الفهرس 
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Abstract
Field Investigation In the southern part of Kuwait Indicates the common existence of calcrete, dolocrete, gypcrete and sllcrete. Three different forms of topographic highs are Identified: calcrete ridges, calcareous sandstone ridges and hills. Direct rela¬tionship between the genesis of durlcrust and pre-existing land topography as well as between the duricrust and development of present-day land morphology are also observed. Based on progressive carbonate accumulation and fabric produced from sequential development, four stages containing six types of calcrete were Identified. Those types are: calcretlzed sand (concretions), calcretized sand (stringers), mottled calcrete, powder calcrete, nodular calcrete and massive calcrete.
PetrographSc Investigation reveals that the calcareous durlcrust of Kuwait is formed from original host grains and cementing material. Original host grains are mainly quartz with subordinate feldspar and clay minerals. Calcite and dolomite are the most common types of cement. Calcite is present as sparry calcite, micrite and less as microspar. Dolomite Is found as microcrystalline (less than 0.01 mm) and macrocrystalline dolomite. Morphologically, microcrystalline dolomite Is observed as clou¬dy core with clear rim, artichoke and zoned dolomite. Using cathodoluminescence. dif¬ferentiation between sparry calcite, filling channel and fenestral porositles on one hand and the Inter-granular porosity on the other hand, is possible. Zoning fatrics were successfully correlated In different locations within some areas I and VI In particular), while, general correlation of areas I, II, VI and IX Is also possible.
Geochemical study Indicated that In acid-sowble fraction, caiclum and magnesium contents are the predominant cations. Detailed Investigation for nodutar calcareous durlcrust revealed that calcium content In nodular part is predominant in areas IV, V, VII, VIII and X, while magnesium content Is concentrated in areas I and 11 only.
Three types of gypcrete are recognized: weakly comented flbroua gypcrete, hard fibrous gypcrete and powdery gypcrete. Petrographically, several types of crystal shapes were recognized: Interlocking anhedral to subhedral crystals, lozenge-shape, feather-like, and poikllotoplc or lustre mottled coarse crystals.
In sllcrete, four types are Identified: massive vitreous, quartzltlc, opaline and porcellanlte. Massive vitreous, quartzltlc and opaline sllcrete are generally belong to the non-weatherlng-proflle, while porcellanlte sllcrete Is considered as weathering pro¬file. Geochemlcal study of the silcrete of Kuwait Indicated that Sio2 and CaO contents are relatively high compared with Cape-Coastal zone and Kalahari beds. South Africa, while Al2O3.Tio2 and Fe2O3 are lower.
Surface and near-surface duricrust In Kuwait started to develop during the Pieistocene and extends to the early Holocene. Pedogenic calcrete and groundwater calcrete are the two main genetic types of calcretes in Kuwait. Gypcrete and sllcrete are formed after the development of the two main types of calcrete. in a later stage, an arid environment prevailed and aeolian processes started acting on the surface and produced relief inversion. Brecciation of calcretic topographic highs helps In forming the third type of calcrete.