Issue 12, 2012Speleogenesisand Evolution of Karst Aquifers 1. Introduction The coldest Holocene event recorded in Greenland ice cores happened 8200 years ago and lasted approximately 300 years as suggested by changes in 18O (Alley et al., 1997). This episode is characterized by a spectacular decrease of temperatures of up to 7.4C from ambient temperatures at the time in the N-Atlantic region. Other deposits, marine as well as lacustrine, from different regions, going from the N-Atlantic region to the Asian regions, strongly suggest at least a Northern-Hemisphere extension of this cold episode (Alley and Agustsdottir, 2005). The cold period seems to be the consequence of the sudden rupture of an ice dam of the northern American icecap releasing important amounts of cold fresh waters of Lake Agassiz in the North-Atlantic ocean (Barber et al., 1999, Wiersma and Renssen, 2006). In Europe, this event decreased the air temperatures of between ~0.5 and ~2C (Alley and populations (Berger and Guilaine, 2009). Despite several indications of a possible relatively sudden cold event around 8.2 ka in NW-European terrestrial proxies, 8.2 ka cold event due to a lack of high resolution chronology. Moreover, some confusion may exist between the 8.2 ka event and another longer lasting cold period between 8000 and 7000 years (Stager and Mayewski, 1997) which could be a consequence of the 8.2 ka event. Secondary chemical cave deposits (e.g. calcite speleothems) may provide high-resolution proxy tools for paleoclimate reconstruction (Genty et al., 2001; Verheyden, 2001; Verheyden et al., 2006). Several contributions highlight achieving precise chronologies of continental climate changes (Wang et al., 2001; Dykoski et al., 2005; Fairchild et al., 2006; Genty et al., 2003). Abrupt changes in 18O were observed in speleothems from Isral (Bar-Matthews et al., 1999), from Corchia cave in Italy (Zanchetta et al., 2007), from Hlloch cave in Germany (Wurth et al., 2004; Niggemann, 2006) and from Pipikin Pot cave and White Scar cave in the UK (Daley et al., 2011). However, other 18 different of other 18O changes during the Holocene, e.g. Spannagel cave in the Central Alps (Vollweiler et al., 2006), Speleogenesis & Evolution of Karst Aquifers )Abstract: The petrographic, isotopic and chemical changes occurring around 8.2 ka in two stalagmites, one from the Pre Nol cave (Han-sur-lesse, Belgium) and one from the Hotton cave (nearby Marche-en-Famenne, Belgium) are presented. The Pre Nol stalagmite presents a particularly dense grey compact calcite around 8.2 ka, while the Hotton stalagmite presents a deposition hiatus of ca 1100 years. Besides the macroscopic aspect of the stalagmites, changes in their isotopic (18O and 13) composition and in their chemical (Sr/ Ca, Mg/Ca) composition are observed. Regarding the early start and the duration of the climate deterioration, it is impossible to link the onset of the observed wet phase in the studied speleothems as directly related to the so-called 8.2 ka event. The question arises if the climate deterioration around 8.2 ka observed in both stalagmites is one among other deteriorations occurring during the early Holocene. Keywords: 8.2 ka event, speleothems, climate, geochemistry, oxygen and carbon isotopesThe 8.2 ka event: is it registered in Belgian speleothems? S. Verheyden1*, E. Keppens2, M. Van Strydonck3 and Y. Quinif 41 Vrije Universiteit Brussel Present address: Royal Belgian Institute of Natural Sciences,Jenner straat 13, B-1000 Brussels, Belgium 2 Vrije Universiteit Brussel, Pleinlaan2, 1050 Brussels, Belgium3 Royal Institute for Cultural Heritage, Parc du Cinquantenaire, 1 B-1000 Brussels, Belgium4 Universit de Mons, Rue de Houdain9, B-7000 Mons, Belgium by the authors. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license
Verheyden S. et al 4 Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012THE 8.2 KA EVENT : IS IT REGISTERED IN BELGIAN SPELEOTHEMS? Carburangeli cave Sicily (Frisia et al., 2006), or show isotopic and/or chemical changes over longer time periods, e.g. Pre Nol cave (Verheyden et al., 2000) and Renella cave Italy (Zornyak et al., 2011) or not exactly at 8.2 ka BP, leaving some doubt on the direct link with the 8.2 ka event as in stalagmites from Ernesto cave, Italy (Frisia et al., 2006). Finally a spectacular minimum in 18O around 8.2 ka in a speleothem from Crag Cave (Baldini et al., 2002) was subsequently shown to be an analytical artefact (Baldini et al 2007). Despite possible explanations of the observed differences in stalagmite records in Europe (Sptl et al., 2010), it remains unclear if the cold periods observed in the stalagmites around 8.2 ka are linked with the cold event. We present the petrographic, isotopic and chemical changes in two stalagmites from the Pre Nol and the Hotton caves (Belgium) occurring around 8.2ka and discuss an eventual link with the 8.2ka cold event.2. Methods The two Holocene low-Mg calcite stalagmites studied were sampled between 1995 and 2000 AD in respectively the Hotton cave and the Pre Nol cave. Both caves are located in Givetian limestone and are located at a distance of approximately 20 km (Figure 1). The stalagmite from the Pre Nol cave (PN) is 64 cm long. The internal longitudinal section of the stalagmite presents a succession of dark brown parts and milky white parts along its longitudinal axis. No clear hiatus is observed in the stalagmite (Figure 2).
Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012 Verheyden S. et alTHE 8.2 KA EVENT : IS IT REGISTERED IN BELGIAN SPELEOTHEMS? The stalagmite was dated by TIMS U-series dating published in Verheyden et al. (2000) with an additional dating done by MC-ICPMS (Thermo-Finnigan Neptune) in the Minnesota isotope laboratory, University of Minnesota. The chemical procedures used to separate the uranium and thorium for 230Th dating are similar to those described in Edwards et al. (1987). All ages are given in years before 2000 AD. The PN stalagmite was deposited between ca. 12.9 ka and 1.8 ka. The candle shaped stalagmite from the Hotton cave is 68 cm long. The longitudinal section of the stalagmite is of rather constant milky-white compact aspect without macroscopically visible lamination. A clear hiatus, consisting of a clay layer occurs at 47 cm from the top of the stalagmite (Figure 3). First U-series dating of this stalagmite failed due to detrital 232Th contamination. Subsequently, 10 AMS 14C datings were performed. Chemical preparation was done at the 14C laboratory of the Royal Institute for Cultural Heritage following the method described in Van Strijdonck and Van den Borg (1991). The 12C/14C ratio was measured with AMS at the Swiss Federal Institute of Technology, Zurich (ETH). 14C dates were calibrated after correction for dead carbon proportion (Genty et al., 1998, 1999) with Calib 4.1 (Stuiver and Reimer, 1993) with a smoothing of 100 years (Trnqvist, 1993). A mean dead carbon proportion (dcp) of 12% was estimated based on former measurements of dcp on Belgian stalagmites (Genty et al., 1999; Genty, 2000). The ages are given in calendar years before 2000 AD and to avoid confusion will be noted as cal y B2k The stalagmite was deposited between 11 200 cal y B2k and 2 800 cal y B2k3. Results Both studied stalagmites exhibit a sedimentological particularity around 8.2 ka. The Pre Nol stalagmite presents a particularly dense grey compact calcite around 8.2 ka over approximately 1.5 cm length along the longitudinal axis (Figure 2). The U-series dating constraints the petrographic change between 8.6 or 8.9 ka and 8.2 ka (see discussion and Figure 4) after which the speleothem returns to the deposition of usual alternation of white porous and dark compact calcite. From 8.0 ka, stalagmite diameter decreases abruptly and a small candle-shaped stalagmite is deposited until ~7.0 ka. Besides the macroscopic aspect of the stalagmite, important changes in its Sr/Ca, Mg/Ca ratios as well as in its stable oxygen and carbon isotopic composition are observed around 8.2 ka (Figure 5) with positive anomalies before and negative anomalies during the deposition of dense calcite. The Hotton stalagmite presents a deposition hiatus (Figure 3) of ca 1100 years between extrapolated ages of 8700 cal yr B2k and 7600 cal yr B2k (Figure 4). The hiatus is
Verheyden S. et al Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012THE 8.2 KA EVENT : IS IT REGISTERED IN BELGIAN SPELEOTHEMS? clearly visible through the presence of a thin clay layer. 18O, 3C, Mg/Ca and Sr/Ca measured along the central stalagmite axis display no consistent important changes (Figure 6) before or after the hiatus. Only 18O exhibit a sudden drop of -0.8 between 8840 and 8750 cal yr B2k. 4. Discussion Since sedimentological anomalies in both the stalagmites, the Pre Nol as well as the Hotton stalagmite start before 8.2 ka, even taking into account the uncertainties on the ages, the onset of the sedimentological anomalies cannot be directly and causally linked to the so-called 8.2 ka cold event as observed in Greenland ice (Alley et al., 1997) and related to the fresh water outburst of Lake Agassiz in the northern Atlantic region (Barber et al., 1999, Wiersma and Renssen, 2006). However, since sedimentological anomalies are observed in the studied stalagmites, beginning before 8.2 ka and lasting longer than ~300 years of the cold event (Alley et al., 1997), environmental and/or climatic changes probably occurred and may be partly linked to the 8.2 ka event or may overprint the 8.2 ka event.4.1. Before and during the sedimentological anomaliesIn the Pre Nol stalagmite, the dense calcite starts at 8.6 ka according to a linear interpolation between two surrounding datings. However, taking into account the similar petrography until the onset of the dense calcite, extrapolation at a similar growth rate towards the onset of the dense grey calcite seems more adequate. In this case, the onset of the dense calcite starts at ca 8.9 ka (Figure 4) with a lower growth rate (3.2 mm/century) than before 8.9 ka (4.6 mm/century), indicating degraded conditions for stalagmite deposition, i.e. cold and/or too wet/too dry conditions decreasing soil activity. The relatively large stalagmite diameter (relative to the mean diameter) during the deposition of dense calcite indicates that enough water was available to cover the whole stalagmite top through calcite deposition, also on the sides of the stalagmite (Figure 2). This is in agreement with lower Mg/Ca, Sr/Ca 3C and 18O values (Figure 5). Low values of these four parameters were interpreted as an indication of higher humidity conditions in the cave related to the water availability and indirectly to rainfall amount (Verheyden et al., 2008a). The lowest values occur at 8.2 ka. These low values characterising the upper part