Arid Setting Research Articles

Field surveysin rural Tanzania reveal key opportunities for targeted larval source management and species sanitation to control malaria in areas dominated by Anopheles funestus.

Larval source management (LSM) is re-emerging as a critical malaria intervention to address challenges associated with core vector control tools, such as insecticide-treated nets (ITNs), and to accelerate progress towards elimination. Presently, LSM is not widely used in rural settings and is instead more commonly applied in urban and arid settings. A systematic entomological assessment was conducted in rural communities of southeastern Tanzania, where insecticide-treated nets (ITNs) are widely used, to explore opportunities for deploying LSM to improve malaria control. Aquatic habitat surveys were conducted in 2022 and 2023 to understand habitat usage by different mosquito vectors, covering five villages during the rainy season and seven villages during the dry season. Additionally, samples of adult mosquitoes were collected to assess the role of various Anopheles species in malaria transmission in the area, and to explore opportunities for species sanitation using targeted LSM. Adult mosquito surveys showed that in this area, the total entomological inoculation rates (EIR) for indoor collections were 20.1 and 6.5 infectious bites per person per year for outdoors. Anopheles funestus and Anopheles arabiensis were the only Anopheles vectors identified. Anopheles funestus was responsible for over 97.6% of the malaria transmission indoors and 95.4% outdoors. The concurrent larval surveys found that habitats with late instar An. arabiensis and An. funestus comprised only a small subset of 11.2%-16.5% of all water bodies in the rainy season, and 9.7%-15.2% in the dry season. In terms of size, these habitats covered 66.4%-68.2% of the total habitat areas in the wet season, reducing to 33.9%-40.6% in the dry season. From the rainy season to the dry season, the surface area of habitats occupied by An. arabiensis and An. funestus decreased by 92.0% to 97.5%, while the number of habitats occupied by An. arabiensis and An. funestus decreased by 38.0% to 57.3%. Anopheles funestus preferred large, permanent habitats with clear water and vegetation year-round, while An. arabiensis showed contrasting seasonal preferences, favouring sunlit still waters in the rainy season and larger, opaque habitats in the dry season. These findings suggest that An. funestus, which is the dominant malaria vector in the area, mediating over 95% of malaria transmission, preferentially occupies only a small subset of uniquely identifiable aquatic habitats in both wet and dry seasons. This presents an opportunity to expand LSM in rural settings by carefully targeting An. funestus habitats, which might be effective and logistically feasible as a complementary approach alongside existing interventions. Further research should assess the impact of targeted LSM for species sanitation compared to blanket LSM.

Influence of flood events on the response of steep and coarse-grained channels to base-level lowering in an arid setting

The Dead Sea level has been undergoing a continuous and rapid lowering, presently ∼ 1.1 m/yr, providing a real time laboratory to examine the response of drainage systems to base level drop. There is a gap of knowledge concerning the impact of floods on the fluvial system in an environment of continuous base level lowering. Such knowledge is of pronounced importance due to the world-wide reduction of natural water recourses caused by human and climate impacts. We relate the effects of flash floods on morphological changes in small, steep and coarse-grained alluvial channels as a response to a rapid base level fall. We studied the steep (7–9 %) David and Qedem channels draining to the Dead Sea by (i) monitoring flow events using depth transducers and (ii) topographic changes by repeat drone-based photogrammetric surveys to quantify fluvio-morphological dynamics, and (iii) analyzed boulder-related bedforms and their distance from the thalweg. Altogether 15 monitored flow events of varying magnitude led to a wide range of fluvio-morphological changes. Considerable erosion occurred as expressed by bank collapse and channel bed incision. Small events displayed incision with morphological changes limited to the downstream reach, while larger events caused morphological changes throughout the entire channel. Substantial deposition at the outlet occurred together with local mechanisms of deposition upstream. The extents of erosion and net volumes of change highly correlated with event peak-discharge and event water volume. Frequent thalweg deflections occurred, some of which were related to the interaction with boulders. Boulder ribs displayed processes of formation/destruction in multiple phases, often occurring in larger events. The examined aspects illustrate the unique dynamics of a continuously unstable fluvial system under a flash-flood hydrological regime and its impact on fan delta incision and sediment transport processes.

