ALBERT

Description: Fluvial aggradation and incision are often linked to Quaternary climate cycles, but it usually remains unclear whether variations in runoff or sediment supply or both drive channel response to climate variability. Here we quantify sediment supply with paleo-denudation rates and provide geochronological constraints on aggradation and incision from the Sfakia and Elafonisi alluvial-fan sequences in Crete, Greece. We report seven optically stimulated luminescence (OSL) and ten radiocarbon ages, eight 10Be, and eight 36Cl denudation rates from modern channel and terrace sediments. For five samples, 10Be and 36Cl were measured on the same sample by measuring 10Be on chert and 36Cl on calcite. Results indicate relatively steady denudation rates throughout the past 80 kyr, but the aggradation and incision history indicates a link with climate shifts. At the Elafonisi fan, we identify four periods of aggradation coinciding with Marine Isotope Stages (MIS) 2, 4, 5a/b, and likely 6, and three periods of incision coinciding with MIS 1, 3, and likely 5e. At the Sfakia fan, rapid aggradation occurred during MIS 2 and 4, followed by incision during MIS 1. Nearby climate and vegetation records show that MIS 2, 4, and 6 stadials were characterized by cold and dry climates with sparse vegetation, whereas forest cover and more humid conditions prevailed during MIS 1, 3, and 5. Our data thus suggest that past changes in climate had little effect on landscape-wide denudation rates but exerted a strong control on the aggradation-incision behaviour of alluvial channels on Crete. During glacial stages, we attribute aggradation to hillslope sediment release promoted by reduced vegetation cover and decreased runoff; conversely, incision occurred during relatively warm and wet stages due to increased runoff. In this landscape, past hydroclimate variations outcompeted changes in sediment supply as the primary driver of alluvial deposition and incision.

Description: The active tectonics of Anatolia is mostly characterized by its westward motion with respect to Eurasia between the Hellenic subduction in the west and Arabia-Eurasia continental collision in the east. Although most of the deformation is suggested to be confined along Anatolia?s boundary elements, viz. the North and East Anatolian shear zones, recent studies indicate a higher magnitude of internal strain accumulation, especially along the parallel/subparallel strike-slip faults of its central province. We present the first morphochronology-based slip rate estimate for one of these strike-slip structures, the Ovacık Fault, by using cosmogenic 36Cl dating of offset fluvial deposits. At the Köseler Site (39.3643°N, 39.1688°E), two faulted risers, bounding the alluvial fan with its subplanar surface (NF1/NF1?) and the inset terrace tread (NF1/T2), are offset 19?24 and 15?22 m, respectively. The scattered surface ages and variability of 36Cl concentrations in depth profiles suggest strong evidence for inheritance in alluvial fan and terrace deposits; thus, we used modelled depth-profile ages for both surfaces. The modelled ages 8?10 ka for NF1 and 6?8 ka for T2 yield slip-rate estimates 2.4 +0.5/?0.4 mm/a and 2.8 +0.7/?0.7 mm/a, respectively, for the upper-tread reconstruction of the NF1/NF1?and the lower-tread reconstruction of the NF1/T2. Our results together with previous slip-rate estimates for other structures show a significant internal deformation for Anatolia, especially along its subparallel strike-slip faults. These secondary faults slice Anatolia into several pieces giving rise to the formation of the Malatya-Erzincan, Cappadocian, and Central Anatolian slices, where the geometry is strongly controlled by the distribution of the Tethyan accretionary complexes.