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Quaternary science journal 72(1), 77-94 (2023). doi:10.5194/egqsj-72-77-2023, Published by Copernicus Publications, Göttingen

At wave-dominated coasts it is common to find coastal barriers that might be in a progradational pattern and can compose sedimentary capes. Those prograding coastal barriers can be characterized by beach ridges or barrier spits, or even by a more complex pattern depending on the processes controlling their formation. In this study geomorphological mapping, topographic surveys, ground-penetrating radar profiles and optically stimulated luminescence (OSL) dating were performed on the coastal barrier systems of Sao Tome cape (north of Rio de Janeiro state, Brazil). The aim was to reconstruct its spatial and temporal evolution and, by this, better understand the interplay between sedimentary cape formation and its driving mechanisms as well as their function as potential archives for long-term environmental dynamics. The study site is characterized by lagoonal and fluvio-lagoonal depressions, and a lagoon surrounded by beach ridges that are interleaved with barrier spits and erosional truncations. Both types of coastal barriers reach up to 6 m above sea-level. Shallow geophysical analysis identified seven radar facies that characterize the stratigraphy of the targeted morphologies. Beach ridges are mainly composed by planar, seaward dipping, subparallel, continuous reflectors which represents their progradation, while barrier spits have planar to convex up, parallel, landward migrating reflectors. Geochronological results demonstrate that the coastal barriers were formed during the Late Holocene. Beach ridge formation until ~2700 years ago was interrupted by the formation of a barrier spit system between ~2300 and ~2000 years ago. This barrier spit system was responsible for the formation of an enclosed lagoon, the Salgada lagoon, and was truncated by a set of beach ridges formed since ~2000 years ago and continuing to the present shoreline. The different types of coastal barriers indicate a change in hydrodynamic processes during the Late Holocene, with an alternation between the predominance of wave-induced cross-shore transport, responsible for the formation of beach ridges, and the predominance of longshore transport, responsible for the formation of barrier spits. Besides that, erosional truncations and unconformities indicate the interruption of shoreline progradation and the impact of erosion due to the storms. This illustrates the complex and highly dynamic development of Sao Tome Cape with wave climate and storms as its most important drivers. More generally, this study shows that sedimentary capes may be regarded as geoarchives with potential for the reconstruction of coastal processes over Holocene timescales.

Wave-transported boulders represent important records of storm and tsunami impact over geological timescales. Their use for hazard assessment requires chronological information on their displacement that in many cases cannot be achieved by established dating approaches. To fill this gap, this study investigated, for the first time, the potential of optically stimulated luminescence rock surface exposure dating (OSL-RSED) for estimating cliff-detachment ages of wave-transported coastal boulders. The approach was tested on calcarenite clasts at the Rabat coast, Morocco. Calibration of the OSL-RSED model was based on samples with rock surfaces exposed to sunlight for ∼ 2 years, and OSL exposure ages were evaluated against age control deduced from satellite images. Our results show that the dating precision is limited for all targeted boulders due to the local source rock lithology which has low amounts of quartz and feldspar. The dating accuracy may be affected by erosion rates on boulder surfaces of 0.02–0.18 mm yr−1. Nevertheless, we propose a robust relative chronology for boulders that are not affected by significant post-depositional erosion and that share surface angles of inclination with the calibration samples. The relative chronology indicates that (i) most boulders were detached from the cliff by storm waves; (ii) these storms lifted boulders with masses of up to ∼ 24 t; and (iii) the role of storms in the formation of boulder deposits along the Rabat coast is more significant than previously assumed. Although OSL-RSED cannot provide reliable absolute exposure ages for the coastal boulders in this study, the approach has large potential for boulder deposits composed of rocks with larger amounts of quartz or feldspar and less susceptibility to erosion.

Coastal alluvial fans (CAF) are important geo-archives due to their sensitivity to both tectonic activity and climatic changes. Thus, they can give key insights for geomorphic and sedimentary processes. In this study we test the potential of K-feldspar post infrared-infrared stimulated luminescence (pIR-IRSL) and quartz electron spin resonance (ESR) methods for dating alluvial fan complexes in arid environments. The existing chronological data from marine terraces that interact with CAF make the Atacama Desert in northern Chile an excellent setting for this research. Samples have been collected from alluvial, marine and aeolian sediments embedded in the CAF complexes, allowing evaluation of the different signal properties and bleaching characteristics of the pIR-IRSL and ESR signals over Late Pleistocene time scales. pIR-IRSL dose distributions of clast-rich alluvial fan samples are characterised by higher scatter and demonstrate heterogeneous bleaching, while matrix-rich alluvial fan deposits show rather homogeneous poor bleaching in the dose dispersion as indicated by a modern analogue sample. In contrast, marine and aeolian deposits are homogeneously well bleached, supported by a modern littoral sample. Following the quartz multiple centre (MC) ESR dating approach (Al and Ti centres), bleaching of the different centres prior to deposition has been achieved. While the Ti–H centre provides mostly lower doses than the Ti–Li centre, in most cases the Al centre provides the highest dose values. This pattern is consistent with their respective bleaching kinetics and suggests that the Ti centre signals most likely provide the closest estimate to the true burial dose for samples with doses >200 Gy. ESR and pIR-IRSL ages are consistent at 2σ for the marine, aeolian and clast-rich debris-flow deposits, which is in agreement with existing chronological data in this area. It appears that the mode of sediment transport on alluvial fans, either as matrix- or clast-rich flows, plays an important role in sediment bleaching. While clast-rich alluvial fan deposits are likely better bleached, we cannot exclude insufficient bleaching during matrix-rich alluvial fan flows; our dating results suggest that both pIR-IRSL and ESR dating overestimate the true burial age. The combination of pIR-IRSL and MC ESR dating can be considered as a promising tool for deciphering alluvial fan formation over (Late) Pleistocene time scales.

