New and revised Cyrtoclymenioidea (Clymeniida, Ammonoidea, Famennian, Upper Devonian)

Conodont investigations in the German standard End_Page 641------------------------------ Upper Devonian sections resulted in establishing a conodont zonation. Altogether 26 conodont zones and subzones have been recognized. The conodont succession was obtained mainly from known ammonoid zones beginning with the uppermost Middle Devonian cephalopod zone of Maenioceras terebratum and extending through the entire Upper Devonian into the Wocklumeria Stage. To determine the regional constancy of conodont succession, more than 100 Upper Devonian sections from Germany were studied. The same Upper Devonian conodont succession, recognized in much of Europe, as detailed investigations have subsequently proved. These zones have been found in eastern Germany, Carnic Alps in Austria, Montagne Noire and northern Massif Central in France, Pyrenees and Cantabria in Spain, and Moravia and Bulgaria in southeastern Europe. In addition, in the Belgian Upper Devonian, where the sediments were laid down in a different environment, similar zonal associations and successions coincide with others. Results of studies in the Upper Devonian outside of Europe (mid-western and northern Africa) support the opinion that conodont succession in the Upper Devonian is the same as that in Europe. Presently known deviations are caused by peculiarities within the local geological sequences (breaks in sedimentation, slow deposition, reworking, redeposition, etc.). A recent study of the ammonoid-bearing Upper Devonian sequence of northwestern Australia carried out by Glenister and Klapper indicates that the European conodont zonation also can be applied effectively in this region. Conodonts can be used to zone the Upper Devonian in greater detail than the standard cephalopod succession. Recent studies reveal that boundaries between some ammonoid stages are inexactly defined or that there are gaps in the ammonoid succession. By means of conodonts such gaps may be bridged with the result that the best and most complete biostratigraphic subdivision of the Upper Devonian at present is based on conodonts. End_of_Article - Last_Page 642------------

Since the 1960s, two gas fields (Lokachi and Velyki Mosty) have been discovered in the Devonian sequence of the Volyn-Podillya Plate, and numerous gas shows have been observed in the Lokachi, Olesko, Horokhiv, and Oglyadiv areas. Organic-rich rocks within the Volyn-Podillya Plate are widespread in the Lower, Middle and Upper Devonian strata. They are represented by terrigenous, clayey and carbonate layers. The objective of this study is to investigate the generation potential of the Devonian rocks of the Volyn-Podillya Plate and the possibility of their participation in the petroleum system of the region. Geochemical studies covered the entire territory of the Volyn-Podillya Plate as well as the entire chronological interval of the Devonian strata. Rock-Eval pyrolysis studies showed that the content of total organic carbon in the Lower Devonian organic-rich rocks ranges from 0.01 to 0.45 % (average values 0.12 %). The organic matter in these rocks contains mainly kerogen of marine origin type II, and has undergone primary and/or secondary oxidation processes. The content of total organic carbon in Middle Devonian sediments varies: in rocks of the Eifelian Stage from 0.02 to 0.64 % (average values 0.08 %), in Givetian from 0.01 to 2.35 % (average values 0.19 %), in Frasnian from 0.04 to 1.43 % (average values 0.08 %), in Famennian from 0.07 to 0.10 % (average values 0.09 %). The thermal maturity level of the Lower (Lochkovian Stage), Middle (Eifelian, Givetian Stages) and Upper (Frasnian, Famennian Stages) Devonian ranges from immature to overmature rocks. The Middle and Upper Devonian rocks are dominated by type II marine kerogen, which underwent primary oxidation during sedimentation and/or secondary hydrothermal oxidation of dispersed organic matter during dolomitization. The pyrolysis temperature Tmax varies from 422 to 527 °C, demonstrating that the degree of thermal transformation of kerogen ranges from immature to overmature, with a significant part of the sediments being within the zones of generation of liquid and gaseous hydrocarbons, which indicates the significant role of Devonian sediments in the formation of the petroleum system of the region. Geochemical studies of the generation properties of the Middle and Upper Devonian sediments within the Volyn-Podillya Plate showed that they can be considered as oil and gas source rocks in the Upper Paleozoic sequence.

