Karst and caves in the Bihor Mountains - ITIM

European Society for Isotope Research9 th editionPost-workshop field tripKarst and cavesin the Bihor MountainsUrsilor and Scarisoara cavesLeaders:Dr. Bogdan P. OnacUniversity of South Florida / “Babeş-Bolyai” University /Speleological Institute ClujDr. Tudor Tămaş“Babeş-Bolyai”University / Speleological Institute ClujAurel PerşoiuUniversity of South Florida / Speleological Institute ClujCluj-NapocaJune 29 – 30, 2007

Scărişoara – Ocoale regionThe Ocoale - Gheţar - Dobreşti karst system (includingScărişoara Ice Cave) is part of the Scãrişoara karstcomplex, located in the central area of the Bihor Massif (thecore unit of the Apuseni Mountains) known as the Gheţar –Ocoale Plateau.The morphologic and hydrologic elements of the areaallow the separation of three relief units: the Gârda SeacăValley, the Ordâncuşa Valley and the divide between them.On this are distinguished two subunits with clearly differentcharacteristics: The Scărişoara Plateau and the Ocoaleclosed basin.The Gârda Seacă Valley springs in Şesul Gârzii, atypical karst plateau over 20 km long. Downstream from thefirst spring, named Gura Apei, the river crosses twolimestone areas where it forms deep gorges, thendisappears underground in the Coiba Mică Cave. Beyondthe cave are the Cheile de la Coibe gorges with less steepwalls, and the valley widens until the Tăuz spring.Downstream from Tăuz, the valley has carved the mostimportant gorge sectors (Hoancele Căldărilor, Cheile de laCerbu, Cheile de sub Dealul Jilip, Cheile de la Tăuz) withthe walls pierced by some tens of cave openings, most ofthem very small.The Ordâncuşa Valley is considerably shorter, but itskarst landscapes are more spectacular. Springing fromunder the Vârful Clujului (1399 m), the valley crosses in itsfirst part a less picturesque zone, but downstream it hascarved over 4 km some of the most impressive gorgesectors in the Apuseni Mountains, with walls rising in someplaces up to 200 m. To date, more than 100 caves havebeen discovered here, but most of them are less than 50 mlong, the Zgurăşti Ice Cave and the Poarta lui Ionel cavesbeing the exceptions. The main tributary of the Ordâncuşais the Pârâul Gheţarului, flowing from Fântâna de la Iapa

and which drains the northeastern part of the ScărişoaraPlateau.The divide between Gârda Seacă and Ordâncuşa isindividualised as a unitary karst platform, rising at 300-400m above the neighboring valleys. Its southern half has atypical plateau landscape, while in the northern half iscrossed by the Gheţar stream and the Ocoale Valley - theformer with a permanent flow. To the north, the plateau isdominated by the line of Ocoale (1325 m) – Stânişoarei(1377 m) – Ordâncuşei (1358 m) hills, beyond which asuccession of other karst plateaus, namely the Muşunoaie– Vârtop – Şesul Gărzii – Călineasa, link the divide to thePadiş Plateau, the authentic center of the Bihor Mountains.The Scărişoara Plateau is described by an alternanceof rounded limestone ridges and doline alignments, namedby the locals hârtoape. Its limit with the Ordâncuşa Valley isa 200 m limestone cliff, while its edge to the Gârda SeacăValley is a normal slope, specific to alpine areas. Thedolines are usually located above the main undergrounddrainages and the water that infiltrates through them arecollected by the Zgurăşti – Poarta lui Ionel and Ocoale –Gheţar – Dobreşti karst systems. The larger closeddepressions named uvalas, or jompuri in the moţi speech,of which the most representative is „Crapul” below TarniţăHill, were formed by the leveling of divides between severaldolines. The only exokarst features where limestones risefrom the thin soil cover are various types of karren.The Ocoale closed basin was modeled by the streamwith the same name between the Ocoale – Ordâncuşa hillridge to the north and the summit Culmea Pârjolii to thesouth. The Ocoale stream rises from below the Ocoale Hill(1324 m) by several springs forming a large marshy areadeveloped on impervious rocks. After a short subaerialpath, the water disappears underground through severalponors and diffuse losses scattered along some kilometers.In this final sector, the stream meanders in a large

