Cambrian sentence example
The breaking up of the old Archean foundation block began in Cambrian and Ordovician times.
We may conclude, therefore, that they were preceded, in Cambrian times or earlier, by Arthropods possessing well developed appendages on all the trunk-segments.
The higher steppes, as far as they are known, consist of Ordovician and Cambrian rocks, with an average elevation of 1500 to 3000 ft.
A narrow Cambrian sea must have extended across central Australia from the Kimberley Goldfield in the north-west, through Tempe Downs and the Macdonnell chain in central Australia, to the South Australian highlands, central Victoria at Mansfield, and northern Tasmania.
Cambrian rocks occur in each of these districts, and they are best developed in the South Australian high= lands, where they include a long belt of contemporary glacial deposits.Advertisement
It has a station on the Cambrian line between Moat Lane and Brecon, and two others (high and low levels) at Builth Road about 14 m.
There are important quarries in Franklin (disambiguation)|Franklin county (at Swanton), the stone being a dark Chazy limestone, in which pink and red ("jasper," "lyonnaise" and "royal red") marbles of Cambrian age are found.
Barmouth is a favourite bathing place, on the Cambrian railway.
Rhayader is a station on the Cambrian railway.
Over the greater part of the Cambrian country the strata are still nearly as flat as when they were first laid down, and the deposits, even of the Cambrian period, are as soft as those of the Mesozoic and Tertiary formations in England.Advertisement
The Cambrian is represented by blue clays, ungulite sandstones and bituminous slates in Esthonia and St Petersburg.
Over a large part of Siberia and in the north of China, even the Cambrian beds still lie as horizontally as they were first laid down.
Little is known of the early geological history of Asia beyond the fact that a large part of the continent was covered by the sea during the Cambrian and Ordovician periods.
Here the folded Archean rocks are overlaid by Cambrian and Ordovician beds, which still lie for the most part flat and undisturbed.
In the northern unfolded region great flows of basic lava lie directly upon the Cambrian and Ordovician beds of Siberia, but are certainly in part of Tertiary age.Advertisement
The occurrence of commercially valuable petroleum is, however, comparatively limited, hitherto exploited deposits being confined to rocks younger than the Cambrian and older than the Quaternary, while the majority of developed oilfields have been discovered north of the equator.
The Cambrian Annals give 570 as the year of his death.
In all species it has the same shape, a shape which has been retained in the adult by the Lower Cambrian genus Iphidea.
The protegulum has been found in members of almost all the families of Brachiopod, and it is thought to occur throughout the group. It resembles the shell of the Cambrian .4 genus Iphidea [Paterina], and the Phylembryo is frequently referred to as the Paterina stage.
Brachiopods first appear in the Lower Cambrian, and reached their highest development in the Silurian, from which upwards of 2000 species are known, and were nearly as numerous in the Devonian period; at present they are represented by some 140 recent species.Advertisement
Undue stress is often laid on the fact that Lingula has come down to us apparently unchanged since Cambrian times, whilst Crania, and forms very closely resembling Discina and Rhynchonella, are found from the Ordovician strata onwards.
Galena occurs in veins in the Cambrian clay-slate, accompanied by copper and iron pyrites, zinc-blende, quartz, calcspar, iron-spar, &c.; also in beds or nests within sandstones and rudimentary limestones, and in a great many other geological formations.
Bergeron has shown that the gneiss and schist which form so much of the chain consist, in part at least, of metamorphosed Cambrian beds.
The genus Agnostus, which belongs to the last category, occurs abundantly in Cambrian strata and is one of the earliest forms A known.
This would lead to the supposition that the great development of metasomatic carapace is a primitive and not a late character, were it not for the fact that Paradcxides and Atops, with an inconspicuous telsonic carapace and numerous free somites, are also Cambrian in age, the latter indeed anterior in horizon to Agnostus.Advertisement
The crystalline rocks are succeeded by beds which have been referred to the Cambrian and Silurian systems. In the valley of the Trombetas, one of the northern tributaries of the Amazon, fossils have been found which indicate either the top of the Ordovician or the bottom of the Silurian.
Sedgwick, who considered it to be the upper part of his Cambrian System.
Overlying these amongst the Palaeozoic rocks, we meet in many parts of Japan with slates and other rocks possibly of Cambrian or Silurian age.
