sedimentological characteristics of the surficial deposits of the jal az-zor area, kuwait
TRANSCRIPT
Sedimentary Geolo~, 59 (1988) 295-306 295 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
Sedimentological characteristics of the surficial deposits of the Jal Az-Zor area, Kuwait
D. AL-BAKRI, W. K I T T A N E H a n d W. S H U B L A Q
Environmental Sciences Department, Environmental and Earth Sciences Division, Kuwait Institute for Scientific Research, P.O. Box 24885, 13109 Safat (Kuwait)
Received December 15, 1987; revised version accepted July 22, 1988
Abstract
A1-Bakri, D., Kittaneh, W. and Shublaq, W., 1988. Sedimentological characteristics of the surficial deposits of the Jal Az-Zor area, Kuwait. Sediment. Geol., 59: 295-306.
The purpose of this article is to discuss the nature and characteristics of the stirface geology of the Jal Az-Zor escarpment and the adjacent area, to better understand the sedimentology of desert landforms, and the main factors controlling depositional and diagenetic processes active in this environment.
The oldest outcrops along the face of the escarpment are the sand and sandstone sequences of the Mutla and Jal Az-Zor Formations of the Kuwait Group (Neogene). Gravelly deposits of the upper member of the Kuwait Group, Dibdibba Formation (Pleistocene) are restricted to a few hillocks and ridges in the summit area of the escarpment. The Neogene deposits in most of the study area are overlain by a veneer of unconsolidated Holocene sediments. These were classified, according to their morphological setting and field occurrence, into: coastal deposits (intertidal mud, sabkha deposits, and sand dunes) and inland deposits (sand drifts, slope deposits, wadi fills, residual deposits and playa deposits). Wind-born quartzitic sand is the most common Holocene sediment in the study area indicating the dominance of the aeolian processes.
Gypsum and carbonate present as cementing materials or in the form of gypcrete and calcrete, respectively, are characteristic sedimentological features of the pre-Holocene deposits. Gypcrete and gypsum cement are abundant in the upper section of the escarpment and decreases downward, whereas the carbonate (calcrete) shows a reverse pattern, i.e., it becomes more dominant in the lower section of the escarpment. The source of sulphate ions in the groundwater that is responsible for the development of gypcrete is believed to be the evaporites in the lower section of the Neogene sequence. The source of ions for the formation of calcrete and calcite cement is less understood due to the lack of significant primary carbonates in the near-surface deposits. It is believed that the nature and distribution of the chemically precipitated material (gypsum and carbonates) are controlled by the chemistry and hydrodynamics of the groundwater which in turn are controlled mostly by the climatic conditions, during their development, and the lithology of the host sediments. Arid and semi-arid climatic and paleoclimatic conditions are considered the most critical factors affecting the depositional and diagenetic processes impacting surficial deposits of the Jal Az-Zor area.
Introduction
Kuwait Muncipality commissioned the Kuwait Institute for Scientific Research to conduct a re- search program to assess the baseline conditions of the Jal Az-Zor region with the intention to select a suitable location for the first national pa rk /na tu re reserve in Kuwait 's desert (Taha et
0037-0738/88/$03.50 © 1988 Elsevier Science Publishers B.V.
al., 1982). This article is based on the findings of a geological investigation carried out in the first phase of the program designed to survey and assess the surficial sediments in an area of about 300 km 2 of the Jal Az-Zor escarpment region (Fig. 1). The escarpment is the most prominent topo- graphic feature in Kuwait, situated along the northern side of Kuwait Bay. It runs in a N E - S W
296
""STATE oF -'7 5.-.-K uwA'T 1
"~'P.~. \ \ ( 40 Km qd>/_ \, ~t
N
Coastal deposits
Inland deposits
Kuwait Group
L E G E N D AGE
Intertidal mud ~ Sabkha deposit I ~
Sand dunes ~ I o)
Slope deposit ~ : I Wadi fill ~ u
Sand d r i f t s ~ o Residual deposH ~ o
Playo deposit ~ J ~"
i DlbdJbba Formation ~P le is focene Jol Az-Zor Formation I~ i
~.-~/Neog ene Mutlo Formation [ _--_--_ .1 J
o J ~ ~J 4 km
Fig. 1. Surface geology of the Jal Az-Zor area and locations of the sampling points.
direction for about 65 km and reaches a maximum height of 165 m above sea level. Behind the escarpment (back slope) the surface primarily
slopes gently towards the north. A bisegrnented depression known as U m m Ar-Rimam is devel- oped in the back-slope area. A representative
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Bench ~ ~ I Kuwait Bay B I Sea Level B
Fig. 2. A representative topographic profile section of the Jal Az-Zor area. Vertical exaggeration: 25 ×.
