Showing papers in "Quarterly Journal of The Geological Society in 1908"

On the Application of Quantitative Methods to the Study of the Structure and History of Rocks

Abstract: 1. Introduction. In the case of nearly all branches of science a great advance was made when accurate quantitative methods were used instead of merely qualitative. One great advantage of this is that it necessitates more accurate thought, points out what remains to be learned, and sometimes small residual quantities, which otherwise would escape attention, indicate important facts. Since it applies to nearly all branches of geology, it is necessarily a wide subject, but so connected together that it seems undesirable to divide it. My object is to apply experimental physics to the study of rocks. At least six different kinds of physical questions are involved, some of which have been sufficiently studied, but others require experiments which would be very difficult to carry out, and all that I can now do is to endeavour to deduce plausible results from what is known. In doing this, it may be necessary to assume cases sufficiently simple for calculation, which may but imperfectly correspond to natural conditions, so that the results may be only approximately correct. In some cases, facts seem to show that there are important properties connected with subsiding material which cannot be explained in a satisfactory manner. Notwithstanding this, it appears desirable to do the best that I can with the material at my disposal, hoping to lead others to do what I intended to do, and correct such errors as are now unavoidable. In order to clear the way for subsequent detail, I describe a few general facts.

The Faunal Succession in the Carboniferous Limestone (Upper Avonian) of the Midland Area [North Derbyshire and North Staffordshire]

Abstract: 1. Introduction. The area of Avonian rocks with which this paper deals, and which I term the Midland Area, includes the large, irregularly-shaped periclinal mass of Carboniferous Limestone, forming the southern termination of the Pennine anticline, south of the Peak, and comprises also a few small inliers adjacent to this main outcrop. (See map, fig. 1, p. 35.) The main part of this area is included in Derbyshire, but a small, south-western portion lies in Staffordshire. In the Geological-Survey Memoir on North Derbyshire, the Carboniferous-Limestone succession of this area, as shown by the extensive section between Buxton and Monsal Dale, is briefly described; details of a few other sections are given; and the nature of the junction between the Carboniferous Limestone and the overlying shales, as seen at various points, is discussed. An account of the elementary tectonics of the area, and of the general features of the Carboniferous Limestone, is contained in a paper by Mr. H. H. Arnold-Bemrose, entitled ‘A Sketch of the Geology of the Lower Carboniferous Rocks of Derbyshire,’ published in the Proceedings of the Geologis9ts’ Association, vol. xvi (1899–1900) p. 165. Details of a new sections in the area are given in papers by Mr. Arnold-Bemrose and by Dr. Wheelton Hind, published in the Quarterly Journal of the Geological Society and elsewhere: I refer to these in the course of the present paper. The tectonic structure of this area has not yet been adequately investigated. However, the detailed mapping of the igneous rocks associated with

On some Fossil Fishes discovered by Prof. Ennes de Souza in the Cretaceous Formation at Ilhéos (State of Bahia), Brazil

Abstract: The precise extent of the Lower Cretaceous formation on the coast of Bahia (Brazil) still remains undetermined. Last year, Mr. Joseph Mawson gave to the Society an account of the deposits referable to it in the neighbourhood of Bahia itself; through Dr. Orville A. Derby, Prof. Eunes de Souza, of Rio de Janeiro, has now submitted to me some fossil fish-remains from Ilheos, which prove that it extends at least to that point, 130 miles south of the area previously described. The specimens represent three new species, but two of them are closely related to those from Bahia, and the third appears to belong to a typically Cretaceous form of Clupeoid fish which has not hitherto been found in America. Prof. de Souza has generously presented these fossils the the British Museum (Natural History), where they form an interesting supplement to Mr. Mawson9s collection. They are preserved in bituminous shale like that in which most of the fossil fishes occur near Bahia. A Cœlacanth is represented by the remains of the greater part of a skeleton of a fish about 60 centimetres long, by part of a cranium, and also by a few bones of a smaller head. The ridged ornament on some of the external bones shows that the species belongs to the genus Mawsonia , which is only known from Bahia. The head of the type-specimen is so much crushed, that it is only of interest as showing the characteristic rugose ornament on part of the cranial roof and

The Carboniferous Rocks at Loughshinny (County Dublin).

Abstract: 1. Introduction [C.A.M.]. Loughshinny, a tiny fishing-village on the coast of County Dublin, about midway between the larger villages of Rush and Skerries, is well known to Dublin geologists for the fine exposures of contorted strata exhibited in the neighbouring cliffs. These exposures form part of an extensive coast-section of Carboniferous rocks which may be followed, with a few interruptions, for about 5 miles from Rush on the south to Skerries on the north. A description of the rocks in the southern portion of this coast section, from Rush as far north as a small cove called Brook9s End, was given by us in 1905, together with an account of the faunal succession and correlation of the beds. The present paper continues the description northward from Brook9s End, and is intended to be read in conjunction with our previous paper. The references given to former literature and maps in that paper apply equally to the ground now to be described. Before, however, describing in some detail the rocks around Loughshinny, it seems desirable to recapitulate very briefly the sequence of the rocks in the Rush portion of the coast-section. At Rush the lowest beds are a thick mass of dark slates (Rush Slates), with intercalated limestone-bands; they pass up into the Rush Conglomerates, and the latter into a calcareous group (Supra-Conglomerate Limestones and Carlyan Limestones). The ascending succession is as a whole from south to north, and the beds mentioned appeared, from the palaeontological evidence available at the time, to

