Nitrous

San Julian on Puerto San Julian, where Ferdinand Magellan wintered, was the centre of a cattle farming colony, and colonists have pushed into the interior up the valley of a now extinct river which in comparatively recent times carried down to Puerto San Julian the waters of Lakes Volcan, Beigrano, Azara, Nansen, and some other lakes which now drain into the river Mayer and so into Lake San Martin. Lake Buenos Aires, the largest lake in Patagonia, measuring 120 kilometers (75 miles) in length, poured its waters into the Atlantic even in post-Glacial times by means of the river Deseado; and it is so depicted on the maps of the 17th and 18th centuries; and so too did Lake Pueyrredon, which, through the action of erosion, now empties itself westward, through the river Las Heras, into the Calen inlet of the Pacific, in 48°S. Into this inlet there flowed at the time of the conquest a voluminous river, which subsequently disappeared, but returned again to its ancient bed, owing to the river Fenix, one of its affluents, which had deviated to the west, regaining its original direction. Puerto Deseado is the outlet for the produce of the Andean region situated between Lakes Buenos Aires and Pueyrredon.

With the exception of certain valleys at Puerto Deseado (Port Desire) and in the transverse basins which occur as far south as Puerto San Julian, and which contain several cattle farms, few spots are capable of cultivation, the pastures being poor, water insufficient and salt lagoons fairly numerous. The territory of Santa Cruz is arid along the Atlantic coast and in the central portion between 46° and 50°S. miles). parallel, as far south as the dividing line with Chile, and between Point Dungeness and the watershed of the Cordillera, has an area of 243,943 km² (94,186 sq.

Santa Cruz, which stretches from the 46° to the 50°S. Every year thousands of fly fishermen flock there for the hope of catching "the big one". In addition it is one of the highest critically acclaimed group of rivers in the the world for fly fishing. Colonies have also been formed in the basin of Lakes Musters and Colhué Huapi; and on the coasts near the Atlantic, along Bahia Camarones and the Gulf of San Jorge, there are extensive farms.

The streams which form the rivers Mayo and Chalia join the tributaries of the Rio Aisen, which flows into the Pacific, watering in its course extensive and valuable districts where colonization has been initiated by Argentine settlers. At Lake Fontana there are auriferous drifts and lignite deposits which abound in fossil plants of the Cretaceous age. This region contains auriferous drifts, but these, like the auriferous deposits, veins of galena and lignite in the mountains farther west which flank the Cordillera, have not been properly investigated. Rio Pico, an affluent of the same river, receives nearly the whole of the waters of the extensive undulating plain which lies between the Rio Tecka and the Rio Senguerr to the east of the Cordillera, while the remainder are carried away by the affluents of Rio Jehua: the Cherque, Omkel, and Appeleg.

The principal affluent of the Palena, the Carrenleufu, carries off the waters of Lake General Paz, situated on the eastern slope of the Cordillera. Other rivers in this territory flow into the Pacific through breaches in the Cordillera, e.g. the upper affluents of the Futaleufú River, Palena and Rio Cisnes. The chief of these colonies is that of 16 de Octubre, formed in 1886, mainly by the inhabitants of Chubut colony, in the longitudinal valley which extends to the eastern foot of the Cordillera. Between the Chubut and the Senguerr there are vast stretches of fertile land, spreading over the Andean region to the foot of the Cordillera and the lateral ridges of the Pre-Cordillera, and filling the basins of some desiccated lakes, which have been occupied since 1885, and farms and colonies founded upon them.

The valley has been irrigated and cultivated, and produces the best wheat of the Argentine Republic. Here is the seat of the governor of the territory, and by 1895 the inhabitants of this part of the territory, composed principally of Argentines, Welsh and Italians, numbered 2585. The town was founded in 1865 by a group of colonists from Wales, assisted by the Argentine government; and its prosperity has led to the foundation of other important centres in the valley, such as Trelew and Gaiman, which is connected by railway with Puerto Madryn on Bahia Nueva. Rawson, the capital, is situated at the mouth of the river Chubut on the Atlantic (42°30'S).

Chubut territory presents the same characteristics as the Río Negro territory. miles), embracing the region between 42° and 46°S;. Chubut, covers 224,686 km² (86,751 sq. In 42°S there is a third broad transverse depression, apparently the bed of another great river, now perished, which carried to the Atlantic the waters of a portion of the eastern slope of the Andes, between 41° and 42°30;S.

To the south of the Rio Negro the Patagonian plateau is intersected by the depressions of the Gualicho and Maquinchao, which in former times directed the waters of two great rivers (now disappeared) to the gulf of San Matias, the first-named depression draining the network of the Collon Cura and the second the Nahuel Huapi lake system. In this depression are several settlements, among them Viedma, the capital of the Rio Negro territory, Pringles, General Conesa, Choele Choel and General Roca. the middle part of which is followed by the railway which runs to the settlement of Neuquen at the confluence of the rivers Limay and Neuquen. The Río Negro River runs along a wide transverse depression.

miles), extending from the Atlantic to the Cordillera of the Andes, to the north of 42°S. Río Negro covers 203,013 km² (78,383 sq. Lake Lacar is now a contributary of the Pacific, its outlet having been changed to the west, owing to a passage having been opened through the Cordillera. These regions are drained by the river Collon Cura, the principal affluent of the river Limay.

