Doktorska disertacija:

Promjene u okolišu tijekom mlađeg pleistocena i holocena – zapisi iz morem potopljenih siga istočnog Jadrana, 2006., PMF Zagreb, mentor: prof. dr. sc. Mladen Juračić

    U-Th i ¹⁴C datiranjem, te RTG difrakcijom dijelova podmorskih siga uzetih iz 7 morem preplavljenih speleoloških objekata na istočnoj obali Jadrana, određene su promjene položaja morske razine u posljednjih 220 tisuća godina i utvrđene paleogeografske promjene uzrokovane fluktuacijama morske razine. Analizirani su i omjeri stabilnih izotopa kisika kao paleoklimatski pokazatelji. Utvrđeno je da su se, usljed klimatskih promjena, okoliši tijekom mlađeg pleistocena i holocena mjenjali s manjim intenzitetom nego u ostalim dijelovima Europe. Istočna obala Jadrana bila je, zbog Alpa i Dinarida kao orografskih barijera, granično područje između periglacijalnog dijela Europe i prostora umjerenih sredozemnih uvjeta, te je predstavljala refugij za biljne vrste iz sjevernih područja. Umjerene temperature, dovoljna vlažnost i adekvatan vegetacijski pokrov omogućavali su i tijekom LGM okršavanje i zasigavanje.

Ključne riječi: paleookoliš, mlađi pleistocen-holocen, U-Th metoda, ¹⁴C metoda, promjena morske razine, podmorske sige, Jadransko more

Late Pleistocene – Holocene palaeoenvironmental changes – records from submerged speleothems from the eastern Adriatic Sea (Croatia)

    U-Th and ¹⁴C dating, and X-ray diffraction of the parts of submerged speleothems taken from 7 submarine caves and pits on the Eastern Adriatic coast, provided insight to the sea-level fluctuations during the last 220 ka and to the palaeogeographic changes caused by sea-level changes. Oxygen stable isotope ratios were analyzed as palaeoclimate indicators. Due to the climate changes, palaeoenvironmental settings also varied, but not so abrupt and intensive as in the rest of Europe . Namely, owing to the Alps and Dinarides acting as orographic barriers, Eastern Adriatic coast was the border region between periglacial Europe and temperate Mediterranean region. It was, also, refuge area for plant species from the north. Appropriate temperature, humidity and vegetation cover ensured favourable conditions for karstification and speleothems formation processes even during LGM.

Key words: Palaeoenvironment, late Pleistocene-Holocene, U-Th dating, ¹⁴C dating, sea-level change, submerged speleothems, Adriatic Sea

Gornjopleistocensko-holocensko kolebanje morske razine na istočnoj obali Jadrana, 2002., PMF Zagreb, mentor: prof. dr. sc. Mladen Juračić

    Mjerenjem ¹⁴C starosti najmlađih dijelova podmorskih siga nastalih u subaerskim uvjetima, te početnog dijela marinskog biogenog obraštaja koji ih prekriva, određeno je razdoblje unutar kojeg su kontinentski uvjeti okoliša u tri, danas potopljena speleološka objekta (Jama u uvali Lučice na Braču, jama Zmajevo uho kraj Rogoznice i Spilja u uvali Tihovac na Pagu) zamjenjeni marinskim. d¹⁸O vrijednosti siga ukazale su na klimatske varijacije vezane za maksimum virmskog glacijala. Utvrđene su brzine rasta siga, mogući uzroci prestanka njihovog rasta, te mehanizmi potapanja speleoloških objekata morem.

    Ključne riječi: ¹⁴C metoda, gornji pleistocen-holocen, Jadransko more, kolebanje morske razine, podmorske sige

    ¹⁴C ages of the youngest parts of the submerged speleothems, which are by their origin typical continental forms, and the starting times of their marine biogenic overgrowths, define the period characterized by changing of terrestrial environment with marine one inside three submerged speleological objects on the Eastern Adriatic coast. The objects are Pit in the Lučice Bay, Brač Island, Pit Zmajevo uho nearby Rogoznica and Cave in the Tihovac Bay, Pag Island. d¹⁸O values have indicated climate variations related to the maximum of Würm glaciation. Possible causes of speleothem growth cessation and the ways of cave submerging have also been discussed.

    Key words: Adriatic Sea, ¹⁴C dating, Late Pleistocene-Holocene, sea level changes, submerged speleothems.

