| Title | Tectonic-paleogeographic implications of a detailed Cretaceous-Cenozoic exhumation history in the Richardson Anticlinorium, northern Yukon, documented by multi-kinetic apatite fission track
modelling |
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| Author | Lane, L S ;
Issler, D R; O'Sullivan, P B |
| Source | Geoconvention 2020 abstracts; 2020 p. 1-2  Open
Access |
| Links | Online - En ligne
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| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20210002 |
| Publisher | GeoConvention Partnership |
| Meeting | GeoConvention 2020; September 13-15, 2020 |
| Document | serial |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Yukon |
| NTS | 106L/01; 106L/02; 106L/03; 106L/06; 106L/07; 106L/08; 106L/09; 106L/10; 106L/11; 106L/14; 106L/15; 106L/16 |
| Lat/Long WENS | -135.5000 -134.0000 67.0000 66.0000 |
| Subjects | tectonics; geochronology; geochemistry; stratigraphy; Science and Technology; Nature and Environment; geological history; tectonic history; faulting; deformation; thermal history; depositional history;
sedimentation; foredeeps; intermontane basins; paleogeography; fission-track dates; apatite; modelling; core samples; vitrinite reflectance; bedrock geology; structural features; folds; anticlinoria; structural features; faults; fault zones;
stratigraphic analyses; Richardson Anticlinorium; Canadian Cordillera; Slats Creek Formation; Eagle Plain; Illtyd Formation; Knorr Fault; Beaufort-Mackenzie Basin; Artificial intelligence; Phanerozoic; Cenozoic; Mesozoic; Cretaceous; Jurassic;
Paleozoic; Devonian; Cambrian |
| Program | GEM: Geo-mapping for Energy and Minerals Energy Component Coordination |
| Released | 2020 09 01 |
| Abstract | (Summary)
Multi-kinetic apatite fission track (AFT) modelling utilizing detailed elemental chemistry increases the resolution of thermal history models compared to conventional methods. Three
Cambrian samples from the core of the southern Richardson Anticlinorium, one Devonian sample from its western flank and one Lower Cretaceous sample from the eastern flank, contain up to three AFT statistical kinetic populations. Different total
annealing temperatures (<75°C to >200°C) for these kinetic populations extend the time-temperature range over which thermal histories can be resolved using AFT data. An inverse multi-kinetic AFT thermal model is used to obtain statistically
acceptable, geologically constrained thermal solutions that fit the observed AFT ages and track length distributions, as well as vitrinite reflectance data. A controlled random search (CRS) algorithm applied to the initial result refines the
best-fitting solution space. To the east, west and south of the anticlinorium, Cretaceous Cordilleran foredeep sedimentation, followed by Cenozoic exhumation, are recorded in the preserved stratigraphy and the AFT thermal histories. However, samples
from the core of the anticlinorium record a different history, indicating cooling from high temperature since earliest Cretaceous time. Two samples from the middle Cambrian Slats Creek Formation in the core of the range were thermally reset during
burial and constrain subsequent cooling (~1°C/m.y.) from earliest Cretaceous time until the present. These results indicate that the actively exhuming Richardson Anticlinorium was a positive paleogeographic feature since Early Cretaceous time. This
result implies that the mid- to Late Cretaceous Eagle Plain restricted intermontane basin in the west was not directly connected to the Cretaceous Peel Cordilleran foredeep to the east, implying that direct stratigraphic correlations between Eagle
Plain and Peel depocentres cannot be assumed. At the eastern margin of the anticlinorium, an early Cambrian Illtyd Formation sample, from a fault-bounded lozenge within the seismically-active Knorr Fault zone, experienced two-stage cooling starting
in the Late Jurassic. Cooling at ~1.6°C/m.y. from ~120 Ma to ~8 Ma was followed by rapid cooling, at ~12-13°C/m.y. after ~8 Ma. We interpret this Neotectonic exhumation pulse as being directly related to Neotectonic reactivation of the Knorr Fault.
This is consistent with active seismicity of the fault zone in this area, and with Late Miocene to Recent deformation in the adjacent Beaufort-Mackenzie Basin. These young deformations have been correlated previously with accretion of the Yakutat
tectonic block in the Gulf of Alaska. |
| Summary | (Plain Language Summary, not published)
Fission tracks are microscopic zones of damage in apatite crystals caused by the decay of trace amounts of uranium in the crystal. The tracks accumulate
over time, but are healed if the damaged crystals experience elevated temperatures. Thus a record of the heating and cooling history of the rock is preserved within the crystals By measuring the uranium content, as well as the number and lengths of
the fission tracks, this preserved history can be understood. We use this method to identify the cooling history along a transect across the Richardon Mountains in northern Yukon. We find that the range has been continuously rising since earliest
Cretaceous time. This has implications for the distribution of Cretaceous sedimentary deposits in the adjacent basins. Also, one sample collected from between two strands of a seismically active fault, the Knorr Fault, was rapidly cooled from high
temperature within the past 8 million years. This direct evidence for the age of the fault's activity provides a positive link to the collision of a plate tectonic block with the Pacific continental margin in the British Columbia - Alaska
area. |
| GEOSCAN ID | 328214 |
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