Transgressive to regressive turnaround in the Middle Devonian Baltic Basin

This doctoral thesis presents detailed facies and facies association studies of the Middle Devonian Narva and Aruküla successions on the Baltic Basin. Detailed, cm-scale descriptions of cores and outcrops were carried out to investigate the architecture, formation, palaeogeography, and evolution of the shallow marine mixed carbonate-siliciclastic deposits and siliciclastic-rich tide-dominated delta deposits. This is the first study where the sequence stratigraphy was used to reconstruct processes and the palaeoegeography of the Middle Devonian Baltic Basin. All together seventeen Facies Associations were separated from studied intervals and divided into three groups, (1) carbonate-rich facies associations, (2) mixed facies associations, and (3) siliciclastic-rich facies associations. The vertical and lateral facies transitions show that carbonate-rich and mixed facies associations dominated in the transgressive part of the basin fill and formed in the shallow epeiric sea. The following progradational part of the basin fill consists of aggradational and progradational siliciclastic-rich facies associations that formed in the shallow sea as tide-dominated delta deposits. The turnaround from the transgressive carbonate dominated environments to the regressive siliciclastic dominated environments occurred during the relative sea-level rise and was caused by the tectonic movements in the hinterland, rather than relative sea-level changes.