COBISS: 1.02 Research frontiers IN speleogenesis. Dominant processes, HYdrogeological conditions AND resulting cave patterns NOVA PODROČJA SPELEOGENETSKIH RAZISKAV: POVEZAVA MED HIDROGEOLOšKIMI RAZMERAMI, PREVLADUJOČIMI PROCESI IN TIPI JAM Philippe Audra1 & Arthur N. PALMER2 Abstract UDC 551.435.84 Izvleček UDK 551.435.84 Philippe Audra & Arthur N. Palmer: Research frontiers in Philippe Audra & Arthur N. Palmer: Nova področja speleo- speleogenesis. Dominant processes, hydrogeological condi- genetskih raziskav: Povezava med hidrogeološkimi razmera- tions and resulting cave patterns mi, prevladujočimi procesi in tipi jam Speleogenesis is the development of well-organized cave sys- Speleogeneza je razvoj dobro (samo)organiziranih jamskih sis- tems by fluids moving through fissures of a soluble rock. Epi- temov, ko podzemna voda vzdolž toka raztaplja stene razpok. genic caves induced by biogenic CO2 soil production are domi- Najbolj poznane so epigene jame v karbonatih, kjer je poglavit- nant, whereas hypogenic caves resulting from uprising deep ni vir kemične agresivnosti pedogeni CO2. Bolj pogoste, kot flow not directly connected to adjacent recharge areas appear se je v preteklosti domnevalo, so hipogene jame, ki nastanejo to be more frequent than previously considered. The concep- z dviganjem globokega toka in niso neposredno povezane z tual models of epigenic cave development moved from early lokalnim napajalnim območjem. Prvotni konceptualni modeli models, through the “four-states model” involving fracture razvoja epigenih jam so se preko modela štirih stanj, ki spe- influence to explain deep loops, to the digital models demon- leogenezo pojasnjuje s frekvenco prevodnih razpok, razvili strating the adjustment of the main flow to the water table. The do računalniških modelov, ki pojasnijo prilagoditev glavnega relationships with base level are complex and cave levels must toka freatični površini. Povezava jamskih sistemov s položajem be determined from the elevation of the vadose-phreatic tran- erozijske baze ni enostavna, saj moramo pri interpretaciji sitions. Since flooding in the epiphreatic zone may be impor- upoštevati višino prehoda iz freatične v vadozno cono. Zaradi tant, the top of the loops in the epiphreatic zone can be found visokih poplav v epifreatični coni so lahko temena jamskih significantly high above the base level. The term Paragenesis is zavojev visoko nad erozijsko bazo. Termin parageneza se upo- used to describe the upward development of conduits as their rablja za opis razvoja kanalov od spodaj navzgor, ko se spod- lower parts fill with sediments. This process often records a nji deli zapolnijo s sedimenti. Ta proces pogosto beleži splošen general baselevel rise. Sediment influx is responsible for the dvig erozijske baze. Vdor sedimentov je tudi razlog za uravna- regulation of long profiles by paragenesis and contributes to the vanje dolgih profilov s paragenezo in prispeva k prehodu jam z evolution of profiles from looping to water table caves. Dating zavoji v navpični ravnini v jame uravnane z vodnim nivojem. methods allow identification of the timing of cave level evo- Različne datacijske metode omogočajo določanje časovnega lution. The term Ghost-rock karstification is used to describe a razvoja jamskih nivojev. Speleogeneza lahko poteka tudi v dveh 2-phase process of speleogenesis, with a first phase of partial fazah; v prvi fazi voda ob nizkem gradientu raztopi topen del solution of rock along fractures in low gradient conditions kamninske matrice (angleško Ghost rock weathering), v drugi leaving a porous matrix, the ghost-rock, then a second phase fazi pa ob visokem gradientu turbulentni tok mehansko odnese of mechanical removing of the ghost-rock mainly by turbu- preostali del matrice, pri čemer praviloma nastane labirintni lent flow in high gradient conditions opening the passages and tip jam. Prva faza je lahko povezana z epigeno infiltracijo ali s forming maze caves. The first weathering phase can be related hipogenim dotokom predvsem na mejnih območjih sediment- either to epigenic infiltration or to hypogenic upflow, especially nih bazenov. Vertikalna geometrija epigenih jam je pogojena in marginal areas of sedimentary basins. The vertical pattern of s časovnim okvirom, geološko strukturo, vrsto toka in spre- epigenic caves is mainly controlled by timing, geological struc- membo erozijske baze. Razvoj mladih (juvenilnih) geometri- ture, types of flow and base-level changes. We define several jskih vzorcev nad nivojem neprepustnih plasti, je povezan 1 University of Nice Sophia-Antipolis, CNRS, IRD, Observatoire de la Cote d’Azur, Geoazur UMR 7329 & Polytech Nice – Sophia, 930 route des Colles, 06903 Sophia-Antipolis, Nice, France, e-mail: [email protected] 2 State University