of the dense grey calcite occur after a peak in Mg/ Ca, Sr/Ca, 18O and 3C values observed just before 8.9 ka B2k. The peak values suggest dry conditions, contrasting, however, with the only limited decrease in stalagmite diameter. The low values at 8.2 ka BP indicate a cold and humid period, which may be linked to the 8.2 ka event. Unfortunately, the signal as registered in the stalagmite is not enough individualised and not generalised among the different studied parameters to 4.2. After the sedimentological anomaliesAfter the sedimentological anomaly characterised by dense grey calcite in the Pre Nol stalagmite and ending at 8.2 ka, a decrease in stalagmite diameter indicates a reduced availability of water in agreement with a slight increase in the measured chemical and isotopic parameters. Increased growth rates of 7.9 mm/century between 8.2 ka and 7.9 ka and up to 17.6 mm/century after 7.9 ka indicate better conditions for stalagmite deposition, i.e. temperate/warm humid conditions with high soil activity. In the Hotton stalagmite, no particular change is observed consistently in the four chemical and isotopic parameters before or after the hiatus dated between 8700 cal yr B2k and 7600 cal yr B2k (Figure 6). However, the muddy layer stalagmite by the nearby river and therefore wet conditions. The position of the stalagmite near the underground river and
Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012 Verheyden S. et alTHE 8.2 KA EVENT : IS IT REGISTERED IN BELGIAN SPELEOTHEMS? periods, the downstream narrowing acts as a natural dam, rapidly amplifying the high-water stand due to the constriction of the passage. Former unpublished investigation on the detrital deposits in front of the narrow passage (Bessems et al., 1999), indicates the existence of a lake during the last glacial period. Nowadays, high-water stands only rarely occur, creating a small muddy lake in front of the narrow passage. During these periods water levels never reach the studied stalagmite, but arrive close to its base. The local settings, the evidence of the former presence of a lake as well as nowadays observed highwater levels, although not covering the stalagmite, indicate in the stalagmite. Other similar clay layers are present in the stalagmite at ca 10.2, 10.0, 9.2 and 5.8 cal ka B2k. 4.3. Combined climatic interpretationThe combined information from both studied stalagmites gives indications for the climatic conditions around 8.2 ka (Figure 4). A short intensive dry period, as suggested by peak values of four chemical and isotopic parameters in the Pre Nol stalagmite ends at ca 8.9 ka. After 8.9 ka the climate is degrading as indicated by a decrease in growth rate. Wet conditions seem to occur as indicated by a relatively large Pre Nol stalagmite diameter, which is in agreement with the stop in deposition of the Hotton stalagmite at ca 8.7 cal ka B2k due and a clearly lower water availability combined with climatic conditions favourable for stalagmite deposition is observed at 7.9 ka in the Pre Nol stalagmite. The Hotton stalagmite starts its growth again at 7.6 cal ka B2k. Indicating the return to fully temperate interglacial conditions. The climatic deterioration as registered in both stalagmites started therefore at ~8.9 ka with on. Temperate conditions seem to return between 7.9 ka and 7.6 ka. The existence of a wet phase between 8.2 ka and 7.1 ka in the Apuan Alps as suggested by a Renella cave speleothem (Zornyak et al., 2011) is in good agreement with the second part of the sedimentological anomalies in the Pre Nol and Hotton stalagmites. The authors link the wet phase to the 8.2 ka event. However, the Renella cave speleothem show, as in the Pre Nol cave a decrease of the 18O starting around 9 ka and lowest values at 8.2 ka, suggesting as in the speleothems studied here the onset of a wetter period before the 8.2 ka event, possibly enhanced at 8.2 ka by the famous 8.2 ka event as argumented in Zornyak et al. (2011). 4.4. Comparison with the Jeita stalagmite (Lebanon)Since the study reported here was presented at the 3rd Middle-East Speleology Symposium (MESS3), it is noteworth to mention that the JeG-stm-1 stalagmite from the Jeita cave (Lebanon, Verheyden et al., 2008b) displays no clear evidence 18O between 8.0 and 7.8 ka is observed suggesting wetter conditions following the interpretation of the 18O in this speleothem soil activity since no important peak is observed in the 3C record.5. Conclusions Sedimentological, chemical and isotopic investigation of the Pre Nol and the Hotton stalagmites give indications for the occurrence of a wet phase between ca 8.9 ka and 8.2 ka. Progressive drying is observed until 7.9 ka with a return to fully temperate interglacial conditions at 7.6 ka. Regarding the early start of the climate deterioration and the duration of 1100 years, it is impossible to link the onset of the observed wet phase in the studied Belgian speleothems as directly related to the so-called 8.2 ka event. Only the lower 18O values in the Pre Nol stalagmite at 8.2 ka may be related periods recorded in the Hotton stalagmite similar to the one recorded before and around 8.2 ka, suggests that the climate deterioration registered in this stalagmite may be one among other deteriorations occurring during the early Holocene. AcknowledgementsThe authors would like to thank the S.A. Grottes de Han and