Scoria cone erosional degradation by incision: Different behaviors in three volcanic fields reflect environmental conditions

Abstract Alluvial processes acting on scoria cones cause the development of a drainage network composed of radially distributed rills and gullies parallel to the volcanic edifice's downslope direction. We quantify the degree of drainage network development by applying the Average Erosion Index (AEI) method to scoria cones from the arid to semi-arid Lunar Crater volcanic field (Nevada, United States) and comparing our results with previously obtained results from two tropical volcanic fields (Sierra Chichinautzin volcanic field and the Parícutin-Tancítaro region, both in central Mexico). We show that the AEI method is useful in determining geomorphic age relations when calibrated separately for each field. Furthermore, the differences in AEI results for the three studied fields indicate that the method provides a way of quantifying the effects of different alluvial erosion rates at volcanic fields across various environments, including a delay in alluvial processes on cones in arid settings that has been qualitatively inferred by previous studies.

Gendered Crafts in the Great Salt Lake Desert: A Comparative Analysis of Late Holocene Cordage and Coiled Basketry

AbstractPerishable artifacts are invaluable tools for reconstructing past lifeways of hunter-gatherers, and when preserved in arid settings, they can inform on dynamic interactions between communities and the environment. Many such materials were recovered from early archaeological surveys in Utah and Nevada but were largely excluded from contemporary analyses because of small sample sizes, their fragmentary nature, and insecure proveniences. This synchronic reanalysis of cordage and coiled basketry from 10 late Holocene sites in the Great Salt Lake Desert utilizes newer approaches to perishables analysis so as to collect data more conducive to statistical comparisons of subsistence and craft traditions absent from earlier Great Basin studies. Regional trends of conformity of fine cordage contrasted with a diversity of basketry manufacture suggest contemporaneous social stressors directing the production of materials and two potentially gendered subclasses of utilitarian objects. Feminine and masculine perishable crafts in the Bonneville Basin follow separate manufacturing traditions, observable despite small sample sizes and poor dating of these curated collections.

Plant water‐use strategies predict restoration success across degraded drylands

Abstract Plant strategies for coping with water limitation are likely to mediate restoration outcomes in degraded dryland ecosystems. Trade‐offs in traits related to water acquisition and use can intensify in more arid environments, making their effects on dryland restoration success even more salient. However, isolating the effects of drought responses from those of other environmental factors, as well as identifying the specific drought resistance traits that influence restoration success, can be difficult. In the present study, we couple a controlled dry‐down experiment with a cross‐site restoration field trial of out‐planted seedlings (RestoreNet) using a suite of dryland herbaceous plant species from the same seed sources. We quantified interspecific variation in physiological responses to drought, specifically reductions in stomatal conductance (gs) and stem water potential (SWP), by comparing well‐watered control plants to those experiencing decreasing soil moisture. Drought responses of SWP and gs varied independently among species, but both were related to survival in the cross‐site restoration field trial when effect sizes were aggregated across all sites. Responses were consistent with acquisitive water‐use strategies resulting in greater success, where species with greater declines in SWP or weaker declines in gs under drought had greater survival. The correlation between SWP drought response and survival also intensified in sites with lower accumulated precipitation following restoration. Differences among functional groups revealed two different paths to restoration success: forbs that maintain high gs and narrow safety margins to maximize exploitation of moisture pulses before going into drought dormancy, or C4 grasses that maintain efficient water uptake in drying soils while risking cavitation. C3 grass species varied between these two strategies. Synthesis and applications. Taken together, the results of this study and others conducted at RestoreNet sites indicate that while a diversity of physiological responses to drought may exist in dryland plant communities, successfully restoring herbaceous species through out‐planting in degraded conditions is likely to be achieved with species that maximize water uptake via one of two strategies, with tolerance of low SWP being particularly important in the most arid settings.

Biodiversity of ecosystems in an arid setting: The late Albian plant communities and associated biota from eastern Iberia.