297
topographic profile section showing the main geo- morphic features of the Jal Az-Zor escarpment is given in Fig. 2.
The oldest exposed formation in Kuwait is the Dammam Limestone which is of Eocene age. It is unconformably overlain by a sequence of mainly clastic deposits, known as the Kuwait Group, which range in age from Miocene to Pleistocene. Salman (1979) classified the Neogene sequence of Kuwait Group, exposed at the Jal Az-Zor escarp- ment, into "Mutla Formation" at the lower part of the escarpment and "Jal Az-Zor Formation" for the upper part of the sequence. The Mutla and Jal Az-Zor Formations are equivalent to Lower Fars Formation of Owen and Nasr (1958). According to Salman (1979), the upper member of Kuwait Group (Dibdibba Formation) was desig- nated for the surficial Pleistocene sandy gravel deposits. The Kuwait Group deposits are partially covered by a veneer of less than 2 m thickness of unconsolidated Holocene deposits. Based on the morphology and field occurrence, Khalaf et al. (1984) classified the surficial deposits of Kuwait into six regional classes: aeolian deposits, residual deposits, playa deposits, desert plain deposits, slope and alluvial deposits, and coastal deposits. This classification was adopted to describe the Holocene deposits covering the surface of the study area. An extensive review of literature of the post-Eocene sedimentary geology of Kuwait is documented by Youash (1984). Most previous studies have been concerned with the stratigraphic classification of the Kuwait Group deposits. De- spite these numerous investigations, only limited attention was devoted to understand the sedimen- tological features that characterize the surficial deposits. This paper is designed to describe and
assess the sedimentology of the study area, to discuss certain sedimentological aspects such as the formation of calcrete and gypcrete and the abundance of aeolian sediments, and to contribute towards a better understanding of the main fac- tors controlling the depositional and diagenetic processes active in the desert environment.
Methods of study
Thirty-six unconsolidated sediment samples and 20 rock samples were collected from the different surficial lithofacies. Samples were taken from three transects (Fig. 1). The unconsolidated sediments, with excess of fine material, were wet-sieved to separate the mud fraction (< 63 /~m) from the sand fraction. The grain size distribution of the coarse fraction (> 63/tm) was determined by dry sieving at 1/2 ~ interval sieves. The mud fractions were granulometrically analyzed using the pipette method, sizes down to 6 ~ were given in 1/2 units, whereas smaller sizes were given in whole units.
Grain size parameter (mean size, standard devi- ation, skewness, and kurtosis) were computed using Folk and Ward's (1957) equations. The scheme developed by Folk (1954) was employed to define the textural classes for the surficial sedi- ments in the study area. The average grain size distribution of the various unconsolidated sedi- ment types were graphically represented by histo- grams.
The mineral constituents of the sand fraction in the unconsolidated sediment were determined using a polarizing microscope. For most of the rock samples, framework composition was determined on the basis of 300 grain counts in
298
thin sections. The petrographic examination also included defining the types and percentages of the chemically precipitated cements, the percentage of the clay matrix, and the mean size of the frame- work grains. The mineralogical classification described in Folk (1974) was adopted to identify the main rock clans of the sandstones. In cases where the carbonates were more abundant than silicates (quartz and feldspars), the term "sandy limestone" was used to describe the rock.
Surficial deposits of the Jal Az-Zor area
The surface deposits of the study area were grouped into the following types:
(1) Neogene sediments comprising the Mutla and Jal Az-Zor Formations.
(2) Pleistocene sediments (Dibdibba Forma- tion)
(3) Holocene sediments that can be grouped into (a) coastal deposits consisting of intertidal mud, sabkha deposits, and sand dunes; and (b) inland deposits consisting of slope deposits, sand drifts, residual deposits, wadi fills, and playa de- posits.
Neogene deposits
The Neogene sequence (Mutla and Jal Az-Zor Formations) is made up primarily of sandstone beds alternated with friable sand layers. The fria- ble sediments of both formations are composed of, on average, 90-92% sand, 2-7% gravel, and 1-8% mud (Table 1). Texturally, they belong to the sand or gravelly sand classes with an average mean size of 1.1-1.4 ~ (medium sand) and a standard devia- tion of 1.0-1.4 q~ (moderately sorted). Mineralogi- cally, the sand fractions are composed of quartz (71-74%), gypsum (12-20%), carbonates (up to 10%), feldspars (4-6%), and minor quantities of mica, heavy minerals, and rock fragments (Table 1).
