Geoarchaeological research into Palaeolithic cave sites as a source of palaeoenvironmental data Janez TURK Izvleček Jamski sedimenti zaradi svoje starosti in dobre ohranjenosti hranijo edinstven zapis o klimatskih dogajanjih v pleistocenu. Sedimenti so v jamah odlično ohranjeni v primerjavi s tistimi na površju, ki so izpostavljeni ne le močnejšemu preperevanju, temveč tudi eroziji in drugim eksogenim procesom. Prav arheološka najdišča iz obdobja paleolitika so zaradi sistematičnih izkopavanj in odkopanih arheoloških profilov verjetno najbolj primerna za interdisciplinarne raziskave različnih sedimentov, vključno peloda, oglja in kostnih ostankov. Te raziskave so zelo pomembne tudi za arheologe, saj nudijo vpogled v klimatske razmere v obdobju, ko so jame obiskovali ljudje in v njih pustili razne sledi. Tako imenovane geoarheološke raziskave zahtevajo tesno sodelovanje arheološke in geološke stroke. Ključne besede: paleolitik, pleistocen, geoarheologija, jamski sedimenti, paleoklima, okoljske spremembe, kronologija, datacije Abstract Cave sediments are more protected from weathering, erosion and other exogenic processes in comparison with sediments that accumulate at the Earth's surface. For this reason, cave sediments keep a unique record of climate variations in the Pleistocene. Archaeological (Palaeolithic) sites, where sediments (including pollen, charcoal and bone fragments) can be systematically studied in one or several profiles, are the most useful for multidisciplinary surveys. Such surveys are very important for archaeologists because they offer insight into climate conditions that prevailed in the period when humans visited the cave and left various traces there. So-called geoarchaeological surveys demand extensive cooperation between archaeologists and geologists. Keywords: Palaeolithic, Pleistocene, geoarchaeology, cave sediments, palaeoclimate, environmental changes, chronology, radiometric dates 1. INTRODUCTION Archaeological investigations of Palaeolithic sites demand a multidisciplinary approach, not only due to palaeontological finds, which are usually much more abundant than artifacts, but also to gain a better understanding of evolution of sedimentary and postsedimentary processes in the cave. These processes have a direct influence on stratigraphy, on sediment characteristics and on preservation of archaeological finds. Archaeological finds do not have great significance if their chronological position is not known. Proper methodological implementation of archaeological excavations is crucial to define the chronological position of Pleistocene finds. Finds need to be linked with environmental changes, which were very significant in the Pleistocene and directly impacted the life-style of humans. Humans preferred to find shelter inside the caves during cool and especially wet climate periods. Because caves are always wet, and therefore less suitable for residence during periods when the climate was relatively warmer, it was more convenient to build primitive dwelling places in the open air in such climate conditions. The age of finds and traces of human presence in the cave can be determined by radiometric dating of sediments. Dating is usually carried out on bones and teeth, but also can be performed on charcoal and burnt artifacts. In the past the age of sediments was determined based on the typology of stone artifacts found within these sediments. However, this method is considered less reliable these days, when more accurate chronology can be obtained by radiometric dating. Besides the chronological position of the sediments, scientists would also like to know the palaeoclimate and environmental conditions that prevailed during the sedimentation. Some common data on palaeoclimate conditions for the Pleistocene exist. Based on these data we can already place the archaeological finds to different climate periods by radiometric dating. However, climate was changeable not only regionally, but also locally, similar to today. More reliable environmental data may be obtained by surveys which are performed directly in caves. There are various approaches to obtain environmental reconstructions; however all are based on the study of sediments, where the finds are situated. Archaeological excavations need to be carefully planned. Accessibility of the sedimentary samples, on which palaeoclimate studies are based, can be limited, especially if the methodology of the excavations was not carefully planned and well considered. Environmental reconstructions carried out at various sites (caves) can be compared and correlated. It is very important to obtain as many radiometric dates as possible, in order to facilitate the correlations. With the help of radiometric data it can be determined whether the reconstructions are really similar, and whether they can therefore be considered reliable. 