Papers by Marc André Conrad
Arabian Journal of Geosciences, 2022
The Fahliyan Formation is an important part of the Khami Group reservoir in the Zagros structural... more The Fahliyan Formation is an important part of the Khami Group reservoir in the Zagros structural zone, particularly in the Dezful Embayment. The main objectives of this study are to investigate the microfacies, depositional environment and sequence stratigraphy based on petrographic data of six hundred and seventy thin sections and gamma ray log. Accordingly, 21 carbonate microfacies and two clastic lithofacies were recognized within the Fahliyan Formation, which were deposited in four distinct facies belts including open marine, shoal, lagoon and tidal flat. Based on facies characteristics and sedimentary features, a carbonate rimmed shelf setting was purposed. The predominant abundance of lagoon facies indicates that the study area is located in the shallow part and margin of Zagros structural zone during sedimentation of the Fahliyan Formation. The lower part of the Fahliyan Formation was deposited in a rimmed carbonate platform, and the upper part gradually passes to a mixed carbonate-clastic environment (Khalij Member of the Gadvan Formation). This transition is well documented in the upper parts of well H3. The Fahliyan Formation comprises two third-order depositional sequences in this oil field and could be subdivided into two parts including lower Fahliyan (Berriasian-Valanginian) and upper Fahliyan (Hauterivian-Barremian). Also based on foraminifers, two biozones including Pseudocyclammina lituus-Trocholina sp. zone (Valanginian-Barremian) and Choffatella-Cyclammina zone (Hauterivian-Barremian) were recognized.
Geologia Croatica, 2008
Palaeontological, environmental and sequence stratigraphic studies were carried out on the shallo... more Palaeontological, environmental and sequence stratigraphic studies were carried out on the shallow carbonate platform facies of the Berriasian – Hauterivian, Fahliyan Formation and the lower part of the Gadvan Formation, at Kuh-e-Surmeh. The studies were based on calcareous green algae (mainly Dasycladales) and accompanying benthic foraminifera, focusing on revision of the considerable, pioneering work of GOLLESTANEH (1965, 1979), initially undertaken on behalf of the National Iranian Oil Company (NIOC). Thirty two species of calcareous green algae and thirty four species of benthic foraminifera were identified from the Fahliyan Formation and from the lower part of the Gadvan Formation. A number of the recognized calcareous green algae were previously given different names by other authors working in SW Iran. Additional taxa were also recorded for the first time in the Zagros basin, including Clypeina dragastani, C. estevezii, C. solkani, C. parasolkani, Holosporella arabica, Ottern...
Geologia Croatica, 2008
Sediment binding crusts of Lithocodium aggregatum and associated Bacinella irregularis abound in ... more Sediment binding crusts of Lithocodium aggregatum and associated Bacinella irregularis abound in a shallow water limestone layer, in South-East France. The sudden appearance of these crusts denotes a local, conspicuous change in the otherwise balanced, open marine depositional environment. Based on regional correlations, the layer is Lower Hauterivian, Ligatus Zone, directly dated by an assemblage of orbitolinids, and indirectly by a specimen of ammonite. It is older than the Faraoni OAE (latest Hauterivian, Angulicostata auct. Zone), and presumably not linked with a global climate change. Two facies are recognized: (1) Lithocodium bindstone, with Bacinella, other microencrusters, and fluorescent automicrite of microbial origin; (2) floatstones containing numerous fragments of Lithocodium and accompanying biota. Coarse rhomboedral dolomite is locally present. Two modern analogues of microbial mediation are put forward to explain the Lithocodium event: (a) Lagoa Vermelha, in Brazil, ...
Acta Palaeontologica Polonica, 2021
ABSTRACT Thèse--Genève. "Thèse no. 1476." At head of title: Université de Genèv... more ABSTRACT Thèse--Genève. "Thèse no. 1476." At head of title: Université de Genève, Faculté des Sciences.
