Showing papers in "Geological Magazine in 1937"

On some Ordovician Fossils from Northern Argentina1

Abstract: The list of fossils described in this paper and their stratigraphical distribution is shown in the Table on p. 122. The Kainella and Leiostegium zones of the Quebrada del Toro are the equivalent of the Late Ozarkian of Western North America. The fauna of the arenaceous-calcareous beds of the marine-glacial deposits of the Saladillo group is not characteristic enough to enable an exact determination of the age. Nevertheless, from the stratigraphical position of these beds, they could be considered as indicating Upper Beekmantown age. The lower part of the Parcha group, with the single determinable fossil Basilicoides taurinus gen. et sp. nov. has been provisionally referred to the Llandeilian. The faunule of the Asaphellus zone of the Quebrada de Chalala shows affinities with part of the Tremadocian of England, the Tomkolian of South Chosen, and the upper zones of the “ Ceratopygeregion ” of Scandinavia. The stratigraphical relationship between the Kainella and Leiostegium zones of the pre-Puna and the Asaphellus zone of Purmamarca is not known.

The Floor of the Arabian Sea

Abstract: During the course of the John Murray Expedition some 22,000 miles of the floor of the Arabian Sea and the neighbouring areas of the Indian Ocean were mapped by means of the Echosounding apparatus. The region between India and Africa was crossed four times, namely: (i) from Aden to Karachi, (ii) from Bombay to Mombasa, (iii) from Zanzibar to Colombo, and (iv) from Colombo to Aden, while more detailed surveys were carried out in the Gulf of Aden, the Gulf of Oman, and the region off Zanzibar.

The Petrology of Katungite

Abstract: The specimens representing the Katunga lavas are compact fine-grained porphyritic rocks of lustrous stone-grey to deep blue-grey colour, the phenocrysts being olivine (up to 3 mm. long) of various tints from nearly colourless to yellow-green, and melilite (up to 2 mm. square) in thin tabular, less conspicuous crystals which, megascopically, have a shining grey to black appearance. Some of the specimens from near the sources of the flows are internally altered and have become fawn or buff in colour, mottledby white zeolitic specks and reddish brown ferruginous pseudomorphs after olivine and melilite. Some weathered specimens have a brown ochreous crust, but within this the rock is normally fresh.

Outgrowths on Zircon in the Middle Jurassic of Yorkshire

Abstract: In view of Mr. J. A. Butterfield's account of outgrowths on zircon in the Millstone Grit of the Pennine region ( Geol . Mag ., LXXIII, 1936, 511–16), it may be of interest to record the occurrence of similar grains in the Middle Jurassic sandstones of Yorkshire.

Scottish Carboniferous Crinoids

Abstract: In a paper published in the Geological Magazine last year (LXXIII, 385–112), it was mentioned that in my collection of Scottish Carboniferous crinoids there remained ten or eleven species to be described. In the present paper eleven species are dealt with, but I find this does not complete the list since there are still a few others, including species of Hydreionocrinus, Eupachycrinus, etc., and some very minute forms belonging to unknown genera which require further elucidation. It is my hope later on to describe these along with a revision of the Scottish Carboniferous crinoids as a whole. Meanwhile, on another page is given a list of all the species known to date so that a comparison can be made with the faunas of other regions. Here, I wish to add to the list of species already given from Coplow Knoll, Clitheroe (C1) (Geol. Mag., 1935, LXXII, p. 205), the following species: Platycrinus coronatus Goldfuss, Dichocrinus sp., Symbathocrinus conicus Phillips, and Mespilocrinus forbesianus de Koninck & Le Hon.

