Petrografi och diagenes i den underkambriska lagerföljden i Skrylle, Skåne

Detta är en Magister-uppsats från Lunds universitet/Geologiska institutionen

Sammanfattning: The Lower Cambrian of Scandinavia consists mainly of light-coloured marine sandstones, with thicknesses reaching approximately 120 m in Skåne (Scania). Two drill cores from the Skrylle Quarry of west-central Skåne were investigated and documented with respect to their petrographic properties, mineral contents, and diagenetic history. The drill cores are divided into three lithofacies, and represent the entire Hardeberga Formation and some 19 m of the overlying Norretorp Formation. The sandstones from Skrylle are predominantly composed of detrital monocrystalline quartz grains and authigenic quartz overgrowths. Petrographic analyses indicate additional diagenetic processes in the form of feldspar dissolution and carbonate cementation. The present porosity is very low, but petrographic investigations show that the deposits once had good reservoir properties. The primary porosity, and partly also the secondary porosity, have been destroyed due to extensive quartz cementation. Stylolites are present in both the Hardeberga Formation and in the Norretorp Formation, indicating that the succession has been deeply buried (possibly > 4 km) and exposed to high pressure and temperature. The diagenetic processes were mainly controlled by temperature, but pressure may also have been important. The ion source for quartz cementation is considered to be internal. From a petrographical perspective, the Lower Cambrian succession of Skåne is comparable to that of Bornholm, Denmark.

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