Middle-Late Miocene palaeoceanographic development of Cyprus (E. Mediterranean) based on integrated study of δ¹⁸O and δ¹³C stable isotope records, supported by Mg/Ca palaeothermometry, nannofossil biostratigraphy, Sr isotopic dating, sedimentology and other geochemical data

Dynamic climate changes and regional tectonic convergence/collision were fundamental factors in the formation of earth, ocean and climate systems during the Middle to Late Miocene. CO2-driven global warming of the Miocene Climatic Optimum (MCO) has been proposed as an analogue for future anthropogenic climate change. However, the nature and extent of both the MCO and the subsequent Middle to Late Miocene cooling had remained poorly constrained in the eastern Mediterranean region. This region was affected by the closure of key ocean gateways, to the Indian Ocean during the Middle Miocene and to the Atlantic Ocean during the Late Miocene. The Late Miocene isolation of Mediterranean basins culminated in dramatic seawater salinity increase and extensive evaporite formation, known as the Messinian Salinity Crisis (MSC). The island of Cyprus exposes uplifted Cenozoic and Neogene deep-sea pelagic sedimentary rocks. These successions have not undergone deep burial diagenesis and can therefore be utilised to produce reliable geochemical records. The Lower to Upper Miocene succession at Kottaphi Hill and the Upper Miocene succession at Lapatza Hill were sampled in order to produce a composite stable isotope record (O and C), which spans the onset of the MCO to the onset of the MSC. The two successions were sampled at a vertical spacing of 5–25 cm and correlated using calcareous nannofossil biostratigraphy and stable isotope data, supported by field observations, X-ray diffraction and X-ray fluorescence data. Fine-fraction bulk rock and planktic foraminifera stable isotope records, together with trace element/Ca records, provide fresh insights into the evolution of sea surface temperature and ocean chemistry. The new data reveal how both global climate changes and the local to regional effects of ocean gateway closures affected Cyprus, and probably also the wider eastern Mediterranean during this time interval. The data also shed light on the sedimentary development related to the tectonic development of the adjacent Mesaoria Basin in Cyprus. In addition, strontium isotope dating of redeposited shallow-water carbonate material (e.g. bivalves) aids interpretation of contemporaneous Miocene reef-related facies elsewhere, in northwest Cyprus. This research demonstrates that pelagic carbonate successions such as at Kottaphi Hill can produce excellent stable isotopic records comparable to those for deep-sea cores, opening the way for comparable land-based isotopic studies elsewhere.