A new ammonite faunal horizon in the Ovale Zone (Middle Jurassic,Lower Bajocian) and observations on the ammonite genus Sonninia at Coombe Quarry,Mapperton, near Beaminster,Dorset

Biostratigraphy is presented for horizons in the Discites to Sauzei zones at Coombe Quarry and Top Field at Mapperton, Dorset. The significance of these horizons is highlighted. Part of a chronocline is described in the Sonniniidae of the Discites Zone. A new ammonite faunal horizon, Docidoceras higginsi sp. nov. is erected as the oldest of the Ovale Zone. A revised subdivision of the zone is presented and the implications for the taxonomy and biogeography of the Stephanoceratidae is discussed. The distribution of Docidoceras may imply entry to western Tethys via a Hispanic Corridor. A method is presented for the allocation of generic names constituting segments of lineages.     

Calcareous nannofossil biostratigraphy of Campanian strata (Abtalkh Formation) from the eastern Koppeh-Dagh Basin,NE Iran

The Campanian of the eastern Koppeh-Dagh Basin (NE Iran) is generally considered to be represented by the upper part of the Abderaz and the Abtalkh formations. The Abtalkh Formation, which is studied here, reaches thicknesses of up to 1750 m in the area. The formation is characterized by abundant, diverse, and poor to moderately well preserved calcareous nannofossil assemblages of Tethyan affinity. The assemblages were studied in detail in two sections in eastern Koppeh-Dagh, allowing construction of a precise biozonation for this stage. The Abtalkh Formation at sections in Abtalkh village and Padeha spans biozones CC20 to CC23a (UC15b^TP to UC16). The results of this study indicate a late early to late Campanian age for the formation in the area. The most complete Campanian sequence is in the southeast, where the Padeha section is located. Nannofossil abundance and diversity decreases upwards, showing a trend from the base to top of the formation. Dominance of warm water taxa, and low abundance of high latitude taxa, confirm placement of the basin in low to mid palaeolatitudes during deposition of the formation.     

Taxonomy and stratigraphy of late Barremian–Albian species of Horiopleura Douvillé (Hippuritida,Polyconitidae) of the Mediterranean and southwestern Asian regions

The genus Horiopleura Douvillé is restricted to the Mediterranean and southwestern Asian regions, and is represented by eight species developed during the late Barremian–Albian. This revision of species contributed to delineate generic and specific characters. The definition of species is based on a set of external and internal qualitative and quantitative characters, the key characters being size, radial bands, ornamentation and the presence of a left posterior canal. Morphometry documents the dimorphism of some species, corroborated by regression analysis. Horiopleura dumortieri is an upper Barremian–lowermost Bedoulian species from SE France, Horiopleura brevis n. sp. is a Bedoulian, Mediterranean species, extending to the lower Gargasian, Horiopleura gigantea (pro Monopleura) is a Bedoulian species, restricted the Ukrainian Carpathes. Horiopleura lamberti and H. almerae are Upper Aptian to lower Albian species, and are known from Southern Europe and North Africa. Horiopleura haydeni is essentially late Aptian and typifies the southwestern Asia “Yasin fauna”. Horiopleura distefanoi and H. gemmellaroi (both formerly placed in Polyconites) are restricted to the Albian of the peri-Adriatic regions and North Africa, the former being present in the Middle East. Multiple correspondence analysis using six categorical variables and their categorical states, applied to the comparison of species, tends to corroborate our overall taxonomic frame-work, and reveals three groups of species with distinctive ages.     

Middle Triassic (Anisian-Ladinian) Tejra red beds and Late Triassic (Carnian) carbonate sedimentary records of southern Tunisia,Saharan Platform: Biostratigraphy,sedimentology and implication on regional stratigraphic correlations

The “red beds” of the Triassic succession outcropping at Tejra-Medenine (southern Tunisia, Saharan Platform) have yielded rich fossil assemblages of both freshwater and brackish-marine invertebrates and vertebrates. The new discovered fauna indicates an Anisian-Lower Ladinian age for the Tejra section. Its lowermost part is considered as equivalent of Ouled Chebbi Formation, while the medium and upper parts are considered as equivalent of the Kirchaou Formation. Both sedimentological characteristics and fossil assemblages indicate the increasing marine influences within the middle part of the section and the migration of brackish and freshwater fauna into the lacustrine/playa environment at the top. The marine fauna-rich interval of the Tejra section correlates well with the well-known Myophoria-rich carbonate stratigraphic marker confirming the Middle Triassic (Ladinian) major transgression well recorded eastward in the Tunisian Jeffara basin and in Libya. The use of this Ladinian stratigraphic event in addition to the Carnian carbonate transgressive events of the Jeffara escarpment outcrops was of great help for regional lithostratigraphic correlations between the Triassic outcropping series and those currently buried in Ghadames and Berkine basins. The age of the sandstones of “Trias Argilo-Gréseux Inférieur” (TAGI) which forms the main oil and gas reservoir in the Saharan domain is attributed to the Anisian-Carnian and considered as coeval of Ouled Chebbi and Kirchaou Formations of the Dahar escarpment. An updated synthetic stratigraphic chart is proposed for the Triassic of Saharan Platform domain on the basis of the compilation of the new obtained results and the subsurface data taken from published literature.     