in particular the Director-General Michel Vankeerberghen as well as the guide Etienne Lanoye for their important help particular in the Pre Nol cave. The authors are also very grateful to the Caves of Hotton for the access to the cave and the permission to sample. The authors acknowledge Anne Laurys form the Royal Belgian Institute of Natural sciences for the graphical material. Part of this study was possible thanks to a grant of the ReferencesAlley, R.B. and Agustsdottir, A.M., 2005. The 8k event: cause and consequences of a major Holocene abrupt climate change. Quaternary Science Reviews 24, 1123 1149. Alley, R.B., Mayewski, P.A., Sowers, T., Stuiver, M., Taylor, K.C. and Clark, U., 1997. Holocene climatic instability: A prominent, widespread event 8200 yr ago. Geology 25, 483-486. Baldini, J.U.L., McDermott F., and Fairchild, I.J., 2002. Structure of the 8200-year cold event revealed by a speleothem trace element record. Science 296: 2203-2206. Baldini J.U.L., McDermott F., and Fairchild I.J., 2007. Retraction of an interpretation. Science 317, 5839: 748b. Barber, D.C., Dyke, A., Hillaire-Marcel, C., Jennings, A.E., Andrews, J.T., Kerwin, M.W., Bilodeau, G., McNeely, R., Southon, J. Morehead,
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Issue 12, 2012 Speleogenesis and Evolution of Karst Aquifers 1. Introduction We have developed a statistical computational model in order to examine some statistical properties of karst: among it of dip and other parameters such as fracture permeability. The examination of such statistical properties is interesting because it contributes to the still lively debate about the but starting from very different basis. Varying some parameters derived from the study of real karst systems are in qualitative model is at the scale of the entire karst: in the current state order to reduce the number of relevant parameters. For that model are more aimed to exemplify some ideas, to propose take in account only basic parameters necessary to explain the peculiar characteristics of karst conduits, in a surprising fashion some results are very close to those from real sumps or cave surveys: this is also quite interesting. 2. Presentation of the model This model is intended to apply to caves formed in soluble applies in the early stages of development of the integrated Nevertheless, some statistical properties remain effective after statistical properties may describe the geometry of actual conduits. This is the case for the mean depth of conduits P. Boudinet 1 1 or under the terms and conditions of the Creative Commons Attribution license Speleogenesis & Evolution of Karst Aquifers Abstract: Keywords:
Boudinet P. conduits that have a greater probability of developing in some places and a poorer probability in other places. We make the particular choice of an allogenic karst: the an early stage development, as an approximate but not limiting circulation is assumed to be driven by the elevation gradient outlet introduces another limitation on the number or extent of for each node the probability is either able or not able to become a conduit after competition We dont focus on the hydrodynamic details because, some of the parameters needed to determine the applicability for a developed conduit to The fact that all the edges dont have the same permeability is described in a very simple probabilistic fashion: an edge lets
Boudinet P. constraints inside the material, are constant. Nevertheless, this model may be close enough to real karsts, for example, variability it often indicates conditions expected in tectonized and meanders commonly found are vadose in evolution and are not the concern of our model. There are other modes of conduit formation in such mountain karsts, for example those The probability of existence of a developed conduit at a Some nodes are forbidden because they are above the displacement in a sense opposite to the hydraulic gradient has been that corresponds to the total probability for the conduits to be able to develop at this distance. This total probability may remain close to unity, or vanish more or less quickly. the bedding planes, determining the dip, is close to the angle 3. Some important results unit according to our model such deep conduits seem likely to be rather scarce. appears that, at any given distance, the mean depth increases varies like the square root of the distance, and it can be
Boudinet P. from the inlet. inlet seems rather independent of p. isnt symmetric. The colour code for the probability ranges from through green for intermediate values. becoming more and more important as p decreases. As previously explained, our model concerns the conduits that are, in probability, present in some areas and
Boudinet P. 4. Application to caving and cave diving study. The probability can be regarded as a function of the h appears that situations can be distinguished: Since
Boudinet P. than a certain threshold, very roughly corresponding to the percolation threshold. at all and if p is too close to unity, only a large number of small epiphreatic caves may come into existence. As discussed decreases appears that all of the necessary conditions for discovering conduit is active and large enough to be dived it becomes to investigate and therefore may be recorded less frequently in the caving literature. Beyond this practical obstacle, Figure the distribution of maximal values of that resembles the survey of a real cave. 5. Re-examination of Worthingtons results dip, length, and other parameters, on the depth of conduits. An E E and the highest recharge point in the aquifer. The correlation
