DOCSLIB.ORG

Orthoceras Limestone" of Southwestern Sardinia (Middle-Upper Silurian) ( * )

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Orthoceras Limestone Mem. Soc. Geol. /t., 20 (1979), 405-423. 9 ff., 4 tabb. PALEOECOLOGICAL REMARKS ON TUE "ORTHOCERAS LIMESTONE" OF SOUTHWESTERN SARDINIA (MIDDLE-UPPER SILURIAN) ( * ) Memoria di MAURIZIO GNOLI (**), GrAN CLEMENTE PAREA (***). FRANCO Russo(**) & ENRICO SERPAGLI (**) (presentata a Siena, nella Seduta /ematica del /8-/9 maggio 1979) CO NTE NT ricco di fauna esclusivamente pelagica nelle parti p age superiori e decisamente tossico verso il fondo. lNTRODUCTION 405 Analisi statistiche ed esperimenti di laborato­ l"Ìo hanno portato gli scriventi a considerare il GEOLOGICAL REMARKS 406 particolare tipo di orientamento presentato dai SEDIMENTOLOGICAL REMARKS 407 fossili come un effetto del moto ondoso. I gusci ed i loro frammenti, sparsi su un fondo di fango Geometry of the "Orthoceras lenses" 407 fine, verrebbero disposti dalle onde a bande suc­ The problem of Nautiloid orientation 410 cessive che rappresenterebbero l'equivalente mec­ Laboratory experiments 411 canico delle increspature di fondo tipiche dei fon­ Orientation analysis of the orthoconic di sabbiosi. Potrebbe trattarsi di un mare epicontinentale nautiloids 413 di profondità limitata tale da permettere al moto GENERAL FEATURES OF THE FAUNA 417 ondoso di agire sul fondo. Nektic organisms associated with the grap- tolites 417 Organisms possibly attached to floating ABSTRACT plants 417 A study of the fauna and of the sedimento­ ENVIRONMENTAL CONCLUSIONS 420 logica! characteristics of the "Orthoceras limestone" REFERENCES 422 has shown that these sediments were deposited in a normally oxygenated sea rich in an exclusively pelagic fauna in the upper parts but definitely KEY WORDS : Shelf environment, death as­ toxic towards the bottom. semblage, sedimentary structures, depth Statistica! analyses along with laboratory ex­ periments have led. the writers to consider that indicators, Silurian. the particular type · of orientation found in the fossils is the result of ware motion. The shells and their fragments, distributed on the fine mud of the bottom, must have been positioned by the RIAS SUNTO waves in successive belts which represent the mechanical equivalent of ripple marks, typical of Dallo studro della fauna e delle caratteristiche sandy bottoms. Possibly this was an epicontinental sedimentologiche dei calcari a « Orthoceras » di sea of Iimited depth so that the ware motion Fluminimaggiore risulta che questi sedimenti si could affect the sea bottom. depositarono in un mare normalmente ossigenato INTRODUCTION (*) Work supported by the Consiglio Naz. delle Ricerche, grants: 78.01881.66, IGCP Project n. 53: Ecostratigraphy and 78.00308.05. The objective of this study was to try (**) Istituto di Paleontologia dell'Università di to define the environmental conditions that Modena, Italy. controlled the deposition of the "Orthoceras (***) Istituto di Geologia dell'Università di Mo­ dena, Italy. limestone" in Southwestern Sardinia. 406 MAURIZIO GNOLI ET Alli Both the fauna content and the litholog­ less flattened prismatic blocks surrounded ical and sedimentological characteristics of by non calcareous pelites. These limestone these limestone are taken into consideration blocks are generally not longer than a meter in this report. From the paleontological and their edges are slightly rounded. The point of view we have tned to determine pelites clearly have flown around the hard the environmental significance of the indi­ blocks which are often folded in various viduai taxa as well as that of the entire ways, sometimes very tightly. association. The sedimentological aspects On the basis of what can be observed of the study were directed towards evalua­ in the field, the breaking up of the calcare­ ting the energetic characteristics of the en­ ous layers and the incorporation of the vironment by means of the sedimentary fragments in the silt-clay matrix have been structures. In particular we based our con­ caused by intense tectonic activity. No signs clusions on the èistribution and orientation of deformation of the blocks in the plastic of the orthoconical shells of nautiloids. state were observed not even at the edges. Further information was obtained from The occasionally observable rounding of the lithological characteristics of the rocks. the edges of the limestone blocks, which is not pronounced however, was caused solely by dissolution and disintegration as­ GEOLOGICAL REMARKS sociated with surface weathering. The "Orthoceras limestones" in the A brief summary of the Silurian rocks is studied region are made,up of sparite or given here in order to piace in perspective microsparite having widely variable crystal the "Orthoceras limestone" dealt with in this sizes, even