John Allen Howe

“ Muds, sands, grits and conglomerates are the predominant types. In Scotland, North America and Canada important deposits of limestone occur and subordinate limestones are found in the Cambrian of central Europe.
In some regions, notably in the Baltic province and in parts of the United States, the rocks still retain their original horizontality of deposition, the muds are scarcely indurated and the sands are still incoherent; but in most parts of the world they bear abundant evidence of the many movements and stresses to which they have been exposed through so enormous a period of time. ”

“ With a series of strata so variable from point to point it is natural that many purely local phases should have received distinctive names; in the Upper Eocene of the Paris basin the more important formations are the highly fossiliferous marine sands known as the “Sands of Beauchamp” and the local fresh-water limestone, the “Calcaire de St Ouen.” The Middle Eocene is represented by the well-known “Calcaire grossier,” about 90 ft. thick. The beds in this series vary a good deal lithologically, some being sandy, others marly or glauconitic; fossils are abundant. ”

“ 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 Persia, Turkestan, Caucasus, south Siberia, China, Japan, Further India, New Zealand and in many of the Pacific Islands.
Being shallow 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 guide to the classification and correlation is found in the fossil contents of the rocks. ”

“ Some confusion has been introduced by the use of the term Cainozoic to include, on the one hand, the Tertiary period alone, and on the other hand, to make it include both the Tertiary and the post-Tertiary or Quaternary epochs; and in order that it may bear a relationship to the concepts of time and faunal development similar to those indicated by the terms Mesozoic and Palaeozoic it is advisable to restrict its use to the latter alternative. Thus the Cainozoic era would embrace all the geological periods from Eocene to Recent. ”

“ The flora of the Eocene period, although full of interest, does not convey the impression of newness that is afforded by the fauna of the period. The reason for this difference is this: the newer flora had been introduced and had developed to a considerable extent in the Cretaceous period, and there is no sharp break between the flora of the earlier and that of the later period ”

“ In Europe the type of rock varies rapidly from point to point, limestones, shales, sandstones, current-bedded grits and conglomerates or their metamorphosed equivalents are all found within limited areas; but in northern Europe particularly the paucity of limestones is a noteworthy feature in contrast with the rocks of like age in the south, and still more with the Ordovician of North America, in which limestones are prevalent. ”

“ In south Russia, the 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 marbles; the ammonites in this region differ in certain respects from those of western and central Europe. The Oxfordian, Callovian, Corallian and Astartian stages are also present. The Upper Jurassic is mainly represented by a uniform series of limestones, with a peculiar and characteristic fauna, to which Oppel gave the name “Tithonian.” ”

“ Thickness of Carboniferous Rocks.—The great variety of conditions under which the sediments and limestones were formed naturally produced corresponding inequalities in the thickness. In the Eurasian land area the greatest thickness of Carboniferous rocks is in the west; in North America it is in the east. In Britain the Carboniferous limestone series is 2000–3500 ft. thick; in the Ural mountains it is over 4500 ft.; the Culm in Moravia is credited with the enormous thickness of over 42,000 ft. The Upper Carboniferous in Lancashire is from 12,000 to 13,000 ft. ”

“ As a natural result of the open character of the great Silurian periarctic sea referred to above, there are many points of resemblance between the fauna of the several regions of the N. hemisphere; this has been specially noticed in the community not only of genera but of species between Britain, Sweden and the interior of N. America (Iowa, Wisconsin, Illinois) . Goniophyllum pyramidale is common to Iowa and Gothland ; Atrypa reticularis, Orthoceras annulatum and not a few others are common to Europe and N. America. ”

“ Many of the formations of this period can be shown by their fossil contents to belong to early quaternary time, but since so many of these deposits are strictly local in character, and since the fauna and flora present in any one spot have been determined by local geographical conditions which have assisted or retarded the migration of certain forms, it is a matter of extreme difficulty one may say impossibility—to reduce the Pleistocene formations to any generally applicable chronological order. ”

“ In north-western Europe the close of the Cretaceous period was marked by an extensive emergence of the land, accompanied, in many places, by considerable erosion of the Mesozoic rocks; a prolonged interval elapsed before a relative depression of the land set in and the first Eocene deposits were formed. The early Eocene formations of the London-Paris-Belgian basin were of fresh-water and brackish origin; towards the middle of the period they had become marine, while later they reverted to the original type. In southern and eastern Europe changes of sea-level were less pronounced in character ”

“ The superior limit of pre-Cambrian rocks is fixed by the Olenellus fauna at the base of the Cambrian (some geologists speak of certain pre-Olenellus beds as eo-Cambrian) ; the lower limit has not yet been generally established, though it is sufficiently clear in certain regions. The rocks of this period are much more obviously of sedimentary origin than those of the Archean; they include conglomerates, sandstones, greywackes, quartzites, slates, limestones and dolomites, which appear to have been formed under conditions similar to those which obtained in later epochs. ”

“ Economic Products.—Foremost among the useful products of the Carboniferous rocks is the coal (q.v.) itself; but associated with the coal seams in Great Britain, North America and elsewhere, are very important beds of ironstone, fire-clay, terra-cotta clay, and occasionally oil shale and alum shale. Oil and gas are of importance in the Lower Carboniferous Pocono sandstone of West Virginia and in the Berea grit of Ohio, where brine also occurs. ”

