JURASSIC , ingeology, the
See also:period of the Mesozoic era, that is to say, succeeding the Triassic and preceding the Cretaceous periods . The name Jurassic (French jurassique; German Juraformation or Jura) was first employed by A . Brongniart and A. von Humboldt for the rocks of this age in the western Jura mountains of
See also:Switzerland, where they are well
See also:developed . It was in England, however, that they were first studied by
See also:Smith, in whose hands they were made to
See also:lay the
See also:foundations of stratigraphical geology . The names adopted by him for the subdivisions he traced across the
See also:country have passed into universal use, and though some of them are uncouth
See also:English provincial names, they are as
See also:familiar to the geologists of France, Switzerland and Germany as to those of England . During the following three decades Smith's
See also:work was elaborated by W . D . Conybeare and W .
See also:Phillips . The Jurassic rocks of fossils of the
See also:European continent were described by d'
See also:Orbigny, 184o–1846; by L. von Buch, 1839; by F . A . Quenstedt, 1843–1888; by A .
See also:Oppel, 1856–1858; and since then by many other workers: E . Benecke, E . Hebert, W . Waagen, and others . The study of Jurassic rocks has continued to attract the
See also:attention of geologists, partly because the bedding is so well defined and
See also:regular-the strata are little disturbed anywhere outside the Swiss Jura and the Alps—and partly because the fossils are numerous and usually well-preserved . The result has been that no other
See also:system of rocks has been so carefully examined throughout its entire thickness; many "zones" have been established by means of the fossils—principally by ammonites—and these zones are not restricted to limited districts, but many of them hold
See also:good' over wide areas . Oppel distinguished no fewer than
See also:thirty-three zonal horizons, and since then many more sub-zonal divisions have been noted locally . The existence of faunal regions in Jurassic times was first pointed out by J .
See also:Marcou; later M .
See also:Neumayr greatly extended observations in this direction . According to Neumayr, three distinct
See also:geographical regions of deposit can be made out among the Jurassic rocks of
See also:Europe: (I) The Mediterranean province, embracing the Pyrenees,
See also:Alps and Carpathians, with all the tracts lying to the south . One of the biological characters of this
See also:area was the
See also:great abundance of
See also:ammonites belonging to the groups of Heterophylli (Phylloceras) and Fimbriati (Lytoceras) .
(2) The central European province, comprising the tracts lying to the
See also:north of the Alpine
See also:ridge, and marked by the
See also:comparative rarity of the ammonites just mentioned, which are replaced by others of the groups Inflati (Aspidoceras) and Oppelia, and by abundant reefs and masses of
See also:coral . (3) The boreal or
See also:Russian province, comprising the middle and north of Russia, Spitzbergen and
See also:Greenland . The
See also:life in this area was much less varied than in the others, showing that in Jurassic times there was a perceptible diminution of temperature towards the north . The ammonites of the more
See also:southern tracts here disappear, together with the corals . The cause of these faunal regions Neumayr attributed to
See also:climatic belts—such as exist to-day—and in
See also:part, at least, he was probably correct . It should be
See also:borne in mind, however, that although Neumayr was able to trace a broad, warm
See also:belt, some 6o° in width, right
See also:round the
See also:earth, with a narrower mild belt to the north and an arctic or boreal belt beyond, and certain indications of a repetition of the climatic zones on the southern side of the thermal equator, more
See also:recent discoveries of fossils seem to show that other influences must have been at work in determining their distribution; in
See also:short, the identity of the Neumayrian climatic boundaries becomes increasingly obscured by the advance of our knowledge . The Jurassic period was marked by a great extension of the
See also:sea, which commenced after the close of the Trias and reached its maximum during the
See also:Callovian and
See also:Oxfordian stages; consequently, the Middle Jurassic rocks are much more widely spread than the
See also:Lias . In Europe and elsewhere Triassic beds pass gradually up into the Jurassic, so that there is difficulty some-times in agreement as to the best
See also:line for the
See also:base of the latter; similarly at the top of the sytsem there is a passage from the Jurassic to the Cretaceous rocks (Alps) . Towards the close of the period
See also:elevation began in certain regions; thus, in
See also:America, the Sierras, Cascade Mountains,
See also:Klamath Mountains, and Humboldt Range probably began to emerge . In England the estuarine
See also:Portlandian resulted partly from elevation, but in the Alps marine conditions steadily persisted (in the Tithonian stage) . There appears to have been very little crustal disturbance or volcanic activity; tuffs are known in
See also:Argentina and California; volcanic rocks of this age occur also in
See also:Skye and
See also:Mull . The rocks of the Jurassic system
See also:present great petrological diversity .