within the same thin section, paper. (generai between 30 and 300 microns). These Silurian marine sediments, which are sparites must be derived from the recrystal­ exposed in two main areas (lglesiente at lization of a very fine calcareous mud in SW an d Gerrei at SE), are represented chief­ which fragments and shells of orthoceratids ly by black shales rich in graptolites. Well - were scattered with a few bivalves and bedded black limestone with cephalopods some gastropods as described in the para­ ("Orthoceras"), Cardiola, graptolites, gastro­ graph regarding the fauna. pods, brachiopods, ostracods and conodonts The orthoceratid shells have varying occurs- in the upper part of the sequence. sizes from a few millimeters to around 30 On the basis of conodonts, the "Orthoceras centimeters in length for whole specimens. Iimestone" was dated by SERPAGLI (1967, Some fragments of living chambers reach 1971) as Uppermost Wenlockian-Ludlovian a diameter of about 20 centimeters, hence, in age. considering an angle of expansion of approxi­ A complete Silurian stratigraphic record mately 2°, these chambers must have been is unknown in Sardinia since it is impossible part of a 2 meter long shell. to find continuous sequences of fossiliferous In the microspar surrounding the nauti­ marine strata. Furthermore, it is virtually loids, shell fragments of ali dimensions down impossibile to trace individuai beds over to a few microns are present. The overall long distances. Latera! facies changes and aspect is that of a completely random as­ intrusions of magmatic rocks, to which sociation of shells and shell fragments. Con­ mineralized veins are connected, greatly centrati o n of small shells in the "shadows" complicate the geologica! mapping of this of those having greater dimensions were regio n. never observed. Because of the intense tectonic activity Some chemical analyses gave values of and poor outcrops, it is impossible to Ca C03 close to 96-98%, which can certainly measure the thickness of the "Orth.oceras be considered a little in excess given the limestone" with any precision; however, the impossibility of eliminating with certainty overall thickness should be of the order of every spot or veinlet of sparry calcite. X-ray 30 meters. diffraction analyses of the small amount of The "Orthoceras limestones" in the Flu­ insoluble residue, after removal of the or­ minimaggiore area are found as more or ganic fraction, showed the presence of " " PALEOECOLOGICAL REMARKS ON THE ORTHOCERAS LIMESTONE OF SARiliNIA 407 quartz, mica, chlorite and/or montmoril­ cumulation of particular organisms, or sedi­ lonite and feldspar (l). ments derived from them, on certain areas Often the calcareous mud partialiy pen­ of the bottom particularly favorable to etrated the shelis, occupying only the low­ the organisms concerned. In a situation er part and decreasing in thickness towards of this type, there should exist a tran­ the apical portion (fig. l). The remaining sition belt in which the favorable con­ upper parts of the shelis are filled by ditions progressively disappear outwards blocky calcite cement. until they no longer exist. In this way lenticular accumulation would be produced whose dimensions are greater by one or SEDIMENTOLOGICAL REMARKS more orders of magnitude to those of the constituent elements. Various other ways of GEOMETRY OF THE "0RTHOCERAS LENSES" accumulation of Ienticular deposits can be hypothesized, ali of which, however, imply The term "Orthoceras lens", used by the the existence of sedimentary structures or first authors that delt with them {TARICCO, characteristics which change from the center 1921-1922, p. 13; GORTANI, 1922, p. 365; No­ to the margins because of the variation in VARESE & TARICCO, 1922, p. 318-319) and genetic conditions. SERPAGLI recently adopted also by (1970) On the contrary, the most evident aspect and SERPAGLI & GNOLI (1977), is purposely in ali of the blocks of "Orthoceras lime­ not used in this artide since the lenticular stone" examined is the uniformity of the form in any sedimentary body implies the characteristics aver the entire external sur­ existence of different environmental condi­ face and in the observable sections. In ad­ tions "between the thicker center and the dition, the observable blocks have sizes of ends. The difference in environmental con­ the same arder of magnitude of the shells ditions, far example, could be a different they contain and in certain cases the di­ distribution of the action of the current mensions of the blocks are less than those between the bottom and the sides of a of the enclosed shells. channel of which the kns represents the ·From these considerations it foliows that filling. lt is important to note here that if the Orthoceras formations must have origi­ "Orthoceras the so called lenses" represent naliy consisted of an alternation of calcare­