Systematic archaeological exploration of southern Qatar started in the 1950s. However, detailed local and regional data on climatic fluctuations and landscape changes during the Holocene, pivotal for understanding and reconstructing human–environment interactions, are still lacking. This contribution provides an overview on the variability of geomorphic environments of southern Qatar with a focus on depression landforms, which reveal a rich archaeological heritage ranging from Palaeolithic(?) and Early Neolithic times to the Modern era. Based on a detailed geomorphic mapping campaign, sediment cores and optically stimulated luminescence data, the dynamics of riyad (singular rawdha; shallow, small-scale, sediment-filled karst depressions clustering in the central southern peninsula) and the larger-scale Asaila depression near the western coast are studied in order to put archaeological discoveries into a wider environmental context. Geomorphic mapping of the Asaila basin shows a much greater geomorphic variability than documented in literature so far with relict signs of surface runoff. An 8 m long sediment core taken in the sabkha-type sand flats of the western basin reveals a continuous dominance of aeolian morphodynamics during the early to mid-Holocene. Mounds preserved by evaporite horizons representing capillarites originally grown in the vadose zone are a clear sign of groundwater-level drop after the sea-level highstand ca. 6000–4500 years ago. Deflation followed the lowering of the Stokes surface, leaving mounds where the relict capillarites were able to fixate and preserve the palaeo-surface. Abundant archaeological evidence of Early and Middle Neolithic occupation – the latter with a clear focus inside the central Asaila basin – indicate more favourable living conditions than today. In contrast, the sediment record of the investigated riyad in the south is very shallow, younger and controlled by surface discharge, deflation and the constantly diminishing barchan dune cover in Qatar over the Middle and Late Holocene. The young age of the infill (ca. 1500 to 2000 years) explains the absence of findings older than the Late Islamic period. Indicators of current net deflation may relate to a decrease in surface runoff and sediment supply only in recent decades to centuries. In the future, geophysical prospection of the riyad may help to locate thicker sedimentary archives and the analysis of grain size distribution, micromorphology, phytoliths or even pollen spectra may enhance our understanding of the interplay of regional environmental changes and cultural history.

Geological records indicate that the hyper-aridity in the Atacama Desert has prevailed since at least the mid-Miocene, with shorter periods of increased humidity punctuating long-term aridity. The 7-m-high accumulation of colluvial sediments at the Salar Grande (21°S/70°W) studied here provides a key palaeoclimate record to understand hillslope dynamics and its relation to humid periods. While 10Be surface exposure ages point to long-term surface stability of the flat upslope surface, a combination of humidity-driven soil creep, overland flow and soil creep related to seismic shaking, caused denudation of the hillslope and accumulation of several metres of colluvium over much shorter timescales during the last 130 ka. A robust chronology for the hillslope sediments has been established by using Infrared Stimulated luminescence (pIR-IR225 protocol) on K-feldspar extracts from nine samples collected within the accumulation. A series of tests has been carried out to confirm the suitability of the method. The estimated ages indicate accelerated sedimentation at 35–80 ka, and 100–130 ka, which are interpreted as periods with more humid climate conditions than present. These findings agree with climate variations in the hyper-arid Atacama indicated by the activity of coastal alluvial fans and river catchments.

In 1755 CE, a strong earthquake followed by a transatlantic tsunami destroyed large coastal areas; it also left its sedimentary imprints in the Boca do Rio valley (western Algarve, Portugal). This tsunami layer is very well preserved and has been analysed in several studies. Deposits of preceding extreme wave events, however, have rarely been described for the entire Algarve coast. In this study, we present a multiproxy analysis of seven sediment cores from the Boca do Rio region, organized in two crossing transects, one parallel and the other perpendicular to the coastline. The geochronological framework has been established by combining radiocarbon and optically stimulated luminescence dating with sedimentological and geochemical analyses (XRF, C/N, magnetic susceptibility, granulometry, micropalaeontology), and covers the palaeogeographical evolution of that area for the last four millennia. As expected, the 1755 CE tsunami was easily identified at all coring sites, as a sandwiched stratum between fine-grained alluvium. This event layer presents several tsunami characteristics, such as erosive basal contact, rip-up clasts, a fining-upward sequence, and a mud cap. At one coring site, a second extreme wave event layer of marine origin was detected within floodplain deposits, due to its granulometric, XRF, magnetic susceptibility and micropalaeontological properties. It is stratigraphically located below the 1755 CE Lisbon tsunami layer and can be associated with another yet undocumented extreme wave event, most likely dating to the mid or late 1st millennium CE.

The Laacher See volcano (LSV) is located at the western margin of the Neuwied Basin, the central part of the Middle Rhine Basin of Germany. Its paroxysmal Plinian eruption c. 13 ka ago (Laacher See event; LSE) deposited a complex tephra sequence in the Neuwied Basin, whilst the distal ashes became one of the most important chronostratigraphic markers in Central Europe. However, some other impacts on landscape formation have thus far been largely neglected, such as buried gully structures in the proximity of the LSV. In this contribution, we map and discuss the spatial extent of these landforms at the site Lungenkärchen c. 4 km south of the LSV based on geophysical prospection as well as contrasting pedo‐sedimentary characteristics of the gully infill (particle‐size distribution, bulk‐sediment density, thin‐section analysis, saturated hydraulic conductivity) and the surrounding soils and tephra layers. These data are combined with a luminescence‐ and carbon‐14 (14C)‐based age model that relates them to the LSE. It is demonstrated how these gullies seem to have been formed and rapidly infilled by rainfall and surface discharge both during and subsequent to the eruptive phase, with modern analog processes documented for the 1980 Mount St Helens eruption (Washington State, USA). Given the density of the gullies at the site and their deviating pedo‐sedimentary properties compared to the surrounding soils, we propose a significant influence on agricultural production in the proximity of the LSV, which remains to be tested in future studies. Finally, in contrast, gullies of similar lateral and vertical dimensions identified in post‐LSE reworked loess and tephra deposits of the Wingertsbergwand (close to the main study site and proximal to the LSV) have shown to be unrelated to the LSE and can either be attributed to periglacial processes at the Younger Dryas‐Preboreal transition or to linear incision during the early Holocene., Linear subsurface gullies were identified close to the Laacher See volcano in magnetometer and ground‐penetrating radar prospection. Optically stimulated luminescence data indicate they incised during or shortly after the Laacher See event 13 ka ago. Pedo‐sedimentary characteristics of the gully infill differs from the surrounding regosols and brown earths, possibly influencing regional agricultural land use. image, University of Cologne http://dx.doi.org/10.13039/501100008001, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

