Jean-Claude Gall AncientSedim.entary Environm.entsandthe Habitatsof LivingOrganism.s Introduction to Palaeoecology With130 Figures Springer-Verlag Berlin Heidelberg New York Tokyo1983 Professor JEAN-CLAUDEGALL,Universite Louis Pasteur,1,rue Blessig,F-67084 Strasbourg Translator Dr.PEIGIWALLACE,ImperialCollegeof ScienceandTech-nology,DepartmentofGeology,RoyalSchoolofMines, Prince Consort Road, GB-London SW7 2BP Translation of the French Edition: J.C.Gall,EnvironnementSedimentairesAnciensetMilieuxdeVie.Intro-duction a laPaleoecologie. Doin, Editeurs, 8,place de l'Odeon, F-75006 Paris (C) Doin, Paris1976 Coverpicture.Desiccationcracksandreptilefootprints(Cheirotherium)in relief onasandstonebeddingplane.Theanimalmusthavewalkedacross theslabafterthepuddlehaddriedupsincethefootprintscutacrossthe cracks.Fromaslabof BunterSandstonefromHildburghausen(Thuringia) in the collections of the Institute of Geology in Strasburg (x'14) Library of Congress Cataloging in Publication Data. Gall, Jean-Claude,1936-Ancient sedimentary environments and the habitats ofliving organisms. Translation of:Environnements sedimentaires anciens et milieux de vie. Includes bibliographies and index. I.Paleoecology. I. Title. QE720.G34131983554.4s [560'.45]82-19697 ISBN-13:978-3-642-68911-6 DOl:10.1007/978-3-642-68909-3 e-ISBN-13:978-3-642-68909-3 Thisworkissubjecttocopyright.Allrightsarereserved,whether thewhole or part of thematerial isconcerned, specifically- those of translation,reprint-ing,re-useof illustrations,broadcasting,reproductionbyphotocopyingma-chine or similar means, and storage in data banks. Under 54of theGermanCopyrightLawwherecopiesaremadeforother thanprivateuse,afeeispayabletothe"VerwertungsgesellschaftWort", Munich. by Springer-Verlag Berlin Heidelberg 1983 Softcover reprint of the hardcover1st edition1983 Theuseof registered names,trademarks, etc.in this publication doesnot im-ply,evenintheabsenceof aspecificstatement, that suchnames areexempt fromtherelevant protective lawsandregulationsandthereforefreeforgen-eral use. ProductLiability:The publisher can give no guarantee forinformation about drug dosageand application thereof contained inthis book.Inevery individual casetherespectiveusermustcheckitsaccuracybyconsultingotherpharma-ceuticalliterature. Reproduction of the figures:Gustav Dreher GmbH, D-Stuttgart 2132/3130-543210 Foreword Iampleasedtobeableto introduce this book by Monsieur lean-ClaudeGall,firstlybecauseitisabook,secondly becauseitsauthorhasbeenacolleaguefor15years,and finallybecauseitisa book which demonstrates the growing importance of Palaeobiology. "Becauseitisabook".Ihavealreadycommentedelse-whereonthevaluewhichtheEarthSciencecommunity placesonabook. AndhereIamspeaking, not of a thesis or aspecialisedmemoir,whicharealwaysprecious,butof a manualor text, which draws on the experts in the service of all.IntheyearsprecedingandfollowingtheSecondWorld War,thenumberof"books"writtenbyFrenchgeologists couldbecountedonthefingersof onehand.TodayIam happy to see that the number of geological "books" is increas-inginFrance,takingtheword"geology"initsbroadest sense.ThisI seeasa sign of the growth of the Earth Sciences. Without doubt there are many more geologists,but they have alsobecomemorespecialised.Universities,exceptwhen they specialise in studies which are of immediate application, orwhentheyareheldbackbyfinancialproblems,devote themselvestotheirtruework:theeducationof theyoung andthe pursuitof research.During this time, the geological surveyshaveexpanded,providingjobsforstudentsand appliedgeologists.Thisisa balanced profession,andspecia-listson both sidesmanage to findthe incentive andthe time to writebooks. "BecauseMonsieurJean-ClaudeGallismycolleague". IhaveheldtheChair of GeologyatStrasbourgforalmost 21years,andduringthattimeIhavelivedamongfirstan increasing,thenastabilising,groupof geologistswhoare active,inventiveand,a particular blessing, veryco-operative andhappy.Inthisenvironment,teachers,researchers, engi-neers andtechnicians have taught me a great deal about many things.Amongstthese,MonsieurJean-ClaudeGallisthe teacherinchargeof palaeobiology.It isnot that Strasbourg VIForeword hasaspecialvocationinthisfield,but thetheoreticaland practicalteaching,thecurationofcollectionsandalsothe positionof palaeobiologyinthesedimentologicalresearch of our Institute, requireateamknowledgeablein thisdisc-ciplineinourlargeestablishment.Iwouldliketothank MonsieurJean-ClaudeGallherefortheexcellenceof his teaching,forthequiethelpfulness of hisserviceandfor his rock-like loyalty. "Becausethis book demonstrates the growing importance of Palaeobiology".Thefortunesof mycareerhavemeant thatfor30yearsIhavebeeninvolvedinteachingpalaeo-biology,thoughmypersonalresearcheswereinvolvedin sedimentarygeochemistryanddiagenesis.ThismeansIcan befrank.There is a continuous feeling in the Earth Sciences whichthreatenstherespectduetopalaeobiology,or even itssimplesurvival.Thisisnotrational,andthose geologists who are not palaeobiologists must be aware of this. Palaeobiologyisthefoundationof thescienceof evolu-tion- theoriginaltheoryof evolutionisderivedfromit. Fromthere,ithaspermeatedalldisciplines,includingthe humanities. Through palaeobiology, wecan demonstrate the "rhythmsandscaleof evolution"throughtime.Thisisa major philosphicalandscientificquestion, which is based in the Earth Sciences. Palaeobiologyisoneof the main disciplines in which one canlearn the laws and lessons of biometry. Nostudy of syn-chronousbiometry,undertakenamongstcontemporaneous populations,canneglectdiachronousbiometry,whichhas affected evolutionary lineages throughout their development. Thisisof greatpresent-dayinterestwhenweconsiderthe dynamics of populations andof societies. Palaebiologyisthemostprecisetool whichmanhasfor themeasurementof time.At the present time, great efforts arebeingmadeinthefieldof absolutegeochronology,by meansofisotopedating.Theresultsarespectacularand allowus todatethe Precambrianrocks of Africa,lava from themoonandtheappearanceofmanineasternAfrica. Nevertheless,palaeobiologyisstillthemostaccuratetool wehavefor identifying relative geochronology. Ammonites, foraminifera,pollenandplankton,rodentsandthelarger vertebrates are all used to give relative ages not only in strati-graphy, but also in tectonics, petroleum geologyandapplied geology.Inmodernplatetectonicstheory,withoutthe use Foreword VII of micropalaeontologyit could not be proved that the plates move, that they are fonnedandsink, and travel over younger andyoungerdeposits.Toneglectchronologicalpalaeobio-logy is to refuse to take advantage of the fmest chronometer of the history of the earth. Palaeobiology includes not only the study of extinct orga-nismsbut alsothatof the waytheywereassociatedand of the conditions under which they lived. This is where palaeo-ecologycomesinandmanypalaeo biologiststodayare palaeoecologists.Inthefootsteps of Monsieur Jean Piveteau, whowrotetheadmirablelittlebookontheImagesdes mondesdisparus,MonsieurJean-ClaudeGallhasherepro-ducedatextbookonpalaeoecology.Faunal and floral asso-ciationsexistinequilibriumwiththeirenvironment.No studyof sedimentology,of palaeogeographyorof palaeo-oceanographyshouldignoreancient environments and their populations,withtheirstoryof evolution, of migration and of death.Therearethousands of examples in historical geo-logy, in mining and in petroleum geology. Palaeobiology discusses the organic content of sedimentary rocks,both thatwhichispresentandthatwhich,although now disappeared, has affected them. Asa man who has spent hislifetryingtounderstandsedimentsandtheir alteration intennsof inorganicchemistry,Iknowthatthisworkis onlyjustbeginning.Thegeochemistryandthehistoryof rocksdependsnotonlyonthemineralstheycontain,but alsoon their organiccontent.Theorganicgeochemistryof sedimentsisindispensable:itcontrolsthepHandredox potentialof environments,thesolubilityandcombination of certain elements and their migration, their deposition and theiraccumulation.Thisbiogeochemistryiscontrolledby the living organisms which inhabited the sedimentary environ-mentsandthesurfaceof thecontinents:palaeobiologyis fundamental to modern biogeochemistry. For these reasons, it is quite clear to me that palaeobiology hasalwaysbeenpartof the Earth Sciences and must always remaina partof them.Thedevelopmentof our disciplines can be furtheredonly by close collaboration between palaeo-biologists, structural geologists, geochemists and mining geo-logists in exploring newfields. Itisinthisspiritthat Monsieur J ean-Claude Gall has pre-paredthis book. Asa man who spans the boundary between palaeobiologyandsedimentology,heisasfamiliar with the VIIIForeword Mississippideltaaswiththe ancient deltas andshorelines of theTriassicseasof theVosges.Heblends the knowledge of a sedimentologist, the learning of a palaeo biologist, the care-fuluseof hispen andthe skills of a draftsman. The descrip-tionof nineancientenvironments,whichclosesthisbook, isfascinatingreading.Iwishgoodluckto this Introduction to Palaeoecology. 1st April1975 Georges Millot Preface One of the main aims of geology is to reconstruct the environ-mentswhichhavefollowedoneanotheron thesurfaceof theEarththroughoutitslonghistory.Suchan undertaking involvesthedescriptionof living organisms andtheir modes of lifeaswell asthe physico-chemical characteristics of their environments.Palaeoecologyplaysamajor part in this field of research.Being the science of the environment, it includes thestudyof the changing relationships which exist between fossilorganismsandthesediment;itcallsondisciplinesas variedas palaeontology, petrology, sedimentology, geochem-istry,etc.Atatimewhenthedivisionsbetweendisciplines arebecoming blurred, palaeoecology appears to be rather an attitudeof mind,awayof approachingthesubject,thana separate science. Thisworksetsout to showsome of the different ways in whichthe geologistcan study ancient environments.Its aim istointroducethe reader tothe methods of deduction used inpalaeoecologyandtofamiliarisehimwithlong-gone environments which are often differentfromthose of today. Theinformationwhichthefossilsandthesedimentcan giveus about ancient sedimentary environments is examined in the first part of the book. Thesecondpartconcentratesonpalaeoecologicalsyn-thesesbymeansof thedescriptionof ninereconstructions of continentalandmarineenvironments.ApartfromEdia-cara,whichisincludedbecauseofitsimportanceinthe history of life,allthe examples are fromEurope. If thisconjuring-upof thepastsucceeds in making histo-ricalgeologycomealiveforthereader,the goal whichI set myself willbe fullyrealised. Strasbourg, Easter1975 lean-Claude Gall Table of Contents Part One Infonnation Deduced from the Fossils and the Sediment Chapter 1: Modes of Life. . . . . . . . . . . . . . . . . . . . . . .2 I.Mobility.................................2 1.Aquatic Organisms. . . . . . . . . . . . . . . . . . . . . ..2 a)Benthos.............................2 i)Sessile Benthos. . . . . . . . . . . . . . . . . . . .2 ii)VagileBenthos.. . . . . . . . . . . . . . . . . . .5 iii)Infauna. . . . . . . . . . . . . . . . . . . . . . . . . .5 b)Nekton.............................6 c)Plankton............................6 d)Pseudop1ankton.......................9 2.Land Organisms.. . . . . . . .. . . . . . . . . . . . . . . ..10 a)Movement on Land.. . . . . .. . . . . .. . . . . ..10 b)Flight..............................10 II.Nutrition........ . . . . . . . . . . . . . . . . . . . . . . . ..12 1.Autotrophic Organisms.. . . . . . . . . . . . . . . . . ..12 2.Microphagous Organisms.. . . . . . . . . . . . . . . . ..12 a)Suspension Feeders.. . . . . . . . . . . . . . . . . ..12 b)Detritus Feeders. . . . . . . . . . . . . . . . . . . . ..13 c)MudFeeders.. . . . . . . . .. . . . . . . . . . . . . ..13 3. Macrophagous Organisms'.. . . . . . . . . . . . . . . ..14 a)Herbivores...........................14 b)Carnivores...........................14 c)Saprophages.........................15 d)Parasites............................15 III. Reproduction. . . . . . . . . . . . . . . . . . . . . . . . . . . ..15 1.Asexual Reproduction.. . . . . . .. . . . . . . . . . . ..15 2.Sexual Reproduction.. .. . . . . . . . . . . . . . . . . ..16 IV.Growth.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..17 V.Behaviour.. ...............................17 XIITableof Contents Chapter 2:Constraints on Living Conditions.. . . . . . ..20 I.Natureof the Substrate. . . . . . . . . . . . . . . . . . . ..20 1.HardBottoms. .. . .. . . .. .. . . .. .. .. .. .. ..21 2.Soft Bottoms. . .. . . . .. . . .. . . . . .. ... . .. ..21 II.Salinity.................................22 1.Marine Organisms. . . .. . . . . .. .. . . .. . .. . ..22 2.Brackish Water Organisms.. . . . .. . . . . .. . . ..22 3.Freshwater Organisms... . .. . . . . .. .. . . .. ..24 III.WaterTurbulence. . . . . . . . . . . . . . . . . . . . . . . ..24 IV.Oxygenation of theWater.. . . . . . . . . . . . . . . . ..26 V.Bathymetry..............................26 VI.Turbidityof theWater.. . . . . . . . . . . . . . . . . . ..29 VII.Temperature and Climate. . . . . . . . . . . . . . . . . ..30 1.LandOrganisms.. . .. .. .. . . .. .. .. .. . . . . ..30 a)The Fauna. .. . .. . .. . .. . . . . .. . . . . . . ..30 b)The Flora. . .. . .. . .. . .. . .. .. . . .. . . ..30 2.Aquatic Organisms.. . . . . .. . . .. . . . . .. . . ..32 a)Warm Water Organisms. . .. . . . . ... . .. ..32 b)Cold Water Organisms.. . .. . . . . . . . .. . ..32 3. Palaeotemperature Measurements... . . .. . . ..33 4. Seasonal Cyclicity. . .. . .. . . . . .. . .. . .. . . ..33 Chapter 3: Evidence of Biological Activity.. . .. . .. ..35 I.Evidence of Reproductive Activity. . . . . . . . . . ..35 1.Spores and Pollen. . . .. .. . . .. . .. . .. .. . . ..35 2.Eggsand Clutches.. . . . . .. . .. . . . . .. . .. . ..35 a)Invertebrate EggsandClutches.. . .. . .. ..36 b)Vertebrate EggsandClutches... .. . . .. ..37 i)Fish............................37 ii)Reptiles.........................37 iii)Birds. . . . . . .. . .. . . . . . . . . . . .. . . ..37 c)Reasons for Studying EggsandClutches...38 II.Evidence of Feeding.. . . . . . . . . . . . . . . . . . . . ..38 1.Signs of Predation... .. . .. . .. . . .. .. . .. . ..38 2.Fossil Excrement.. . .. . .. . . .. .. . .. . .. . . ..39 III.Trails and Burrows (Ichnology).. . . . . . . . . . . . ..40 1.Dwelling Traces.. . .. . . . . .. .. . . .. . .. . .. ..41 2.Movingand Resting Traces.. . .. . .. . . .. .. ..42 a)Moving Traces.. .. . . . . . . .. . . .. .. . . . ..43 b)Resting Traces... . . .. .. . . . . .. .. . . .. ..44 Table of ContentsXIII 3. Feeding Traces......... . . . . . . . . . . . . . ..44 4. Reasons for Studying Trace Fossils.. . . . . . . ..45 a)Bathymetry.........................45 b)Oxygenation of the Environment. . . . . . ..46 c)Sedimentation Rate.. . .. . . . . . . . . . . . . ..46 d)Cohesion of the Substrate. . . . . . . . . . . . ..47 Chapter 4: The Sediment. . . . . . . . . . . . . . . . . . . . . ..48 I.Observations on Sedimentary Particles: Sedimentary Petrology. . . . . . . . . . . . . . . . . . . ..48 1.Petrological Characteristics of the Sediment. . . ..48 a)InformationonRegionsUpstreamofthe Site of Deposition. . . . . . . . . . . . . . . . . . ..48 i)Source Areas. . . . . . . . . . . . . . . . . .. ..48 ii)Climate.........................49 b)InformationAbouttheEnvironmentof Deposition.. . . . . .. . . . . . . . . . . . . . . . . ..50 i)Redox Potential. . . . . . . . . . . . . . . . ..50 ii)Salinity.........................50 iii)Information fromClayMinerals. . . . ..50 iv)Information from Geochemistry.. . . ..51 c)Information on Diagenetic Changes.. . . . ..51 2. Petrography.. . . . . . . . . .. . . . . . . . . . . . . . . ..51 a)Surface Appearance of Quartz Grains. . . ..51 b)Shape andRoundness of Pebbles.. . . . . . ..52 3. Grain Size Measurement. . . . . . . . . . . . . . .. ..53 a)Detrital Rocks.. . .. . . . . .. . . . . . . . . . . ..53 b)Carbonate Rocks... . . . . .. . . . . . . . . . . ..55 4. Particle Distribution. .. . . . . .. . . . . . . . . . . ..56 a)Graded Bedding.. .. . .. . . . . . . . . . . . . . ..56 b)Parting Lineation. . . . . . . . . . . . . . . . . . . ..56 c)Pebble Orientation. . . . . . . . . . . . . . . . . ..56 d)Pebble Imbrication. . . . . . . . . . . . . . . . . ..58 II.Observations on Beds: Stratinomy... . . . . . . . ..58 1.Stratification and Bedding.. . . . . . . . . . . . . . ..58 a)Stratification........................58 b)Bedding............................59 i)Horizontal Bedding. . . . . . . . . . . . . . ..59 ii)Cross-Bedding....................59 iii)Flaser Bedding.. .. . . . . .. . . . . . . . . ..60 iv)Convolute Bedding.. . . . . . . . . . . . . ..61 XIVTable of Contents 2.Sedimentary Structures. . . . . . . . . . . . . . . . . ..62 a)Structures on the Top of the Beds.. . . . . ..62 i)Ridges or Ripple Marks.. . . . . . . . .. ..62 ii)Crescent Marks. . . . . . . . . . . . . . . . . ..64 b)Structures on the Baseof the Bed.. . . . . ..64 i)Structures Indicating the Physico-Chemi-calEnvironment of the Underlying Bed65 ii)Structures Made by Currents.. . . . . . ..65 iii)Deformation Structures.. . . . . . . . . . ..67 c)Structures Within Beds. . . . . . . . . . . . . . ..67 3. Conclusions.. . . . . . . .. . . . . . . . . . . . . . . . . ..67 III.Observations at Outcrop:Analysis of Sequences..68 1. The IdealisedNormal Sequence.. . . . . . . . . . ..68 2.Lithological Sequences. . . . . . . . . . . . . . . . . ..69 a)Positive andNegative Sequences. . . . . . . ..69 b)Sequences DerivedfromSoils. . . . . .. . . ..69 3.Rhythmic Series.. . . . . . . . . . . . . . . . . . . . . ..70 a)Varves.............................70 b)Alternation of Limestones andMarls.. . . ..71 i)Hallam's Theory of Eustatic Control...71 ii)Lombard's Theory of GravityFlow.. ..72 iii)Climatic Variations. . . . . . . . . . . . . . ..73 iv)Diagenetic Origin.. . . . . . . . . . . . . . . ..73 c)Molasse............................73 d)Flysch.............................75 e)Coal...............................75 Chapter 5: Sedimentary Environments. . . . . . . . . . . ..78 I.Continental Environments.. . . . . . . . . . . . . . . . ..78 1.Fluviatile Environments. . . . . . . . . . . . . . . . ..78 a)Alluvial Cones.. . . . . . . . . . . . . . . . . . . . ..78 b)Fluviatile Deposits.. . . . . . . . . . . . . . . . . ..79 2.Lacustrine Environments.. . . . . . . . . . . . . . . ..81 3. Aeolian Sedimentation. . . . . . . . . . . . . . . . . ..81 4. The Glacial Environment.. . . . . . . . . . . . . . . ..81 II.Marine Environments.. . . . . . . . . . . . . . . . . . . ..82 1.The Intertidal Zone or Shoreface. . . . . . . . . ..83 a)The Sediments.. . . . . . . . . . . . . . . . . . . . ..83 b)The Organisms.. . . . . . . . . . . . . . . . . . . . ..83 2.Neritic Environments.. . . . . . . . . . . . . . . . . ..84 Table of ContentsXV a)Neritic Environments Subject to Terrigenous Sedimentation. . . . . . . . . .. .. . . . . . . . . ..84 i)The Sediments.. .. .. . . . . . . . . . . . . ..84 ii)The Organisms.. . . . . . . .. . . . . .. . . ..85 b)Neritic Environments with Carbonate Depo-sition.. . . .. .. . . .. .. . . .. . . . . . . . . . . ..85 c)Reef Environments.. . . . .. . .. . . . . . .. ..86 i)The Sediments.. .. . .. . . . . . . . . . . . ..86 ii)The Organisms.. .. . . . . . . . . . . . . . . ..86 iii)Environmental Parameters of the Reef.86 iv)Zonation of Reefs.. . . .. . . . . . . . .. ..87 3. The Ocean. .. . . . . .. . . .. .. .. . . .. . .. . . . ..87 a)The Sediments... .. . . .. . . .. .. .. . . . . ..87 b)The Organisms... . . . . . . . .. . . . . . . . .. ..87 III.Deltas and Estuaries. . . . . . . . . . . . . . . . . . . . . ..88 1.Deltas.. .. . . . . .. .. . .. . . . .. .. .. .. . . .. ..88 a)The Sediments.. . . . .. . . . . .. . . .. . . .. ..89 b)The Organisms.. . . . .. .. .. .. . . .. . . . . ..90 2.Estuaries.. .. . . .. . . . . .. .. . . . . .. . . . . . . ..90 IV.Lagoons.................................91 1 . The Sediments.. . . . . .. .. . . .. . . . . . . .. . . ..91 2. The Organisms.. . . .. . . .. .. . . . . .. . . . . .. ..91 V.TurbidityCurrents. . . . . . . . . . . . . . . . . . . . . . ..91 1.The Sediments.. .. .. . .. . .. .. . . . . . . . . . . ..92 2. The Organisms.. . . .. .. . . .. .. . . . .. . . . .. ..93 VI.Environments of Deposition of Evaporites.. . . ..93 1.Lagoons... . . . . .. . . .. .. . . .. . . . . . . .. . . ..93 2. Major Marine Platforms... .. . . .. . . .. . . . . ..94 3. Precipitation Within the Sediment. . . . . . . .. ..94 Chapter 6:Fossiliferous Horizons... . . . . .. . . . . .. ..95 I.Originof Fossiliferous Horizons- Taphonomy..95 1.Accumulation of Organisms. . . . . . . . . . . .. ..95 a)Dense Populations.. .. . ... .. . . .. . . . . ..96 b)MassMortality. . . . .. . .. . . .. .. . . . . .. ..96 c)Transport..........................96 2.Burial of Organisms.. .. . .. . .. .. . . . . . . . . ..96 3. Diagenesis.. . .. .. . .. . .. .. .. . . . . .. . . .. ..97 XVITable of Contents 4. Classification of Fossiliferous Horizons.. . . . ..98 a)Horizons Fonned by Concentration. . . . ..98 b)Horizons Fonned by Preservation.. . . . . ..99 II.Associations of Organisms- Palaeosynecology...99 1.Palaeobiocoenoses.. . . . . . . . . . . . . . . . . . . . ..99 2. Thanatocoenoses.. .. . . . . . . . . . . . . . . . . . . ..101 a)Orientation of Fossils. . . . . . . . . . . . . . . ..101 b)Sorting by Sizeand Weight .............103 c)State of Preservation.. . . . . . . . . . . . . . . ..103 d)Indicators of Recycling.. . . . . . . . . . . . . ..104 e)The Mixture of Floras andFaunas........104 III.The Study of Fossiliferous Horizons.. . . . . . . . ..104 1.Uniqueness of Palaeoecological Methods.. . . ..104 2.Collection of Infonnation .................105 3. Presentation of Results: Palaeoecological Profiles105 Part two Reconstruction of Some Ancient Environments.. . . ..109 Chap ter 7:The Ediacara Fauna. . . . . . . . . . . . . . . . . ..110 I.The Sediment.. . . . . . . . . . . . . . . . . . . . . . . . . ..110 II.The Fossils. . . . . . . . . . .. . . . . . . . . . . . . . . . . ..111 1.TheFauna ............................. 