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Glacial terminations commence when ice-sheets from the Northern Hemisphere reach a supercritical size and their ablation is enhanced due to the increase of insolation during the Northern Hemisphere summer. Terminations reach a no-return point when the thermohaline circulation shuts down abruptly and triggers the bipolar seesaw mechanism that causes non-linear modifications on the global climate. Because of progressive variations of the solar forcing, suitable temporal windows for the occurrence of the bipolar seesaw mechanism exceed 10 ka, which represent a limitation on understanding the precise inception time of the bipolar seesaw mechanism and its causes. Therefore, controls that affect the structure and timing of terminations are still poorly understood. We studied a tufa deposit from the Iberian Peninsula that covers Termination II (T- II) and the previous interglacial period. The studied tufa sequence provides a continuous record due to its specific hydrological and geomorphological setting and enables the possibility to study multiple proxies difficult to study in other karst records. The chronology of the tufa sequence was previously dated by U-Th and geomagnetism techniques and the oxygen isotope signal of the carbonates was synchronized to speleothem records from the Mediterranean to provide the age model of the deposit. We used the same chronology to synchronize ocean sediments from the North Atlantic to correlate major climate events in a common timescale. We identify two stages within T-II. The first stage started with the increase of boreal summer integrated solar insolation, and during this stage three millennial climate oscillations were recorded. These oscillations resulted from complex ocean- atmosphere interactions in the Nordic seas, caused by the progressive decay of Northern Hemisphere ice-sheets. The second stage commenced after a glacial outburst that caused the collapse of the Thermohaline Circulation, a massive Heinrich event (HS11), and the onset of the bipolar seesaw mechanism that eventually permitted the completion of T-II. The pace of the millennial oscillations during the first stage of T-II controlled the onset of the second stage, when the termination became a non-reversible and global phenomenon that accelerated the deglaciation. During the last two terminations, the bipolar seesaw mechanism was triggered by different detailed climate interactions, which suggests the occurrence of different modes of terminations.

Paleoclimate studies for long-term records are often obtained from speleothems fed with very slow drips that have a diffusional flow and consequently a limited amount of water available for monitoring studies. Using a HOBO U24-001 data logger, we have implemented a methodology for measuring electrical conductivity (EC) in drip water samples with volume

Rock weathering plays important role in landscape formation, especially in carbonate areas. Here, soluble carbonate rocks are being chemically weathered (dissolved) resulting in development of karst landscape. Rock dissolution products are quickly removed from the surface (mostly transported underground), allowing measurements of surface denudation. Northern Velebit National Park and Krka National Park are built from carbonate rocks of different susceptibility to weathering, resulting in their differential weathering and formation of the karst relief. To measure the intensity of rock weathering and the rate of surface denudation, we used two methods: (1) the method of measuring the mass loss of rock tablets exposed to natural environment and (2) direct measurements on exposed surfaces using micro-erosion meter. In rock tablet method we used (a) "standard" limestone tablets and (b) tablets of local rocks, placing the sets of tablets on the surface, but also in the ground, i.e., at the soil-rock contact. Preliminary results show that the intensity of rock weathering measured using rock plates depends on their lithology, but also on local environmental factors. Furthermore, the intensity of denudation measured with a micro- erosion meter is lower than that measured with rock tablets.

Pedogenic carbonates are secondary carbonate deposits that are often found in soils developed over carbonate rocks in Mediterranean region. Their formation is a result of dissolution and reprecipitation of existing geogenic, biogenic and/or pedogenic carbonates. Intensity of the dissolution processes affecting carbonates depends on multitude of factors but is mostly controlled by soil water drainage and concentration of soil air CO2. While percolating through soils and carbonate rocks, water dissolves carbonate minerals until reaching saturation state. Change in environmental conditions impacting concentration of soil air CO2 (e.g., increase of temperature, decrease of soil water content), change of the soil water chemistry and evapotranspiration can lead to supersaturation of water in regard to Calcite and formation of pedogenic carbonates. In case of physicochemical precipitation, pedogenic carbonates precipitate in form of diffuse, small crystals and nodules. On the other hand, biologically influenced precipitation commonly results in different morphologies such as rhizolits, bacterial/fungal mats, etc. Pedogenic carbonates can occur in wide range of climates, thus their morphology and accumulation depth depend on mean annual precipitation. If sufficient time has passed, translocation of carbonates in the soil profile results in formation of calcic horizon. We studied a 0.6 m deep Red Mediterranean Soil profile in Dalmatia (Croatia) having a calcic horizon at the bottom. Diffuse calcite particles and small nodules forming this horizon record different events of dissolution and precipitation. Based on data on soil temperature, soil water content, soil bulk electrical conductivity and soil air CO2 collected during a 3-month monitoring period we developed a thermodynamic model for dissolution and precipitation of calcite in the soil. Results show that soil air CO2 (affected by soil water content and temperature) is the main control of the calcite reactions. Furthermore, during the monitoring period 83% of the calcite dissolved was reprecipitated as pedogenic carbonate. Therefore, although dissolution is the main process governing denudation rate of karst areas (i.e., lowering of the surface), formation of pedogenic carbonates in soils could impact denudation rate of carbonate terrains.