depression whose flat bottom is mostly flooded both duringheavy rains and at snow melting. The waters reappear atthe surface at two different locations: Poliţei spring andCoteţul Dobreştilor resurgence.Downstream from the last ponor in the depression, thevalley shape is hardly visible, but the old meanders maystill be noticed. Then, after a short gorge sector beyond thewell at Vuiagă the valley ends in a small ponor, in front of asteep cliff. On top of the cliff, in a large doline, opens theentrance shaft of the Şesuri Pothole. The doline is closed tothe south by the Culmea Pârjolii, the massif which hosts theScărişoara Ice Cave.The proper depression extends over 3.6 km 2 and isdominated by the Ocoale Hill to the north, the Comărniceland Bocului hills to the west, Culmea Pârjolii to the southand Piatra Corbului hill to the east. Its sides are slopinggently because subaerial streams quickly infiltrateunderground when they cross karst areas and the reducedflowrates of the streams from the western and northernedges cannot induce erosion. The exokarst consists ofdolines and numerous types of karren, of which the bestrepresented are the channel karren types.The geological setting of the Ocoale - Gheţar Plateau israther simple. The entire plateau is developed on Mesozoicsedimentary rocks belonging to the Bihor Unit(autochthonous). To the west, the autochthonous isoverthrust by the Permian detrital formation developed in atypical Verrucano facies (purplish-red colored quartzitesandstone, conglomerates, and shales). This latter one ispart of the Gârda Nappe.The existence of the Scărişoara Cave has stimulatedmany speleological investigations in the area. In particular,the water divide between Gârda Seacă and Ordâncuşavalleys, dominated by the Ocoale – Scărişoara closecatchment basin, was the object of many observations.Among these, groundwater flow directions and flow rate

values were measured in combination with fluoresceinetracer tests (ORĂŞEANU, 1996).The Munună – Gheţar Fault, crossing the plateau (N-S),is of crucial importance in the hydrogeology of this regionas it separate two distinct tectonic blocks (Fig. 3).Fig. 3. Hydrogeological map of the Gârda Seacă - Ordâncuşawater divide territory.

