Lower Eifelian Research Articles

Revised taxonomy and biostratigraphy of brachiopods from the upper Přídolí-lower Eifelian of the Rhenish Massif (Germany)

Brachiopods from the upper Přídolí–lower Eifelian (uppermost Silurian–lowermost Middle Devonian) of the Rhenish Massif (Rheinisches Schiefergebirge, Germany) are taxonomically revised in a long-term project. Currently, nearly 270 species have been distinguished. Stratigraphic intervals with characteristic ecological-evolutionary faunas are separated by events caused by the interplay of changing subsidence, sedimentation and eustatic sea-level, in combination with possible climatic factors. A detailed biostratigraphy consisting of 24 spiriferids and 17 assemblage zones is proposed; these are currently further subdivided into subzones. The revised biostratigraphy provides the prerequisite for new studies on the palaeoenvironment and palaeobiogeography.

CRINOIDEOS DEL GÉNERO Bactrocrinites DEL DEVÓNICO INFERIOR Y MEDIO DE LA CORDILLERA CANTÁBRICA (NO DE ESPAÑA)

Se describen nuevas formas de Bactrocrinites de ambas vertientes de la Cordillera Cantábrica. En la vertiente asturiana: Bactrocrinites longibrachiatus n. sp., Bactrocrinites aff. fusiformis y Bactrocrinites sp., proceden respectivamente de la Punta del Aguión, cerca de Luanco, Formación Aguión (Emsiense superior), de la Ensenada de Moniello, Luanco, base de la Formación Moniello (Emsiense superior) y de Arbeyales, Somiedo, techo de la Formación Santa Lucía (Eifeliense inferior). En la leonesa: Bactrocrinites breimeri n. sp., Bactrocrinites truyolsi n. sp., un segundo ejemplar de Bactrocrinites aff. fusiformis y ? Bactrocrinites sp.; los dos primeros proceden de Huergas de Gordón, Pola de Gordón, en la Formación Portilla (Givetiense) y Formación Santa Lucía (Eifeliense inferior), respectivamente, el tercero, de Valporquero, Valle de Torío, Grupo La Vid (Emsiense superior) y el último de Colle, también en el Grupo La Vid (Emsiense superior). Todas las especies recogidas y descritas en el presente trabajo son relativamente pequeñas y esbeltas y muestran evidentes afinidades con la especie tipo fusiformis

New data on psammosteid heterostracans (Pteraspidomorpha) and acanthodians (Acanthodii) from the Pärnu Regional Stage (Lower Eifelian, Middle Devonian) of Estonia

New data on psammosteid heterostracans (Pteraspidomorpha) and acanthodians (Acanthodii) from the Pärnu Regional Stage (Lower Eifelian, Middle Devonian) of Estonia

Palynology, dacryoconarids and the lower Eifelian (Middle Devonian) Basal Choteč Event: case studies from the Prague and Appalachian basins

Abstract During recent studies of the Basal Choteč Event (BCE) at its type locality (Na Škrábku Quarry at Choteč Village, Prague Basin of the Barrandian area, Czech Republic) and selected sections of time-equivalent strata in the Appalachian Basin (USA), palynomorphs and dacryoconarids have proven responsive to changing environmental conditions. To date, there have been no detailed reports of dacryoconarids from the Appalachian Basin (AB) and none of palynomorphs from Bohemia or elsewhere. Palynomorphs of the Barrandian area comprise a more or less monospecific assemblage of prasinophycean algae interpreted here to represent an ecological epibole. Mazuelloids and scolecodonts are also present, whereas acritarchs, spores and chitinozoans are accessory components. Prasinophytes also predominate in coeval strata of the Appalachian Basin's northern region, whereas a chitinozoan species and morphotypes possibly assignable to fungi abound in the central region. Scolecodonts and acritarchs are regionally variable throughout the interval. The former are rare in the central region of the basin but are ubiquitous and sometimes abundant in the northern region. Dacryoconarids of the Appalachian Basin are also regionally variable. The dacryoconarid fauna of the northern region, however, descended from a previous Emsian fauna that diversified during the BCE and subsequently functioned as the foundation of the upper Eifelian faunas, while dacryoconarids of the central region represent an incursion epibole of Old World forms that entered the basin at the onset of the event interval and became extinct at its close. Among the dacryoconarids there are key taxa that serve as excellent biostratigraphic markers to identify the BCE in the Appalachian Basin. In both the Prague and Appalachian basins, the BCE occurs near the maximum transgression of the Devonian Ic sequence. Additional faunal changes are found in the Appalachian Basin leading up to the main body of the event.