of New York, Earth Sciences Department, Oneonta, NY 13820, USA, e-mail: [email protected] Received/Prejeto: 26.04.2015 ACTA CARSOLOGICA 44/3, 315–348, POSTOJNA 2015 Philippe Audra & Arthur N. PALMER cave types as (1) juvenile, where they are perched above un- s hitrimi tektonskimi dvigi in vrezovanji erozijske baze. V derlying aquicludes; (2) looping, where recharge varies greatly pogojih omejenega odtoka ob spremenljivem napajanju zaradi with time, to produce epiphreatic loops; (3) water-table caves poplavljanja epifreatične cone nastajajo zavoji v navpični rav- where flow is regulated by a semi-pervious cover; and (4) caves nini (angl. loops). Jame vodnega nivoja nastajajo na področjih, in the equilibrium stage where flow is transmitted without sig- kjer je kras pokrit z delno prepustnimi plastmi oz. kjer je spe- nificant flooding. Successive base-level drops caused by valley leogeneza uravnotežena z največjimi poplavami. Spreminjanje entrenchment make cave levels, whereas baselevel rise is de- erozijske baze ob vrezovanju dolin se odraža v jamskih nivojih, fined in the frame of the Per ascensum Model of Speleogenesis medtem ko dviganje erozijske baze diktira razvoj jam od spodaj (PAMS), where deep passages are flooded and drain through navzgor (Speleogeneza Per ecensum, PAMS) in nastanek izvi- vauclusian springs. The PAMS can be active after any type of rov vokluškega tipa. PAMS se lahko aktivira ob različnih vrstah baselevel rise (transgression, fluvial aggradation, tectonic sub- dviga erozijske baze (zaradi transgresije, rečnega naplavljanja, sidence) and explains most of the deep phreatic cave systems tektonskega ugrezanja) in pojasnjuje nastanek večine globokih except for hypogenic. freatičnih jamskih sistemov, razen hipogenih. Izraz hipogena The term Hypogenic speleogenesis is used to describe cave de- speleogeneza se uporablja za opis razvoja jam zaradi dvigan- velopment by deep upflow independent of adjacent recharge ja globokega regionalnega toka. Zaradi izvora iz globin ima areas. Due to its deep origin, water frequently has a high CO2- voda pogosto visoko koncentracijo CO2–H2S in temperaturno H2S concentration and a thermal anomaly, but not systemati- anomalijo. Pri hipogeni speleogenezi lahko sodelujejo številni cally. Numerous dissolution processes can be involved in hy- procesi raztapljanja, ki so povezani z globokimi viri CO2 in pogenic speleogenesis, which often include deep-seated acidic H2S, "hidrotermalnim" ohlajanjem, korozijo mešanice, speleo- sources of CO2 and H2S, “hydrothermal” cooling, mixing cor- genezo žveplene kisline (Sulphuric Acid Speleogenesis, SAS), rosion, Sulfuric Acid Speleogenesis (SAS), etc. SAS particularly itd. Zlasti SAS vključuje kondenzacijsko-korozijske procese, involves the condensation-corrosion processes, resulting in the zaradi česar prihaja do hitrega nastanka jam nad vodno gla- fast expansion of caves above the water table, i.e. in an atmo- dino v atmosferskem okolju. Hidrogeološke razmere pri hipo- spheric environment. The hydrogeological setting of hypogenic geni speleogenezi so povezane z regionalnim gravitacijskim speleogenesis is based on the Regional Gravity Flow concept, tokom, kjer je korozija najmočnejša na območju stekanja in which shows at the basin scales the sites of convergences and dvigovanja vodnih tokov. Vsak del porečja (obrobni, notranji, upflows where dissolution focuses. Each part of a basin (mar- globoka cona) ima posebne pogoje. Eden od podtipov je tudi ginal, internal, deep zone) has specific conditions. The coastal obalno območje. V deformiranih slojih je tok bolj zapleten in basin is a sub-type. In deformed strata, flow is more complex strukturno pogojen, pri čemer sta vodni tok in hipogena spe- according to the geological structure. However, upflow and hy- leogeneza praviloma vezana na strukturne vrhove (prekrite an- pogenic speleogenesis concentrate in structural highs (buried tiklinale) in na območja večjih strukturnih prekinitev (prelomi, anticlines) and zones of major disruption (faults, overthrusts). narivi). V prekinjenih bazenih geotermalni gradient "črpa" me- In disrupted basins, the geothermal gradient “pumps” the me- teorske vode v globine, kar povzroča zanke na različnih globi- teoric water at depth, making loops of different depths and nah in z različnimi značilnostmi. Vulkani zem in magmatizem characteristics. Volcanism and magmatism also produce deep tudi povzročata globoke hipogene zanke s "hiperkraškimi" hypogenic loops with “hyperkarst” characteristics due to a značilnostmi, ki nastajajo zaradi kombinacije globokih virov combination of deep-seated CO2, H2S, thermalism, and micro- CO2, H2S, termalnih procesov in mikrobiološke aktivnosti. bial activity. In phreatic conditions, the resulting cave patterns Geometrijski