Load more

Recommended publications
  • Nautiloid Shell Morphology
    MEMOIR 13 Nautiloid Shell Morphology By ROUSSEAU H. FLOWER STATEBUREAUOFMINESANDMINERALRESOURCES NEWMEXICOINSTITUTEOFMININGANDTECHNOLOGY CAMPUSSTATION SOCORRO, NEWMEXICO MEMOIR 13 Nautiloid Shell Morphology By ROUSSEAU H. FLOIVER 1964 STATEBUREAUOFMINESANDMINERALRESOURCES NEWMEXICOINSTITUTEOFMININGANDTECHNOLOGY CAMPUSSTATION SOCORRO, NEWMEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Alvin J. Thompson, Director THE REGENTS MEMBERS EXOFFICIO THEHONORABLEJACKM.CAMPBELL ................................ Governor of New Mexico LEONARDDELAY() ................................................... Superintendent of Public Instruction APPOINTEDMEMBERS WILLIAM G. ABBOTT ................................ ................................ ............................... Hobbs EUGENE L. COULSON, M.D ................................................................. Socorro THOMASM.CRAMER ................................ ................................ ................... Carlsbad EVA M. LARRAZOLO (Mrs. Paul F.) ................................................. Albuquerque RICHARDM.ZIMMERLY ................................ ................................ ....... Socorro Published February 1 o, 1964 For Sale by the New Mexico Bureau of Mines & Mineral Resources Campus Station, Socorro, N. Mex.—Price $2.50 Contents Page ABSTRACT ....................................................................................................................................................... 1 INTRODUCTION
    [Show full text]
  • Cambrian Cephalopods
    BULLETIN 40 Cambrian Cephalopods BY ROUSSEAU H. FLOWER 1954 STATE BUREAU OF MINES AND MINERAL RESOURCES NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY CAMPUS STATION SOCORRO, NEW MEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Eugene Callaghan, Director THE REGENTS MEMBERS Ex OFFICIO The Honorable Edwin L. Mechem ...................... Governor of New Mexico Tom Wiley ......................................... Superintendent of Public Instruction APPOINTED MEMBERS Robert W. Botts ...................................................................... Albuquerque Holm 0. Bursum, Jr. ....................................................................... Socorro Thomas M. Cramer ........................................................................ Carlsbad Frank C. DiLuzio ..................................................................... Los Alamos A. A. Kemnitz ................................................................................... Hobbs Contents Page ABSTRACT ...................................................................................................... 1 FOREWORD ................................................................................................... 2 ACKNOWLEDGMENTS ............................................................................. 3 PREVIOUS REPORTS OF CAMBRIAN CEPHALOPODS ................ 4 ADEQUATELY KNOWN CAMBRIAN CEPHALOPODS, with a revision of the Plectronoceratidae ..........................................................7
    [Show full text]
  • Part I. Revision of Buttsoceras. Part II. Notes on the Michelinoceratida
    MEMOIR 10 PART I Revision of Buttsoceras PART II Notes on the Michelinoceratida By ROUSSEAU H. FLOWER 1 9 6 2 STATE BUREAU OF MINES AND MINERAL RESOURCES NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY CAMPUS STATION SOCORRO, NEW MEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Alvin J. Thompson, Director THE REGENTS MEMBERS Ex OFFICIO The Honorable Edwin L. Mechem ........................................ Governor of New Mexico Tom Wiley .......................................................... Superintendent of Public Instruction APPOINTED MEMBERS William G. Abbott ............................................................................................... Hobbs Holm 0. Bursum, Jr. ......................................................................................... Socorro Thomas M. Cramer ......................................................................................... Carlsbad Frank C. DiLuzio ...................................................................................... Albuquerque Eva M. Larrazolo (Mrs. Paul F.) ............................................................... Albuquerque Published October I2, 1962 For Sale by the New Mexico Bureau of Mines & Mineral Resources Campus Station, Socorro, N. Mex.—Price $2.00 Contents PART I REVISION OF BUTTSOCERAS Page ABSTRACT ....................................................................................................................... INTRODUCTION .............................................................................................................................
