Distribution Pattern Of Clay Minerals Research Articles

Potassium Behavior with Clay Minerals Composition under Soil Ecosystem: it's Adequacy for Maize Plants

Purpose: The target area for the study is one of the agricultural areas of importance in Egypt. It is a suitable area for studying the origin and distribution patterns of clay minerals. Therefore, the focal aims of this study were: (1) to examine the clay minerals' origins in semi-arid regions of Egypt. (2) The behavioral pattern of K in clay minerals in ecological changes, (3) the reflection of K-behavior in soil on the maize plant's nutrient content under soil systems.
 Methodology: Evaluation of water samples were: Evaluate the pH and EC, soluble ions, sodium adsorption ratio (SAR), soluble sodium percentage (SSP), sodium to calcium activity ratio (SCAR), residual sodium bicarbonate (RSBC), and residual sodium carbonate (RSC). Also, Evaluation of soil samples were: Evaluate the particle size distribution, OM content, soil pH, Gypsum, CaCO3 content, cation exchange capacity (CEC), exchangeable sodium percentage (ESP), EC, soluble ions, Soil available K, exchangeable K, and total K. Separation of the clay fraction: preparation of soil samples for mineralogical analysis. Qualitative clay mineralogical analysis: X- ray diffactograms were obtained for some selected clay samples using Philips equipment pw (1140/90). Evaluation of plant samples were: Evaluate the N, P, and K concentrations. Statistical analysis: SPSS (v. 20) was used to determine the descriptive statistics and correlation analysis.
 Findings: Achieving study aims, a series of methodological steps were implemented to study soil and water properties, and their reflection on maize plants. The irrigation water results analysis showed no problems. The soil properties were also distinguished by the results: common features of this type of soil are a depth of greater than 120 cm, a slightly well-drained clay texture, and poor OM content. The CaCO3 content increases with depth. The available N, P, K were (slight to moderate, very low, and good) respectively. The EC values range from non-saline to moderate saline. As indicated, the X-ray diffraction patterns of the clay fractures are separated from those features. It appears from the analysis that the mineral composition of the clay fracture at both areas is dominated by montmorillonite, kaolinite, and then hydrated mica. Based on the studied soil characteristics, there was a reflection on the maize plant grown, which showed the following: A strong positive correlation between the soluble K content and K in maize plants at the age of 30 days. The multiple correlations were significantly positive between the N and P content available to the grain of maize plants. The results exposed a negative correlation between the available K and K content of maize plants at 45 days of age. Also, there was a significant negative correlation between the exchangeable K and K content in maize plants at 60 days of age.
 Contribution to theory, practice and policy: The results presented the significant relationships between the evaluation of the physical and chemical properties of the soil, the content of available nutrients, as well as the type of soil minerals, and their reflections and contributions on the elements contained in the different parts of the maize plants (stems and grains), according to the state of the maize plants age.

Geochemistry of Sub-Depositional Environments in Estuarine Sediments: Development of an Approach to Predict Palaeo-Environments from Holocene Cores

In the quest to use modern analogues to understand clay mineral distribution patterns to better predict clay mineral occurrence in ancient and deeply buried sandstones, it has been necessary to define palaeo sub-environments from cores through modern sediment successions. Holocene cores from Ravenglass in the NW of England, United Kingdom, contained metre-thick successions of massive sand that could not be unequivocally interpreted in terms of palaeo sub-environments using conventional descriptive logging facies analysis. We have therefore explored the use of geochemical data from portable X-ray fluorescence analyses, from whole-sediment samples, to develop a tool to uniquely define the palaeo sub-environment based on geochemical data. This work was carried out through mapping and defining sub-depositional environments in the Ravenglass Estuary and collecting 497 surface samples for analysis. Using R statistical software, we produced a classification tree based on surface geochemical data from Ravenglass that can take compositional data for any sediment sample from the core or the surface and define the sub-depositional environment. The classification tree allowed us to geochemically define ten out of eleven of the sub-depositional environments from the Ravenglass Estuary surface sediments. We applied the classification tree to a core drilled through the Holocene succession at Ravenglass, which allowed us to identify the dominant paleo sub-depositional environments. A texturally featureless (massive) metre-thick succession, that had defied interpretation based on core description, was successfully related to a palaeo sub-depositional environment using the geochemical classification approach. Calibrated geochemical classification models may prove to be widely applicable to the interpretation of sub-depositional environments from other marginal marine environments and even from ancient and deeply buried estuarine sandstones.

