Structural Geology of the Škocjan Caves

The Škocjan Caves are developed inside 300 m thick column of Cretaceous and Paleocene limestones. Most of the underground Reka River flows within the 130 m thick Lipica Formation (K2 4-5). Data from field structural geological mapping (1:500) performed in 1991-1992 (Hankejev Kanal) and in 1997- 2007 (Tiha and Šumeča Jama) are analysed and presented on a new structural geological map. The Reka River follows bedding- plane strike and dip direction in Šumeča Jama and Hankejev Kanal. From the western part of Hankejev Kanal to the ponor in Martelova Dvorana the Reka River flows perpendicular to strike direction of bedding-planes with dip direction of the bedding contrary to river flow. Bedding planes with interbedded slips were especially favourable for the development of initial passages. The bend of the Reka River in Hankejev Kanal is developed at the intersection of multiple fault zones. Cross- Dinaric oriented faults in Podorna Dvorana and at northern edge of Martelova Dvorana can potentially be neotectonically active

Morphological and Geological Characteristics of Two Denuded Caves in SW Slovenia

Denudirane ali brezstrope jame lahko velikokrat določimo iz originalne kraške topografije. Za ta članek sem preučila morfologijo in geologijo dveh denudiranih jam. V letu 1994 je bila pri vasi Povir odkrita prva denudirana jama, in sicer ko je gradnja avtoceste Divača-Dane že potekala. Originalno jamsko morfologijo smo lahko določili iz topografskih kart 1:1.000. V letu 1996 pa smo s predhodnimi krasoslovnimi raziskavami še pred začetkom gradnje avtoceste Divača-Kozina določili 4 denudirane jame. Posebno denudirana jama pri kraju Kačiče-Pared je bila morfološko zelo dobro izražena.Denuded or unroofed caves can be identified from original karst topography many times. For this article the morphology and geology of 2 denuded caves were studied. In 1994 first denuded cave was discovered near village Povir when the highway construction Divača-Dane was already taking place. Original cave morphology was realized from topographic maps 1:1.000. In 1996 with preliminary karst studies before beginning of highway construction Divača-Kozina 4 denuded caves were discovered. The one near Kačiče-Pared was very well morphologically expressed

Effects of earthquakes in Postojna cave system

Regarding the studied historic references there are sufficient proofs that during the 1st January 1926 earthquake (M=5.6) in Postojna cave system (Sala del Candore or Pralnica) a stalag­mite column of 1 meter in diameter collapsed. This is a not so common event in karst caves and took place due to the close vicinity of the epicentre located at the SE end of Idrija Fault or at the Javorniki Mountain. During earthquakes in karst caves brontides are generally heard, but ground movement is rarely felt. Only strong and close earthquakes can be felt as ground shaking or waving inside the caves also, withsome possible collapses as well.

Historic inscriptions in Predjama cave system and high floods in 2010

High floods of September 2010 partly ruined historic inscription made by charcoal »Slovenski gadje 1882« in Predjama cave system. Regarding studied historic records the September 2010 floods were the highest in Predjama at least since 1882. If we thrust the well-documented floods in 1826 they can even be higher than ones in 2010. In 2010 the water reached 489.60 m above the sea level at entrance parts of the cave and about 485 m at Vetrovna Luknja causing that the old inscription from 1882 was under water and partly destroyed. Another old inscription »Nagel 1748«, probably done by more resistant pencil, did not suffer from the 2010 floods. Contrary, it was twice partly destroyed by carless visitors, first in 1991 and secondly in the period 1991 – 2005

The Use of Structural Geological Terms and their Importance for Karst Caves

Strukturno geološke raziskave na kraških terenih zajemajo enake strukturno geološke izraze kot na drugih geoloških terenih. Ker pa imamo na krasu opravka s posebnimi geomorfološkimi izrazi, se nekateri strukturno geološki elementi, ki so na poseben način povezani z določenimi kraškimi oblikami, uporabljajo kot posebni termini, ki so različni od terminov v uporabi na nekraških terenih. Na slovenskem krasu lahko ločimo dva najpomembnejša strukturna elementa, ki sta pomembna za razvoj jamskih rovov, in sicer lezike in tektonske strukture. Med lezikami so za razvoj inicialnih rovov posebno ugodne tektonsko deformirane lezike. V najdaljših slovenskih jamah, kot so Postojnska, Predjama in Škocjanske jame so za razvoj rovov v inicialnih, kot tudi v starejših in mlajših obdobjih zelo ugodni medplastni zmiki, deformacije narivanja in gubanja ter tektonsko pretrte cone (razpoklinske, porušene in zdrobljene).Structural geological studies on karst areas operate with the same structural geological terms as on other geological regions. But because of special geomorphologic terms characterized for karst areas, some structural geological elements, which are in a special way connected with particular karst forms, are used as a special terms, different from those used on non-karstic areas. For Slovene karst we need to divide two most important structural elements that are important for development of cave passages, bedding planes and tectonic structures. And between bedding planes the ones that are tectonically disrupted are very favorable for development of initial cave passages. In the longest Slovene karst caves as Postojnska jama caves, Predjama and Škocjanske jame caves interbedded movements, thrusting and folding deformations, and tectonically broken zones (fissured, broken and crushed zones) are very favorable for initial, and also for older and younger stages of passage development

