Vasconez F. J., Samaniego Pablo, Phillips J., Andrade S. D., Simbana E., Nogales V., Roman-Carrion J. L., Muller A. V., Vasquez M. A. (2022). Evidence of destructive debris flows at (pre-) Hispanic Cayambe settlements, Ecuador. Quaternary International, 634, 65-80. ISSN 1040-6182.
Titre du document
Evidence of destructive debris flows at (pre-) Hispanic Cayambe settlements, Ecuador
Année de publication
2022
Auteurs
Vasconez F. J., Samaniego Pablo, Phillips J., Andrade S. D., Simbana E., Nogales V., Roman-Carrion J. L., Muller A. V., Vasquez M. A.
Source
Quaternary International, 2022,
634, 65-80 ISSN 1040-6182
In Ecuador, a country with numerous potentially active volcanoes, recurrent large earthquakes, and regular climate-related events, it is surmised that phenomena such as debris flows have affected pre-Hispanic pop-ulations since their settlement in-5000 cal BC. Here, using a multidisciplinary approach, we studied the most recent debris flow events that affected the Cayambe city area, located 15 km west of the active glacier-clad Cayambe volcano. Based on detailed characterization of the deposits, including sedimentological, archaeolog-ical, and paleontological analyses, as well as radiocarbon dating. We found that two debris flow (i.e., Rio Blanco I and II) destroyed Caranqui settlements in 665-775 cal AD and 774-892 cal AD, respectively, while another event impacted a Spanish colonial farm in 1590-1620 cal AD (Rio Blanco III). The grain size distribution of these deposits indicates a gravel-rich flow for Rio Blanco I and clay-rich flow for Rio Blanco II and III, whilst com-ponentry suggests low juvenile volcanic content for all three deposits. Juvenile components include pumice and lustrous dense dacites, while accidental clasts are dull dense dacites, oxidized and hydrothermally-altered ma-terial, as well as archaeological artifacts. These results, in addition to radiocarbon ages, suggest that the debris flows could either be post-eruptive or not related to volcanic eruptions. Potential non-volcanic trigger mecha-nisms for these events include rainfall and/or earthquakes, which implies that they can occur at any time and without forecast. Currently, the city of Cayambe is rapidly expanding and, consequently, our findings are rele-vant for creating impact scenarios for future debris flows forming in the Rio Blanco headwaters and descending to the city.
Plan de classement
Géologie et formations superficielles [064]
;
Géophysique interne [066]
;
Sociétés, développement culturel [112]
Description Géographique
ÉQUATEUR ; ANDES
Localisation
Fonds IRD [F B010086313]
Identifiant IRD
fdi:010086313