Boudinet P. important dips. quantity of smaller scale, dips and displaying conduits of the same length may have quite different values for the mean depth if the values of arent the plays an important role in the scaling 6. Final considerations means of p, it put the emphasis on a very important factor, even sometimes unrecognized: the existence of tectonic constraints put the emphasis on another important parameter: the mean porosity, but a very large number of conduits that are not large systems that are sometimes neglected: the fact that the to take in account, for example, the preference for conduits article, and especially to precise some important points. This Table 1 in a blind manner may lead to expressions rather different than those related to a precisely determined value of Properties of conduits Worthington Present article Weak dip Strong dip Weak dip Strong dip
Boudinet P. References the evolution of karst aquifers and speleogenesis. The step from
Issue 12, 2012Speleogenesisand Evolution of Karst Aquifersonline scienti c journal www.journal.speleogenesis.info/journal/ IntroductionAt the western shores of Messinian Mani peninsula, in south Greece, 49km to south-east of Kalamata city and south of Agios Dimitrios village, an impressive, composite karstic system is developed below and above sea-level (Papadopoulou, 1999). It comprises Â‘Â‘SelinitsaÂ’Â’ Cave and Â‘Â‘DrakosÂ’Â’ underground river, which are located on the shoreline and in + 8 m a.s.l. and -10 m, respectively. This karstic system is over 4 km in length, comprising the fourth longest cave system in Greece. It is developed in limestone benches of Plattenkalk unit tilted at 10o, which are characteristic in the wider area. Â‘Â‘SelinitsaÂ’Â’ Cave has about 3000 m of mapped passages, of which most of passages (about 2000 m) are terrestrial. The cave passages are vadose and phreatic. The cave presents rich speleothemic decorations and has the largest in Hellenic region single collapse chamber of 250x200 m in cross dimensions. Â‘Â‘DrakosÂ’Â’ underground river has 1232 m in length and is developed entirely below the sea level. Its entrance lies at depth of 10 m but cave passages are developed in three levels, with the deepest parts at -48 m. In the third level and at -28 m depth, Â‘Â‘DrakosÂ’Â’ is connected with Â‘Â‘SelinitsaÂ’Â’ Cave through a chimney-shaped passage of 28 m length. The presence of a big chamber of 50x100 m of cross dimensions and of a big stalagmite in the eastern entrance, is notable, too. Generally, speleothemic decoration in Â‘Â‘DrakosÂ’Â’ is poor. Passages are exclusive phreatic and siphons act as lifting tubes, transferring water drained from Â‘Â‘SelinitsaÂ’Â’, underwater from -28m to -10m (Papadopoulou-Vrynioti and Kampolis, 2011). The aim of this study is to clarify the formation and development of this composite coastal karstic system.GeologyThe impressive composite karstic system of Messinian Mani is developed into typical white and grayish, medium bedded, limestones of Upper Senonian Â– Upper Eocene age of total thickness of 300-500 m, which belong to the Mani (Plattenkalk) geotectonic unit (Fig. 1), relative autochthon of Peloponnesus. In the wider area, slightly metamorphic ysch (Upper Eocene Â– Oligocene) overlies stratigraphicaly the Upper Senonian Â– Upper Eocene limestones. Also, limestones of the Vigla series (Upper Jurassic Â– Cretaceous), silicate schists (Lower Â– Middle Jurassic) and Formation and development of a karstic system below and above sea level in Messinian Mani Peninsula (S. Greece)Kyriaki Papadopoulou-Vrynioti1 and Isidoros Kampolis21Faculty of Geology & Geoenvironment, University of Athens, Platanon 16b, 14578, Athens, Greece. 2Odyssea Elyti 15, 13341, Athens, Greece. orresponding author: email@example.com or firstname.lastname@example.org by the authors. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution licensePapadopoulou-Vrynioti, Kyriaki and Kampolis Isidoros. 2012. Formation and development of a karstic system below and above sea level in Messinian Mani Peninsula (S. Greece). Speleogenesis & Evolution of Karst Aquifers 12, 17-21 (http://www. speleogenesis.info/content/)Abstract: At the western shores of Messinian Mani Peninsula in South Greece, the composite, integrated karstic system of Â‘Â‘SelinitsaÂ’Â’ cave and Â‘Â‘DrakosÂ’Â’ underground river is developed above and below sea-level respectively, in the medium-bedded limestones of the Mani geotectonic unit. The formation and the development of these caves started, most likely, during Middle Pleistocene. Initially, these caves were terrestrial and developed separately. They were connected probably during Holocene through a ssure. The development of this united karstic system is controlled by tectonics. Â‘Â‘SelinitsaÂ’Â’ cave is older than Â‘Â‘DrakosÂ’Â’. The sequential base levels of karsti cation demonstrate the continuous sea-level changes during Pleistocene and Holocene, induced by the relative tectonic activity. This united karstic system is characterized by Â‘incomplete linkageÂ’ to the sea. Key words : integrated karstic system, tectonic control, sea-level changes, karsti cation.
