Though Angiosperms become dominant in all known plant-bearing Upper Cretaceous deposits, their origin dates even earlier.
In the Cretaceous period the waters withdrew from the N.E., but in the S.
Tertiary Cretaceous Ievel of the Miocene sea, which was very shallow to the N.
The later beds of the island belong to the Jurassic, Cretaceous and Tertiary systems. At the western foot of the Ida massif calcareous beds with corals, brachiopods (Rhvnchonella inconstans, &c.) have been found, the fossils indicating the horizon of the Kimmeridge clay.
Lower Cretaceous limestones and schists, with radiolarian cherts, are extensively developed; and in many parts of the island Upper Creta 1 See L.
The structure is further complicated by a great thrust-plane which has brought the Jurassic and Lower Cretaceous beds upon the Upper Cretaceous and Eocene beds.
The Cretaceous region includes, with the exception of the Lower Carboniferous, all that part of the state eastward of a line cutting the Tennessee boundary in 88° 50' W.
There are four formations of Cretaceous strata in Mississippi, defined by lines having the same general direction as the one just described.
Westward to Houston and southward to about 32° 48' on the Alabama boundary and occupying a much larger area than the other Cretaceous formations, is the Selma chalk, called "Rotten Limestone" by Hilgard; it is made up of a material of great uniformity, - a soft chalky rock, white or pale blue, composed chiefly of tenacious clay, and white carbonate of lime in minute crystals.
The latest Cretaceous is the Ripley formation, which lies west of the northern part of the last-named, and, about Scooba, in a small strip, the most southerly of the Cretaceous - it is composed of coarse sandstones, hard crystalline white limestones, clays, sands, phosphatic greensands, and darkcoloured, micaceous, glauconitic marls; its greatest thickness is about 280 ft.
Deposits of the Tertiary period form the basis of more than half the state, extending from the border of the Cretaceous westward nearly to the Yazoo Delta and the Mississippi Bottom, and southward to within a few miles of the Gulf coast.
The older formation of the Quaternary period is the Lafayette (also called "Orange-sand" or "stratified drift"), which immediately overlies all the Cretaceous groups except the prairies of the Selma chalk, and all the Tertiary except the Porters Creek and Vicksburg formations and parts of the Jackson.
The high land in the west of the island and the somewhat less elevated region in the east are formed of Upper Tithonian and Lower Cretaceous limestones, the latter containing Rudistes.
The greater part of western Asia, including the basin of the Obi, the drainage area of the Aral Sea, together with Afghanistan, Baluchistan, Persia and Arabia, was covered by the sea during the later stages of the Cretaceous period; but a considerable part 3f this region was probably dry land in Jurassic times.
Excepting in the extreme north, where marine Jurassic and Cretaceous fossils have been found, there is no evidence that this part of Siberia has been beneath the sea since the early part of the Palaeozoic era.
The sea in which these strata were deposited seems to have attained its greatest extension in Upper Cretaceous times, when its waters spread over the whole of western Asia and even encroached slightly upon the Indian land.
Leaving out of consideration all evidence of more ancient volcanic activity, each of the three regions, into which, as we have seen, the continent may be divided, has been, during or since the Cretaceous period, the seat of great volcanic eruptions.
C. Marsh, by finding the imperfect fossilized tibia of a bird in the middle cretaceous shale of Kansas, Marsh, began a series of wonderful discoveries of great im portance to ornithology.
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.
Cretaceous limestones cover the greater part of Palestine and rocks of the same period form Mt Lebanon, the Casius Mons, &c., farther north.
Nummulitic limestone (Eocene) overlies the Cretaceous in Philistia, and north of Lebanon Eocene and Miocene deposits cover the greater part of the country.
The faulting which formed the depressions is certainly later than the deposition of the Cretaceous beds and probably belongs to the later portion of the Tertiary era.
In the north the plateau is overlain by red and purple unfossiliferous sandstones, capped near its edge by a cherty limestone also unfossiliferous but possibly of Lower Cretaceous age.
The coal belongs to the Cretaceous beds, and while not so heavy as that of the Coal Measures is of excellent quality.
Mogilev is built up of Devonian deposits in the north, of Cretaceous in the east, and of Tertiary elsewhere, but generally is covered with a thick layer of Glacial and later alluvial deposits.
There are many sandy districts in the uplands, also sandy clays; in the " second bottoms " of the streams fertile sandy loams; abundant tertiary marls in the north-central region; some gypsum in the cretaceous " islands "; and some fossiliferous marls with decomposed limestones.
These ancient rocks have hitherto yielded no fossils and their age is therefore uncertain, but they are probably pre-Cretaceous at least.
Fossiliferous Cretaceous limestones containing Rudistes have been found in several parts of the island (Santiago de los Banos, Santa Clara province, &c.).
Along the west frontier there appear broad and strongly marked zones of Cretaceous limestone, alternating with Jurassic and Triassic, joined by a strip of Palaeozoic formations running from the north-west corner of Bosnia.
