Coniston Limestone Research Articles

Field meeting in Lower Kingsdale and Chapel-le-Dale, Ingleton, northwest Yorkshire: Lancashire Group, 9 August 2003

Almost continuous exposures of late Precambrian and Upper Ordovician strata occur within the Ingleton inlier of northwest Yorkshire. Here, usually tightly folded, sequences of slates, greywackes and occasional conglomerates (Ingleton Group — commonly termed ‘Ingletonian’: Precambrian or possibly Lower Ordovician/Arenig), and faulted against Upper Ordovician argillaceous limestones and calcareous mudstones (Dent/‘Coniston Limestone’ Group) were demonstrated in the river gorges at Ingleton. Both groups are intruded by several lamprophyre dykes. The southern limit of the inlier is formed by the well-exposed North Craven Fault. Elsewhere the inlier is overlain by the basal Carboniferous unconformity, which was particularly seen in the classic section at Thornton Force. The Lower Carboniferous (Viséan) limestones are almost continuously exposed in a 175 m thick sequence of escarpments (Scars) and benches (Pavements). A distinctive, white-weathering micrite, the Porcellanous ‘Bed’, facilitated the tracing of a small mineralized fault. The occurrence of the Lower Carboniferous Mealbank Coal, a fine glacial erratic boulder and the effects of active landslipping were also examined during the meeting.

Chapter 13 The stratigraphy of ‘Otley III’

Abstract So we turn to the work done in the twentieth century on the elucidation of the sequence and structure of the rocks of Jonathan Otley's third major subdivision of the Lakeland rocks - up to the time of the establishment of the 'Lakeland Project' in 1982, and with a preliminary forward glance to the end of the century. The rocks of 'Otley III' consist of limestones, mudstones, shales, slates, grits and conglomerates, with one substantial igneous unit, the Yarlside (or Stockdale) Rhyolite, which runs westwards from the Shap district, parallel with the strike of other rocks low in 'Mr Otley's third great physical subdivision' as Sedgwick (1852 b , p. 137) called the unit. The 'Otley III' rocks are of generally quite low relief, but, as mentioned previously, many are highly cleaved, the cleavage frequently being more pronounced than the bedding. As we have seen, some of the beds are highly fossiliferous (or were so before they became the subject of close attention by generations of amateur and professional geologists, dealers, or even historians of geology). There is (or once was) a rich fauna of graptolites, molluscs, corals, cystoids and trilobites, and in the past more exotic types like starfish were reported by Sedgwick. As we have seen, the lowest part of 'Otley III' was formerly called the Coniston Limestone (Series) and was initially likened (by Sedgwick) to the Bala Limestone in Wales. Later it was placed in the Caradoc subdivision of the Ordovician; and still later it was subdivided and the

Field relations and movement history of the Coniston Fault, Cumbria

The Coniston Fault is one of the largest and most fundamental faults in the Lake District. It is most easily appreciated near to Coniston where the Coniston Limestone is displaced horizontally (north to south) by 1.5 km, but, although the fault complex is easily traced for more than 40 km from the Vale of St John to well south of Coniston Water, the displacements in other areas are not always easy to determine. It is unlikely that the fault is entirely strike-slip, but if this were the case a dextral displacement at Coniston would be theoretically wrong for a north-south fault formed in the NW-SE Caledonian stress field, although such anomalies are common in geology. A possible explanation would be for a shallow wedge between the Coniston Fault and Brathay Fault to have been pushed forward during the Acadian movements, giving rise to the Coniston Thrust where it was overridden by the Coniston Grits. In any case the field evidence shows that the Coniston Fault had a long history of movement which started during, or before, the Borrowdale Volcanic episode, with any strike-slip (wrench) component most probably belonging to the late Caledonian (Acadian) phase. To the east of Coniston the fault, together with the adjacent Brathay Fault, maps out as a composite structure, bending into an ENE-bedding thrust, and then bending back again into the Beacon Tarn wrench fault. To the north the Coniston Fault extends through the Borrowdale Volcanics to Grasmere where it splits, one branch following the line across Dunmail Raise to Thirlmere and the Vale of St John, and the others crossing the fells to Ullswater. One concern of this paper is to consider the relationship of the Coniston Fault and other structures to the Borrowdale Volcanic sequences, parts of which change abruptly at the fault. Much of this I believe to have been a result of fault movements during the volcanic episode, possibly related to the caldera formation further west. Regional folding was also influenced by the Coniston Fault since the well-defined NE-trending Wrynose Anticline and Fault, also likely to have been initiated during the volcanic episode, terminate at the fault. Renewed post-volcanic-pre-Coniston Limestone movement of the Coniston Fault, followed by erosion, resulted in the absence of the Tarn Hows Formation west of the fault, a clear demonstration of pre-Coniston Limestone movement. The Tarn Hows Formation is the highest part of the volcanic sequence in this area. The latest demonstrable movements were post-Bannisdale Slates and of presumed Acadian age, although by analogy with adjacent areas there may have been posthumous activity in post-Carboniferous and post-Triassic times.