Glacial Beds of Cambrian Age in South Australia

Abstract: 1. Introduction. In April 1901, the present writer read a ‘Preliminary Note on the Existence of Glacial Beds of Cambrian Age in South Australia,’ before the Royal Society of South Australia. Subsequent investigations have demonstrated the great extent of these beds, both in thickness and in geographical prevalence, and have materially strengthened the evidences of their glacial origin. Publication of these results was delayed until the stratigraphical relationships of the beds in question had become better known. Researches into the geology of the Mount-Lofty and the Flinders Ranges were undertaken for this purpose, with the result that the subject can now be discussed upon definite data. The beds under review have their southernmost outcrop on the Onkaparinga River, 20 miles south of Adelaide. South of this position they become obscured by the Tertiary sandstones of McLaren Vale, and by a fault of some magnitude in which the higher beds of the Cambrian series are brought into juxtaposition with the lower beds at a divergent strike. North of the Onkaparinga, the glacial beds are occasionally seen as inliers of the Tertiary sandstones and clays, until the River Sturt is reached, 7 miles south of Adelaide. Here the beds cross the stream obliquely, about 1 mile from the main South Road, and occupy both sides of the valley for a distance of nearly 2 miles up stream. The glacial beds in this locality are determined on their northern side by a dip-fault, which cuts them off. From this point, northwards, the deep

On a Collection of Fossil Plants from South Africa

Abstract: 1. Introduction. Since the publication of my account of the ‘Fossil Floras of Cape Colony’ in the fourth volume of the ‘Annals of the South African Museum’ (1903) additional records of some of the floras have been obtained from several localities by members of the Geological Survey of that Colony. It is this recently-acquired material, forwarded to me for examination by the Director of the geological staff, Mr. A. W. Rogers, which forms the subject of the present communication. The majority of the specimens were collected from the Molteno Beds and from the Burghersdorp Beds; a few were obtained from the Uitenhage Series, a higher geological horizon; and others from the Lower Karroo rocks. The Lower Karroo plants are dealt with in a separate paper by Mr. Leslie and myself on the Vereeniging flora; the Uitenhage species are described elsewhere. With the exception of Schizoneura africana , a Permian species from the lowest beds of the Beaufort Series, we are now concerned with the Molteno and Burghersdorp species alone. It is customary to divide the Karroo system of Cape Colony into three sections: the Lower Karroo, comprising, in ascending order, the Dwyka Series and the Ecca Series; the Middle Karroo or Beaufort Series; and the Upper Karroo or Stormberg Series. The uppermost strata of the Beaufort Series have been named the Burghersdorp Beds, from the typical development of the rocks in the neighbourhood of Burghersdorp, a small town about 30 miles south of the frontier of the Orange-River Colony, on the

The Geological Structure of the St. David's Area (Pembrokeshire).

Abstract: 1. Introduction. There is probably no district in Wales with regard to the geology of which such serious divergencies of opinion exist as the neighbourhood of St. David9s. The only rocks upon which authorities are in any way agreed are the sedimentary Lower Cambrian deposits, which form the geological datum-line for the area; and differences exist even here, as to whether they include contemporaneous tuffs, and as to the composition of the basal conglomerate and sandstone. With regard to the age of the various acid and basic tuffs, the basic igneous rocks, the quartz-porphyries, and the granitoid rock of St. David9s, relatively to the Cambrian and inter se, entire disagreement exists throughout. The interpretations of the sequence fall, however, into two main groups, associated respectively with the names of Dr. Hicks and Sir Archibald Geikie. The former is, on the whole, supported by Prof. Bonney, Prof. McKenny Hughes, and the late J. F. Blake, who were all well acquainted with the district; and the conclusions arrived at by Sir Archibald Geikie and Dr. B. N. Peach have been confirmed after careful examination by Prof. C. Lloyd Morgan. The problem may be simplified by eliminating one point of disagreement. The late Dr. Hicks considered that the tuff9s, sheets, and dykes could be divided into two unconformable series, termed by him Arvonian (earlier) and Pebidian. No other observer has confirmed this hypothesis, and, in order to avoid prolixity, it is proposed not to make any special reference to it. Eliminating, then, this

The Bala and Llandovery Rocks of Glyn Ceiriog North Wales.

