The induration of Upper Cretaceous Yorkshire and Irish chalks

Geochemical and stable isotope patterns of calcite cementation in the Upper Cretaceous Chalk, Uk: Direct evidence from calcite-filled vugs in brachiopods

“…The role of the increasing deformation on the hardness and composition of the Middle (Turonian) and Upper ('Senonian') Chalk associated with post-Cretaceous steep, asymmetrical east-west folding in southern England (Surrey; Isle of Wight; Dorset) and Yorkshire has been investigated by Mimran (1975Mimran ( , 1977Mimran ( , 1978, making comparison to his own findings (ideas) on the unfolded chalk of Northern Ireland (Mimran 1978) which differ significantly from those of Wolfe (1968) and Scholle (1974). Mimran (1977Mimran ( , 1978 modelled the effects of increasing deformation using measurements of acid insoluble residue, bulk specific gravity (intact dry density), concentration and distortion of calcispheres (assumed to be originally spherical in form), values of various elements (Sr, Mg, Ti, Ba), and stable isotopes (δ 18 O, δ 13 C) in bulk chalk calcite, and microfabric analysis.…”

“…The exceptionally hard chalks of Northern Ireland overlain by a thick basalt pile were a topic of much interest -ideas ranged from baking by the volcanic pile to the possibility that the Irish Chalk had a higher proportion of aragonite in the original sediment (Hancock 1963). In Yorkshire and southwest England, the association of faulting and high dips was thought to be related to the general hardening (Mimran 1977(Mimran , 1978.…”

“…Mimran (1977Mimran ( , 1978 modelled the effects of increasing deformation using measurements of acid insoluble residue, bulk specific gravity (intact dry density), concentration and distortion of calcispheres (assumed to be originally spherical in form), values of various elements (Sr, Mg, Ti, Ba), and stable isotopes (δ 18 O, δ 13 C) in bulk chalk calcite, and microfabric analysis. Isotope evidence suggested that the hardening process in southern England, Yorkshire and Northern Ireland all took place with porewaters of differing Sr contents but of meteoric origin.…”

Early Submarine Lithification in the Red Chalk and Lower Chalk of Eastern England: A Bacterial Control Model and Its Implications

“…The constant Fe 2+ value suggests that if the cement is either (a) autochthonous, it was precipitated out in the general vicinity of its source, or (b) allochthonous and derived from some distant source by porewater movement, the solutions precipitating cement must have produced a similar Fe 2 " 1 " content in the calcite to that of the original chalk. Scholle (1974;and in Hancock and Scholle 1975) and Mimran (1978) have considered the general causes and mechanisms for the hardening of the Yorkshire Chalk, although neither author dealt specifically with the Red Chalk or Lower Chalk. Scholle (1975) concluded from the oxygen isotope evidence that (a) the late calcite cement was autochthonous, (b) it originated from pressure dissolution of the Chalk, and (c) the cement was precipitated out of the connate pore waters of the Chalk sediment.…”

Strontium, .DELTA.18O and .DELTA.13C as palaeo-indicators of unconformities: Case of the Aleg and Abiod formations (Upper Cretaceous) in the Miskar Field, Southeastern Tunisia

“…One of the El Haria samples of Miskar W3 has carbon and oxygen isotope values comparable to those of the Abiod, whereas the other shows the lightest carbon isotope value (1.21‰) registered in all wells; this might be attributed to contamination with oil. through burial diagenesis has been demonstrated by numerous previous studies (e.g., Scholle, 1974Scholle, , 1977Mimran, 1978;Jørgensen, 1986Jørgensen, , 1987 as being a consequence of re-equilibration of the carbonate phase with the interstitial water and the imposed geothermal gradient. Jørgensen (1987) pointed out that lower δ 18 O values, generated by the temperature-induced isotopic re-equilibration of chalk with increasing depth, are highly influenced by deep-burial derived chemical processes (pressure-dissolution, precipitation of calcite cement, recrystallisation and ion-exchange).…”