Deserts are stressful environments where the living beings must acquire different strategies to survive due to the water stress conditions. From the late Albian to the early Cenomanian, the northern and eastern parts of Iberia were the location of the desert system represented by deposits assigned to the Utrillas Group, which bear abundant amber with numerous bioinclusions, including diverse arthropods and vertebrate remains. In the Maestrazgo Basin (E Spain), the late Albian to early Cenomanian sedimentary succession represents the most distal part of the desert system (fore-erg) that was characterised by an alternation of aeolian and shallow marine sedimentary environments in the proximity of the Western Tethys palaeo-coast, with rare to frequent dinoflagellate cysts. The terrestrial ecosystems from this area were biodiverse, and comprised plant communities whose fossils are associated with sedimentological indicators of aridity. The palynoflora dominated by wind-transported conifer pollen is interpreted to reflect various types of xerophytic woodlands from the hinterlands and the coastal settings. Therefore, fern and angiosperm communities abundantly grew in wet interdunes and coastal wetlands (temporary to semi-permanent freshwater/salt marshes and water bodies). In addition, the occurrence of low-diversity megafloral assemblages reflects the existence of coastal salt-influenced settings. The palaeobotanical study carried out in this paper which is an integrative work on palynology and palaeobotany, does not only allow the reconstruction of the vegetation that developed in the mid-Cretaceous fore-erg from the eastern Iberia, in addition, provides new biostratigraphic and palaeogeographic data considering the context of angiosperm radiation as well as the biota inferred in the amber-bearing outcrops of San Just, Arroyo de la Pascueta and La Hoya (within Cortes de Arenoso succesion). Importantly, the studied assemblages include Afropollis, Dichastopollenites, Cretacaeiporites together with pollen produced by Ephedraceae (known for its tolerance to arid conditions). The presence of these pollen grains, typical for northern Gondwana, associates the Iberian ecosystems with those characterising the mentioned region.

Origins of clay-rich strata in Cenozoic paleochannel deposits: an example from Suttor Formation, Queensland

Cenozoic sediments cover much of Queensland’s landscape and record changes in climate and flora that evolved in tandem with the tectonic evolution in eastern Australia, associated with uplift and erosion events arising from Late Cretaceous sea-floor spreading in the Coral Sea, leading to the passive margin we see today. In eastern Australia, incised and potentially fault-bounded valleys developed on the pre-Cenozoic landscape and were variably infilled at different times by siliciclastic sediments, carbonaceous muds and peat, and basaltic lava flows. This study examines a 100 m-deep drill core through one such siliciclastic-dominated paleochannel incised into upper Permian coal measures on the western limb of the Bowen Basin. Palynological analysis, core logging, hyperspectral logging of the core, X-ray diffraction (XRD), SEM–EDS and U–Pb zircon geochronology were used to investigate the age and origins of these clay-rich deposits. Palynological analysis confirmed that the strata belong to the upper Paleogene and Neogene Suttor Formation, a time when Australia’s climate has been interpreted to shift from wet and warm to a more arid setting. Core logging revealed that the sequence in the studied channel began as a breccia/alluvial fan with chaotic angular clasts of Permian laminated siltstone, tuff and coal floating in disturbed poorly lithified sand with evidence of soft sediment deformation, possibly initiated by localised faulting. These clasts were continually reworked and broken down into a clast supported pebble conglomerate capped by a series of claystone with intermittent carbonaceous claystone and lignite, interpreted to have formed in a lacustrine environment that could be localised on the floodplain (oxbow) or more regional in extent. Above this, and interpreted from palynology as corresponding to a climatic shift to more arid conditions, are well sorted but subrounded sugar sands and intermittent clays with abundant iron staining (?paleosols) interpreted to represent sandy ephemeral channels. These are overlain by extremely weathered undated basalts. The hyperspectral logging of the core and XRD studies of the white claystone samples indicate that they are kaolinite-rich, but observations under SEM–EDS noted that their honeycomb structure mimicked that of smectite. The presence of abundant zircon suggested the possibility of syndepositional volcaniclastics, but U–Pb zircon geochronology recorded an age of 272–254 Ma (middle to late Permian). Hence local recycling of the tuffaceous smectite-rich coal measures within the incised alluvial system, assisted by intense weathering under a warm and wet climate, and potentially acid leaching from the organic-rich layers was the origin of the kaolinite-rich clay strata. KEY POINTS Clay-rich Cenozoic paleochannels in the northern Bowen Basin belong to the upper Paleogene and Neogene Suttor Formation, based on palynological study. The clay-rich strata are developed by local recycling of middle to late Permian tuffaceous smectite-rich coal measures. The interpretation based on palynology and clay mineralogy confirm that Australia experienced a shift from wet and warm to a more arid climate during the upper Paleogene and Neogene.

