Mats Eriksson

The transition between the Volkhov and Kunda Baltoscandian stages (Darriwilian, Middle Ordovician) is associated with a notable sea-level fall. This study documents the lithologic and sedimentologic expression of this event in the orthoceratite limestone at the Hällekis quarry, Kinnekulle, Sweden. The uppermost Volkhov strata are characterized by abundant limonitic hardgrounds and relatively coarse carbonate textures, including intraclasts and ferruginous coated grains. The top of a conspicuous wacke-packstone interval is identified as the local Volkhov-Kunda and Lanna Limestone-Holen Limestone boundary. The boundary is overlain by marly limestone, in which limonitic hardgrounds become uncommon and a temporary fining of carbonate textures occurs. An overall trend of increasing (mainly skeletal) grain concentration and diversity is seen throughout the studied succession. Based on the collective observations, a sea-level curve for the upper Volkhov and lower Kunda is presented.