Eolian and Associated Pedogenic Features of the Jornada Basin Floor, Southern New Mexico
In the Jornada Basin floor of southern New Mexico, some eolian deposits are distinct whereas others are not readily identifiable, because slopes grade smoothly into adjacent deposits that differ greatly in age and morphology, with little or no landscape evidence to suggest such differences. This study was conducted to determine if soil characteristics would be helpful in establishing a chronology for eolian deposits in this setting. Totals of pedogenic carbonate at three sites and observations at other sites indicate at least six episodes of substantial erosion and deposition since downcutting of the Rio Grande Valley began in middle to early Pleistocene time. The first episode is recorded by ancient longitudinal dunes that occur just east of the Rio Grande Valley. Prominent stage V carbonate horizons in the dunes indicate that they probably started to form soon after valley entrenchment began. The second episode is marked by a late Pleistocene deposit with a stage III horizon and 289 kg m-2 of carbonate. The third episode is recorded by a younger late Pleistocene deposit with a weaker stage III horizon and 137 kg m-2 of carbonate. For the fourth episode, stage I carbonate associated with a late Holocene deposit totals 7 kg m-2. One historical deposit accumulated during the fifth episode, soon after the 1880s and the introduction of large numbers of cattle. The final episode occurred after the great drought of 1951–1956. Both historical deposits consist of fresh-appearing, stratified sediments. The late Holocene and late Pleistocene deposits may be eolian correlatives of drought-caused alluviums. Pedogenic carbonate is a major morphological and analytical tool for estimating soil and landscape age, for determining possible eolian-alluvial correlatives, and for estimating the timing of climatic changes and eolian events. Subtle erosion and deposition can profoundly alter the evolutionary progression from stage III to stage IV carbonate.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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