The Stockdale (Yarlside) Rhyolite - a rheomorphic ignimbrite?

SUMMARY The Stockdale Rhyolite Member of the Coniston Limestone Formation is exposed discontinuously for 13 km from Kentmere to Shap in the eastern Lake District. It occurs within marine sedimentary rocks of Cautleyan age (Ashgill Series). The member consists of a maximum of 185 m of pink to pale grey, massive to intensely fractured, platy-jointed, flow-banded and flow-folded rocks of rhyolitic composition, locally underlain and overlain by impersistent beds of clastic rocks composed largely of pumice and felsic fragments. The Stockdale ‘Rhyolite’ has previously been interpreted as a line of coeval lava flows, but outcrop length to thickness ratios, textural characteristics and associated sedimentary rocks are more diagnostic of it being a rheomorphic ignimbrite.

Lower Palaeozoic lithostratigraphical classification in the English Lake District

AbstractIn the English Lake District lithostratigraphical classification has not kept pace with either the international and national codes or the code of the Geological Society (Holland et al. 1978). Probelms arise, firstly, from acceptance by several of those working in the area, of terms used in by‐gone days, such as ‘Borrowdale Volcanic Series’, and secondly, and more importantly, because individuals have specialized on certain parts of the sequence (the Skiddaw Slates, the Coniston Limestone, etc.), and have erected classifications for these rocks without reference to other parts of the succession. These classifications are examined and modified in such a way that the lithostratigraphical subdivisions are consistent for the whole of the Lower Palaeozoic sequence of the Lake District, and also relate to the international code as it is applied in other regions. The basic Lake District stratigraphical terminology of the last century is, however, retained in all its essentials.

The age, stratigraphy and genesis of the coniston limestone group in the southern lake district

AbstractThe Coniston Limestone Group (Ashgill Series) in the southern Lake District shows greater lithological variation and lateral facies variation than hitherto suspected. The oldest part, the Longsleddale and Stile End Formations, is shown to correlate with the Cautleyan Stage, Zone 2, at Cautley; consequently the entire Coniston Limestone Group in the southern Lake District is considered to belong within the Ashgill Series. In the early Cautleyan, sedimentation was largely influenced by a central ridge which extended northward into a southerly transgressive sea. Later Cautleyan and Rawtheyan sedimentation was affected by an area of positive tectonic activity in the east of the region.

The age, stratigraphy and genesis of the Coniston Limestone Group in the southern Lake District

AbstractThe Coniston Limestone Group (Ashgill Series) in the southern Lake District shows greater lithological variation and lateral facies variation than hitherto suspected. The oldest part, the Longsleddale and Stile End Formations, is shown to correlate with the Cautleyan Stage, Zone 2, at Cautley; consequently the entire Coniston Limestone Group in the southern Lake District is considered to belong within the Ashgill Series. In the early Cautleyan, sedimentation was largely influenced by a central ridge which extended northward into a southerly transgressive sea. Later Cautleyan and Rawtheyan sedimentation was affected by an area of positive tectonic activity in the east of the region.

Lost & Found: 17. M.R. Hughes fl. c.1870

Names in CAPITALS in the lists below refer to TYPE specimens. Dr. Robin Cocks is engaged in preparing a synoptic supplement of the "Silurian" i.e. Lower Palaeozoic portions of Thomas Davidson's Monograph of British Fossil Brachiopoda mentioned above. As users of other synoptic supplements to classic Pal. Soc. monographs will know they are immensely useful. In connection with this revision Dr. Cocks seeks information about the whereabouts of the following collections (13 to 17) containing specimens figured by Davidson. nothing known but he provided the following Ordovician brachiopod from the Coniston Limestone made type of ORTHIS LEWISII var. HUGHES! Plate 38, fig. 26 by Davidson in 1871. Any information on any of...

