scholarly journals Age of the basement beneath the Mesozoic Lusitanian Basin revealed by granitic xenoliths from the Papôa volcanic breccia (West Iberia)

2020 ◽  
Vol 18 ◽  
pp. 1-14
Author(s):  
M.F. Pereira ◽  
C. Gama ◽  
J.B. Silva ◽  
Í. Dias da Silva
Keyword(s):  
Biotite Granite ◽  
Lower Jurassic ◽  
Variscan Belt ◽  
Volcanic Breccia ◽  
Margin Of Error ◽  
Meguma Terrane ◽  
Rhenohercynian Zone ◽  
First Time ◽  
Lusitanian Basin ◽  
Jurassic Sequence

The dyke of the Papôa volcanic breccia cross-cutting the Lower Jurassic sequence of the Lusitanian Basin (West Iberia) contains granitic xenoliths. In this study, for the first time, U-Th-Pb zircon analysis of two xenoliths yielded 298±4Ma for biotite granite and of 292±2Ma for two-mica granite, indicating that the pre-Mesozoic basement of the Lusitanian Basin includes Permian intrusions. These ages are close within the margin of error of the age of the Late Carboniferous granites of the Berlengas isle that with the Late Devonian high-grade metamorphic rocks of the Farilhões isles, located northwest of the study area, which form the pre-Mesozoic basement of the Lusitanian Basin. These new geochronological findings enable it to be established that Permo-Carboniferous magmatism lasted at least 13Ma, in this region of the Appalachian-Variscan belt. Furthermore, a comparison with available data from Paleozoic tectonic units of the Appalachian-Variscan belt located both in the Iberian Massif and outside it enables the suggestion to be made that the Lusitanian Basin (Peniche) most probably rests on the South Portuguese Zone, which may also be correlated with the Rhenohercynian Zone present in southwest England, and the Meguma terrane of Nova Scotia.

scholarly journals MESOZOIC RADIOLARIANS FROM RHYTHMICALLY LAYERED SEDIMENTS OF THE RIMSKY-KORSAKOV ISLANDS (PETER THE GREAT BAY, JAPAN SEA) AND THEIR SIGNIFICANCE FOR DETERMINING THE TRIASSIC-JURASSIC BOUNDARY

2021 ◽  
pp. 39-54
Author(s):  
O.L. Smirnova ◽  
◽  
E.A. Bessonova ◽  
T.A. Emelyanova ◽  
◽  
...  
Keyword(s):  
Peter The Great Bay ◽  
Japan Sea ◽  
Research Area ◽  
Lower Jurassic ◽  
Upper Triassic ◽  
Peter The Great ◽  
Great Bay ◽  
The Pacific ◽  
Stratigraphic Division ◽  
First Time

The results of the biostratigraphic study based on the radiolarian analysis of the rhythmically layered terrigenous deposits from the Islands of the Rimsky-Korsakov Archipelago (Peter the Great Bay, Japan Sea) have been presented. These deposits are most similar to the medium-grained turbidites. For the first time the distribution and stratigraphic division of the boundary sediments of the upper Triassic and lower Jurassic separated by a marking layer were substantiated in the research area. On the basis of comparisons with isochronous zonal units of the Pacific and Tethyan areas in the upper Triassic sediments of the studied sections, layers with Globolaxtorum tozeri (upper Rhaetian) were established, and in the lower Jurassic zone Pantanellium tanuense Zone (Hettangian) was traced and layers with Parahsuum simplum (Sinemurian – Pliensbachian) were established.

Rare metals on shatter cone surfaces from the Steinheim Basin (SW Germany) – remnants of the impacting body?

2017 ◽  
Vol 155 (6) ◽  
pp. 1205-1229 ◽  
Author(s):  
E. BUCHNER ◽  
M. SCHMIEDER
Keyword(s):  
Hydrothermal Activity ◽  
Upper Jurassic ◽  
Lower Jurassic ◽  
Iron Meteorite ◽  
Rare Metals ◽  
X Ray ◽  
Central Uplift ◽  
Post Impact ◽  
Shatter Cones ◽  
First Time

