Middle Devonian (Givetian) conodonts from the northern margin of Gondwana (Soh and Natanz regions, north-west Isfahan, Central Iran): biostratigraphy and palaeoenvironmental implications

2015 ◽  
Vol 95 (4) ◽  
pp. 555-577 ◽  
Author(s):  
Ali Bahrami ◽  
Peter Königshof ◽  
Iliana Boncheva ◽  
Mahbobeh Sadat Tabatabaei ◽  
Mehdi Yazdi ◽  
...  
Keyword(s):  
Middle Devonian ◽  
Central Iran ◽  
Northern Margin ◽  
North West

scholarly journals Middle Givetian to late Famennian (Middle to Late Devonian) conodonts from the northern margin of Gondwana (Kerman region, Central Iran)

2020 ◽  
pp. 1-19
Author(s):  
Fatane Zamani ◽  
Mehdi Yazdi ◽  
Ali Bahrami ◽  
Catherine Girard ◽  
Claudia Spalletta ◽  
...  
Keyword(s):  
Central Iran ◽  
Late Devonian ◽  
Northern Margin

scholarly journals Review of the Ordovician stratigraphy and fauna of the Anarak Region in Central Iran

2015 ◽  
Vol 65 (4) ◽  
pp. 403-435 ◽  
Author(s):  
Leonid E. Popov ◽  
Vachik Hairapetian ◽  
David H. Evans ◽  
Mansoureh Ghobadi Pour ◽  
Lars E. Holmer ◽  
...  
Keyword(s):  
North China ◽  
Cold Water ◽  
Central Iran ◽  
Metamorphic Complex ◽  
North African ◽  
Northern Margin ◽  
Faunal Assemblages ◽  
Lower Ordovician ◽  
Low Diversity ◽  
Sedimentary Succession

Abstract The Ordovician sedimentary succession of the Pol-e Khavand area, situated on the northern margin of the Yazd block, has important differences from those in other parts of Central Iran. It has been established that the presumably terminal Cambrian to Lower Ordovician volcano-sedimentary Polekhavand Formation, exposed in the Pol-e Khavand area, has non-conformable contact with greenschists of the Doshakh Metamorphic Complex. The succeeding, mainly siliciclastic Chahgonbad Formation contains low to moderately diverse faunal assemblages, including brachiopods, cephalopods, trilobites and tentaculitids. The Darriwilian age of the lower part of the formation is well established by the co-occurrence of brachiopod genera Camerella, Phragmorthis, Tritoechia and Yangtzeella. The associated rich cephalopod fauna is different from the Darriwilian cephalopod associations of the Alborz terrane and may show some affinity with warm water faunas of North China and South Korea. It is likely that the Mid Ordovician fauna recovered from the lower part of the Chahgonbad Formation settled in the area sometime during a warming episode in the late Darriwilian. By contrast the low diversity mid Katian brachiopod association includes only three taxa, which occur together with the trilobite Vietnamia cf. teichmulleri and abundant, but poorly preserved tentaculitids questionably assigned to the genus Costatulites. This faunal association bears clear signatures linking it to the contemporaneous cold water faunas of the Arabian, Mediterranean and North African segments of Gondwana. Four brachiopod species recovered from the Chahgonbad Formation, including Hibernodonta lakhensis, Hindella prima, Lomatorthis? multilamellosa and Yangtzeella chupananica are new to science.

scholarly journals NORTH-WESTERN-KORYAK VOLCANIC BELT AND ITS ORE-BEARING VOLCANOGENES

2018 ◽  
Author(s):  
Г.П. Яроцкий
Keyword(s):  
Volcanic Belt ◽  
Magmatic Activity ◽  
Northern Margin ◽  
North West ◽  
The North ◽  
Basement Rocks ◽  
Deep Faults ◽  
Gold Silver ◽  
Metallogenic Zone ◽  
North Western