Quantifying moisture recycling of a leeward oasis in arid central Asia using a Bayesian isotopic mixing model

Locally recycled moisture from transpiration and surface evaporation is of great importance in the terrestrial hydrological cycle, especially in the widely distributed oases across arid central Asia. Quantitative assessment of the proportional contribution of recycled moisture to local precipitation, i.e., the recycling ratio, is useful to understand the land-air interaction as well as the anthropogenic impact on the regional water cycle. Here we analyzed the stable hydrogen and oxygen isotopes in precipitation samples collected at six stations across the Kaxgar-Yarkant Oasis in the western Tarim Basin of central Asia from April 2018 to June 2020. Using this data, the moisture recycling ratio in this typical oasis was assessed using a Bayesian three-component isotopic mixing model. For the plain stations, the annual weighted mean δ18O value in precipitation ranged from −5.94 ‰ to −1.46 ‰, and the mountain station has a lower annual mean precipitation isotopic ratio. The average recycling ratio during the summer months ranged between 17.0 % and 63.9 % for each sampling station in the Kaxgar-Yarkant Oasis, and the proportional contribution from transpiration ranged from 15.1 % to 61.3 %. The contribution of plant transpiration to local precipitation is much larger than that of surface evaporation. The recycled portion in total precipitation amount may increase the local precipitation under an oasis expansion background but is insufficient to change the arid background. In addition, the Bayesian isotopic mixing model is promising to determine the recycling ratio in an arid setting, and provides more spatial details than the climate reanalysis-based calculation.

Relict canals of the Tehuacán Valley, Mexico: A Middle- to Late-Holocene dryland socio-hydrological system

The travertine-lined irrigation canal networks of the Tehuacán Valley, Mexico allowed pre-Hispanic indigenous communities to overcome risks of crop failures in an arid setting. Segments of these systems are still in use today, therefore understanding when and how these irrigation networks functioned allows us to identify which attributes of a coupled socio-hydrological system are important for maintaining the long-term resilience of irrigation systems in drylands. This paper summarizes the results of an interdisciplinary study of this prehispanic irrigation network involving mapping, radiometric dating, and diatom analyses of materials extracted from the travertine lined canals. All of the canal networks were functioning by ca. 2000 BC, at the transition from the Late Archaic to the Formative period, which is before archeological evidence for widespread community-level aggregation. Provocatively, some canals are potentially as old as 6000–4000 BC, which would mean that hunter-gatherers initiated irrigation coevally with the introduction of semi-domesticated maize, a tropical species which would require supplemental water in this arid context. The canals both facilitated agricultural intensification and enhanced the distribution of aquatic ecosystems. The resilience of these systems to their unique spring dependent context demanded frequent maintenance and the integration of multiple canal networks to mitigate geohydrological vulnerabilities of reduced discharge. These conditions set up a long-term reciprocal dynamic between people and water in the Tehuacán Valley. The results demonstrate that rigidities inherent to tightly coupled socio-hydrological systems in dryland settings were overcome by institutional arrangements first developed by indigenous communities deep in prehistory.

Soil moisture variability affected by sand mulch: An isotope‐based assessment of irrigated farmland in Northwest China

AbstractAs a practical agricultural technique in Northwest China, the sand mulch reduces the soil moisture loss of irrigated farmland under an arid setting. To understand the soil moisture variability affected by sand mulch, we selected an irrigated orchard of peach (Amygdalus persica L.) in Northwest China and examined the soil moisture movement conditioned by irrigation using a stable water isotope method. Based on the isotopic variability of continuously collected soil, plant, and irrigation water samples, the infiltration and evaporation of soil moisture were assessed. The results showed that (1) during the sampling period, the average soil water content and infiltration volume of the sand mulch plot were 1.63% and 6.82%, respectively, which are higher than those of the uncovered plot, indicating a better soil water retention after sand mulch. (2) The slope of the evaporation line of the sand mulch plot (4.79) was greater than that of the uncovered plot (4.11), and the average evaporation loss of the sand mulch plot (0–30 cm) was 10.29% lower than that of the uncovered plot. The average evaporation rate of the sand mulch plot was 5.02% per day, which is lower than that of the uncovered plot 8.41% per day. The isotope‐based evidence shows that sand mulch effectively reduces soil water evaporation, which provides a theoretical basis for agricultural water management and optimization of water‐saving methods for arid land.