Broken Speleothems as Indicators of Tectonic Movements

In karst caves broken and non-ideal speleothems are very wide­spread. Mostly they develop because of the instability of the ground due to its composition (loose sand or loam). The pres­ence of recent cryoturbation in some caves in higher altitudes suggests that some ancient breaks of the speleotheme can be caused by ice in the cave. And we also have some good proofs for recent and past tectonic activity in karst caves. In many cases it is very difficult to determine the real reason for broken speleothems, because several reasons could be interacting. In Postojna Cave some examples related to tectonics were stud­ied

Monitoring of Active Tectonic Structures – Project COST 625

 Za zahodno Slovenijo je značilna zmerna zgodovinska in recentna seizmičnost. Glavni cilj pridružitve Slovenije k projektu COST 625 je bil, da bi z izmenjavo izkušenj in metodologije ugotovili aktivnost ali neaktivnost določenih prelomov v zahodni Sloveniji. V okviru projekta smo se odločili za večletni monitoring, zato smo v zahodni Sloveniji namestili štiri ekstenziometre TM 71. V prvi polovici letu 2004 smo v Postojnski jami na dinarski prelom, ki je od Predjamskega preloma oddaljen okrog 1 km severno, postavili dva inštrumenta. Tretji inštrument je postavljen na Raškem prelomu na JV pobočju Vremščice in četrti v dolini Učje na Idrijski prelom. Peti inštrument TM 71 bo postavljen na Kneškem prelomu, ki se nahaja južno od Ravenskega preloma. Prvi rezultati v Postojnski jami kažejo na manjše horizontalne premike velikosti do 0,05 mm v enem letu.   For Western Slovenia moderate historical to recent seismicity is characteristic. The principal aim for Slovenia to join the COST 625 project was to exchange the experiences and methodology and in this way to determine the activity or non-activity of selected faults in Western Slovenia. Within the project frame we decided for several years of monitoring, and in this sense four TM 71 extensometers were installed in Western Slovenia. In the firsthalf of the 2004 two TM 71 instruments were installed in Postojnska Jama on the Dinaric oriented fault that is situated about 1 km North from Predjama fault. The third instrument was installed on Raša fault on the SE slope of Vremščica and the fourth instrument in Učja valley on Idrija fault. The fifth instrument TM71 will be set upon Kneža fault that is situated south from Ravne fault. The firs tresults from Postojnska Jama are showing the small horizontal movements for 0.05 mm in one year

Hydrochemic Characteristics and Tectonic Situation of Selected Springs in Central and NW Yunnan Province, China

The Yunnan Province lies on the eastern rim of the collision zone between the Indian plate and Eurasia. This region is characterized by complex Cenozoic structures and active seismotectonics. In the year 2004 the areas north from Kunming and the NW part of Yunnan were studied. The measurements of the temperature, conductivity and the analyses of carbonate, phosphate and nitrate were performed in Quinglongtan spring and in the accumulation lake that is situated lower than the spring. The springs are situated in the wider zone of the Xiaojiang fault along which left horizontal movements are taking place. Along the wider zone of the Zhongdian fault between the town of Zhongdian and the Yangtze River on the south there are more springs. Tiansheng Qiao (T = 57.5ºC) and Xiageiwenquan (T = 48,3 − 66.8ºC) are thermal springs along which tufa is deposited. The Baishuitai spring has high mineralization and lower temperature (T = 11.1 − 13.3ºC) and deposits calcium carbonate in the form of gours. All studied springs are connected with active fault zones. The studied areas mostly represent the contact areas between carbonate and non-carbonate rocks

Hydrogeological research as a basis for the preparation of the plan of monitoring groundwater contamination: A Case Study of the Stara Vas Landfill near Postojna (SW Slovenia)

