thus is the most diagnositic for shallow-water, being deposited in oolitic or thick-bedded bioclastic limestone (Austin, 1976, p. 223). The macrofossil debris is fragmen- tary and shows no sign of having been deposited in place. Bedding is planar and the bioclasts are locally graded. The meagre information suggests redeposition of the bio- clasts possibly as debris flows. However, the absence of any deeper water fauna mixed with the shallow may argue against far travelled redeposition. The Alex Allan Formation consists of muddy lime- stone and shale which contain a mixed conodont fauna, all of which are compatible with deep water deposition. The absence of Cavusgnathus, which represents very shallow-water conditions (see von Bitter, 1976, and Merril and Martin, 1976), hints at deeper water deposition for the Alex Allan Formation. The lack of macrofossils and the presence of black fine grained clastics suggest a quiet water situation deeper than the wave base. The mixed fauna may result from very slow deposition or from reworking of older material, either case being compati- ble with a quiet moderately deep-water environment. Unnamed Pennsylvanian limestone Pennsylvanian crinoidal, fusulinid limestone found on the island at the north end of Spectacle Lakes is distinguished from the dark grey micritic limestone of the Alex Allan Formation by being more lightly coloured and bioclas- tic. It is similar to Greenberry Formation limestone but has a much lower percentage of crinoid fragments and contains fusulinids. The unit is confined to the island on Spectacle Lakes and is exposed with Greenberry Formation limestone and Guyet Formation conglomerate. It was previously in- cluded in the Greenberry member of the Guyet Forma- tion by Sutherland Brown (1963) and Campbell et al. (1973). Contacts with nearby units are not exposed. Light grey weathering grey finely crystalline limestone supports approximately 6% poorly preserved fusulinids, 5% crinoid stem fragments (1-3 mm long) and minor forams and conodonts. The limestone is pervasively veined with white calcite (fracture filling). Age and correlation. Conodonts from this unit are like the Middle Pennsylvanian ones of the Alex Allan Formation (M.J. Orchard, personal communication, 1984). The fusulinids may be Lower Permian (C. Ross, written communication, 1980) or Middle Pennsylvanian (W.R. Danner, written communication, 1980). Unnamed Permo-Triassic clastic rocks Olive-grey greywacke and slate overlies the Greenberry Formation on Two-Bit Creek in northern Wells map area and on the south slopes of Mount Tinsdale in Cariboo Lake map area. The rocks are similar to feldspathic micaceous quartzites in parts of the Snowshoe Group of Barkerville Terrane. The distribution of the unit is a 36 function of structural extrapolation and interpretation. The lower contact with Greenberry Formation on Two- Bit Creek is sharp and apparently sedimentary. The greywacke clasts consist mainly of subrounded quartz with small amounts of potassium feldspar, plagio- clase, muscovite and chlorite. The matrix is of sericite, chlorite and calcite. The grain size ranges from silt to very coarse sand and beds locally display grading. The slates are mainly olive, platy and thinly bedded. Beds of coarse grained greywacke are thick and massive whereas in fine grained sequences they are thin. Age and correlation. The sequence overlies the Green- berry limestone and does not occur between the Green- berry and Alex Allan formations. Parts of the limestone on the island at the north end of Spectacle Lakes are age equivalent to the Alex Allan Formation but some of it may be Lower Permian. It is presumed that the olive-grey clastics overlie these limestone units and therefore are younger and may be Permian and/or Triassic. Intrusive rocks Intrusive rocks of the Cariboo Terrane are divided into three categories on the basis of relationships with host rocks and their lithology. They are intrusions of diabase, quartz porphyry and lamprophyre. The Mount Murray intrusives were defined to include intrusives of both the Antler Formation and Cariboo Group (Sutherland Brown, 1957, 1963). Because there is doubt as to corre- lation of intrusive rock between these units, the term ‘“‘Mount Murray intrusives’’ is not used here. Diabasic intrusives Dykes and sills invading the Black Stuart Group south of Cariboo River and a dyke cutting Cariboo Group in the Roundtop Mountain area are volumetrically the most important of a series of diabasic intrusives (Table 12). Less conspicuous and smaller intrusions of diabase occur in scattered localities. Two of the dykes from the Black Stuart Mountain area contain myrmekite. Edges of oligoclase grains show various stages from unaltered to the development of worm-like quartz intergrown with oligoclase or albite. Though the quartz growths are usually around edges they locally invade cores. Complete replacement of the origi- nal oligoclase appears to result in the symplectic inter- growth of quartz and albite. A black aphanitic basalt sill intrudes the black pelite unit of the Black Stuart Group on Cunningham Creek just downstream from its junction with Roundtop Creek. This sill is included with the diabases because it could be their finer equivalent. It is the only one of its kind found in the area. Crosscutting relationships with host rocks demonstrate a Devonian or younger age because the youngest rock intruded is the black pelite unit of the Black Stuart Group.