An update on British Tonsteins

Spears, D. A.; Lyons, Paul C.

doi:10.1144/gsl.sp.1995.082.01.07

Cited by 8 publications

(8 citation statements)

References 34 publications

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“…However, the levels of these elements usually are very low in the Upper Carboniferous silty claystones, which implies that their parent heavy minerals are rare. However, moderate enrichments of Be, W, and Sn can be associated with tonstein horizons (Spears and Zheng, 1997;Spears and Lyons, 1995;Pearce et al, 2005a).…”

Section: U Cleavermentioning

confidence: 99%

“…Knowledge of the abundance and distribution of elements in coals is vital from an economic and environmental point of view. According to Spears and Zheng (1997), the major elements occur in the minerals rather than the organic matter, so the major-element geochemistry might provide some insight into trace-element-mineral associations in most of the UK coals. Si and Al are linked chiefly to kaolinite and illite, Ca and Mg are associated mainly with carbonate minerals, and Fe is linked to pyrite.…”

Section: Coal Chemostatigraphymentioning

confidence: 99%

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Chemostratigraphy of Upper Carboniferous (Pennsylvanian) Sequences from the Southern North Sea (United Kingdom)

Pearce¹,

Martin²,

Cooper³

et al. 2010

Application of Modern Stratigraphic TechniquesTheory and Case Histories</Subtitle>

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Important gas reservoirs occur in the Upper Carboniferous coal measures and red beds of the Southern North Sea. The thick red beds of the Boulton and Ketch formations are difficult to correlate, due to poor internal seismic definition, repetitive e-log signatures, and their barren nature. Although the underlying coal measures of the Westoe, Cleaver, and Caister Formations have better seismic resolution and contain palynomorphs, coals that die out laterally and the lack of diagnostic taxa over certain intervals contribute to their correlation being problematical. However, the application of chemostratigraphy to more than sixty wells from numerous fields in UK Quadrants 44 and 49, as well as from Dutch sector Blocks E, F, and K, allows the establishment of an independent, robust, detailed correlation framework for the aforesaid red beds and coal measures.Presented in this paper are correlative chemostratigraphic reference sections for the Caister, Westoe, Cleaver, Ketch, Boulton, and Step Graben formations. The chemostratigraphic zonations erected for these formations are based on variations in silty claystone geochemistry that can be tied to changes in provenance, climate, and depositional environment. In addition, the zonations are supported by stratigraphic changes in sandstone and coal geochemistry, the geochemical correlation of tonsteins and marine bands, and the recognition of different types of paleosol in the above formations.The chemostratigraphic correlation framework enables specific broad intervals ("packages") to be correlated between fields and is also used to constrain seismic correlations with a view to highlighting potential exploration targets. Furthermore, the same framework allows much thinner intervals ("units" and "subunits") to be correlated within fields: these smaller-scale correlations enhance reservoir correlations with respect to the development of fields such as Boulton, Schooner, Tyne, Ketch, and Topaz. In addition to using inorganic geochemical data to characterize and correlate sedimentological packages, data can also used to identify and correlate marker horizons and surfaces (tonsteins, coals, marine bands, major paleosols), which may be highly correlative low-diachrony surfaces, which greatly enhance the overall validity of the stratigraphic correlation scheme.

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Section: U Cleavermentioning

confidence: 99%

Section: Coal Chemostatigraphymentioning

confidence: 99%

Chemostratigraphy of Upper Carboniferous (Pennsylvanian) Sequences from the Southern North Sea (United Kingdom)

Pearce¹,

Martin²,

Cooper³

et al. 2010

Application of Modern Stratigraphic TechniquesTheory and Case Histories</Subtitle>

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“…Winchester & Floyd, 1977;Pearce et al 1984;Leat et al 1986), and their use has been expanded to the study of bentonites (e.g. Roberts & Merriman, 1990;Huff et al 1993;Spears & Lyons, 1995). A plot of Zr/TiO 2 against Nb/Y indicates that samples are acidic, with a rhyodacite-rhyolite-comendite/pantellerite composition (Fig.…”

Section: Composition and Origin Of The Volcanismmentioning

confidence: 99%

Identification and long-range correlation of bentonites in Turonian–Coniacian (Upper Cretaceous) chalks of northwest Europe

Wray

1999

Geol. Mag.

