Jama Kaltbach je razvita v Hochgantskem eocenskem peščenjaku na območju Siebenghengste v Švici. Rezultat ponovne izmere jame je precej večja dolžina, nov načrt jame in številna opažanja, ki kažejo ...na to, da jama ni nastala z »normalno speleogenezo«, ampak je t.i. fantomska jama. Fantomske jame nastajajo pri delnem preperevanju nečistega apnenca v toplih klimah, v pogojih nizkega hidravličnega gradienta. Ob povečanju gradienta, voda izpere netopni preostanek, pri čemer nastane jama. Članek obravnava geomorfološke značilnosti jam, ki nam omogočajo prepoznavati fantomske jame. Kaltbach cave is developed within the Eocene Hohgant sandstone in the Siebenhengste area in Switzerland. A remapping project of the cave resulted in a huge increase in length. It also produced a complete, updated map and longitudinal section. The cave’s morphology does not fitwiththe“normal”speleogenesis:itisaso-calledphantom cave. Phantoms are created by differential weathering of impure limestone under a preferably warm climate and a very low hydrologic gradient. Once the gradient steepens, the undissolved residual sediments are piped out; the “cave” manifests itself. The paper discusses the geomorphological features that permit to recognize the phantom caves.
The vertical organisation of karst conduit networks has been the focus of speleogenetic studies for more than a century. The four state model of Ford and Ewers (1978), which still is considered as ...the most general, relates the geometry of caves to the frequency of permeable fissures. The model suggests that the ‘water table caves’ are common in areas with high fissure frequency, which is often the case in natural settings. However, in Alpine karst systems, water table caves are more the exception than the rule. Alpine speleogenesis is influenced by high uplift, valley incision rates and irregular recharge. To study the potential role of these processes for speleogenesis in the dimensions of length and depth, we apply a simple mathematical model based on coupling of flow, dissolution and transport. We assume a master conduit draining the water to the spring at a base level. Incision of the valley triggers evolution of deeper flow pathways, which are initially in a proto-conduit state. The master conduit evolves into a canyon following the valley incision, while the deep pathways evolve towards maturity and tend to capture the water from the master conduits. Two outcomes are possible: a) deep pathways evolve fast enough to capture all the recharge, leaving the master conduit dry; or b) the canyon reaches the level of deep pathways before these evolve to maturity. We introduce the Loop-to-Canyon Ratio (LCR), which predicts which of the two outcomes is more likely to occur in certain settings. Our model is extended to account for transient flow conditions. In the case of an undulating master conduit, floodwater is stored in troughs after the flood retreat. This water seeps through sub-vertical fractures (‘soutirages’) connecting the master conduit with the deep pathways. Therefore, the loops evolve also during the dry season, and the LCR is considerably increased. Although the model is based on several approximations, it leads to some important conclusions for vertical organisation of karst conduit networks and stresses the importance of base-level changes and transient recharge conditions. It therefore gives an explanation of speleogenesis that relies much more on the dynamic nature of water flow than on the static fracture density.
•Looping caves are very common due to rapid valley incision and recharge fluctuations.•Speleogenesis is modelled mathematically.•Recharge fluctuations are shown to be much more important than previously thought.•A speleogenetic model is proposed that replaces the one commonly in use.
Caves are important markers of surface evolution, since they are, as a general rule, linked with ancient valley bottoms by their springs. However, caves can only be dated indirectly by means of the ...sediments they contain. If the sediment is older than common dating methods, one has to use multiple dating approaches in order to get meaningful results. U/Th dating, palaeomagnetic analysis of flowstone and sediment profiles, cosmogenic dating of quartz pebbles, and mammalian dating allowed a robust estimate of speleogenesis, sediment deposition, climatic change at the surface, and uplift history on the Periadriatic fault line during the Plio-Pleistocene. Our dates indicate that Snežna jama was formed in the (Upper) Miocene, received its sedimentary deposits during the Pliocene in a rather low-lying, hilly landscape, and became inactive due to uplift along the Periadriatic and Sava faults and climatic changes at the beginning of the Quaternary. Although it is only a single cave, the information contained within it makes it an important site of the Southern Alps.
•We present a comprehensive dating approach to sediments of a Slovenian cave.•We interpret the results in the light of climatic change and tectonic uplift.•We show that collaborative work on one single cave can yield results of broader interest.
The northwestern part of the Ljubljana Basin is filled mostly with fluvioglacial sediments deposited by rivers coming from Alpine mountain groups. The Trziska Bistrica River, flowing from the ...Karavanke Mountains, has deposited a large alluvial fan consisting predominantly of carbonate pebbles with sub-ordinate amounts of siliciclastic pebbles. The oldest infill, cemented into a conglomerate terrace named Udin Borst, overlies an erosional surface on Oligocene mudstone. The thickness of the conglomerate terrace is up to 50 m. The conglomerate terrace is well karstified; the surface is dissected by numerous dolines and covered with a thick soil sequence. There are several caves. The most important are spring caves formed on the contact with the underlying impermeable basement. Samples of quartz pebbles were taken from the walls and ceiling in the 815 m long spring Arneseva Luknja Cave for cosmogenic nuclides burial age dating. The calculated burial age yielded an age of 1.86 ± 0.19 Ma that gives (i) the age of the oldest known infill in the Ljubljana Basin and (ii) indicates the time of change of the sedimentary system in the Basin from erosion to deposition. The age of the Udin Borst karst and caves is significantly younger. The age dates provide grounds for a first relatively firm estimate of the long-term tectonic uplift of the Udin Borst terrace to be between 0.06 and 0.04 mm/yr. This tectonic uplift rate may be related to the activity of the regional Sava Fault.
Observations in St. Beatus Cave and neighbouring caves revealed complex water flowpaths that can be used for explaining thebehaviour of tracing experiments. The observations prove that even in vadose ...conditions, cross-formational flow, diffluences andtransfluences are a quite common feature. Therefore, also the vadose karst has a very complex organisation.
While stalagmites within caves are commonly used to obtain information about past climate change, little attention has so far been given to the cave, its morphology, and many other types of deposits ...contained in it. The discontinuous nature of cave sediments and the possibility that caves are re-shaped by more recent water circulations has discouraged many researchers, despite the fact that it is just this intimate relationship between the cave and surface conditions that makes caves such valuable archives. This article presents a method of determining a relative chronology which can then be dated numerically. Information from St. Beatus Cave and other nearby caves provides evidence of glacial advances that occurred within the following time windows: >350, 235–180, 160–135, 114–99, 76–54, and 30–16
ka. It also describes the following dated periods of valley deepening: 805–760
m a.s.l. (>350
ka), 760–700
m a.s.l. (235–180
ka), 700–660
m a.s.l. (160–135
ka), and 660–560
m a.s.l. (30–16
ka). These dates are new for this part of the Alpine Arc.
Mount Granier lies in the northeast corner of the Chartreuse Mountains. It contains a vast cave system, whose uppermost levels were thought to be of pre-Quaternary age. 10Be/26Al burial dating of two ...cave deposits in the oldest passages, widely spaced but belonging to a same gallery level which formed after the last folding phase, gave ages of 4.3 Ma and 3.4 Ma, indicating that these levels are of at least Pliocene age. In addition, the rates of denudation estimated according to the analytical data are unusually low in this alpine context but show an acceleration during the pre-Quaternary period of interest, ranging from 7 m/Ma to 14 m/Ma. Data from karst deposits serve as reference and comparison site for Alpine chronology as well as for cave genesis and palaeogeographical reconstructions, similar to that of the Siebenhengste massif in Switzerland.
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