Xueping Ma

Biological, depositional, microspherule, and geochemical records of the Frasnian/Famennian boundary beds, South China

Abstract The investigation of shallow subtidal, inter-reef depression, and inter-reef platform sections from central Hunan of China shows that a transgression–regression cycle occurred in the Late Frasnian (linguiformis Zone?). The lowest triangularis Zone to Middle triangularis Zone deposits are either very thin or variously missing in some shallow-water sections of Hunan. The uppermost Frasnian (upper linguiformis zone) black-shale interval (including black shale and carbonates) was not ubiquitously developed and probably formed in a regressive, shallower water and anoxic to dysoxic conditions suggested from higher Ce/La ratios, penecontemporaneous dolomitization of carbonates, and low faunal diversity. Two steps of the Frasnian/Famennian (F/F) mass extinction are postulated. The first is the extinction of the benthos near the end of the Frasnian which was probably caused by the sudden onset of anoxic environments. Shallow-water rugose corals and ostracods experienced sudden biomass loss right at the deposition of the black shale. The second is the extinction of pelagic fauna at the end of the Frasnian. Microspherules of probable impact origin are found in several layers in the Xikuangshan F/F boundary section, including two major peaks, respectively, at the Upper rhenana Zone and upper linguiformis zone, and two minor peaks, respectively, near the top of the linguiformis Zone and Lower triangularis Zone. The microtektites are white or brownish in color, characterized by high contents of Si, Al, and intermediate CaO, MnO, and FeO, and minor K2O and Na2O. Occurrences of these microtektites do not seem to be directly related to the F/F mass extinction. From the Lower rhenana Zone through the Upper crepida Zone there are four elemental anomalous layers. These elemental anomalies are interpreted to have resulted from the contemporaneous active rifting process and hydrothermal activities in South China.

Large sulphur isotopic perturbations and oceanic changes during the Frasnian-Famennian transition of the Late Devonian

The Frasnian–Famennian transition of the Late Devonian was one of the most critical intervals in the Phanerozoic. Sulphur isotopic pairs of carbonate-associated sulphate and pyrite sulphide from coeval sections in South China and Poland reveal frequent perturbations of sulphur cycling during this time interval. These data suggest a sudden oceanic overturn during a rapid sea-level fall probably induced by jerky block tilting in the latest Frasnian. This event was followed by long-lasting photic-zone euxinia during a rapid sea-level rise in the earliest Famennian. Large increases in continental nutrient fluxes, and subsequent primary productivity and organic burial, could have greatly enhanced bacterial sulphate reduction, producing excessive sulphide through the water columns owing to iron depletion. Subsequently, rapid ventilation of oceanic basins occurred, during which direct aerobic oxidation of sulphide into sulphate predominated in bottom waters and even surface sediments with minimal fractionation. This oxygenation was probably induced by intensive climatic cooling and/or large-scale sea-level fall. The temporal coincidence of two extinction phases with the oceanic overturn and succeeding photic-zone euxinia suggests that these extreme oceanic events played an important role in the severe biotic crisis. Furthermore, photic-zone euxinia coupled with subsequent climatic cooling may have delayed post-extinction recovery of some taxa. Supplementary materials: Two supplementary tables (S1 and S2) indicating pyrite and CAS contents and sulphur isotopic results (δ34SCAS, δ34Spy and Δ34S) across the F-F boundary at Fuhe, South China and Kowala, Poland, respectively, and a supplementary figure showing systematic sulphur isotopic variations across the F-F boundary and their correlations between the two studied sections are available at www.geolsoc.org.uk/SUP18593.

Upper Devonian (Famennian) and Lower Carboniferous (Tournaisian) ammonoids from western Junggar, Xinjiang, northwestern China—stratigraphy, taxonomy and palaeobiogeography

