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2024 (vol. 24)

The Kalkowsky Project - Chapter VI. A panorama of synsedimentary broken ooids
Bruno R.C. GRANIER & Philippe LAPOINTE

 | HTML  | PDF [3,988 KB]  | DOI: 10.2110/carnets.2024.2405

 Abstract:  Broken ooids are known to occur in both aragonitic and calcitic ooids with radial fabrics. In the literature, it has been suggested that synsedimentary breakage could be related to attrition/mechanical impacts, hypersalinity, or desiccation. However, this paper demonstrates that none of the aforementioned phenomena provides a valid explanation. Although the exact process remains unknown (potentially involving some synsedimentary recrystallization), it is shown that: 1) the breakage is genetically linked to the radial fabrics; 2) the ratio of ooid breakages increases with the relative thickness of the radial cortical layers; 3) fracture growth in broken ooids proceeds centripetally.

Carnets Geol., vol. 24, no. 5, p. 91-112

Online since February 29, 2024


A new record of ground sloth in the Ribeira de Iguape valley, southeastern Brazil
Artur CHAHUD, Gabriella da C. PEREIRA, Paulo R. de O. COSTA & Mercedes OKUMURA

 | HTML  | PDF [377 KB]  | DOI: 10.2110/carnets.2024.2404

 Abstract:  In the early 1980s, an assemblage of extinct and extant vertebrates was collected from the Abismo Ponta de Flecha, a vertical cave in southern São Paulo, Brazil, for archaeological, geological, and paleontological analyses. While materials identified as ground sloths have been referenced in earlier publications, they have never been thoroughly described. In this study, we provide the first detailed description of a large, previously unidentified taxon found in Brazil, interpreted herein as belonging to the family Nothrotheriidae. Although direct dating of the specimen was not possible, other dated occurrences from the Ribeira de Iguape Valley suggest that it may have inhabited the region during the Late Pleistocene, coinciding with the local presence of a dense forest cover.

Carnets Geol., vol. 24, no. 4, p. 83-89

Online since January 31, 2024


The Kalkowsky Project - Chapter V. Asymmetric ooids from the Yacoraite Formation (Argentina)
Bruno R.C. GRANIER & Philippe LAPOINTE

 | HTML  | PDF [2,420 KB]  | DOI: 10.2110/carnets.2024.2403

 Abstract:  Asymmetric ooids are documented in a brackish Maastrichtian to Danian paleolake in NW Argentina. Their distinctive asymmetric growth pattern is likely related to an uneven distribution of the Extracellular Polymeric Substances (EPS) around the coated allochem, within which calcite fibers (i.e., the 'fibrite') have grown. This pattern is unlikely to be mistaken for that of other 'eccentric' ooids, such as wobbly ooids, spiny ooids, hiatus ooids, half-moon ooids, 'broken' ooids sensu lato, or collapsed oomolds (referred to as 'distorted' ooids).

Carnets Geol., vol. 24, no. 3, p. 75-82

Online since January 20, 2024


The Central South Atlantic: The origin of its waters, its evolution and effects beyond
Ricardo L.M. AZEVEDO, Rogério L. ANTUNES, Mauro D.R. BRUNO, Thomas R. FAIRCHILD & Dimas DIAS-BRITO