    [Show full text]
  • The Carboniferous Evolution of Nova Scotia
    Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021 The Carboniferous evolution of Nova Scotia J. H. CALDER Nova Scotia Department of Natural Resources, PO Box 698, Halifax, Nova Scotia, Canada B3J 2T9 Abstract: Nova Scotia during the Carboniferous lay at the heart of palaeoequatorial Euramerica in a broadly intermontane palaeoequatorial setting, the Maritimes-West-European province; to the west rose the orographic barrier imposed by the Appalachian Mountains, and to the south and east the Mauritanide-Hercynide belt. The geological affinity of Nova Scotia to Europe, reflected in elements of the Carboniferous flora and fauna, was mirrored in the evolution of geological thought even before the epochal visits of Sir Charles Lyell. The Maritimes Basin of eastern Canada, born of the Acadian-Caledonian orogeny that witnessed the suture of Iapetus in the Devonian, and shaped thereafter by the inexorable closing of Gondwana and Laurasia, comprises a near complete stratal sequence as great as 12 km thick which spans the Middle Devonian to the Lower Permian. Across the southern Maritimes Basin, in northern Nova Scotia, deep depocentres developed en echelon adjacent to a transform platelet boundary between terranes of Avalon and Gondwanan affinity. The subsequent history of the basins can be summarized as distension and rifting attended by bimodal volcanism waning through the Dinantian, with marked transpression in the Namurian and subsequent persistence of transcurrent movement linking Variscan deformation with Mauritainide-Appalachian convergence and Alleghenian thrusting. This Mid- Carboniferous event is pivotal in the Carboniferous evolution of Nova Scotia. Rapid subsidence adjacent to transcurrent faults in the early Westphalian was succeeded by thermal sag in the later Westphalian and ultimately by basin inversion and unroofing after the early Permian as equatorial Pangaea finally assembled and subsequently rifted again in the Triassic.
    [Show full text]
  • Colour Patterns in Early Devonian Cephalopods from the Barrandian Area: Taphonomy and Taxonomy
    Colour patterns in Early Devonian cephalopods from the Barrandian Area: Taphonomy and taxonomy VOJTĚCH TUREK Turek, V. 2009. Colour patterns in Early Devonian cephalopods from the Barrandian Area: Taphonomy and taxonomy. Acta Palaeontologica Polonica 54 (3): 491–502. DOI: 10.4202/app.2007.0064. Five cephalopod specimens from the Lower Devonian of Bohemia (Czech Republic) preserve colour patterns. They in− clude two taxonomically undeterminable orthoceratoids and three oncocerid nautiloids assigned to the genus Ptenoceras. The two fragments of orthocone cephalopods from the lowest Devonian strata (Lochkovian, Monograptus uniformis Zone) display colour patterns unusual in orthoceratoids. They have irregular undulating and zigzag strips that are pre− served on counterparts of adapertural regions of specimens flattened in shale, despite their original aragonitic shell having been completely dissolved. These are probably the result of the proteinous pigment inside the shell wall, being substituted during diagenesis by secondary minerals leaving only an altered trace of the original shell. Orthoceratoids from sediments unsuitable for preservation of this feature discussed here thus demonstrate an exceptional case of preservation of colour patterns, not only within Devonian cephalopods but also within other Devonian molluscs. Three specimens of Ptenoceras that preserve colour patterns come from younger Lower Devonian strata. Oblique spiral adaperturally bifurcating bands are preserved in P. alatum from the Pragian and zigzags in P. nudum from the Dalejan. Juvenile specimen of Ptenoceras? sp. from the Pragian exhibits highly undulating transversal bands—a pattern resembling colour markings in some Silu− rian oncocerids. Dark grey wavy lines observed on the superficially abraded adapical part of a phragmocone of nautiloid Pseudorutoceras bolli and interpreted formerly to be colour markings are here reinterpreted as secondary pigmented growth lines.