Legend: 1- Carbonate Mesozoic series (limestones and dolomites), highlyfractured and karstified, characterised by very high effective infiltration andintensive groundwater flow. Numerous karst systems with various size andprevelant binary type. Important water resources in large karst systems. 2-Unconsolidated Quaternary deposits with reduced water resources; 3-Mesozoicmolasse deposits with groundwater flow mostly confined to the weathering andfracture zones. Local importance; 4- Areas devoid of water resources; 5-(qh),recent alluvia. Bihor Autochthon: 6-(br+ap 1), undivided Urgonian limestones; 7–(th), black bedded oolithic limestones; 8-(ox-th 1), reef limestones; 9-(J 2), redoolithic limestones, yellowish spoted limestones, redish and grey encriniticlimestones; 10- (si 2-to), redish and grey encrinitic limestones, marls; 11-(he+si 1),quartzitic sandstones and conglomerates, argillaceous shales, black limstones;12-(ld+cr 1), white reef limestones - Wetterstein limestone; 13-(an), grey dolomites.Bihor Autochthon and Gârda Nappe: 14-(w), quartzitic sandstones andconglomerates, red argillaceous shales; 15- Crystalline schists; 16-Normalgeological boundary; 17-Discordant geological boundary; 18-Fault; 19-Overthrustfront; 20-Stream with perennial runoff; 21-Stream with temporary runoff; 22-Karstic loss in river valley labelled with tracer; 23-Limit of internally drained areas;24- Limit inside of internally drained areas; 25-Village road; 26-Forest road; 27-Contour line; 28-Proved groundwater flow direction; 29-Direction ofhydrogeological cross section; 30-Perennial spring, discharge in l/s: a-under 1; b-1 to 10; c – 11 to 50; d: 200 to 350; 31-Temporary spring; 32-Dug well, perennialwater; 33-Dug well, temporary water; 34-Degassing hypothermal spring; 35-Perennial outflow cave; 36-Temporary outflow cave; 37-Temporary inflow cave,tapping an underground stream; 38-Fossil cave; 39- Pothole tapping anunderground stream; 40-Fossil pothole; 41-Perennial swallet; 42-Temporaryswallet; 43-Meteorological station; 44-Karst depression, doline; 45-Cavepassage; 46-Hill.Key of the numbers: 1-Peştera cu Apă cave from Brustur brook; 2-Spring ofBăii brook; 3-Big ponor from La Hoape (Muşuroaie); 4-Ştiubei spring; 5-Tăuzspring; 6-Spring from Podul Cerbului; 8-Gârjel (La Ţâraie) spring; 9-Hoanca Apeispring and cave; 10-Peştera cu Apă cave from La Tău (Codobana); 11-PojarulPoliţei cave; 12-Poliţei spring; 13-Dobra’s spring; 14-Spring and cave from CoteţulDobreştilor; 15-Mill’s spring; 16-Feredeu spring; 17-Negreştilor dug well; 18-Jimboieşti (La Cârceni) dug well; 19-Ponor from Trei Cărări (Aprozar); 20-Ţuţerilorspring; 21-Debii spring; 22-Oncheştilor dug well and spring; 23-Costenilor spring;24-Buleştilor dug well; 25- Maciura dug well; 26-„Izbucul” from Dealul Brăzdeştilorspring; 27-Ponor of Gogului brook; 28-„La Izvoare” spring; 29-Mii spring; 30-Groapa cu Apă a lui Miron ponor; 31-Miron’s dug wel; 32-Ilii Florea’s dug well; 33-„Apa Rece” dug well; 34-Fântâna de După Deal dug well; 35- Spring and ponor atVuiaga Veche; 36-Dug well at Vuiagă; 37-Dug well at Şesuri; 38-Pothole atŞesuri; 39-Gheţarul de la Scărişoara ice cave; 40-Troaca spring; 41-Bărâcia dugwell; 42-„Apa din Cale” dug well; 43-Dug well from Gard de la Dubi; 44- Potholefrom Pociocişte; 45-Pusta pothole; 46-Old dug well and spring from Dăgârţeşti;47-Bolf spring; 49-Gheţarului spring; 50-Iapa spring; 51-Losses in flow ofOrdâncuşa brook from Moara lui Ivan (Ivan’s mill); 52-Spring from Moara lui Chipa(Chipa’s mill); 53-Ţeghe spring; 54-Poarta lui Ioanele cave; 55-Zgurăşti cave.

Each block contains is own karst aquifer and resurgentspring. Waters entering the aquifer on the eastern side ofthe fault (Munună – Hănăşeşti Block) resurge out in Poartalui Ioanele spring (average flow rate 90 l/s). However,recent dye tracer markings have shown that part of thesewaters are drained towards west, crossing the fault line,and flowing out through the Coteţul Dobreştilor spring. Onthe western side of the fault (Ocoale Block) waters enteringthe aquifer are drained by the Coteţul Dobreştilor spring.This latter drainage is the longest (2800 m) and it has thelargest relief (390 m) recorded in the Upper Arieşul MareBasin. It drains the waters of Ocoale rivulet that sink withinthe Ocoale - Scărişoara close catchment basin(ORĂŞEANU, 1996). The average flow rate recorded forthe Coteţul Dobreştilor spring between October 1984 andSeptember 1985 was 280 l/s. A flow volume of 1.06 m 3 /swas the monthly maximum. During periods of prolongdraught the spring flow rate declines progressively untilcomplete dry. The Coteţul Dobreştilor outlet is actually anoverflow spring of the system. The lowermost outlet isIzbucul Morii, located some 100 m downstream fromCoteţul Dobreştilor, as well as a number of springs thatoccur nearby. These springs (including the Izbucul Morii)have occasionally been gauged (during periods whenCoteţul Dobreştilor outlet dried up) giving resulting valuesof approximately 85 l/s. Parameters measured from thecorrelative and spectral analysis of Coteţul Dobreştilorindicates the karst system has relatively importantgroundwater reserve.Parts of the waters sinking in the southern part of theOcoale – Scărişoara close catchment basin (within Ocoaleblock, see above) are drained through Avenul din Şesuri(Şesuri Pothole) – Poliţei spring (mean average flow ~5 l/s)hydrokarstic system (part of the Ocoale - Gheţar - Dobreştikarst system).

