GM8.1

High-resolution analysis of late Quaternary aeolianites on the southeastern Mediterranean coast of Israel

Mokaya, B.L.^1,2, Roskin, J.^2,3, Koren, A.⁴, Filin, S. ⁴, Bookman, R¹.,

• Charney School of Marine Sciences, Department of Marine Geosciences, University of Haifa, Israel
• Geomorphology and Portable Luminescence Laboratory, the Leon Recanati Institute for Maritime Studies (RIMS), University of Haifa, Israel
• Department of Geography and Environment, Bar-Ilan University, Israel
• Mapping and Geo-Information Engineering, Technion - Israel Institute of Technology, Israel

Aeolianites ridges are petrified sand dunes deposited at low to mid-latitude coasts. The location, structure and lithification properties of aeolianite ridges is generally understood to reflect changes in sea level, strong wind power, fetch parameters, and sediment availability. The Israeli coast has a chain of both submerged and inland aeolianites ridges running parallel to the southeastern Mediterranean coastline. The aeolianites consist of discontinuous accumulations of fine-and cross-bedded Nilotic sands, differentially lithified by carbonate. Red, sandy palaeosoils divide the aeolianite units and represent periods of reduced wind power and stabilization. Previous studies present low-resolution dating and finds are poorly correlated with climatic and environmental events related to deposition or lithification.

This study describes the vertical and lateral evolution of an elongated aeolianite ridge, at first a sand dune that accumulated and lithified along the palaeo Israeli Mediterranean coast during the last glacial period. The main objective is to explore the dune development at single-bed to sand package stages in time and their relation to local environmental conditions and regional climatic trends and possible changes.

The methodology included high-resolution LiDAR scanned enriched by RGB image data of exposed sections, detailed Portable OSL analysis accompanied with OSL dating, and sedimentological characterization. Sedimentological analysis shows that aeolian accumulation occurred as discrete laminae that built-up cross-bedded sediment packages. Beds continuously alternate between loose sand to cemented ones. The loose laminae consist almost entirely of quartz grains, while the lithified laminae are dominated by calcium carbonate cement. Since cementation is parallel to the aeolian accumulation, it is proposed that this incipient lithification may represent a surficial process that occurred while the dune was still active and accumulating. It may represent microbiotic crusts activated by moisture conditions. These can serve as biomarkers for wind power and wetness duration.

POSL measurements have bright blue OSL signals (12-17 million) and very similar depletion and IRSL-OSL ratios that demonstrate sedimentological similarity that is suitable for reliable POSL profiling. POSL profiling revealed a high-resolution and in-order chronostratigraphy. This may suggest that the sand laminations represent specific wind events at a very high seasonal to even diurnal resolution. Lateral POSL results reveal a certain value range and it does not demonstrate evidence for a significant change in depositional age, while the vertical profile demonstrates a linear upwards decrease in count values. The trends also demonstrate that the quartz grains do not possess a saturated OSL signal. Upcoming OSL dating and outcrop image analysis will better constrain the accumulation rates and their possible connection to environmental and climatic drivers. 

How to cite: Mokaya, L., Bookman, R., Roskin, J., Filin, S., and Koren, A.: High-resolution analysis of late Quaternary aeolianites on the southeastern Mediterranean coast of Israel, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10249, https://doi.org/10.5194/egusphere-egu22-10249, 2022.

Here, we review four decades of research on Aeolian-Fluvial (A-F) interactions, in particular, dune-damming impoundments that deposited expanses of playa-like fine-grained sediments in the Sinai-Negev erg. We focus mainly on the erg’s eastern edge, the arid northwestern Negev dunefield (Israel), where wadis flood 1-2 times a winter. The review relates to the mechanisms of formation, timing, morphology, sedimentology, landscape response, relations with prehistoric settlements, palaeoclimate, and methodological approaches.

Vegetated linear dune (VLD) incursion, mainly during the Heinrich 1 and Younger Dryas, indicated by spatially dense but well-spread OSL chronologies, initially dammed and impounded medium-sized (10¹-10² km²) fluvial systems, usually in a perpendicular angle. The impounded water bodies generated a dunefield margin landscape of widespread, playa-like flats comprised of sequences of A-F sediments. These sequences, usually <7 m thick, found to often lay over eroded dune sand, reveal distinct sedimentological structures such as massive loam and couplets that in some places overlap sand, and fluvial sand associated with adjacent VLD truncation. Couplets, indicative of single dune-dammed impoundment events are usually <dozen, per section, representing several flood seasons within a sequence spanning several thousands of years. This discrepancy may imply that impoundments were seasonally successive for only several years, recording high discharge floods transporting large amounts of fine-grained bedload. More likely, the sequences are incomplete, having gone through depo-erosional cycles.