The chronostratigraphy of coastal sedimentary records such as washover fans or beach-ridge sequences may be used to reconstruct storm chronologies on centennial to millennial time scales. However, modern analogues are crucial for interpretations of depositional processes and for reducing uncertainty in evaluating the typically complex chronostratigraphic architecture of these landforms. Such a modern analogue was provided by category 3 tropical cyclone (TC) Olwyn in 2015, which caused a significant storm surge in the Gulf of Exmouth, Western Australia, and which activated large washover fans located in the southwestern part of the Gulf. Pre- and post-TC Olwyn geomorphological surveys and high-resolution drone-derived topographical data of one of these washover fans document a detailed history of erosion and deposition during the event. The modern analogue deposits provided an excellent opportunity to evaluate the use of luminescence-based proxies (luminescence inventories) including quartz single-grain age distributions and associated remnant ages, as well as quartz and feldspar luminescence signal comparisons for tracing event-related sediment source environments and understanding transport processes (May et al., 2020). Sediments deposited during Olwyn show a systematic relationship between luminescence characteristics and washover fan position. Seaward and central washover sections are indicated by well-bleached deposits due to the beach as the dominant source and/or long transport distances across the fan. Lateral washover deposits, in contrast, are characterised by rather local source areas and short transport distances, resulting in higher remnant ages of 70-140 a. This data shows that the combination of sediment source environments and sediment transport length across the fan represents the main control in resetting the luminescence signal and enabling reliable depositional ages to be calculated. It documents the benefit of investigating luminescence inventories when establishing chronologies from complex sedimentary records, thereby demanding a careful consideration of local processes and source areas when interpreting sedimentary TC records.May, S. M., Callow, J. N., Brill, D., Hoffmeister, D., & May, J.-H. (2020). Revealing sediment transport pathways and geomorphic change in washover fans by combining drone-derived digital elevation models and single grain luminescence data. Journal of Geophysical Research: Earth Surface, 125, e2020JF005792. https://doi.org/10.1029/2020JF005792

Chronostratigraphic investigations on coastal sedimentary records such as washover fans or beach‐ridge sequences may be used to reconstruct storm chronologies on centennial to millennial time scales. However, modern analogs are pivotal in interpreting depositional processes and reducing uncertainty in evaluating the complex chronostratigraphic architecture of these landforms. Such a modern analog was provided by category 3 tropical cyclone (TC) Olwyn in 2015, which caused a significant storm surge in the Exmouth Gulf (Western Australia). Pre‐ and post‐TC Olwyn geomorphological surveys and high‐resolution drone‐derived topographical data of a large washover fan document a detailed history of erosion and deposition during the event. The modern analog deposits provided an excellent opportunity to evaluate the use of luminescence‐based proxies (luminescence inventories) for tracing event‐related sediment source environments and understanding transport processes. Sediments deposited during Olwyn show a systematic relationship between luminescence characteristics and washover fan position. Seaward and central washover sections are indicated by well‐bleached deposits due to the beach as the dominant source and/or long transport distances. Lateral washover deposits are characterized by rather local source areas and short transport distances, resulting in higher remnant ages of 70–140 a. Our data show that the combination of sediment source environments and sediment transport length across the fan represents the main control in resetting the luminescence signal and enabling reliable depositional ages to be calculated. It documents the benefit of investigating luminescence inventories when establishing chronologies from complex sedimentary records, thereby demanding a careful consideration of local processes and source areas when interpreting sedimentary TC records., Key Points: We investigated deposits of tropical cyclone Olwyn by combining drone‐derived digital elevation models and single grain luminescence data. High‐resolution pre‐ and post‐TC Olwyn DEMs helped to quantify the complex pattern of erosion and deposition in a large washover fan. The single grain luminescence data revealed differences in sediment source areas and transport distances of the washover deposits., Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659

In southern Iberia, the surroundings of the Strait of Gibraltar are known as a crossroad for population movements, cultural exchanges, and trade from Late Prehistory to modern times. However, questions remain about the impact of this historical development on the environment. The settlement of La Silla del Papa, an important hillfort in southern Andalusia (Cádiz), was occupied during the entire Iron Age, replaced by the coastal town Baelo Claudia during Roman times, and re‐occupied during Early Medieval times. As such, La Silla del Papa and its territory represent an ideal location for long‐term studies on human‐environment interactions. Within the framework of the interdisciplinary project “Archeostraits,” geoarchaeological investigations in the surroundings of La Silla del Papa aimed at constraining ecological conditions and human‐environment interactions during the mid‐ and late Holocene and during major human occupation phases. Our results document an early mid‐Holocene marine embayment in the lower floodplain of the Río del Cachón, rapidly turning into a coastal lagoon and later into freshwater‐dominated wetlands. After approximately 2100 BP (c. 150 BC), fluvial and alluvial deposition i600ing a high anthropogenic impact on the local landscape during Roman or post‐Roman times. Palynological results reveal fluctuating agricultural and pastoral activities and distinct periods of landscape opening during the Neolithic and Iron Age., Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Agence Nationale de la Recherche http://dx.doi.org/10.13039/501100001665

In seismically-active regions, mapping capable faults and estimating their recurrence time is the first step to assess seismic hazards. Fault maps are commonly based on geologic and geomorphic features evident at the surface; however, mapping blind faults and estimating their seismic potential is challenging because on-fault diagnostic features are absent. Here, we study the Pichilemu Fault in coastal Chile, unknown until it generated a M7.0 earthquake in 2010. The lack of evident surface faulting suggests a partly-hidden blind fault. Using off-fault deformed marine terraces, we estimate a slip-rate of 0.42 ± 0.04 m/ka, which when integrated with deformation estimated from satellite geodesy during the 2010 earthquake suggests a 2.5 ± 0.25 ka recurrence time for M6.6-6.9 extensional earthquakes. We propose that extension is associated with stress changes during megathrust earthquakes and accommodated by sporadic slip during upper-plate earthquakes. Our results have implications for assessing the seismic potential of cryptic faults along seismically-active coasts.

