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Early and Middle Frasnian brachiopod faunas and turnover on the South China shelf

100%

Ma X. P., Becker R. T., Li H., Sun Y.-Y.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 4

789-812

The first appearance of the brachiopod Cyrtospirifer and related forms in the Late Devonian of South China significantly postdates the beginning of the Frasnian and the entry of the group in other parts of the world. Scattered data from different sections suggest that its first entry, associated with the emergence of other plicate spiriferids, such as theodossid and conispiriferid brachiopods, was late in the Middle Frasnian. At the same time, many rhynchonellids disappeared or became extinct locally in South China. This brachiopod faunal overturn near the Palmatolepis punctata–Early Pa. hassi zonal boundary is the most significant event in the Early–Middle Frasnian of South China, characterized by about a 35% loss of existing species and the flourishing of the plicate spiriferids, which was coeval with the end of a major biogeochemical perturbation recently recognized in the Pa. punctata Zone. By contrast, atrypid brachiopods do not seem to show any significant diversity change. The brachiopod faunal change was probably related to a (local?) transgressive event in South China, which also brought new pelagic faunas northwards into some intra−shelf deeper water areas, such as the Shetianqiao area in central Hunan Province. Fifteen brachiopod species are described and illustrated, which include some taxa that are first recorded or recognized in South China, e.g., the spiriferid Pyramidaspirifer, which is now known from both North America and South China. One new species, Desquamatia qiziqiaoensis, is erected.

2

Early Frasnian ostracods from the Arche quarry (Dinant Synclinorium, Belgium) and the Palmatolepis punctata Isotopic Event

80%

Casier J.-G., Olempska E.

Acta Palaeontologica Polonica

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2008

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tom 53

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nr 4

Ostracods from the Arche quarry at Frasnes are analysed. Twenty−seven species are recognised in the Chalon Member and in the very base of the Arche Member of the Moulin Liénaux Formation. Three new species: Scrobicula gracilis, Microcheilinella archensis, and Bairdia (Rectobairdia) chalonensis, and one subspecies Plagionephrodes laqueus praelaqueus, are proposed. The fauna is in the Favulella lecomptei Zone based on metacopid ostracods and belongs to the Eifelian Mega−Assemblage. Ostracods are indicative of a regressive trend from a moderately deep poorly oxygenated marine environment below fair weather wave base to very shallow well oxygenated and agitated environments. Comparison of the ostracod fauna present in the Arche quarry with faunas described from the Frasnes railway section and from the Lion quarry shows that ostracods did not suffer a crisis during the Palmatolepis punctata Conodont Zone and close to the Early–Middle Frasnian boundary.

3

Early Frasnian acanthodians from Central Iran

80%

Hairapetian V., Valiukevicius J., Burrow C. J.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 3

Two vertebrate−bearing horizons in the basal Frasnian carbonate of the Chahriseh section, northeast of Esfahan, yielded microremains of thelodonts, placoderms, acanthodians, actinopterygians, chondrichthyans, and sarcopterygians, considerably expanding the vertebrate faunal list for the strata. Acanthodians comprise a diverse association of climatiids, diplacanthids, and ischnacanthiforms, including the previously recorded climatiid Nostolepis sp. cf. N. gaujensis, as well as one new climatiid genus and several taxa left in open nomenclature. Climatiid Iranolepis ginteri gen. et sp. nov. is diagnosed by having scales with a highly raised medial crown area separated by steep slopes from lateral crown areas; an odontocytic mesodentine of maximum extent in the crown, distinguished by extensive network of fine canaliculi with abundant tiny osteocytes; and a poorly developed stranggewebe system. Other scales with fan−like symmetrically grooved crowns conform to the Diplacanthus−type histologically, and have many characters in common with Milesacanthus antarctica from the Aztec Siltstone of Antarctica. Osseous gnathal elements include mesodentinous tooth whorls from an ischnacanthiform or climatiid, and ischnacanthiform jaw bones with large chambers for vascular canals, distinctly separated cylindrical tooth cusps along the lingual ridge, and wide−based, triangular, weakly striated cusps on the main lateral ridge. The acanthodian association, accompanied by the Frasnian conodonts of the middle Mesotaxis falsiovalis to Palmatolepis hassi zones and zonal thelodonts Turinia hutkensis and Australolepis seddoni, is proving useful for biostratigraphy, showing similarities with assemblages from both Gondwana and the Old Red Sandstone Continent.