Despite VLD stabilization at the end of the Younger Dryas, fluvial fine-grained sediments continued to accumulate until the early Holocene due to successions of dune-dammed impoundments, inland of the dunefield margins. This process demonstrates that the reopened fluvial systems gradually propagated downstream. Previously reported anomalic amounts of lithic-dominated concentrations and hearths, usually from the Epipalaeolithic period, appear near and within mapped A-F sediments. Recent OSL chronologies of the A-F deposits and radiocarbon dates of hearths and hearth-like remains, support these and newly found sites, some dating to the Neolithic period. The resultant landscape is a result of unique environmental transitions at a time-window of high up-basin loess availability, from open fluvial domination to aeolian domination (dune-damming) and finally, partial and gradual dune-dam breaching, reopening of the fluvial systems and incision within A-F sediments. The patchy landscape response during this transition is controlled by basin size and its accumulated sediment load, and dune-dam properties. Altogether, the studies reveal a dramatic geomorphic and direct fluvial landscape response to dune incursion during windy late Pleistocene periods where precipitation changes appear to constitute only a minor role.

How to cite: Roskin, J., Robins, L., Yu, L., and Greenbaum, N.: Palaeoclimatic and geomorphic implications of late Quaternary aeolian-fluvial interactions in the northwestern Negev dunefield (Israel) - A review, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4344, https://doi.org/10.5194/egusphere-egu22-4344, 2022.

Aeolian-Fluvial (A-F) processes formed vast and flat landscapes during the late-Pleistocene along dunefield margins. A-F research examines the impacts of extrinsic processes of the aeolian and fluvial systems on one another, which formed these unique landscapes. However, the mechanisms and depositions of A-F processes are not fully understood. In this study, a 120 m wide and 7 m high, wadi bank exposure of an A-F sequence reveals the sedimentary units, where the northwestern Negev (Israel) dunefield desert margins interact with the Atadim fluvial system (64 km²). A chrono-stratigraphic analysis by laboratory measurements (Particle size distribution & Total of carbon), relative and absolute luminescence dating (POSL & OSL), radiocarbon and archeological dating, enabled conclusions regarding the depositional mechanisms and environment. Finally, DEM (~12.5 m pixel) and GPS-RTK (0.3 m resolution) were used to assess A-F depositional boundary.

The results demonstrate a unique perseverance of aeolian sand units covered by low-energy fluvial deposits. The sand and dune units illustrate several sand incursions into the fluvial system since the Last Glacial Maximum until the mid-Holocene. We observed  low-energy fluvial deposits, which resulted from these sand incursions: (a) couplets deposited in an ever-emptying waterbody, impounded by a dune-dam. (b) massive fine-grained formation – deposition of suspended sediments in an impounded waterbody, near the damming-dune where the waterbody is the deepest. (c) Fining upwards with fine laminas deposits – embedded between couplet formations, deposited in a low-energy fluvial environment. The fine laminas indicate small tributaries income to the main low-energetic flow.

We demonstrate that in A-F sequences, not only are the aeolian sand units preserved but also they act as palaeo-fluvial archives. The section reflects that late-Pleistocene dune-damming build-up resulted in a lagged fluvial response enabled by a climatic change during the early-Holocene. The combination of stabilized dune-dams within the fluvial systems and high discharge flows with large available sediment supply resulted in vast aggregation of A-F sediments, forming the alluvial plain.

How to cite: Robins, L., Roskin, J., Yu, L., and Greenbaum, N.: Aeolian-Fluvial response to late-Pleistocene dunefield encroachments along the northwestern Negev dunefield margins (Israel), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13303, https://doi.org/10.5194/egusphere-egu22-13303, 2022.

Large (1-50 km), coalescing alluvial fan systems extend eastwards from Hajar Mountain catchments to the Batinah Coast of northern Oman, representing an important environment for both sediment transfer and storage. As sediment stores, these alluvial fans have great potential to act as archives of Quaternary palaeohydrological changes in their mountain catchments. This has been shown by work carried out on interior draining fans west of the Hajar (e.g. Blechschmidt et al., 2009; Parton et al., 2013, 2015), which has highlighted the sensitivity of fan systems to periods of intensified Indian Ocean Summer Monsoon (IOSM) rainfall. However, the timing of fluvial activity and fan aggradation on the east of the Hajar Mountains is currently poorly constrained due to limited quantitative geochronology. This is, in part, due to the difficulty of dating Batinah alluvial sediments using luminescence techniques because of their low quartz abundances (Hoffmann et al., 2015).