Can We Use the Water Budget to Infer Upland Catchment Behavior? The Role of Data Set Error Estimation and Interbasin Groundwater Flow

AbstractWater budgets are essential for characterizing water supplies from snow‐dominated upland catchments where data are sparse, groundwater systems are complex, and measurements are prone to error (ε). One solution is imposing water budget closure (CWB) by ignoring difficult‐to‐measure variables, including inter‐basin groundwater fluxes (G) and ε. However, conventional CWB‐based analyses, which derive evapotranspiration (ET) from precipitation (P) and streamflow (Q) (e.g., the Budyko hypothesis), are limited in their ability to take advantage of recent advances in ET products, physically‐based frameworks for improving inferences about G, or tools to statistically characterize ε (Triple Collocation [TC]); all of which offer promise for improved water supply predictions via open water budgets (OWB). We clarify the value of these advances in upland settings by comparing standard land surface model, Ensemble Mean, and TC‐Merged P and ET products in 114 upland catchments. When compared against a long‐term OWB, we find that the CWB assumptions are unsupported in 75%–100% of our 114 catchments, depending on the product. We then show how applying these CWB assumptions in snowy, steep catchments where ε is large can inflate inferences about streamflow response to climate change by up 9 times more than independent (OWB) estimates of ET using TC. Finally, we demonstrate how advances in OWB analysis reveal that high, arid settings with deep permeable substrate are groundwater exporters while most other basins are groundwater importers. Our results highlight the advantages of OWB analyses that harness new products, tools, and frameworks for characterizing inter‐basin groundwater fluxes in critical upland settings.

Perennial Flowering Plants Sustain Natural Enemy Populations in Gobi Desert Oases of Southern Xinjiang, China.

Simple SummaryNatural habitats are essential providers of biological conservation services. The crucial role of the Gobi Desert, a dominant landscape of desert-oasis ecosystems in natural predator conservation is poorly understood, especially in southern Xinjiang, China’s Tarim Basin, where the Gobi Desert is directly adjacent to farmland and characterized by extremely sparse vegetation and more severe climatic conditions. In this context, we investigated the floral composition of the Gobi Desert and gauged the identity, relative abundance, and temporal dynamics of predatory insects associated with the prevailing plant species. We also explored whether certain plant traits and herbivore abundance are related to either natural enemy identity or relative abundance. Our results demonstrate that perennial flowering plants, such as Apocynum pictum (Apocynaceae), Phragmites communis (Poaceae), Karelinia caspia (Asteraceae), and Tamarix ramosissima (Tamaricaceae), are the dominant species of vegetation community in the Gobi Desert, and could sustain diversified arthropod predators, i.e., ladybeetles, spiders, and other natural enemies. This work not only informs sustainable pest management initiatives, but also shows how non-crop habitats at the periphery of agricultural fields underpin ecological resilience under adverse climatic conditions.Natural habitats play crucial roles in biodiversity conservation and shape the delivery of ecosystem services in farming landscapes. By providing diverse resources to foraging natural enemies, they can equally enhance biological pest control. In this study, we described the plant community and foliage-dwelling invertebrate predators within non-crop habitats of the Gobi Desert oases in southern Xinjiang, China. We assessed whether plant-related variables (i.e., species identity, flowering status) and herbivore abundance affect natural enemy identity and abundance. A total of 18 plant species belonging to 18 genera and 10 families were commonly encountered, with Apocynum pictum (Apocynaceae), Phragmites communis (Poaceae), Karelinia caspia (Asteraceae), and Tamarix ramosissima (Tamaricaceae) as the dominant species. Certain plant species (P. communis) primarily provide shelter, while others offer (floral, non-floral) food resources or alternative prey. Predatory ladybeetles and spiders were routinely associated with these plants and foraged extensively within adjacent field crops. Plant traits and herbivore abundance explained up to 44% (3%–44%) variation in natural enemy community and exhibited consistent, year-round effects. Among all plant species, A. pictum consistently had a significantly higher abundance of resident natural enemies, except for August 2019. Our study underlines how perennial flowering plants, such as A. pictum, are essential to sustain natural enemy communities and related ecosystem services in arid settings. This work not only informs sustainable pest management initiatives but also shows how non-crop habitats at the periphery of agricultural fields underpin ecological resilience under adverse climatic conditions.

