Cathedral Formation

The Cathedral Formation consists primarily of massive, cliff-forming carbonate rocks. It was originally deposited as limestone, much of which may have been secreted by marine algae. The limestone was subsequently altered to dolomite in many areas. The formation also includes several beds of shale with fossil trilobites ==Cathedral escarpment==

The Cathedral escarpment is an abrupt cliff on the westernmost edge of the Cathedral Formation. It was probably a submarine cliff that marked the edge of the original carbonate platform. It is approximately 100 to 300 metres (330 to 1000 feet) high and extends for about 100 kilometres (62 miles) running through and around Yoho National Park, although only small portions of it are exposed. ==Distribution and stratigraphic relationships==

The Cathedral Formation is present in the southern Canadian Rockies of southwestern Alberta and southeastern British Columbia. It reaches a maximum thickness of about 610 metres (2000 feet) at Mount Stephen. It is in gradational contact with the underlying Mount Whyte and Naiset Formations, and with the overlying Stephen Formation. ==Economic resources==

The Cathedral Formation hosts deposits of magnesite (MgCO3) at Mt. Brussilof, about 35 km (22 miles) northwest of Radium Hot Springs in British Columbia. The ore consists of magnesite-rich sparry carbonate masses that have been mined by open-pit methods since 1982. The ore is processed to produce magnesium oxide (MgO) at Exshaw, Alberta. The formation also hosts deposits of lead, zinc, and silver in the Kicking Horse Pass east of Field, British Columbia. They were discovered in 1884 during the construction of the Canadian Pacific Railway, and are Mississippi Valley-Type (MVT) deposits. They were mined intermittently for more than 60 years. The primary ore minerals are pyrite, sphalerite, and galena, which are associated with dolomite, minor quartz, and calcite. The abandoned mine portals and adits can still be seen along the cliffs that flank the Transcanada Highway. ==References==