Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.
|
See also:PLIOCENE (from the Gr. sr?eiov, See also:mere, and xatvbs, See also:recent)
, in See also:geology, the name given by See also:Sir C
.
See also:Lyell to the formations above the See also:Miocene and below the See also:Pleistocene (Newer See also:Pliocene) strata
.
During this See also:period the See also:great See also:land masses of the See also:earth were rapidly approaching to the configuration which they exhibit at the See also:present See also:day
.
The marine Pliocene deposits are limited to comparatively few areas; in See also:Europe, in the beginning of the period, the See also:sea washed the shores of See also:East Anglia and parts of the See also:south See also:coast of See also:England; it extended well into See also:Belgium and See also: See also:Kayser in his Formationskunde (3rd ed., igo8) distinguishes three stages under the names Arnian (upper), Astian (middle) and Messinian (lower) = Zanclean . The lower stage, however, includes the Pontian, Epplesheim, Pikermi and other formations which are here placed in the Miocene . This stage has been referred to a so-called Mio-Pliocene inter-period . The Pliocene rocks of See also:Britain now occupy but a small See also:area in See also:Norfolk, See also:Suffolk and See also:part of See also:Essex; but from the presence of small outlying patches in See also:Cornwall (St Erth and St See also:Agnes), See also:Dorsetshire (Dewlish) and See also:Kent (Lenham), it is evident that the Pliocene Sea covered a considerable part of southern England . Moreover, these patches show by their present See also:altitude above the sea that the See also:Downs of Kent must have been elevated more than 85o ft., and the See also:west coast of Cornwall 400 ft. since Pliocene times . The Pliocene rocks See also:rest with strong unconformity upon the older strata in Britain . In the eastern counties the shelly, sandy beds are called " See also:Crag"; this name has come into very See also:general use for all the members of the series, and it is frequently employed as a synonym for Pliocene . The See also:English Pliocene strata are classified by the See also:Geological Survey of England and See also:Wales as follows: Yoldia (See also:Leda) myalis See also:bed (provisionally placed here) . See also:Forest-bed See also:group and Dewlish gravels with Elephas meridionalis . Newer Weybourne crag (and Chillesford See also:clay?) . Pliocene Chillesford crag . See also:Norwich crag and Scrobicularia crag .
Red crag of See also:Batley
.
Red crag of See also:Walton, Newbourn and Oakley
.
St Erth and St Agnes beds
.
Coralline crag
.
Lenham beds (Diestian)
.
See also:Box-stones and phosphatic beds with derived early Pliocene and other fossils
.
The box-stones are rounded pieces of See also: Marine fresh-water and land shells are found in these beds, together with many mammalian remains, including Elephas antiquus, Mastodon arvernensis, Equus stenonis, Cervus carnulorum, and dolphins, See also:cod and other See also:fish . The Forest-Bed group or See also:Cromer forest-bed is exposed beneath the See also:boulder clay cliffs of the Norfolk coast; it contains transported stumps of trees and many See also:plants still See also:familiar in Britain, many living fresh-water and estuarine molluscs and a large number of mammals, many of which are See also:extinct (Ma-haerodus, Canis See also:lupus, Ursus spelaeus, Hyaena crocuta, See also:Hippopotamus amphibius, Rhinoceros etruscus, Elephas antiquus and E. meridionalis, Bison bonasus, Ovibos moschatus, numerous See also:species of deer, Equus caballus and E. stenonis, See also:Castor fiber, Talpa europaea and many others) . The only See also:record of Pliocene remains in the northern part of England consists of a few See also:teeth of Elephas meridionalis found in a fissure in the See also:limestone at See also:Dove Holes, See also:Derbyshire . The Pliocene deposits of Belgium and Holland and the northern extremity of France are closely related with those of Britain, though as a whole they are very