Wave-transported boulders represent important records of storm and tsunami impact over geological timescales. Their use for hazard assessment requires chronological information that in many cases cannot be achieved by established dating approaches. To fill this gap, this study investigated, for the first time, the potential of optically stimulated luminescence rock surface exposure dating (OSL-RSED) for estimating transport ages of wave-emplaced coastal boulders. The approach was applied to calcarenite clasts at the Rabat coast, Morocco. Calibration of the OSL-RSED model was based on samples with rock surfaces exposed to sunlight for ~ 2 years, and OSL exposure ages were evaluated against age control deduced from satellite images. Our results show that the dating precision is limited for all boulders due to the local source rock lithology which has low amounts of quartz and feldspar. The dating accuracy may be affected by erosion rates on boulder surfaces of 0.06–0.2 mm/year. Nevertheless, we propose a robust relative chronology for boulders that are not affected by significant post-depositional erosion and that share surface angles of inclination with the calibration samples. The relative chronology indicates that (i) most boulders were moved by storm waves; (ii) these storms lifted boulders with masses of up to ~ 40 t; and (iii) the role of storms for the formation of boulder deposits along the Rabat coast is much more significant than previously assumed. Although OSL-RSED cannot provide reliable absolute exposure ages for the coastal boulders in this study, the approach has large potential for boulder deposits composed of rocks with larger amounts of quartz or feldspar, older formation histories and less susceptibility to erosion.

Paleoclimate records from the Atacama Desert are rare and mostly discontinuous, mainly recording runoff from the Precordillera to the east, rather than local precipitation. Until now, paleoclimate records have not been reported from the hyperarid core of the Atacama Desert (

Lake Ladoga in northwestern Russia is Europe's largest lake. The postglacial history of the Ladoga basin is for the first time documented continuously with high temporal resolution in the upper 13.3 m of a sediment core (Co1309) from the northwestern part of the lake. We applied a multiproxy approach including radiographic imaging, (bio‐)geochemical and granulometric analyses. Age control was established combining radiocarbon dating with varve chronology, the latter anchored to a correlated radiocarbon age from a lake close by. The age‐depth model reveals the onset of glacial varve sedimentation at 13 910±140 cal. a BP , when Lake Ladoga was part of the Baltic Ice Lake. Linear extrapolation of published retreat rates of the Scandinavian Ice Sheet provides a formation age of the Luga moraine close to Lake Ladoga's southern shore of 14.5–15.9 cal. ka BP , older than previously assumed. Varve sedimentation covers the Bolling/Allerod interstadial, the Younger Dryas stadial and the Early Holocene. Varve‐thickness variations, conjoined with grain‐size and geochemical variations, inform about the relative position of the Scandinavian Ice Sheet and the climate during the deglaciation phase. The upper limit of the varved succession marks the change from glaciolacustrine to normal lacustrine sedimentation and post‐dates the drainage of the Baltic Ice Lake as well as the formation of the Salpausselka II moraine north of Lake Ladoga, by c . 250 years. The Holocene sediment record is divided into three periods in the following order: (i) a lower transition zone between the Holocene boundary and c . 9.5 cal. ka BP , characterized by mostly massive sediments with low organic content, (ii) a phase with increased organic content from c . 9.5 to 4.5 cal. ka BP corresponding to the Holocene Thermal Maximum, and (iii) a phase with relatively stable sedimentation in a lacustrine environment from c . 4.5 cal. ka BP until present.

The archaeological site of Taibeh located south of Wadi Musa, Jordan, incorporates at least two, maybe even five, successive layers associated with the Late Ahmarian, also known as Masraqan, technocomplex. The Masraqan is elsewhere connected with the beginning of the intensive use of plant food and with permanent settlements. Taibeh could be the first site to present as much as 5 successive layers of this cultural unit. The Masraqan is relatively well constrained in time, usually dated between 18 and 25 ka BP. A series of heated flints was collected at Taibeh to be dated using TL. Two informations are required for the estimation of a TL age: the equivalent dose ( D e ) which is the dose accumulated in the flint since it had been heated, and the dose rate ( D ˙ ) to which the flint is exposed during the burial time. The D e estimation was done applying two different protocols, and both produced consistent results. The D ˙ estimation was realised using a modified version of DRAC (Durcan et al., 2015) which allows to use different radio-element concentrations for the flints and the surrounding sediment.

Loess-paleosol sequences (LPS) represent an important terrestrial archive for the reconstruction of the paleoenvironmental evolution during the Last Glacial cycle in Europe. In the Rhine-Meuse area and the southwestern Germany, there are only few numerical ages determined with state-of-the-art luminescence methods, which limits the robustness of established chronostratigraphies. This study presents a comparative dating approach using quartz and feldspar post-infrared (pIRIR 290 ) optically stimulated luminescence (OSL) from fine- and medium-grained samples of five loess-paleosol sequences. Paleoenvironmental dynamics are reconstructed by high-resolution grain-size analysis. The OSL ages are evaluated as being robust and consistent with other records. Furthermore, we show that ages for hillslope deposits are sometimes overestimated due to low-frequency high-magnitude erosive processes. The integration of OSL ages, stratigraphy and high-resolution grain-size data contributes to a temporal more complete data record from Western and Central Europe. Secondly, we propose a combined stratigraphic model for LPS of the Last Glacial cycle, which is developed and discussed in the context of other key sites such as Havrincourt, Schwalbenberg II, Tonchesberg, Nussloch and Dolni Vĕstonice. Comparable chronologies and patterns in proxy data between sites with a large spatial distance suggest a possible semi-synchronous response to climatic changes in Europe. By combining our data with the Eifel-Laminated-Sediment-Archive (ELSA) and the NGRIP ice core, a relationship of loess archives and large-scale climatic signals is discussed and a proxydata based event-stratigraphy is developed. This model refines existing chronostratigraphic models and contributes to solve open discussion concerning the timing and demarcation of sedimentary units and sequences from for Western and Central Europe.

The Shirasuka lowlands, located on the Enshu-nada coast of central Japan, record evidence for numerous extreme wave events. Here we test the applicability of using the luminescence signal from feldspars to date these young (130 procedure. We demonstrate that this IRSL50 (pre-IR130) signal results in reliable ages when corrected for fading, and the post-IR IRSL130 stimulation functions as an optical wash for both the natural/regenerated luminescence signal (Lx) and the test dose signal (Tx), lowering the recuperation and removing any remaining charge from previous steps in the protocol. The single grain IRSL50 (pre-IR130) ages generated cover the historical record of the past 800 years and correlate well with past earthquakes and tsunamis in 1361 CE, 1498 CE and 1605 CE. Another identified tsunami deposit may correlate with the 1707 CE earthquake and tsunami. A slope failure deposit, probably caused by the earthquake in 1944 CE, is also identified. This study demonstrates that accurate ages can be determined for the young, extreme wave events at this site using the luminescence signal from feldspars.

