MSc student Adam Wiest has published a new fieldwork article in Yukon Exploration & Geology!
The Late Triassic to Early Jurassic was a time of changing tectonics along the Cordilleran margin. In central Yukon, these changes are partially recorded by the lower and upper members of the Faro Peak formation, which crop out near the boundary between ancestral North America and the innermost Cordilleran terranes. In 2018, a two-year project was initiated to examine the Faro Peak formation, determine its physical stratigraphy, and further constrain the tectonic evolution of the Canadian Cordillera. Wiest et al. (2020) summarize the past season of fieldwork in the Faro area and provide two new stratigraphic sections to describe the age and regional significance of the lower member and the contac relationships between the lower and upper members. Wiest et al. (2020) provide evidence that these two members are unconformable, lithologically distinct, of mappable extent, and therefore should be separated into two new formations. Future detrital zircon U-Pb-Hf studies will be used to correlate stratigraphic units across the study area and determine their tectonic significance. This project is supported by the Geo-mapping for Energy and Minerals (GEM) program at Natural Resources Canada and the Yukon Geological Survey. Summer 2019 fieldwork by MSc student Maya Soukup focused on latest Neoproterozoic(?) to Lower Cambrian strata in the Gros Morne, Humber Arm, and Port au Port Peninsula regions of western Newfoundland that document the rift to drift history of the ancient Iapetan margin. The field objectives of Maya Soukup's project are to identify basement-cover contact relationships and principal lithofacies of Labrador and Curling group strata, whereas the lab objectives are to constrain the maximum depositional age and provenance of sampled units with laser ablation split stream (LASS) detrital zircon U-Pb-Hf techniques. This project is supported by Nalcor Energy and is part of our reservoir quality and regional stratigraphic correlation research program in western Newfoundland.
MSc student Adam Wiest completed his second and final season of fieldwork on Mesozoic synorogenic strata that crop out along the Yukon-Tanana - Slide Mountain terrane boundary in the Faro area of central Yukon. The objectives of 2019 field studies were to investigate contact relationships between Lower Jurassic debris-flow and Upper Triassic(?) turbidite units of the Faro Peak formation (outlined in Wiest and Beranek, 2019) with metasedimentary and volcanic rocks of the Yukon-Tanana and Slide Mountain terranes. Rock samples collected during this field season will undergo detrital zircon laser ablation split-stream (LASS) ICP-MS analysis to constrain the provenance and maximum depositional age of the Faro Peak formation and its significance to the exhumation histories of Intermontane terranes in the northern Canadian Cordillera. This research is supported by the Yukon Geological Survey and Geo-mapping for Energy and Minerals (GEM) Program at Natural Resources Canada.
Roddy Campbell (M.Sc., 2018), Luke Beranek, and colleagues from Memorial University and University of British Columbia have published a new article in Geosphere.
The precise age and tectonic significance of post-breakup igneous rocks along the Cordilleran margin of western North America are uncertain. In this article, Campbell et al. (2019) use the volcanic and intrusive rock record from the Kechika group, south-central Yukon, to test published models for Cordilleran rift evolution that have populated the literature since the 1980s. New chemical abrasion (CA-TIMS) U-Pb dates indicate that Kechika group mafic rocks were generated during the late Cambrian (488–483 Ma) and Early Ordovician (473 Ma), which post-dated the presumed timing of lithospheric breakup by 10s of Myr. Whole-rock trace-element and Nd- and Hf-isotope results are consistent with the low-degree partial melting of an enriched lithospheric mantle source during margin-scale extension. We concluded that ancient post-breakup igneous successions along western North America were generated in a plate tectonic setting analogous that that of the magma-poor Newfoundland-Iberia rift system. MSc student Adam Wiest has published a new fieldwork article in Yukon Exploration & Geology!
