Conodont Zones Research Articles

FORAMINIFERAL BIOSTRATIGRAPHY ACROSS THE VISEAN/SERPUKHOVIAN BOUNDARY IN THE VEGAS DE SOTRES SECTION (CANTABRIAN MOUNTAINS, SPAIN)

A continuous succession of the upper part of the Alba Formation is recorded in the Vegas de Sotres section in the Cantabrian Mountains, northern Spain. This section contains slightly shallower-water facies than elsewhere and as a result is particularly rich in foraminifers. Characterization of the late Visean to Serpukhovian interval in coeval deeper water settings is accomplished by means of integrating conodont, ammonoid and foraminiferal data. The foraminiferal assemblages recorded in units 1–4 of the Alba Formation enabled correlation with the Russian substages in the Moscow Basin, Urals and Donets Basin. The upper part of the Canalon Member (unit 1) is correlated with the Venevian, the lower part of unit 2 is correlated with the Tarusian, and the Steshevian is recognized in the middle and upper part of unit 2. Most of unit 3 is correlated with the Protvian and is equivalent to the E2a ammonoid zone. The youngest Millaro Member (unit 4) contains undiagnostic foraminifers and lies within the Gnathodus truyolsi Conodont Zone equivalent to the E2b/E2c ammonoid zones. The base of the Serpukhovian is defined on the first occurrence of the conodont Lochriea ziegleri . Slightly below this horizon are recorded Neoarchaediscus parvus, N . aff. N . postrugosus, Biseriella paramoderata, Asteroarchaediscus rugosus, Howchinia hemisphaerica and Rectoendothyra latiformis . At the Visean/Serpukhovian (V/S) boundary, species of Tubispirodiscus are recorded and just above, the presence of Asteroarchaediscus baschkiricus is confirmed. The late Serpukhovian is characterized by the occurrence of diverse Eostaffella pseudostruvei, E . sp. cf. E. postmosquensis, Eostaffellina “ protvae ”, Eost. actuosa and Plectostaffella varvariensis . Two new genera and four new species are described: Janischewskina gibshmanae n. sp., Endostaffellopsis umbilicata n. gen. n. sp., Vachardites spinosus n. gen. n. sp., V. priscelloides n. gen. n. sp.

Integrated radiolarian and conodont biostratigraphy of the Middle Permian Gufeng Formation (South China)

Radiolarians are usually abundant in chert sequences and they have thus been widely used for the biostratigraphy of deep-water sediments. However, there are many difficulties in the correlation of radiolarian biostratigraphic schemes with the standard conodont zones. In this study, 21 radiolarian species were extracted from the Gufeng Formation that crops out in the Luojiaba (LJB) section (western Hubei, China), together with 5 co-occurring conodont species. In this way, it is the first time that the Pseudoalbaillella globosa, Follicucullus monacanthus and F. scholasticus radiolarian zones can be directly correlated with the Jinogondolella nankingensis gracilis, J. aserrata and J. postserrata conodont zones. Accordingly, the 3 radiolarians zones are now firmly correlated with the Roadian to middle Capitanian interval (Middle Permian).

Biostratigraphy and biofacies of the Middle Darriwilian (Ordovician) conodonts from the Laoshidan section in the western margin of the North China Craton

Abstract Middle Ordovician conodonts from the Sandaokan and Zhuozishan formations of the Laoshidan section at the western margin of the North China Craton, consist of 39 identified and six indeterminate species belonging to 21 genera, and three taxa left in open nomenclature at both genus and species levels. Of particular biostratigraphic importance is the presence of morphologically advanced species of Histiodella associated with several age-diagnostic endemic taxa, making it possible to recognize international conodont biozones in the main part of the sequence. Three Histiodella-based zones are recognized in the studied section; including the Histiodella cf. holodentata, Histiodella kristinae and Histiodella bellburnensis zones, in ascending order. They can be directly correlated with the conodont zonations established in western Newfoundland, Canada and Tarim, western China, and compared well with the conodont biozones of Baltoscandia and Yangtze, central China. However, the same stratigraphic interval on the North China Platform is barren of conodonts. Multivariate statistical studies on these conodonts allow recognition of four conodont biofacies: Scalpellodus biofacies, Panderodus biofacies, Drepanoistodus biofacies and Phragmodus biofacies. Turnovers of the conodont biofacies are related to either sea-level changes or mixing of shallow water conodonts due to down slope transportation. Excluding the effect of the allochthonous conodonts, the transgressive-regressive patterns demonstrated by the conodont biofacies compare closely to the published sea-level curves for the western margin of the North China Craton.