2. CAVE SEDIMENTS AND SEDIMENTARY PROCESSES This paper is focused on Palaeolithic sites in caves which are filled with clastic sediments. Clastic cave sediments include autochthonous (derived from host rock of the cave) and alloch-thonous (derived from outside) stone fragments in all size ranges (clay to cave gravel and large boulders). Allochthonous sediments also include bones, artifacts, charcoal, etc. Cave sediments can be roughly divided into three groups, based on their origin (Lau et al. 1997; Farrand 2001; White 2007; Ghinassi et al. 2008): - Geogenic sediments (rubble which spalled from the cave ceiling and walls; clay which was washed into the cave through the cave mouth or through fissures in the cave ceiling; flowstone which deposited chemically from dripping water; loess and other aeolian - fine - sediments; alluvial sediments if the cave is hydrologically active or used to be active in the past; colluvium - gravel from external slopes above the cave mouth and other material from scree above the cave). - Biogenic sediments (fossil remains of animals that inhabited the cave - mainly bones and teeth; coprolites; remains of plants such as charcoal and pollen). - Anthropogenic sediments (artifacts; hearths; other material which humans brought to the cave such as pebble, dust, wood, etc.). Biogenic and anthropogenic sediments are mixed with geogenic sediments, but the abundance of biogenic and anthropogenic sediments is usually minor in comparison with the dominating geo-genic sediments. Processes that lead to deposition and accumulation of sediments are called sinsedimentary. Post-sedimentary processes lead to modifications of the sediments, after their deposition on the cave floor. Postsedimentary processes have the most effect on the topsoil layer of the sedimentary sequence. 2.1 Sinsedimentary processes Accumulation of cryoclastic sediments in the caves takes place because of mechanical weathering of cave ceiling and walls. Weathering is most effective directly at the cave mouth. The influence of external climate (i.e. frost action) diminishes toward the interior part of the cave; for this reason mechanical weathering is less significant or even does not have any role there. Mechanical weathering is more intensive under climate conditions where the frequency of freeze and thaw cycles is higher. Also high humidity is an important factor. Cryoclastic gravel is most abundant just at the cave mouth; for this reason talus forms there. Also colluvium can contribute to the formation of talus. Colluvium can roll down through the cave entrance toward the interior part of the cave. Therefore, depending on the morphology of the cave bottom, colluvium can also be found deeper inside the cave. Great collapse blocks, which can be found in some caves, had presumably spalled from the ceiling during extremely strong earthquakes. If the cave mouth is large enough, then aeolian deposits may be transported and deposited in the cave. Loess is a typical aeolian deposit. Wind may also bring to the cave volcanic ash and other fine deposits from near or far surroundings. Deposition of alluvium takes place in hydrologically active caves. Soil and clay can be washed from the surface into the cave. Washing takes place through fissures, which connect the surface and the cave. As mentioned, all these sediments are of geogenic origin. 2.2 Postsedimentary processes The main postsedimentary processes that take place in caves are (Lau et al. 1997; Angelucci, Zilhäo 2009): - Bioturbation by faunal and animal activity (root action, compaction, displacement, burrowing). - Mass movement due to periglacial conditions (cryoturbation, solifluction). - Carbonate dissolution. - Secondary mechanical and chemical weathering. Mechanical weathering is due to frost action and chemical weathering is due to dissolution (corrosion) of sediments that are water soluble (carbonates and partly bones). - Various diagenetic processes such as dissolution, cementation, recrystallization. Bioturbation and processes that are linked with a periglacial climate (cryoturbation, solifluction) can lead to mixing of sediments and displacement of archaeological finds between various layers. For this reason, caution is necessary while interpreting the chronological position of finds that occur in sediments where such postsedimentary processes took place. 