Pop. (1901) 9579 It is on a branch from the Chester line of the Great Western railway, and on the Cambrian main line.
The Cambrian railway engine and carriage works are here; and there are tanneries, malting works, machinery works and iron foundries.
It is the terminal station of the Cambrian railway, and also of the Manchester and Milford line.
They are found in formations of all ages from the Cambrian to those which are accumulating at the present day.
No Cambrian rocks have as yet been discovered, but the Ordovician system is represented by the Aorere beds in the north-western part of the South Island.
The Paleozoic sediments, ranging in age from Cambrian to Permian, occupy the Great Valley, the Valley Ridges and the plateaus still farther west.
The greater part of the Ardennes is occupied by a large area of Devonian beds, through which rise the Cambrian masses of Rocroi and Stavelot, and a few others of smaller size.
Slates belong mostly to the older geological systems, being commonest in Pre-Cambrian, Cambrian and Silurian districts, though they may be found of Carboniferous or even of Tertiary age, where mountain-building processes have folded and compressed these more recent formations.
In the east portion of the mountainous region the soil so well adapted to peach culture contains much clay, together with particles of Cambrian sandstone.
Miller's opinion, their separation into the families now living may have already taken place in the Cambrian period.
Such restorations are possible because of the intimate fitness of animals and plants to their environment, and because such fitness has distinguished certain forms of life from the Cambrian to the present time; the species have altogether changed, but the laws governing the life of certain kinds of organisms have remained exactly the same for the whole period of time assigned to the duration of life; in fact, we read the conditions of the past in a mirror of adaptation, often sadly tarnished and incomplete owing to breaks in the palaeontological record, but constantly becoming more polished by discoveries which increase the understanding of life and its all-pervading relations to the non-life.
Walcott has described a tiny lamellibranch (Modioloides) from the inferior Cambrian, and he reports the gastropod (?) genus Chuaria from the preCambrian.
The loss of the power to coil, observed in the terminals of many declining series of gastropods from the Cambrian to the present time, and the similar loss of power among Natiloidea and Ammonoidea of many genetic series, as well as the ostraean form assumed by various declining series of pelecypods and by some brachiopods, may be cited as examples.
This is not due to environmental conditions solely, because senescent branches of normal progressive groups are found in all geologic horizons, beginning, for gastropods, in the Lower Cambrian.
It is with respect to this number of segments that respectively constitute the pygidium and the midregion of the body that Trilobites differ most markedly from each other; and it is a singular fact that the extremes in structural organization in this particular to be met with in the Trilobita are found side by side in strata of Cambrian age.
There is only one line of railway, over which several companies, however, have running powers, so that the town may be reached by the Brecon & Merthyr railway from Merthyr, Cardiff and Newport, by the Cambrian from Builth Wells, or by the Midland from Hereford and Swansea respectively.
The erosion of the region must have been far advanced, perhaps practically completed, in very ancient times, for the even surface of the peneplain is overlapped by fossiliferous marine strata of early geological date (Cambrian); and this shows that a depression of the region beneath an ancient sea took place after a long existence as dry land.
A few geologists regard the sedimentary rocks here classed as Keweenawan as Palaeozoic; but they have yielded no fossils, and are unconformable beneath the Upper Cambrian, which is the oldest sedimentary formation of the region which bears fossils.
In all but a few places where their relations are known, the Proterozoic rocks are unconformable beneath the Palaeozoic Where conformity exists the separation is made on the basis of fossils, it having been agreed that the oldest rocks carrying the Olenellus fauna are to be regarded as the base of the Cambrian system.
Cambrian System.The lower part of the Cambrian system, characterized by the Olenellus fauna, is restricted to the borders of the continent, where it rests on the older rocks unconformably in most places.
In Wisconsin, where the Upper Cambrian only is present, the thickness is about Iooo ft.
The Cambrian formations have not been notably metamorphosed, except in a few regions where dynamic metamorphism has been effective.
Ordovician System.The succeeding Ordovician (Lower Silurian) system of rocks is closely connected with the Cambrian, geographically, stratigraphically and faunally.
Its distribution is much the same as that of the Upper Cambrian, with which it is conformable in many places.