Inactive shorelines represent valuable records for sea level change, shoreline variations and tectonics if we can constrain the timing of their formation. Where the associated beaches are cobble dominated, luminescence rock surface dating is a promising alternative to established dating approaches, since unlike other techniques it offers the potential to identify clasts unaffected by inherited ages. While luminescence rock surface dating has successfully been used on Holocene and Late Pleistocene beach ridges previously, in this study the potential of IRSL rock surface dating is evaluated for the magmatic cobbles of uplifted Pleistocene terraces along the tectonically active coast of northern Chile. Cobbles from an active beach were used to investigate the influence of cobble lithology on IRSL signal properties and the effectiveness of IRSL signal resetting in the rock. While alkaline and andesitic cobbles yield low IRSL intensities and limited signal resetting due to strong light attenuation, more favourable characteristics for dating were observed for some diorite and granite cobbles. Their IRSL signals were well reset in the uppermost few mm without any systematic difference between upper and lower surface. Some of them revealed bleaching plateaus with inherited ages close to zero after correction for laboratory residuals. For dating, cobbles from three Pleistocene marine terraces, for which new uranium‑thorium and ESR control ages on molluscs provide age control, were targeted. None of the associated IRSL rock surface burial ages agrees with the MIS 5 control ages of the terraces. Most of the selected cobbles are either too dark to allow for effective signal resetting or yield IRSL properties unsuitable for dating. Only one of the targeted cobbles shows both signs of signal resetting at its surface and sensitive IRSL signals, but its signal was already in field saturation due to dose rates >6 Gy/ka. In conclusion, our data indicate that beach cobbles with granitic to dioritic lithology combine appropriate IRSL properties and sufficient IRSL signal resetting for dating Holocene landforms. Last interglacial terraces may already be beyond the limit of IRSL dating for most cobbles of this lithology since they show large dose rates compared to IRSL sediment dating.

Reliable age dating of coastal sedimentary landforms is crucial for inferring storm frequencies and magnitudes from geological archives. However, in highly energetic coastal settings, radiocarbon dating is often biased by reworking and/or poorly constrained marine reservoir effects. Due to this, most cyclone-driven sediment archives from the semiarid coast of NW Australia – a region frequently affected by tropical cyclones but with a historical record limited to ∼150 a, and therefore strongly in need of long-term data inferred from geological evidence – are affected by chronological inaccuracies. Optically stimulated luminescence dating (OSL) may overcome these shortcomings by dating the transport of sediment directly. In turn it may be related to other challenges when applied to cyclone deposits from semiarid environments. The cyclone-induced washover fans at Point Lefroy, NW Australia, are composed of a heterogeneous mixture of coral fragments, shell hash and siliciclastic sand. This makes them particularly prone to high dose scatter resulting from a combination of partial bleaching, sediment mixing and dose-rate heterogeneity. The washover fans are further characterised by a discontinuous nature of cyclone deposition, as indicated by erosional features and macroscopic brunification horizons. By using a combination of quartz single grain dating, autoradiography, alpha counting and gamma spectrometry, sediment mixing and dose rate heterogeneity are identified as the main sources of dose scatter. The resulting chronology allows us to discriminate at least four well constrained phases of washover fan activity at ∼180, ∼360, ∼870, and ∼1300 a ago. Older but less well constrained activity phases occurred ∼1950, ∼2300, and ∼2830 a ago. While these phases of increased cyclone activity correlate with depositional units separated by potential palaeosols, OSL ages, quasi-continuous portable OSL reader measurements and gamma spectrometry measured with increased sampling resolution point to deposition of distinct washover units within a very short period of time. However, unambiguous discrimination between deposition of individual units by single events and deposition by several cyclones within periods of only a few decades is currently not possible.

Washover fans typically form due to barrier overwash or breaching and coastal inundation and generally represent geomorphological and depositional evidence of intense storms. Few studies have investigated the chronostratigraphy of washover fans in order to infer magnitude/frequency patterns of extreme-wave events over longer time scales. Here we present new data on the chronostratigraphy of late Holocene washover fans in the Exmouth Gulf (Western Australia) by using ground penetrating radar and unmanned aerial vehicle (UAV) survey techniques, as well as geomorphological, sedimentological and chronological investigations. This study aims to (i) provide a detailed characterization of the washover fans' geomorphology and stratigraphical architecture; (ii) document depositional processes involved in their formation; (iii) establish a chronostratigraphy based on optically stimulated luminescence (OSL); and (iv) understand the significance of the washover fans for recording past tropical cyclone (TC) activity. The fans consist of multiple sequences of sand, shell debris and coral rubble comprising depositional units related to TC-induced inundation. The units are separated by palaeosurfaces with incipient soil formation, formed during periods of reduced depositional activity. In combination with the interpretation of a UAV-based high-resolution digital surface model, multiple phases of reactivation are inferred. OSL results allow the establishment of a local long-term TC record and suggest storm-induced deposition at ∼170, ∼360, ∼850 and ∼1300 years ago. Further units were dated to ∼1950, ∼2300, and ∼2850 years ago. The chronology of TC events is consistent with other work relating TC activity with El Nino Southern Oscillation (ENSO) and sea surface temperature (SST) patterns, corroborating the regional palaeotempestological relevance of this unique geomorphological record.