Based on the microscopic examination of the rock samples, the consolidated sediments of the Mutla Formation are grouped into: fossiliferous sandy limestone, calcareous subarkose sandstone, and sandy limestone. The calcareous subarkose sandstone is the most dominant and is char-
acterized by an abundance of calcite cement mostly of Poikilotopic texture while gypsum cement never exceeds 10% of the total constituents (Table 2). The sandy limestone rocks are characterized by the abundance of micritic calcite cement and the evidence of the partial or complete replacement of the framework grains by the carbonates. The framework grains in the rocks of Mutla Formation are dominantly of quartz (82-96%) with feldspars upto 8%, and small amounts of rock fragments (Table 2).
Rocks of Jal Az-Zor Formation are grouped into two main types: gypsiferous subarkose sand- stone, and gypsiferous/calcareous subarkose sandstone. The clastic grains are composed prim- arily of quartz (80-91%), feldspars (5-10%), and rock fragments (1-6%). Fibrous gypsum forms the main cement material in the Jal Az-Zor Forma- tion, but micritic calcite cement is also present.
When gypsum and carbonate cements co-exist in some rocks of the Neogene sequence, the calcite grains tend to coat the framework grains whereas the gypsum fills the pore spaces left vacant by the carbonates. This cement pattern suggests that the carbonates were first to precipitate from the solu- tion. The gypsum then precipitated after the solu- tion lost most of its carbonate cement.
The main differences in the sedimentological characteristics between the two formations of the Neogene sequence are that the Jal Az-Zor forma- tion tends to have coarser and slightly better sorted deposits (medium to coarse sand) than those of the underlying Mutla Formation (fine to medium sand), and the cement material in the former is dominated by gypsum while calcite ce- ment is abundant in the latter. This is in addition to the fossiliferous limestones characterizing the older formation.
The dominance of the sand size material, the presence of the fossiliferous bed and the reported, but not observed, evaporite sequence support the notion put forward by previous authors (Fuchs et al., 1968; Hunting Geology and Geophysics, 1981) that the deposition of the Neogene sequence of the Kuwait Group took place at the junction of shal- low marine and continental environments indicat- ing lagoonal, deltaic or fluviatile conditions of sedimentations.
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Pleistocene deposits (Dibdibba Formation)
The Dibdibba Format ion unconformably overlies the Jal Az-Zor Formation (Salman, 1979) and consists of a mixture of coarse sand and gravel with weakly cemented sandstone and con- glomerate lenses. With the exception of restricted areas at the crest of the escarpment, where about a 3 m thick layer of gravelly deposit was recognized, this formation is absent in most parts of the study area (Fig. 1).
The Dibdibba sediments are cemented by gypsum in some areas and are underlain by a layer of gypcrete consisting typically of a cellular frame- work of recrystallized fibrous gypsum. Surface gypcrete is present on other bedrocks in Kuwait, but is no where else is it as well developed. It is believed that this is a result of the exceptional high permeability of the underlying bedrock that allows extensive upward capillary migration of groundwater and leads to a higher concentration of salts at the surface (Hunting Geology and Geophysics, 1981).
Dibdibba sediments belong to the sandy gravel textural class with an average composition of 55% gravel, 44% sand and 1% silt. Gravel reach up to 20 cm in size and are composed primarily of
301
rhyolites (38%), quartzites (35%), granites (22%), and basalts (2%). Recrystallized gypsum grains represent a major constituent (42%) of the sand fraction with quartz forming 55% of the total mineral grains. Feldspars, carbonates, and heavy minerals are found in minor quantities (Table 1). The Dibdibba Formation is believed to have been deposited under fluvial conditions.