The Classification of the Ordovician Rocks

Abstract: The classification of the British Ordovician Rocks has gone through many phases of instability in the past, and at the present time seems to be passing through another such phase. There are probably many causes contributing to this state of things, two of which seem to be fundamental; the first, the differentfacies of development exhibited in different districts by the formations making up the system; the second, the varied elements entering into the composition of the shallow water faunas apart from the considerations of facies; these would seem to be governed largely by possibilities of migration into the British region of the Lower Palaeozoic geosyncline from different directions, i.e. from America, from Northern Europe, and from Central Europe, so that a different type of “shelly” fauna characterizes the north-west and south-east margins.

On a Specimen of Eusthenopteron from the Old Red Sandstone of Scotland

Abstract: While examining the collection of Old Red Sandstone fishes in the Royal Scottish Museum, the writer found the frontoethmoid shield of a Crossopterygian fish, from Eoghole, on the Muckle Burn, near the boundary between Elginshire and the county of Nairn. Though imperfect, the skull fragment retains its natural shape, and at once recalled the similar region of Eusthenopteron, from the famous fish-bearing beds of Scaumenac Bay, Province of Quebec, Canada. Further comparison seems to prove the generic identification. The stratigraphical relationships of the find are known with some precision, and the implications are of considerable importance. It is especially opportune that Dr. Erik Jarvik, of Stockholm, has just finished an account of Eusthenopteron species from the Baltic and Russia, with a discussion of the stratigraphy of those localities which yield the fish. Certain features of the Canadian Eusthenopteron are discussed in the present paper for comparison with the Scottish form: this is in no way prejudicial to the monograph on the Scaumenac Bay material, now in preparation by Dr. Jarvik.

The Cairnsmore of Fleet Granite and its Metamorphic Aureole

Abstract: The Cairnsmore of Fleet granite is the second in point of size of the four plutonic masses which penetrate the Lower Palaeozoic rocks of the Southern Uplands of Scotland, being exceeded in area only by that of the Criffel. Its outline is roughly oval and it measures 11 miles by 7 miles, the long axis trending N.E.—S.W., exactly parallel to the strike of the rocks of the Southern Uplands.

Intrusion of Cone-Sheets

Abstract: Evidence from Mull and Ardnamurchan is brought forward to show that the injection of cone-sheets is accompanied by a vertical lifting of the upper wall. This confirms Anderson's explanation. It is argued that the fracturing and injection are of a quite sudden character and that it is in the nature of the process that no evidence from recent volcanoes has yet been obtained of contemporary cone-sheet injection.

The Zonal Position of the Elsworth Rock and its Alleged Equivalent at Upware

Abstract: (1) The Elsworth Rock of Elsworth and St. Ives is a condensed deposit belonging to the plicatilis zone. (2) There is no evidence that it contains any ammonites derived from earlier zones. Statements that it does are based on misidentifications. (3) The Elsworth Rock at Elsworth overlies at least 8½ feet of ironshot clays with thin bands and nodules of limestone, the clays containing abundant ammonites of the cordatus zone and no others. (4) The so-called Elsworth Rock at Upware is the equivalent of the ironshot cordatus zone developed below the Elsworth Rock at Elsworth. (5) The true Elsworth Rock ( plicatilis zone) is represented at Upware by the Coralline Oolite and Lower Coral Rag. (6) For convenience in stratigraphical nomenclature it is desirable to group together the condensed ironshot cordatus and plicatilis beds of Elsworth as the Elsworth Series. (7) The Elsworth Series, as defined in 6, corresponds with the Oolithe ferrugineuse and the greater part of the Oolithe de Trouville on the Normandy coast. At Trouville the plicatilis zone to some extent combines the developments at Elsworth and Upware. (8) The ironshot cordatus zone was proved in the Upware well to rest directly upon normal clays of the mariae zone, and the same zone was proved in the vale below Elsworth in the Fen Stanton brewery boring. I am greatly indebted to Mr. E. E. L. Dixon and Mr. A. G. Brighton for criticisms and suggestions, and especially to Mr. Brighton for the trouble he has taken in sending me all the fossils on loan and supplying the relevant information.

