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Munn, Donald
(1981).
DOI: https://doi.org/10.21954/ou.ro.000100e8
Abstract
A detailed study of the porosity development in the dolomitised Lower Carboniferous Limestone of the Wirksworth area has revealed a complex diagenetic history. The massively-bedded Asbian and Brigantian micarenites and sparenites became indurated largely during the Lower Carboniferous, within the active phreatic zone (saturated groundwater zone). The very high porosities of the carbonate sediments became occluded during this phase of diagenesis, to give the characteristic limestone porosity (2-8 percent).
Dolomitisation occured prior to the late Triassic mineralisation, either at depth beneath the cover of Middle and Upper Carboniferous sediments or during the exposure of the limestone through the Edale Shales (Namurian) beneath the Zechstein Sea (Permian). Jointing has been shown to have had a primary control upon dolomitisation, although karstification, developed during the pre-Namurian exposure of the limestone, and stylolitisation were also important processes.
The dolostones consist mainly of xenotopic-hypidiotopic types showing many calcite-filled polyhedral pores, although less common xenotopic and idiotopic dolostones do occur. The completely dolomitised xenotopic dolostones are thought to represent dolomitised micarenites, whilst the less completely dolomitised hypidiotopic and idiotopic.