High-resolution Conodont Biostratigraphy Research Articles

Carboniferous-Permian high-resolution conodont biostratigraphy and paleoclimate change in North China

The Carboniferous-Permian transition is a critical period for the Late Paleozoic Ice Age that evolved from an acme to the subsequent demise with the initiation of long-term drying in low latitudes. During this time interval, extensive epicontinental deposition occurred in North China in the eastern tropical Tethyan region, and archived important information of climate and sea-level changes. Though several high-precision zircon UPb ages have been reported, they have some conflicts with previously defined biostratigraphic correlations, especially for the Taiyuan Formation. Lack of high-resolution conodont biostratigraphy has impeded the correlation with other well-studied Pangean records. In this study, five conodont zones were established for the successions of the Taiyuan Formation in southern North China. They are Streptognathodus wabaunsensis, S. isolatus, S. sigmoidalis, S. constrictus and S. fusus biozones in ascending order, constraining a late Gzhelian to late Asselian age for the Taiyuan Formation in southern North China, which is consistent with published high-precision zircon UPb ages. The Unitary Association (UA) analysis was used to reconcile the conodont biostratigraphy of the Taiyuan Formation in North China, and was combined with previously published high-precision UPb ages to construct a new chronostratigraphic framework for the Carboniferous-Permian strata across North China. It explicitly indicates an earlier initiation of climate aridification in the northern part than in the southern part of North China possibly due to northward drift and/or increased atmospheric pCO2 and associated global warming.

Upper Devonian conodont fauna from Western Hubei, China and its significance

ABSTRACT Pelagic standard conodont biozonation is less applicable to nearshore shallow-water depositional settings close to the peritidal, where it is needed to establish its own conodont zonation. The Upper Devonian Xiejingsi Formation in South China is an important unit for nearshore conodont biostratigraphy investigation as its deposits in the nearshore argillaceous-carbonate mixed facies which yield numerous marine fossils. 25 conodont species belonging to 6 genera of platform elements were described in four sections of this formation in western Hubei, including 9 new species. Based on the conodont distribution in these sections, six nearshore conodont biozones are introduced in ascending order: Polygnathus brevis – Polynodosus changyangensis sp. nov. Assemblage Zone, Icriodus cornutus – Pelekysgnathus arcuatus sp. nov. – Polygnathus brevilaminus Assemblage Zone, Palmatolepis angulata Zone, Palmatolepis angulata – Palmatolepis quadrantinodosalobata Assemblage Zone, Palmatolepis quadrantinodosalobata Zone and Polygnathus planirostratus Zone. The correlation of these biozones with those of pelagic standard ones indicates an age of the Xiejingsi Formation in western Hubei from at least the Frasnian linguiformis Zone to the Famennian Lower rhomboidea Zone. Through constructing nearshore shallow-water conodont biozones based on the establishment of comprehensive conodont succession, this paper provides a case study for high-resolution conodont biostratigraphy investigation in the shallow-water settings.

Temporal and spatial variations of high-resolution strontium, carbon, and oxygen isotopic chemostratigraphy at the end-Permian crisis boundary in South China

Variable degrees of strontium, carbon, and oxygen isotopic perturbations related to the end-Permian mass extinction (EPME) were recorded from the Latest Permian (i.e., the Lopingian stage prior to the extinction event) to the Earliest Triassic recovery (i.e., the Induan stage), while the underlying causes for their temporal and spatial variations and marine paleoenvironmental indications were poorly understood. In this study, integrated high-resolution 87Sr/86Sr, δ13C, and δ18O proxies are presented across the Wuchiapingian/Changhsingian and Permian/Triassic boundaries within the stratigraphic framework calibrated with high-resolution conodont biostratigraphy and high-precision geochronology in three South China sections, i.e., the Liangfengya, the Meishan, and the Shangsi sections. High-resolution strontium isotopes revealed that the water-mass segregation and accelerated precipitation rate of strontium probably resulted in local heterogeneity and provincial features of 87Sr/86Sr values at short-time interval less than 1 Myr. This provincialism of 87Sr/86Sr values can serve high-resolution chemostratigraphy. Integrated δ13C and 87Sr/86Sr isotopes from the studied sections at the Wuchiapingian/Changhsingian boundary (WCB) revealed that spatial heterogeneity with respect to drift magnitudes and peak values of δ13C negative excursion was not associated with oceanic stratification or high terrestrial input, while the releasing of 13C-depleted CO2 by deep-marine volcanism could be a plausible cause. Moreover, integrated δ18O and 87Sr/86Sr isotopes indicated that the “cooling event” occurring at the WCB was a provincial event, which was influenced by water depth and marine volcanism. The integrated high-resolution 87Sr/86Sr, δ13C, and δ18O proxies confirmed that the oceanic stratification was an ultimate cause for shallow-to-deep-water δ13C gradient at the Permian/Triassic boundary (PTB), but having no link to paleoproductivity increase. The positive excursion of 87Sr/86Sr postdated negative shift of δ13C by ∼ 40 Kyr across the PTB from the studied intervals. This temporal chemostratigraphic variation revealed that terrestrial influx was not a major cause for negative excursion of δ13C. The shallow-to-deep-water 87Sr/86Sr gradient was observed across the PTB in the studied sections, which was probably caused by water segregation resulting from oceanic stratification and distances from high- or low-radiogenic strontium sources supplied by terrestrial input or marine volcanism.

