Clay cortex from the contact zone between the host rock (chalk) and infilling deposits were examined in

paleokarst forms (pockets, pipes, and dolines of different age) from the Lublin–Volhynia chalk karst region. In light of the sedimentological and micromorphological analyses, it seems possible to work out a model as the basis for genetic and stratigraphic discussions. (1) Dolineswith the Paleogene orNeogene mineral infills are characterized by (a) homogeneous, residual type of massive clay gradually passing into the chalkmonolith, and at the sametime(b) relatively thickweathered zone. (2) Pipeswith glacigenic mineral infill fromthe Saalian Glacial are characterized by (a) sharp contact between host rock and clay, (b) narrow weathering zone of chalk, (c) diffuse nature of the contact zone between residual clay and mineral infill, and (d) contamination of clay by clastic material. (3) Pocketswith glacigenic mineral infill and traces of theWeichselian periglacial transformation are characterized by (a) strong contamination of chalk by quartz grains, (b) diffuse transition between clay and infill: fromclayey matrixwith single quartz grains (at the contactwith chalk) to clayey coatings and intergranular bridges (in the infill), (c) intensive weathering (cracking) of mineral grains in the infill.

Alunite minerals occur as white powdery lumps  and laminated coloured deposits within cavity and solution  channel infill of the palaeokarst zone of the Upper Eocene  Dammam Formation. This formation is exposed in a quarry  located on the Al Ahmadi ridge within the Greater Burgan oil  field in southern Kuwait. Field occurrences and sedimentary  structures of the alunite deposits were described. Collected  samples were petrographically described, and their mineralogy  and geochemistry were determined using X-ray diffraction  and X-ray fluorescence, respectively. Microfabrics were investigated  using SEM, revealing that they are primarily composed  of fibrous alunogen (hydrous aluminium sulphate) and  pseudo-cubical K-alunite (hydrous potassium aluminium sulphate).  Their mode of occurrence suggests a hypogenetic  origin, where sulphide gases associated with hydrocarbon  gases reacted with an Al-rich solution leached from clay  minerals and feldspars of the cavity-fill muddy sand sediments.  The hydrocarbon gases may have seeped from subsurface  petroliferous formations within the Greater Burgan oil  field along vertical fractures. This study suggests that these  acidic seeps may have played a role in the development of the  palaeokarst zone of the Dammam Formation.

Ambal ridge, covering 4 km2, is a salt pillowof Gachsaran Formationwith significant salt exposures in direct contact  with the Karun River, Zagros Mountains. The highly cavernous salt dome is currently being flooded by the  Gotvand Reservoir, second largest in Iran. Geomorphic evidence, including the sharp deflection of the Karun  River and defeated streams indicate that Ambal is an active halokinetic structure, probably driven by erosional  unloading. Around 30% of the salt dome is affected by large landslides up to ca. 50 × 106 m3 in volume. Slope  oversteepening related to fluvial erosion and halokinetic rise seems to be the main controlling factor. A total of  693 sinkholes have been inventoried (170 sinkholes/km2), for which a scaling relationship has been produced.  The depressions occur preferentially along a belt with a high degree of clustering. This spatial distribution is  controlled by the proximity to the river, slope gradient and halite content in the bedrock. A large compound  depression whose bottom lies below the normal maximum level of the reservoir will likely be flooded by  water table rise forming a lake. The impoundment of the reservoir has induced peculiar collapse structures  220–280 m across, expressed by systems of arcuate fissures and scarps. Rapid subsurface salt dissolution is  expected to generate and reactivate a large number of sinkholes and may reactivate landslideswith a significant  vertical component due to lack of basal support.

Anisotropy and heterogeneity of karstified rocks make them the most problematic media for various interventions which are needed in engineering practice. The long history of attempts to adapt karstic nature to human needs started with the utilization of karstic aquifers: tapping large springs, transferring their waters to the long distances, improving minimal flows or capturing fresh water in coastal areas. During the 20th century the number of other challenges such as building dam and reservoirs, and constructing roads and railways, bridges, tunnels, new settlements open a new era in engineering works but also in collecting new knowledge and experience for the karstology and hydrogeology sciences. Today, almost no engineering projects can be implemented without a proper environmental impact assessment, which establishes a better balance between human and ecological needs.