Middle Devonian Limestones Research Articles

Xenacanthid shark teeth in Middle Devonian limestones of the Rhenish Schiefergebirge, West Germany

During investigations in the Rhenish Schiefergebirge, West Germany, concerning the Devonian biostratigraphy of forereef limestones in the Brilon area (Figure 1) several diplodont teeth of fossil sharks were discovered by chance. Remains of xenacanthid teeth from marine Givetian beds are rare. They have been described by Hotton (1952) of probable Givetian/Frasnian age from North America, by Gross (1973) from Middle Devonian Hunsrück Shales, and by Young (1982) from Middle/Upper Devonian strata of Australia and Antarctica.

Textural, Elemental, and Isotopic Variations Among Constituents in Middle Devonian Limestones, North America

ABSTRACT Biogenic components (brachiopods, crinoids, and corals) in Middle Devonian limestones were manually separated from their enclosing matrix and analyzed by textural, elemental, and isotopic methods in order to assess the preservational state of these components. In general, brachiopods in these rocks are better preserved texturally than other constituents, as determined by SEM and cathodoluminescence observations. Elemental variations among the major components are compatible with a differential response to diagenesis governed by the relative stability of the original mineralogy of the component. However, among the most stable, low-Mg calcite brachiopods, the relationship between textural preservation and trace element content is complex. This apparent complexity may be due at least par ially to our method of textural characterization of whole brachipod samples. The nonluminescent portions of a set of well-preserved brachipods have textural characteristics and elemental contents which are virtually indistinguishable from modern representatives. Consequently, their 18O values (-3.7 ± 0.2) are assumed to represent primary biogenic calcite. These 18O values are in the heavy end of the range of values from texturally well-preserved whole brachiopods (-6.6 to -2.5), texturally altered whole brachiopods (-6.7 to -3.7), and texturally altered crinoids and cora s (-6.7 to -2.7). This comparison suggests that marine-derived pore waters were a predominant component during the principal phase of diagenesis. The relatively low l8O values of well-preserved brachiopods compared with modern representatives implies that Middle Devonian seawater was either warmer (by about 10°C) or depleted in 18O (by about 2-3) relative to modern seawater.

Facies and sedimentology of part of the Middle Devonian limestones of Brixham, South Devon, England

The carbonates and argillites studied range in age from early Eifelian to Givetian. The stratigraphic sequence corresponds with a succession of three facies. First, a laminated shale facies was deposited in quiet waters. Later, a thick sequence of interbedded bioclastic limestones and shales accumulated. Beds of bioclastic sands resulted from periodic storms. Dome shaped stromatoporoids dominate this sequence, but higher in the succession a tabular stromatoporoid-crinoidal biosparite facies developed. Due to variations in sedimentation and growth, the tabular stromatoporoids produced ‘sub-sediment frames’ up to 5 m wide and tens of centimetres deep. The lithological and faunal variations represent a progressively shallowing carbonate buildup. This structure apparently did not grow into the permanent wave zone as did some other contemporary buildups.

Tertiary and Cretaceous sediments in solution pipes in the Devonian Limestone of South Devon, England

SummaryLarge sediment-filled solution pipes in Middle Devonian Limestone near Newton Abbot are described. A succession of gravels, sands and clays is identified in the pipes, and the presence of umber, ochre and residual clays is noted. The unusually large size of the pipes is discussed and the infilling sediments are related to the Cretaceous and Tertiary formations of the nearby Bovey Basin and Haldon Hills.

