Micropaléontologie

Factors controlling the deformation of benthic foraminifera in the Manzala lagoon, Egypt Publication date: June 2019 Source: Revue de Micropaléontologie, Volume 63 Author(s): A.M. Badr-El Din, A.A. El-Badry, O.H. Orabi Abstract Morphological deformations among hyaline and porcelaneous benthic foraminiferal were observed at stations with high contents of trace metals within the Manzala Lagoon. Energy Dispersive X-ray Analyses (EDX) were conducted on deformed and non-deformed specimens of this population. Deformed Adelosina sp. specimens show high sulfur, magnesium, iron and low copper content. The deformed Ammonia tepida show high aluminum, chloride, calcite and copper in the shell. Analyses of non-deformed foraminifera tests at unpolluted localities show that A. tepida displays high calcium content only, whereas Adelosina sp. shows calcium and magnesium. It is worth mentioning that the non-deformed tests of both species are free from copper and sulfur. We conclude that the low salinity and/or high trace metals in the western and southern regions of the Manzala Lagoon are the main cause for the reduction in overall size of the foraminiferal shells. Porcelaneous Adelosina sp. is very rare (0 to 2%) and mainly found on the northern side, where salinity increases, whereas hyaline A. tepida is the most dominant species in the lagoon and covers more than 97% of the total benthic foraminifera.

Eocene larger benthic foraminifera (alveolinids, nummulitids, and orthophragmines) from the eastern Alborz region (NE Iran): Taxonomy and biostratigraphy implications Publication date: June 2019 Source: Revue de Micropaléontologie, Volume 63 Author(s): Mehdi Hadi, György Less, Mohammad Vahidinia Abstract Shallow marine Eocene successions are described and illustrated with major focus on the systematics and biostratigraphic interpretation of larger benthic foraminifera in two stratigraphic sections (Mojen & Kalateh) of the Ziarat Formation from the eastern Alborz zone (Iran). Based on the larger benthic foraminifera assemblages, six shallow benthic zones (SBZ8-SBZ10 and SBZ16?-SBZ17-SBZ18b) during the middle Ilerdian-early Cuisian and Late Lutetian?-Bartonian interval are identified for the first time. The Mojen section is mainly composed of Alveolina horizons as index markers, such as Alveolina decipiens (Schwager), A. tumida (Hottinger), A. ilerdensis (Hottinger), A. sp. cf. A. ilerdensis, A. laxa (Hottinger), A. citrea (Drobne), A. trempina (Hottinger), A. fornasinii (Checchia-Rispoli), A. canavarii (Checchia-Rispoli), A. cf. canavarii and A. aff. cayrazensis, which are consistent with the SBZ8 to SBZ10 interval, whilst the exact age of the top of the interval was not distinctly recognizable. The studied interval of the Kalateh section was assigned to the SBZ16?-SBZ17-SBZ18b with identifications of larger hyaline-lamellar foraminifera represented by Nummulites cf. deshayesi, N. lyelli (D'Archiac & Haime), Orbitoclypeus zitteli (Checchia-Rispoli) and Asterocyclina stella stella (Gümbel).

Dynamics of development of the small foraminiferal biota during early Kungurian (Permian) as evidenced from the Chikali section, Middle Urals, Russia Publication date: June 2019 Source: Revue de Micropaléontologie, Volume 63 Author(s): Tatiana V. Filimonova, Tatiana N. Isakova Abstract The study of taxonomic diversity and dynamics of development of the small foraminifera (SF) at the Artinskian/Kungurian transition in the Chikali section, one of the typical Kungurian successions, revealed four stratigraphically successive SF assemblages. The lowermost assemblage corresponds to the upper part of the Artinskian and three younger assemblages characterize the Kungurian interval. It is shown that the stratigraphic potential of SF makes possible their use for detailed subdivision of a typical Kungurian succession (Chikali section) and interregional correlation of sedimentary successions. The taxa common for Urals, North and North-East Russia include Hemigordius permicus, H. longus, Midiella ovata minima, Omoloniella prima, small specimens of Howchinella (H. semiovalis, H. breggeri, H. impolita), Nodosinelloides mirabilis, N. bella, N. shiknanica, N. cubanicus elongatus, N. pugioidea, Geinitzina chapmani sylvae, G. postcarbonica, G. ex gr. spandeli, Pachyphloia angulata irregularis and Lateenoglobivalvulina ovalis. New comprehensive description of the characteristic species of the early Kungurian Saranian Horizon such as Hemigordius permicus and Midiella ovata minima are given based the study of topotypical material.