The outcrops of the system appear for the most part in close association with the outcrops of the Cambrian system, but the system appears in a few places where the Cambrian does not, as in southern Ohio and central Tennessee.
The life, like that of the later Cambrian, was singularly cosmopolitan, being in contrast with the provincial character of the life of the earlier Cambrian and of the early (Upper) Silurian which followed.
Beside the expansion of types which abounded in the Cambrian, vertebrate remains (fishes) are found in the Ordovician.
The departure of the Ordovician life from that of the Cambrian was perhaps most pronounced in the great development of the molluscs and crinoids (including cystoids), but corals were also abundant for the first time, and graptolites came into prominence.
This older classification, which has little support except that which is traditional, is still adhered to by many geologists; hut the fact seems to be that the system is set off from the Pennsylvanian (Upper Carboniferous) more sharply than the Cambrian is from the Ordoviciao, the Silurian from the Devonian, or the Devonian from the Mississippian.
The explanation of the apparent conformity of the strata from the Cambrian to the Pennsylvanian in some parts of the west, with no fossils defining with certainty any horizon between the Ordovician and the Mississippian, is one of the open problems in the geology of the United States.
This section is fairly representative for the Appalachian Mountain tract, though the Cambrian is often more fully represented.
A series of quartzites and slates referred to the Cambrian, and holding numerous and important veins of auriferous quartz, characterize its Atlantic or southeastern side, while valuable coal-fields occur in Cape Breton and on parts of its shores on the Gulf of St Lawrence.
This latest and also highest range was formed by tremendous thrusts from the Pacific side, crumpling and folding the ancient sedimentary rocks, which run from the Cambrian to the Cretaceous, and faulting them along overturned folds.
The latter are represented in the Upper Cambrian formations, together with Lamellibranchia and Gastropoda, and there are no earlier Molluscan fossils than these.
It is formed chiefly of slates, grits and porphyries of the Cambrian and Silurian systems. It consists of five "ribs" converging at the summit, 3560 ft.
The age of a great part of the Palaeozoic belts is somewhat uncertain, but Permian, Carboniferous, Devonian and Silurian fossils have been found in various parts of the chain, and it is not unlikely that even the Cambrian may be represented.
In the Ardennes the rocks which constitute the ancient mountain chain belong chiefly to the Devonian System, but Cambrian beds rise through the Devonian strata, forming the masses of Rocroi, Stavelot, &c., which appear to have been islands in the Devonian sea.
The Ordovician and Silurian are absent here, and the Devonian rests unconformably upon the Cambrian; but along the northern margin of the Palaeozoic area, Ordovician and Silurian rocks appear, and beds of similar age are also exposed farther north where the rivers have cut through the overlying Tertiary deposits.
The Cambrian, for example, is exposed at Leimitz near Hof in the Frankenwald, and the important coal-field of the Saar lies on the southern side of the Hunsruck, while Ordovician and Silurian beds have been found in several localities.
There the boulder clay lies immediately on the primitive rock, except in the south-western corner of the island, where a series of strata appear belonging to the Cambrian, Silurian, Jurassic and Cretaceous formations, the true Coal formation, &c., being absent.
Such beds of salt are found in strata of very varied geological age; the Salt Range of the Punjab, for instance, is probably of Cambrian age, while the famous saltdeposits of Wieliczka, near Cracow, have been referred to the Pliocene period.
The Central Wales section of the London & North-Western railway from Craven Arms to Swansea crosses the north-west corner of the county, and is intersected at Builth Road by a branch of the Cambrian, which, running for the most part on the Radnorshire side of the Wye, follows that river from Rhayader to Three Cocks; the Midland railway from Hereford to Swansea runs through the centre of the county, effecting junctions at Three Cocks with the Cambrian, at Talyllyn with the Brecon & Merthyr railway (which connects the county with the industrial areas of East Glamorgan and West Monmouthshire), and at Capel Colbren with the Neath and Brecon line.
Here it projects in irregular bastions and buttresses, there retires into deep recesses and tunnels, but shows everywhere a ruggedness of aspect eminently characteristic. In striking contrast to these precipices are those of the Cambrian red sandstone a few miles to the east.
On the west the most notable cliffs south of those of Cape Wrath and the Cambrian sandstones of Sutherland are to be found among the basaltic islands, particularly in Skye, where a magnificent range of precipices rising to moo ft.
