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2021 (vol. 21)

Biostratigraphic distribution of orbitolinids in the ammonite biozones (Urgonian platform of southeastern France). Part 2: Barremian p.p.
Bruno GRANIER, Bernard CLAVEL, Robert BUSNARDO, Jean CHAROLLAIS, Pierre DESJACQUES & Didier BERT

 | HTML  | PDF [27,925 KB]  | DOI : 10.2110/carnets.2021.2118

 Abstract:   The biostratigraphic distribution of orbitolinids for the Barremian of SE France proposed hereafter is calibrated on the ammonite biozonation. This work is based on the study of eleven sections with orbitolinids associated to macrofossils (ammonites and/or echinids) significant in terms of biostratigraphy or overlain with levels bearing the above macrofossils.

Carnets Geol., vol. 21, no. 18, p. 399-521

Online since October 24, 2021


The ichnospecies Linichnus bromleyi on a Miocene baleen whale radius preserving multiple shark bite-shake traces suggests scavenging
Stephen J. GODFREY & Annie J. LOWRY

 | HTML  | PDF [508 KB]  | DOI : 10.2110/carnets.2021.2117

 Abstract:  An isolated Miocene baleen whale left radius was marked repeatedly by shark bite-shake traces. The radius probably derives from the Plum Point Member of the Calvert Formation, Calvert Cliffs, Calvert County, Maryland, U.S.A. At least three successive bite-shake traces marking the radius, made by multiple teeth, are attributed to the trace fossil Linichnus bromleyi. These bite-shake traces consisting of shallow, thin arching gouges on a radius, likely indicate scavenging rather than active predation. The most likely means of producing the bundle of L. bromleyi within each of the three sets of traces would be through repeated biting as the shark re-positioned the prey in its mouth or, perhaps, by a shark species with multiple functional teeth within its tooth row. If the bite traces were produced by a non-serrated tooth (as they appear to have been), then the most likely candidate would be Carcharodon hastalis.

Carnets Geol., vol. 21, no. 17, p. 391-398

Online since October 24, 2021


New genera and species of ostracods from the El Ma El Abiod Miocene Basin (Tébessa, NE Algeria)
Francesco SCIUTO & Abdelhakim BENKHEDDA

 | HTML  | PDF [10,561 KB]  | DOI : 10.2110/carnets.2021.2116

 Abstract:  Two new ostracod genera of the family Trachyleberididae Sylvester-Bradley, 1948, each based on a new species, are described and commented here. The specimens were collected in Tortonian sediments cropping out at El Hadjra Safra in the El Ma El Abiod basin (region of Tébessa, north-eastern Algeria).

Carnets Geol., vol. 21, no. 16, p. 383-390

Online since October 24, 2021


Nomenclatural Note, p. 180


The late Berriasian early evolutionary burst of the Orbitolinidae: New insights into taxonomy, origin, diversification and phylogeny of the family based on data from eastern Serbia
Felix SCHLAGINTWEIT & Ioan I. BUCUR

