Kenya Rift Research Articles

Eruptive history and volcano-tectonic evolution of Paka volcanic complex in the northern Kenya rift: Insights into the geothermal heat source

In this paper, we provide insights into the eruptive history and volcano-tectonic evolution of the Paka volcanic complex in a revised stratigraphic framework. We integrate all available 40Ar/39Ar radiometric dates along with field observations, remote sensing data, and the analysis of surface and cutting samples from a 2552 m deep borehole (PK-01). Chemical analyses distinguish basalt, hawaiite, mugearite, benmorite, and trachyte rock type in Paka. It also indicates that the eruptive products are genetically related by fractional crystallization. Major element mass balance and Rhyolite-MELTS models are consistent with the trachyte being generated by 74–83% fractional crystallization of Paka basalt. Before the growth of the volcano, volcanic activity was characterised by plateau fissure eruptions at 582–405 ka. Eruptions directly related to the Paka edifice are divided into four different volcanic sequences. Sequences 1–4 span the periods 390–278 ka, 247–205 ka, 160–36 ka, and 36–8 ka. The Pre-Paka plateau eruption products outcrop at the base of the volcano flanks and are overlain by edifice-forming trachyte. Initial caldera-related subsidence is expressed by arcuate structures to the west and southeast parts of the volcano. These initial collapses are associated with tuff and pyroclastic eruptions estimated to have occurred at ~38 ka. Following these explosive eruptions, a ~1.5 by ~1.6 km main caldera developed. The lithological information from the drilled geothermal exploration borehole PK-01 indicates a minimum thickness of ~2200 m for the extrusive lava sequences, with the uppermost 1050 m of the strata being directly related to eruptions from the Paka volcano (Phases 1–4). We estimate a minimum total bulk volume of ~50 km3 for the volcanic material erupted from Paka during the last ~390 ka. This translates to an average eruption rate of ~1.2 × 10−4 km3/yr. The associated advected magmatic heat supported an ‘excess’ heat flux ranging between 110 and 138 mW/m2 or about twice present day average continental flux (57 mW/m2) and about 1.3 times the background values in geothermal areas (90 mW/m2). The apparent high heat flux implies a magma-driven geothermal system, where convection of the hydrothermal fluid is occurring above the heat source. Structural mapping revealed normal faults, strike-slip faults, lineaments, and an array of eruptive vents and domes as the main volcano-tectonic structures. We infer at least four faulting and fault reactivation events that have occurred during Paka geological history. The structural orientations in the area are dominated by NNE and NW with subordinate N-S and NNW striking structures. Evidence suggests that the intersection of NNE and NW trending structures may have had a major influence on the volcanism in the area.

New IR spectroscopic data for determination of water abundances in hydrous pantelleritic glasses

Abstract To aid current work on the genesis of pantelleritic magmas, and the desire to use IR spectroscopy to measure water contents in natural (e.g., melt inclusions) and experimental glasses of pantelleritic composition, we have determined molar absorptivities for near-infrared (NIR) absorption bands related to molecular water (5200 cm–1) and OH groups (4500 cm–1) in synthetic hydrous pantelleritic glasses, with compositions similar to natural pantellerites from the Eburru complex of the Kenya Rift Valley. The experiments were conducted at P = 30 to 150 MPa and T = 850–900 °C using a synthetic pantelleritic starting composition with (wt%) SiO2 = 76.60, Al2O3 = 8.48, FeO* = 5.48, K2O = 3.68, Na2O = 4.72, and with molar ratio (Na+K)/Al = 1.38. The experiments were H2O undersaturated (~1.1 to 6.5 wt% H2O), and the run products were analyzed by Karl-Fischer Titration (KFT) for total dissolved H2O abundance. Different combinations of baseline types (GG or TT) and intensity measurements (peak height and peak area) were applied to measure both hydroxyl group (OH) and molecular water (H2O) in the experimental samples. For instance, evaluating the peak heights and using the TT baseline ε4500 results to be equal to 0.98(4) (L mol-1cm–1) and ε5200 to 1.92(2) (L mol-1 cm–1); these values differ by ~20 to 50% from published values for metaluminous rhyolitic compositions.