La plate-forme carbonatée urgonienne (Hauterivien supérieur-Aptien inférieur
In Western Kopet Dagh, the lower Cretaceous carbonate series contains distinctive assemblages of ... more In Western Kopet Dagh, the lower Cretaceous carbonate series contains distinctive assemblages of calcareous algae, chiefly Dasycladales which are primarily studied in this work. Based on the significant presence of certain species, the Zard Formation, assigned to the Valanginian and, in its upper part, to the Hauterivian or base of the Barremian, is subdivided into two intervals, respectively A and B. Higher up, the Urgonian-type Tirgan Formation, assigned to the Barremian and Lower Aptian, is subdivided into intervals C and D. On this occasion, the taxonomy and systematics of 17 species of Dasycladales and one incertae sedis found in the series are discussed, in relation to some recent standpoints. Out of this inventory, the biogeographic distribution of 11 species is particularly interesting. During the Lower Cretaceous, the Kopet Dagh region was quite isolated, northeast of the Izanca, a branch of the Tethys. Assemblages encountered in this region are compared with other areas, e...
Marine and Petroleum Geology, 2021
Abstract A regional sequence-stratigraphic framework is proposed for the Berriasian-Barremian sha... more Abstract A regional sequence-stratigraphic framework is proposed for the Berriasian-Barremian shallow platform succession in the Zagros Fold-Thrust Belt (FTB), based on outcrop sections, in combination with subsurface data. The time framework is supported by new biostratigraphic results, using benthic foraminifera, dasycladalean algae and tintinnids, calibrated by Sr-isotope data. We identified and described four large-scale sequences and sixteen small-scale sequences throughout the studied succession. Large-scale sequences occur in the Berriasian-earliest Valanginian, Valanginian, Hauterivian and early to late Barremian. Based on facies associations, a relative water depth has been assigned to distinct depositional environments. Four successive architectures were observed in the platform growth: rimmed platform during the early-middle Berriasian, isolated rimmed platform in the middle Berriasian-earliest Valanginian, non-rimmed open platform to ramp in the Valanginian, and finally a mixed siliciclastic-carbonate platform to ramp in the Hauterivian-Barremian.
Journal of Paleontology, 1991
Calcareous algae are frequent constituents in the shallow-marine limestone intercalations of late... more Calcareous algae are frequent constituents in the shallow-marine limestone intercalations of late Aptian–Maastrichtian strata of the Eastern Desert of Egypt, the Sinai, and southern Jordan. A total of 18 species of green algae (among them 16 dasycladaceans withPraturlonella hammudain. comb. andPraturlonella jordanican. sp., two udoteaceans) and eight species of red algae (among them two gymnocodiaceans, three solenoporaceans, and one squamariacean) are described and compared with algae from several Tethyan occurrences. The stratigraphic distribution is calibrated by 10 assemblage-zones based on the associated foraminiferids and compared with 10 ammonite assemblage-zones.The algal contents vary within the different strata: their total contents and diversities increase from the late Aptian–Albian carbonates to the Cenomanian and decrease to the Turonian–Coniacian; no algae were proved in the Santonian–Campanian. The Maastrichtian occurrences are limited to one outcrop.
Swiss Journal of Geosciences, 2016
In the course of the HARMOS project of the Swiss Geological Survey, the lithostratigraphic subdiv... more In the course of the HARMOS project of the Swiss Geological Survey, the lithostratigraphic subdivisions of the Cretaceous sedimentary rocks outcropping in the Swiss Jura Mountains were revisited. New formation names are proposed where only inadequate facies terms existed so far. As in some cases outcrop conditions in the Swiss Jura do not allow for logging complete sections to characterise the formations, type localities in neighbouring France have been chosen. The following formations (Fm.
