bluuebunny/crossref_metadata_2025 huggingface dataset:
The Conchostraca of the Cambrian Area of Comley, Shropshire, with a note on a New Variety of
Atops reticulatus
Walcott
Authors: Cobbold Edgar Sterling
Published: October 2009

The principal object of this paper is to record species of Conchostraca that have been left over from my previous communications for more detailed study. Opportunity is also taken to record a specimen of
Atops reticulata
(Walcott) var., and thus to complete my account of the Cambrian faunas of Comley.

The index letters for the horizons used in this paper are those set out in my paper of 1921 (table facing p. 326). An index to the exposure numbers will be found in my 1927 paper (p. 553).

In the study of these fossils I am much indebted for guidance to the work of Drs. Ulrich and Bassler (1931), and I have followed their classification and, to a great extent, their nomenclature and method of description. It is most important, in dealing with these small fossils, to give a clear statement of their form. In the following pages the method generally adopted is : first, a note on the hinge-line; then, in consecutive order, the antero-dorsal angle, the anterior curves, the ventral curves, the posterior curves to the post-dorsal angle and hinge-line. The term “length” indicates the greatest extension parallel with the hinge-line; the “greatest length” (when necessary) is a measurement diagonally across the valve; “depth” is the extension at right angles to the hinge-line; “thickness,” the measure of the test may be smooth, punctate (like sharp needle punctures), pitted (relatively large punctæ), granular, tubercular, or scabrous. This last term is used when the test appears to have been broken
The Carboniferous Succession in the Slaidburn District, Yorkshire
Authors: Parkinson Donald
Published: October 2009

I. Introduction

The district which forms the subject of this paper covers an area of about 30 square miles in north-western Yorkshire, and comprises the north-eastern part of the region known as “Bolland” or “Bowland”. It lies almost entirely within the valley of the Hodder, a tributary of the Ribble, but the water-shed is crossed in the north-east, where the streams flow directly into the Ribble. The reservoir recently constructed by the Fylde Water Board is situated within the area, this part of the ground having been examined before submergence.

The area is bounded on the north and west by the grit hills of Bowland Forest, which rise to altitudes of from 1400 to 1800 feet, and on the south-east by the grits of Easington, Newton, and Waddington Fells. The steep hillsides below the grit escarpments are occupied by the Bowland Shales, whilst the lower ground is usually Carboniferous Limestone with its associated shales; the harder rock sometimes forms prominent features, of which the more notable are knolls of reef-limestone.

The stratigraphical sequence is as shown on the diagram (Pl. XXIV). It varies in detail from place to place as a result of facies changes and non-sequences, but is similar in a general way to that in the type area of Clitheroe-Pendle to the south-south-east. Figure 1 illustrates the variation in thickness and the positions of the non-sequences in different localities within the area to be described (Pendle being included for comparison).

Bolland is noted geologically by reason of the
The Evolution of the Lower Archæan Rocks in Central Sweden and their Iron, Manganese, and Sulphide Ores
Authors: Magnusson Nils H.
Published: October 2009

The high-grade iron and manganese ores of central Sweden are well known to geologists, many of whom, however, are not aware of modern views of the relationship of the ores to the enclosing rocks and the origin of the latter. The ores are found in an ancient complex of highly altered rocks, including an extensive development of gneisses which differ so widely from their parent material that their genesis can only be elucidated by carefully tracing the sequence of metamorphic changes through a series of transitional types. In recent years much work has been done on these lower Archæan rocks, and the following account, which is mainly for non-Scandinavian readers, has been written to provide a summary of the results and to record the present state of opinion concerning the many problems encountered.

Nearly all iron ores of central Sweden belong to the leptite formation, which is the oldest formation known in Fennoscandia. It consists of volcanic rocks (lavas and tuffs) and of sediments such as slates, greywackes, and conglomerates. The volcanic rocks comprise leptites and hälleflintas, the difference between them consisting in the grade of their metamorphism, the hälleflintas having dense groundmasses, the leptites fine-grained, recrystallized groundmasses. The leptites are, in effect, more or less metamorphosed hälleflintas.

The volcanic rocks are best preserved in the westernmost part of the ore-bearing region. In the Grythytte field, for instance, N. Sundius has found extremely well-preserved hälleflint-lavas, with euhedral phenocrysts of quartz and felspar, spherulites, micro-poikilitic quartz, and fluidal and granophyric structures.
The Cairnsmore of Fleet Granite and its Metamorphic Aureole
Authors: Gardiner Charles Irving , Reynolds Sidney Hugh
Published: October 2009

The Cairnsmore of Fleet granite, the second largest of the four major intrusions of the Southern Uplands of Scotland, is a roughly oval mass, measuring eleven miles by seven, with the long axis trending north-east and south-west: that is, parallel to the strike of the sediments, mainly Silurian, into which it is intruded.

It is the most acid of the four intrusions and consists entirely of granite: an incomplete ring of biotite-granite, with an average specific gravity of 2·64, surrounds a larger area of biotite-muscovite-granite, with an average specific gravity of 2·61. The rocks vary very little, and the authors consider that they are the product of two successive intrusions separated by no great interval of time, the biotite-granite being the earlier.