New haplochromine cichlid from the upper Miocene (9\u201310 MYA) of Central Kenya

BackgroundThe diversification process known as the Lake Tanganyika Radiation has given rise to the most speciose clade of African cichlids. Almost all cichlid species found in the lakes Tanganyika, Malawi and Victoria, comprising a total of 12–16 tribes, belong to this clade. Strikingly, all the species in the latter two lakes are members of the tribe Haplochromini, whose origin remains unclear. The ‘out of Tanganyika’ hypothesis argues that the Haplochromini emerged simultaneously with other cichlid tribes and lineages in Lake Tanganyika, presumably about 5–6 million years ago (MYA), and that their presence in the lakes Malawi and Victoria and elsewhere in Africa today is due to later migrations. In contrast, the ‘melting pot Tanganyika hypothesis’ postulates that Haplochromini emerged in Africa prior to the formation of Lake Tanganyika, and that their divergence could have begun about 17 MYA. Haplochromine fossils could potentially resolve this debate, but such fossils are extremely rare.ResultsHere we present a new fossil haplochromine from the upper Miocene site Waril (9–10 million years) in Central Kenya. Comparative morphology, supported by Micro-CT imaging, reveals that it bears a unique combination of characters relating to dentition, cranial bones, caudal skeleton and meristic traits. Its most prominent feature is the presence of exclusively unicuspid teeth, with canines in the outer tooth row. †Warilochromis unicuspidatus gen. et sp. nov. shares this combination of characters solely with members of the Haplochromini and its lacrimal morphology indicates a possible relation to the riverine genus Pseudocrenilabrus. Due to its fang-like dentition and non-fusiform body, †W. unicuspidatus gen. et sp. nov. might have employed either a sit-and-pursue or sit-and-wait hunting strategy, which has not been reported for any other fossil haplochromine cichlid.ConclusionsThe age of the fossil (9–10 MYA) is incompatible with the ‘out of Tanganyika’ hypothesis, which postulates that the divergence of the Haplochromini began only 5–6 MYA. The presence of this fossil in an upper Miocene palaeolake in the Central Kenya Rift, as well as its predatory lifestyle, indicate that Haplochromini were already an important component of freshwater drainages in East Africa at that time.

Animal bioturbation preserved in Pleistocene magadiite at Lake Magadi, Kenya Rift Valley, and its implications for the depositional environment of bedded magadiite

Magadiite, a rare hydrous sodium-silicate mineral [NaSi7O13(OH)3·4(H2O)], was discovered about 50 years ago in sediments around Lake Magadi, a hypersaline alkaline lake fed by hot springs in the semi-arid southern Kenya Rift Valley. Today this harsh lacustrine environment excludes most organisms except microbial extremophiles, a few invertebrates (mostly insects), highly adapted fish (Alcolapia sp.), and birds including flamingos. Burrows discovered in outcrops of the High Magadi Beds (~25–9 ka) that predate the modern saline (trona) pan show that beetles and other invertebrates inhabit this extreme environment when conditions become more favourable. Burrows (cm-scale) preserved in magadiite in the High Magadi Beds are filled with mud, silt and sand from overlying sediments. Their stratigraphic context reveals upward-shallowing cycles from mud to interlaminated mud-magadiite to magadiite in dm-scale units. The burrows were formed when the lake floor became fresher and oxygenated, after a period when magadiite precipitated in shallow saline waters. The burrows, probably produced by beetles, show that trace fossils can provide evidence for short-term (possibly years to decades) changes in the contemporary environment that might not otherwise be recognised or preserved physically or chemically in the sediment record.

Early syn-rift igneous dike patterns, northern Kenya Rift (Turkana, Kenya): Implications for local and regional stresses, tectonics, and magma-structure interactions

