The structural Geometry of Rocks of the Torrens group near Adelaide, south Australia

Abstract

Rocks of Upper Precambrian age near Adelaide show evidence of two or more phases of deformation. The first phase has resulted in concentric and similar folds with an associated slaty cleavage. Structures of this phase are overprinted by folds with associated crenulation cleavage. Minor occurrences of later kink folds are also observed. The hypothesis that the first phase folds overprint very large folds not observable in the field is examined. The observed variation in the attitude of first phase folds could also have resulted from large scale inhomogeneities of strain. 1 “Torrens Group” is used in place of the “Torrensian Series” of Mawson and Sprigg (1950) at the suggestion of Daily (1963) since the Torrensian Series has an unwarranted time significance. 2 The scale of folds follows that of Weiss (1957). Macroscopic‐folds larger than a single outcrop. Mesoscopic‐folds on the scale of a hand specimen or single outcrop. Microscopic‐folds on the scale of a thin section.