4

Ostracods and facies of the Early and Middle Frasnian at Devils Gate in Nevada: Relationship to the Alamo Event

80%

Casier J. G., Berra I., Olempska E., Sandberg C., Preat A.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 4

813-828

In order to document the Alamo Event and to investigate its influence on shallow−marine environments, we undertook a study of ostracods, conodonts, and analysis of the sedimentology of the lower member of the type Devils Gate Limestone. Six major carbonate microfacies (MF1–MF6) ranging from open−marine environments below storm wave base to pre−evaporitic supratidal lagoons were recognized. The sedimentological study detected no important sedimentological changes during the Alamo Event; only an influx of detrital material and lithoclasts indicate that an unusual event had occurred. Ostracods are generally rare or absent in the lower member of the Devils Gate Limestone, and only 2,000 carapaces, valves and fragments were extracted; from these some 26 taxa were identified. Two new species, Voronina? eureka and Serenida dorsoplicata are proposed. The ostracods belong to the Eifelian Mega−Assemblage and their distribution was influenced by strong salinity variations. Because of the rarity and low diversity of ostracods and conodonts in samples collected from the lower part of the lower member of the Devils Gate Limestone it is not adequate to demonstrate conclusively an extinction event close to the Alamo Event Bed. Nevertheless the greater abundance and diversity of ostracods above this bed seems to indicate that the Alamo Event did not result in significant extinction of ostracod taxa in this shallow water setting. The ostracod fauna present in the lower member of the Devils Gate Limestone suggests faunal exchanges between Nevada and the Russian Platform via the Western Canadian platform.

5

Molluscs from the Early Frasnian goniatite level at Kostomloty in the Holy Cross Mountains, Poland

61%

Jagt-Yazykova E., Krawczynski W., Rakocinski M.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 4

707-718

The unique goniatite−rich pyritic level, 1.6 m thick, exposed at Kostomłoty (Holy Cross Mountains, central Poland) represents a distinct, local biotic event in the Early Frasnian interval corresponding to the inception of a major geochemical (carbon cycling) perturbation in the stagnant deep−water and oxygen−deficient Kostomłoty basin. The taxonomic and palaeoecologic characteristics of molluscan fossil associations from the Goniatite Level are presented. Most of the goniatitids and orthoconic nautiloids from the studied fossil assemblages are juvenile conchs or protoconchs, or incomplete phragmocones and represent the genera Acanthoclymenia and Linguatornoceras, the former being predominant, and a single adult specimen probably of the genus Koenenites. In contrast, gastropods and bivalves are generally well preserved and identifiable to species level. Two new species are described: a gastropod Palaeozygopleura (Bohemozyga) pyritica sp. nov. and a bivalve Glyptohallicardia multicostata sp. nov. These studied molluscs and also amphiporoids are allochthonous elements which must have been transported into the deeper settings during sea−level rise and flooding of fringing reefs (Timan Event) and/or storm events, and there were mixed with pelagic cephalopods. Probably, a sea−level rise even led to flooding of nearby areas, and thus to introduction of pelagic material (juvenile cephalopods) into reefal settings, and then back to the deeper water again by the quasi−estuarine circulation of water masses.

Ograniczanie wyników

5 Acta Palaeontologica Polonica

2 Olempska E.

1 Becker R. T.

1 Berra I.

1 Burrow C. J.

1 Casier J. G.

1 Casier J.-G.

1 Hairapetian V.

1 Jagt-Yazykova E.

1 Krawczynski W.

1 Li H.

1 Ma X. P.

1 Preat A.

1 Rakocinski M.

1 Sandberg C.

1 Sun Y.-Y.

1 Valiukevicius J.

1 2008

4 2006

Early and Middle Frasnian brachiopod faunas and turnover on the South China shelf

Early Frasnian ostracods from the Arche quarry (Dinant Synclinorium, Belgium) and the Palmatolepis punctata Isotopic Event

Early Frasnian acanthodians from Central Iran

Ostracods and facies of the Early and Middle Frasnian at Devils Gate in Nevada: Relationship to the Alamo Event

Molluscs from the Early Frasnian goniatite level at Kostomloty in the Holy Cross Mountains, Poland