TIMING OF POST-LGM DEGLACIATION OF THE CENTRAL CONEJOS RIVER VALLEY, SOUTHERN SAN JUAN MOUNTAINS, COLORADO

An ice cap covered much of the San Juan Mountains of Colorado during the Last Glacial Maximum. Few studies have examined the timing of post-LGM deglaciation in the southern San Juan Mountains. This study attempts to add constraints to the history of deglaciation by examining a sediment core taken from Trail Creek campground bog in the central part of the Conejos River Valley. That core extends 170 cm below the surface of the bog and has about 40% recovery. It comprises sandy and gravelly mud at the base grading up through silty mud to gytta and peat, recording the formation and filling of a kettle pond. The kettle pond formed on the uppermost (glacial) terrace in this portion of the Conejos River Valley. Charcoal, pollen and insect fragments from the sandy mud in the lowest section of the core (CRV-TCCB-1A-3B-1 31-33 cm) have been collected and submitted for AMS ¹⁴C dating. Potentially, the ¹⁴C results will confirm the post-LGM landscape evolution model proposed by Layzell (2010) which is based on ¹⁴C-calibrated soil chronosequences from alluvial fans, strath and fill terraces, and colluvial deposits in the central Conejos River Valley.