High quality (>2% TOC) Upper Devonian source rocks are developed in several sequence types. The commonest type, accounting for 70% of the studied examples is the transgressive sequence with a basal hiatus. Others include shallowing upward sequences (12%), lacustrine sequences in fault-controlled basins (7%), distal slope sequences (7%), and evaporite capped sequences (4%).Starting from the synthesis of Johnson, Klapper, and Sandberg (1985) it has been possible to demonstrate correlativity of Upper Devonian transgressive episodes globally. The marked association of epeiric sea Upper Devonian source rocks with transgressions heightens interest in their causation. Could they have been produced by glacio-eustatic sea-level change as Stanley (1984; 1988) implies? Quantitative paleoclimate modeling and isotopic paleotemperatures for the Upper Devonian suggest not. Modeling using CCM1 at NCAR, including five year seasonal cycles, suggests the absence of any large southern hemisphere ice volume. Because much of the Upper Devonian land mass was either in equatorial or high latitude regions, there was little development of monsoonal climates. Midlatitude cyclonic activity was also much less than at present, meaning less polar transport of moisture and drier polar areas. Precipitation maxima largely coincided with topographic elevations. In contrast to the Late Ordovician to earliest Silurian, there was no Upper Devonian perennial snow cover even over the high latitude southern land mass. This was in spite of winter land temperatures as low as -40°. in eastern Gondwana. In that area and elsewhere, there was thin winter snow cover which melted in late spring resulting in no build-up of snow cover to produce glaciation. This was mainly the consequence of low winter precipitation in Gondwana. High latitude sea surface temperatures were certainly cold enough to displace or exclude some organisms. However, in low latitude areas where Upper Devonian extinctions also took place, modeled sea surface temperatures range between 27° and 34°. Such areas would have been refuges for any organisms displaced by cold, high latitude waters. The higher temperature values of low latitudes are convergent with the isotopic paleotemperatures determined by Brand (1989) using well preserved Upper Devonian brachiopods. Brand's determinations suggest temperatures even reaching lethal values for many plankton (37°). The extinction of reefs by the close of Frasnian time could have been partly a result of such elevated temperatures. Stacked extinctions of conodonts (Ziegler and Lane, 1987) and acritarchs may have been a further result. The loss of reefs, an important consumer of plankton, may have permitted a relative increase in plankton abundance crossing from more oceanic areas into epeiric seas, possibly contributing to high quality source rock deposition.

Exploration and development activities in Western Canada were at or near the high levels established in 1952, with Alberta continuing in first place, and Saskatchewan, in second place, showing a high rate of growth. In all, 1,319 development wells were drilled, and a daily average of 222,440 barrels of crude oil produced. One hundred and fifty-eight geophysical parties were operating in December. Exploratory drilling remained high, with 896 wells making 139 oil discoveries and 118 gas discoveries for an over-all success ratio of 28.7%. Most significant oil discoveries were made in the Cardium sand at Pembina in west-central Alberta; and in the Viking sand at Smiley in western Saskatchewan. Important extensions to the Sturgeon Lake reef field were made. Other discoveries were made in Alberta in the Viking and Upper Devonian, and in Saskatchewan and Manitoba in Cretaceous, Jurassic, and Mississippian reservoirs. New pay zones were encountered in the Upper Cretaceous and in the Upper and Middle Devonian. A 645-mile extension of the Interprovincial Pipeline from Superior, Wisconsin, to Sarnia, Ontario, was constructed and put in service. A 24-inch oil pipeline from Edmonton westward to Vancouver constructed during 1952 and 1953 was put in service in October. The line has a length of 718 miles and a present capacity of 120,000 barrels per day.

In Soviet Central Asia (Tien Shan and Pamirs) corals are unknown in the Lower Ordovician, rare and unstudied in the Middle Ordovician. The tabulate coral record from the Upper Ordovician, Silurian and Devonian is excellent and numerous common and Key genera and species are enumerated for each stage or substage. Tabulata reached their peak development in the Wenlock, and had markedly decreased in numbers and variety by late Middle Devonian time. Tabulata are rare in Upper Devonian and later rocks but occur through the Carboniferous and into the Upper Permian. -- W. A. Oliver, Jr.

Over 30 depositional sequences have been identified in the Paleozoic and lower Mesozoic of the Ghadames basin of eastern Algeria, southern Tunisia, and western Libya. Well logs and lithologic information from more than 500 wells were used to correlate the 30 sequences throughout the basin (total area more than 1 million km{sup 2}). Based on systematic change in the log response of strata in successively younger sequences, five groups of sequences with distinctive characteristics have been identified: Cambro-Ordivician, Upper Silurian-Middle Devonian, Upper Devonian, Carboniferous, and Middle Triassic-Middle Jurassic. Each sequence group is terminated by a major, tectonically enhanced sequence boundary that is immediately overlain (except for the Carboniferous) by a shale-prone interval deposited in response to basin-wide flooding. The four Paleozoic sequence groups were deposited on the Saharan platform, a north facing, clastic-dominated shelf that covered most of North Africa during the Paleozoic. The sequence boundary at the top of the Carboniferous sequence group is one of several Permian-Carboniferous angular unconformities in North Africa related to the Hercynian orogeny. The youngest sequence group (Middle Triassic to Middle Jurassic) is a clastic-evaporite package that onlaps southward onto the top of Paleozoic sequence boundary. The progressive changes from the Cambrian to themore » Jurassic, in the nature of the Ghadames basin sequences is a reflection of the interplay between basin morphology and tectonics, vegetation, eustasy, climate, and sediment supply.« less

