Bituminous coals on emergent surfaces in an Asbian, lower Carboniferous (Mississippian) limestone succession on the North Wales carbonate platform, UK, and implications for palaeoclimate

2021 ◽  
pp. pygs2020-006
Author(s):  
Peter del Strother ◽  
Andrew Giże ◽  
Cathy Hollis ◽  
Duncan McLean
Keyword(s):  
Carbonate Platform ◽  
Local Development ◽  
Vitrinite Reflectance ◽  
Terrestrial Organic Matter ◽  
The North ◽  
North Wales ◽  
Bituminous Coals ◽  
Coal Petrology ◽  
Mississippian Limestone ◽  
Peat Formation

Emergent surfaces in the Mississippian (Asbian to Brigantian) carbonate platform succession of North Wales record periods of plant colonisation and peat formation that led ultimately to the local development of coals. Examination of bituminous coals on three emergent surfaces within Cefn Mawr Quarry reveals information on palaeoclimate that is not available from study of the limestones alone. Three coal seams in the Asbian Loggerheads Limestone Formation were identified and the lowest one studied in detail. Vitrinite reflectance data from alternating bands of vitrite and duroclarite microlithotypes, the distribution of pyrite within them, and the sharp contacts between them, suggest that there were abrupt changes in marine influence during the development of the peats that formed the coals. It is inferred that local palaeoclimate alternated between periods of high and low rainfall, the amount of rainfall influencing the extent to which seawater encroached into the peats, with higher rainfall suppressing the ingress of saline waters into groundwater. On the basis of modern peat growth rates, the timescale of the alternation indicated by each duroclarite-vitrite couplet is suggestive of an annual cycle, such as would arise in a monsoonal climate. The low proportion of ash in the three coals, the preservation of internal lamination, the low diversity of spore species in the lowest coal compared with the over- and underlying mudrock, and the presence of rhizoconcretions in palaeokarstic limestone beneath the lowest and highest coals, demonstrate that the peat swamps were isolated from the hinterland and autochthonous. This study demonstrates that a wider application of palynology and coal petrology is an important contribution to the study of marine carbonate successions of any age where terrestrial organic matter, formed during emergence, has been preserved.

scholarly journals The Lower–Middle Jurassic of the Anholt borehole: implications for the geological evolution of the eastern margin of the Danish Basin

2003 ◽  
Vol 1 ◽  
pp. 585-609
Author(s):  
Ole B. Nielsen ◽  
Marit-Solveig Seidenkrantz ◽  
Niels Abrahamsen ◽  
Birthe J. Schmidt ◽  
Eva B. Koppelhus ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Vitrinite Reflectance ◽  
Gradual Change ◽  
Freshwater Algae ◽  
Volcanic Origin ◽  
Fine Grained ◽  
The North ◽  
Inclination Shallowing ◽  
Palaeomagnetic Data ◽  
Coal Petrology

This study of Upper Pliensbachian – Bajocian/Bathonian deposits in a borehole drilled on the island of Anholt, Denmark incorporates sedimentology, biostratigraphy (palynomorphs and foraminifera), palaeomagnetism and coal petrology. The studied succession records a gradual change from marine inner shelf storm-influenced clays to mainly terrestrial sands, clays, and lignite containing a flora of mainly freshwater algae and pollen. The regression was initiated at the Pliensbachian–Toarcian boundary and marine influence ceased during Bajocian–Bathonian times; the regression thus took place earlier at Anholt than in the centre of the Danish Basin. The sediments in the Anholt borehole are referred to the Fjerritslev and Haldager Sand Formations. Although the Lower–Middle Jurassic boundary is commonly placed at the boundary between the two formations, our data indicate that at Anholt the upper Fjerritslev Formation (member F-IV) is of Aalenian age. The Lower–Middle Jurassic boundary occurs close to the boundary between members F-III and F-IV of the Fjerritslev Formation. In contrast to other Lower–Middle Jurassic successions in the North Sea region, smectites of inferred volcanic origin are preserved in the Anholt section, suggesting limited burial and hence less intense diagenetic illitisation or chloritisation of smectites. A down-hole increase in diagenetic influence is reflected by the increase down-section both in the thermal stability of kaolinite and in the vitrinite reflectance. Kaolinite of inferred authigenic origin forms a white powder in the quartz-dominated sands of the Haldager Sand Formation; this kaolinite is thermally very unstable and is interpreted to be of late diagenetic, post-uplift origin. The vitrinite reflectance data indicate that the Jurassic formations have been exposed to thermal maturation corresponding to burial to a depth of 1000–1200 m below their present depth. Post-maturation uplift of the order of 1 km probably occurred partly during Late Cretaceous – Paleocene inversion in the Kattegat area and partly during Oligocene–Recent regional uplift, the latter being the most important of the two uplift phases. Palaeomagnetic data indicate that the main carrier of magnetic remanence is fine-grained magnetite. The stable remanence shows a pronounced inclination shallowing, which is attributed to post-depositional compaction.

