A tectonic window in central Newfoundland? Geological evidence that the Appalachian Dunnage Zone may be allochthonous

1984 ◽  
Vol 21 (12) ◽  
pp. 1349-1367 ◽  
Author(s):  
S. P. Colman-Sadd ◽  
H. S. Swinden
Keyword(s):  
Local Development ◽  
The United States ◽  
Upper Ordovician ◽  
Geological Evidence ◽  
Middle Ordovician ◽  
Sedimentary Sequences ◽  
Clastic Sediments ◽  
Hill Area ◽  
Major Fault ◽  
Elliptical Area

In the Through Hill area of central Newfoundland, mafic to ultramafic complexes, which preserve varying amounts of ophiolite stratigraphy, mark the trace of a major fault zone that outcrops in a roughly elliptical pattern. The major, northeast-trending axis is about 60 km and the shorter axis is about 30 km in length. The most complete ophiolite stratigraphy is preserved in the Coy Pond and Pipestone Pond complexes, which have steep dips and face east and west, respectively, outwards from the centre of the ellipse.The ophiolitic rocks are bounded on the outside by rocks typical of the Dunnage Zone of central Newfoundland, principally Lower to Middle Ordovician volcanic and volcaniclastic rocks interpreted to be of island-arc affinity (Davidsville, Victoria Lake, and Baie d'Espoir groups, Cold Spring Pond Formation) and Upper Ordovician to Silurian clastic sediments (Botwood Group). The volcano-sedimentary sequences are interpreted to have been deposited on the ophiolite conformably, but the contacts are not exposed. Both ophiolite and volcano-sedimentary sequences have similar structural and metamorphic histories, exhibiting one principal deformation and the formation of folds with subhorizontal axes, local development of second-generation folds and associated cleavage, and an intervening period of metamorphism in the greenschist facies.The elliptical area enclosed by the ophiolite belt is referred to as the Mount Cormack Terrane, and is underlain by variably metamorphosed shale, quartz-rich sandstone, quartzo-feldspathic to amphibolitic gneisses, and granite. A limestone occurrence contains shelly fossils of Early to Middle Ordovician age. An early deformation formed folds with steep axes, and subsequent metamorphism resulted in a progression from greenschist facies to upper amphibolite facies, with the production of migmatite and granodiorite.The preferred interpretation of the geology is that the elliptical Mount Cormack Terrane is exposed as a window through an overlying allochthon composed of ophiolitic and volcano-sedimentary rocks of the Dunnage Zone. The emplacement of the allochthon probably postdated deposition of the Silurian Botwood Group. Paleontologic, lithologic, and structural considerations suggest that the sediments of the Mount Cormack Terrane were deposited at the eastern margin of Iapetus and are perhaps correlatives of rocks exposed in the Gander Zone. This implies that the Dunnage Zone has been thrust, probably in an eastwards direction, on a scale comparable with the allochthons mapped in the Scandinavian Caledonides and proposed for the Appalachians of Quebec and the United States.

scholarly journals Exceptionally preserved conodont apparatuses with giant elements from the Middle Ordovician Winneshiek Konservat-Lagerstätte, Iowa, USA

2017 ◽  
Vol 91 (3) ◽  
pp. 493-511 ◽  
Author(s):  
Huaibao P. Liu ◽  
Stig M. Bergström ◽  
Brian J. Witzke ◽  
Derek E. G. Briggs ◽  
Robert M. McKay ◽  
...  
Keyword(s):  
New Genus ◽  
Impact Crater ◽  
Soft Part ◽  
Basal Bodies ◽  
Upper Ordovician ◽  
Middle Ordovician ◽  
Fine Grained ◽  
New Family ◽  
Clastic Sediments ◽  
The Common