Cretaceous Research, 2016
Abstract A combined biostratigraphic model comprising 12 biozones is proposed for the Berriasian–... more Abstract A combined biostratigraphic model comprising 12 biozones is proposed for the Berriasian–Bedoulian (lower Aptian) shallow-platform deposits of the newly defined Fahliyan, Sar Bisheh, Ghari, Gadvan and Chahoo formations in the Zagros fold-thrust belt. Six biozones are established for the benthic foraminifers, four plus one subzone (taxon-range zone) for the dasycladalean algae and three for the tintinnids. The top and base of these biozones are calibrated with Sr-isotope numerical dating. The dataset is founded on outcrops and subsurface data in the Khuzestan, Fars and Bandar Abbas areas. High resolution biostratigraphic studies reveal that a sedimentary break corresponding to an exposure is present at the base of the Berriasian across the platform, and becomes younger from west toward the east. Another diachronous regional hiatus is detected on top of the Sar Bisheh Formation. Dated late Valanginian pro parte, it is the largest hiatus occurring in the Fars area. This study demonstrates that the boundary between the Sar Bisheh Formation and the Ghari/Chahoo formations, respectively covering the former Lower Fahliyan and Upper Fahliyan/Gadvan-Dariyan formations, is Hauterivian, not Barremian as stated by previous authors. It also shows that the Gadvan Formation does not reach the Aptian, contrary to previous statements. Sr-isotope stratigraphy offers a comparable resolution to that achieved by biostratigraphy. Combining the two methods results in a better resolution, enabling to estimate the depositional rates and importance of missing intervals.
Artificial Neural Networks (ANNs), are used as an additional tool to differentiate Lower Cretaceo... more Artificial Neural Networks (ANNs), are used as an additional tool to differentiate Lower Cretaceous, morphologically closely related species of Salpingoporella. On each specimen, measurements are made on the inner and outer diameters of the thallus, the spacing of the verticils, and the number of laterals per verticil. “NeuralXL Classifier”, a Microsoft Excel plug-in software, is used to calculate a user-defined number of data clusters (categories) for each test. Results are positive: in Salpingoporella, clustering dimensions with an ANN does help to make out a species, or lower rank taxon, especially when visual differences look insignificant. The quite rare Salpingoporella parapiriniae n. sp. is described from Barremian and Lower Aptian Urgonian deposits of southeast France. The protologue is based on regular criteria (essentially enumerative and dimensional values, dealt with by regression analysis) whose outcome is confirmed by the corresponding ANN study. The type-level of the ...
Revue de Paleobiologie
Dissocladella undulata (RAINERI, 1922) PIA, 1936 was established on the basis of heterogeneous sp... more Dissocladella undulata (RAINERI, 1922) PIA, 1936 was established on the basis of heterogeneous specimens originating from the Upper Cretaceous of Libya. The species is quite commonly found elsewhere in North Africa and the Middle East. New material collected in Libya is compared with the type specimens and to Miss R. RAINERIʼs original protologue. A significant feature, the undulation, is clearly of secondary origin. It is present in the herein designated lectotype of the species, which probably belongs to the genus Trinocladus. The resulting incongruity was unfortunately overlooked by J. PIA in his partial review of Miss R. RAINERIʼs material, made in 1936. A new species, Dissocladella bonardii, is introduced for the genuine specimens of Dissocladella, in replacement of D. undulata, now obsolete.
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 2007
In SE-France and nearby Switzerland, biostratigraphic studies on the Urgonian limestone are condu... more In SE-France and nearby Switzerland, biostratigraphic studies on the Urgonian limestone are conducted since decades, mainly using ammonites, echinoids, orbitolinids, and dasycladalean algae. The fundamental outcome, though called into question by other authors, is fully ...
Annales g?ologiques de la Peninsule balkanique, 2009
The Liassic Linoporella buseri is re-examined, on the basis of an abundant material of reefal ori... more The Liassic Linoporella buseri is re-examined, on the basis of an abundant material of reefal origin, originating from the newly described type-locality in Slovenia. It is compared with the Berriasian-Valanginian type-species L. capriotica, studied by BARATTOLO & ROMANO (2005). Both species have three orders of laterals. In L. buseri, however, apart of other, clear cut differences, the tertiary laterals are usually hair-like, occasionally phloiophorous at tip, forming a distal cortex such as in L. capriotica. Consequently, the genus Linoporella is slightly emended, to fit observations made on the two species.