 | HTML  | PDF [3,554 KB]  | DOI: 10.2110/carnets.2024.2402

 Abstract:  The primitive sea that occupied the Central South Atlantic (CSA), part of the intra-Gondwana rift during the Early Cretaceous, allowed precipitation of an extensive and thick layer of evaporites, the Ibura Salt, followed by the deposition of a prominent Albian carbonate package. Although the shallow platform facies do not contain classical benthic Tethys markers, the pelagic open sea carbonates are essentially dominated by planktonic elements coming from the Tethys Realm. This condition led some researchers to think that Tethys waters also contributed to salt formation, an idea that clashes with the geotectonic model of northward separation of Africa and South America and ingression of predominantly Austral marine waters. Now, a new controversy arises as to the age of this salt layer when trying to position bio-events and lithological and chemostratigraphic markers from these rocks with respect to established data for the Global Boundary Stratotype Section and Point for the Aptian/Albian boundary (GSSP-Alb). Biochronostratigraphic information on planktonic foraminifera points to an Aptian age as opposed to the earliest Albian traditionally accepted for the carbonate section that overlies the giant salt layer. On the other hand, stratigraphic and geochronological data suggest an age of 113 Ma for the base of the salt, very near to the 113.2 ± 0.1 Ma arbitrated for the GSSP-Alb. In this study, we adopt the base of the evaporite bed as the Aptian/Albian boundary in the CSA, Equatorial South Atlantic (ESA), and northeastern Brazilian interior basins (BNE) as well. Based on these criteria, a broad review and the integration of available information have led to new interpretations regarding the earliest phase of these segments of the South Atlantic and adjacent areas. Initially, during the Aptian-Albian transition, an ephemeral interior sea within Brazil, drawing its waters from the north, would have contributed to salt deposition in the intra-Gondwana rift (evaporitic stage of the CSA). Afterward, but still within the earliest Albian, the evaporitic system evolved into a carbonate gulf when the northern barrier, the Exception Zone (EZ), disappeared. The lagoonal circulation pattern that then formed in the CSA created a hypersaline and warm outflow plume that swept across the marine bottom of the ESA and part of the Tethys Sea. Paleoceanographic events registered at Site 545, Mazagan Plateau, support this new hypothesis and illustrate the potential complexity of correlation of organic-rich deposits in which local influences have been greater than global ones. This long, narrow, and continuous carbonate gulf disappeared at the end of the Albian with the arrival of southern waters from the Meridional South Atlantic (MSA), and the South Atlantic became consolidated as a proto-ocean.

Carnets Geol., vol. 24, no. 2, p. 29-74

Online since January 20, 2024


Paleoenvironmental changes preceding the onset of the Messinian salinity crisis in the western Mediterranean Sea (pre-evaporitic Messinian of the Melilla-Nador Basin, NE Morocco)
Hanane BAHAJ, Nadia BARHOUN, Naima BACHIRI TAOUFIQ, Jihad RAHMOUNA, Soukaina TARGHI, Naima BERRY, Jean-Pierre SUC & Speranta-Maria POPESCU

 | HTML  | PDF [1,534 KB]  | DOI: 10.2110/carnets.2024.2401

 Abstract:  In order to contribute to the understanding of the evolution of marine and continental environments, preceding the onset of the Messinian salinity crisis in the western Mediterranean, we conducted an integrated study of the pre-evaporitic Messinian sedimentary series in the Melilla-Nador basin. Three sections have been carried out in the marl-diatomite series and were the subject of a detailed biostratigraphic and palynological study. The study of planktonic foraminifera, pollen, dinocysts, and palynofacies allowed us to characterize the evolution of these environments. From 6.83 to 6.52 Ma, the marine environment was relatively open, calm, probably subject to the action of upwellings and received periodic continental inputs. Starting 6.52 Ma, the abundance and diversity of planktonic foraminifera decreased. Continental inputs gradually dominate, alternating with marine ones, and reflecting a succession between proximal and distal neritic environments. The surface water conditions were warm. After 6.35 Ma, began the degradation of marine conditions. The continental environment shows an open vegetal landscape dominated by herbaceous plants, reflecting a tropical to arid subtropical climate, slightly less dry than that of the South Rifian Corridor.
This study confirms the existence of several parameters that contributed to the deposition of the cyclical marl-diatomite series: on the one hand, the hot and dry climate favored the reduction of the plant landscape and therefore erosion (continental inputs); on the other, the tectonics (volcanism and uplift).