Estuarine clay mineral distribution: Modern analogue for ancient sandstone reservoir quality prediction

AbstractThe spatial distribution of clay minerals in sandstones, which may both enhance or degrade reservoir quality, is poorly understood. To address this, clay mineral distribution patterns and host‐sediment properties (grain size, sorting, clay fraction abundance and bioturbation intensity) have, for the first time, been determined and mapped at an unprecedentedly high‐resolution in a modern estuarine setting (Ravenglass Estuary, UK). Results show that the estuary sediment is dominated by illite with subordinate chlorite and kaolinite, although the rivers supply sediment with less illite and significantly more chlorite than found in the estuary. Fluvial‐supplied sediment has been locally diluted by sediment derived from glaciogenic drift deposits on the margins of the estuary. Detailed clay mineral maps and statistical analyses reveal that the estuary has a heterogeneous distribution of illite, chlorite and kaolinite. Chlorite is relatively most abundant on the northern foreshore and backshore and is concentrated in coarse‐grained inner estuary dunes and tidal bars. Illite is relatively most abundant (as well as being most crystalline and most Fe–Mg‐rich) in fine‐grained inner estuary and central basin mud and mixed flats. Kaolinite has the highest abundance in fluvial sediment and is relatively homogenous in tidally‐influenced environments. Clay mineral distribution patterns in the Ravenglass Estuary have been strongly influenced by sediment supply (residence time) and subsequently modified by hydrodynamic processes. There is no relationship between macro‐faunal bioturbation intensity and the abundance of chlorite, illite or kaolinite. Based on this modern‐analogue study, outer estuarine sediments are likely to be heavily quartz cemented in deeply‐buried (burial temperatures exceeding 80 to 100°C) sandstone reservoirs due to a paucity of clay grade material (<0·5%) to form complete grain coats. In contrast, chlorite‐enriched tidal bars and dunes in the inner estuary, with their well‐developed detrital clay coats, are likely to have quartz cement inhibiting authigenic clay coats in deeply‐buried sandstones.

A COMPARATIVE MINERALOGICAL STUDY OF SOME SOILS FORMED UNDER VARYING CLIMATIC CONDITIONS FROM NORTHERN IRAQ

To determine factors controlling abundance and distribution pattern of clay minerals, four soil pedons derived from calcareous sedimentary parent rocks in Northern Iraq were investigated. Results revealed that the regional variation in annual rainfall plays a major role in determining amounts and distribution of clay minerals such as palygorskite,chlorite, vermiculite, smectite, illite and kaolinite. Palygorskite and smectite are available in three studied soils (Al-Khuder, Tel-Auskuf and Sumeel) with average annual precipitation of around 250 mm, 350 mm and 480 mm respectively, but these minerals are totally disappear in Batofa profile (Annual rainfall around 800mm).However vermiculite illite and kaolinite are the dominated clay minerals in Batofa soil.XRD analysis was detected a small amounts of random interstratified layer silicate minerals.Biotite-vermiculite mixed layers were found in Batofa soil,but in Al-Khuder soil an increasing amounts of (chlorite - smectite) mixed layer was detected while in Tel-Auskuf soils it appears that (chlorite-vermiculite) is the dominated mixed layer and (chlorite-smectite) is available at Sumeel soil. The general variations in clay minerals content and distributions in different soil locations can be attributed mainly to weathering conditions and mineral transformation. Palygorskite is considered to be inherited in soils of arid regions with gypsum content and limited annual rainfall, whereas illite, vermiculite and kaolinite occurs in soils with high annual rainfall.

Mineralogical Composition of Particle-Size Fractions of Solonetzes from the North Crimean Lowland

Data on the mineralogical composition of clay ( 10 μm) fractions of meadow solonchakous solonetzes (Calcic Gypsic Salic Stagnic Solonetz (Albic, Siltic, Columnic, Cutanic, Differentic)) developing from loesslike loam and clay in the North Crimean Lowland are presented. Fractions >5 μm constitute nearly 50% of the soil mass and are characterized by the same mineralogical composition in the entire profile; they consist of quartz, plagioclases, potassium feldspars, and micas (biotite and muscovite). The eluvial-illuvial redistribution of clay in the course of solonetzic process is accompanied by changes in the portion of mixed-layer minerals and hydromicas in the upper part of the profile; a larger part of the smectitic phase is transformed into the superdisperse state. In the eluvial SEL horizon and in the illuvial BSN horizon, the clay fraction is impoverished in smectitic phase and enriched in trioctahedral hydromicas. Upon calculation of the content of clay minerals per bulk soil mass, the distribution of mixed-layer minerals is either eluvial, or eluvial-illuvial, whereas the distribution of hydromicas has an illuvial pattern without distinct eluvial minimum in the SEL horizons. The eluvial-illuvial distribution pattern of clay minerals in solonetzes of the North Crimean Lowland is compared with the distribution pattern of clay minerals in solonetzes of the West Siberian Lowland. Coefficients characterizing differentiation of solonetzes by the contents of particular mineral components are suggested.