Scărişoara Ice CaveSpeleogenesisThe speleogenesis of the Scărişoara Ice Cave and itsexistence is closely related to the evolution of the wholecave system to which it belongs. The evolution of the cavesystem is the result of the deepening of the Ocoale Valley,in parallel with the progressive deepening of the GârdaSeacă Valley. The process happened during three majorstages, leading to three karstification levels (Fig. 4).Fig. 4. Ocoale – Coteţul Dobreştilor karst system(after RUSU et. al., 1970).The first and highest level of the system, presently fossil,includes the Scărişoara Ice Cave and Pojarul Poliţei Cave.This level formed when the Ocoale Valley was drained by aswallet located on the northern slope of the Pârjolii Ridge.Nowadays, this cannot be ascertained by the surfacemorphology. The water entering the swallet was directed to“Sânziana’s Palace”, crossing along the whole cave untilreaching the Coman Passage. The water then passed theWhite Hall from Pojarul Poliţei Cave and exited the surfacethrough a confined spring, presently the entrance toScărişoara Ice Cave. The reconstruction of the OcoaleValley underground pathway in this first stage of the karstsystem is based on several solid arguments. First, the twochimneys at the end of the Little Reserve show that thewater entered Scărişoara Ice Cave at this point and not

through the entrance shaft, as one could believe at a firstglance. The surveys of the underground passages provedthat the White Hall from Pojarul Poliţei Cave is separatedfrom the Coman Passage by a mere 5 m long passage,now completely filled with sediment. Finally, it is more likelyto consider that the shaft formation follows a pattern oftenseen in karst, namely the simultaneous evolution of asinkhole at the surface and of a chimney in the alreadyformed underground passage. This hypothesis is alsosustained by the hourglass shape of the entrance shaft, nottaking account of the snow covering its bottom.The second karstification level, temporarily active,formed in two phases (stages). The water from OcoaleValley was first drained through the Şesuri Pothole, shownnowadays by the succession of pits in the first part of thecave. The stream reached the surface through the PoliţeiSpring, 224 m below the entrance to the Pojarul PoliţeiCave. The piracy later moved upstream to the swalletlocated in the place named “La Vuiagă”, which todayreceives only a small temporary brook. Developed over avertical extent of 214 m, the hydrologic connection betweenthe Şesuri Pothole and Poliţei Spring was confirmed asearly as 1957 by dye tracing.The third level of the system was found in 1964 throughdye tracing. This level consists of the permanent presentdaydrainage between the swallets from the middle and theupper basin of the Ocoale Depression and the large springof Coteţul Dobreştilor being located on the edge of theGârda Seacă Valley. The vertical extent between the twoextreme points of the drainage reaches 402 m.Cave descriptionThe Scărişoara Glacier Cave (Fig. 5A, B) opens with anelliptical, funnel shaped shaft of impressive dimensions: upto 60 m in diameter and 48 m in depth. The bottom of the

shaft is covered with a thick layer of snow, which does notmelt even in the hottest summers.Fig. 5. Map (plan and profile) of the Scărişoara Ice Cave.The cave was believed to develop in massive reeflimestone of Ladinian (Middle Triassic) age. The authorsestimated the age of the limestone by using paleontologicaland structural elements. BUCUR & ONAC (2000) haverecently sampled the limestone in different point of the caveand studied by means of microfacies. The association ischaracteristic for the Upper Jurassic, most probably LowerTithonic.The cave entrance is located in the western wall of theshaft and has an imposing arch 24 m high and 17 m wide.Beyond is the “Sala Mare’s” (Big Room’s) ice floor, a 3,000m 2 perfectly horizontal surface, with just four massive conicice formations. One is on the left side and the other threeare attached to each other near the wall opposite to thecave entrance. Usually, these form large ice columns.