AbstractConsiderable numbers of exceptionally preserved conodont apparatuses with hyaline elements are present in the middle-upper Darriwilian (Middle Ordovician, Whiterockian) Winneshiek Konservat-Lagerstätte in northeastern Iowa. These fossils, which are associated with a restricted biota including other conodonts, occur in fine-grained clastic sediments deposited in a meteorite impact crater. Among these conodont apparatuses, the common ones are identified asArcheognathus primusCullison, 1938 andIowagnathus grandisnew genus new species. The 6-element apparatus ofA.primuscomprises two pairs of archeognathiform (P) and one pair of coleodiform (S) elements. The 15-element apparatus ofI.grandisn. gen. n. sp. is somewhat reminiscent of the prioniodinid type and contains ramiform elements of alate (one element) and digyrate, bipennate, or tertiopedate types (7 pairs). Both conodont taxa are characterized by giant elements and the preservation of both crowns and basal bodies, the latter not previously reported in Ordovician conodont apparatuses. Comparison of the apparatus size in the Winneshiek specimens with that of the Scottish Carboniferous soft-part-preserved conodont animals suggests that the Iowa animals were significantly larger than the latter. The apparatus ofA.primusdiffers conspicuously from the apparatuses of the prioniodontidPromissumfrom the Upper Ordovician Soom Shale of South Africa although the apparatus architecture ofI.grandisn. gen. n. sp. shows some similarity to it. Based on the Winneshiek collections, a new family Iowagnathidae in Conodonta is proposed.

Planning Replicable Small Flow Wastewater Treatment Facilities in Developing Nations

1993 ◽  
Vol 28 (10) ◽  
pp. 1-8 ◽  
Author(s):  
A. Gaber ◽  
M. Antill ◽  
W. Kimball ◽  
R. Abdel Wahab
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Local Development ◽  
Treatment Plant ◽  
Development Program ◽  
The United States ◽  
Appropriate Technology ◽  
Funding Agency ◽  
Small Scale ◽  
Technology Choice

The implementation of urban village wastewater treatment plants in developing countries has historically been primarily a function of appropriate technology choice and deciding which of the many needy communities should receive the available funding and priority attention. Usually this process is driven by an outside funding agency who views the planning, design, and construction steps as relatively insignificant milestones in the overall effort required to quickly better a community's sanitary drainage problems. With the exception of very small scale type sanitation projects which have relatively simple replication steps, the development emphasis tends to be on the final treatment plant product with little or no attention specifically focused on community participation and institutionalizing national and local policies and procedures needed for future locally sponsored facilities replication. In contrast to this, the Government of Egypt (GOE) enacted a fresh approach through a Local Development Program with the United States AID program. An overview is presented of the guiding principals of the program which produced the first 24 working wastewater systems including gravity sewers, sewage pumping stations and wastewater treatment plants which were designed and constructed by local entities in Egypt. The wastewater projects cover five different treatment technologies implemented in both delta and desert regions.

scholarly journals First record of a nonpaleotropical intejocerid cephalopod from Darriwilian (Middle Ordovician) strata of central Spain

2019 ◽  
Vol 94 (2) ◽  
pp. 273-278
Author(s):  
Björn Kröger ◽  
Juan Carlos Gutiérrez-Marco
Keyword(s):  
United States ◽  
New Species ◽  
New Genus ◽  
First Record ◽  
The United States ◽  
Central Spain ◽  
Middle Ordovician ◽  
A New Species

AbstractThe order Intejocerida is an enigmatic, short-lived cephalopod taxon known previously only from Early–Middle Ordovician beds of Siberia and the United States. Here we report a new genus, Cabaneroceras, and a new species, C. aznari, from Middle Ordovician strata of central Spain. This finding widens the paleogeographic range of the order toward high-paleolatitudinal areas of peri-Gondwana. A curved conch, characteristic for the new genus, was previously unknown from members of the Intejocerida.UUID: http://zoobank.org/21f0a09c-5265-4d29-824b-6b105d36b791

Oxygen isotope (δ18O) trends measured from Ordovician conodont apatite using secondary ion mass spectrometry (SIMS): Implications for paleo-thermometry studies

2021 ◽  
Author(s):  
Cole T. Edwards ◽  
Clive M. Jones ◽  
Page C. Quinton ◽  
David A. Fike
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Matrix Effects ◽  
Analytical Techniques ◽  
Upper Ordovician ◽  
Bulk Analysis ◽  
Middle Ordovician ◽  
Ion Mass Spectrometry ◽  
Oxygen Isotopic ◽  
Secondary Ion