An intrusion, about 250 yards long, of a dioritic rock bearing nickel and cobalt penetrates the sediments near the western margin of the granite and is the only mass in any way comparable with the marginal basic intrusions of the Loch Doon area.

Dykes of any kind are very scarce, not only in the granite, but in the immediately surrounding metamorphosed sediments. They are mostly quartz-biotite-hornfelses, cordierite being less plentiful than in the Loch Doon area. The metamorphism is sometimes very conspicuous, as at Knocknairling Hill near New Galloway. While at the north-eastern and south-western ends the granite cuts across the sediments, along the north-western and south-eastern margins the latter dip off the granite, which may be regarded as an intrusion essentially laccolithic in character.
The Pleistocene Geology of the Area between the Tees and the Trent
Authors: Gayner John Stansfield , Melmore Sidney
Published: October 2009

The Pleistocene detritus in Ryedale above Helmsley is described. A study of its distribution leads to the conclusion that at one time the surface of “Lake Pickering” stood at between 300 and 400 feet O.D. If this were so, the water must have overtopped a large part of the Howardian Hills, and evidence derived from these hills has proved this inference to be correct. Erratics of easterly derivation, now found at the same altitude on the western side of the Vale of York, have been known for a considerable time, and support the conclusion that “Lake Pickering” and “Lake Humber” formed one sheet of water. Lacustrine deposits in South Durham, of which those representing the deeper water facies extend to a height of 250 feet O.D., are described in detail.

As the result of this work, a number of conclusions have been reached, including the following: (1) a “Lake Humber”, the surface of which stood at a height of over 300 and not far short of 400 feet O.D., existed in late Glacial times; (2) even after the retreat of the Stainmore glacier from the Vale of York and the Tees basin this lake was still in existence, and its surface still at about the same level; (3) the land ice was in retreat before the North Sea ice-sheet had begun to withdraw.

The hypothesis of glacial lateral drainage, as it has been applied in the Vale of York, is briefly discussed in the light of the above conclusions.

A note is added on the character aqnd distribution of the Hessle Clay.
The Geology of Part of the Upper Luangwa Valley, North-Eastern Rhodesia
Authors: Dixey Frank
Published: October 2009

The Luangwa Valley is a deep, broad depression that runs in a south-westerly direction down the whole length of north-eastern Rhodesia for a distance of about 400 miles (Fig. 1). Except for a short distance near the south-western end, the floor of the valley is occupied throughout by Karroo sediments, and these continue for another 400 miles in the same direction as far as the Wankie area of Southern Rhodesia. The presence of the Karroo in the Luangwa Valley is due partly to synclinal folding and partly to marginal faulting which has brought down the sediments against the margin of the crystalline plateau. Near the southern end, the western boundary fault has a throw of 5000 feet (Molyneux 1909, p. 434), and at the upper end, near Chikonta, the main eastern fault probably has a throw of about 2500 feet.

In 1907 L. A. Wallace showed that the rocks occupying the floor of the Luangwa Valley consisted of sandstones and limestones that were presumably of Karroo age. Subsequently, A. J. C. Molyneux (1909), in his account of the Karroo of Northern Rhodesia, described the sediments of the Luano Valley near the southern end of the Luangwa depression; here the beds ranged from the basal conglomerates upwards as far as the Escarpment Grits, and comprised a total thickness of about 4800 feet. They yielded fragments of fossil wood at various horizons. Fine-grained sediments of Forest Sandstone type were not seen in the Luano area nor in the Luangwa Valley (Molyneux 1909,
The pre-Karroo Landscape of the Lake Nyasa Region, and a Comparison of the Karroo Structural Directions with those of the Rift Valley
Authors: Dixey Frank
Published: October 2009

In the course of an examination of part of the upper Luangwa Valley of north-eastern Rhodesia (Dixey 1937a) some features of unusual interest were observed in the relation of the Karroo sediments to the land surface of that time, and it was found that certain elements of that old surface still play an important part in the modern landscape. An extension of these observations into northern Nyasaland has yielded similar results, which, with those from the Luangwa Valley, are described in the following pages.

With the exception of the Livingstone Mountains (8000–9000 feet), overlooking the opposite shores of Lake Nyasa, and the neighbouring Rungwe group (10,400 feet), northern Nyasaland includes the highest and the most striking uplands throughout this part of central Africa. The nearest highlands of equal or greater height are the Mlanje Mountains (8000–10,000 feet), 400 miles to the south by east, the highlands around the northern end of Lake Tanganyika and around Lake Kivu (9000–14,000 feet) 600 miles to the north-north-west, and the highland masses of northern Tanganyika Territory (9000–19,000 feet) 600 miles to the north-north-east.

The Mlanje Mountains consist of syenite, in all probability of late Karroo or early post-Karroo age; Rungwe and the highest mountains of northern Tanganyika Territory consist of volcanic rocks, principally of Tertiary and later age; with these exceptions the highlands named, including North Nyasa, consist mainly of Muva-Ankole, Basement Complex, and other pre-Karroo formations.