3. DATING Age of finds and chronological position of determined environmental changes are obtained by dating methods. The most reliable absolute dating methods for cave deposits are: thermoluminiscence on burnt flints (which occur in the vicinity of hearths); U/Th dating on animal bones and spe-leothems; radiocarbon dating (AMS 14C) on wood, charcoal, bone, pollen or other organic material preserved in the sedimentary sequence; electron spin resonance (ESR) of cave bear teeth (of teeth enamel) (Lau et al. 1997; Angelucci, Zilhäo 2009; Blackwell et al. 2009). The upper age limit of 14C dating methods is 50,000 BP; it is not possible to date the older organic sediments. This method is applicable only for the final phase of the Middle Palaeolithic and for the Late Palaeolithic. Reliability of this method is already questionable at age 45,000 years. The upper age range of U/Th dating is around 350,000 or at most 600,000 years (Low, Walker 1997; White 2007), and the upper age range of the ESR method is five or ten million years (Blackwell 2006). The lower age range of the thermoluminiscence method depends on the sensitivity of the sample (artifact made from flint, ceramic^); the upper limit is usually around 100,000 years (Low, Walker 1997). 4. PALAEOCLIMATE RECONSTRUCTIONS Cave sediments are better preserved in comparison with sediments that occur at the Earth's surface because cave sediments are more protected from erosion and weathering. This is especially true for preservation of bones, charcoal and organic artifacts, which are of main interest for archaeologists and palaeontologists. The study of one or more types of sediments (for example charcoal, pollen or bones) may reveal some information about environmental conditions that governed during the deposition of the studied sediments at a certain level. However, high resolution environmental reconstructions can be obtained only by systematic study of prevailing sediments. For this reason, the main focus in this paper is given to the study of fine grained sediments (sand, silt, clay) and gravel. These sediments usually greatly dominate in archaeological caves. Sedimentary and postsedimentary processes are important indicators of climate conditions. Based on the study of dominating sediments (clay, silt, sand, gravel), we may presume which sedimentary and postsedimentary processes took place in the cave at a certain sedimentary level and then we may try to also interpret the climate conditions. Postsedimentary processes are the most effective at the topsoil of the sedimentary sequence. When topsoil sediments become buried by a new sedimentary sequence of sufficient thickness, all weathering processes stop. Postsedimentary characteristics of buried sediments are preserved, as no further modification takes place in buried sediments. During and after the excavations, archaeologists or geologists can study these modifications, which reflect certain past conditions (i.e. conditions of a limited time period when these sediments occurred at the topsoil). Archaeological (Palaeolithic) caves are probably the most suitable places, where sediments can be collected from profiles and then studied. Based on the study of sedimentary samples from various levels, environmental or even temperature conditions can be interpreted for the time period when studied sediments were exposed to weathering and other modifications of the topsoil. All modifications are direct reflections of climate and environmental conditions on the surface, above the cave. Sediments need to be dated; otherwise it is not possible to place the determined environmental changes into the Pleistocene chronology. The changeable rate of sedimentation and sedimentary gaps, which can last for more than 10,000 years, present the main problems for environmental reconstructions that are performed in caves. 4.1 Classical approaches to study fossil bones and pollen found in the sedimentary sequence Classical environmental reconstructions from Palaeolithic sites (caves, rock shelters) are based on bones of Pleistocene fauna and pollen. Pollen may be carried to the cave by wind or by biotic transport (cave bear, small mammals, owl etc.). Pollen passes through the digestive tract, hence faecal material may contain reliable pollen spectra. Also percolating water that infiltrates through bedrock can be a source of pollen. Cave morphology, especially size of the cave mouth, is an important factor affecting the transport of airborne pollen to the cave. The highest concentrations of pollen are usually at the cave entrance (Navarro et al. 2001). Such environmental reconstructions are problematic, due to the fact that pollen concentrations are low and only rare species of cave fauna are significant environmental indicators. The majority of taxa are (were) adapted to all kinds of climate conditions, and for this reason it is not possible to make conclusions about environmental or climate conditions for layers where many bone remains of Ursus spelaeus occur. Reliable indicators of severe climate conditions are arctic and tundra species, such as arctic fox, mammoth, woolly rhinoceros, reindeer, but remains of these species are usually very rare in karst infillings. Bones of small mammals are more frequent. Moles for example cannot live in cold climates, where the ground is frozen for most of the year. Marmot is adapted to more severe climate conditions; today it populates mountainous regions such as the Alps. Many environmental reconstructions are based on bones of rodents. Rodents are probably the most reliable environmental indicator, because their remains are quite frequent in cave sediments, especially in comparison with other (bigger) mammals (Madey-ska, Cyrek 2002; Bona et al. 2006; Toškan 2009). Pollen concentrations are usually very low in caves. Moreover, pollen is subjected to displacement, differential destruction or selective preservation of palynomorphs and reworking of sediments. For these reasons its representativeness and its primary stratigraphic position may be questionable (Woodward, Goldberg 2001; Groner 2004). Preservation of pollen is higher in caves with low humidity, but such conditions are rare in caves. Occurrence of bacteria is high under humid conditions, and bacteria are responsible for the degradation of pollen (Navarro et al. 2001). A more reliable indicator of environmental conditions than pollen is charcoal. It may be concentrated at hearths or scattered through the sediments (Culiberg, Šercelj 1997). Analysis of charcoal reveals the identity of the vegetation at a certain time period and consequently the environmental conditions. 4.2 Study of cave sediments Rock fragments usually dominate cave sediments. They are of all sizes, from clay to rubble and large boulders. Of all sediments (including organic), the dominating ones keep the most continuous palaeoclimate record. There are several approaches to studying cave sediments; some of them are more appropriate for environmental (or palaeoclimate) reconstructions and some less. The most used methods are granu-lometry, micromorphological analysis, magnetic susceptibility, geochemical analysis and study of autogenic minerals, which were formed after the deposition of sediments on the cave floor. 4.2.1 A granulometric histogram A granulometric histogram shows the particle-size distribution of the total sediment. Cave sediments can originate from two or more simultaneous inputs (primary weathering of cave ceiling, wind action, colluvium etc.), and the source of the sediment can be presumed by analysis of the histogram. Multiple peaks or modes occurring on histograms are attributed to different sources of the material. For example, a peak at fine fraction can originate by aeolian transport or transport with water trickles, and a peak at coarse fraction can originate by grain to grain disintegration of the rock fragments composing the walls and ceiling (Mandel, Simmons 1997; Farrand 2001). Sedimentary samples need to be acid treated, if we want to determine the original size of the grains, before secondary cementation of grains and formation of aggregates. Clay and silt may cement together and form aggregates. In such a case, granulometrical analysis will reveal dominance of the sand fraction, but the sand fraction is composed mostly of sand-size aggregates. Organic material may also cause disturbance. Organic matter can be removed with H2O2. To remove carbonate and phosphate cements, the samples can be reacted with 10 % HCl, and embedded mineral grains are added to the silt and clay bars of the histogram (Farrand, McMahon 1997). 4.2.2 Micromorphological analysis For micromorphological analysis, undisturbed sedimentary samples need to be collected from profiles. Only fine grained sediments are suitable for this analysis (clay, silt and partly sand). Samples are impregnated by low-viscosity polyester resin. Then thin sections are made, which are studied under a petrographic microscope. Fine sediments are mainly of allochthonous origin in caves, i.e. they were transported to the cave from the external environment. Based on mineralogical composition of the samples, the ratio between different mineral grains, their microstructure (b-fabric), roundness of rock fragments and other characteristics, we may make some conclusions about their origin and also about the environmental conditions that prevailed at the time when these sediments were deposited in the cave. Aeolian sediments (fine