A GLOBAL REVIEW OF SOLUTIONAL WEATHERING FORMS ON QUARTZ SANDSTONES

Solutional landforms in limestone have been described for over a hundr ed years, but landforms of similar morphology on highly siliceous sand stones and quartzites have also been identified in a wide variety of e nvironments and generally termed pseudokarst. These include large bedr ock pinnacles and towers, caves, corridors, grikes, solution basins an d runnels, and even silica speleothems. Quartzites and quartz sandston es have been held to be amongst the most chemically resistant of rocks , but the similarity, both in morphology and genetic process of many l andforms developed from them to features of known solutional origin on limestone, has prompted some authors to refer to these quartzose land forms as true karat. The most detailed studies of quartzose karst land forms have been in present-day tropical regions, or areas believed to have been tropical in the geologically recent past. This concentration of research in hot-wet areas, allied with the long held assertion of the insolubility of silica, especially quartz, has led to a belief tha t tropical climatic conditions are necessary for karstic solution of t hese rocks. However, the existence of quartzose karat landforms in tem perate and even sub-polar latitudes, especially where there is no evid ence of prior tropical conditions, suggests that the requirement of tr opical weathering is no longer tenable. The reports of these quartzose solutional landforms are widely scattered through the geomorphologica l and geological literature, but a comprehensive world-wide review of the range of solutional landforms on quartzose rocks has not previousl y been published. Because of the increasing awareness in this karst ty pe such a summary is sorely overdue.