Palaeoenvironmental significance of clay minerals in Upper Cenomanian–Turonian sediments of the Western High Atlas Basin (Morocco)

Clay Minerals ◽  
2008 ◽  
Vol 43 (4) ◽  
pp. 615-630 ◽  
Author(s):  
L. Daoudi ◽  
F. Rocha ◽  
B. Ouajhain ◽  
J. L. Dinis ◽  
D. Chafiki ◽  
...  
Keyword(s):  
Sea Level ◽  
Clay Mineral ◽  
Mixed Layer ◽  
Black Shales ◽  
High Atlas ◽  
Mineral Assemblages ◽  
Differential Settling ◽  
Vertical Evolution ◽  
Layer I ◽  
Depth Of Burial

AbstractUpper Cenomanian–Turonian clay mineral assemblages of sediments cropping out in the Western High Atlas basin are studied in four sections. Smectite and mixed-layer illite-smectite (I-S) have been identified as major constituents of the deposits. The composition of clay associations in black shales and associated sediments varies considerably according to age, but usually depends either on the general lithology, the abundance of organic matter, or the depth of burial. A distinct correlation is evident between clay mineral distribution and sea-level. Smectite and mixed-layer I-S with greater percentages of smectite layers increase in sediments deposited during transgressive periods, whereas they decrease progressively in the shallower facies deposited during regression in favour of illite and mixed-layer I-S with a greater percentage of illite. The vertical evolution and lateral distribution of clay assemblages and their relationships with sea-level as well as the palaeogeographic conditions prevailing during the Late Cenomanian–Turonian period (flattened topography and arid climate), indicate a detrital origin of the smectite minerals and a distribution pattern controlled by differential settling processes.

Jurassic clay mineral assemblages and their post-depositional alteration: upper Great Estuarine Group, Scotland

1987 ◽  
Vol 124 (3) ◽  
pp. 261-271 ◽  
Author(s):  
Julian E. Andrews
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Mixed Layer ◽  
Middle Jurassic ◽  
Water Circulation ◽  
Hot Water ◽  
Geothermal Gradients ◽  
Fine Grained ◽  
Igneous Intrusions ◽  
Mineral Assemblages

AbstractClay minerals from Middle Jurassic lagoonal mudrocks, siltstones and silty fine-grained sandstones of the upper Great Estuarine Group (Bathonian) are divided into four assemblages. Assemblage 1, the most common assemblage, is rich in mixed-layer illite–smectite with attendant illite and kaolinite. Assemblage 2 is dominated by smectitic clay. These assemblages are indicative of primary Jurassic deposition. Illite and kaolinite were probably derived from the weathering of older rocks and soils in the basin hinterland and were deposited in the lagoons as river-borne detritus. The majority of smectite and mixed-layer illite–smectite is interpreted as the argillization product of Jurassic volcanic dust, also deposited in the lagoons by rivers. Near major Tertiary igneous intrusions these depositional clay mineral assemblages have been altered. Assemblage 3 contains smectite-poor mixed-layer illite–smectite, whilst Assemblage 4 contains no smectitic clay at all. Destruction of smectite interlayers occurred at relatively shallow burial depths (< 2500 m) due to enhanced geothermal gradients and local convective hot-water circulation cells associated with the major Tertiary igneous intrusions.

scholarly journals Clay diagenesis and low-grade metamorphism of Tithonian and Berriasian sediments in the Cameros Basin (Spain)

Clay Minerals ◽  
2001 ◽  
Vol 36 (3) ◽  
pp. 325-333 ◽  
Author(s):  
J. F. Barrenechea ◽  
M. Rodas ◽  
M. Frey ◽  
J. Alonso-Azcárate ◽  
J. R. Mas
Keyword(s):  
Clay Mineral ◽  
Mixed Layer ◽  
Sedimentary Facies ◽  
Metamorphic Grade ◽  
Metamorphic Event ◽  
Low Grade ◽  
Grade Metamorphism ◽  
Mineral Assemblages ◽  
Cameros Basin ◽  
Southern Border