Geologic Framework of a Transect of the Central Brooks Range: Regional Relations and an Alternative to the Endicott Mountains Allochthon

The authors have investigated palaeomagnetically the Ordovician, Upper Devonian and Lower Carboniferous strata in Tuva. In the rocks, postfolding secondary and prefolding magnetization components were isolated. Paleomagnetic poles were calculated from primary magnetization components: for the Ordovician — Φ = 4° N, Λ = 307°E, A95 = 5.4°, if the Ordovician strata were formed in the Northern hemisphere and Φ = −41° N, Λ = 127°E, A95 = 5.4°, if the strata accumulated in the southern hemisphere; for the lower part of the Upper Devonian — Φ = 3.7° N, Λ = 139.8° E, A95 = 9.3°, for the upper part of the Upper Devonian — Φ = 51.7° N, Λ = 148.8° E, A95 = 16°; for the lower carbon — Φ = 53.8° N, Λ = 141.7° E, A95 = 9.6°. Probably, at least since the Ordovician, Tuva was part of the Siberian structure and was moving latitudinally with it. The Devonian and Lower Carboniferous strata are rotated in different degrees in the horizontal plane in relation to Siberia. The rotations could be associated with local deformations of rocks, but it is also possible that the rotation of a large geological block was caused by large-amplitude shifts after the Early Carboniferous.

An estimated total of over 20,000 feet of Palaeozoic sediments accumulated in the Bonaparte Gulf Basin. The thickest known continuous section is that in Bonaparte No. 1 Well, abandoned at 10,530 feet in Upper Devonian sandstone and shale. Rocks of the Basin margins are mainly sandstones and limestones (in part reef), whereas a thick shale section has been discovered in the deeper parts. Data from recent seismic surveys indicate that the seaward extension of the Basin is considerable and that a thick pile of sediments is preserved there.The Bonaparte Gulf Basin formed as a result of subsidence of the north-eastern part of the Kimberley Block along fault lines associated with the Halls Creek Mobile Zone. This zone borders the south-eastern margin of the Basin and trends north-east. One basement block, represented by the presentday Pincombe Range, remained relatively high. The Bonaparte Gulf Basin can be divided into two subsidiary basins, the Carlton Basin to the west and north-west and the Burt Range Basin in the east and south-east. The Pincombe Range separates the two.Marine sediments were deposited in the Carlton Basin during the Middle and Upper Cambrian, Lower Ordovician, Upper Devonian and Lower Carboniferous epochs. Angular unconformities have been mapped between the Lower Ordovician and Upper Devonian rocks, and between Upper Devonian and Lower Carboniferous rocks. In the Burt Range Basin, deposition began in the Upper Devonian and continued with minor breaks through the Lower Carboniferous. Faults along the south-eastern margin were active through this period and affected the character of the sediments.Permian sediments are widely distributed and lie with unconformity on older units.