In England the name " Oolites " was given to the middle and higher members of the system onaccount of the prevalence of oolitic structure in the limestones and ironstones; the same character is a
See also:common feature in the rocks of
See also:northern Europe and elsewhere, but it must not be overlooked that
See also:clays and sandstones together bulk more largely in the aggregate than the oolites . The thickness of Jurassic rocks in England is 4000 to 5000 ft., and in Germany 2000 to 3000 ft . Most of therocks represent the deposits of shallow seas, but estuarine conditions and
See also:land deposits occur as in the Purbeck beds of Dorset and the coals of
See also:Yorkshire .
See also:Coal is a very important feature among Jurassic rocks, particularly in the Liassic division; it is found in Hungary, where there are twenty-five workable beds; in
See also:Persia, Turkestan,
See also:Caucasus, south
See also:Japan, Further India, New Zealand and in many of the Pacific Islands . Being shallow
See also:water formations, petrological changes come in rapidly as many of the beds are traced out; sandstones pass laterally into clays, and the latter into limestones, and so on, but a reliable
See also:guide to the
See also:classification and correlation is found in the fossil contents of the rocks . In the accompanying table a
See also:list is given of some of the zonal fossils which regularly occur in the
See also:order indicated; other forms are known that are equally useful . It will be noticed that while there is general agreement as to the order in which the zonal forms occur, the line of division between one formation and another is liable to vary according to factors in the
See also:personal equation of the authors . The Jurassic formations stretch across England in a varying
See also:band from the mouth of the
See also:Tees to the
See also:coast of
See also:Dorsetshire . They consist of harder sandstones and limestones interstratified with softer clays and shales . Hence they give rise to a characteristic type of scenery—the more durable beds
See also:standing out as long ridges, sometimes even with low cliffs, while the clays under-lie the level spaces between . Jurassic rocks cover a vast area in Central Europe . They rise from under the Cretaceous formations in the north-east of France, whence they range southwards down the valleys of the
See also:Saone and Rhone to the Mediterranean .
They appear as a broken border round the old crystallinenucleus of
See also:Auvergne . Eastwards they range through the Jura Mountains up to the high grounds of Bohemia . They appear in the
See also:outer chains of the Alps on both sides, and on the south they rise along the centre of the Apennines, and here and there over the
See also:Spanish Peninsula . Covered by more recent formations they underlie the great plain of northern Germany, whence they range eastwards and occupy large tracts in central and eastern Russia .
See also:Lower Jurassic rocks are absent from much of northern Russia, the stages represented being the Callovian, Oxfordian and Volgian (of
See also:Professor S .
See also:Nikitin) ; the
See also:fauna differs considerably from that of western Europe, and the marine equivalents of the Purbeck beds are found in this region . In south Russia, the
See also:Crimea and Caucasus, Lias and Lower Jurassic rocks are present . In the Alps, the Lower Jurassic rocks are intimately associated with the underlying Triassic formations, and resemble them in consisting largely of reddish limestones and
See also:marbles; the ammonites in this region differ in certain respects from those of western and central Europe . The Oxfordian, Callovian, Cor2llian and Astartian stages are also present . The Upper Jurassic is mainly represented by a
See also:uniform series of limestones, with a
See also:peculiar and characteristic fauna, to which Oppel gave the name Tithonian." This includes most of the horizons from
See also:Kimeridgian to Cretaceous; it is developed on the southern flanks of the Alps, Carpathians, Apennines, as well as in south France and other parts of the Mediterranean
See also:basin . A characteristic formation on this
See also:horizon is the " Diphya
See also:limestone," so-called from the fossil Terebratula diphya (Pygope janitor) seen in the well-known escarpments (Hochgebirge
See also:Kalk) . Above the Diphya limestone comes the Stramberg limestone (Stramberg in Moravia), with " Aptychus " beds and coral reefs .