AbstractFour areas (Loriu, Lojamei, Muranachok-Muruangapoi, Kamutile Hills) of well-developed Miocene-age dikes in the northern Kenya Rift (Turkana, Kenya) have been identified from fieldwork and satellite images; in total, >3500 dikes were mapped. Three areas display NNW-SSE– to N-S–oriented dike swarms, with straight, radial, and concentric patterns in zones <15 km long, and indicate NNW-SSE to N-S regional maximum horizontal principal stress (SHmax) directions in the early to middle Miocene. Individual dikes are typically <2 m wide and tens to hundreds of meters long and have accommodated <2% extension. In places (Loriu, Lojamei, Lokhone high), dikes trend at a high angle to the rift trend, suggesting some local influence (e.g., overpressured magma chamber, cracked lid–style dike intrusions over a sill or laccolith, preexisting fabric in basement) on orientation, in addition to the influence from regional stresses. Only a minor influence by basement fabrics is seen on dike orientation. The early- to middle-Miocene dikes and extrusive activity ended a long phase (up to 25 m.y.) of amagmatic half-graben development in central Kenya and southern Turkana, which lay on the southern edge of the early (Eocene–Oligocene) plume activity. The Miocene dike sets and extension on major border faults in Turkana contrast with larger, more extensive arrays of dikes in evolved systems in the Main Ethiopian Rift that are critical for accommodating crustal extension. By the Pliocene–Holocene, magmatism and intrusion along dikes had become more important for accommodating extension, and the tectonic characteristics began to resemble those of rift basins elsewhere in the eastern branch of the East African Rift.

Early pastoral mobility and seasonality in Kenya assessed through stable isotope analysis

Eastern African pastoralists today depend on mobility to access seasonally available pastures for their livestock. Here, we evaluate the importance of mobility strategies for maintaining herds during the Pastoral Neolithic era in southern Kenya through stable isotope analysis. We use carbon and oxygen isotope ratios of sequentially sampled modern and archaeological cattle, sheep, and goat tooth enamel to reconstruct seasonal vertical mobility strategies of early pastoralists in the region from 3000 to 1200 years ago. An altitudinal transition from C4 grasses at low elevations to C3 grasses at higher elevations permits tracking vertical mobility in the Kenya Rift Valley. Results from eight Pastoral Neolithic sites from southern Kenya show that cattle, sheep, and goats were almost exclusively herded at low elevations throughout the year. Higher variability in carbon isotopes of caprines compared to cattle suggests that caprines had greater seasonal dietary flexibility. Oxygen isotopes were not consistently useful for identifying seasonal patterns: intra- and interannual variability in tropical precipitation and plant water isotopic composition are confounding factors. Archaeological contexts representing local foragers that adopted pastoralism show herding strategies similar to those from established pastoral sites. These results suggest that lower elevation savannas were productive enough to support pastoralism year-round during the Pastoral Neolithic era.

The assessment of water quality in river Molo water basin, Kenya

The monitoring of water quality for both domestic and commercial use is absolutely essential for policy formulation that affects both public and environmental health. This study investigates the quality of water of river Molo system which lies in the Kenyan Rift Valley. The river is considered a vital source of water for the residents and industrial activities in Nakuru and Baringo Counties. Six water samples were collected during the dry season of December 2017. Various physicochemical parameters were determined in situ by use of a portable pH meter. These parameters included pH, temperature, electrical conductivity and total dissolved solids (TDS). Anions such as fluorides, sulfates, phosphates, nitrates, chlorides, carbonates and bicarbonates were determined using conventional methods such as titrimetry and (ultra-violet visible) UV–Vis techniques. The cations including sodium, potassium, calcium and magnesium were determined using flame photometry. The results showed that the water had pH values ranging from 7.90 to 9.66 units, temperature ranged from 14.02 to 31.5 °C, while electrical conductivity ranged from 181 to 1637 μS/cm, TDS (69–823 mg/L), F (2.76–3.28 mg/L), sulfates (4.97–85.66 mg/L), phosphates (0.13–11.06 mg/L), nitrates (1.73–6.16 mg/L), chlorides (38.5–69.4 mg/L), carbonates (18–148 mg/L), bicarbonates (54–384 mg/L), sodium (19–1800 mg/L), potassium (8.9–121 mg/L), magnesium (4.8–106.8 mg/L) and calcium (13.4–77.4 mg/L). The pH, temperature, fluorides and sodium were above the World Health Organization permissible limits for drinking water in S4 and S5. All the water samples fall under bicarbonate or freshwater zone. The sampling points can be classified into five water types: Na–Mg–Ca–HCO3, Na–HCO3, Na–Ca–Mg–HCO3–CO3, Na and Na–Ca–HCO3–CO3. Chemical indices such as sodium adsorption ratio, magnesium hazard, percent sodium and permeability index are reported. Accordingly, the findings from this work indicate that the river Molo water in general is good for irrigation.