This study presents new Mid-Late Pleistocene OSL ages from alluvial sediments exposed by incised channel systems in fan-head trenches in the lower reaches of the catchment and one section near the apex of the Rustaq fan. Ages from the upper fan represent the first dates on unconfined fan deposition from the Batinah Coast. The depositional contexts of ages are important for understanding the nature of fan dynamics over time. However, ages will also be considered in the context of regional palaeoenvironmental records to investigate the role of IOSM variability in landscape evolution on the Batinah Coast.  

References

Blechschmidt, I., Matter, A., Preusser, F. and Rieke-Zapp, D., 2009. Monsoon triggered formation of Quaternary alluvial megafans in the interior of Oman. Geomorphology, 110(3-4), pp.128-139.

Hoffmann, G., Rupprechter, M., Rahn, M. and Preusser, F., 2015. Fluvio-lacustrine deposits reveal precipitation pattern in SE Arabia during early MIS 3. Quaternary International, 382, pp.145-153.

Parton, A., Farrant, A.R., Leng, M.J., Schwenninger, J.L., Rose, J.I., Uerpmann, H.P. and Parker, A.G., 2013. An early MIS 3 pluvial phase in Southeast Arabia: climatic and archaeological implications. Quaternary International, 300, pp.62-74.

Parton, A., Farrant, A.R., Leng, M.J., Telfer, M.W., Groucutt, H.S., Petraglia, M.D. and Parker, A.G., 2015. Alluvial fan records from southeast Arabia reveal multiple windows for human dispersal. Geology, 43(4), pp.295-298.

How to cite: Woor, S., Durcan, J., Burrough, S., Parton, A., and Thomas, D.: Using OSL dating to constrain the timings of Late Quaternary palaeohydrological activity on the Rustaq alluvial fan system, northern Oman., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9516, https://doi.org/10.5194/egusphere-egu22-9516, 2022.

The Kalkkop meteorite impact crater, situated within the semi-arid Nama-Karroo biome, has long been the subject of investigation. Palaeolake deposits were confirmed after three cores were drilled in the 1990s describing the fine-grained, laminated limestone stratigraphy interspersed with an abundance of fossil material. Investigations based on these cores, suggested that during the period of deposition the region experienced alternating wetter and drier climates. However, the environmental reconstruction was based on a limited number of samples over the length of the core (~90 m) and very sparse chronology. Additionally, the core was severely disintegrated due to poor handling and storage post-retrieval. New cores were drilled at Kalkkop crater in early 2019 and are curated in a custom-built cold storage facility at the University of Cape Town. Here we present data from the longer of the two cores, an 89 m long core from the centre of the crater with close to 80% core recovery. Surface palaeolake samples have been dated to the beginning of MIS 7 (~250 ka) using U–Th series, suggesting the lake deposits may cover, at least in part, the glacial termination III, a period rarely documented for southern Africa. Here, we provide preliminary results from the top 20 m based on sediment colour characteristics, XRF, ICP, biogenic silica and CNS analyses. Future research will focus on a more detailed U-Th chronology, annual layer counting and the generation of a detailed age model. The implications of this new palaeoclimate archive presented here, plus its future age model, are significant given the sites close proximity to the rich archaeological record of early modern human behaviour on the adjacent southern Cape coast.

How to cite: Kirsten, K., Haberzettl, T., Edwards, T., Mavuso, S., Murungi, M., Mpangala, L., and Pickering, R.: The Kalkkop Impact Crater, South Africa, an environmental archive for MIS 7 and beyond, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-456, https://doi.org/10.5194/egusphere-egu22-456, 2022.

Playas are endorheic sediment basins in drylands that are temporally filled with water. During dry seasons, their surfaces are generally covered with a thick crust of clay-rich clastic material and soluble salts. Strong winds can mobilize that fine-grained material, including the salts, from the playa surfaces as aeolian dust that strongly affects the surrounding ecosystems and human livelihood. During recent decades, climate change strongly altered the salinity regimes of many playas, leading to an increase of surface salinity. During this study we investigated the impact of climate change on soil salinity dynamics in the Bajestan Playa, Northeast Iran, over a period of three decades (1992-2021). The studied region is particularly exposed to the "Sistan winds of 120-Days" during the dry season in summer. Therefore, it is one of the main dust source areas in eastern Iran.