The Flint Gravel Deposit of Orleigh Court, Buckland Brewer, North Devon

Abstract: The deposit to be described is situated at Orleigh Court, in the parish of Buckland Brewer, some four miles west of south from Bideford, where it rests unconformably on the steeply dipping Upper Culm sandstones. Its greatest extent is from Orleigh Mill to Yeo Bridge, a distance of about three-quarters of a mile in a northwest to south-east direction, and from this line it extends to the south-west for an average distance of about one-third of a mile, only exceeding that amount to the south of the Higher Lodge. The only extensive section was seen in the Rookery, where 25 feet of material rest on a yellow clay. The highest point reached by the deposit, to the south-west of the Higher Lodge, is about 400 feet above O.D. From this point it slopes to the north-east, extending down to about the 100 ft. contour on the left bank of the River Yeo. It is possible that the north-eastern boundary does not reach such low levels as those indicated on the map, Text-fig. 1, for it is difficult to distinguish the original gravel from relatively recent hill wash; and, without a good deal of trenching or augering, it would not be possible to determine the boundary more closely than has been done in the present work.

Old Shore Lines of Palestine

Abstract: The object of this article is to bring up to date the known history of the earth's crust in the south-east Levant.

The Relationship of the Pilton Beds of North Devon to their Equivalents on the Continent

Abstract: Having made a general study of the Devonian-Carboniferous junction in North-West Europe and a more detailed one of special areas, the author discusses here the correlation of the Pilton Beds of North Devonshire and the “K beds” of the Bristol and Forest of Dean areas with the Etroeungtian and other horizons near the Devonian-Carboniferous boundary on the Continent.

Arctic and Some Other Species of Streptelasma

Abstract: Collections of fossils from the Lower Palaeozoic rocks of the Arctic usually contain species of Streptelasma . These, with other forms, have often been considered indicative of horizon. Now it is unfortunately true that none of the original descriptions or figures of species described from the Arctic, or of those relevant species long known in America, are adequate for strict identification. It is a matter for no surprise, therefore, that many false identifications have been made.

Intrusions of the Glen Falloch Area

Abstract: Recent work in the Glen Falloch area has revealed that certain small masses shown as diorite on 1 inch Sheet 46 of the Geological Survey (Scotland) contain rocks belonging to the kentallenite and appinite suites. As these intrusions have not been previously mentioned in geological literature it has been considered worth while placing a short description on record.

On Camarotoechia borealis (von Buch 1834, ex. Schlotheim 1832)

Abstract: The name of this species was proposed by Schlotheim (1832, 65, No. 88), but the history of the form really goes back to Linnaeus. The earlier writers on the Scandinavian Palaeozoic took the name Anomia plicatella Linn. (1758, 702) to cover a great number of different ribbed brachiopods, and referred in their synonymies to the form figured in fig. 5, of tab. v, of Linnaeus's Museum Tessinianum (1753), a work published some years before the adoption of binomial nomenclature. When different authors began to subdivide this group, the name plicatella came to be restricted to a species referable to the genus Spirifer, and though some authors, Wahlenberg (1821, 67) and Dalman (1828, 140, Tab. vi, fig. 2), continued to use the name plicatella in a wide sense, so as to include the species under consideration, the latter seems to have come within the range of forms described by Schlotheim (1813, 36) as Terebratulithes lacunosus. This author apparently had the intention of separating a group of ribbed Silurian brachiopods, under the name of Terebratula borealis, for in the catalogue of his collection (Schlotheim, 1832, 65, No. 88) six specimens from the “Uebergangskalkstein” of Sweden are entered under this title. The term, however, remained a nomen nudum until von Buch (1834) gave an adequate description, and it is to this author that the species should correctly be ascribed. He chose as type a specimen from the Encriniten-Ubergangskalkstein of Gotland, figured in an earlier work by Schlotheim (1822, 68, Taf. xx, fig. 6a—c) as Anomia Terebrat. lacunosus.