Basement Carboniferous in Upper Teesdale, N. Yorks.

1950 ◽  
Vol 87 (4) ◽  
pp. 297-299 ◽  
Author(s):  
W. T. Harry
Keyword(s):  
Vein Quartz ◽  
Lower Palaeozoic ◽  
Unconformable Contact

AbstractExcavations in Upper Teesdale, N. Yorks, exposed basement Carboniferous at its unconformable contact with underlying shales of probable Silurian age. The lowest basement beds are tough conglomerates cut by compression joints. The constituent pebbles are unsorted, locally derived, and mainly andesites and rhyolites, with vein quartz and shale pebbles. A dreikanter outline is common. The conglomerate is contrasted with others also between the Carboniferous and Lower Palaeozoic in England.

Generation and origin of natural gas in Lower Palaeozoic shales from southern Sweden

1969 ◽  
pp. 37-40
Author(s):  
Niels Hemmingsen Schovsbo ◽  
Arne Thorshøj Nielsen
Keyword(s):  
Source Rocks ◽  
Southern Sweden ◽  
Hydrocarbon Gases ◽  
Biogenic Gas ◽  
South Central ◽  
Alum Shale ◽  
Marine Source ◽  
Lower Palaeozoic ◽  
Background Gas ◽  
Origin Of Natural Gas

The Lower Palaeozoic succession in Scandinavia includes several excellent marine source rocks notably the Alum Shale, the Dicellograptus shale and the Rastrites Shale that have been targets for shale gas exploration since 2008. We here report on samples of these source rocks from cored shallow scientific wells in southern Sweden. The samples contain both free and sorbed hydrocarbon gases with concentrations significantly above the background gas level. The gases consist of a mixture of thermogenic and bacterially derived gas. The latter likely derives from both carbonate reduction and methyl fermentation processes. The presence of both thermogenic and biogenic gas in the Lower Palaeozoic shales is in agreement with results from past and present exploration activities; thermogenic gas is a target in deeply buried, gas-mature shales in southernmost Sweden, Denmark and northern Poland, whereas biogenic gas is a target in shallow, immature-marginally mature shales in south central Sweden. We here document that biogenic gas signatures are present also in gas-mature shallow buried shales in Skåne in southernmost Sweden.

scholarly journals I.—History of the Names Cambrian and Silurian in Geology

1873 ◽  
Vol 10 (111) ◽  
pp. 385-395 ◽  
Author(s):  
T. Sterry Hunt
Keyword(s):  
Great Britain ◽  
North America ◽  
Upper Cambrian ◽  
History Of ◽  
Lower Palaeozoic ◽  
The Subject

It is proposed in the following pages to give a concise account of the progress of investigation of the lower Palæozoic rocks during the last forty years. The subject may naturally be divided into three parts: 1. The history of Silurian and Upper Cambrian in Great Britain from 1831 to 1854; 2. That of the still more ancient Palæozoic rocks in Scandinavia, Bohemia, and Great Britain up to the present time, including the recognition by Barrande of the so-called primordial Palæozoic; fauna; 3. The history of the lower Palæozoic rocks of North America.

Interpretation of Pb isotope compositions of galenas from the Midland Valley of Scotland and adjacent regions

1984 ◽  
Vol 75 (2) ◽  
pp. 85-96 ◽  
Author(s):  
John Parnell ◽  
Ian Swainbank
Keyword(s):  
Lower Devonian ◽  
Lead Isotope ◽  
Sedimentary Rocks ◽  
Isotope Ratios ◽  
Igneous Rocks ◽  
Pb Isotope ◽  
Lower Carboniferous ◽  
Granite Magma ◽  
Lower Palaeozoic ◽  
Caledonian Granite

ABSTRACTThe lead isotope compositions of 61 galenas from central and southern Scotland vary markedly between different regions. Most galenas from the southern Grampian Highlands yield isotope ratios (206Pb/204Pb 17·77 ± 0·25, 207Pb/204Pb 15·47 ± 0·05, 208Pb/204Pb 37·63 ± 0·26) less radiogenic than those from Midland Valley galenas (18·22 ± 0·12, 15·55 ± 0·05, 38·13 ± 0·14) whilst galena lead from the Southern Uplands (18·28 ± 0·12, 15·56 ± 0·03, 38·21 ± 0·18) is more radiogenic than that from the southern Midland Valley (18·12 ± 0·06, 15·52 ± 0·02, 38·06 ±0·10). The change in isotopie composition across the Highland Boundary fault reflects the presence or absence of Dalradian rocks which included a magmatic component of lead. Galenas from the Dalradian sequence in Islay, where igneous rocks are lacking, have a composition (18·14±0·04, 15·51±0·01, 37·90±0·02) more like Midland Valley galenas. In the Southern Uplands, galenas yield lead isotope ratios similar to those of feldspars from Caledonian granite (18·30 ± 0·14, 15·57 ± 0·04, 37·96 ± 0·15) analysed by Blaxland et al. (1979). The similar ratios reflect the incorporation of Lower Palaeozoic sedimentary rocks into the granite magma, rather than a granitic source for the mineralisation. The granites were then thermal-structural foci for later mineralising fluids which leached metals from the surrounding rocks. Within the Midland Valley, galenas hosted in Lower Devonian-Lower Carboniferous lavas are notably more radiogenic (18·31 ±0·12, 15·58 ± 0·06, 38·20 ± 0·16) than sediment-hosted galenas (18·14 ± 0·07, 15·52 ± 0·02, 38·08 ± 0·10). The Devonian lavas at least may have inherited lead from subducted (? Lower Palaeozoic) rock incorporated in the primary magma.