During springtime, ice stalactites form on the room’s ceiling,but their existence is ephemeral.To the north, there is a second opening towards thesurface Towards the NW, the horizontal floor ends with asteep slope dipping 8 m that can be descended by stepscarved into the ice leading into a second room. Localresidents have named this area “Biserica” (The Church).Here, ice speleothems dominate the underground scenery.On sunny days, the tips of the stalagmites shine in thereflected light from the snow accumulated at the bottom ofthe shaft, creating the impression of gigantic lightedcandles. The “Biserica” continues with a narrow sidepassage lacking ice formations. At its end is a successionof three small circular-shaped cavities with walls bearingtraces of water flow.Another ice slope can be descended on the left side ofthe Sala Mare before entering the “Biserica”. At its base, anarrow space between the glacier and the cave’s limestonewall (crevice) formed due to wall’s higher temperature.The shaft, the Sala Mare, and the “Biserica“ are parts ofthe tourist section of the cave and are toured without cavinggear. On the other two sides of the Sala Mare, the spacebetween the ice and the limestone walls allows access intothe deep parts of the cave that have been declaredscientific reserves. Visiting these areas requires a minimumof underground climbing experience, as both passages areeither vertical or almost vertical cliffs.The Rezervaţia Mică (Small Reserve) is on the northernside of the Sala Mare and can be entered by descending a15 m vertical cliff (Fig. 5A), along which the ice stratificationis visible. Two other crevices form at the side edges of theice cliff near the limestone walls, which both descendsteeply and almost reach the base of the ice block. In thecentral part of the room, not far from the ice block, a field ofice stalagmites forms. They differ from the ice stalagmitesfound in the “Biserica” in that they do not appear as massifs

ut as isolated stalagmites. Beyond these, the cave floor ispartly covered by a calcite crust and rises abruptly towardsa short passage called “Palatul Sânzienelor” (Sânziana’sPalace) in which there are only calcite speleothems. Thereare still two unexplored chimneys at its end, which could bevery important in the depicting the genesis of theScărişoara Glacier Cave.The entrance to the Rezervaţia Mare (Big Reserve) ismuch larger than the previous one and is located on thesouthern side of the Sala Mare. Within this part of the cave,the largest rooms are found (20 to 45 m wide and up to 20m high). Here the ice forms a steep slope to a depth of 90m below the surface. This passage was named Galeria“Maxim Pop” (the Maxim Pop Passage) in the memory ofthe leader of the 1947 expedition. On the horizontalbedrock floor in the central part of the Rezervaţia Mare isanother field of ice stalagmites similar to the ones in theRezervaţia Mică. Beyond this area, the cave floor risesabruptly and is covered by huge collapsed limestoneblocks. On top of these, large calcite domes have formed.Thus, this part of the Rezervaţia Mare is called “Catedrala”(The Cathedral). At the end of "Catedrala", a narrowpassage opens through agrate of stalagmites and entersthe Coman Passage. Besides being well decorated, thispassage reaches the cave's maximum depth of -105 m(RACOVIŢĂ & ONAC, 2000).Based on topographic surveys performed on 1965, thetotal length of the Scărişoara Glacier Cave is 700 m.ClimateFrom a climatic point of view, the cave has a complexstructure, with four meroclimatic zones (RACOVIŢĂ, 1984):a transition meroclimate in the entrance shaft, a glacialzone in the vicinity of the ice block, a periglacial one atcertain distances from the block, and a warm meroclimate