High-resolution conodont biostratigraphy in two key sections from the Carnic Alps (Grüne Schneid) and Graz Paleozoic (Trolp) – implications for the biozonation concept at the Devonian-Carboniferous boundary

High-resolution conodont biostratigraphy in two key sections from the Carnic Alps (Grüne Schneid) and Graz Paleozoic (Trolp) – implications for the biozonation concept at the Devonian-Carboniferous boundary

High-resolution conodont biostratigraphy from the Darriwilian Stage (Middle Ordovician) of the Argentine Precordillera and biodiversity analyses: a CONOP9 approach

High-resolution conodont biostratigraphy from the Darriwilian Stage (Middle Ordovician) of the Argentine Precordillera and biodiversity analyses: a CONOP9 approach

Depositional conditions and revised age of the Permo-Triassic microbialites at Gaohua section, Cili County (Hunan Province, South China)

In many tropical shallow water regions the end-Permian mass extinction event occurs at the top fossiliferous packstone beds and is immediately followed by the development of microbialite facies. Both the age and redox conditions of the microbialite have been debated and both factors are addressed here in a study of the Gaohua section (Cili County, Hunan Province, China): specifically the size distribution of pyrite framboids and high-resolution conodont biostratigraphy. The framboids populations show a broad size range with examples up to 30microns in diameter, and indicating dysoxic but not anoxic depositional conditions. More intense dysoxia is recorded in interbedded laminated micrites but not beds of giant ooids. Both the Hindeodus parvus zone and Isarcicella isarcica zones were established with the microbialite beds being confined to the H. parvus zone. Therefore, the formation of microbialite postdates the end Permian main mass extinction and records oxygen-poor conditions even in a shallow-water setting such as Gaohua section at Cili.

Timing and patterns of the Frasnian–Famennian event: Evidences from high-resolution conodont biostratigraphy and event stratigraphy at the Yangdi section, Guangxi, South China

Continuous centimeter-scale sampling for conodonts with microfacies and carbon isotope analysis has been carried out across the Frasnian–Famennian (F–F) transition at the Yangdi section, Guangxi, South China. The newly revised conodont biostratigraphy reveals a succession of six zones, ranging from the upper Palmatolepis rhenana zone to lower Palmatolepis crepida zone in ascending order. Based on a detailed analysis of conodont abundance and diversity changes through the section, two intervals involving significant conodont faunal changes were recognized in the uppermost Palmatolepis linguiformis zone at the Yangdi section. The first conodont change occurred at the transition between the lower and upper Pa. linguiformis zone and is marked by the disappearance of Pa. linguiformis, accompanied by the successive disappearances of Pa. eureka, Pa. rhenana, Pa. nasuta, Pa. gigas, Ad. ioides, and Ad. nodosa. The second conodont change appeared in a horizon equivalent to the uppermost Upper Kellwasser Horizon (UKH) and is indicated by the elimination of nearly all Frasnian palmatolepids, ancyrodellids, and polygnathids. Furthermore, the second conodont change is coincident with the decimation of ostracods and tentaculitids and is synchronous with the turnovers of conodont biofacies. In addition, the onset of the δ13Ccarb perturbation is a little earlier than the second conodont change, with the maximum amplitude of excursion right at the start of the Famennian. Therefore, we conclude that the second conodont change represents the F–F mass extinction based on the temporal correlation among δ13Ccarb excursions, pelagic faunal changes, and conodont biofacies turnovers during the F–F boundary interval. According to the high-resolution conodont biostratigraphy together with cyclostratigraphy, the uppermost UKH and whole UKH contain 1 and 12 bundle cycles, respectively. Thus, the time span of the mass extinction and the entire Upper Kellwasser crisis lasted 16–18kyr and ~200kyr, respectively.