Holocene deposits
In most of the study area, the Kuwait Group deposits are covered by a variable thickness of unconsolidated sediment of the Holocene age (Fig. 1). These deposits are classified into coastal de- posits (intertidal mud, sabkha deposits, and sand dunes) and inland deposits (sand drifts, slope de- posits, residual deposits, wadi fill, and playa de- posits). The sand size fraction is dominant in most types of the Holocene surficial deposits, forming between 21% and 98% of all sediments (Table 1). The mud (silt and clay) is the second most com- mon fraction in the Holocene deposits. It forms more than 60% of the total sediments in the intertidal fiat, sabkhas and playas, but it usually forms less than 10% in the other types of uncon- solidated sediments. The gravel is the least com-
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302
mon fraction with maximum percentages (12-21%) recorded in the slope deposits and residual de- posits. The histograms of the average grain size distributions (Fig. 3) show unimodel distributions for the sand dunes and sand drifts, bimodel distri- butions for the slope, residual, wadi, and playa deposits, and trimodel distributions for the inter- tidal and sabkha deposits. The average mean size of the Holocene sediments ranges from 1.1 q5 (slope deposits) to 5.8 ~ (intertidal mud) with the fine to medium sand fractions representing a major portion of these sediments (Table 1). With the exception of the sand dunes and sand drifts, whose standard deviations are 0.7 ff and 1.4 ff respec- tively, the sediments are moderately to poorly sorted with standard deviations ranging from 1.6 q~ (wadi fills) to 2.7 ~ (sabkha deposits). Although the textural characteristics of the Holocene de- posits indicate that more than one depositional agent was involved in developing each of the deposit types, the aeolian processes seem to be the major factor influencing the Holocene sediment in the study area.
The sand fraction is primarily made of quartz (66-90%), and gypsum (2-28%) with subordinate amounts of feldspars and carbonates. Rock frag- ments, micas, and heavy minerals collectively form less than 2% (Table 1). The gravels are similar in lithology to those of the Dibdibba Formation. They are mainly of igneous and metamorphic origin such as rhyolites, quartzites, and granites. It is believed that the residual deposits in general and the residual gravel in particular were mainly derived from the Dibdibba Formation by defla- tion processes, where fine material were removed by winnowing action, leaving gravels and coarse sand as lag deposits. Sheet washing at times of heavy rains is partly responsible for the redistri- bution of the gravel. In some locations of the study area, the residual deposits underwent sec- ondary cementation with gypsum forming a gypcrete duricrust.
Discussion
One of the major features characterizing the sedimentology of the surficial deposits in the study area is the abundance of wind-born sediments and
the dominance of the aeolian processes, both as depositional and erosional agents. Substantial ac- cumulations of aeolian sand deposits in the form of dunes, drifts and rugged vegetated sand sheet are developed on parts of the back slope of the escarpment and the upper section of the coastal plain (Fig. 1). Even in areas such as the intertidal flats, sabkhas, playas, and wadis, where other processes are supposed to play a major deposi- tional role, the wind-borne sediments represent the bulk of their deposits. According to A1-Bakri et al. (1985), the sand fraction and most of the silt size material of the intertidal zone and the sabkha fiats in the study area come from the nearby desert and the mesopotamian plain in southern Iraq, and are transported to this area as bedload and suspended dust, respectively, by the prevailing northwest winds. The important contribution of aeolian dust to the tidal flats in the northern Arabian Gulf was also stressed by Kukal and Saadallah (1973). Khalaf et al. (1984) pointed out that due to the scarcity of rain, the fluvial processes play a subordinate role to the wind in forming the wadi fill. The steep walls of the relatively deep wadis and the abundance of vegetation in the shallow and wide wadis act as sand traps and facilitate the accumulation of wind-born sediment. The flat-floored bottom of the playas which are occupied by alluvial deposits, are either totally or partially masked by aeolian sand. Dust fallout was also considered an important source of the fine material in the slope deposit (A1-Asfour, 1980; Hunting Geology and Geophysics, 1981). As an erosional agent, the wind was very active in de- flating the finer fraction from the exposed bed- rock leaving the coarser material (gravel and coarse sand) as lag deposit (residual).
Another interesting sedimentological feature is the common occurrence of gypsum and carbonates. The gypsum in the sabkha deposit is formed as an authigenic mineral from the evaporation of seawater that seeps into the supratidal zone both laterally during the tidal flooding or vertically through the sabkha surface by the upward move- ment of the water table. The genesis, facies, and sedimentology of the sabkha in the Arabian Gulf region have been extensively investigated (Evans et al., 1964; Kinsman, 1964; Evans and Bush,
1969; Gunatilaka et al., 1980). The gypsum is also present as lenses or masses at or near the crest of the escarpment and as cement material in the upper section of the escarpment. In this case the gypsum represents different forms of gypcrete de- veloped by diagenetic processes. Here the parent material was originally deposited as sand, and the gypsum was chemically precipi ta ted from groundwater close to the surface. The evaporites reported in the Miocene sequence of the Kuwait Group (Fuchs et al., 1968; Hunting Geology and Geophysics, 1981) are believed to be the source of the sulphate ion in the groundwater. Upward movement of the groundwater, during the dry season, apparently removed gypsum from the source bed end re-deposited it as a secondary cementation at or near the surface. Coarse recrys- tallized gypsum grains recorded in the various types of the unconsolidated deposits are primarily derived from the gypcrete and, in some localized areas, from the sabkha's gypsum, and were trans- ported and redistributed by the wind action.