in the non-glaciated parts of the cave. The repartition ofthese meroclimates is reflected by the thermal pattern ofthe cave: while in Great Hall the mean annual temperatureis around –0.9ºC, it increases to –0.2ºC in the GreatReservation and 4.3ºC in the Coman passage.Air circulation is one of the most important factors for icedynamics in the cave (Fig. 6). We can distinguish betweentwo seasonal types of circulation: summer and winter,respectively.Fig. 6. Seasonal air circulation in the Scărişoara Ice Cave.During winter, airflow, triggered by the high density ofexternal cold air, is directed from the surface downward intothe cave. The cold airflow first reaches the Big Hall, fromwhich it descends into both the Little and the GreatReservation. The cold air replaces the warm air from thecave; the warm air rises is “pushed out” along the ceiling ofthe cave. This type of circulation (lasting for approximately5 months between November and April (RACOVIŢĂ &

ONAC, 2000), transports large quantities of cold and dry airin the cave, leading to a diminution of humidity (less than80%).Since the cold air in the cave is denser than the externalair in the summer, there is no air mass exchange betweenthe cave and the outside (equilibrium occurs between theoutside air and inside air of the cave). Differences intemperature (and thus the air density) between variousparts of the cave cause two convective cells between theBig Hall and the two reservations. Cold air maintained bythe overcooled walls and the ice block, flows down into thereservations replacing the warm air. This warmer air risesand follows the ceiling of the cave, but as it reaches the BigHall’s walls it cools down, thus maintaining the convection.This type of circulation is occurs from May until October.In April and October, rapid changes between summerand winter types of circulation occur, as temperature variesaround 0ºC.Due to the ventilation system, the Scărişoara Ice Cave issubdivided in three distinct parts, called meroclimaticsectors. These sectors are differentiated through thephysical (air) parameters and the types of speleothems thatdevelop in each of them. The glacial sector covers theGreat Hall, where external influences are the most intenseand the ice forms a compact block; the periglacial sectorcovers the three halls surrounding the ice block, whereexternal influences are reduced and ice stalagmitesdevelop; the warm sector characterizes the farthest parts ofthe cave, where external influences are practicallyeliminated and the speleothems are exclusively calcitic.The ice speleothemsThe ice block formed by the freezing of the water thatwas supplied from two sources. The first source is therainwater that infiltrated through surface fissures in the

limestone or through the chimney located close to theentrance in the Church. The second source is partialthawing of the snow accumulating at the entrance shaftbottom and that of the surface ice layer from the Great Hallfloor.The ice block consists of 0.5 to 15 cm thick sandwichedice layers and mineral and organic impurity layers, usuallythinner, of only 2 – 7 mm. The organic layers form duringthe summer when the temperature of the undergroundatmosphere increases slightly above zero. Consequentlythe level floor of the Great Hall is covered by a water filmapproximately several centimeters thick, but deeper in frontof the portal. Limestone dust formed from the weathering ofthe wall due to alternative freezing-thawing is deposited atthe base of this film of water. The soil and plant remainsare brought in by water flowing down the shaft walls. Thewater film freezes in the following winter, forming a new icelayer which ultimately encloses all sediments. Therefore,the elementary stratigraphic unit corresponding to one yearin the primary structure of the ice block is represented byan ice layer and an impurity layer.The ice stalagmites are formed by a mechanism similarto the one of calcitic speleothems, the difference being thatthe seeping water freezes instead of depositing calciumcarbonate. Both speleothem growth and their overallmorphology are controlled by air temperature and dripfrequency. The amount of ice deposited on stalagmite tipsdepends on how fast the water freezes. When this processis fast, water drops freeze almost instantly, causing anincrease in height. When the process is slow, water dropsfirst ooze down the sides of the stalagmite, contributingmainly to an increase in thickness. This also explains whymost ice stalagmites have the upper part expanded in theshape of a warclub.The ice stalagmites are made up of hexagonal icecrystals whose growth is governed by the law of geometric