STRUCTURAL RELATIONSHIPS OF THE SHAP GRANITE

(Short communication) The Shap Granite crops out over an area of about five square kilometres in the eastern Lake District. The granite, its contact aureole and associated metasomatism have been described by Harker and Marr (1891 Harker and Marr (1893), Grantham (1928) and Firman (1957). These authors established that the intrusion was emplaced after the Ordovician country rocks had undergone folding and cleavage-formation in end-Silurian or earliest Devonian time. This communication describes the effect of the intrusion on the pre-existing cleavage and attempts to draw some conclusions on the mechanism and timing of its emplacement. The stratigraphical sequence in the area is as follows: | Silurian | Coniston Grits | || | | Coldwell Beds | | | Brathay Flags | | | Stockdale Shales | | Ordovician | Ashgill Shales | | | Coniston Limestone | | | Stockdale (Yarlside) Rhyolite | | unconformity | | | Borrowdale Volcanic Group | The Borrowdale Volcanic country rocks have been described by Mitchell (1934). They consist of a variety of lava types, ranging from basic andesite to rhyolite, and pyroclastic rocks which include ash-flow, detrital and probably air-fall tuffs. The lavas are hardly cleaved, while the tuffs outside the aureole exhibit a well-developed planar fabric which appears to be the combination of a fracture cleavage and a truly penetrative slaty cleavage. As the finer tuffs are traced into the aureole, their fabric becomes coarser owing to the mimetic crystallization of platy minerals with basal planes roughly parallel to the cleavage. At several localities close to the contact (for example NY 5618 1008), mimetic crystallization of biotite is accompanied by growth of the mineral in random orientation across the cleavage. This confirms ...

Discussion

In a written contribution Dr. G. H. M itchell said: Of the many problems of Lake District tectonics two in particular are outstanding. One is the relationship of the Borrowdale Volcanic Group to the Skiddaw Slates. The other concerns the nature of the junction between the Coniston Limestone Group and the Borrowdale Volcanic Group. Over the past too years these two junctions have provided geologists with the problem of tectonic relationships. The upper junction is now generally held to be an unconformity. The lower junction has been described as conformable; at other places an unconformity has been invoked while elsewhere a normal fault, a thrust, or a lag fault have been postulated. Unfortunately exposures of the actual junction between the Borrowdale Volcanic Group and the Skiddaw Slates are for long distances poor and obscured by drift deposits, or disturbed by the passage of ice. There is often ample excuse for controversy regarding the structural relationships. Furthermore it is clear that the incidence of cleavage varies greatly from place to place and from bed to bed. Nevertheless during the last few years much new mapping has been done and it is good to attempt to correlate present knowledge. This Dr. Moseley has done, including in his account the Caledonian, end-Silurian, Variscan and Alpine movements and so providing information for discussion of the tectonics of the north-west of England as a whole. The road to the solution of these problems lies in detailed field surveys covering the whole district. Meanwhile Dr. Moseley's present

The borrowdale volcanic series of the dunnerdale fells, lancashire

AbstractIn the Dunnerdale Fells, south‐west of Coniston, Lancashire, a succession of tuffs, andesites and rhyolites, over 8,000 ft. thick, forming the lower part of the Borrowdale Volcanic Series, has been mapped. These rocks are overlain with marked unconformity by the Coniston Limestone Series, which dips steeply south‐eastwards and oversteps most of the Borrowdale succession in a south‐westerly direction. The Borrowdale Series is affected by two major periods of earth‐movements, the earlier of pre‐Caradoc and the later of Devonian age. The general dip of the Borrowdale Series is eastwards. It shows little folding but is traversed by large tear‐faults with northerly trend. An important belt of faulting closely follows the outcrop of the Coniston Limestone and includes reversed faults. Both sets of faults appear to be of Devonian age.

