Sledgers Group

K-Ar dates of slate and of volcanic rocks of the Sledgers Group in Fig. 4.20 and Appendix 4.8.4.1 range from 332 7 to 467 3 Ma (Adams et al. 1982 Adams 2006). Two whole-rock samples of volcanic rocks yielded K-Ar dates of 328 7 Ma (Lower Carboniferous) and 360 6 Ma (Late Devonian). AU of the K-Ar dates of the Sledgers Group are lower than the late Middle Cambrian age (i.e., -500 Ma, lUGS 2002) indicated by polymerid trilobites. The evident... 

Most workers now regard the Husky Conglomerate to be a basal facies of the Sledgers Group that does not warrant the status of a formation (Cooper et al. 1983 Bradshaw and Laird 1983 Wodzicki and Robert 1986). The discussion in the literature concerning the Husky Comglomerate was reviewed by Stump (1995). 

Whole-rock K-Ar dates of slate and siltstones of the Mariner Group in Appendix 4.8.4.2, reported by Adams et al. (1982), range from 417 3 (Lower Devonian) to 380 3 Ma (Middle Devonian) and are lower than the age indicated by fossils (late Middle to late Late Cambrian), although they do overlap with the K-Ar dates of the Sledgers Group in Fig. 4.20. 

The rocks consist of quartz-feldspar schist and phyllite derived from sedimentary protoliths of the Robertson Bay Group, from the Molar Formation (Sledgers Group), and from metavolcanic rocks of mafic composition. In contrast to the rocks of the Robertson Bay Group, the Millen Schist was multiply deformed (Bradshaw et al. 1982 Jordan et al. 1984 Findlay 1986) presumably during tectonic activity along the boundary fault. 

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