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Terrestrial analogue sites have been crucial for studying Martian geology and mineralogy, integrating the direct evidence available from Mars through remote sensing and in situ measurements carried out by the instruments on board robotic missions. Studying readily available and accessible terrestrial analogues of Martian fossil or extant environments is considered the most efficient way to answer crucial scientific questions. These analogues offer opportunities to collect a range of geological and microbiological data. The Makgadikgadi Basin (MKB) in Botswana is one of such environments hosting a system of salt pans presenting striking similarities with Mars playa deposits. The MKB presents layered mounds, relict fan deltas with inverted channels, polygonal structures and evaporitic crusts harboring communities of extremophiles. The present-day MKB is predominantly fed by groundwater and local precipitations in an overall arid to semi-arid climate, characterized by high UV radiation and salinity, deposition of evaporitic minerals and authigenic clays. The shallow subsurface of the MKB pans is covered by diagenetic features (duricrusts) including silcretes and calcretes. These pans can serve as test beds for the physical and chemical characteristics of playa deposits on Mars and help improve our understanding of the conditions that might support life outside our planet. • The Makgadikgadi pans physical and chemical conditions resemble early Mars. • Morphologies in the pans formed by the interplay of water upwelling and evaporation. • Polygonal fractures, inverted channels and paleo-shorelines were identified. • Evaporitic crust and duricrusts harbor communities of extremophiles. • The pans are natural laboratory for the study of Mars habitability. [ABSTRACT FROM AUTHOR]

Abstract Oxygen and carbon (δ18Ο/δ13C) isotope, growth rate and trace element data are reported for a U-Th dated, annually-laminated stalagmite, GM1 from Goda Mea Cave, Ethiopia. The stalagmite grew intermittently around the last interglacial. The proxy records are used to develop a conceptual growth model of the stalagmite and to assess its potential for revealing a climate signal in this climatically sensitive northeastern African region during an important period in the evolution of Homo sapiens and dispersal of Anatomically Modern Humans out of Africa. Speleothem deposition is of short-duration occurring at ∼129 ka, ∼120 ka, in an undated growth phase, and at ∼108 ka; probably due to tectonic activity. δ18Ο composition is very stable within growth phases (1σ variability < 0.76‰), as are Mg/Ca, Sr/Ca and Ba/Ca, all indicative of well-mixed source-waters. A shift to positive δ18Ο values and increased variability in Mg/Ca, Sr/Ca and Ba/Ca prior to growth hiatuses is observed, indicating a loss of the well-mixed water source prior to growth cessation. Mean δ18Ο composition (−3.82 to −7.77‰) is lower than published modern and Holocene stalagmites from the region. Geochemical data, statistical analyses, and a conceptual model of stalagmite growth, demonstrate that climatic conditions recorded by GM1 were wetter than the Holocene. The ∼129 ka growth phase particularly presents an annual record of the relative Intertropical Convergence Zone (ITCZ) position. The GM1 record, the oldest high-resolution continental climate record from Ethiopia so far published, presents evidence that any early human migrations which occurred during MIS 5 are likely to have occurred during a wet event in northeast Africa. Highlights • Stalagmite GM1 discontinuously deposited at ∼129 ka, 120 ka, an undated growth phase, and ∼108 ka. • Multi-proxy analysis necessary to identify climatic from karstic signal. • Low δ18O at ∼129 ka and ∼108 ka attributed to wetter climatic conditions. • The first annually-resolved stalagmite record of the last interglacial from Ethiopia. • The earliest Modern Human dispersal out of Africa occurred during humid climate conditions. [ABSTRACT FROM AUTHOR]

The Melka Wakena archaeological site-complex is located at the eastern rift margin of the central sector of the Main Ethiopian Rift (MER), in south central Ethiopia. This wide, gently sloping rift shoulder, locally called the “Gadeb plain” is underlain by a succession of primary pyroclastic deposits and intercalated fluvial sediments as well as reworked volcaniclastic rocks, the top part of which is exposed by the Wabe River in the Melka Wakena area. Recent archaeological survey and excavations at this site revealed important paleoanthropological records. An integrated stratigraphic, petrological, and major and trace element geochemical study has been conducted to constrain the petrogenesis of the primary pyroclastic deposits and the depositional history of the sequence. The results revealed that the Melka Wakena pyroclastic deposits are a suite of mildly alkaline, rhyolitic pantellerites (ash falls, pumiceous ash falls and ignimbrites) and slightly dacitic ash flows. These rocks were deposited by episodic volcanic eruptions during early to middle Pleistocene from large calderas along the Wonji Fault Belt (WFB) in the central sector of the MER and from large silicic volcanic centers at the eastern rift shoulder. The rhyolitic ash falls, pumiceous ash falls and ignimbrites have been generated by fractional crystallization of a differentiating basaltic magma while the petrogenesis of the slightly dacitic ash flows involved some crustal contamination and assimilation during fractionation. Contemporaneous fluvial activities in the geomorphologically active Gadeb plain deposited overbank sedimentary sequences (archaeology bearing conglomerates and sands) along meandering river courses while a dense network of channels and streams have subsequently down-cut through the older volcanic and sedimentary sequences, redepositing the reworked volcaniclastic sediments further downstream. [ABSTRACT FROM AUTHOR]