Temperature in inner sections of most caves has limited variability and its value is close to the mean annual temperature above the cave. Nevertheless, any cave atmosphere temperature has long-term changes. Away from the cave entrances and in the absence of streams, the long-term thermal variability of caves is controlled by the surface atmosphere temperature and its transfer to the cave is the result of thermal conduction. The surface thermal signal takes time in its propagation underground by conduction, causing a temporary decoupling between surface and cave atmosphere temperatures. Such thermal decoupling depends on the cave depth and the duration of the thermal anomaly. Since temperature is a main control on the oxygen isotope composition of speleothems, we explored the potential impact of this thermal decoupling in speleothem records from a series of hypothetical caves located at different depths. We have explored the theoretical impact of thermal decoupling in speleothem oxygen isotope records during the last glacial cycle. A synthetic surface atmosphere temperature record was constructed from sinusoidal signals inspired in alkenone paleotemperature ocean records from the North Atlantic off-shore Portugal and the Western Mediterranean. The synthetic surface atmosphere temperature includes 15 stadial periods and 4 interstadial periods during the MIS5 that are superimposed to a full glacial cycle. The result of the underground thermal model suggests that thermal decoupling is very limited in shallow caves (e.g., 10 m), whereas in deeper caves (e.g., 500 m) can reach anomalies (either positive or negative) in the order of 4 ºC. The largest long-term temperature change is simulated during the Termination II (i.e., up to 8 ºC within

Parent material is an important factor in soil formation, especially in soils formed in Mediterranean region dominated by calcareous sedimentary rocks. Their basic properties (mineralogical composition, coherence, and permeability for water) influence the resistance to weathering and type of weathering products, its amount, particle size distribution, as well as the intensity of physicochemical transformations within the original rock residue. Thus, the aim of this study was to investigate the impact of parent material on soil properties in southern part of Krka National Park, Croatia. Weathering of carbonate parent material (limestones, dolomites, conglomerates, marls) along with other soil forming factors was the base for soil development in this area. Thus, Calcocambisols and Terra rossa, typical and ilimerized are the most widespread soil types, while Calcomelanosols, Colluvium and Rendzinas are as well represented, but in much lesser extent. Soil depth, presence of coarse fragments and carbonate content in these soils vary considerably depending on parent material, although factors such as relief, vegetation and anthropogenic impact cannot be neglected. In general, shallow soils ( 35 cm) were formed on limestones and conglomerates, while medium deep soils (35-70 cm) were formed on marly substrates. The content of coarse fragments of variable size in soils (fine gravel 2-6 mm to boulders 60-200 cm) is related to different weathering processes of parent material. The presence of carbonate nodules on soil surface and within soil profile also indicates pedogenetic processes related to different types of carbonate parent material.

The morphostratigraphical record of paleoglaciers is an important paleoclimatological and paleoenvironmental archive in Quaternary studies. In the Mediterranean region, most of the glaciers during this period were hosted in carbonate mountains, where establishing a glacial chronology is complex. Diagenetical processes such as cementation, dissolution and increase of organic content, together with the carbonate nature of the deposits, prevents the application of most of available absolute dating method to accurately date carbonate tills. As well, processes such as percolation of water through sediment, propagation of rootlets and carbonate corrosion/surface denudation are impediments to obtain suitable glacial chronologies. Radiocarbon analyses of calcite cements are known to be inaccurate due to dead-carbon contribution from dissolved carbonate bedrock. U-series dating of carbonate cements is not applicable since: (1) cements generally have several phases of growth ranging from the time of deposition to present and (2) more importantly, a closed carbonate system is unlikely to be preserved, implying isotopic leaching. Due to lack of significant amounts of quartz and feldspars in the bedrock carbonates OSL dating is not applicable to carbonate tills. Exposure dating could be applicable to some till boulders by in situ produced cosmogenic nuclides using 36Cl, but surface weathering and denudation rate must be taken into account. For this reason, 36Cl burial dating is likely to be the best option to reproduce accurate chronologies. Here we show a study of a carbonate tills from southern part of Velebit Mt. were we evaluate their depositional environments and the diagenetical processes that affect them.