Radovi objavljenim u znanstvenim časopisima referiranim u Current Contents-u:

Surić, M. Lončarić, R., Lončar, N. (2010): Submerged caves of Croatia – distribution, classification and origin
  Presently, 235 submerged caves and pits have been recorded along the Croatian coast and islands, partly or completely submerged by sea water. Contrary to the inland situation, recorded submerged features are predominantly horizontal (60%), though there are indications that the real situation is similar to that of the continental part where 69% are vertical pits. Completely marine conditions are established in 126 caves and the rest are anchihaline caves and submarine springs. Speleothems are found in more than 140 caves. By their origin, the investigated caves are all continental features formed in Mesozoic and Palaeogene carbonates, subsequently submerged owing to sea transgression. Due to the relatively low wave energy, rapid sea level rise and maturity of the host rock, they do not fit into concepts of a sea cave or a flank margin cave development, but they fulfil several conditions for being the blue holes. Since the term ‘blue hole’ is mainly associated with the Bahamian karst, our attempt is only to show the possible similarities with no intention of ascribing that term to the Croatian caves. Beside karstological issues, Croatian submerged caves are unique environmental, archaeological and tourism assets.

    Key words: submerged caves, karst, Adriatic Sea, Croatia

Surić, M., Roller-Lutz, Z., Mandić, M., Krajcar Bronić, I., Juračić, M . (2010): Modern C, O, and H isotope composition of speleothem and dripwater from Modrič Cave, eastern Adriatic coast (Croatia)

Modrič Cave is a shallow horizontal cave situated in the middle of the eastern Adriatic coast ( Croatia ). The cave entrance is located 120 m from the coast at an altitude of 32 m above sea level, and due to its position on the SW slope of the Dinaridic mountain range, a Mediterranean climatic influence is dominant. Due to the stable environmental conditions [(15.6 ± 0.1) °C] Modrič Cave was recognized as a potential site for detailed palaeoclimatic studies. Isotope analyses of modern carbonate speleothems, rain and dripwater were conducted in order to evaluate the isotopic equilibrium conditions. The d¹⁸O composition of rain and cave seepage waters shows an absence of kinetic isotopic fractionation within the epikarst zone, whereas the relation between d¹³C and d¹⁸O in modern carbonate samples and dripwater suggests the isotopic equilibrium conditions during the carbonate deposition. These results contribute to a better understanding of the present-day isotopic composition and they provide a basis for interpretation of speleothem-derived palaeoclimatic records.

   Surić, M., Richards, D., Hoffmann, D., Tibljaš, D., Juračić, M.: Sea level change during MIS 5a based on submerged speleothems from the eastern Adriatic Sea (Croatia)

 Two stalagmites were collected from below sea level in U Vode Pit on the Krk Island , eastern Adriatic Sea , at elevations of -14.5 and -18.8 m. They exhibit a growth history indicating a double high sea-level stand during marine isotope stage (MIS) 5a (~ 87-77 ka). Thin layers of halite and gypsum were found to be associated with hiatuses in speleothem growth probably caused by sea water inundation during sea level highstands. These mineral deposits are likely to have been precipitated during a marine regression phases under evaporitic conditions. We constrain the age of the speleothem growth below and above growth hiatuses, and hence timing of possible marine incursions, using multi-collector inductively coupled plasma mass-spectrometry (MC-ICPMS) U-Th techniques. Age estimates indicate that, during MIS 5a, relative sea level elevations were greater than - 14.5 m from ~87 to ~82 ka and -18.8 m from ~77 to ~64 ka, and constrained to be lower than -18.8 m from >93 to ~90 ka, ~82 to ~77 ka and ~64 to ~54 ka, assuming no tectonic adjustment. However, present speleothem depths could indicate long term regional tectonics.

    Maša Surić, Robert  Lončarić, Anica Čuka, Josip Faričić: Geological issues in Alberto Fortis' Viaggio in Dalmazia (1774)

 The Italian abbot Alberto Fortis (1741-1803) educated in geology, petrology, mineralogy and palaeontology by eminent 18 th century naturalists, performed several extensive explorations in Istria and Dalmatia – provinces of the former Venetian Republic, now the littoral part of Croatia . Notes from some of these journeys, collected in 1774 in the book Viaggio in Dalmazia , encompass observations of almost all aspects of social and physical features of Dalmatian people and land. From a geological point of view, Fortis' remarks generally correspond to recent studies, with some exceptions in palaeontological and petrological issues. His understanding of natural processes, mainly in karstology and hydrology, is mostly surprisingly good. Besides, he addressed critics to previous writers whose theories, influenced by older authorities, had been taken for granted instead of being re-examined by field explorations. His unjustly neglected work was the first extensive and comprehensive study of this part of Europe, little known in the then scientific community.

     Key words: Alberto Fortis, geology, history of science, Dalmatia , Croatia

    Maša Surić, Mladen Juračić, Nada Horvatinčić, Ines Krajcar Bronić: Late Pleistocene-Holocene sea-level rise and the pattern of coastal karst inundation - records from submerged speleothems along the Eastern Adriatic Coast (Croatia)

    In order to reconstruct the Late Pleistocene – Holocene sea-level rise along the Eastern Adriatic Coast , eight speleothems were collected from three submerged caves along the Croatian coast from depths of -38.5 m to -17 m. The marine biogenic overgrowth layer and the youngest and the oldest parts of the speleothems were dated by the ¹⁴C method. Their stable isotope ( ¹³C/¹²C and ¹⁸O/¹⁶O ) contents were also measured. From the measured ¹⁴C activity of the marine overgrowth, and using the model of Alessio et al. (1992), the start of overgrowth (i.e. , the time of flooding by sea water) was determined to be 10,185 cal BP at -36 m, 9,160 cal BP at -34 m and 7,920 cal BP at -23 m.