Close to these are the famous apple orchards supposed to have been planted by the Jesuits in the 17th and 18th centuries. The wide valleys occur near Rio Malleo, Lake Huechulafquen, the river Chimehuin, and Vega de Chapelco, near Lake Lacar, where are situated villages of some importance, such as Junin de los Andes and San Martin de los Andes. In the centre of the territory, also in the neighborhood of the mining districts, are the valleys of Norquin and Las Lajas, the general camp of the Argentine army in Patagonia, with excellent timber in the forest on the Andean slope. More to the west is the mining region, in great part unexplored, but containing deposits of gold, silver, copper and lignite.

Chos Malal, the capital of the territory, is situated in one of these valleys. As the Cordillera is approached the soil becomes more fertile, and suitable districts for the rearing of cattle and other agricultural purposes exist between the regions which surround the Tromen volcano and the first ridges of the Andes. The Neuquen river is not navigable, but as its waters are capable of being easily dammed in places, large stretches of land in its valley are utilized; but the lands on each side of its lower part are of little commercial value. On the upper plains of Neuquen territory thousands of cattle can be fed, and the forests around Lakes Tiaful and Nahuel-Huapi yield large quantities of valuable timber.

miles), including the triangle between the Limay River and Neuquén River, which extends southward to the northern shore of Lake Nahuel-Huapi (41°S) and northward to the Rio Colorado. Neuquén covers 94,078 km² (36,324 sq. Population = 1,740,000 (2001 census).
Land Area = 787,000 km²
Population Density = 2.21 / km²
. With the exception of the discoveries at the inlet of Ultima Esperanza, which is in close communication with the Atlantic valley of Río Gallegos, none of these remains have been discovered in the Andean regions.

The animals undoubtedly reached these localities from the east; it is not at all probable that they advanced from the north southwards across the plateau intersected at that cime by great rivers and covered by the ice-sheet. One fact, however, which apparently demonstrates with greater certainty the existence in recent times of land that is now lost, is the presence of remains of pampean mammals in Pleistocene deposits in the bay of Puerto San Julian and in Santa Cruz. There are besides, in the neighborhood of the present coast, deposits of volcanic ashes, and the ocean throws up on its shores blocks of basaltic lava, which in all probability proceed from eruptions of submerged volcanoes now extinct. From an examination of the pampean formation it is evident that in recent times the land of the province of Buenos Aires extended farther to the east, and that the advance of the sea, and the salt-water deposits left by it when it retired, forming some of the lowlands which occur on the littoral and in the interior of the pampas, are much more recent phenomena; and certain caps of shingle, derived from rocks of a different class from those of the neighboring hills, which are observed on the Atlantic coasts of the same province, and increase in quantity and size towards the south, seem to indicate that the caps of shingle which now cover such a great part of the Patagonian territory recently extended farther to the east, over land which has now disappeared beneath the sea, while other marine deposits along the same coasts became converted into bays during the subsequent advance of the sea.

They are composed of caps of shingle, with great, more or less rounded boulders, sand and volcanic ashes, precisely of the same form as occurs on the Patagonian plateau. Some of the promontories of Chiloé are still called huapi, the Araucanian equivalent for "islands"; and this may perhaps be accepted as perpetuating the recollection of the time when they actually were islands. In so far as its main characteristics are concerned, Patagonia seems to be a portion of the Antarctic continent, the permanence of which dates from very recent times, as is evidenced by the apparent recent emergence of the islets around Chiloé, and by the general character of the pampean formation. Several of the high peaks are still active volcanoes.

These ice-sheets, which scooped out the greater part of the longitudinal depressions, and appear to have rapidly retreated to the point where the glaciers now exist, did not, however, in their retirement fill up with their detritus the fjords of the Cordillera, for these are now occupied by deep lakes on the east, and on the west by the Pacific channels, some of which are as much as 250 fathoms (460 m) in depth, and soundings taken in them show that the fjords are as usual deeper in the vicinity of the mountains than to the west of the islands. In Patagonia an immense ice-sheet extended to the east of the present Atlantic coast during the first ice age, at the close of the Tertiary epoch, while, during the second glacial age in modern times, the terminal moraines have generally stopped, 30 miles (50 km) in the north and 50 miles (80 km) in the south, east of the summit of the Cordillera. Glaciers occupy the valleys of the main chain and some of the lateral ridges of the Cordillera, and descend to lakes San Martín Lake, Viedma Lake, Argentino Lake and others in the same locality, strewing them with icebergs. It would not be surprising if this latter animal were still in existence, for footprints, which may be attributed to it, have been observed on the borders of the rivers Tamangoand Pista, affluents of the Las Hefas, which run through the eastern foot-hills of the Cordillera in 47°S.

