Sedimentology and paleogeography of some Kaihikuan Torlesse rocks in mid Canterbury

Abstract Three sedimentary facies are recognised within Fingers Formation, a stratigraphic unit of Kaihikuan age within the Torlesse terrane. A thick‐bedded sandstone facies, which is most abundant, has features indicating deposition by high‐concentration mass‐flow processes, and it is interpreted as a submarine fan‐channel deposit. Rocks of a subordinate thin‐bedded flysch and siltstone facies are interpreted as relatively low‐concentration turbidity current deposits and are inferred to be interchannel, proximal submarine fan deposits. A rare third facies, pebbly mudstone, most likely had a debris flow origin. It is concluded that Fingers Formation is a base‐of‐slope, proximal submarine fan deposit, in contrast to the more deep water, turbidite‐rich Pudding Hill Formation to the east, and to the transgressive shallow shelf Mount Potts Group to the west, both of which are also of Kaihikuan age. The distribution of sedimentary environments during Kaihikuan time in mid Canterbury therefore suggests an east‐facing paleoslope within at least part of the Torlesse terrane at that time.