    [Show full text]
  • Smithsonian Miscellaneous Collections
    SMITHSONIAN MISCELLANEOUS COLLECTIOXS. 227 AEEANGEMENT FAMILIES OF MOLLUSKS. PREPARED FOR THE SMITHSONIAN INSTITUTION BY THEODORE GILL, M. D., Ph.D. WASHINGTON: PUBLISHED BY THE SMITHSONIAN INSTITUTION, FEBRUARY, 1871. ^^1 I ADVERTISEMENT. The following list has been prepared by Dr. Theodore Gill, at the request of the Smithsonian Institution, for the purpose of facilitating the arrangement and classification of the Mollusks and Shells of the National Museum ; and as frequent applica- tions for such a list have been received by the Institution, it has been thought advisable to publish it for more extended use. JOSEPH HENRY, Secretary S. I. Smithsonian Institution, Washington, January, 1871 ACCEPTED FOR PUBLICATION, FEBRUARY 28, 1870. (iii ) CONTENTS. VI PAGE Order 17. Monomyaria . 21 " 18. Rudista , 22 Sub-Branch Molluscoidea . 23 Class Tunicata , 23 Order 19. Saccobranchia . 23 " 20. Dactjlobranchia , 24 " 21. Taeniobranchia , 24 " 22. Larvalia , 24 Class Braehiopoda . 25 Order 23. Arthropomata , 25 " . 24. Lyopomata , 26 Class Polyzoa .... 27 Order 25. Phylactolsemata . 27 " 26. Gymnolseraata . 27 " 27. Rhabdopleurse 30 III. List op Authors referred to 31 IV. Index 45 OTRODUCTIO^. OBJECTS. The want of a complete and consistent list of the principal subdivisions of the mollusks having been experienced for some time, and such a list being at length imperatively needed for the arrangement of the collections of the Smithsonian Institution, the present arrangement has been compiled for that purpose. It must be considered simply as a provisional list, embracing the results of the most recent and approved researches into the systematic relations and anatomy of those animals, but from which innova- tions and peculiar views, affecting materially the classification, have been excluded.
    [Show full text]
  • Colour Patterns on Silurian Orthocerid and Pseudorthocerid Conchs from Gotland – Palaeoecological Implications
    Estonian Journal of Earth Sciences, 2015, 64, 1, 74–79 doi: 10.3176/earth.2015.13 Colour patterns on Silurian orthocerid and pseudorthocerid conchs from Gotland – palaeoecological implications Štěpán Mandaa and Vojtěch Turekb a Czech Geological Survey, Klárov 3, 11821 Praha 1, Czech Republic; [email protected] b National Museum, Department of Palaeontology, Václavské náměstí 68, 115 79 Praha 1, Czech Republic; [email protected] Received 30 June 2014, accepted 17 October 2014 Abstract. The longitudinal colour pattern – an adaptively controlled feature functioning in cephalopods as camouflage – is described in two straight-shelled cephalopods from the Silurian of Gotland. A shell of the orthocerid Dawsonoceras annulatum (Sowerby) exhibits relatively broad longitudinal colour bands around the entire shell circumference, which in combination with transverse annuli and undulated growth ridges form a visually reticulate ornament. Such a combination is not known in other Silurian straight-shelled cephalopods. Dawsonoceras annulatum is the only known Palaeozoic cephalopod retaining an almost identical colour pattern in populations inhabiting different palaeo-continents. The shell of the pseudorthocerid Lyecoceras? columnare (Marklin) has densely packed narrow longitudinal colour bands on the entire smooth shell. In this feature the species is very similar to other Silurian and Ordovician pseudorthocerids. However, in Ordovician pseudorthocerids colour bands are restricted dorsally. The type of colouration described herein differs from that of Devonian and younger pseudorthocerids where the shell bears zig-zag bands. Longitudinal colouration around the entire shell circumference supports vertical or subvertical life orientation in both described species. Key words: Silurian, Orthocerida, Pseudorthocerida, colour pattern, palaeoecology. INTRODUCTION poorly known in comparison with oncocerids and discosorids (Nautiloidea).
