A δ13C COMPOSITE STANDARD FOR THE ORDOVICIAN OF SOUTHERN SWEDEN

δ¹³C chemostratigraphy is used as an important method for correlation of sedimentary strata on basin-wide to intercontinental scale. The herein presented δ¹³C standard is based on more than 300 whole-rock samples from two continuous core sections from southern Sweden. Together the two cores represent a characteristic record of the highly condensed, temperate-water Ordovician limestone succession of the area. The Tingskullen core derives from the island of Öland and constitutes the Lower and most of the Middle Ordovician part of the succession. The Borenshult core originates from Östergötland province and represents the upper Middle through Upper Ordovician part of the succession. The total thickness of the preserved Ordovician in the two cores is less than 115 m and our δ¹³C record rely on a sampling density of up to four samples per meter (whole-rock samples retrieved with a micro-drill). Most of the major Ordovician carbon isotope excursions are recognized and the data provide a reliable base for intra- and intercontinental correlation of the Swedish Ordovician. A protracted positive excursion of more than 1.5‰ spans much of the upper part of the Tingskullen core and is assigned as the Middle Darriwilian carbon isotope excursion (MDICE). δ¹³C peak values for the MDICE are identified ca. 13 m below the top of the Tingskullen core succession. Based on conodont biostratigraphy the bottom of the Borenshult core corresponds to just above the level of the peak of the MDICE and four named δ¹³C excursions are recognized in the overlying strata. These are the Guttenberg carbon isotope excursion (GICE, peak value of 1.9‰ in the Freberga Formation); the Kope (or Rakvere) carbon isotope excursion in the in the uppermost Freberga Formation and possibly the Slandrom Formation (peak value 1.67‰); the Whitewater (or Moe) in the Jonstorp Formation (peak value + 1.53‰); and the Hirnantian carbon isotope excursion (HICE, peak value of +3.7‰, in the Loka Formation).