Resultat från kärnborrning vid Grönhögen. Litologisk och geokemisk karaktärisering av berggrundsavsnitt på södra Öland. SGU-rapport 2016:15

In the spring of 2015 a core drilling, Grönhögen-2015, was performed adjacent to Mörbylånga municipality’s groundwater wells at Grönhögen. The well was drilled in cooperation between the Geological Survey of Sweden, Mörbylånga municipality and Lund University. The purpose, in addition to increase the overall knowledge about the subsurface bedrock geology, was to  collect new sample material for a chemical characterization of the bedrock. The work has in  addition to the core drilling included geophysical borehole logging and a detailed XRF-scanning of the core. The XRF results show a clear variation in the prevalence of various chemical elements that can be linked to both stratigraphic intervals and different rock types. The Grönhögen core consists of the following main stratigrapic intervals: 0–7.40 m Ordovician limestone formations, 7.40–9.40 m glauconitic limestone and shale (Djupvik and Köpingsklint formations), 9.40–32.15 m alum shale with interbeds of anthraconite and limestone (Alum Shale Formation) and 32.15–50.6 m alternating layers of siltstone and claystone (Borgholm Formation). The investigation of the Grönhögen core can be correlated with the results of a corresponding XRF investigation of the core from Segerstads Fyr. The lithological, geophysical and chemical characterization is a first step in building knowledge and data on the subsurface bedrock units in relation to the groundwater situation on Öland. This report presents a summary of the results obtained from an R&D project performed by SGU. Any further studies on the core will be performed in  collaboration with the Geological Department at Lund University.