112 a)Benthic Organisms ....................112 b)Nektonic Organisms. . . . . . . . . . . . . . . . ..112 2. The Flora.............................112 3. Evidence of Biological Activity.. . . . . . . . . . ..113 III.Preservation ..............................113 IV.The Environment. . . . . . . . . . . . . . . . . . . . . . . ..114 Chapter 8:The OldRed Sandstone Continent.......115 I.The FluviatileComplex.. . . . .. . . . . . . . . . . . . ..115 1.The Sediment. . . . .. . . . . .. . . . . . . . . . . . . ..115 a)Petrology...........................115 b)The Cyclothems. . . . . . . . . . . . . . . . . . . ..116 2. The Organisms.. . . . . . . . . . . . . . . . . . . . . . . ..117 a)Vertebrates.........................117 b)The Invertebrates.. . . . . . . . . . . .. . . . . ..117 c)The Flora.......................... 118 Table of Contents XVII 3.F ossilisation. . . . . . . . . . . . . . . . . . . . . . . . . ..118 4. The Environment....................... 118 II.The OrcadianLake. . . . . . . . . . . . . . . . . . . . . . ..119 1. The Sediment. . . . . . . . . . . . . . . . . . . . . . . . ..119 a)Petrology...........................119 b)Stratinomy.........................119 i)Bedding.........................119 ii)Sedimentary Structures. . . . . . . . . . . ..120 2. The Fossils........................... ,120 a)The Fauna.. . . . . . . . . . . . . . . . . . . . . . . ..120 b)The Flora..........................120 c)Evidence of Biological Activity. . . . . . . . ..120 3. Preservation.. . . . . . . . . . . . . . . . . . . . . . . . . ..121 4. The Environment. . . . . . . . . . . . . . . . . . . . . ..122 III.The Rhynie Peat Bogs.. . . . . . . . . . . . . . . . . . . ..122 1. The Sediment. . . . . . . . . . . . . . . . . . . . . . . . ..122. 2. The Fossils............................123 a)The Fauna. . . . . . . . . . . . . . . . . . . . . . . . ..123 b)The Flora..........................123 3. Fossilisation. . . . . . . . . . . . . . . . . . . . . . . . . ..124 4. The Environment.......................124 IV.ConclusionsontheEnvironmentsof the Old Red Sandstone Continent. . . . . . . . . . . . . . . . . . . . . ..125 Chapter 9:The Decazeville Coal Basin. . . . . . . . . . . ..126 I.The Sediments . ...........................126 1.Petrology.. . . . . . . . . . . . . . . . . . . . . . . . . . . ..126 a)Terrigenous Sediments. . . . . . . . . . . . . . ..126 b)Plant-Derived Sediments:Coals ..........127 2. Stratinomy. . . . . . . . . . . . . . . . . . . . . . . . . . ..128 a)Bedding ............................128 b)Rhythmic Deposition. . . . . . . . . . . . . . . ..128 II.TheFossils. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..130 1. The Flora. . . . . . . . . . . . . . . . . . . . . . . . . . . ..130 a)Thallophytes ........................130 b)Bryophytes .........................130 c)Pteridophytes....................... 130 d)The Prephanerogames . . . . . . . . . . . . . . . ..131 e)The Phanerogames ....................131 XVIIITable of Contents 2.The Fauna .............................131 a)Terrestrial Animals. . . . . . . . . . . . . . . . . ..131 b)Aquatic Animals .....................131 III.The Environment. ........................132 1. The Limnic Nature of the Sedimentary Basin ..132 2.Sedimentary Processes.. . . . . . . . . . . . . . . . . ..132 3. The Climate ............................133 4. Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . ..133 Chapter 10: The Gres a Voltzia Delta ..............134 I.TheSediment. ...........................134 1.Petrology .............................. 134 a)The Sandstones. . . . . . . . . . . . . . . . . . . . ..134 b)The Shales.. . . . . . . . . . . . . . . . . . . . . . . ..135 c)The Carbonates.. . . . . . . . . . . . . . . . . . . ..13 5 2.Stratinomy. . . . . . . . . . . . . . . . . . . . . . . . . . ..135 a)Bedding ............................135 b)Sedimentary Structures ................135 3. Geochemistry..........................136 II.The Fossils. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..137 1. The Fauna .............................137 a)Foraminifera ........................137 b)Coelenterates........................137 c)Brachiopods........................137 d)Annelids...........................138 e)Molluscs...........................138 oArthropods .........................138 i)Chelicerates......................138 ii)Crustacea........................138 iii)Myriapods.. . . . . . . . . . . . . . . . . . . . ..139 iv)Insects ..........................139 g)Fish ...............................139 h)Tetrapod Vertebrates.................140 2.The Flora.............................140 a)Pteridophytes.......................140 b)Prephanerogames .....................140 c)Phanerogames.......................140 3. Evidence of Biological Activity. . . . . . . . . . . ..140 a)Eggs and Clutches ....................140 b)Coprolites ..........................141 c)Trace Fossils ........................ 141 Table of ContentsXIX III.TheEnvironment. . . . . . . . . . . . . . . . . . . . . . . ..141 1.Fluviatile Channels.. . .. . . . . .. . . . .. . . .. ..143 2.Temporary Pools of Water .................143 a)Water Salinity .......................143 b)The Ephemeral Nature of the Pools .......144 c)The Hydrodynamic System .............144 d)Oxygenation ........................144 3. Littoral Muds.. . . .. .. . . .. . . .. . . .. . . .. ..145 IV.Fossilisation. . . . . . . . . . . . . . . . . . . . . . . . . . . ..145 1.The Plant-Bearing Sandstones.. . . .. .. . . . . ..145 2.The Clay Horizons.......................145 a)Palaeobiocoenoses ....................145 b)Mass Mortality of the Aquatic Fauna. .. ..146 c)Preservation of Organic Matter ..........146 V.Conclusion..............................147 Chapter 11: The Reefs of Hoher Goll . . . . .. .. . . .. ..149 I.Hallstatt Limestones. . . . . . . . . . . . . . . . . . . . . ..149 l. The Sediment..........................149 2.The Fossils. . .. . . . . . . . . .. .. . .. . .. . . . . ..150 3. The Environment.......................150 II.The Dachstein Reef Complex. . . . . . . . . . . . . . ..150 1.The Fore-Reef Zone. . .. . . . .. . . .. .. . . . . ..152 The Sediment. .. . . . . . .. .. .. .. . .. . .. ..152 2.The Reef ..............................152 a)The Sediment. .. .. .. . . .. . . . . .. . . . . ..152 b)The Organisms.. . .. . .. . .. . . . . . . .. . . ..152 3.The Back-Reef Zone. .. .. . . .. .. .. . . .. .. ..154 a)The Proximal Region.. .. .. . . .. . . . . .. ..154 b)The Distal Region.. . . . . .. . . . . .. . .. . ..155 III.The Hauptdolomit . ........................156 IV.Conclusion..............................157 Chapter12: The Holzmaden Bituminous Shale Sea....158 I.TheSediment.. . . . . . . . . . . . . . . . . . . . . . . . . ..158 1.Petrology.. . . .. . . .. .. . . . . .. . . .. .. . . .. ..158 2.Stratinomy............................158 II.TheFauna.. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..159 1.Burrowing Organisms.................. "159 2.Benthic Organisms.. . . . .. . .. . . . . . . . .. . . ..159 xxTable of Contents 3. Nektonic Organisms. . . .. .. . . .. . . .. .. . . ..159 a)Cephalopods........................159 b)Fish ...............................160 c)Reptiles ............................160 4. Pseudoplanktonic Organisms ...............162 5.Flying Organisms.. . .. . .. . . . . .. . . .. .. . . ..163 III.The Flora. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..163 IV.Fossilisation. . . . . . . . . . . . . . . . . . . . . . . . . . . ..163 1.Anaerobic Conditions ....................163 2.Burial................................164 3. Diagenesis .............................165 Chapter 13: The Solnhofen Lagoon...............167 I.The Sediment. . . . . . . . . . . . . . . . . . . . . . . . . . ..167 1.Petrology.... . . .. . .. .. .. .. . . . . . .. .. . ..167 2. Stratinomy............................167 a)Bedding ............................167 b)Sedimentary Structures ................168 II.The Fauna.. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..169 1.Burrowing Organisms. . .. .. . . .. . .. . .. . . ..169 2. Benthic Organisms ..................... "169 3. Nektonic Organisms.....................169 a)Coelenterates........................169 b)Cephalopods ........................170 c)Fish ...............................170 d)Reptiles ............................170 4. Planktonic Organisms....................170 5. Pseudoplanktonic Organisms. . .. . ... . .. . . ..171 6. Terrestrial Organisms.....................171 7.Flying Organisms.. . .. . . . .. . . .. .. . .. . .. ..171 a)Insects.............................1 71 b)Pterosaurs..........................1 71 c)Birds..............................172 III.The Flora. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..172 IV.Evidence of Biological Activity . ..............172 1.Dying Tracks. . . .. .. .. . . . . .. .. . .. . ... . ..172 2.Locomotion Traces.. . .. . .. . .. . .. . . .. .. ..172 3. Coprolites and Stomach Pellets.. . .. . . . . . . ..172 V.Fossilisation.............................173 1.Water Movement... .. . .. . . .. .. . . .. .. . . ..173 Table of ContentsXXI 2.Rate of Sedimentation. . . . . . . . . . . . . . . . . ..173 3. Anaerobic Conditions ....................173 4. Salinity of the Water .....................174 5. Fineness of the Sediment.................174 6. Diagenesis.. . . . . . . . . . . . . . . . . . . . . . . . . . ..174 VI.TheEnvironment. ........................175 Chapter 14: The Shores of the Auversian Sea ........178 I.The Sediment. . . . . . . . . . . . . . . . . . . . . . . . . . ..179 1.Petrology.. . . . . . . . . . . . . . . . . . . . . . . . . . . ..179 a)Grain Size..........................179 b)Heavy Minerals...................... 179 c)Organic Matter......................179 2. Stratinomy............................180 a)Bedding............................180 b)Beach Rock.. . . . . . . . . . . . . . . . . . . . . . ..180 c)Palaeosols..........................180 II.The Fossils. .............................181 1.The Flora.............................181 2. The Fauna .............................181 a)The Microfauna ......................181 b)The Macrofauna.....................182 i)Benthic Organisms .................182 ii)Nektonic Organisms. . . . . . . . . . . . . ..182 iii)Terrestrial Organisms.. . . . . . . . . . . . ..182 III.Environmental Factors. ....................183 1.Salinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..183 2. Bathymetry ............................183 3. Temperature ...........................183 4. The Hydrodynamic Regime and Associations of Organisms . . . . . . . . . . . . . . . . . . . . . . . . . . . ..184 a)Thanatocoenoses .....................184 b)Pa1aeobiocoenoses....................184 c)The Submarine Meadows ...............184 d)Lagoons ............................184 IV.Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..185 Chapter 15: The Acheulian Hunters' Cave at Le Lazaret.186 I.ExcavationTechniques.. . . . . . . . . . . . . . . . . . ..186 II.The Sediment. ...........................186 XXIITable of Contents 1. The Nature of the Sediment...............187 2. The Occupation Level. . . . . . . . . . . . .. . . . . ..188 3. Deposits Post-Dating the Riss Glaciation ......188 III.The Fauna and Flora.. . . . . . . . . . . . . . . . . . . . ..189 1. The Fauna ............................. 189 2. The Flora.............................189 IV.HumanOccupation . ....................... 