The highlands of northern Nyasaland (Pl. V) comprise principally the Nyika plateau (6000–8000 feet), with five similar
The Overstep of the Sandgate Beds in the Eastern Weald
Authors: Kirkaldy John Francis
Published: October 2009

Comparatively little work has been done on the Lower Greensand of the eastern Weald for the last fifty years, whilst the current maps of H.M. Geological Survey are based on the original survey made under Topley prior to 1875. The general succession and fauna of the beds are fairly well known in East Kent, but in East Sussex, where the beds are thin, great difficulty has been found in the past in subdividing them and correlating them with the lithological subdivisions recognizable in other parts of the Weald.

Detailed mapping of the outcrop has, however, shown that in the extreme east of Sussex the Sandgate Beds overstep the Hythe Beds to rest on the Weald Clay. A similar overstep is traceable in the Boulonnais and in the boreholes of the East Kent coalfield.

The only literature relating to the Lower Greensand of Sussex is to be found in the pioneer accounts of Martin, Mantell, and Fitton, and in the memoirs of H.M. Geological Survey. In Topley's classic memoir (1875, p. 126) the Lower Greensand is described as retaining its usual lithological units to beyond Henfield, but farther east, owing to the disappearance of the distinctive stone bands, it was found to be incapable of subdivision. At a later date, part of the area was resurveyed by Lamplugh (Reid 1903), whilst the country farther east was redescribed, but not remapped, by Osborne White (1924, 1926), who also experienced difficulty in the correlation of the beds of the Lewes area with the
The Geology of the Solwezi District, Northern Rhodesia
Authors: Hatfield Willis Charles
Published: October 2009

The Solwezi district lies on the southern side of the Congo-Zambezi divide along the Rhodesian-Belgian Congo border, approximately 100 miles west of N'Changa. It comprises nearly 450 square miles and forms part of the great Central African Plateau. It is a previously unmapped portion of the Northern Rhodesian copper belt, of which the climate, vegetation, and general features are adequately described in many of the works referred to on p. 152. The district is named after the Government post at Solwezi, the officials at which generously gave assistance at numerous times during my investigation of the area.

I am greatly indebted to Dr. J. A. Bancroft, who directed the field work in 1929, and to Dr. C. P. Berkey and Professor R. J. Colony, who guided the laboratory work at Columbia University.

The Solwezi district forms a small part of an uplifted peneplain now in the youthful stage of dissection by the headwaters of small tributaries of a major branch of the Zambezi river. The average elevation is approximately 4500 feet. Numerous low ridges and scarps and a few isolated hills interrupt an otherwise gently rolling surface, and the present physical features strikingly reflect the character of the underlying rocks.

The rocks, a continuation of the complexly folded and faulted Pre-Cambrian formations of Katanga to the north, range from the Basement Series through the Mine Series and part of the Kundelungu, and in this paper are divided into five natural groups, as was done in the field for convenience in mapping
The Geological Basis of the Present Search for Oil in Great Britain by the D'Arcy Exploration Company, Ltd.
Authors: Lees George Martin , Cox Percy Thomas
Published: October 2009

Seepages of oil at the surface or in coal mines have been known in Great Britain for several centuries. Records of the use of oil from the Coalport seepages date from 1684. James Young in 1847 extracted wax, burning oil, and lubricating oil from a crude oil obtained in the Biddings colliery, near Alfreton in Derbyshire. In 1902, some boring was carried out in the Sussex Weald, stimulated by the accidental discovery of natural gas at Heathfield, but this enterprise was soon abandoned.

In 1918, a serious search for oil was made under the pressure of war-time conditions, and Messrs. S. Pearson & Son, Limited, between 1918 and 1921, under contract for H.M. Government, drilled 11 test-wells: seven in Derbyshire, two in Staffordshire, and two in Scotland. In every case the objective was an oil accumulation in Carboniferous beds. A small production was obtained from their first well, Hardstoft No. 1 in Derbyshire, and showings of oil were struck elsewhere, notably in the D'Arcy well in Scotland. Although the results up to that time may not have been conclusive, they were not considered sufficiently encouraging to justify further Government expenditure, and operations were suspended. Two wells were drilled later (1924–26) on the Hardstoft structure on the initiative of the Duke of Devonshire, owner of the property, but neither obtained any oil-production.

Other attempts during the last 20 years to find oil by drilling have been those at Kelham, near the site of a coal exploration borehole, which found a show
The Coal Measures of Bristol and Somerset
Authors: Moore Leslie Rowsell , Trueman Arthur E.
Published: October 2009

The Coal Measures of Bristol and Somerset are in some ways less completely known than those of most other English coalfields. This is partly due to the fact that the Coal Measures are to a great extent concealed under newer rocks, while the interpretation of the sequence has been made still more difficult by the complexity of the structure, especially in those areas where the lowest part of the sequence is exposed. Maps of the area on the one-inch scale were published in 1845, and some revision has been made since; an account of the sequence and structure was prepared by Prestwich in 1871, and a memoir by H. B. Woodward was published in 1876. Since that time sections of colliery shafts have been issued by the Geological Survey (sheets 11, 48-52). Other works on the area are referred to incidentally below.

The general lithological sequence has been recognized for many years, but the correlation of the various parts of the coalfield has been largely a matter of speculation: there has been little palæontological evidence on which even a tentative correlation could be based.