Devonian/Carboniferous boundary glacioeustatic fluctuations in a platform-to-basin direction: A geochemical approach of sequence stratigraphy in pelagic settings

We investigated high-resolution stratigraphic distribution of selected major and trace elements and gamma-ray spectra of fourteen Devonian/Carboniferous (D/C) boundary sections of Europe located in the late Palaeozoic Laurussia and Gondwana. The aim was to trace the geochemical signature of a marked forced and normal regressive interval which was associated with rapid progradation of siliciclastics into the marine carbonate systems (Rhenish Massif) and a prominent hiatus in shallow-water ramp settings (Namur–Dinant Basin). This interval represents the late Devonian Hangenberg event (HBE) sensu lato (middle praesulcata conodont zone) as defined by previous authors. This regressive interval (FSST to LST) correlates with thin shale layers (HBE shale) sandwiched between monotonous nodular calcilutite/calcisiltite successions at five pelagic sections of Moravia, Carnic Alps, Montagne Noire, and Pyrenees. In all sections with continuous D/C sedimentation (i.e., except those of the Namur–Dinant Basin), the HBE s.l. interval is accompanied by elevated percentages of detrital proxies (Al, K, Rb, Zr) and changes in their ratios (Zr/Rb, K/Al, Rb/K) which are normally interpreted as indicators of increased siliciclastic input, provenance, and grain size. Zr/Rb and other proxies are traceable even without apparent lithological evidence and can, therefore, facilitate stratigraphic correlation. Paleoredox and productivity proxies (U/Th and Ni/Rb enrichment factors) only rarely show elevated values in the Hangenberg black shale interval, indicating that the associated water dysoxia/anoxia was a local rather than global phenomenon. Global correlations based on the HBE black shales should therefore be dropped in favor of the HBE s.l. interval. Moreover, analysis of sedimentation rates in the upper expansa to kockeli zone interval using the published radiometric ages suggests that the HBE s.l. was a time of significant increase in the rate of siliciclastic supply into the ocean, even in the most distal pelagic sections. Consequently, the previous interpretation of the HBE black shale as a condensed succession deposited during rapid sea-level rise seems unlikely. We interpret the HBE s.l. (i.e., including the HBE black shale) as a marine record of glacioeustatic sea-level drop and increased aeolian transport in connection with late Devonian climatic cooling and glaciation. The set of geochemical markers related to the late Devonian sea-level fluctuation can be used for super-regional to global correlations from platform to basin settings. Moreover, they can facilitate current efforts to determine a new D/C boundary definition.

Concentrations of silicified cephalopods within upper Frasnian carbonate concretions from the Holy Cross Mountains, Poland

Concentrations of silicified juvenile cephalopods from upper Frasnian carbonate nodules from the Jaźwica quarry in the Holy Cross Mountains are described here for the first time. Using conodonts, the age of the investigated cephalopod-rich nodules has been determined as the linguiformis conodont Zone, and may correspond to the Upper Kellwasser Event. The concentrations of silicified juvenile ammonoids described here resulted from a combination of biological and physical factors related to environmentally-driven mass mortality (induced by storms and perhaps additionally by anoxia) following mass spawning and post-mortem transport with the aid of bottom currents, which enabled them to drift to small depressions on the sea floor. Rapid silification led to excellent preservation of the fossil assemblage.