189 1.The Dwelling.. . . . . . . . . . . . . . . . . . . . . . . . ..190 2. The Implements. . . . . . . . . . . .. . . . . . . . . . ..191 3. Human Activity. . .. . . . . . . . . . . . . . . . . . . . ..192 4. The Length of Occupation. . . . . . . . . . . . . . ..192 V.The Climate . ............................. 193 VI.Conclusion..... . . . . . . . . . . . .. . . . . . . .. . . ..194 Appendix I:GuidetothePalaeoecologicalStudyof Fossiliferous Horizons.. . . . . . . . . . . . ..195 Appendix II:Table Summarizing the Principal Features of the Environment. . . . . .. . . . . . . . . ..196 Appendix III: StratigraphicPosition of Some European Fossiliferous Horizons... . . . . . . . . . . ..198 References ................................... 200 Index....................................... 205 Part One Information Deduced from the Fossils and the Sediment Chapter 1Modes of Life Animals and plants arehighly dependent on their immediate environment tosatisfytheirvitalneedsforfeedingandreproduction.Within popula-tions,naturalselectionfavourstheformsbestadaptedtothephysico-chemicalandbiologicalconditionswhichdominatetheir environment. Thusrecognitionoftheadaptivecharactersoffossilorganismsandan understanding of theirsignificanceforms an important part of the recon-struction of fossil environments. This is the aimof functional morphology. Broadly,thefunctionofvariousstructurescanbereconstructedfrom the morphology of the hard parts preservedby fossilisation. Aknowledgeoftheworkingsandmodeof lifeof present-dayorga-nismsisobviouslyfundamentaltotheinterpretationoffossilspecies. Asinsomanyaspectsof theearthsciences,thepresentis,toacertain extent, the key to the past. 1.Mobility Howanorganismfeeds,protects itself against its enemies and reproduces itself iscontrolledtoagreatextentbyitsmobility,andone canbasea broad classification of livingbeings on this (Fig.1). 1.Aquatic Organisms a)Benthos Benthicorganismsorbenthosliveina very close relationship to the bot-tom.Epibionticformsliveonthesurfaceof thesedimentwhileen do-biontic formslivewithin it, either buriedor in holes. o Sessile Benthos Theadults of sessile species are fixedto, or sit on, the substrate or another organism(epizoans,epipnytes).Sincetheydonotmove,theyarecom-Sessile Benthos )) Forms flying above the surface 3 Fig.1.Classificationof marineorganisms according to their mobility. (Ager inBabin 1971) pletelyunder the influence of their environment. They arethus excellent environmental indicators. There are many adaptations to a fixedmode of life: osome organisms simply sit on the surface of the unconsolidated sedi-. ment (Fig.2)by means of spines (productid brachiopods) or on their shell (Liassic gryphaeids, whose left valve, in contact with the bottom, is shaped likea cradle to raisethe animal above the mud, while the right valve acts as an operculum); omany other organisms arefixedto the substrate (Fig.3): - byaflexiblestalk;forexample:mostaquaticplants,brachipods, fixedechinoderms(blastoids,crinoidsetc.),some crustacea (goose-necked barnacles) etc; 4Modes of Life A Fig ..2A,B.Sessilebenthicformslivingon amobilesubstrate.Abivalve(Gryphaea arcuata,L i a s ~ brachiopod (Upper Palaeozoic productid) B Fig.3A,B.Methodsof fixationof sessilebenthos.A by a flexibleorgan:1siliceous sponge (Hyalonema); 2 cirripede crustacean (Lepas; 3 brachiopod (Magadina);4 bivalve (Modiolus);5crinoid (Cenocrinus).(Zeigler 1972); B by their shell:valveof a Sparna-cian Ostrea unci/era showing the impression of its attachment area. (Plaziat1970) - bypartof their shellor skeleton which welds itself to the substrate andmimics its shape; for example:sponges, corals, bryozoans, anne-lids(serpulids),bivalves(oysters,rudistids),crustacea(barnacles), etc.; - byaspecio.lisedorgan;forexample:theexothecallamellaeof archaeocyathids, the byssus of bivalves etc. Ingeneral,afixedmodeof lifefavoursthedevelopmentof external skeletons, shells and carapaces, asa means of protection against predators. Infauna5 Theyfrequentlyhavearadialsymmetry (sponges, coelenterates, echino-derms), andtheir distribution takes place by meansof free larvae. ii)Vagile Benthos Themovementof vagileor freespeciesislimitedbytheir contactwith thesubstrate,whicheffectivelycontrolstheirsearchforfood.They move in several different ways: - by contractions of their body muscles; for example:worms; - by a contractile foot; for example:many molluscs (gastropods); - by appendagesforlocomotion;forexample:the parapodia of annelid worms, arthropod feet(trilobites, limulids, crustacea); - bypropulsionorgans;forexample:cephalopodjets,finsof benthic fish(skatesandrays,Palaeozoicarmouredfish),bilaterally symmetri-cal shells of somebivalves (pectinids), etc.; - byspecialisedstructures;forexample:theambulacralsystemand spines of echinoderms. Animals which move activelyare generally bilaterally symmetrical. iii} Infauna Theinfaunaincludesorganismswhichburrow intounconsolidatedsedi-ments(Fig.4)orboreintohardsubstrates(Figs.17,36). They are also describedasendobiontic.Theycomefromseveraldifferentzoological groups:worms,molluscs,crustacea,echinoderms.Thismodeoflife requires certain morphological adaptations: ..... .. .,.. ,.. . .. ,. .' , ' .. . . " Fig.4.TheendofaunaofRecentmobilebottoms:brachiopod(Lingula),bivalve (Scrobicularia),gastropods (Aporrhais,Turritella).(Zeigler1972) 6Modes of Life - atrend towardsthe reductionof carapaces and shells whose protective rolehasbecomeunnecessarybecauseof theburialof theanimal;for example:wood-boring(teredinids)or rock-boringbivalves(pholads); - thedevelopmentof a siphon,afleshy,tubular extensionof the body of certainmolluscs(bivalves,gastropods)whichpasseswaterthrough thepallialcavity.Inthebivalves(Fig.5),the formationof a notch in thepallialline,thesinus,showswhereitentersthevalves.Theshell alsobecomes elongated in an antero-posterior direction andfrequently gapes around the siphon; - achangeintheambulacralareasontheupper surfaceof thetestof irregular echinoderms into branchiae (petaloid ambulacra)(Fig.6). If bodyfossilsarenotpresent,thein faunaleaves traces of its activity in the sediment which have great palaeoecological interest (p. 40). b)Nekton Nektonicorganismsornektonliveinthebodyof theseawherethey moveactivelyinsearchoffood.Theymovebymeansofswimming organs: - thefinsof aquaticvertebrates;infishandsometetrapods(ichthyo-saurs,dolphins,whales)thebodyispropelledbythecaudalfin; else-where,thisfunctioniscarriedoutbypairedstructureschangedinto paddle-likefinsbytheelongationorincreaseinnumberof joints (plesiosaurs, turtles, seals) (Figs.9, 116); - the jet and funnelsof cephalopods; - the caudal fanand swimming appendagesof decapod crustacea. Thebodiesof animalswelladaptedto swimming often have a spindle-shapedhydrodynamicprofile(fish,reptiles,mammals). This isa remark-able example of morphological convergence (Fig.7). c)Plankton Planktonicorganismsorplanktonlivefreeintheseaandarepassively sweptaboutbyit.Dependingonwhethertheyareanimalor vegetable, theyareknown aszooplankton or phytoplankton.Ingeneral, planktonic species do not have organsto helpthem move.Because of their lowbody density,theyareabletofloat.This lowbodydensity can be achieved in several different ways (Fig.8): - byaverysmallsize;manyformsaremicroscopic;forexample:the protista, the larvaeof various metazoans, etc.; Plankton Pallialsinus---fir--+-+-Pallial line -imprint of the. edge of the mantle: A : :t. 7 t ........ : .'. .. B Fig.SA,B.Adaptationtoaburrowingmodeof lifeinthebivalves(Myaarenaria): Ainternalviewof the leftvalve;Banimalinpositionof life.(ModifiedafterBoue and Chanton 1958) A B Fig.6A,B.Adaptation to a burrowing mode of life in the irregular echinoids (Micraster - UpperCretaceous).Ajawlessoralface;Bapicalfacewithpetaloidambulacra. (Devilliers1973) 8 o Modes of Life Fig.7A-F.Hydrodynamicshapesof thebodiesofswimmingvertebrates. Abonyfish(tuna:Thunnus);Bcarti-laginousfish(shark:Lamna); C reptile (Jurassicichthyosaur);Dmammal (porpoise:Phocaena);Emammal (sea-cow:Trichechus);Fbird(penguin: Spheniscus).(Gutmann1966) - bytheabsence(medusids)orthereductionof theskeleton(theper-foratedshellsof radiolaria;the reduced shells of heteropod and ptero-pod gastropods); - byexpandingthebody,thusincreasing itssurfacearea;for example: thecalcareousspinesof globigerinids and some coccolithophorids; the appendagesof certainacritarchs;thedevelopmentof appendagesand bristles on crustacean larvae, etc.; - bythesecretionof smalldropletsof oil;forexample:thecoccoid familyof green algaewhich giveriseto algalhydrocarbons; - by gas-filledfloats; for example: some algae (sargassids),graptolitesetc.; - byhightissuewaterretention;forexample:medusids, some tunicates etc. Pseudoplankton DIArDMEAE:E @FORAMINIFERA' F,- 't-,':':,,- >. -DINOFLAGELLATA: PPridm/um PTEROPODA-Diacr/a SILICOFLAGELLATA: RADIOLARIA ' H.xaslylus COCCOUTHOPHORIDA: Coccolilhus Fig.8.Recent and fossilplanktonic organisms.(Zeigler1972) 9 RADIOLARIA: Crypioprora COCCOL! THOPHORIDA: Rhabdosphaera Theplanktonplayanimportantrolein the food chain of present-day seasandlakes.Theirsmallsizeandtheir reductioninskeletaldevelop-ment means their importance has often been underestimated. Nektonandplanktonarealsogroupedaspelagicssince,unlikethe benthos, they are independent of water depth. d) Pseudoplankton Thetermpseudoplanktongroupstogether sessileorganismswhich occa-sionallyfixthemselvestofloatingobjects(algae,wood,shells,etc.) (Fig.117). Like the plankton, they are subject to the play of the currents. Theycomefrommany groups of organisms:coelenterates (hydrozoans), bryozoans,annelids(serpulids),molluscs(bivalves,gastropods),arthro-pods (cirripede crustaceans), echinoderms (crinoids), etc. Whenthe float-ingsupportisnotfossilised,pseudoplanktonicspecies can easilybe con-fusedwithbenthicformsandthiscanleadtoinaccurateenvironmental interpretations. 10Modes of Life 2.Land Organisms Theability to liveon land isone of the great developments in the history oflife.DuringthePalaeozoic,plantsandseveralgroupsofanimals (arthropods,gastropods,vertebrates)inturncolonisedthecontinents. Airbreathingandprotectionagainstdesiccationwereamongthemany adaptations requiredby thischange in environment. Afixedmodeoflifeisfoundonlyamongautotrophicorganisms whichtaketheirnourishmentdirectlyfromthesoil.This issoforthe plants.Intheanimals, however,the search for foodrequires active travel on the ground or in the air. a)Movement on Land Travel on land can occur in various ways: ocrawlingby means of contraction of the body muscles(worms, caterpil-lars)orby the use of a specialised organ such asthe footof the gastro-pods; owalkingwitharticulatedappendages; for example:the arthropods and the vertebrates. Tetrapodvertebrates,withpentadactylextremities,providegood examples of adaptation to different modes of travel (Fig.9): - running,helpedbyamoreerectposturecombinedwithareduction in the number of digits (horses); - climbingby the acquisition of claws, adhesive pads or by the ability to opposethedigitstomakegraspingstructures(primates,somemarsu-pials); - jumpingusinganarticulatedhindlimbwiththree sub-equal segments (frogs, kangaroos, rabbits); - burrowing by shortening and enlarging the fore-limbs(moles). Elsewhere,amongtetrapodswhichhavereturnedtoanaquatic mode of life,the pentadactyl extremity canbechanged into swimming paddles byan increase in the number of joints or digits (ichthyosaurs, plesiosaurs, cetaceans etc.). b)Flight Thedevelopmentof wingshasoccurredinthearthropods(insects)and the vertebrates. Thetwopairsof wings in insects area membraneous expansion of the dorsal sideof the thorax.They are lost in parasitic species. R H R a,e p p 2 3 4 5 Fig. 9. Adaptations of fore-limbs in tetrapod vertebrates. 