OSTRACODS FROM THE LATE TRIASSIC (NORIAN) OF YUKON, CANADA: NEW TAXONOMIC AND PALAEOBIOGEOGRAPHIC INSIGHTS

The present work investigates the significance of Late Triassic ostracods from the Yukon Territory, Canada, and adds to the scientific knowledge of the taxonomy of these organisms during the Norian, which remain poorly documented and understood. Fifteen limestone samples representing distinct marine palaeoenvironments cropping out at Lime Peak, Stikinia terrane, provided 90 species, including 9 newly described: Alatobairdia? sohni n. sp., Bairdia aksala n. sp., B. taan n. sp., B. yukonensis n. sp., Cornutobairdia yukonella n. sp., Lobobairdia whitella n. sp., Mirabairdia canadia n. sp., Hungarella limella n. sp., Leviella riedeli n. sp. Most assemblages point to neritic conditions in the photic zone. A similarity analysis demonstrates the distinct composition of reef-related and algae-related ostracod assemblages. The ostracod-algae associations in Lime Peak reveal that the affinity of Bairdiidae for algae (Dasycladaleans in the case of Lime Peak) was already established in the Norian. A faunal link is identified during the Norian between eastern and western Panthalassa and Japan, in line with studies on other taxa. The flux of species between eastern Panthalassa and Tethyan areas appears very unbalanced in the Late Triassic with most migrations originating from the Tethys. Further data from other Middle and Upper Triassic Panthalassan localities and stages (i.e. Ladinian and Carnian) are needed to confirm whether this apparent trend is due to sampling bias or reflects real dispersal fluxes

APPENDICES

Appendix 1, complete list of the ostracods species occurring in the Anisian, Middle Triassic of North Dobrogea, Romania (Mirăuță et al. 1993; Crasquin-Soleau & Grădinaru 1996; Sebe 2013; Sebe et al. 2013; this work).; appendix 2, matrix of ostracod species distribution during the Anisian, Middle Triassic; appendix 3, matrix of ostracod genera distribution during the Anisian, Middle Triassic

Data from: First report of ostracods (Crustacea) associated with Bithynian (Anisian, Middle Triassic) Tubiphytes-microbial reef in the North Dobrogean Orogen (Romania)

The Mahmudia Quarry is located in the North Dobrogean Orogen (Romania), representing the western tip of the Palaeotethys-issued Cimmeride Orogenic System. One sample from the Tubiphytes-microbial reef exposed in the quarry yielded an abundant well-preserved ostracod assemblage of Bithynian, early Middle Anisian, Middle Triassic age. We report the occurrence of 56 ostracod species distributed among 23 genera. Ten species are newly described: Acratia caeracella sp. nov., Bairdia mandruella sp. nov., B. liviae sp. nov., Hungarella mahmudiaensis sp. nov., Kempfina tineriella sp. nov., Liuzhinia antalyaformis sp. nov., L. bithynica sp. nov., L. edvardgriegi sp. nov., Microcheilinella contrariella sp. nov., Paracypris oanaella sp. nov. One species is renamed, Bairdia monostorii nom. nov. and the diagnosis of the genus Palaeocypridina is emended to include the central muscle scars pattern. The Tubiphytes ecosystem is a complex with a multi-layer food chain as shown by the presence of diversified carnivorous nekton-benthic ostracods, being both preys and predators of other organisms. The palaeoenvironmental requirements of the main ostracod taxa indicate a deposition in an open marine environment, on the outer platform-upper slope zone, in accordance with information provided by other proxies. We discuss the relationship of ostracods and microbial mats during the Triassic and conclude that the composition of assemblages are rather related both to the characteristics of this chemosynthetically-driven habitat and to bathymetry. However, some taxa, such as the genus Liuzhinia, are typical of Triassic microbial ecosystems. We perform the first analysis of ostracods provincialism during the Anisian and identify a distinct peri-Palaeo-Tethyan province

Upper Triassic Carbonate Records: Insights from the Most Complete Panthalassan Platform (Lime Peak, Yukon, Canada)

Upper Triassic carbonate platforms from the Panthalassa Ocean remain less-understood and less-studied than their Tethyan equivalents. This imbalance is largely due to the poorer preservation state of Panthalassan carbonate rock successions in terms of rock quality and depositional geometries, which prevents good appreciation of depositional systems. In this context, carbonate exposures from Lime Peak (Yukon, Canada) represent an outstanding exception. There, the remains of an Upper Norian Panthalassan carbonate platform are well-exposed, show remarkably preserved depositional geometries and overall superior rock preservation. In this work, we analyse the carbonates from the Lime Peak area with particular attention to the vertical and lateral distribution of biotic assemblages and microfacies at the platform scale. Results demonstrate that the Lime Peak platform was surrounded by a basin with an aphotic sea bottom. The carbonate complex developed in warm waters characterized by high carbonate saturation. The area was also defined by moderate to high nutrient levels: this influenced the type of carbonate factory by favouring microbialites and sponges over corals. During its growth, Lime Peak was influenced by tectono-eustatism, which controlled the accommodation space at the platform top, primarily impacting the internal platform environments and the stability of the slope. Gaining better knowledge of the spatial distribution and dynamics of Upper Triassic organisms and sedimentary facies of Panthalassa in relation to tectono-eustatism lays the first foundations for reconstructing more robust platform models and understanding the evolution of other, more dismantled Upper Triassic Panthalassan carbonate systems through time.</p

Lower triassic (Olenekian) microfauna from Jadar block (Gučevo mt., Nw serbia)

Systematic study of microfossil associations on the Krivi Potok section (Gučevo Mt. area, NW Serbia) has been carried out to document and to refine the Lower Triassic stratigraphic correlations within Alpine-Mediterranean domain. Field investigation and laboratory process have enabled the identification of lowermost Olenekian (lower Smithian) conodonts, ostracodes and pyrite framboids. Two conodont zones are established in this region, in ascending order they are: Pachycladina obliqua-Foliella gardenae Assemblage Zone and Neospathodus planus Zone. A new ostracode species Paracypris ? krivipotokensis FOREL n. sp. has been described, it co-occurs with conodont Neospathodus planus within the Zone of the same name. The pyrite framboids were formed within the ostracode carapaces after their death. The size distribution of pyrite framboids supports the former suggestion that large size (>6 μm in diameter) is not suitable for the reconstruction of seawater redox conditions

Invitation to Magnetism and Magentic Resonance

This paper constitutes an elementary introduction to magnetism and spin resonance