much thicker, The older marine beds may be traced from Lenham across the Channel at See also:Calais and through See also:Cassel to Diest . The newer marine Pliocene runs in a parallel See also:belt to the north of the older beds through See also:Antwerp . Belgian geologists have divided the local Pliocene into the following groups (from above downwards) : Poederlian, Scaldisian, Casterlian, Diestian . F . W . Harmer (Quart . Journ . Geol . See also:Soc., 1898 and 1900) proposed the following See also:scheme for the Pliocene of Britain and the See also:Low Countries: Cromerian = Forest-bed of Cromer . (Iceno-Cromerian = Chillesford beds and Weybourne crag . Icenian = marine crag of Norwich . Amstelian = Red Crag, comprising the Newbournian and Butleyan sub-stages . Waltonian = Walton crag and Poederlian and Scaldisian . Gedgravian = Coralline crag and Casterlian . Lenhamian = Diestian . In addition to the deposits just mentioned in See also:French See also:Flanders, the early Pliocene sea has See also:left numerous small patches of marls and sands in See also:Brittany and See also:Normandy . In southern France marine sands, gravels and marls of Plaisancian and Astian ages occur in the depression of See also:Roussillon, followed by Sicilian marls and gravels . In See also:Languedoc (See also:Montpellier, See also:Nimes, See also:Beziers) marine marls and sands are followed by calcareous See also:conglomerate (40 metres) or by marls and See also:lignite; gravels and loalns constitute the uppermost beds . In the Rhone basin the earliest deposits are the Congeria beds of Bollene (See also:Vaucluse); this brackish formation differs from the beds of the same name in See also:Vienna, but resembles those of Italy and See also:Rumania . Then followed a marine invasion (groupe de See also:Saint-See also:Aries) ; these beds are now found at considerable elevations increasing northward and westward . The later formations in this area are fluviatile or lacustrine in origin, with remarkable torrential See also:gravel deposits at several horizons . The marine Pliocene of the maritime See also:Alps, consisting of See also:blue and yellow See also:clays and limestone, are now elevated 170 metres above the sea, and even up to 35o M. in the neighbourhood of See also:Nice . In central France no marine beds are found, but many interesting and in some cases highly fossiliferous deposits occur in association with volcanic rocks, such as the lower conglomerate and upper trachytic See also:breccia of Perrier (See also:Issoire), the See also:fine tuffs (cinerites) with plants of See also:Cantal, the lignitiferous sandstones beneath the See also:basalt of Cezallier, the diatomite of Ceyssac, &c . In Italy, Pliocene rocks See also:form the low ranges of hills on both sides of the See also:Apennines, hence the See also:term " sub-Apennine " given to these rocks by A. d'See also:Orbigny . They are marine marls and sands; the blue marls which See also:crop out near See also:Rome at the See also:base of Mt See also:Mario and Mt Vatican with the succeeding sands and gravels; the conglomerate followed by deep-sea marls of See also:Calabria, and the marls, sands, limestones and blue clay of Sicily, all belong to the Plaisancian stage . To the next stage belong the yellow sands full of massive fossils, including the conglomerate of Castrovillari in Calabria and the white marls of the Val d'See also:Arno . In the final (Sicilian) stage fluvio-lacustrine sands and gravels are found in Italy, except in Calabria and in Sicily where thick marine beds were formed . In See also:Switzerland some of the deposits of Nagelfuk and Deckenschotter, glacial See also:plateau gravels, belong to the Sicilian stage . In south-eastern Europe a great series of sands and marls with lignites, termed the Paludina beds, rests directly upon the Pontian formation . From their great development in the See also:Levant, they have been given the See also:rank of a " Levantine stage " by F. von See also:Hochstetter; they are found in See also:Dalmatia, Croatia, Slavonia, Bosnia, Rumania, See