107-2 Paragenetic evolution and implications of a mixed carbonate-evaporite system; The Givetian Dawson Bay Formation, Elk Point Basin

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

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This study re-evaluates the depositional setting and diagenetic history of the Middle Devonian (Givetian) Dawson Bay Formation in the Elk Point Basin of southern Saskatchewan and western Manitoba. The Dawson Bay Formation, with an average thickness of 35 m, is a halite-cemented carbonate unit that is part of the second sequence in a cyclic carbonate–evaporite sequence that repeats multiple times in the Middle to Late Devonian Elk Point Basin. Despite being buried to depths of up to 2,500 m in the study area, it exhibits minimal deep compactional features, highlighting the role that evaporite cementation plays in suppressing burial-related deformation. This study uses the Dawson Bay Formation as a natural archive to explore how evaporite diagenesis influences the preservation of primary sedimentary facies, paragenesis, and geochemical markers in similar carbonate systems. In other similar studies early halite cementation has been interpreted as a main mechanism for inhibiting burial compaction. To test this, we utilize a new dataset of 17 potash industry cores collected along a 200 km transect across the Canadian prairies of southern Saskatchewan, supplemented by outcrop data in western Manitoba. Core and thin section analyses were used to establish lithofacies relationships, sequence stratigraphy, and diagenetic histories, resulting in comprehensive sequence stratigraphic and paragenetic models for the formation. The data suggest that carbonate deposition was followed by reflux dolomitization and porosity generation. Halite brines subsequently permeated the formation, with some early compactional features preserved, implying some compaction occurred prior to halite cementation. Halite precipitation then "froze" the diagenetic system, preserving early features and halting any further burial compaction. Fracturing likely occurred later during uplift phases. Regional lithofacies variability controls localized differences in paragenesis. For example, the informal ‘worm burrowed’ unit is more pervasively bioturbated than the laterally equivalent facies, leading to a higher percentage of euhedral dolomite in the matrix and thus higher porosity, due to the abundance of burrows. This heterogeneity facilitated early halite cementation and restricted later alteration. These rocks demonstrate the importance of understanding carbonate diagenesis in the context of how evaporite cementation can hinder or halt the normal evolution of diagenesis in a mixed carbonate-evaporite system.

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

doi: 10.1130/abs/2025AM-7388

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