Micropaleontological Analysis and Sequence Stratigraphy through Upper Tournaisian Substage in Aladağ Unit (Central Taurides, Turkey)

Abstract

The purpose of this study is to investigate the Upper Tournaisian substage within the Carboniferous carbonate deposits of the Aladağ Unit in the Hadim region (Central Taurides) based on foraminiferal diversity and to study the meter-scale cycles in order to explain the sequence stratigraphic evolution of the carbonate succession. In this study, a 27 m thick stratigraphic section consisting of limestones and shales has been measured and 89 samples have been collected on a bed-by-bed basis. Micropaleontological analyses are based on benthic foraminifera and two biozones have been identified, Zone Ut1 and Zone Ut2, within the Upper Tournaisian. Zone Ut1 is characterized by a poor foraminiferal assemblage while the Zone Ut2 consists of a diverse Upper Tournaisian foraminiferal fauna. In order to construct a sequence stratigraphic framework and detect depositional environmental changes, seven microfacies types have been recognized and depending on the stacking patterns of these microfacies types, two fundamental types of cycles were identified. Twenty-five shallowing-upward meter-scale cycles and two sequence boundaries were determined through the measured section. Quantitative analysis of benthic foraminifera was used to demonstrate the biological response to cyclicity. Since foraminifers are sensitive to sea level changes, the abundance of benthic foraminifera displays a good response to sedimentary cyclicity. In order to apply a worldwide sequence stratigraphic correlation, the sequence boundaries and meter-scale cycles were compared with those described from South China, Western European platform and the Moscow Syneclise. In the Tournaisian paleogeography, an Early Tournaisian transgression was followed by a major fall in relative sea level and a new depositional regime started in the Late Tournaisian. Two sequence boundaries recognized in the measured section correspond to global sea level falls in this Upper Tournaisian substage.