    Our results partially match the sea-level curves reconstructed for adjacent areas (Tyrrhenian Coast and French Mediterranean Coast). However, the start of the marine overgrowth on speleothems in pit caves indicates strong dependence on the steepness of the terrain. On steep, extensively karstified coasts, marine overgrowths on speleothems coincided with the submersion of the speleothems due to the relatively short distance between the pit and the open sea, and fast penetration of sea water into the pit. In contrast, marine overgrowths on speleothems in pits in the flat terrains occurred later because speleothem growth ceased due to flooding with fresh groundwater. Later, the fresh water was replaced by sea water due to the greater distance of the inland pits to the former coast.

    Key words: Late Pleistocene – Holocene; sea level; submerged speleothem; ¹⁴C dating; karst; Adriatic Sea .

    Maša Surić, Nada Horvatinčić, Axel Suckow, Mladen Juračić, Jadranka Barešić: Isotope records in submarine speleothems from the Adriatic coast, Croatia

    Isotope studies, using ¹⁴C dating, d¹³C and d¹⁸O measurements, were performed at eight speleothems taken from three submerged caves situated along the Eastern Adriatic coast, Croatia . The speleothems were taken from 17 m to 38.5 m depth below mean sea level. The samples consist of four stalagmites and four stalactites in position of growth, covered with marine biogenic overgrowth, and the length of speleothems ranges from ~80 mm to ~190 mm.

The youngest (surface) and the oldest (base) layers of speleothems were radiocarbon dated and the ¹⁴C ages range from 21,600 cal BP to >37,000 yr BP. During that period the global sea level was more than 40 m below the recent one, so presently submerged objects were under the subaerial conditions necessary for speleothem deposition. ¹⁴C ages of the youngest layer range from 21,600 to 32,200 cal BP for different submerged speleothems. This indicates the time when the speleothem growth ceased, most probably due to flooding of the cave with either fresh or brackish water. Speleothem growth during the Last Glacial Maximum (30-19 kyr ago) and different time of growth cessation for the different speleothem samples suggest that climate change was not the reason for cessation of deposition.

    Samples for d¹³C and d¹⁸O measurements were taken from six submerged speleothems with sampling distances of ca. 5-10 mm from the surface to the base of speleothems. Most of the d¹³C values are in the range from -10.5‰ to -8.5‰, with few exceptions to -6‰. These values are typical for Dinaric karst, and very different values for marine biogenic overgrowth indicate that no isotopic exchange took place during the submerged period. d¹⁸O values range from -6.7‰ to -4.1‰. A weak correlation between d¹³C and d¹⁸O values indicates possible kinetic isotope fractionation during the calcite precipitation. If the d¹⁸O record is interpreted as climatic signal, it suggest similar climatic conditions for the Late Pleistocene and the Holocene, especially no significant differences in temperature and/or moisture transport.

    Key words: karst; submarine speleothem; ¹⁴C dating; d¹³C; d¹⁸O; climate change; Adriatic Sea, Croatia

Surić, M., Juračić, M. (2010): Late Pleistocene – Holocene palaeoenvironmental changes – records from submerged speleothems from the Eastern Adriatic Sea ( Croatia )

U-Th and ¹⁴C dating, and X-ray diffraction of the parts of submerged speleothems taken from 7 submarine caves and pits on the Eastern Adriatic coast, provided insight to the sea-level fluctuations during the last 220 ka and to the palaeogeographic changes caused by sea-level changes. Oxygen stable isotope ratios were analyzed as palaeoclimate indicators. Due to the climate changes, palaeoenvironmental settings also varied, but not so abrupt and intensive as in the rest of Europe . Namely, owing to the Alps and Dinarides acting as orographic barriers, Eastern Adriatic coast was the border region between periglacial Europe and temperate Mediterranean region. It was, also, refuge area for plant species from the north. Appropriate temperature, humidity and vegetation cover ensured favourable conditions for karstification and speleothems formation processes even during LGM.