grained, having sharp angles and corners, mineral composition is various: quartz, feldspar, mica) indicate cool and arid climate conditions, while washed clay (having the same mineral composition as surface clay) indicates mainly humid climate conditions. We are also interested in postsedimentary modifications of the sediments and (climate) conditions that are responsible for such modifications. Micromorphological analysis is especially applicable in those caves where allochthonous sediments are relatively frequent throughout the sedimentary sequence and where sediments are strongly anthropogenically reworked (Ioconis, Boschian 2007; Boschian, De Santis 2010). Angeluci and Zilhao (2009) used micromorpho-logical analysis to study the sediments in Gruta da Oliviera cave (Portugal). Samples for thin layer preparation were taken from all layers and the constituents, microstructure and pedofeatures were studied. Based on microscopy, they determined the porosity, color of the cement, b-fabric (crystallic, granostriated, undifferentiated), aggregation, pe-dofeatures (coatings on voids or around grains), sedimentary features etc. They determined four main groups of sediments (>1 mm) based on microscopy. Grains of quartz dominate in the first group; also feldspars and mica occur there, but carbonate grains are not present. Carbonate fragments of various size and shape dominate in the second group. In the third group, other carbonate components occur (calcite crystals, fragments of speleothem, carbonate crusts). Anthropogenic and biogenic components (lithic artifacts, bones, phosphates) are found mainly in the fourth group. Based on the results, they interpreted the processes that led to the deposition of sediments at a certain level, and interpreted the origin of the sediments. Alluvial sediments were recognized in some layers. The build-up of the sequence between layers 14 to 9 resulted from slope-wash (probably through fissures communicating with the surface). Secondary carbonates (flowstone) were detected in all samples, indicating continuous flow of carbonate-saturated water into the cave or continuous percolation. The same may be said for the accumulation of phosphates. Both flowstone and phosphates indicate continually humid conditions, during the time interval corresponding to the accumulation of the strata. Results of micromorphological analysis offer an insight into the occurrence and magnitude of various sedimentary and postsedimentary processes in the cave. Climate conditions may be interpreted only indirectly, due to the fact that the discussed processes are linked with external climate conditions. Temporal resolution of determined climate changes depends on the magnitude of climate variations and on sensitivity of the site (cave environment) to such variations (important roles are played by the morphology of the cave mouth, thickness of the cave ceiling, topography of the surface area above or near the cave etc.). However, in the literature this method is often interpreted as the most appropriate approach for palaeoclimate reconstructions. 4.2.3 Magnetic susceptibility This survey is performed mainly in those caves where allochthonous sediments dominate or at least represent a significant portion of the Fig. 1: The stratigraphic section for the excavation within Caldeirao cave (right). Plotted are the samples for which magnetic susceptibility was measured (left, in log scale, m3/kg). Magnetic susceptibility decreases to the left; the lower the value, the cooler the climate. Gradual increase in magnetic susceptibility indicates warming. A specific cool phase was determined to have occurred after 26,500 BP (14C dating). This phase may be correlated with the Last Glacial maximum (24,000-22,000 BP) (adapted from Ellwood et al. 1998). Sl. 1: Izkopano sedimentno zaporedje v jami Caldeirao (desno). Črtkano so prikazani sedimentni vzorci, na katerih je bila merjena magnetna susceptibilnost - MS (levo, v logaritemski skali, m3/kg). MS ki pada proti levi nakazuje ohlajanje podnebja, naraščanje MS proti desni pa ogrevanje. Izrazito ohladitev so ugotovili v obdobju po 26.500 pred sedanjostjo (datacija s 14C), ki jo korelirajo z zadnjim glacialnim vrhuncem 24.000-22.000 let pred sedanjostjo (prirejeno po Ellwood et al. 1998). sedimentary sequence. Such is, for example, terrigenous material eroded into the cave from the surface above the cave; another example is alluvial material. Changing climate alters the magnetic properties of materials, mainly as the result of pedogenesis. Pedogenesis outside the cave during times of cool climate produces sediments with low magnetic susceptibility magnitudes, while warmer climate yields