Seven ammonoid levels/assemblages are recognised in the Devonian (Famennian) and Carboniferous (Tournaisian) of the northwestern Junggar Basin, Xinjiang, northwestern China. Eleven genera and 20 species, including six new species (Becanites sp. nov., Protactoclymenia junggarensis sp. nov., Prot. magna sp. nov., Cyrtoclymenia? parallela sp. nov., Sporadoceras impressum sp. nov. and “Mimimitoceras” transiens sp. nov.) are described from the Hongguleleng and Heishantou formations in the Bulongguoer, Hebukehe, Emuha and Hashatu sections. The first assemblage is characterised by Platyclymenia subnautilina (Sandberger), Prionoceras frechi (Wedekind) and Sp. impressum sp. nov. It is assigned to the basal upper Famennian Pl. annulata Zone (UD IV-A) and indicates that the global, transgressive Annulata Event enabled the first spread of ammonoids to the region. The second assemblage is characterised by large-sized Cyrtoclymeniaceae (Protactoclymenia and Cyrtoclymenia?) and Sporadoceras aff. muensteri (Münster) and correlates with the orbiculare Zone (UD IV-C) of North Africa, which also contains very large clymeniids and goniatites. The third regional assemblage consists of rare Gonioclymenia sp. and a related, more evolute form. The fourth assemblage is a peculiar Cymaclymenia“Mimimitoceras” fauna, including C. striata (Münster) s.l., C. cf. involvens Lange, Sporadoceras sp., “Mimimitoceras” cf. geminum Korn, “M.” transiens sp. nov. and M. cf. rotersi Korn, most of which are discovered for the first time in the vast Junggar and adjacent areas. Based on conodont (associated Protognathodus fauna) and palynomorph data (LN Zone), this assemblage corresponds to the lower Hangenberg Event Interval (UD VI-E). Rare records from a fifth level suggest that cymaclymeniids survived regionally into the conodont Pr. kockeli Zone, as in other regions. The sixth level consists of a single Lower Tournaisian Acutimitoceras (Stockumites)?. The seventh level also has a low diversity and includes Weyerella angularia (Liang and Wang) and Becanites sp. nov. in the Emuha section. It falls in the Middle Tournaisian, as do Weyerella faunas that were previously reported from the region. The endemic species and the distinctive lack of otherwise widespread genera provide a strong regional signature of the overall ammonoid fauna.

REVISION OF SELECTED NORTH AMERICAN AND EURASIAN LATE DEVONIAN (FRASNIAN) SPECIES OF CYRTOSPIRIFER AND REGELIA (BRACHIOPODA)

Abstract Study of the shell features of Givetian and Frasnian spiriferid brachiopods attributed to the genus Cyrtospirifer shows that the type species C. verneuili has micro-ornament consisting of fine concentric growth lines, radial capillae, with microspines arising from some capillae, spine bases appear to extend into the primary shell layer. Its dorsal interior features a pseudoseptum supporting the cardinalia. Micro-ornament of Cyrtospirifer varies widely and is a useful criterion for characterization of species of the genus. Most Frasnian species retained in the genus have micropustulate shells. Two late Givetian and Frasnian phylogenetic species groups of Cyrtospirifer are recognized based on similarities of shell form and external and internal shell features. Species of the verneuili-syringothyriformis group have transverse alate shells, and are the most abundant and widespread group in Frasnian deposits worldwide. The verneuiliformis group includes the oldest known species of Cyrtospirifer with narrow hinges and more inflated ventral valves where shell width is close to or equal to length. The oldest Cyrtospirifer originated in western Europe during the late Givetian, and subsequently migrated at different times during the Frasnian into other shelf areas of Eurasia, North America and China. The initial migration of Cyrtospirifer into tropical and subtropical shelf settings in North America coincided with the middle Frasnian eustatic sea level rise of Devonian Transgressive-Regressive (T-R) cycle IIc of Johnson and others. A second late Frasnian dispersal from western Canada to subtropical carbonate and clastic shelves in the southwestern and central U.S. coincided with the initial sea level rise of T-R cycle IId of Johnson and others. The Frasnian species Cyrtospirifer glaucus Crickmay, 1952a (middle Frasnian of western Canada) is the type species for Regelia Crickmay, 1952b, and is considered a valid genus, and is not a synonym of C. chemungensis (Conrad, 1842) as previously interpreted by some authors. Regelia differs from Cyrtospirifer in the absence of a delthyrial plate, complete in-filling of the delthyrial cavity by secondary shell material, its simpler rod-like teeth, and its fewer medial sinal shell plications. Species of Regelia are restricted to the middle to late Frasnian of North America.

Revision of Tenticospirifer Tien, 1938, and similar spiriferid brachiopod genera from the Late Devonian (Frasnian) of Eurasia, North America, and Australia