Integrated conodont biostratigraphy and carbon isotope chemostratigraphy in the Lower–Middle Ordovician of southern Sweden reveals a complete record of the MDICE

AbstractOne of the few and most complete records of the MDICE (Middle Darriwilian Isotope Carbon Excursion) is herein documented from Baltoscandia. Based on a core section penetrating the condensed Lower–Middle Ordovician succession (~46 m) on the island of Öland, southeastern Sweden, we provide an integrated scheme for carbon isotope chemostratigraphy (313 samples) and conodont biostratigraphy (29 samples) for this period. The carbonate succession in the Tingskullen core records 12 conodont zones and 6 subzones, including theOepikodus evae, Trapezognathus diprion, Baltoniodus triangularis, B. navis, B. norrlandicus, Lenodus antivariabilis, L. variabilis, Yangtzeplacognathus crassus, Eoplacognathus pseudoplanus(Microzarkodina hagetianaandMicrozarkodina ozarkodellasubzones),E. suecicus, Pygodus serra(E. foliaceus, E. reclinatus, E. robustusandE. lindstroemisubzones) andPygodus anserinuszones in ascending order. The δ13Ccarbrecord reveals an apparently complete record of the MDICE, including a rising limb, a well-defined peak and a falling limb. The anomaly covers a thickness ofc. 27 m in the core and spans theEoplacognathus pseudoplanus, E. suecicus, Pygodus serraandP. anserinusconodont zones. Combined with the new, detailed conodont biostratigraphy, the MDICE in the Tingskullen core can be used for detailed correlation with successions from Baltica, North America, the Argentine Precordillera, South China and North China.

Devonian operculate corals (Calceolidae, Cnidaria) from the Massif Armoricain, France

Wright, A.J., Plusquellec, Y. & Gourvennec, R., February 2016. Devonian operculate corals (Calceolidae, Cnidaria) from the Massif Armoricain, France. Alcheringa 40, xxx–xxx. ISSN 0311-5518The operculate coral Calceola gervillei Bayle, 1878 is described for the first time on the basis of the type material from the Cotentin region of Normandy (North Armorican Domain), from Early Devonian (likely upper Lochkovian to lower Pragian) strata, and is chosen as the type species of the monotypic new genus Gerviphyllum. The new genus is also present in the l’Armorique Formation (lower Pragian) of the Plougastel Peninsula (Central Armorican Domain) as Gerviphyllum sp. cf. G. gervillei. One locality in the upper Emsian (Polygnathus serotinus Conodont Zone) Le Fret Formation, on the northern coast of the Crozon Peninsula, has yielded operculate coral specimens described here as ?Chakeola sp., the first (tentative) record of the genus outside eastern Australia, south China and Vietnam. The operculate coral Calceola collini sp. nov. is described from six localities in the early Middle Devonian (Eifelian: Polygnathus costatus Conodont Zone) Saint-Fiacre Formation of the Plougastel and Crozon Peninsulas (Central Armorican Domain), despite the fact that knowledge of the internal characters, especially of the operculum, of the type species Calceola sandalina is very limited. From an extensive review of published references to Calceola from France, we conclude that only the record of Collin (1929) is valid.Anthony Wright (tony.wright@optusnet.com.au), GeoQuEST Research Centre, School of Earth & Environmental Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia; Yves Plusquellec (yves.plusquellec@univ-brest.fr) and Rémy Gourvennec (remy.gourvennec@univ-brest.fr), Université de Bretagne Occidentale, CNRS-UMR 6538 ‘Domaines océaniques’, Laboratoire de Paléontologie, UFR Sciences et Techniques, 6 avenue Le Gorgeu, CS 98837, F-29283, Brest, France. Received 1.10.2015; revised 8.12.2015; accepted 14.12.2015.

New conodont taxa and biozones from the Lower Ordovician of the Cordillera Oriental, NW Argentina