Our study focuses on the ephemeral stream deposits of Wadi Selloum to identify phases of morphodynamic stability (pedogenesis) and activity (flooding) in the direct vicinity of the rock shelter of Ifri n'Ammar (NE Morocco). As one of the oldest settlement sites of anatomically modern humans (AMH) in North Africa, Ifri n'Ammar documents periodical occupations since ~ 170 ka. Since the discontinuous settlement record may reflect climate forcing with subsequent landscape changes, we aim at reconstructing the palaeoenvironmental variability recorded in the ephemeral stream deposits. In addition to the use of micromorphological, sedimentological, geochemical and mineralogical methods, the geochronological framework of ephemeral stream deposits was established by the application of different luminescence dating techniques. The deposition ages between 102 ± 8 ka and 1.3 ± 0.2 ka span different morphodynamically stable and active phases. Periods of enhanced aggradation occurred around ~ 100 ka, ~ 75 ka, ~ 55 ka, after the LGM, and during the Holocene, whilst sedimentation ended after ~ 1.3 ka. The Wadi Selloum might be characterised by enhanced flooding during humid phases. Pedogenesis may be used as environmental indicator for more humid climate conditions during MIS 3 (palaeo-Calcisol), the early Holocene (Calcisol) and the late Holocene (Fluvisol). This study thus provides first insights into the palaeoenvironmental changes around the rock shelter of Ifri n'Ammar during the last glacial-interglacial cycle.

In the hyperarid environment of the Atacama Desert, alluvial fans are the principle fluvial geo-archive reflecting variations in climate and tectonics in their architecture. While they have been studied in the core of the desert to reconstruct long-term palaeoenvironmental changes from the Oligocene to the Quaternary and, in particular, to constrain the onset of hyperaridity, alluvial fans along the coast (20.5°S – 25.5°S) are younger and show a much higher activity; thus, they can serve as archives during the Pleistocene to Holocene evolution. However, past and recent morphodynamics of the coastal alluvial fans (CAF) are yet poorly reconstructed so that the understanding of an interplay between climatic, geologic, and biotic controls is still challenging.We related climatic, lithologic, and tectonic source-area characteristics to geomorphometric parameters of the CAF and their catchments. Geomorphometric analyses were conducted based on the 12.5 m TanDEM‑X WorldDEM™, lithological and tectonic data were extracted from regional geological maps, and the frequency of heavy rainfall events derived from a regional Weather Research and Forecasting (WRF) model was used as a climate parameter. We further combined luminescence dating, cosmogenic nuclide exposure dating, and existing chronological data to constrain the timing of Pleistocene alluvial fan deposition as well as the ages of interbedded marine terraces.Results indicate a primary climatic control on CAF dynamics shown in the functional relationships with catchment hydromorphometrics that mirror a high susceptibility to debris-flows as well as in the temporal pattern of CAF activity. Distinct phases of CAF activity occurred during the late Pleistocene (95–80 ka, 60–45 ka, and 35-20 ka) and the Holocene – driven by atmospheric changes from the Pacific Ocean. The primary source of precipitation is reflected along the latitudinal gradient: frontal systems and cut-off lows mainly originating from the extratropics. Towards the south, an increasing density of Loma vegetation can be observed so that also possible feedback mechanisms of biota on sediment supply need to be considered. While source-area lithology is of negligible relevance for CAF morphodynamics, an important long-term influence of tectonics can be seen in the regional uplift, which in turn controls the catchment shape and relief. From the numerical dating of the marine terraces, uplift rates ranging between ~0.06 and ~0.57 m/ka were derived for the late Pleistocene period.Acknowledgement: TanDEM-X WorldDEM™ data is provided by a DLR Science grant, 2017.References: Bartz, M., Walk, J., Binnie, S.A., Brill, D., Stauch, G., Lehmkuhl, F., Hoffmeister, D., Brückner, H., in press. Late Pleistocene alluvial fan evolution along the coastal Atacama Desert (N Chile). Global and Planetary Change, 103091. https://doi.org/10.1016/j.gloplacha.2019.103091Walk, J., Stauch, G., Reyers, M., Vásquez, P., Sepúlveda, F.A., Bartz, M., Hoffmeister, D., Brückner, H., Lehmkuhl, F., 2020. Gradients in climate, geology, and topography affecting coastal alluvial fan morphodynamics in hyperarid regions – The Atacama perspective. Global and Planetary Change 185, 102994. https://doi.org/10.1016/j.gloplacha.2019.102994

Timothée Jautzy1,2, Dominik Brill3, Laurent Schmitt1, Gilles Rixhon4Obtaining robust chronological data on landforms and their related deposits together with constraining rates of earth surface processes have constantly represented a major challenge in Quaternary science. In the fluvial context, Optically Stimulated Luminescence (OSL) is particularly well-established but still faces several limitations. It notably requires expensive and time-consuming sample processing and measurement, frequently resulting in a poor spatial and stratigraphical distribution of sampling which may negatively impact the chronological information. To overcome this main limitation, a Portable OSL reader (POSL) has been recently developed (Sanderson & Murphy, 2010). It consists in directly capturing a luminescence signal (counts per seconds) on unprepared sediment samples. This technique is quick and affordable but, unlike conventional OSL, is not able to yield numerical age estimates.This contribution explores POSL capacities to provide useful relative age information on alluvial sediments from the last centuries. We study and compare 42 samples collected from three alluvial profiles located in the floodplain of a gravelly-sandy mid-sized river: the Bruche (i.e. a sub-tributary of the Upper Rhine, France). POSL stimulations, including both blue and infra-red signals, are performed in combination with grain size analysis. We observe (i) an overall increase of signal intensity with increasing depth, (ii) a very good match between blue and IR signals and (iii) no systematic correlation between signal intensity and grain size. Whilst this last point must still be confirmed (i.e. signal intensity does not primarily depend on grain size), our preliminary results positively suggest that POSL is a promising tool to provide a relative chronology for very young alluvial sediments. Furthermore, it may also provide information on geomorphic processes. These results will be combined soon to numerical dating (OSL and 14C) and compared to outcomes of a planimetric analysis to thoroughly reconstruct the historical lateral mobility of the Bruche river.

