Sedimentation and early tectonic history of the Greenland group, Reefton, New Zealand

The Greenland Group of the Reefton area, of probable pie-Devonian age, consists of alternating beds of indurated mudstone and sandstone, and is interpreted as a turbidite succession. Sedimentary features of the sandstone beds include common graded bedding, sharp basal contacts, directional sole marks, load casts, flame structures, internal cross- and parallel-laminations, and top surface ripple marks. The Reefton sediments cannot be differentiated on either lithology or facies from the Greenland Group succession in the Paparoa Range to the west, and the rocks in both areas are considered to form part of the same sequence. They probably formed proximal deposits on a submarine fan or fans. A secondary lithological layering is developed parallel to the slaty cleavage of some beds. This layering is interpreted as the result of grain movement in wet, unconsolidated sediments undergoing compression. The possible geological significance of these results is discussed.