A S O C I A I A G E O M O R F O L O G I L O R D I N R O M N I A
REVISTA DE GEOMORFOLOGIE
13
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REVISTA DE GEOMORFOLOGIE / REVIEW OF GEOMORPHOLOGIE
Editori/Editors: Prof. univ. dr. Virgil SURDEANU Preedintele A.G.R., Universitatea Babe-Bolyai, Cluj Napoca Prof. univ. dr. Florina GRECU, Universitatea din Bucureti
Colegiul de redacie/Editorial boards: Dr. Lucian BADEA, Institutul de Geografie, Bucureti Prof. dr. Yvonne BATHIAU-QUENNEY, Universitatea din Lille, Frana Prof. dr. Dan BLTEANU, Universitatea din Bucureti Prof. dr. Costic BRNDU, Universitatea tefan ce! Mare, Suceava Prof. dr. Doriano CASTALDINI, Universitatea din Modena, Italia
Prof. dr. Adrian CIOAC, Universitatea Spiru Haret, Bucureti Prof. dr. Morgan de DAPPER, Universitatea din Gand, Belgia
Prof. dr. Mihaela DINU, Universitatea Romno-American, Bucureti Prof. dr. Francesco DRAMIS, Universitatea Roma 3, Roma, Italia
Prof. dr. Eric FOUACHE, Universitatea Paris 12, Frana Prof. dr. Paolo Roberto FEDERICI, Universitatea din Pisa, Italia
Prof. dr. Mihai GRIGORE, Universitatea din Bucureti Prof. dr. Mihai IELENICZ, Universitatea din Bucureti Prof. dr. Ion IONI, Universitatea Al.I. Cuza, Iai Prof. dr. Aurel IRIMU, Universitatea Babe-Bolyai, CIuj-Napoca Prof. dr. Nicolae JOSAN, Universitatea din Oradea
Prof. dr. Ion MAC, Universitatea Babe-Bolyai, Cluj-Napoca Prof. dr. Andr OZER, Universitatea din Lige, Belgia Prof. dr. Kosmas PAVLOPOULOS, Universitatea din Atena, Grecia
Prof. dr. Dan PETREA, Universitatea Babe-Bolyai, Cluj-Napoca Prof. dr. docent Grigore POSEA, Universitatea Spiru Haret, Bucureti Prof. dr. Ioan POVAR, Institutul de Speologie, Bucureti Prof. dr. Maria RDOANE, Universitatea tefan cel Mare Suceava Prof. dr. Nicolae RDOANE, Universitatea tefan cel Mare, Suceava Prof. dr. Contantin RUSU, Universitatea Al. I. Cuza, Iai Dr. Maria SANDU, Institutul de Geografie, Bucureti Prof. dr. Victor SOROCOVSCHI, Universitatea Babe-Bolyai, Cluj-Napoca Prof. dr. Petre URDEA, Universitatea de Vest, Timioara Prof. dr. Emil VESPREMEANU, Universitatea din Bucureti Prof. dr. Fokion VOSNIAKOS, Universitatea din Salonic, Grecia
Redacia tehnic/Tehnical assistants: Prof. dr. Bogdan MIHAI (Universitatea din Bucureti) Cercet. t. drd. Marta JURCHESCU (Institutul de Geografie al Academiei Romne) Lector dr. Robert DOBRE (Universitatea din Bucureti)
os. Panduri, 90-92, Bucureti 050663; Telefon/Fax: 021.410.23.84 E-mail: [email protected]
Internet: www.editura.unibuc. ro
Tehnoredactare computerizat: Meri Pogonariu
ISSN 1453-5068
R E V I S T A D E G E O M O R F O L O G I E
VOL. 13 2011
C U P R I N S / C O N T E N T S
A r t i c o l e / P a p e r s
Rolul proceselor periglaciare n morfodinamica actual n bazinul superior al Rului Doamnei (Munii Fgra). Procesele periglaciare (sau crionivale, n funcie de accepiunea diferit a acestor termeni) dein rolul principal n dinamica actual a reliefului situat deasupra limitei superioare a pdurii (1780 m). Dac lum n considerare izoterma de 3
0C, ca limit inferioar de manifestare a fenomenelor periglaciare (French, 1996), relieful situat la peste 1800m altitudine n bazinul Rului Doamnei (adic 94 kmp) este modelat de procese periglaciare. Acestea se suprapun i continu la scar mai mic procesele i formele periglaciare mai vechi, pleistocene i postglaciare, se mbin sau alterneaz sezonier cu procesele fluviale, toreniale, gravitaionale, eoliene etc.
Procesele periglaciare sunt determinate de climatul rece, aspru i umed specific zonei nalte a Munilor Fgra i influenate de o serie de ali factori (litologia, structura, panta i expoziia versanilor, depozitele superficiale, solurile, vegetaia), rezultnd astfel un sistem complex de modelare actual a reliefului situat la altitudini ce depesc limita superioar a pdurii.