1 for flight (bat); 2 for swimming (ichthyosaur); 3 for gripping (opos-sum); 4 for running (horse); 5 for burrowing (mole). H humerus; R radius; C cubitus; P phalanges (finger-and toe-joints). (1 and 5 from Grasse 1967,2, 3 and 4 from Devilliers 1973) 'Tl I:r. CJ} -12Modes of Life Vertebratewingsarealteredfore-limbs(Fig.9).Inflyingreptiles (pterosaurs)andbats(cheiropterans),theyconsist of a web of skin, sup-portedbyoneor severaldigits.Incontrast, in thebirds,theliftingsur-face of the wing ismade of the arms covered in feathers. II.Nutrition Thesearchforfoodcontrolsthedistributionanddensityof organisms. 1.Autotrophic Organisms Chlorophyll-bearing plants use solar energy to carry out organic synthesis frommineralconstituents.Autotrophicformsalsoexistinthe bacteria. Someof them can occur in the absenceof freeoxygen. They are amongst the first signs of life on earth. Allanimalsareheterotrophic.Theyfeedon organicmatter of animal or vegetable origin. 2.Microphagous Organisms Microphagousorganismseatsmallnutrient particlesor smallorganisms (plankton)eitherfromsuspensioninthewater or mixedwiththe sedi-ment. a) Suspension Feeders Nutrientparticlesinsuspensioninthewater canbecollectedinseveral ways: - bybeatingvibratingciliawhichproduceawatercurrenttendingto directnutrientstowardsthemouth;forexample:flagellarcellsof sponges,tentacularplumesof someattachedpolychaetes(serpulids), thelophophoreofbrachiopodsandbryozoans,thefoodgrooveson crinoids' arms,etc.; - byfiltermechanisms;forexample:theappendagesof trilobitesand cirripedecrustaceans,thestickyfIlamentsof somepolychaetes (tere-bellids),thegillsofbivalves(oysters)andtunicates(ascidians),etc.; - byorganscatchingfoodandcarryingit tothemouth;forexample: the tentacles of fixedcoelenterates. The ability to capture larger prey leads to a macrophagous diet. Mud Feeders13 b)Detritus Feeders Organicmatter often accumulates on the surface of the sediment where it formsathinfilm.Thisisactivelygatheredby detritus feeders in various ways: - grazingmadepossiblebythe development of a mouth (gastropods) or labial palps (Nucula- bivalve); - by the elongation of the siphonof burrowing bivalves (tellinids); - scufflingof thesedimentwiththeirappendagesbymanycrustaceans (copeopods, amphipods); - by the movement of their ambulacral feet by various ophiuoids. c)MudFeeders Mudfeeders eat the organic matter which isdisseminated in the sediment by swallowing large quantities of mud or sand. They thus do a considerable amount of re-working of mobile substrates:thisiscalledbioturbation.At the same time they produce a large num ber of faecal pellets which become mixed with the sediment. Manyannelidsdothis (arenicolids, lumbricids), as do echinoderms (holothurians, spatangoids), enteropneusts etc. Themicrophagousdietischaracterisedbytheabsenceof chewable pieces.It is often associated with a sedentary or barely mo bile mode of life. Severalfixedsuspensionfeedersbelonging tovariousgroupsdevelop cone-shapedshellsor skeletonswhoseopeningisorientated towards the watersurface.Withinespeciallydensepopulations,suchanorientation allowsefficientinterceptionoffoodparticlesinsuspension.Thisisa good example of morphological convergence (Fig.10). Fig.lOA-I. Cone-shapedtestsinvarioussuspension-feedingorganisms.AJurassic sponge (Tremaclictyon); B Cambrian archaeocyathid; C Palaeozoic conularid; D Jurassic hexacoral(Montlivaltia);EPermian brachiopod (Richthofenia); F Cretaceous bivalve (Hippurites);GTertiarygastropod(Rothplezia);HTertiarycirripedecrustacean (Pyrgoma);I Ordovician echinoderms (Cyathocystis).(Zeigler1963) 14 Modes of Life 3.Macrophagous Organisms Theingestionof largefoodparticlesandthecaptureof preyareessen-tially attributes of mobile organisms (Fig.11). AB E o Fig.llA-E. Adaptation of the dentition of the higher vertebrates to their diet. A carni-vorousdiet(lion:Leo);B herbivorous diet (horse: Equus); C omnivorous diet (chim-panzee:Pan);Ddentitionforgrinding(lizard:Dracaena);Edentitionforfiltering (Permo-Carboniferous reptile: Mesosourus).(Zeigler1972) a)Herbivores Becauseherbivorousorganismstearupplants, they need hard parts asso-ciated with their mouth. This function iscarried out: - bythechitinousjawsoffree-movingannelids;theyarefrequently found separated in sediments:these are scolecodonts; - by the radulaof gastropods; - by the Aristotle's Lanternof regular echinoderms; - bythejawsandpostbuccal appendagesof arthropods(insects,some crus tacea); - bythecontinuously-growingteethandcuttingridgesof mammals (ungulates, rodents). b)Carnivores Carnivorousorganismsfeedonlivingpreywhichtheypursueortrap. Prey isseized by specialised organs: Asexual Reproduction15 - tentacles armed with stinging (urticant)cells in the cnidarids; - the jawsof annelids; - the radula of some gastropods which bore into shells (muricids, naticids); - thebuccal appendagesof arthropods:claws (eurypterids, spiders) and mandibles (crustacea, insects); - the arms of echinoderms (asterids); - thetentacles and beak of cephalopods; - theteethofvertebrates(fish,amphibians,reptiles,mammals)- the carnivorous mammals are the most specialised. c)Saprophages Saprophagesfeedon deadbodies. This is verydifficult to demonstrate in fossils.Examples:wormsfoundinthebodiesof insectlarvaefromthe Bunter Sandstone of the Vosges; fungal sclerotes preserved in the rhizomes of Devonian psilophytes fromRhynie (PI.I Fig. 4). d)Parasites Infossils,evidenceofparasitescanbeseenwheretheyhavedeformed thehost(protuberances caused in the body cavity of decapod crustaceans bybopyrids)or wheretheyarefoundwithintissues(nematodes in the cuticle of some Carboniferous scorpions). Ill.Reproduction Methodsof reproductioncontroltheability of anorganismto invade an environment and colonise it. 1.Asexual Reproduction Asexualreproductionoccursinlowerformsof lifewhereitallowsan exponential development of colonies and in consequence a rapid take-over of theenvironment(bacteria).Inmostoftheprotista(foraminiferids, diatoms),italternateswith sexualreproduction.Insomeforaminiferids (miliolids,nummulites)thealternationof thesetwo modes of reproduc-tioncanbeidentifiedbythesizeof theinitialchambers(Fig.12):the microsphericformproducessporesforasexual reproduction, the macro-spheric produces gametes. 16 AB Modes of Life Fig. 12A,B. Alternationof generationsinmiliolids. Amacrosphericform (gamont); B microspheric form (agamont) In more highly evolved organisms, asexual reproduction helps in: - thedisseminationof thespecies;forexample:plantspores,budsof sponges and hydrozoans, etc.; - the formationof colonies where individuals formedbybudding do not detachthemselvesfromtheirparents;forexample:coralcolonies, bryozoans, graptolites, tunicates, etc. 2.Sexual Reproduction Sexualreproductionrequirestwogametestomeet.Thiscanhappenin thesurroundingwater,asisthecasewithfish,echinodermsandfixed organisms(bivalves,cnidarids,etc.).Thepollenof thehigherplants is carriedtowardstheovulebythewind(for example:pollenwith little air-filled sacs), water or animals. Ontheotherhand,amongthegastropods,thecephalopodsandthe majorityofspecieslivingonland,fertilisationoccursaftercopUlation. I t is possible to distinguish between males and females in fossil organisms whentheydisplay sexual dimorphism.Apart fromthe classic example of thehornscarriedbythemalesof manyruminants,onecanalsoshow sexualdimorphisminbrachiopods,bivalves,arthropods,echinoderms andvertebrates.It isparticularlyclearwhenthedifferencebetween the twosexesisshownbythegenitalapparatus(insects,eurypterids), the sizeofthegenitalopening(someechinoderms),orwhenthereare pouches for inCUbating the young (ostracods).In molluscs,and especially intheammonites,theco-existenceinsomeoutcropsof two varieties of thesamespecies(formerlyplacedindifferentspecies)differingonlyin their sizeandsomeornamentationof theadults,hasbeenattributed to sexual dimorphism (Fig.13). Eggsgenerallydevelop outside the mother (ovipares). Many vertebrates (mammals, some fish and reptiles) areviviparous:the development of the eggtakesplaceentirelyinthe genitaltractof themother. Embryos can thusbefossilisedinsitu(forexample:theLiassicichthyosaursfrom Wtirttemberg). Behaviour17 A B Fig.13A, B.Sexual dimorphism in Jurassic ammonites previously classifiedasseparate genera.ACadomitesdeslongchampsi(femaleform?);BPolyplectiteslingui!erus (male form?).(Makowski in Babin1971) IV.Growth Whenonehaslargepopulationsof a given species available, it is possible tostudygrowth.For manytrilobites,onehasthusbeenabletofollow the different larval stages successively fromeggto adult. Thegrowthofarthropodsisdiscontinuousbecauseittakesplaceby successivemoults.A graphof the distribution of carapace size shows the different moult stages (Fig.14).In molluscs, one can distinguish juveniles fromadultsbythedensityof growthlinesontheshell.Inmanycases, thismakesitpossibletodistinguishbetweenadwarf population(small sizedadultswhosegrowthhasbeenimpeded)anda juvenile population (accumulation of young stages). V.Behaviour Ethology, the study of the behaviour and habits of fossilorganisms, often lends itself to highly imaginative reconstructions, above allwhere a group isnowextinct.Withinthelasttwentyyears, researchon the mechanical significanceofmorphologicalpeculiaritiesandtheconstructionof arti-ficialmodelshasenabledustounderstandthemodesof lifeof fossil speciesmuch moreclearly. This isthe case with the feeding habits of the Tertiarylargecatswhosecanineteethdevelopedintosabres(Fig.15). 18 Shell height 0 . 6 mm 0 .5 0.4 0.3 0 . 2 0.1 ... .!: 5 4 3 Modes of Life ., . .,f 'l ~ .. .. 8 . ::tF:. 7 ,.:. 6 o ~__ __-L__ ____ __ __-L__ ____ __ ____ Length . 0.10.20.30.40.50.60.70.80.9mm one specimen . two specimens three specimens 3,4,5 ....Moult stages Fig.14.Successionofmoultstagesinapopulationof Hemicyprideismontosa,an ostracod fromthe Sannoisian of Cormeilles-en-Parisis. (Keen1972) Fig.1 S.Skull of Eusmilus bidentatus fromtheOligoceneofQuercy.The uppercaninesacted like daggers. The anteriorof the jaw played the part of the scabbard.(Piveteau1961) Onecanshowthatthearrangementof theirteethallowedthemto stab theirpreybecauseof thepowerfuldevelopmentof theirneckmuscles, butpreventedthemfrompulverisingthebones.Thesecarnivorescould feedonly on soft tissue, especially the liver, which they reachedby open-ing the abdomen of their victims. Behaviour19 .----f------- Centre of buoyancy Centre of gravity Body chamber Fig.16.Orientationof anammonite shellinits lifeposition.