 | HTML  | PDF [10,561 KB]  | DOI : 10.2110/carnets.2021.2115

 Abstract:  New data from the Carpatho-Balkanides of eastern Serbia evidence the more or less near-simultaneous "explosive" first appearances of several genera of the Orbitolinidae in the late Berriasian. Most of the observed taxa were previously recorded from strata not older than the Late Hauterivian (= classical Urgonian of southeastern France), evidence that these ages refer to local first appearance data. The diversified assemblage from Serbia includes representatives of the subfamilies Dictyoconinae: genera Cribellopsis Arnaud-Vanneau, Montseciella Cherchi & Schroeder, Orbitolinopsis Henson, Urgonina Foury & Moullade, Valserina Schroeder & Conrad, Vanneauina Schlagintweit, and Dictyorbitolininae: genus Paracoskinolina Moullade. Representatives of the Orbitolininae (with complex embryo) have not been observed. They appeared later in the fossil record seemingly during the Late Hauterivian-early Barremian. All together 17 taxa are reported, of which three in open nomenclature. A new species is described as Cribellopsis sudari n. sp. The majority of the observed species display medium- to high-conical tests and a rather simple exoskeleton lacking horizontal partitions (rafters). The new data contradict a phylogenetic evolution of distinct genera displaying different internal test structures one after the other in time (= ancestor-descendant relationships) as postulated by some authors. The explosive radiation ("early burst") of the Orbitolinidae in the late Berriasian is accompanied by the first appearance date of several other large benthic foraminifera including mostly agglutinating (e.g., Ammocycloloculina, Choffatella, Drevennia, Eclusia, Moulladella, Pfenderina, Pseudotextulariella) but also complex porcelaneous taxa (Pavlovcevina) providing evidence for a bioevent in this time period that exceeds the number of taxa originating in the previous (Tithonian) and the following stage (Valanginian). The early evolutionary history of the Orbitolinidae can be considered a classical example of adaptive radiation within the clade's history.

Carnets Geol., vol. 21, no. 15, p. 343-382

Online since August 17, 2021


Nomenclatural Note, p. 136


Rudist bivalves (Hippuritoidea) from the Clifton Limestone (Lower Campanian) of western Jamaica and a reassessment of the genus Vaccinites in the Americas
Simon F. MITCHELL

 | HTML  | PDF [3,583 KB]  | DOI : 10.2110/carnets.2021.2114

 Abstract:  The lower Campanian (Upper Cretaceous) Clifton Limestone of Jamaica yields three species of hippuritid bivalve: Barrettia ruseae Chubb, Whitfieldiella luceae sp. nov. and Vaccinites vermunti Mac Gillavry, and the plagioptychid: Plagioptychus sp. The hippuritids are described in detail using statistics. Barrettia ruseae is demonstrated to be a more primitive species of Barrettia than B. monilifera Woodward or B. multilirata Whitfield, and the species Whitfieldiella luceae is shown to be a more primitive species of Whitfieldiella than W. gigas Chubb. The specimens of Vaccinites from the Clifton Limestone are compared with populations of Vaccinites from elsewhere in the Americas, and five species (probably representing a single evolutionary lineage) are recognized: V. alencasteri sp. nov. (?late Turonian-?Coniacian), V. martini Mac Gillavry (probably early to mid Santonian), V. macgillavryi Palmer (probably mid to late Santonian), V. vermunti Mac Gillavry (earliest Campanian), and V. temazcali sp. nov. (late early Campanian). The Vaccinites species can be distinguished using statistical techniques. The ages of the Clifton Limestone and the five Vaccinites species are reviewed. This research demonstrates the value of using hippuritids for biostratigraphy in the Upper Cretaceous of the Americas.

Carnets Geol., vol. 21, no. 14, p. 315-341

Online since July 7, 2021


Nomenclatural Note, p. 342


Kimmeridgian and early Tithonian cephalopods from the Kisújbánya Limestone Formation, Zengővárkony (Mecsek Mountains, southern Hungary), their faunal composition, palaeobiogeographic affinities, and taphonomic character
László BUJTOR, Richárd ALBRECHT, Csaba FARKAS, Bertalan MAKÓ, Dávid MARÓTI & Ákos MIKLÓSY

