Abstract

Isotopic analyses of carbon and strontium in diagenetic dolomite and ankerite present in the eolian Lower Permian Rotliegend Sandstone, southern North Sea, show an excellent linear correlation between δ13C and 87Sr/86Sr (r = 0.93), suggesting that the sources of these elements were interlinked. The isotopic data indicate that Late Permian Zechstein seas flooded the basin and displaced the interstitial meteoric Rotliegend pore fluids, producing early dolomite with predominantly marine bicarbonate (δ13C = -15‰) and strontium (87Sr/86Sr = 0.7076) isotopic signatures. The isotopic values of this dolomite form a trend to merge with the diageneticafly later ankerite, which has lower 13C/12C (δ13C = -4‰) and more radiogenic strontium (87Sr/86Sr = 0.7112). The obvious source of low-δ13C carbon was thermal decarboxylation of organic matter in the underlying Upper Carboniferous mudstones. We also suggest that the increasing quantities of radiogenic strontium (87Sr/86 = 0.720) were released when organic acids dissolved silicates (feldspar?) in the same underlying mudstones. The upward movement of fluid or diffusion of ions across formation boundaries, therefore, progressively became the dominant control on carbonate precipitation in the Rotliegend Sandstone.

First Page Preview

First page PDF preview
You do not currently have access to this article.