(Trueman1940) Thehydrodynamicbehaviouroffossilcephalopodshellshasbeen studied onmodelswherethe respective positions of the centre of gravity andthecentreof buoyancywereworkedout (Fig.16). Similarly, water circulationintheshellsofvariousbrachiopodsandmolluscshasbeen studied. PartTwoof thisbook will provide another opportunity to discuss the habits of many fossilorganisms. Chapter 2Constraints on Living Conditions Throughouttheirlives,livingbeingsaresubjecttotheinfluenceof the physico-chemicalconditionsoftheirenvironment.Anychangewhich occursintheoutsideworldaffectsorganic life; species disappear, others establishthemselves.In most cases the forms or populations which occur reflecttheconditionsobtainingintheirenvironment.Providedoneis surethat the fossilanimals andplants really lived in the place where they were buried,they are a useful indicator of ancient environments. Ourknowledgeoftheconditionsof lifeof fossilorganismsdepends stronglyon observationsmadeontheir livingrelatives.Thisistheprin-cipleofuniformitarianism,whichcan,however,leadtodubiousextra-polationssincethelifeconditionsof many organisms may have changed throughgeologicaltimewithoutanydetectablechangeinmorphology. Agercitesa particularlyeloquentexample:intheshallowseas of the Jurassic,thebivalvegeneraPholadomya,TrigoniaandAstarteoccur together inthesame outcrops.At the present day, their distributions are verydifferent:Pholadomyalivesinthedeepoceans,Trigoniainthe warm, shallow water off Australia and Astarte is a cold water form. Thusonemustbeextremelycareful in deducing the life requirements of fossilorganismsfromtheirlivingrelatives.Obviously,theolder the horizons,the more likely areflorasandfaunasto differ frompresent-day populations. I.Nature of the Substrate The substrate is the support on which organisms live. Onland,itconsistsofsoils,whicharerarelyfossilisedandwhose naturedependsonbothbedrockandclimate.Thephysicalaspectof thesecontinentallandscapesisdemonstratedinthecompositionof the vegetationand of the herbivorous animals (flora and fauna of the steppes, forests,etc.). Inaquaticenvironments,thetextureofthesedimentisprimarily relatedto its grain size.Moreover, the establishment of benthic commun-itiesislargely controlled by the nature of the bottom. From this, one can Soft Bottoms21 detenninethe natureof thesubstrateatthemomentwhenit was occu-pied by the organisms. Therearetwo categories of substrate:hard bottoms and soft bottoms. 1.Hard Bottoms Themaintypeof hardsubstrateistherockybottom,thoughtheexo-skeletonof otherorganismsalsocomes intothiscategory.Thehetero-geneityof thesurface,whichcausesacertainroughness, favourscoloni-sation by vagile and sessilebenthos. Hardgrounds,whichare especiallycommon in Jurassic and Cretaceous carbonates,areformedduringa lengthyperiodof interruptionof sedi-mentation(Fig.17).Thisresults in an induration of the sediment. These surfaces are often mineralised. They are colonised by encrusting organisms (bryozoans,bivalves,serpulids,etc.)andboredintobylithophagous animals(sponges,worms,bivalves,cirripedes,crustacea,etc.).These borers penetrate rock and skeletal fragments indiscriminately. Reefs also establish themselves on hard bottoms. Holes made by bOring organisms Bryozoan Oyster Serpulid Encrusting organisms Shell fragment Indurated sediment Fig.17. Section through a hardground in a Bathonian limestone 2.Soft Bottoms Mobilesubstrates,sandsandmuds,havefewepibionticorganisms.The endofauna,however,isboth abundantandvaried.Theburrows and gal-lerysystems which traverse the sediment turn aside when they come into contactwithhardobjects,suchaspebblesandshells.Thus,whenlater thesandsandmudsareinduratedintorock,onecan distinguishthem from boring;. 22Constraints on Living Conditions Thedistributionof burrowing forms isdeterminedbythe grain size of thesediments.Inargillaceous sediments, the amount of organic matter is extremelyimportant,andfavoursmudanddetritusfeeders.Sandspro-videamoremobilebottomwherethewatercirculationiseasy.Their populations arepoorer. II.Salinity Thesalinityof water isprimarily definedasits sodium chloride content. Ingeneral,landorganismsavoidsalt.However, some plants can grow on saline soils(halophytes). Manyaquaticorganisms are inosmotic equilibrium with the surround-ingwater.Other groupshavean efficientosmoregulatory system in their organsandtissues.Dependingontheirabilitytotoleratesalinityvaria-tions, one can distinguish (Fig.18): - stenohaline organisms which do not tolerate salinity variation; - euryhaline organisms which can tolerate significant variations in salinity. 1.Marine Organisms Normal seawater (average 350/00salt) is characterised by stenohaline forms. During geological time, whole groups haveexisted under these conditions: radiolaria,brachiopods,scaphopods,coelenterates(corals),bryozoans, hemichordates,etc.Somestenohalineformsareonlyknownasfossils, includingthearchaeocythids,trilobites,tentaculitids,graptolites,etc. Thehighestfaunaldiversities occur in marine waters of stable salinity. 2.Brackish Water Organisms Euryhalineorganismsareableto colonise environments whose salinity is markedlylowerthanthatofseawater.Speciesadaptedtothesecondi-tionscanbefoundinmostpartsof theanimalkingdom;foraminifera (agglutinatedtest),bivalves(oysters),gastropods,andthecrustacea (ostracodes) areparticularly rich intheseforms. WithinthePhylumBrachipoda,lingulidshaveinhabitated a nearshore environmentsubjecttomajorsalinityvariationssincethePalaeozoic. Theirpresenceindicatesbrackishwater.Similarly,moststromatolites canbeattributedtoalgalstructuresdevelopedclosetotheshorelinein waterofvaryingsalinity(Fig.22).Theeurypterids,giantPalaeozoic Brackish Water Organisms23 j 1--Limits of the marine realm -I Brackish water I True marine I Hypersaline !l environment water "-Salinity0102030 Normal salinity 405060/_ ------j- --3 , ; ====--f--Red algae - - - T - ----==::: Green algae T Blue-green algae I Js RadiolariaI siliconagellates Coccoliths:::::>-Diatoms..:::.:: --II II Calcareous foraminifera -,I Agglutinated test forarns -II Oemosponges >-Calcareous sponge Hexactinellids -----I I Annelids withcalcareous tubes--, "'::::;- -=::Bryozoans _I_BrachiopodS:::>' ----.INII09roTiidS

I , Demosponges -II , Hexactinellids >c::::: Calcisponges , Ahermatypic corals I II -c::::::::::-Hermatypic corals) Annelids withcalcareous tubes I Bryozoans I Brachiopods I Echinoderms iI Chilons and scaphopods II Cephalopods II Bivalves II Gastropods Ostracodes II II Other crustacea I ----l- 1-Fig.21.Distribution of present-day organisms in relation to depth. (Heckel1972) 28 Fig.22. Morphology of stromatolites Constraints on Living Conditions Active algal coating Sectionthrough calcareous lami nae E E o o I '" o o Fig.23.Internalstructureof an oncolith Bivalves, gastropods111IBptjBrachiopodsa. Aspidoceratids Perisphinctids, cardioceratidsCJ CJ Phylloceratids, Iytoceratids Fig. 24.Bathymetric zonation inthe Upper Jurassic of Central Europe. (Zeigler 1972) Turbidity of the Water29 Theyarecommon inahot climate.Oncolithsaresimilar, being nodules afewmillimetresor a fewcentimetres in diameter, formedof concentric laminaeproducedbyalgae(Fig.23).However,onecanalsofindsuch algal structures in freshwater. Depthzonations,oflocalvalue,havebeenestablishedforseveral ancientenvironments.IntheUpperJurassicof Central Europe,Zeigler has described the following faunal successions (Fig.24): - from0-20 m, reef forms are dominant; they are associated with algae, brachiopods,molluscs(gastropods,bivalves)andregularechinoids; ammonites are rare; - from20-50m,bivalvesthrive;theyareaccompaniedbygastropods and irregular echinoids; ammonites are still rare (perisphinctids); - from 40-70 m, bivalves are still abundant; ammonites form20%-30% of the fauna (perisphinctids, aspidoceratids); - below80m,ammonitesaredominant (perisphinctids, aspidoceratids, oppelids,phylloceratids,lytoceratids);bivalvesandgastropodsare rare; brachiopods are still well represented; - atdepthsgreaterthan500m,ammonitesin their turndisappear;all organisms are planktonic (radiolaria). Theremainsof landplants arenotanabsoluteindicator of the prox-imityof landbecausecurrentscancarrythemforgreatdistances.Thus coconutfrondshavebeendredgedfromthePhi1lipinestrench.Plant rootsinsitu inthesediment indicate,on the other hand, that any water must be shallow (for example: the stigmariaofthe Carboniferous forests). Nevertheless, the bathymetric requirements of many aquatic organisms mayhavebeenconsiderablymodifiedduringgeologicaltime.Atthe presentday,the greatoceandeepsarearefugeformanygroupswhich occupiedtheneriticzoneinthepast.This is the case, for example, with thehexactinellidsponges,themonoplacophorians,somedecapodcrus-tacea(eryonids),attachedcrinoids,coelocanthsand,toa lesserextent, theterebratulidsandthecidarids.Someof theseseemto have migrated to deeper waters at the time of the late Cretaceous regression. VI.Turbidity of the Water Tophotosynthesise,aquaticplantsneedlight,clearwater.Suspension feedinganimalsalsoseektheseconditions.Watertoo heavily laden with detrituscanclogtheirfood-gatheringapparatusandevenasphyxiate them.Reeforganismsneedparticularlypurewater.However,some formssuchaslingulids,starfishandseveralbivalveseasilyadaptthem-selves to a turbid environment and a high rate of sedimentation. 30Constraints on Living Conditions VII.Temperature and Climate Living organisms are normally only active within a well-defined temperature range.Even when adult forms can tolerate major thermal variations, repro-duction and the development of juveniles have much stricter requirements. 1.Land Organisms Ondryland,organismshavetofacelargefluctuationsof temperature and humidity associated with the climate. a) The Fauna Onlyhomoeothermic(warmblooded)animals,birdsandmammals,can maintainadegreeof independep.ceof externalenvironmentalvariations andcontinuenormalactivitybelowOC.Poikilothermic(cold-blooded) vertebratesflourishonlywherethereisahighermean temperature. The extictionof the large reptiles of the Mesozoic can doubtless be explained by climatic cooling on alllandmasses. DuringtheQuaternary.thealternationofglacialandinterglacial phases was marked in Europe by a succession of different mammal faunas (Fig.25).Thewarmingwhichcorrespondstothelastinterglacialstage wasfavourabletotheelephantandhippopotamus,whilethelast glacia-tionischaracterisedbyreindeer,mammothsandwoollyrhinoceros, which were protected fromthe coldby a thick coat. b) The Flora Plantsfaithfullyreflectthelocalclimate.Theflora of warm countries is morevariedthanthatof lowerlatitudes.Inadryclimate,plantsshow xerophyticcharacteristics,thick,hairycuticle,recessedstomata,etc.), forexample:theTriassicflora.Ontheotherhand,the Carboniferous flora,whichthrived in the coal swamps, mainly consisted of hygrophytic species with thin cuticle andpoorly developed roots. In post-glacial sediments, palynology hasdemonstrated several climatic fluctuations:cold phases arecharacterised by birch and pine, while hazel, oak andbeech thrived in the warm phases. Thereconstructionof climate fromthe flora must take account of the factthatbothaltitudeandlatitudecanhaveasimilar effectonthe dis-tribution of plants. The Flora 1 7 2 ~ ..... .. " 4 8 31 10 Fig.25.Successionofmammalianfaunasduringtheclimaticoscillationsofthe Quaternary. (Thenius and Kuhn-Schnyder in Theobald1972) Beginningof theQuaternary(1to8).Warmfaunaof the midQuaternary (9 to 13). Coldfaunaof the lateQuaternary(14 to 17).1 Dolichopithecus; 2Epimachairodus; 3Tapirus;4 Hipparion; 5 Mastodon (Anancus) arvernensis; 6 Leptobos; 7 Allohippus; 8Archidiskodon(EZephas)meridionalis;9RhinocerosfromMerck; 