Annales g?ologiques de la Peninsule balkanique, 2013
Pseudoclypeina? crnogorica was first described in 1972 from the Lower, Cretaceous limestone of th... more Pseudoclypeina? crnogorica was first described in 1972 from the Lower, Cretaceous limestone of the Njegos Mt. area, Montenegro, Dinaric Carbonate Platform. It differs from other species of the genus Pseudoclypeina by its calcification pattern, the shape and relative length of the first and second order laterals, and by the presence in the type-material (a thin section containing the holotype) of sections standing for the sterile portion of the thallus. This is why in this paper, the generic name is left in open nomenclature. On this occasion the species, whose presence is also reported from southern Iran, is re-described and better illustrated, based on material originating from other outcrops in Montenegro. The stratigraphic position is reviewed as well. Pseudoclypeina? crnogorica occurs in shallow water inner platform facies of early Neocomian age, along with Selliporella neocomiensis.
Swiss Journal of Geosciences, 2012
Sedimentology, 2011
MARC A. CONRAD*, BERNARD CLAVEL , BRUNO GRANIER , JEAN CHAROLLAIS§, ROBERT BUSNARDO– , ELISABETTA... more MARC A. CONRAD*, BERNARD CLAVEL , BRUNO GRANIER , JEAN CHAROLLAIS§, ROBERT BUSNARDO– , ELISABETTA ERBA**, SILVIA GARDIN , ROGER JAN DU CHÊNE , DANIELLE DECROUEZ§§, ANTONIETTA CHERCHI–– , ROLF SCHROEDER***, JACQUES SAUVAGNAT§§ and MARC WEIDMANN *71 ch. de Planta, CH-1223 Cologny, Switzerland (E-mail: [email protected]) 24 ch. des Champs d’Amot, F-74140 Messery, France UMR 6538 Domaines Océaniques, Département des Sciences de la Terre et de l’Univers, UFR des Sciences et Techniques, Université de Bretagne Occidentale (UBO), 6 avenue Le Gorgeu – CS 93837, F-29238 Brest Cedex 3, France §Département de géologie et de paléontologie, Université de Genève, 13 rue des Maraı̂chers, CH-1211 Genève 4, Switzerland –ch. Meruzin, F-69370 St Didier au Mont d’Or, France **Section of Geology and Paleontology, Department of Earth Sciences, Università degli Studi di Milano, via Mangiagalli 34, I-20133 Milano, Italy UMR 7207 CR2P, case 104, Université de Paris VI, 4 place Jussieu, F-75252 Paris Cedex 05, France Geological Consultant, 81 rue Soubiras, F-33200 Bordeaux, France §§Muséum d’histoire naturelle de la Ville de Genève, 1 route de Malagnou, CH-1211 Genève 6, Switzerland ––Dipartimento di Scienze della Terra, Università di Cagliari, via Trentino, I-09100 Cagliari, Sardegna, Italy ***Forschungsinstitut Senckenberg, Senckenberg-Anlage 25, D-60325 Frankfurt am Main, Germany 3 sentier du Molard, CH-1805 Jongny, Switzerland
Facies, 2013
Early Cretaceous shallow carbonate deposits in the Zagros fold-thrust belt, SW Iran, are being st... more Early Cretaceous shallow carbonate deposits in the Zagros fold-thrust belt, SW Iran, are being studied for a high-resolution stratigraphic pattern and detailed environmental analysis. These carbonates contain diversified assemblages of dasycladalean algae, indicating shallow subtidal depositional environments. A new dasycladalean alga and interesting marker is described as Mizzia zagarthica sp. nov. from Late Berriasian-Early Valanginian deposits of the Fahliyan Formation. Focusing on the presence of reproductive organs (cysts) in the laterals, the genus, which so far has been reported only from the Permian, is emended. Based on newly described material from Greece and New Mexico, the genus Mizzia is reassessed. The paper also includes a critical revision of the genera Neomizzia and Banciloporella.
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Papers by Marc André Conrad