Sylvain Rigaud

Bio: Sylvain Rigaud is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Benthic zone & Water column. The author has an hindex of 16, co-authored 56 publications receiving 907 citations. Previous affiliations of Sylvain Rigaud include University of Bordeaux & University of Montana.

Taxonomy and phylogeny of the Trocholinidae (Involutinina).

Abstract: Exceptionally well-preserved trochospirally coiled Involutinina have been found in Late Triassic (Wallowa Mountains, Oregon, U.S.A.) and Early Jurassic (northern Calcareous Alps, Austria) carbonate rocks. Their remarkable preservation, related to impregnation of the test prior to recrystallization, allowed us to observe features usually obliterated by diagenetic and metamorphic processes. This paper provides a revision of the morphology, structure, systematic position, phylogeny, and stratigraphic range of the family Trocholinidae Kristan-Tollmann. New criteria permitting the distinction between trocholinid genera, even in cases of intense recrystallization, are presented. An identification key and a new, monophyletic tree are proposed for the whole family. The main outcomes of this work are that 1) Neotrocholina Reichel is definitively excluded from the Involutinina; 2) the genera Andersenolina Neagu, Hottingerella Piller, and Septatrocholina BouDagher-Fadel and Banner are placed in synonymy with Coscinoconus Leupold; 3) the genus Ornatoconus di Bari is considered a synonym of Trocholina Schlumberger; 4) the distinction between the genera Auloconus Piller and Lamelliconus Piller is abandoned; 5) five new genera ( Coronaserra n. gen., Frentzenella n. gen., Kristantollmanna n. gen., Papillaconus n. gen., and Wallowaconus n. gen.) and three new species ( Frentzenella frentzeni n. gen., n. sp., Frentzenella perforata n. gen., n. sp., and Wallowaconus oregonensis n. gen., n. sp.) are introduced; 6) the species “ Trocholina intermedia ” Henson is reinstituted; 7) “ Trocholina gigantea ” Pelissie and Peybernes, and “ Semiinvoluta verrucosa ” Tollmann and Kristan-Tollmann are renamed Coscinoconus limognensis nom. nov. and Papillaconus kristani nom. nov., respectively; and 8) new combinations for several species of Trocholinidae are provided. The recognition of two subfamilies (Lamelliconinae and Trocholininae) and twelve genera within the Trocholinidae underlines the high diversity of the family. The rapid diversification and widespread distribution characterizing the group suggest that the potential of trochospirally coiled Involutinina in stratigraphic and paleoenvironmental studies is greatly undervalued.

The Lhasa Terrane: Record of a microcontinent and its histories of drift and growth

Abstract: article i nfo The Lhasa Terrane in southern Tibet has long been accepted as the last geological block accreted to Eurasia before its collision with the northward drifting Indian continent in the Cenozoic, but its lithospheric architecture, drift and growth histories and the nature of its northern suture with Eurasia via the Qiangtang Terrane remain enigmatic. Using zircon in situ U-Pb and Lu-Hf isotopic and bulk-rock geochemical data of Mesozoic-Early Tertiary magmatic rocks sampled along four north-south traverses across the Lhasa Terrane, we show that the Lhasa Terrane has ancient basement rocks of Proterozoic and Archean ages (up to 2870 Ma) in its centre with younger and juvenile crust (Phanerozoic) accreted towards its both northern and southern edges. This finding proves that the central Lhasa subterrane was once a microcontinent. This continent has survived from its long journey across the Paleo-Tethyan Ocean basins and has grown at the edges through magmatism resulting from oceanic lithosphere subduction towards beneath it during its journey and subsequent collisions with the Qiangtang Terrane to the north and with the Indian continent to the south. Zircon Hf isotope data indicate significant mantle source contributions to the generation of these granitoid rocks (e.g., ~50-90%, 0-70%, and 30-100% to the Mesozoic magmatism in the southern, central, and northern Lhasa subterranes, respectively). We suggest that much of the Mesozoic magmatism in the Lhasa Terrane may be associated with the southward Bangong-Nujiang Tethyan seafloor subduction beneath the Lhasa Terrane, which likely began in the Middle Permian (or earlier) and ceased in the late Early Cretaceous, and that the significant changes of zircon eHf(t) at ~113 and ~52 Ma record tectonomagmatic activities as a result of slab break-off and related mantle melting events following the Qiangtang-Lhasa amalgamation and India-Lhasa amalgamation, respectively. These results manifest the efficacy of zircons as a chronometer (U-Pb dating) and a geochemical tracer (Hf isotopes) in understanding the origin and histories of lithospheric plates and in revealing the tectonic evolution of old orogenies in the context of plate tectonics.

Evolution and Geological Significance of Larger Benthic Foraminifera

Abstract: 1. Biology and history of larger benthic foraminiferaHistory and biological classification of foraminiferaEcology of the living larger foraminiferaPalaeontological and evolutionary history of the larger foraminiferaTaxanomic features used in larger foraminiferal classificationBiostratigraphic distribution over time of larger foaminiferaGeneral factors effecting the evolution of marine species in the mid to late Phanerozic2. The Palaeozoic larger benthic foraminifera: The Carboniferous and PermianMorphology and taxonomy of Palaeozoic larger benthic foraminiferaBiostratigraphy and phylogenetic evolutionPalaeoecology of the fusulinidsPalaeogeographic distribution of the fusulinids3. The Mesozoic larger benthic foraminifera: the TriassicMorphology and taxonomy of Triassic larger benthic foraminiferaBiostratigraphy and phylogenetic evolutionPalaeoecology of Triassic foraminiferaPalaeogeographic distribution of Triassic foraminifera4. The Mesozoic larger benthic foraminifera: the JurassicMorphology and taxonomy of Jurassic larger benthic foraminiferaBiostratigraphy and phylogenetic evolutionPalaeoecology of Jurassic foraminiferaPalaeogeographic distribution of Jurassic foraminifera5. The Mesozoic larger benthic foraminifera: the CretaceousMorphology and taxonomy of Cretaceous larger benthic foraminiferaBiostratigraphy and phylogenetic evolutionPalaeoecology of Cretaceous foraminiferaPalaeogeographic distribution of Cretaceous foraminifera6. The Palaeogene larger benthic foraminiferaMorphology and taxonomy of Palaeogene larger benthic foraminiferaBiostratigraphy and phylogenetic evolutionPalaeoecology of Palaeogene foraminiferaPalaeogeographic distribution of Palaeogene foraminifera7. The Neogene larger benthic foraminiferaMorphology and taxonomy Neogene larger benthic foraminiferaBiostratigraphy and phylogenetic evolutionPalaeoecology of Neogene foraminiferaPalaeogeographic distribution of Neogene foraminifera8. SynthesisImportance of application of larger foraminifera in biostratigraphyImportance of larger foraminifera as marine environmental indicatorsThe significance of the larger foraminifera assemblages in the understanding of the global distribution of carbonate sediments and their value in contributing raw data to palaeoenvironmental and palaeoclimatic modelsAppendixNomenclature terminology and glossary