Abstract

Beachrock is a reliable marker of the strand in ancient sediments, and also suggests the possibility of a tropical or subtropical climate at the time of deposition. Recognition of beachrock in the stratigraphic record requires evidence of preferential early cementation of a layer within a succession of sandstone beds showing independent evidence of intertidal deposition. Several such layers can be recognized within dolarenites of the Proterozoic McLeary Formation. The beachrock interpretation is strengthened by evidence of penecontemporaneous joints in the preferentially cemented layers, micritic crusts of probable algal and vadose origin on some of the layers, sharply incised microtopography shown by the upper surfaces of some layers. and local reworking of the cemented layers to form distinctive conglomerates that can be traced laterally to undisrupted source beds.

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