The Sof Omar Cave System, a spectacular and extensive cave system in Southeastern Ethiopia represents a maze of dry cave passages, which subsequently were crossed by a subterranean watercourse formed by the Weib River, forming combined underground passages of a total length of 15.1 km, the longest and most extensive in Ethiopia. The Sof Omar cave and subterranean river system developed on Jurassic limestone beds particularly on the Gebredarie Series (massive, crystalline limestone beds intercalated with thin marl and mudstone beds). The cave system and the subterranean River developed along a generally horizontal outline within a 20 m thick layer. The Sof Omar gorge is a wide but shallow doline, whose central section is incised by the ancient surface route of the Weib River. Prominent half dolines opening toward the sink and resurgence areas, as well as consistently inward dipping limestone beds at these localities imply collapse phenomenon. Karstification triggered by rift-related uplifting and extension during the mid-Miocene East African rifting, accompanied by extensive collapse along bedding planes likely initiated the caving process. The rifted and collapsed chambers were later widened by slow but persistent dissolution. The dry cave passages were formed earlier than the subterranean river course, though the latter might have partly followed the pre-existing cave passages and enlarged them to form the current subterranean river course. The Sof Omar caves are still at the heart of the cultural and religious life of the local population, where the dry cave passages, domes, and chambers are considered as important religious and cultural locales. With its subterranean river, large chambers connected by narrow and long rift passages, a unique and prominent sinkhole above the caves, wooded gorge teeming with numerous and unique tropical plant and bird species, the Sof Omar Cave System and adjoining gorge has outstanding scenic values. Apart from these naturally outstanding values, what makes the Sof Omar Cave System unique and unsurpassed in the world is its cultural significance. The caves form part of the cultural and religious life of the local population leading to the unique harmony between nature and culture. The cave system and its adjoining forested gorge is a natural–cultural heritage site that requires an active geoconservation. [ABSTRACT FROM AUTHOR]

In central Ethiopia, litho-structural setup of the three sub-basins of the southern flank of the Middle Blue Nile basin (Guder, Muger and Jema) and the adjacent Upper Awash River basin have been investigated to develop conceptual groundwater flow model and to characterize the groundwater hydrodynamic relationship between the aquifer systems of the two basins. The development of conceptual groundwater flow model is based on interpretation of Digital Elevation Model (DEM) from SRTM and Landsat images together with field geological observation, integrated with existing boreholes lithologic logs and pumping test data. The litho-structural framework, reconstructed from regional stratigraphy and analysis of major regional fault systems, controls the size of recharge area for aquifer systems and aquifer distributions in the groundwater sub-basins. The study has indicated the distinctive geometric setting of the litho-strata of aquifers and aquicludes. The NW–SE trending horsts beneath the volcanic successions and the overlying volcanic ridges control aquifer distribution in the Guder, Muger and Jema groundwater sub-basins, while the E–W trending horsts control aquifer distribution between the Middle Blue Nile and the Upper Awash Rivers basins. Impermeable mudstone constitutes the upper part of the E–W oriented horst at the center of the Muger River sub-basin. This mudstone capped horst underlying the volcanic aquifers is a groundwater divide channeling recharged water in the Blue Nile basin partly towards the Upper Awash basin. Significant proportion of groundwater recharged in the Middle Blue Nile basin (Muger and Jema River sub-basins) contributes to the storage of the aquifer systems of the Upper Awash basin. [ABSTRACT FROM AUTHOR]

Abstract: Lalibela is a medieval settlement in Northern Ethiopia famous for its 11 beautifully carved rock hewn churches, registered as World Heritage Site in 1978. The rock hewn churches are grouped into three based on their proximity: the Bete Medhane Alem (Church of the Holy Saviour), Bete Gabriel–Rufael (Church of St. Gabriel–Rafael) and Bete Giorgis (Church of St. George) groups. The churches are carved out of a single, massive scoriaceous basalt hill which was deposited along an East–West extending palaeovalley in the Oligo-Miocene Trap basalt of the northwestern Ethiopian plateau. The Rock Mass Rating (RMR) classification scheme was used to classify the rock mass (assuming each church as a separate rock mass) based on their uniaxial compressive strength and the spacing and conditions of discontinuities. Though most of the churches are hewn from medium to high strength rock mass, discontinuities make them vulnerable to other deteriorating agents mainly weathering, and water infiltration. Most of the rock hewn churches are affected by pre-carving cooling joints and bedding plane discontinuities, and by mostly but not necessarily post-carving tectonic and seismic induced cracks and fractures. Material loss due to deep weathering triggered by rain water infiltration and uncontrolled groundwater seepage affects most of the churches, particularly the Bete Merqorios (Church of St. Mark) and Bete Aba Libanos (Church of Father Libanos) churches. The scoriaceous basalt which is porous and permeable allows easy passage of water while the underlying basalt is impermeable, increasing the residence time of water in the porous material, causing deep weathering and subsequent loss of material in some of the churches and adjoining courtyards. [ABSTRACT FROM AUTHOR]

Abstract: We combine surface and cave climate monitoring with multiple stalagmite parameters to help understand and calibrate the climate records contained within stalagmites from a region with strong rainfall seasonality. Two actively growing stalagmites from Ethiopia were analysed in order to investigate the climate signal contained within δ18O and growth rate parameters. The δ18O and growth rate of the two stalagmites give different responses to surface climate due to variations in the climate signal transfer. Both stalagmites (Merc-1 and Asfa-3) have a climate response that is seasonal; however this signal is subsequently smoothed by the mixing of event and storage water within the aquifer. Merc-1 responds more to high frequency (‘event’) climate, due to a greater ratio of event to storage water in this sample, whereas Asfa-3 responds more to low frequency (‘storage’) climate. In addition, different parameters respond to different seasons. For example, stalagmite Asfa-3, from greater depth from the surface and with a slow drip rate, has a growth rate that responds to the amount of summer rain. In contrast, Merc-1, closer to the surface and with a faster drip rate, exhibits no clear response to surface climate, probably due to a more complex climate signal transfer. δ18O response varies with stalagmite due to the interplay between rainfall forcing factors (amount, seasonality) and disequilibrium kinetics, with opposing correlations between seasonal rainfall and δ18O between the samples. Our results demonstrate that analysis of seasonal climate forcing, and transfer functions reflecting the mixing of event and storage water, may be the most appropriate approach to develop of transfer functions appropriate for high-resolution, stalagmite climate reconstruction. [Copyright &y& Elsevier]

