Northern Arabian Gulf Research Articles

Sedimentological characteristics of the surficial sediments of the Kuwaiti marine environment, northern Arabian Gulf

ABSTRACTThe textural characteristics, carbonate content and the coarse fraction components of the Recent bottom sediments of the marine environment off Kuwait are described and the faunal‐sediment associations discussed. The sediments were subdivided into seven textural classes, namely sand, silty sand, muddy sand, sandy silt, sandy mud, silt and mud. Most of the study area is covered with muddy sediments whereas sandy deposits are restricted to the rocky bottoms near the southern flat of Kuwait Bay, the southern coast of Kuwait and around the islands and bathymetric highs. The textural classes, carbonate contents and faunal types of the coarse fraction were used to construct a biolithofacies map of the marine bottom sediments off Kuwait, in which nine facies are identified. The sedimentological characteristics of the Recent marine bottom sediments off Kuwait reflect the interaction between autochthonous calcareous fragments mostly of biogenic origin, lime rock fragments derived from beachrocks and submerged reef flats, and allochthonous terrigenous detritus transported to the area mainly by dust storms. The Kuwaiti offshore area is generally a low energy depositional environment with little sediment transport.

Mineralogy, Genesis, and Sources of Surficial Sediments in the Kuwait Marine Environment, Northern Arabian Gulf

ABSTRACT This article shows the results of a detailed mineralogical investigation of the Recent bottom of the Arabian Gulf bordering Kuwait. The main objective of this study is to determine the sources of the study area and to define their relative importance. Heavy and light minerals in the very fine sand and coarse silt fractions were estimated microscopically. These size fractions were selected for heavy mineral analysis because they represent a large proportion of the total budget and their results will be readily comparable with the published results of the potential sources (wind-bore and river-bore sediments). X-ray diffraction was utilized to determine the mineralogical composition of the whole sediment and the mineral constituents of the clay-size fraction The light minerals are chiefly composed of carbonates, quartz, and feldspars with lesser quantities of chert, gypsum, and mica. Dolomite was found to be the most common heavy mineral followed by amphiboles, pyroxenes, mica, opaques, and epidotes. Aragonite, garnet, zircon, and tourmaline were recorded in lesser quantities. The gross mineralogy is biased toward carbonates, clay minerals, and a small amount of quartz and feldspars. Carbonates are represented by low-Mg calcite, dolomite, high-Mg calcite, and aragonite. Low-Mg calcite and dolomite were found to be the most common carbonate species. They are thought to be of detrital origin carried into the study area primarily as dust fallout. Clay minerals are composed of illite, palygorskite, an illite-montmorillonite mixed layer, kaolinite, and chlorite. Illite and palygorskite are the most important clay minerals, forming more than 70% of the clay-size fraction. It is suggested the palygorskite is most probably developed as a diagenetic mineral in the lower Mesopotamian plain and transported to the study area by eolian processes. Other clay minerals are thought to be of detrital origin derived from many sources. The results show that the dust storms which originate in southern Iraq and Kuwait by the prevailing northwestern wind are a major contributor to the total budget, particularly with respect to dolomite, palygorskite, and low-Mg calcite. Other sources which have impact upon the study area are local coastal sediment, direct precipitation from Gulf water, Shatt-al-'Arab river sediments, and the submerged ancient off Kuwait.

Aeolian sedimentation in the north-western part of the Arabian Gulf

Dust storms are common in the northern Arabian Gulf region. They move mainly in a south-easterly direction. The State of Kuwait, near the site of deposition of the sediments, is continuously subjected to considerable amounts of dust. Dust fallout samples were collected on a bi-weekly basis from locations along the coastal area of Kuwait during the period April 1979 to March 1980. They were analysed for grain size distribution. The mean monthly maxima and minima of dust fallout were recorded in July 1979 (1002·7 tonnes/km2 and November 1979 (9·8 tonnes/km2), respectively. It was found that the dust fallout of Kuwait is generally sandy silt with an average composition of 32 per cent sand, 62 per cent silt and 6 per cent clay. Particles range in size between 0·125 mm and 0·015 mm, constitute 80 per cent of the average dust fallout. The contribution of dust to sediment of the north-western part of the Arabian Gulf is found to be 1 mm/year, assuming a uniform thickness of deposition throughout the coastal area of Kuwait.

Sedimentology and mineralogy of Kuwait Bay bottom sediments, Kuwait—Arabian Gulf

Textural and mineralogical properties of the Recent bottom sediments of Kuwait Bay, northern Arabian Gulf, were investigated. Six sediment types were identified, namely silty clay, clayey silt, sandy mud, silt, muddy sand and sand. It was found that most of the northern shelf and the central channel of the Bay are covered with muddy sediments, while sand and sandy deposits are restricted only to the southern offshore area of the bay. Based on the textural characteristics of its sediments, Kuwait Bay environment was divided into two energy zones: (a) low-energy zone, including most of the bay area; and (b) a moderate-energy zone, restricted to the southern offshore area of the bay. The detailed mineralogical investigation of the various size classes of Kuwait Bay sediments revealed that they are of polygenetic origin. Two main sources of the bay sediments were recognized, namely: (a) autochtonous materials which are derived from the degradation of recent shells of various fauna, erosion of the submerged ancient sediments and sub-Recent coastal sediments; and (b) allochtonous materials, which are derived from the onshore desert sediments by the action of the prevailing NW winds. It was also concluded that fallout from dust storms, contributes considerably to the sediment budget of the bay.