Chronostratigraphic accuracy of Ordovician ecostratigraphic correlation

Six stratigraphic sections along a 34 km transect down a Middle Ordovician depth gradient (Trenton Group, New York) were ecostratigraphically correlated to 10⁵ year accuracy by pairwise statistical cross-correlation of curves describing each section's depth history in terms of the distribution of fossil marine benthic communities along the gradient. This accuracy is about an order of magnitude greater than that of ordinary biostratigraphic correlation in the sequence, and it is attained even in correlating between very different biofacies. New ecostratigraphic methods illustrated here promise comparable improvements in analyzing many stratigraphic sequences.     

The fate of the homoctenids (Tentaculitoidea) during the Frasnian–Famennian mass extinction (Late Devonian)

The homoctenids (Tentaculitoidea) are small, conical‐shelled marine animals that are among the most abundant and widespread of all Late Devonian fossils. They were a principal casualty of the Frasnian–Famennian (F‐F, Late Devonian) mass extinction, and thus provide an insight into the extinction dynamics. Despite their abundance during the Late Devonian, they have been largely neglected by extinction studies. A number of Frasnian–Famennian boundary sections have been studied, in Poland, Germany, France, and the USA. These sections have yielded homoctenids, which allow precise recognition of the timing of the mass extinction. It is clear that the homoctenids almost disappear from the fossil record during the latest Frasnian ‘Upper Kellwasser Event’. The coincident extinction of this pelagic group, and the widespread development of intense marine anoxia within the water column, provides a causal link between anoxia and the F‐F extinction. Most notable is the sudden demise of a group, which had been present in rock‐forming densities, during this anoxic event. One new species, belonging to Homoctenus is described, but is not formally named here.     

Environmental distribution of colony growth form in the favositid Pleurodictyum americanum

Pandolfi, John M. & Burke, Collette D. 1989 01 15: Environmental distribution of colony growth form in the favositid Pleurodictyum americanum. Lethaia , Vol. 22, pp. 69–84. Oslo. ISSN 0024–1164.
Colony growth form is of fundamental importance to understanding the ecology of both modern and ancient marine sessile colonial animals. Fourier shape analysis of the coral Pleurodictyun americantum (Tabulata: Favositida) from the Middle Devonian Hamilton Group of New York State, indicates that colony growth form is variable between environments. Discriminate function analysis of harmonics 2–6 of 51 assemblages of Pleurodictyum americanum (N = 1900) shows that this species displays an onshore to offshore gradient in colony shape. Offshore environments characterized by low levels of turbidity, oxygen, and light contain more flattened, less hemispherical growth forms, whereas onshore environments characterized by high levels of turbidity, oxygen, and light contain more hemispherical, less flattened growth forms. Harmonic shape analysis detected subtle differences among samples of P. americanum from different environments, but also showed that distinctive morphotypes are distributed within horizons. as well as between them. In fact, no one-to-one correspondence in growth form to environment is apparent; growth forms are distributed within environments, suggesting that genetic factors may have had a greater influence over coral growth form than environment. In tabulate corals, patterns of within species variability must be determined before growth form may be useful in interpreting ancient environments. □ Tabulate coral, Fourier shape analysis, morphological variability, growth form, Devonian, Hamilton Group, New York .     

Early Devonia benthic communities of the Alexander Terrane, southeastern Alaska

Emsian (upper Lower Devonian) limestones exposed on Kasaan, Round, and Wadleigh Islands in southeastern Alaska are part of an allochthonous suitc of island are deposits preserved within the accrctionary Alexander Terrane. Ten benthic marine communities, including several new brachiopod associations, are defined on the basis of field data correlated with a cluster analysis. Biologic and sedimentologic evidence is integrated with community group assignments in order to substantiate the paleoecology and evolutionary history of each community. These faunas were adapted to a spectrum of quiet and rough water habitats, including restricted, shallow subtidal areas nearshore, offshore biostromal banks, and open and restricted portions of a lagoon or shelf. Comparisons with coeval assemblages from the Cordillera and elsewhere reveal that these communities are unique to southeastern Alaska. Their origin within an early Paleozoic island are appears to have led to biogeographic isolation from other parts of the Cordillera and the development of a distinct biota at a site offshorc from the ancient continental margin. ▭ Emsian, paleocommunities, community groups, cluster analysis, Alexander Terrane.     