higher magnetic susceptibility magnitudes. During warm climate conditions, strong chemical modifications take place on the Earth's surface, such as oxidation due to intense micro-bial catalysis. On the contrary, reduction takes place during cool climate conditions. A result of oxidation is accumulation of maghemite (Fe2O3) in the sediments, and consequently the magnetic susceptibility of these sediments is higher. After the removal of these surface sediments to the cave, magnetic susceptibility no longer changes, due to minimal pedogenesis and biological disturbance in caves. These disturbances may be significant only during long depositional breaks (hiatuses), when postsedimentary modifications at the topsoil take place for a relatively long time. Continuously sampled profiles of cave sediments allow palaeo-climatic estimates for all archaeological levels. The concentration of iron minerals is measured in samples: the higher the concentration, the higher the magnetic susceptibility (Ellwood et al. 1998). Continuously sampled sediments collected from two profiles were studied by this method in Cal-deirao Cave (Portugal). The chronology of climate changes was corroborated by 14C dates. Sediments with the lowest magnetic susceptibility (indicating cool climate) were dated to 24,000-22,000 BP, which coincides with the last glacial maximum. Additionally, three glacial cycles were identified, each of them lasting around 2500 years (fig. 1) (Ellwood et al. 1998). The method yielded good correlation with other independent surveys of climate in the Pleistocene. However, it is limited to those archaeological sites in caves where allochthonous sediments (derived from the surface) occur continuously between autochtonous sediments. Another limitation of the method is the expensive analytical procedure to measure the magnitude of magnetic susceptibility in sedimentary samples. 4.2.4 Geochemical analysis and study of diagenetic modifications The mineral composition of cements (in breccias and aggregates) can be studied by geochemistry. Moreover, interest is given also to the mineral composition of coatings on the clasts and to the origin of allochthonous sediments. Based on geochemical analysis of sediments, diagenetic modifications and especially chemical conditions under which modifications take place can be interpreted. Indirectly, palaeoclimate and environmental conditions may be inferred. Underground (percolating) water, which is directly linked with the amount of precipitation, is the main driver of diagenetic modifications. In dry caves, modifications usually do not occur (Woodward, Goldberg 2001). Dissolution and corrosion of carbonate grains (clasts) and also bones are two of the most characteristic modifications. Etching of clasts and bones by corrosion is an indicator of humid climate (Turk et al. 2005). Water dissolves the carbonate and bones, calcium, and phosphorous migrate and precipitate as a cement. Rock and bone fragments of various sizes are cemented together, and for this reason autogenic aggregates (smaller fragments are cemented together) and breccias (larger fragments are cemented together) occur in sediments. Phosphate occurs in those caves which are rich in organic material (bones, guano) (Turk et al. 2007). Coatings that occur on sediments are usually manganese and iron dioxide, or clay coatings. Coatings are formed during humid and oxidizable conditions. Coatings are usually thin (<1 mm) (White 2007). 4.2.5 Study of autogenic minerals Autogenic minerals are formed in situ within the cave sediments, (i.e. postsedimentary), under specific chemical conditions (pH, Eh) and in the presence of high calcium, phosphate or aluminum concentrations. There are several autogenic minerals; each is stable under certain chemical conditions only. Any change in water chemistry leads to recrystallization into more stable mineral forms. All changes in chemical properties of the water are linked with biological activity outside the cave; the latter depends on climate and the dynamics of the external environment (Woodward, Goldberg 2001; Madeyska, Cyrek 2002). Various assemblages of autogenic minerals occur through the sedimentary sequence in Theopetra cave (Greece). Each assemblage reflects specific conditions that prevailed at the time of mineral formation. Formation takes place in topsoil exclusively (Karkanas et al. 2000). When water passes through sediment rich in organic material, it reacts with calcite (or dolomite), which is altered to dahllite (carbonate apatite). Dahllite is the main component of fossil bones. Dahllite is stable under alkaline conditions only (pH > 7). Alkaline conditions prevail in caves