Louisette Zaninetti

Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis

The evolution of life on Earth is marked by catastrophic extinction events, one of which occurred ca. 200 Ma at the transition from the Triassic Period to the Jurassic Period (Tr-J boundary), apparently contemporaneous with the eruption of the worlds largest known continental igneous province, the Central Atlantic magmatic province. The temporal relationship of the Tr-J boundary and the provinces volcanism is clarified by new multidisciplinary (stratigraphic, palynologic, geochronologic, paleomagnetic, geochemical) data that demonstrate that development of the Central Atlantic magmatic province straddled the Tr-J boundary and thus may have had a causal relationship with the climatic crisis and biotic turnover demarcating the boundary.

A molecular approach to biodiversity and biogeography in the planktonic foraminifer Globigerinella siphonifera (d'Orbigny)

DNA-based studies have revealed that biodiversity has been underestimated in most groups of pelagic organisms. Recently, higher diversity has also been molecularly detected in planktonic foraminifera, which challenges the morphological concepts applied to define the species level in this group, and provides new insight in interpretation of their fossil record. Here, we present a genetic analysis based on small subunit ribosomal DNA genes from 189 individuals of the morphospecies Globigerinella siphonifera, collected along an Atlantic transect covering 57° of latitude. Four different, strictly homogeneous genotypes, called types I, II, III and IV, were detected. Their origin occurred in the late Miocene according to the absolute molecular clock estimation based on genetic distances calibrated within the fossil record. Biogeographic analysis shows that each G. siphonifera genotype is adapted to a specific environment: type I prefers oligotrophic waters, type II, although cosmopolitan, is probably adapted to mesotrophic waters, types III and IV live in highly productive waters. This emphasizes the importance of the water column stability and resulting trophic structure for planktonic foraminiferal evolution. The phenomenon of adaptive radiation of slightly different morphotypes described here in G. siphonifera is compared to analogous evolutionary patterns molecularly revealed in two other planktonic foraminifera, Orbulina universa and Globorotalia truncatulinoides. It implies that closely related morphotypes within classically defined planktonic foraminiferal taxa may be different species and can be markers of highly different environments.

PHYLOGENY AND RATES OF MOLECULAR EVOLUTION OF PLANKTONIC FORAMINIFERA : SSU RDNA SEQUENCES COMPARED TO THE FOSSIL RECORD

Abstract. Planktonic foraminifera are marine protists, whose calcareous shells form oceanic sediments and are widely used for stratigraphic and paleoenvironmental analyses. The fossil record of planktonic foraminifera is compared here to their molecular phylogeny inferred from ribosomal DNA sequences. Eighteen partial SSU rDNA sequences from species representing all modern planktonic families (Globigerinidae, Hastigerinidae, Globorotaliidae, Candeinidae) were obtained and compared to seven sequences representing the major groups of benthic foraminifera. The phylogenetic analyses indicate a polyphyletic origin for the planktonic foraminifera. The Candeinidae, the Globorotaliidae, and the clade Globigerinidae + Hastigerinidae seem to have originated independently, at different epochs in the evolution of foraminifera. Inference of their relationships, however, is limited by substitution rates of heterogeneity. Rates of SSU rDNA evolution vary from 4.0 × 10−9 substitutions/site/year in the Globigerinidae to less than 1.0 × 10−9 substitutions/site/year in the Globorotaliidae. These variations may be related to different levels of adaptation to the planktonic mode of life. A clock-like evolution is observed among the Globigerinidae, for which molecular and paleontological data are congruent. Phylogeny of the Globorotaliidae is clearly biased by rapid rates of substitution in two species (G. truncatulinoides and G. menardii). Our study reveals differences in absolute rates of evolution at all taxonomic levels in planktonic foraminifera and demonstrates their effect on phylogenetic reconstructions.

