A mineralogical and geochemical study of turbidite sandstones and interbedded shales, Mam Tor, Derbyshire, UK

Abstract

Eleven shales and fourteen turbidite sandstones from the Mam Tor Beds were analysed chemically and by XRD. The ratio of kaolinite to illite plus mixed-layer clay was higher in the sandstones than in the shales, size fractions demonstrating that this ratio decreased as the grain size decreased. Shales more basinal in character than those of the Mam Tor Beds contain more illite and mixed-layer clay and less kaolinite and it is suggested that there was a lateral variation in clay mineralogy with distance from the shore line due to particle size sorting and that the character of the clay mineral fraction was retained as the turbidity current transported sediment from a nearshore environment deeper into the basin. Support for this model was obtained from the geochemistry which showed that the sandstone matrix differed compositionally from the shales. Systematic variations occurred in the turbidite sandstones but not in the shales which are therefore considered to be non-turbiditic. Only minor mineralogical changes appear to have occurred during diagenesis.

Fluvial organic carbon flux from an eroding peatland catchment, southern Pennines, UK

“…This ∼50% load is confirmed by measurement of OC contents of a range of peat samples at UNG, in which carbon contents where 50.1±1.70% (95% confidence). Characterisation of other sediment sources measured very low total carbon (TC) concentrations similar to the conclusions made by Spears and Amin (1981). Total carbon contents of 2.30±1.50% for shale, 0.17±0.07% for sandstone and 1.09 ± 0.73% for head deposits were recorded in this study.…”

Fluvial organic carbon flux from an eroding peatland catchment, southern Pennines, UK

“…* denotes that the loads have been inferred from reported organic sediment concentrations and applying 50% C rule (e.g. Francis, 1987;Worrall et al, 2003 Francis (1990) made by Spears and Amin (1981). Total carbon contents of 2.30±1.50% for shale, 0.17±0.07% for sandstone and 1.09±0.73% for head deposits were recorded in this study.…”

Liberation of selenium from alteration of the Bowland Shale Formation: evidence from the Mam Tor landslide

“…Near-surface groundwater drains down through the landslide, oxidizing the pyrite and emerging as acidic, ochre-precipitating springs (Vear & Curtis 1981;Steward & Cripps 1983;Banks et al 1996;Adams et al 2007). There have been several studies on the water chemistry, whole-rock geochemistry and mineralogy of the shales, the acidic and ferruginous water runoff, and the associated ochre and gypsum precipitates (Allen 1960;Smith et al 1967;Spears & Amin 1981;Banks et al 1996;Banks 1997;Adams et al 2007). Fe concentrations show a qualitative correlation with sulphate, suggesting that pyrite oxidation to iron oxide and sulphuric acid is occurring, and the Mam Tor waters have a pH of between 3.1 and 3.7 (Vear & Curtis 1981;Banks et al 1996;Banks 1997).…”