Palynostratigraphy and palaeogeography of the Padeha, Khoshyeilagh, and Mobarak formations in the eastern Alborz Range (Kopet-Dagh region), northeastern Iran

A total of 113 surface samples collected from the Padeha, Khoshyeilagh, and Mobarak formations of Kuh-e-Ozum, northeast of Jajarm town were processed for palynomorphs, in order to determine age relationships. Well-preserved and abundant palynomorphs dominated by organic-walled-marine microphytoplankton (acritarchs and prasinophyte phycomata), miospores and subordinate chitinozoans, and scolecodonts were recovered. Seven species of prasinophyte phycomata (four genera), 19 acritarch species (14 genera), one species of chitinozoa, and 26 miospore species (19 genera) were recorded and assigned to eight local Assemblage Zones. Assemblage Zones I-IV occur in the Padeha Formation and suggest an Early Late Devonian (Frasnian) age whilst assemblages zones V-VII are present in the Khoshyeilagh Formation and indicate Late Devonian (Famennian) ages. Assemblage zone VIII, which occurs in the basal part of Mobarak Formation, suggests a Lower Mississippian (Tournaisian) age for this formation. Many of the palynomorph groups encountered are closely comparable with coeval assemblages recorded from Western Australia, southwest Ireland, England, Turkey, Saudi Arabia, North Africa, and South America, indicating the close relationship of the Iranian Platform to other parts of the northern Gondwana Domain during the time interval represented by these strata. The presence of marine palynomorphs (acritarchs/prasinophyte phycomata, chitinozoans, and scolecodonts), and shelly macrofauna (brachiopods, gastropods, and corals) in Member c of the Padeha Formation (as well as the Khoshyeilagh and Mobarak formations), together with associated miospores, indicate an open marine (moderately nearshore) depositional environment for the Upper Devonian and Lower Carboniferous deposits in northeastern Alborz Range (Kopet-Dagh region) of Iran.     

New radiolarians from the Devonian of the southern Ural Mountains: 2. Middle-Late Devonian

Middle-Late Devonian Radiolarians are recorded for the first time in the southern Ural Mountains in Bashkortostan, in a section of Kariukmas Mountain (Upper Eifelian) and on the southern slope of Argagan Mountain (Middle Frasnian). The new Late Eifelian assemblage is composed of 17 species of 11 genera, and Middle Frasnian radiolarians comprise 13 species of 7 genera of spherical, discoidal, pylomate, and spiny radiolarians. A new species, Primaritripus kariukmasensis, sp. nov., is described. The prevalence of discoidal forms in the oryctocenosis suggests shallow marine conditions in the Late Eifelian and Middle Frasnian basins. Two new biostratons, the Upper Eifelian beds with Primaritripus kariukmasensis and Middle Frasnian beds with Primaritripus chuvashovi, are established based on radiolarians.     

新疆中天山汗吉尕组Helenifore robustum放射虫动物群及其年代地层学意义

汗吉尕组是新疆中天山温泉小区中泥盆统的一个地层单元,为海相碎屑岩夹火山碎屑岩沉积。过去在灰岩团块和灰岩砾石中发现较为丰富的中泥盆世珊瑚和腕足类化石。这次,我们在该组上部地层硅质岩透镜体中首次发现晚泥盆世弗拉晚期的放射虫Helenifore robustum动物群。对于温泉地区该组地层的时代归属,我们认为:由于已发现的中泥盆世珊瑚、腕足类化石主要产于灰岩砾石或外来块体中,因此,这些化石的时代并不代表该组形成的时代;而产于硅质岩透镜体中的晚泥盆世弗拉晚期的放射虫化石很可能代表该组的年代。全文共描述放射虫5属11种,归属3目4科。     