Isolated occurrences of Lower Jurassic(?) strata known informally as the Faro Peak formation crop out along the Yukon-Tanana – Slide Mountain terrane boundary near Faro, Yukon. Wiest and Beranek (2019) outline a two-year project to investigate the origin of the Faro Peak formation and constrain its physical stratigraphy, depositional age, and relationship to equivalent synorogenic rock units in the Whitehorse trough region of central Yukon. The exposed base of the Faro Peak formation includes argillite and organized to disorganized sandstone units to the southwest of the Vangorda fault. Lower Faro Peak formation units have mafic-intermediate volcanic provenance and were deposited by concentrated density flows or turbidity currents. The upper Faro Peak formation contains massive, disorganized conglomerate and sandstone units that were sourced from the Yukon-Tanana and Slide Mountain terranes and deposited by non-turbulent debris or density flows. These field observations will be integrated with future detrital zircon U-Pb-Hf studies to confirm the age and provenance of Faro Peak formation rock units and determine the spatial extent of Jurassic exhumation and synorogenic sedimentation in the northern Cordillera. This project is supported by the Geo-mapping for Energy and Minerals (GEM) program at Natural Resources Canada and Yukon Geological Survey. Summer 2018 field studies by MSc student Adam Wiest and Luke Beranek focused on Jurassic strata in the Faro area of central Yukon that document the exhumation of the Yukon-Tanana and Slide Mountain terranes during the early development of the North American Cordillera. The objectives of Adam Wiest's project are to identify the principal lithofacies of stratigraphic units and determine the timing, source, and tectonic setting of Jurassic sedimentation in central Yukon with laser ablation split stream (LASS) detrital zircon U-Pb-Hf techniques. This research is supported by the Geo-mapping for Energy and Minerals Program at Natural Resources Canada and Yukon Geological Survey.
MSc student Leigh van Drecht has published a new fieldwork article in Yukon Exploration & Geology!
The Whitehorse trough of central Yukon is a Jurassic sedimentary basin that likely records the exhumation of the Intermontane terranes (Yukon-Tanana, Stikinia, Cache Creek) during a time of plate tectonic change along western North America. van Drecht and Beranek (2018) report new field observations from the Whitehorse trough and focus specifically on the depositional contact relationships between syntectonic strata of the Jurassic Laberge Group and underlying arc and arc-marginal rocks assigned to Stikinia. Pre-Early Jurassic unconformities in the Whitehorse area are consistent with variable basin topography throughout the Whitehorse trough. Our current research is integrating these geological field constraints with detrital zircon U-Pb and Hf isotope studies to more fully reconstruct the timing and significance of Jurassic sedimentation in central Yukon during the exhumation of the Intermontane terranes. This project is supported by the Yukon Geological Survey. Luke Beranek has published the article “A magma-poor rift model for the Cordilleran margin of western North America” in the December 2017 issue of Geology.
The Cordilleran margin of western North America has an uncertain rift evolution that includes >300 Myr of lithospheric extension, breakup, and syn- to post-breakup magmatism. Published models for Cordilleran rift evolution since the 1980s have called for homogeneous pure shear or heterogeneous simple shear extension to explain Neoproterozoic-early Paleozoic deformation and magmatism along western North America. In this article, I use the Newfoundland-Iberia rift system as a modern analogue to propose a new magma-poor rift model for the Cordilleran margin. Based on North Atlantic analogues, it is predicted that early Cambrian lithospheric breakup resulted in a base-level fall and generation of the basal Sauk I megasequence boundary along western North America. A lower to middle Cambrian breakup succession developed over this lithospheric breakup surface and from bottom to top consists of lowstand, transgressive, and highstand systems tract deposits. Lower Cambrian volcanic strata are recognized in proximal breakup successions and predicted to be more voluminous in outboard regions with hyperextended crust and exhumed mantle. Off-axis, post-breakup volcanic strata were generated during the release of in-plane tensile stresses and focusing of extension toward the nascent plate boundary. The Beranek research group is currently studying Newfoundland-Iberia stratigraphy and tectonics to further understand North Atlantic rift evolution and apply these ideas to ancient rift margins, including the Cordilleran, Franklinian, and Iapetan margins of North America. Fall 2017 field studies by Stefanie Lode (postdoc researcher) focused on Cambrian-Ordovician siliciclastic rocks in the Bay of Islands and Port au Port peninsula areas that have the potential to be economically important to Newfoundland and Labrador. Dr. Lode’s research uses SEM-MLA (Mineral liberation analysis) techniques to quantify sandstone mineralogy and porosity, which will be used to constrain the reservoir quality and porosity evolution of western Newfoundland rock units. This research is supported by Nalcor Energy and NL Department of Natural Resources.
Congratulations to Leigh van Drecht (MSc candidate in Geology) who received her second Chevron Canada Limited Rising Star Award! This award is generously supported by Chevron Canada and given on the basis of academic merit, potential to carry out meaningful research, interest in potential employment in the oil and gas industry, and record of community service. Leigh’s thesis is focused on the Jurassic stratigraphy and tectonic evolution of the Whitehorse trough, central Yukon. |