 V Sloveniji je na krasu trenutno aktivnih devet odlagališč komunalnih odpadkov, med drugimi tudi Stara vas pri Postojni. Ker je za kraška območja značilna močna razpokanost kamninske osnove in zelo dobra prepustnosti, izcedne vode z odlagališč še posebej ogrožajo podzemno vodo. Sposobnost naravne filtracije je v krasu majhna,obseg možnega negativnega vpliva pa zelo velik. Sedaj veljavna zakonodaja predpisuje obratovalni monitoring, del katerega je tudi merjenje parametrov onesnaženosti podzemnih vod z nevarnimi snovmi, če so v vplivnem območju odlagališča. Temelj za izdelavo načrta monitoringa so ustrezne hidrogeološke raziskave. Za primer Stare vasi smo poleg osnovnih geoloških in hidrogeoloških podatkov uporabili še rezultate sledilnih poskusov, ožje območje odlagališča pa smo podrobno tektonsko-litološko kartirali v merilu 1:5000. Na osnovi ugotovljenih značilnosti pretakanja vode v podzemlju in v skladu s predpisi smo določili 3 točke monitoringa znotraj (izvira Malenščica in Vipava, jama Fužina) in eno izven vplivnega območja odlagališča (Matijeva jama) ter določili način spremljanja kakovosti vode in izdatnosti   For the present 9 land fills on karst are still active in Slovenia, among them also the Stara vas land fill near Postojna. As strong fissuration of the rock base and very good permeability istypical for karst areas, the waste waters from the landfills particularly endanger the groundwater.The capacity of natural filtration in karst is very low and the dimension of possible negative impact is very high. The actual legislation regulates the performance of operational monitoring, a part of which is also the measurement of parameters of contamination of groundwater by hazardous substances, if they are in the area of influence of the landfill. Preparation of the monitoring plan is based on adequate hydrogeological researches. Besides basic geological and hydrogeological data also the results of tracer tests were used in the case study of the Stara vas landfill.Additionally, the detailed tectonic-lithological mapping in the scale 1:5000 was performed in the narrow area of the landfill.Based on defined characteristics of underground water flow and in accordance with the regulations 3 monitoring points inside (Malenščica and Vipava springs, Fužina cave) and one point outside the area of influence of the landfill (Matijeva jama cave) were selected. The monitoring plan for the observation of water quality and capacity was suggested

Vulnerability Mapping in the Recharge Area of the Korentan Spring, Slovenia

Zaradi dobro razvitega sistema kraških kanalov in razpok, ki omogoča hiter tok podzemne vode in tudi hiter prenos škodljivih snovi, so kraški vodonosniki zelo ranljivi za onesnaženje. Osnovo za njihovo ustrezno varovanje predstavljajo karte ranljivosti. Za izdelavo teh kart so bile razvite različne metode, pri oceni ranljivosti zaledja izvira Korentan pri Postojni pa smo uporabili metodo EPIK, ki je bila že večkrat uspešno preizkušena na krasu in stopnjo ranljivosti določa v odvisnosti od štirih parametrov: razvitosti epikrasa, učinkovitosti varovalnega pokrova, pogojev infiltracije in razvitosti kraške mreže. Za oceno posameznih parametrov smo uporabili različne raziskovalne metode kot so podrobno strukturno-litološko in geomorfološko kartiranje ter vzporedna analiza hidravličnih in fizikalno-kemičnih odzivov izvira na padavinske dogodke. Izdelana karta ranljivosti opredeljuje območja zelo velike, velike in zmerne ranljivosti znotraj zaledja izvira Korentana in jo lahko uporabimo kot osnovo za omejitev varstvenih pasov.Karst aquifers are very vulnerable to pollution due to well developed system of karst channels and fissures which enable fast groundwater flow and also fast transport of pollutants. An expert bases for their protection are vulnerability maps. Different methods for the construction of these maps were developed, and to assess the vulnerability of the recharge area of the Korentan spring near Postojna the EPIK method was used. In this method, which was many times successfully tested on karst, the degree of vulnerabilty is defined on the basis of four parameters: developement of the epikarst, effectiveness of the protective cover, infiltration conditions, and development of the karst network. For the assessment of individual parameters different research methods were used, such as detailed structural-lithological and geomorphological mapping, and combined analysis of hydraulic and physico-chemical responses of the spring to recharge events. Final result is the vulnerability map, which defines the areas of very high, high and moderate vulnerability within the recharge area of the Korentan spring and can be used to set up the protection zones