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2024 (vol. 24)
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Shell injuries in Densepustula Lazarev, 1982, Pennsylvanian productidine brachiopod from the Donets Basin, Ukraine
Vitaly DERNOV
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| DOI: 10.2110/carnets.2024.2409
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Abstract: Nine injured ventral valves of productidine brachiopods belonging to the genus
Densepustula Lazarev, 1982, from the Mospyne, Smolyanynivka, Belaya Kalitva, and
Kamensk formations (Upper Bashkirian-lower Moscovian, Lower and Middle Pennsylvanian) of the Donets Basin (eastern Ukraine)
were studied. Three morphological types of damage traces have been recognized: Type A) longitudinal,
sublongitudinal, and transversal thin straight or sinuous furrows, about 5-7 mm
long and 0.5-1.5 mm thick; Type B) rounded and ellipsoidal pits, about 3-4 mm in
diameter, located on the umbo, the anterior margin of the ventral valve, and the lateral slopes of the ventral valve;
and Type C) irregularly-shaped dimples on the anterior margin and in the sulcus, 2-3 mm in size. These injuries are present
on 9 out of 61 (15%) of ventral valves studied, but entirely absent from dorsal
valves (0 out of 25). The most likely producers of these damage traces
are cartilaginous fishes and parasites of unclear affinity.
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Carnets Geol., vol. 24, no. 9, p. 143-162
Online since September 20, 2024
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Tooth marks of the Great White Shark from a Pliocene outcrop of the Northern Apennines (Castell'Arquato, Italy)
Alessandro FRESCHI & Simone CAU
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| DOI: 10.2110/carnets.2024.2408
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Abstract: We
describe and analyze a rib fragment of a small cetacean from the Castell'Arquato
Plio-Pleistocene Basin (Northern Apennines, Italy) that displays various tooth
marks featuring parallel striations similar to those left by the serrated tooth
of the extant white shark, Carcharodon carcharias. The discovery
locality,
known as "Buca della Balena", was an inner-shelf marine setting where sharks
may have scavenged on drifting cetacean carcasses in Piacenzian times. The high
number of marks found on the small bone fragment suggests multiple bites by one
or more shark individuals. The rib fragment studied is one of the few
osteological specimens from the Pliocene of the Mediterranean Basin to preserve
white shark tooth marks.
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Carnets Geol., vol. 24, no. 8, p. 135-141
Online since July 24, 2024
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Octahedronoides tethysianus n.gen., n.sp., enigmatic clusters of microspheres at the Jurassic-Cretaceous transition
Bruno R.C. GRANIER
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| DOI: 10.2110/carnets.2024.2407
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Abstract: In
the literature, numerous accounts exist of microspheres scattered in the pelagic
environments of the Tethys realm at the Jurassic-Cretaceous transition. These
microspheres are commonly associated with genera such as Cadosina, Colomisphaera,
or Stomiosphaera, and attributed to calcareous dinocysts. On the
other hand, there are few records of the microsphere, initially described as Cadosina
minuta Borza, 1980, which are arranged
in small clusters, likely comprising six cells. This distinctive grouping
and its architecture preclude attribution to the calcareous dinocysts. A new
genus and a new species (as Octahedronoides tethysianus n.gen., n.sp.) are introduced to define these
clusters of leiospheres, which are here reascribed to the acritarchs.
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Carnets Geol., vol. 24, no. 7, p. 127-133
Online since May 8, 2024
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A new fossil psychodomorphan fly from Lower Barremian Lebanese amber elucidates the relationship of the Tanyderinae stat. nov. within the Psychodidae
Dany AZAR, Sibelle MAKSOUD, Di-Ying HUANG, Mounir MAALOUF & Chen-Yang CAI
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| DOI: 10.2110/carnets.2024.2406
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Abstract: A new species, Nannotanyderus granieri sp. nov.,
belonging to the Tanyderidae (Diptera, Nematocera), from Lower Barremian amber
of Bqaatouta (Lebanon), is characterized, described, figured, and its
taxononomic position discussed. The possible confusion regarding the attribution of new fossils to either the Tanyderidae or the Psychodidae,
in addition to the results of recent molecular phylogenies, have led us to re-evaluate
the taxonomic position of the Tanyderidae and to consider it as a subfamily
within the Psychodidae. The fossil described herein is a tiny tanyderine sensu
nov. species, and the second one belonging to the genus Nannotanyderus
from Lebanese amber. A tentative molecular phylogeny of recent Psychodidae and
an exhaustive catalogue of fossil Tanyderinae stat. nov. are provided.