Carnets Geol., vol. 24, no. 1, p. 1-27

Online since January 17, 2024


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2023 (vol. 23)

Chapter 1 - Preliminary investigations on the Zard Formation at its type locality (North Khorasan Province, Iran)
Bruno GRANIER, Seyedeh Saeideh S. MORTAZAVI, Morteza TAHERPOUR-KHALIL-ABAD & Farokh GHAEMI

 | HTML  | PDF [5,168 KB]  | DOI: 10.2110/carnets.2023.2309

 Abstract:  This chapter presents a revision of the Zard Formation in its type area, i.e., in the North Khorasan Province (Iran), including at its type locality. It comprises a description of the sedimentological and micropaleontological criteria that permit it to be distinguished from the Mozduran Formation (below) and the Tirgan Formation (above). At its type locality, its lower boundary is a heavily bored surface. Actually, both contacts with the framing formations correspond to transgressive surfaces, which imply that this lithostratigraphic unit is an Unconformity-Bounded Unit. With respect to biostratigraphy, this formation contains a few second-order markers: Holosporella sugdeni, Kopetdagaria sphaerica, and Torinosuella peneropliformis, which are also found in the unit above, i.e., in the Tirgan Formation. Because the latter contains markers that first appear in the Barremian: Bakalovaella elitzae, Pseudoactinoporella iranica, and Balkhania balkhanica, but also Montseciella arabica, the total range of which spans the Upper Barremian, the Zard Formation (i.e., the Zardian regional stage) should partly covers the Hauterivian to Barremian interval. Finally, although it cannot be definitely excluded that the lowermost part of the Zard Formation could be Valanginian in age, this option still requires proper documentation.

Carnets Geol., vol. 23, no. 9, p. 161-189

Online since September 10, 2023


A new pseudolepidinid foraminifer, Hanovolepidina browni gen. nov. sp. nov., from the middle Eocene (mid-Lutetian) of Jamaica and its significance
Simon F. MITCHELL

 | HTML  | PDF [3,090 KB]  | DOI: 10.2110/carnets.2023.2308

 Abstract:  The new larger benthic foraminifer, Hanovolepidina browni gen. nov. sp. nov., is described from the Chapelton Formation (mid-Lutetian, middle Eocene, ABZ7) of Jamaica. The genus shows the characteristic transition from a single to double equatorial layer about mid-way across the radius as seen in axial sections that characterises the family Pseudolepidinidae. Equatorial sections show the embryo followed by 4 or 5 spiral rotaliid chambers with the last chamber giving rise to a primary spiral and secondary (counter-) spiral of equatorial chambers. The presence of a long rotaliid stage suggests a more primitive form that Pseudolepidina, and Hanovolepidina gen. nov. differs also from the latter in lacking the extra principal accessory chamber seen in axial section. Hanovolepidina gen. nov. is provisionally suggested as an ancestor of the late Eocene Triplalepidina. The new discovery demonstrates a greater diversity of the family Pseudolpeidinidae in the Caribbean that previously recorded, although occurrences of this family are very restricted stratigraphically suggesting that it may appear in the region due to migration events.

Carnets Geol., vol. 23, no. 8, p. 149-159

Online since August 27, 2023


Nomenclatural Note, p. 160


Hiatuses and redeposits in the Tithonian-Berriasian transition at Le Chouet (Les Près, La Drôme, SE France): Sedimentological and biostratigraphical implications
Bruno R.C. GRANIER, Serge FERRY & Mohamed BENZAGGAGH

 | HTML  | PDF [4,420 KB]  | DOI: 10.2110/carnets.2023.2307

 Abstract:  Our new study of the Tithonian and lower Berriasian succession of Le Chouet (Les Pr s, La Dr me, France) better characterizes the lithological succession, the macro- and microfacies, and the stratigraphic ranges of some microfossils mostly calibrated on the calpionellid biozonation. On the lithological side, the Tithonian strata are dominantly characterized by thick-bedded breccias representing debris flows and related calciturbidites whereas the Berriasian strata are typically white limestones that also comprises scattered intercalations of thin-bedded breccias and calciturbitides (including cryptic mud calciturbidites). In thin sections, these white limestones display mud- to wackestone textures and their allochems are mostly tiny bioclasts (e.g., radiolarians, calpionellids, saccocomids). Breccias are lithoclastic rudstones and/or floatstones with a matrix similar to the calciturbidites. Their lithoclasts are either extraclasts sensu stricto (i.e., material derived from updip shallow-water areas) or pseudointraclasts, representing reworked subautochthonous material (i.e., mud- and wackestone lithoclasts with radiolarians, saccocomids and/or calpionellids). In addition to the erosional features observed at the bases of the gravity flows, these pseudointraclasts document the intensity of submarine erosion. Locally they help to estimate the depths of erosion updip of the deposit. A number of bioclasts are reworked from updip shallow-water areas; among them, it is worth mentioning the foraminifer Protopeneroplis ultragranulata (Gorbatchik), the first occurrence of which is dated to late early Tithonian. Saccocomids are part of the dominating pelagic biota reported from the lower and lower upper Tithonian interval whereas calpionellids replace them in the uppermost Tithonian to lower Berriasian interval. Intervals with saccocomids characteristic of zones 4-5 and zones 6-7 are respectively ascribed here to the lower Tithonian (4-5) and pro parte to the upper Tithonian (6-7). The biozonation of the calpionellid group sensu lato allows identification of the Boneti Subzone of the chitinoidellids, the Crassicollaria Zone with its four subzones (A0-A3), and the Alpina Zone with its first subzone (B1). On the basis of biostratigraphical and sedimentological data (including the rates of sedimentation), most zonal boundaries are located at the erosional bases of breccia or turbidite layers and thus coincide with hiatuses.

