Doctor of Philosophy
Brunton, Frank R.
The upper Silurian–Middle Devonian succession was dominated by carbonate and evaporite deposits, with minor siliciclastic sedimentation, and a significant hiatus across the Siluro-Devonian (S-D) boundary in southwestern Ontario. The stratigraphic units include, in ascending order: Late Silurian Bass Islands/Bertie formations and Salina G Unit, the Devonian Oriskany Formation, Bois Blanc Formation (including Springvale Member), Detroit River Group (including the Lucas, Amherstburg and Sylvania formations), Onondaga Formation, and Dundee Formation.
Below the S-D unconformity, the upper Silurian Bass Islands/Bertie formations are predominantly dolostone of peritidal-sabkha origin and episodic subaerial exposure. Revised stratigraphic correlation shows that the Bertie Formation is older than the Bass Islands Formation, and the regional uplift of the study area has eroded the top of the Silurian deposits in the Niagara Peninsula. Four types of paleokarst systems are recognized in the strata below the S-D unconformity: 1) evaporite-dissolution; 2) syn-depositional brecciation; 3) surface karstification below S-D unconformity; and 4) deep burial dissolution. Climatic conditions during S-D boundary interval were probably semi-arid and the regional uplift of the North American craton led to marine regression and karstification.
The S-D compound boundary comprises three unconformity surfaces. In the Niagara region, these unconformities are marked by three levels of regionally distributed siliciclastic sandstones, including the Oriskany Formation, Springvale Member of the Bois Blanc Formation and an unnamed sandstone unit below the Onondaga Formation. These units are interpreted as eolian sandstones, reworked and remobilized during the regional-scale regressions and exposure of large parts of Laurentia. In the Michigan Basin, the lower two unconformities merge into one and the upper sandstone unit may be coeval with the Sylvania Formation.
In Ontario, the Lower-Middle Devonian Onondaga Formation is restricted to the Niagara area. Onondaga facies reveal fossiliferous carbonate deposition on a carbonate ramp sloped easterly into the Appalachian Basin centre. Temporally, the Onondaga facies in Ontario reflect one third-order sequence. The open marine facies of the Onondaga Formation grade southwestward into the intracratonic and lagoonal facies of the Amherstburg Formation and the Lucas Formation. The Dundee Formation in Niagara area can be correlated to the upper Moorehouse and Seneca Members of the Onondaga Formation, evidenced by the conodont data and the regional occurrence of Tioga ash bed. The sequence stratigraphic framework shows that the depositional systems are influenced by both eustatic changes and the migration of paleo-highlands in Ontario.
Sun, Shuo, "Stratigraphy of the Upper Silurian to Middle Devonian, Southwestern Ontario" (2018). Electronic Thesis and Dissertation Repository. 5230.