The Horn Plateau Formation: A Middle Devonian Coral Reef, Northwest Territories, Canada

ABSTRACT The Horn Plateau Formation is a Middle Devonian limestone reef approximately 0.4 mi diameter and 400 ft thick which crops out the Interior Plains about 110 mi west of Yellowknife, Northwest Territories. The study is based on examination of material collected from the outcrop and 5 core-holes drilled on and near the reef. Corals are the most important framebuilders present and crinoid ossicles contribute most to the sediment volume. Three macrofacies of this coral patch-reef are recognized: 1) organic reef, an area where framebuilders grew profusely, 2) reef flat, an area characterized by sand-sized sediments, and 3) reef flank, an area of predominantly gravel-sized sediments. Strongly agitated water conditions prevailed over the organic-reef and reef-flank macrofacies whereas moderately agitated water covered the reef flat. Subdivision of the macrofacies has produced 11 microfacies of distinctive texture-composition combinations. Paleoecologic analysis of the individual organism or group permits recognition of 6 successive biotopes from a deeper offreef position up onto the reef flat, namely; (1) bryozoan, (2) solitary coral, (3) massive coral and stromatoporoid, (4) Thamnopora, (5) crinoid and brachiopod, and (6) Stachyodes; prevailing winds were from the northeast. The Horn Plateau reef may be analogous to the Recent Sahul Shelf reefs off Western Australia. A new interpretation of the age of the Horn Plateau reef results from consideration of the additional fauna collected. The reef is middle Givetian age, and is correlative with the middle Pine Point and upper Ramparts formations. It roots in the Lonely Bay Formation, and is overlain by the black shale of the Horn River Formation.

Sedimentology and ecology of the horn plateau formation: A middle devonian coral reef, Northwest Territories, Canada

The Horn Plateau Formation is a Middle Devonian limestone reef approximately 0.4 miles in diameter and 400 feet thick which crops out on the Interior Plains about 110 miles west of Yellowknife, Northwest Territories. The study is based upon examination of material collected from the outcrop and 5 core-holes drilled on and near the reef.

RECENT INFORMATION AND PROSPECTS IN THE KIDSON SUB-BASIN

A deep sedimentary depression, the Kidson Sub-basin, has been indicated within the southern Canning Basin by gravity and aeromagnetism. The wells, Sahara 1, Kidson 1 and Wilson Cliffs 1, showed that at least 15,000 feet of Phanaerozoic sediments were present. This paper aims to summarise information given by these wells and to indicate prospects and techniques for further exploration in the sub-basin.Previous surface geology had indicated Mesozoic and Permian sediments in the area bordered by Proterozoic outcrop. Geomorphological mapping techniques have been successfully used by Aquitaine to indicate possible structures for seismic work.Seismic results from Wapet and Aquitaine indicate gentle diastrophism within the sub-basin with the existence of a palaeogeographic limit to pre-Permian sediments in the east.The western Canning Basin had previously shown a Mesozoic and Permian sequence overlaying Ordovician shales, limestones and sandstones on igneous and metamorphic basement.Sahara 1, and later Kidson 1 and Wilson Cliffs 1, proved the presence of a Middle and pre-Middle Devonian limestone — red bed — evaporite sequence in the sub-basin: the MellinjerieLimestone, Tandalgoo Red Beds and Carribuddy Formation. The underlying Ordovician shales and tight sandstones in Wilson Cliffs 1 can be correlated with the Horn Valley to Pacoota Formations in the Amadeus Basin. In Wilson Cliffs 1 these sandstones overlie Proterozoic shales.The only show noted was minor wet gas associated with Ordovician dolomites in Wilson Cliffs 1. A major petroleum prospect of the sub-basin could be sought in improvement in the reservoir capabilities of the Ordovician sandstones along the palaegeographic eastern margin of the basin.Favourable pinchout forms of these Ordovician sandstones have been found by recent refraction seismic. Refraction, combined with gravity, geomorphology and detailed seismic techniques, can outline drillable prospects along the Kidson Sub-basin.

A Correlation of Some Devonian Limestones of New South Wales and Victoria

AbstractA sequence of 11 tetracoral and conodont faunas, ranging from early Gedinnian to late Givetian, is recognized in the Lower and Middle Devonian limestones of New South Wales and Victoria. These faunas are not only important stratigraphically in eastern Australia, but also provide a basis for the correlation of the Australian Devonian with overseas stages. A table of correlation is given for the principal Devonian limestone sequences of New South Wales and Victoria.