Recharge from soil to karst was estimated in a 0.6 m deep soil profile developed on dolomite marbles with a small cave system, at a location in central Spain [1]. Soil water content (SWC) was simulated for six layers in soil by reservoir cascade scheme (RCS) approach. In RCS approach, soil is considered as a unit made of imaginary layers, i.e., reservoirs. Each reservoir gains and loses water by major hydrological processes which include precipitation, runoff, plant interception, evaporation, transpiration, infiltration, redistribution, and drainage or deep percolation [2, 3]. Soil field capacity (FC) is considered a key parameter in RCS approach since it represents a threshold that controls process of drainage in a way that whenever SWC exceeds FC of a certain layer, drainage occurs [4]. Besides when FC of soil is exceeded, drainage as well occurs in the form of preferential flows. Drainage from the deepest soil layer enters as recharge from soil to the vadose zone of karst. Therefore, three different configurations of the model are assumed. Configuration 1 considers only basic RCS module, while configurations 2 and 3 include preferential flows. Configuration 2 considers RCS module together with a continuous preferential flow module, where 1 to 5% of available SWC from each layer is drained every day along preferential pathways, while Configuration 3 contains discontinuous preferential flow module in addition to all previous modules. The discontinuous preferential flow is only activated during rainfall events occurring after long dry periods. Therefore, model provides three different estimations of recharge. The simulation shows that preferential flows significantly impact the amount of soil-karst recharge. When only RCS module is considered (Configuration 1), recharge occurs only during winter-spring period, while during summer months, no recharge occurs. When preferential flows are considered, recharge occurs during summer months as well. Furthermore, cave hydrology depends on recharge amount from the surface, impacting speleothems formation. Therefore in order to accurately interpret paleoclimate proxies from speleothems it is important to understand water dynamics in soil and at soil-rock interface.

Otprilike četvrtina svjetske populacije potpuno je ili djelomično ovisna o zalihama podzemne vode u krškim područjima [1]. Prije nego što dospije do vodonosnika, voda će se kretati kroz tlo, epikršku i vadoznu zonu, te će upravo procesi u navedenim zonama odrediti količinu i svojstva vode koja dospije do vodonosnika. U svrhu razumijevanja raspodjele i kretanja vode u zoni tla, izrađen je jednodimenzionalni dnevni hidrološki model, koji simulira udio vode u tlu na dubinama 10, 20, 30, 40, i 50 cm. Sustav za monitoring postavljen je na lokaciji u središnjoj Španjolskoj (40°9′15″N, 5°4′20″W). Na istraživanoj lokaciji matične stijene izgrađene su od metamorfoziranih karbonata na kojima je razvijeno karakteristično crveno tlo bogato željezovitim mineralima, često dubine preko pola metra [2]. U tlu na dubinama 10, 20, 30, 40 i 50 cm postavljeni su senzori za mjerenje volumnog udjela vode u tlu. Na udaljenosti

Pedogenic carbonates can form in wide range of climates. They precipitate from supersaturated soil solutions during dry periods when evapotranspiration exceeds rainfall. These solutions are impacted by the chemistry of rainwater that equilibrates with soil CO2, which is released by root and microbial respiration as well as by organic matter decay. Consequently, isotopic signature of pedogenic carbonates is highly influenced by climatic conditions present during their formation, and its study in carbonate nodules of paleosoils can be used to unravel changes in climate conditions during the geological record. The δ18O values of pedogenic carbonates are mostly related to the isotopic signal of meteoric water, while the δ13C signal reveals information about dominant vegetation cover at the time of their formation. However, the isotope signals represent only the conditions at the time of carbonate precipitation. So, it is key to understand any possible seasonal bias in the rate of pedogenic carbonate formation to prevent any misinterpretation of the data as paleoclimate indicators. We studied a 0.6 m deep Red Mediterranean Soil profile in Dalmatia (Croatia) having a calcic horizon at the bottom. Over the period of 3 months, soil temperature, soil water content, soil bulk electrical conductivity and soil air CO2 were measured at the location. Based on the data collected, a thermodynamic model was developed for dissolution and precipitation of calcite in the soil. According to the results, two phases can be distinguished. From mid-April to mid-July a stage dominated by calcite dissolution is present. In this period soil water content was still high and progressive rise in temperature caused CO2 to build up in the soil, eventually resulting in dissolution of calcite, including some of the previous pedogenic carbonates. From mid-July until the end of our record high temperatures caused a negative soil water balance and eventually leaded to supersaturation of the soil solution and precipitation of pedogenic calcite. In both stages temperature controlled indirectly the chemistry of the solution. During the first stage, rise in temperature enhanced the microbial activity and/or other processes that increased the concentration of soil CO2 and caused the dissolution of calcite. During the second stage, however, temperature resulted in a negative effect on soil water balance by enhancing evapotranspiration, which controlled the chemistry of the solution causing precipitation of pedogenic carbonates. This research proves that at our studied site dissolution and precipitation events of pedogenic carbonates are related to specific stages within the year. Although a full year was not modelled, preliminary monitoring results suggest that not one, but two cycles of precipitation (summer and winter) and dissolution (spring and autumn) can be identified in a year at the studied site. Our results highlight the importance of understanding site specific soil dynamics for interpreting isotope records from pedogenic carbonates. Thus, pedogenic carbonates might be useful archives of seasonality rather than average climate and environmental conditions of the past. Continuous monitoring and modeling studies at the studied site, together with isotope analyses on carbonate nodules, will allow us to identify the potential of isotope studies to characterize seasonality over full annual cycles.

