RELIEF UNITS and PREVALENT SOILS in DÂMBOVIŢA COUNTY ŞTEFAN ISPAS* Dâmboviţa County Is Characterized by a Very Varied Relie
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The Annals of Valahia University of Târgovişte, Geographical Series, Tome 8 / 2008 _____________________________________________________________________________________________________________ RELIEF UNITS AND PREVALENT SOILS IN DÂMBOVIŢA COUNTY * ŞTEFAN ISPAS Summary: Dâmboviţa County is characterized by a very varied relief, which includes three big different units: the mountain unit, the hill unit and the plain unit. The mountain unit (9%) is represented by Bucegi Mountains and Leaota Mountains. The hill unit, which is much more extended (30%), includes The Ialomiţei Sub-Carpathians and Cândeşti Piedmont. The Ialomiţei Sub-Carpathians represent a hilly subunit, which was formed at the end of the alpine orogenesis, by the folding of the sedimentary deposits accumulated in the Carpathian deep syncline; Cândeşti Piedmont represent a tableland subunit, with a monocline structure, whose genesis has begun much earlier before The Sub-Carpathians. The plain unit, which is the most extended (61%), includes piedmont plains (such as Târgoviştei Plain, Cricovului Plain, Ploieştilor Plain, Piteştilor Plain, Găvanu-Burdea Plain), flaggy plains (Vlăsiei Plain) and subsidence plains (Titu Plain and Ibrianu Plain). Key words: mountain, hill, piedmont, plain, dejection cone, subsidence, flaggy relief, soil. Rezumat: Judeţul Dâmboviţa se caracterizează printr-un relief foarte variat, în cadrul căruia au fost separate trei mari unităţi: de munte, colinară şi de câmpie. Unitatea montană (9 %) este reprezentată de Munţii Bucegi şi Munţii Leaota. Unitatea colinară, mult mai extisă (39 %), cuprinde Subcarpaţii Ialomiţei şi Piemontul Cândeşti. În timp ce Subcarpaţii Ialomiţei reprezintă o subunitate deluroasă, care s-a format la sfârşitul orogenezei alpine, prin cutarea depzitelor sedimentare acumulate în avanfosa carpatică, Piemontul Cândeşti reprezintă o subunitate de podiş, cu structură monoclinală, a cărei geneză a început cu mult înaintea Subcarpaţilor. Unitatea de câmpie, cea mai extinsă (61 %), are în componenţa sa câmpii piemontane (Câmpia Târgoviştei, Câmpia Cricovului, Câmpia Ploieştilor, Câmpia Piteştilor şi Câmpia Găvanu – Burdea), câmpii tabulare (Câmpia Vlăsiei) şi câmpii de subsidenţă (Câmpia Titu şi Câmpia Ibrianu) Dâmboviţa County is characterized by a very varied relief which lowers from north to south, like a flight of steps, from over 2500 m. in the north to approximately 100 m. in the south. We can also notice the same big variety in the lithological structure; this fact, associated with climate and vegetation, has determined the vertical soil zonality. As a result, we can notice inside Dâmboviţa County three big different relief units: the mountain unit (9%), the hill unit (30%) and the plain unit (61%); each of the above mentioned units includes several subunits. I. THE MOUNTAIN UNIT The mountain unit lies in the Northern side of Dâmboviţa County and includes Bucegi Mountains and Leaota Mountains, which are very different if we take into account their geological structure and their relief appearance. Bucegi Mountains have the form of an amphitheatre with southern opening, delimited by almost vertical abrupts compared with the coterminous areas; for example, the abrupt towards The Valley of Prahova is characteristic. These mountains are mainly made up of conglomerates and sandstones and less of limestone. From the structural point of view, they correspond to a suspended syncline; the Ialomiţa river installed on the axle of this suspended syncline. The maximum height is 2505 m., reached by Omu Peak. There are several glacial valleys around this peak (The Valley of Ialomiţa, Mălăieşti Valley, Gaura Valley). The superior side of these mountains has the form of an extended structural surface, bearing the * Valahia University of Targoviste 65 The Annals of Valahia University of Târgovişte, Geographical Series, Tome 8 / 2008 _____________________________________________________________________________________________________________ name of ,,the plateau of Bucegi”; strange relief forms, such as “Babele” and “Sfinxul”, were created within this plateau as a result of the differential erosion. The structural relief is also characteristic for Bucegi Mountains and it is more obvious of the flanks of the syncline. The carst relief is present along The Valley of Ialomiţa, where caves and gorges can be met, such as: The Cave of Ialomiţa River, Urşilor, Tătarului, Zănoagei, Scropoasei and Orzei Gorges. Leaota Mountains lie in the west side of Bucegi Mountains; these two mountains are separated by Brăteiului Valley, continued with the Valley of Ialomiţa until the locality bearing the name of Moroeni. Leaota Mountains are made up of crystalline