. – The complex of high ranges, plateaus and hills, which constitutes the Romanian Carpazîs, can be divided, according to the shapes of the relief and the geological structure, into five sections, of which only in the recent Pliocene the grouping and the orographic importance.
The external arch, which runs from the Iron Gates to the Polish border, is in turn formed by two large units, two ancient massifs, connected by an area of recent chains. The Transylvanian-Banatic Massif, to the south-west, formed almost completely by crystalline schists, is the largest, the highest and the most anciently consolidated; in fact, the main corrugation effort took place there in the Middle Cretaceous period. The Bucovina-MaramureŞ massif, to the north-east, has almost the same structure, but with greater complexity, accentuated by the intervention of volcanic phenomena.
These two mighty masses are welded to each other by the series of Moldavian Chains, formed of flysch sandstone, whose corrugation continued throughout the Tertiary, continuing towards the plain during the Quaternary, in the region of maximum curvature of the arch between Buzău and Prahova.
While the chain was thus delineating and widening at the expense of the foreland area, its internal side underwent a fractionation, to which Transylvania owes its appearance. The Bihor Massif, which does not reach 2000 m., Is the most impressive witness of a very complex tectonic construction. Most of the building disappeared by sinking until the middle of the Tertiary, and was covered, over a considerable thickness, by the sediments of continental seas or by löss, definitively dried up in the Pliocene, and then engraved by erosion in undulating hills. It is the Transylvania basin.
The Transylvanian-Banatic Massif, which extends into the Banat and southwestern Transylvania for a length of 250 km. (from the Iron Gates to Dâmboviţa) and for a length ranging from 40 to 100 km., it is the complex of the highest peaks not only of the Romanian Carpazî, but of the whole Carpathian chain; in fact, if the Tatras overtake the Negoi, this latter peak has a large number of rivals in Romania, exceeding 2000 m. Furthermore, the crystalline rocks do not form reliefs on such a considerable extent anywhere else, accompanied and penetrated by powerful intrusions of granite and green rocks.
Geologists distinguish two metamorphic series, the oldest and the most typically crystalline (gneiss, micacysts) of the primary era; the most recent of the secondary. It is believed that they underwent corrugations accompanied by carriageways that affected a blanket of non-metamorphosed sediments, including limestone masses of various periods (Triassic, Liassic, Jurassic). These limestones, whose picturesque appearance interrupts the monotony of the crystalline ridges, appear only in narrow bands along the lines of abnormal contact. The last important orogenic phase would date from the Cretaceous period, because the Danian of the Haţeg Basin is not at all corrugated. In these conditions it is understood how most of the time the anticlinal and synclinal axes do not function as guidelines for the survey. From the Cretaceous period, the
The peaks appear as rounded ridges: sometimes true undulating platforms have survived, as in the Boresco, at more than 2000 m. high. The age of this platform of the highest peaks has been fixed in the Bihor to the Eocene.
A more recent and very extensive leveling area is still well preserved in the region of the sources of the Riu Ses: but others can also be recognized.
To finish outlining the physiognomy of these mountains, it is necessary to note two characteristic phenomena: the gorges carved through the crests of streams born on the Transylvanian side, such as the Jiu and Olt (Aluta), and the glacial modeling of the highest peaks.
The gorges, often with the appearance of wild corridors, were initiated, or even entirely engraved, in less accentuated phases, when the erosion had not yet excavated the great valleys of the Neogenic region in Transylvania: therefore, under a certain point of sight, they have characters of antecedent throats. The glacial modeling, similar to that of the Tatras, denotes that in the Quaternary the limit of permanent snow was between 1700 and 1900 m.
The extension of the Transylvanian-Banatic massif obliges to divide it into a certain number of massifs, separated by more or less deep and more or less wide gorges, according to whether they are due to tectonic depressions (with the preservation of the Neogenic deposits) or only to the erosion. These massifs can be grouped into two series, a western one which includes the banatic massicus proper (although its borders go beyond those of the Banat) and an eastern one, which can retain the name of the Transylvanian Alps.
The Banatic Massif is a mighty complex, measuring 120 km. from west to east and about 100 from north to south. A great meridian groove, of tectonic origin, the Neogenic corridor of CaransebeŞ, in which the upper TimiŞ and the lower Cerna flow in an opposite direction, divides it into two unequal parts: to the west the Banat Ore Mountains, culminating at 1447 m. in the Piatra Semenicului, they are formed by small chains and plateaus, where crystalline, schistose and calcareous formations alternate in tight folds, and where eruptive flows have created rich deposits of metals, exploited above all in ReŞita. To the east the mountain is itself divided again by two deep cracks. The first, with an east-west direction, is a tectonic shower crossed by the Bistra, which isolates the Massif of Rusca, remarkable because there are preserved erosion platforms between 900 and 1000 m.; the second, much narrower and with a direction from south-west to north-east, is crossed in the opposite direction by the Cerna through wild gorges, and by the Jiu, which has carved a large depression in the neogenic layers, rich in lignite, of the PetroŞani Basin. South of this last furrow, the crystalline masses are less high (the Vulcan Mountains do not exceed 1700 m.); to the north, on the other hand, we find ourselves in front of a compact block of high peaks over 2000 m., monotonous platforms flared by small cirques such as the Boresco (2200 m.) or real alpine chains such as the Retezat (2480 m.) with acute crests eroded by vast circuses containing lakes.