The Negash pluton (50 km2) consists of late Pan-African, high-K, calc-alkaline granitoids intruded into low-grade metavolcanics–metasediments. This almost circular massif consists of monzogranites, granodiorites, diorites–gabbrodiorites, and hybrid diorites. The anisotropy of magnetic susceptibility (AMS) method was used to determine internal structures of the pluton. The foliation trajectories are concentric and inward dipping. The lineation pattern displays an external zone characterised by horizontal concentrically oriented lineations and an internal zone with NW–SE oriented lineations. These petro-structural data clearly locate the feeder zone at the north-western tip of the pluton and indicate the subsequent expansion of the magmas towards the SE. The pluton is a result of in-situ assembly of four magma batches, which were forcefully injected into pre-existing foliated country rocks in relation to transpressional tectonic regime. Two types of mafic–felsic magma interactions are recognised: homogeneous and heterogeneous hybrid diorites at the north-western part, and mingled interfaces at the diorite–granodiorite contact zones mainly visible in the eastern and south-eastern parts. The in-situ mingling along diorite–granodiorite contacts was achieved at the level of emplacement during the injection of dioritic magma into the felsic magmas while the hybrid diorites are assumed to result from two-way conduit mixing and mingling during simultaneous rising of mafic and felsic magmas. [Copyright &y& Elsevier]

The hypothesis of a connection between the onset (or intensification) of Northern Hemisphere Glaciation, the stepwise increase in African aridity (and climate variability), and an important mammalian (including hominin) species turnover is a textbook example of the initiation of a scientific idea and its propagation in science. It is, however, also an example of the persistent popularity of a hypothesis despite mounting evidence against it. A critical review of key publications on the topic and statistical re-analysis of key records of global ice volume and African climate leads to three conclusions: (1) The Northern Hemisphere Glaciation was a gradual process occurring between ∼3.5 and 2.5 Ma, not a single event at ∼2.8 Ma or at any other time. (2) A consistent stepwise (+/−0.2 Ma) transition toward greater aridity in Africa at ∼2.8 Ma does not exist; instead, there are regionally different, gradual transitions partly in connection with the intensification of the Northern Hemisphere Glaciation, but above all with the establishment of the tropical Walker Circulation after ∼2 Ma. (3) Mammalian (including hominin) species turnovers at this time also appear to have been gradual, rather than stepwise. • We falsified the hypothesis of a connection between Northern Hemisphere Glaciation, African climate and human evolution. [ABSTRACT FROM AUTHOR]

The Chew Bahir Drilling Project (CBDP) aims to test possible linkages between climate and hominin evolution in Africa through the analysis of sediment cores that have recorded environmental changes in the Chew Bahir basin (CHB). In this statistical project we used recurrence plots (RPs) together with a recurrence quantification analysis (RQA) to distinguish two types of variability and transitions in the Chew Bahir aridity record and compare them with the ODP Site 967 wetness index from the eastern Mediterranean. The first type of variability is one of slow variations with cycles of ∼20 kyr, reminiscent of the Earth's precession cycle, and subharmonics of this orbital cycle. In addition to these cyclical wet-dry fluctuations in the area, extreme events often occur, i.e. short wet or dry episodes, lasting for several centuries or even millennia, and rapid transitions between these wet and dry episodes. The second type of variability is characterized by relatively low variation on orbital time scales, but significant century-millennium-scale variations with progressively increasing frequencies. Within this type of variability there are extremely fast transitions between dry and wet within a few decades or years, in contrast to those within Type 1 with transitions over several hundreds of years. Type 1 variability probably reflects the influence of precessional forcing in the lower latitudes at times with maximum values of the long (400 kyr) eccentricity cycle of the Earth's orbit around the sun, with the tendency towards extreme events. Type 2 variability seems to be linked with minimum values of this cycle. There does not seem to be a systematic correlation between Type 1 or Type 2 variability with atmospheric CO 2 concentration. The different types of variability and the transitions between those types had important effects on the availability of water, and could have transformed eastern Africa's environment considerably, which would have had important implications for the shaping of the habitat of H. sapiens and the direct ancestors of this species. [ABSTRACT FROM AUTHOR]

The Tulu Kapi syenite-hosted gold mineralization in the Western Ethiopian Shield has been under exploration during the last few decades. The geochemical and petrological characterization of the intrusive rocks and their alterations including the gold hosting syenites are crucial in appraising the economic potential of the mineralized belt on a larger scale. The present study concerns with the geochemical and petrogenetic behaviour of the gold-hosting syenites and other associated intrusions using an integrated field, geochemical and petrological investigation. The Tulu Kapi area is situated within a strongly sheared and NE-SW foliated, low-grade (lower greenschist to lower amphibolite facies) volcano-sedimentary belt (the "Birbir belt") that is intruded by mafic-ultramafic and granitic intrusives (chlorite-serpintine-talc schist, birbirite, metagabbro, metadiorite, metagranite and metasyenite). Major and trace element geochemistry revealed that the gold mineralization hosting syenites, associated diorites and granites are ferroan, calc-alkaline, metaluminous to slightly peraluminous bodies formed in a volcanic arc subduction to syn-collisional tectonic setting by the fractionation of underplated, LREE-enriched basaltic magma with substantial crustal input to possible crustal melting. The underplated basaltic magma was sourced from a LREE-enriched mantle by reworking of sediment laden crustal slabs at depth in a subduction zone. Fractional crystallization resulted in the formation of Ca-rich plagioclase, which continually reacted with hydrothermal fluids to more fractionated Na-rich plagioclase, forming the gold mineralization hosting altered syenites viz. albitization. • Geochemically the Tulu Kapi gold-hosting intrusives are ferroan, calc-alkaline, and metaluminous to slightly peraluminous. • The intrusives formed in a volcanic arc subduction/syn-collisional setting in the southern part of the African Nubian Shield. • The intrusives formed by fractionation of underplated, LREE-enriched basaltic magma with substantial crustal input. • The gold-hosting Tulu Kapi Syenites show strong hydrothermal alteration (albitization). • Continuous interaction of Ca-plagioclase with the hydrothermal fluids resulted in albitized domains. [ABSTRACT FROM AUTHOR]