Clay mineral distributions in surface sediments of the Liaodong Bay, Bohai Sea and surrounding river sediments: Sources and transport patterns

Clay mineralogy of surface sediments throughout the Liaodong Bay and surrounding fluvial samples has been analyzed in order to reveal sources and spatial transport patterns of the detrital fine-grained sediments. Four characteristic end-members in clay compositions were observed from four major provenances, respectively: high content of smectite and scarce chlorite from northern rivers, and Luan River, high illite and low smectite from southern rivers, highest content of illite from eastern rivers, mediate content from western rivers. The sources and distribution patterns of clay minerals are closely related to river inputs, the regional currents, and tide systems. The clays covered in the southwest (SW zone) are primarily supplied by the Luan River and the Liugu River. While the clays in the northern Liaodong Bay (North Zone) derived from the northern rivers seem to be transported mainly via the surface currents. The clay minerals in the southeast (SE zone) sourced from the Laotieshan passage are attributed to the northward residual currents. Furthermore, the materials resulted from bedrocks erosion may bring a few clay minerals.

Distribution and dispersal pattern of clay minerals in surface sediments, eastern Beibu Gulf, South China Sea

Clay minerology of sediments are useful in determining distribution, sources and dispersal routes of fine-grained sediments. In the present paper, clay minerals of surface sediments throughout the eastern part of Beibu Gulf has been investigated to reveal sources and transport of detrital finegrained sediments. Four distinct clay mineral suites were observed from cluster analysis of clay mineral compositions of the samples. From the distribution pattern of clay minerals, we conclude that kaolinte in the eastern gulf is mainly derived from South China Landmass; Smectite could not be transported mainly by surface current from north-western Hainan Island, and maybe minor portion of it from Red River; Illite is mainly transported by the currents from South China Sea. Chlorite has two sources, namely South China Sea and South China Landmass. The Zhujiang River derived sediments could not be one of the sources for the clay mineral here, because of very different composition and ratios. The distribution pattern of clay minerals in the eastern Beibu Gulf is mainly controlled by fine-grained sediment source and local currents. The Silt/Clay, Smectite/Kaolinte, and Smetite/(Chlorite+Illite) ratios could be used as indicators of fine-grained sediment dispersal in the gulf.

DISTRIBUTION PATTERN AND ASSEMBLAGE FEATURE OF CLAY MINERALS IN SURFACE SEDIMENTS FROM THE COASTAL AREA OF SHANDONG PENINSULA

By analyzing the clay minerals in 200samples of surface sediments from the Coastal area of Shandong Peninsula,the distribution pattern of clay minerals(illite,chlorite,smectite,and kaolinite)was constructed.Results show that illite is the dominant clay mineral(61%),followed by smectite(16%),chlorite(13%),and kaolinite(10%).There are two areas in accordance with clay minerals assemblage.The first one,characterized by illite-smectite-chlorite-kaolinite assemblage and extensively distributed in the north,east and southeast offshore areas,was defined as the area dominated by the Huanghe-derived sediments.The other one located at the southern offshore area and characterized by a clay minerals assemblage of kaolinite-illite-smectite-chlorite or illite-kaolinite-smectite-chlorite,was defined as the area with Peninsula-source sediments dominating.The distribution pattern and assemblage features of clay minerals indicate that the transport and dispersal processes of sediments around the Shandong Peninsula were strongly controlled by the near shore circle currents.