    Key words : Palaeoenvironment, Late Pleistocene-Holocene, U-Th dating, ¹⁴C dating, sea-level change, submerged speleothems, Adriatic Sea , Croatia

Surić, M.: Reconstructing sea-level changes on the Eastern Adriatic Sea (Croatia) – an overview
  Rocky karstified coast, low tidal range, indented shoreline with numerous islands, diverse coastal biocenoses, abundant palaeontological, archaeological and historical evidence, relatively dense tide-gauge stations and developing GPS network – all these facts offer optimal prerequisite for the sea-level changes studies on the Croatian coast. Through various methodological approaches (geomorphological, biostratigraphical, archaeological/historical, mareographic, geodetic, radiometric), most of these issues have been used in order to reconstruct relative sea and land motions, yielding scattered and sometimes erroneous results. Unfortunately, some of them have been often uncritically used as the basis for the subsequent research. Only recently, with multidisciplinary approach, sequences of relative sea-level variations have been successfully revealed, but opportunities that eastern Adriatic coast offers will, undoubtedly, ensure relatively rapid research progress.
    Key words: sea-level change, Adriatic Sea, Croatia

Maša Surić, Branko Jalžić, Donat Petricioli: Submerged speleothems – expect the unexpected. Examples from the Eastern Adriatic coast (Croatia)

    With the intention of reconstructing Late Pleistocene – Holocene sea-level changes along the Eastern Adriatic coast, a series of speleothems were collected from several submerged caves and pits, in order to constrain periods of their deposition and ceased growth related to sea-level fluctuations. For that purpose, stalagmites provide more reliable records than stalactites, due to their successive layers deposited perpendicularly to the growth direction. Therefore, stalagmites have been collected preferably. But, two of 17 speleothems displayed unexpected interior morphology – speleothem L-1 collected at the depth of 1.5 m in Medvjeđa spilja Cave on Lošinj Island , and speleothem M-25 from Pit near Iški Mrtovnjak Islet collected at the depth of 25 m. Both of the samples were taken from the cave floor, in the growth position of the stalagmite. But the insight into the perpendicular cut with evident central tube revealed their true (stalactitic) origin and additional confirmations were obtained by longitudinal cut and U-Th and 14 C dating.

    Just as the causes of their breakdowns were probably different, so were their falls; speleothem M-25 (together with several other speleothems around it) stuck in the marine sediment in its primary position, while L-1 turned upside-down and even continued crystallizing during the lower sea level. These events are possible in the continental caves, as well. Evidently, it is much easier to recognize and avoid these problems in air-filled caves than in the submarine ones where the speleothems are almost always covered with marine overgrowth, which disguises their outer morphology. Additionally, the bases of the stalagmites are also sometimes covered with marine sediment, which makes correct estimation rather difficult.

Key words: submerged speleothems, Adriatic Sea , Croatia

Maša Surić: Submerged karst – dead or alive? Examples from the Eastern Adriatic Coast (Croatia)

    Numerous karst features submerged by the last Late Pleistocene-Holocene transgression are found along the Eastern Adriatic (Croatian) coast. Generally, most of karstification processes cease at the base level, that is, in case of coastal karst, the sea level. However, evidence of continued karstification (corrosion) and related processes (mechanical erosion and bioerosion), as well as remarkable change in hydrogeological settings of some hydrological systems, are quite common in Croatian submarine and coastal area.

Key words: submarine karst, karstification, bioerosion, Adriatic Sea, Croatia

    U podmorju duž cijele istočne obale Jadrana nalaze se brojni krški oblici potopljeni posljednjom gornjopleistocensko-holocenskom transgresijom. Općenito, većina procesa u okviru okršavanja prestaje na razini erozijske baze koja je u slučaju priobalnog krša apsolutna erozijska baza – razina mora. Međutim, u podmorju i priobalnom dijelu istočnog Jadrana brojni su primjeri gdje se i ispod morske razine djelomično nastavilo okršavanje (korozija) i okršavanju bliski procesi (mehanička erozija i bioerozija), a poznati su i primjeri značajne promjene hidrogeoloških funkcija pojedinih priobalnih hidroloških sustava uzrokovanih izdizanjem morske razine.

Ključne riječi: podmorski krš, okršavanje, bioerozija, Jadransko more, Hrvatska

Damir Magaš, Maša Surić: Contribution to the Knowledge about Speleological Features of the Dugi otok Island

   The paper deals with the Strašna Peć Cave (Horrible Cave) situated on the SW side of the Dugi otok island, as one of 57 already known speleological objects on the island. The cave is developed in Cretaceous limestone as the main part of the island, and presents the biggest speleological feature in Zadar’s Archipelago.

    The very first description was given anonymously in 1898, probably by Pietro Rolli, at the time the owner of the surrounding land and the cave. It actuated a well known Croatian naturalist Luka Jelić to make the first precise investigation of the Strašna peć (Horrible Cave), but, unfortunately, without any saved sketches. The first plan was given in 1930 and corrected later in 1953 and finally in March 2000. During the last exploration, the authors visited a few other locations and made an inventory of already known speleological objects on the Dugi otok Island.

    Stories about visits of famous persons to this cave, such as the English Royal Family (heir apparent Edward and Miss Simpson) and Austro-Hungarian emperor Franz Joseph I., are yet to be closely investigated.