The oxygen isotopic compositions (δ18O) of minimally altered phosphate minerals and fossils, such as conodont elements, are used as a proxy for past ocean temperature. Phosphate is thermally stable under low to moderate burial conditions and is ideal for reconstructing seawater temperatures because the P-O bonds are highly resistant to isotopic exchange during diagenesis. Traditional bulk methods used to measure conodont δ18O include multiple conodont elements, which can reflect different environments and potentially yield an aggregate δ18O value derived from a mixture of different water masses. In situ spot analyses of individual elements using micro-analytical techniques, such as secondary ion mass spectrometry (SIMS), can address these issues. Here we present 108 new δ18O values using SIMS from conodont apatite collected from four Lower to Upper Ordovician stratigraphic successions from North America (Nevada, Oklahoma, and the Cincinnati Arch region of Kentucky and Indiana, USA). The available elements measured had a range of thermal alteration regimes that are categorized based on their conodont alteration index (CAI) as either low (CAI = 1−2) or high (CAI = 3−4). Though individual spot analyses of the same element yield δ18O values that vary by several per mil (‰), most form a normal distribution around a mean value. Isotopic variability of individual spots can be minimized by avoiding surficial heterogeneities like cracks, pits, or near the edge of the element and the precision can be improved with multiple (≥4) spot analyses of the same element. Mean δ18O values from multiple conodonts from the same bed range between 0.0 and 4.3‰ (median 1.0‰), regardless of low or high CAI values. Oxygen isotopic values measured using SIMS in this study reproduce values similar to published trends, namely, δ18O values increase during the Early−Middle Ordovician and plateau by the mid Darriwilian (late Middle Ordovician). Twenty-two of the measured conodonts were from ten sampled beds that had been previously measured using bulk analysis. SIMS-based δ18O values from these samples are more positive by an average of 1.7‰ compared to bulk values, consistent with observations by others who attribute the shift to carbonate- and hydroxyl-related SIMS matrix effects. This offset has implications for paleo-temperature model estimates, which indicate that a 4 °C temperature change corresponds to a 1‰ shift in δ18O (‰). Although this uncertainty precludes precise paleo-temperature reconstructions by SIMS, it is valuable for identifying spatial and stratigraphic trends in temperature that might not have been previously possible with bulk approaches.

Maturation thermique et histoire de l'enfouissement et de la génération des hydrocarbures du bassin de l'archipel de Mingan et de l'île d'Anticosti, Canada

1990 ◽  
Vol 27 (6) ◽  
pp. 731-741 ◽  
Author(s):  
Rudolf Bertrand
Keyword(s):  
Carbonate Platform ◽  
Burial History ◽  
Upper Ordovician ◽  
Southeastern Part ◽  
Middle Ordovician ◽  
Oil Generation ◽  
Wide Range ◽  
History Of ◽  
Anticosti Island ◽  
Depth Of Burial

Carbonate platform sequences of Anticosti Island and the Mingan Archipelago are Early Ordovician to Early Silurian in age. With the exception of the Macasty Formation, the sequences are impoverished in dispersed organic matter, which is chiefly composed of zooclasts. Zooclast reflectances suggest that the Upper Ordovician and Silurian sequences outcropping on Anticosti Island are entirely in the oil window but that the Lower to Middle Ordovician beds of the Mingan Archipelago and their stratigraphic equivalents in the subsurface of most of Anticosti Island belong to the condensate zone. Only the deeper sequences of the southwestern sector of Anticosti Island are in the diagenetic dry-gas zone. The maximum depth of burial of sequences below now-eroded Silurian to Devonian strata increases from 2.3 km on southwestern Anticosti Island to 4.5 km in the Mingan Archipelago. A late upwarp of the Precambrian basement likely allowed deeper erosion of the Paleozoic strata in the vicinity of the Mingan Archipelago than on Anticosti Island. Differential erosion resulted in a southwestern tilting of equal maturation surfaces. The Macasty Formation, the only source rock of the basin (total organic carbon generally > 3.5%, shows a wide range of thermal maturation levels (potential oil window to diagenetic dry gas). It can be inferred from the burial history of Anticosti Island sequences that oil generation began later but continued for a longer period of geologic time in the northeastern part than in the southeastern part of the island. Oil generation was entirely pre-Acadian in the southern and western parts of Anticosti Island, but pre- and post-Acadian in the northern and eastern parts.

