TIMING OF GLACIAL EVENTS AT PARAMO DEL SOL, COLOMBIA USING 10BE SURFACE EXPOSURE DATING

The tropics play a major role in the global climate system by exporting moisture and heat to the rest of the planet. However, the influence of the tropics in past climate changes, including glacial-interglacial cycles, remains unclear. During the Last Glacial Maximum (LGM), global average temperature has been relatively well-constrained at ~6°C cooler than during the pre-industrial era. The amount of LGM cooling in the tropics is debated, yet some proxies indicate that the tropics cooled less than higher latitudes. In addition, high-altitude terrestrial proxies suggest a steepened lapse rate since the LGM, but temperature reconstructions in these areas are poorly constrained. In this study, I use glacial geologic mapping and 10Be surface exposure dating to determine the ages of glacial features in the Páramo del Sol, Western Cordillera, Colombia (6°N latitude, ~4000 m asl). I present an updated glacial geomorphic map of the Páramo del Sol study area based on field observations as well as remote imagery and an integration of prior work. I also present new cosmogenic 10Be surface exposure ages that indicate timing of glacial extents. From the mapping, I reconstruct Equilibrium Line Altitudes (ELAs) associated with former glacial extents and compare these to ELAs of glacial extents in Colombia and broader tropical regions. Constraining the timing of glacial retreat with exposure dating techniques and updated mapping presents a high-altitude, terrestrial proxy for temperature in the tropics that clarifies changes in lapse rate in these areas during the LGM.