Sea level induced variations in clay mineral composition in the southwestern South China Sea over the past 17,000 yr

Variations in clay mineral composition of sediment cores from the margin and continental slope of the Sunda Shelf (southern South China Sea, SE Asia) covering the past 17,000 yr reflect changing influences of sediment sources together with clay mineral partitioning processes in shallow waters. We identify the deglacial sea level rise as the principal factor driving these changes. During the late glacial, high values of kaolinite are interpreted to reflect a higher contribution of clays from soils that have formed on the exposed Sunda Shelf and in the southern archipelagos of Indonesia. At this time core sites were located in close proximity to the mouths of the Sunda Shelf palaeo-drainage systems on the emerged shelf (“Sundaland”). The progressive landward displacement of the coastline and breakdown of these vast drainage systems during deglaciation led to a decrease in influence of the kaolinite-rich southern sources. When the coastline had retreated closely to its present-day position in mid-Holocene times, the former dominance of southern sources was replaced by a stronger influence of illite-rich sources (e.g. Borneo). The overriding control of sea level changes on the clay mineral distribution patterns precludes a definite climatic interpretation of clay mineral data in terms of climatic/monsoonal changes in such highly dynamic sedimentary environment.

Clay-mineral distribution patterns in late Neogene fluvial sediments of the Subathu sub-basin, central sector of Himalayan foreland basin: implications for provenance and climate

The late Neogene (6–0.5 Ma) fluvial succession of the Subathu sub-basin, a part of the Himalayan foreland basin, comprises a 2.4-km-thick pile of conglomerate, grey and buff sandstone, and mudstone, representing Middle and Upper Siwalik subgroup. This basin is filled mainly by major trunk and piedmont drainage, which are nearly perpendicular to each other. The clay-mineral assemblages of this sedimentary succession have illite (7–82%), smectite (0–90%), chlorite (2–23%) and kaolinite (1–13%). The grey sandstones have moderate to abundant smectite (23–90%), whereas the buff sandstones have abundant illite (66–79%) and low to absent smectite (0–14%). The mudstones that dominates the succession (>50%) have clay-mineral assemblages similar to grey and buff sandstones, or intermediate proportion. The temporal distribution of clay minerals in mudstones shows occasional intense zigzag pattern with either smectite (3–81%) or illite (15–82%) abundance. The smectite-rich grey sandstones and mudstones are deposited by trunk drainage, and the illite-rich buff sandstones and mudstones are deposited by piedmont drainage. The intense zigzag distribution pattern of clay minerals in mudstone indicates interfingering of floods from trunk and piedmont drainages. The interfingering was severe, ranging between 4.8 and 3.36 Ma and between 2.60 and 1.77 Ma, related to tectonic activity. The association of smectite (>36%) bearing mudstones and piedmont source-derived buff sandstone and conglomerate towards the upper part of the section (above 1.77 Ma) suggests either floodwater of trunk drainage over spill on the fringe of piedmont alluvial fan or derivation from smectite bearing Middle Siwalik rocks, exposed due to the activity of an intra-foreland thrust (IFT) in the piedmont zone. The occurrence of smectite and its variable proportion with time suggests its probable derivation not only from the sparsely exposed basic rock in the catchment area but also from siliceous and metamorphic rocks under favourable climatic conditions between 6 and 0.5 Ma.

Clay mineral distributions in the continental shelf sediments between the Ganges mouths and Madras, east coast of India

Clay minerals have been determined in samples of shelf sediments along the east coast of India between the Mahanadi River in the north and Madras in the south. The data have been collated with published clay mineralogy of the east coast shelf sediments, and fluvial and estuarine sediments of the adjacent rivers to evaluate the clay mineral distribution patterns in the shelf visávis clay mineral provenance. Trends in the relative proportions of the clay minerals define three major clay mineral provinces along the shelf from north to south: the Himalayan, Eastern Ghats and Deccan Provinces. The Himalayan Province is characterized by abundant illite followed by chlorite, and the Deccan Province by abundant smectite from the Deccan basalts. The Eastern Ghats Province is mixed, the northern region being dominated by illite and kaolinite and the southern region by smectite and illite. The Eastern Ghats Province is not represented in the clay assemblages from the deep Bay of Bengal, while the other two are. Chlorite is virtually absent in the fluvial sediments of the Peninsular rivers and its presence in the adjacent shelf sediments is attributed to three sources: (a) southerly transport of chlorite-rich Ganges sediments over the shelf in suspension, (b) advection of the Ganges-derived suspended solids from east to west across the Bay of Bengal, and (c) reworking of Pleistocene and early Holocene sediments in the shelf. The present study suggests that the clay mineralogy of the distal Bengal Fan is controlled by the relative rates of sediment supply from Himalayan and Deccan sources. The chlorite-rich sediments in the distal fan are derived primarily from the former source and the smectite-rich sediments primarily from the latter source.