The Petrology of Middle Devonian Limestones in South Devon, England

ABSTRACT The petrographic examination of the diagenetic and metamorphic history of these Devonian limestones, in the light of work on Recent carbonates, shows them to be a predominantly bioclastic series, ranging in composition from calcilutites to coarse biomicrites and biosparites with variable allochems and pelsparites. Six main microfacies are recognized. Despite low grade metamorphism, recognizable diagenetic events include initial cementation, subsequent solution and the introduction of secondary calcite, and the formation of authigenic minerals, quartz and felspar. The rocks are locally dolomitized, and there is evidence of limited de-dolomitization. Metamorphism has resulted primarily in the production of new fabrics, the degree of recrystallization depending upon the stress environment of the rock. In extreme examples all previous textures are destroyed. Some quartz may have been introduced concurrently with the deformation but in general there is no development of metamorphic minerals. Lack of stratigraphic correlation prevents detailed environmental reconstruction, but present evidence suggests that current interpretations of these limestones as a reef formation are erroneous. The limestones are shown to be clastic accumulations of skeletal material, probably from and within areas of prolific growth of carbonate secreting organisms. These organisms at no time formed a growth lattice having topographic expression comparable to modern reefs. Separate ecological habitats are recognized, but little explanation can be offered of the limiting factors.

On the New Red Sandstone Neptunian dykes of the Tor Bay area (Devonshire)

Beyond the main outcrop of the New Red Sandstone there occur in the Middle Devonian Limestone of the Tor Bay area certain dykes and pockets of New Red Sandstone material. While these generally represent the infilling of small caves which were caused by solution, genuine sandstone dykes appear in the more or less flat-lying limestone sheet around Brixham. They are of great depth and are persistent. Lithological differences indicate certainly two, and possibly three, generations of sandstone dykes. The genesis of the clastic dykes is referable to tectonic stretching.

Devonian Limestone Pebbles in Central Devon

AbstractThe presence of locally abundant pebbles of Middle Devonian Limestone in the New Red Sandstone near North Tawton, Devonshire, is recorded. It is suggested that these were derived in Permian times from a nearby outcrop of Devonian limestones which projected through the Culm Measures of the mid-Devon syncline.

Stratigraphie du Paleozoique de la zone axiale pyreneenne a l'E de l'Ariege

Abstract The Paleozoic section in the axial zone of the Pyrenees east of the Ariege, France, consists, from the bottom upward, of the Canaveilles series of interbedded graphitic schists, limestones, and metavolcanics (attributed to the Cambrian), the more homogeneous Jujols schists (lower and middle Ordovician), dated Ashgillian and Gotlandian (Silurian) schists and fossiliferous limestones, grading upward into undifferentiated lower Devonian beds, gray massive middle Devonian limestones, diversified upper Devonian formations, and a zone of transgressive Dinantian (Carboniferous) beds which forms the transition to shaly Visean so-called Culm deposits.

A Middle Devonian lichid Trilobite from South-Eastern Australia

A new lichid trilobite belonging to the subgenusMephiarges is described from delicately silicified fragments present in a massive Middle Devonian limestone in South-eastern Australia. Previously this subgenus was limited to one species of which only the cephalon is known.