10 EZephas anti-quus;11Hippopotamus;12Macaque;13Buffalo; 14Woollyrhinoceros; 15Mam-moth; 16 Reindeer; 17 Musk ox 32Constraints on Living Conditions 2.Aquatic Organisms Thermal variations are less marked in an aquatic environment than on land. a) WarmWater Organisms Araisedtemperaturefavourstheprecipitation of calcium carbonate and itsfixingbyorganisms.Shellsandcarapacesarethickandornamented. Thesecharacteristicsareparticularlystrikingamongstorganismswhich livenear reefs(forexample:thebrachiopodsUncUesand Stringocepha-Iusand the bivalve Eumegalodonof Devonian reefs). Present-dayreefsonlydevelopinwaterwhosetemperatureremains above18C.Fossilreefsbuiltbyhexacoralscanreasonablybeassumed tohavebeenconstructedunder similarconditions.IntheFrenchJura, theirdistributionin space and time during the late Jurassic was previously interpretedastheresultof themigrationof a reef zone fromthe NWto theSEfollowingclimaticcooling(Fig.26).Infact,bathymetricvaria-tioncausedbyaflexingof thecontinentalshelf caneasilyaccountfor the distribution of these reefs. Similarly,rudistsandPalaeozoiccoralsmust haveflourishedin warm water. N.W.S.w. BesanyonEchaillon I Lons-le-5aunierII SI ClaudeII La FaucilleII SaleveI ------.;------------------ ----- -------- --------- --------- -----i------++++ PortlandianTIthonian __ l : . . _ _ ~ _ ~ _ _ ___ ++++++++++ ----t--------------------------------Virgulian pterocian ----------------- ------+++++++++++ Kimmeridgian ++++++++ +++++++ -----------------------4-----Sequanian Rauracian ++++++++ +++++++ i--+-++-+-+-+-+---- ---------- ------- --------- ---- -- -----+++++++ ----+---------------------------------------------------Argovian Oxfordian ___---' ______________________________________________________ . ___L..-___ Fig.26.Distribution in space and time of coralline facies in the Upper Jurassic of the French Jura. (Gignoux1936) b)Cold Water Organisms The low concentration of dissolved lime in cold waters is hardly conducive totheformationof thickexoskeletons.Lowlatitudebivalvesgenerally have small, thin shells.The faunasare less varied andtrue reefsare absent. Siliceousorganismsbecomeproportionatelymoreabundant(diatoms, radiolaria, etc.). Seasonal Cyclicity33 3.Palaeotemperature Measurements Ureyhasshown that the relative abundance of the isotopes 0 16and 0 18 incarbonatesvarieswiththetemperatureof thewater intheenviron-ment of deposition.Theamountof this element in the hard parts of dif-ferentfossilsallows usto calculate the absolute temperature of the water wheretheorganismslived.ThustheUpper Jurassicbelemnitesof Scot-land show that the temperature of the sea at that time was between15C and20C, that the animal probably livedthrough four winters (the curve hasfourminima)andthatthe juvenileslivedinwarmerwaterthanthe olderforms(Fig.27).Thislastobservationprobablyimpliesthatthe youngbelemnites lived in shallower ( thus warmer)water than the pelagic adults. Water temperature 20\ IBo 16 140IDiameter of rostrum o0.200.400.60O.BOf.O1.201.40 em(= age of animal) Fig.27.Palaeotemperatures of theUpperJurassicseainScotlandasdeducedfrom 016/018ratios in a belemnite rostrum. (Modified fromUreyet al.1951) 4.Seasonal Cyclicity Thegrowthofpresent-dayscleractiniansfollowsdiurnalandannual rhythms.Thesevariationsareindicatedbyfinestriationson the surface of the calyces. Between two annual events, one can count about 360 daily growth rings. A similar count on Devoniantetracorals gives higher figures, oftheorderof 400rings.Thus,intheDevonian,theyearmusthave beenabout400 days long. These results can be explained by the progres-sive slowing of the rotation of the earth about its axis. Similarly, the succession of the seasons isreflected in the annual growth ringsof livingtrees(springwoodand autumn wood). A similar zonation 34Constraints on Living Conditions isknowninfossilplantsasfarbackasthe Devonian. This indicates that seasonal climates havebeen established at least since that time. The identification of the different factorswhich influence the distribu-tionof organismsis purely arbitrary. One single factor isnever dominant inanenvironment.Moreover,interactionsoccur.For example, tempera-tureinfluencestheoxygencontentandthesalinityof waterandis,in itstum,determinedbydepth.Inordertoreconstructancientenviron-ments,itisextremlyimportanttobeabletodeterminetheirphysico-chemicalcharacteristicsand,throughthem,toexplainthediversityof habitats and their populations. Chapter 3Evidence of Biological Activity The evidence of biological activity includes remains, other than body fos-sils,whichhavebeenleftinsedimentsby livingorganisms.They reflect differentaspects of life:reproduction (spores, pollen, eggs), feeding (bite marks,coprolites),movement(tracksandtrails),habitat(borrows), etc. Thedifficultiesof interpretingthissortof palaeontological evidence are unique:eggs,coprolitesandtrailsareveryrarelyfoundassociatedwith their maker.In the majority of cases,the makers are unknown. Thisevidence of biological activity reflects the behaviour of organisms. Insofarasthisisa response to environmental conditions, it can provide informationabouttheenvironmentitself.Moreover,thesetracesareof evengreaterinterestsincetheyoften providetheonlyevidenceof life insedimentswhicharelackinginbodyfossils.Also,since their fragility meanstheycannotbetransported,theyareaguaranteethattheorga-nisms were living in the environment in which they werepreserved. I.Evidence of Reproductive Activity 1.Spores and Pollen Sporesandpollen,thestudyof whichformspartof palynology,have mainlybeenusedforthereconstructionoffossilflorasandclimates, especiallyintheTertiaryandQuaternary.However,becauseof their smallsizeandresistance,theyareeasilytransportedbywindand water forlongdistances.Thustheinformationwhichtheycan giveaboutthe vegetation of ancient environments must be usedcarefully. 2.Eggs and Clutches Whentheeggsof oviparousorganismsareprotectedagainstimpactand desiccation by a resistant envelope, they havefossilisationpotential. 36 Evidence of Biological Activity a)Invertebrate EggsandClutches F or over 100 years, small spherical objects, rich in phosphates and organic matter,whichareabundantinPalaeozoicrocks,havebeenidentified as trilobiteeggs.Similarly,Ordovicianchitinozoanshavebeeninterpreted ascephalopod spawn. Estherians(branchiopodcrustacea)fromtheCarboniferous,Triassic and Tertiary have yielded egg clusters from inside their carapaces (Fig. 28). Thewholemasswouldbeeasilydispersedbythewind,whichexplains theabundanceof estheriidsin discontinuous environments such aspools andponds.IntheLowerTriassicof theVosges,theoccurrenceof two typesofeggsuggestsanalternationofgenerationsbetweenclutches whichdevelopimmediately(small,numerouseggs),whichassurethe continuityof theanimalsinthesameenvironment,andlonger-lasting eggs(fewerandlargerinsize),whichrepresentresistantformsforthe dissemination of the species . .. ,.. . ..'... " Fig.28.Shellof conchostracan crusta-cean(estheriid)fromthe Bunter Sand-stone of the Vosges containing eggs Insecteggs(Fig.109)havebeendescribedfromthesamehorizonin theBunterof theVosges.Theeggs,whichhave anaveragediameter of 0.25mm,areencasedinachitinousshellwhichopensalong amedian slit(Fig.29).Theclutchescontainupto3000eggsjoinedtogetherby mucilage.Depending on genus, these are laidout like beads on a necklace or stucktogetherinalumplikethoseof present daychironomids.It is possibletoworkouttheinternalstructuresandtheirrelationtothe Reptiles Fig.29.InsecteggsfromtheBunter Sandstone of the Vosges 37 . 00%0'" , .. ,.{ : .. .. .00(J . . ~ O n ..~ ....1...:17 :: ....... ~ ...... . .- ., .Go (JO ...t%10..... v eJO 1mm . .....- - _ _....J e'; .... ;'., ',. .\) embryo.Thesheathof mucilagewhichsurroundstheeggactsasapro-tection againstthedesiccationproducedduringthedryphasesof the Triassic climate. b)Vertebrate Eggsand Clutches oFish Eggsofcartilaginousfish,selaciansandchimeranshavebeendescribed fromthe Carboniferous andthe Triassic.They wereprotected by a horny shellwhichwasoftenextendedbyfilamentsusedfor fixation (Fig.30). iOReptiles Largeeggs(upto20cmdiameter),oftenclusteredinnests,havebeen foundintheUpperCretaceousof France(BasseProvence,Languedoc, Corbieres),China,Russia,etc.(Fig.31).Theyhavebeenattributedto dinosaurswhichlaidtheirclutchesclosetothebanksof lakesor rivers. Theseeggsareusuallyunhatched.ASenonianexamplefromtheGobi Desertevenshowstheremainsof anembryo.Inthe South of France (in theHautes-Roquesregionatthefootof Mt.SaintVictoire)Dughiand SiruguehaveshownthatshellsfromtheuppermostCretaceousshow interruptionsingrowth.Accordingtothem,thesebreaks,whichinter-ruptedtheformationoftheshellwalls,areduetoabruptcoldspells, 38 E u C\j Chitinous shell Remains of the embryo RxatiOn filaments Fig. 30. Selacian (Paiaeoxy-ris)eggfromtheCarboni-ferousof England. (Pruvost 1930) Evidence of Biological Activity Fig.31.NestofdinosaureggsfromtheCretaceous oftheGobiDesert(afteranAmericanMuseumof Natural History photograph). Each eggis about10cm long whichtemporarilyinterruptedthesecretoryactivityof theoviduct.In theseclimaticdisturbances,theyseeoneof thecauses of the extinction of the large reptiles atthe endof the Mesozoic. iii} Birds Birds'eggscanbe distinguishedfromreptiles' eggsby the microstructure of the shell. They arecommon in severalhorizons of the Tertiary. c)Reasons for Studying EggsandClutches Insect,reptileandbird'seggsaregenerallylaidclose to the shore. There ahighrateof sedimentationwasnecessarytoburythemrapidlyand generally prevent them fromhatching. II.Evidence of Feeding 1.Signs of Predation It ispossibleto seewear andbreakages which have healed during the life-timeoftheanimalonthesurfaceof shells,carapacesandskeletonsof fossilorganisms.Inmostcases,theycanbeattributedtotheactions of predators.Perfectlycircularholes,occurringinvariousshells,aremade Fossil Excrement Fig.32.Bivalveshellbored by a carnivorous gastropod (Natica) 39 bycarnivorousgastropods(naticids,muricids,etc.)whichperforatethe shellsbeforeingestingthesoftparts (Fig.32). One can seemarks leftby echinoidjaws or fishteeth on Jurassic belemnite guards.Bite marks from the teeth of carnivores havebeen described frommany Tertiary and Qua-ternary mammals. 2.Fossil Excrement Invertebratefaecalpelletsformaconsiderablepartof themobilesedi-mentsoftheneriticzone.Inancientrocks,theyappearassphericalor ovalbodieswithadiameterlessthan5mm.Their surfaceoften shows constrictionsor longitudinalgrooves.Elongated faecal pellets with longi-tudinalinternalcanals,common in the Mesozoic and Tertiary, are attrib-utedtodecapod crustaceans (anomours) (Fig.33). The organic matter in faecalpellets may be replacedby glauconite, pyrite or phosphates. ....' .. :'.....'C.:::.:;':,:,::.: ..-"'-.. ::.:-:.::;:::.. ::.....-..:.....:.:'-'.:.;.:.: ..-.... .-.-,.'.,:.:.:.:.::.-... AB Fig.33A, B.Decapod crustacean faecal pellet from the Trias of the mid Prealps. A trans-versesection; B longitudinal section. (Bronnimann etal.1972) Largespecimensof fossilexcrementor coprolites (several centimetres long)areattributedtovertebrates.Theyarecharacterisedbyanabnor-malconcentrationof bonefragmentsor broken shell and by a high level of organic matter or phosphates. 