The hyperarid parts of the Atacama Desert, N Chile, are among the driest places on Earth, and a number of studies have emphasized the remarkable slowness of Earth surface processes since the late Tertiary. Despite episodic overland flow or flash flood activity, salt-driven shrink-swell processes, dust deposition, and seismic shaking have significantly contributed to the formation of the characteristic landscape. The enigmatic and Atacama-specific zebra stripes are contour-parallel, thin lateral bands of rather angular gravels on hillslopes, characterized by grain sorting, a lateral succession of 1-3 m-wide frontal lobes, and specific wavelengths, occurring generally in areas with lowest rainfall and low to no fog occurrence. While previous investigations suggest that zebra stripes represent fossil evidence of overland flow, a recent study challenged their water-related evolution and emphasized the role of seismicity in their formation, and in shaping the Atacama landscape in general. Similar landforms may also be found on Mars, although related processes may be different to those on Earth.We use UAV-derived orthophotos and digital elevation models, geomorphological surveys and sediment sampling, as well as OSL rock surface dating and cosmogenic nuclide (21Ne, 10Be) analysis of surface clasts to provide new insights into zebra stripe activity and stability in the Atacama Desert. Our investigations show that zebra stripes are found in numerous areas in the hyperarid core of the Atacama, implying a wider distribution of zebra-striped hillslopes than previously suggested. Inter-site comparison illustrates considerable differences between individual zebra stripe sites, and geomorphological characteristics suggest that zebra stripes may be active or inactive forms, depending on their location. Active forms are indicated by well-developed frontal lobes, reduced dust contents, and clearly developed downslope sorting trends with a high percentage of freely floating clasts, whereas inactivity seems to be indicated by poorly visible frontal lobes, high dust contents, poor sorting trends and a high proportion of clasts embedded into the underlying vesicular soil horizon. At the same time, preliminary chronological data based on OSL rock surface dating suggests that active stripes contain clasts with active bleaching fronts at top and bottom sides, pointing to late Pleistocene to Holocene activity and clast overturning. Inactivity, in contrast, is indicated by similar IR50 and pIR225 bleaching curves (equilibrium of bleaching and dosing) in upper clast surfaces and the lack of a bleaching front at the bottom side, pointing to long exposures without clast overturning. Combined with cosmogenic nuclide concentrations, our results allow for inter-site comparisons and a better understanding of (relative) stripe chronologies and activity-stability patterns. Alongside further investigations on the significance of fog, wind, rain and seismicity, future work will aim at constraining time scales on which active/young and inactive/old forms have developed. If these forms are seismicity-related, our study contributes important information on the paleoseismic evolution of the central Atacama.

Wave transported boulders represent important records of storm and tsunami impact over geological timescales. Their use for hazard assessment requires chronological information that in many cases cannot be achieved by established dating approaches such as radiocarbon and U-Th dating. To fill this gap, we investigated the potential of optically stimulated luminescence rock surface exposure dating for estimating transport ages of coastal boulders. The approach was applied to wave-emplaced calcarenite clasts at the Rabat coast, Morocco. Calibration of the OSL surface exposure model was based on samples with rock surfaces exposed for ~2 years, and OSL exposure ages were evaluated against age control deduced from satellite images. The dating precision is very limited for all boulders due to the local source rock lithology, which contains low amounts of quartz and feldspar and was formed after MIS 5 (OSL signals are not in field saturation). Nevertheless, we propose a robust relative chronology for boulders that are not affected by significant post-depositional erosion and that share surface angle of inclination with the calibration samples. The relative chronology indicates that most boulders were moved by storm waves; these storms lifted boulders with masses of up to ~40 t; indicating that the role of storms for the formation of boulder deposits along the Rabat coast is much more significant than assumed previously. While OSL rock surface exposure dating cannot provide reliable absolute exposure ages for the coastal boulders from Rabat, the approach has great potential for boulder deposits composed of rocks with larger amounts of quartz or feldspar, older formation histories and lower susceptibility for erosion.

Reconstructing exposure histories of rock surfaces with luminescence dating is a recently developed tool which has proven valuable to chronologically constrain archaeological rock structures (e.g. Sohbati et al., 2012). Here, we explore the possibility to use infrared stimulated luminescence (IRSL) exposure dating to constrain the period of usage of two dry stone enclosure complexes (MZ001S and MZ005S) in Val di Sole, Trentino, Italy. Archaeological investigations confirm that the enclosures were used to keep livestock and radiocarbon ages and archaeological finds from MZ005S restrain the oldest time of use to the Late Middle Ages or Early Modern Period (Carrer and Angelucci, 2018). One 19th-century potshard has been recovered from MZ001S and interviews with residents indicate that MZ001S may have been in use until the mid-20th century. Mica and quartz-rich gneiss rocks of both structures were sampled, together with calibration rock surfaces which had been exposed for one year. Cores were extracted from the rocks with a water-cooled bench drill and cut with a cooled precision saw. Whole rock slices (approx. 0.7 mm thin) were heated to 180 °C for 100 seconds and were subsequently measured with infrared diodes at 50 °C for 300 seconds to create IRSL-depth profiles. Exposure ages were calculated with the exposure dating model developed by Sohbati et al. (2011) for which we used de-trapping rates calculated from the exposed calibration surfaces. IRSL-with-depth profiles are presented from both natural and calibration surfaces. Preliminary ages severely underestimate expected exposure ages (decades of exposure, compared to expected centuries of exposure) and precision of the ages is low. More investigations are necessary but possible reasons for this age discrepancy are denudation of the rock surface, heterogenic mineralogy with patches of opaque minerals which locally increase light attenuation, or the calibration samples do not represent good analogues for the rocks from the stone structures. The low precision of the ages appears to originate from variations in the IRSL-depth profiles between different cores cut from the same sample. ReferencesCarrer, F., Angelucci, D.E., 2018. Continuity and discontinuity in the history of upland pastoral landscapes: the case study of Val Molinac and Val Poré (Val di Sole, Trentino, Eastern Italian Alps). Landscape Research 43, 862–877. doi:10.1080/01426397.2017.1390078.Sohbati, R., Murray, A., Jain, M., Buylaert, J.P., Thomsen, K., 2011. Investigating the resetting of OSL signals in rock surfaces. Geochronometria 38. doi:https://doi.org/10.2478/s13386-011-0029-2.Sohbati, R., Murray, A. S., Chapot, M. S., Jain, M., and Pederson, J. 2012. Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating J. Geophys. Res., 117, doi:10.1029/2012JB009383.

Increasing population and economic pressures along the world's coastlines have made, and are continuing to make coastal communities more vulnerable to hazards. The hazard management of tsunamis and other extreme waves (storm waves, seiches, infragravity waves) is based on the assessment of the frequency-magnitude relationship of these events, which uses instrumental, historical and, critically for the evaluation of long-term recurrence patterns, geological evidence. The identification of tsunami deposits in coastal sedimentary environments is challenging and has systematically evolved as a subdiscipline of sedimentology only over the last. 30 years (i.e., paleotsunami research). Nevertheless, a wide range of field sampling methods, proxy analyses, and dating approaches have been successfully applied to identify tsunami deposition in different sedimentary environments and infer tsunami impacts in the past. This compendium summarizes the state of the art in paleotsunami research in an effort to provide detailed methodological insights and aims at guiding workflows and site-specific research designs.