Weathering processes affect carbonate rocks exposed to natural environment (on surface or buried under soil cover), resulting in formation of different karst morphologies, and controlling surface denudation. To quantify these processes different methodological approaches can be used, among which rock tablet method is one of the most comprehensive. North Dalmatian plain is one of the most emblematic parts of Dinaric karst and its development has been attributed to corrosional planation process. However, it has not been measured locally. Thus, to determine the speed of karst relief formation and surface denudation in this area we used rock tablets method. Actual weathering was measured using rock tablets of several local lithologies, while “standard” Lipica rock tablets were used to measure potential weathering rate. Rock tablets have been exposed to natural environment at the surface, but as well buried in cambic soil profile at 50 cm depth for a period of one year. Average values measured on the surface were from 4.96 to 5.44 m/a for local lithologies and 5.9 m/a for Lipica tablets. At the same time, values measured in the soil were from 1.62 to 2.73 m/a for local lithologies and 3.64 m/a for Lipica tablets. Results show significant difference of values measured at different settings and highlight importance of using local lithologies when measuring denudation rates of a certain area.

Due to high secondary porosity, karst areas are characterized by rapid water infiltration into the underground. Therefore, soil cover plays an important role since it is the first media that controls the amount and quality of water on its path to the aquifer. To better understand processes that impact water distribution and transport through soil cover, one-dimensional model at daily resolution was developed, which simulates water content at 6 levels in a 50 cm deep soil. The study site is located in central Spain (40°9′15″N, 5°4′20″W) and is characterized by red soil rich in iron minerals that is half meter thick and overlies metamorphosed carbonates. At a soil monitoring station, sensors are measuring soil water content every three hours, at depths of 10, 20, 30, 40 and 50 cm. Amount of precipitation, temperature, relative humidity, air pressure, wind velocity and direction are recorded every 10 minutes at a meteorological station installed at a study location. To determine basic soil properties, laboratory analyses were performed. Model is developed by using modified water balance equation, where assumed initial soil water content, precipitation, actual evapotranspiration and percolation are used as input parameters, while modelled soil water content represents the output parameter. Preliminary results show that preferential flows are important mechanisms of water flow through karst soil, which implies that water is rapidly and almost directly infiltrated from the soil surface to deeper soil sections. Correlation coefficients show strong positive relationship between measured and modelled results. Once the model will be completed, simulated soil water content and temperature records will be used as input parameters for CO2 concentration and transport model.

Sadržaj: (1) UVOD, (2) GEOGRAFSKI POLOŽAJ I POLITIČKO- TERITORIJALNI USTROJ, (3) PROSTORNO PLANSKA DOKUMENTACIJA, (4) PRIRODNA OBILJEŽJA, (5) ANTROPOGENA OBILJEŽJA, (6) STRUKTURNO-VIZUALNA OBILJEŽJA, (7) PROCJENA KARAKTERA KRAJOBRAZA, (8) VREDNOVANJE POSTOJEĆIH KVALITETA KRAJOBRAZA, (9)VREDNOVANJE OSJETLJIVOSTI KRAJOBRAZA, (10) SMJERNICE ZA OČUVANJE I RAZVOJ KRAJOBRAZA

Na području Parka, Velebita, kao i čitavog dinarskog područja korozija, odnosno krška denudacija je jedan od temeljnih procesa u oblikovanju reljefa. Kao jedno od temeljnih pitanja nameće se brzina, odnosno intenzitet krške korozije. S obzirom da intenzitet korozije ovisi o cijelom nizu čimbenika (litološkim, strukturnim, reljefnim, klimatskim, hidrološkim, pedološkim biogenim, a u novije vrijeme i antropogenim) ono je predmet brojnih istraživanja. Radi što boljeg upoznavanja intenziteta površinske korozije od 50 -tih godina ovog stoljeća, na poticaj akademika Ivana Gamsa, počinje se primjenjivati metoda stijenskih pločica - kalcitnih tableta. Zbog mogućnosti objašnjenja oblikovanja površinskih krških reljefnih oblika, ali i svoje jednostavnosti, ova je metoda među geomorfolozima naišla na potporu, te je na 7. međunarodnom speleološkom kongresu, održanom 1977. g. u Sheffieldu (V. Britanija), komisija za kršku denudaciju odredila njihov standardan izgled i postupak prilikom upotrebe (Gavrilović, D. 1984. i Gams, I. 1985., i 1987.). Standardne pločice su izrađene od 97, 9 - 98, 7% CaCO3 gornjokredne starosti iz kamenoloma Lipice kod Sežane, promjera su 42 mm, a debljina im je 3 - 4 mm. Nedostatak metode mjerenja intenziteta površinske korozije, pomoću standardnih pločica je nemogućnost spoznaje o točnom intenzitetu korozije na određenom području zbog litoloških razlika matičnih karbonatnih naslaga i onih od kojih je izrađena pločica. Zbog toga su za potrebe mjerenja izrađene autohtone karbonatne pločice od vapnenaca, dolomita i karbonatnih breča trijaske, jurske, kredne i tercijarne starosti. Setovi pločica postavljeni su na osam lokacija unutar NP, na površini i u tlu, odnosno na kontaktu tlo-stijena. Preliminarni rezultati pokazali su razlike u trošenju prema mjestima mjerenja, kao i među određenim vrstama pločica.