AbstractThe clay mineral assemblages of the Tithonian and Berriasian sediments (Tera and Oncala Groups) in the eastern part of the Cameros basin are investigated at seven localities. The lowest-grade assemblage, located on the southern border of the basin, contains calcite + quartz + hematite + kaolinite + mixed-layer illite-smectite (R = 1, 65 85% illite layers) + discrete illite (IC = 0.5 0.65Δ°2θ). Systematic increases in the illite and chlorite crystallinities suggest increasing metamorphic grade from the northwest part of the basin to the southeast. This trend does not follow the pattern previously described for the overlying late Berriasian–early Aptian sediments (Urbión and Enciso Groups), which exhibit a higher metamorphic grade. This may result from local variations in sedimentary facies, as well as the circulation of hot migratory fluids. Tertiary compression occurring long after the main metamorphic event is considered to be responsible for the enhanced illite and chlorite crystallinities measured in the SE extreme of the basin.

Palaeogeographic Significance of Clay Mineral Distributions in the Inferior Oolite Group (Mid Jurassic) of Southern England

Clay Minerals ◽  
1989 ◽  
Vol 24 (1) ◽  
pp. 91-105 ◽  
Author(s):  
L. E. Jones ◽  
B. W. Sellwood
Keyword(s):  
Shallow Water ◽  
Clay Mineral ◽  
Mixed Layer ◽  
Southern England ◽  
Mineral Assemblages ◽  
Platform Carbonates ◽  
Basinal Facies

AbstractFive areally distinct mineral assemblages are recognized in the Inferior Oolite of S. England. In each area, vertical (stratigraphic) variations are insignificant. The five assemblages comprise varying proportions of illite, illite-smectite, kaolinite, chlorite and kaolinite-smectite, the mixed-layer clays being largely poorly crystalline and randomly interstratified. A predominantly detrital rather than authigenic origin is suggested for most of the clays. Shallow-water platform carbonates contain kaolinite with illite and illite-smectite. Kaolinite decreases in abundance away from former mid-Jurassic land areas, the deeper shelf and more basinal facies being dominated by illite and/or illite-smectite. Possible volcanic contributions to clay suites are suggested but cannot yet be fully evaluated. The palaeogeographic usefulness of clay mineral suites is confirmed, even in carbonate-dominated systems.

Clay mineralogy of the Permo-Triassic strata of the British Isles: onshore and offshore

Clay Minerals ◽  
2006 ◽  
Vol 41 (1) ◽  
pp. 309-354 ◽  
Author(s):  
C. V. Jeans
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
North Sea ◽  
Mixed Layer ◽  
Early Stage ◽  
Regional Distribution ◽  
Clay Mineralogy ◽  
British Isles ◽  
Mineral Assemblages ◽  
Red Bed

AbstractThe regional distribution, mineralogy, petrology and chemistry of the detrital and authigenic clay minerals associated with the Permo-Triassic strata (excluding the Rotliegend: see Ziegler, 2006; this volume), of the onshore and offshore regions of the British Isles are reviewed within their stratigraphical framework. The origin of these clay minerals is discussed in relation to current hypotheses on the developments of the Mg-rich clay mineral assemblages associated with the evaporitic red-bed Germanic facies of Europe and North Africa.Composite clay mineral successions are described for seven regions of the British Isles — the Western Approaches Trough; SW England; South Midlands; Central Midlands; the Cheshire Basin; NE Yorkshire; and the Central North Sea. The detrital clay mineral assemblages of the Early Permian strata are variable, consisting of mica, smectite, smectite-mica, kaolin and chlorite, whereas those of the Late Permian and the Trias are dominated by mica, usually in association with minor Fe-rich chlorite. The detrital mica consists of a mixture of penecontemporaneous ferric mica, probably of pedogenic origin, and recycled Pre-Permian mica. In the youngest Triassic strata (Rhaetian), the detrital clay assemblages may contain appreciable amounts of poorly defined collapsible minerals (irregular mixed-layer smectite-mica-vermiculite) and kaolin, giving them a Jurassic aspect. There are two types of authigenic clay mineral assemblages. Kaolin may occur as a late-stage diagenetic mineral where the original Permo-Triassic porewaters of the sediment have been replaced by meteoritic waters. A suite of early-stage diagenetic clay minerals, many of them Mg-rich, are linked to the evaporitic red-bed facies — these include sepiolite, palygorskite, smectite, irregular mixed- layer smectite-mica and smectite-chlorite, corrensite, chlorite and glauconite (sensu lato). The sandstones and mudstones of the onshore regions of the British Isles display little or no difference in their detrital and authigenic clay mineral assemblages. In contrast, the sandstones of the offshore regions (North Sea) show major differences with the presence of extensive chloritic cements containing Mg-rich and Al-rich chlorite, irregular mixed-layer serpentine-chlorite, and mica.

