The interglacial periods of the late Quaternary are frequently investigated as they constitute potential analogues for our modem climate and may shed light on the key questions of natural climate variability and future developments. Speleothems (stalagmites, stalactites) have great potential for documenting the records of past climatic conditions.

The most important and frequently used climate related parameter in speleothems is δ¹⁸O of calcite. Provided that a stalagmite grows in isotopic equilibrium with its parent drip water, δ¹⁸O of calcite is dependent on temperature (an increase of 1˚C in cave air temperature results in a negative isotopic shift of ≈0.25‰ in δ¹⁸O of calcite). However, in all caves the temperature-dependent fractionation of ¹⁸O during calcite precipitation is masked by precipitation-controlled variations in δ¹⁸O of cave drip water from which the speleothem is formed. δ¹⁸O of calcite values are therefore primarily influenced by δ¹⁸O of cave seepage waters and meteoric precipitation respectively, whereas δ¹⁸O and δD of precipitation are controlled on different times scales by a variety of climatic variables [1]. This makes δ¹⁸O of calcite and δD in speleothem fluid inclusions useful parameters for reconstructing climate-related changes [2]. δ¹⁸O values of fluid inclusion water provide direct information on the isotope composition of paleo-precipitation as cave seepage water is fed by water with a meteoric origin. Fluid inclusion water thus represents paleo-rainwater which can be used to reconstruct the hydrological cycle of the past. Studies where “fossil” rainwater can be measured directly are scarce, as rainwater normally does not fossilize. The only other direct measurements are derived from snow in ice cores. Fluid inclusions in speleothems are a new tool providing independent temperature information and direct measurements of fossil rainwater.

Speleothems commonly contain microscopic waterfilled cavities. These so-called fluid inclusions are a geologic archive of paleoprecipitation and paleotemperatures. In the present study we application a technique to analyze the stable isotope composition of fossil drip-water trapped as fluid inclusions in a stalagmite [3]. The measurements of the isotopic composition of fluid inclusion water from speleothems are complicated, the main error is due to adsorption of the inclusion water onto fresh sample fracture surfaces generated during crushing.

Stalagmite presented in this paper was colleted from Nerja Cave (Southern Spain). We present the paleoclimatic information by dating periods of stalagmite growth and by measuring δ¹⁸O and δD of speleothem and fluid inclusions respectively. The combination age of speleothem, δ¹⁸O and δ¹³C values of calcite and δ¹⁸O values of fluid inclusions can be considered to identify the climatic evolution during peak interglacial periods (MIS5a) in Southern Spain.

The Nerja Cave is located in Andalusia (southern Spain), in the province of Malaga, about 5 km east of the coastal town Nerja. The climate outside the cave is typically Mediterranean, with a wet season from October to February and a long dry season that is especially notable during the summer. The mean annual values for rainfall and temperature are 490 mm and 18.8˚C respectively.

From the geological viewpoint, the Nerja Cave is situated on the southern border of Sierra Almijara, within the Alpujarride Complex of the Betic Cordillera (Figure 1). This complex has two lithological formations: a lower formation, made up of metapelites of Paleozoic age and an upper one made up of carbonate rocks of middle-upper Triassic [4]. At the base of this latter formation outcrop white dolomitic marbles whilst at its top appears blue calcareous marbles. The cave is developed in the dolomitic marbles which are highly fractured. In some places, this rock is completely shattered, giving rise to a typical sugar texture, with grains made up of single dolomite crystals. Outside the cave, detrital Neogene deposits outcrop discordantly over the Alpujarride rocks. Although the structure of the Alpujarride complex is very complicated on a regional scale, in the surroundings of the cave is quite simple because the marbles have an almost tabular structure, dipping 15˚ - 20˚ towards the south [5]. Marbles are limited to the south by normal and strike-slip faults, which have caused significant vertical movements since Pliocene. Karst landforms (karren, dolines, sinkholes) hardly exist in these carbonate rocks but on the other hand, there is a well-developed super-

ficial drainage system, favoured by the considerable slopes of the Almijara mountain, as well as the texture of the dolomitic marbles. Karst cavities are rare in the Alpujarride carbonate aquifer; so Nerja Cave is a major exception.

