Cenozoic exhumation history of the northern Richardson Mountains: Results from apatite and zircon (U-Th-Sm)/He analysis

New low-temperature thermochronology data from clastic sedimentary rocks in the northern Richardson Mountains, Canada, indicate significant exhumational cooling during late Eocene–early Oligocene time. Apatite (U-Th-Sm)/He (AHe) data were collected from 19 Proterozoic–Paleocene rocks across a 115 km transect. Eighty-eight single-grain AHe dates range from 300 ± 5 Ma to 16 ± 4 Ma but most dates (65%) range 56–24 Ma. AHe dates are generally younger than the stratigraphic ages, indicative of thermal resetting by burial. Additionally, zircon (U-Th)/He (ZHe) data were collected from two Jurassic sandstones. The ten ZHe dates range from 831 ± 12 Ma to 291 ± 4 Ma and are older than the stratigraphic age, which limits maximum burial to <160°C. Our results from thermal history modeling indicate three phases of cooling, during the Paleocene–early Eocene (>65–50 Ma), late Eocene–early Oligocene (40–30 Ma), and late Oligocene–early Miocene (30–15 Ma). Most samples were sensitive to cooling during the first and second phases, whereas the third phase is not as well constrained. The rocks were close to surface temperatures and below the sensitivity of AHe analysis since the early–middle Miocene. The results suggest a previously unrecognized phase of cooling and inferred deformation in the northern Richardson Mountains during late Eocene–early Oligocene time. Our findings contribute to previous work that recognizes Late Cenozoic deformation along the eastern margin of the Northern Cordillera, in the northeastern Brooks Range (e.g. O’Sullivan et al., 1993; 1998b) and in the Mackenzie Mountains (Enkelmann et al., 2019). We investigated the potential mechanisms of this widespread deformation and found that the exhumation may relate to kinematic changes of the North American plate relative to structural trends along the margin of the Northern Cordillera.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Geoscience

Grantor dc:publisher.institution

Science

Year dc:date.issued

2020

Author dc:creator

• McKay, Ryan D.

Advisors dc:contributor.advisor

• Enkelmann, Eva
• Hadlari, Thomas

Committee members dc:contributor.committeemember

• Enkelmann, Eva
• Hadlari, Thomas
• Hubbard, Stephen
• Eaton, David

• thermochronology
• tectonics
• deformation
• Cordillera

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

English, en

DOI

http://dx.doi.org/10.11575/PRISM/39635

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/114475