Lectotype designation for Alveolina boscii and Fabularia discolites (Foraminifera) from the rediscovered part of the Defrance collection Publication date: June 2019 Source: Revue de Micropaléontologie, Volume 63 Author(s): Jérôme Tréguier, François Le Coze, Roch-Alexandre Benoit Abstract Five lots of Foraminifera, belonging to the Marin Defrance (1758–1850) collection, were discovered in the collection of the Musée des Sciences in Laval (Mayenne, France). The original material used by Defrance to describe Alveolina boscii (Defrance in Bronn, 1825) and Fabularia discolites Defrance in Bronn, 1825 was identified among them, allowing the designation of a lectotype and paralectotypes for those two species. The systematic description of A. boscii and F. discolites is reviewed. The presence of these specimens in the museum collections is still puzzling, since the complete Defrance's collection was thought to have been lost during World War II.

Terrestrial plant microfossils in palaeoenvironmental studies, pollen, microcharcoal and phytolith. Towards a comprehensive understanding of vegetation, fire and climate changes over the past one million years Publication date: June 2019 Source: Revue de Micropaléontologie, Volume 63 Author(s): Anne-Laure Daniau, Stéphanie Desprat, Julie C. Aleman, Laurent Bremond, Basil Davis, William Fletcher, Jennifer R. Marlon, Laurent Marquer, Vincent Montade, César Morales-Molino, Filipa Naughton, Damien Rius, Dunia H. Urrego Abstract The Earth has experienced large changes in global and regional climates over the past one million years. Understanding processes and feedbacks that control those past environmental changes is of great interest for better understanding the nature, direction and magnitude of current climate change, its effect on life, and on the physical, biological and chemical processes and ecosystem services important for human well-being. Microfossils from terrestrial plants – pollen, microcharcoal and phytoliths – preserved in terrestrial and marine sedimentary archives are particularly useful tools to document changes in vegetation, fire and land climate. They are well-preserved in a variety of depositional environments and provide quantitative reconstructions of past land cover and climate. Those microfossil data are widely available from public archives, and their spatial coverage includes almost all regions on Earth, including both high and low latitudes and altitudes. Here, we (i) review the laboratory procedures used to extract those microfossils from sediment for microscopic observations and the qualitative and quantitative information they provide, (ii) highlight the importance of regional and global databases for large-scale syntheses of environmental changes, and (iii) review the application of terrestrial plant microfossil records in palaeoclimatology and palaeoecology using key examples from specific regions and past periods.

Editorial Board Publication date: June 2019 Source: Revue de Micropaléontologie, Volume 63 Author(s):

Palynostratigraphic, palynofacies, organic geochemical and palaeoenvironmental analysis of the Silurian Tanezzuft Formation in the Ghadames Basin of north-west Libya Publication date: March 2019 Source: Revue de Micropaléontologie, Volume 62, Issue 1 Author(s): Waleed Shukry El Diasty, Salah Youssef El Beialy, Fadeel Ibrahim Fadeel, David J. Batten Abstract Two palynofacies associations are documented from the Silurian Tanezzuft Formation in the Ghadames Basin. These are characteristic of the basal 'Hot Shale' and the overlying deposits, referred to here as the Cold Shale. The former reflects deposition in distal suboxic anoxic conditions and is dominated by highly oil-prone amorphous organic matter (AOM) typical of deposition in generally anoxic, restricted marine basins. Only a few acritarchs, prasinophyte algae and chitinozoans occur in association: virtually no spores or cryptospores were recorded. Thick-walled prasinophytes are most numerous in this part of the Tanezzuft Formation in both the Ghadames and Murzuq basins, suggesting enhanced surface water productivity. Deposition took place after the melting of the Late Ordovician ice sheets, which led to a major marine transgression. The palynofacies recorded from the overlying 'Cold Shale' deposits indicate deposition in distal shelf and basin conditions that were also relatively anoxic. They contain more palynomorphs, especially acritarchs, and generally less AOM. The phytoplankton assemblages are dominated by simple and thin-walled prasinophyte algae (leiospheres), suggesting dysoxic–anoxic conditions. Overall the middle and the upper parts of the Tanezzuft Formation are regarded as being deposited in distal dysoxic–anoxic shelf, distal dysoxic–oxic shelf and distal suboxic–anoxic basin respectively. Because chitinozoans are very rare, age determinations of the samples investigated are based mainly on acritarchs. The Hot Shale is dated as early-mid Rhuddanian (early Llandovery) whereas the rest of the formation is considered to late Rhuddanian–Telychian in age. As documented previously from other samples of the Tanezzuft Formation in both the Ghadames and Murzuq basins, the Hot Shale has a very high TOC content and excellent source potential for liquid hydrocarbons, whereas rest of the formation is less rich in organic matter with larger terrestrial and oxidized components and hence reduced potential for sourcing hydrocarbons (both oil and gas).