Depositional history of a talus cone in an arid intermontane basin in Central Asia: An interdisciplinary study at the Late Pleistocene–Late Holocene Obishir‐I site, Kyrgyzstan

AbstractCliff‐related talus accumulations are often highly affected by post‐depositional processes, and the sedimentological characteristics are poorly documented, especially in arid settings. In the southern margin of the Fergana Valley, Kyrgyzstan, the Obishir‐I is an archaeological site of the Epipaleolithic Obishirian industry, located within a talus cone. Archaeological excavations have allowed us to study the internal structure, chronology, and depositional history of the cone as well as the relationship between the slope processes and the archaeological assemblage. We applied a multiproxy approach, including sedimentological studies supported by the basic geochemistry of sediments, luminescence dating, paleoecology of fossil mollusks, and archaeological analyses. The Obishir‐I rockfall talus accumulated from the Last Glacial Maximum to the early part of the Middle Holocene. The talus onlaps the bedrock at the foot of a limestone cliff, and its chronology is coherent, spanning from ca. 19–8 ka B.P. The material is an unconsolidated, poorly sorted mixture of angular rock fragments accumulated by rockfall and fine‐grained materials accumulated by aeolian processes, illuviation, and in situ weathering. The sequence bears an archaeological collection attributed to two settlement phases: unidentified Upper Paleolithic and the Obishirian. Both assemblages are affected by post‐depositional relocation within the slope.

DO RADIOCARBON AGES OF PLANT WAX BIOMARKERS AGREE WITH 14C-TOC/OSL-BASED AGE MODELS IN AN ARID HIGH-ALTITUDE LAKE SYSTEM?

ABSTRACTTo elucidate the dynamics of terrestrial leaf waxes in a high-altitude lake system, we performed compound-specific radiocarbon analysis (CSRA) of long-chain n-alkanes in two sediment core sections from Lake Karakul (Pamirs, Tajikistan) and in surface soil samples from the catchment area. We aimed to answer the question whether the n-alkanes are delivered into the lake sediment with substantial delay due to storage in soils, which may cause a potential bias when used as paleoenvironmental proxies. In the surface soils, the CSRA results reveal an age range of n-alkanes from modern to 2278 ± 155 cal BP. In the two sediment core samples, three of the four n-alkane ages fell on the lower ends of the 1σ-uncertainty ranges of modeled ages of the sediments (based on AMS 14C-TOC and OSL dating results). We conclude that sedimentary leaf waxes represent compounds with intermediate turnover time in soils, for example originating from alluvial plains close to the shores. Overall, the results provide evidence that sedimentary leaf wax compounds in this cold and arid setting are potentially older than the conventional age model indicates, but these findings need to be interpreted in context of the generally large uncertainty ranges of such age models.

A transient south subtropical forest ecosystem in central China driven by rapid global warming during the Paleocene-Eocene Thermal Maximum

Rapid global warming during the Paleocene-Eocene Thermal Maximum (PETM) profoundly affected the marine and terrestrial environments. However, details of the climate and vegetation of subtropical and arid regions of central China during the hyperthermal event are poorly understood. Here, we report a palynological record from the black shale of the lowermost Yangxi Formation exposed in Songzi city, western Jianghan Basin, central China. Biostratigraphy, magnetostratigraphy and isotope stratigraphy indicate a PETM age for the sedimentary succession. The palynological assemblage was characterized by high abundances of diverse tropical and subtropical broadleaved tree pollen, providing strong evidence of a dense south subtropical forest ecosystem that once existed in the arid belt of central China during the PETM. The reconstructed climatic parameters indicate an extremely warm and humid south subtropical climate, with mean annual temperatures (MAT) ranging from 21 to 24 °C and mean annual precipitation (MAP) ranging from 1396 to 1997 mm. The reconstructed precipitation was surprisingly high for such an arid setting that widespread arid climate prevailed in central China at that time. These findings demonstrate that rapid global warming during the PETM significantly increased precipitation, leading to the growth of dense forest ecosystems as well as increasing lake eutrophication in central China. The changes to precipitation and terrestrial ecosystems during this warming event are considerably more significant than previously reported in other mid-latitude regions, and highlighting the need to consider regional geographic characteristics to fully understand how the environment responds to rapid global warming.

