A PRELIMINARY INVESTIGATION OF HOLOCENE HYDROLOGY USING ALLUVIAL SEQUENCES IN THE RIO TULAROSA, NEW MEXICO

Since the Last Glacial Maximum, much of the American southwest has experienced an evolution in terrestrial hydroclimate, largely linked to the development of the North American Monsoon (NAM). This resulted in less perennial moisture, while lakes were replaced by wetlands as prominent freshwater sources in the landscape. Geoarchaeological studies of areas associated with Paleoindian and/or Archaic sites found evidence of variable wetland expansion and increased fluvial activity during the middle Holocene (~5-7 ka) and the late Holocene (~3 ka). These dynamic environmental changes occurred during key time periods culturally, when an increase in semi-permanent settlements were established and long-term land management strategies such as the introduction of nonnative species and anthropogenic burning was undertaken.

This research synthesizes the current body of work regarding Holocene wetlands in New Mexico’s Rio Grande Rift region while introducing a new alluvial section at Tularosa Creek (TRC-1), which contains multiple intervals of wet conditions recorded as coarse-grained fluvial deposits and organic-rich peat layers (“black mats”). The lowermost black mats have radiocarbon ages spanning ~4.6-4.1 ka, whereas the upper units containing organic rich materials are bracketed by radiocarbon ages of ~3.8 and ~1.7 ka, respectively. These periods of wet conditions correspond with prolonged negative excursions in d¹⁸O in the Pink Panther Cave speleothem (of Asmerom et al. 2007), ~160 km to the southeast. Our ongoing efforts will characterize the evolution of these environments at TRC-1 using geochemical proxies and phytolith counts. The varied physiography of New Mexico and the Rio Grande region likely resulted in a dynamic, fluctuating landscape in response to climatic forcings from both the Gulf of Mexico and the Pacific Ocean, with both closed and through-flowing basins responding in different ways at different times. This created a challenge for the humans that lived there, and further geoarchaeological work is needed to understand the impact of regional climatic events on geomorphic, ecological, and cultural landscapes.