Several workers have, however, made important contributions to the palæontology of the coalfield. The rich floras of the upper part of the Coal Measures, long famous in the Radstock district, were investigated by Kidston (1887) and more recently by Dr. R. Crookall (1925, 1929). The lower part of the sequence, which is generally less fossiliferous, received less attention, and its floras are very incompletely known; from
The Tectonic Problems of an Area of Salopian Rocks in North-Western Denbighshire
Authors: Boswell Percy George Hamnall
Published: October 2009

The area which forms the subject of this communication comprises nearly 300 square miles of country in north-western Denbighshire; its boundaries are the Gonway valley on the west, the Irish Sea on the north, the Vale of Clwyd on the east, and the road from Bettws-y-coed to Cerrig-y-druidion and Derwen on the south. This area is occupied by Salopian rocks, and its interesting tectonic features have engaged my attention for several years. Certain parts of the work on the district have already been published (Boswell 1926, 1928A, B, 1930, 1932; Boswell and Double 1934), and an account of the tectonic features was to have followed the completion of the re-survey of the area on the six-inch scale, a task that has been delayed because of the limited opportunities now available to me for field-work.

Recently, however, certain of the disturbed beds in the area have been interpreted as the result of slumping movement (contemporaneous submarine sliding), and since this explanation differs from the interpretation that I should offer, it seems desirable that some details supplementary to the earlier accounts should now be put on record. Certain of the tectonic phenomena about to be described anoear to be novel.

One of the most complete successions of graptolite-bearing Salopian rocks is displayed in the region. Moreover, the area is sufficiently large to permit many interesting lateral changes in facies to be traced. For the most part, the succession and geographical distribution of these rocks have been described in earlier papers, but the
Rock Succession and Structure in South Cornwall: a Revision. With Notes on the Central European Facies and Variscan Folding there present
Authors: Hendriks Eileen M. Lind
Published: October 2009

The area dealt with in this paper is the coast of South Cornwall from Porthleven in Mount's Bay to Pentewan in Mevagissey Bay. It is separated by the Carrick Roads and tributary creeks into two parts, Meneage and the Roseland-Gorran country. The similarity of the rocks and problems in the two areas is recognized in the memoirs of H.M. Geological Survey (Flett and Hill 1912; Hill and MacAlister 1906; Reid 1907; Reid and Scrivenor 1906), but no detailed correlation based on local developments has been made, and the stratigraphical terms in use (“Mylor,” “Falmouth,” “Portscatho,” “Veryan,” “Manaccan” and “Grampound”) have never been satisfactorily defined, so that the geological history of Cornwall is still unexplained.

The rock succession of South Cornwall begins with the altered rocks of two peninsulas (the Lizard and Dodman), of unknown age, related to one another and to the Start in South Devon by their rock types and by certain peculiar features in their boundary lines. The Lizard differs from the other two in the presence of an intrusive complex, also of unknown age, of serpentine-gabbro and granite-gneiss, described in 1912 by Sir John Flett, who regarded the serpentine as injection-foliated, and the Lizard boundary features as compatible with both dislocation and intrusion (Flett and Hill 1912, pp. 213–6, 242). In 1896, Professor Bonney had pointed to Kiberick valley, near Veryan, as a locality likely to afford crucial evidence of the age of the Lizard serpentine (1896, p. 48), and he had previously (1877)
Observation on the Geology of Northern Central Africa
Authors: Sandford Kenneth Stuart
Published: October 2009

The object of this lecture is to sketch the geological history of a remote continental region, much of which remains to be surveyed, between the Belgian Congo and Cyrenaica, the Nile and the French Sahara and Soudan. Only incidental reference is made to Egypt, East and South Africa, and territories where British official surveys are established. An effort is also made to review recent Belgian, French, and Italian work in this region. I am especially indebted to Mr. H. B. Maufe, who read the text and gave much valuable advice, to M. Blondel, Director of the Bureau d'Études géologiques et Minières coloniales, Paris, and to M. T. Monod, of the Muséum d'histoire naturelle, Paris, for their unstinted help. My thanks are due also to M. R. Perret for the photograph reproduced as Plate XXXII, to MM. Perret and J. Bourcart for permission to reproduce Figure 2, and to my wife for the photograph of Plate XXXIII and for much help in preparing the text and bibliography.

This attempt to visualize the geology of the region as a whole is based on my field work in the critical central area. The whole of the well-known and broad coastal and marginal lands are omitted from consideration : they can be studied in official publications and in the works of Krenkel (1925–34) and other authors. Reference is made also to the Congo basin-Zambesi watershed.

These rocks may be divided into an Archaean basement complex and a series of altered, often highly folded, sediments
New Pteraspids from South Wales
Authors: White Errol Ivor
Published: October 2009

Recently a number of specimens of pteraspids have been collected from different localities in the Lower Old Red Sandstone of South Wales, and these have proved to belong to two forms hitherto undescribed and a third not previously recorded from Britain, thus bringing the number of British species up to nine. In two instances specimens have been collected before, but they were fragmentary and were determined and recorded as belonging to well-established forms. The identity of these fossils is of interest, since they are in each case the only completely determined organic remains in the beds in which they occur, and may therefore be expected to throw some light on tlieir age, about which there has been a degree of uncertainty; with regard to this point, we may note at once that the palæontological evidence is not altogether in accord with the stratigraphical, for in two of the localities the fossils seem to indicate a younger age for the beds than field-workers are willing to admit.