In order to better understand and predict the geochemical composition of aeolian dust, it is necessary to monitor and map regional salinization processes. Thus, we applied a multi-disciplinary approach that encompased remote sensing, field-based ground truthing, and climatic data analysis. Remote sensing analysis on Landsat data (first week of July of all studied years) were carried out on three generations of sensors (TM, ETM+, OLI 8) that were uniformly corrected for atmospheric and geometrical conditions. During a field campaign in July 2021, a total number of 130 soil sampleswere collected from the upper 20 cm of soil of areas that represent seven soil salinity classes that were preliminary identified based on multispectral remote sensing analysis and regional geological maps. In addition, the electrical conductivity (EC) was subsequently measured on the soil surface samples in the laboratory. Based on these field measurements and the remote sensing analyzes, we were finally able to derive twelve soil salt indices. Two among all indices (S12 and S13) showed the most satisfactory calibration accuracies between the field and remote sensing-based EC values. Finally, the index SI2 was applied to the Landsat images for temporal and spatial quantitative soil salinity mapping. Furthermore, to validate the impact of climate change on the salinity changes, the Standardized Precipitation Index (SPI) and the Mann-Kendal Index were calculated based on temperature and precipitation data at different time scales of the last 60 years.

How to cite: Khosravichenar, A., Aalijahan, M., Moaazeni-Noghondar, S., Ulrich, M., Parvian, N., Sadeghi, A., and Von.Suchodoletz, H.: Assessing the impact of climate change on three decades of soil salinity dynamics in the Bajestan Playa, Northeast Iran, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12243, https://doi.org/10.5194/egusphere-egu22-12243, 2022.

Most of weathering processes are connected to moisture presence and flow that affects salt transport and crystallization. However, knowledge of moisture distribution and capillary flow in areas with cavernous weathering forms is scarce. Honeycombs and tafoni, common cavernous weathering forms, occur on different types of rocks and in different climatic conditions, but in arid environments such as south Jordan, tafoni are clearly actively evolving and abundant in the local sandstones, both on natural outcrops and on ancient carved monuments such as in the historic city of Petra.

The depth of the evaporation front was measured in 3 sites with tafone near Petra in Jordan in November 2018, December 2019 and December 2021 (in a cold and relatively wet period of a year). The first site (A) is a tafone situated 5 m below the sub-horizontal surface allowing infiltration. It is facing to the north.The second site (B) is located at the foot of a 50 m high rock cliff. This tafone is facing to the south.The rock is fractured, so it likely allows faster infiltration.The third site (C) is a tafone situated at the foot of the rock cliff, 15 m below the top, facing to the southeast.

The evaporation front is the boundary within the rock that separates the dry layer usually and the capillary zone, and its depth has a major effect on weathering as salts accumulate and crystallize here. The depth of the evaporation front was measured by the ‘uranine-probe’ method, inside tafoni (6 measuring points) and in visors i.e. the thin rock separating the tafone hollows (5 measurement points). We compared the measured depths of the evaporation front with the period of time since the last precipitation event. In 2018, only 14 days elapsed from the significant 83 mm precipitation event, in 2019 only 33 days elapsed from single 244 mm rain event, while in 2021 there were just 2 mm of rain followed by 316 days of no rain (very dry period).

At the site A, the evaporation front was not detected in any measurement, as it was deeper than 10 cm, meaning that evaporation strongly dominates over inflow from sandstone massive. At the site B, the evaporation front was at nearly constant depth at all visits (the average 75 mm, time oscilation only +-5%).  At the site C, there is the largest fluctuation in the depth of the evaporation front. The greatest depth of the evaporation front (average 52 mm) was measured in 2018. In 2019 the average depth of the evaporation front was 42 mm. In contrast, in 2021, the depth of the evaporation front was only 24 mm below the surface. It is clear from the measured data that the depth of the evaporation front does not correspond to antecedent precipitation. From this we can conclude that water does not respond to individual precipitation events, but changes in water reserves are probably controlled by longer cycles or by evaporation demand, rather than rain.

This research was funded by the Charles University Grant Agency (GAUK - 265421).

How to cite: Mares, J., Weiss, T., and Bruthans, J.: Temporal changes in moisture distribution in sandstones near Petra, Jordan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12806, https://doi.org/10.5194/egusphere-egu22-12806, 2022.