Coenocorrelation: gradient analysis of fossil communities and its applications in stratigraphy

Coenocorrelation is the correlation of positions in a stratigraphic sequence with corresponding positions along a paleoenvironmental gradient through gradient analysis of fossil communities. By ordination of community samples, the distribution and abundance of taxa along a depth gradient can be translated into a continuous scale that accurately measures the gradient and thus makes possible analysis of facies change on a continuum. The procedure is tested using data on marine benthic invertebrates along ten time-parallel transects down an Ordovician basin slope (Trenton Group, New York). Reversals between transgression and regression revealed in coenocorrelation curves served nearly as well as bentonite beds in time-correlation of sections. Ordinations gave estimates of depositional strike in close agreement with estimates from physical indicators. Walther's Law of Facies is evidently a more rigorous, quantifiable generalization than it has been revealed to be through classificatory approaches to communities and environments.     

SVALBARDIA BANKSII SP. NOV. FROM THE UPPER DEVONIAN (FRASNIAN) OF NEW YORK STATE

Svalbardia banksii sp. nov., is described from the Upper Devonian (Frasnian) Fish Cabin Creek locality near Pond Eddy, New York. The compression consists of ultimate branches bearing spirally arranged, unwebbed leaves. The unwebbed leaves are up to 3.2 cm long, are somewhat flexuous, and dichotomize in more than one plane. The new species is similar to the reconstruction of Actinoxylon banksii from the Middle Devonian (Givetian) of New York and strengthens the supposed relationship between Svalbardia polymorpha and Actinopodium nathorstii from Mimerdalen, Spitzbergen.     

The history of Devonian-Carboniferous reef communities: Extinctions,effects, recovery

Summary Analysis of the taxonomic composition, diversity and guild structure of five “typical” reef and mud mound communities ranging in age from Late Devonian-Early Carboniferous indicates that each of these aspects of community organization changed dramatically in relation to three extinction events. These events include a major or mass extinction at the end of the Frasnian; reef communities were also effected by less drastic end-Givetian and mid-late Famennian extinctions of reef-building higher taxa. Peak Paleozoic generic diversities for reef-building stromatoporoids and rugose corals occurred in the Eifelian-Givetian; reef-building calcareous algal taxa were longranging with peak diversity in the Devonian. These three higher taxa dominated all reef-building guilds (Constructor, Binder, Baffler) in the Frasnian and formed fossil reef communities with balanced guild structures. The extinction of nearly all reef-building stromatoporoids and rugose corals at the end of the Frasnian and the survival of nearly all calcareous algac produced mid-late Famennian reef communities dominated by the Binder Guild. Despite the survival of most calcareous algae and tabulate corals, the mid-late Famennian extinction of all remaining Paleozoic stromatoporoids and nearly all shelf-dwelling Rugosa brought the already diminished Devonian reef-building to a halt. These Devonian extinctions differ from mass extinctions by the absence of a statistically significant drop in taxonomic diversity and by their successional and cumulative effects on reef communities. Tournaisian mud mounds contain communities markedly different from the frame-building communities in Late Devonian and Visean reefs. Mound-building biotas consist of an unusual association dominated by erect, weakly skeletonized members of the Baffler Guild (chiefly fenestrate Bryozoa; Pelmatozoa) and laterally expanded, mud-binding algae/stromatolites and reptant Bryozoa. The initial recovery to reefs with skeletal frameworks in the Visean was largely due to the re-appearance of new species of abundant colonial rugose corals (Constructor Guild) and fenestrate Bryozoa. This Frasnian-Visean evolution in the taxonomic composition and structure of the reef-building guilds is also expressed by abrupt changes in biofacies and petrology of the reef limestones they produced. Thus, “typical” Frasnian reef limestones with balanced guild structures are framestones-boundstones-bafflestones, Famennian reefs are predominantly boundstones, Tournaisian mud mounds are bafflestones and Visean reefs are bafflestones-framestones.     