that are filled with carbonate sediments (limestone, dolomite). The reaction between acid water and carbonate uses acid, and the remaining solution becomes more alkaline. As long as calcite is present in the sediments, the calcite acts as a buffer, which in turn prevents the associated dahllite from being dissolved. However, if the pH decreases between 6 and 7 (acid), then dahllite is dissolved and reprecipitates in the form of more stable crandallite or montgomeryite. If the acidity increases, both minerals finally reprecipitate to taranakite (a potassium aluminum phosphate mineral). Properties of the autogenic minerals can be used to reconstruct ancient palaeonvironmental chemical conditions of water and its corrosion capability. Bones, charcoal and pollen may be totally dissolved by percolating water under acid conditions (pH < 7), and for this reason organic remains do not occur in the cave. Identification of autogenic minerals is done by X-ray diffraction or infra-red spectroscopy (Karkanas et al. 2000; Shahack-Gross et al. 2004). 4.2.6 Sedimentary analysis of coarse fraction (rubble) There has been some belief in geoarchaeologi-cal science that it is not possible to obtain high resolution palaeoclimate records from data derived from the analysis of bulk coarse-grained samples. It has been presumed that sensitivity of the coarse sedimentary fraction to climate changes is relatively low. By contrast, fine-grained sediments have been presumed to be much more sensitive to climate changes and to have a much higher stratigraphic resolution. Environmental reconstructions based on micromorphology have been presumed to be the most accurate and to have the highest temporal resolution (Woodward, Goldberg 2001). Such a presumption may be correct, if we have in mind the classical analysis of coarse-grained sediments. Cryoclastic rubble accumulates due to weathering (frost action) of cave walls and ceiling. Frost action is the most intensive at the cave mouth; its role diminishes toward the cave interior. That is, the greater the distance from the cave mouth, the lower the temperature variations (or the role of freezing) in the cave. Accumulation of cryoclastic material (angular, corners are sharp) indicates cool climate. However, some caution should be taken into consideration. Angular and sharp edged material can also be produced by other geomorpho-logical processes, such as degree of (tectonically) fracturing of the host rock, hydration shattering, seismic activity etc. (Woodward, Goldberg 2001). Also colluvial sediments are an indicator of cool climate (Cremaschi 1990). The presence of flowstone within sediments is an indicator of relatively warm climate. Flowstone precipitates only in relatively warm and especially humid conditions (fig. 2). When rain water percolates through organic rich soils, the CO2 concentration rises. Such water is corrosive, and when it percolates through fissures that link the surface and the cave, it dissolves carbonate and becomes supersaturated. The CO2 concentration in the cave atmosphere is typically ten times that of the surface atmosphere. CO2 is degassed into the cave atmosphere and CaCO^ is precipitated in the form of flowstone (White 2007). Breccias, where clasts are cemented by calcite or phosphate, are also an indicator of warm and humid climate. Dissolution and reprecipitation of calcite or phosphate takes place in humid conditions (Campy et al. 1994; Quinif 2006). Chemical weathering is the most intense in warm periods. A consequence of such weathering is the formation of iron, manganese or clay coatings or crusts around clasts. Residual clay and cave loam (the products of limestone dissolution) also occur, but production is very low (Madeyska 2002). Research by Cremaschi (1990) is represented as an example of classical analysis of clastic sediments. Such classical research offers only a rough palaeoclimate interpretation. Cremaschi studied both coarse and fine-grained sediments from seven Italian caves (Palaeolithic sites). He divided the sediments into three pedo-sedimentary cycles, which reflect climate changes in the Pleistocene. Colluvium was deposited during the first cycle, interpreted as wet and moderately cold. Colluvium was still deposited during the second cycle, but also deposition of thermoclastic breccias and loess took place. Soil horizons were identified within the sedimentary sequence that belongs to the second cycle. These sediments indicate successive climate conditions. Colluvium was deposited in a wet and cold climate; deposition of thermoclastic breccias should take place in even more severe conditions. Loess indicates a dry, but still cold, climate. After