Обосновано выделение орогенного Северо-Западно-Корякского вулканического пояса. В методологии авторской глыбово-клавишной структуры литосферы определён на границе регионального прогиба и северной активной окраины Корякского микроконтинента механизм образования вулканогенов пояса. На пересечении поперечными межглыбовыми глубинными разломами литосферы границы регионального прогиба и северной окраины микроконтинента образовались локальные впадины вулканогенов. В них в эпоху олигоценовой тектоно-магматической активизации внедрились породы гранитно-метаморфического слоя коры, в которых образовались рудные столбы с золотом, ртутью, ураганным серебром, сопутствующими месторождениями  олова в породах фундамента. Обосновано выделение олово-золото-серебряных рудных районов вулканогенов пояса. Простирание пояса в пределы и Чукотки дает основание определить Северо-Западно-Корякскую металлогеническую зону. We managed to reveal the North-Western-Koryak orogenic volcanic belt. Using the authors'methodology of block and key structure of lithosphere at the boundary of the regional downfold and the northern active margin of the continent we defined the mechanism of the belt volcanogenes formation. The local regional downfolds were formed at the intersection of the transverse intra-block deep faults of regional downfold lithospheric boundary and the Koryak microcontinent's northern margin. During Oligocene tectonic-magmatic activity rocks from the crustal granitic-metamorphic layer with ore columns of gold, mercury, hurricane silver, associated with Sn deposits in basement rocks were introduced in them. The allocation of the tin-gold-silver ore regions in volcanogenic belts is proved. The trend of the belt within the margins and Chukotka gives the basis to determine the North-West Koryak metallogenic zone.

SUBMARINE GRAVITY SURVEYS IN ST. VINCENT GULF AND INVESTIGATOR STRAIT, SOUTH AUSTRALIA, IN RELATION TO OIL SEARCH

1965 ◽  
Vol 5 (1) ◽  
pp. 168
Author(s):  
C. Sprigg ◽  
W. F. Stackler
Keyword(s):  
South Australia ◽  
Maximum Error ◽  
Structural Elements ◽  
Sea Floor ◽  
Northern Margin ◽  
North West ◽  
Gravity Station ◽  
The North ◽  
Upper Proterozoic ◽  
Coastal Beach

A total of 476 submarine and 307 coastal (beach) stations has been observed in and about St. Vincent Gulf and Investigator Strait. These were observed from the oceanographic vessel 'Saori' by manned sea-floor diving chamber, and/or scuba-operated encapsuled meter. Location control was by theodolite fix as from the shore and/or by sextant fix.The survey has provided Bouguer gravity station data contourable on 1 milligal intervals with an estimated maximum error of ± 0.3 milligals in the more remote seaward situations (principally due to surveying), down to ± 0.1 in closer inshore situations.The survey hasdefined the principal structural elements in and about St. Vincent Gulf and Investigator Strait;defined the western margin of the Upper Proterozoic to Cambrian Adelaide Geosyncline;provided a more detailed understanding of coastal block-faulting about the western escarpment of the Mt. Lofty Ranges;defined a longitudinal series of gravitational maxima beneath the Orontes Platform which are predicted to relate primarily to Cambrian fold structures, and which are probably erosionally breached in the north;outlined the probable margin of the submarine portion of the Troubridge (Permian) infra-basin;located a gravitational cross-feature displaying a strong north-south gradient opposite Port Vincent that relates in part to the northern margin of the Troubridge Permian infra-basin, but which appears also to be a locus of transcurrent faulting displaying south-block-west movement;subdivided the St. Vincent Basin into two provinces via a north-west-south-east structure extending south-east from about Macintosh Bank. Possible faulting in this zone indicates downthrow to the north defining potential southern limits of deeper Tertiary basin development.

Metamorphic evolution of the Petersen Bay assemblage, Ellesmere Island: What can we learn about Pearya - Laurentia accretion?

2020 ◽  
Author(s):  
Karolina Kośmińska ◽  
Jane Gilotti ◽  
William McClelland ◽  
Matthew Coble
Keyword(s):  
Middle Devonian ◽  
Bulk Composition ◽  
Arctic Region ◽  
Ellesmere Island ◽  
The Arctic ◽  
Garnet Growth ◽  
Fold Belt ◽  
Weighted Mean ◽  
Northern Margin ◽  
Garnet Core