The first discovery to be noted is that os a form of the Continental Coblentzian species
Pteraspis (Rhinopteraspis) dunensis
(Roemer), in beds which on field evidence have been considered to be of Dittonian (II.2) age.

The specimens, the occurrence of which has already been noted by Mr. Dixon (19836) in a discussion, were collected in July 1935 after the excursion arranged during the centenary celebration of H. M. Geological Survey and led by Mr. Dixon and Dr. Pringle. During the excursion, the party visited
The Age of the Mountains of Snowdonia
Authors: Greenly Edward
Published: October 2009

The Development of Opinion on the Problem.
—Half a century ago, it seems to have been widely held that the mountains of North Wales were, as mountains, very ancient; much older, it was remarked, than some which are loftier and more famous. Yet by 1867–1870 it had come to be generally recognized that the mountains of the Inner Hebrides (which are very nearly as high) are, as mountains, of Tertiary age (Geikie 1897, pp. 114–5). Why did not this arouse speculation with regard to the mountains of Wales?

Some ten years later it was urged by Goodchild (1880; repeated, more fully, in 1888 and 1889) that the mountains of Lakeland had been sculptured out of a high plateau which was a sub-Cretaceous floor, so that, as mountains, they must be of Tertiary age.

About the same time, Ramsay (1881, p. 319) expressed an opinion which approached Goodchild's somewhat nearly: “During the deposition of the chalk, there is no proof that the higher parts of Wales were altogether submerged, but rather the opposite.” He does not (so far as I know) specify the grounds for this “opposite”, and seems indeed not to have thorough-going confidence in it, for he says on p. 320: “It thus appears that since the beginning of the Permian epoch, the higher ground of Wales has formed land well raised above the level of the sea, and even if there be some doubt about this while the chalk was being deposited, that must have formed merely an episode
The Higher Silurian Rocks of the Kerry District, Montgomeryshire
Authors: Earp John Rowland
Published: October 2009

The north-western part of the upland tract of Clun Forest is shown on the Geological Survey maps (sheets 56 and 60) to be composed of a wide belt of rocks of Ludlovian age, overlain to the south-east by a roughly circular outlier of “Old Red Sandstone” known as the Bettws-y-crwyn outlier. The area dealt with here includes the north-western part of that outlier and a considerable part of the Ludlovian belt to the north and west, forming the borderland of the counties of Radnorshire, Shropshire, and Montgomeryshire. The district has been studied on the six-inch scale: namely, on the Ordnance Survey maps, Montgomeryshire XLIV NW. and SW., XLIII NE. and SE., Radnorshire IV NE., and Shropshire LXVIII NW.

Like all the Clun Forest district, the general elevation of the ground is from 1000 to 1500 feet, and the southern and eastern sides of the hills are mostly gentle dip-slopes, while the northern and western sides are steeper scarp slopes. The main ridge of high ground, Kerry Hill, forms the watershed between the streams flowing north-eastwards into the Severn, and the south-easterly flowing Teme and its tributaries. The south-westward extension of Kerry Hill and the high ground around Gorddwr Bank form the watershed between these two drainage systems and the south-westerly flowing tributaries of the Ithon. The valleys are mostly filled with drift, and the glacial geology of the district has been discussed by Dwerryhouse and Miller (1930).

Murchison (1839) gave a general description of the “OuTliers of Old Red Sandstone
The Tertiary Volcanic Rocks of Central Victoria
Authors: Edwards Austin Burton
Published: October 2009

The Tertiary era in Victoria was marked by two extensive periods of intermittent vulcanicity; one ranging from the Oligocene to the Middle Miocene (Older Volcanic Series), the other from the Pliocene to the Recent (Newer Volcanic Series). The Older Volcanic Series, now greatly eroded, occurs mostly south and east of Melbourne. The Newer Volcanic Series, which has suffered much less erosion, extends north-west and west from Melbourne as a broad plain of about 10,000 square miles in area, and forms the floor of the Great Valley of Victoria. This paper is concerned with lavas of the Newer Volcanic Series lying between longitudes 144° E. and 145° E. (Fig. 1).

The Geological Survey of Victoria generously provided facilities for cutting 500 thin sections, and lent to me another 500 slides on my departure for England, besides putting at my disposal maps, literature, and unpublished analyses.

Mr. D. E. Thomas, of the Survey, in conjunction with whom the detailed field work was done, generously withdrew from the work.

Fifty chemical analyses were prepared in the Geochemistry Department, Imperial College of Science and Technology, London, under Dr. H. F. Harwood. Much helpful criticism was received from Professors Boswell and Brammall, and my thanks are due to Dr. G. W. Tyrrell of Glasgow and Dr. E. S. Hills of Melbourne for reading the manuscript, and to Professor Brammall for seeing the paper through the press.