Archean gneiss, Cambrian sandstone, Silurian quartzite, limestone and schist, Jurassic sandstone and limestone, Cretaceous sandstone, and Tertiary basalts, gabbros, and granitic rocks all enter into the composition of the islands.
The Cambrian system - including the Upper (Durness-Eriboll Limestone) and the Lower (Serpulite grit, Fucoid Beds, Quartzite) - forms a narrow band which can be traced for too m.
Rocks of Cambrian age have not been identified elsewhere in Scotland, though it may ultimately be shown that the quartzites and limestones of the Central Highlands are equivalents of those of the north-west coast.
In the same year Sedgwick introduced the name "Cambrian series" for the older and lower members.
Murchison published his Silurian system in 1839, wherein he recognized the Cambrian to include the barren slates and grits of Harlech, Llanberis and the Long Mynd.
So far, the two workers had been in agreement; but in his presidential address to the Geological Society of London in 1842 Murchison stated his opinion that the Cambrian contained no fossils that differed from those of the Lower Silurian.
Salter, the palaeontologist; and in 1852 he included the Llandeilo and Bala beds (Silurian) in the Upper Cambrian.
Meanwhile in Europe and America fossils were being collected from similar rocks which were classed as Silurian, and the use of "Cambrian" was almost discarded, because, following Murchison, it was taken to apply only to a group of rocks without a characteristic fauna and therefore impossible to recognize.
Most of the Cambrian rocks were coloured as Silurian on the British official geological maps.
Nevertheless, from 1851 to 1855, Sedgwick, in his writings on the British palaeozoic deposits, insisted on the independence of the Cambrian system, and though Murchison had pushed his Silurian system downward in the series of rocks, Sedgwick adhered to the original grouping of his Cambrian system, and even proposed to limit the Silurian to the Ludlow and Wenlock beds with the May Hill Sandstone at the base.
This attitude he maintained until the year of his death (1873), when there appeared his introduction to Salter's Catalogue of Cambrian and Silurian Fossils.
To-day the recognition of the earliest fossil-bearing rocks, below the Llandeilo formation of Murchison, as belonging to the Cambrian system, and the threefold subdivision of the system according to palaeontological evidence, may be regarded as firmly established.
Renevier proposed to use Silurique to cover the same period with the Cambrian as the lowest series, but these differences of treatment are merely nominal.
Jules Marcou and others have used Taconic (Taconian) as the equivalent of Cambrian, and C.Lapworth proposed to apply the same term to the lowest sub-division only; he had also used "Annelidian" in the same sense.
The lithological characters of the Cambrian rocks possess a remarkable uniformity in all quarters of the globe.
In Scotland, North America and Canada important deposits of limestone occur and subordinate limestones are found in the Cambrian of central Europe.
In the Cambrian limestones, as in their more recent analogues, layers and nodules of chert and phosphatized material are not wanting.
In the Cambrian of Brittany there are acid lavas and tuffs.
These formations lie at the base of the lowest Cambrian strata and may possibly be included in the pre-Cambrian, though in Norway they are clearly resting upon a striated floor of crystalline rocks.
With the exception of the vertebrates, every one of the great classes of animals is represented in Cambrian rocks.
Medusa-like casts have been found in the lower Cambrian of Scandinavia (Medusina) and in the mid-Cambrian of Alabama (Brooksella).
Corals, Archaeocyathus, Spirocyathus, &c., lived in the Cambrian seas along with starfishes (Palaeasterina), Cystideans, Protocystiles, Trochocystites and possibly Crinoids, Dendrocrinus.
In the Cambrian period trilobites had already attained their maximum size; some species of Paradoxides were nearly 2 ft.
Many of the Cambrian trilobites appear to have been blind, and they had not at this period developed that flexibility in the carapace that some forms acquired later.
Certain markings on slates and sandstones, such as the "fucoids" of Scandinavia and Scotland, the Phycoides of the Fichtelgebirge, Eophyton and other seaweed-like impressions, may indeed be the casts of fucoid plants; but it is by no means sure that many of them are not mere inorganic imitative markings or the tracks or casts of worms. Oldhamia, a delicate branching body, abundant in the Cambrian of the south-east of Ireland, is probably a calcareous alga, but its precise nature has not been satisfactorily determined.