Terranes

1992 ◽  
Vol 13 (1) ◽  
pp. 1-4 ◽  
Author(s):  
B. J. Bluck ◽  
W. Gibbons ◽  
J. K. Ingham
Keyword(s):  
Hanging Wall ◽  
Fault System ◽  
Upper Proterozoic ◽  
Lower Proterozoic ◽  
Central Highland ◽  
Thrust Zone ◽  
Lower Palaeozoic ◽  
Moine Thrust Zone ◽  
Shallow Marine Sediments ◽  
Northern Highlands

AbstractThe Precambrian and Lower Palaeozoic foundations of the British Isles may be viewed as a series of suspect terranes whose exposed boundaries are prominent fault systems of various kinds, each with an unproven amount of displacement. There are indications that they accreted to their present configuration between late Precambrian and Carboniferous times. From north to south they are as follows.In northwest Scotland the Hebridean terrane (Laurentian craton in the foreland of the Caledonian Orogen) comprises an Archaean and Lower Proterozoic gneissose basement (Lewisian) overlain by an undeformed cover of Upper Proterozoic red beds and Cambrian to early mid Ordovician shallow marine sediments. The terrane is cut by the Outer Isles Thrust, a rejuvenated Proterozoic structure, and is bounded to the southeast by the Moine Thrust zone, within the hanging wall of which lies a Proterozoic metamorphic complex (Moine Supergroup) which constitutes the Northern Highlands terrane. The Moine Thrust zone represents an essentially orthogonal closure of perhaps 100 km which took place during Ordovician-Silurian times (Elliott & Johnson 1980). The Northern Highlands terrane records both Precambrian and late Ordovician to Silurian tectonometamorphic events (Dewey & Pankhurst 1970) and linkage with the Hebridean terrane is provided by slices of reworked Lewisian basement within the Moine Supergroup (Watson 1983).To the southwest of the Great Glen-Walls Boundary Fault system lies the Central Highlands (Grampian) terrane, an area dominated by the late Proterozoic Dalradian Supergroup which is underlain by a gneissic complex (Central Highland Granulites) that has been variously interpreted as either older

Structure of the Lower Palaeozoic rocks around Cairnsmore of Fleet, Galloway

1979 ◽  
Vol 15 (3) ◽  
pp. 187-202 ◽  
Author(s):  
D. R. Cook ◽  
J. A. Weir
Keyword(s):  
Lower Palaeozoic

Late- to post-Variscan tectonics and the kinematic relationship with W-Sn vein-type mineralisation: evidence from Late Carboniferous intramontane basins (Porto-Sátão syncline, Variscan Iberian belt)

2021 ◽  
pp. jgs2020-223
Author(s):  
Dominique Jacques ◽  
Philippe Muchez ◽  
Manuel Sintubin
Keyword(s):  
Structural Analysis ◽  
Late Carboniferous ◽  
Early Permian ◽  
Regional Structure ◽  
Crenulation Cleavage ◽  
Kinematic Relationship ◽  
Structural History ◽  
Vein Type ◽  
Lower Palaeozoic ◽  
Intramontane Basins

Many studies have constrained that late-Variscan buckling produced the arcuate geometry of the Ibero-Armorican belt. Nonetheless, debate remains on the associated geodynamic framework. Poorly studied Late Carboniferous intramontane basins offer an excellent framework to decipher the timing and kinematics of the late- to post-Variscan tectonics. Understanding the latter also helps constrain the structural emplacement mode of contemporaneous W-Sn-Nb-Ta-Li mineralisation. In Iberia, the Porto-Sátão syncline is exemplary of such a Late Carboniferous intramontane basin. We present a structural analysis of the syncline, its basement and the associated W-Sn deposits. The regional structure is dictated by the Alcudian angular unconformity, caused by Cadomian tectonics (575-555Ma) and separating tilted Ediacaran and subhorizontal Lower Palaeozoic formations. Superposed Variscan deformation led to F1-F3 folds with steep and gentle plunges, respectively. The late-orogenic D3 fabric is locally affected by post-orogenic F4 kink folds and a S4 crenulation cleavage. W-Sn bearing vein systems occur along granite-hosted cone sheets, or exploit cross-fold joints associated with the F3 and F4 fold generations, revealing a close kinematic relationship between granite-related mineralisation and the late- to post-Variscan deformation style. This structural history is interpreted as a plate-scale geodynamic change from Late Carboniferous N-S (D3) to Early Permian WNW-ESE (D4) convergence.

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