P
revious
L
iterature

A bibliography of references to Victorian basalts is provided in Professor Skeats's Presidential Address, on the volcanic
The Red Measures of the Menaian Region of Carnarvonshire
Authors: Greenly Edward
Published: October 2009

The Red Measures of Arvon (that is, the country between the Menai Strait and the mountain-land) were briefly alluded to in the Geological Survey memoir on Anglesey (1919; hereafter referred to as
G.A.
), chapters XXV and XXVI, but they have now been mapped on the 6-inch and “25-inch” scales, and much more is known about them. They appear as tracts along the Strait, let in by the Dinorwic fault (Fig. 1).

For the determination of the minerals of the finer beds I am indebted to Mr. I. S. Double, for the determination of certain fossils to Dr. Helen Muir-Wood, and for opinions on the sources of some of the blocks to Drs. Howel and David Williams.

I. P
etrology

The chief component of the Red Measures is bright red marl, with seams of pale green, which are apt to occur in groups. There are a few thin beds with small angular fragments. But a special feature of Arvon is the purple boulder-bed, the blocks in which range from an inch or less up to two feet in diameter. The great majority are lavas.

The Red Marls
.—The great bulk is argillaceous, fine to impalpability, and reddened by ferric iron. There is much dust of quartz, as well as ill-defined aggregate matter which reacts to polarized light and may be micaceous or chloritic, or both. With cold dilute HC1 there is effervescence, with a loss of 9.52 per cent. Out of 50 grains only 0.006 grains were “heavy”. The minerals identified, and the
Slip-Planes and Breccia Zones in the Tertiary Rocks of Peru
Authors: Baldry Robert Ashley
Published: October 2009

The Peruvian oilfields lie on the coast about 4° south of the Equator, where South America juts out farthest west into the Pacific. At Ancon, in the Santa Elena peninsula of Ecuador, is another oilfield with rocks of the same age.

The Tertiary rocks on the coast are cut off by the Amotape mountains on the south-east, about 20 to 25 miles inland. These mountains are a complex of Carboniferous slates and quartzites metamorphosed by intruded granites, with small outcrops of unmetamorphosed Cretaceous rocks. The range runs north-east and south-west, and most of the main tectonic features are parallel to this axis.

The oil-bearing strata are Middle and Upper Eocene at Negritos, Talara, Lobitos, and Cabo Blanco in Peru, Upper Oligocene or Lower Miocene at Zorritos, 70 miles farther north, and Middle and Upper Eocene again at Ancon in Ecuador.

A north-east and south-west section through Cabo Blanco shows the following features (Fig. 1) : a geofault five miles off-shore, where the sea-bottom drops to 2000 fathoms; a flat coastal shelf; a narrow belt of deeply dissected Tertiary rocks; the Mancora Tablazo (a flat tableland of Quaternary deposits 15 miles wide and 1000 feet above sea-level); foothills of Tertiary rocks; and the Amotape mountains of metamorphic rocks.

The geology has been well described by Bosworth and again by Olsson and Iddings.

The most striking feature, the slip-planes and breccia zones, have been described only in my private geological reports during the last twelve years. I have to thank the directors
On a theory of Gravitational Sliding applied to the Tertiary of Ancon, Ecuador
Authors: Brown Charles Barrington
Published: October 2009

I wish to make it quite clear from the beginning that the conception of large-scale sliding due to gravitation within the mass of Tertiary sediments of North-West Peru is entirely due to Mr. Robert Ashley Baldry. My work and conclusions upon the structure of the Tertiary of the Santa Elena peninsula, Ecuador, are the result of the inspiration of that thesis, which I have extended to accord with the evidence as I read it. Mr. Baldry does not necessarily agree with all my conclusions, because he has not so far examined my evidence in the field.

The earliest workers in North-West Peru—J. Grzybowski, C. Maddocks and E. R. Blundstone—described the coastal structure as a series of folds parallel to the trend of the Amotape mountains. Only Grzybowski published an account (1899), and showed in diagrammatic sections some block-faulting at Grau and folding in the Amotapes.

The first published works of real importance were those of T. O. Bosworth, in the form of two papers read before this Society (1920
a, b
) which were later expanded into a book (1922). He described the structure as a mosaic of faulted blocks, the faults having throws up to 5000 feet, and considered folding to be negligible.

Up to 1925, Mr. Baldry and I had examined a considerable part of the tract from the Pariñas valley to Tumbez, between the Amotape mountains and the sea, and had realized its complexity. Further detailed mapping of the Cabo Blanco region by Mr. Baldry presented such difficult
The Fauna of the Baton River Beds (Devonian), New Zealand
Authors: Shirley Jack
Published: October 2009

Research into the geology of New Zealand has shown the existence of rocks containing faunas of Silurian or Devonian age in not widely separated localities in the north of South Island. These faunas were named, after the localities, the Reefton and the Baton river faunas. The Reefton fauna has been studied in detail by Dr. R. S. Allan (1935), who proved conclusively that it was of Lower Devonian age with great similarity to the Upper Siegenian and Lower Emsian (= Lower Coblenzian) faunas of western Europe. The Baton river fauna is the subject of the present study.

The collection upon which the work is based consists of three parts. First, the collections of the New Zealand Geological Survey under J. Hector from locality 128 (Baton river); second, the collections of a more recent survey; and third, a series of specimens from Auckland University College. The collections were brought to England by Dr. R. S. Allan, together with that from Reefton. He was unable to make a detailed study of the Baton river fossils, which he left with Professor O. T. Jones, at that time at the University of Manchester. With the consent of the Director of the New Zealand Geological Survey, Professor Jones asked me to take up the study of the fauna.