AbstractThe upper strata of the Santa Rosita and the Acoite formations (Lower Ordovician) exposed at Chulpíos Creek in the Santa Victoria study area of the Cordillera Oriental, NW Argentina, are analysed by means of conodont biostratigraphy. Four conodont zones are analysed for the referred formations, i.e. the Acodus apex, Acodus triangularis, Gothodus vetus and Gothodus andinus zones, on the basis of a collection with ca. 2800 conodont specimens that includes new conodont taxa. Acodus apex Albanesi and Zeballo, Acodus triangularis (Ding), Acodus zeballus n. sp., Gothodus andinus (Rao et al.), Gothodus vetus n. sp., and Paltodus cf. inaequalis (Pander) are described herein. The conodont genus Zentagnathus is diagnosed including two previously known species: Zentagnathus argentinensis (Rao et al.) and Zentagnathus primitivus (Voldman et al.). The Tetragraptus akzharensis and Baltograptus cf. deflexus graptolite zones were identified as well in the ∼1800‐m‐thick stratigraphic section. The incertae sedis Phosphannulus universalis Müller et al. is discussed for the Cordillera Oriental for the first time. The lower part of the Chulpíos section that involves the contact between the Santa Rosita and the Acoite formations is not able to be dated with precision either as upper Tremadocian or lower Floian because the ranges of the index taxa recorded in that interval of the study section span the stage boundary. Copyright © 2016 John Wiley & Sons, Ltd.

Early Pennsylvanian conodonts from the Luokun section of Luodian, Guizhou, South China

An abundant and taxonomically diverse conodont association was recovered from the Bashkirian strata at the Luokun section, southern Guizhou, South China. Forty-six species and subspecies, which belong to 10 genera, were identified. Seven conodont zones were recognized. They are, in ascending order, the Declinognathodus noduliferus, Idiognathoides sulcatus sulcatus, Idiognathoides sinuatus, Idiognathoides sulcatus parvus, “Streptognathodus” expansus M1, “Streptognathodus” expansus M2, and Diplognathodus cf. ellesmerensis zones. The base of the Bashkirian in the Luokun section is identified by the first occurrence of Declinognathodus noduliferus. Declinognathodus praenoduliferus and D. cf. bernesgae occur in the underlying beds. The base of the Moscovian can be recognized by the first occurrence of Diplognathodus cf. ellesmerensis, which is one of the most significant markers for the Bashkirian–Moscovian boundary in China. The conodont zonation is compared with that of the Naqing section nearby, as well as with that of the contemporaneous deposits of the South Urals, Donets Basin, North America and other areas.

On the diachronous nature of the top of the Ordovician Kuniutan Formation on the Yangtze Platform: Implications of the conodont biostratigraphy of the Dacao section, Chongqing

The top part of the Kuniutan Formation in the Dacao section at Chengkou, Chongqing in the northern part of the Yangtze Platform contains the conodonts Baltoniodus variabilis (Bergström), B. variabilis(Bergström)-B. gerdae (Bergström) transitional form, B. cf. alobatus (Bergström), Complexodus pugionifer (Drygant), Dapsilodus viruensis (Fåhraeus), Panderodus gracilis (Branson et Mehl), Periodon aculeatus Hadding, Protopanderodus varicostatus (Sweet et Bergström), Scabbardella altipes (Henningsmoen), and Yangtzeplacognathus jianyeensis (An et Ding). This species association is referred to the B. variabilis Zone. The transitional form between Baltoniodus variabilis and its descendent B. gerdae is recorded for the first time in China but it has been reported previously from a thin (0.5m thick) interval at the top of the B. variabilis Subzone in Sweden and a coeval interval in much thicker successions in the Appalachians of eastern United States. This form is important because it is present in a vertically limited stratigraphic interval near the top of the Nemagraptus gracilis graptolite Zone. The new conodont data indicate that the top part of the Kuniutan Formation at the Dacao section is about three conodont zones higher than that of the same formation at the well-known Huanghuachang section in the Yichang area, Hubei and the Waigangou section at Tangshan in Nanjing, Jiangsu. This illustrates the conspicuous diachronous nature of the Kuniutan/Miaopo formation contact in the Yangtze Platform region, which has not been recognized previously in China. The widely present gap at the top of the Kuniutan Formation is at least due partly to the late Darriwilian eustatic event that can be recognized also in Baltoscandia, North America, and Argentina.