 | HTML  | PDF [3,000 KB]  | DOI : 10.2110/carnets.2021.2113

 Abstract:  A new collection at Zengővárkony (Mecsek Mountains, Hungary) provided a rich and diverse but poorly preserved cephalopod-dominated fossil assemblage representing the Kimmeridgian and the lower Tithonian. The material came from mixed scree, soil, and amongst roots affected by weathering processes having been exposed to the elements for a long time. The nautiloid Pseudaganides strambergensis is the first record from the Mecsek Mountains. Due to the weathering, the ammonite fauna consists of mainly fragmentary and dissolved individuals that comprises 528 specimens belonging to 34 species and 30 genera out of which 20 species and 15 genera are reported for the first time from the Mecsek Mountains. The fauna includes specimens of known taxa. No new taxa are introduced. Based on the comparison with other faunas, this assemblage most closely resembles the fauna of the Venetian Alps (Italy). Additional faunal elements include aptychi (Laevaptychus latus, Lamellaptychus murocostatus), belemnites (Hibolithes semisulcatus), and an indetermined brachiopod. The first record of Spiraserpula spirolinites, an encrusting fossil polychaete preserved on the internal mould of a Taramelliceras shell fragment indicates favourable bottom conditions for the epifauna. The presence of Aspidoceras caletanum, Gravesia aff. gigas, and Pseudowaagenia inerme indicates faunal connections with the Submediterranean Province of the Tethys, which is in line with the tectonic and palaeogeographical position of the Mecsek Zone during the Late Jurassic. The ammonite assemblage represents elements of five Tethysian ammonite zones of the Kimmeridgian and Tithonian. The lower Kimmeridgian Herbichi Zone is indicated by Streblites tenuilobatus and Praesimoceras herbichi. The upper Kimmeridgian Acanthicum Zone is indicated by Aspidoceras acanthicum, and the Cavouri Zone by Mesosimoceras cavouri and Aspidoceras caletanum. The upper Kimmeridgian Beckeri Zone is suggested by Hybonoticeras pressulum and Pseudowaagenia inerme. Whereas Gravesia aff. gigas, Lithacoceras aff. siliceum, and Malagasites? denseplicatus are faunal elements characterising the Early Tithonian Hybonotum Zone. Phylloceratid and lytoceratid specimens account only for 12% of the fauna, while the majority of the specimens belong to the Oppeliidae and Ataxioceratidae (60%).

Carnets Geol., vol. 21, no. 13, p. 265-314

Online since July 4, 2021


The Cretaceous nautiloid genus Anglonautilus Spath, 1927, in France
Cyril BAUDOUIN, Gérard DELANOY, Jens LEHMANN, Camille FRAU, Roland GONNET & Jean VERMEULEN

 | HTML  | PDF [4,157 KB]  | DOI : 10.2110/carnets.2021.2112

 Abstract:  The occurrence of the nautiloid genus Anglonautilus Spath in France was limited to the report of Anglonautilus dorsoplicatus (Wiedmann) from the Albian of Escragnolles (Alpes-Maritimes) and Anglonautilus sp. from the Aptian of Les Ferres (Alpes-Maritimes). Here we document the presence of the successive species Anglonautilus praeundulatus Lehmann et al., Anglonautilus undulatus (Sowerby) and Anglonautilus dorsoplicatus (Wiedmann) from the Cretaceous of France. The stratigraphic range of Anglonautilus Spath, hitherto unknown before Aptian times is extended downward to the Hauterivian. The Hauterivian species Nautilus begudensis Kilian & Reboul, sometimes assigned to the genus Anglonautilus Spath, is revised and re-assigned to the genus Cymatoceras Hyatt.

Carnets Geol., vol. 21, no. 12, p. 235-263

Online since June 24, 2021


New insights into the depositional environment and stratigraphic position of the Gugu Breccia (Pădurea Craiului Mountains, Romania)
Traian SUCIU, George PLEŞ, Tudor TĂMAŞ, Ioan I. BUCUR, Emanoil SĂSĂRAN & Ioan COCIUBA

 | HTML  | PDF [3,293 KB]  | DOI : 10.2110/carnets.2021.2111

 Abstract:  The study of the carbonate clasts and matrix of a problematic sedimentary formation (the Gugu Breccia) from the Pădurea Craiului Mountains reveals new information concerning its depositional environment and stratigraphic position. The identified microfacies and micropaleontological assemblages demonstrate that all the sampled limestone clasts from the Gugu Breccia represent remnants of a fragmented Urgonian-type carbonate platform. The Barremian age of the clasts suggests that the stratigraphic position of the Gugu Breccia at its type locality could be uppermost Barremian-lowermost Aptian, a fact demonstrated also by the absence of elements from Lower Cretaceous carbonate platforms higher in the stratigraphic column (e.g., Aptian or Albian) of the Bihor Unit. The sedimentological observations together with the matrix mineralogy bring new arguments for the recognition of terrigenous input during the formation of the Gugu Breccia.