Wherever the Cambrian strata have been carefully studied it has now been found possible and convenient to arrange them into three series, each of which is characterized by a distinctive genus of trilobite.
Thus we have a Lower Cambrian with Olenellus, a middle series with Paradoxides and an Upper Cambrian with Olenus.
It is true that these fossils are not invariably present in every occurrence of Cambrian strata, but this fact notwithstanding, the threefold division holds with sufficient constancy.
The table on p. 660 contains the names that have been applied to the subdivisions of the Cambrian strata in the areas of outcrop in Wales and England; at the same time it indicates approximately their relative position in the system.
The Cambrian rocks of Ireland, a great series of purple and green shales, slates and grits with beds of quartzite, have not yet yielded sufficient fossil evidence to permit of a correlation with the Welsh rocks, and possibly some parts of the series may be transferred in the future to the overlying Ordovician.
The Cambrian system is covered by his stages "B" and "C"; the former a barren series of conglomerates and quartzites, the latter a series of grey and green fissile shales 1200 ft.
Here the Cambrian system is only distinguished clearly on the eastern side, where the three subdivisions are found in a thin series of strata (400 ft.), in which black concretion-bearing shales play an important part.
On the Norwegian side the Cambrian is perhaps represented by the Roros schists which lie at the base of a great series of crystalline schists, the probable equivalent of Ordovician and Silurian rocks.
The Cambrian rocks in this region are nearly all soft sediments, some 600 ft.
This division is the equivalent of the Lower Cambrian.
Farther south, around the old lands of Languedoc, equivalents of the two upper divisions of the Cambrian have been recorded; and the uppermost members of the system appear in Herault.
Patches of Cambrian rocks are found in the Pyrenees.
Cambrian rocks occur also in the provinces of Seville and Ciudad-Real.
Upper Cambrian strata have been found in upper Alemtejo in Portugal.
In the Thiiringer Wald are certain strata, presumably Cambrian since the uppermost beds contain the Euloma-Niobe fauna.
Sardinia contains both middle and upper Cambrian.
The Cambrian system is represented in the Salt Range of India by the Neobolus or Khussack beds, which may possibly belong to the middle subdivision.
In South America upper Cambrian rocks have been recorded from north Argentina.
The Lower Cambrian has been found at various places in South Australia; and in Tasmania a thick series of strata appears to be in part at least of Upper Cambrian age.
The Cambrian rocks previ-, ously described are all such as would result from deposition, in comparatively shallow seas, of the products of degradation of land surfaces by the ordinary agents of denudation.
Evidences of shallow water conditions arc abundant; very frequently on the bedding surfaces of sandstones and other rocks we find cracks made by the sun's heat and pittings caused by the showers that fell from the Cambrian sky, and these records of the weather of this remote period are preserved as sharply and clearly as those made only to-day on our tidal reaches.
No Cambrian rocks are such as would be formed in the abysses of the sea - although the absence of well-developed eyes in the trilobites has led some to assume that this condition was an indication that the creatures lived in abyssal depths.
At the close of the pre-Cambrian, many of the deposits of that period must have been elevated into regions of fairly high ground; this we may assume from the nature of the Cambrian deposits which are mainly the product of the denudation of such ground.
Over the land areas thus formed, the seas in Cambrian time gradually spread, laying down first the series known as Lower Cambrian, then by further encroachment on the land the wider spread Upper Cambrian deposits - in Europe, the middle series is the most extensive.
Consequently, Cambrian strata are usually unconformable on older rocks.
Compared with some other periods, the Cambrian was free from extensive volcanic disturbances, but in Wales and in Brittany the earlier portions of this period were marked by voluminous outpourings; a condition that was feebly reflected in central and southern Europe.
No definite conclusions can be drawn from the fossils as to the climatic peculiarities of the earth in Cambrian times.
Considerable variations occur in the thickness of Cambrian deposits, which may generally be explained by the greater rapidity of deposition in some areas than in others.
Any attempt to picture the geographical conditions of the Cambrian period must of necessity be very imperfect.
Further, there is a marked likeness between the Cambrian of western Europe and eastern America; many fossils of this period are common to Britain, Sweden and eastern Canada; therefore it is likely that a north Atlantic basin existed.