New algae and problematica of algal affinity from the permian of the Aseelah Unit of the batain plain (East Oman)

Permian microfloras occur in limestone boulders of the Aseelah Unit at the lower part of the Batain Group (NE Oman). The boulders are composed of bioclastic limestones deposited during the Permian on a shallow marine warm shelf environment. They yield several rich associations of Dasycladales, tubiphytids and Archaeolithophyllaceae indicating a Yakhtashian to Dzhulfian age (dated by fusulinids). The algal-bearing Aseelah Unit overlies conformably the Permian Qarari Unit deposited on the distal slope of the Arabian carbonate platform. The conglomerate and sandstone sheddings of the Aseelah Unit indicate the end of a major transgressive-regressive cycle at the Permian/Triassic boundary. The oldest age of the depositional event is given by the Dzhulfian age of the youngest reworked boulders. The age of the sandstones and sandy matrix is not well established; it is post-Dzhulfian, probably Triassic on the basis of some palynological indications. Several new taxa are described: Aphralysiaceae nov. fam., Sparaphralysia orientalis nov. sp., Mellporellopsis corpulenta nov. gen. nov. sp., Aseelahella granieri nov. gen. nov. sp., Claracrustinae nov. subfam., Claracrusta ungdarelloidea nov. sp. and Sphairionia galinae nov. sp.

Use of the ITS rDNA for elucidation of some life-cycles of Mesometridae (Trematoda, Digenea)

Identification of larval stages is crucial for elucidating the life-cycles of various Digenea. However, in many digenean species, the larvae lack distinctive morphological features and it is impossible to establish the affiliation between the larval and adult stages by using morphological criteria. Molecular methods, based on DNA sequencing or PCR-restriction fragment length polymorphism analysis, can offer a new tool for larval-stage identification. In this study, the sequences of internal transcribed spacer of the ribosomal DNA were used to identify the cercariae of three out of five species of the family Mesometridae (Centroderma spinosissima, Elstia stossichianum and Wardula capitellata). The three species differ from one another by number of repeats in the region of internal transcribed spacer 1. The phylogeny of Mesometridae was inferred from their internal transcribed spacer ribosomal DNA sequences. The PCR-linked restriction fragment length polymorphism approach was developed for future life-cycle and ecological studies of this family.

Triassic pelagic deposits of Timor: palaeogeographic and sea-level implications

Abstract In West Timor, Triassic deposits are found in the Parautochthonous Complex, as well as in the Allochthonous series of Sonnebait. A detailed biostratigraphic investigation, integrating field observations and facies analysis, allowed the reconstruction of a synthetic lithostratigraphic succession for the Upper Triassic; a stratigraphic transition from Carnian shales to Upper Norian–Rhaetian limestones is also shown by this study. The fossil content predominantly originates from an open marine environment; lithostratigraphic Units A–E are dated on the basis of radiolaria and palynomorphs, and Unit H, on ammonites and conodonts. The presence of pelagic bioclasts, together with normal grading, horizontal laminations, and current ripples, is indicative of a distal slope to basin environment. The ammonite rich condensed limestone of Unit H was deposited on a ‘pelagic carbonate plateau’ exposed to storms and currents. The organic facies have been used as criteria for biostratigraphy, palaeoenvironmental interpretation, and sequence stratigraphy. The palaeontological analysis of the Triassic succession of West Timor is based on the investigation of radiolaria and palynomorphs, in the marls and limestones of Units A–E, and also on ammonites and conodonts in the condensed limestone of Unit H. Units A and B are Carnian (Cordevolian) in age, based on the occurrence of the palynomorph Camerosporites secatus , associated with ‘ Lueckisporites ’ cf. singhii , Vallasporites ignacii , Patinosporites densus and Partitisporites novimundanus . Unit C is considered as Norian, on the basis of a relatively high percentage of Gliscopollis meyeriana and Granuloperculatipollis rudis. Unit D contains significant palynomorphs and radiolaria; the organic facies, characterized by marine elements, is dominated by the Norian dinocysts Heibergella salebrosacea and Heibergella aculeata ; the radiolaria confirm the Norian age. They range from the lowermost Norian to the lower Upper Norian. Unit E also contains radiolaria, associated in the upper part with the well-known marker of the Upper Norian, Monotis salinaria . For Unit E, the radiolaria attest to a Lower to Upper Norian age based on the occurrence of Capnodoce and abundant Capnuchosphaera ; the upper part is Upper Norian to Rhaetian based on the presence of Livarella valida . Finally, the blocks of condensed limestone with ammonites and conodonts of Unit H allowed the reconstruction of a synthetic stratigraphic succession of Upper Carnian to Upper Norian age. Our stratigraphic data lead to the suggestion that the Allochthonous complex, classically interpreted as a tectonic melange of the accretionary prism of the Island Arc of Banda, is a tectonically dismembered part of a Triassic lithostratigraphic succession.