AbstractThe ~3.8 km Steinheim Basin in SW Germany is a well-preserved complex impact structure characterized by a prominent central uplift and well-developed shatter cones that occur in different shocked target lithologies. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and electron probe microanalysis have revealed, for the first time, the occurrence of rare metals on the Steinheim shatter cone surfaces. Shatter cones produced from the Middle Jurassic (Aalenian) Opalinus Claystone (‘Opalinuston’), temporarily exposed in the central uplift in spring 2010, and shatter cones in Upper Jurassic (Oxfordian) limestones from the southeastern crater rim domain are commonly covered by faint coatings. The Opalinus Claystone shatter cone surfaces carry coatings dominated by Fe, Ca, P, S and Al, and are covered by abundant small, finely dispersed microparticles and aggregates of native gold, as well as locally elevated concentrations of Pt. On several surfaces of the claystone shatter cones, additional Fe, Ni and Co was detected. The Ca–Mn-rich coatings on the limestone shatter cone surfaces locally include patches of Fe, Ni, Co, Cu and Au in variable amounts and proportions. The intriguing coatings on the Steinheim shatter cones could either stem from the impacted Lower Jurassic to Palaeogene sedimentary target rocks; from the crystalline-metamorphic Variscan crater basement; or, alternatively, these coatings might represent altered meteoritic matter from the Steinheim impactor, possibly an iron meteorite, which may have been remobilized during post-impact hydrothermal activity. We here discuss the most plausible source for the rare metals found adherent to the shatter cone surfaces.

scholarly journals The biostratigraphy of the Upper Pliensbachian-Toarcian (Lower Jurassic) sequence at Ilminster, Somerset

2009 ◽  
Vol 28 (1) ◽  
pp. 67-85 ◽  
Author(s):  
I. Boomer ◽  
A. R. Lord ◽  
K. N. Page ◽  
P. R. Bown ◽  
F. M. D. Lowry ◽  
...  
Keyword(s):  
Lower Jurassic ◽  
Calcareous Nannofossils ◽  
Marked Contrast ◽  
Evolutionary Patterns ◽  
Southern England ◽  
Carbonate Deposit ◽  
Temporary Road ◽  
Insight Into ◽  
Jurassic Sequence

Abstract. Temporary road sections for the A303 bypass at Ilminster, Somerset, revealed Upper Pliensbachian and Toarcian sediments from an alternating limestone–marl facies, in marked contrast to the limestone-dominated Dorset coast succession. The lithostratigraphy is described, with the standard ammonite zonation providing chronostratigraphical correlation. The uppermost Pliensbachian (Spinatum Chronozone) and much of the Toarcian (Serpentinum, Bifrons, Variabilis, Thouarsense and Pseudoradiosa chronozones) of the classic Dorset coast Lower Jurassic sequence are represented by the Beacon Limestone Formation, formerly the ‘Junction Bed’ (a highly condensed carbonate deposit). The Tenuicostatum Chronozone is largely missing from the sequence. Elsewhere in southern and eastern England this interval is poorly or rarely exposed. The argillaceous units have yielded rich microfaunas and -floras (foraminifera, ostracods, calcareous nannofossils and palynomorphs), the biostratigraphical distributions of which are analysed and discussed in relation to contemporary evolutionary patterns and other UK records. This study provides an insight into the micro-biostratigraphy of the Late Pliensbachian to Toarcian interval for onshore southern England.

scholarly journals MINERAL - PETROGRAPHICAL, PETROCHEMICAL CHARACTERISTICS OF XUAN THU GRANITOID MASSIF, QUANG NGAI PROVINCE

2009 ◽  
Vol 12 (10) ◽  
pp. 119-131
Author(s):  
Phuc Duc Le ◽  
Hung Phu Tran ◽  
Thang Dai Tran
Keyword(s):  
Biotite Granite ◽  
Geological Mapping ◽  
Geochemical Characteristics ◽  
Material Component ◽  
First Time ◽  
Granitoid Massif

The first time, Xuanthu granitoid massif was researched and arranged into component of Bana complex in project of 1/50,000 scale geological mapping and minerals prediction of Quangngai sheets (Than Duc Duyen et al, 1999). The investigations carried out within area of Nuocnhieu stream, SE corner of Xuanthu massif which has displayed mainly plutonic formations, such as biotite granite, medium - coarse granular 2 mica granite, fine granular granite and fine granular 2 mica granite. Vein phases are commonly aplite, pegmatoid, porphyry granite.... This paper is mainly to research on mineral - petrography and petro - geochemical characteristics as well as to make more clearly about material component, mineral forming order, forming original explaining and related mineralizations of Xuanthu granitoid massif.