The Adwa – Yeha felsic plugs and domes are chain of towering inverted cone-shaped isolated plugs and circular domes with wide basal diameters and steep-sided, narrow tops. They form contrasting prominent topography from the Trap basalt ridges of the Adwa – Axum - Tekeze volcanic ridge, located just west of the Northern Afar Depression. The felsic plugs and domes are concentrated in the Adwa – Yeha area, in a zone of about 20 km wide and 30 km long and generally aligned along NNE-SSW direction, parallel to the regional structural grain of the Precambrian basement and the Miocene - Pliocene rift margin faults. In this study, we investigated these felsic plugs and domes using petrological and major and trace element geochemical methods in order to constrain their petrogenetic evolution. Their possible tectonic link to the Western Afar Margin has also been investigated combining our geochemical data, with assessment of regional tectonic setting and geochronological data from previous studies. The results ascertain that the felsic plugs and domes are peralkaline trachytes and peralkaline to sub-alkaline rhyolites, formed by Assimilation Fractional Crystallization (AFC) of basaltic magma which involved removal of olivine, pyroxene, plagioclase, and Fe–Ti oxides, and moderate amount of crustal input. The eruption of the felsic plugs and domes occurred along reactivated Precambrian weakness zones during the formation of the western Afar boundary faults. • The Adwa – Yeha felsic plugs are concentrated along a NNE-SSW aligned zone west of the Western Afar Margin. • The felsic plugs and domes erupted during the Miocene along reactivated Precambrian weakness zones along terrane boundaries. • The eruption of the felsic plugs and domes possibly occurred following the formation of the western Afar boundary faults. • The plugs and domes are peralkaline rhyolites and trachytes. • The felsic plugs and domes are formed by Assimilation Fractional Crystallization of basaltic magma. [ABSTRACT FROM AUTHOR]

An integrated field, petrological, as well as major and trace element geochemical study of a suite of basaltic and associated rhyolitic rocks of the Alaje Formation from the continental flood basalts of the Aiba area of northern Ethiopia has been conducted. The study constrained the geochemical and petrogenetic association of the basaltic and rhyolitic rocks. The results show that the Alaje Formation is constituted by three layers of transitional to tholeiitic basaltic suites intercalated with three layers of alkaline, pantelleritic trachytes/trachy dacites and comenditic rhyolites. The dominant phenocrysts in the porphyritic basalts are plagioclase, with some clinopyroxene, Fe–Ti oxide and olivine. The basalts: (i) have high-Ti concentrations, (ii) show uniform LREE enriched and slightly HREE depleted pattern, and (iii) have low Y/Nb and Zr/Nb ratios, all implying their co-genesis and evolution from homogeneous source parental magma, and their derivation by shallow level fractional crystallization of magma sourced from an enriched component of the mantle. The associated rhyolitic rocks: (i) contain some plagioclase phenocrysts, (ii) plot along the differentiation lines of the associated basalts, (iii) show strong negative anomalies in P, Ti, and Sr, (iv) show general LREE enrichment and HREE depletion, and (v) have very low La/Nb, Rb/Nb, Ta/Nb and Th/Nb ratios. All these suggest their derivation by low-pressure fractionation of mantle derived basaltic magma, with little or no crustal contamination. The rhyolitic rocks of the Alaje Formation from the Aiba area have nearly the same geochemical signatures as other well-constrained rhyolitic rocks of similar stratigraphic context and age in other parts of the Northwestern Ethiopian plateau. • The Alaje Formation is a cyclic intercalation of tholeiitic to transitional basalts and pantelleritic trachytes and rhyolites. • All the basalt layers show uniform geochemical signature implying their co-genesis from homogeneous source parental magma. • The basalts are derived by shallow level fractional crystallization of magma sourced from an enriched mantle component. • The rhyolitic rocks are derived by low-pressure fractionation of mantle derived basaltic magma. [ABSTRACT FROM AUTHOR]

Cave carbonate minerals are an important terrestrial paleoclimate archive. A few studies have explored the potential for applying carbonate clumped isotope thermometry to speleothems as a tool for constraining past temperatures. To date, most papers utilizing this method have focused on mass-47 clumped isotope values (Δ 47) at a single location and reported that cave carbonate minerals rarely achieve isotopic equilibrium, with kinetic isotope effects (KIEs) attributed to CO 2 degassing. More recently, studies have shown that mass-47 and mass-48 CO 2 from acid digested carbonate minerals (Δ 47 and Δ 48) can be used together to assess equilibrium and probe KIEs. Here, we examined 44 natural and synthetic modern cave carbonate mineral samples from 13 localities with varying environmental conditions (ventilation, water level, pCO 2 , temperature) for (dis)equilibrium using Δ 47 -Δ 48 values, in concert with traditional stable carbon (δ13C) and oxygen (δ18O) isotope ratios. Data showed that 19 of 44 samples exhibited Δ 47 -Δ 48 values indistinguishable from isotopic equilibrium, and 18 (95 %) of these samples yield Δ 47 -predicted temperatures within error of measured modern temperatures. Conversely, 25 samples exhibited isotopic disequilibria, 13 of which yield erroneous temperature estimates. Within some speleothem samples, we find Δ 47 -Δ 48 values consistent with CO 2 degassing effects, however, the majority of samples with KIEs are consistent with other processes being dominant. We hypothesize that these values reflect isotopic buffering effects on clumped isotopes that can be considerable and cannot be overlooked. Using a Raleigh Distillation Model, we examined carbon and oxygen isotope exchange trajectories and their relationships with dual clumped isotope disequilibria. Carbon isotope exchange is associated with depletion of both Δ 47 and Δ 48 relative to equilibrium, while oxygen isotope exchange is associated with enrichment of both Δ 47 and Δ 48 relative to equilibrium. Cave rafts collected from proximate locations in Mexico exhibit the largest average departures from equilibrium ( Δ Δ 47 ¯ = −0.032 ± 0.007, Δ Δ 48 ¯ = −0.104 ± 0.035, where ΔΔ i is the measured value – the equilibrium value). This study shows how the Δ 47 -Δ 48 dual carbonate clumped isotope framework can be applied to a variety of tcave carbonate mineral samples, enabling identification of isotopic equilibria and therefore quantitative application of clumped isotope thermometry for paleoclimate reconstruction, or alternatively, constraining the mechanisms of kinetic effects. [ABSTRACT FROM AUTHOR]

