Features Of Geological Structure Research Articles

SOME APPLICATIONS OF AERIAL INFRARED IMAGERY

ABSTRACT This paper, by showing various applications of infrared imagery, is intended to stimulate thinking among geographers toward the potentiality of airborne infrared imaging systems as geographic research tools. By making use of the capabilities of airborne infrared systems the researcher will gain valuable supplemental information which in many cases is unattainable from conventional aerial photography. The geographer interested in earth science investigations will find infrared imaging systems quite valuable in the determination of certain geological formations and structural features. Hydrographic features, owing to the variation in land-water heat capacities, show quite well on most infrared imagery. Certain types of vegetation may be differentiated more readily in the infrared, than in the visible, portion of the electromagnetic spectrum. Other applications to archeological research, rural applications, such as wildlife inventories, and urban investigations, such as commuter studies are also suggested. High resolution infrared radiometers are already being used to great advantage in meteorological studies from orbital altitudes. By applying infrared imaging devices in their research geographers, while gaining valuable supplemental information, may provide data useful in systems development. At present, the geographer may find it difficult to apply infrared sensors to his research because of the relative expense of the system or U.S. Department of Defense security classification of the imagery, but he should be prepared to employ this new tool as more infrared imagery is declassified and more systems come into use.

THE DISTRIBUTION OF TIN-ORE DEPOSITS WITHIN FOLDED ZONES

The author makes an attempt to establish the general laws governing distribution in time and position of tin-bearing centers and areas in the course of the geological history of the earth; on the basis of methods of regional metallogenic analysis, developed in the U. S. S. R. by a group of scientists under the guidance of G. A. Bilibin. The author has considered the principal geotectonic and structural geological features and factors controlling the regular occurrence during a certain stage of development of a folded zone, of a certain type of tin-bearing intrusions and, hence, of a certain mineralogical-geochemical type of tin deposits. Considerable tin concentration evidently did not take place during the initial and early stages in development of folded zones. The middle stages of development, corresponding to the period of transformation of a geosyncline into a folded belt, were highly productive with regard to tin. Tin accumulations are associated with syntectonic batholithic intrusions of acid and ultra-acid “potassium” granites. Tin-bearing batholiths and their linear belts are controlled by regional ancient deepseated fractures, confined either to the points of anticlinorium contact (central upheavals) with the adjacent inner synclinoria or to the contact points of downwarpings with consolidated geoanticlinal zones. The late stages of development of geosynclinal regions corresponding to the period of consolidation of the folded territory also produced considerable tin concentrations. According to the depth of the controlling intrusions, the showings of tin occurrences belonging to the late stages of development are subdivided into two natural groups: the hypabyssal and the subvolcanic. Tin ore-bearing areas belonging to the late stages of development, are confined to the following two types of geotectonic environments: 1) the mobilized marginal parts of geosynclines in places of their contact with projections of platforms of intermediate massifs (blocks) and consolidated geoanticlinal structures. A number of large tin ore-bearing areas is confined to structures of late superimposed graben-like downwarpings (complicated by fractures) with a powerful development of terrestrial volcanism; 2) the inner portions of geosynclines, where the tinore-bearing areas are confined to structural facial zones of inner synclinoria, more frequently in places of contact of the latter with zones of central uplifts. The distribution of the world tin resources in the course of geological times is as follows: The Precambrian: 3. 3 percent (Nigeria, Rhodesia, Congo, Union of South Africa); The Caledonian folding: 6. 6 percent (Africa and Australia); The Variscian folding: 18.1 percent (Cornwall, Erzgebirge, the Pyrenees, Australia, Tasmania); The Kimmeridgian folding: 63.1 percent (South- Eastern Asia). Simultaneously with the growth of commercial tin concentrations from the Pre-Cambrian to the Mesozoic, complication of the nature of tin mineralization is observed; from tin-bearing pegmatites in the Pre-Cambrian to complex multicomponent deposits in the Mesozoic and the Cenozoic. Author