Carnets Geol., vol. 21, no. 11, p. 215-233

Online since June 24, 2021


Another thermophilic "Miocene survivor" from the Italian Pliocene: A geologically young occurrence of the pelagic eagle ray Aetobatus in the Euro-Mediterranean region
Alberto COLLARETA, Marco MERELLA, Simone CASATI, Giovanni COLETTI & Andrea DI CENCIO

 | HTML  | PDF [669 KB]  | DOI : 10.2110/carnets.2021.2110

 Abstract:  Aetobatus (Myliobatiformes: Aetobatidae) is a living genus of eagle rays that occurs in shallow-marine, tropical and subtropical environments of the Atlantic, Pacific, and Indian Oceans. Nowadays, Aetobatus does not inhabit the cool- to warm-temperate European and Mediterranean waters, though it is known from this broad region by virtue of several fossil teeth ranging chronostratigraphically from the lower Palaeogene to the upper Neogene. The present paper reports on a fossil aetobatid tooth discovered in mid-Pliocene (upper Zanclean to lower Piacenzian, 3.82-3.19 Ma) marine deposits exposed in the vicinities of Certaldo (Tuscany, Italy) and identified as belonging to †Aetobatus cf. cappettai. This specimen comprises the youngest occurrence of Aetobatus along the coasts of mainland Europe; furthermore, together with previous finds from roughly coeval deposits of Mallorca (Balearic Islands, Spain), it represents the most recent record of this genus in the whole Euro-Mediterranean region. In light of the environmental preferences of extant Aetobatus spp., our discovery suggests palaeoenvironmental conditions favourable to the persistence of tropical/subtropical taxa of "Miocene survivors" along the Pliocene coasts of Tuscany. In addition, it raises the question of whether or not the Messinian Salinity Crisis really resulted in the complete collapse of the Mediterranean marine biota and in the subsequent recolonisation of the Mediterranean Basin from the adjoining Atlantic waters and/or scattered marginal intrabasinal refugia at the beginning of the Pliocene. The possibility of Aetobatus recolonising the Mediterranean Sea through the Suez Canal in the near future is discussed.

Carnets Geol., vol. 21, no. 10, p. 203-214

Online since June 24, 2021


The Kalkowsky Project - Chapter I. Ooid - stromatoid relationship in a stromatolite from the Maiz Gordo Fm (Argentina)
Bruno R.C. GRANIER & Philippe LAPOINTE

 | HTML  | PDF [1,400 KB]  | DOI : 10.2110/carnets.2021.2109

 Abstract:  The comparative study of oolites and stromatolites demonstrates striking similarities between Kalkowsky's German Triassic material (drawn from the scientific literature) and our Argentinian Paleogene material. However, the latter better illustrates that ooids and stromatoids, hence oolites and stromatolites, which share the same dual (i.e., organic and mineral) nature, are merely the end-members of a continuum of microbial carbonate structures.