The evaluation of groundwater geochemistry of transboundary aquifers has an important role in the management and sustainable use of groundwater resources in arid and semi-arid regions. This study presents the results of an integrated hydrogeochemical study of the Bulal transboundary aquifers located in the Borena zone, along the Ethiopia-Kenya border. The main aquifers are basic volcanic rocks, subordinate felsic pyroclastic deposits, and metamorphic basement rocks. These aquifers are overlain by alluvio-lacustrine sediments, eluvial soil and regolith. The groundwaters are dominated by Na+ and HCO 3 − and mixed water types. Silicate weathering and evaporation are the dominant hydrogeochemical processes controlling the chemistry of the groundwaters in most parts of the catchment. However, dissolution of evaporitic minerals might have also played a significant role in adding major ions into the groundwater system. Groundwater in the volcanic aquifers are Na–HCO 3 , Ca–Mg–HCO 3 , Na–Ca–HCO 3 and Na–Cl–SO 4 water types while Ca–Mg–HCO 3 , Na–Ca–Cl–SO 4 and Ca–Mg–SO 4 water types are dominant in the metamorphic basement aquifers. The groundwater in the catchment mainly evolved from Na–HCO 3 in the west, Ca–Mg–HCO 3 in the north, and Na–Ca–Cl–SO 4 in the central east and southeast to Na–Ca–HCO 3 type in the southern low-lying areas along the groundwater flow direction. The study has significant implications for the management of groundwater quality in the region. • Groundwater chemistry is investigated using an integrated approach. • Ca–Mg–HCO 3 , Na–Ca–Cl–SO 4 and Na–Ca–HCO 3 are the dominant hydrochemical facies. • Groundwater chemistry is governed by silicate weathering and evaporation. • The study has significant implications for managing groundwater quality. [ABSTRACT FROM AUTHOR]

There is ongoing debate concerning whether or not changes in the eastern African climate, both long-term and short-term, affected the evolution, dispersal, cultural development, and technological innovations of Homo sapiens – and if so, in what way. We present the wavelet spectral analysis results of a ∼620 kyr record of environmental change from the Chew Bahir (CHB) basin in the southern Ethiopian rift, approximately 120 km from the Omo-Kibish fossil locality, which boasts one of the oldest documented appearances of H. sapiens. Our results indicate that the long-term wet-dry changes in the eastern African climate recorded in the CHB sediments were mainly caused by changes in orbital eccentricity, with relatively dry but variable climates occurring during eccentricity minima within the 400 kyr eccentricity cycle, and increased precipitation, interspersed with distinctly dryer phases associated with orbital precession, during eccentricity maxima. Such insolation-forced precipitation changes would have affected the habitat of H. sapiens in the region; the transition from Acheulean to Middle Stone Age (MSA) documented in the Olorgesailie Basin of southern Kenya coincides with a distinct eccentricity minimum with reduced precipitation and repeated abrupt climatic transitions. In contrast, at the time of the subsequent, first documented occurrence of H. sapiens in eastern Africa the climate was distinctly wetter and less variable. • Orbitally controlled variation in insolation have caused wet-dry climate cycles in the CHB over the las 620 kyrs. • The climate of the CHB was characterized by a long term drying trend coinciding with an increase in variability. • Short term increases of variability correspond to changes in eccentricity translating into fast climate transitions. • During the transition from Acheulean to MSA technologies the climate of the CHB was highly variable. [ABSTRACT FROM AUTHOR]

Current models of early hominin biological and cultural evolution are shaped almost entirely by the data accumulated from the East African Rift System (EARS) over the last decades. In contrast, little is known about the archaeological record from the high-elevation regions on either side of the Rift. Melka Wakena is a newly discovered site-complex on the Southeastern Ethiopian Highlands (SEH) (>2300 m above mean sea level) just east of the central sector of the Main Ethiopian Rift (MER), where eight archaeological and two paleontological localities were discovered to date. Nine archaeological horizons from three localities were tested so far, all dated to the second half of the early Pleistocene (∼1.6 to >0.7 Ma). All the lithic assemblages belong to the Acheulian technocomplex. Here we report on geochronological, stratigraphic, paleontological and lithic technological aspects of the tested localities and contextualize them in the broader framework of hominin cultural evolution in eastern Africa. Findings from Melka Wakena, assessed against the backdrop of the few other highland sites (Melka Kunture and Gadeb), support a scenario of expansion rather than dispersal from the Rift to the highlands. When considered in the context of the Rift-highlands interface, results of the first-phase research at Melka Wakena help to parse existing general models into archaeologically testable hypotheses and demonstrate the site's potential to contribute to research of early prehistory and to understanding the dynamics of early Pleistocene hominin populations in eastern Africa. • Initial investigations at the new early Pleistocene site-complex Melka Wakena, southeastern Ethiopian Highlands (>2300 m above sea level). • Several stratified Acheulian localities on a dynamic flood plain, dated by 40Ar/39Ar between 1.6 Ma and >0.7 Ma. • Lithic production consists of locally-made small flakes, large flakes. Spatially segmented reduction and shaping of Large Cutting Tools. • Reconstruction of extensive Acheulian land-use of the floodplain, based on fauna, sedimentology and material culture evidence. • This addition to the few known early Pleistocene highland sites contributes to understanding highland-Rift Valley occupation dynamics. [ABSTRACT FROM AUTHOR]