Abstract: 1. Introduction. It was in continuation of the work which we had begun at Corwen that in 1892 we paid our first visit to Glyn Ceiriog. At Corwen we had been unable to detect any decisive proof of unconformity at the base of the Corwen Grit; but in the Bala Beds below we did not find the characteristic fossils of the Sholeshook Limestone or of other Upper Bala deposits, and were therefore led to believe that the highest beds of the Bala Series were absent, and that there was probably an unconformity which was too slight to be visible in so small an area. The section at Glyn Ceiriog encouraged the hope that higher Bala Beds might there be found, and it seemed, moreover, to afford excellent opportunities for the examination of the whole Bala Series. To judge from the map of the Geological Survey, or from a cursory inspection of the ground, it would be difficult to imagine a locality more favourably situated for the purpose. The valley of the Ceiriog appears to cut through the whole of the Bala Series, from the lowest ash-band up to the Glyn Grit; and, owing to the steepness of its banks, the rocks are admirably exposed, while most of the beds are fossiliferous almost to excess. It was not long, however, before we found unexpected difficulties. The same succession, or rather the upper portion of it, should appear in the nearly parallel valleys of Tyn-y-twmpath and Nantyr; but when we examined those

On a Deep Channel of Drift at Hitchin (Hertforbshire).

Abstract: 1. Introduction. Deep channels filled with Drift occurring in Scotland and in the North of England have long been noticed by geologists, and more recently the existence of similar buried valleys has been discovered in the East of England. In 1890 Mr. W. Whitaker drew attention to a deep channel of Drift in the valley of the Cam; and in 1898 Dr. A. Irving recorded a great depth of Drift in the valley of the Stort. It has long been known that a considerable thickness of Drift covers the Chalk immediately to the south of Hitchin, wells and road-cuttings indicating that deposits of sand, gravel, or Boulder-Clay were at least 60 feet thick in certain localities; a boring at Messrs. Lucas & Co.9s brewery at Hitchin in the year 1831 was carried to a depth of 466 feet, passing through 3 feet of soil and 77 feet of sand. But the Chalk is so frequently seen that an exceptional thickness of Drift was unsuspected. During the last few years five borings have been made in the neighbourhood of Hitchin, all of which have disclosed a greater thickness of Drift than was expected. They happen to have been made in a line running about north and south nearly at right angles to the outcrop of the Chalk, the southernmost being 3 miles south of Hitchin, and the northernmost 4 miles north of the town. The object of this paper is to record these borings, which, with other evidence, seem to point

Permo-Carboniferous Plants from Vereeniging, Transvaal

Abstract: 1 Introduction The township of Vereeniging, on the northern bank of the Vaal River, close to its junction with the Klip River, is situated on the southern boundary of the Transvaal Colony, rather more than 40 miles south of Johannesburg on the railway which runs to Bloemfontein and Naauw Port Geologically, Vereeniging is important as the locality from which the greater number of Palaeozoic South African plants have been obtained; the species hitherto described are frequently cited by authors—not always with the same conclusions—in reference to the geological age of the strata in this part of the Transvaal The large striated boulders weathered out of the surrounding matrix on the bank of the Vaal River afford a striking demonstration of the nature of the Glacial Conglomerate, the term advocated by Mr E T Mellor in preference to that of the Dwyka We are not concerned with the precise method of formation of the conglomerate, but we are convinced that Sutherland was correct in his opinion, expressed more than 40 years ago, that the boulder-beds owe their origin to the action of ice, and this (we believe) is the view of those geologists who have had an opportunity of examining the evidence at first hand The conglomerate, as shown in the accompanying section (fig 1, p 110), is succeeded by coal-seams, sandstones, and shales; it is mainly from the sandstones that the plants have been obtained Most of the specimens were found in a sandstone-quarry a mile and a half from

The Origin of the Pillow-Lava near Port Isaac in Cornwall

Abstract: The volcanic mass which we are about to describe occupies a definite horizon in the Upper Devonian, in the part of North Cornwall lying between Padstow and Bodmin Moor. We propose to confine our remarks to this limited area; for the point with which we deal is merely the mode of origin of this particular eruptive rock. Our views may, or may not, be applicable to other pillow-lavas; but the subject is so beset with difficulties, that we prefer to confine our attention to a limited region, where cliff-sections are exceptionally fine and inland quarries are also clear. We will not deal with the question of correlation, even with neighbouring areas. The volcanic rocks near Port Isaac were noticed by De la Beche in 1839. He mentions the vesicular character of some of them, and suggests that they were contemporaneous with the slates in which they occur. He does not allude to their peculiar structure. In 1848 Nicholas Whitley noticed and figured the peculiar concentric structure, ‘as if it had rolled down a declivity and become partially cooled during its progress, and then consolidated into the rock which it now constitutes; in fact, much like the ends of bales of cloth piled one on another. He speaks of the centre of each circle being generally composed of a nodule of crystallized gypsum, and compares this structure with that of some of the Vesuvian lavas. The petrological characters of these rocks were described in 1878 by J. A. Phillips, who gave