Rb–Sr age and geochemical distinctions between the Carboniferous tin-bearing Davis Lake complex and the Devonian South Mountain batholith, Meguma Terrane, Nova Scotia

1989 ◽  
Vol 26 (10) ◽  
pp. 2044-2061 ◽  
Author(s):  
Jean M. Richardson ◽  
Keith Bell ◽  
John Blenkinsop ◽  
David H. Watkinson
Keyword(s):  
Nova Scotia ◽  
Trace Element ◽  
Biotite Granite ◽  
Granitic Magma ◽  
Trace Element Geochemistry ◽  
Magmatic Differentiation ◽  
Element Geochemistry ◽  
South Mountain Batholith ◽  
Granitoid Rocks ◽  
Meguma Terrane

The Davis Lake complex (DLC), composed of biotite monzogranite, leucomonzogranite, and cassiterite–topaz greisen, hosts the East Kemptville tin mine in southwestern Nova Scotia. The DLC monzogranite contains glomeroporphyritic biotite with ilmenite and many rare-earth-element (REE) bearing accessory minerals, zircon-bearing quartz phenocrysts, and xenoliths of biotite granite. Primary muscovite is rare. Major- and trace-element geochemical trends indicate well-defined, but limited, magmatic differentiation trends. REE patterns of the least-evolved granites are flat and show a Ce/Yb ratio of 10.The DLC was previously considered cogenetic with the Devonian South Mountain batholith (SMB) on the basis of its location, lithologies, and similarities in major- and trace-element geochemistry. However, new Rb–Sr whole-rock isotopic data indicate an Rb–Sr date of 330 ± 7 Ma (mean square of weighted deviates (MSWD) = 2.8) for the DLC, implying that it is at least 35 Ma younger than the SMB. The initial 87Sr/86Sr ratio of 0.727 ± 0.004 is significantly higher than those for other Meguma Terrane granites and is the highest yet reported from Appalachian granitoid rocks. Rb–Sr data from biotite indicate open-system behaviour between 260 and 240 Ma and provide more evidence for previously documented tectonothermal events after 300 Ma in the Meguma Terrane.The peraluminous nature of the DLC, its high Rb/Sr and high 87Sr/86Sr ratios, high P, F, and Sn contents, low Ca and B contents, and high differentiation indices indicate that the complex was derived from a highly evolved felsic source. Geochemical distinctions indicate that the DLC is neither derived from nor cogenetic with the SMB. A more probable source for the DLC magma is a dehydrated felsic granulite from which a previous H2O-, B-, Cl-, and Zn-rich granitic magma (perhaps the SMB) had been extracted. Such a source is analogous to that postulated for A-type granites and topaz rhyolites.The DLC shows more similarities to the "stitching" Carboniferous Appalachian volatile- and metal-rich granites than to Devonian Meguma granites. Unlike most of these Appalachian plutons, which occur marginal to terrane boundaries and were probably crystallized from locally generated, anatectic magmas, the DLC was emplaced in the centre of the most-outboard Meguma Terrane, adjacent to the Tobiatic shear zone.

The origin of celestine–quartz–calcite geodes associated with a basaltic dyke, Makhtesh Ramon, Israel

2013 ◽  
Vol 151 (5) ◽  
pp. 798-815 ◽  
Author(s):  
MICHAEL ANENBURG ◽  
OR M. BIALIK ◽  
YEVGENY VAPNIK ◽  
HAZEL J. CHAPMAN ◽  
GILAD ANTLER ◽  
...  
Keyword(s):  
Low Temperature ◽  
Fluid Inclusions ◽  
Lower Cretaceous ◽  
Meteoric Water ◽  
Hydrothermal Activity ◽  
Lower Jurassic ◽  
Specific Location ◽  
Melting Temperatures ◽  
Jurassic Sequence