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Carnets Geol., vol. 24, no. 6, p. 113-125
Online since April 1, 2024
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Nomenclatural Note, p.
126
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The Kalkowsky Project - Chapter VI. A panorama of synsedimentary broken ooids
Bruno R.C. GRANIER & Philippe LAPOINTE
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[3,988 KB]
| DOI: 10.2110/carnets.2024.2405
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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.
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Carnets Geol., vol. 24, no. 5, p. 91-112
Online since February 29, 2024
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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
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[377 KB]
| DOI: 10.2110/carnets.2024.2404
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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 S o 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.
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Carnets Geol., vol. 24, no. 4, p. 83-89
Online since January 31, 2024
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The Kalkowsky Project - Chapter V. Asymmetric ooids from the Yacoraite Formation (Argentina)
Bruno R.C. GRANIER & Philippe LAPOINTE
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[2,420 KB]
| DOI: 10.2110/carnets.2024.2403
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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).
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Carnets Geol., vol. 24, no. 3, p. 75-82
Online since January 20, 2024
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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
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| DOI: 10.2110/carnets.2024.2402
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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.
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Carnets Geol., vol. 24, no. 2, p. 29-74
Online since January 20, 2024
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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
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[1,534 KB]
| DOI: 10.2110/carnets.2024.2401
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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).
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Carnets Geol., vol. 24, no. 1, p. 1-27
Online since January 17, 2024
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2023 (vol. 23)
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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
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| DOI: 10.2110/carnets.2023.2309
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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.
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Carnets Geol., vol. 23, no. 9, p. 161-189
Online since September 10, 2023
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A new pseudolepidinid foraminifer, Hanovolepidina browni gen. nov. sp. nov., from the middle Eocene (mid-Lutetian) of Jamaica and its significance
Simon F. MITCHELL
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| DOI: 10.2110/carnets.2023.2308
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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.
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Carnets Geol., vol. 23, no. 8, p. 149-159
Online since August 27, 2023
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Nomenclatural Note, p.
160
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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
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| DOI: 10.2110/carnets.2023.2307
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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.
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Carnets Geol., vol. 23, no. 7, p. 123-147
Online since June 27, 2023
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Gzhelian (latest Carboniferous) Pseudoacutella partoazari foraminiferal assemblage from the Tabas Block (Central Iran)
Hamed YARAHMADZAHI & Daniel VACHARD
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| DOI: 10.2110/carnets.2023.2306
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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.
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Carnets Geol., vol. 23, no. 6, p. 107-122
Online since June 30, 2023
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The first record of Middle Jurassic serpulids from SE Turkey, equatorial Tethys
Olev VINN & İzzet HOŞGÖR
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| DOI: 10.2110/carnets.2023.2305
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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.
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Carnets Geol., vol. 23, no. 5, p. 97-105
Online since June 30, 2023
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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
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[3,997 KB]
| DOI: 10.2110/carnets.2023.2304
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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.
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Carnets Geol., vol. 23, no. 4, p. 77-95
Online since April 1, 2023
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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
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[1,318 KB]
| DOI: 10.2110/carnets.2023.2303
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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.
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Carnets Geol., vol. 23, no. 3, p. 53-75
Online since April 1, 2023
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Peculiar tube-like bivalve with densely packed concave tabulae (Štramberk Limestone, Tithonian-Berriasian)
Olev VINN, Bogusław KOŁODZIEJ & Zuzana KOZLOVÁ
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| DOI: 10.2110/carnets.2023.2302
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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.
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Carnets Geol., vol. 23, no. 2, p. 43-51
Online since February 15, 2023
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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
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[2,009 KB]
| DOI: 10.2110/carnets.2023.2301
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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.
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Carnets Geol., vol. 23, no. 1, p. 1-42
Online since January 1, 2023
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