The rocks of the Mediterranean basin are on the whole more calcareous than those of corresponding age in north-west Europe; thus the Lias is represented by 1500 ft. of
See also:white crystalline limestone in
See also:Calabria and a similar
See also:rock occurs in
See also:Sicily, Bosnia,
See also:Epirus, Corfu; in Spain the Liassic strata are frequently dolomitic; in the Apennines they are variegated limestones and marls . The Higher Jurassic beds of
See also:Portugal show traces of the proximity of land in the abundant plant remains that are found in them . In Scania the Lias succeeds the Rhaetic beds in a regular manner, and Jurassic rocks have been traced northward well within the polar circle; they are known in the Lofoten Isles, Spitzbergen, east Greenland,
See also:Island, Cape
See also:Stewart in
See also:Scoresby Sound,
See also:Grinnell Land,
See also:Prince Patrick Land, Bathurst and Exmouth Island; in many cases the fossils denote a
See also:climate considerably milder than now obtains in these latitudes . In the
See also:American continent Jurassic rocks are not well developed . Marine Lower and Middle Jurassic beds occur on the Pacific coast (California and
See also:Oregon), and in
See also:Wyoming, the Dakotas,
See also:Colorado, east Mexico and
See also:Texas . Above the marine beds in the interior are brackish and fresh-water deposits, the Morrison and
See also:Como beds (Atlantosaurus and Baptanodon beds of
See also:Marsh) . Later Jurassic rocks are found in northern
See also:Columbia and perhaps in
See also:Alaska, Wyoming,
See also:Montana, Colorado, the Dakotas, &c . In California some of the gold-bearing, metamorphic slates are of this age . Marine Jurassic rocks have not been clearly identified on the
See also:Atlantic side of America . The Patuxent and Arundel formations (non-marine) are doubtfully referred to this period . Lower and Middle Jurassic formations occur in Argentina and
See also:Bolivia . Jurassic rocks have been recognized in
See also:Asia, including India,
See also:Afghanistan, Persia,
See also:Kurdistan, Asia Minor, the
See also:Caspian region, Japan and
See also:Borneo .
The best marine development is inCutch, where the following groups series = Bathonian . In the western
See also:half of the
See also:Salt Range and the Himalayas,
See also:Spiti shales are the equivalents of the European Callovian and Kimeridgian . The upper part of the
See also:Gondwana series is not improbably Jurassic . On the
See also:African continent, Liassic strata are found in Algeria, and Bathonian formations occur in
See also:Somaliland, Cape Colony and western
See also:Madagascar . In
See also:Australia the Permo-Carboniferous formations are succeeded in
See also:Queensland and Western Australia by what may be termed the Jura-Trias, Stages 1 Ammonite Zones a Substages Von A. de Lapparent, Trait, Alpine o, of Buch 5th ed . O Quenstedt E.% o
See also:Purbeckian Perisphinctes transitorius e as Purbeckien a ar q O O Perisphinctes giganteus g , ., or ?; . a Ce Di h a Kalke a . Olcostephanus gigas 7 x Aquilonien o .o p Y Reineckia
See also:eudoxus a 3 F' Acanthicus Oppelia tenuilobata 3' o a o Beds E2 m a) •-+ °
See also:ooh o as a) ..sa x c a) Portlandian Bononien Kimeridgian Virgulien ' . 0
See also:gib _ Pteroceran Peltoceras bimammatum E as —
See also:Corallian O a 72, Astartien I) Rauracien Oxfordian Peltoceras transversarium Aspidoceras perarmatum Peltoceras athlete Cosmoceras