   Key words: Strašna Peć, Dugi otok, history of speleology

  Maša Surić, Mladen Juračić & Nada Horvatinčić: Comparison of ¹⁴C and ²³⁰Th/ ²³⁴U dating of speleothems from submarine caves in the Adriatic Sea (Croatia)

    Among the 16 speleothems that were collected from 7 submarine caves and pits for the purpose of ¹⁴C and U-Th dating and reconstructing sea-level changes, two speleothems were dated by both methods. Different environmental conditions during the speleothem deposition and after the submergence resulted with different appropriateness for speleothem dating by these techniques. Well preserved speleothems gave reliable results by both methods, while U-Th method showed disadvantage in the case of carbonates contaminated with detrital material, as well as in the case of carbonate from marine overgrowth that covers the speleothems. However, U-Th method using MC ICPMS technique which requires only 100-300 mg of sample per analysis (instead of ca. 30 g for ¹⁴C conventional method), offers better age resolution that is essential for speleothem dating.

    Key words: ¹⁴C dating, U-Th dating, submerged speleothems, submarine karst, Adriatic Sea, Croatia

Neobjavljeni radovi sa znanstvenih skupova:

Richards, D. A., Hoffmann, D. L., Smart, P. L., Moseley, G. E., Edwards, R. L.., Surić, M.: U-Th ages of submerged speleothems and Quaternary sea levels,
  U-Th ages of calcite growth phases in submerged flowstone and stalagmite sequences serve to constrain both the timing and elevation of past sea-level variation for the middle and late Pleistocene. The most robust sea-level evidence based on speleothems is the presence of continuous calcite growth phases, which provide maximum constraints on past sea-level elevation because they could only have formed when cave passages were air-filled. U-Th ages also provide minimum ages for cave passage formation, which is intimately linked to past sea level positions in carbonate island margin settings. Growth hiatuses can be caused by submergence by rising sea levels or cessation of drip during periods of aridity, lack of soil cover or fissure blockage. Ideally, then, temporal constraints on sea level change are derived from samples with unambiguous evidence of submergence (serpulid worm encrustation, phreatic overgrowths, marine borings). Elevation constraints are the most robust in regions subject to minimal tectonic movement or glacio-hydro-isostatic adjustment. We have adapted mass-spectrometric techniques (TIMS ; conventional and laser ablation MCICPMS) to achieve high precision U-Th ages for speleothem growth. To assess the accuracy of temporal constraints and potential diagenetic effects, we are focussing on increased sampling resolution at the expense of precision. We use a combination of microdrilling and laser-ablation sampling to analyse thin growth layers that might represent millennial-scale sea level fluctuations during interglacial high sea-stands. We present a range of past sea level constraints using speleothems from the Bahamas, Turks and Caicos, Croatia and Yucatan, Mexico. For the most part, material from caves in these locations is useful to constrain high sea-stands when sea levels were greater than -20 m. - Bahamas: Ages for initiation of growth after three major growth hiatuses of a flowstone sequence are ~370 ka, 302 ± 6 ka, 191 ± 4 ka, 68 ± 1.5 ka (2s uncertainty). The hiatuses were caused by major high sea-stand events (> -18 to -10 m below present sea level) and constrain the timing of the marine isotope stage (MIS) boundaries 11/10, 9/8, 7/6 and 5/4 respectively. - Croatia: Confirmatory evidence of the timing of the double high sea-stand associated with MIS 5a also recorded in Barbados terraces - Turk and Caicos: Cave passages formed at sea level during former high sea stands (MIS 7 or older) are found at present sea level or higher and will be discussed in light of the current understanding of subsidence rates and glacio-hydro-isostatic adjustment for this region

Lončarić, R., Surić, M.: Karst and Tourism in Croatia

    Croatia is relatively small Central European and Mediterranean country with surface of 56 538 km 2 and population of 4.44 million according to 2001 census. Recent economic development, abruptly interrupted during 1991-1995 Croatian War for Independence , is primarily based on tourism. Becoming one of the most popular destinations, Croatia recorded total of 9.9 millions tourist arrivals with 51.4 millions tourist nights and over 7 billions of $ of tourist income in 2005. Natural landscape diversity represents a foundation of tourist progress.

    Karst covers almost half of Croatian territory. It also includes entire coast and islands (1246 islands, islets and rocks) with belonging submarine, and all (7) national parks (1.8 millions visitors in 2004). Regions with predominantly karst relief account for 90% of total tourist arrivals and 96.5% of total tourist nights. In the pre-war period, valorization of specific karst forms as possible tourist attractions has been limited to the parts of national and nature parks, and tourism, has had limited offer based on the "sea and sun" principle. Recently, this strategy has been abandoned in favor of "active" vacation offer, thus, some particular karst features such as cliffs, caves, canyons, rapids etc., found their place in Croatian tourist offer, resulting in increasing numbers of tourists visiting aforementioned places and in appearance of new types of tourism, i.e., free climbing, mountain biking, trekking, rafting, kayaking, sea-canoeing, cave diving etc. On the other hand, karst relief might have regressive influence on Croatian tourism in the near future. Due to the specific karst hydrology, coastal and insular parts of Croatia suffer water deprivation in drier years. This problem is especially emphasized on most of the small Croatian islands in the peak of tourist season when island population rapidly increases. However, Croatian karst region remains a stronghold of future tourism and economic development in general.