<p>The accretion of the Pearya terrane to the northern margin of Laurentia plays an important role in the paleogeographic reconstructions for the Arctic region. Earlier workers proposed a timing of its juxtaposition spanning from Late Silurian (Trettin, 1998) to Late Ordovician (Klaper 1992). In this study, we focus on the pressure-temperature-time (P-T-t) evolution of the Petersen Bay assemblage. This subduction related unit crops out between the crystalline basement of Pearya and volcano-sedimentary sequence of Clements Markham fold belt. The highest grade rocks, garnet-kyanite-bearing schist (sample 17-66) and garnet-kyanite-staurolite garbenschiefer (sample 17-64) were selected for P-T studies and in-situ monazite U-Pb dating by sensitive high resolution ion microprobe.</p><p>Thermodynamic modelling of sample 17-66 gives a P-T condition of 7.8-8.1 kbar and 590-610°C for garnet core formation, whereas a pseudosection calculated for the effective bulk composition indicates garnet rim growth at 8-9 kbar and 650-660°C. The QuiG Raman barometry coupled with Ti-in-biotite thermometry yield conditions of 6.5-7.5 kbar and 540-600°C for the garnet growth. The combination of QuiG barometry and Ti-in-biotite thermometry indicate garnet growth at 7.5-8 kbar and 500-550°C for the garbenschiefer sample.</p><p>Monazite shows distinctive zonation and 2, up to 3, domains were recognized based on textures and X-ray microprobe maps. For the sample 17-66, Monazite-I forms inclusions within garnet rims or cores of bigger matrix grains. It defines a weighted mean <sup>206</sup>Pb/<sup>238</sup>U age of 397±2 Ma (n=18, MSWD=1.6). Monazite-II occurs in the matrix and gives an age of 385±2 Ma (n=19, MSWD=1.5). Monazite-I from sample 17-64 yields a weighted mean <sup>206</sup>Pb/<sup>238</sup>U age of 394±2 Ma (n=11, MSWD=0.6). Monazite-II defines the age of 388±2 Ma (n=7, MSWD=0.8). Monazite-III was distinct only in garbenschiefer. It yields a younger age of 374±6 Ma (n=6, MSWD=3.1).</p><p>The P–T data coupled with monazite dating suggest a Middle Devonian metamorphism of the Petersen Bay assemblage under amphibolite facies conditions. These new results suggest that the juxtaposition of the Pearya terrane, Petersen Bay assemblage and the Clemens Markham fold belt is Middle Devonian or younger, i.e. much younger than previously thought.</p><p>References</p><p>Klaper E.M. 1992. The Paleozoic tectonic evolution of the northern edge of North America: A structural study of Northern Ellesmere Island, Canadian Arctic Archipelago Tectonics, 11, 854–870.</p><p>Trettin H.P. 1998. Pre-Carboniferous geology of the northern part of the Arctic Islands: Northern Heiberg Fold Belt, Clements Markham Fold Belt, and Pearya; northern Axel Heiberg and Ellesmere islands GSC Bulletin, 425, 401 p.</p>

Palaeomagnetic study of the Cairnsmoor of Fleet Granite and Criffel-Dalbeattie granodiorite contact aureoles: Caledonian tectonics of the Southern Uplands of Scotland and Devonian palaeogeography

2007 ◽  
Vol 144 (5) ◽  
pp. 811-835
Author(s):  
J. D. A. PIPER ◽  
N. J. McARDLE ◽  
Y. ALMASKERI
Keyword(s):  
Middle Devonian ◽  
Foreland Basin ◽  
Plate Motion ◽  
Irish Sea ◽  
Significant Feature ◽  
Slow Cooling ◽  
Polar Wander ◽  
Northern Margin ◽  
Magnetic Fabrics ◽  
Dual Polarity

