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Impact of Facies and Tectonics on Provenance Signal: Zircon Age and Heavy Mineral Evidence from the Miocene Sand in Denmark

Olivarius, Mette; Rasmussen, Erik S.; Siersma, Volkert; Knudsen, Christian; Kokfelt, Thomas F.; Keulen, Nynke

Zircon age distributions, heavy mineral analyses, and grain size and shape parameters in combination with a detailed stratigraphic model have been used to interpret the provenance of the fluvio-deltaic sand that prograded into the North Sea Basin in large delta lobes during the Miocene. The setting of the depositional environment resulted in restricted mixing of supplies from different source areas in the fluvial and coastal facies, whereas a wave-induced shallow current and a tidally-induced deeper current transported the sediment longshore in opposite directions in the marine facies. Comparison of the zircon age distributions with age markers defined on the basis of published ages of the Scandinavian basement terranes shows that the major part of the sand has a range of Sveconorwegian source areas in south-eastern Norway and south-western Sweden. Distinct contributions are also found from the Svecofennian Orogen, the Caledonian belt and the Oslo Rift area. The presence of Archaean zircon grains indicates that the upland of the river systems reached to Finland. Depositional ages were interpreted from the stratigraphic model in order to reconstruct the river pathway system for each time slice. Changes in grain size parameters and mineral assemblage across Denmark were used to calculate the overall sediment transport direction for southern Scandinavia as south-western, and the magnitude of change shows that the sediments are immature with regard to transport length. This suggests, in combination with the dominance of mature minerals in the heavy mineral assemblages, that kaolinization has been widespread in the source areas. An eastward migration of the dominating provenance area was observed for both the early Miocene inversion and the intra early Miocene tectonic phase and may indicate rapid uplift and/or extensive denudation. The zircon age distributions are thus shown to be dependent on both facies and tectonics.


AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013