Prof. Kayser suggests that there was also a Pacific basin more extensive than at present; this is borne out by the similarity between the Cambrian faunas of China, Siberia and Argentina.
Cambrian, Silurian, Devonian and Carboniferous deposits are found on the coasts of the Gulf of Finland and Lake Ladoga, and also along the coasts of the Arctic Ocean (probably Devonian), and in the Kjolen.
The lines of the Cambrian railway serve North and Mid-Wales, and branches of the London & North-Western and the Midland penetrate into South Wales as far as Swansea.
The Cambrian formation generally occurs along with the Ordovician, and consists of many divisions.
The oldest beds which have hitherto yielded fossils, belong to the Ordovician system, but it is highly probable that the underlying " Haimantas " of the central Himalaya are of Cambrian age.
Large areas have been referred to the Cambrian, but it is only at Villa Boim, about 6 m.
The Palaeozoic beds have yielded fossils of Cambrian, Ordovician, Devonian and Carboniferous age.
In southern Bolivia Cambrian and Ordovician beds form the greater part of the eastern Andes, but farther north the, Devonian and Carboniferous are extensively developed, especially in the northeastern ranges.
The benevolent institutions include the general hospital, founded in 1817, removed to the present site in 1867, extended by the addition of two wings in 1878 and of an eye department in 1890; a convalescent home for twenty patients from the hospital only (1903); the Royal Cambrian Institution for the Deaf and Dumb, established in 1847 at Aberystwyth, removed to Swansea in 1850, and several times enlarged, so as to have at present accommodation for ninety-eight pupils; the Swansea and South Wales Institution for the Blind, established in 1865 and now under the Board of Education; the Swansea and South Wales Nursing Institute (1873), providing a home for nurses in the intervals of their employment; a nursing institution (1902) for nursing the sick poor in their own homes, affiliated with the Queen's Jubilee Institute of London; the Sailors' Home (1864); a Sailors' Rest (1885); and a Mission to Seamen's Institute (1904).
Cambrian rocks have not yet been discovered in New South Wales; but Pittman has recorded an Agnostus from Mandurama, near Orange.
The Phyllopoda, Ostracoda and Cirripedia (Thyrostraca) are represented in Cambrian or Silurian rocks by forms which seem to have resembled closely those now existing, so that palaeontology can have little light to throw on the mode of origin of these groups.
There is considerable reason for believing that the Ceratiocaridae, which are found from the Cambrian onwards, were allied to the existing Nebalia, and may possibly include the forerunners of the true Malacostraca, but nothing is definitely known of their appendages.
Around the western and northern edge of the Old Red Sandstone plain the underlying Silurian rocks (and even the Cambrian and Archaean in places) have been bent up so that their edges form hills of singular abruptness and beauty.
Lake Superior lies in a deep rift in rocks principally of Archean and Cambrian age, of the Laurentian, Huronian and Keweenaw formations, rich in minerals that have been extensively worked.
Regarding now the outcrops of bed-rock, there are exposures of Algonkian (doubtful, and at most a mere patch on Pilot Knob), Archean, Cambrian, Ordovician, Silurian, Devonian, sub-Carboniferous and Carboniferous.
The haematites are found not only in the archean porphyries but in Cambrian limestone and sandstone, and in the sub-Carboniferous formations; while the limonites are confined almost exclusively to the Cambrian.
In the first, of which St Francois county is the centre, it occurs generally alone disseminated in Cambrian limestone; in the second, of which the counties immediately south-west of Jefferson City are the centre, Y.VIII.
Both groups make their first appearance together near the end of the Cambrian; but while in the succeeding Ordovician and Silurian the Dendroidea are comparatively rare, the Graptoloidea become the most characteristic and, locally, the most abundant fossils of these systems.
The fact that no Cambrian strata have been established by palaeontological evidence in the west of Ireland has made it equally difficult to establish any pre-Cambrian system.
Their rocks have been variously held to be Archean, Cambrian and Silurian, and their general trend has undoubtedly been determined by post-Silurian earth-movements.
The radial or fan-shaped markings known as Oldhamia were first detected in this series, but are now known from Cambrian beds in otter countries; in default of other satisfactory fossils, the series of Bray and Howth has long been held to be Cambrian.