Key words : Croatia , karst, tourism, coast, islands, national and nature parks, economy

Surić, M., Richards, D., Hoffmann, D., Tibljaš, D., Juračić, M.: Sea level change during MIS 5a recorded in submerged speleothems from the Eastern Adriatic Sea (Croatia)

INTRODUCTION

 In order to reconstruct relative sea-level changes on the Eastern Adriatic coast, 16 speleothems were collected from submerged caves and pits along the Croatian coast. Their growth provides an unambiguous indicator of former low sea levels and can be used to constrain past sea level elevation and timing. Two of them, taken from the U Vode Pit on the Krk Island , apparently recorded Late Pleistocene transgression known as marine isotope stage (MIS) 5a that occurred at ~ 80 ka. Similar research, for example, has been undertaken on submerged speleothems from the Tyrrhenian Sea (Bard et al., 2002), from Bahamas (Richards et al., 1994, Lundberg & Ford, 1994), from Balearic Islands (Fornós et al.,2002) and from the Eastern Adriatic Sea (Vrhovec et al., 2001, Surić et al., 2005).

 The Adriatic Sea is a semi-enclosed epicontinental basin situated between the Apennines and Dinaric mountain ranges, characterized by a relatively shallow northern part (0 to -120 m) with low gradient (0.02°). Such morphology makes it very sensitive to the eustatic changes, so after the Last Glacial Maximum (LGM), postglacial sea-level rise generated eight-fold widening of the shelf area (Correggiari et al ., 1996; Cattaneo et al ., 2003). Much of submarine Eastern Adriatic and Croatia is karstic, developed mostly in Cretaceous and Palaeogene limestones. During the global sea-level low stand associated with the LGM (-121 ± 5 m, Fairbanks , 1989), much of the coastal submarine karst (caves, pits with speleothem deposits) would have been above sea level. More than one hundred submarine caves and pits have been discovered and most of them have been explored, but comparing with adjacent coast and islands, their density is probably several times higher. Currently, the deepest speleothems found within them are those from the submarine of Ist Island from the depth of 60 m (Vrhovec et al., 2001).

Krk Island is the second largest Croatian island and situated in the northern part of the Adriatic Sea (Fig. 1). Two stalagmites from the depths of 14.5 m (K-14) and 18.8 m (K-18) were collected from the U Vode Pit situated in the southern part of the island. Pit is formed in the Upper Cretaceous limestone and it is not completely submarine feature. The entrance of the pit is on the coast, at the elevation of 5.5 m, and the bottom is at -24 m. Relatively thin bordering bedrock allows free circulation between the pit and open sea, as well as settling of marine organisms (serpulids) within the pit. Only upper 0.5 m is filled with brackish water.

METHODS AND RESULTS

 Stalagmites K-14 (26 cm long) and K-18 (15 cm) were taken from their growth position and elevation recorded with digital depth gauge. Each sample was cut along the growth axis and polished to enable insight into the growth layers. Sub-samples (230-415 mg) for MC-ICPMS U-Th measurements were drilled from the polished surface to constrain the timing and duration of what appeared to be hiatuses in deposition – recognised by changes in crystallography, morphology and colour of speleothem calcite and a thin red sediment layer (arrows in Fig 2 and 3). After several days of being exposed on the air, a white substance also appeared on the discontinuities that contain the red layer. The nature of this material was analysed using X-ray diffraction measurements directly on speleothems.

U-Th: The age range of sub-samples is ~94 to 54 ka (Fig 2 and 3). Uranium concentrations are low (30 - 70 ng g -1 ) and errors are typically 1-6% (2?), depending on the extent of detrital contamination. Combining the data for both samples, three phases of growth are observed >90 to 80 ka, a short period at ~80 ka, and ~65 to ~54 ka. We consider the initiation of the extended hiatus in K-18 (and perhaps also that in K-14) to be related to the sea level high event correlated with marine isotope stage 5a. In addition to changes in the morphology, crystallography and colour of calcite between the growth phases, initial 234 U/ 238 U also shows abrupt shifts indicating substantial differences between the hydrological regime for each phase of growth.

XRD: Qualitative X-ray diffraction measurements were done by PANalytical X'pert Pro thete-theta diffractometer equipped with multilayer parabolic monochromator using CuK? radiation. Measurements were performed directly on speleothems. On both speleothems, in the region marked by red line, halite and gypsum peaks were recorded in addition to calcite. No evidence for gypsum was observed for in situ analysis of the speleothem growth just above and below the hiatuses, where only small peaks for aragonite and halite were found in addition to calcite.