“ The gradual inception of colder conditions in the northern hemisphere which lead up to the more extreme conditions of glaciation clearly began in the latter part of the Pliocene period, and the effects of this cooling are seen not only in northern Europe and America but as far south as the Mediterranean. The result of this is that there is a certain indefiniteness as to the exact base line to be adopted for the Pleistocene formations ”

“ The Bajocian rocks of Europe are mostly limestones of various kinds, very frequently oolitic. At Bayeux, the type district, they are ferruginous oolites; in the Jura and Lorraine a coral limestone overlies a crinoidal variety; calcareous sandy and marly beds occur in Maine and Anjou; in Poitou the limestone is dolomitic and bears nodules of chert. Rocks of the same age, as recognized by their fossil contents, have a wide range; they are found in north Africa, Goa, Somaliland, German East Africa, and north-west Madagascar ”

“ The stratified rocks of this system include marine limestones, shales and sandstones; estuarine, lagoonal and fresh-water shales, sandstones and marls with beds of coal, oil-bearing rocks, gypsum and salt.
In many parts of the world there is no sharp line of demarcation between the Devonian and the Carboniferous rocks; neither can the fossil faunas and floras be clearly separated at any well-defined line; this is true in Britain, Belgium, Russia, Westphalia and parts of North America. ”

“ In Belgium a sandy series (Wemmelian, Asschian, Henisian) , mainly of brackish-water origin, is succeeded by the marine sands of Bergh (with the clay of Boom) , which pass up through the inferior sands of Bolderberg into the Miocene. In Switzerland, beyond the limits of the Flysch, nearer the Alpine massif, is a belt of grits, limestones and clays in an uncompacted condition, to which the name “molasse” is usually given; mixed with the molasse is an inconstant conglomeratic littoral formation, called Nagelfluh. ”

“ Turtles became well established during this period (Psammochelys, Chelyzoon) . Of great interest is the discovery of the earliest traces of mammals in the Trias of Europe, South Africa and North America. The imperfect remains (teeth and jaw-bones) do not admit of any certainty in deciphering their relationships. Microlestes from the Rhaetic of England and Württemberg and Dromatherium from North America are perhaps the best known; Tritylodon from South Africa may also be added. Among the lower forms of marine life foraminifera and sponges play a subordinate part. ”

“ The Alpine-Mediterranean Trias sea evidently had a prolongation into Western Asia, for in Asia Minor, Armenia and Bokhara rocks with closely related fossils have been found. In Central Asia Triassic rocks are known in Afghanistan (sandstones with coal) , Russian Turkestan, and in the Pamir. In India the lower Trias of the Salt Range presents the most typical example of the marine deposits of this stage. The Himalayan Trias more perfectly represents the upper portion of the system. Triassic limestones are found also in Kashmir and Hazara, and shales in Baluchistan. ”

“ 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 white crystalline limestone in Calabria and a similar rock occurs in Sicily, Bosnia, Epirus, Corfu; in Spain the Liassic strata are frequently dolomitic; in the Apennines they are variegated limestones and marls. The Higher Jurassic beds of Portugal show traces of the proximity of land in the abundant plant remains that are found in them. ”

“ Elsewhere in France similar mixed marine, fresh-water and brackish beds are found: in Aquitaine there are marine and lacustrine marls, limestones and molasse; marine beds occur at Biarritz; lacustrine and fresh-water marls and limestones with lignite appear in the sub-Pyrenees; in Provence there are brackish red clays, conglomerates and lignites, with limestones in the upper parts; and in Limagne there are mottled sands, arkoses, clays and fresh-water limestones. ”

“ The molasse occurs also in Bavaria, where it is several thousand feet thick and contains lignites. Oligocene deposits occur in the Carpathian region and Tirol; as Flysch and brackish and lacustrine beds with lignite in Klausenburg, lignites at Haring in Tirol. In the Spanish Pyrenees they are well developed; in the Apennines the scaly clays (“argille scagliose”) are of this age; while in Calabria they are represented by thick conglomerates and Flysch. Flysch appears also in Dalmatia and Istria (where it is called “tassello”) and in North Bosnia, where it contains marine limestones. ”

“ Looking eastward, towards central and northern Russia, we find a wider and much more open sea; but the continental type of deposit prevailed in the northern portion, and here, as in Scotland, we find coal-beds amongst the sediments (Moscow basin) . Farther south in the Donetz basin the coals only appear at the close of the Lower Carboniferous.
In North America, the crustal movements at the beginning of the period are less evident than in Europe, but a marked parallelism exists ”

“ In subdividing the strata of the Carboniferous system and correlating the major divisions in different areas, just as in other great systems, use has to be made of the fossil contents of the rocks; stratigraphical units, based on lithology, are useless for this purpose. The groups of organisms utilized for zoning and correlation by different workers include brachiopods, pelecypods, cephalopods, corals, fishes and plants; and the results of the comparison of the faunas and floras of different areas where Carboniferous rocks occur are generalized in the table below. ”

“ The term drift is now applied generally to the Quaternary deposits, which consist for the most part of gravel, sand, loam or brickearth and clay; it naturally refers to strata laid down at some distance from the rocks to whose destruction they are largely due; but, although applied to river deposits, the word drift is more appropriately used in reference to the accumulations of the Glacial period. ”