Structural Development of Eastern Interior Basin: ABSTRACT

Much of the early Paleozoic history of the Eastern Interior basin is obscure because of the general lack of drilling to pre-Cambrian rocks. From earliest Paleozoic time, however, a gentle slope seems to have been present southward from Wisconsin. The Ozark region also appears to be a very ancient positive area that has been periodically subject to differential uplift. Slow subsidence may have occurred during the Cambrian in the Eastern Interior basin but at that time the basin was probably only a part of a much larger basin that extended eastward to Appalachia and southward for an unknown distance. The first evidence of important structural disturbance is provided by the unconformity at the base of the St. Peter sandstone which overlaps progressively older Ordovician and Cambrian formations in northern Illinois and southeastern Wisconsin. It appears to be related to the uplift of a northwest-southeast arch extending through southeastern Wisconsin, more or less in line with the Kankakee arch as the latter occurs in northwestern Indiana. This movement may have been an early stage in the separation of the Michigan and Eastern Interior basins. At the end of Ordovician time there was sufficient uplift to permit deep erosion of the Maquoketa formation near this arch and also along the borders of the Ozark uplift and the Mississippi River arch. This can be interpreted either as broad regional doming with the principal erosion on the borders of the domed area or as differential uplift and erosion of the borders of a basin which was an early expression of the Eastern Interior basin. Silurian sedimentary rocks in the basin provide little evidence of important structural changes. Cayugan strata, however, are absent in most if not all of the eastern Interior basin, although present in considerable thickness in the Michigan basin. Beginning in late Silurian or early Devonian time, a broad gentle transverse uplift, the Pana arch, restricted lower Devonian deposits on the southeast, separated Middle Devonian limestones on the northwest and southeast, and restricted Kinderhook deposition mostly on the northwest. It may have had some effect on the character of Osage sediments. Slow general subsidence of the Eastern Interior basin, which extended an unknown distance toward the south, occurred during Mississippian time, and was perhaps somewhat accentuated in Chester time. Although first evidence of the LaSalle anticline may be indicated in early Mississippian strata, most of the structural features of the present basin were initiated at the close of the Mississippian and developed progressively throughout the Pennsylvanian period. These features include the DuQuoin axis, which is the structural boundary between the basin and the Ozark area, the major LaSalle anticlinal zone, and numerous smaller structures. Strata deposited throughout the Paleozoic thicken generally southward so that no southern boundary of the depositional basin is indicated. The present southern boundary was produced by uplift, accompanied by faulting, in southern Illinois and western Kentucky at the close of the Paleozoic era. There is scant evidence of subsequent important structural movement in the basin. End_of_Article - Last_Page 300------------

Middle Devonian bone beds of Ohio

The Middle Devonian limestones of central Ohio consist of two formations, the Columbus (late Ulsterian) and the Delaware (early Erian). Within these are at least four thin bone beds: the First, 10 feet below the top of the Columbus in Franklin and southern Delaware counties, the Second, at the contact of the Columbus and the Delaware from Franklin county north to Lake Erie, the Third, 26 to 30 feet above the base of the Delaware in Franklin and Delaware counties, and the Fourth, 2 feet above the Third at Delaware. The Rocky Branch bone bed occurs in southeastern Indiana at the approximate horizon of the Second. These beds vary considerably in development, being absent at some localities and a foot or slightly thicker at others. They consist of clastic accumulations of crinoidal debris, innumerable scales, plates, teeth, and bones of fishes, conodonts, ostracods, and Foraminifera, relatively few macrofossils, mixed with rounded sand grains and a small amount of clay-size constituents, more or less thoroughly cemented by calcite. Another bone bed, the East Liberty, occurs between the Columbus formation and the Upper Devonian Ohio shale in the Bellefontaine Devonian outlier in Logan County, Ohio. It is mostly sand grains cemented by dolomite, with some fish material and a few phosphatic nodules, and is considered younger than the bone beds of central Ohio—perhaps of Olentangy age. The Kiddville layer in the lower part of the Boyle limestone of eastern Kentucky is similar to the East Liberty bone bed lithologically and faunally and probably represents approximately the same horizon. All these bone beds occur on the flanks of the Cincinnati arch, and none is now known in equivalent formations away from this structure. Most of the fish material is believed to have come from the fresh-water environments of the middle Paleozoic lowland area of Cincinnatia and is found not only concentrated in the bone beds but also thinly diffused throughout the enclosing limestones. These bone beds do not represent catastrophic annihilation of indigenous marine fish communities but are rather concentrates accumulated during diastems resulting from the fluctuations with respect to wave base of the very shallow sea bordering Cincinnatia. In places they represent lag concentrates, in others rapid subaqueous accumulations of coarser material transported from areas of lag concentrates with bypassing of finer particles, and in still others aeolian deposits derived from subaerial exposures of lag concentrates.