Benthic foraminiferal assemblages in the severely polluted coastal environment of Drapetsona-Keratsini, Saronikos Gulf (Greece) Publication date: March 2019 Source: Revue de Micropaléontologie, Volume 62, Issue 1 Author(s): Margarita D. Dimiza, Alexandra Ravani, Vasilios Kapsimalis, Ioannis P. Panagiotopoulos, Elisavet Skampa, Maria V. Triantaphyllou Abstract Surface sediments were collected from the coastal zone of Drapetsona–Keratsini (Saronikos Gulf, Greece) in December 2012 for determining the local benthic foraminiferal community, identifying their spatial distribution patterns, and evaluating the response of foraminiferal species to geochemical composition through the hierarchical cluster analysis, principal component analysis and Spearman's rho correlation. Foraminifera can be classified into three distinct assemblages associated with the granulometry, elemental geochemistry, particulate organic carbon content and degree of sediment contamination. A relatively low-diversity assemblage, dominated by stress-tolerant taxa with Ammonia tepida Bolivina spathulata and Bulimina elongata being the prevailing species, is characteristic of the silty seabed of the main part of Drapetsona coastal zone and the Keratsini Port central basin, where organic carbon content, aliphatic and polycyclic aromatic hydrocarbons concentrations and trace metal loads are greatly elevated. On the sandy bottom of the investigated area, relatively high frequencies of miliolids prevail. An epiphytic rotaliid-dominated assemblage is recorded in the slightly-polluted sedimentary bottom of the inner and western part of the Keratsini Port.

Paleobiogeographic implications of the Middle Eocene ostracods from Cairo–Suez district, Egypt Publication date: March 2019 Source: Revue de Micropaléontologie, Volume 62, Issue 1 Author(s): Sherif M. El Baz, Mohamed M. Khalil Abstract The main targets of this paper are to examine the Middle Eocene ostracod assemblages collected from a succession exposed in the Cairo–Suez district, Egypt and to detect their paleobiogeographical implications. The studied succession is subdivided into two rock units: the Observatory and Qurn formations, in ascending order. The analysis of the ostracod assemblages led to the identification of 18 species, none of which is new. Three local biozones are established, Digmocythere ismaili - Xestoleberis kenawyi Assemblage Zone, Grinioneis moosi - Loxoconcha pseudopunctatella Assemblage Zone and Cativella qurnenis - Soudanella triangulataAssemblage Zone. The multivariate analyses indicate that there are three distinct bioprovinces, one of them represents the North Africa bioprovince, including Egypt, Libya, and Tunisia. The second bioprovince represents the Middle East, including Jordan and Israel. The third represents the West Africa bioprovince, including Senegal, Togo, Ivory Coast and Nigeria. Therefore, this deduction supports a migration of Eocene ostracods along the southern Tethys.

New insights in late Miocene lower Chelif basin biostratigraphy based on planktonic foraminifera (Algeria) Publication date: March 2019 Source: Revue de Micropaléontologie, Volume 62, Issue 1 Author(s): Mostapha Benzina, Hakim Hebib, Mustapha Bensalah Abstract Quantitative and qualitative analyses based on planktonic foraminifera of two sections (Oued Derdoussa and Djebel Meni) from lower Chelif basin (northern Algeria) enable us to identify for the first time a sequence of bioevents calibrated with the geomagnetic polarity time scale. The identified bioevents of late Miocene formations are useful for a high-resolution correlation in the whole western Mediterranean at local and regional scales. In particular, this work reveals that the sequence covers an interval of time that extends from the upper Tortonian up to the pre-evaporite Messinian period. Indeed, the base of the succession starts with a change in the coiling direction (from dextral to sinistral) of Neogloboquadrina acostaensis as the first bioevent. This later corresponds to the bioevent (1–8) assigned to the Tortonian sediments. This period is marked by the presence of Globorotalia menardii in sinistral coiled form that was substituted gradually with dextral coiled. The Tortonian/Messinian (T/M) boundary coincides to some extent with a sharp replacement of G. menardii group (I and II) with the first common occurrence (FCO) of Globorotalia miotumida plexus few meters below the development of the Tripoli diatomite formation (bioevent 9). This later is dominated mainly by highly convex species (G. miotumidaplexus) marked by the presence of Globorotalia mediterranea in contrast with the marly formation at the base of the section. In this part, the recorded bioevents (10 to 17) are assigned to the Messinian sediments. Thus, the Tripoli formation shows the influx of Globorotalia nicolae and a small incursion of the dextrally coiled of Globorotalia scitula at the top of Oued Derdoussa section as a local bioevent that may be related to the local palaeoenvironment. We notice the absence of the change in the coiling from sinistral to dextral of N. acostaensis during the upper Messinian, this may be due to the coincidence of this bioevent with the barren levels.

Alexandros Sfakianakis
Anapafseos 5 . Agios Nikolaos
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alsfakia@gmail.com