N and C Isotopic Compositions of the Lower Triassic of Southern Primorye and Reconstruction of the Habitat Conditions of Marine Organisms

N and C isotopic data are recorded and presented for the first time for the Lower Triassic claystones of Southern Primorye (Abrek Section). Five N isotope intervals and 11 more or less pronounced negative C isotope excursions, likely to reflect instability of the temperature regime and the oceanographic situation in the Early Triassic, are recognized in the section. The most favorable conditions for ammonoid recovery and other marine organisms in the Early Triassic (after the end- Permian ecological crisis) were associated with the late Induan—early Olenekian transgression and probable cooling.     

Global correlation of basal Triassic layers in the light of the first carbon isotope data on the Permian-Triassic boundary in Northeast Asia

This paper is dedicated to the global correlation of the marine Permian-Triassic boundary layers based on some published and original data on the δ¹³C_org and δ¹³C_carb values obtained for the section along the Suol Creek (Setorym River, southern Verkhoyansk region). The section includes six carbon-isotope intervals readily distinguished in the corresponding curves obtained for several Permian and Triassic reference sections in Eurasia and North America including palleontologically well substantiated sections of central Iran, Kashmir, and South China. This provides grounds for assuming the Permian-Triassic boundary’s position in the Suol Creek section as being close to the carbon-isotope minimum of Interval IV. In the light of new data, the upper part of the Upper Permian Changhsingian Stage in Siberia is proposed to correspond in range to the Otoceras concavum range zone, and the lower substage of the Lower Triassic Induan Stage, to the Tompophiceras pascoei and Wordieoceras decipiens zones. The Otoceras concavum Zone of the Verkhoyansk region in its new understanding is likely correlative with the upper Changhsingian Hypophiceras triviale Zone of Greenland. Carbon-isotope intervals II, III, IV, and V defined in the Permian-Triassic boundary layers of the Verkhoyansk region, which are traceable in several reference sections of Eurasia and North America, evidently coincide with the period of some intensification of the volcanic activity in the initial late Changhsingian and with the first phases of extensive eruption of Siberian trappes in the terminal Changhsingian and initial Induan ages. New data imply the probable survival of some ammonoid species from the superfamily Otoceratoidea after the mass extinction of organisms in the terminal Permian Epoch.     

Contact metamorphism of siliceous dolomite and impure limestones from the Werfen formation in the eastern Monzoni contact aureole

Summary ?The intrusive complex of Monzoni in the western central Dolomites (northern Italy) comprises a suite of pyroxenites, monzogabbros and monzodiorites with solidus temperatures in excess of 1000 °C which intruded previously unmetamorphosed Permotriassic sediments at less than 5 km depth. At the eastern intrusive contact an approximately 860 m wide contact aureole is developed in the carbonate country rocks. The prograde sequence of mineral parageneses in a siliceous dolomite of the Cencenighe member and in marly limestones of the Val Badia and Cencenighe members of the Lower Triassic Werfen formation indicate peak metamorphic temperatures in excess of 698 °C at 185 m from the intrusive contact and an outward temperature decrease of approximately 65 °C per 100 m. The high temperatures in the inner aureole caused formation of periclase from the prograde breakdown of dolomite and formation of melilite and esseneite-rich clinopyroxene. Present address: Mineralogisch-Petrographisches Institut, Universit?t Basel, Switzerland Received April 7, 2001; revised version accepted December 6, 2001     

The first detailed δ13Соrg record in Permo-Triassic boundary deposits in the Kolyma–Omolon region (Northeast Asia)

Doklady Earth Sciences - We have obtained the first detailed δ13Сorg record in Permian-Triassic boundary sediments in deepwater facies in Northeast Asia (Kolyma–Omolon region,...     

The First Data on the N Isotopic Composition of the Permian and Triassic of Northeastern Russia and Their Significance for Paleotemperature Reconstructions

Doklady Earth Sciences - It is proposed that unstable temperature conditions in the Late Wuchiapingian and Early Changhsingian (Late Permian) changed in the Boreal Superrealm to less contrasting...     

N and C Isotopic Compositions of the Lower Triassic of Southern Primorye and Reconstruction of Habitat Conditions of Marine Organisms after Mass Extinction at the End of the Permian

Data on the N and C isotopic composition are presented for the Lower Triassic claystones of the Abrek section of southern Primorye (Far East). The results showed five N isotopic intervals and several negative C isotopic excursions of the Induan–lower Olenekian stages of the Abrek section.     

The Position of the Wuchiapingian–Changhsingian Boundary in Northeast Russia on the Basis of Radioisotopic and Chemostratigraphic Data

Doklady Earth Sciences - The approximate position of the Wuchiapingian–Changhsingian boundary of the Upper Permian in Northeast Russia was determined for the first time on the basis of the...     

Lower Triassic δC isotope curve from shallow-marine carbonates in Japan, Panthalassa realm: Confirmation of the Tethys δC curve

δ¹³C data from Tethyan sections provide evidence of profound changes in the carbon cycle during the Lower Triassic. Sections from the Panthalassa realm were investigated to establish whether these variations are also present there. In the Jurassic accretionary wedges in Japan, exotic blocks having a Panthalassan affinity, have been incorporated. The majority of the blocks are pelagic cherts but rare shallow-water carbonates are also present. We present a δ¹³C study on the Lower Triassic of a shallow-water carbonate succession deposited on a mid-oceanic seamount and accreted to the Chichibu Belt, Japan. Two sections have been measured at Kamura, central Kyushu Island. The carbon isotope curve shows depleted values across the Permian–Triassic boundary (PTB), subsequently followed by an increase to heavier values into the Dienerian, culminating in a maximum of almost +4‰ V-PDB, before a steep drop at a stratigraphic gap. Low values are recorded in the Smithian, but rise to enriched δ¹³C values > +3.5‰ near the Smithian–Spathian boundary. The observed trend of the stable carbon isotope curve from Japanese sediments mirrors the curves derived from sections in the Tethys (e.g. Italy, Iran, Turkey, Oman and the South China Nanpanjing Basin). Our results support the interpretation of this curve as representing a global trend across the PTB and in the Lower Triassic, although some distinct features are absent around the Dienerian/Smithian boundary. Profound variations of the carbon isotope curve in the Lower Triassic are presented for the first time from a marine section outside of the Tethys. They indicate severe, global changes in the Lower Triassic carbon cycle, and the causative processes must have significantly contributed to the delayed biotic recovery after the PTB. Large amounts of carbon were shifted between carbon reservoirs, most probably between shallow- and deep-ocean waters, and/or ocean and sediment. Anoxia followed by overturn of the ocean water masses may have been the mechanism which quickly altered ecological conditions in the ocean leading to variable availability of nutrients and oxygen, and changes in isotope composition of the available carbon in the surface waters that was incorporated in the precipitated carbonate.