Procteria (Pachyprocteria) vermifera n. sp., an unusual Hicetes-bearing species of tabulate coral from the lower Eifelian of the Gaspé Sandstones Group, Rimouski County (Quebec, Canada)

Procteria (Pachyprocteria) vermifera n. sp. is described from the upper part of the York River Formation (Gaspé Sandstones Group), lower Eifelian (brachiopod Amphigenia Zone), Rimouski County (Quebec, Canada). This new species is considered part of a new lineage of Pachyprocteria characterized by the presence of interstitial corallites. This study reveals for the first time that the granules on the lower (proximal) side are distributed irregularly, their density being higher in the central area of this side than at the periphery. The unusual association of the tabulate coral Procteria (Pachyprocteria) with the “worm” Hicetes is pointed out. The record of the new species adds to the known paleogeographic distribution of Pachyprocteria in North America (Laurussia).

Dohmiella Lütke 1990 (Trilobita) a valid proetid genus, with two new species from Belgium and Germany

Dohmiella is recorded from Belgium for the first time. The genus is represented here by at least three distinct species that occur in strata of early to latest Eifelian age, namelyDohmiella dewildei n. sp.,Dohmiella sp. 1 andDohmiella sp. 2.Dohmiella prescheri n. sp. is recorded from the lower Eifelian of the Eifel, Germany. Relationships ofGerastosGoldfuss,RhenocynproetusBasse andDohmiella are briefly discussed. Contrary to some previous studiesDohmiella is here retained as a distinct genus.

New Middle Devonian trilobites from Vireux-Molhain (Ardennes, northern France)

Lower Eifelian (Middle Devonian) strata cropping out in the vicinity of Vireux-Molhain, Ardennes, France, have yielded a rich trilobite fauna. Four trilobite species are recorded, namelyCeratarges cognatus n. sp.,Rhenocynproetus catervus n. sp.,Cyphaspis n. sp. A andThysanopeltella (Septimopeltis) magnispina (Maillieux 1938).Ceratarges cognatus n. sp. is regarded as a possible transitional form betweenCeratarges faouensisMorzadec 1969 from the Massif armoricain and stratigraphically younger species from the Rhenohercynian.

Eine neueOtarion-Art (Trilobita, Arthropoda) aus dem Greifensteiner Kalk (unteres Mittel-Devon, Unter-Eifelium) von Greifenstein bei Herborn (Hessen, Deutschland)

en|This paper deals with a new species ofOtarion [Otarion (Otarionella) greifensteinen.se n. sp.] from the ‘Greifenstein Limestone’ of the ‘Wiege’ near Greifenstein, close to the village Greifenstein near Herborn (Lahn-Dill area, Hesse, Germany), which is described, figured and compared with all known species of this subgenus. It is a typical trilobite of the hercynian-bohemian shallow marine facies near the Lower-/Middle Devonian boundary (Upper Emsian / Lower Eifelian), which extends up into the lower part of the Middle Devonian (Lower Eifelian). The trilobites are transported for short distances only and, thus, are parautochthonous elements of the Greifenstein Facies.

Persistance de Favositides microlamellaires (Cnidaria, Tabulata) dans le Dévonien

The structural and microstructural study of some devonian ‘ Favosites’ shows the persistence of the microlamellar species related to Paleofavosites until the lower Eifelian. The evolution of the wall is characterized by an increase of the size of the microlamellae and the substitution of the granules of the median dark line by fiber-like units.

Révision de Gourdonia, trilobite duDévonien des Pyrénées centrales: Morphologie, évolution, environnement

The study of the type-material and new samples makes it possible to redefine the genus Gourdonia with his two species Gourdonia gourdoni (Barrois) and Gourdonia destombesiStruve. Despite a very strong tectonic deformation of the material in the shales, thanks to the use of computer-aided shape restoration, it is possible to propose a reconstruction of these species. The genus Gourdonia probably originates in the genus Protacanthina and can be attributed to the sub-family Asteropyginae. The relative abundance of these trilobites in the North of Garin from the Cathervielle shales, Lower Eifelian, in the Central Pyrenees (France) contrasts with the rarity of this group in the pyrenean Devonian. The trilobites association, as well as the sediment and the whole fauna indicate, for this formation, an open shelf environment. These observations well agree with the transgressive event known in Europe and North Africa at the Lower-Middle Devonian transition.

Dutrochus, a new microdomatid (Gastropoda) genus from the Middle Devonian (Eifelian) of west-central Alaska

A new gastropod genus, Dutrochus, is established for members of the family Microdomatidae that are characterized by a reticulate ornament of spiral cords and intersecting, finer collabral threads, with all but one spiral cord being of nearly equal strength, and the single remaining cord being of stronger (nearly twice the order) magnitude and being situated at the periphery. It is represented by the type and only known species, Dutrochus alaskensis n. gen. and sp., from the upper part (lower Middle Devonian; lower Eifelian) of the Lower? and Middle Devonian Cheeneetnuk Limestone, McGrath A-5 quadrangle, west-central Alaska. The genus is very close and nearly homeomorphic to the Permian microdomatid genus Glyptospira, but differs from the latter in possessing an extremely strong, peripheral spiral cord and an extremely thick, multi-layered apertural margin.