also:Bulgaria, southern See also:Russia, the See also:Cyclades, and the Caspian region . On the north coast of See also:Africa marine and brackish sands and marls occur in See also:Morocco, See also:Algeria and See also:Egypt; and the " rifts " of the Red Sea and See also:Suez have been assigned to this period . In North See also:America marine Pliocene is found fringing the coasts of See also:California and the Gulf of See also:Mexico . In the latter region marine marls, clays and limestones are best See also:developed in See also:Florida and can be traced into the Carolinas and See also:Virginia; they have been classed as-the See also:Lafayette group (with lignites), the Florida group, and the Calooshatchis stage . On the Pacific coast the marine beds have attained great thicknesses, notably in the Merced series of See also:San Francisco . In the San Luis Obispo region the non-marine Paso Robles beds, said to be moo ft. thick, belong to this period . Other local formations of Older Pliocene marine origin in California are those of San Diego and See also:Wild See also:Cat . I See C . See also:Reid, " The Pliocene Deposits of Britain (Mem . Geol . In the Rocky Mountains are large lacustrine formations of consider- Survey, 189o) ; E . T . See also:Newton, " The Vertebrates of the Pliocene able thickness, and certain conglomerates in See also:Wyoming and See also:Bishop Deposits of Britain " (Mem . Geol . Survey, 1891) (both contain a See also:Mountain are assigned to this See also:age . The sands and clays with bibliography) : C . Reid, Origin of the See also:British See also:Flora (1899) ; and See also:gypsum of Entre Rios in South America contain fossils of the '..Geological Literature " (Geol . Soc . See also:London See also:Annual, since 1893) . See also:Atlantic type . (J . A . H.) Lignitiferous shale with See also:petroleum and great thickness of volcanic tuffs have been found in southern Sumatra . In New South Wales Pliocene See also:river terraces and alluvial deposits are covered by See also:Mid-Pliocene lavas and from these " deep leads " or buried river beds much See also:gold has been obtained . In See also:Victoria great basaltic and doleritic flows have filled up the Pliocene river valleys, and marine beds have been found at elevations of woo ft. above present sea-level . Very similar deposits and volcanic See also:rock, belonging to the See also:Wanganui See also:system of F . W . See also:Hutton, are found in New See also:Zealand . Stages . England . Belgium Rhone Basin . Languedoc Italy . Eastern Other Countries . and and Europe . Holland . Roussillon . Sicilian . Cromer Forest C I a y s o f Marls of St See also:Durfort beds Sands of Val d'Arno . Upper Marine beds of Bed . Campine . Cosme. with Elephas Limestones of Paler- Paludina Entre Rios . Fluvio-marine Amstelian . G r Chagny. a v e 1 s of meridionalis. motand clays (Vivipara) tuffs of N o r w i c h Conglomerates Volcanic Sumatra . Red crag rag of of Suffolk . Chambaran . Sands of Tre- voux and Mollon . Travertine of Meximieux . Astian . Base of Red — -- crag . Poederlian . Scaldisian sands with Trophon antiquum . Conglomerates Marls of Val d'Arno Middle Petroleum-bearing of Montpellier with Mastodon Paludina beds of Sumatra . and Fourres. arvernensis. beds . Marine sands of Sands of See also:Rous- Yellow sands of See also:Asti, Moghara and sillon with Plaisantin, See also:Monte Mokatta . M a s t o d o n Maria and See also:Tuscany . arvernensis . Conglomerates of Castrovillari . 1 Plaisancian . Coralline crag . Sands with Marine marls Yellow sands of Blue marls of Pia- Marine beds of Lenham beds . Isocardia of See also:Bresse, Montpellier. cenza, See also:Bologna, See also:car . Hauterives . Blue marls of and Vatican . Diestian Congeria beds Millas . sandstones. of Bollene . Lower Florida . Paludina Lacustrine beds of beds . Rocky Moun= tains . |
|
|
[back] THE YOUNGER PLINY |
[next] PLOCK, or PLOTSK |
There are no comments yet for this article.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.
Links to articles and home page are encouraged.