Isle Of Mull Research Articles

A Correlation Between Remanent Magnetism and Petrological and Chemical Properties of Tertiary Basalt Lavas from Mull, Scotland.

A description is given of a petrological examination of a set of normally and reversely magnetized samples from tertiary basalt lava flows on the Isle of Mull. The collected evidence suggests that the normally magnetized samples are most likely to retain part of their original thermo-remanence. The reversely magnetized samples probably acquired their magnetization during a diffusion process in the opaque minerals which took place at an undetermined time after the consolidation of the lavas. The distribution of four features is found to correlate with the two senses of natural remanent magnetization. These features are the alteration products of decomposed olivine, the grain size and crystal form and the internal nature of the primary opaque minerals—especially exsolution of ilmenite from titanomagnetite. Normally magnetized samples are found to contain olivine replaced only by serpentinous minerals together with relatively small well-crystallized, optically-homogeneous (unexsolved) primary magnetite grains. On the other hand, reversely magnetized samples are found to contain olivine replaced by serpentine, secondary iron oxides and a red hydrated iron oxide (iddingsite). In addition, the primary magnetite grains in this group are relatively large, show poor crystal form and are typified by varying amounts of ilmenite exsolved as lamellae in the octahedral planes of the magnetite.

THE MAGNETIC PROPERTIES OF SOME TERTIARY INTRUSIVES OF THE ISLE OF MULL

Summary The magnetic properties of oriented rock samples from some Tertiary igneous intrusions in the Isle of Mull have been investigated. Analysis of the directions of natural residual magnetization, supported by some subsidiary experiments, shows that most of the natural magnetization could have been acquired by cooling in an ambient magnetic field. The analysis reveals two main directions of magnetization, one approximately in the direction of the present terrestrial field and the other in opposition to it. Various possible causes of the reversed magnetization are discussed and a suggestion is put forward that it may have been produced by reversals of the terrestrial field in the past.

X.—Notes on Eocene Homoptera from the Isle of Mull, Scotland

X.—<i>Notes on Eocene Homoptera from the Isle of Mull, Scotland</i>

V.—The Eocene insects of the Ardtun Beds, Isle of Mull, Scotland

(1941). V.—The Eocene insects of the Ardtun Beds, Isle of Mull, Scotland. Annals and Magazine of Natural History: Vol. 7, No. 37, pp. 82-100.

V.—The Eocene Insects of the Ardtun Beds, Isle of Mull, Scotland

V.—<i>The Eocene Insects of the Ardtun Beds, Isle of Mull, Scotland</i>

Beerbachite at the Lizard

IN my paper on the Lizard this rock is mentioned, but without a specific name, for I had not then seen the figure given in 1898 by Rosenbusch (Elemente der Gesteinslehre, 1898, p.51). He calls it Beerbachite, and describes it on p. 219 as one of his Ganggesteine, among those von malchitischem Habitus, quoting an analysis. The name appears to have been given by Chelius to a rock from Frankenstein in the northern Odenwald, where it forms small veins in a gabbro, and has the following analysis: SiO2 = 47·21, Al2O3 = 20·52, Fe2O3 = 7·48, FeO = 5·32, MgO = 4·16, CaO = 8·63, Na2O = 5·17, K2O = 0·33, H2 = 0·34, P2O5 = 0·46, with 0·19 FeS2 and 0·10 hygroscopic water. He states that the rock is fine-grained to compact, not lustrous, grey to pale grey in colour, consisting of a panidiomorphic mixture of labradorite and diallage, with a variable amount of hypersthene and magnetite, and that olivine-bearing varieties occur. In these commonly a brown hornblende replaces the diallage, in which the above-named constituents are pæcilitic. He states that beerbachite also occurs in gabbro near Harzburg and in the Isle of Mull.

XXV.—Notes on the Structure of the Chalk occurring in the West of Scotland

The general succession of the Cretaceous rocks discovered by Professor Judd on Morvern, along the shores of Loch Aline, Argyllshire, and in the Isle of Mull may be briefly summarised:—

II.—On a Granophyre Dyke intrusive in the Gabbro of Ardnamurchan, Scotland

Last year, while on an excursion to Scotland, I visited the Ardnamurchan peninsula, which, as is well known, consists to a great extent of rocks belonging to the gabbro family. On the road leading from the little village of Kilhoan, opposite the Isle of Mull, on the north coast, a small quarry has been opened for road-metal, which shows an exquisite section of a granophyre dyke intrusive in a dark and almost black fine-grained rock, which the microscopic examination proved to be a gabbro. This is, therefore, a similar occurrence to that of Barnavave, Carlingford, Ireland, which has been admirably described by Professor Sollas, and also that of Strath in the Isle of Skye, of which Mr. Harker has given us a detailed account. As occurrences of this kind seem to be rather rare and, as far as I am aware, hitherto not known from Ardnamurchan, I may be excused for calling your attention to the following short description of these rocks, although there is but little to be added to the results attained by the skilful researches of the above-mentioned authors, and it only shows again that on Ardnamurchan we are to expect very nearly the same geological phenomena as in the adjacent islands, in particular in Skye and Rum.

Lobster Culture in the Isle of Mull

Lobster Culture in the Isle of Mull

On the large Porphyritic Crystals of Felspar in certain Basalts of the Isle of Mull

In the basaltic lavas of Iceland certain porphyritic crystals of unusually large dimensions, occur embedded in the matrix of the rock, and from an early date have received the notice of writers on the geology of that island. Amongst these authors might be mentioned :—Professor Forchhammer, Dr. F.A. Genth, M. A. Damour, Prof. Zirkel, M. P. Schirlitz, and M. R. Bréon.

Remarks on some Fossil Leaves from the Isle of Mull (Scotland).

Journal Article Remarks on some Fossil Leaves from the Isle of Mull (Scotland) Get access J. Starkie Gardner, F.L.S., F.G.S. J. Starkie Gardner, F.L.S., F.G.S. Search for other works by this author on: Oxford Academic Google Scholar Botanical Journal of the Linnean Society, Volume 22, Issue 145, July 1886, Pages 219–221, https://doi.org/10.1111/j.1095-8339.1886.tb00464.x Published: 05 January 2009

Metamorphic Origin of Granite.—Prehistoric “Giants”

Metamorphic Origin of Granite.—Prehistoric “Giants”

Notice of a Diatomaceous Earth found in the Isle of Mull

Notice of a Diatomaceous Earth found in the Isle of Mull

On Tertiary Leaf-Beds in the Isle of Mull

The Island of Mull is deeply indented in a direction nearly east and west by two long arms of the sea, Loch na Kael and Loch Scridden, forming the three natural divisions described by Macculloch as the Northern, the Middle, and the Southern Trap Districts. The Northern division is of comparatively low elevation, and composed chiefly of terraces of trap. I am not aware that it has ever been carefully examined in detail; but it has been understood not to present any features of remarkable geological interest. The middle division is a lofty and rugged tract, containing the fine summits of Ben Tulla and Ben More, the latter being one of the highest mountains on the western coast, and visible from a great distance among the Hebrides. These mountains are raised far above the highest level to which the traps of the island attain. A portion of it is coloured by Macculloch as syenite, and specimens in my possession from the Peak of Ben More belong to this class of rock. But the whole of the long and high promontory stretching westward from the flank of Ben More, and lying between Loch na Kael and Loch Scridden, exhibits great terraces of trap, piled one above the other, and terminates in that striking headland of Bourg or Gribon, whose lofty horizontal lines rise from the ocean with almost perfect regularity in a pyramidal form, until the final cap attains an elevation of about 2000 feet. The southern division has been long