On the occurrence of native gold at Hope's Nose, Torquay, Devonshire

Some thirty-five years or so ago small quantities of free gold were found in calcite in or near a crush-breccia filling an east and west fault, in the patch of Middle Devonian limestone which forms that portion of the coast known as Daddy Hole Plain directly south-east of Torquay. The name of the actual discoverer I have been unable to ascertain, neither do any specimens appear to have been preserved ; but the late Mr. T. Harrison, the then proprietor of the Queen's Hotel, Torquay, and several other persons subscribed about s and a small amount of prospecting work was carried out, apparently with little result. The only reference to this discovery which I know of is a brief one in 'The geology of the country around Torquay' (Mere. Geol. Survey, 1903, p. 48). To Mr. B. W. Stedham of Torquay I am indebted for the additional particulars given and also for pointing out to me the exact spot, which is on the side of a fissure formed by a large pinnacle of rock standing away from the cliff below the old quarry.

Societies and Academies

LONDON. Mineralogical Society, Jan. 15.—A. Holmes and H. F. Harwood: The tholeiite dikes of the north of England. These dikes, bounded on the north by the Acklington dike and on the south by the Cleveland dike, form an outlying part of the Mull swarm. To the Salen, Brunton, and Talaidh types, already recognised in Mull, the authors add Cleveland and Acklington types, and anorthite-bearing varieties of each. Chemical and mineral analyses are presented, and from a comparative study of the evidence it is shown that there are many features in the series as a whole which are not in accordance with the theory of crystallisation-differentiation.—A. Russell: On the occurrence of gold at Hope's Nose, Torquay, Devonshire. A detailed description of a remarkable occurrence of crystallised arborescent gold in calcite, in Middle Devonian limestone at Hope's Nose, where it was discovered by Prof. W. T. Gordon in 1922. Specimens have since been obtained from five distinct veins. The gold varies in colour from a bright rich gold to almost silver-white, and has a silver content of only 1.89-8.41 per cent.—H. E. Buckley: Crystallography of some organic compounds. Collected records of goniometric measurements on crystals of various organic compounds.

V.—The Fossils Found on the Site of the Torquay Museum

The fossils which form the subject of this notice were obtained from the slates exposed in the excavations for the foundations of the “Pengelly” Lecture Hall, which was added to the Museum of the Torquay Natural History Society in 1894. They were collected by Mr. W. J. Else, the late Curator of the Museum, and were examined by the late Rev. G. F. Whidborne, who published some account of them in the Geological Magazine for 1901, p. 533.When Mr. Whidborne's paper was published I was not specially interested in the details of the geological structure of Torquay, but since then I have paid much attention to these local details and have collected fossils from all existing exposures. I was consequently surprised to find on reference to the note published by Mr. Whidborne that he had regarded these fossils as a Lower Devonian assemblage, in spite of the fact that the Museum is in close contiguity to a tract of Middle Devonian Limestone, as shown on the map of the Geological Survey published in 1898. Moreover, he quoted a statement made by the late Mr. A. Somervail regarding the stratigraphical position of the slates which is entirely incorrect. It is not true that in ascending the Torwood valley from The Strand one passes over a descending series of rocks. The beds underlying The Strand are shaly slates, which dip northward under limestone, and the same slates run up the valley to and a little beyond the Museum; they are then succeeded by limestone which crosses the valley in a south-east direction, and about 100 yards higher up this is faulted against slates which are believed to be of Lower Devonian age.

II.—On Oolitic and other Limestones with Sheared Structure from Ilfracombe

In 1886 the author, during a visit to Ilfracombe, obtained some specimens of Middle-Devonian limestones which, at the time of collecting, he supposed to be formed of Syringopora, on account of the granulated weathered surface, and especially since the coral named had been recorded from the locality.