With the remains of Grypotherium have been found those of the horse (Onoshippidium), which are known only from the lower pampas mud, and of the Arciotherium, which is found, although not in abundance, in even the most modern Pleistocene deposits in the pampas of Buenos Aires. In deposits of much later date, formed when the physiognomy of the country did not differ materially from that of the present time, there have been discovered remains of pampean mammals, such as Glyptodon and Macrauchenia, and in a cave near Last Hope Inlet, a gigantic ground sloth (Grypoiherium listai), an animal which lived contemporaneously with man, and whose skin, well preserved, showed that its extermination was undoubtedly very recent. In the Tertiary marine formation a considerable number of cetaceans has been discovered. Other specimens of the interesting fauna of Patagonia, belonging to the Middle Tertiary, are the gigantic wingless birds, exceeding in size any hitherto known, and the singular mammal Pyrotherium, also of very large dimensions.

The Patagonian Myolania belongs to the Upper Chalk, having been found associated with remains of Dinosauria. This, together with the discovery of the perfect cranium of a chelonian of the genus Myolania, which may be said to be almost identical with Myolania oweni of the Pleistocene age in Queensland, forms an evident proof of the connection between the Australian and South American continents. The Upper Cretaceous and Tertiary deposits have revealed a most interesting vertebrate fauna. They are divided by Wilckensi into the following series (in ascending order):.

The Tertiary deposits are greatly varied in character, and there is considerable difference of opinion concerning the succession and correlation of the beds. Porphyritic rocks occur between the schists and the quartzites. First come Lower Cretaceous hills, raised by granite and dioritic rocks, undoubtedly of Tertiary origin, as in some cases these rocks have broken across the Tertiary beds, so rich in mammal remains; then follow, on the west, metamorphic schists of uncertain age; then quartzites appear, resting directly on the primitive granite and gneiss which form the axis of the Cordillera. The Tertiary plateau, flat on the east, gradually rising on the west, shows Upper Cretaceous caps at its base.

The geological constitution is in accordance with the orographic physiognomy. This latter depression contains the richest and most fertile land of Patagonia. There, in contact with folded Cretaceous rocks, uplifted by the Tertiary granite, erosion, caused principally by the sudden melting and retreat of the ice, aided by tectonic changes, has scooped out a deep longitudinal depression, which generally separates the plateau from the first lofty hills, the ridges generally called the pre-Cordillera, while on the west of these there is a similar longitudinal depression all along the foot of the snowy Andean Cordillera. In the central region volcanic eruptions, which have taken part in the formation of the plateau from the Tertiary period down to the present era, cover a large part with basaltic lava-caps; and in the western third more recent glacial deposits appear above the lava.

Besides these transverse depressions (some of them marking lines of ancient inter-oceanic communication), there are others which were occupied by more or less extensive lakes, such as the Yagagtoo, Musters, and Colhue Huapi, and others situated to the south of Puerto Deseado, in the centre of the country. Among the depressions by which the plateau is intersected transversely, the principal are the Gualichu, south of the Rio Negro, the Maquinchao and Valcheta (through which previously flowed the waters of lake Nahuel Huapi, which now feed the river Limay); the Senguerr, the Deseado River. Towards the Andes the shingle gives place to porphyry, granite, and basalt lavas, animal life becomes more abundant and vegetation more luxuriant, acquiring the characteristics of the flora of the western coast, and consisting principally of southern beech and conifers. In the hollows of the plains are ponds or lakes of brackish and fresh water.

The general character of the Argentine portion of Patagonia is for the most part a region of vast steppe-like plains, rising in a succession of abrupt terraces about 100 meters (330 feet) at a time, and covered with an enormous bed of shingle almost bare of vegetation. . East of the Andes the Argentine portion of Patagonia includes the provinces of Neuquén, Río Negro, Chubut, Santa Cruz, and Tierra del Fuego, as well as the southern tip of the Buenos Aires Province. The Chilean portion embraces the southern part of the region of Los Lagos, and the regions of Aysen and Magallanes (excluding the portion of Antarctica claimed by Chile).

Patagonia is that portion of South America which, to the east of the Andes, lies south of the Neuquén and Río Colorado rivers, and, to the west of the Andes, south of (42°S). Confined to the eastern part of the region. Pliocene. Sandstones and conglomerates with marine fossils.

Paranfl series. Middle and Upper Miocene. Containing remains of mammals. Santa Cruz series.

Lower Miocene. Partly marine, partly terrestrial. Patagonian Molasse. Eocene and Oligocene.

Of terrestrial origin, containing remains of mammalia. Pyrotherium-Notostylops beds.