Conodont and carbon isotope stratigraphy near the Frasnian/Famennian (Devonian) boundary at Wulankeshun, Junggar Basin, NW China

Conodont faunas from the Wulankeshun section in the northwestern Junggar Basin of Xinjiang, NW China, are characterized by shallow-water assemblages with many endemic taxa. This study presents separate local icriodid and polygnathid conodont zonations for the Lower Member of the Hongguleleng Formation, which can only roughly be correlated with the pelagic “standard zonation”. The basal beds of the Hongguleleng Formation are assigned to a low diverse Icriodus praealternatus ferus n. ssp. Zone, which possibly includes latest Frasnian strata but it continues into the basal Famennian. At present, the Frasnian/Famennian boundary cannot be defined unequivocally by conodonts and there are no obvious Upper Kellwasser equivalents. However, the carbon isotope data are comparable with the Bulongguor Reservoir stratotype, where the top-Frasnian lies within the basal Hongguleleng Formation. In the early Famennian, partly endemic icriodid lineages provide successive Icriodus cornutus, I. stenoancylus junggarensis n. ssp., and I. plurinodosus n. sp. (sub)zones. The basal Famennian is possibly marked by the oldest, endemic species of Neopolygnathus, Neo. huijunae n. sp. It is followed by local Neo. communis communis, “Polygnathus” pomeranicus, Po. cf. szulczewskii, and “Po.” pseudocommunis n. sp. zones. The new local conodont zonations provide a high biostratigraphic resolution for further future studies. The Wulankeshun shallow-water conodont faunas show restricted similarities with contemporaneous faunas from eastern Europe, Kazakhstan, and Iran. There are a few taxa that were originally described from other distant regions, such as NW Canada and eastern Australia. The local high number of endemic taxa (17 (sub)species, 46%) points to a significant plate tectonic isolation of the Junggar Basin in the early Famennian.

Potyphyllum, a new phillipsastreid genus of rugose corals in the Upper Frasnian of Belgium with precisions about the age of the Petit-Mont Member

1. Introduction This work serves as conclusion for the revision of massive rugose corals belonging to the family Phillipsastreidae Roemer, 1883 and occurring in the Upper Frasnian of Belgium. The diverse species of Frechastraea Scrutton, 1968 have been investigated in detail by Coen-Aubert (2012, 2015). As for Phillipsastrea D’Orbigny, 1849, P. falsa Coen-Aubert, 1987 and P. ranciae Coen-Aubert, 1987 were described by Coen-Aubert (1987) and P. conili Tsien, 1978 was studied by Coen-Aubert (1994). The present paper is concerned with two pseudocerioid species like Frechastraea, but with larger corallites, which have been previously ascribed to Phillipsastrea, but which are herein assigned to the new genus Potyphyllum based on Cyathophyllum ananas Goldfuss, 1826 as type species. Most Belgian occurrences of Potyphyllum ananas and P. veserense (Coen-Aubert, 1974) characterize the Upper Palmatolepis rhenana conodont Zone. As mentioned by Coen-Aubert (2012, 2015), the base of the Upper Frasnian has been fixed by the Subcommission on Devonian Stratigraphy, at the entry of the conodont Palmatolepis semichatovae. In Belgium, the entry of P. semichatovae is observed within the Lower Palmatolepis rhenana Zone, together with the first occurrence of Ancyrognathus triangularis whereas the massive rugose coral Frechastraea coeni Coen-Aubert, 2012 can be considered as an excellent marker for the base of the Upper Frasnian. As it is explained by Coen-Aubert (2015), the expression Namur Basin i

Conodont zonation of Lower Triassic strata in Slovenia

The paper presents the results of a conodont study carried out in the Triassic strata in the area of the Slovenian part of the Southern Alps, External Dinarides and the Transition region between the External and Internal Dinarides. The following conodont zones have been distinguished: Hindeodus praeparvus Z., H. parvus Z., Isarcicella lobata Z., I. staeschei – I. isarcica Z., H. postparvus Z., Hadrodontina aequabilis Z., Ha. anceps Z., Eurygnathodus costatus Z., Neospathodus planus Z., N. robustus Z., Platyvillosus corniger Z., Pl. regularis Z., Pachycladina obliqua Z., Foliella gardenae Z., Triassospathodus hungaricus Z., T. symmetricus Z., N. robustispinus T. homeri Z. and T. triangularis Z. The introduced conodont zonation spans from the Induan, including the Permian-Triassic boundary interval to the late Olenekian and is valid for the shallow shelf environments of western Tethys.

