Late quaternary glacial stades in the Cordillera Central, Colombia, based on glacial geomorphology, tephra–soil stratigraphy, palynology, and radiocarbon dating
✍ Scribed by Jean-Claude Thouret; Thomas Van Der Hammen; Barry Salomons; Etienne Juvigné
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 903 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0267-8179
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✦ Synopsis
Using data from glacial geomorphology, tephra-soil stratigraphy and mineralogy, palynology, and radiocarbon dating, a sequence of glacial and bioclimatic stades and interstades has been identified for the last ca. 50 000 yr in the Ruiz-Tolima massif, Cordillera Central, Colombia. Six Pleistocene cold stades separated by warmer interstades occurred: before 48 000, between 48 000 and 33 000, between 28 000 and 21 000, from Ն16 000 to ca. 14 000, ca. 13 000-12 400, and ca. 11 000-10 000 yr BP. Although these radiocarbon ages are minimumlimiting ages obtained from tephra layers on top of tills, the tills are not significantly older because most are bracketed by dated tephra sets in measured stratigraphic sections. Two minor moraine stages likely reflect glacier standstill during cold intervals ca. 7400 yr BP and slightly earlier. Finally, glaciers readvanced between the seventeenth and nineteenth centuries.
In contrast to the ice-clad volcanoes of the massif, ca. 34 km 2 in area above an altitude of ca. 4800 m, the ice cover expanded to 1200 km 2 during the Last Glacial Maximum (LGM) and was still 800 km 2 during Late-glacial time (LGT). Glacier reconstructions based on the moraines suggest depression of the equilibrium line altitude (ELA) by ca. 1100 m during the LGM and 500-600 m during LGT relative to the modern ELA, which lies at ca. 5100 m in the Cordillera Central. Glaciers in this region apparently reached their greatest extent when the climate was cold and wet, e.g. during stades corresponding to Oxygen Isotope Stage 3; glaciers were still expanding during the LGM ca. 28 000-21 000 yr BP, but they shrank considerably after 21 000 yr BP because of greatly reduced precipitation.