noun
definition
A shell or husk; a cod or pod.
definition
A fine-grained sedimentary rock of a thin, laminated, and often friable, structure.
verb
definition
To take off the shell or coat of.
Examples of shales in a Sentence
In the extreme north-east are found the oldest rocks in the state - lower Devonian (the New Scotland beds of New York) and, not so old, an extension of the Lower Carboniferous which underlies the Warrior coalfields of Alabama, and which consists of cherts, limestones, sandstones and shales, with a depth of 800 to 900 ft.
The Mesozoic begins with a Triassic land period in the mainland of Australia; while the islands of the Australasian festoon contain the Triassic marine limestones, which fringe the whole of the Pacific. The Triassic beds are best known in New South Wales, where round Sydney they include a series of sandstones and shales.
In this sea were laid down the shales of the Rolling Downs formation.
Another well-known bed, formerly known as the "Bristol" or "Lias" Bone Bed, exists in the form of several thin layers of micaceous sandstone, with the remains of fish and saurians, which occur in the Rhaetic Black Paper Shales that lie above the Keuper marls in the south-west of England.
Five well-contrasted types of scenery in Derbyshire are clearly traceable to as many varieties of rock; the bleak dry uplands of the north and east, with deep-cut ravines and swift clear streams, are due to the great mass of Mountain Limestone; round the limestone boundary are the valleys with soft outlines in the Pendleside Shales; these are succeeded by the rugged moorlands, covered with heather and peat, which are due to the Millstone Grit series; eastward lies the Derbyshire Coalfield with its gently moulded grasscovered hills; southward is the more level tract of red Triassic rocks.
A series of black shales with nodular limestones, the Pendleside series, rests upon the Mountain Limestone on the east, south and north-west; much of the upper course of the Derwent has been cut through these soft beds.
Mam Tor, or the Shivering Mountain, is made of these shales.
Next in upward sequence is a thick mass of sandstones, grits and shales - the Millstone Grit series.
Schists in the common acceptance of that term are really highly crystalline rocks; fissile slates, shales or sandstones, in which the original sedimentary structures are little modified by recrystallization, are not included in this group by English petrologists, though the French schistes and the German Schiefer are used to designate also rocks of these types.
We may mention also graphiticschists containing dark scaly graphite (often altered forms of carbonaceous shales), and haematite-schists which may represent beds of ironstone.
Towards the Caspian, especially between Petrovsk and the river Sulak, the Cretaceous system is well represented, and upon its rocks rest marls, shales, and sandstones of the Eocene period.
Particulars of the shales which yield oil on destructive distillation are given in the article on paraffin.
The beds are usually thin false-bedded sandstones with an almost complete absence of shales.
The Ecca shales contain some of the best coals of South Africa, but the seams contain much unmarketable coal.
The Ecca series graduates upwards into the highly coloured sandstones and shales of the Beaufort series.
This consists of sandstones and shales with thin seams of coal.
The lower group (Hospital Hill slates) consists of quartzites and shales, resting on the eroded surface of the older granites and schists, and estimated to be from 10,000 to 12,000 ft.
The upper group consists of conglomerates, grits and quartzites with a few bands of shales.
The Pretoria Series, formerly known as the Gatsrand series, consists of repeated alternations of flagstones and quartzites, shales and sheets of diabase.
In the Marico district the shales become highly ferruginous and resemble the Hospital Hill slates of the Witwatersrand series.
The Ecca series, as in the Cape, consists of sandstones and shales.
The Lower Cretaceous consists chiefly of sandstones and shales and the Middle Cretaceous of very fossiliferous limestone.
Lower Cretaceous rocks, consisting of thick limestones, shales and marls, occur in Central Tunisia.
Farther north, in the department of Ancachs, the Mesozoic belt is composed chiefly of sandstones and shales, and the limestones which form so prominent a feature above Lirna seem to have disappeared.
It is formed almost entirely of a succession of sandstones and shales of Cretaceous and Tertiary age - the so-called Carpathian Sandstone - and these are thrown into a series of isoclinal folds dipping constantly to the south.
