Quartz cementation and diagenetic controls in sandstone – an analog study of Cambrian quartz arenite from Baltica

Quartz arenite of Cambrian age has a world-wide occurrence but the diagenetic processes rarely have been taken into account in order to explain their existence. In this study, Lower Cambrian quartz arenite from the... [ view full abstract ]

Quartz arenite of Cambrian age has a world-wide occurrence but the diagenetic processes rarely have been taken into account in order to explain their existence. In this study, Lower Cambrian quartz arenite from the paleocontinent Baltica has been examined in a state of complete quartz cementation to study the effect of processes leading to decreasing and/or destructing reservoir quality. This gives us detailed information on the combined chemical compaction and cementation. We estimated the quartz cementation in sandstone reservoirs by examining and comparing the amount of cement present in the reservoir to the expected amount of quartz cement based on a modeled time-temperature history. The findings will not only contribute to an increased understanding of the quartz-cementation processes, but also to diagenetic reactions forming clay minerals as end products, as well as other types of cement. Our results are based on petrographical and mineralogical analysis on thin sections and rock samples. They mainly comprise the quartz-rich Ringsaker Member from Southern Norway and the corresponding Hardeberga Formation on Bornholm, Denmark, and include both core and outcrop samples. The units reflect the incipient stage of Early Cambrian transgression on Baltica and they represent shallow-marine deposition. The quartz arenite from Southern Norway has an intergranular volume of around 20% with close to 100% of the initial porosity being replaced by quartz cement. For the majority of the samples, authigenic minerals, together with detrital phyllosilicates, represent close to 5% of the present day composition. This indicates that the sediment composition was extremely quartz-rich already during deposition. Reworking by wave activity and subsequent removal of authigenic components is believed to severely have influence the composition. This topic represents the first part of a study on Cambrian quartz arenite in Baltica with emphasis on both predepositional and postdepositional processes that result in quartz arenite formation.