Abstract The cyrtospiriferid brachiopod genus Tenticospirifer Tien, 1938, is revised based on restudy of the type species from the Frasnian (Late Devonian) of the Russian Platform. As revised the genus includes cyrtospiriferid species with pyramidal ventral valves, catacline ventral interareas, a narrow delthyrium, few sinal plications, and lack a median dorsal septum and pseudodeltidium. All species retained in the genus are of Givetian and Frasnian age. All Famennian age species described from South China and North America are rejected from the genus. It appears that Tenticospirifer evolved during the early Givetian in western Europe and remained endemic to that region during the remainder of the Givetian. Successive migrations of Tenticospirifer from eastern Laurussia to North America, then to South China and possibly Australia, coincided with middle and late Frasnian eustatic sea level rises, respectively. The North American species Spirifera cyrtinaformis Hall and Whitfield, 1872, and related species identified as Tenticospirifer by North American workers, are reassigned to Conispirifer Lyashenko, 1985. Its immigration to and widespread dispersal in carbonate platforms of western Laurussia, northern Gondwana and tropical island arcs (?) coincided with a major late Frasnian eustatic sea level rise. The new family Conispiriferidae is proposed with Conispirifer Lyashenko, 1985, selected as the type genus. The new family also includes the new genus Pyramidaspirifer with Platyrachella alta Fenton and Fenton, 1924, proposed as the type species. The affinity of the new family remains uncertain pending restudy of key genera currently included in the Superfamily Cyrtospiriferoidea. Available data from the Devonian brachiopod literature indicate that species of Pyramidaspirifer are restricted to late Frasnian deposits of central and western North America.

MORPHOLOGY AND REVISION OF LATE DEVONIAN (EARLY FAMENNIAN) CYRTOSPIRIFER (BRACHIOPODA) AND RELATED GENERA FROM SOUTH CHINA AND NORTH AMERICA

Abstract Study of abundant well-preserved specimens of cyrtospiriferid brachiopods from early Famennian triangularis Zone shelf deposits from South China shows that none of them can be attributed to the genera Cyrtospirifer Nalivkin in Fredericks, 1924, or Tenticospirifer Tien, 1938, as previously assigned. Some of these forms are reassigned to the new genus Plicapustula, with Spirifer (Sinospirifer) gortanioides Grabau, 1931 serving as the type species. Restudy of the Upper Devonian cyrtospiriferids of North America and South China indicates that genera of the subfamily Cyrtospiriferinae all developed a delthyrial covering usually composed of two or more thin plates referred to as a composite pseudodeltidium. The delthyrial covering of Cyrtiopsis Grabau, 1923 and other genera of the subfamily Cyrtiopsinae is a convex pseudodeltidium. The lack of a pedicle foramen penetrating the pseudodeltidia of Frasnian Cyrtospirifer indicates that most species had an atrophied pedicle. The pseudodeltidia of most early Famennian cyrtospiriferids are perforated by a pedicle tube or a central hypothyrid foramen as in Sinospirifer Grabau, 1931, or a hypothyrid-to-submesothyrid foramen as in Lamarckispirifer Gatinaud, 1949 and Plicapustula n. gen. The orientation and concavity of the interarea, used with other shell characteristics, are useful characters in species-level taxonomy of Famennian cyrtospiriferids. Four major types of radial micro-ornament characterize Late Devonian species of Cyrtospirifer and other genera of the Cyrtospiriferinae. These are 1) the verneuili type, consisting of microspines arising from the shell surface with spine bases extending into the primary shell layer, with radial capillae; 2) the whitneyi-subextensus type with small pustules both in the grooves and on the plications; 3) the subarchiaci type characterized by pustules only on plications; and 4) the hayasakai type with coarse elongated pustules on plications and capillae in grooves. There is a notable increase in complexity of the medial plication patterns of shells of Late Devonian cyrtospiriferinids. Simple sinal plication patterns characterize shells of Frasnian species of Cyrtospirifer and related genera, whereas most early Famennian cyrtospiriferinids developed complex patterns. We have documented three variations in the structure of the cardinal processes of the Late Devonian cyrtospiriferids. These consist of 1) unsupported; 2) supported by callus (secondary shell material) from below; or 3) supported by a median septum. In Hunan-South China, cyrtospiriferid diversity was low in the late Frasnian, but a postextinction radiation of cyrtospiriferids in the very early Famennian resulted in the evolution of numerous new genera within the interval of the undifferentiated triangularis Zone shortly after the Frasnian–Famennian (F–F) mass extinction. Cyrtospiriferid brachiopods of the subfamilies Cyrtospiriferinae and Cyrtiopsinae are important elements of the early Famennian post-extinction survivor and recovery faunas that migrated and radiated rapidly to occupy niches vacated by extinct clades of late Frasnian brachiopods.