    [Show full text]
  • Middle Devonian)
    F-l Paleontological Problems of the Hamilton Group (Middle Devonian) H.B. Rollins, N. Eldridge, R.M. Linsley The stratigraphy of the Hamilton Group of the'Middle Devonian of New York State was most recently treated in its entirety by Cooper (1930, 1957). The Hamilton Group of the Chenango Valley (see chart 1) consists primarily of fine clastic sediments and occupies a mid position in this wedge shaped body of rock. In the east the wedge is thickest (about 1,680' in Schoharie Valley (Gruban, 1903, p. 213) and it thins to 285' at Lake Erie in the west (Cooper, 1930, p. 121). In the Chenango Valley the Hamilton Group is 1, 465' thick (op. cit. p. 121) and has a dip to the southwest of 65-75 feet per mile (op. cit. p. 119). The Hamilton Group lies unconformably on the Onondaga Limestone and is overlain unconformably by the Tully Formation. In a very crude sense the Hamilton Group of the Chenango Valley is composed of fine-grained black shales and limestones at the base (the Marcellus Formation) and more clastic units in the upper portion (Skaneateles, Ludlowville and Moscow Formations). However within each of these formations there exists considerable variation from true mud shales through siltstones and up to fine-grained sandstones. The nature of the substrate obviously had a great effect on the faunas associated with them. The black shales are typically associated with a Leiorhynchus fauna, gray shales and siltstones with a Tropidoleptus fauna and the fine-grained sandstones are dominated by bivalves. A more detailed discussion of some of these problems will follow in sections relating to each of the three stops of this trip.
    [Show full text]
  • High-Level Classification of the Nautiloid Cephalopods: a Proposal for the Revision of the Treatise Part K
    Swiss Journal of Palaeontology (2019) 138:65–85 https://doi.org/10.1007/s13358-019-00186-4 (0123456789().,-volV)(0123456789().,- volV) REGULAR RESEARCH ARTICLE High-level classification of the nautiloid cephalopods: a proposal for the revision of the Treatise Part K 1 2 Andy H. King • David H. Evans Received: 4 November 2018 / Accepted: 13 February 2019 / Published online: 14 March 2019 Ó Akademie der Naturwissenschaften Schweiz (SCNAT) 2019 Abstract High-level classification of the nautiloid cephalopods has been largely neglected since the publication of the Russian and American treatises in the early 1960s. Although there is broad general agreement amongst specialists regarding the status of nautiloid orders, there is no real consensus or consistent approach regarding higher ranks and an array of superorders utilising various morphological features has been proposed. With work now commencing on the revision of the Treatise Part K, there is an urgent need for a methodical and standardised approach to the high-level classification of the nautiloids. The scheme proposed here utilizes the form of muscle attachment scars as a diagnostic feature at subclass level; other features (including siphuncular structures and cameral deposits) are employed at ordinal level. We recognise five sub- classes of nautiloid cephalopods (Plectronoceratia, Multiceratia, Tarphyceratia nov., Orthoceratia, Nautilia) and 18 orders including the Order Rioceratida nov. which contains the new family Bactroceratidae. This scheme has the advantage of relative simplicity (it avoids the use of superorders) and presents a balanced approach which reflects the considerable morphological diversity and phylogenetic longevity of the nautiloids in comparison with the ammonoid and coleoid cephalopods.
    [Show full text]
  • Review of the Ordovician Stratigraphy and Fauna of the Anarak Region in Central Iran
    See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/286025445 Review of the Ordovician stratigraphy and fauna of the Anarak Region in Central Iran ARTICLE in ACTA GEOLOGICA POLONICA · JANUARY 2015 Impact Factor: 0.84 · DOI: 10.1515/apg-2015-0022 READS 26 6 AUTHORS, INCLUDING: Leonid E. Popov Vachik Hairapetian National Museum Wales Islamic Azad University Khorasgan (Isfahan) Branch 231 PUBLICATIONS 2,239 CITATIONS 33 PUBLICATIONS 130 CITATIONS SEE PROFILE SEE PROFILE Mansoureh Ghobadi Pour Lars E Holmer Golestan University Uppsala University 69 PUBLICATIONS 365 CITATIONS 211 PUBLICATIONS 2,319 CITATIONS SEE PROFILE SEE PROFILE Available from: Leonid E. Popov Retrieved on: 11 December 2015 Acta Geologica Polonica, Vol. 65 (2015), No. 4, pp. 403–435 DOI: 10.1515/agp-2015-0022 Review of the Ordovician stratigraphy and fauna of the Anarak Region in Central Iran LEONID E. POPOV1, VACHIK HAIRAPETIAN2, DAVID H. EVANS3, MANSOUREH GHOBADI POUR4, LARS E. HOLMER5 and CHRISTIAN BAARS1 1Department of Geology, National Museum of Wales, Cardiff CF10 3NP, Wales, United Kingdom. E-mail: [email protected], [email protected] 2Department of Geology, Isfahan (Khorasgan) Branch, Islamic Azad University, PO Box 81595−158, Isfahan, Iran. E-mail: [email protected] 3Natural England, Suite D, Unex House, Bourges Boulevard, Peterborough PE1 1NG, England, United Kingdom. E-mail: [email protected] 4Department of Geology, Faculty of Sciences, Golestan University, Gorgan, Iran. E-mail: [email protected] 5Institute of Earth Sciences, Palaeobiology, Uppsala University, SE-752 36 Uppsala, Sweden. E-mail: [email protected] ABSTRACT: Popov, L.E., Hairapetian, V., Evans, D.H., Ghobadi Pour, M., Holmer, L.E.