Papadopoulou-Vrynioti K. and Kampolis I. 18online scienti c journal www.journal.speleogenesis.info/journal/ Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012KARSTIC SYSTEM BELOW AND ABOVE SEA LEVEL IN MESSINIAN MANI PENINSULA Pantokrator limestones (Middle Triassic Â– Lower Jurassic) occur at the lower stratigraphic level of the Mani unit (Papanikolaou et al., 1990). Late Cenozoic post-alpine clastic deposits, Pliocene marine marls and Pleistocene clays are observed in unconformity along the coastal zone (Kelletat and Gassert, 1975). Late Pleistocene and Holocene fans cover the plain areas, too. The tectonism of the wider area is represented by faults with NNW-SSE main orientation and minor E-W orientation, formed mainly during Early Miocene (Mariolakos et al., 1985, 1994), which affects the whole Mani peninsula. Since Middle Pleistocene, the stresses have been reversed in the area, became extensional in WNW-ESE direction, and faults of the same direction have been formed. The NE-SW directions of fractures which observed during the eld work, south-east of Â“DrakosÂ” underground river, must be relatively younger tectonic structures, as a NW-SE to NNESSW fault interrupts and displaces a NW-SE fault of Miocene age in Kotroni hill (Fig. 1). Also, due to an anticlinal structure, reversed strata have been observed in the wider area. Due to the anticlinal structure and the dips in the area of caves, the ysch and the silicate schists act as barrier of impermeable lithology (Pavlakis et al., 1989). These comprise the regional karsti cation base levels (Fig. 2) of the studied karstic system. For this reason, the karstic system is characterised by Â‘the incomplete linkageÂ’ to the sea (Mijatovic, 1975, 1977). Based on the rose diagram analysis (Figs 3 and 4) which results from 105 measurements of joint directions from the marbles area above Â‘Â‘SelinitsaÂ’Â’ and Â‘Â‘DrakosÂ’Â’, it is apparent that: joints around Â‘Â‘SelinitsaÂ’Â’ have a NNW-SSE to NW-SE principal direction, consequently they must correspond to the Miocene tectonism. On the contrary, joints around Â‘Â‘DrakosÂ’Â’ have a NE-SW principal direction corresponding to a younger tectonism.Figure 1. Geological map of the studied area (IGME, 1983). 1 Â– Old and recent fans (Holocene), 2 Â– Terrraces consisting of red clays, clayey sand with dispersed angular pebbles and alterations of breccio-conglomerates (Pleistocene), 3 Â– Marine sediments (Pliocene), Alpine Basement (Plattenkalk / Mani Unit): 4 Â– Flysch (Upper Eocene-Oligocene), 5 Â– Limestones (Upper Senonian-Upper Eocene), 6 Â– Limestones of Vigla series (Upper Jurassic-Cretaceous), 7 Â– Silicate schists (Lower-Middle Jurassic), 8 Â– Pantokrator limestones (Middle Triassic-Lower Jurassic), 9 Â– Phyllitic crystalline basement (Permian (?)-Lower Triassic), 10 Â– Strike and dip of strata, 11 Â– Fault, 12 Â– Fault probable, 13 Â– Geological boundary, 14 Â– Cave.
19Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012 online scienti c journal www.journal.speleogenesis.info/journal/Papadopoulou-Vrynioti K. and Kampolis I.KARSTIC SYSTEM BELOW AND ABOVE SEA LEVEL IN MESSINIAN MANI PENINSULA Formation and development of Â‘Â‘Selinitsa DrakosÂ’Â’ karstic systemIn Â‘Â‘SelinitsaÂ’Â’ Cave, the larger part of its passages demonstrate NW orientation, and a small part has E-W orientation (Fig. 3), as follows from the mapping analysis of Â‘Â‘SelinitsaÂ’Â’ and the respective rose diagram (PapadopoulouVrynioti and Kampolis, 2011). The large chamber of the cave with 250x200m crossdimensions is developed along two main axes of NW-SE and E-W directions, respectively. Also, Â‘Â‘SelinitsaÂ’sÂ’Â’ passage, through which it is connected with Â‘Â‘DrakosÂ’Â’, has NE-SW direction. Small branches are developed in N-S direction, too. Â‘Â‘DrakosÂ’Â’ passages are developed mainly in NE-SW directions, and minor passages are of E-W directions, as the majority of passages present a general NE orientation and only a small part a WSW orientation (Fig. 4). Small branches are developed in NW-SE and NNW-SSE direction, too. With comparison of rose diagrams of passage directions of both Â‘Â‘SelinitsaÂ’Â’ and Â‘Â‘DrakosÂ’Â’ and respective rose diagrams of joints directions (Figs. 3 and 4), a great similarity between them is evident. This is due to the fact that the development of the studied composite karstic system has been controlled by tectonics. Further analysis suggests that Â‘Â‘SelinitsaÂ’Â’ development is in uenced mainly by NW-SE, NNW-SSE faults of Miocene, whereas Â‘Â‘DrakosÂ’Â’ is controlled by NE-SW faults of younger age. The fact that both caves have passages in WNW-ESE direction, controlled by tectonics of Middle Pleistocene, means that the development of those caves is most likely to have started during Middle Pleistocene. During Pleistocene glacial periods, the sea level uctuated from -120m to -40 m, below the present one (Lambeck, 1996). Considering the relative tectonic activity, this level must have been the base level of karsti cation. In this way, initially both Â‘Â‘SelinitsaÂ’Â’ and Â‘Â‘DrakosÂ’Â’ caves were developing above sea level, having a terrestrial character. The terrestrial character of Â‘Â‘DrakosÂ’Â’ Cave is also ascertained by the presence of the big stalagmite at the eastern entrance, at -10 m depth, and by the existence of stalactites and stalagmites in the third level, at a depth of approximately -30 m.Figure 2. Geological pro le WSW-ENE through the karstic system based on the geological map of gure 1 and photo of Â“SelinitsaÂ’sÂ” entrance. Figure 3. A map of Â“SelinitsaÂ” cave and rose diagramms of its passage directions (1) and joints above and around its entrance ( 2).
Papadopoulou-Vrynioti K. and Kampolis I. 20online scienti c journal www.journal.speleogenesis.info/journal/ Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012KARSTIC SYSTEM BELOW AND ABOVE SEA LEVEL IN MESSINIAN MANI PENINSULA The location of the connection point of the caves, the smaller length of Â‘Â‘DrakosÂ’Â’ Cave in comparison with Â‘Â‘SelinitsaÂ’Â’ Cave, and the limited speleothemic decoration of Â“DrakosÂ” are evidence of the short time period during which Â‘Â‘DrakosÂ’Â’ Cave was located above sea level. By the end of the last glacial period of Pleistocene, sea level began to rise gradually. This can be ascertained by the high frequency of karst tubes in -25 m to -20 m and in -12 m to -8 m, which are responsible for the submarine discharges in the Vlychada Cave area located to south of the studied area (Giannopoulos, 2000) and probably for the submarine spring in Stoupa Bay, north of the studied area (Stamatis et al, 2011). Also, a small number of widened conduits is observed in altitudes -45m to -40m. It is likely that these ranges re ect the gradual sea level rise and the presence of temporary sea level stands within them. Initially, the two caves developed separately. This is suggested by the fact that their connection is through a narrow chimney-shaped passage, which is developed along a NE-SW tectonic discontinuity, corresponding to the younger tectonism. The width of that passage also, re ects the recent age of development. Consequently, Â‘Â‘SelinitsaÂ’Â’ and Â‘Â‘DrakosÂ’Â’ connection and the integration of the karstic system must have taken place recently, probably during Holocene.Conclusions The Â‘Â‘SelinitsaÂ’Â’ Cave and the underground river of Â‘Â‘DrakosÂ’Â’, developed below and above sea level respectively, are now united. Initially both of these caves were developing above