Notes on the River Wey

Abstract: 1. Introduction. That part of the River Wey which lies within the Wealden area may for convenience be divided into six sections; but it is almost entirely with the last three that the present paper is concerned. (See Pl. XXXVI.) Section I is a consequent river, cutting through the Chalk at Guildford, and is marked on Pl. XXXVI as ‘River Wey (Consequent).’ It is the only portion of the Wey that rises in the Weald Clay, its upper waters being mainly derived from a subsequent river running nearly parallel to the Lower Greensand escarpment. Section II is a subsequent stream flowing in from the east, parallel with the Chalk escarpment, and joining Section I at Shalford. It is described in Topley9s ‘Geology of the Weald’ as the Tillingbourne. Section III is another subsequent river joining Section I from the west at Broadford. Between Godalming and Broadford its course is north-easterly, but from Tilford to Godalming its general direction is easterly, parallel to the Hog9s Back, which lies about 3 miles to the north. This branch, which may for convenience be called the Godalming River, receives several tributaries from the south, some from Hindhead, others from the Lower Greensand ridge between Hindhead and Hascombe. The latter form notches in that ridge, and seem to have been reduced in length by the retreat of the Lower Greensand escarpment before branches of the River Arun, Some unimportant obsequent streams drain the Lower Greensand area to the north, between this river and the Hog9s

The Two Earth-Movements of Colonsay

Abstract: The field-work which forms the basis of the present communication was carried out by Mr. E. B. Bailey and the Author in the summer of 1907, in the course of the geological survey of the island of Colonsay. The systems of folding displayed here and in the sister isle of Oronsay were found to possess features of more than usual interest, and special attention was given to the subject as far as the rapid nature of the work permitted. The investigation was facilitated by the rocky character of the islands, the surface of which is but little obscured by superficial deposits. A fairly continuous series of observations was thus rendered possible, and although a thorough understanding of the subject was by no means arrived at, yet certain facts came to light which may possibly have an important bearing on the orogenic history of the Highlands. For clearness and convenience of reference the subject will be discussed under the following heads:— I.The Stratigraphy and Chief Tectonic Features of the Islands. II.The Igneous Rocks. III.The Two Earth-Movements. IV.The Relation of the Earth-Movements to the Lamprophyres. V.The Relation of the Earth-Movements to the Plutonic Masses. VI.The Varied Age of the Lamprophyres. VII.The Nature of the Second Cleavage. The sedimentary rocks of supposed Lower Torridon age which form the greater part of Colonsay and Oronsay consist of an alternating

On the Fossiliferous Silurian Rocks of the Southern Half of the Tortworth Inlier.

Abstract: 1. Introduction. In the Quarterly Journal of the Geological Society for 1901 (vol. lvii, pp. 267–84 & pis. x-xi) is a paper by one of us, in collaboration with Prof. C. Lloyd Morgan, dealing with the igneous rocks and the associated sedimentary deposits of the Tortworth Inlier. The present communication may be regarded as, to some extent, supplementary to the above. Full references to the earlier work on the district having been given in the paper just mentioned, they will not be repeated here. The field-work has been carried out by one of us (S. H. R.); the identification of the fossils, involving the re-examination of the various public and private collections, by the other (F. R. C. R.). The expense of the work, which has involved the digging of a number of trenches and the opening-up of a series of old quarries, has been lightened latterly by means of a grant from the British Association for the Advancement of Science. We are much indebted to the landlords, the Earl of Ducie, Earl Fitzhardinge, and Sir George Jenkinson, Bart., for their kindness in facilitating these excavations. We desire also to thank Mr. J. Harle, Lord Ducie9s agent, and Mr. J. Peter, Lord Fitzhardinge9s agent, for help and information. The Llandovery rocks crop out along an area generally from 1 to 2 miles wide, which follows the general trend of the Carboniferous Limestone rim of the Bristol Coalfield, and stretches in a north-westerly direction from Charneld Green to the neighbourhood of

Brachiopod Homœomorphy: ‘Spirifer Glaber’

Abstract: It is easy, but it is very dangerous, to group together under one name a series of shells of similar appearance, especially when they are in the smooth catagenetic stage; because this smooth stage may have been attained by the loss of different distinctive features, pointing to polygenetic origins. An instructive case in this respect is found in the series of forms called Spirifer glaber . As Spirifera glabra , Davidson figured a series of shells which do not all agree in being smooth; for, though most of them are smooth, some are radially costate. And they do not agree in shape: some have a pronounced mesial fold, others hardly any; some are very transverse, others are narrow. Then in his synonymy he combined under this name many species of other authors: Sp. obtusus, Sp. oblatus , Sowerby, Sp. linguifera, Sp. symmetrica, Sp. decora , Phillips, Sp. laevigatus , von Buch. Of late years this glaber -series of the Carboniferous, and certain smooth Spiriferids of the Devonian, have been ranged in M9Coy9s genus Martinia . A somewhat similar series of Spiriferids is grouped under Reticularia , M9Coy: their distinguishing character is a reticulate surface. Davidson makes the principal species Spirifera lineata (Martin), and ranges under it Terebratula (?) imbricata , Sowerby, Spirifera elliptica and Sp. mesoloba , Phillips, Reticularia reticulata and Martinia stringocephaloides , M9Coy. In Reticularia the ornament is in the catagenetic stage, decreasing in intensity; so that partially or wholly smooth Reticulariœ are to be expected. There is good evidence that several of the forms ranged under Spirifera glabra

The High-Level Platforms of Bodmin Moor and their Relation to the Deposits of Stream-Tin and Wolfram.

