplurimetricsedimentarystructures.Therearefossilanaloguestothefeatureslistedabove.PhycologistsknowbestHalimeda,Penicillus,AcetabulariaandCymopolia;micropaleontologistsandcarbonatesedimentologistsaremostknowledgeableaboutAcicularia,Clypeina,Neoteutloporella,Salpingoporella,Anthracoporella,Boueina,andEugonophyllum.TheCaCO3precipitatedtoformthecoatingisgenerallyaragonite(theorthorhombicform)butthereareshortperiodsinthegeologicrecordduringwhichitscalcitevariant(therhombohedricform)existedcontemporaneouslyindiscretespecies.RecentstudiesonHalimedahaveshownthatsomeoftheBryopsidaleshavethecapabilitytocalcifystronglyinthelowerportionoftheeuphoticzone(whererespirationbecomesmoreimportantthanphotosynthesisintheprocessofmineralization)andtoproducepositivesedimentaryreliefs(bioherms)insitubelowthefair-weatherwavebase.PreviousmodelsofpaleoenvironmentsconsideredthepresenceofDasycladalesorBryopsidalestoindicateshallow-water,thatistheuppereuphoticzone(fromtheseasurfacedownto-25m),andpredominantlylow-energy,protected,lagoonalenvironments.Whenthealgalremainswerefoundingrain-supportedfacies,theyweretakentohavebeensubjectedtodynamictransportandthereforeindicativeofhigh-energyenvironmentsofdeposition.Thenewdeeper-waterfindshavechangedinterpretationsoftheenvironmentsascribedfossilalgae.AcurrentconceptionisthatancestralinarticulatedBryopsidalescouldhavegrownatdepthsasgreatas-120m(nearthebaseofthelowereuphoticzone).Thispreliminaryreviewconcludeswithsuggestionsaboutfieldsforcontinuinginvestigations.

【 授权许可】

Unknown