The plutons of Cairnsmoor of Fleet (392±2 Ma) and Criffel-Dalbeattie (397±2 Ma, both mineral isochron ages) comprise two of four major post-tectonic granitic complexes emplaced into the Southern Uplands, an Ordovician–Silurian back-arc and foreland basin complex formed at the northern margin of the Iapetus Suture. To expand the palaeomagnetic record of the Southern Uplands we have studied palaeomagnetism and magnetic fabrics in traverses spanning contacts of these intrusions with host mudrocks. A uniform anisotropy of magnetic susceptibility (AMS) fabric across the Cairnsmoor of Fleet contact has been enhanced by recrystallization into hornfels near the contact and records a late Acadian regional stress operative during, or soon after, emplacement of the pluton in Middle Devonian times. Magnetization during slow cooling recorded a dual polarity (‘A’) remanence in granite and hornfels with mean direction D/I = 92/−2° (α95 = 6.5°) yielding a palaeopole (Q = 6) at 2°N, 265°E linked to cooling at c. 392 Ma. Subsidiary magnetizations are overprints imparted during Variscan tectonism (‘B’, D/I = 194/6°) and Jurassic rifting within the adjoining Irish Sea Basin (‘C’, c. 160–140 Ma, D/I = 172/−52°). The Criffel-Dalbeattie pluton has more complex AMS fabrics recording both deformation and emplacement effects. Hematite of secondary hydrothermal origin is a significant feature of the rock magnetic record in the aureole, which is otherwise dominated by paramagnetism. The granodiorite is more strongly magnetized than the country rocks, accounting for a positive aeromagnetic anomaly. A fairly dispersed dual polarity remanence (mean D/I = 115/55°, α95 = 18°) in granodiorite and late tectonic porphyrite dykes is probably the oldest magnetization preserved in this pluton because it correlates with an excursion of Britain into southerly palaeolatitudes at c. 410 Ma and indicates an Early Devonian emplacement age. The palaeofield at c. 397 Ma, the currently accepted isotopic age, is recorded by a minority overprinted remanence (mean D/I = 272/2°, α95 = 12°) similar to the record in the Cairnsmoor of Fleet pluton and granites from the adjoining Lake District terrane. Granite complexes of the Southern Uplands Block collectively record regional rotation and excursion of Britain into southerly latitudes between c. 410 and 390 Ma. Comparable Silurian–Devonian palaeomagnetic poles identify common apparent polar wander (APW) in paratectonic and orthotectonic terranes from the Variscan Front in the south to the Laurentian foreland in the north following climactic Acadian deformation. APW between 430 and 390 Ma embracing the (post-closure) history of the Caledonian orogen is a loop executed at rates much higher than typical rates of plate motion and appears to record a component of true polar wander. The ∼110° arc length is identical to polar shift identified between mid-Silurian and Lower–Middle Devonian poles from Gondwana. The two paths superimpose to show that the western margin of Gondwana was in proximity to the SE margin of Laurentia during Acadian deformation in Early–Middle Devonian times and remote from the Caledonides; the residual Rheic Ocean subsequently closed by a combination of pivotal and left lateral strike-slip motions.

SEISMIC DELINEATION OF STRUCTURE-CONTROLLED CARBONATE CEMENT AND POTENTIAL ECONOMIC IMPLICATIONS, ANGEL FIELD, NORTH WEST SHELF

1995 ◽  
Vol 35 (1) ◽  
pp. 280
Author(s):  
S. Ryan-Grigor ◽  
J.P. Schulz-Rojahn
Keyword(s):  
Seismic Data ◽  
High Amplitude ◽  
Fault System ◽  
3D Seismic ◽  
Economic Implications ◽  
Northern Margin ◽  
North West ◽  
The North ◽  
Migration Pathways ◽  
3D Seismic Data

Major carbonate-cemented zones occur in Late Jurassic Angel Formation sandstones of marine mass flow origin that contain large hydrocarbon reserves in the Angel Field, Dampier Sub-basin. Preliminary results suggest that poikilotopic dolomite cement is dominant. The carbonate-cemented zones are identifiable from wireline log response and 3D seismic data, and occur in discrete intervals with a cumulative thickness of approximately 165m at Angel-2. These intervals produce a zone of high amplitude reflections of about 100 ms two-way time. Field-wide seismic mapping indicates that these carbonate-cemented zones sharply abut the northern margin of a major east-west trending strike-slip fault system that traverses this field. The carbonate-cemented zones extend in a wedge-like shape towards the northeast and concentrate along the crest of the main structural trend.The results underscore the importance of 3D seismic data for a better estimation of reservoir risk and reserves in variably carbonate-cemented sandstones.The carbonate-cemented zones may represent a 'plume' related to migration of petroleum and/or carbon dioxide. Therefore delineation of major carbonate-cemented zones using seismic data may aid in the identification of petroleum migration pathways and pools in the North West Shelf. Alternatively, carbonate cements dissolved south of the major fault zone and possibly in downdip locations in which case dissolution pores may exist in these areas. Further research is required to evaluate these hypotheses.

Planatophyton gen. nov., a late Early or Middle Devonian euphyllophyte from Xinjiang, North-West China

2014 ◽  
Vol 208 ◽  
pp. 55-64 ◽  
Author(s):  
Philippe Gerrienne ◽  
Brigitte Meyer-Berthaud ◽  
Nan Yang ◽  
Philippe Steemans ◽  
Cheng-Sen Li
Keyword(s):  
Middle Devonian ◽  
West China ◽  
North West
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