Origin of the Whewellite-Rich Rock Crust in the Lower Pecos Region of Southwest Texas and its Significance to Paleoclimate Reconstructions

摘要: Abstract A calcium oxalate (whewellite)-rich crust occurs on exposed limestone surfaces in dry rock and open air shelters the Lower Pecos region of southwest Texas. The crust, which also contains gypsum clay, formed over silica-rich during Holocene. SEM optical photomicrographs reveal similarities between whewellite microstructures lichen Aspicilia calcarea. This desert is known to produce oxalate, has been found several sites region. ubiquity whewellite-rich suggests that flourished past. Since A. calcarea a species, virulence organism likely peaked xeric climate episodes then waned mesic periods. Thus, radiocarbon ages would correspond periods experienced region, while with few or no 14 C data indicate wet episodes. preliminary paleoclimate reconstruction based fourteen AMS dates indicates fluctuations late generally agrees other models established for