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In the Priego area, central Spain, extensive tufa deposits are located in three small tributaries located at the head of the 1000 kmlong Tagus River. The deposits are originated after karst-origin running waters emerged from the confines of the canyons and expanded outward. Old tufa deposits of Priego are mainly present as terraced alluvial plain deposits where different autochthonous and allochthonous facies appear. Extraclastic deposits of quartzite and limestone clasts derived from Mesozoic rocks are interbedded with the tufa marking pulsatory high-flow periods. Using the geomorphologic analysis six terraced levels were differentiated and sampled for ostracode amino acid racemization analysis. D/L ratios of aspartic acid and glutamic acid were used for dating purposes. Cluster analysis defined six aminozones (AMI-AM7) which were dated as follows: AMI: 407 ± 12 ka oxygen isotope stages (OIS 11); AM2: 263 ± 14 ka (OIS 7e); AM3: 181 ± 17 ka (OIS 7a); AM4: 136± 13 ka (OIS 5-6); AM5: 108 ± 14 ka (OIS 5); AM7: 11 ± 4 ka (OIS 1), indicating that tufa deposition took place during warm periods. Models of riverine and riverinebarrage tufa accumulation indicate that their maximum build-up took place between the canyon mouth and the point of depletion of dissolved CO 2 , and this affected the elevation of the top of the deposits and their relative chronology.

A high correlation between chronometric determinations based on aspartic acid racemization ratios and radioactive dating methods is described from samples of cave bear (Ursus deningeri and Ursus spelaeus) dentine. For samples from a very restrictive environment, as deep cave bear sites are (in view of their highly stable geochemical and thermal history), an age calculation algorithm was obtained. It has been found that there is a very close relationship between collagen preservation, from total aspartic acid in the > 3500 D fraction, and the amino acid racemization.

During a survey of the genus Bromus for the ongoing Flora Iberica, B.picoeuropeanussp. nov., a new orophilous species of perennial Bromus from Picos de Europa National Park, was found, and it is described and illustrated here. This new species belongs to the Bromuserectus complex and differs from the other perennial species of this group occurring in the Iberian Peninsula in its well-developed rhizome, the small innovation leaves and all peduncles and branches shorter than the spikelets. B.picoeuropeanus grows on calcareous stony soils associated with dry places. We provide a description and illustrations of the new species and an identification key for the most related European perennial species belonging to the complex.