The source of moisture is an important part of the hydrological cycle that affects climate system. Potentially, moisture sources are important controls of the isotope composition of precipitation, but their studies in the continental mid- and low-latitudes are still scarce. We identify moisture uptake locations of precipitation over Postojna (Slovenia) for period from 2009 to 2013. By using HYSPLIT trajectory model of NOAA, we did 5-day reconstruction of air mass history for the days with precipitation and determined the moisture uptake locations along back trajectories. Moisture uptake locations were identified along each trajectory using HYSPLIT output data and standard equations for saturation humidity mixing ratio, saturation vapour pressure and specific humidity. Our analysis showed that during studied period around 45% of the precipitation over Postojna originated from Mediterranean and south Atlantic area, with majority of locations originated in the Adriatic Sea. On the other hand, 41% of precipitation originated from moisture recycled over continents, predominantly from Pannonian basin. Multivariable analyses of source regions do not explain any variability of the oxygen isotope composition of precipitation over Postojna. The large proportion of recycled moisture is originated from transpiration rather than evaporation, which produced water vapour with less negative δ18O values. Thus, recycled moisture has and isotope signature undistinctable from the oceanic moisture sources. Climate parameters partly control δ18O values of precipitation, being highly important in paleoclimate studies. In case of Postojna δ18O values of precipitation, surface temperature is the main climate control, whereas amount effect was not recorded, and winter North Atlantic Oscillation (NAO) does not impact the δ18O values of precipitation. We corelated Western Mediterranean Oscillation (WeMO) with oxygen stable isotope composition and found small, but significant correlation. However, multivariate analyses correlation of WeMO and temperature do not explain more variability than temperature alone. Therefore, our interpretation of δ18O values of precipitation in terms of climate is limited to surface temperature, although at least half of the variability observed still depends on unknown controls of the hydrological cycle. Speleothems from Postojna Cave are under investigation and have the potential to record a δ18O signal related to the δ18O values of precipitation. Therefore, these speleothems may be used to reconstruct temperature in the region.

volution of cave systems is in great extent impacted by rock weathering. These processes include widening of cave passages and collapse of blocks from cave ceilings. Denudation of the surface above cave system additionally enhances thinning of bedrock above caves, favouring the cave ceiling collapses. These processes result in exposure of cave passages to the surface and formation of unroofed caves. In the area of Eagle Cave, in central Spain, collapse breccias and flowstone speleothems exposed at the surface indicate the existence of unroofed caves. The cave has a main hall where subsidence and ceiling collapses are ubiquitous, showing that collapses, whether they result in unroof caves or not are common. To quantify the denudation rate on the region, we measured denudation rate using rock tablet method at this location. Depending on the lithology that composed the cave bedrock the denudation rate varied between 1.75± 0.66 and 2.48 ± 1.07 μm/yr. However, dating of speleothems exposed to the surface (outside the cave) in unroof caves around Eagle Cave, provides dates as young as 213 ka BP. This is surprising, since apart from existence of speleothems exposed at the surface, cave morphology of the unroof caves is completely lost, supporting a very dynamic process of destruction of cave galleries. The denudation rate calculated by the rock tablet method seems to be too small even to eliminate the collapse blocks of a thin ceiling over the studied speleothem. As previously highlighted in previous studies, different methods to estimate denudation rate provides results that differ in orders of magnitude. Our result supports such conclusions. Therefore, the main goal of this ongoing research is to apply different methodologies to measure denudation rates, compare their results and estimate which are the benefits and problems that the different methods are providing. As well to improve our understanding of karst denudation rates and the accuracy of the methods used for their evaluation. Acknowledgements: This research is a part of the research project “Inter-comparison of karst denudation measurement methods” (KADEME) (IP-2018-01-7080) financed by Croatian Science Foundation.