See also:Jason Macrocephalites macrocephalus Argovien o 0 ,,.., a, k b O Neuvizien Callovian Upper Divesien a) Lower Divesien :=„-3: o Bathonian O v o Oppelia aspidoides ,. a a Bathonien o a a Posidonien Parkinsonia ferruginea co 3 o a a Beds S.Alps) Parkinsonia Parkinsoni bu ti o y m c' ( Cceloceras Hum hresianus o a a; l~ a Klauss Beds p Q b '4 ° (N . Alps) Sphaeroceras Sauzei w a' Sauzei-Kalke Sonninia Sowerbyi a W Oolite of
See also:San Harpoceras Murchisonae Vigilio ° -k v ~ Ce v m ;a l~ o a U 0.'C a U pa Tr, ^ a) O Ba'ocian (InferiorOolite) Bajocien (passage beds) Harpoceras (Lioceras) opalinum Toarcien Upper Lias Lytoceras jurense .as b a Posidonia Bronni 7 a) Amaltheus spinatus 14 ,.a Amaltheus margaritatus a Dactylioceras Davoei Phylloceras
See also:ibex Aegoceras Jamesoni Arietites raricostatus Oxynoticeras oxynotum Arietites obtusus Arietites Bucklandi Schlotheimia angulata Psiloceras planorbis Middle Lias Charmouthien Lower Lias Sinemourien Hettangien (part ) Hettangien (part) Rhetien are distinguished from above downwards: the Umia series=Portlandian and Tithonian of south Europe, passing upwards into the Neocomian; the Katrol series =Oxfordian (part) and Kimeridgian; the Chari series = Callovian and part of the Oxfordian; the Patcham 1 Purbeckian from the " Isle " of Purbeck . Aquilonien from Aquilo (
See also:Nord) . Bononien from
See also:Bononia (
See also:Boulogne) . Virgulien from Exogyra virgula .
Pteroceran from Pteroceras oceani . Astartien from
See also:Astarte supracorallina . Rauracien from Rauracia (Jura) . Argovien from Argovie (Switzerland) . Neuvizien from Neuvizy (
See also:Ardennes) . Divesien from Dives (
See also:Calvados) . Bathonien from Bath (England) . Bajocien from
See also:Bayeux (Calvados) . Toarcien from Toarcium (
See also:Tours) . Charmouthien from Charmouth (England) . Sinemourien from Sinemurum, Semur (
See also:ate d'Or) . Hettangien from Hettange (
See also:Lorraine).which include the coal-bearing "
See also:Ipswich " and " Burrum " formations of Queensland .
In New Zealand there is a thick series of marine beds with terrestrial
See also:plants, the Mataura series in the upper part of Hutton's Hokanui system .
See also:Sir J .
See also:Hector included also the Putakaka series (as Middle Jurassic) and the
See also:Flag series with the
See also:River and Bastion series below . Jurassic rocks have been recorded from New
See also:Guinea and New
See also:Caledonia . Life in the Jurassic Period.—The expansion of the sea during this period, with the formation of broad sheets of shallow and probably warmish water, appears to have been favourable to many forms of marine life . Under these conditions several groups of organisms developed rapidly along new directions, so that the Jurassic period as a whole came to have a fauna differing clearly and distinctly from the preceding Palaeozoic or succeeding
See also:Tertiary faunas . In the seas, all the
See also:main groups were represented as they are to-
See also:day Corals were abundant, and in later portions of the period covered large areas in Europe; the
See also:modern type of coral became dominant; besides
See also:building forms such as Thamnastrea, Isastrea, Thecosmilia, there were numerous single forms like Montivaltia . Crinoids existed in great numbers in some of the shallow seas; compared with Palaeozoic forms there is a marked reduction in the
See also:size of the calyx with a great extension in the number of arms and pinnules; Pentacrinus, Eugeniacrinus, Apiocrinus are all well known; Antedon was a stalkless genus . Echinoids (urchins) were gradually developing the so-called " irregular " type, Echinobrissus, Holectypus, Collyrites, Clypeus, but the " regular " forms prevailed, Cidaris, Hemicidaris, Acrosalenia .