[Abstract] The Atacama Desert in northern Chile is one of the driest deserts on Earth. Hyperaridity persists at least since the Miocene and was punctuated by pluvial phases. However, very little is known about the timing, regional spread and intensities of precipitation changes. Here, we present a new precipitation record from a sedimentary sequence recovered in a tectonically blocked endorheic basin that is located in the hyperarid core of the Atacama Desert. The chronostratigraphic framework of the record is given by a multi-disciplinary dating approach, suggesting an age of ca. 68 ka BP for the core base. The sequence consists of three sediment types, whose sedimentological and geochemical characteristics suggest different depositional processes that reflect different degrees in humidity. First, particularly fine-grained sediments with high clastic but low calcium sulfate and carbonate contents reflect a particularly dry climate with only sporadic precipitation events and fluvial supply via channel systems. Second, more coarse-grained sediments with lower clastic and higher calcium sulfate and carbonate contents reflect more moist conditions with stronger precipitation events that lead to fluvial activity not restricted to the channels but involving the slopes and plains in the catchment. Third, normally graded layers with an equally high proportion of calcium sulfate and carbonate reflect occasional high-precipitation events that caused sediment supply also from most distant parts of the catchment via severe flash floods. The sedimentary succession suggests that precipitation changes took place on orbital but also on millennial time scales. Rather moist periods occurred during most of MIS 2, several shorter periods within MIS 3 and parts of MIS 4. Comparison of the findings from the Huara record with selected climate records from continental and marine sites in South America suggests a strong precipitation heterogeneity across the Atacama. This heterogeneity is caused by pronounced differences in the dominating climate patterns and a shift from predominant summer rain in the north to winter rain in the south. Precipitation supply to the Huara clay plan is controlled by the atmospheric circulation rather than the surface temperature of the adjacent ocean.

Hillslopes represent areas of predominant denudation and constitute the transition and trajectory to floodplains; they play a crucial role in understanding the longterm landscape evolution of desert environments. However, although hillslope processes are known to be very slow or even stagnant in (hyper-) arid environments, process mechanisms under the virtual absence of water are poorly understood, and process rates are essentially unknown. Based on irrigation experiments, different monitoring techniques including drone-based high-resolution digital elevation models, geomorphological, stratigraphical, geochronological (OSL), sedimentological and geochemical investigations, as well as mu CT scans of sediment cores, this contribution presents detailed insights into the chronostratigraphy of tongue-shaped, 50 m-long and 30 m-wide fine sediment lobes located along a 10-30 degrees steep thrust-related slope east of the Salar Grande (Atacama, Chile). Irrigation experiments were performed to gain insights into precipitation thresholds for surface runoff and hillslope dynamics. Although artificial rainfall intensities were similar to 46 mm/h, infiltration was 100%, and the experiments did not initiate surface runoff or (detectable) slope material displacements. In addition, a distinct stratigraphic pattern with buried paleo-surfaces and paleo-biological surface crusts suggests increased hillslope activity during the late Pleistocene, potentially driven by changes of (fog-induced) humidity, salt-related shrink and swell processes, or paleo-seismic activity. While a variety of geo-bio-archives document periods of increased precipitation in the Andean parts of the Atacama Desert throughout the Quaternary, evidence for contemporaneous paleoclimatic changes from areas disconnected to Andean precipitation fluctuations (i.e., the Coastal Cordillera) is scarce. In this regard, the investigated landforms potentially represent one of only few sediment records recording paleoclimatic changes in the central desert, independent from Andean rainfall.

This chapter informs about optically stimulated luminescence (OSL) as an approach to date tsunami and storm deposits. Despite larger uncertainties compared to radiocarbon and U/Th dating, OSL dating has been regarded advantageous for a range of sedimentary environments. Arguments in favor of OSL dating are ubiquitous applicability to abundant quartz and feldspar minerals of the entire Holocene and late Pleistocene, and direct determination of the time of the depositional event and not the death of organisms in or around the tsunami and storm layers. Typical challenges in OSL dating of tsunami and storm deposits include incomplete OSL signal resetting during tsunami and storm transport, complex radiation fields in nearshore environments, and problematic quartz OSL properties in seismically active regions. In this chapter, these challenges and solutions to handle them are summarized along with a general outline of OSL dating.

Typhoon Durian in November 2006 was most notable for a series of devastating lahars that buried communities at the base of Mayon volcano in Bicol, Philippines. Typhoon Durian delivered extreme rainfall that remobilized volcanic debris that caused more than ~1200 deaths and extensive property damage. Although not as deadly as the lahar, Typhoon Durian also generated a storm surge that caused localized dune breaching on Malinao barrier sand spit in Lagonoy Gulf. In the absence of instrumental data of the storm surge, we used the geomorphical and sedimentary imprints including erosion scarps, washover fans and terraces to infer the inundation heights on the barrier spit. The surface elevations of washover fans, terraces and relic dunes indicate inundation heights above 1.5 m but not exceeding 3 m. Typhoon Durian's overwash deposit is characterized by typical washover fan stratigraphy, and exhibits horizontal to sub-horizontal lamination on the front to mid-fan and foreset stratification near the fan terminus. Subsurface stratigraphy using shore-normal ground penetrating radar (GPR) imaging reveals at least two buried erosional surfaces farther inland from the erosional surface of Typhoon Durian. Similar to Durian, the older erosional surfaces were probably sustained from previous typhoons. We infer that episodic erosional events most likely have repeatedly disrupted the prograding development of the Malinao barrier spit. Typhoon Durian highlights the exposure of volcanic landscapes to multiple hazards from cyclone landfall. Ministry of Education (MOE) National Research Foundation (NRF) Published version This research is supported by the Singapore National Research Foundation fellowship scheme (Grant No: NRF-RF2010-04) and the Singapore Ministry of Education under the Research Centres of Excellence initiative.