that, climate conditions seem to have mitigated (as indicated by the soil horizon). This cycle should belong to the glacial period. Sedimentation during the third cycle was similar to during the second cycle. The third cycle was also interpreted as a glacial one. On the basis of the stratigraphic relationships of the lithic assemblages and of some radiocarbon datings, the determined climate cycles were placed in Pleistocene chronology. The first cycle was correlated to OIS (oxygen isotopic stage) 5a to 5d (115,000-74,000 BP). It is a stage after the last interglacial (Eemian); climate conditions Fig. 2: Comparative sedimentary record from Palaeolithic cave sites in Perigord, Franche-Comte and the northern Alps. Sedimentation was the most continuous in Perigord. The longest sedimentary gap occurred at sites from the northern Alps, where sediments from the whole Würm are missing (OIS 5-OIS 2). Cryoclastic fragments are an indicator of cool climate. Sedimentary levels where the abundance of cryoclastic fragments is lower and where carbonate cements or traces of chemical weathering occur indicate moderate climate (interstadial). Flowstone and secondary calcite are indicators of warm climate (last interglacial) (adapted from Campy et al. 1994). Sl. 2: Značilnosti sedimentov v izkopanih profilih v arheoloških najdiščih Perigord, Franche-Comte in v severnih Alpah. Sedimenti so se najbolj zvezno odlagali v Perigordu, največja sedimentacijska vrzel je v najdiščih v severnih Alpah, kjer manjkajo sedimenti celotnega Würma (OIS 5 do OIS 2). Krioklastični grušči nakazujejo mrzlo klimo, nivoji z manj izrazitim krioklastičnim gruščem, kjer se pojavljajo tudi kalcitni cementi in sledovi kemičnega preperevanja, kažejo bolj zmerno klimo (interstadiali). Siga in sekundarno izločeni kalcit kažeta toplo klimo (zadnji interglacial) (prirejeno po Campy et al. 1994). were becoming gradually more and more severe during OIS 5. The second pedo-sedimentary cycle was correlated to OIS 4 (74,000-59,000 BP - interstadial) and to OIS 3 (59,000-29,000 BP - stadial). The third pedo-sedimentary cycle was correlated to OIS 2 (29,000-11,000 BP - stadial). Such classical palaeoclimate reconstructions were very rough, and direct correlations with high resolution climate records (such as GRIP - see chapter 6. Correlations) were not possible. Lack of dates is a big problem. Correspondence with reliable dates is a preliminary condition for determination of the chronology of climate changes. Ivan Turk (2006; 2007) developed some innovative methods to reconstruct palaeoclimate from cave sediments. The methods are based on the study of coarse grains and were performed in Divje babe I cave. He studied autochtonous congelifracts to reconstruct palaeotemperature conditions. Palaeohumidity was assumed, based on the occurrence of autogenic aggregates and corrosionally etched clasts or bones throughout the sedimentary sequence. High resolution palaeotemperature records may be obtained by studying the morphological characteristics of coarse-grained sediments, which are a direct result of (postsedimentary) frost action taking place in the cave topsoil. The abundance of congelifracts was studied in samples, corresponding to 10 cm thick sedimentary levels. These samples were collected from two profiles (J. Turk, M. Turk 2010). The main characteristic of congelifracts is that they are diagenetically linked with mechanical weathering and frost action, respectively. However, the methodology of I. Turk (2006) takes into consideration only those congelifracts which were frost-shattered post-depositionally (in the topsoil layer of cave sediments). Sediments only freeze to a certain depth; when topsoil sediments become buried with a new sedimentary sequence, all weathering processes stop and the buried clasts remain preserved from further modifications. The higher the percentage of congelifracts in a certain sedimentary level, the cooler the climate was (mechanical weathering was more intense) during the time period when sediments from this level were exposed to weathering at the topsoil (Turk et al. 2006; Turk et al. 2007; J. Turk, M. Turk 2010). Continuous sampling and analysis of sedimentary samples revealed that two significantly cool phases occurred between 80,000 and 40,000 BP in Divje babe I. These two dates are approximately the ages of the uppermost and lowermost sedimentary lev- Paleotemperature proxy Paleotemperaturna krivulja Cool-mrzio -215 -223 -232 -240 -249 -258 -264 -273 -281 -289 -300 E -314 O -319 -329 g -334 15 -337 O -343 CD -349 -357 £ -362 L -369 ® -375 Q -: 457 464 -472 481 Warm-topio > HIATUS S g It 5 HIATUS Radiometric dates(dataclje) 4g,6i