They are found on both sides of Smith Sound, rising to heights of 2000 ft., and underlie the Miocene and Cretaceous rocks of Disco Island, Noursoak Peninsula and the 2 E.
These beds, as well as the Cretaceous series, from which they are as yet only imperfectly distinguished, are associated with sheets of basalt, which penetrate them in great dikes, and in some places, owing to the wearing away of the softer sedimentary rocks, stand out in long walls running across the beds.
The only Mesozoic system which is represented in Brazil by marine beds is the Cretaceous, and the marine facies, is restricted to the coasts and the basin of the Amazon.
In the province of Sergipe, on the east coast, the beds are approximately on the horizon of the Cenomanian; in the valley of the Amazon they belong to the highest parts of the Cretaceous system, and the fauna shows Tertiary affinities.
The geological formations represented include: Post-Cretaceous and Recent Cretaceous.
They are exceedingly prolific in fossils which prove them to be of Upper Cretaceous age.
These are composed chiefly of Triassic beds, but Jurassic and Cretaceous beds take some share in their formation.
They may be of Cretaceous age or even later, and in any case belong to the same class as those of Kimberley.
In the latter range a few Ordovician fossils have been found, but in general the oldest strata which have yielded organic remains belong to the Cretaceous system.
The Cretaceous beds form a band along each side of the Cordillera and along the southern flank of the Caribbean chain, and they spread over the greater part of the provinces of Falcon and Lara.
There is considerable difference of opinion as to the chronology of the succeeding beds, and the boundary between the Cretaceous and Tertiary systems is drawn at various horizons by different observers.
It belongs either to the Upper Cretaceous or to the Lower Tertiary, or possibly in part to the one and in part to the other.'
Its upheaval above the great sea which submerged all the north-west of the Indian peninsula long after the Himalaya had massed itself as a formidable mountain chain, belongs to a comparatively recent geologic period, and the same thrust upwards of vast masses of cretaceous limestone has disturbed the overlying recent beds of shale and clays with very similar results to those which have left so marked an impress on the Baluch frontier.
Elsewhere the plants generally indicate a higher horizon and are considered to correspond with the Rhaetic of Europe_ Jurassic beds are known only in the Cordillera itself, and the Cretaceous beds, which occur in the west of the country, are of freshwater origin.
Towards the end of the period, however, during the deposition of the Portlandian beds, the sea again retreated, and in the early part of the Cretaceous period was limited (in France) to the catchment basins of the Sane and Rhnein the Paris basin the contemporaneous deposits were chiefly estuarine and were confined to the northern and eastern rim.
During the later part of the Cretaceous period the sea gradually retreated and left the whole country dry.
The Cretaceous period was initiated by the subsidence of a large area to the south of the Gulf of Carpentaria, whereby a Lower Cretaceous sea spread southward, across western Queensland, western New South Wales and the north-eastern districts of South Australia.
The Cretaceous sea gradually receded and the plains of the Rolling Downs formation formed on its floor were covered by the sub-aerial and lacustrine deposits of the Desert Sandstone.
The finest opal known is obtained in the Upper Cretaceous formation at White Cliffs, near Wilcannia, New South Wales, and at these mines about 700 men find constant employment.
Kossmat has shown that the Atlantic had substantially its present form during the Cretaceous period.
The older rocks are early Tertiary or late Cretaceous but there are no fossils to indicate age.
Schraufite is a reddish resin from the Carpathian sandstone, and it occurs with jet in the cretaceous rocks of the Lebanon; ambrite is a resin found in many of the coals of New Zealand; retinite occurs in the lignite of Bovey Tracey in Devonshire and elsewhere; whilst copaline has been found in the London clay of Highgate in North London.
Upper Cretaceous formations in America have yielded a copious flora of a warm-temperate climate from which it is evident that at least the generic types of numerous not closely related existing dicotyledonous trees had already come into existence.
Sequoia (which had already appeared in the American Upper Cretaceous) and the deciduous cypress (Taxodium distichum) are found in Europe.
Marsh, who, after 1870, discovered a great number of bird remains in the Cretaceous strata of North America.
The most important result is the proof that, until the end of the Cretaceous epoch, most, if not all, birds were still possessed of teeth.
A wide gap separates Archaeopteryx from the next order of fossil birds of the Cretaceous epoch, and, since freshwater deposits of that age are rare, bird remains are uncommon.
From the Cretaceous rocks of North America a large number of birds have been described by O.
Of these the most interesting are Ichthyornis (= Graculavus) and Hesperornis, from the Cretaceous shales of Kansas.
Probably all birds of Cretaceous age were still possessed of teeth.
Laornis from the Cretaceous marls of New Jersey was as large as a swan.
Cretaceous of Kansas.
Cretaceous beds - sands, loose sandstones, marls and white chalk - occupy nearly the whole of the region S.
The Lower Cretaceous consists chiefly of sandstones and shales and the Middle Cretaceous of very fossiliferous limestone.