Early Triassic conodonts and carbonate carbon isotope record of the Idrija–Žiri area, Slovenia

The first recovery of the conodont Hindeodus parvus from Žiri (Slovenia) a few years ago highlights this area for Early Triassic biostratigraphical study. Systematic sampling of five sections in the Idrija–Žiri area has yielded the new species Platyvillosus corniger sp. nov. and Neospathodus planus sp. nov. Based on these new species and other conodont elements collected here, nine discrete conodont Unitary Association (UA) zones are proposed for this area. In ascending order they are: Eurygnathodus costatus Zone (UA 1), Eurygnathodus hamadai Zone (UA 2), Foliella gardenae Zone (UA 3), Neospathodus robustus Zone (UA 4), Platyvillosus corniger Zone (UA 5), Platyvillosus regularis Zone (UA 6), Triassospathodus hungaricus Zone (UA 7), Triassospathodus symmetricus Zone (UA 8), and Neospathodus robustispinus Zone (UA 9). The conodont and δ13C data indicate that these conodonts span the Dienerian/Smithian (i.e. Induan/Olenekian) boundary interval to the Spathian, and they also indicate that Triassospathodus hungaricus Zone (UA 7) does not occur at the base of the Spathian. These conodont zones are valuable for stratigraphic correlation within Central and southern Europe, and they also promote a better correlation worldwide. Conodonts in the Idrija–Žiri area were adapted to a shallow-water environment in an epeiric ramp.

Biostratigraphic and sedimentary record of the Annulata Events in the Moravian Karst (Famennian, Czech Republic)

The biostratigraphy and facies of halfgraben limestones in the southern part of the Moravian Karst (Czech Republic) have been studied from Uppermost Palmatolepis crepida to Upper Palmatolepis gracilis expansa conodont Zones. Only one Annulata Event horizon was detected, reflecting condensed sedimentation with the possible influence of erosion on the bypass slope. The “Wagnerbank” equivalent above the Annulata Events in the uppermost part of the Upper Palmatolepis rugosa trachytera Zone was not clearly recognized. The conodont data suggest the event beds in the Ochoz, Hosteˇnice 2, and Mokra sections represent the Lower Annulata Event. Correlation of the Annulata Event bed in the Hosteˇnice 1 section with the Upper Event remains tentative. Recorded microfacies were deposited slightly below or above the storm wave base. The Annulata Event beds correspond to mudstones/ wackestones to floatstones/rudstones with cephalopods and other fauna. Other microfacies include mostly various wackestones to packstones up to floatstones/rudstones. Conodont biofacies show the increase in both epipelagic taxa in the Annulata Event beds and “granulated” polygnathids above the Annulata Event beds. The cause of the increase in alternognathids in the Annulata Event beds remains questionable. Both the microfacies and conodont biofacies are generally similar to those seen widely distributed in other European and Moroccan sections, thus documenting the global nature of the Events.

Dynamics of cyclic carbonate deposition and biotic recovery on platforms during the Famennian of Late Devonian in Guangxi, South China: Constraints from high-resolution cycle and sequence stratigraphy

To better understand the dynamics of platform carbonate deposition, evolution and biotic recovery during the Famennian, high-resolution cycle and sequence stratigraphic analyses were carried out upon three platform sections (one in ramp, and two in rimmed platforms), along with a biostratigraphically well-constrained basinal section, in Guangxi, South China. Four main facies and fourteen lithofacies are identified in the three isolated platforms; these are vertically arranged into decimetre- to metre-scale, shallowing-upward peritidal and subtidal cycles (or parasequces), in which the peritidal cycles predominate over the lower-middle Famennian. Six third-order sequences (S1 to S6) are identified based on the cycle stacking patterns as illustrated by Fischer-plots and vertical facies changes; these sequences are temporally calibrated through correlation with basinal sequences constrained with conodont zonation, and match well the six main Famennian transgressive–regressive cycles (T1 to T6) in Euramerica and elsewhere, indicating a eustatic control. However, an opposite longer-term trend in accommodation change (S3 to S4) between platform interior and deeper open shelf-to-basin settings during the middle Famennian suggests a differential subsidence across the platform–basin section, likely driven by block tilting. Thus, both eustatic fluctuations and local tectonism had played an important role in platform development and evolution. After the Frasnian–Famennian biotic crisis, main marine benthos preferentially recovered in the normal marine niches on the nearshore open shelves, and radiated gradually into offshore restricted platforms. Brachiopods, notably rhychonellides, were the taxa recovering the earliest (S1) in the normal (or near normal) marine conditions, then echinoderms (S3), stromatoporoids (upper S3) and corals (S5) stepped in episodically. However, these benthos generally appeared later in the restricted platform interiors only as if the ecological conditions were improved well enough for their colonization. Therefore, the biotic recovery processes were diachronous: both taxonomically- and ecologically-specified.