Formele periglaciare mai mari sunt, n general, relicte sau fosile, multe dintre acestea fiind distruse sau acoperite de pdure (grohotiuri fosile, gheari de pietre). Alte forme i continu evoluia din pleistocen, cu o intensitate mai redus (creste, vrfuri, abrupturi), iar unele forme actuale le acoper pe cele mai vechi, avnd dimensiuni mai reduse (grohotiurile actuale). Formele actuale difer ca tip, mrime i extindere spaial i altitudinal, fiind n general mai mici (microforme) i mai puin diversificate dect precedentele.
n arealul studiat nu ntlnim toat varietatea de forme periglaciare: ondulaiile i terasetele de solifluxiune, muuroaiele nierbate, conurile de grohoti, torenii de pietre, culoarele de avalan, niele nivale i potcoavele nivale sunt frecvent ntlnite; ns alte forme periglaciare distinctive, cum ar fi solurile poligonale, cercurile de pietre i ghearii de pietre sunt rar ntlnite i doar n forme embrionare sau inactive.
Cuvinte cheie: procese periglaciare, forme de relief periglaciare, bazinul Rului Doamnei, Munii Fgra Key words: periglacial processes, periglacial landforms, Doamnei River basin, Fgra Mountains
1. Introduction
The periglacial processes (or the cryonival processes, depending on the different acceptance of the terms) play a major role in the present dynamics of the landforms situated above the timberline (1780m). Considering the 3
0C isotherm to be the
lower limit of manifestation of the periglacial phenomena (French, 1996), the landforms situated above 1800m altitude in the Doamnei River basin (namely 94 sq.km) are shaped by the periglacial processes. They overlap and continue at a smaller scale the older Pleistocene and postglacial processes and landforms, combining and alternating seasonally with fluvial, torrential, gravitational and aeolian processes.
The mountain (upper) basin of Doamnei River (fig. 1) is located on the central-eastern part of the southern side of the Fgra Mountains (Meridional Carpathians). Geology is represented by the
crystalline rocks (crystalline schists, micaschists, gneisses and intercalated parallel east-west stripes of harder rocks, crystalline limestones and amphibolites) of the Arge Nappe (Cumpna Unit) and the Moldoveanu Nappe (Supragetae Unit) for the main ridge.
The mountain basin of Doamnei River is characterized by a typical alpine, subalpine and mountainous morphology. The main features of this subunit are: prevalence of high hypsometric steps that exceed 1600m altitude (including 4 peaks over 2500m and 18 peaks over 2400m), high values of landform energy (400-600m, and locally over 1000m for the area adjacent to the glacial valleys), very high and steep slopes (predominant slopes of and over 30
0-50
0), high massiveness. Because it
spreads over one third of the southern slope of the Fgra Massif, the Doamnei River basin preserves a great variety and complexity of landforms, as a genuine geomorphologic book: erosion leveled
Rev is ta d e geo morfo log ie vol. 13, 2011, pp. 109-121
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landforms, relict glacial landforms, periglacial and nival landforms, fluvial landforms, structural and lithologic landforms.
2. The Periglacial Processes
The periglacial processes are generated by the
severe, cold and wet climate specific to the high
Fgra Mountains and are influenced by other factors, too (lithology, structure, declivity, aspect,
surface deposits, soils, and vegetation), the result
being a complex morphodynamic modelling system
acting at present above the timberline.
The research for the Meridional Carpathians
(Passoti, 1994; Urdea, 1992, 2000, 2001; Urdea et
al., 2003; Voiculescu 2000, 2001, 2002; Kern et al.,
2004) showed two permafrost sublevels: the
discontinuous (possible) permafrost sublevel
above 2300m altitude, and the sporadic
permafrost sublevel at 2050-2300m altitude (with
200m difference depending on the slope aspect).
According to the temperature limits (average yearly
temperature), the vertical thermic gradient (0,630C/
100m) and the references, two morphoclimatic
levels were identified in the Fgra Mountains (Voiculescu, 2002; Urdea, 2000): the periglacial
level above the 2-30C isotherm (table 2) and the
fluvio-denudation level below this isotherm (below
the upper timberline). In the Doamnei River basin,
the landforms situated above 1800m altitude represent
94 sq.km and 25 % of total mountain basin.
There are some favorable areas for permafrost
formation and preservation (rock glaciers, protalus
rampart, rock streams, talus cones) as the
avalanches supply a mixture of snow and debris.
There are many snow patches preserved from one
year to another and they indicate the sporadic
permafrost (fig. 1).
The processes that shape the landforms of alpine
and subalpine Fgra Mountains are determined by the temperature variation and the freeze-thaw
processes that alter the substratum (rock,
mantlerock, debris, soil) differently (by frost
weathering, frost shattering, frost heaving); the ice
in the soil, the snow and the meltwater moisten this
substratum and facilitate its movement. The
characteristic alpine and subalpine vegetation
reduces the material movement on lower slopes.
Frost weathering and nivation are the dominant
periglacial processes and they combine and alternate
seasonally with the fluvio-torrential processes.
Table 1. The periglacial morphoclimatic level in the Doamnei River basin
