EVOLUTION OF QUATERNARY DURICRUSTS IN KARINGA CREEK DRAINAGE SYSTEM, CENTRAL AUSTRALIAN GROUNDWATER DISCHARGE ZONE, 1991, Arakel Av,

Quaternary calcrete, silcrete and gypcrete duricrusts in Karinga Creek drainage system, central Australia, contain abundant late-stage diagnetic features. These indicate repeated episodes of dissolution, precipitation and mobilization of duricrust components in the landscape, following the initial development of the duricrust mantle. 'Mature' duricrust profiles incorporate assemblages of diagnostic textural features and fabrics that clearly indicate the extent of karstification during the past 27 000 years. Diagenetic features in the duricrusts permit recognition of the stages involved in vadose modifications of compositional, textural and morphological features and, hence, assessment of the impact of karst dissolution, precipitation and mobilization of duricrust components under prevailing environmental conditions. At landscape level, the continued development of secondary porosity-permeability zones in topographically elevated areas, and maintenance of effective topographic gradients for soil creep are considered essential for redistribution of duricrust components and lateral and vertical extension of karst features within the Quaternary duricrust mantle. Although developing over a comparatively short span of time, late-stage modification of the Quaternary duricrusts has important implications for evolution of Quaternary landscapes and distribution of groundwater discharge-recharge patterns. Accordingly, differential dissolution and reprecipitation within the duricrust profiles have progressively given way to development of karst solution pipes and cavities, with the latter now acting as effective conduits for recharge of local aquifers in the region

Karst and caves in salt diapirs, SE Zagros Mts. (Iran), 1999, Bosá, K Pavel, Bruthans Jirí, , Filippi Michal, Svoboda Tomá, š, , Š, Mí, D Jakub

About 200 salt diapirs (plugs) have been known in the region of the Persian Gulf. numerous are still active. Karst rocks are represented by a rock salt, less frequently by gypsum and anhydrite. Karst developed especially in relics of planated surfaces. Karst forms are completely comparable with karsts in classical carbonate rocks. Different forms can be distinguished: karren, solution pipes, solution dolines, solution-collapse dolines, uvala-like to polje-like depressions, blind valleys, canyon-like forms, ponors, springs and caves. Two World longest caves in salt were discovered and explored here. Long caves are developed especially in a watertable, large ones in plugs near the seacoast. Caves are often outlets of closed depressions (polje-like). Some caves at bottoms of collapse-solution dolines or swallow holes are subvertical. Karst processes are caused dominantly by dissolution of salt, less frequently of gypsum. The process of subrosion of halite under gypcretes plays the main role. Deep circulation of meteoric waters was proved in some plugs.