Flexible crinoids from the Upper Ordovician Maquoketa Formation of the northern midcontinent and the evolution of early flexible crinoids

2001 ◽  
Vol 75 (2) ◽  
pp. 370-382 ◽  
Author(s):  
James C. Brower
Keyword(s):  
New Species ◽  
North America ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Middle Ordovician

Three flexible crinoids occur in the Upper Ordovician Maquoketa Formation of Illinois, Iowa, and Minnesota:Protaxocrinus girvanensisRamsbottom, 1961,Clidochirus anebosnew species, andProanisocrinus oswegoensis(Miller and Gurley, 1894).Protaxocrinus girvanensisis also found in the Upper Ordovician of Scotland which indicates that the ocean was narrow enough to allow at least one crinoid species to cross the barrier. The Upper Ordovician of North America and Scotland also share many common crinoid genera. Both phenetic and cladistic methods result in similar phylogenies of flexible crinoids.Protaxocrinuswas derived from a cupulocrinid ancestor during the Middle Ordovician.Clidochirusevolved fromProtaxocrinusor its ancestral stock prior to the Richmondian of the Late Ordovician. The RichmondianProanisocrinusand later anisocrinids are most closely related toClidochirusor its immediate predecessor. Thus, three major lineages of flexible crinoids,Protaxocrinus(taxocrinid group),Clidochirus(icthyocrinid), andProanisocrinus(anisocrinids and homalocrinids), appeared during the Ordovician. Despite their rarity during the Ordovician, all three flexible lineages survived the Latest Ordovician extinction, whereas their more abundant and successful cupulocrinid ancestors were eliminated.

scholarly journals Zircon age of vaugnerite intrusives from the Central and Southern Vosges crystalline massif (E France): contribution to the geodynamics of the European Variscan belt

2020 ◽  
Vol 191 ◽  
pp. 26
Author(s):  
François Guillot ◽  
Olivier Averbuch ◽  
Michel Dubois ◽  
Cyril Durand ◽  
Pierre Lanari ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Granite Gneiss ◽  
Upper Ordovician ◽  
Inductively Coupled ◽  
Sedimentary Sequences ◽  
Magmatic Rocks ◽  
Continental Block ◽  
Plasma Mass Spectrometry ◽  
Granite Complex ◽  
Subduction System

