Transportation controls in the formation of Lower Cambrian quartz arenite on Baltica

The effect of transportation is here investigated as a controlling factor for formation of quartz-rich deposits on Baltica during the Cambrian period. There, the transportation processes on a low-relief peneplain have been... [ view full abstract ]

The effect of transportation is here investigated as a controlling factor for formation of quartz-rich deposits on Baltica during the Cambrian period. There, the transportation processes on a low-relief peneplain have been studied. There is a global occurrence of similar, quartz-arenitic, shallow marine deposits. We have studied Cambrian quartz arenite from Southern Norway, Bornholm in Denmark and Scania in Sweden. Detrital zircons from ten samples were U-Pb dated using LA-ICP-MS. Preliminary results from Bornholm indicate dominating ages of 1.6–1.8 Ga and less 0.9-1.3 Ga. The samples from Southern Norway and Scania show a reversed trend, with a dominating population in the 0.9-1.3 Ga interval. These ages are in accordance with transport from the Transscandinavian Igneous Belt and the Sveconorwegian Orogen, indicating a short distance of transportation. The majority of the sampled rocks contain few zircon grains. This, together with the pronounced U-Pb age-interval and the short transport, may signify that the rocks represent first-cycle deposits. Nearly 50 meters of continuously cross-bedded and rippled medium to coarse sand represent a relatively stable shallow marine environment. These geometries may have resulted from landward reworking of marine sand deposits in a period of little sediment supply from land. This topic represents the second part of a study on Cambrian quartz arenite in Baltica with emphasis on both predepositional and postdepositional processes that result in quartz-arenite formation.