selection. According to this law, the only crystals thatdevelop unrestrained are those growing perpendicular tothe column axis or disposed radial around the stalagmitetip. In the stalagmite mass, crystals form concentric layersof several centimeters thick, but it is not yet known howsuch layering is initiated.The main factor in the dynamics of ice speleothemes(i.e. ice stalagmites) in Scărişoara Ice Cave is the drippingwater which, depending on temperature, can act as afavorable element for both the growing and melting of ice(PERŞOIU, 2004). Between January and April thesespeleothemes had a growing phase, more important inMarch and April, while between April and December theywent through a melting phase.The ice block has a more complex dynamics, beinginfluenced by both external and internal factors. Drippingwaters and heat transfer through conduction in summerdetermines the melting of ice at the surface of the ice blockand development of a shallow lake (up to 20 cm in depth).In addition, the warm water of this lake (directly heated bysunshine) contributes to the general melting of the iceblock, both on the top and on the sides.Cold air, with water vapor content frequently below 90%, enters the cave in the winter months leading to rapidablation of the surface of the ice block. The geothermalheat flux melts the base of the ice block, leading to thedevelopment of sub-glacial tunnels. Later these tunnels areenlarged through sublimation processes by the same coldand dry air circulating under the ice block. This cold air isalso responsible for the onset of ice development in lateautumn (October-November). During this period, the rapidinfiltration of cold air regulates the freezing of the water ontop of the ice block and thus its thickness.Scărişoara Ice Cave stands out among the other greatice caves in the world due to the fact that it hosts not onlyvaried ice speleothems in a relatively restricted space, but

also a large selection of calcite speleothems. Concentratedmostly in the Cathedral and in the Coman Passage, thesespeleothems are represented by stalactites, stalagmites,columns, domes, draperies, clusterites, flowstones, andgours, to which are added the bizarre cave pearls.ReferencesBucur, I. & Onac, B. P. 2000. New data concerning the age of theMesozoic limestone from Scărişoara from Scărişoara (BihorMoutains). Studia Univ. Babeş-Bolyai, Geologia, XLV (2):13-20.Orăşeanu, I. 1996. Contributions to the hydrogeology of the karstareas of the Bihor-Vlădeasa Mountains (Romania). Theor.Appl. Karst., 9: 185-214.Perşoiu, A. 2004. Ice speleothems in Scãrisoara Cave: dynamicsand controllers. Theor. Appl. Karst., 17: 71-76.Racoviţă, G. 1984. Sur la structure meroclimatique des cavitessouterraines. Theor. Appl. Karst., 1: 123-130.Racoviţă, G. & Onac, B. P. 2000. Scărişoara Glacier Cave.Monographic study. Ed. Carpatica, Cluj Napoca, 140 p.Rusu, T., Racoviţă, G. & Coman, D. 1970. Contribution à l'étudedu complexe karstique de Scărişoara. Ann. Spéléo., 25, 2:383-408.

Urşilor CaveThe Urşilor Cave is located in the north-western part ofRomania (80 km south-east of Oradea) at 482 m a.s.l., onthe west-facing slope of Apuseni Mountains. The cave hasno known natural entrance, being accidentally discoveredby Traian Curta in 1975 after blasting in a marble quarry.The first exploration revealed that the cave preservedimportant paleontological remains (mainly Ursus spelaeus)and also a great variety of speleothems. Consequently, itwas gated and fitted for tourism, and has become the mostimportant show cave in Romania.The cave is carved in Upper Jurassic (Tithonic)thermally recrystallized limestone and consists of 1500 m oflarge passages developed along two distinct levels, locatedat 100 to 200 m beneath the surface (Fig. 7 e). The lowerone, still active, hosts most of the cave bear remains;therefore it is preserved as a scientific reserve. The upperlevel is no longer hydrologically active; it is highly decoratedand open for tourist access (RUSU, 1981). The twoartificial entrances are well sealed in order to preserve theoriginal cave microclimate so that the upper level remainsfree from vigorous air flow and maintains a stabletemperature. The mean annual temperature in the cave is9.81°C (ranging between 9.52° and 10.1°C), and therelative humidity is 100% (RACOVIŢĂ et al., 2003).The speleogenetic evolution of Urşilor Cave is closelylinked to the lowering of the local base level. Analyzing itslongitudinal section and following the disposition of thepassages, as well as morpho-hydrographic elements bothunderground and at the surface, one can reconstruct thepaleogeographic evolution of the region. By such anapproach, RUSU (1981) identifies the following evolutionstages:

• The water infiltrating from the karst plateau above thefuture cave fed an unconfined aquifer that discharged atthe surface through the Twisted Passage (Fig. 7a, I-1).The passage is located 50 m above the present baselevel, so it appears that in the first stage of caveevolution, the base level established by the localMiocene Bay was much higher. Therefore, by that timethe Lower Passage (Scientific Reserve), "EmilRacoviţă" and Candles passages began their formationat or below the water table.• As the water table dropped, the water abandoned theTwisted Gallery (Fig. 7a, II). The surface stream nowentered the cave using a different sinking point (Fig. 7a,2).• In the next stage, after a new lowering of the PliocenePannonian Lake, the water level also dropped in theBeiuş Depression (Fig. 7b, III), and the cave streamwas drained to the surface through the Bones Passage(Fig. 7b, 3). At the beginning this passage was mainlybelow the water table, but later it became air-filled(vadose conditions). By draining the cave stream viaBones Passage, the Candles Gallery was completelyabandoned by water. The only passage still active atthat time was "Emil Racoviţă" Passage.• During late Neogene the extension of the PannonianSea decreased significantly, causing complete drain ofits gulfs (including Beiuş). After this event, the cavestream abandoned the Bones Passage and emptied atthe level of Crăiasa Valley, which represents the baselevel ever since (Fig. 7c, 6). Karst conduit flow inScientific Reserve and Passage 6 in Fig. 7c & d wasstill under phreatic conditions.• Following the uplift of the Bihor Mountains the flowregime in the cave changed to a vadose one. The

altitude of the discharge point changed and in order tokeep pace with the rapid downward progress of CrăiasaValley, the cave stream now begins the incision of floorin the Scientific Reserve and Passage 6, transformingthe gallery into canyons (Fig. 7d, 5 & 6).• During the Pleistocene, speleothem deposition in theupper passages was extremely active, while in theScientific Reserve several filling and reactivatingphases occurred as consequences of the outsideclimate variations. In the last interglacial, the amount ofsediments was so large that it blocked the drainage toPassage 6, thus causing in almost complete filling ofthe Scientific Reserve and redirecting the flow through"Emil Racoviţă and Bones passages. This hypothesisis sustained by the presence of massive speleothemsand clastic deposits that cover the floor of "EmilRacoviţă" Passage in its upstream sector, as well as theaccumulation of fossils in Bones Passage.• The reactivation of the drainage between the ScientificReserve and Huda de la Chişcău Cave marks thebeginning of clastic sediments removal from theScientific Reserve. The underground stream deepenedits bed in its own alluvia. It is considered that during theWürm glacial period the cave bears entered andhibernated in the cave, using Huda de la Chişcău Caveas access point.• The last stage of evolution of Urşilor Cave took place inthe Atlantic phase, characterized by a large amount ofprecipitations. The Scientific Reserve was completelyfilled with sediments in the lowermost part, and at thesame time the entrance in the Huda de la Chişcău Cavewas blocked, leading to the complete isolation of thecave until 1975.

Fig. 7. Evolution of Urşilor Cave (after RUSU, 1981, modif.).

FigFrom a paleontological point of view, over 40 species ofPleistocene and Holocene mammals have been identifiedin the cave. Dominant is Ursus spelaeus, and in the LowerPassage of this cave one of the skeleton has been found inanatomical connection (Fig. 8).Fig. 8. Cave bear skeleton in the lower part of theUrşilor Cave.ReferencesRacoviţă, G., Onac, B. P., Feier, I. & Menichetti, M. 2003. Étudethermométrique de la Grotte de Ours de Chişcău (Roumanie).Trav. Inst. Spéol. „E. Racovitza” XLI-XLII: 177-190.Rusu, T. 1981. La Grotte des Ours de Chişcău. Rev. Roum.Géol., Géophys., Géogr., Géographie, 25: 193-204.