A NEW MERISTID BRACHIOPOD GENUS FROM THE LOWER CARBONIFEROUS OF GUIZHOU, CHINA

The rowleyellinae is a small subfamily of meristelloid athyridid brachiopods, previously with only one genus, Rowleyella Weller, 1911 (Alvarez and Brunton, 1995; Alvarez et al., 1998; Alvarez and Rong, 2002). In this paper we report a new meristelloid athyridid brachiopod genus Muhuathyris from a newly discovered, very diverse Tournaisian brachiopod fauna in South China. It is noteworthy that this newly discovered fauna is slightly older than that reported earlier from the same outcrop (Balinski, 1999). A full discussion of the newly discovered fauna is currently in preparation. Morphological features of Muhuathyris n. gen. suggest that it is probably an evolutionary intermediate between Camarophorella Hall and Clarke, 1893 and Rowleyella Weller, 1911. The new genus differs from Camarophorella and Rowleyella only in the nature of the structures beneath the septalium in the dorsal valve. In Camarophorella a shoe lifter is present in front of or beneath the septalium. In Rowleyella a cruralium rests on the dorsal median septum under the septalium and extends to the front of septalium. Lateral to the dorsal median septum, two thin and short plates, asymmetrically disposed, are present posteriorly under the cruralium, which were considered by Carter (1991) as a very posteriorly placed shoe lifter. In the new genus a structure consisting of two plates lateral to the dorsal median septum is attached to the dorsal surface of septalium near the crural bases. This structure extends from the dorsal beak to the posterior of the adductor muscle fields. It may be developed as two vertical plates lateral to the median septum, or, when the plates converge medially, as a sessile or median septum-supported cruraliumlike platform. The structure primarily acts as support to the crural bases and septalium rather than a dorsal adductor muscle platform, but may also serve as part of dorsal …

Origination and diversification of Devonian ambocoelioid brachiopods in South China

The superfamily Ambocoelioidea is an important group of the Brachiopoda in the Devonian, both globally and in South China. In the Devonian, this group is also most diverse compared with that in other periods. Based on features of cardinal process and cruralium, three types of cardinalia are recognised, including Ambocoelia-type, Emanuella-type, and Rhyncospirifer-type. Our study shows that the Rhynchospirifer-type cardinalia is a distinct character that distinguishes them from the rest of the Ambocoeliidae; therefore, the Rhynchospiriferinae is re-elevated to the family rank. Guangxiispirifer of the previous Ambocoeliinae is reassigned to the Rhynchospiriferidae while Ambothyris, Choperella, Crurispina, Diazoma, Emanuella, Ilmenia, Ilmospirifer, Ladjia, Moravilla, and Zhonghuacoelia of the previous Rhynchospiriferinae are transferred to the Ambocoeliidae (= previous Ambocoeliinae). Three earliest ambocoelioids in South China are Ambothyris, Amboglossa, and Prolazutkinia in the upper Emsian; their emergences were likely associated with the global Upper Zlichov Event. The upper Emsian occurrences of Amboglossa and Prolazutkinia are their FADs (first appearance datum) globally. These two genera probably gave rise to the Rhynchospiriferidae and the Lazutkiniidae, respectively. After an initial gradual increase in generic richness, the Ambocoelioidea reached the highest diversity (10 genera including four endemic genera) in the late Eifelian and Early Givetian in South China. From then on, the diversity gradually decreased till the end of the Devonian (two genera) and was least affected by the Frasnian–Famennian Event. The Ambocoelioidea is a strongly facies-controlled group. Their temporal and spatial distributions show a close relationship with sea level changes. Ambocoeliids and rhynchospiriferids were adapted to different environments. The former inhabited deeper and partly dysoxic environments, therefore showed greater capabilities to migrate and survive extinctions. On the other hand, the rhynchospiriferids dwelled in a reef-related, high energy, and oxic environments, which were probably more sensitive to environmental changes; they also showed high diversity and endemism and more easily experienced rapid and regional extinctions. Three species representing the three types of cardinalia, Ambocoelia yidadeensis sp. nov., Ambothyris panxiensis, and Rhynchospirifer sp., are described.

Hangenberg Black Shale with cymaclymeniid ammonoids in the terminal Devonian of South China

The Hangenberg Crisis at the end of the Devonian is marked by a sudden global mass extinction (main Hangenberg Event), which was especially severe for ammonoids. Among the order Clymeniida, only the cymaclymeniids survived for a short time. We report the first discovery of Postclymenia cf. evoluta in South China in equivalents of the Hangenberg Black Shale (the regional Changshun Shale) at the Jiarantang section in Guizhou. The South China plate was far away and completely different from the Euramerica continent, where the Hangenberg Event/Crisis was first recognised. The presence of similar ammonoids as in contemporaneous beds of the Rhenish Massif, Germany, suggests close faunal relationship through the Palaeotethys Ocean. It agrees with a sudden spread of opportunistic extinction survivors with the initial Hangenberg Transgression. The regional facies and faunal succession at Jiarantang confirms previous concepts of a eustatically driven, significant transgressive-regressive couplet in the lower/middle crisis interval. The near-global distribution of cymaclymeniid survivors shows that their extinction at the end of the extended crisis interval must have been caused by a so far neglected, small-scale global extinction event in the open marine realm.