High-resolution δ13Ccarb chemostratigraphy from latest Guadalupian through earliest Triassic in South China and Iran

Large carbon cycle perturbations are associated with the end-Permian mass extinction and subsequent recovery, but Late Permian (Lopingian) carbon cycle dynamics prior to the mass extinction event remain poorly documented. Here we present a high-resolution δ13Ccarb chemostratigraphic framework from latest Guadalupian to earliest Triassic time, calibrated with high-resolution conodont biostratigraphy and high-precision geochronology. We observe two large negative excursions in δ13Ccarb, the first in uppermost Guadalupian strata and the second at the end of the Changhsingian stage, and between these events distinctive excursions from the middle Wuchiapingian to the early Changhsingian. The end-Changhsingian excursion represents a major reorganization of the global carbon cycle associated with the end-Permian mass extinction. However, the extent to which the end-Guadalupian and Wuchiapingian/Changhsingian boundary excursions result from local versus global controls remains unresolved. Regardless of their underlying causes, these three excursions provide chemostratigraphic markers for global correlation of Lopingian strata.

Lower Triassic Smithian-Spathian Boundary at West Pingdingshan Section in Chaohu, Anhui Province

The West Pingdingshan Section in Chaohu, Anhui Province, has been extensively studied in recent years and become one of the classic Lower Triassic sequences well-clarified in multiple stratigraphies. Also it is an important section that defines the Smithian-Spathian (S-S) boundary within the Olenekian Stage. The S-S boundary strata at the section are restudied in high-resolution conodont biostratigraphy and carbon isotopes. The refined S-S boundary defined by the FAD of conodont Neospathodus pingdingshanensis is at 30 cm above the base of Bed 52, corresponding to a rapid diversification of conodonts. A sharp positive shift of δ13Ccarb curve co-occurs at the S-S boundary and it can be used as a key reference to define the boundary. The defined S-S boundary position and carbon isotopes curve can be well correlated globally.

The mid-Capitanian (Middle Permian) mass extinction and carbon isotope record of South China

Conodont, C isotope and fossil and facies data are presented for the Capitanian (Middle Permian) mass extinction record seen in platform carbonates (Maokou and Wuchiaping formations) of South China, where limestones interdigitate with the volcanic succession of the Emeishan large igneous province. The Maokou Formation provides an extinction record marked by the loss of keriothecal-walled fusulinaceans and a turnover in calcareous algae. In sections within the Emeishan province this crisis occurs at the base of the oldest record of volcanism from the Jinogondolella altudaensis conodont zone (of mid-Capitanian age). Around the periphery of the Emeishan province this extinction level lies within the upper part of the Maokou Formation at a level where platform carbonate deposition was frequently interrupted by thick volcanic ash depositional events. The assemblages of the uppermost Maokou Formation are characterised by typical “Late Permian” taxa although these levels still lie within the Middle Permian (Guadalupian Series). “Disaster” taxa, such as Earlandia and Diplosphaerina are locally prolifically abundant in the aftermath of the mass extinction. The crisis is particularly noteworthy amongst photosynthetic taxa such as calcareous algae and fusulinaceans that probably harboured photosymbionts. Therefore, a kill mechanism involving cooling from explosive volcanism and potentially acid rain from sulphate aerosols appears appropriate. A composite δ 13C carb curve, calibrated against a high-resolution conodont biostratigraphy reveals a major intra-Capitanian negative excursion (of > 5‰) superimposed on typically heavy (4–5‰) Middle Permian values. This curve can also be recognised in Panthalassan seamount carbonates of Japan although this requires reassignment of apparently Upper Permian limestones to the Middle Permian. In both China and Japan the Capitanian mass extinction occurs during the early stage of this major, intra-Capitanian negative excursion. Assuming typical platform carbonate accumulation rates, the records of the Maokou Formation suggest δ 13C carb values fell at ∼ 0.01‰/kyr suggesting a catastrophic origin (such as gas hydrate destabilisation) is unlikely, although a volcanic source is possible.