Stratigraphy of Cretaceous to Lower Pliocene sediments in the northern part of Cyprus based on comparative 87Sr/86Sr isotopic, nannofossil and planktonic foraminiferal dating

Abstract

AbstractNew age data from Sr isotope analysis and both planktonic foraminifera and nannofossils are presented and discussed here for the Upper Eocene–Upper Miocene sedimentary rocks of the Değirmenlik (Kythrea) Group. New dating is also given of some Cretaceous and Pliocene sediments. In a revised stratigraphy the Değirmenlik (Kythrea) Group is divided into ten formations. Different Upper Miocene formations are developed to the north and south of a regionally important, E–W-trending syn-sedimentary fault. The samples were dated wherever possible by three independent methods, namely utilizing Sr isotopes, calcareous nannofossils and planktonic foraminifera. Some of the Sr isotopic dates are incompatible with the nannofossil and/or the planktonic foraminiferal dates. This is mainly due to reworking within gravity-deposited or current-affected sediments. When combined, the reliable age data allow an overall biostratigraphy and chronology to be erected. Several of the boundaries of previously defined formations are revised. Sr data that are incompatible with well-constrained biostratigraphical ages are commonly of Early Miocene age. This is attributed to a regional uplift event located to the east of Cyprus, specifically the collision of the Anatolian (Eurasian) and Arabian (African) plates during Early Miocene time. This study, therefore, demonstrates that analytically sound Sr isotopic ages can yield geologically misleading ages, particularly where extensive sediment reworking has occurred. Convincing ages are obtained when isotopic dating is combined with as many forms of biostratigraphical dating as possible, and this may also reveal previously unsuspected geological events (e.g. tectonic uplift or current activity).