Luke Beranek and colleagues from the University of Iowa, Geological Survey of Canada, Yukon Geological Survey, and University of Minnesota-Duluth have published a new article in Tectonics.
Cordilleran-type batholiths record the non-steady state development of continental arcs and their subduction systems, including short periods (~5-20 m.y.) of high-volume magmatic addition that punctuate longer periods (~30-50 m.y.) of low-level background activity. In the orogen cyclicity model of DeCelles et al. (2009), short-lived “flare-up” events occur in response to the rapid underthrusting of melt-fertile lower crust and lithospheric mantle beneath a continental arc as a result of craton-directed retroarc deformation. High-volume magmatic additions thicken the crust and generate large residual roots that may subsequently founder beneath continental arcs. Jurassic to Eocene intrusive rocks of the Coast Mountains batholith in western Canada represent one of the great continental arc systems of the world and have significant potential to identify the orogenic linkages proposed by DeCelles et al. (2009). In this paper, a Late Jurassic flare-up event in the Coast Mountains arc system of SW Yukon is reported using a combination of SIMS zircon U-Pb geochronology, zircon REE geochemistry, and whole-rock lithogeochemistry. Estimated intrusive rates in the Coast Mountains batholith were ~350 km2/m.y., analogous in scale to the Late Jurassic flare-up of the Sierra Nevada arc system. Episodes of late Middle to early Late Jurassic hinterland thrusting and metamorphism in the Intermontane and Omineca belts of the Canadian Cordillera preceded this high-volume event and therefore support the hypothesis that retroarc shortening was dynamically linked to flare-up activity. Late Jurassic magmatism was followed by a lull in most of the Coast Mountains batholith, which may be linked to ridge subduction, lithospheric delamination, mantle cooling, or plate reorganization.
Congratulations to Alex Hutter (MSc candidate in Geology) who received a 2017 GSA Student Research Grant ($1550) and CSPG Regional Graduate Student Scholarship ($2500) for his thesis project "Detrital thermochronometry and provenance of Jurassic and Cretaceous reservoir sandstones, Jeanne d'Arc basin, Grand Banks, offshore Newfoundland".
MSc. students Roddy Campbell and Leigh van Drecht have published new fieldwork articles in Yukon Exploration & Geology 2016!
Campbell & Beranek (2017) summarizes the physical stratigraphy and tectonic significance of lower Paleozoic mafic volcanic successions in the Pelly Mountains, south-central Yukon. This work is part of our "Secular evolution and metallogeny of continental margin basins" research program in the Canadian Cordillera. This project is supported by the GEM (Geo-Mapping for Energy and Minerals) program at NRCan and Yukon Geological Survey.
van Drecht et al. (2017) outlines our new project on the Whitehorse trough, a Jurassic synorogenic basin that records the exhumation of Intermontane terranes in central Yukon. This work is part of our “Tectonics and paleogeography of ancient orogens” research program. This project is supported by the Yukon Geological Survey.
Luke Beranek and colleagues from Idaho State & Australian National University have published a new article in Lithosphere.
Long-lived accretionary orogens like the North American Cordillera are built sequentially over tens to hundreds of millions of years. Although field evidence for the oldest mountain-building events in such convergent settings can be obscured by younger tectonism, ancient sedimentary rocks are known to be important archives of early-orogen evolution. This paper reports new data from ancient sandstones to investigate the earliest plate convergence in the northern U.S. Rocky Mountains, which culminated in the Antler orogeny and early growth of the North American Cordillera. The oldest convergent margin sandstones demonstrate stratigraphic ties with lithospheric blocks to the west that were juxtaposed against the Cordilleran margin ~20 m.y. prior to the Antler orogeny. These lithospheric blocks now reside in British Columbia, California, and Oregon, but are far-travelled and probably have origins near northern Europe. The Antler orogeny was likely a non-collisional mountain-building event that featured sinistral-oblique deformation and foreland basin sedimentation inboard of a west-facing arc system.
Summer 2016 field studies by Leigh van Drecht (M.Sc. student) focused on Jurassic strata of the Whitehorse trough that document synorogenic sedimentation in central Yukon during the early development of the North American Cordillera. This work is part of our “Tectonics and paleogeography of ancient orogens” research program. Leigh’s project will identify the stratigraphic architecture of the Whitehorse trough and determine contact relationships with underlying basement rocks assigned to Stikinia. Detrital zircon (U-Pb & Hf isotope) studies of key rock units will reconstruct the source-to-sink history of the Whitehorse trough and constrain the crustal evolution of adjacent source terranes. This work is supported by the Yukon Geological Survey and NSERC.
Summer 2016 field studies by Stefanie Lode (postdoc researcher) focused on sandstones of the Humber Zone that have the potential to be economically important to Newfoundland and Labrador. This work is part of our “Reservoir quality and sandstone provenance” research program in Atlantic Canada. Stef Lode’s project integrates field stratigraphic studies with SEM-MLA (Mineral Liberation Analysis) techniques in order to constrain the reservoir quality and porosity evolution of west-derived, Cambrian passive margin sandstones and east-derived, Ordovician foreland basin sandstones in the Bay of Islands & Port au Port Peninsula areas of western Newfoundland. This research is supported by NL Department of Natural Resources and Nalcor.
Summer 2016 field studies in south-central Yukon by Luke Beranek and Roddy Campbell (MSc. student) focused on Paleozoic rocks that preserve evidence for mafic to felsic volcanism and marine sedimentation along the ancient Pacific margin of North America. This work is part of our "Secular evolution and metallogeny of continental margin basins" research program in the Canadian Cordillera. The objectives of Roddy Campbell’s MSc. project are to identify the principal lithofacies of Cambrian-Ordovician volcanic successions in the Pelly Mountains and determine the timing and tectonic setting of mafic magmatism with whole-rock lithogeochemistry, Nd-Hf isotope geochemistry, and CA-TIMS zircon U-Pb geochronology. This research is supported by the Geo-mapping for Energy and Minerals Program at Natural Resources Canada, Yukon Geological Survey, and NSERC.
Congratulations to Roddy Campbell (MSc. candidate in Geology) who received a best poster prize from the Mineral Deposit Division at this year’s GAC-MAC conference in Whitehorse, Yukon. His research on “Early Paleozoic magmatism and stratigraphy of the Kechika group, Pelly Mountains, Yukon” is collaborative with Luke Beranek and Steve Piercey (Memorial University) and Richard Friedman (University of British Columbia). This research is supported by the Geo-mapping for Energy and Minerals Program at Natural Resources Canada, Yukon Geological Survey, and NSERC.