The Transylvanian Alps begin to the east of the great transverse depression: Haţeg Basin, upper Streiu, PetroŞani Basin. The Olt gorge distinguishes two groups: to the west the SebeŞ mountains and the Sibiu mountains, which for the extension of the platforms would resemble the Poiana Rusca, if several massifs carved by glacial cirques did not rise above 2000 m. (Surian 2061 m., Cindrelu 2245 m.); and the Parângului Mountains, which are a mighty block, notable for its cirques and lakes, culminating at 2529 m. in the Vârful Mândra; to the east the Făgăraş Mountains, crystalline, rocky, partly shaped by glaciers and culminating in M. Negoi (2544 m.), the highest peak in all of Romania.
The Bucovina Massif, less extensive than the Transylvanian-banatic one, is however more complex. The crystalline schists form rounded reliefs, where the remains of platforms are still found, dominated by jagged ridges engraved by glacial cirques, as in Rodna (2305 m.); some picturesque peaks are given by limestone blocks (Rareu); narrow furrows, due to river erosion, pass from one side to the other (gorges of Bistriţa); and tectonic basins filled by the Neogenic (Borga Basin, Vatra-Dornei Basin) form communication routes in the midst of fairly inaccessible mountains.
A new fact is represented by the flanking of the ancient crystalline massif of an area of recent corrugations, affecting the sandstones of the Cretaceous flysch, forming a series of squat chains (rarely exceeding 1500 m.) And clearly oriented longitudinal corridors. This recent growth of the mountain on the outside is offset by its losses on the inside. It is marvelous to see the grandiose relief of the Rodna abruptly lowering on the high Someş instead of the high banatic massifs appear the hills of the Transylvanian Basin. The sinking led to volcanic eruptions, which built, south of the Vatra-Dornei Basin, the enormous andesitic massif of Căliman, culminating at 2102 m.
The splitting of the Bucovina massif is a prelude to its definitive disappearance at the height of Gheorgheni, since the picturesque peak of Hăsmasul Mare (1793 m.) Is the last trace of the Jurassic coverage. For 200 km. in length, up to Prahova, the Carpathian arc will be closed only by the detrital sediments of the Cretaceous and Paleogenic flysch rising in tight folds above the Neogenic plains of Moldavia and eastern Wallachia. The advance of the mountain front must have continued at least up to the upper Pliocene, progressing in stages, since erosion attacked the already raised internal aquifer, at the very moment in which new folds were formed. The oldest elements cover the most recent along an arched line.
Longitudinal basins, due to subsidence or attenuation of the uplift, form depressions sought as human sites sometimes up to the very heart of the mountain, but more often in the external area. This offers only a few paleogenic wedges in the midst of neogenic folds, which are of interest up to the Levantian.
The internal area (Cretaceous and Paleogenic) was probably leveled and owes its relief to a resumption of the uplift, which accompanied the Neogenic bending. The longitudinal arrangement of the valleys and ridges is less clear-cut. Above the rounded yokes, the highest peaks rise like ancient witnesses escaped from erosion, always made up of harder sandstones or conglomerates preserved in the synclines, with bold and picturesque shapes such as the Ceahlău (1904 m.), Which for a long time it was considered the highlight of Moldavia, and above all the Bucegi (2506 m.), whose formidable slopes dominate the delightful Prahova valley and the royal residence of Sinaia.
The external, neogenic zone, called the Subcarpazî or the high subcarpathian hills, assumes all its extension towards the south. In Odobeşti, near Focşani, the Levantian can be seen rising in a continuous slope up to 1000 m.: towards Buzău it is taken within the folds: towards Ploeşti, anticlines emerge from the terraces which rise rapidly and whose surface is disturbed by movements of the soil extended up to the Quaternary. The sandstones, clays and sands are intensely shaped by erosion, favored by deforestation. Strange landscapes are created by the rock salt, which sometimes surfaces, and by the oil, extracted on a large scale around Târgu Ocna and especially around Ploeşti.
The Bihor Massif – which the Romanians of Cluj also give the name of Mun ţ ii Apuseni (Sunset Mountains) – is the most important witness of the inner wing of the Carpazî. If the height does not reach 2000 m. (Cucurbeta 1849 m.), The extreme variety of the structure and orientations of the outcrops, indicates that several wrinkles of different ages and nature have intervened here. The dislocations have given rise to manifestations of volcanism since the beginning of the Tertiary and the eruptions have continued until the Neogenic.
The leveling phases observed in the Transylvanian-Banatic Massif have left evident traces: and the oldest, to which the undulating platforms of the upper Bihor are due, has been able to be dated in the vicinity of Cluj, where it can be seen lowering and disappearing under deposits eluvial, with which limestone and Eocene nummulites are mixed or superimposed: the dislocations of the contact surface, easily traceable, allow us to affirm that the relief is due to a posthumous uplift on the type of overall movements.
Narrow valleys are carved into the crystalline plateau sloping towards the Transylvanian Basin: an arch of limestone chains, cut by wild gorges, gives it a picturesque front from the south-east side, above the Mureş valley; while in the schists and in the sandstones of the lower Cretaceous period a very deep network of valleys developed, dominated by the eruptive mamelons of the surroundings of Abrud. To the south-west and west, the massif descends in steps dislocated by faults, and is partly submerged under the Neogenic layers, which are mixed with great effusions of lava and above all of andesitic tuffs. Small isolated basins have exerted an attraction for their mineral riches (gold, copper near Brad and Zlatria) or for the hospitality they offered to peaceful agricultural populations (Beiuş). The limestone plateaus, modeled by codru), and the crystalline blocks with rounded backs are increasingly submerged in the tertiary sediments towards the north-west and north.