Pliocene-Pleistocene sedimentary development of the syntectonic Polis graben, NW Cyprus: evidence from facies analysis, nannofossil biochronology and strontium isotope dating

The recently uplifted and exposed Pliocene and Pleistocene sedimentary infill of the neotectonic Polis graben provides an excellent opportunity to understand extensional basin development in a marine setting. Fieldwork, facies analysis and dating using nannofossils and strontium isotopes reveal how the sedimentary conditions evolved during infill of the Polis graben during Pliocene and Pleistocene time, and allow a composite succession for the depocentre to be determined for the first time. Six lithofacies are recognized in the northern Polis graben, allowing evolving palaeoenvironments to be inferred. By the end of Miocene time (Messinian) a major c. N-S-trending graben was established; extensional faulting continued during the Pliocene-Pleistocene until recent time. Post-Messinian salinity crisis deposition began with deposition of hemipelagic muds (c. 5.08-2.76 Ma), equivalent to the Nicosia Formation. This was followed by upwards incoming of repeated normal-graded bioclastic carbonates (couplets) (c. 2.76-1.6 Ma), which are interpreted as age-equivalents of the Athalassa Formation elsewhere in Cyprus. The upwards sudden facies change is explained by tectonically controlled shallowing which enabled neritic carbonate production on the basin margins. The appearance of basement-derived material (e.g. ophiolitic extrusive detritus) in the highest stratigraphic levels of the basin fill in the north (c. 1.7-1.6 Ma) reflects onset of rapid surface uplift focused on the Troodos ophiolitic massif. Overall, the syntectonic basin infill appears to document a two-stage, pulsed uplift related to early-stage collision of the African and Eurasian plates in the easternmost Mediterranean region.