Carnets Geol., vol. 23, no. 7, p. 123-147

Online since June 27, 2023


Gzhelian (latest Carboniferous) Pseudoacutella partoazari foraminiferal assemblage from the Tabas Block (Central Iran)
Hamed YARAHMADZAHI & Daniel VACHARD

 | HTML  | PDF [1,906 KB]  | DOI: 10.2110/carnets.2023.2306

 Abstract:  A foraminiferal assemblage is reported from the Zaladou Formation in the Tabas Block (Shishtu Section), Central Iran. This assemblage comprises 16 species belonging to 14 genera, and encompasses the fusulinids Pseudoacutella partoazari, Grovesella tabasensis, Gr. aff. australis, Gr. sphaerica, Gr. sphaerica var. quadrata, Gr. cf. staffelloides, Schubertina sp., Schubertella sp., and the smaller foraminifers Eotuberitina sp., Lasiodiscus tenuis, Raphconilia cf. minor, R. multihelicis, R. modificata, Tetrataxis cf. parviconica, Globivalvulina ex gr. bulloides, Gl. graeca, Calcivertella heathi, Tansillites sp., Palaeonubecularia? sp., Hemigordiellina sp., Nodosinelloides longa, and N. longissima. The age of this assemblage is considered to be Gzhelian. The assemblage is dominated by the fusulinid Pseudoacutella partoazari with a low total diversity of smaller foraminifers. This assemblage is compared to similar assemblages in other parts of Iran and well as the USA. An evolutionary lineage of Pseudoacutella partoazari is also proposed. It is confirmed that Pseudonovella differs from Pseudoacutella by the periphery rounded-carinate (carinate in Pseudoacutella), pseudochomata less developed, and the type of coiling (Pseudoacutella is truly planispiral involute). Pseudonovella is suggested here as the ancestor of Pseudoacutella. This assemblage bears one unusual attribute, the overwhelming dominance of the fusulinid Pseudoacutella and the relatively low total diversity, compared with similar foraminifera from Alborz, Sanandaj-Sirjan, Sabzevar and central Iran, which present warm and humid conditions during the Late Carboniferous.

Carnets Geol., vol. 23, no. 6, p. 107-122

Online since June 30, 2023


The first record of Middle Jurassic serpulids from SE Turkey, equatorial Tethys
Olev VINN & İzzet HOŞGÖR

 | HTML  | PDF [846 KB]  | DOI: 10.2110/carnets.2023.2305

 Abstract:  The Jurassic platform margin succession in the Hezan area, called the "Hezan Unit" (Diyarbakır), on the north of the Arabian platform in southeastern Turkey includes five formations of carbonate-dominated rocks. The most interesting is the upper part of the Hezan unit (the Kuran Formation) that contains unique layers of oolitic and clayey limestone. A first record of the calcareous polychaete tubeworm Propomatoceros lumbricalis is described from the Middle Jurassic lower part of the Kuran Formation of the Hezan area. Most knowledge of fossil serpulids is centered on European material, and little has been done on Middle East fossil calcareous tubes. The taxonomic information recorded as a result of this study will add to our understanding of the biogeographic history of the Middle Jurassic calcareous polychaete associations and help to interpret the structure and paleoecology of its marine communities.