The Gohatsion Formation consists of a cyclic intercalation of fine siliciclastic and evaporite/carbonate beds and has been subdivided into three informal members, namely the Lower Mudrock Member, the Gypsum Member and the Upper Mudrock Member. Four lithostratigraphic sections were constructed at the Gohatsion, Dejen, Mugher and Jemma localities. Lithofacies analysis of the succession at outcrop and petrographic scales indicate a broad tidal belt influenced by seasonal and regional climate and sea level changes. Integrated lithofacies depositional models for the corresponding informal members have been proposed in order to demonstrate the lithological response to local and global climate change and sea level fluctuations that occurred during the initial phase of the Tethyan Sea transgression during the early to middle Jurassic. Lithofacies of the Lower Mudrock Member show deposition within a siliciclast-dominated back barrier tidal flat system. Deposition of the Gypsum Member occurred in a marine coastal sabkha belt, whereas the Upper Mudrock Member was deposited in a broad coastal shelf prone to seasonal marine flooding. The models show that all the members of the Gohatsion Formation were formed within a broad coastal tidal belt with continental influence and sediment delivery from the northwest, and a slowly encroaching transgressive marine influence from the southeast. • The Gohatsion formation has been reclassified into 3 informal members. • Depositional environment for the Lower Mudrock Member is mixed tidal flat. • Depositional environment of the Gypsum member is marine coastal sabkha. • Depositional environment of the Upper Mudrock Member is a broad coastal shelf. [ABSTRACT FROM AUTHOR]

Abstract Archaeological findings, numerical human dispersal models and genome analyses suggest several time windows in the past 200 kyr (thousands of years ago) when anatomically modern humans (AMH) dispersed out of Africa into the Levant and/or Arabia. From close to the key hominin site of Omo-Kibish, we provide near continuous proxy evidence for environmental changes in lake sediment cores from the Chew Bahir basin, south Ethiopia. The data show highly variable hydroclimate conditions from 116 to 66 kyr BP with rapid shifts from very wet to extreme aridity. The wet phases coincide with the timing of the North African Humid Periods during MIS5, as defined by Nile discharge records from the eastern Mediterranean. The subsequent record at Chew Bahir suggests stable regional hydrological setting between 58 and 32 kyr (MIS4 and 3), which facilitated the development of more habitable ecosystems, albeit in generally dry climatic conditions. This shift, from more to less variable hydroclimate, may help account for the timing of later dispersal events of AMH out of Africa. Highlights • Multiproxy record from S Ethiopia extends knowledge about environment and climate of past 116,000 yrs during human expansion. • Hydroclimate during Marine Isotope Stage (MIS) 5 was much more variable (frequency and amplitude) than during MIS 3 and 4. • Earth system models and model simulations of intermediate complexity emulate corresponding amplitude shifts in hydroclimate. • Environment was arid during MIS 3 and 4, but permanent lake water bodies existed as inferred from our biological proxies. [ABSTRACT FROM AUTHOR]

Given its proximity to the Strait of Bab el Mandeb and the Red Sea, the Horn of Africa is particularly important for understanding human and faunal migration events to and from Africa. Towards the end of the Pleistocene, the Middle/Later Stone Age (MSA/LSA) transition represents a critical step in human cultural evolution. However, in the Horn of Africa, the environmental conditions associated with this transition remain poorly understood. The Goda Buticha (Buticha cave) sequence, located in southeastern Ethiopia, and dated from ca. 63 ka cal BP to ca. 1 ka cal BP, provides a rare opportunity to examine the environmental contexts associated with major cultural sequences documented in the region during this time period. A preliminary analysis of the rich microvertebrate (and especially rodent) remains recovered from the levels dated between 43 and 4 ka BP identified fourteen different rodent genera, including two species that are locally extinct in southeastern Ethiopia today. While the taphonomic signature is similar throughout the sequence, indicating an in situ accumulation by an owl without major perturbation, the palaeoecological analysis showed environmental change through time, characterized by open-dry setting during the Late Pleistocene, shifting to wetter and more wooded conditions heading to the Holocene. These results are generally consistent with other diverse records which include the large mammals, speleothems and lake basins records, and allow a better understanding of the dynamics of environmental contexts associated with observed cultural change and continuity in eastern Africa from the Late Pleistocene to Late Holocene. [ABSTRACT FROM AUTHOR]

The African continent is characterised by a wide range of hydroclimate regimes, ranging from humid equatorial West Africa to the arid deserts in the northern and southern subtropics. The livelihoods of much of its population are also vulnerable to future climate change, mainly through variability in rainfall affecting water resource availability. A growing number of data sources indicate that such hydroclimatic variability is an intrinsic component of Africa's natural environment. This paper, co-authored by members of the PAGES Africa 2k Working Group, presents an extensive assessment and discussion of proxy, historical and instrumental evidence for hydroclimatic variability across the African continent, spanning the last two millennia. While the African palaeoenvironmental record is characterised by spatially disjunctive datasets, with often less-than-optimal temporal resolution and chronological control, the available evidence allows the assessment of prominent spatial patterns of palaeomoisture variability through time. In this study, we focus sequentially on data for six major time windows: the first millennium CE, the Medieval Climate Anomaly (900–1250 CE), the Little Ice Age (1250–1750 CE), the end of the LIA (1750–1850 CE), the Early Modern Period (1850–1950), and the period of recent warming (1950 onwards). This results in a continent-wide synthesis of regional moisture-balance trends through history, allowing consideration of possible driving mechanisms, and suggestions for future research. [ABSTRACT FROM AUTHOR]

