Proterozoic basement and Palaeozoic sediments in the Ringkøbing–Fyn High characterized by zircon U–Pb ages and heavy minerals from Danish onshore wells

Abstract

New data from the Proterozoic basement and scattered Palaeozoic sediments in the Ringkøbing–Fyn High including zircon U–Pb geochronometry, heavy mineral compositions and whole rock geochemistry is presented here to provide a frame of reference for detrital provenance studies. The Ringkøbing–Fyn High is a WNW–ESE trending structural high including subcropping basement rocks, and the results indicate that it is a southerly extension of the Fennoscandian Shield. The zircon data show matching age distribution patterns in crystalline basement rocks obtained from two drill sites, the Glamsbjerg-1 and Grindsted-1 wells. They both record a characteristic Telemarkian accretionary event at 1.51 and 1.48 Ga and a Sveconorwegian metamorphic overprinting at 1.08 Ga. Furthermore, the dominant age intervals in the Glamsbjerg High (1.55–1.48 Ga) and the Grindsted High (1.51–1.44 Ga) suggest that rocks of the Gothian orogeny (that ended at 1.52 Ga) are only present in the eastern part of the Ringkøbing–Fyn High. Thus, the buried basement in central Denmark may be youngest towards the west, which is consistent with the general westward age progression trend in the Sveconorwegian Orogen. The basement breccia in the Arnum-1 well on the southern flank of the Ringkøbing–Fyn High has zircon ages (c. 1.54–1.53 Ga) that resemble those of gneiss in the Glamsbjerg High. The conglomeratic sandstone in the Ringe-1 well on the Glamsbjerg High has a dual age distribution as the matrix has late Palaeoproterozoic to early Mesoproterozoic ages, whereas the granitic clasts have a distinct middle Neoproterozoic age (c. 0.76 Ga) that may indicate an Avalonian source. The quartzite in the Slagelse-1 well on the northern flank of the Ringkøbing–Fyn High has a broad age span with late Palaeoproterozoic to late Mesoproterozoic zircon ages. Supplementary material: Detailed documentation of U/Pb analytical procedures, results and analysed zircon spots are available below.