A late Devonian (Frasnian) coral-bafflestone reef at Houshan in Guilin, South China

Summary Givetian to early Carboniferous sediments of South China are characterized by carbonates. Middle and Late Devonian strata are best developed in the Guilin area. Reefs and organic shoals are recorded by various lithofacies types indicating the existence of an extended carbonate platform and a change of the composition of reef communities in time. Starting in the late Devonian, stromatoporoids and corals were replaced by algae that subsequently played an important role together with stromatoporoids, receptaculitids and fasciculate rugose corals in reef communities. In Houshan, 5 km west of Guilin, a coral-bafflestone reef occurs in the Frasnian strata, situated near an offshore algal-stromatoporoid reef. The coral reef was formed in a back-reef area adjacent to the inner platform margin. The coral-bafflestone reef is unique among the late Devonian reefs of South China with regard to the biotic composition. The reef is composed of fasciculate colonies ofSmithiphyllum guilinense n. sp. embedded within in packstones and wackestones. The height of colonies reaches 1 m. The community is low-diverse. The species ofSmithiphyllum occurring in the Frasnian reef complexes of Guilin exhibit a distinct facies control:Smithiphyllum guilinense occurs in or near to margin facies and formed bafflestone, constituting a coral reef whereasSmithiphyllum occidentale Sorauf, 1972 andSmithiphyllum sp.—characterized by small colonies with thin corallites—are restricted to the back-reef and marginal slope facies. The bush-like coral colonies baffled sediments. Algae and stromatoporoids (mainlyStachyodes) are other reef biota. Reef-dwelling organisms are dominated by brachiopods. The reefs are composed from base to top of five lithofacies types: 1) cryptalgal micrite, 2) peloidal packstone, 3) stromatactis limestone, 4) coral-bafflestone, and 5) pseudopeloidal packstone. The reef complex can be subdivided into back-reef subfacies, reef flat and marginal subfacies, and marginal fore-slope subfacies. The Houshan coral-bafflestone reef is not a barrier reef but a coral patch reef located near the inner margin of a carbonate platform.     

Diversity,speciation, endemism and extinction in Devonian reef and level-bottom communities,eastern North America

Lower Devonian late Emsian (Bois Blanc and Clear Creek Limestones; Schoharie Formation) level-bottom communities in New York, Michigan and Illinois were moderately cosmopolitan and diverse and dominated by brachiopods and solitary rugose corals. Subsequently (Early Eifelian?), there was an important episode of cratonal patch reef building in New York (Edgecliff Member, Onondaga Limestone), southwestern Ontario (Formosa Reef Limestone, lower Detroit River Group), and the Hudson Bay Lowland (Kwataboahegan Formation) by highly diverse endemic communities. The Edgecliff reefs were built by corals whereas the Formosa and Kwataboahegan reefs were built primarily by stromatoporoids. The strong correlation between high diversity and high endemism during the reef-building episode suggests that these communities contained numberous, small species populations belonging to several major taxa — an example of rapid speciation by geographic isolation and genetic drift.     

Microbial communities across nearshore to offshore coastal transects are primarily shaped by distance and temperature

Recent studies have focused on linking marine microbial communities with environmental factors, yet, relatively little is known about the drivers of microbial community patterns across the complex gradients from the nearshore to open ocean. Here, we examine microbial dynamics in 15 five-station transects beginning at the estuarine Piver's Island Coastal Observatory (PICO) time-series site and continuing 87 km across the continental shelf to the oligotrophic waters of the Sargasso Sea. 16S rRNA gene libraries reveal strong clustering by sampling site with distinct nearshore, continental shelf and offshore oceanic communities. Water temperature and distance from shore (which serves as a proxy for gradients in factors such as productivity, terrestrial input and nutrients) both most influence community composition. However, at the phylotype level, modelling shows the distribution of some taxa is linked to temperature, others to distance from shore and some by both factors, highlighting that taxa with distinct environmental preferences underlie apparent clustering by station. Thus, continental margins contain microbial communities that are distinct from those of either the nearshore or the offshore environments and contain mixtures of phylotypes with nearshore or offshore preferences rather than those unique to the shelf environment.     