First Occurrence of Lithostrotion (Diphyphyllum) from the Mississippian Redwall Limestone in the Beaver Dam Mountains, Washington County, Utah

The Paleozoic stratigraphy of the Beaver Dam Mountains of southwestern Utah correlates well with the better known deposits of the Grand Canyon, Arizona. However, a detailed list of the fossil fauna from the Beaver Dam Mountains is lacking. Here we describe a rugose coral from the Mississippian Redwall Limestone from Washington Country, Utah. The rugose coral is highly recrystallized, but identified as Lithostrotion (Diphyphyllum) based on morphology and geographic extent. An analysis was conducted to determine conodont zonation, but proved inconclusive. This is the first documented case of Lithostrotion (Diphyphyllum) from the Beaver Dam Mountains.

Comparative study of Late Devonian (Famennian) brachiopod assemblages, sea level changes, and geo-events in northwestern and southern China

Abundant brachiopods have been recovered from the Upper Devonian of western Junggar, Xinjiang, northwestern China. However, their diversity and succession, as well as a detailed comparison with other regions, remain to be explored. These issues are of importance since conodonts and ammonoids are generally sparse for dating the sequence. Based on collections in the past years from the Famennian sequence of the Bulongguoer section and adjacent sections, we recognize five brachiopod assemblages in ascending order: the Caenanoplia? aff. logani Assemblage; the Palaeospirifer–Megalopterorhynchus Assemblage, which can be divided into the Cyrtospirifer sulcifer Subassemblage and the Rugaltarostrum Subassemblage; the Ambocoelia? cf. unionensis Assemblage; the Austrospirifer? sp. Assemblage; and the Syringothyris–Spirifer Assemblage. Comparison of these assemblages with those of the Xikuangshan and other sections, central Hunan, southern China, indicates a strong biogeographic differentiation. There are opposite trends of raw diversity changes during the middle Famennian in these two regions, whereas similar trends, with a decline followed by an increase in diversity, occurred during the late and latest Famennian. Two transgression–regression cycles are recognized in the Bulongguoer section of western Junggar. Comparisons of sea level changes among the Bulongguoer section (western Junggar), central Hunan (platform facies of South China), and Euramerica indicate that regional tectonic activities may have played important roles in both western Junggar and central Hunan. In the Palmatolepis rugosa trachytera conodont Zone, sea level rose gradually to the maximum at approximately the Annulata level in the Bulongguoer section, whereas a contemporaneous prolonged lowstand (“Oujiachong regression”) was recognized in central Hunan. The replacement of the Rugaltarostrum Subassemblage by the Ambocoelia? cf. unionensis Assemblage in western Junggar is correlative to the Oujiachong event (the regression and brachiopod diversity decline in South China at the top of Palmatolepis marginifera Zone). During the latest Famennian, the Syringothyris–Spirifer Assemblage replaced the Austrospirifer? sp. Assemblage in western Junggar, as a response to the Hangenberg Event.