Stromatoporoid Biostratigraphy--A Case History: ABSTRACT

End_Page 552------------------------------Stromatoporoids have a plastic morphology which makes them sensitive indicators of paleoenvironments but which presents problems for stratigraphic correlation. A zone at adjacent outcrops may have different genera and species. Nevertheless, stromatoporoids can be useful to determine the time framework of strata. An Amphipora Zone has been recognized for years in the Mid-Continent North American Middle Devonian. Range charts also have been made previously, and at least one work has established several stromatoporoid zone fossils, but authors have noted difficulties of correlation. A small fauna was collected from two adjacent localities in the Niagara Peninsula of Ontario, near the contact of the Onondaga Limestone with the underlying Bois Blanc Formation. The fauna consists of seven species belonging to three genera (22 specimens), not a statistically significant number. However, the stratigraphic ranges of previously reported occurrences of the species accurately determine the correct age when equated to the continental European standard section. The plotted ranges are based on systematic works in which descriptions and illustrations can give some idea of the validity of species identifications. Stratigraphic works with species lists which cannot be documented were not considered. The longest ranging species is Stromatoporella granulata from the lower middle Siegenian well into the Frasnian. Other previously described species in the fauna are confined to the Eifelian, especially to the lower Eifelian. Three species (representing 77% of the specimens collected)--S. granulata, S. selwyni, and S. tuberculatum--were all previously reported many years ago from the Corniferous Limestone at Port Colborne by H. A. Nicholson. S. selwyni has also been reported from the basal Jeffersonville Limestone of Indiana. Stictostroma excellens and Stromatoporella perannulata are described from the area for the first time. Both have been described previously from the Jeffersonville Limestone; Stictostroma excellens from Indiana and Stromatoporella perannulata from Kentucky. One s ecimen is compared with Stromatoporella composita Yavorsky. Although Yavorsky's species is not conspecific, it is morphologically similar enough to be of stratigraphic significance. Yavorsky's species comes from the lower Eifelian beds on the margin of the Kuznetz basin. A question has been raised as to whether Nicholson's fauna reported from nearby Port Colborne came from Onondaga or Bois Blanc beds. Despite of the relatively small number of specimens, one can say that due to strong faunal similarities, Nicholson's material came from the same zone as the material herein reported and further, that both faunas are probably lower Eifelian in age, equivalent to the Edgecliff Member of the Onondaga Formation, which is in agreement with previous correlations based especially on corals and brachiopods. Although stromatoporoid faunas may differ significantly from outcrop to outcrop at the same stratigraphic zone, and although stromatoporoid faunas are frequently represented in collections by small numbers of specimens, they can give a good indication of their position in geologic time when the identified taxons are compared with the world literature. End_of_Article - Last_Page 553------------

Middle Devonian Stratigraphy of Northeastern Spanish Sahara

In support of petroleum exploration, four stratigraphic sections were measured and described in the Middle Devonian outcrop area of northeastern Spanish Sahara. These sediments are exposed in an east-west belt along the south flank of the Tindouf basin. Near the Mauritanian border the Middle Devonian is 106 meters thick, and about 140 kilometers farther west (10° 12^primeW. Long.) it is 356 meters thick, the increased thickness being due to a progressively greater amount of clastics entering the sequence from the west. It is postulated that Caledonian movements affected the West African Paleozoic geosyncline and that emergent areas existed in late Silurian and early Devonian time, located at the western end of the cratonic Tindouf basin. These uplifted areas furnished more Middle Devonian clastics than did the Reguibat arch, which was probably a low, peneplaned area forming the southern boundary of the Tindouf basin. Five major lithologic units are recognized. Unit 1: At the base of the sequence, which rests with slight angular unconformity on Lower Devonian beds, is a uniform shale unit, lower Eifelian in age. Unit 2: Shale with many thin beds of blocky, calcareous siltstone. Includes the only sandstone found in the Middle Devonian and a faunal zone characterized by Uncinulus lodanensis Lower Eifelian. Unit 3: Has characteristics of deposition in an environment of restricted circulation. The beds include two well developed phosphatic limestones, some shales with dwarfed and phosphatized fossils, and a coquinal limestone yielding phosphatic nodules. It is believed to be upper Eifelian in age. Unit 4: Fossiliferous limestone, including patch reefs, interbedded with yellowish gray, calcareous to marly, fossiliferous shale. The circular or elliptical reefs appear to have developed on topographic highs, with bottom sediment type not an important factor. The largest is 24 meters high and 500 meters in basal diameter. Two faunal zones are described from this unit. It is characterized by the presence of Calceola sandalina and is lower Givetian in age. Unit 5: Alternating shale or siltstone and biostromal limestone, characterized by the presence of Phillipsastraea. Upper Givetian. The contact with the Upper Devonian is conformable, but chemical and biological changes are believed to indicate a colder climate following the warm conditions of the Givetian.