COUPLING CARBONATE FACIES AND GEOCHEMICAL ANALYSES FOR IMPROVED UNDERSTANDING OF CONNECTIONS BETWEEN BIOLOGICAL, CHEMICAL AND PHYSICAL ROCK RECORDS: EXAMPLES FROM THE EARLY PALEOZOIC OF BALTOSCANDIA

As carbonate sediments are strongly influenced by syndepositional conditions, carbonate rocks form an invaluable source of paleoenvironmental information. Analyses of late Cambrian (Furongian) to Middle Ordovician cool-water carbonates from the Baltoscandian paleobasin typically reveal consistent overall stratigraphic patterns and trends in microfacies (carbonate texture, fossil grain assemblage) data between localities across an area of ~250,000 km². Many of the observed patterns and trends appear to result from fluctuations in (relative) sea level, and rhythmicity/cyclicity is common. Spatiotemporal changes/trends in abiotic and biotic microfacies characteristics largely reflect variations in relative water depth and/or distance to weathering sources; generally, carbonate texture varied inversely with depth, and fossil grain assemblages changed from echinoderm- and mollusk-rich to arthropod-rich along bathymetric gradients. Geochemical records (δ¹³C_carb, δ¹⁸O_carb, major and trace elements) typically show co-variation with microfacies characteristics within rock successions and a number of trends also coincide between localities. For example, δ¹³C and δ¹⁸O consistently show long-term trends of increasing values, and both records appear to respond to variations in sea level; regionally, δ¹³C values largely varied inversely with sea level as deduced from microfacies characteristics. Bulk δ¹⁸O trends support prevailing paleoenvironmental and paleogeographic scenarios. Many major and trace elements show interesting patterns of co-variation with microfacies data, and investigations of XRF data sets are ongoing. Despite the overall similarity of microfacies and/or geochemistry data between localities, some notable differences can be seen especially in high-resolution and small-amplitude details. Hence, care should be taken not to overestimate the correlative significance of minor/temporary variations in data sets. In summary, systematic coupling of quantitative carbonate facies, element and stable isotope analyses can increase our understanding of what processes drove biological, chemical and physical signals preserved in the ancient rock record, and yield more robust paleoenvironmental interpretations and scenarios.