The soft shales or clays of the hills bounding the valley render these hills especially subject to the action of denudation, and the result, in rounded slopes and easily accessible crests, determines the nature of the easy tracks and passes which intersect them.
These are also called the Upper Limestone Shale, a similar group being found in places below the limestone, and called the Lower Limestone Shale, or, in the north of England, the Tuedian group. Going northward the beds of limestone diminish in thickness, with a proportional increase in the intercalated sandstones and shales, until in Scotland they are entirely subordinate to a mass of coal-bearing strata, which forms the most productive members of the Scotch coalfields.
The Coal Measures, forming the third great member of the Carboniferous series, consist of alternations of shales and sandstones, with beds of coal and nodular ironstones, which together make up a thickness of many thousands of feet - from 12,000 to 14,000 ft.
These very thick seams are, however, rarely constant in character for any great distance, being found commonly to degenerate into carbonaceous shales, or to split up into thinner beds by the intercalation of shale bands or partings.
Cannel coals are generally variable in quality, being liable to change into shales or black-band ironstones within very short horizontal limits.
The actual coal measure strata, consisting mainly of shales and clays, are generally impervious to water, but when strata of a permeable character are sunk through, such as the magnesian limestone of the north of England, the Permian sandstones of the central counties, or the chalk and greensand in the north of France and Westphalia, special methods are required in order to pass the water-bearing beds, and to protect the shaft and workings from the influx of water subsequently.
They are underlain by Jurassic rocks, from beneath which sandstones and shales yielding Glossopteris browniana var.
In the vicinity of Lakes Nyasa and Tanganyika, sandstones and shales of Lower Karroo age and yielding seams of coal are considered to owe their position and preservation to being let down by rift faults into hollows of the crystalline rocks.
In Ankole and Koki rocks consisting of granular quartzite, schistose sandstone, red and brown sandstone, and shales with cleaved killas rest on the Archean platform and possibly represent the Lower Witwatersrand beds of the Transvaal.
The Mataura beds are largely of estuarine formation; they contain oil shales and gas springs.
In southern Otago the Oligocene beds are brown coals and lignites with oil shales, which, at Orepuki, contain 47% of oil and gas, with 8% of water.
There are large deposits of glacial and residual clays and clay shales throughout the state.
The Dwyka Conglomerate forms a narrow outcrop in the north-west, and is known from boreholes to extend over large areas beneath the Ecca Shales and to rest directly on rocks of older age.
It consists mainly of sandstones, but these are often thin-bedded and pass into shales.
The prevailing rocks are sandstones, mudstones and shales.
They are rarely metamorphosed to the point of recrystallization, though locally shales are altered to roofing slates, sandstones are indurated, limestones slightly marblized, and coals, originally bituminous, are changed to anthracite in northern Pennsylvania, and to graphite in Rhode Island.
Former tributaries have given place to others developed with reference to the distribution of more or less easily eroded strata, the present longitudinal valleys being determined by the out-crop of soft shales or soluble limestones, and the parallel ridges upheld by hard sandstones or schists.
Above these, marine Rhaetic beds appear at intervals, notably near Lame, where they are succeeded by Lower Lias shales and limestones.
Carboniferous and Permian strata are possibly represented by some black and grey micaceous shales with beds of coal in the Jurjura.
At Jebel-kahar and west of Traras, Pomel attributes certain conglomerates, red sandstones and purple and green shales to the Permian.
The highest beds, consisting of quartzites, shales, marls and sandstones with the remains of fucoids, are found in the Jurjura and Shellata.
They are usually fine-textured limestones and shales, lying horizontal; the moderate or small relief that they were given by mature preglacial erosion is now buried under the drift, but is known by numerous borings for oil, gas and water.
The carbon-bearing shales, slates and schists, and the limestone, are indications that life was relatively abundant, even though but few fossils are preserved.
In the eastern half of the country the system consists of shales and sandstones chiefly, btit there is some limestone, and coal enough to be of great importance economically, though it makes but a small part of the system quantitatively.
Sweetland Creek shales 20 40