Clay minerals in shales of the Lower Silurian Longmaxi Formation in the Eastern Sichuan Basin, China

Clay Minerals ◽  
2017 ◽  
Vol 52 (2) ◽  
pp. 217-233
Author(s):  
Geng Yi-Kai ◽  
Jin Zhen-Kui ◽  
Zhao Jian-Hua ◽  
Wen Xin ◽  
Zhang Zhen-Peng ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Mixed Layer ◽  
Shale Gas ◽  
Mineral Content ◽  
High Pressures ◽  
Gas Reservoirs ◽  
Longmaxi Formation ◽  
Lower Silurian ◽  
Layer I

AbstractThe present study examines the characteristics of clay minerals in shale gas reservoirs and their influence on reservoir properties based on X-ray diffraction and scanning electron microscopy. These analyses were combined with optical microscopy observations and core and well-log data to investigate the genesis, distribution characteristics, main controlling factors and pore features of clay minerals of the Lower Silurian Longmaxi Formation in the East Sichuan area, China. The clay mineral assemblage consists of illite + mixed-layer illite-smectite (I-S) + chlorite. This assemblage includes three sources of clay minerals: detrital, authigenic and diagenetic minerals. The lower section of the Longmaxi Formation in the Jiaoshiba area has sealing ability which resulted in abnormal high pressures during hydrocarbon generation which inhibited illitization. Therefore, an anomalous transformation sequence is present in which the mixed-layer I-S content increases with depth. This anomalous transformation sequence can be used to infer the existence of abnormal high pressures. The detrital components of the formation also affect the clay-minerals content indirectly, especially the abundance of K-feldspar. The transformation of mixed-layer I-S to illite is limited due to the limited availability of K+, which determines the extent of transformation. Three types of pores were observed in the shale reservoir rocks of the Longmaxi Formation: interparticle (interP) pores, intraparticle (intraP) pores and organic-matter pores. The clay-mineral content controls the development of intraP pores, which are dominated by pores within clay particles. For a given clay mineral content, smectite and mixed-layer I-S were more conducive to the development of shale-gas reservoirs than other clay minerals.

Clay mineralogy of the Jurassic strata of the British Isles

Clay Minerals ◽  
2006 ◽  
Vol 41 (1) ◽  
pp. 187-307 ◽  
Author(s):  
C. V. Jeans
Keyword(s):  
Clay Mineral ◽  
North Sea ◽  
Mixed Layer ◽  
Clay Mineralogy ◽  
List Type ◽  
British Isles ◽  
Southern England ◽  
The North ◽  
Wide Range ◽  
Mineral Assemblages