    [Show full text]
  • Ordovician Cephalopod Biofacies of South China and Its Provincialization
    J ournal of China University o f Geosciences , Vol. 17 , No. 3 , p. 221 - 230 , September 2006 ISS N 1002 - 0705 Printed in China Ordovician Cephalopod Biofacies of South China and Its Provincialization Xiao Chuantao*(肖传桃) Faculty o f Earth Sciences , China University o f Geosciences , Wuhan 430074 , China ; Geosciences College , Y angtze University , J ingz hou 434023 , China Chen Zhiyong (陈志勇) Faculty o f Earth Sciences , China University o f Geosciences , Wuhan 430074 , China ; Qinghai Oil f ield Com pany , Dunhuang 736202 , China Liu Li (刘莉) He Youbin (何幼斌) Geosciences College , Y angtze University , J ingz hou 434023 , China ABSTRACT :The research on biofacies and its provincialization is of important significance not only for the increasing of precision of stratigraphic subdivision and correlation in South China, the reconstruction of ancient environment and paleogeography and even the guiding of oil and gas exploration, but also for the study of paleobiogeogrphy and sea level changes of southern China in Ordovician. On the basis of the studies of the ecological characteristics of Ordovician cephalopods from South China , eighteen cephalopod biofacies are recognized and described :(1)Open platform Proterocameroceras biofacies ;(2) Restricted platform Pseudoectenolites-Xiadongoceras biofacies; ( 3 ) Open platform Retroclitendoceras- Pararetroclitendoceras biofacies;(4)Open platform Prona jaceras-Mamagouceras biofacies;(5) Shelf slope-basin Cyclostomiceras biofacies;(6) Open platform Cameroceras-Cyrtovaginoceras biofacies ; (7) Open
    [Show full text]
  • Annual Meeting 1996
    PALAEONTOLOGICAL ASSOCIATION 40th Annual Meeting Lapworth Museum, University of Birmingham 16-19 December 1996 Abstracts Compiled and edited by M. Paul Smith and Alan T. Thomas Print out a form and register for the meeting now! Trilobites, phylogenetic context, and the Palaeozoic Evolutionary Fauna JONATHAN M. ADRAIN Department of Palaeontology, Natural History Museum, Cromwell Road, London SW7 5BD Trilobites represent the dominant component of Sepkoski's (1981, 1984) Cambrian Evolutionary Fauna. As a clade, they reached peak taxonomic diversity from the Late Cambrian to the Middle Ordovician. Their subsequent history reflects crisis at the end-Ordovician mass extinction followed by continuous reduction until their end-Permian disappearance. Conventional interpretation of this pattern recognizes a transition near the base of the Middle Ordovician (Whiterockian), involving a shift in marine communities from earlier trilobite-dominated assemblages to articulate brachiopod- rich faunas of the rapidly radiating Palaeozoic Fauna. The actual mechanisms remain controversial (e. g. passive dilution v. active displacement), but there is little question that trilobites as a whole became relatively minor components of many mid-Palaeozoic communities. The overall pattern of Ordovician-Silurian trilobite decline is, however, misleading. While the clade as a whole was in quantitative taxonomic decline, no single natural subgroup of trilobites has a diversity history corresponding to this cumulative pattern. In addition, the best available estimates of trilobite alpha diversity (Adrain and Westrop, 1996) indicate stasis in within-community trilobite species richness from Upper Cambrian to Upper Silurian. This disparity is accounted for in part by a new phylogeny-based compilation of trilobite generic abundance. When post-Ordovician trilobites are resolved as suprageneric monophyla, these clades may be traced to encompass their Ordovician origins.
    [Show full text]