The Gediz River fluvial archive: A benchmark for Quaternary research in Western Anatolia

The Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River Project (2001–2010) and present new data which leads to a revised stratigraphical model for the Early Pleistocene development of this fluvial system. In previous work we confirmed the preservation of eleven buried Early Pleistocene fluvial terraces of the Gediz River (designated GT11, the oldest and highest, to GT1, the youngest and lowest) which lie beneath the basalt-covered plateaux of the Kula Volcanic Province. Deciphering the information locked in this fluvial archive requires the construction of a robust geochronology. Fortunately, the Gediz archive provides ample opportunity for age-constraint based upon age estimates derived from basaltic lava flows that repeatedly entered the palaeo-Gediz valley floors. In this paper we present, for the first time, our complete dataset of 40Ar/39Ar age estimates and associated palaeomagnetic measurements. These data, which can be directly related to the underlying fluvial deposits, provide age constraints critical to our understanding of this sequence. The new chronology establishes the onset of Quaternary volcanism at ∼1320ka (MIS42). This volcanism, which is associated with GT6, confirms a pre-MIS42 age for terraces GT11-GT7. Evidence from the colluvial sequences directly overlying these early terraces suggests that they formed in response to hydrological and sediment budget changes forced by climate-driven vegetation change. The cyclic formation of terraces and their timing suggests they represent the obliquity-driven climate changes of the Early Pleistocene. By way of contrast the GT5-GT1 terrace sequence, constrained by a lava flow with an age estimate of ∼1247ka, span the time-interval MIS42 – MIS38 and therefore do not match the frequency of climate change as previously suggested. The onset of volcanism breaks the simple linkage of terracing to climate-driven change. These younger terraces more likely reflect a localized terracing process triggered by base level changes forced by volcanic eruptions and associated reactivation of pre-existing faults, lava dam construction, landsliding and subsequent lava-dammed lake drainage. Establishing a firm stratigraphy and geochronology for the Early Pleistocene archive provides a secure framework for future exploitation of this part of the archive and sets the standard as we begin our work on the Middle-Late Pleistocene sequence. We believe this work forms a benchmark study for detailed Quaternary research in Turkey

Urban multi-model climate projections of intense heat in Switzerland

This paper introduces a straightforward approach to generate multi-model climate projections of intense urban heat, based on an ensemble of state-of-the-art global and regional climate model simulations from EURO-CORDEX. The employed technique entails the empirical-statistical downscaling method quantile mapping (QM), which is applied in two different settings, first for bias correction and downscaling of raw climate model data to rural stations with long-term measurements and second for spatial transfer of bias-corrected and downscaled climate model data to the respective urban target site. The resulting products are daily minimum and maximum temperatures at five urban sites in Switzerland until the end of the 21st century under three emission scenarios (RCP2.6, RCP4.5, RCP8.5). We test the second-step QM approach in an extensive evaluation framework, using long-term observational data of two exemplary weather stations in Zurich. Results indicate remarkably good skill of QM in present-day climate. Comparing the generated urban climate projections with existing climate scenarios of adjacent rural sites allows us to represent the urban heat island (UHI) effect in future temperature-based heat indices, namely tropical nights, summer days and hot days. Urban areas will be more strongly affected by rising temperatures than rural sites in terms of fixed threshold exceedances, especially during nighttime. Projections for the end of the century for Zurich, for instance, suggest more than double the number of tropical nights (Tmin above 20 ºC) at the urban site (45 nights per year, multi-model median) compared to the rural counterpart (20 nights) under RCP8.5.This research has been partly supported by the European Commission (HEAT-SHIELD 668786). EH is supported by the German Research Foundation under project number 40805747

Revealing the pace of river landscape evolution during the Quaternary: recent developments in numerical dating methods