Denudation of Earth surface as a result of rock weathering is the fundamental process governing the landscape development. Weathering of rocks occurs by physical, chemical and biological processes. Ultimately, these processes transform rocks, and provide the material that forms soils. In karst regions, dissolution of carbonate rocks is a dominant process controlling denudation. In order to quantify weathering and/or denudation rate of a certain carbonate area several different methodological approaches can be used. The most used methods are: [1] the exposure of rock tablets to the natural environment, [2] the use of micro-erosion meters on rock surfaces, [3] measuring the concentration of cosmogenic radionuclides on exposed rocks, [4] measuring water hydrochemistry to infer amount of carbonates being dissolved and [5] quantifying the differential erosion on bare-rock surfaces of known age. Every method has pros and cons and there is no consensus on which method provides the more reliable denudation rates. Not all methods quantify denudation over the same timescale and in all cases there are assumptions between acquired data (measurements) and the calculated denudation rates (interpretations). Since weathering is a slow geological process, the accuracy of denudation rate measurements is difficult to validate. Significant differences among methods have been reported by researchers that have used more than one method at the same location. Additinally, comparison of denudation results at regional scale suggests that different methods may have results differences exceeding one order of magnitude. Although local factors can be important contributors to explain the scatter of reported denudation rates, the different methods never have been calibrated together using the same boundary conditions at one single location. As a consequence, at the moment there is no evaluation on the accuracy of available methods, and it is uncertain if any particular method provides results significantly biased compared to other methods. Therefore, the aim of this study is to apply all possible methods that could be studied in a single location to evaluate if their results replicate within their uncertainties. Two study sites in Mediterranean climate region with different soil properties have been selected: Krnić (Croatia) and Ramacastañas (Spain). The different context will allow evaluating if the conclusions are extrapolated to different scenarios. The inter-comparison of denudation measuring methods will allow for the first time the unequivocal identification of strengths and flaws of the different methods. This is an important study to know the accuracy of available methods for the study of denudation and its important implications for the study of the Quaternary. Acknowledgements: This research is a part of the research project “Inter-comparison of karst denudation measurement methods” (KADEME) (IP-2018-01-7080) financed by Croatian Science Foundation.

Precipitation is a major natural control on the amount of karst groundwater resources. However, not all amount of precipitation in karst regions results in aquifer recharge, since evapotranspiration uses significant hydrological resources. We have developed a soil model that quantifies the recharge at different sites in Slovenia and Croatia. To characterize the regional climate variability, the selected locations have different thermal regimes and hydrological balances across the Dinarides. The implemented model assumes that actual evapotranspiration results from the potential evapotranspiration and the available soil water content. The same hydrological soil characteristics were assumed for all studied locations to isolate the impact of climate on the hydrological recharge. The input data to run the model at each site are the monthly values of precipitation and temperature, and the values of the field capacity and initial soil water content have to be specified. For each site, the model was run for a period of 15 years, from 1975 to 1989, when the global warming had still limited impact on the region. The model quantifies the amount of rain water that finally reaches the aquifer. In sites with a clear positive hydrological balance more than 50% of precipitation turns into hydrological recharge. However, in sites with a clear negative water balance only between 20 and 25% of precipitation turns into hydrological recharge. The model highlights how vulnerable are the groundwater resources in most Mediterranean karst regions to drought or rise in temperatures. In the context of the ongoing climate change, the model shows that a warming of 2ºC results in higher actual evapotranspiration rates and decreases on the hydrological recharge by 15-20% in Mediterranean sites and by 30% in sites with a continental climate. This model also forecasts the karst groundwater hydrological recharge as a result of different scenarios of climate change.