sea level but Â‘Â‘DrakosÂ’Â’ has remained above sea for a short time period. Initially, the two caves developed separately. They were probably connected during Holocene, through a ssure with NE-SW direction in -28 m depth, creating an integrated karstic system. The tectonism has strongly in uenced the development of the studied karstic system that can be characterized as directed by tectonics. The tectonic control of Â‘Â‘SelinitsaÂ’Â’ is NW-SE whereas that of Â‘Â‘DrakosÂ’Â’ is NE-SW. Â‘Â‘SelinitsaÂ’Â’ cave is older than Â‘Â‘DrakosÂ’Â’ because Â‘Â‘SelinitsaÂ’Â’ is located in a higher position related to Â‘Â‘DrakosÂ’Â’, the most passages of Â‘Â‘SelinitsaÂ’Â’ are above the present sea level and has almost three-fold length of passage development. The development of both caves is most likely to have started during Middle Pleistocene. The older base level of karsti cation of this composite karstic system is in -48 m. Also, widened conduits from -12 to -8 m, observed in the underground river of Â‘Â‘DrakosÂ’Â’, corresponds to the most recent base level of karsti cation. The above mentioned levels demonstrate the continuous sea level changes during Holocene induced by the relative tectonic activity. The studied karstic system is characterised by Â‘incomplete linkageÂ’ to the sea.ReferencesAvagianos, G., Zoupis, K., Patiraki, Th., Koniari, H., 1978. Mapping of Â“SelinitsaÂ” cave, Ag. Dimitrios, Messinian Mani Hellenic Speleological Society Archive. Giannopoulos, I. B., 2000. Contribution to the study of contemporary and old environments of the most important Greek caves PhD Thesis, Uni. of Athens, 443 p. IGME, 1983. Geological sheet Â‘XirokampionÂ’ 1:50000, by Psonis C. & Latsoudas C. Kelletat, D., Gassert, D., 1975. Quartar morphologische Untersuchungen in Kustenraum der Mani Halbinsel, Peloponnes Z. Geomorph., Suppl-Bd 22, 58-56 s. Koryllos, K., Tzavelas, G., 2004. Mapping of the underground river of Â“DragonÂ”, Ag. Dimitrios, Messinian Mani SPELEO Archive. Lambeck, K., 1996. Sea-level change and shore-line evolution in Aegean Greece since Upper Palaeolithic time. Antiquity 70 588611 p. Mariolakos, I., Papanikolaou, D., Lagios, E., 1985. A neotectonic geodynamic model of peloponnesus based on: morphotectonics, repeated gravity measurements and seismicity. Geol. Jb. Band 50, 3-17 p.Figure 4. A map of the Â“DrakosÂ” underground river and rose diagrams of its passage directions (1) and joints above the cave (2).
21Speleogenesis and Evolution of Karst Aquifers, Issue.12, 2012 online scienti c journal www.journal.speleogenesis.info/journal/Papadopoulou-Vrynioti K. and Kampolis I.KARSTIC SYSTEM BELOW AND ABOVE SEA LEVEL IN MESSINIAN MANI PENINSULA Mariolakos, I., Badekas, I., Fountoulis, I., Theocharis, D., 1994. Reconstruction of the Early Pleistocene paleoshore and paleorelief of SW Peloponnesus area. 7th Congress of the Geol. Soc. Greece Vol. XXX/2, 297-304 p. Mijatovic, B., 1975. Exploitation rationelle des eau karstique. Hydrogeology of karstic terrain published by IUGS-IAH, Paris, 123136 p. Mijatovic, B., 1977. Current problems in the rational exploitation of karst water, in R. Dilamarter-S.Csallany: Hydrologic problems in karst regions 262-278 p. Military Geographic Service, 1991. Topographic sheet Â‘XirovounionÂ’ 1:50000. Papadopoulou-Vrynioti, K., 1999. Zusammenfassenede Bemerkugen uber Verbreitungen, Nutzung und Schutz der Karstgebiete Griechenland. Die Hohle H 5, Wien, 548-552 s. Papadopoulou-Vrynioti, K., 2004. The role of Epikarst in the morphogenesis of the karstic forms in Greece and specially of the kartic hollow forms. Acta Carsologica Vol. 33/1, 14, 219-235 p. Papadopoulou-Vrynioti, K., Kampolis I., 2011. The Â“Selinitsa DrakosÂ” coastal karstic system of Messinian Mani peninsula (southern Greece) in relation to the terrestrial geoenvironment. Geologica Balcanica 40(1-3),So a, 75-83 p. Papanikolaou, D., Paquin, C., Bloyet, J., Foudoulis, D., Moschopoulos, P., 1990. In site stress measurements in Messinia after the 1986 Kalamata earthquakes. Bull. Geol. Soc. Greece Vol. XXIV, Athens, 95-101 p. Pavlakis, P., Papanikolaou, D., Chronis, G., Lykousis, V., Anagnostou, Ch., 1989. Geological structure of inner Messiniakos Gulf. Bull. Geol. Soc. Greece Vol. XXIII/3, Athens, 333-347 p. Stamatis, G., Migiros, G., Kontari, A., Dikarou, E., Gambroula, D., 2011. Application of tracer method and hydrochemical analyses regarding the investigation of the coastal karstic springs and the submarine spring (Anavalos) in Stupa Bay (W. Mani Peninsula). 9th Int. Hydrogeological Congress of Greece VI, Springer, 459-467 p.