Carnets Geol., vol. 21, no. 9, p. 193-201

Online since June 14, 2021


Messinian ostracodes from the western Betic Strait (SW Spain)
Verónica ROMERO, Francisco RUIZ, María Luz GONZÁLEZ-REGALADO, Josep TOSQUELLA, Manuel ABAD, Tatiana IZQUIERDO, Antonio TOSCANO & Paula GÓMEZ

 | HTML  | PDF [620 KB]  | DOI : 10.2110/carnets.2021.2108

 Abstract:  During the Neogene, the Betic Strait was one of the gateways that connected the Atlantic Ocean and the Mediterranean Sea. In this paper, we have analyzed the ostracod faunas of samples collected from sediments crossed by a long borehole in southwestern Spain. These sediments were deposited in the Betic strait just before the Messinian Salinity Crisis. During the middle Messinian (6.8-6.0 Ma), the scarce and low diversified ostracod assemblages (Krithe, Parakrithe, Henryhowella) are typical of upper bathyal palaeoenvironments (200-400 m water depth). This period includes a short transition (6.26-6.25 Ma) to outer neritic palaeoenvironments, coinciding with a glaciation and characterized by the presence of Acanthocythereis hystrix (Reuss, 1850) and the disappearance of Krithe and Parakrithe. The most abundant species have a wide biostratigraphic distribution, most of them ranging from the Tortonian until the Holocene.

Carnets Geol., vol. 21, no. 8, p. 181-192

Online since April 1, 2021


Jurassian brachiopods of the Valanginian - Hauterivian interval. Their contribution to the dating of the Salima Formation in Mount Lebanon
Yves ALMÉRAS, Serge FERRY, Bruno R.C. GRANIER & Yann MERRAN

 | HTML  | PDF [1,734 KB]  | DOI : 10.2110/carnets.2021.2107

 Abstract:  The Jurassian French or Swiss outcrops of the lowermost Cretaceous (Valanginian or Hauterivian) yield numerous brachiopod species including 3 species: Lamellaerhynchia desori (Loriol in Pictet & Campiche, 1872), Sulcirhynchia valangiensis (Loriol, 1864), and Terebratulina arzierensis (Loriol, 1864), which are not found in Lebanon. The fossiliferous site of the Salima Formation at Zeghrine, a locality close to Bikfaya (Mount Lebanon), yields an assemblage made of Belothyris pseudojurensis (Leymerie, 1842), Lamellaerhynchia hauteriviensis Burri, 1953, Loriolithyris valdensis (Loriol, 1868), Lor. latifrons (Pictet, 1872), Sellithyris carteroniana (Orbigny, 1847), and Terebratulina biauriculata Orbigny, 1850; all are also present in Jurassian localities. On the basis of the study of its brachiopod assemblage, the Salima Formation is therefore ascribed an undifferentiated Valanginian age.

Carnets Geol., vol. 21, no. 7, p. 163-179

Online since March 24, 2021


First record of late Campanian paleoceanographic and paleoclimatic changes, Arabian Platform, Mazidag-Mardin area, SE Turkey
İsmail Ömer YILMAZ, Izzet HOŞGÖR, Sevinç ÖZKAN-ALTINER, Michael WAGREICH & Jiří KVAČEK

 | HTML  | PDF [1,897 KB]  | DOI : 10.2110/carnets.2021.2106

 Abstract:  The sedimentology, geochemistry and paleontology of the pelagic upper Campanian Maastrichtian Bozova Formation in the "Mazidag" (Mazıdağı) - Mardin area, SE Turkey, reveal paleoceanographic and paleoecological changes for the first time. A 119.25 m-thick composite stratigraphic section is characterized by alternating marls, clayey limestones, shales, and black shales; no coarse siliciclastic admixture or turbidite intercalations were recorded in the section. Biostratigraphic data indicate the presence of the Radotruncana calcarata Zone, and the UC15de/UC16 nannofossil zones. Stable isotope and elemental geochemical analyses have been carried out in the studied section. The isotope curves display similar patterns compared to reference curves from European and Chinese basins in the same interval. The prominent negative carbon isotope excursion determined in the upper interval can be correlated with the Late Campanian Event. Proxy elements display generally two relative rising trends in productivity from the lower part and the middle part of the succession. The lower part of the section records relatively more dysoxic/anoxic conditions and coincides with common black shale beds.
The presence of both diverse planktonic foraminifera and calcareous nannofossils in the studied interval indicates a fully marine, warm-water, low-latitude Tethysian oceanic environment. In addition, the plant fossils derived from the nearby land mass indicate that a tropical humid climate was similar to that in northeast Australia. Therefore, warm water, tropical humid atmospheric conditions developed in the studied area causing the rise in productivity, precipitation and transportation of plant debris into offshore environments.