1. UVOD Stijene izložene na površini ili plitko ispod površine Zemlje podložne su trošenju. Raspad stijena na manje blokove preduvjet je za njihov transport, stoga možemo tvrditi da je trošenje stijena temeljni proces oblikovanja reljefa. Na dinarskom području dominantno izgrađenom od kemijski „čistih“ vapnenaca, dominira proces kemijskog trošenja (otapanja) stijena. Produkti kemijskog trošenja (ioni) momentalno su transportirani vodom, bez zadržavanja na trošenoj površini, stoga je na karbonatnim područjima moguće mjeriti intenzitet denudacije, odnosno snižavanja (i razvoja) krškog reljefa. Denudacija ne samo da mijenja debljinu karbonatnih stijena, već se mijenjaju hidraulika i kemijski uvjeti koji utječu na trošenje stijena i oblikovanje reljefa. Područje NP Krka, smješteno u središnjem dijelu Sjevernodalmatinske zaravni, izgrađuju karbonatne stijene (vapnenci, dolomiti, konglomerati, lapori…) različite podložnosti trošenju, te dolazi do diferencijalnog oblikovanja krškog reljefa. S ciljem određivanja brzine oblikovanja reljefa na području NP Krka, te čimbenika koji na nju utječu (litologija, reljef, klima, vegetacija, antropogeni utjecaj), provedeno je istraživanje intenziteta trošenja stijena. 2. MJERENJA TROŠENJA STIJENA NA PODRUČJU NP „KRKA“ Mjerenja intenziteta trošenja (denudacije) stijena na području NP Krka vršena su upotrebom dviju metoda: (1) metodom mjerenja gubitka mase stijenskih pločica izloženih otapanju u različitim okolišima i (2) direktnim mjerenjima na izloženim površinama s mikro-erozijskim metrom. Prilikom mjerenja metodom stijenskih pločica korištene su (a) „standardne“ vapnenačke pločice i (b) pločice od autohtonih stijena. Ishodišni materijal za „standardne“ vapnenačke pločice su jezgre gornjekrednog (senonskog) vapnenca iz kamenoloma pokraj Lipice (Slovenija). Ovi vapnenci sadrže 97, 9 - 98, 7 % CaCO3, a pločice su promjera su 42 mm, te debljine 3 - 4 mm (Gams, 1985). Upotreba ovih „standardnih“ pločica omogućava usporedbu rezultata s drugim istraživanjima regionalno (npr. Gams, 1985 ; Gavrilović, 1986), ali i globalno (npr. Ivanov et al., 1983 ; Day, 1984 ; Delannoy, 1982 ; Droppa, 1985 ; Zhang, 1989). S druge strane, zbog razlike u litologiji od stijena u okolišu u kojemu se vrše mjerenja, nemoguće je dobiti podatke za intenzitet trošenja za taj okoliš. Stoga su pripremljene i „autohtone“ stijenske pločice izrađene od lokalnih stijena. Setovi pločica postavljeni su na nekoliko lokacija unutar NP, na površini, ali i u profil tla, odnosno na kontakt tlo/stijena. Dubina postavljanja pločica ovisila je o dubini pedološkog pokrova i skeletnosti tla. Preliminarni rezultati pokazali su da se „standardne“ vapnenačke pločice troše brže od autohtonih stijenskih pločica. Direktna mjerenja intenziteta denudacije vršena su i upotrebom modificiranog mikro-erozijskog metra (Trudgill et al., 1981). Mikro-erozijski metar baziran je na mikrometru položenom na vijke od nehrđajućeg čelika koji su fiksirani u površinu stijene. Sastoji se od metalnog jednakostraničnog trokuta u osnovi, postavljenog na nožice koje se nalaze u svakom uglu tog trokuta. Svaka nožica posebno je oblikovana u svrhu sprečavanja pomicanja mikro-erozijskog metra tijekom mjerenja. U svakom uglu trokuta premještanjem mjernog mehanizma moguće je očitanje vrijednosti. Na mjernim mjestima (lokacije raspoređene duž NP) u stijenu su fiksirani vijci od nehrđajućeg čelika u unaprijed određenom rasporedu koji omogućava očitanje vrijednosti na 6 mjernih točaka na jednoj lokaciji. Preliminarni rezultati ukazuju na nešto nižu stopu denudacije u usporedbi s rezultatima dobivenih upotrebom stijenskih pločica. 3. ZAKLJUČAK Upotrebom autohtonih stijenskih pločica u kombinaciji s mjerenjima mikro-erozijskim metrom dobiveni su točni rezultati intenziteta denudacije stijena u pojedinim dijelovima Parka. S druge strane, „standardne“ vapnenačke pločice (iz kamenoloma Lipica, Slovenija) korištene su u istraživanjima diljem svijeta, čineći ove rezultate usporedivima s podacima iz drugih krških područja. Daljnja istraživanja fokusirati će se na utvrđivanje faktora koji su uzrok varijabilnosti rezultata mjerenja stope denudacije upotrebom dviju različitih metoda.