A Reinterpretation of the Microlithic Industries of Wales

1963 ◽  
Vol 29 ◽  
pp. 99-132 ◽  
Author(s):  
G. J. Wainwright
Keyword(s):  
Short Distance ◽  
The South ◽  
The West ◽  
The North ◽  
South Wales ◽  
North Wales ◽  
River Valleys

The distribution of Mesolithic sites in Wales is controlled to a great extent by the terrain, for physiographically, Wales is a highland block defined on three sides by the sea and for the greater part of the fourth side by a sharp break of slope. Geologically the Principality is composed almost entirely of Palaeozoic rocks, of which the 600-foot contour encloses more than three quarters of the total area. There are extensive regions above 1,500 feet and 2,000 feet and in the north the peaks of Snowdonia and Cader Idris rise to 3,560 feet and 2,929 feet respectively. Indeed North Wales consists of an inhospitable highland massif, skirted by a lowland plateau and cut deeply by river valleys, providing only limited areas for settlement. The hills and mountains of Snowdonia with their extension at lower altitudes into the Lleyn Peninsula, and the ranges of Moelwyn, Manod Mawr, Arenig Fach and Cader Idris, are discouraging obstacles to penetration, save for a short distance along the river valleys. To the east of these peaks are extensive tracts of upland plateau dissected by rivers, bounded on the west by the vale of the river Conway and cleft by the Vale of Clwyd. To the east of this valley lies the Clwydian Range and further again to the east these uplands descend with milder contours to the Cheshire and Shropshire plains.To the south the district merges into the uplands of Central Wales, which are continuous until they are replaced by the lowland belt of South Wales.

scholarly journals VIII.—The Millstone Grit of the North-Wales Border

1870 ◽  
Vol 7 (69) ◽  
pp. 122-127
Author(s):  
D. C. Davies
Keyword(s):  
Total Thickness ◽  
The North ◽  
North Wales ◽  
Middle Member ◽  
Coal Measures

The total thickness of Millstone Grit in North Wales does not quite reach 300ft. This thickness is, I am aware, considerably below that given by several authors, who notice this formation incidentally; but I am prepared to say, from. actual and computed measurement, made on the spot, that the above figures are substantially correct. The Carboniferous system, from the base of the Mountain Limestone to that of the Coal Measures in North Wales, is but an epitome of the same beds in the North of England, the middle member, the grits and sandstones, being thin in proportion.

Magnetic Seed Localization (Magseed) for excision of impalpable breast lesions—The North Wales experience

2021 ◽  
Author(s):  
Meena Powell ◽  
Tim Gate ◽  
Onneile Kalake ◽  
Carmen Ranjith ◽  
Mandana O. Pennick
Keyword(s):  
Breast Lesions ◽  
The North ◽  
North Wales ◽  
Seed Localization

New insights on the age of the post-Urgonian marly cover of the Apt region (Vaucluse, SE France) and its implications on the demise of the North Provence carbonate platform

2017 ◽  
Vol 359 ◽  
pp. 44-61 ◽  
Author(s):  
Camille Frau ◽  
Antoine Pictet ◽  
Jorge E. Spangenberg ◽  
Jean-Pierre Masse ◽  
Anthony J.-B. Tendil ◽  
...  
Keyword(s):  
Carbonate Platform ◽  
The North ◽  
Se France

Darwin at Llanymynech: the evolution of a geologist

1996 ◽  
Vol 29 (4) ◽  
pp. 469-478 ◽  
Author(s):  
Michael B. Roberts
Keyword(s):  
Charles Darwin ◽  
Field Trip ◽  
The North ◽  
North Wales ◽  
Field Notes ◽  
Geological Work

1831 was a momentous year for Charles Darwin. He passed his BA examination on 22 January, stayed up in Cambridge for two further terms and returned to The Mount, his home in Shrewsbury, in mid-June. On 6 August he left Shrewsbury with Adam Sedgwick for a geological field trip to North Wales, and after his lone traverse over the Harlech Dome returned to The Mount on Monday 29 August to find letters from John Stevens Henslow and George Peacock inviting him to joint HMSBeagle. This geological field trip was crucial for his work on theBeagle. For example, when he began his first geological work of the voyage on Quail Island, he was by that time a competent geologist. Though others have studied the North Wales tour in some detail, there is also another earlier and much briefer episode to consider. Darwin appears to have geologized on his own at Llanymynech in July. The contrast between his first recorded attempts at Llanymynech in July 1831 and then elsewhere in North Wales in August 1831 is most instructive, as his development as a geologist can be followed in his field notes. Retracing his steps today, and comparing his measurements and observations with new ones, throws light on what he might have learnt at different points during that summer.