A missing link in the mid‐late Permian record of north‐eastern Pangea: A sedimentological evaluation of the Permian Belfast Harbour Evaporite Formation of County Antrim, Northern Ireland

AbstractAncient salt deposits preserve a record of highly specific environmental, climatic and biological conditions, including past surface water chemistry and water depths, local air temperatures, atmospheric composition and halophilic microorganisms. This paper presents the first sedimentological study of the mid‐Late Permian Belfast Harbour Evaporite Formation of Northern Ireland. This formation is dominated by bedded halite, contains some siliciclastic mudstone and bedded anhydrite, and is cross‐cut by intrusive igneous rocks. The bedded halite lithology contains bottom‐growth chevron and cornet crystals, efflorescent crusts and dissolution pipes, which are evidence of a saline surface brine that underwent periods of evapoconcentration, desiccation and flooding. The mudstone lithology contains dewatering structures, intraclasts and mudcracks, which indicate flooding and desiccation in dry mudflats. Bedded anhydrite was deposited as beds of gypsum cumulate crystals in saline surface waters. The Belfast Harbour Evaporite Formation was formed by saline lakes with associated mudflats, based on sedimentary characteristics and supported by mineralogical, geochemical and stratigraphic context. Diagenetic features reflect dissolution and cementation at the surface and shallow subsurface in the depositional environment and limited late‐stage alterations. Syndepositional dissolution pipes in bedded halite were formed by flooding events. Early halite cement is present in dissolution pipes and mudstones. Gypsum/anhydrite repeatedly dehydrated and rehydrated to form an interlocking crystal mosaic. Later features include fluid migration and the intrusion of mafic rocks. The Belfast Harbour Evaporite Formation was deposited by an ephemeral saline lake and dry mudflat system in an arid climate. This study, when compared to age‐equivalent continental deposits elsewhere, suggests that arid settings with saline lakes existed across much of Pangea during the Permo‐Triassic. The Belfast Harbour Evaporite Formation stratigraphically underlies the extremely low pH saline lakes of the Mercia Mudstone Group, implying that it aids in understanding the formation of Pangean acid brine lakes.

Nubian Levallois reduction strategies in the Tankwa Karoo, South Africa.

The Middle Stone Age record in southern Africa is recognising increasing diversity in lithic technologies as research expands beyond the coastal-montane zone. New research in the arid Tankwa Karoo region of the South African interior has revealed a rich surface artefact record including a novel method of point production, recognised as Nubian Levallois technology in Late Pleistocene North Africa, Arabia and the Levant. We analyse 121 Nubian cores and associated points from the surface site Tweefontein against the strict criteria which are used to define Nubian technology elsewhere. The co-occurrence of typically post-Howiesons Poort unifacial points suggests an MIS 3 age. We propose that the occurrence of this distinctive technology at numerous localities in the Tankwa Karoo region reflects an environment-specific adaptation in line with technological regionalisation seen more widely in MIS 3. The arid setting of these assemblages in the Tankwa Karoo compares with the desert context of Nubian technology globally, consistent with convergent evolution in our case. The South African evidence contributes an alternative perspective on Nubian technology removed from the ‘dispersal’ or ‘diffusion’ scenarios of the debate surrounding its origin and spread within and out of Africa.

Unusual dinosaur trackway preservation as clues to paleo-landscape and behavior from the Lower Cretaceous Luohe Formation, Shaanxi Province, China

Poorly preserved tracks have limited ichnotaxonomic or biotaxon utility, but may reveal useful information about the paleoenvironment, behavior and track taphonomy. Eight mostly parallel to sub parallel trackway segments (T1–T8) were registered on a truncation surface in the Lower Cretaceous Luohe Formation of Shaanxi Province. These attest to the passage of several bipeds, probably all theropods, in a paleo-contour-parallel, south-north direction in an arid setting. Quality of preservation in these trackways is poor, but notably superior in two additional trackways (T9–T10) on a foreset surface. Trackway T9 indicates a didactyl trackmaker, probably a deinonychosaurian, heading north to south. This is the 13th report of deinonychosaurian tracks from the Lower Cretaceous of China. If any or all the eight south-north oriented trackway segments represent continuations of other segments in the same trackways, the total number of individual trackmakers heading in this direction may have been as low as three. Although the trackway pattern and sedimentological evidence could indicate a physically controlled pathway influencing the direction taken by these trackmakers, the possibility that the trackways also represented small social or gregarious group cannot be ruled out.

