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The Proterozoic metamorphic belt of northern and central New Mexico contains rocks of two distinctly different metamorphic grades, locally lying in direct contact. A large region exhibits coexisting kyanite, andalusite, and sillimanite. The triple-point assemblages resulted from peak metamorphic conditions falling near 500°C, 4 kb, and they occur across 75,000 km 2 in 14 separate mountain ranges. Triple-point metamorphic grade was attained after north-verging folding and ductile thrusting but before southverging mylonitic shearing. Prograde and retrograde P-T paths were nearly isobaric.However, two mountain ranges preserve a different metamorphic history. Granitic and migmatitic gneiss in the Santa Fe Range formed at 650° to 750°C. Sillimanite-Kfeldspar gneiss in the northern Taos Range records peak conditions as high as 700° to 800°C, 9 to 11 kbar. In the latter area, high-grade metamorphism was followed by south-verging shearing, southeast-verging folding, and decompression, on a retrograde P-T path that passed through 500°C, 4 kb. Deformation produced a thick mylonitic shear zone that appears in scattered outcrops across the entire mountain range. The shear zone separates gneiss from structurally overlying kyanite-andalusite-sillimanite quartzite. Mineral textures indicate that the shearing occurred during and after the thermal peak in the gneissic rocks, and during the thermal peak in the overlying triplepoint rocks.We suggest that the kyanite-andalusite-sillimanite rocks are separated from the rocks of higher metamorphic grade by a synmetamorphic ductile detachment fault represented by the thick mylonitic shear zone. The detachment separated an actively extending lower crust from an upper crust that was not being thinned. We infer that the detachment extends in the subsurface beneath the entire belt where rocks show kyaniteandalusite-sillimanite metamorphic grade. Lower-crustal extension, with heat carried upward toward the detachment, seems to have caused the triple-point metamorphism.

This paper describes a sequence of Pliocene(?) to Quaternary age calcretes developed within alluvial fan and fluvial gravels in the Tabernas Basin, Almería Province, southeast Spain. Calcrete profiles are described from sites adjacent to major tributaries of the Rambla de Tabernas. Six distinct calcrete units are identified within the basin. These have variable distributions but have developed in an identifiable evolutionary sequence. Two pairs of calcrete units are widely present across the basin preserving two former land surfaces. Each of the former land surfaces has been planated and subsequently buried by alluvial fan or fluvial gravels. A massive calcrete unit is present at the base of each gravel sequence, immediately in contact with the underlying bedrock, with a less well developed calcrete unit situated at the top of the gravel sequence. The lowest two calcrete units within the basin are more spatially restricted and are confined to the floors and flanks of incised drainage lines.The geochemistry, macro-and micromorphological properties and geomorphological positions of the calcrete units are outlined and, on the basis of this information, their mode of origin identified. Two main modes of calcrete genesis appear to be present: massive calcretes situated in direct contact with bedrock are suggested to have formed by groundwater processes, whilst calcretes situated at the top of gravel sequences are likely to have developed by pedogenic processes. Calcrete genesis is subsequently considered in the context of the reconstruction of the early phases of landscape development, and is suggested to have been controlled by phases of uplift and stability within the Tabernas Basin.

The extent to which a species has declined within its historical range is commonly used as an important criterion in categorizing the conservation status of wild populations. The greater prairie chicken (Tympanuchus cupido) has been extirpated from much of the area it once inhabited. However, within a large part of this area the species is not considered to be native, warranting no recovery effort or special protection. Demographic analysis based on provenance data from 238 specimens from museum collections in addition to genetic analyses of 100 mtDNA sequences suggest this species was native to the northern prairies, extending from central Minnesota to Alberta, Canada. Provenance data from 1879 to 1935 indicate that T. cupido would have required colonization and establishment of populations on an average 11,905 km 2 every year, with an estimated per capita growth rate of 8.9% per year. These rates seem unrealistic given the limited dispersal and high mortality rates reported for this species. A survey of mtDNA sequences from ''original'' and ''expanded'' ranges revealed no differences in levels of sequence diversity within ranges (p=0.018; SE=0.004) but significant levels of genetic differentiation (F ST =0.034; P=0.013), which suggest that these populations have been relatively isolated for significant evolutionary time periods. DNA mismatch distributions fit a sudden expansion model consistent with a post-Pleistocene expansion of the species, which coincides with the expansion of prairies into the Canadian plains about 9000 years before present. This study demonstrates the value of museum collections as stores of ecological and genetic information fundamental for the conservation of natural populations, and suggests that the current status of the greater prairie chicken should be re-evaluated within all areas where this species may occur, but is now considered non-native.