Abstract: In the south-west of Cornwall the ancient marine platform, of Pliocene age, rises to a height of 430 feet above the sea, and its upper limit is a steep slope, often a bluff. In the same area the uplift of this platform has led to the deepening and cutting-back of the larger valleys, giving rise to a steepening of slopes in the lower part of the banks. This feature becomes less marked as the valleys are ascended, and in the case of the River Camel it disappears altogether at a distance of 22 miles from the sea. Above this point the river-banks and also the ground above them, now much over 430 feet high, retain in the main the same angle of slope as that which they had in Pliocene times, though of course they have been lowered to some extent by denudation. The retention of the characters of the older scenery is naturally most marked in the still higher grounds about the watershed of the River Camel, part of which includes Davidstow Moor. This moor also forms the gathering-ground of the Inney (a tributary of the Tamar); and, if the watershed be crossed and the valley of this river descended, the features just noted will be met with in reverse order, as that area is approached within which the denudation of post-Pliocene times has produced its most characteristic effects. Of the older topography thus partly destroyed by post-Pliocene denudation, the most striking feature in the higher part of the

On the Occurrence of Footprints in the Lower Sandstones of the Exeter District.

Abstract: I have long felt, for reasons which need not be detailed here, that the Red Rock Series of the Exeter district was mainly of subaerial origin, the breccias and associated sands having accumulated on a strip of country bounded on the west by high hills carved out of the folded Culm, while a large sheet of water lay to the east. The frequent indications of aqueous deposit would be due to variations in the level of the water such that it occasionally over-spread much of the littoral region, and rearranged and levelled the subaerial accumulations. Such a district seems to be exactly suited for the preservation of the footprints of any animals which might descend from the hills to wander over the low-lying sandy shores. I have, therefore, repeatedly searched the surfaces of blocks freshly fallen from the cliffs near Exmouth, where the ‘Lower Marls with occasional Sandstones’ reach the coast, and every other section that I could find in which the natural surfaces were laid bare. Sun-cracks on the surfaces of thin lenticular seams of marl are often to be found, as well as other signs of the s opposed conditions. The upper part of some of the sandstones weathers out in a curious way, leaving an irregular network of concretionary structures, strongly suggestive of a matted network of underground stems, such as those of the sand Carex or the recent Equisetaceas. But nothing of undoubtedly organic origin has been found. Away from the coast suitable exposures are rare.

On the Subdivisions of the Chalk of Trimingham (Norfolk).

Abstract: The Chalk in question is seen on the sea-shore when freed from shingle and sands by favourable tides, and portions of it rise as bluffs in the more recent deposits of the cliffs, being exposed from time to time as these beds in their turn are denuded away. This Chalk, by the evidence of its fossil contents, is younger than the Chalk of the mucronata-zone, which is the highest member of the White Chalk exposed elsewhere in England. This mucronata-Chalk dips generally eastwards, and, although exposed between Weybourne and Cromer, disappears just east of the latter place and is seen no more. The Chalk described in this paper lies on the top of mucronata-Chalk, and is correlated by its fossil-contents with the Chalk of Rugen. It is, therefore, in normal succession to the mucronata-Chalk, and represents the highest beds of the Cretaceous System existing in this country. It has not been found in any other part of the British Islands. The literature on it is scanty, and for present purposes it will be useful to call attention to Mr. Clement Reid9s ‘Geology of the Country around Cromer’ Mem. Geol. Surv. 1882; to the present writer9s ‘Stratigraphy & Fauna of the Trimingham Chalk,’ 8vo, London (Dulau) 1900, and Geol. Mag. 1906, which gives a complete fauna of these beds and of the mucronata-Chalk between Weybourne and Cromer; also to Mr. A. J. Jukes-Browne9s ‘Upper Chalk of England,’ vol. iii of the ‘Cretaceous Rocks of Britain’ Mem. Geol. Surv. 1904. In a

Notes on the Geology of Burma.

