107-12 A Huronian Age for the Knife Lake Group of Minnesota, USA

Session: Sedimentary Geology Division/SEPM Student Research Poster Competition: Dynamics of Stratigraphy and Sedimentation

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Here we present detrital zircon age data for four samples of siliciclastic rocks of the Knife Lake Group in Minnesota (n=556), part of the Southern Superior Province, and reassess its tectonic evolution. Traditionally considered to be of the Vermillion Greenstone Belt and late Archean age we investigate the possibility that these rocks are indeed younger—specifically correlating with the Paleoproterozoic Huronian Supergroup.   Zircons were analyzed by LA-ICPMS at the University of Arizona Laserchron Center.  Each of the samples have a prominent age peak of ~2700 Ma, and maximum ages of deposition between 2650-2600 Ma.  Each of these units are deformed and regionally metamorphosed.  A comparison to published and unpublished Huronian strata from the Paleoproterozoic continental margin successions in Michigan, Ontario, and Wyoming reveals that most of the paired relationships to be statistically indistinguishable. We propose that the upper Ogishkemuncie Sequence, and perhaps the entire Knife Lake Group, deposited during rifting associated with the breakup of the Superia supercontinent. This supports a shared provenance and depositional context along a rifted passive margin during the Paleoproterozoic. We interpret the Knife Lake Group as a marginal rift succession deposited during the Neoarchean–Paleoproterozoic transition, contemporaneous with the fragmentation of Superia and the formation of the Huronian passive margin.  This reinterpretation suggests that deformation and greenschist-facies metamorphism could be Penokean in age (~1.9-1.8 Ga), aligning with contractional deformation observed farther south.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8669

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