The Rock-Eval source rock characteristics, mineral composition and type-porosity of reservoir horizons, and origin of natural gas in the Devonian of the Lublin and Lviv basins are described. In the Lower Devonian, the TOC content ranges from 0.01 to 1.82 wt.% in the Lublin Basin, and from 0.01 to 0.45 wt.% in the Lviv Basin. Transformation of organic matter varies from immature in the Lochkovian (Lviv Basin) to mature and overmature in the Emsian (Lublin Basin). The organic matter contains mainly Type-II kerogen, and underwent primary and/or secondary oxidation processes. In the Middle Devonian, the TOC content varies from 0.00 to 1.63 wt.% in the Lublin Basin, and from 0.02 to 0.64 to 2.35 wt.% in the Lviv Basin. The organic matter contains mainly Type-II kerogen and is immature in the Givetian of the Lviv Basin and mature in the Eifelian of the Lviv Basin and in the Eifelian and Givetian in the Lublin Basin. In the Upper Devonian, the TOC content is from 0.02 to 2.62 wt.% in the Lublin Basin, and from 0.04 to 1.43 wt.% in the Lviv Basin. Type-II kerogen dominates in both basins. Organic matter is mature in the Upper Devonian in the Lublin Basin and in the Famennian of the Lviv Basin and overmature in the Frasnian of the Lviv Basin. The reservoir horizons in the Devonian of the Lublin and Lviv basins are developed in clastic, carbonate and sulphate rocks. Terrigenous rocks form several separate horizons in the Lower and Middle Devonian of the Lviv Basin, and in the Upper Devonian (Famennian) of the Lublin Basin. Their filtration properties relate to intergranular porosity, while the fracture space has subordinate significance. Carbonate rocks form thick saturated horizons in the Givetian in the Lviv Basin, and in the Eifelian, Givetian and Frasnian in the Lublin Basin. Their filtration properties are produced by fracture porosity. Sulphates and carbonate-sulphate rocks with fracture and cavern porosity play a role as reservoir horizons in the Middle Devonian of the Lublin Basin. The natural gas collected from the Upper Devonian of the Lublin Basin was generated mainly during low-temperature thermogenic processes, from Ordovician–Silurian Type-II kerogen. The gas from the Middle Devonian reservoirs of the Lviv Basin was produced from Ordovician–Silurian Type-II kerogen and partly from the Middle and Upper Devonian mixed Type-III/II kerogen with maturity from about 0.9 to 1.4%. Carbon dioxide was formed by both thermogenic and microbial processes. Molecular nitrogen was generated mainly through thermal transformation of organic matter and also from destruction of NH 4 -rich illite of the clayey facies of the Ordovician–Silurian strata

Detrital zircon populations from six samples of upper Triassic sandstone (Algarve Basin) were analysed, yielding mostly Precambrian ages. zircon age populations of the Triassic sandstone sampled from the western and central sectors of the basin are distinct, suggesting local recycling and/or lateral changes in their sources. Our findings and the available detrital zircon ages from the Palaeozoic terranes of SW Iberia, Nova Scotia and NW Morocco were jointly examined using the Kolmogorov–Smirnov test and multidimensional scaling diagrams. The obtained results enable direct discrimination of competing Laurussian-type and Gondwanan-type sediment sources, involving recycling and mixing relationships. The detrital zircon populations of the Algarve Triassic sandstone are very different from those of the lower–upper Carboniferous Mértola and Mira formations (South Portuguese Zone), upper Devonian – lower Carboniferous Horta da Torre, Represa and Santa Iria formations (Pulo do Lobo Zone), and the late Carboniferous Santa Susana and early Permian Viar basins, which are ruled out as potential sources. The detrital zircon populations of Triassic sandstone from the central sector and those from the Ossa–Morena Zone Ediacaran–Cambrian siliciclastic rocks, upper Devonian – Carboniferous Ronquillo, Tercenas, Phyllite-Quartzite and Brejeira formations (South Portuguese Zone), and Frasnian siliciclastic rocks of the Pulo do Lobo Zone are not statistically distinguishable. Thus, sedimentation in the central sector was influenced by Gondwanan- and Laurussian-type putative sources exposed in SW Iberia, in contrast to the western sector, where Meguma Terrane and Sehoul Block Cambrian siliciclastic rocks allegedly constituted the main (Laurussian-type) sources. These findings provide insights into the denudation of distinctive source terranes distributed along the late Palaeozoic suture zone that juxtaposed the Laurussian and Gondwanan margins.

Upper Devonian reefs and microbialite at Maoying, South China—implications for paleoenvironmental changes