The Prehistory of the Isle of Man

‘Rising from the middle of the Irish Sea, within sight of each of the three Kingdoms, with a history and associations so distinct, yet so intimately linked with those of the rest of Britain, this interesting Island presents in its geological structure features which connect it alike with England, Scotland, and Ireland, while at the same time it retains a marked individuality in regard to some of the rocks that form its framework.’—Sir Archibald Geikie.The prehistory no less than the geology of the Isle of Man is of absorbing interest from its geographical position in relation to the larger units of the British Isles. The island is placed (fig. 1) at an equal distance (31 miles) between the coasts of Ireland and of Cumberland; its northern tip, the Point of Ayre, reaches to within 16 miles of Wigtonshire, and Anglesey lies 45 miles to the south of Langness Point. An observer on Snaefell (2034 feet) can view England, Scotland, Ireland and Wales in one sweep. Since the first settlement of the island, cultural and ethnic influences have approached from all directions, but its size (227 sq. miles) and the distance of sea which isolates it from the coasts of the mainlands have been sufficient to ensure vigorous local developments. The interaction of British and Irish influences and the occasional insular developments are the chief features of the prehistory of the island.Apart from a triangle of flat ground to the north, broken only by the Bride Hills (200–300 feet), and so far as its drift deposits are concerned, relatively recent in origin, the island consists almost entirely of slate diversified by local intrusions of igneous rocks (granite and diabase), by the sandstone of the Peel area, and by the carboniferous limestone of the Castletown district in the south. Most of the area of older rocks lies above the 400 foot contour and quite large areas are more than 1000 feet above sea level. The mountainous mass of the island, divided by the valley between Douglas and Peel, remained almost uninhabited throughout prehistoric and historic times.

A Reconnaissance Study of the Salado Arch, Nuevo Leon, and Tamaulipas, Mexico

In the part of Northeastern Mexico that borders the Rio Grande are a number of geological structural features which may mark important oil possibilities. The Salado Arch is a prominent anticline with northwesterly axial trend, approximately 100 miles long, in Nuevo Leon and Tamaulipas. Upper Cretaceous rocks are exposed along the crest of the arch and to the west where an east-facing escarpment marks the westward dip of the beds. A few miles east of the axis of the arch and running parallel to it is a very prominent west-facing escarpment, the upper rocks of which are of Eocene age. A measured section of the latter shows a total thickness of 5,422 feet. The anticline plunges southeast and the steeper limb of the fold is on the basinward rather than the mountainward side. rospects of oil production are favorable on account of the probable occurrence within drilling distance of petroliferous formations equivalent to those of the Tampico embayment.

On the Connexion of the Geological Structure and Physical Features of the South-east of England with the Consumption Death-rate

Abstract T he author stated that his investigation of this subject, which was carried on in conjunction with Dr. Buchanan, was suggested by the fact that improved drainage had been found to exert a marked influence upon the average number of deaths by consumption in certain districts. The chief result arrived at by an examination of fifty-eight registration districts in Kent and Sussex was, that “wetness of the soil is a great cause of consumption;” and this depends not only upon the perviousness or imperviousness of the soils, but upon their position as regards elevation and slope.

Notes on the Wealden Strata of the Isle of Wight, with an account of the Bones of Iguanodons and other Reptiles discovered at Brook Point and Sandown Bay

The author commenced with some remarks on the general geological structure and picturesque features of the Isle of Wight, and then proceeded to direct special attention to some extensive ledges of low rocks visible from a considerable distance, and occurring seaward of Brook Point, a low promontory near and to the east of Compton Bay. The face of the cliff is here formed by the bassetting edges of the Wealden clays and sands, which alternate with occasional layers of argillaceous shelly limestone, rolled blocks of which are strewed along the beach. This limestone is formed of the shells of Paludina, Cyclas and other Wealden species, and is in every respect identical with the Petworth marble and Ashburnham beds of Sussex. The cliff at Brook Point is between thirty and forty feet high, and is capped by an alluvial bed of loam, sand and gravel. It is composed of beds of laminated clay and shale, with sands and sandstones of a bluish and reddish-gray colour, and these are interspersed with layers and isolated masses of lignite and lumps of iron pyrites. East of the Point a chine or chasm occurs, from the summit of which a stream gushes out and dashes down the face of the cliff to the sea-shore. This stream rises from beneath the sand beds islands, and flows through the alluvial gravel to the summit of the cliff. The auhtor then proceeded to qoute a graphic description of this spot, written nearly thirty-five years ago by Mr. Webster,