Abstract: I. Historical. It is the object of this paper to present the results of geological expeditions in the Irawadi valley carried out by my uncle Mr. W. H. Dalton, F.G.S., and myself in the season of 1904–1905, and by myself alone in 1905–1906, and to correlate these observations with those made by previous writers, thus summarizing our present knowledge of the geology of Burma generally and of the Tertiary System of that country in particular. Dr. Fritz Nœtling in 1895 reviewed the work done on the geology of Burma before that date, pointing out the remarkably-accurate hypothetical arrangement of the rocks of Burma made by Buckland in 1828, and the absence of subdivision of the Tertiary System previous to W. Theobald9s paper on Lower Burma in 1873. In this summary the ‘Axial Group’ of Theobald is referred to as certainly not of Triassic age—a statement controverted by later examination of the fossils of the Arakan Yoma and other parts of Lower Burma—although found true in the sense that the group is a complex one (as we now know), and neither Triassic nor Cretaceous alone, but assignable to both of these. While Dr. Nœtling9s paper thus reviews the greater number of the works published on the geology of Burma, and in particular those relating to the Tertiary of the better-known regions of the Irawadi basin, there are certain other papers to which it is necessary to refer here, as they deal with the outlying districts. Of these the earliest is that

The Basic Intrusion of Bartestree, near Hereford.

Abstract: 1. Introduction, and Field-Relations. The field-relations of the basic intrusion of Lowe9s-Hill Quarry near Bartestree were fully described by Murchison, but, although the dyke has been several times mentioned by later geologists no detailed account has yet been given of its structure. The dyke is of considerable interest, both from its own character and from the alteration to which it gives rise in the Old Red Sandstone. It has a thickness of about 35 feet, and strikes in an east-north-easterly direction through the Old Red marls and sandstones which here lie almost horizontally. As represented in the 1-inch Geological-Survey map, the dyke has a length of about half a mile, striking across the road which leads southwestwards from Bartestree, and extending from about the middle of Tidnor Wood on the south-west to near Bartestree Convent on the north-east. At present, however, the only exposures are at Lowe9s-Hill Quarry and for a short space immediately to the south-west. No trace of trap could be found west of the road; and, although fairly abundant debris occurs in Tidnor Wood, it appears to be derived entirely from Old-Red-Sandstone rocks. The Lowe9s-Hill rock, though not now worked, has formerly been largely quarried; and a long cutting has resulted, the sides of which are formed by Old Red sandstone and marl, while the trap is exposed at the end. ( a ) North of the trap.—On the northern side of the cutting, an undulating line, fairly easily followed up the face of the cliff, marks the edge

On Metriorhynchus Brachyrhynchus (Deslong.) from the Oxford Clay near Peterborough

Abstract: This species of Metriorhynchus was first described by E. Eudes-Deslongchamps in 1868 in his ‘Notes Paleontologiques,’ and was based on an imperfect skull obtained from Oxfordian strata in the department of Calvados (Lower Normandy). He was led to distinguish it from other species of Metriorhynchus on account of the shortness of the snout (‘museau’ is the word which he employed, under which term he included every thing in front of the orbits), the principal feature determining the species being found in these bones. In his table of Metriorhynchidae ( op. cit. p. 294) he defines it as follows:— ‘Museau tres court, pointe des os nasaux atteignant et meme depassant la suture des os intermaxillaires.’ He mentions one other mutilated skull found near Poitiers, and now in the Museum at Paris. Besides this, Prof. Bigot, of the University of Caen, to whom I owe my best thanks for photographs of the type-specimen and for much valuable information, tells me that there is in the Museum de la Faculte des Sciences at Caen a very mutilated skull with part of the vertebral column, and another fragment of a skull, which may probably be referred to Metriorhynchus brachyrhynchus . Apart from these, I can learn of no other specimens. The species is not mentioned in the ‘Catalogue of Fossil Reptilia in the British Museum’ (Lydekker, 1885) nor in ‘British Fossil Vertebrata’ (Smith Woodward & Sherborn, 1890). Prof. E. Fraas, in his monograph on the Thalattosuchia, among which he includes the Metriorhynchidae, compares it with Dacosaurus

The St. David's-Head ‘Rock-Series’, Pembrokeshire

Abstract: 1. Introduction. In a former paper, communicated to this Society, I gave a general description of the St. David9s-Head intrusions. On that occasion I expressed the opinion that this area would repay a more detailed investigation, and I have since made a systematic examination of these rocks, both in the field and in the laboratory, confining my attention to the two large parallel intrusions forming the St. David9s-Head and Carn-Llidi masses respectively. With the exception of the general account given in my former paper, these rocks do not appear to have been previously described in any detail. Several distinct types of rock occur in these masses, and it is the purpose of this paper to discuss their differences with the object of examining the problem of their origin. Briefly, the main point to be determined is whether these are to be regarded as an igneous complex, or whether they constitute a ‘rock-series,’ derived from a common magma by some process of differentiation. The two intrusions take the form of vertical sills intruded between almost perpendicular shales of Arenig age. They are composed of at least four types of rock, which, although closely allied, present marked mineralogical differences, often easily distinguishable in the field. There is a dark, basic variety, typically seen in parts of Cam Llidi, Carn Llidi Bechan, Carn Hen, and occasionally at Pen Lledwen and in parts of the St. David9s-Head mass. This melanocratic type is moderately coarse in grain. It stands in conspicuous contrast to a leucocratic

On Antigorite and the Val Antigorio, with Notes on other Serpentines containing that Mineral

