Antonio J. Prado-Pérez

The development of new isotopic laser-based analyzers currently represents a clear alternative to conventional isotope ratio mass spectrometers. However, this analytical technique also suffers some disadvantages such as the memory effect, problems related to the overall stability of the equipment and other issues associated with the injection system, essentially regarding the syringe's longevity. This paper aims to minimize these disadvantages in order to increase the overall performance, in terms of precision and accuracy, of these kinds of analyzers. The main results of the experiments carried out in this paper have shown that: (i) the minimum number of discarded injections needed to eliminate the memory effect can be determined just considering the expected isotopic signature difference between two consecutive samples; (ii) both accuracy and precision of the isotopic measurements increase with increasing injection volume up to 2.1–2.2 µL; (iii) it is possible to extend the syringe lifetime by almost a factor of 6 by using n-methyl 2-pyrrolidone as a lubricant. Besides, it has been concluded that, by using the appropriate procedure, the main disadvantages associated with CRDS laser spectroscopy analyzers can be minimized, achieving measurement accuracy and precision of the order of ±0.05 ‰ for δ18O and ±0.3 ‰ for δ2H.

A comprehensive palaeoenvironmental reconstruction of the last 219 ka has been carried out by determining the isotopic signatures (δ¹⁸O and δ¹³C) in 766 samples of a thermogene travertine formation in the Guadix-Baza Tertiary basin (Granada, SE Spain). This travertine formation was dated from ≈ 220 to ≈ 5 ka by means of the alpha-spectrometry technique. Initially, the study of the δ¹⁸O values of the travertine formation was carried out because they are excellent indicators of the overall palaeoclimatic condition of a particular site. Likewise, the evolution of δ¹³C values, which can be directly related to the biomass development of the site, has also been studied. Finally, an integrated study of both isotopic records has been performed, identifying a total of 12 climatic periods based on their palaeoclimatic and palaeoenvironmental conditions. These periods are grouped into four climatic scenarios: scenario A, characterized by warm and dry periods; scenario B, characterized by cold and humid periods; scenario C, constituted by warm and humid periods; and scenario D, which is characterized by cold and dry periods. Palaeoclimatic scenarios A and B mainly characterized the palaeoclimatic evolution of the site, while in northern Europe the palaeoclimatic evolution is mainly characterized by scenarios C and D. Therefore, it is suggested that the palaeoenvironmental evolution at lower latitudes on the Iberian Peninsula is the opposite of that identified in northern Europe. However, the main climatic events identified at higher latitudes are also reflected in the studied area.