Upper Pleistocene–Recent Coastal-Fluvial Terrace Deposits of the Polis Graben, NW Cyprus: Implications of New Luminescence Dating

Traditional tools for coastal-fluvial terrace correlation (e.g. height above sea level, terrace morphology, sedimentary facies) are useful but often insufficient to resolve the complex interplay of tectonic, glacio-eustatic sea level and climatic changes that control the formation of terraces. Absolute age constraints are therefore essential to quantify the external signals and landscape changes, and to link with regional- to global-scale palaeoenvironmental changes. Here, we present a multidisciplinary study of shallow-marine, to littoral, to fluvial sediments of the three lowermost terraces (<5 m, 8-12 m, 15-35 m) that are exposed along the coastal plain of the Neogene Polis graben in NW Cyprus. We utilise new quartz luminescence dating of littoral to fluvial fine-grained sands, and existing uranium-series dating of solitary corals, together with sedimentological and geomorphological analysis of the terrace deposits. Our main aim is to establish a chronological framework for the terrace development and to aid regional mapping of the terrace surfaces. Previous terrace correlations (coastal to inland) suggest that the three lower shallow-marine terraces correspond to marine isotopic stages (MIS) 7 (c. 185-219 ka), 5e (c. 116-141 ka) and younger. Our new luminescence dating of inland littoral to fluvial terrace deposits reveals substantially younger ages of c. 45-63 ka, corresponding to overall regression during MIS 4-3. Luminescence dating and profiling results establish a detection limit of c. 1.22 ka (MIS 1), representing the youngest resolvable coastal sediment age. Assuming these dated deposits accumulated near sea level, uplift rates of 1.35-1.65 mm/year are implied. This contrasts with uplift rates (0.2-0.5 mm/year), as calculated from previous uranium-series dating of solitary corals from marine terraces correlated with MIS 5-7, elsewhere in Cyprus. However, there is no reason for greatly increased uplift rates after c. 45-63 ka, particularly within the active Polis graben, in which subsidence is indicated by localised modern marine erosion of older non-marine deposits (e.g. terra rossa palaeosols). Instead, we hypothesise that the luminescence-dated littoral-fluvial sediments accumulated up to c. 1 km inland, either in a contemporaneous setting and/or involving reworking of older shallow-marine terrace deposits, and that this was followed by downslope fluvial reworking of mixed siliciclastic-bioclastic sediments. Shifts from cooler, semi-arid conditions to warmer, wetter conditions during MIS 4-3 regressions repeatedly enhanced continental runoff. Alluvial fans prograded seawards episodically, followed by partial marine erosion. Later stage eustatic sea-level changes (MIS 3-2) culminated in erosional downcutting to near present sea level. Coastal sands near present-day sea level accumulated during MIS 1 transgressions, culminating in the development of the modern storm-influenced rocky shoreface, including beachrock. To conclude, uplifted coastal marine–fluvial terraces were partially eroded and covered by mixed siliciclastic-bioclastic sediments, reworked from upslope, that yielded relatively young depositional ages. Such deposits should not be misinterpreted as shoreface deposits, which would lead to calculation of anomalously high uplift rates.