Structure, stratigraphy, and provenance of Cenozoic sediments in the Princhester Creek area, northern Takitimu Mountains

Kirby, Marian, 1958-

A structurally complex Cenozoic sequence overlies two basement terranes in the Princhester Creek area. Basement rocks comprise Permian Takitimu Group and Triassic Murihiku Supergroup. They are juxtaposed by a major N-S striking fault. The basal Cenozoic sediments are 450 metre thick Eocene coal measures of the Nightcaps Group (Beaumont Formation). A low angle unconformity separates the Beaumont Formation and the Murihiku basement on the NW flanks of Mount Hamilton. Elsewhere there are faulted contacts against basement rocks. Overlying the non-marine unit is a thick sequence of Oligocene marine basin sediments of the Waiau Group. Spear Peak Formation (900 metres thick) is in sedimentary contact with the Beaumont Formation. It is overlain by thick mudstone (possibly over 1000 metres) of the Waicoe Formation. Faulted against both these formations is the Weydon Formation of unknown thickness and similar Whaingaroan age. Younger pre-Quaternary sediments do not appear in the Princhester area.
Sediments record that the Takitimu block underwent rapid uplift early in the Whaingaroan and that the Fiordland block remained uplifted throughout the Eocene and Oligocene. From the Miocene to the present, right-lateral transpression (associated with strain on the Indian-Pacific plate boundary) has been partly concentrated along the Moonlight Fault system and partly distributed throughout the basement. The resultant rotation, shortening and uplift of basement blocks in the Princhester area is shown by basement structures and reflected in the highly deformed Cenozoic cover.

v, 98 p., 1 folded leaf of plates : ill. (some col.), maps ; 30 cm.

1989Kirby

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