Abstract:
The Anatoki Formation belongs to the Haupiri Group, probably Cambrian in age, of north-west Nelson. In the Boulder Lake area the formation is about 4,000 feet thick and contains coarse conglomerate, grit, sandstone, argillite and greenschist. The conglomerate is associated with graded bedded sandstone and argillite, and was probably deposited by submarine sliding.
Possible grativational glide structures occur. Detailed study shows that the Anatoki and Haupiri Faults are thrusts. Cleavage folds and the thrust faults support Grindley's (1961) interpretation of northward directed over thrusting of the Haupiri Group over underlying Ordovician strata.
All rocks examined have mineral assemblages of the quartz-albite-muscovite-chlorite subfacies of the greenschist facies. The greenschists form sills which were probably intruded into uncompacted wet sediments. Progressive introduction of CO2 during metamorphism is shown by the greenschists.