The earliest detailed account of the stratigraphy of the Baton river and Wangapeka districts is by Mackay (1879, pp. 121–31). He mentions (pp. 125–6) that a large collection of fossils was made from the Baton river series
The Geology of the Country around Pwllheli, Llanbedrog and Madryn, South-West Carnarvonshire
Authors: Matley Charles Alfred
Published: October 2009

A number of papers have been published in recent years dealing with the geology of the southern part of the Lleyn peninsula. Mr. T. C. Nicholas in 1915 described the eastern horn, known as St. Tudwal's peninsula; papers by myself (1902, 1913, 1925, 1928, 1932) dealt with the western coast from Bardsey Island to Nevin and inland to Rhiw and Sarn, and one in 1930 by Dr. Heard and myself with the Bodfean tract. The purpose of the present communication is to describe the remaining area (about 42 square miles), which extends from Porth Neigwl (or Hell's Mouth) northward to Bodfean and eastward to the coast between Abersoch and Pwllheli, and thence to the neighbourhood of Four Crosses.

This country is built of Ordovician sediments accompanied by members of the “Bala Volcanic Series” and its associated intrusives. Glacial drift covers large areas, but the igneous rocks often project as prominent ridges and hills, of which the dominant peak is Carn Fadryn, 1217 feet high. The southern part of the area is a plain of thick drift which has filled up the head of the wide-mouthed bay of Porth Neigwl. The western horn of the bay at Rhiw and the eastern horn south of Llanengan are prolonged inland as pre-glacial cliffs and slopes, and the glacial deposits between them, which must have once extended farther south, are being removed by sea-erosion; yet at their truncated southern margin they still extend below sea-level.

The Afon Sôch, with its tributary the Afon Horon,
Eddies in Mountain Structure
Authors: Bailey Edward Battersby
Published: October 2009

In regions of compression it is common to find some stratigraphical group or groups broken up into a multitude of minor thrust-slices, which are packed in characteristic imbricate fashion. The slices, so arranged, are called
schuppen
, a German word meaning scales. Individual schuppen incline steeply towards the direction from which overthrust has occurred. Their relative movement is trivial, as concerns adjacent members, but may in the aggregate lead to impressive telescoping of the affected zone.

Schuppen structure is generally attributable to the passage overhead of some major thrust-mass. It is abundantly represented in the North-West Highlands of Scotland (Fig. 1). I well remember how B. N. Peach in conversation would compare the advance of a thrust-mass, riding upon schuppen, to the launching of a ship, carried upon rollers (the idea is expressed in print [Home 1907, p. 472]). It is the purpose of the present paper to show that Peach's simile finds much closer illustration in some of the deformations characteristic of the metamorphic sediments which constitute the interior of the Scottish Highlands.

The word “thrust” is to be found in the earliest British writings on tectonics: for instance, in those of James Hall of Edinburgh. This probably influenced Peach and Home in their application of the term to the great fold-faults of the North-West Highlands. Study of Peach and Horne's writings makes it clear that their more important thrusts are covered by the following definition, which with verbal modifications, I have repeatedly given:—

A thrust is a fold-fault which
The Glaciation of the London Basin and the Evolution of the Lower Thames Drainage System
Authors: Wooldridge Sidney William
Published: October 2009

The superficial deposits of the London Basin fall broadly into three groups on a basis of elevation and age. The highest and oldest deposits include marine sand and shingle of Pliocene age, and also the Pebble Gravel, which is younger than these marine deposits, though most workers have agreed that it is pre-glacial, in the local sense. At somewhat lower elevations are hill and plateau gravels, associated north of London with undoubted glacial deposits. Finally, at the lowest levels we have the terrace and valley gravels of the Thames and its tributaries. It is apparent that these superficial deposits constitute a record which should enable us to trace the stages of development of the existing surface features of the area. The oldest group of deposits (Pliocene beds and Pebble Gravel) were accumulated before any of the existing valleys were excavated, forming thus, in an essential sense, constituents of the “solid geology” of the area. The valley and terrace drifts reveal a drainage system agreeing in all essential features of plan with that of the present day. The long period of time representing the important “middle term” of our three-fold series proves to be critical for two main reasons. It witnessed the appearance of ice-sheets on at least one and probably two occasions. During the same period the course of the lower Thames shifted from far north of the centre of the basin to the neighbourhood of its present course. The following communication is an attempt to elucidate these important events
The Petrography and Petrology of the Lower Cambrian Manganese Ore of West Merionethshire
Authors: Woodland Austin William
Published: October 2009

The Cambrian manganese ore of the Ardudwy district of Merionethshire occurs interstratified in that series of rocks which locally forms the lowest Cambrian and which is known as the Harlech Grit series. This series crops out in a broad, irregularly oval, mountainous tract, with the long axis alined north and south. It extends from Barmouth in the south to within about one mile of Ffestiniog in the north and from the coast on the west to the Ganllwyd valley on the east.

Ramsay (1881, p. 19) first described these rocks, but no attempt was made to classify the series until in 1893 Good-child grouped them as follows (Dewey and Dines 1923, p. 59):—

4.