Carnets Geol., vol. 21, no. 6, p. 137-162

Online since March 24, 2021


Bioerosion in Ostrea lamellosa shells from the Messinian of the Tafna basin (NW Algeria)
Mohammed N. NAIMI, Olev VINN & Amine CHERIF

 | HTML  | PDF [1,139 KB]  | DOI : 10.2110/carnets.2021.2105

 Abstract:  Bioerosional trace fossils (borings) are reported for the first time in Algeria. Three ichnotaxa observed in the shells of Ostrea lamellosa from the lower Messinian (upper Miocene) deposits of the Tafna basin (NW Algeria) are described. The ichnotaxa are Entobia cf. geometrica, Gastrochaenolites cf. torpedo and Trypanites isp.. Ostrea lamellosa shells are encrusted by balanid barnacles which are bored by Trypanites isp.. The ichnoassemblage is assigned to the Trypanites ichnofacies. Besides the bioerosion and encrustation described herein, specimens permitted the identification of the different phases of the Messinian transgression across the Souk el Khemis shoal.

Carnets Geol., vol. 21, no. 5, p. 127-135

Online since February 28, 2021


Mediterranean Neocomian belemnites, part 5: Valanginian temporal distribution and zonation (and some lithological remarks)
Nico M.M. JANSSEN

 | HTML  | PDF [5,238 KB]  | DOI : 10.2110/carnets.2021.2104

 Abstract:  A zonation based on the temporal distribution of belemnites is presented for the Valanginian and its boundaries. It is calibrated on ammonite controlled and bed-by-bed correlated sections from the pre-Vocontian Basin (southeast France). Three new sections are introduced herein that have previously not been investigated. All together, seven zones and six subzones are introduced. In addition, both within the Vocontian area, as well as outside (Bulgaria, Crimea, Czech Republic, France, Hungary, Morocco, Romania, Slovakia, Spain, Switzerland), differences regarding the spatial distribution of belemnites are investigated. Also, in two addenda, some remarks are given regarding lithological oddities.

Carnets Geol., vol. 21, no. 4, p. 67-126

Online since February 28, 2021


Revision of Ostrea (Gigantostrea) gigantica Solander var. oligoplana Sacco and Ostrea (Ostrea) isseli Rovereto (Oligocene, Tertiary Piedmont Basin, NW Italy)
Maria Cristina BONCI, Davide DAGNINO, Andrea MANDARINO, Aaron MAZZINI & Michele PIAZZA

 | HTML  | PDF [1,573 KB]  | DOI : 10.2110/carnets.2021.2103

 Abstract:  The aim of this paper is the revision and redocumentation of Ostrea (Gigantostrea) gigantica Solander var. oligoplana Sacco, 1897, Ostrea (Ostrea) isseli n. denom. Rovereto, 1897, and Ostrea (Ostrea) isseli n. denom. var. elongata Rovereto, 1897. These taxa are from the Oligocene strata of the Molare Formation (Tertiary Piedmont Basin, southern Piedmont - central Liguria, NW Italy). The syntypes of O. (G.) gigantica var. oligoplana are in the "Collezione Bellardi e Sacco", at the Museo Regionale di Scienze Naturali di Torino; the syntypes of O. (O.) isseli and O. (O.) isseli var. elongata are in the "Collezione BTP" (BTP Collection, at the Dipartimento di Scienze della Terra, dell'Ambiente e della Vita - DISTAV - of the Universitŕ di Genova). The var. oligoplana is here moved to the species rank and allocated to the genus Pycnodonte Fischer von Waldheim, 1835. O. (O.) isseli and O. (O.) isseli var. elongata are recognized as junior synonyms of the Sacco's taxon. Rovereto (1897) compared his new species with Ostrea subgigantea Raulin & Delbos, 1855, a poorly known taxon, that is here figured for the first time and shown to represent a species different from P. oligoplana (Sacco, 1897).