Late Devonian benthic marine communities of the central Appalachian Allegheny Front

Four benthic marine communities occur in the clastic facies of the prograding Upper Frasnian-Lower Famennian (Upper Devonian) Foreknobs Formation in the Central Appalachians along the Allegheny Front in Maryland, West Virginia, and Virginia. Deep-water, rapidly prograding environments were inhabited by the Ambocoelia-Chonetes Community, dominated by an epifauna of unattached brachiopods. Offshore bar environments were inhabited by the Cyrtospirifer-Camarotoechia Community, exhibiting adaptations to shallow-water, high-energy conditions and probably lowered salinities. Shallow-water, sublittoral environments were inhabited by the Atrypa-Cypricardella Community, a community in which existed a variety of life habitats and a diverse epifaunal and infaunal association of brachiopods and bivalve molluscs. The Leptodesma-Tylothyris Community flourished in nearshore bar-protected environments in the southern region of the study area, whereas in the north the Cyrtospirifer-Camarotoechia Community inhabited nearshore environments in conjunction with the onshore development of a large fluviodeltaic system.     

Progressive drowning of carbonate platform in the Moravo-Silesian Basin (Czech Republic) before the Frasnian/Famennian event: facies,compositional variations and gamma-ray spectrometry

The Moravo-Silesian Basin (MSB; eastern Czech Republic and southern Poland) hosted an extensive shallow-water carbonate platform in the Middle Devonian to Frasnian interval. The platform drowned in a stepwise fashion from the Palmatolepis hassi to the Pa. linguiformis zone. Three types of drowning successions were revealed from conodont biostratigraphy, facies, microfacies and gamma-ray spectrometry data: (A) drowning to periplatform turbidite setting; (B) drowning to (hemi)pelagic seamount setting and (C) drowning associated with the stratigraphical gap. In the lower Pa. hassi zone, rapid subsidence caused the platform to drown locally along the N–S to NW–SE trending faults (type A drowning). In the upper Pa. rhenana to the Pa. linguiformis zone, the drowning accelerated in the western part of the MSB due to locally higher subsidence rates combined with the Late Frasnian biotic crisis (type B). In the southern part of the basin, the platform emerged shortly before the Frasnian/Famennian (F/F) boundary and drowned in the Early to Late Famennian (type C). The primary cause of drowning was differential subsidence at the Laurussian passive margin. Eustatic sea-level fluctuations, if any, contributed only to a minor extent to the Late Frasnian drowning, but were effective in type C drowning during the Famennian. The drowning boundaries are associated with increased contents of K and Th, reflecting the deceleration of carbonate production. Uranium contents display isolated peaks that roughly correlate with the drowning boundaries or the stratigraphic gaps associated with the F/F boundary. The uranium contents are considered to reflect local depositional conditions and are not suitable for stratigraphic correlation. On the other hand, from the K and Th contents, we can infer Late Frasnian sea-level fluctuations with duration on the order of 1 Myr. These cyclic variations in K and Th contents proved to be useful in platform-to-basin stratigraphic correlation.     

Paléobiogéographie des faunes d'Ostracodes au Dévonien supérieur

About one hundred papers and studies have been utilized for a synthesis of ostracode palaeobiogeography during the Frasnian and Famennian. The pelagic entomozoid species have worldwide distributions: they are not used for distinguishing the palaeobiogeographic areas. Five provinces probably existed during the Frasnian and five during the Famennian. The palaeobiogeographic area of the Palaeotethys is constant during this time. There are important faunistic relations between the Western Canadian Platform and the Russian Platform, that is to say, along the Northern margin of the North-Atlantic Continent, during Late Devonian time. The province of Southeastern Asia remains isolated. The number and limits of the palaeobiogeographic areas have been controlled by climate and some geographical barriers.     