Sediments in Arctic sea ice: Implications for entrainment, transport and release

Despite the Arctic sea ice cover's recognized sensitivity to environmental change, the role of sediment inclusions in lowering ice albedo and affecting ice ablation is poorly understood. Sea ice sediment inclusions were studied in the central Arctic Ocean during the Arctic 91 expedition and in the Laptev Sea (East Siberian Arctic Region Expedition 1992). Results from these investigations are here combined with previous studies performed in major areas of ice ablation and the southern central Arctic Ocean. This study documents the regional distribution and composition of particle-laden ice, investigates and evaluates processes by which sediment is incorporated into the ice cover, and identifies transport paths and probable depositional centers for the released sediment. In April 1992, sea ice in the Laptev Sea was relatively clean. The sediment occasionally observed was distributed diffusely over the entire ice column, forming turbid ice. Observations indicate that frazil and anchor ice formation occurring in a large coastal polynya provide a main mechanism for sediment entrainment. In the central Arctic Ocean sediments are concentrated in layers within or at the surface of ice floes due to melting and refreezing processes. The surface sediment accumulation in central Arctic multi-year sea ice exceeds by far the amounts observed in first-year ice from the Laptev Sea in April 1992. Sea ice sediments are generally fine grained, although coarse sediments and stones up to 5 cm in diameter are observed. Component analysis indicates that quartz and clay minerals are the main terrigenous sediment particles. The biogenous components, namely shells of pelecypods and benthic foraminiferal tests, point to a shallow, benthic, marine source area. Apparently, sediment inclusions were resuspended from shelf areas before and incorporated into the sea ice by suspension freezing. Clay mineralogy of ice-rafted sediments provides information on potential source areas. A smectite maximum in sea ice sediment samples repeatedly occurred between 81°N and 83°N along the Arctic 91 transect, indicating a rather stable and narrow smectite rich ice drift stream of the Transpolar Drift. The smectite concentrations are comparable to those found in both Laptev Sea shelf sediments and anchor ice sediments, pointing to this sea as a potential source area for sea ice sediments. In the central Arctic Ocean sea ice clay mineralogy is significantly different from deep-sea clay mineral distribution patterns. The contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms.

Clay mineral and heavy metal distributions in the northeastern North Sea

Clay mineralogy and heavy metal distribution of surface sediments of the northeastern North Sea have been analysed in order to show the origin and transport pathways of fine-grained sediments. The distribution patterns of clay minerals largely reflect regional current patterns. Fine material enriched in smectite, derived mostly from the German Bight sector in the south, is transported by the Jutland current parallel to the west coast of Denmark into the Skagerrak, where a decreasing proportion of smectite indicates the increasing influence of the central and northern North Sea currents. Illite and chlorite have identical distribution patterns in the northeastern North Sea which suggests a common origin for both clay minerals. This origin is located in Pleistocene relict sediments of the northern North Sea rather than in a contribution from the North Atlantic. Zinc, cadmium, copper and lead in surface sediments of the North Sea, when compared to background values, are significantly enriched. Sediments of the Inner German Bight are in comparison with other North Sea sediments highly polluted. A zone of high heavy metal contents (Zn, Cd and Cu) is found along the German and Danish coasts comparable to the smectite distribution indicating the transport of fine-grained polluted sediments to the north. Further to the north these sediments are diluted by less polluted sediments. Finally in the Skagerrak and the Norwegian Trench a relatively low stage of pollution is reached.

DISTRIBUTION OF CLAY MINERALS IN SELECTED OKLAHOMA SOILS

We quantified the distribution patterns of clay minerals in the coarse (2.0 to 0.2 micrometer) and fine clay fractions of six Oklahoma “Benchmark soils” that vary in climate and geology. The contents of the different clay minerals are needed of the fine and coarse fractions for these soils to obtain a better understanding of crusting, shrinkswell, and other physical and chemical properties of Oklahoma soils. Alkali-soluble amorphous materials from the deferrated clays were not found in large amounts in any of the soils studied. These small amounts of amorphous clays have Si and Al composition similar to montmorillonite. Micaceous minerals were the major clay minerals in the coarse and fine clay fractions of the underlying weathered shales. Montmorillonite dominated the fine clay fractions of all the soils. It was also the major clay mineral in the coarse clay fractions of the soils obtained from subhumid, semiarid areas of Oklahoma. The kaolinite content was high in soils of eastern Oklahoma, which receives more precipitation. Kaolinite, however, was lower in the coarse clay fractions of the A horizons in these soils. Quartz was found in relatively larger amounts in the coarse clay fractions of the A horizons of the highly developed soils in eastern Oklahoma. Vermiculite and chlorite were not found in appreciable amounts in any of the soils studied. The Dennis and Bernow soils contain large amounts of interlayered clay minerals that appear to be common to many Oklahoma soils.