An Excavation revealing the junction between Ingletonian and Coniston Limestone at Ingleton

While conducting elementary field-classes in the Ingleton area it is not possible to show students any convincing grounds for separating the Ingletonian Series from the Coniston Limestone above. The field-evidence which so strongly impressed Hughes, Goodchild, Gunn, and Green, and which apparently convinced Aveline against his will, still exists. In all three streams the highest beds of the Ingletonian are slates, which might be thought to show a gradation into the Coniston Limestone above, and the dip and strike of the Coniston Limestone appear closely similar to that of the near-by Ingletonian. Against these tangible facts arguments based on petrological similarities, even the evidence of the Neptunian dyke, are apt to seem slightly strained. Accordingly, during a field-excursion I suggested that an attempt be made to excavate the actual junction, and during the summer three students of Imperial College, Messrs. R. W. D. Elwell, G. J. H. McCall, and A. F. Trendall, have succeeded in laying it bare. To their enthusiasm and hard work the success of the attempt is wholly due. Owing to the kindness of Mr. W. S. Worthington, of Ingleton, the new exposure will be left open indefinitely.

The Coniston Limestone Series of the Kentmere District

The paper by Dr. B. Smith, recently published in the Geological magazine, has drawn attention to the interesting relations of the Coniston Limestone Series in the Coniston District.

Conditions of Deposition of the Stockdale Shales of the Lake District

I. Introduction. A detailed account of these shales was written by the late Prof. H. A. Nicholson and myself, and some remarks upon their mode of deposition were made therein; but some further notes may be useful to those who are interested in the physical conditions under which sediments were accumulated. The beginning of the deposition of the Coniston Limestone marks the start of a long period of sedimentation, characterized essentially by the accumulation of fine muds with nodular bands of limestone, as noted by Prof. O. T. Jones. The Caradocian portion of the Coniston Limestone contains much detrital matter of coarse character, with interbedded limestones; but in Ashgillian times the sediments were much finer, and these fine muds continued almost uninterruptedly, save by the above-mentioned limestones, to the end of Wenlock times. There are fine grits in the Browgill division of the Stockdale Shales, and the nodular limestone-bands are almost absent in the Brathay Flags, of Wenlock age. Otherwise, conditions of sedimentation, so far as supply of mechanical material is concerned, were very similar in Ashgillian, Valentian, and Lower Salopian times; and graptolites are found in the deposits of these three periods. Details of the sediments of Ashgillian age will be found in a paper by myself, and of the Stockdale Shales in the paper to which reference has already been made. The following tabular statement summarizes the facts:— The wide distribution of these argillaceous sediments in this country and abroad, presenting generally similar characters where-ever found, indicates

The Unconformable Base of the Coniston Limestone Series in the Lake District

During the course of a recent excursion of the Cambridge Sedgwick Club to the Coniston District, under the guidance of Professor J. E. Marr, important evidence was obtained upon the relationship of the Coniston Limestone Series to the Borrowdale Volcanic Series. A visit was paid to the area south-west of Torver Beck, when, after Professor Marr had pointed out the marked difference between the strike of the Coniston Limestone and that of the underlying Borrowdale rocks at High Pike Haw, the actual strongly discordant junction was located by Professor O. T. Jones and the writer. This was found to be one of unconformity and not a fault, and was traced by the party for some distance.

I.—A Case of Metamorphism of Chalk

Cases of metamorphosed limestones where the calcium carbonate has been converted by contact with some igneous magma into a calc-silicate rock are by no means rare, one of the best known being the conversion of the Coniston Limestone of the Lake District by the Shap Granite into a rock with various calc-silicate and other minerals such as Wollastonite, Omphacite, etc., as described by Messrs. Harker and Marr. But as far as I know, no case has been recorded where ordinary white chalk has been similarly changed. Dr. Hibsch describes a case of baculite marl containing Foraminifera which has been altered by contact with dolerite. The Foraminifera disappear and the rock becomes a granular limestone with epidote, forming a calc-silicate hornstone. This seems the nearest case to the alteration in co. Antrim I am about to describe.

