3 results on '"Romain Vaucher"'
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2. Palynomorphs of the Fezouata Shale (Lower Ordovician, Morocco): Age and environmental constraints of the Fezouata Biota
- Author
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Romain Vaucher, Bernard Pittet, Thijs R.A. Vandenbroucke, Mustapha Akodad, Hendrik Nowak, Robert R. Gaines, Thomas Servais, Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
010506 paleontology ,Acritarch ,Lagerstätte ,Biozone ,Chitinozoan ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Paleontology ,Floian ,Chitinozoans ,Index fossil ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Palynology ,Acritarchs ,biology ,Fezouata Shale ,15. Life on land ,biology.organism_classification ,Tremadocian ,Morocco ,[SDU]Sciences of the Universe [physics] ,Lower Ordovician ,Geology - Abstract
The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstatte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300 km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1-2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstatte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision. (C) 2016 Elsevier B.V. All rights reserved.
- Published
- 2016
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3. Tropical cyclone deposits in the Pliocene Taiwan Strait: Processes, examples, and conceptual model
- Author
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Sébastien Castelltort, Ludvig Löwemark, Romain Vaucher, Shahin E. Dashtgard, Jessica E. Pilarczyk, and Yu-Yen Pan
- Subjects
010506 paleontology ,Hummocky cross-stratification ,Stratigraphy ,Trough (geology) ,Geology ,010502 geochemistry & geophysics ,01 natural sciences ,Waves and shallow water ,Paleontology ,13. Climate action ,Clastic rock ,Typhoon ,14. Life underwater ,Sedimentology ,Tropical cyclone ,Foreland basin ,0105 earth and related environmental sciences - Abstract
The characteristics of tropical cyclone (TC) deposits are highly variable, and in the shallow waters of straits their character has not been established. Multiple coarse-grained beds in lower Pliocene strata in the Western Foreland Basin of Taiwan are interpreted as TC deposits, and the sedimentology of these beds reflects evolving TC processes and storm stages. By comparing sedimentological data from these beds with previous research on TCs, and with analysis of TCs that cross Taiwan from east to west, a conceptual model is built for understanding deposition in the Taiwan Strait during tropical cyclones. Taiwan is impacted by more than three TCs per year, including more than two super-typhoons every 10 years. These storms can deliver immense volumes of rain over very short time periods and are associated with intense winds. During TCs, and in shallow water in the Taiwan Strait (10–35 m water depth), hyperpycnal discharge, strong bottom currents, and oscillatory wave motion all impact deposition. These processes are manifested in the resulting deposits, and we propose that the best sedimentological criteria for recognizing TC deposits, include: 1) a basal scour surface; 2) an absence of within-bed bioturbation; 3) trough cross-stratification that preserves multi-directional, mainly shore-parallel flow with a 180° change in flow direction; 4) preservation of oscillatory structures towards the top of the bed; and, 5) organic lamina and clasts throughout the bed. Mudstone intercalated with trough cross-stratification is also a useful indicator of TC deposition as it probably reflects wave- and current-redistribution of sediment delivered to the strait through hyperpycnal and hypopycnal discharge from rivers. Contemporaneous mud deposition within TC beds is manifested as mudstone drapes on foresets and toesets, and discontinuous mudstone beds between trough cross-stratified sandstone beds. While not all TC beds exhibit all sedimentological characteristics, we hypothesize that high-probability TC beds should show three or more of them.
- Published
- 2020
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