Abstract: I. The Original Specimen and the Val Antigorio. The exact locality of the type-specimen of antigorite is apparently unknown, as I found when preparing my portion of the paper by Miss Raisin and myself on the minerals forming serpentine. E. Schweizer, who first described it, states that the specimen (5 inches long, 2 inches wide, and 2 inches thick) was in the collection of D. F. Wiser of Zurich, who had bought it the year before ‘von einem mit Mineralien handelnden Bauer aus Oberwallis, nach dessen Aussage diese Substanz in kleineren und grosseren, bisweilen einen Fuss langen, dunnschiefrigen Platten im Antigoriothale bei Domo d9Ossola gefunden werden soil’; and was unable to obtain any more precise information from the man. It has been subsequently noticed, among others, by Des Cloizeaux, Naumann, Hintze, Levy & Lacroix, Tschermak, Brush, Rosenbusch, and Zirkel; the last adding to a full and precise description an extensive bibliography. But none of these authorities define the locality more exactly: each, as is not unnatural, being content with stating that the mineral came from the Val Antigorio, though Dr. Hussak and one or two of the later writers have noted its occurrence in other places. I failed, though some time was spent on the search, to obtain any better information from books on Italian geology, or the maps in our Society9s Library; moreover, no serpentine is recorded in the Val Antigorio on sheet xviii of the Swiss Geological Survey-map. That, however, hardly amounted to proof of its non-occurrence, because

Solution-Valleys in the Glyme Area (Oxfordshire)

Abstract: In the plateau composed of Great Oolite rocks between the Evenlode and the Cherwell there is a series of remarkable valleys of similar character running in various directions. The area to be briefly considered is triangular: the base is formed by the strike-valley of the Upper Swere running north-eastwards, and by its continuation from the Great Rollright water-parting running south-westwards. The Dorn and the Glyme define an inner triangle in this area (see map, p. 336). It will be seen that the streams run in many different directions. Reference to a contoured map will show that there are innumerable valleys connected with and opening into the numerous streams draining the area, and that their trend varies. In the main, however, they are either strike-valleys or dip-valleys, though in the field their trend is not so evident. The valleys always begin suddenly upon the plateau, and descend with steep sides along winding courses into the nearest evident stream. The upper part of each valley is always dry. The cross-valleys are usually dry throughout. There are no terraces in the valleys, and there is no drift upon the plateau, nor any alluvium in the streams. The general appearance of the plateau-valleys is not of erosion but subsidence, as if an enormous snake had left a cast upon a yielding surface. Taking any part of the area, such as that where Grimm9s Brook enters the Glyme west of Wootton on the right bank (Pl. XXXVIII, fig. 2), it will be seen that the

Some Recent Discoveries of Palæolithic Implements.

Abstract: By the kind courtesy of Mr. Worthington G. Smith, F.L.S., of Dunstable, I am enabled to call attention to some recent discoveries of palaeolithic implements on the southern borders of Bedfordshire and in the north-western part of Hertfordshire. Mr. Worthington Smith9s remarkable discoveries of implements and of a palaeolithic floor at Caddington, not very far from Dunstable, are well known and have been fully recorded in his excellent and profusely-illustrated book ‘Man, the Primeval Savage’ published in 1894—a summary of which I gave in the second edition of my ‘Ancient Stone-Implements,’ which appeared in 1897. The original surface of the ground at some of the Caddington brick-fields was as much as 550 to 590 feet above the Ordnance-datum; but at Kensworth, about 2 miles to the west of Caddington, Mr. Smith found a palaeolithic implement upon the surface at an elevation of 760 feet. Quite recently an excellent ovate implement (5 × inches), black and lustrous, was found by a Dunstable school-boy at the surface on Blow Downs at an elevation of 600 feet. The exact position is slightly to the south of ‘Little John9s Wood,’ as shown on the 6-inch Ordnance-Survey Map of Bedfordshire. It is far from any existing stream, and the ground slopes away from the direction of the Ver. From Whipsnade Heath, about 2½ miles to the south of Dunstable, Mr. Smith has obtained a good ovate implement (3 × 2 inches), ochreous, from brown clay, a thin water-laid material resting upon

On a Formation Known as ‘Glacial Beds of Cambrian Age’ in South Australia

Abstract: Some 8 miles south of Adelaide a typical exposure of the conglomerate is bounded on the east by a series of alternating quartzitic and argillaceous bands of rock, comprising the central and western portions of a fan-fold, partly cut off by a fault. Further evidence of stress in this margin is given in the fissility, pseudo-ripple-marks, contortion and fracture, and obliteration of bedding in the quartzite-bands, and in the pinching-out of them into lenticles and false pebbles. On the west side the conglomerate is bounded by the ‘Tapley9s-Hill Clay-Slates,’ and there is evidence from the nature of the junction-beds that the conglomerate itself is isoclinally folded. In that portion of the conglomerate which is adjacent to its confines, ‘boulders’ of quartzite are apparently disrupted portions of quartzite-bands, since these are in alignment with the truncated portions of bands still existing, and are of similar composition. The Authors are not at present in a position to account for the presence in the conglomerate of boulders of rocks foreign to the beds that border the conglomerate, or of such as possess markings comparable to glacial striae, by their theory of differential earth-movements; but they consider that a boulder-bed subjected to lateral pressure would probably lend itself to the production of ‘false pebbles,’ through the disruption of intercalated hard bands within itself or on its boundaries. Dr. A. Strattan considered the first paper to be lucid and convincing account of an extremely-interesting series of deposits. The association of schistose rocks and slates with