Calcite cement tends to be more abundant, than gypsum, in the lower section of the Neogene sequence (Mutla Formation). Calcite cement in the study area is believed to have been developed as a result of diagenetic processes essentially simi- lar to those of calcretization. During time of rela- tive aridity, when frequent and long dry spells occur, the groundwater migrates upwards by the capillary action due to continuous evaporation at the surface. This mechanism leaves the ground- water with high ionic concentration and subse- quently high precipitation of salts which leads to the formation of calcrete. In some localized areas of the sequence, the calcretization was properly developed and mature calcretes (sandy limestones) were formed. In other parts, this process was not fully developed and only calcareous sandstones were formed. The presence of different forms of calcretes a n d / o r calcareous sandstones reflects, to a great extent, different stages of calcretization and different types of calcite diagenesis. Based on the arguments put forward by Khalaf (1987), it seems that the presence of mud-size material in the host sand plays an important role in control- ling the diagenetic processes responsible for the development of calcrete. Calcrete starts by pre-
303
cipitation of microcrystalline calcite crystals within the mud matrix of the host sediment forming micro-calcrete nodules. These nodules grow in number, displace the clay matrix and partially or completely replace some of the framework grains. The extent of this process is controlled by the availability of calcium-rich solution. Thus differ- ent forms of calcretes are developed.
In case of clean and well sorted sand, macro- crystalline calcite crystals precipitate to fill the intergranular pores as well as the fractures and cavities of the host sediment. This calcite crystals act as a cement agents interlocking the framework grains, producing friable to hard lithified sand- stones, depending on the availability of the solu- tion.
For more details on the factors and mecha- nisms controlling the process of calcretization and its stages and products, the reader is referred to the relevant literature (e.g. Reeves, 1976; Arakel, 1982; Blumel, 1982) and to the recent works of Khalaf (1987) and A1-Sulaimi (1988).
The source of carbonate ions in the solution that are responsible for the formation of calcrete and calcareous sandstones is not well understood because of the lack of significant primary carbonate deposits in the near surface sequence. With the exception of few horizons of marine limestones in the Kuwait Group, the Dammam Formation is the only major primary carbonates in Kuwait. In the study area the Dammam Forma- tion is overlain by more than 100 m of clastic sequence (Kuwait Group). It is believed, therefore, that the Dammam Formation is too deep to have a significant impact on the ion concentration in the solution responsible for the development of calcrete in the near surface deposits. A1-Sulaimi (1988) suggested that the dust fallout is the main source of carbonates in the groundwater. Despite the fact that the northern Arabian Gulf region does receive a high rate of calcareous dust fallout (Emery, 1956; Kukal and Saadallah, 1973; Khalaf et al., 1984) significant accumulations of such deposits (loess) hardly exist on the surface or in the subsurface sequence of Kuwait. Most of the dust fallout in Kuwait is removed by the wind action from the ground surface and re-deposited in the marine environment of the Gulf (A1-Bakri
304
et al., 1985). For this reason and due to the fact that dolomite is the main conStituent of the calcareous dust particles, the dust fallout cannot be a major source of the carbonate ions in the groundwater.
Another potential source of the carbonate ion are the carbonates that could have been precipi- tated directly or indirectly from seawater in as- sociation with the beach deposits during the for- mation of the Kuwait Group. In this case it is assumed that shells, shell fragments and other type of marine carbonates are dissolved by meteoric water and the dissolved carbonate ion is carried into the groundwater.
There is no evidence to support the dominance of either one of the above discussed alternatives. The authors believe that all those sources, rather than a single one, could be collectively responsible for increasing the concentration of the carbonate ions in the solution and, ultimately, the develop- ment of the calcrete in the study area and in Kuwait in general.