The growth of new dental practices established in the North West of England and North Wales between 1985 and 1990

BDJ ◽  
1995 ◽  
Vol 179 (5) ◽  
pp. 180-182 ◽  
Author(s):  
M A Lennon ◽  
J C Ingleby ◽  
P J Young
Keyword(s):  
North West ◽  
The North ◽  
North Wales ◽  
Dental Practices

Block tilting of the North Provence early Cretaceous carbonate margin: stratigraphic, sedimentologic and tectonic data

2009 ◽  
Vol 180 (2) ◽  
pp. 105-115 ◽  
Author(s):  
Jean-Pierre Masse ◽  
Michel Villeneuve ◽  
Emmanuelle Leonforte ◽  
Jean Nizou
Keyword(s):  
Early Cretaceous ◽  
Biological Diversity ◽  
Carbonate Platform ◽  
Depositional Environments ◽  
Structural Elements ◽  
The North ◽  
Subaerial Exposure ◽  
Tectonic Events ◽  
Complete Series ◽  
Structural Architecture

Abstract In the western part of the Castellane tectonic arc, the so-called “ Provence platform area “, corresponding to the foreland of the Alpine nappes (figs. 1–2), is marked by Tithonian-Berriasian shallow water carbonates capped by hemipelagic sediments deposited from the Valanginian up to the Aptian-Albian. A detailed biostratigraphic study of the Berriasian succession, based on calcareous algae and foraminifera, allows us to distinguish a Lower to Middle Berriasian, with Clypeina sulcata, Clypeina isabellae and Holosporella sarda, from an Upper Berriasian with Pfenderina neocomiensis, Danubiella cernavodensis, Falsolikanella campanensis and Macroporella praturloni (fig. 3). We performed a field survey of 30 sites located from Quinson to the west, and Escragnolles to the east (figs. 4–5) including the study of measured stratigraphic sections and the collection of samples for biostratigraphic interpretations. These stratigraphic investigations show that below the Valanginian beds, the Berriasian platfom carbonate succession, is locally incomplete, i.e. Upper Berriasian beds are frequently absent. During the Early and Middle Berriasian, depositional environments are marked by a strong bathymetric instability, with frequent subaerial exposure events, and a significant marine restriction; by contrast, during the Late Berriasian, the overall biological diversity increases and water agitation as well, which means a significant marine opening towards the basin. The Upper Berriasian hiatus is consequently regarded as the result of a Berriasian/Valanginian and/or a lowermost Valanginian erosion (fig. 6). The spatial distribution of complete or truncated Berriasian successions identifies east-west bands, in each band truncated series are located northward and complete series are located southward. Bands are limited by thrust or strip faults interpreted as palaeofaults reactivated during the Alpine orogeny (fig. 7). These fault-bounded blocks, 3 to 10 km in width, known as the Aiguine, La Palud-sur-Verdon, Carajuan-Audibergue and Peyroulles-La Foux blocks, are southerly rotated by 1 to 2o. We regard this structural architecture as the result of basinward tilting of blocks. Due to their rotation, the uplifted parts were eroded whereas the depressed parts were protected against erosion (fig. 8). Such a dynamic behavior reflects a distensive tectonic regime, which has been active at least during the Valanginian, that is after the drowning of the North-Provence carbonate platform. These structural events are considered as the regional expression of the Neocimmerian tectonic phase coupled with an enhancement of the Atlantic rifting. The orientation of the major Alpine structural elements (folds and faults) of the Castellane arc, is mostly inherited from these early Cretaceous tectonic events.

scholarly journals A missing link in the peri-Gondwanan terrane collage: the Precambrian basement of the Moroccan Meseta and its lower Paleozoic cover

2018 ◽  
Vol 55 (1) ◽  
pp. 33-51 ◽  
Author(s):  
Dominik Letsch ◽  
Mohamed El Houicha ◽  
Albrecht von Quadt ◽  
Wilfried Winkler
Keyword(s):  
Carbonate Platform ◽  
Source Area ◽  
Source Rocks ◽  
Lower Paleozoic ◽  
Northern Margin ◽  
Precambrian Geology ◽  
The North ◽  
Late Cambrian ◽  
Paleozoic Rocks ◽  
Rifted Margin

This article provides stratigraphic and geochronological data from a central part of Gondwana’s northern margin — the Moroccan Meseta Domain. This region, located to the north of the Anti-Atlas area with extensive outcrops of Precambrian and lower Paleozoic rocks, has hitherto not received much attention with regard to its Precambrian geology. Detrital and volcanic zircon ages have been used to constrain sedimentary depositional ages and crustal affinities of sedimentary source rocks in stratigraphic key sections. Based on this, a four-step paleotectonic evolution of the Meseta Domain from the Ediacaran until the Early Ordovician is proposed. This evolution documents the transition from a terrestrial volcanic setting during the Ediacaran to a short-lived carbonate platform setting during the early Cambrian. The latter then evolved into a rifted margin with deposition of thick siliciclastic successions in graben structures during the middle to late Cambrian. The detritus in these basins was of local origin, and a contribution from a broader source area (encompassing parts of the West African Craton) can only be demonstrated for postrifting, i.e., laterally extensive sandstone bodies that seal the former graben. In a broader paleotectonic context, it is suggested that this Cambrian rifting is linked to the opening of the Rheic Ocean, and that several peri-Gondwanan terranes (Meguma and Cadomia–Iberia) may have been close to the Meseta Domain before drifting, albeit some of them seem to have been constituted by a distinctly different basement.

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