40Evidence of Biological Activity Thecoprolitesofcertainfishhaveatwistedshapewhichhasbeen imposedonthembythespiralvalvuleoftheintestine.Larger-sized examples havebeen attributed to the reptiles (Fig.34). Hyena excrement lendsitself particularlywelltofossilisationbecauseitisrichincalcium derivedfrombones ground upby these animals. 2- 1 0 em Fig.34.Reptilecoprolitefromthe Lias of England. (Buckland in Hiintschel et al. 1968) Special mention shouldbemade of regurgitated pellets fromnocturnal birdsof prey,whichare frequent in Quaternary cavedeposits.They pro-videimportantinformationaboutthemicromammal(rodent)fauna which was the prey of thesebirds. III.Trails and Burrows (Ichnology) Ichnology describes and interprets tracesleft in sediment by animal activ-ity. These traces or ichnofossils (Lebensspurenof German authors) include trails,burrows,mines,etc.Theyaredescribedasexogenous or endogen-ousaccordingtowhethertheyareproduced at the surface or within the sediment. Many animal tracesareproduced asnatural moulds atthe inter-facebetweentwobedsof differinglithologies(forexample:sand-clay): thustheyformepireliefsontheupper sideof thebeds,hyporeliefson their lower side (Fig.35). ----- ---- Jr---- Exogenoustrace ----- ------ ----=-- -------------IHyporelief Fig.3 s.Positionand nomenclature of traces of animalactivity Dwelling Traces41 Ichnofossilsarechieflytheworkofvagilebenthos,morerarelyof terrestrialanimals.It isonlyexceptionallythattheyarefoundwith the animalsthatmadethem.Similartracescanbemadebyanimals belong-ingtodifferentzoologicalgroups.Equally, one animal can produce very differenttracesdependingonthenatureofitsactivity(locomotion, feeding,digging,etc.).Thustheclassificationof ichnofossilsisbased onlyonthebehaviourof organisms,corresponding,toacertainextent, to the demands of the environment. 1.Dwelling Traces Manysuspension-feedingorganismsbuildburrowswhichthey inhabit permanently.Therethey findprotection against predators, and, on occa-sion,againsttemporarydrying-outof theenvironment.Their occupants collect nutrient particles which pass close to the openings of the burrows. Thesehavetobefrequentlyrenewedbecauseofwateraction.Thisis whydwellingtracesarecommoninshallowwaterenvironments,espe-cially in the intertidal zone. Inthehighenergyenvironmentof the intertidal zone, hard substrates arebored into by lithophagous organisms (sponges, annelids, hydrozoans, bivalves,crustacea,echinoderms,etc.)(Fig.36).Onmobilesubstrates, theconstructionandmaintenanceofburrowsrequiresalowlevelof water movement. One can identify two types of habitat: a)simpleburrowsintheformof astraighttubeor pocket. The orga-nismsmaintaincontactwiththesurfaceofthesedimentbymeansof siphons (bivalves) or by the action of a retractile pedicle (lingulids). Arthro-pods (crustacea, some trilobites) protrude their anterior appendages from theburrow,whileseaurchinscirculatethewaterbythemovementof their tube feet. b)V-burrowsconnectto the surface by two openings (Fig. 37). In such dwelling,watercirculationcanbe maintainedby contractions of the ani-mal'sbody(annelids)or bythemovementof appendages(arthropods). Fig.36.Dwellingcavitiesof alithophagous bivalve (Lithophaga).(Zeigler1972) 42 A - -- Opening +----+- Tube H----/- Spreite B 2cm '------' Evidence of Biological Activity Fig.37.Crustacean dwelling burrows (Rhizocorallium).(Gall1971) Fig.38A,B.Developmentof aU-burrowasaresultoftherateof sedimentation.Anormalgrowth; Bfightagainstburialinaturbid environment.(ModifiedfromSei-lacher1967) Whentherateofsedimentationislow,thegrowthof theorganisms requiresanenlargement of the burrow. If this occurs at depth, successive growthstagescanbeseeninthesedimentasspreite spread between the internalwallsof thetwoverticalbranchesof theburrow.Ontheother hand,whentherateof sedimentationishigh,theanimalreacts against burialbycontinuouslyraisingitsburrow:thespreite thus occurson the outsideof theburrow (Fig.38).V-burrowsare made by various animals: annelids (Arenicoia,Polydora),crustacea (Corophium),insects (epheme-ridlarvae),etc. Rhizocorallium isa spreite burrow known fromthe Cam-briantotheTertiary:thescratches on the walls of the tubes suggest it is made by a crustacean (PI.I,Fig.3). 2.Moving and Resting Traces Vagileorganismscreatetracksinthesedimentwhich recordtheir move-ment or their resting marks. Moving Traces43 a)Moving Traces Arthropodsandtetrapod vertebrates leave the marks of their appendages or feet on the surface of an unconsolidated sediment (Figs.39,118). The resultingtraceis generallypreserved in relief on the base of the overlying bed.Whenthesedimentisfinelybedded,theprintscanbetransmitted from one lamina to another. Incertaincases,thearrangement of footprints enables one to identify themakerandthelengthof itsstride.For 19uanadon (Cretaceousdino-saur), one can recognise running,walking and resting tracks. Movementtraces are good depth indicators:reptile and bird footprints areformedbeneathathinlayerofwater(Fig.40);limulidtracksare limited to intertidal waters (Fig.41). Fig.39. Trilobite movement trace(Cruziana) Fig.40.Printofthe lefthind footof a Tri-assicreptile(Cheiro-therium) Q) o oMediumHighVery high Available energy Fig.52.Differentstagesof maturityof adetritalsedimentinrelation to the energy availableduring transport. (Folk1951) Carbonate RocksSS b) Carbonate Rocks Carbonatesaretransportedeither asfragments or in solution. In the first case,theybehaveexactlylikedetritalparticles.Inthe second case, they aredeposited either chemically or through the action of living organisms. Dependingonthe sizeof the calcite crystals, classically one can distin-guish: - micritewhoseelementsarealwayslessthan10microns indiameter (Fig.53);itisformedfromchemicallyor mechanicallyderivedcar-bonatemudsandthusindicatesacalm,current-freeenvironment. Micrite isthe chief constituent of lithographic limestone. - spariteformedbylarger (greater than10microns)clear crystals preci-pitatedinthespacesbetweentherecongisabledebris(Fig.53).This carbonate cementdevelops when micrite does not fillthe intergranular voids.Itspresenceimpliesahighenergyenvironmentof deposition. However,sparitecanalsoformby recrystallisation of smaller crystals. Spa rite 1f!!j.'iiiJ,'tJ!:!,A:d::o,- Echinoderm debris (bioclast) ,I;l')'JH4I!I!!I!-'r- Ool ite Rock debris (Iithoclast) \'.,.

ri. .,:', .' , , \ ".' .. ;B Fig.S3A,B.Thinsectionsof twolimestones.Aooliticlimestone(calcarenite). The roundingof thegrains,thesortingandthe presence of sparite indicate ahigh energy environment.B Chalk (calcilutite). The micritic character of the rock and the presence of planktonic foraminifera indicate a quiet water deposit Ingeneral,detritalsedimentscantellusabouttheirsourceareaand theirmeansoftransport,whilechemicallyororganicallyfonnedrocks tell us more about the nature of the environment of deposition. 56The Sediments 4.Particle Distribution a)Graded Bedding Astheenergylevelof thetransporting medium progressivelydrops, par-ticlesaredepositedindecreasingorderof sizeandgradedbeddingis formed.Whenthishappens,thereisaverticaldecreaseingrainsize (Fig.54).If, ontheotherhand,energyincreaseswithtime,thereisa resultingincreaseingrainsize.Thisgradingcanbeverticalorlateral (Fig.55). Frequently grading is seen by the naked eye asa colour change: thecoarsepart islighterthanthefinepart,whichisricher inclay min-erals and organic matter. Fig.54.Varves:fining-upperiglacialsediments(each sequenceisseveral millimetres thick) Gradedbeddingdevelopsbest inwater.Glacialdeposits, on the other hand,arecharacterizedby poor gradingduetothehigh viscosity of the ice.Claysfullof bouldersaredepositedinbulk during thaws- the geo-logical equivalents arecalledtillites. b) Parting Lineation Partinglineationcanbeseenonbeddingplanesingritsaselongated splinterswithperfectlyparallellongaxes(Fig.56).Thisflakingisthe resultof theorientationandsegregationof particlesduringdeposition. It only occurs in a high energy environment. c) Pebble Orientation Elongatedpebblesarealignedbythe action of currents. On beaches, the longaxesof thepebblesarealignedparalleltothe shore by wavemove-ment.Inafluviatileenvironment,thelongaxesof thepebbleshavea .. Beltorl o50km ,I /Palaeocurrent d!rectionroO./Thickness (inmetres) of the from cross-binding;- Middle Bunter Sandstone Mean diameter of the largest pebble Fig.55.Reconstructionof palaeocurrents in the Middle Bunter Sandstone of eastern FranceandsouthernGermanyfromthelateralgradingofthepebblesandcross-bedding measurements. (F orche1935) Fig.56. Parting lineation on the sur-faceofaslabof sandstone.Arrow indicates current direction 58The Sediments tendency to be alignedeither parallel to or perpendicular to the direction of flow.Irregularly shaped pebbles areanchored in the sedimentby their largest part:the protruding part points downstream. d)Pebble Imbrication Whenflatpebblesaredepositedbya unidirectional current, they lielike tilesof aroof withtheirlongaxisdippingupstream.Thisorientation is frequently seen in fluviatiledeposits (Fig.57). Fig.57.Pebbleimbricationinafluviatiledeposit. Arrow indicates currentdirection II.Observations on Beds:Stratinomy 1.Stratification and Bedding Stratification isthe arrangement of sedimentary deposits in separate hori-zons,thebedsor strata.Theyareseparated fromeach other by bedding planesorbyinterbeddedstrata of adifferentlithology.Each bed repre-sents a sedimentary episode. Withinthesebeds,geometricalstructureswhichareproducedduring deposition can be seen. a) Stratification From the geometry, twotypes of stratification can bedistinguished: - planarparallelstratificationwherethesurfaceswhichdefine the beds arenoticeably parallel over long distances. The deposits may thus have alateralextentof theorderof kilometresor even tens of kilometres. Theyformbeneathbodiesof waterwhichhavea great lateral extent: seas, lakes, etc.; - lenticular stratification where each bed is shaped like a lens whose extent ranges froma fewdecimetres to several tens of metres (Fig.105). These desposits are thus restricted in space:depression or channel fills,dunes reefs, etc. Cross-Bedding59 Fluviatileor tidal channels aredefinedby a basal erosion surface which isirregularandgenerallyconcave(Fig.76).Usuallytheyarefilledin several stages. They often contain locally derived rock fragments. b)Bedding Beddingismostoftenseenasasuccessionof sedimentarylayersona millimetrescalecalledlaminae.Thesedevelopasa result of fluctuations intherateof depositionor inthetypeof sedimentsupplied.Theycan begraded.Caremustbetakennottoconfusesedimentarybedding, whichisofmechanicaloriginandcontemporaneouswithdeposition, withcleavage,whichistectonicallyformed,or withthebanding caused by algae (stromatolites). Withinthebeds,thearrangementof the laminae gives different forms of bedding: i} Horizontal Bedding The surfaces of the laminae areplanar andparallel to the top and bottom of the beds.In a fine-grainedsediment (clay, micrite), horizontal bedding is produced by simple settling-out of particles: it indicates a quiet environ-ment.Incontrast,inacoarse-grainedsediment(grits), it occurs because of the action of currents, in a high energy environment. ii) Cross-Bedding Thelaminaeformanacuteanglewithmajorbedding planes(Fig.58). Thistypeofbeddingdevelopsinaunidirectionalcurrentsystem.The transportedgrains buildanoblique slope on