High‐Resolution Floating Point Time Scale (FPTS) of the Permian Capitanian Stage in South China

AbstractHere we present a magnetic susceptibility (χ) dataset from the Permian Capitanian strata exposed in the Tieqiao section, Laibin area, South China, a supplementary reference section for the Guadalupian‐Lopingian (Middle‐Upper Permian) Global Boundary Stratotype Section and Point (GSSP). The succession consists of alternating thin‐bedded chert with micritic limestone of basinal and slope facies, with a carbonate cap indicating shallow‐water platform deposition. χ datasets, which are mostly negative (diamagnetic), suggest that the Laibin area was isolated from terrigenous sources during most of the Capitanian. A sudden increase in the χ signal just below the Guadalupian‐Lopingian (G‐L) boundary is recorded. Although regression at the terminal Capitanian might have contributed to the increase, the coincidence of the increase with the onset of the Emeishan Large Igneous Province (LIP) eruptions demonstrate pronounced volcanic effects controlling χ in this part of the section. χ and thermomagnetic susceptibility measurements indicate that the dominant magnetic constituents in this study are diamagnetic calcite and chert, with subordinate paramagnetic and ferrimagnetic minerals, derived from eolian and volcanic sources, and producing the cyclicity observed in the dataset.Spectral (time‐series) analyses of χ data were performed using Multi Taper Method (MTM) and Fourier Transform (FT) analysis. Five frequencies that are consistent with Milankovitch‐band orbital forcing were compared to the dataset: eccentricity E1 and E2 (100 and 405 ka, respectively), obliquity O2 (44.10 ka), and precession P1 (17.70 ka) and P2 (20.95 ka). Interpretation of these results indicates that the duration for the Capitanian in the Tieqiao section was ∼3.85 Ma. Likewise, the mean sediment accumulation rate (SAR) for the whole Capitanian was ∼2.91 cm·ka−1. In addition, graphic comparison of the Tieqiao χ data to a floating point time scale for Upper Wordian through Capitanian time allows estimates of the duration for conodont zones identified from the section; these ranging from 26.6 ka to 2.3 Ma before extinction of individual conodont species. Therefore, timing of the onset age of Emeishan LIP eruptions is estimated to yield an age of 262.7 Ma, with placement of these eruptions at 1.4 Ma below the G‐L boundary.

Middle–Late Ordovician (Darriwilian–Sandbian) decoupling of global sulfur and carbon cycles: Isotopic evidence from eastern and southern Laurentia

Middle–Late Ordovician sequences from the Appalachian Basin and Arbuckle Mountain regions of North America were analyzed for carbonate-associated sulfate (δ34SCAS) and pyrite (δ34Spyr) paired with carbonate (δ13Ccarb) and organic matter (δ13Corg) chemostratigraphy. Two major negative drops in δ34SCAS (12‰ excursions) are recognized: the older decline in δ34SCAS occurs within the Histiodella holodentata–Phragmodus polonicus Conodont Zones and the younger drop is within the Cahabagnathus sweeti–Amorphognathus tvaerensis (Baltoniodus gerdae subzone) Zones. These overall these negative shifts in δ34SCAS have an antithetical relationship with positive shifts in δ34Spyr (~+10‰) and δ13Ccarb (~+2‰) recorded in the same successions. The older negative δ34SCAS shift is coincident with the widely documented mid-Darriwilian δ13C excursion (MDICE), and the younger negative δ34SCAS shift is coincident with another positive δ13Ccarb shift in the early Sandbian. Geochemical modeling of these sulfur isotope shifts suggests that a decrease in the global rate of pyrite burial or isotope fractionation between seawater sulfate and sedimentary pyrite could account for these negative δ34SCAS trends. Additionally, a substantial increase in the weathering flux of pyrite to the global oceans could also explain these secular sulfur isotope trends. While increased crustal weathering is broadly consistent with a sea-level lowstand, and the seawater 87Sr/86Sr isotope record of change in continental weathering in the late Darriwilian Stage of the Ordovician, geologic and geochemical proxy evidence do not support distinct pulses of continental weathering required to generate two separate negative shifts in δ34SCAS. These antithetical isotope trends may be best explained by changes in the marine redox state that significantly reduced microbially mediated pyrite burial and organic matter remineralization rates. Pulses of oceanic ventilation would have expanded habitable environments for marine organisms, and thus is broadly consistent with major increases in biodiversification during this period of the Ordovician.