Geochemical insights into the relationship of rock varnish and adjacent mineral dust fractions

Rock varnishes are μm-thin, dark, manganese(Mn)-rich crusts that accrete in the order of few μm/ka on weathering-resistant lithologies. Although these crusts can form in all climates, they are best known in arid to semi-arid settings. Aeolian dust is understood as a major contributor to the distinct trace metal and REE enrichments in rock varnish. However, the exact proportions of abiotic and biotic formation mechanisms that may explain the oxidation-reactions of Mn2+ to Mn4+, present as Mn oxyhydroxides in the varnish, are still a matter of ongoing debate.We present here the first systematic study of trace element enrichment processes between the uppermost layer of the varnish sequence and their adjacent <50 μm and >50 μm dust fractions across a selection of 41 major and trace elements. This approach is used to investigate samples from three fully arid deserts: the An Nafud in Saudi Arabia, the Negev in Israel, and the Mojave in the USA, which are compared to the significantly different environment of the semi-arid Knersvlakte in South Africa. A new in situ trace element analysis protocol was developed to perform femto- and nanosecond sector-field LA-ICP-MS microanalyses at high-spatial resolution, which allows us to measure the most recent varnish layers for their comparison with recent dust. In agreement with previous studies, all varnishes are enriched in Mn, Pb, Ce, Co, Ba, Zn, Ni, and the Rare-Earth Elements (REE). Here we demonstrate that fine (<50 μm) dust is characterized by similar trace element trends as the varnishes, at overall lower mass fractions. Dust >50 μm has low trace element mass fractions, and enrichment patterns plotting distinctly away from varnish and fine dust. Based on these geochemical patterns, our results indicate a general enrichment mechanism from fine dust to varnish. Previous studies suggested dust to play an integral role in providing the trace elements that are incorporated into the varnish by pH-Eh fluctuations in short-term rain and fog events. We amalgamate and refine previous growth models by providing direct evidence that leaching of about 10% of the Mn and other trace elements from clay minerals in rain or fog droplets at pH ~5 and subsequent scavenging on varnish surfaces at pH ~8 leads integrated over time to the distinct enrichment patterns of the varnish, while initial Mn oxyhydroxide formation is suggested to follow pathways of metal oxide mediated photo-catalysis.For the semi-arid occurrence in the Knersvlakte we present a distinct growth model as both environment, varnish, and dust composition differ significantly from the arid settings. Here, thick, metallic-looking varnish occurs mainly on the rim of quartz pebbles, lacks microlamination, and likely has upscaled growth processes. Among other aspects, we suggest a more complex interplay between photo-catalysis, nocturnal condensation events on quartz pebbles with subsequent water trapping at the rock-soil-atmosphere interface, due to a salic top-soil layer, to mainly account for these differences.

The fishing behaviour of Metopograpsus messor (Decapoda: Grapsidae) and the use of pneumatophore-borne vibrations for prey-localizing in an arid mangrove setting

AbstractThis study presents the first documented observations of a brachyuran crab's proactive fishing behaviour in conjunction with mangrove pneumatophores which are employed as prey-localization devices. All ecological data were recorded in situ using simple behavioural observations, visual census and field experiments. Field experiments were based on stimulus-response and ecological surveys on random displacement. Assemblages of Metopograpsus messor were observed daily performing a foraging/predatory tide-related cyclic behaviour pattern in an arid mangrove ecosystem which experiences challenging environmental conditions. Prey-localizing behaviour was observed during the flood tide when pneumatophore-borne vibrations were used to identify potential prey. The prey simulation field experiment (where a single pneumatophore was stimulated by knocking) showed that in &amp;gt;93% of instances a crab approached the exact pneumatophore being stimulated. As water levels increased during the tidal cycle M. messor was observed climbing pneumatophores. The crabs anchored themselves to the pneumatophore just above the water level with their pereiopods. The chelipeds were positioned in a pincher-like trap, and remained in a ‘capture-position’ waiting for prey to move within striking range. This characteristic fishing behaviour was performed daily by a population of M. messor. Ecological observations suggest that both these predatory behaviours are associated with the fish Aphanius dispar dispar in a direct prey–predator relation. Evidence suggests that these fishing behaviours evolved due to characteristics within the M. messor phylogeny (foraging in intertidal zones; daily displacement following tidal levels; high sensitivity to vibrations; and an opportunist diet) and its associated environment (presence of pneumatophores and high availability of a fish resource).