RECORDS OF ORDOVICIAN CARBON CYCLING IN DEEP WATER SETTINGS FROM BALTICA: KRAPPERUP AND LERHAMN DRILL CORES–SCANIA, SWEDEN

Reconstructing local-regional scale carbon cycling of Lower-Middle Ordovician deep-water marine sediments off the margin of the paleocontinent Baltica is paramount to understanding environmental perturbations that may have facilitated changes in marine biodiversification in this region. The Great Ordovician Biodiversification Event (GOBE), or Ordovician Radiation, was one of the most significant radiations of marine animal life in the entire Phanerozoic. Previous work has postulated atmospheric oxygen’s fundamental role for the GOBE; however, little work has been done on Lower-Middle Ordovician deep-water marine shale successions which represents deeper water facies.

During the Lower-Middle Ordovician, Baltica was located in a mid-latitude position on the eastern side of the Iapetus Ocean. Our study successions are deeper marine mudstones deposited on the western side of the paleocontinent of Baltica with open connection to the Iapetus Ocean and Tornquist Sea. Due to this open marine connectivity and being on the western side of this paleocontinent, our study sites may record fluctuations in organic matter (OM) burial possibly linked to regional oxygen minimum zones and/or changes within the global carbon cycle. These shifts in organic carbon burial can be tracked in these mudstones via measuring total organic carbon contents (TOC%) for local changes and the organic carbon isotope (δ¹³Corg) values for global perturbations.

While extensive research has been conducted on the adjacent shallow carbonate banks, the deeper marine settings remain relatively unexplored beyond biostratigraphy. The Lerhamn and Krapperup drill cores from the Skåne province, Sweden are the focus of this study. They are composed of deep-marine graptolite-bearing shales and mudstones from the Tøyen Formation and have been biostratigraphically constrained to be upper Tremadocian through early Darriwillian. These δ¹³C datasets are paramount for comparison and correlation with global δ¹³C trends, biostratigraphy, and other redox proxy data. Specifically, they will allow us to generate a regional transect from shallow carbonate shelf successions to these deeper marine graptolite-mudstones that will facilitate higher-resolution correlations across sedimentary facies and different biostratigraphic groups on Baltica.