Showing papers by "Sylvain Rigaud published in 2013"

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.

A methods assessment and recommendations for improving calculations and reducing uncertainties in the determination of 210Po and 210Pb activities in seawater

Abstract: In marine systems, 210 Po and 210 Pb disequilibria are being increasingly used to examine oceanic particle for mation and export. Here, an updated assessment of current methods for determining 210 Po and 210 Pb activity in marine samples is provided and includes a complete description of the vast number of calculations and uncer tainties associated with Po and Pb loss, decay, and ingrowth during sample processing. First, we summarize the current methods for the determination of 210 Po and 210 Pb activities in dissolved and particulate seawater sam ples and recommend areas for improvement. Next, we detail the calculations and associated uncertainties using principles of error propagation, while also accounting for radionuclide ingrowth, decay, and recovery. A spread sheet reporting these calculations is included as a downloadable Web Appendix. Our analysis provides insight into the contributions of the relative uncertainty for each parameter considered in the calculation of final 210 Po

Effects of flow rates and composition of the filter, and decay/ingrowth correction factors involved with the determination of in situ particulate 210Po and 210Pb in seawater

Abstract: NSF [OCE-0851032, OCE-0851462]; Korea Ocean Research and Development Institute; Marine Pubic Welfare Project [201005012-3]; Fujian Natural Science Foundation [2009J06026]; U.S. National Science Foundation, Chemical Oceanography Program

Live (stained) benthic foraminifera from the Cap-Ferret Canyon (Bay of Biscay, NE Atlantic): A comparison between the canyon axis and the surrounding areas

Abstract: Living (Rose Bengal stained) benthic foraminiferal faunas were investigated at 13 deep-sea stations sampled in the Cap-Ferret Canyon area (NE Atlantic). One station (151 m) is located on the continental shelf close to the canyon head. All other stations are located along 2 bathymetric transects: 7 sites along the canyon axis with depths ranging from 300 to 3000 m and 5 stations along the adjacent flank with depths ranging from 300 m to 2000 m. Sedimentological analyses indicate that the Cap-Ferret Canyon is at present inactive in terms of sediment gravity flow. Compared to stations on the adjacent flank, canyon-axis stations are generally characterised by shallow oxygen penetration depths, high diffusive oxygen uptakes (DOU) and high lipid contents. Higher mineralisation rates recorded in the canyon axis are likely due to a preferential focusing of labile organic matter in the canyon axis. Foraminiferal standing stocks do not exhibit any straightforward correlation with the different descriptors of organic matter available in the sediment. However, foraminiferal standing stock and diversity along the canyon axis are generally higher than on the adjacent flank. Canyon axis sites yield dominant species that are similar to those at adjacent flank and open slope stations located at comparable water depths. However, intermediate and deep infaunal species were only recorded in the lower canyon axis, where high amounts of organic matter were observed in deeper sediment layers. Finally, the faunal composition in the Cap-Ferret Canyon is different compared to the nearby Cap-Breton Canyon, where sediment gravity flows are active. The absence of pioneer species and the occurrence of highly specialized taxa are both consistent with the much more stable conditions in terms of hydro-sedimentary conditions prevailing in the Cap-Ferret Canyon.

Taxonomy, phylogeny, and functional morphology of the foraminiferal genus Involutina

Abstract: Early Jurassic aragonitic foraminifers are outstandingly well-preserved in the Marmorea crust, a multiphased ferromanganese layer limiting the Schnoll and Adnet formations (Adnet, Northern Calcareous Alps, Austria). This remarkable preservation, related to the pervasive impregnation of aragonitic tests prior to their recrystallization, allowed observing unknown diagnostic features of the genus Involutina, which typifies the Suborder Involutinina. Thanks to a detailed examination of the Adnet specimens, this paper clarifies the taxonomy, systematic position, and phylogeny of Involutina. A new diagnosis, structural model, and lineage are introduced for the group. Involutina is the direct descendant of Aulotortus and the two taxa probably showed a parallel evolution. As Aulotortus, Involutina presents a high intraspecific variability and its diversity must be revised downward. Current phylogenetic and taxonomic frames of the Suborder Involutinina are firmly questioned as, contrary to previous schemes, the type-genus possesses more than one lamellar deposit per whorl. In Involutina, the height and distribution of papillae on the test surface is not random and probably related to a biological function. We here propose that the papillose lamellae and tube infoldings that characterize representatives of the genus were rudimentary features for light catching and symbiont positioning, respectively.