Carnets Geol., vol. 21, no. 3, p. 55-66

Online since February 24, 2021


Systematic revision and evolution of the Tithonian family Chitinoidellidae Trejo, 1975
Mohamed BENZAGGAGH

 | HTML  | PDF [1,884 KB]  | DOI : 10.2110/carnets.2021.2102

 Abstract:  Several new genera and species of the family Chitinoidellidae Trejo, 1975, were erected by Pop (1997, 1998a, 1998b). Some of these taxa are justified, but others are inadequately defined, and require revision. I discuss herein the non-validity of some taxa and propose a new systematic classification and an evolutionary framework for the family Chitinoidellidae, with two subfamilies: 1) Dobeninae, which include small-sized chitinoidellids, with the genera Borziella Pop, 1997, Carpathella Pop, 1998a, Daciella Pop, 1998a (amended), Dobenilla n. gen., and Popiella Reháková, 2002, and 2) Bonetinae, which includes larger-sized chitinoidellids, with the genera Bermudeziella n. gen., Bonetilla n. gen., and Furrazolaia n. gen.. These two families are separated in time. Small species of the subfamily Dobeninae characterise the Dobeni Subzone (Ponti ammonite Zone) and disappear immediately before the occurrence of the larger specimens of the subfamily Bonetinae, which characterise the Boneti Subzone (Microcanthum p.p. ammonite Zone).

Carnets Geol., vol. 21, no. 2, p. 27-53

Online since February 15, 2021


Nomenclatural Note, p. 54


Apianella nom. nov. (Dasycladales, Triploporellaceae): New name for the preoccupied algal genus Apinella Granier et al., 1986
Bruno GRANIER & François MICHAUD

 | PDF [123 KB]  | DOI : 10.2110/carnets.2021.21NN1

 
Carnets Geol., vol. 20, Nomenclatural Note 1, p. 26

Online since January 21, 2021


Bacinella, a discrete type of Mesozoic calcimicrobial structure
Bruno R.C. GRANIER

 | HTML  | PDF [3,800 KB]  | DOI : 10.2110/carnets.2021.2101

 Abstract:  The controversy surrounding Bacinella irregularis Radoičić, 1959, and Lithocodium aggregatum Elliott, 1956, has involved both sedimentologists and paleontologists. Arguments to exclude them from the Codiaceae are reviewed. The same arguments may be advanced to exclude their ascription to most other organisms. The only hypothesis resisting all elements of disproof is that of a consortium involving microbial communities. Accordingly, these structures are treated here as biosedimentary structures, namely bacinella structures, and not as taxa. One of the features specific to the organisms that built these structures is their strong corroding ability, as shown by the examples of fossils partly or fully cannibalized. This represents one state of corrosion beyond surficial etching and borings. Besides their capacity to corrode calcareous substrates, these microbial organisms formed nodules or oncoids and even built biostromes, which, depending on their stage of development, may have formed soft, firm or even hard substrates. However, to our knowledge, microbial communities contributing to bacinella structures never built up any bioherm. To complete this summary review, a building-block model that coherently takes into account most architectural variations is presented in the form of a figure sketch. The endolithic foraminifer Troglotella incrustans, which is commonly found associated with bacinella structures, is not an encruster or a borer. Lastly, contrary to certain erroneous hypotheses, no major bacinella episode has been ever found coeval with any significant Oceanic Anoxic Event.

Carnets Geol., vol. 21, no. 1, p. 1-25

Online since January 21, 2021


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