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Recent papers on the origin and classification of cross-stratification by Allen have revived and stimulated interest in the use of cross-stratification as a tool for the interpretation of paleocurrents and environment of deposition. Cross-stratification has been described throughout the geological literature in numerous articles. Relationships between individual sets of large-scale cross-strata of relatively small size (5-30 cms. thick) have been frequently observed in outcrops that are sufficiently well preserved to allow a reconstruction of the pattern of the sets in three dimensions. However, descriptions of the stratification patterns of large (1-3 m. thick) cross-stratified units are rare. This is understandable since such units outcrop over large areas, and the outc ops required for the measurement of these units occur very infrequently.
Large cross-stratified units are well preserved along the coastline of eastern New South Wales in the vicinity of Sydney where sandstones of Triassic age, forming part of the Triassic-Permian Sydney basin, outcrop in horizontal or nearly horizontal attitudes along the rocky cliffs and headlands. At many localities it is possible to measure the areal extent of individual sets of cross-strata, enabling the construction of diagrams showing the cross-stratification pattern in three dimensions. Large individual sets of cross-strata commonly appear to be planar in random sections or in surfaces of small areal extent, but where they can be seen preserved over large areas, they are generally trough-shaped. The shape and distribution of the troughs may lend support to the theory that they have been formed due to migration of very large-scale linguoid or lunate asymmetrical ripples as suggested by Allen.
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