During the last twenty years, several technical developments have considerably intensified the use of numerical dating methods for the Quaternary. The study of fluvial archives has greatly benefited from these enhancements, opening new dating horizons for a range of archives at distinct time scales and thereby providing new insights into previously unanswered questions. In this contribution, we separately present the state of the art of five numerical dating methods that are frequently used in the fluvial context: radiocarbon, Luminescence, Electron Spin Resonance (ESR), 230Th/U and terrestrial cosmogenic nuclides (TCN) dating. We focus on the major recent developments for each technique that are most relevant for new dating applications in diverse fluvial environments and on explaining these for non-specialists. Therefore, essential information and precautions about sampling strategies in the field and/or laboratory procedures are provided. For each method, new and important implications for chronological reconstructions of Quaternary fluvial landscapes are discussed and, where necessary, exemplified by key case studies. A clear statement of the current technical limitations of these methods is included and forthcoming developments, which might possibly open new horizons for dating fluvial archives in the near future, are summarised

Time-integrated 3D approach of late Quaternary sediment-depocenter migration in the Tagus depositional system: From river valley to abyssal plain

Quantification of sediment volumes in continental to deep ocean basins is key to understanding processes of sediment distribution in source-to-sink depositional systems. Using our own and published data we present the first quantification of sediment-volume changes in basins along the course of a major southwest European river during the deglaciation. The salient points of this quantitative record in the Tagus and equivalent North Atlantic basins show crucial roles for sea level, climate and land-use in the distribution of sediments. The bypass of sediments starved the Tagus basins, and subsequently sedimentation mainly occurred on the Tagus Abyssal Plain during the sea-level lowstand of the Last Glacial Maximum. The main sediment depocenter rapidly shifted via the continental shelf to the Lower Tagus Valley during sea-level rise in the deglaciation period. Finally, the main sediment depocenter shifted further landward into the Lower Tagus Valley during sea-level high stand in the Holocene. During the high-stand phase (last 7 ky), sediment flux increased up to 2.5 times, due to climate and land-use changes. The average catchment denudation rate during the last 12 ky (0.04–0.1 mm/y) is in agreement with those of other European catchments. Our study clearly demonstrates the added value of detailed knowledge of 3D depocenter distribution, size and chronology. This allowed us to identify an increased sediment flux during the last 7 ky, which was not identified using local observations from boreholes alone. The uniqueness of the Tagus depositional system lies in the combination of a large accommodation space in the bedrock-confined Lower Tagus Valley, the steep lowstand-surface gradient and the narrow continental shelf with canyons indenting the shelf break

New data on the chronology of the Vale do Forno sedimentary sequence (Lower Tejo River terrace staircase) and its relevance as a fluvial archive of the Middle Pleistocene in western Iberia

The Vale do Forno archaeological sites (Alpiar\ue7a, central Portugal) document the earliest human occupation in the Lower Tejo River, well established in geomorphological and environmental terms, within the Middle Pleistocene. In a staircase of six fluvial terraces, the Palaeolithic sites were found on the T4 terrace (\ufe24 m, above river bed) which is made of a basal Lower Gravels unit (LG) and an overlying Upper Sands unit (US). Geomorphological mapping, coupled with lithostratigraphy, sedimentology and luminescence dating (quartz-OSL and K-feldspar post-IRIR290) were used in this study. The oldest artefacts found in the LG unit show crude bifacial forms that can be attributed to the Acheulian. In contrast, the US unit has archaeological sites stratigraphically documenting successive phases of an evolved Acheulian. Luminescence dating and correlation with the Marine Isotopic Stages suggest that the LG unit has a probable age of ca. 335 to 325 ka and the US unit an age of ca. 325 to 155 ka. This is in contrast to previous interpretations ascribing this terrace (and lithic industries) to the Last Interglacial and early phases of the Last Glacial. The VF3 site (Milharos), containing Micoquian (Final Acheulian) industries (with fine and elaborated bifaces), found in a stratigraphic level located between the T4 terrace deposits and a colluvium associated with Late Pleistocene aeolian sands, is younger than 155 ka but much older than 32 ka