DISCUSSION AND CONCLUSION

 According to the results obtained by radiometric measurements and X-ray diffraction, we can assume that deposition of speleothems K-14 and K-18 had been more or less continuous in subaerial conditions from 94 to 80 ka and 65 to 54 ka (and perhaps another short period of growth at ~ 80 ka. Sea level must have been lower that -14 to -18 m at these times.

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Maša Surić, Mladen Juračić, Nada Horvatinčić: Kvartarni okoliši: zapisi promjena uvjeta u okolišu u sigama iz podmorja istočnog Jadrana

 Sige taložene u krškom podzemlju vrlo dobro arhiviraju uvjete okoliša u vrijeme njihova taloženja. Sedimentacijom, najčešće kalcita, iz krških podzemnih voda, sige uključuju određene stabilne i radioaktivne izotope različitih elemenata na temelju kojih je moguće rekonstruirati uvjete okoliša koji su vladali tijekom taloženja siga te odrediti apsolutnu starost karbonata/sige, odnosno vrijeme kad su određeni uvjeti vladali. Sige, koje nastaju isključivo u subaerskim uvjetima, a danas ih nalazimo ispod morske razine, pružaju dodatnu mogućnost da se na temelju njihove starosti i trenutne dubine mora na kojoj se nalaze rekonstruiraju lokalne promjene morske razine koje su se odvijale tijekom geološke prošlosti. Nadalje, znajući relativne promjene obalne linije i korelacijom s globalnim promjenama morske razine, moguće je apsolutno datirati tektonske pokrete lokalnog, pa i regionalnog karaktera.

Istraživanje paleookoliša na istočnoj obali Jadrana temeljeno je na određivanju omjera ¹⁸O/¹⁶O i ¹³C/¹²C, te radiometrijskom datiranju siga metodama ¹⁴C i ²³⁰Th /²³⁴U (U-Th). Ukupno 16 uzoraka siga uzeto je iz 7 morem potopljenih speleoloških objekata s dubina od 1,5 do 41,5 metara:

•  Jama u uvali Lučice (Brač): stalagmiti s dubina 38,5 m (B-38), 36 m (B-36), 34 m (B-34) i s 28 m (B-28), te stalaktit s dubine 26 m (B-26)

•  Zmajevo uho (Rogoznica): stalaktiti s dubina od 17 m (R-17) i 21,4 m (R-21)

•  Spilja u uvali Tihovac (Pag): stalaktit s dubine od 23 m (P-23)

•  Jama U vode (Krk): stalagmiti s dubina od 14,5 m (K-14) i 18,8 m (K-18)

•  Medvjeđa spilja (Lošinj): siga s dubine 1,5 m (L-1) i stalagmit s dubine od 10 m (L-10)

•  Spilja kraj Iškog Mrtovnjaka (Iž): stalaktiti s dubina od 14 m (M-14), 19 m (M-19) i 23 m (M-23)

•  Vrulja Zečica (Starigrad): stalagmit s dubine od 41,5 m (Z-41).

 U prvoj seriji mjerenja starosti korištena je konvencionalna ¹⁴C metoda s plinskim proporcionalnim brojačem (Institut Ruđer Bošković , Zagreb). Iz 8 uzoraka siga datirano je 19 poduzoraka i to najstariji i najmlađi dijelovi siga taloženih u subaerskim uvjetima, te marinski biogeni obraštaj koji prekriva podmorske sige i siguran je indikator marinskog okoliša. Zbog isprepletenog rasta i inkrustacije marinskih organizama, za određivanje vremena početka rasta obraštaja korišten je matematički model ( Alessio et al., 1992). Nedostatak ove metode je u tome što je za mjerenje potrebno izdvojiti oko 30 g kalcita što kod siga obuhvaća više slojeva odnosno razmjerno velik vremenski raspon, a za samo datiranje obraštaja moraju se uzeti u obzir određene pretpostavke.

Za drugu seriju mjerenja koje je obuhvatilo 9 siga, korištena je U-Th metoda, MC ICPMS (Earth Sciences Department Laboratory, University of Bristol) gdje je za jedan uzorak bilo potrebno svega 100-250 mg uzorka i time su se mogali izdvojiti pojedini slojevi sige. Međutim, nedostatak ove metode je osjetljivost na kontaminaciju zbog prisutnosti glinene komponente u sigi, a posebno u marinskom biogenom obraštaju koji se ovom metodom praktički ne može datirati.

Na temelju dobivenih rezultata, zaključilo se da se promjena razine mora na istočnoj obali Jadrana krajem pleistocena i tijekom holocena odvijala približno jednako kao i na obalama Tirenskog mora (Antonioli et al ., 2001) te na mediteranskoj obali Francuske ( Lambeck & Bard , 2000) (Slika 1.).