The vertical distribution pattern of the chem- ically precipitated materials in the study area, which is characterized by the abundance of gypcrete at or near the surface and a dominance of carbonates in the lower section of the sequence, is commonly observed in other parts of Kuwait. This pattern suggests that, when groundwater con- tains both carbonate and sulphate ions, the latter precipitates after the solution loses most of its carbonate. The fact that carbonate is less soluble than gypsum and the precipitation of the latter is more related to the evaporation mechanism sub- stantiates this explanation. In rock samples where both cements co-exist it was often noticed that the carbonate occurs as pore-lining or grain-coating cement, whereas the gypsum filled the pore spaces left by the calcite grains. This microscopic phe- nomenon also supports the given explanation of the observed vertical distribution pattern and it represents a transitional phase where the precipi- tation of carbonate ends and the deposition of gypsum starts. It should also be mentioned that the carbonates and gypsum cements were formed as a result of multiple phases of precipitation rather than by a single phase.
Conclusions
(1) Aeolian quartzitic sand is the most com- mon constituent in the Holocene surficial deposits and gypsum was recorded as the second most abundant mineral. With the exception of the authigenic gypsum of the sabkha deposits, this mineral occurs in the different types of the uncon- solidated Holocene deposits as detritals trans- ported into the areas and redistributed by the wind action. It can therefore be concluded that the aeolian processes have played the major role in shapping the surficial deposits, while fluvial, marine and mass-wasting processes are sub- ordinates. This distribution of sedimentary par- ticles reflects the effect of the arid climatic condi- tions and the relatively low relief topography.
(2) Gypsum and carbonates present as cement- ing materials or in the form of gypcrete and calcrete, respectively, are common and character- istic features of the pre-Holocene deposits. These chemically precipitated material were deposited from groundwater close to the surface where evaporation was increasing the concentration of dissolved salts to a level where they could crystal- lize as a cement binding the sand grains. The process of gypcretization and calcretization is probably continuing at the present time. The source of the sulphate ion in the groundwater is believed to be the evaporites in the lower section of the Neogene sequence. The source of carbonate ion responsible for the formation of calcrete and calcareous sandstones is less understood due to the lack of significant carbonate deposits in the near-surface sequence. It is believed that the marine limestone horizons in the Kuwait Group, the Dammam Formation, the calcareous particles in the dust fallout, and probably the shells and organisms associated with sand of Kuwait Group which were deposited under beach conditions, are collectively contributing to increase the carbonate ion concentration in the groundwater.
(3) Presence of different forms of calcrete and calcareous sandstones in the study area reflects different stages of calcretization and calcite di- agenesis. It is believed that the availability of calcium-rich solution and the presence or absence of appreciable amounts of clay matrix in the host
sand are responsible, to a certain degree, for the
var ia t ion in the development of the calcrete-like
deposits.
(4) Gypcrete and gypsum cement tend to con-
centrate at or near the surface of the escarpment ,
whereas the c o n c e n t r a t i o n of calcrete a nd
carbonate cement increases downward. Such a
pa t te rn of d is t r ibut ion has also been observed
elsewhere in Kuwait . Microscopic examina t ion of
thin sections also revealed a t ransi t ional stage
where bo th cements co-exist in the same rock
samples. In this case, the carbonate occurs as a
pore- l ining or grain-coat ing cement while gypsum
filled the pore spaces. This pa t te rn of d is t r ibut ion
results from the fact that the carbonates precipi-
tate prior to the sulphates. Thus, gypsum starts
forming after the solut ion loses most of its
carbonate ions. This pa t te rn also indicates that
mult iple phases of precipi ta t ion were responsible
for forming the cement materials.
(5) Results of this s tudy support the conclusion
of earlier work (e.g. Basu, 1976; Sut tner et al.,
1981; Du t t a and Suttner, 1986) that the climate is
the chief cause of var ia t ion in the composi t ion of
the sand and sandstone. Consequent ly , the cl imatic
and paleoclimatic condit ions, relatively arid times,
can be considered as the ma in factor control l ing
the deposi t ional and diagenetic processes and
hence the surface sedimentology and geomor-
phology of the s tudy area.
Acknowledgements
The authors would like to thank the Kuwai t
Munic ipal i ty for providing the f inancial suppor t
and the Kuwai t Ins t i tu te for Scientific Research
for the use of the research facilities. Acknowledge-
men t is made to Dr. F. Khalaf for his critical
review of the manuscr ip t and for suggesting
improvements . Acknowledgement is also due to
Dr. F. Taha, the project manager of the research
program from which this article was developed.
Special note of thanks are due to Mr. Z. A1-Sheikh
for assisting in the field survey and for Mr. A.
Qassim for analyzing the sediment samples.
305
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