The karstification process which gave rise to this cave occurred throughout the Pliocene and the Pleistocene. During the temperate and hot periods of the Quaternary age enormous quantities of calcite or aragonite deposits were generated. The Triassic marbles outcroping in Sierra Almijara constitute an aquifer of regional importance, which recharge is produced mainly by infiltration of rainwater. As a result of the Plio-Quaternary tectonic activity which affected this area, the cave is currently located in the unsaturated zone of the aquifer, above the piezometric level. The thickness of the unsaturated zone above the cave is highly variable, from 4 to 50 m in the external part, while in the internal area it exceeds 90 m. Except for the gardens near the entrance, only low shrubs or soil are found above the cave. The cave has three entrance points, two of them are sinkholes (at 161 and 162 m.a.s.l.) and the third is a wider entrance which is equipped for tourist visits, found at 158 m.a.s.l. The cave extends almost horizontally between limits of 123 and 191 m.a.s.l. and occupies a volume of about 300,000 m³. This cave is an excellent fossil record of its own history and the paleoclimatic and neo-seismotectonic evolution of the area where the cave is located. Nerja Cave consists of numerous halls with a north-south orientation. The sample focus of this study is a stalagmite which was collected in the Montaña Hall. The isotopic composition of the seepage water the interior of the Nerja cave site can be considered as the mean isotopic value for precipitation water surrounding area (d¹⁸O = −4.8‰) [6].

The mineralogical composition of the stalagmite was determined by powder X-ray diffraction (XRD) analysis using a X’PERT PRO, PANalytical equipped with a Cu X-ray tube (45 kV, 40 mA). Results from the XRD analysis show that all the studied material consists of aragonite.

The stalagmite was cut along its growth axis. One longitudinal section was polished and crystallographic observations were performed with a binocular microscope. The sample studied was between 60 and 90 mm long. A regular lamination with alternation of thin layers (<0.2 mm) and thick is present. The stalagmite diameter is variable with maximum of 70 mm. The light and dark laminae visible in hand specimen are related to changes in the fabrics. The stalagmite was divided into two parts, the first clear beige translucent crystals, in the middle displays a brown thin layer which was interpreted as a clayey inclusion, this discontinuity does not suggest a long interruption in deposition, and the second part greywhite crystals are observed. Based upon optical and crystallographic features, the crystals displays mainly microcrystalline fabrics and subordinately columnar ones [7]. Stalagmite consists of aragonite crystals and the mineralogical composition appears uniform throughout, with no observed evidence to indicate recrystallization of aragonite to calcite or the presence of alternating mineral laminae.

Ages were determined by Electron Spin Resonance (ESR) indicate that the samples was deposited between 70,000 - 90,000 yr ago [8,9].

Stables isotope analyses (d¹⁸O and d¹³C) were taken along the growth axis of speleothem and two selected growth layers (Figure 2). A total of 34 samples were colleted and the sampling for this isotopic study was carried out using a Dremmel tool fitted with a fine tip diamond studded drill bit. The drill bit was cleaned between each sample with an acid wash and de-ionized water and dried. Between five and fifteen milligrams of sample were used and CO₂ was extracted from calcite at 70˚C by reaction with H₃PO₄ [10] using a mass spectrometer “Dual Inlet” SIRA-II model (VG-Isotech, actually Micromass). Data were corrected for fractionation factors for aragonite. Results of these analyses are shown as the per-mil deviation between the sample and the Vienna Pee Dee Belemnite standard (VPDB) in delta notation. Analytical precision was 0.1‰ for d¹⁸O and 0.05‰ for d¹³C.

For the analysis of the fluid inclusions the samples were crushed to 0.8 - 2 mm fragments and heated in a vacuum of 10⁻³ mbar. Following crushing and heating the released water is cryo-distilled into cold trap and held

at liquid nitrogen temperature, for a period of up to 10 minutes at static vacuum. After the initial capture, the trap temperature is raised to −120˚C and any CO₂ and other non-condensable gases are pumped to waste. During this process ≈3 - 5 μl of water were extracted [3]. The inclusion water was trasferred to crimp top vials with rubber/PTFE crimp caps which were perfectly sealed with a crimping tool. Stable hydrogen (δ²H) isotopes in water samples were measured using a continuous-flow GV Instruments mass spectrometer attached to an Elemental analyzer with a liquid autosampler (EuroVector). Water samples (0.7 µl) are injected into an injector port heated at 150˚C. The injector is connected to a reaction tube filled with Cr and heated at 1080˚C [11]. The reduction of the water occurred into the reaction tube. The memory effect was evaluated and minimized analysing two sample replicates. The δ²H results are given with respect to VSMOW with a precision better than ±0.5‰.