See also:Sponges were important rock-builders in Upper Jurassic times (Spongilen Kalk) ; they include lithistids such as Cnemediastrum, Hyalotragus, Peronidella; hexactinellids, Tremadictyon, Craticularia; and horny sponges have been found in the Lias and 'Middle Jurassic .
See also:Polyzoa are found abundantly in some of the beds, Stomatopora, Berenicia, &c . Brachiopods were represented principally by terebratulids (Terebratula, Waldheimia, Megerlea), and by rhynchonellids; Thecae, Lingula and Crania were also present .
The Palaeozoic spirifirids and athyrids still lingered into the Lias . More important than the brachiopods were the pelecypods; Ostrea, Exogyra, Gryphaeawerevery abundant (Gryphite limestone, Gryphite grit); the genus Trigonia, now restricted to Australian
See also:waters, was present in great variety; Aucella,
See also:Lima, Pecten, Pseudomonotis Gervillia, Astarte, Diceras, Isocardia, Pleuromya may be mentioned out of many others . Amongst the gasteropods the Pleurotomariidae and Turbinidae reached their maximum development; the Palaeozoic Conularia lived to see the beginning of this period (Pleurotomaria, Nerinea, Pteroceras, Cerithium, Turritella) . Cephalopods flourished everywhere; first in importance were the ammonites; the Triassic genera Phylloceras and Lytoceras were still found in the Jurassic waters, but all the other numerous genera were new, and their shells are found with every variation of size and ornamentation . Some are characteristic of the older Jurassic rocks, Arietites, Aegoceras, Amaltheus, Harpoceras, `Oxynoticeras, Stepheoceras, and the two genera mentioned above; in the middle stages are found Cosmoceras, Perisphinctes, Cardioceras, Kepplerites Aspidoceras; in the upper stages Olcostephanus, Perisphinctes, Reineckia, Oppelia . So regularly do certain forms characterize definite horizons in the rocks that some thirty zones have been distinguished in Europe, and many of them can be traced even as far as India . Another cephalopod
See also:group, the belemnites, that had been dimly outlined in the preceding Trias, now advanced rapidly in numbers and in variety of
See also:form, and they, like the ammonites, have proved of great value as zone-indicators . The Sepioids or cuttlefish made their first appearance in this period (Beloteuthis, Geoteuthis,) and their
See also:ink-bags can still be traced in examples from the Lias and lithographic limestone . Nautiloids existed but they were somewhat rare . A great
See also:change had come over the crustaceans; in place of the Palaeozoic
See also:trilobites we find long-tailed
See also:lobster-like forms, Penaeus, Eryon, Magila, and the broad crab-like type first appeared in Prosopon . Isopods were represented by Archaeoniscus and others .
See also:Insects have
See also:left fairly abundant remains in the Lias of England, Schambelen (Switzerland) and Dobbertin (
See also:Mecklenburg), and also in the English Purbeck .
