New stratigraphical results and significance of reworking based on nannofossil, foraminiferal and sedimentological records in the Lower Tertiary sequence from the northern Isparta Angle, Eastern Mediterranean

Abstract

This study presents new stratigraphical data on the sediments of the Lower Tertiary sequence outcropping in the northern Isparta Angle, Southwest Anatolia. These data, which are based on field observations, foraminifera and nannofossil studies, and sedimentological findings, contribute to the paleoenvironmental and structural interpretations. Reworking of fossils that was neglected in previous work is an important factor for understanding and clarifying the Early Tertiary geological evolution of the region. This investigation particularly focuses on the significance of reworking in the stratigraphic record. The Early Tertiary unconformity-bounded unit consist of two transitional lithofacies, varying from marine clastics to carbonates. The first lithofacies mainly composed of clastics, whereas the second contains carbonate-dominated sediments. The Lower Tertiary sequence unconformably overlies an irregular surface composed of ophiolitic rocks, deep marine bedded cherts and carbonates of early Mesozoic age, Mesozoic carbonates and marine clastics and carbonates of Late Cretaceous age. The unit is unconformably overlain by Lower Miocene marine clastics. Both the unconformity and tectonic relationships between the Eocene and Lower Miocene sequences are seen in the northern study area. These exposures are proof of pre-Miocene erosion and post-Miocene deformation. In this study, two nannofossil interval zones, NP12 and NP13, were identified from fine-grained clastics and carbonates. According to benthic foraminifera and nannofossil contents, the formation is Early Eocene (Ypresian) in age. The percentages of reworked (older) fossils range from 75% in the lower levels to 15% in the higher levels of the Lower Tertiary sequence. This study demonstrates that detailed analyses of fossil reworking are needed in order to obtain more reliable results. The evidence of strong reworking, plant traces, biostratigraphical and sedimentological data indicate that a single cycle of Early Eocene sedimentation occurred in a shallow to open-marine depositional environment, becoming shallower as time progressed. The obtained data indicate a marine transgression from north to south in the northern part of the Isparta Angle during Eocene time.