Abstract

Discrete mounds and lenses of carbonate rock occur within argillaceous strata in the vicinity of Mount MacKenzie and Cardinal Mountain and are related to a nearby carbonate complex. The mounds developed on a biostromal platform and have sharp contacts with adjacent strata, whereas the lenses occur as isolated bodies that grade into and interfinger with the surrounding argillaceous beds. The mounds consist of porous, coarsely crystalline saccharoidal dolomite from which almost all traces of primary texture have been obliterated, in strong contrast to the non-porous limestones which make up the lenses. The largest and most conspicuous lenses crop out on inaccessible cliffs. Details of their lithology are derived from similar smaller but accessible bodies, composed of fine and medium-grained calcarenites which include skeletal remains and traces of algae. Coral colonies occur in laterally equivalent limestone beds and also form small lenses.

The mounds and lenses are significant because they reflect different sedimentary environments. The mounds probably developed in rather deep water during periods of rapid rise in sea level, whereas the lenses developed in relatively shallow water during periods of constant sea-level. Both mounds and lenses reflect the proximity of a carbonate complex.