Carnets Geol., vol. 23, no. 5, p. 97-105

Online since June 30, 2023


Upper Triassic (Norian-Rhaetian) Foraminifera from the Nayband Formation of the Lut Block (Garm Ab section, Northeast Iran)
Fatemeh AMIRHASSANKHANI, Baba SENOWBARI-DARYAN & Koorosh RASHIDI

 | HTML  | PDF [3,997 KB]  | DOI: 10.2110/carnets.2023.2304

 Abstract:  Studies of Nayband Formation from the Garm Ab section in Lut Block in Central Iran led to the identification of 26 foraminiferal taxa. Nine species are reported from Iran for the first time: Involutina ex gr. liassica (Jones), Involutina sp., Lamelliconus permodiscoides (Oberhauser), Palaeolituonella cf. meridionalis (Luperto), Palaeolituonella cf. angulata Senowbari-Daryan & Cacciatore, Gaudryinella cf. kotlensis Trifonova, Ammobaculites eumorphos Kristan-Tollmann, Frondicularia rhaetica Kristan-Tollmann, Frondicularia cf. xiphoidea Kristan-Tollmann, and Orthotrinacria ? expansa  (Zaninetti et al.). The taxa restrict the Upper Triassic interval to probably just the Rhaetian. Based on the foraminifera and their abundance, three different association-types could be distinguished, i.e., the Decapoalina schaeferae-Miliolipora cuvillieri, Trocholina turris-Agathammina iranica and Involutina ex gr. liassica-Trocholina umbo associations. Comparisons of foraminiferal associations in different parts of central Iran, such as 1) Hassan Abad section, SW of Ferdows in Lut Block, 2) the type locality of the Nayband Formation in Tabas Block, NE of Esfahan in the eastern part of Central Domain Block, and 3) the Garm Ab section in Lut Block, indicate that the hyaline foraminifers are most abundant in the Garm Ab. Besides, in the Lut Block, the reef environments in the Garm Ab section are deeper water than those of the Hassan Abad section. The association of Trocholina umbo with Miliolipora cuvillieri is similar to the foraminiferal association from the NE of Esfahan and shows similar conditions in Lut Block and Central Domain Block. The two assemblages of hyaline foraminifers, especially the new report of Involutina and Trocholina, prove to be Rhaetian in age.

Carnets Geol., vol. 23, no. 4, p. 77-95

Online since April 1, 2023


Late Miocene biostratigraphy and paleoenvironment of the Sais Basin (southern Rifian Corridor, Morocco): New insights from the Moulay Yakoub area
Soukaina TARGHI, Nadia BARHOUN, Naima BACHIRI TAOUFIQ, Mohamed ACHAB, Rachid ESSAMOUD, Hanane BAHAJ, Jihad RAHMOUNA & Naima BERRY

 | HTML  | PDF [1,318 KB]  | DOI: 10.2110/carnets.2023.2303

 Abstract:  During the Late Miocene, the Rifian Corridor was one of the two main corridors allowing exchanges between the Atlantic and the Mediterranean Seas. Sedimentary records accumulated along this corridor and specifically, in the Sais Basin, constitute case-study material for understanding the impact of the South Rifian Corridor on the evolution of the fauna, phytoplankton and environment during the Late Miocene. In order to reconstruct the evolution of marine paleoenvironments in the Moulay Yakoub region and to compare this evolution with other areas of the Sais basin, we conducted an integrated biostratigraphic and palynological study of the Upper Miocene of borehole KA 102. High-resolution biostratigraphy based on planktonic foraminifera revised and defined the chronostratigraphic framework of the Upper Miocene sedimentary series of the Moulay Yakoub region providing an age of 7.8 Ma to 6.52 Ma (Late Tortonian to Early Messinian). In the Late Tortonian, the planktonic foraminiferal assemblages suggest an open and relatively deep marine environment. At the Tortonian/Messinian boundary, planktonic foraminiferal and dinoflagellate associations, as well as distal indices, suggest a relatively deep and neritic distal marine environment with a decrease in diversity and an increase in reworked taxa. Surface waters are warm with a minor cooling trend observed just below this boundary. In comparison to previously studied sections in the Sais Basin, the Lower Messinian is characterized by a deeper and more distal marine environment. However, proximal trends and warm surface water conditions persisted in all studied areas from the basin during this period.