Our understanding of the impact of climate-driven environmental change on prehistoric human populations is hampered by the scarcity of continuous paleoenvironmental records in the vicinity of archaeological sites. Here we compare a continuous paleoclimatic record of the last 20 ka before present from the Chew Bahir basin, southwest Ethiopia, with the available archaeological record of human presence in the region. The correlation of this record with orbitally-driven insolation variations suggests a complex nonlinear response of the environment to climate forcing, reflected in several long-term and short-term transitions between wet and dry conditions, resulting in abrupt changes between favorable and unfavorable living conditions for humans. Correlating the archaeological record in the surrounding region of the Chew Bahir basin, presumably including montane and lake-marginal refugia for human populations, with our climate record suggests a complex interplay between humans and their environment during the last 20 ka. The result may contribute to our understanding of how a dynamic environment may have impacted the adaptation and dispersal of early humans in eastern Africa. [ABSTRACT FROM AUTHOR]

The Main Ethiopian Rift (MER) is renowned as a focus of investigations into human origins. It is also the site of many large volcanic calderas, whose eruptions have spanned the timeframe of speciation, cultural innovation, and dispersal of our species. Yet, despite their significance for dating human fossils and cultural materials, the timing and geochemical signatures of some of the largest eruptions have remained poorly constrained at best. Here, through a programme of field surveys, geochemical analysis and 40Ar/39Ar dating, we report the ages of MER ignimbrites and link them to widespread tephra layers found in sequences of archaeological and paleoenvironmental significance. We date major eruptions of Fentale (76 ± 18 ka), Shala (ca. 145–155 ka), Kone (184 ± 42 ka and ca. 200 ± 12 ka) and Gedemsa (251 ± 47 ka) volcanoes, and correlate a suite of regionally important tephra horizons. Geochemical analysis highlights the predominantly peralkaline rhyolitic melt compositions (7.5–12 wt% Na 2 O + K 2 O, 70–76 wt% SiO 2) across the central MER and remarkable similarity in incompatible trace element ratios, limiting the correlation of deposits via glass composition alone. However, by integrating stratigraphic and geochronological evidence from proximal deposits, lake sediment cores and distal outcrops at archaeological sites, we have traced ash layers associated with the ca. 177 ka Corbetti, ca. 145–155 ka Shala and ca. 108 ka Bora-Baricha-Tullu-Moye eruptions across southern Ethiopia. In addition to strengthening the tephrochronological framework that supports paleoenvironmental and archaeological work in the region, our findings have wider implications for evaluating the hypothesis of a middle Pleistocene 'ignimbrite flare-up' in the MER, and for evaluating the impacts of these great eruptions on landscapes, hydrology, and human ecology. • Quaternary explosive eruptions in the Main Ethiopian Rift linked to palaeoanthropological and archaeological archives. • Review of the Pleistocene calderas of Main Ethiopian Rift. • An improved middle to late Pleistocene tephrostratigraphy for the Ethiopian Rift. [ABSTRACT FROM AUTHOR]

Detailed geological and geochemical characterization is crucial to support soil studies in such geologically and topographically complex systems as the Gilgel Gibe catchment in southwestern Ethiopia. Field studies, as well as mineralogical, petrological and geochemical analyses on selected rock samples and their weathering products revealed that the catchment is dominantly underlain by rhyolites and trachytes, which occur as both lava flows and pyroclastic associations. Most of the lavas have a trachytic texture, while few others are massive or show spherulitic or perlitic texture. The rocks have a SiO 2 -content ranging from about 62 to 73 wt% (intermediate to felsic composition, on an anhydrous base) and a relatively high Na 2 O + K 2 O content ranging from about 9 to 12 wt% (anhydrous base). The dominant phenocrysts present in the rocks are plagioclase, sanidine and Fe–Ti oxide minerals. Alkali-rich amphiboles and quartz occur in most of them, while hornblende, titanite and clinopyroxene are rare. The amount of phenocrysts varies from less than 1 vol.% to about 30 vol.%. The pyroclastic associations are discontinuously scattered within the study area. They all have a glassy matrix (vitrophyric texture) and are composed of a mixture of lithics, crystals and glass. In comparison with the lava samples, the pyroclastic samples exhibit a more variable chemistry. In contrast, the X-ray diffractograms of the pyroclastic deposits and the lavas show little difference. The Chemical Index of Alteration values for the studied samples vary from 53 to 99 indicating moderate to high intensity of weathering. Samples from lava flows have shown less degree of weathering than samples of the pyroclastic associations. [ABSTRACT FROM AUTHOR]

Goda Buticha is a newly discovered cave site in southeastern Ethiopia, containing MSA and LSA cultural material, faunal remains, beads, and human skeletal remains. A 2.3 m-deep sedimentary sequence records two occupational phases separated by a sharp chronological hiatus, in the Upper Pleistocene (∼ 43–31.5 ka cal BP) and in the mid- Holocene (7.8–4.7 ka cal BP). Faunal remains suggest changes in paleoecological conditions that are in agreement with patterns documented in regional speleothem-based reconstructions. The lithic assemblage at the base of the sequence is clearly MSA, with Levallois production, unifacial and bifacial points, relatively large debitage and use of local raw materials, associated with a microlithic component. The overlaying LSA assemblage contains diagnostic artifacts (backed microliths and bladelet production), with ubiquitous use of obsidian and MSA elements that appear in the Holocene. In the absence of indications for post-depositional mixture, the apparent cultural continuity of MSA elements from the Upper Pleistocene into the Middle Holocene at Goda Buticha may represent yet another variation of the elusive MSA/LSA transition. Goda Buticha is a key site for reevaluating the dynamics and tempo of this transition in eastern Africa. [ABSTRACT FROM AUTHOR]