AbstractSpectacular celestine geodes occur in a Jurassic peri-evaporitic sequence (Ardon Formation) exposed in Makhtesh Ramon, southern Israel. The geodes are found only in one specific location: adjacent to an intrusive contact with a Lower Cretaceous basaltic dyke. Celestine, well known in sedimentary associations worldwide and considered as a low temperature mineral, may therefore be associated with magmatic-induced hydrothermal activity. Abundant fluid inclusions in celestine provide valuable information on its origin: gas-rich inclusions in celestine interiors homogenized at T≥200°C whereas smaller liquid-rich inclusions record the growth of celestine rims at T≤200°C. Near 0°C melting temperatures of some fluid inclusions and the occurrence of hydrous Ca-sulphate solid crystals in other inclusions indicate that celestine precipitated from variably concentrated Ca-sulphate aqueous solutions of meteoric origin. Celestine crystallized from meteoric water heated by the cooling basaltic dyke at shallow levels (c. 160 m) during a Lower Cretaceous thermal perturbation recorded by regional uplift and magmatism. The 87Sr/86Sr ratio of geode celestine, 0.7074, is similar to that measured in the dolostones of the host Jurassic sequence, but differs markedly from the non-radiogenic ratio of the dyke. Strontium in celestine was derived from dolostones preserving the 87Sr/86Sr of Lower Jurassic seawater, while sulphur (δ34S = 19.9‰) was provided by in situ dissolution of precursor marine gypsum (δ34S = 16.8‰) indicated by relict anhydrite inclusions in celestine. Low-temperature meteoric fluid flow during the Campanian caused alteration of the dyke into secondary clays and alteration of geodal celestine into quartz, calcite and iron oxides.

HIGH-RESOLUTION STRATIGRAPHY, PALYNOFACIES AND SOURCE ROCK POTENTIAL OF THE ÁGUA DE MADEIROS FORMATION (LOWER JURASSIC), LUSITANIAN BASIN, PORTUGAL

2012 ◽  
Vol 35 (2) ◽  
pp. 105-126 ◽  
Author(s):  
L.V. Duarte ◽  
R.L. Silva ◽  
J.G. Mendonça Filho ◽  
N. Poças Ribeiro ◽  
R.B.A. Chagas
Keyword(s):  
High Resolution ◽  
Source Rock ◽  
Lower Jurassic ◽  
Lusitanian Basin

Uncommon preservation of dinosaur footprints in a tidal breccia: Eubrontes giganteus from the Early Jurassic Mongisty tracksite of Aveyron, southern France

2021 ◽  
pp. 1-18
Author(s):  
Jean-David Moreau ◽  
Jacques Sciau ◽  
Georges Gand ◽  
Emmanuel Fara
Keyword(s):  
Scale Up ◽  
Lower Jurassic ◽  
Depositional Environments ◽  
Early Jurassic ◽  
Coarse Grained ◽  
Southern France ◽  
Fine Grained ◽  
The North ◽  
Dinosaur Tracks ◽  
First Time

Abstract A recent excavation yielded 118 large tridactyl footprints in the Lower Jurassic Dolomitic Formation of the Causses Basin, at Mongisty in southern France. Most of the tracks are ascribed to Eubrontes giganteus Hitchcock, 1845. They are preserved on a surface of 53 m2 and form parallel rows with a preferential orientation towards the north. Such an abundance and density of E. giganteus is observed for the first time in the Early Jurassic from the Causses Basin. Sedimentological and ichnotaphonomical analyses show that the footprints were made at different time intervals, thus excluding the passage of a large group. In contrast to all other tracksites from the Dolomitic Formation, where tracks are preserved in fine-grained sediments corresponding to low-energy depositional palaeoenvironments, the tracks from Mongisty are preserved in coarse-grained sediment which is a matrix- to clast-supported breccia. Clasts consist of angular to sub-rounded, millimetric to centimetric-scale (up to 2 cm), poorly sorted, randomly oriented, homogeneous dolostone intraclasts floating in a dolomudstone matrix. Sedimentological analysis shows that the depositional environments of Mongisty varied from subtidal to intertidal/supratidal settings in a large and protected flat marsh. The lithology of the track-bearing surfaces indicates that the mudflat of the Causses Basin was sporadically affected by large mud flows that reworked and redeposited mudstone intraclasts coming from the erosion of upstream, dry and partially lithified mud beds. Throughout the world, this type of preservation of dinosaur tracks in tidal matrix- to clast-supported breccias remains rare.

scholarly journals Belemnites from the Lower Jurassic of East Greenland and their biostratigraphical and biogeographical significance

1991 ◽  
Vol 39 ◽  
pp. 123-141
Author(s):  
Peter Doyle
Keyword(s):  
Western Europe ◽  
Lower Jurassic ◽  
East Greenland ◽  
Northwest Europe ◽  
First Time