Fault blocks and inliers of uppermost Silurian to Middle Devonian strata in the Yarrol Province of central coastal Queensland have been interpreted either as island-arc deposits or as a continental-margin sequence. They can be grouped into four assemblages with different age ranges, stratigraphic successions, geophysical signatures, basalt geochemistry, and coral faunas. Basalt compositions from the Middle Devonian Capella Creek Group at Mt Morgan are remarkably similar to analyses from the modern Kermadec Arc, and are most consistent with an intra-oceanic arc associated with a backarc basin. They cannot be matched with basalts from any modern continental arc, including those with a thin crust (Southern Volcanic Zone of the Andes) or those built on recently accreted juvenile oceanic terranes (Eastern Volcanic Front of Kamchatka). Analyses from the other assemblages also suggest island-arc settings, although some backarc basin basalt compositions could be present. Arguments for a continental-margin setting based on structure, provenance, and palaeogeography are not conclusive, and none excludes an oceanic setting for the uppermost Silurian to Middle Devonian rocks. The Mt Morgan gold–copper orebody is associated with a felsic volcanic centre like those of the modern Izu–Bonin Arc, and may have formed within a submarine caldera. The data are most consistent with formation of the Capella Creek Group as an intra-oceanic arc related to an east-dipping subduction zone, with outboard assemblages to the east representing remnant arc or backarc basin sequences. Collision of these exotic terranes with the continent probably coincided with the Middle–Upper Devonian unconformity at Mt Morgan. An Upper Devonian overlap sequence indicates that all four assemblages had reached essentially their present relative positions early in Late Devonian time. Apart from a small number of samples with compositions typical of spreading backarc basins, Upper Devonian basalts and basaltic andesites of the Lochenbar and Mt Hoopbound Formations and the Three Moon Conglomerate are most like tholeiitic or transitional suites from evolved oceanic arcs such as the Lesser Antilles, Marianas, Vanuatu, and the Aleutians. However, they also match some samples from the Eastern Volcanic Front of Kamchatka. Their rare-earth and high field strength element patterns are also remarkably similar to Upper Devonian island arc tholeiites in the ophiolitic Marlborough terrane, supporting a subduction-related origin and a lack of involvement of continental crust in their genesis. Modern basalts from rifted backarc basins do not match the Yarrol Province rocks as well as those from evolved oceanic arcs, and commonly have consistently higher MgO contents at equivalent levels of rare-earth and high field strength elements. One of the most significant points for any tectonic model is that the Upper Devonian basalts become more arc-like from east to west, with all samples that can be matched most readily with backarc basin basalts located along the eastern edge of the outcrop belt. It is difficult to account for all geochemical variations in the Upper Devonian basalts of the Yarrol Province by any simplistic tectonic model using either a west-dipping or an east-dipping subduction zone. On a regional scale, the Upper Devonian rocks represent a transitional phase in the change from an intra-oceanic setting, epitomised by the Middle Devonian Capella Creek Group, to a continental margin setting in the northern New England Orogen in the Carboniferous, but the tectonic evolution must have been more complex than any of the models published to date. Certainly there are many similarities to the southern New England Orogen, where basalt geochemistry indicates rifting of an intra-oceanic arc in Middle to Late Devonian time.

Abstract: Tetrapod trackways are described for the first time from the Upper Devonian St. Finan's Sandstone Formation at Tooreen in St. Finan's Bay, southwest County Kerry. The St. Finan's Sandstone Formation is a 1,240m thick sandstone-dominated sequence that occurs in the middle part of the continental Old Red Sandstone Munster Basin succession. The trackways comprise 140 imprints that show variable depth and shape. This variability is attributed to changes in the firmness of the substrate and water depth along the length of the trackways. One of the trackways preserves an imprint with possible five-digit impressions and another displays a tapered elongated depression that is tentatively interpreted as a tetrapod body impression. Analysis of three trackways indicates they were made by a population of similar-sized tetrapods (just under 1m in length) that moved by lateral sequence walking. The trackways are preserved in a current-rippled and parallel-laminated sandstone sequence that was deposited on a flood plain bordering a river channel margin. A spore assemblage obtained from a mudstone within the trackway-bearing sequence is assigned to the Rugospora bricei - Cymbosporites acanthaceus BA Biozone, which biostratigraphically dates the trackway as Upper Devonian (mid Frasnian) in age. The Tooreen tetrapod trackways are very similar in size, spatial arrangement and palaeoenvironment to those recorded from the older Middle Devonian (Givetian) Valentia Slate Formation that occur nearby on Valentia Island. This new evidence extends the geographic and geological range of these ichnological datasets and provides a better understanding of the early stages of colonisation of continental (terrestrial) environments by Devonian tetrapods.

The hydrogeological features of the central part of the Moscow artesian basin (MAB) under the natural conditions provided the existence of the downward vertical flows of the groundwater, the formation of the fresh underground waters of the Carboniferous complex, desalination of the Upper Devonian subterranean waters. The long exploitation of the Aleksin-Protvino horizon in the central part of the MAB led to the formation of a depression of the piezometric level with a depth of 80 m, as well as a change in the ratio of the absolute marks of the piezometric surfaces of the groundwater of the Lower Carboniferous and the Upper Devonian, and the creation of prerequisites for the changing of the orienfafion of the vertical wafer exchange between them. A map of the difference in pressures between the Aleksin-Protvino and the Upper Devonian horizons, compiled by the author, shows this situation. In a vast zone of the central part of the MAB, the pressure surface of the Alexin-Protvino horizon is 30-50 m below the upper Devonian horizon. Under these conditions, it seems important to study the Upper Devonian aquiferous complex as a possible source of the «contamination» of the groundwater of the Lower Carboniferous, especially in the zones of active lineaments of the Moscow syneclise.