Abstract:

The timing of the deposition of the well-preserved Quaternary marine terraces in the coastal region of northeastern Turkey are crucial in understanding the Quaternary tectonics of the Pontides. The chronology of raised marine terraces between Trabzon and Rize has remained unrevealed because of chronologic limitations. This study aims to establish chronology for the terrace deposits by applying optically stimulated luminescence (OSL) dating methods using single aliquot regenerative dose (SAR) techniques on quartz grains extracted from marine terraces. Eleven samples were collected from the lowest three Quaternary marine terraces. The OSL ages clusters into three groups: 52.4 ± 4.6 to 60.0 ± 4.7 ka (terrace level T1); 16.8 ± 0.8 to 33.9 ± 2.8 ka (T2); and 11.7 ± 0.9 ka (T3). This chronology is consistent with the classical terrace stratigraphy; i.e. younger terraces are located at lower elevations and vice versa for the older terraces. We correlate the established terrace chronology with MIS 3c, MIS 3a, and MIS 1. We calculated apparent uplift rates are 0.98 ± 0.12 mm/year, 1.39 ± 0.26 mm/year, and 1.50 ± 0.78 mm/year from marine terrace levels 1, 2, and 3, respectively. Based on the existing eustatic sea-level data/curve, we estimated tectonic uplift rates up to 5 mm per year. Our results indicate that the coastal region of the Eastern Pontides experienced three accumulation periods, with sea-level highstands overprinting the uplifting coastline, and the coastal region of Eastern Pontides has been tectonically active from Late Pleistocene to Early Holocene. This study reveals that marine terraces in the coastal region of northeastern Anatolia might have displaced by the South Black Sea Fault which ultimately points to a regional subsidence with the higher uplift rate, and it points to a differential uplift along the Eastern Pontides.

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