Upper Mudstones (Lingula Flags and Menevian) with Upper Manganese Bed at base.

3.

Upper or Moelfre Grits.

2.

Lower Mudstones; Lower Manganese Bed near base.

1.

Lower Grits.

He thus recognized two manganese horizons separated by at least 850 feet of rocks.

Charles Lapworth and T. Stacey Wilson, recognizing only one ore bed, divided the Harlech Grit series of the Survey as follows (Andrew 1910, p. 161):—

5.

Gamlan Shale group: grey, greyish green, and sometimes purple shales, slates and flags with occasional grit bands increasing in number eastward. 750–1200 feet.

4.

Barmouth Grits: massive grits and conglomerates. 600 feet.

3.

Hafotty or Manganese Shale group: grey and green mudstones with rare grits in west, becoming more frequent
The Early Cretaceous Valley-floor Pene-Plain of the Lake Nyasa Region and its Relation to Tertiary Rift Structures
Authors: Dixey Frank
Published: October 2009

On the floor of the upper Luangwa Valley of North-Eastern Rhodesia there are early Cretaceous Dinosaur Beds closely comparable with those occurring on the north-western floor of the Nyasa rift, and in recent papers (1937) I have given evidence to show that at least the northern ends of these two features, apart from the basin actually occupied by Lake Nyasa, had attained their present dimensions as far back as the early Cretaceous. Furthermore, having shown that the post-Karroo pebble beds of the upper Luangwa Valley belonged to the Dinosaur Beds, I suggested that the pebble beds of the lower Luangwa Valley were similarly assignable. On this and other grounds I suggested that the great system of troughs developed in this part of Africa, namely, those of the Luangwa and the middle and lower Zambezi, and the Nyasa-Shire rift, had attained to much of their present form in the early Cretaceous, and that the Dinosaur Beds and comparable formations filling these troughs had been base-levelled with the adjacent plateau during the Miocene peneplanation.

Also, in a recent paper (1937c) on the early Cretaceous and Miocene peneplains of Nyasaland I described the secondary early Cretaceous peneplain on which rest the Dinosaur Beds and the Lupata series. I now adduce evidence to show that this secondary peneplain was an important feature in the early Cretaceous geology of this region, and that it extended as a great valley-floor surface of erosion, still recognizable, throughout the length of the system of troughs referred to. This
Further Notes on Lower Devonian Plants from South Wales
Authors: Heard Albert
Published: October 2009

In 1926 I recorded the occurrence of a Lower Devonian flora from the Senni Beds near Brecon, and described one new genus,
Gosslingia
, in detail. In 1931 a “thalloid-like” plant,
Thallomia
, from the Lower Downtonian of the Llandovery district, was recorded (Heard and Jones 1931).

Other fragmentary plant remains are present in both the above localities, and it is the object of this communication to place on record some of the more interesting of these fossils. Most of the material is badly preserved, and has proved unsuitable for examination by transfer or “film-pull” methods.

As previously recorded (Heard and Jones 1931, p. 552), the plant
Thallomia
occurs with a few fragments of dichotomously branched stems and obscure carbonaceous material at Capel Horeb near Llandovery. The fossil plants are associated with a lenticle of mudstone which is intercalated with the flaggy sandstones (Tilestones) of Lower Downtonian age.

Only one fairly complete specimen was obtained by Mr. J. F. Jones, who found the plant bed (Pl. XII, fig. 1). This consists of a slender stem, about 4–5 cms. long and 0–8 mm. wide, which shows two dichotomous branchings. Each of the two upper and equal divisions of the stem is terminated by a capsule-like body (5 mm. by 2 mm.), which tapers at the base and has an obtuse end. This is regarded as a sporangium.

A “film-pull” from these sporangia shows only a broken carbonaceous margin to the sporangium. No spores are to be seen. The greater part of the fossil
Explanatory note on the Block Diagram of the Great Rift Valley from Nakuru to Lake Magadi (Plate XIV)
Authors: Busk Henry Gould
Published: October 2009

This diagram was constructed during an examination of the Rift Valley region on behalf of the D'Arcy Exploration Company and the Anglo-Saxon Petroleum Company. The author is greatly indebted to these companies for permission to publish this work, and acknowledges with gratitude the assistance rendered during the examination by the Department of Mines, Kenya Colony.

It is difficult to give an effective picture of the Great Rift Valley by contour maps, and in those that exist the topographer has tended rather to round off his contour lines in the conventional manner, so that, where in nature there exists bold ruggedness, there appears on the map only flowing curves. An attempt has been made in this projection to bring out the steepness of the fault scarps, and the colouring has been progressively deepened to show the increasing depth to which the plateau has been faulted down. Thus the plateau round Nairobi, lying on the Kapiti plains, is coloured lightly, and the depth of colour increases northward from Limuru along the Kainankop plateau, and then down to Naivasha. Yet Naivasha is at a greater height above sea-level than Nairobi, the sides and bottom of the Rift Valley having together been raised to the northward relative to sea-level. There is a considerable slope of the whole of the Rift Valley and its sides towards the south. Thus, Lake Magadi lies at the lowest point in the diagram, though the difference between the level of this lake and the sides of the valley is