metamorphic schists and their maximum height is 2135 m., reached by Leaota Peak; the periglacial phenomena are intensely developed around this peak. It has recently been proved the existence of the glacial relief, too, within these mountains (Murătoreanu G., 2008). Generally, the relief has the form of some summits with rounded backs, whose morphology was influenced by the crystalline metamorphic schists, which are very resistant to erosion. Some little carst areas are encountered only in the north-western and south-eastern side, awarding picturesque aspects to the relief. Within the mountain unit, there are some hazy opinions concerning the compartment situated in the south of Bucegi Mountains, between Ialomicioara Valley and The Ialomiţei Sub-Carpathians. In “The Geography of Romania”, III-rd volume, this compartment is included in Bucegi Mountains (page 244 and page 247), although the southern limit of these mountains has previously been settled at Ialomicioarei Valley (Velcea Valeria, 1961). The above-mentioned area is included in Gârbovei Mountains, from which it has probably been separated as a result of the formation of the superior valley of the Prahova river, in “The Geography of the Romanian Carpathians and Sub- Carpathians” (Velcea Valeria, 1982), on the map of Bucegi mountain complex (page 111). Because of the specific features of its relief (Gurguiatu Peak is 1338 m. high), the above-mentioned compartment is different from Bucegi Mountains, as well as from The Sub-Carpathians; if it is included in Gârbovei Mountains, this means that The Valley of Prahova is no more such a categorical bound between The Eastern Carpathians and The Meridional Carpathians. II. THE HILL UNIT (THE HILL AND TABELELAND UNIT) It is represented by The Ialomiţei Sub-Carpathians and by Cândeşti Piedmont, which represent the central-northern side of the county. The Ialomiţei Sub-Carpathians lie in the east of the valley of the Dâmboviţa river, having very clear bounds both to the north, towards the mountain area, and to the south, toward the plain area. They were formed at the end of the alpine orogenesis, by the folding of the sedimentary layers accumulated in the Carpathian deep syncline. The Sub-Carpathian relief consists in hills, depressions and valley passages. The adaptation of the relief to the folded structure is obvious, because some hills correspond to the anticlines, and the valleys correspond to the synclines. But there are relief inversions, too. Depending on the genesis, petrographical structure and the special features of the relief, we can distinguish the internal Sub-Carpathians in the northern half and the external Sub-Carpathians in the southern half. The internal Sub-Carpathians are older and consist in cretaceous and paleocene flysch; they are represented by hills that have the form of some summits, being 600-800 m. high. In the northern side, at the contact with The Carpathians, there is an alignment of the contact depressions, having a tectonic and erosive nature (Mihăilescu V., 1966); Pucheni, Runcu and Moroeni depressions are representative. 66 The Annals of Valahia University of Târgovişte, Geographical Series, Tome 8 / 2008 _____________________________________________________________________________________________________________ Văleni Dâmboviţa Depression lies approximately on the same alignment, but in the west of the valley of the Dâmboviţa river; within Văleni Dâmboviţa Depression, the folded structure in the Sub-Carpathians interferes with the monocline structure of Cândeşti Piedmont, which causes the appearance of a sector having a very complex structure. To the south, at the bound between the internal Sub-Carpathians and the external Sub-Carpathians, there is a second range of depressions: Voineşti, on the Dâmboviţa river, Pucioasa, on the Ialomiţa river and Valea Lungă on the Cricovul Dulce river. We must notice the appearance of several isolated hills, known with the name of knolls. The external Sub-Carpathians are younger, consist in soft pliocene deposits, less resistant to erosion and are represented by hills having more reduced altitudes (400 – 600 m.) and more gentle slopes; that is why they are called table lands: Pietrei Table Land, Stânei Table Land, Pârliturii Table Land. We must notice the appearance of a new range of depressions, some of them being smaller, but very well individualized, such as Glodeni and Ocniţa depressions. To the west, Moreni Depression on the Cricovul Dulce river is much larger. Ocniţei Depression is a buttonhole resulted from the differential erosion within a diapire fold. The increased fragmentation of the relief and the alternation of the rocks (sandstones, clays, marls), which are specific elements for the entire Sub-Carpathian area, has encouraged the intense progress of erosion process and of landslides. As a matter of fact, the eroded