A Note on the Petrology and Physiography of Western Liberia, West Coast of Africa

Abstract: I. Petrology. By the kind permission of Sir Harry Johnston, G.C.M.G., I am enabled to make the following brief contribution to the geology of part of Western Liberia. The district described lies to the north and north-east of Monrovia, in Montserrado county, and includes the lower part of the basin of the St. Paul or Ding River. These notes are the result of a seven months9 journey in the Republic. Taking the southern part first, it should be noted that garnetschists and various gneisses, for the most part greatly decomposed, are exposed in the neighbourhood of Whiteplains and along the Caresburg Road. In typical specimens of the former collected near Whiteplains, garnets are abundant, much cracked and very irregular in outline. Flakes of biotite are common, quartz is occasionally plentiful; and the felspar is, at least partly, an acid plagioclase. Phenocrysts are rare. Kyanite-schists are probably associated with these rocks, for the distinguishing mineral is common in the gravels of the streams, but it has not yet been traced to the parent rock. These garnet-biotite-granulites or schists form a well-marked group, probably distinct from the commoner gneisses with which they are associated. In the latter the occurrence of a monoclinic, and possibly also of a rhombic, pleochroic pyroxene is worthy of note. Quartz is common, and occurs typically in elongated lenticles. The Whiteplains garnetiferous rocks may be correlated with others petrographically similar, found between Suen and Arthington on the western bank of the St. Paul, and with garnet-graphitegneisses and tremolite-schists

On the Stratigraphy and Structure of the Tarnthal Mass (Tyeol).

Abstract: The Tarnthaler Kopfe are an isolated mountain-mass in the north of the Tuxer Alps. The appended sketch-map (fig. 1), together with the sections (figs. 2 & 3) copied from Pichler and Rothpletz, affords a general idea of the geographical distribution of the rocks of which the mass is composed and the vertical section of their arrangement in the mountain-mass itself. The stratigraphy of the mass has been very differently interpreted by various investigators. Their views will be found in the papers noticed below. Adolf Pichler in 1859 supposed the sequence of strata to be normal throughout, the capping mass of serpentine being treated as a sedimentary rock. He enumerates the following fossils, found in a grey limestone in place:— Belemnites, Pentacrinus, Gervillia inflata, Lithodendron, Rhynchonella . The whole mass of dolomite, with the calcareous schists above it, is shown in his section, as Lias, in which formation the author includes the Rhaetic. In 1894 Prof. A. Rothpletz announced a further discovery of Rhaetic fossils in this locality— Terebratula gregaria, Modiola minuta , and several others. The igneous character of the serpentine is recognized; but otherwise the descriptions and sections seem to assume a normal and continuous succession of beds, from the Triassic dolomite below to the youngest ‘Kalk-thon’ and Wetzschiefer above. In the same year Dr. F. E. Suess published the results of his own studies in this region. The serpentine and quartzite-schists are held to be older than the calcareous schists and dolomites, and it is supposed that they were brought into

On the Structure and Relations of the Laurentian System in Eastern Canada

Abstract: 1. Introduction. When Sir William Logan, in the early years of the Geological Survey of Canada, was gradually unravelling the stratigraphical succession as displayed in the Dominion, he found that at the base of the whole column lay the crystalline rocks of the Laurentian Mountains. The name ‘Laurentian Mountains’ had been previously given to that great stretch of iron-bound coast which lies along the north of the Gulf of St. Lawrence and is not, properly speaking, a mountain-range at all, but is merely the margin of a great rock-plateau—the Laurentain peneplain—which forms a portion of the northern protaxis of the North American continent. Logan9s studies in the Province of Quebec led him to believe that the Laurentian System, as he termed it, consists of a series of highly-crystalline limestones interstratified with quartzites and gneisses, which in their turn overlie a great thickness of foliated orthoclase-gneiss, the foliation of the latter being regarded by him as the survival of an almost obliterated bedding. He subsequently found in Eastern Ontario a series of rocks which he considered in all probability to represent the Grenville Series in a less altered state, and to this he gave the name of the ‘Hastings Series.’ Later investigations showed that the anorthosite of the Laurentian System is of intrusive origin; but little further light was thrown upon the relations of the underlying limestone-series (which is now termed the Grenville Series) to the Lower or Fundamental Gneiss. The relation of the Grenville and the Hastings Series also remained