I Silurian (and Cambrian?) "Dalradian" Metamorphic Series .Diorite and allied Basic Rocks '?-t =i=' Granite and allied Acid Rocks montory the conglomerates of this period rest with striking unconformity on the Dingle Beds and Upper Silurian series.
In Bohemia and Moravia the whole of the beds from the Cambrian to the Lower Carboniferous are of marine origin; but after the Carboniferous period the area appears to have been dry land until the beginning of the Upper Cretaceous period, when the sea again spread over it.
In the apparent absence of any Cambrian formation above them, there is little doubt that these rocks are Archean, although this cannot be absolutely proved.
They are unfossiliferous, and in the absence of undoubted Cambrian, Ordovician and Silurian strata in Africa they may be regarded as of older date than any of these formations.
Some unfossiliferous conglomerates, sandstones and dolomites in South Africa and on the west coast are considered to belong to the Cambrian, Ordovician and Silurian formations, but merely from their occurrence beneath strata yielding Devonian fossils.
The Lower Palaeozoic systems begin with the Cambrian, which are found in northern Tasmania near Latrobe, and contain Cambrian fossils as Dikelocephalus Tasmanicus and Conocephalites stephensi.
The inner or eastern ridge farther north of Argentina consists of crystalline rocks with infolded Ordovician and Cambrian beds, often overlaid unconformably by a sandstone with plant-remains (chiefly Rhaetic).
All the geological systems,from the Cambrian to the Carboniferous, are represented and they are all strongly folded, the folds leaning over towards the west.
Girvanella, found in Cambrian, Ordovician and Silurian rocks, as well as in later deposits, appears to have played a part in the origination of oolitic rock-structure.
Little trace of Confervaceae has been found; Confervites chantransioides, apparently consisting of branched cellular filaments, may perhaps represent a Cambrian Confervoid.
No recognizable plant-remains, if we accept one or two doubtful Algal specimens, have so far been yielded by the Cambrian.
The county has some of the best upland bogs in the UK on the Cambrian Mountains.
Photograph taken at the ceremony to cut the first sod of the Cambrian colliery No 4 Pit.
About 540 million years ago the so-called Cambrian explosion took place.
The opening of the Cambrian Railroad in 1867 brought immense changes to the settlement patterns of the coastal strip.
The Wynne slate quarry opened in 1750 followed by a larger concern, the Cambrian Slate Company, which was formed in 1854.
This includes a thin tract of Torridonian together with the overlying Cambrian quartzites.
To the west Cambrian quartzites lie directly above the Ben More Thrust.
Upon a plinth of Torridonian sandstones lies the continuous cliff-line of bright white Cambrian quartzites.
The railroad track is the incredibly scenic Cambrian Coast line - recommended!
The Wynne slate quarry opened in 1750 followed by a larger concern, the Cambrian slate quarry opened in 1750 followed by a larger concern, the Cambrian Slate Company, which was formed in 1854.
They are best developed in the Macdonnell chain in Palaeozoic U Mesozoic Dolerite '&c. ' ® central Australia and in Victoria, where the fullest sequence is known; while they also extended north-eastward from Victoria into New South Wales, where, as yet, no Cambrian rocks have been found.
The mountain group of North Wales is the largest and loftiest; its scenery resembles that of the Scottish Highlands because of the juxtaposition of ancient Palaeozoic rocks - Cambrian and Ordovician, often altered into slate - and contemporaneous volcanic outbursts and igneous intrusions.
Rectory Cottage is en route for the Cambrian Way and the Marches Way.
This came after the sad demise of my Cambrian kit Mustang at the 2001 RAFMAA Champs.
The railroad track is the incredibly scenic Cambrian Coast line - recommended !
Located in the historic former Cambrian Mills, the Museum is a special place with a spellbinding story to tell.
The rocks are generally Cambrian, which is pretty old, and you can see some folded strata here.
Their ticklish problem was having to traverse the tortured terrain of the Cambrian Mountains yet keep the biking within the bounds of a beginner.
Cambrian, Ordovician and Silurian beds have been recognized, the Upper Cambrian consisting of a limestone which is very rich in metalliferous ores (especially galena and calamine).
In the western Sierras, which are more or less closely attached to the main chain of the Cordillera, Cambrian and Silurian fossils have been found at several places.