The 1997 core drilling through Ordovician and Silurian strata at Rostanga,S. Sweden: Preliminary stratigraphic assessment and regional comparison

A core drilling at Rostanga, the first such drilling ever undertaken in thi s classical Lower Paleozoic outcrop area in W-central Scania, penetrated an approximately 96 m thick succession of Lower Silurian-upper Middle Ordovic ian marine rocks. The drilling was stopped at a depth of 132.59 m in an int erval of crushed rocks, probably a prominent fault zone, that proved imposs ible to drill through. The core contains a stratigraphical sequence from th e basal Upper Llandoverian (Telychian Stage) to the upper Middle Ordovician (Harjuan Stage). The following units are recognized in descending stratigr aphic order (approximate thickness in parenthesis): Kallholn Formation (35 m), Lindegard Mudstone (27 m), Fjacka Shale (13 m), Mossen Formation (0.75 m), Skagen Formation (2.5 m), and Sularp Shale (19 m+). Except for the Skag en Formation, the drilled sequence consists of shales and mudstones with oc casional thin limestone interbeds and is similar to coeval successions else where in Scania. There are 11 K-bentonite beds in the Kallholn Formation, 2 (3?) in the Lindegard Mudstone, 1 in the Mossen Formation, 7 in the Skagen Formation, and 33 in the Sularp Shale. The core serves as an excellent Lowe r Silurian-upper Middle Ordovician reference standard not only for the Rost anga area but also for southernmost Sweden in general because the cored seq uence is the stratigraphically most complete one known anywhere in this reg ion.