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A geochemical and mineralogical study of thin (2–20 cm) clay-rich beds found in Turonian–Coniacian chalks from the Anglo-Paris Basin has been undertaken. On the basis of their rare-earth element (REE) and mineralogical composition it is possible to subdivide beds into bentonites, characterized by a negative Eu anomaly and elevated smectite content, and detrital beds (characterized by a minimal or absent Eu anomaly and a greater proportion of illite). Six beds are considered to be bentonites (Glynde 1, Southerham 1, Caburn, Bridgewick 1, Lewes and Shoreham 2). Trace-element discriminant diagrams add support, as does comparison with similar studies undertaken in eastern England and northern Germany. Geochemical evidence demonstrates that the tephra was variably acidic in composition (rhyodacite–rhyolite–comendite/pantellerite), and was probably derived from crustal melting associated with initial rifting of the North Atlantic. Correlation of bentonites between the Anglo-Paris Basin, eastern England and northern Germany can be demonstrated and independently tested, establishing a tephro-event stratigraphy across northwest Europe for this period.

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“…Both groups are present in the Westphalian of the English Midlands. Representative tonstein analyses from Spears & Lyons (1995) are plotted in Fig. 5.…”

Section: Comparison With Tonsteinsmentioning

confidence: 99%

“…In the majority of tonsteins, however, clay minerals other than kaolinite are not present, and other minerals are present only in trace amounts. The volcanic origin of tonsteins has been established from ®eld relationships, mineralogy, including volcanigenic minerals, and geochemistry (reviewed in Lyons et al, 1993;Spears & Lyons, 1995). In the work of Spears & Kanaris-Sotiriou (1979), the derivation of British Westphalian tonsteins from both acid and basic ash was demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Namurian bentonites in the Pennine Basin, UK – origin and magmatic affinities

1999

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Nine Namurian clay bands retrieved from boreholes in the northern part of the Pennine Basin are, on the basis of their petrography, mineralogy and geochemistry, shown to be volcanic in origin and are therefore bentonites. The bentonites, which have a fragmental texture, are normally graded and show rare preservation of shard textures, representing vitric tuff deposits that have been altered subsequently to clay‐dominated horizons. Crystals are a minor component of the bentonites, but biotite, in particular, is concentrated at the base of the beds. A clay mineral assemblage of mixed‐layer illite–smectite with subordinate kaolinite identifies most of the samples as K‐bentonites, but kaolinite dominates two samples that can be classed as tonsteins. Temporal variation of salinity within the depositional basin is suggested to explain these different clay assemblages. The major element geochemistry of the bentonites reflects their clay mineralogy and the compositions of diagenetic minerals present, the latter including pyrite, carbonates and hydroxyapatite. Enrichment of the bentonites in some trace elements (including Ba, Sr, Pb, Cu and Ni) can be related to the presence of the diagenetic minerals, but the extent to which the elements are added from external sources as opposed to being redistributed within the ash is unclear. Immobile trace element systematics suggest a rhyodacite/dacite composition for the original ash and derivation from the collision of plates, this being supported by evidence provided by the rare earth elements (REE) in one group of samples. However, in another group of samples, variations in REE concentrations may be caused by mobility of these elements during alteration. The chemistry of the Namurian bentonites contrasts markedly with that of the local Carboniferous volcanics but is comparable, in some respects, with one group of Westphalian tonsteins, although the latter are more rhyolitic in character. It is suggested that the Namurian bentonites and the Westphalian tonsteins of acid affinities originated from volcanic activity associated with a destructive plate margin in the Variscan externides and that the observed compositional trend may reflect magma evolution possibly related to the progressive east–west closure.

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An update on British Tonsteins

Cited by 8 publications

References 34 publications

Chemostratigraphy of Upper Carboniferous (Pennsylvanian) Sequences from the Southern North Sea (United Kingdom)

Chemostratigraphy of Upper Carboniferous (Pennsylvanian) Sequences from the Southern North Sea (United Kingdom)

Identification and long-range correlation of bentonites in Turonian–Coniacian (Upper Cretaceous) chalks of northwest Europe

Namurian bentonites in the Pennine Basin, UK – origin and magmatic affinities

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