The horn of Africa provides the setting for the evolution of early modern humans and their dispersal out of Africa as well as for the entry, many thousands of years later, of pastoralists who brought Near Eastern and, later, South Asian livestock into Africa. However, significant gaps remain in our understanding of the late Upper Pleistocene archaeological record of the horn of Africa, mainly due to the paucity of well-stratified sites from the period. The discovery in southeastern Ethiopia of a number of caves with rich Upper Pleistocene and Holocene archaeological deposits, many of which also had rock art depicting domestic animals, offers an unprecedented opportunity for exploring the later prehistory of the region. In 2007, 2008 our survey documented twenty-one cave sites and shelters with evidence of cultural deposits, including Middle Stone Age (MSA) and Later Stone Age (LSA) stone artifacts, faunal remains, and rock art. Active and fossil speleothems, important for paleoclimatic reconstructions and chronology, were found from two other caves in eastern and western Harerghe. Test excavations were conducted at three sites, with abundant archaeological material documented from stratified deposits at two of these sites – Gilbo Tate and Goda Buticha. The latter is a subject of another paper in this volume. Rock art was recorded at eighteen sites, three of which (in western Harerghe) had not previously been documented. At many of the sites, much of the art is faded and in a vulnerable state, and continued efforts to document and conserve this art are urgently needed. [ABSTRACT FROM AUTHOR]

Abstract: East African paleoenvironments are highly variable, marked by extreme fluctuations in moisture availability, which has far-reaching implications for the origin, evolution and dispersal of Homo sapiens in and beyond the region. This paper presents results from a pilot core from the Chew Bahir basin in southern Ethiopia that records the climatic history of the past 45 ka, with emphasis on the African Humid Period (AHP, ∼15–5 ka calBP). Geochemical, physical and biological indicators show that Chew Bahir responded to climatic fluctuations on millennial to centennial timescales, and to the precessional cycle, since the Last Glacial Maximum. Potassium content of the sediment appears to be a reliable proxy for aridity, showing that Chew Bahir reacted to the insolation-controlled humidity increase of the AHP with a remarkably abrupt onset and a gradual termination, framing a sharply defined arid phase (∼12.8–11.6 ka calBP) corresponding to the Younger Dryas chronozone. The Chew Bahir record correlates well with low- and high-latitude paleoclimate records, demonstrating that the site responded to regional and global climate changes. [Copyright &y& Elsevier]

Abstract: Landslide hazard is one of the crucial environmental constraints for the development of Ethiopia, representing a limiting factor for urbanization and infrastructures. The high relief and the rugged topography induced by a strong Plio-Quaternary uplift, the occurrence of clayey horizons within the sedimentary sequences, the dense network of tectonic fractures and faults, the thick eluvial mantles on volcanic outcrops, and the thick colluvial–alluvial deposits at the foot of steep slopes are the predisposing factors for a large variety of mass movements. Heavy summer rainfall is the main triggering factor of most landslides, some of which undergo a step-like evolution with long-lasting quiescence intervals. First generation movements are commonly restricted to shallow phenomena, such as soil slips or mud flows in eluvial–colluvial material. Fast moving slope failures, such as rock slides, topplings and falls, are also triggered by earthquakes. To mitigate the landslide risk, any first priority measure should include adequate drainage of slopes in order to reduce water infiltration. On the other hand, appropriate site selection for buildings, transferring risky settlements, accurate geological control of works, and education campaigns are all strongly recommended. [Copyright &y& Elsevier]

Despite eastern Africa being a key location in the emergence of Homo sapiens and their subsequent dispersal out of Africa, there is a paucity of long, well-dated climate records in the region to contextualize this history. To address this issue, we dated a ∼293 m long composite sediment core from Chew Bahir, south Ethiopia, using three independent chronometers (radiocarbon, 40Ar/39Ar, and optically stimulated luminescence) combined with geochemical correlation to a known-age tephra. The site is located in a climatically sensitive region, and is close to Omo Kibish, the earliest documented Homo sapiens fossil site in eastern Africa, and to the proposed dispersal routes for H. sapiens out of Africa. The 30 ages generated by the various techniques are internally consistent, stratigraphically coherent, and span the full range of the core depth. A Bayesian age-depth model developed using these ages results in a chronology that forms one of the longest independently dated, high-resolution lacustrine sediment records from eastern Africa. The chronology illustrates that any record of environmental change preserved in the composite sediment core from Chew Bahir would span the entire timescale of modern human evolution and dispersal, encompassing the time period of the transition from Acheulean to Middle Stone Age (MSA), and subsequently to Later Stone Age (LSA) technology, making the core well-placed to address questions regarding environmental change and hominin evolutionary adaptation. The benefits to such studies of direct dating and the use of multiple independent chronometers are discussed. • Four independent dating methods applied to ∼293 m lake core from southern Ethiopia. • Reveals 620 ka high-resolution sedimentary record near key fossil hominin sites. • Mean accumulation rate of 0.47 mm/a comparable to other African lacustrine sediments. • Accumulation rate fell to 0.1 mm/a during MIS 2, likely due to reduced sediment supply. • Use of multiple independent chronometers is a powerful approach in lake settings. [ABSTRACT FROM AUTHOR]