AbstractThe nature and origin of the clay mineralogy of the Jurassic strata of the British Isles are described and discussed within their lithological and biostratigraphical framework using published and unpublished sources as well as 1800 new clay mineral analyses. Regional clay mineral variation is described systematically for the following formations or groups:England and Wales(i)Hettangian-Toarcian strata (Lias Group): Redcar Mudstone Fm.; Staithes Sandstone Fm.; Cleveland Ironstone Fm.; Whitby Mudstone Fm.; Scunthorpe Mudstone Fm.; Blue Lias Fm.; Charmouth Mudstone Fm.; Marlstone Rock Fm.; Dyrham Fm.; Beacon Limestone Fm.; Bridport Sand Fm.(ii)Aalenian-Bajocian (Inferior Oolite Group): Dogger Fm.; Saltwick Fm.; Eller Beck Fm.; Cloughton Fm.; Scarborough Fm.; Scalby Fm. (in part); Northampton Sand Fm.; Grantham Fm.; Lincolnshire Limestone Fm.; Rutland Fm. (in part); Inferior Oolite of southern England.(iii)Bathonian (Great Oolite Group): Scalby Fm. (in part); Rutland Fm. (in part); Blisworth Limestone Fm.; Great Oolite Group of southern England; Forest Marble Fm.; Cornbrash Fm. (in part).(iv)Callovian-Oxfordian: Cornbrash Fm. (in part); Kellaways Fm.; Oxford Clay Fm.; Corallian Beds and West Walton Beds; Ampthill Clay Fm.(v)Kimmeridgian-Tithonian: Kimmeridge Clay Fm.; Portland Sandstone Fm.; Portland Limestone Fm.; Lulworth Fm.; Spilsby Sandstone Fm. (in part). Scotland(vi)Hettangian-Toarcian: Broadfoot Beds, Dunrobin Bay Fm. Aalenian-Portlandian: Great Estuarine Group (Dunkulm, Kilmaluag and Studiburgh Fm.s); Staffin Shale Fm.; Brora Coal Fm.; Brora Argillaceous Fm.; Balintore Fm.; Helmsdale Boulder Beds (Kimmeridge Clay Fm.).Dominating the Jurassic successions are the great marine mudstone formations — the Lias Group, Oxford Clay, Ampthill Clay and Kimmeridge Clay. These are typically characterized by a detrital clay mineral assemblage of mica, kaolin and poorly defined mixed-layer smectite-mica-vermiculite minerals with traces of chlorite. Detailed evidence suggests that this assemblage is derived ultimately from weathered Palaeozoic sediments and metasediments either directly or by being recycled from earlier Mesozoic sediments. A potassium-bearing clay is a persistent component and formed at approximately the same time as the deposition of the host sediment, either in coeval soils or during very early diagenesis.At three periods during the deposition of the Jurassic (Bajocian-Bathonian, Oxfordian and late Kimmeridgian-Tithonian), the detrital clay assemblage was completely or partially replaced by authigenic clay mineral assemblages rich in kaolin, berthierine, glauconite or smectite minerals. Associated with these changes are major changes in the lithofacies, with the incoming of non-marine and proximal marine strata. The authigenic clay assemblages rich in kaolin and berthierine are generally restricted to the non-marine and very proximal marine beds, those rich in glauconite or smectite are typical of the marine lithofacies. Clay mineral assemblages containing vermiculite and mixed-layer vermiculite-chlorite sometimes occur in the non-marine and proximal marine facies. The causes of these major changes in lithofacies and clay mineralogy are discussed, and present evidence favours an important volcanogenic influence and not climatic control. It is suggested that the Bajocian-Bathonian, Oxfordian and Late Kimmeridgian-Tithonian were periods of enhanced volcanic activity, with centres probably located in the North Sea and linked to regional tectonic changes which caused major modifications of the palaeogeography of the British Isles. The most important of these changes was the development of the central North Sea Rift Dome during the Bajocian and Bathonian. Volcanic ash was widespread in both the non-marine and marine environments and its argillization under different conditions provided the wide range of authigenic clay mineral assemblages.Metre-scale clay mineral cyclicity is widespread in most of the Jurassic mudstone formations that have been examined in sufficient detail. The cyclicity is defined by systematic variations in the mica/ collapsible minerals (mixed-layer smectite-mica-vermiculite) ratio. This variation is unrelated to changes in lithology and its possible origins are discussed in detail using data from the Kimmeridge Clay provided by Reading University's contribution to the Rapid Global Geological Events (RGGE) Project.