Clay mineral distribution patterns as influenced by depositional processes in the Southeastern Levantine Sea

ABSTRACTAnalysis of the clay minerals in stratigraphically defined cores (23,000 years BP to the present) in the southeastern Levantine‐Nile Cone sector of the eastern Mediterranean indicates that depositional processes are very significant in determining the distribution of clay assemblages. The interplay of long‐distance transport by water mass circulation, downslope mass gravity transport and wind dispersal is recorded by the clay assemblages in each of the stratigraphic layers. The temporal variations and spatial distribution of smectite, the dominant clay mineral of the River Nile, can be related closely to downslope gravity‐related processes and to deposition from water mass flow. Increased kaolinite, in part of wind‐blown origin from North Africa, correlates with areas receiving low terrigenous input but influenced by enhanced suspended sediment transport. Illite and chlorite distributions are most closely associated with a northern Levantine provenance and dispersal by the circulation of eastern Mediterranean water masses. Climatically induced changes may have altered the clay minerals in the region and minor diagenetic changes may have occurred, but these factors do not fully explain observed vertical clay mineral changes in the Late Quaternary. We conclude that palaeoclimatic interpretations based on vertical clay mineralogical changes at single core localities should be approached cautiously in small ocean basins such as the Mediterranean.

Provenance and Diagenesis of Clay Minerals in Sediments from Anclote River and Anchorage, West-Central Florida: ABSTRACT

Surface and subsurface sediments from a small river basin and lagoon (the Anclote River system in west-central Florida) were examined by X-ray diffraction methods to reveal the factors controlling clay minerals distribution in paludal (swamp), fluviatile, estuarine, and nearshore marine environments. In the swamp environment, smectite is the predominant clay mineral in surface sediments. Relative concentration and crystallinity of smectite increase with a corresponding decrease in kaolin minerals (including kaolinite, halloysite, and kaolinite-montmorillonite mixed-layer) from the surface down the cores indicating kaolinization is prevalent in the upper swampy sediments. In the fluviatile environment, clay minerals in surface sediments are transported from upper stream swamps and mixed with the residual clays of the bed rock. Subsurface clay minerals in the Tampa Limestone are mainly illite with minor amounts of smectite. In downstream estuarine surface sediments, smectite decreases while chlorite, chlorite-vermiculite mixed layer, and illite increase. This change results from the combined effects of tidal inflow and transport by the river as indicated by the study of suspended sediments in this area. The relatively high concentration of smectite in the subsurface sediments of the lower Anclote River, an estuarine environment, suggests that the distribution pattern of clay minerals in this area may have been affected by the lower stand of sea level during the last glacial period. Clay mineral assemblages in the Anclote Anchorage are a combination of residual sedimentary clays mixed with river-borne and marine clays. The uniformly distributed clays indicated a mixed and reworked environment (by current and wave) rather than one formed by a uniform, single source. End_of_Article - Last_Page 1683------------

Clay-Mineral Distribution in Recent Sediments from Northern Pacific Coast of Mexico: ABSTRACT

The clay-mineral composition of 86 samples from the Northern Pacific coast of Mexico was identified and the relative abundance of each clay mineral was obtained. The known minus 2µ fraction was analyzed in oriented aggregates using X-ray diffraction. Prior to X-ray, the samples were freed of carbonates, organic End_Page 637------------------------------ matter, iron oxides, and colloidal silica and alumina. Montmorillonite, illite, and chlorite were found to be the most abundant clay minerals. Kaolinite and vermiculite were present in some samples, usually in minor amounts. The distribution patterns of clay minerals in the lower Gulf of California are determined by the source areas and strong diagenetic effects ensuing on contact with sea water. The clay-mineral distribution shows a sharp contrast in clay-mineral assemblages between the marine and non-marine sediments. The montmorillonite, illite, and chlorite content of the normal marine samples is very uniform. In the warmer hypersaline environment of the swamps, formed in the depressions between cheniers, the clay-mineral assemblages have greater proportions of chlorite, indicating that intense chemical conditions behind cheniers are particularly effective in modifying the composition and structure of the clays entering the sea from rivers. The clay mineralogy of the terrestrial samples is controlled by the source material and the weathering conditions of the area. In both terrestrial and marine environments, anomalous clay-mineral assemblages reflect small-scale or local geographic conditions (provenance). End_of_Article - Last_Page 638------------