Deposition and diagenesis of the Upper Red River formation (Upper Fort Garry Member) and Stony Mountain formation (Upper Ordovidian) north and west of Winnipeg, Manitoba

Abstract

The upper Ordovician (Richmondian) upper Red River and Stony Mountain Formations were studied in detail from drill core and quarry exposures at Headingley, Stonewall and Stony Mountain, Manitoba. The stratigraphy, depositional history and diagenetic alterations were documented for the upper portion of the Fort Garry Member (Red River Formation) and the Gunn, Penitentiary, Gunton and Williams Member (Stony Mountain Formation). The upper Fort Garry was deposited in a low to high energy tidal flat setting characterized by clean carbonate sedimentation. Following a period of subaerial exposure at the end of Fort Garry time the Gunn Member was deposited. Sedimentation during Gunn time took place in a shallow marine environment characterized by low energy conditions, an influx of terrigenous material and the development of low-relief mud banks... Diagenetic processes such as; borings, burrowing, the development of Phase I cements, some secondary porosity, eearly (primary) dolomite, authigenic feldspar, length slow chalcedony and some pyrite occurred relatively early in the diagenetic history of the sediments in the eogenetic to shallow mesogenetic environments. The development of chert, some pyrite and hematite, Phase II cement, neomorphic spar, secondary dolomite, and some secondary stylolites occurred later in the diagenetic history of the sediments in the mesogenetic environment. The development of Phase III cement, some secondary porosity and some hematite occurred in the telogenetic environment and represent the last diagenetic processes to occur.