To provide a better picture of the active geodynamics along the Variscan suture zones during the late collisional stage (particularly regarding the evolution of the orogenic system towards HT conditions), we focused here on vaugnerites, which consist of mafic ultra-potassic magmatic rocks, intrusive into the granite-gneiss sequences of the Variscan Vosges crystalline massif. Those rocks, though subordinate in volume, are frequently associated with late-collisional granites. In the Central-Southern Vosges, they appear either as (1) pluton margin of the Southern Vosges Ballons granite complex or (2) composite dykes intrusive into migmatite and metamorphic sequences classically referred to as granite-gneiss unit (Central Vosges). Both types correspond to melanocratic rocks with prominent, Mg-rich, biotite and hornblende (20–40% vol., 64 < mg# < 78), two-feldspar and quartz. Those Vosges vaugnerites display geochemical signatures characteristic of ultra-potassic mafic to intermediate, metaluminous to slightly peraluminous rocks. Zircon U-Pb ages were obtained by Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Zircon grains were extracted from a sillimanite-bearing gneiss from the granite-gneiss unit hosting the Central Vosges vaugnerites. They yielded an age at 451 ± 9 Ma, indicating a pre-Variscan Upper Ordovician protolith for the host sequence. Zircon from the four vaugnerite intrusives display U-Pb ages (± 2σ) of 340 ± 2.5 Ma (Ballons), 340 ± 25 Ma, 340 ± 7 Ma and 336 ± 10 Ma (Central Vosges). Synchronous within uncertainty, vaugnerite age data suggest a relatively early emplacement during the Late Variscan collisional history (i.e. Middle Visean times). These results are in line with previously published ages from the Southern Vosges volcano-sedimentary sequences (Oderen-Markstein) and the nearby ultra-potassic granite complexes from the Central and Southern Vosges (Ballons, Crêtes) thereby arguing for a magmatic event of regional significance. Recent petrological studies on vaugnerites suggest that they derive from partial melting of a metasomatized mantle contaminated to some different degrees by elements of continental crust. We propose here that the major ultra-potassic magmatic pulse at 340–335 Ma is a consequence of a significant change into the dynamics of the Rhenohercynian subduction system below the Central-Southern Vosges. In the light of recent thermo-mechanical modelling experiments on mature continental collision, magmatism could result from a syn-collisional lithospheric delamination mechanism involving (1) first, continental subduction evolving towards (2) the underthrusting of the Avalonian continental margin lower crust and (3) the initiation of lithospheric delamination within the supra-subduction retro-wedge (Saxothuringian-Moldanubian continental block). This delamination would drive the emplacement of an asthenospheric upwelling, initially localized along the Variscan suture zones, and gradually propagating towards the southern front of the belt during the Late Carboniferous, as the delamination front migrated at the base of the crust.

SOUTHERN GEORGINA BASIN: A NEW PERSPECTIVE

1990 ◽  
Vol 30 (1) ◽  
pp. 137 ◽  
Author(s):  
W.R. Lodwick ◽  
J.F. Lindsay
Keyword(s):  
Mirror Image ◽  
Source Rocks ◽  
Carbonate Production ◽  
Northern Margin ◽  
Middle Ordovician ◽  
Upper Proterozoic ◽  
Clastic Sediments ◽  
Early Palaeozoic ◽  
New Perspective ◽  
Reservoir Potential

The Georgina Basin formed as a shallow intracratonic depression on the Australian craton along with a number of other basins in the Proterozoic and early Palaeozoic, probably in response to the break up of the Proterozoic supercontinent. Since all of these basins evolved under similar tectonic and sea-level controls, the basins all have similar sediment successions and, it might thus be assumed, similar petroleum prospectivity. One basin, the Amadeus Basin, currently has petroleum production, suggesting a potential for exploration success in the other intracratonic basins.In the Amadeus Basin the main petroleum prospects lie within or adjacent to major sub-basins that formed along the Basin's northern margin. The Georgina Basin has sub-basins that formed along its southern margin, almost as a mirror image of the Amadeus Basin. The lower Palaeozoic section of the Toko Syncline in the southern Georgina Basin has hydrocarbon shows in Middle Cambrian to Middle Ordovician rocks. Source rocks appear to have developed within the transgressive systems tract and the condensed interval of the highstand systems tract, at times when the basin was starved for clastic sediments and carbonate production was restricted.Seismic data acquired in the 1988 survey are of a higher quality than that previously obtained in the area. Its interpretation portrays the westward thrusting French Fault at the eastern edge of the Toko Syncline with potential hangingwall and footwall traps. Cambro- Ordovician Georgina Basin sediments subcrop the overlying Eromanga Basin with angularity, providing potentially large stratigraphic traps. Fracturing of the Cambrian and Ordovician carbonates within fault zones, and solution porosity at the unconformity, would also enhance reservoir potential in the area. Perhaps most significantly, the new data also shows an earlier, apparently independent basin completely buried beneath the Georgina section. The concealed section may simply be a very thick, early Upper Proterozoic section, or perhaps an equivalent to, or a lateral extension of the McArthur Basin. Recent work in the McArthur Basin has shown considerable source potential in the McArthur and Roper Groups, which may support the possibility of an additional, as yet unrecognised, source beneath the Georgina Basin.