Carnets Geol., vol. 23, no. 3, p. 53-75

Online since April 1, 2023


Peculiar tube-like bivalve with densely packed concave tabulae (Štramberk Limestone, Tithonian-Berriasian)
Olev VINN, Bogusław KOŁODZIEJ & Zuzana KOZLOVÁ

 | HTML  | PDF [1,263 KB]  | DOI: 10.2110/carnets.2023.2302

 Abstract:  The fossils described here are from the Tithonian-lower Berriasian tramberk Limestone of the Czech Republic. The specimens consist of densely packed, straight to slightly curved short tubes. Each tube is composed of a single valve rather than two valves. Some tubes show constrictions in the wall, generally on just one side. The lumen is almost completely filled with numerous densely packed slightly to strongly concave tabulae. In some tubes, the tabulae form complete internal floors while in others they connect to the wall with another tabula or seal the concavity in the underlying tabula. The tubes somewhat resemble tubeworms, rudists, vermetids and calcareous algae. However, based on morphological similarities such as the tube-like morphology in longitudinal section and the shapes of the lamellae and tabulae, these tubes resemble oysters described from the Albian of Brazil. Accordingly, we infer that the tramberk tubes represent oysters or oyster-related bivalves.

Carnets Geol., vol. 23, no. 2, p. 43-51

Online since February 15, 2023


Issues in the identification of the Aptian/Albian boundary in South Atlantic basins and beyond
Ricardo L.M. AZEVEDO, Rogério L. ANTUNES & Mauro D.R. BRUNO

 | HTML  | PDF [2,009 KB]  | DOI: 10.2110/carnets.2023.2301

 Abstract:  The use of taxonomic-phylogenetic criteria established for planktonic foraminifera in the 2000's and the definition of the Albian Global Stratotype Section Point (GSSP-Alb) have resulted in a major change in the interpretation of the carbonate sections overlying the giant layer of salt present in basins of the South Central Atlantic (CSA) and their equivalent strata in the Equatorial South Atlantic (ESA), and interior of northeastern Brazil (BNE). These post-salt carbonates have long been considered Albian in age, but they contain a planktonic foraminifera association characteristically Aptian. Great conflicts arise, however, when this faunal association is compared with biostratigraphic successions based on other fossil groups or with lithostratigraphic and geochronological data. Controversies similar to those observed at sites 363 and 364 of the Deep Sea Drilling Project (DSDP) leg 40, drilled almost 45 years ago, have resurfaced. Thus, it is paradoxical that the remarkable disappearance of large species of planktonic foraminifera, associated with the top of the Paraticinella rohri Zone (of the upper Aptian), occurred stratigraphically above a typical Albian calcareous nannofossil succession (as the First Stratigraphic Occurrences of Hayesites albiensis, Tranolithus orionatus, Axopodorhabdus biramiculatus, and Eiffellithus turriseiffelli) or the FOs of three known species of pelagic calcispheres, all assumed to be of Albian age. Another notorious conflict lies in the fact that these carbonates rest directly on the salt layer onlapping the South Atlantic Middle Barrier (SAMB), where trachyandesite has been dated at 113.2 0.1 Ma, identical to the value established for the GSSP-Alb. Detailed examination of 16 stratigraphic sections from around the world shows that the difficulties of fully applying the GSSP-Alb criteria are not limited to the CSA, ESA, and BNE basins. The explanation of these controversies may lie in the specific conditions of the water mass of the primitive South Atlantic that may have influenced morphological alterations or affected the temporal amplitude of taxa. But until geochronological, biostratigraphic, and lithostratigraphic incompatibilities can be clarified, it is here recommended to use the base of the evaporitic layer as the reference for the Aptian/Albian transition in CSA, ESA, and BNE basins.

Carnets Geol., vol. 23, no. 1, p. 1-42

Online since January 1, 2023


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