Fikry I. Khalaf

Occurrence of phreatic dolocrete within Tertiary clastic deposits of Kuwait, Arabian Gulf

Abstract The term dolocrete is used in the present study to describe siliciclastic sediments which are partially or completely cemented and/or replaced by terrestrial phreatic dolomite. Several successive dolocrete profiles occur within the subsurface Tertiary fluviatile muddy sand and mudstone deposits in Kuwait City. Three zones were recognized within these dolocrete profiles; these are in descending order: (1) dolocrete band, (2) dolocrete nodules, and (3) incipient dolocrete. Dolocrete also occurs within the compact green mudstone layers. The studied dolocrete comprises detrital grains inherited from the host sediment, and authigenic minerals precipitated during the dolocretization processes. The detrital grains include mainly quartz, feldspars, illite, and smectite. The abundance of authigenic minerals (dolomite, calcite and palygorskite) relative to detrital grains, reflects the degree of dolocrete maturation. Mature dolocrete is chiefly composed of dolomite and palygorskite. Several dolomite fabrics and textures were recognized; however, dolocretic dolomite is generally present as incomplete rhombohedra with spiky terminations. Variation in the nature of host sediment and diagenetic conditions are responsible for the degree of dolocretization and diversity of fabrics and textures. It is suggested that the dolocrete was developed by the precipitation of dolomite from pore solution saturated with respect to dolomite within the phreatic zone. Three main sources of chemicals required for dolocretization are suggested: (1) Mg-rich groundwater from the dolomitic Dammam Formation, (2) Mg and CO 2 released from clay minerals and organic matter in the host sediment mud matrix, and (3) infiltrated meteoric water.

Mineralogical composition and potential sources of dust fallout deposits in Kuwait, Northern Arabian Gulf

Abstract Detailed mineralogical investigations of dust fallout deposits collected at eleven locations in Kuwait during April 1979–March 1980 were carried out. The mineralogy of five size fractions, medium sand, fine sand, very fine sand, coarse silt and clay, was determined. Occurrence, frequency and potential sources of the mineral grains that form the various size fractions are discussed and the gross mineralogical composition of the dust fallout calculated. It was found that dust fallout deposited in Kuwait is quartzitic calcareous sandy silt and is mostly derived from the dry Mesopotamian flood plain in the middle and south of Iraq. The occurrence of sand-size particles is attributed to pick up from local recent surface deposits.

Roundness parameters of quartz grains of Recent aeolian sand deposits in Kuwait

Abstract Roundness properties of quartz grains from various types of Recent aeolian deposits in Kuwait were examined. The results confirmed that rounded and well-rounded grains are relatively rare. The investigated quartz grains were found to be mainly subangular and subrounded. Although no difference was noted in the roundness properties of the various types of aeolian deposits, significant variation was recorded among the size fractions. Grain-size distribution and the maturity of source sediments are considered to be the main factors controlling the roundness properties of Recent aeolian sediments.

Sources and genesis of the Pleistocene gravelly deposits in northern Kuwait

Abstract The Dibdibba Formation is of Pleistocene age and consists of a fluviatile sequence of ungraded, often cross-bedded sand and gravels intercalated with minor sandy clay layers. It occurs in the northern desert of Kuwait as subparallel elongated ridges trending NE-SW. Structures and mineralogy of the Dibdibba deposits suggest that they have been derived from the basement complex of the northeastern area of Saudi Arabia as sheet floods and deposited in the alluvial fan of the Wadi Ar-Rimmah-Al Batin valley system. Floods transporting these deposits were intermittent; the gravelly bands were deposited during severe floods and the sandy beds during relatively quiet floods.

Occurrence of barite-bearing mud balls within the Mio-Pleistocene terrestrial sand (Kuwait Group) in southern Kuwait, Arabian Gulf

Abstract Epigenetic barite concretions embedded within reworked mud balls occur in the upper Kuwait Group fluviatile clastic in southern Kuwait. The barite was precipitated displacively within flood plain muds during an epigenetic stage, possibly as a result of mixing of barium-rich brines with sulfate rich water. The mud balls formed during erosion of the barite-bearing flood plain mud layers by flood mass wasting.