THE INGLETONIAN SERIES OF WEST YORKSHIRE

The true stratigraphical position of the group of rocks which are commonly spoken of as the “Ingleton Green Slates and Grits” has long been a matter of doubt. They have been considered by many writers to be the equivalents of the Borrowdale Volcanic Series of the Lake District, and they are coloured as “Lower Silurian” in the one-inch maps of the Geological Survey (97, S.W.). But this correlation, as was pointed out by Dr. Marr[*][1] in 1892, rests on somewhat slender foundations. It is true that the rocks possess a prevailing greenish tinge, somewhat like that of many of the Borrowdale lavas and ashes, and they certainly occur in juxtaposition with an undoubted representative of the Coniston Limestone, but the resemblance goes no further. There is nothing to show that the junction with the Coniston Limestone is a natural, conformable one, and the green rocks themselves, apart from their colour, are utterly unlike any of the members of the Borrowdale series. They are true sediments of a well-defined and peculiar type, and their constitution shows no resemblance to that of the great lava-flows, ashes, and agglomerates of the central part of the Lake District, or the thinner representatives of the same in the Cross Fell inlier. In the absence, therefore, of any direct stratigraphical evidence as to their age and relationships I propose to apply to the pre-Caradocian rocks of this district the purely local and territorial designation of the “Ingletonian Series.” Some suggestions as to possible correlations will be ... [1]: #fn-1

The Kildare Inlier

I.Introduction. The Geological Survey of Ireland, in 1858, published a memoir describing the geology of the Kildare Hills and neighbouring country. In this memoir are given lists of fossils from the limestone and from an underlying ash-bed, attention is drawn to the resemblance which some of the igneous rocks bear to those of Lambay Island, and reference is made to the presence of a northand-south fault dividing the inlier into two portions. In 1877 Messrs. Harkness and Nicholson, in their paper on the Strata between the Borrowdale Series and,Coniston Flags,’ give some account of the Kildare rocks. They mention that the limestone is in the direct line of strike of contemporaneous beds at Portraine, near Dublin, and also of the Coniston Limestone of the Lake District. Moreover they judge from the strike of the Kildare limestone that it is faulted against the rocks east of it, and note that the beds west of the north-and-south fault above mentioned are entirely dissimilar to those lying east of it. The area has been repeatedly referred to by Mr. J. E. Marr in his various papers on the Coniston Limestone Series of the Lake District. In them he draws special attention to the resemblance between the Keisley Limestone and that of the Chair of Kildare. II. General. Description of the Area. The Carboniferous limestone to the south-west of Dublin has been thrown into a series of gentle undulations, and to the north and north-west of the town of Kildare the crest of one

II.—Woodwardian Museum Notes

I undertook this description of certain fossils from the Lower Palaeozoic rocks ofYorkshire at the request of Mr. Marr. The late Mr. Thomas Roberts had begun the piece of work, but left it unfinished. Nearly all the fossils referred to were collected by a party of Cambridge geologists, under the guidance of Prof. Hughes, in the Summer of 1889. The fossils come from two horizons, viz.:—1. The Phacops elegans zone≍Stockdale Shale series (Valentian) of Wharfe.2. The Bala beds≍:Coniston Limestone series of Norber Brow and Wharfe.

On the Sequence of Perlitic and Spherulitic Structures: a Rejoinder to Criticism

In a paper on ‘The Shap Granite and the Associated Igneous and Metamorphic Rocks’ the authors, Messrs. Harker and Marr, did me the honour to refer to certain statements made by me in the year 1884 with regard to the microscopic structures of a perlitic felsite, associated with the Coniston Limestone where it crosses the northern end of the Long Sleddale Valley in Westmoreland. The opinion which I then expressed was that “spherules may cause the devitrification of a rock after it has solidified and after perlitic fission has supervened.” A list of the structures, present in the section examined, was also given in the following order of sequence:—1. Fluxion-bands. 2. Perlitic structure traversing these bands. 3. Minute spherules constituting the whole rock, so far as spherules can do so, and passing through the perlitic fissures. 4. Subsequent fractures. 5. Formation of quartz-veins along these lines of fracture. In the following year (1885) I again referred to this rock in one of the Memoirs of the Geological Survey, remarking that “Spherulitic devitrification followed the development of the perlitic structure.” Messr. Harker and Marr, after alluding to the microscopic drawings of tis rock published in Mr. Teall's ‘British Petrography’ (1888) pl. xxxviii. and to my own remarks, namely those which have just been cited, made the following observation:—“ The latter author has expressed the opinion that the spherulitic structure is here an effect of devitrification sudsequent to the perlitic ranking; but we are unable to see that he has given any