Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Geology

Supervisor

Patricia Corcoran

Abstract

The Espanola Formation of the Paleoproterozoic Huronian Supergroup is a mixed carbonate-siliciclastic succession. Detailed sedimentological analysis of the formation in the Bruce Mines-Elliot Lake region reveals 17 sedimentary lithofacies, which comprise three distinct lithofacies associations. The lithofacies associations represent, in ascending order, shoreface, offshore, and nearshore (or lagoon) depositional environments along a wave- and storm-dominated shallow siliciclastic marine shelf. Major, trace, and rare earth element analyses of the siliciclastic component indicate derivation from a mainly granodioritic Archean upper continental crust with some contributions from mafic volcanic and/or sedimentary rocks. The results show that the source rocks were subjected to relatively low to moderate chemical weathering conditions. Stable isotope and elemental analyses of whole-rock limestone samples reveal strongly and consistently negative carbon and oxygen isotopic compositions, generally high Mn and Fe concentrations, and low Sr and Mg concentrations, suggesting post-depositional diagenetic alteration and re-equilibration with hot meteoric waters or infiltrating metamorphic fluids. The carbon and oxygen isotopic compositions are spatially highly variable, indicating local rather than global control, with no clear systematic stratigraphic trends. Petrographic analysis also revealed evidence of intense diagenetic alteration, including recrystallization textures, stylolite structures, widespread dolomitization, and the presence of minerals known to be associated with contact metamorphosed carbonate-rich rocks, such as diopside and scapolite. The Espanola Formation contains evidence of syn-depositional, rift-related seismic activity, including widespread load casts, ball-and-pillow structures, convolute bedding and lamination, dish-and-pillar structures, clastic dykes, and slump structures. With the exception of slump structures and associated slip faces, the majority of these deformation features are restricted to discrete stratigraphic horizons, laterally traceable over 100s of meters, and confined between undisturbed strata of similar lithology. It is proposed that normal fault systems bounding the study area were active during lower Huronian basin subsidence, and may have been the main control on sedimentation.


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