A review of the history of the nomenclature of the Medina Formation and of the previous studies of its members, particularly those studies dealing with the source of the Whirlpool sandstone. This is an attempt to show the direction of origin of the detrital materials of the Whirlpool sandstone by a study of the lateral variation of its grain size along the Niagara Escarpment. It is illustrated with maps and with photographs taken by the writer. / Thesis / Master of Science (MSc)

<p> Four measured sections of the Whirlpool Sandstone were prepared from outcrops in the Niagara Gorge and Hamilton areas. Sedimentary structures and constituents present in the lower two-thirds of the unit are consistent with the sandy braided fluvial depositional model. proposed by Salas [1983]. The upper one-third of the unit has been deposited in a near shore, shallow marine environment. All samples have been classified as Quartzarenites, or Sublitharenites after Folk [1974] and the source of the Whirlpool lies to the southeast in primarily pre-existing sediments, with some input from low grade metamorphic and hydrothermally veined terrains. </p> <p> Cathodoluminescent microscopy has proven to be a safe, relatively inexpensive, easy to use method, that offers a great deal of new information. The technique's only drawback is the gradual destruction of thin sections by the electron beam. The CL study demonstrated that pressure solution was not the source of the massive, pore occluding, mesodiagenetic quartz cement. Since very low diagenetic temperatures have been calculated for the Whirlpool in the study area [360C]; the local generation of silica would be impossible. Instead, it has been suggested that silica was carried in by saturated pore fluids that had migrated up-dip from source areas deep within the depositional basin to the southeast. Similarly, pyrite was precipitated as H2S bearing fluids migrated through the unit. These reducing fluids also produced the reduced zone at the top of the Queenston Formation. The H2S was produced during the maturation of hydrocarbons. Calcite cement is more abundant in the upper marine units of the Whirlpool. This suggests that the source of the calcite was local detrital carbonate in the upper marine units. Quartz cementation ceased when the porosity had been reduced sufficiently to inhibit the passage of the migrating pore fluids. Thus, the calcite cement precipitated from static pore fluids. The local detrital carbonate was dissolved by the acidic fluids that carried in the silica. This Ca+2 rich fluid was prevented from mixing with the bulk porewater and calcite precipitation occurred due to an increase in C02 by the decay of organic detritus in the upper marine units. The major proportion of secondary porosity was formed during mesodiagenesis by the dissolution of calcite. The pore fluids became undersaturated with respect to calcite when local intershale water was released into the porewater. The formation of dolomite cement was in response to a decrease in the amount of available iron relative to magnesium due to the precipitation of ferroan calcite. The zonation of the dolomite reflects rapid changes in porewater composition. Four morphologies of illite have been identified: two represent direct precipitation from alkaline, K+ rich solution; one may be detrital in origin, or it could represent illite that has been mechanically infiltrated down into the sand after deposition; and the fourth is a mixed layer assemblage that has been formed by the replacement of earlier clays by illite. The oil and gas found in the Whirlpool Sandstone in the Lake Erie area have probably migrated up-dip from source areas deep within the depositional basin to the southeast. </p> / Thesis / Bachelor of Science (BSc)

<p> The transition from the Whirlpool Sandstone to the Manitoulin Dolomite represents a marine transgression. Within the Manitoulin Formation, the proportion of siliclastics to carbonates shows a marked upward decrease. The Manitoulin Formation consists of four main facies. The lower two facies indicate an inner shelf environment, while the upper two represent a middle to outer shelf environment. </p> <p> These sediments have been almost totally dolomitized. Cathodoluminescent microscopy was employed to determine the diagenetic history of quartz, calcite, and dolomite cements. The petrographic characteristics of the dolomite using CL and normal light indicate a late stage (epigenetic) dolomitization. </p> <p> Dolomitization is thought to have been a late diagenetic process brought about by Mg-rich fluids expelled during compaction of adjacent shales and supplemented by brines circulating through fracture systems. </p> / Thesis / Bachelor of Arts (BA)