Prestanak taloženja siga koji na području istočne obale Jadrana nije nastupio istovremeno isključuje mogućnost da su uzrok prestanka rasta bile klimatske promjene. Štoviše, za razliku od brojnih drugih područja, taloženje se nastavilo i tijekom posljednjeg glacijalnog maksimuma (LGM) 30000 – 19000 godina cal BP (prije sadašnjosti) koji je određen kao razdoblje trajanja maksimalnog volumena ledenog pokrova (Lambeck & Chappell, 2001, Lambeck et al. , 2002a , 2002b). Prestanak rasta siga u priobalnom kršu, uz neke druge moguće uzroke, uzrokovan je najvjerojatnije potapanjem speleoloških objekata prvo bočatom, a zatim i morskom vodom usljed izdizanja globalne morske razine ( Surić et al., 2005a).

Također, i d¹³C i d¹⁸O vrijednosti datiranih uzoraka ukazuju na to da je za vrijeme posljednjeg glacijalnog maksimuma klima u podru č ju isto č nog Jadrana bila znatno blaža u odnosu na područje sjeverno od Alpa . Alpe su zajedno s Dinaridima predstavljale orografsku barijeru utjecajima sa sjevera , te je u jadranskom podru č ju dominirao mediteranski utjecaj (Surić et al., 2005b).

    Maša Surić: Submerged karst in Croatia – dead or alive?

    Eastern Adriatic (Croatian) coast, one of the most indented ones and locus typicus of Dalmatian type of coast, is typical submergent (ingressional) coast formed during the last, Late Pleistocene - Holocene transgression, of the order of 125 ± 5 m. Rising sea flooded pre-existing karstified area and its numerous exo- and endokarstic landforms that were formed in tectonically fractured Mesozoic to Early Palaeogene carbonate sediments (limestones and dolomites). Processes of karstification took place downward to the former erosional basis that is, in the case of coastal objects, most often sea level. Prevalence of easily soluble carbonate rocks in the drainage area of most of the rivers on Eastern Adriatic coast resulted with very slow sedimentation rate. Namely, only approximately 20% of river-borne material is suspended and the rest is dissolved, so most of the karstic forms, erosional and depositional (speleological objects with speleothems, dolines, poljes, karrens etc.), can still be recognized at the sea bottom, in spite of the millenniums in the sedimentary environment. Most of them seem to be simply submerged, the others changed their function and in some of them, the process of karstification even continues despite their position under the present sea level.

    Mladen Juračić, Maša Surić, Nada Horvatinčić: Coastal karst forms and dating of sea flooding. Data from the eastern Adriatic coast (Croatia)

    Eastern Adriatic coast (referred in geomorphological literature as the classical Dalmatian type coast, Von Richthofen, 1886; in Fairbridge, 1968) borders the classical karst region of the Dinarics. There, in up to 8000 m thick Mesozoic carbonates, all karst forms are developed. Along the coast, at the land/sea interface, as well as below the sea surface, some peculiar features developed: karstic estuaries (Sondi et al., 1995), marine lakes (Ćosović et al., 2002), drowned canyons, submarine springs and submarine caves and pits, some of them with speleothems (Surić et al., 2002). Most of the forms are of subaerial origin and are only submerged by Late Pleistocene – Holocene sealevel rise. However, accumulation forms (marine biogenic overgrowth, marine sediments) can help in dating of the sea-level changes.

    Several speleothems were collected from three submerged speleological objects along the Croatian coast at depths from 38.5 m to 17 m below present sea level. The marine biogenic overgrowth layer, the youngest and the oldest parts of the speleothems were dated by the ¹⁴C method, and their stable isotope (d¹³C and d¹⁸O) contents were measured. From the measured ¹⁴C activity of the marine overgrowth, the start of overgrowth, i.e. the time of flooding by sea water, was determined (9.1 ka ago at -36 m and 7.1 ka ago at -23 m). The obtained results generally fit into the sea-level curves reconstructed for adjacent areas (Tyrrhenian Coast and French Mediterranean Coast).

Ćosović, V., Juračić, M., Bajraktarević, Z., & Vaniček, V. (2002): Benthic foraminifers of the Mljet Lakes – potential for (paleo)environmental interpretation. Mem. Soc. Geol. Italiana, 57, 533-541

Fairbridge, R. W. (ed) 1968): The encyclopedia of Geomorphology, Reinhold Book Corp. New York, 325-329.

Sondi, I., Juračić, M. & Pravdić, V. (1995): Sedimentation in a disequilibrium river-dominated estuary. The Raša River Estuary (Adriatic Sea-Croatia). Sedimentology, 42, 769-782.

Surić, M., Juračić, M., & Horvatinčić, N. (2002): Late Pleistocene – Holocene changes of the eastern Adriatic coast line. In: F. Veloso-Gomes, F. Taveira-Pinto, & Luciana das Neves (eds.) Littoral 2002. The Changing Coast. Eurocoast/EUCC (Proceedings of the 6 th int. symposium Porto, 22-26 September 2002, Vol III), Eurocoast-Portugal association 259-263.

   Keywords : Late Pleistocene – Holocene; submerged speleothems; ¹⁴C dating; karst; Adriatic Sea