Belemnites collected in the 1920s from the Lower Jurassic Neill Klinter Formation of East Greenland are described for the first time. Two belemnite faunas are recognised. The Rrevekl0ft Member yielded Nannobelus, Pseudohastites, Passaloteuthis?, Gastrobelus? and a hastitid, giving an age of the Lower Pliensbachian Uptonia jamesoni to Prodacty/ioceras davoei zones for the molluscan-rich lower fauna! division. The Ostreaelv Member yielded Parapassaloteuthis, Acrocoelites (Toarcibelus), A. (Odontobe­/us), Simpsonibelus and "Parabrachybeus" representative of a Toarcian Hildoceras bifrons to Haugia variabilis Zone age as previously determined. However, the presence of Parapassaloteuthis gives a oldest age of at least Dactylioceras commune Subzone, with a loose specimen of a possible juvenile Acrocoe/ites trisulcu!osus suggesting that the Ostreaelv Member may range into the Harpoceras falciferum Zone. The Pliensbachian species are identical to those from western Europe and are the most northerly repre­sentatives of their taxa. The Toarcian species have closest affinity to those of northwest Europe rather than the distinct and endemic Siberian Toarcian belemnite fauna which arose at this time.

scholarly journals Lower Jurassic biostratigraphy and ostracods of the Danish Embayment

1975 ◽  
Vol 104 ◽  
pp. 1-287
Author(s):  
Olaf Michelsen
Keyword(s):  
New Genus ◽  
Lower Jurassic ◽  
Ontogenetic Development ◽  
Muscle Scar ◽  
Scar Area ◽  
European Area ◽  
Ostracod Species ◽  
Jurassic Sequence

The Lower Jurassic sequence and ostracods from 36 borings within the Danish Embayment are analysed and described.Hettangian, Sinemurian and Pliensbachian are demonstrated on the basis of extensive ostracod faunas, whilst only weak indications of Aalenian have been found.The following ostracod zones are defined as a basis for a biostratigraphical subdivision of the Lower Jurassic series in the Danish Embayment:The Ogmoconchella adenticulata - Nanacythere (Nanacythere) simplex Zone (Upper Pliensbachian).The Ogmoconchella danica Zone (Upper Sinemurian and Lower Pliensbachian).The Gramannella apostolescui - Kinkelinella (Klinglerella ) foveolata Subzone (Lower Pliensbachian).The Progonoidea reticulata Subzone (lowest Upper Sinemurian, Lias Beta-1a).The Cristacythere betzi - C. crassireticulata Zone (upper Lower Sinemurian).The Ogmoconchella aspinata Zone (Hettangian and lower Lower Sinemurian).The chronostratigraphical subdivision of the Lower Jurassic sequence in the Danish Embayment is presented, based upon the ostracod faunas described here and upon previous investigations of sediments, foraminifera and megafossils.The conditions prevailing in the basin are discussed, with descriptions of the sedimentary and faunal developments, and an evaluation of the relationships with other parts of the Northwest European area.124 ostracod species are described; 23 are described as new, whilst 30 species which cannot be referred to any known species are described with open nomenclature owing to limited or badly preserved material. The remaining 71 species have all been described previously and are more or less well-known. The 124 species fall into 27 genera or subgenera, of which 2 genera (Pseudomacrocy pris and Cristacythere) and 1 subgenus (Nanacythere (Goniocythere)) are established as new.A subdivision is made of the described Lower Jurassic "Procytheridea". The genus Klinglerella Anderson, 1964 is placed as a subgenus under Kinkelinella Martin, 1960. Pleurifera Gramann, 1962 and Progonoidea Gramann, 1962 are regarded as independent genera placed together with Kinkelinella and the new genus Cristacythere.The family Healdiidae is regarded as being represented by only three genera in the Lower Jurassic: Ogmoconcha, Ogmoconchella and Pseudohealdia. The Ontogenetic development of the muscle scar area in Ogmoconchella is shown to be a development from a simple muscle scar of the Pseudohealdia-type to a typical Ogmoconchella-scar.ree genera in the Lower Jurassic: Ogmoconcha, Ogmoconchella and Pseudohea!dia. The Ontogenetic development of the muscle scar area in Ogmoconchella is shown to be a development from a simple muscle scar of the Pseudohea/dia-type to a typical Ogmoconchella-scar.

Sign in / Sign up

Export Citation Format

Share Document