It is sufficiently evident that the rocks of the Newark series are not marine, but just how they were accumulated is a question as to which there is much disagreement. It has been usual to consider the strata as of estuarine origin, but their lithological character, the surface markings of many of the beds, and the contained fossils make such an origin improbable. It is likely that fiuviatile and subaerial agencies have had more to do with the accumulation of the materials than had any body of water in communication with the sea. At the southern end of the trough, the coal-beds point unmistakably to the existence of fresh-water swamps and bogs, while the red colour and the sun-cracks prevalent in the remainder suggest conditions resembling those of the German Bunter and Keuper, though the absence of gypsum and salt indicates that the climate was less arid than in Europe. If we could be sure that the plant-bearing beds of Virginia were contemporaneous with those of New Jersey and the Connecticut valley, the difference in the floras would confirm the inference that the climate was sub-arid in the North, growing more moist southward, but the difference may be geological rather than geographical.

No doubt lakes of greater or less duration were formed and are now registered in the fish-bearing shales.

Igneous activity was a conspicuous feature of the Newark epoch, both in the volcanic and the intrusive form. Lava-flows were poured out on the surface and were subsequently buried, and beds of fragmental products have been found in the Connecticut valley and in New Jersey, while dykes and sills accompany the strata throughout their extent. Now that they are exposed by denudation, these plutonic bodies form very striking features of the topography. One of the most remarkable of the intrusive masses is the great Palisades-Rocky Hill sill, the outcrops of which are separate, though their subterranean connection is well ascertained. An account of the Palisades has already been given in Chapter XV (Unstratified Or Massive Rocks). All the known fossil-bearing horizons, with perhaps one exception, correlate the Newark rocks, with the Keuper, possibly extending up into the Rhaetic. The exception noted is in southeastern Pennsylvania, where the beds reach their maximum thickness and where the deeper portions are said to have yielded Permian plants, but this awaits confirmation.

In the Mexican States of Sonora and Oaxaca are beds' similar to those of the Newark, which contain plants that show the formations to be of upper Keuper age, passing into the Rhaetic. Still farther south, similar beds occur in Honduras.

A third facies of the North American Trias is that of the western interior, which has much the same distribution as the interior Permian, extending from Texas, Arizona, and New Mexico, on the south, around the Colorado island, north to the Canadian provinces, though not continuously. In many areas the beds have as yet yielded no fossils and are referred to the Triassic upon strati-graphical grounds, which are not always trustworthy. However, the presence of the Trias is definitely ascertained at many points in the region defined, though how much of the system, or what part of it, is present at any particular locality, can rarely be determined. As in the underlying Permian, the occurrence of gypsum and salt is evidence of salt lakes and an arid climate, but, as was probably true in the Newark region of the East, the climate appears to have become less arid southward, for fresh-water Trias has been found in Texas, northeastern New Mexico, and southwestern Colorado.

South America, like so many of the other continents, has both the continental and marine facies of the Trias; the former is found east of the Andes, in the Argentine Republic, and is coal-bearing, with plants which correlate it with the Rhaetic. On the west side of the Andes the marine Trias is upturned in the mountains.

African

In South Africa the Karroo system, as already pointed out, is a continental formation, extending in apparently unbroken continuity from the Permian into the Jurassic. The Triassic portion is the upper part of the Beaufort series and has yielded a remarkable array of fossil Reptiles. The land connection with India, "Gondwana Land," was still maintained. In northern Africa Trias of the German type covers extensive areas in the province of Constantine, Algeria, corresponding to the Muschel-kalk and Keuper, the latter containing gypsum.

Australasian

Oceanic Trias, especially of the Upper Triassic, is found in many of the Indo-Pacific islands, Borneo, Sumatra, the Moluccas, New Caledonia, and others. In Australia continental Trias is found in New South Wales, where the lower portion is coal-bearing, and in Queensland, where the upper division carries coal-beds, as also in the northwest. In New Zealand, there is evidence of glaciation in this period and the glacial beds are overlaid by marine deposits.

Climate

In the Triassic of the northern hemisphere there is evidence of very widespread aridity of climate, accompanied by general warmth; central Europe, north Africa, the western interior of North America and, in lesser degree, the northeastern part of the same continent. From the distribution of the fossils, there is reason to believe that in the Arctic Sea the water was cooler than in lower latitudes and that the remarkable changes in the faunal relations of our Pacific coast during the period are to be explained rather by the closing and reopening of Bering Straits than by the upheaval and depression of land bridges across the wider parts of the Pacific. This problem will again present itself in the subsequent periods.