A revised ammonoid biostratigraphy for the Aptian of NW Africa: Essaouira-Agadir Basin,Morocco

A revised ammonoid biostratigraphy is presented for the Aptian of NW Africa, Essaouira-Agadir Basin (EAB), Morocco, based on detailed analysis of 5 key sections. A number of bio-events are documented and 26 genus and 43 species fully documented, forming the largest published Aptian ammonite collection made from NW Africa. The section at Tiskatine is documented as the type section, and 8 zones and subzones are defined, of which 5 are new. This work allows correlation of the Aptian of the EAB to the Standard Mediterranean Ammonite Scale (SMAS).Two main hiatuses are identified at the scale of the basin scale: a major one that includes most of the lower Aptian and the base of the upper Aptian and a second one encompass the top of the upper Aptian and the base of the lower Albian. The ammonite fauna displays a clear Tethyan palaeobiogeographic character affected by a fairly high degree of endemism at the genus and species level. The new genus and species Elsaisabellia tiskatinensis is introduced.     

Charophyte biostratigraphy of the non-marine Lower Cretaceous in the Central Tunisian Atlas (North Africa): Palaeobiogeographic implications

The chronostratigraphic framework of the non-marine deposits of the Central Tunisian Lower Cretaceous (Kebar Formation) is reviewed from a biostratigraphic viewpoint. The outcrops located in the Jebel Kebar, Jebel Ksaïra and Jebel Koumine localities provided charophyte assemblages belonging to two biochronozones: Ascidiella cruciata-Pseudoglobator paucibracteatus (upper Barremian–lower Aptian) and Clavator grovesii lusitanicus (upper Aptian–lower Albian). Clavatoraceans from the upper Barremian–lower Aptian in the Tunisian Atlas are reported here for the first time. The assemblage consists of Atopochara trivolvis var. triquetra, Ascidiella iberica var. inflata, Globator maillardii var. trochiliscoides, Globator maillardii var. biutricularis, Echinochara peckii var. lazarii, Clavator harrisii var. harrisii and Clavator harrisii var. reyi. In addition, a new characean species, Mesochara magna nov. sp. Trabelsi and Martín-Closas, is described herein. The results show that the Kebar Formation is diachronous in Central Tunisia, with a more complete record to the north (Jebel Koumine) than in the type locality (Jebel Kebar). Barremian–Aptian diapiric activity is proposed as the factor that controls the diachronous nature of this formation.The late Barremian–early Aptian charophyte assemblages from the Kebar Formation display strong affinities with the contemporaneous floras of the European basins, thus suggesting that intense supraregional floristic exchanges occurred between the Tethyan islands scattered throughout what is now Western Europe and North Africa. The biogeographic distribution of these charophytes leads to the hypothesis that the peri-Tethyan Archipelago acted as an effective bridge for the intercontinental exchanges of these plants between Laurasia and Gondwana.     

Tithonian–early Berriasian perisphinctoid ammonites from the Štramberk Limestone at Kotouč Quarry near Štramberk,Outer Western Carpathians (Czech Republic)

The present contribution deals with the taxonomy of 11 species of perisphinctoid ammonite recovered recently from the Štramberk Limestone as exposed at the Kotouč Quarry (Štramberk, Moravia). The majority of these are described from this unit for the first time. In the stratigraphic evaluation, finds of ammonites from other localities within the quarry, which were published by us in 2013 and 2014, are included. Ammonites recorded from beyond the continuous section document a stratigraphic range from upper lower Tithonian to lower Berriasian inclusive. In addition to taxonomy and new ontogenetic data of some species, we also present information on the distribution of species recognised and on their palaeogeographic distribution, as well as data on the structural composition of the Homole Block at Kotouč Quarry.     

Paleogene-Neogene calcareous nannofossil biostratigraphy and paleoecological inferences from northern Campos Basin,Brazil (well Campos-01)

Quantitative analyses of calcareous nannofossils were performed on 50 ditch-cuttings samples from a well drilled in the northern Campos Basin, Brazil. Nine zones and two subzones were recognised in the Paleogene-Neogene section. The absence of zones NN9-NN7 (earliest late-latest middle Miocene), NP25-NP21 (Oligocene) and NP18-NP1 (earliest late Eocene-Paleocene) implies the occurrence of three stratigraphic breaks/unconformities within the studied interval. Nannofossil assemblages present suggest an open-ocean depositional environment under oligotrophic-surface water conditions for the Miocene section of the well. Hughesius spp. and Umbilicosphaera spp., here named the “small dark” group, were recognised as an index of high nutrient concentration. We suggest that small coccolith/nannolith size is a better indicator of eutrophic condition than taxonomic affinity. Morphometric analysis of specimens of Sphenolithus belemnos and Sphenolithus disbelemnos showed that size tends to decrease within the highstand system tract. The influx of nutrients associated with the highstand could explain this size reduction and may also support our hypothesis that small specimens are indicative of high nutrient concentrations in the surface water.