New Mexico Geological Society Annual Spring Meeting — Abstracts

The climate of northern New Mexico has undergone significant changes throughout the Quaternary, as demonstrated by glacial landforms and deposits. Recent evidence, from soils and geomorphic observations, suggests a unique neoglacial event occurred within the Santa Fe Range around 3500 y.b.p. (Wesling, 1988). High alpine lakes and bogs preserved behind late Pliestocene moraines offer an outstanding setting to investigate post-glacial sedimentologic and climatic characteristics of this portion of northern New Mexico. Bogs in particular provide excellent proxies of the local environment by trapping and preserving material in an anoxic environment. Extraction of a complete high-resolution core in a Pecos bog provided sedimentologic, biologic, and chemical information that could corroborate the change in climate associated with neoglacial conditions.

Analysis of recoverable core material revealed measurable information on climate change. Sedimentological descriptions, standardized color values, and Loss on Ignition (LOI) were employed to characterize depositional changes with depth in a 2 m bog core. Radiocarbon analysis were obtained at I m-intervals in the core, returning dates of 1777 +/- 50 and 2597 +/- 40 y.b.p. (calibrated ages) respectively. These dates
were utilized to create a simple time series based on standardized color values and LOI results. Periodicities revealed in the time series suggest changes on the order of 230-150 years; possibly corresponding to drought induced stand-replacing fires in the Pecos Wilderness.

Recovery of material older than 2600 y.b.p. was impeded by a thick, resistant sand horizon. It is possible that the sand horizon represents a more fluvial environment prior to 2600 y.b.p. during the period characterized by the neoglacial advance.