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Low‐temperature thermochronology of the northern Cordillera Real, Ecuador: Tectonic insights from zircon and apatite fission track analysis
Author(s) -
Spikings Richard A.,
Seward Diane,
Winkler Wilfried,
Ruiz Geoffrey M.
Publication year - 2000
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2000tc900010
Subject(s) - thermochronology , geology , fission track dating , zircon , terrane , geochronology , tectonics , cretaceous , paleontology , basin and range province , geochemistry
The post Early Cretaceous tectonic development of the northern Andean segment (north of 5°S) is loosely constrained by a series of partially and fully reset K/Ar ages. New apatite and zircon fission track data from three traverses across the Cordillera Real of Ecuador reveal distinct periods of accelerated crustal cooling during the Cenozoic. Fission track ages range from 65 to 14 Ma (zircon) and 44 to 8 Ma (apatite), with apatite mean track lengths ranging from 14.6 to 12.1 μm. These results record rapid cooling rates during ∼ 43 – 30 Ma, 23–15 Ma, and 10–0 Ma occurring at temperatures below ∼ 275°C. The events reflect up to ∼ 9 km of crustal exhumation in various regions of the Cordillera in response to relative changes in the kinematics of the Farallon, Nazca, and South American plates. The exhumation history of the Cordillera Real was not continuous but rather evolved during separate phases. These phases persisted for ∼ 10 Myr and are partly coincident with tectonic phases of the central Andes, although extend for longer time periods, possibly as a result of isostatically driven crustal exhumation. Large spatial variations in the zircon and apatite fission track data within the Cordillera Real indicate that local fault‐bounded massifs have experienced different thermal histories since ∼ 43 Ma. Major variations are not restricted to the regional scale and exist within individual terranes. Faulted slivers within terranes demonstrate highly variable exhumation histories, suggesting that deformation was not dominated by terrane‐bounding faults. Additionally, N‐S variations in exhumation depths suggest that ∼ NE‐SW trending faults have been active since ∼ 10–9Ma.