Middle permian (midian) foraminiferal assemblages from the batain plain (Eastern Oman): Their significance to neotethyan paleogeography

Exceptionally rich Permian fusulinid assemblages, varying in age from Yakhtashian to Dzhulfian, were found in reworked limestone blocks from conglomerates of the Aseelah Unit, recently defined in the Batain Plain and dated possibly as Upper Triassic. This paper only deals with the Middle Permian, Midian (= Capitanian) microfaunas from the conglomerates. The Aseelah Unit is found associated with the Triassic Sal Formation, tectonically overlying the Qarari Unit, and is dated as Middle to Late Permian based on ammonoid assemblages and conodonts. The boulders of the Aseelah Unit are composed of exclusively Permian skeletal limestones in a sandy matrix; the limestones were deposited on a shallow marine shelf environment from the southern Neotethys. The Qarari Unit is interpreted as a hemipelagic series deposited on the distal slope of the Arabian carbonate platform. The Midian foraminifers from the Batain Plain are similar to some assemblages of Transcaucasia, of the Abadeh area (Iran), of SW Turkey (Taurus Mountains), and some, especially the Neoschwagerinidae, exhibit affinities with microfaunas of the eastern Tethys terranes of Japan. However, similar Neoschwagerinid assemblages were not found in any significant area of the Arabian Peninsula (Oman Mountains, Huqf-Haushi area, and Khuff area).

Sedimentology, stratigraphy, and micropalaeontology of the Upper Triassic reefal series in Eastern Sulawesi (Indonesia)

An Upper Triassic (Upper Norian-Rhaetian) carbonate complex, composed of open marine to reefal deposits, has been investigated for the first time in Eastern Sulawesi. The age is based on the occurrence of benthic foraminifera, and also of the Upper Sevatian to Rhaetian conodont Misikella posthernsteini Kozur and Mock. Palynological assemblages contain Upper Triassic-Lower Jurassic palynomorphs. The scleractinian coral Retiophyllia seranica and the chaetetid sponge Blastochaetetes intabulata, together with Solenoporacean algae, are the main framebuilders of the reefal facies. The entire carbonate series, composed of conodont bearing limestones, reefal deposits, and intertidal/supratidal cryptalgal laminites, shows a general regressive trend from a marginal to an inner platform environment. The relationship between microfaunal distribution and sequence analysis is discussed. The Upper Triassic foraminifers and palynomorphs of Eastern Sulawesi show affinities to microfaunas of the Australian-Indonesian southern Tethyan domain, and the general organisation of the platform should be investigated through further studies from Banda Sea dredgings.

DNA analysis of “Ammonia beccarii” morphotypes: one or more species?

Abstract Partial large subunit ribosomal DNA (LSU rDNA) sequences were obtained from six morphotypes of “ Ammonia beccarii s.l.” collected from different localities. Each morphotype is characterized by a different LSU rDNA sequence. Sequences of similar morphotypes from geographically distant regions resemble each other more than sequences of different morphotypes from the same locality. DNA analysis and morphologic comparisons allow the distinction of three species: A. tepida A. beccarii and A. parkinsoniana .

Upper Triassic shallow water limestones in the Sinta Ridge (Banda Sea, Indonesia)

Ten rock samples were dredged during the Banda Sea I cruise in the northern slope of the Sinta Ridge, which separates the North and South Banda basins. Some of the samples are limestones from a very shallow marine environment, with Upper Norian (to Rhaetian?) benthic Foraminifera. Similarities with eastern Sulawesi, Buru and Seram are consistent with an independant Upper Triassic block and the origin of the Banda Sea microcontinents is questionable.