Limestone weathering in contemporary arid environments: A case study from southern Tunisia

Weathering features are described from a meteorologically arid area in sout hern Tunisia. Active weathering is concentrated in topographic lows (pits a nd pans) that concentrate available moisture and are associated with endoli thic and epilithic algae responsible for algal boring, plucking and etching of the limestone substrate. Deposits of gypsum have concentrated through e vaporation within hollows and occur as isolated patches of tabular crystals indicating an additional weathering agent characteristic of arid environme nts. The active development of a complex microkarst and associated salt wea thering are combining to destroy linear karstic features such as rillenkarr en, widespread case-hardening and in places patches of iron- and manganese- rich rock varnishes. The complexity of active and inherited weathering feat ures belies the perceived simplicity and lack of weathering opportunities a ssociated with aridity. Instead it focuses on the need to consider the natu re of microclimatic conditions at the rock/air interface especially when se eking to define desert weathering environments. It also highlights the diff iculties of interpreting polygenetic landforms and the importance of micros cale studies for identifying the impact of contemporary climatic conditions . Copyright (C) 2000 John Wiley & Sons, Ltd.