Cupulocrinus angustatus (Meek and Worthen, 1870), a cladid crinoid from the Upper Ordovician Maquoketa Formation of the northern midcontinent of the United States

2002 ◽  
Vol 76 (1) ◽  
pp. 109-122 ◽  
Author(s):  
James C. Brower
Keyword(s):  
United States ◽  
Correlation Coefficients ◽  
The United States ◽  
Significance Tests ◽  
Upper Ordovician ◽  
Developmental Constraints ◽  
Stratigraphic Position

Cupulocrinus angustatus (Meek and Worthen, 1870) is common and widely distributed in the Maquoketa Formation of the northern midcontinent of the United States, and specimens are known from the Isotelus and Vogdesia Zones of the Elgin, the Clermont, Fort Atkinson, and Brainard Members. Cluster significance tests indicate that crinoids from all stratigraphic horizons are conspecific. The most numerous primibrachs are located in the A and B rays, whereas the C ray exhibits the fewest plates. The largest and smallest numbers of secundibrachs occur in the B and C rays, respectively. The number of brachs is independent of stratigraphic position and the size of the crinoids. Correlation coefficients for the numbers of brachs demonstrate that the arms are divided into two overlapping and covarying levels: the proximal arms from the primibrachs to tertibrachs, and distal arms ranging from the tertibrachs to quintibrachs. Growth of the aboral cup is generally isometric or roughly so. Conversely, the width:height ratios of brachs typically increase in progressively larger individuals. Similarly, most deposition of calcite on the columnals affects their width rather than height. The correlations for the aboral cup and its plates generally exceed those of brachs and stem plates. The contrasts in allometry and integration and coordination between the aboral cup versus the brachs and column are attributed to differences in basic geometry and developmental constraints. Similar patterns are seen in other Paleozoic and perhaps all or most crinoids.

Cupulocrinid crinoids from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota

1992 ◽  
Vol 66 (1) ◽  
pp. 99-128 ◽  
Author(s):  
James C. Brower
Keyword(s):  
Niche Differentiation ◽  
Upper Ordovician ◽  
Average Width ◽  
Positive Allometry ◽  
Middle Ordovician ◽  
Surrogate Variable ◽  
Crown Volume ◽  
Food Particles ◽  
Anal Sac ◽  
Food Groove

Two cupulocrinids,Cupulocrinus crossmanin. sp. andPraecupulocrinus conjugans(Billings) n. gen., are known from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota. Various morphologic and ontogenetic features demonstrate thatPraecupulocrinusis more primitive thanCupulocrinus. The two species commonly occur together. In addition, both taxa coexisted at similar levels with stem lengths ranging from about 1.5 cm in juveniles to 15 cm in adults. Relatively complete growth sequences illustrate growth and variation and show how two related crinoids subdivided feeding niches. The crown volume provides a satisfactory surrogate variable for the size of the animal. The food-gathering system of the cupulocrinids is mainly augmented by the addition of new plates at the ends of the arms. The number of plates in the arms and the arm length exhibit positive allometry relative to crown volume, largely due to development of new branches at the arm tips. The food-gathering capacity equals the number of food-catching tube-feet multiplied by the average width of the food grooves. Food-gathering capacity is also positively allometric with respect to crown volume and the amount of tissue that must be supplied with food. Consequently, the ratio of food-gathering capacity:crown volume is either constant or declines slightly with increasing size and age. The food groove width increases throughout ontogeny so adult crinoids ate larger food particles than juveniles.Praecupulocrinus conjugans(Billings) n. gen. has more narrow food grooves thanCupulocrinus crossmanin. sp. of comparable size and age, which suggests niche differentiation based on food-particle size. The arm and tube-foot geometry indicates that both cupulocrinids utilized the same type of suspension feeding.The morphology of the anal sac and the lack of “patelloid” processes in the arms indicate thatCupulocrinus sepulchrumRamsbottom from the Upper Ordovician of Scotland belongs toDendrocrinus.

Sign in / Sign up

Export Citation Format

Share Document