A record of the Jurassic/Cretaceous boundary climatic variation on the southern margin of the Tethys : clay minerals and palynofacies of the early Cretaceous Jebel Meloussi section (Central Tunisia, Sidi Kralif Formation)

2005 ◽  
Vol 176 (2) ◽  
pp. 171-182 ◽  
Author(s):  
Johann Schnyder ◽  
Georges Gorin ◽  
Mohamed Soussi ◽  
François Baudin ◽  
Jean-François Deconinck
Keyword(s):  
Climatic Change ◽  
Sea Level ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Climatic Variation ◽  
Northern Margin ◽  
Sequence Stratigraphic ◽  
Central Tunisia ◽  
Mineral Assemblages

Abstract In order to precise the paleogeographic extension of the climatic variation known at the Jurassic/Cretaceous boundary, the sedimentary organic matter (palynofacies and Rock-Eval) and the clay minerals content of Berriasian sediments of the Sidi Kralif Formation are studied on the Jebel Meloussi section, central Tunisia. Standard sedimentological and palynofacies analysis allow to reconstruct the bathymetric curve and the sequence stratigraphic scheme. Using existing biostratigraphy based on calpionellids and ammonite zonation, the sequence stratigraphic interpretation can be correlated with the established eustatic chart. Clay mineral assemblages are characterized by a shift in the kaolinite content, recorded at the end of the calpionellid zone B, at the early/middle Berriasian boundary, at a time of high long-term sea-level (MFS Be2, second order eustatic peak). A contemporary change in the clay mineral assemblages, interpreted as a climatic change, is known from the boreal area, and from the northern margin of the Tethys Sea. That change is also documented southerly in southern Morocco (Agadir area), on the Atlantic domain. A late Tithonian to early Berriasian dry and cooler phase is replaced by a middle to late Berriasian more humid phase, indicated by a general increase in kaolinite in the clay mineral assemblages. The trend from a dry climatic phase to a more humid one, recorded on the boreal domain and along the northern margin of the Tethys is also recorded in lower paleolatitudes of Tunisia, on the southern margin of the Tethys, in better dated outcrops than the ones of Morocco. The results obtained in Tunisia show that the beginning of the climatic change was precisely synchronous on both margins, and occurred within the same long-term high sea-level context.

The origin of the Triassic clay assemblages of Europe with special reference to the Keuper Marl and Rhaetic of parts of England

1978 ◽  
Vol 289 (1365) ◽  
pp. 549-636 ◽  
Keyword(s):  
Special Reference ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Mixed Layer ◽  
North Africa ◽  
Western Europe ◽  
Water Masses ◽  
Mineral Assemblages

Hypotheses are reviewed on the origin of the magnesium-rich Triassic clays which characterize the Germanic facies of western Europe and north Africa. Relations between clay minerals, megafacies and stratigraphy are described from 28 localities in the Triassic Keuper Marl, Tea Green Marl and Rhaetic sediments of England. Two clay mineral assemblages are recognized: (1) a detrital assemblage of mica with minor chlorite which occurs throughout all the sediments investigated, and (2) a neoformed assemblage of magnesium-rich clay minerals with a limited occurrence related to certain megafacies cycles which resulted from the transgression and regression of the Alpine facies into the Germanic facies; this assemblage includes sepiolite, palygorskite, chlorite, smectite, corrensite and irregular mixed-layer smectite/mica and smectite/chlorite minerals. The clay mineral neoformations resulted from reactions between the water masses in which the Germanic and Alpine facies were deposited. Controlling the distribution and types of minerals neoformed were the general and local variations in the chemistries of the Alpine and Germanic water masses, as well as competition for available magnesium from other mineral-forming reactions.

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