Neuropterous forms predominate, buthemiptera occur from the Lias upwards; the earliest known flies ,(
See also:Diptera) and ants (Hymenoptera) appeared; orthoptera,
See also:cock-roaches, crickets, beetles, &c., are found in the Lias, Stonesfield
See also:slate and Purbeck beds . Fishes were approaching the modern forms during this period, heterocercal ganoids becoming scarce (the Coelacanthidae reached their maximum development), while the homocercal forms were abundant (Gyrodus, Microdon, Lepidosteus, Lepidotus, Dapedius) . The Chimaeridae, sea-
See also:cats, made their appearance (Squaloraja) . .The ancestors of the modern sturgeons, garpikes and
See also:selachians, Hybodus, Acrodus were numerous . Bony-
See also:fish were represented by the small Leptolepis . So important a place was occupied by
See also:reptiles during this period that it has been well described as the " age of reptiles." In the seas the fish-shaped Ichthyosaurs and long-necked Plesiosaurs dwelt in great numbers and reached their maximum development; the latter ranged in size from 6 to 40 ft. in length . The Pterosaurs, with
See also:bat-like wings and pneumatic bones and keeled
See also:bone, flew over the land; Pterodactyl with short tail and Rhamphorhyncus with long tail are the best known . Curiously modified crocodilians appeared
See also:late in the period (Mystriosaurus, Geosaurus, Steneosaurus, Teleosaurus) . But even more striking than any of the above were the Dinosaurs; these ranged in size from a creature no larger than a
See also:rabbit up to the gigantic Atlantosaurus, too ft. long, in the Jurassic of Wyoming . Both herbivorous and carnivorous forms were present; Brontosaurus, Megalosaurus, Stegosaurus, Cetiosaurus, Diplodocus, Ceratosaurus and Campsognathus are a few of the genera . By comparison with the Dinosaurs the mammals took a very subordinate position in Jurassic times; only a few jaws have been found, belonging to quite small creatures; they appear to have been marsupials and were probably insectivorous (Plagiaulax Bolodon, Trironodon, Phascolotherium, Stylacodon) . Of great
See also:interest are the remains of the earliest known
See also:bird (
See also:Archaeopteryx) from the Solenhofen slates of
See also:Bavaria .
Although this was a great advance beyond the Pterodactyls in avian characters, yet many reptilian features were retained . Comparatively little change took place in the vegetation in the
See also:time that elapsed between the close of the Triassic and the middle of the Jurassic periods . Cycads, Zamites, Podozamites, &c., appeared to reach their maximum; Equisetums were still found growing to a great size and Ginkgos occupied a prominent place; ferns were common ; so too were pines, yews, cypresses and other conifers, which while they outwardly resembled their modern representatives, were quite distinct in
See also:species . No flowering plants had yet appeared, although a
See also:primitive form of angiosperm has been reported from the Upper Jurassic of Portugal . The economic products of the Jurassic system are of considerable importance; the valuable coals have already been noticed; the well-known iron ores of the
See also:district in Yorkshire and those of the Northampton sands occur respectively in the Lias and Inferior Oolites . Oil shales are found in Germany, and several of the Jurassic formations in England contain some petroleum . Building stones of great value are obtained from the Great Oolite, the Portlandian and the Inferior Oolite; large quantities of
See also:cement and lime have been made from the Lias . The celebrated lithographic
See also:stone of Solenhofen in Bavaria belongs to the upper portion of this system . See D'Orbigny, Paleontologie frangaise, Terrain Jurassique (184o, 1846) ; L. von Buch, " Uber den Jura in Deutschland " (Abhand. d . Berlin Akad., 1839); F . A . Quenstedt, Flotzgebirge Wiirttembergs (1843) and other papers, also Der Jura (1883-1888); A .
Oppel,Die Juraformation Englands, Frankreichs and s.w . Deutschlands (1856-1858) . For a good general account of the formations with many references to
See also:original papers, see A. de Lapparent, Traite de geologie, vol. ii . 5th ed . (1906) . The standard work for Great Britain is the series of
See also:Memoirs of the
See also:Geological Survey entitled The Jurassic Rocks of Britain, i and ii . " Yorkshire " (1892) ; iii . " The Lias of England and
See also:Wales " (1893) ; iv . " The Lower Oolite Rocks of England (
See also:shire excepted)" (1894) ; v . " The Middle and Upper Oolitic Rocks of England (Yorkshire excepted)" (1895) . The map is after that of M . Neumayr, " Die geographische Verbreitung der Juraformation," Denkschr. d. k .
Akad. d . Wiss., Wien, Math. u . Naturwiss., cl . L., Abth. i., Karte 1 . (1885) . (J . A .
JURA (" deer island ")
JURAT (through Fr. from med. Lat. juratus, one swor...
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