Speleothems rarely grow continuously for more than some thousand years. However, the composite speleothem record based on multiple samples from the same cave can have tens or even hundred of thousands years in duration. The geological evolution of the cave systems (e.g., re-routing of drip flow, opening/colmatation of conduits affecting ventilation, etc) is often a common cause for changes in speleothem growth. These non-climate change related cave processes can also be recorded in the geochemical and petrological speleothem proxies, causing problems when interpreting paleoclimate from speleothem records. Identification of hydrological or inside-cave climate events unrelated to climate changes in speleothem records is difficult, although the study of the erosive and/or depositional record of caves often provide valuable information. Here we present a study of an extreme case of condensation corrosion in Eagle Cave (central Spain). Large speleothems were formed in this cave, although a sudden ceiling collapse caused a drastic change in cave ventilation that resulted in a net dissolution of speleothems over the main hall of the cave due to the condensation corrosion process. Speleothems affected by dissolution show blunt morphologies and their internal structure (i.e., layers) is visible on their surface. Cyclic thermal changes related to the new ventilation dynamics, forced the condensation of water droplets on the cave walls and the speleothems. The droplets had an acidic pH as a result of cave atmosphere CO2 diffusion in the solution, causing the corrosion of carbonates where the drops were standing or flowing. The dissolution of speleothems by this event is recorded through the cave, although the magnitude of the process varies locally. Based on the morphology of speleothems, the thickness of carbonate lost by dissolution was in the order of tens of centimetres for most speleothems. Progressively, the collapse sinkhole that enabled the large thermal variability in the cave was filled with gravitational sediments and the ventilation regime became once more stable enough for speleothems to have net accumulation. Thus, a distinctive series of speleothems overgrew the dissolved speleothems. Dating of several speleothems before and after the dissolution event framed the condensation corrosion event between 60 and 55 ka BP, suggesting that dissolution rates might have been as high as 100 μm/yr. Petrology and geochemistry of speleothems differed before and after the dissolution event as the result of ventilation dynamic differing from the previous stage of speleothem formation. This research highlights the potential of speleothem proxies to record non-climate change related processes. Acknowledgements: This research is a part of the research project “Inter-comparison of karst denudation measurement methods” (KADEME) (IP-2018-01-7080) financed by Croatian Science Foundation.

Morphometry of karren features developed on two adjacent carbonate surfaces with different exposure times was compared. One of the surfaces was exposed after a rockslide that occurred ~2400 years ago (as determined by cosmogenic 36Cl analyses), whereas the other was exposed to weathering for a longer time period. Karst morphologies on both surfaces were measured and results show that the surface affected by the slide has less grikes with majority inherited from previous weathering stage indicating that exposure time since the rockslide event has not been sufficient to homogenize these features between both rock surfaces. Tritkarren and rillenkarren preferentially found on the rockslide surface indicate that their genesis is likely to occur at decadal to centennial timescale. It is impossible to distinguish the size parameters of kamenitzas and solution pits found on both rock surfaces. Due to clear correlation between area and depth parameters of these forms we define a morphometric index: A/D ratio as the slope between these two parameters within each population. After an initial stage, preferential weathering occurs along the vertical axis in solution pits and laterally in kamenitzas. Therefore, we suggest that the A/D ratio is related to the evolution/relative age of the karren features. Thus, under rock surfaces affected by the same weathering conditions, lower A/D ratios of solution pits and higher A/D ratios of kamenitzas indicate longer time exposed to weathering. Although solution pits and kamenitzas are likely to be developed in decadal to centennial timescales, their morphology changes through time at millennial timescale and it can be tracked by morphometric analysis.

Hydrological dynamics of a submarine spring and its coastal karst aquifer in Krka Estuary (Croatia) were studied in order to evaluate the potential of temperature as a tracer of hydrological processes. To study the system we monitor the anchialine cave (Litno Cave) that connects the aquifer with the sea, and installed a series of thermometers and depth loggers along vertical profiles in order to continuously monitor the system. The experiment was conducted during three weeks at the end of the dry season and captured the response of the system to the first significant precipitation events. Due to stratification of waters in Krka Estuary, the studied profiles captured the vertical evolution of the thermocline in the estuary and the cave. Temperature was highly correlated to conductivity enabling this parameter to be used as a proxy to identify the source of water in the system. Our results showed that the location of the thermocline in the system depends on the recharge of aquifer via infiltration of precipitation, the evolution of the thermocline in the estuary and the tidal oscillations. As well, we identified the source of water discharging in the submarine spring. At the end of the dry season, the outflow was mostly brackish water resulting from (1) a shallower and inland displaced saline wedge and (2) the aquifer being flooded with estuarine waters due to absence of a significant hydraulic head. However, the aquifer was partially recharged with freshwater after the first significant precipitation event, preventing estuarine waters to flood the aquifer due to the gravitational barrier of the freshwater hydraulic head and the displacement of the saline wedge towards offshore and to deeper positions. Thus, after the initial significant precipitation events the spring discharged freshwater from the aquifer.

na karbonatnim stijenama koje pretežito izgrađuju sjeverni dio Velebita razvijeni su raznovrsni krški reljefni oblici. Na površini, svojom raznolikošću i čestinom pojave ističu se "izjedline" ili grižine. Oblikovanje pojedinih tipova grižina, kao i učestalost njihove pojave posljedica je međuovisnosati geoloških, klimatskih, hidroloških, geomorfoloških, pedoloških i vegetacijskih značajki ovog područja. Među grižinama, prema obliku izdvajaju se razni tipovi žlijebova, škrapa, kamenica, biokorozijskih udubljenja, krških bunara i krških stoliva. Također, uočavaju se dominantni procesi njihova oblikovanja: direktno pod utjecajem atmosferske vode, subkutanom korozijom ili vodom koja je u tlu dodatno obogaćena s CO2 biogenog porijekla, kao i drugim organskim kiselinama.