华南泥盆系法门阶浅海相四射珊瑚的组合序列

晚泥盆世弗拉期末F-F的生物灭绝事件,导致珊瑚以及许多浅海底栖生物灭绝,几乎整个法门期珊瑚群都处于残存阶段,华南地区目前只在湖南的个别地方发现少量的Smithiphyllum。直到法门期末珊瑚和其它一些造礁底栖生物开始复苏,出现了不少与典型泥盆纪珊瑚存在很大差别的新分子。华南泥盆纪最晚期(Strunian)的珊瑚可划分成上、下两个组合:上部Cystophrentis组合;下部Eocaninophyllum组合。泥盆—石炭纪之交的另一次生物灭绝事件,使新生的泥盆纪最晚期的珊瑚又遭灭绝。     

Devonian Vertebrates From Colombia

Vertebrate remains are reported from the Emsian–Eifelian Floresta Formation and the Late Devonian (?Frasnian) Cuche Formation of north‐eastern Colombia. The material from the Floresta Formation is associated with a marine invertebrate fauna and includes an arthrodire and probably a rhenanid. Several vertebrate‐bearing localities are recorded from the Cuche Formation; vertebrates occur with plant remains and lingulid fragments. They include an acanthodian (Cheiracanthoides? sp.), a chondrichthyan (Antarctilamna? sp.), placoderms (Bothriolepis sp., Asterolepis? sp. and an undetermined groenlandaspidid or primitive brachythoracid arthrodire), a stegotrachelid actinopterygianand three sarcopterygians (a cosmine‐covered form tentatively referred to an osteolepidid, the porolepiform Holoptychiussp., and the rhizodontid Strepsodus? sp.). This assemblage suggests a Late Frasnian age and is surprisingly similar to Late Devonian vertebrate assemblages found in similar facies of Europe and North America, notwithstanding the presence of the Gondwanan chondrichthyan Antarctilamna?. key words: Vertebrata, Devonian, Colombia, South America, biostratigraphy, palaeobiogeography.     

ENIGMATIC WORM-LIKE ORGANISMS FROM THE UPPER DEVONIAN OF NEW YORK: AN APPARENT EXAMPLE OF EDIACARAN-LIKE PRESERVATION

Abstract:  The supposed polychaete annelid Protonympha salicifolia , from the Upper Devonian (Frasnian) of New York State, USA, is redescribed. P .  salicifolia has a bilateral and segmented body, but appears to have a 'mattress-like' construction with blade-like extensions along the margins. The affinities of P. salicifolia remain unresolved, but a proposed relationship to the annelids is unlikely. The preservation of the three known fossils, as mouldic imprints in sandstones, is strongly reminiscent of the circumstances associated with Ediacaran fossilization, and as such is an anomalous occurrence of such soft-part preservation in Phanerozoic sediments. Material associated with these enigmatic fossils has been referred to Palaeochaeta devonica , and also compared with the annelids. Such an assignment is also rejected. These fossils appear to be arthropodan, and are possibly myriapods. A supposed example of Protonympha (' P '.  marcellensis ) from the Middle Devonian of New York State is now excluded from this genus, and it may be a crustacean.     

湖南湘乡上泥盆统佘田桥组介形类

本文首次报道了湖南湘乡上泥盆统佘田桥组介形类化石,共有１８属３５种及未定种,其中包括１１新种。通过与国内外泥盆纪和早石炭世介形类进行比较表明,它们与下伏的中泥盆统棋梓桥组介形类组合和上覆的上泥盆统锡矿山组介形类组合均有明显的差别,该介形类动物群的发现,为佘田桥组的地质时代的确定及地层的划分对比提供了新的古生物依据,并对研究介形类动物群的演化增加了新的资料。