Sharanya Manickam HBSc Thesis Abstract

Understanding the formation of the cone-in-cone structures has been a topic of interest for nearly 2 centuries. The cone-in-cone laminae of the carbonate layers in the Paleoproterozoic Rove formation, of the Superior Province, is no exception to the ambiguous nature of their genesis. However, by combining the geochemical analysis of these structures and the associated elongate crystal fans present in the area of study, the depositional setting and physical processes of sedimentation can be inferred. Fourteen samples from the Quarry Site and 6 samples from the Arrow River location of the Thunder Bay region of Ontario, which are a part of the Rove formation, were investigated using this approach. The Rove formation consists of graywacke, argillite, quartzite, carbonate, and locally intraformational conglomerate. The cone-in-cone structures were present in a calcite-rich layer in the Quarry Site and in a carbonate concretion in the Arrow River location. Geochemical analysis of these structures indicate the presence of clay and mud between each of the cones and the cones themselves are made of carbonate. δC13 and δO18 values indicate the influence of seawater in the formation of the carbonate layer associated with the cone-in-cone structures. It is enriched to nearly 4 ± 0.1‰V-PDB when compared to the rest of the samples with a value of - 5 ± 0.1‰V-PDB. The rare earth element patterns provide further evidence for the influence of sea water based on the strong Eu* anomaly visible throughout all the samples. The ratios of iron to manganese provide proof of the influence of pore water as a result of a slight enrichment along the same carbonate layer containing the cone in-cone structures. The diagenetic environment in which these structures were formed is related to the presence of both pore fluid and sea water which is in accordance with the data collected.