Red Earth, Green Glass, and Compositional Data: A New Procedure for Solid-State Elemental Characterization, Source Discrimination, and Provenience Analysis of Ochres

Ochres are a diverse category of naturally occurring iron-enriched earths and rocks, as well as iron oxide minerals, that derive their color from iron-containing chromophores and are suitable for use as pigments. Over the last two decades, provenience studies of archaeological ochres have grown from a rarity largely of interest only to specialists to an accepted and expected part of the archaeological science panoply. The most effective approach to distinguishing among sources of ochre and assigning archaeological pigments to their origin is multi-elemental characterization or “elemental fingerprinting.” In this study, we coupled a sample preparation method not previously used in ochre archaeometry with elemental fingerprinting by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) and Electron Probe MicroAnalysis (EPMA). We present a procedure for lithium borate (LiBo) fusion of samples for solid-state analysis, optimized for use with ochres, and designed for the budget and laboratory equipment constraints faced by many professional and student archaeologists. This method development research is part of the broader project “OLKARIA: Ochre Landscapes of Kenya – Anthropological Research and Iron-oxide Archaeometry,” which seeks in part to characterize the elemental composition of all known geologic ochre sources in the Kenya Rift Valley. Using a subset of project OLKARIA samples prepared by LiBo fusion and measured with LA-ICP-MS and EPMA, we successfully distinguished among six geologic ochre sources and a sample of commercially available iron oxide pigment. Our ability to uphold the Provenience Postulate for this data set compared favorably with source discrimination analyses done using data from Neutron Activation Analysis (NAA) of whole ochre for the same samples. LiBo fusion presents potential solutions to some criticisms of solid-state analysis of ochre using beam techniques, including issues arising from mineralogical heterogeneity, variable surface topography, the presence of free and chemically bound water, and the lack of matrix-matched standard reference materials. We also address the challenges of applying compositional data analysis best practices to ochre with an emphasis on the issues of rounded zero replacement and multivariate normality and highlight the work that remains to be done in this area.

Postharvest Storage Practices of Maize in Rift Valley and Lower Eastern Regions of Kenya: A Cross-Sectional Study.

An assessment of local farmers' knowledge, attitude, and practices on postharvest maize storage and management was carried out with a view of understanding its role in maize contamination with mycotoxins and postharvest losses in Rift Valley and Lower Eastern Regions of Kenya among 165 and 149 farmers, respectively. Differences between the two regions were analyzed using the Chi-square test, Fisher exact test, and two-sample t-test. The median quantity of maize harvested by farmers in the two regions after shelling was 585 kg. A median of 20 kg of maize was put aside as a result of rotting before shelling, and there was a significant mean difference in maize set aside as a result of rotting between the two regions (107.88 kg vs. 31.96 kg; t (306.25) = 5.707, P value <0.001). The quantity of discoloured and mouldy maize consumed ranged from 0 to 90 kg; 7 (2.2%) respondents consumed mouldy maize, 36 (11.5%) fed it to cows, and 19 (6.1%) fed it to poultry. A small percentage (3.5%) believed mouldy maize is safe for human consumption, 23.6% for animal consumption, while 15.0% considered it safe for brewing, with the differences between the two regions being statistically significant (P value <0.05). Nearly half of the respondents (48.4%) kept maize on cobs indoors, 47.1% left it in the field without covering, and 33.1% consumed and sold maize while still green, with more farmers from Lower Eastern practicing this. The results of the study suggest that there were poor postharvest practices and low awareness levels among maize farmers and that this can lead to postharvest losses due to Fusarium spp. infection and mycotoxin contamination that poses a threat to human and animal food safety. This calls for interventions on better postharvest practices.

The Cenozoic magmatism of East Africa: Part III – Rifting of the craton

Magmatic activity in the Tanzania Craton-influenced regions of the East African Rift System (EARS) exhibits clear evidence of derivation from a variety of metasomatic sources. These metasomatic sources, which may span a range of ages, have likely been preserved within the lithospheric mantle. The influence of these metasomes on the composition of the rift magmas represents the single greatest heterogeneity in the composition of erupted lavas within the EARS. The earliest widespread magmatic event in the craton-influenced regions of the EARS south of Lake Turkana is the Samburu Phase (ca. 20–17 Ma), which manifests as alkaline volcanics derived from the lithospheric mantle. This phase represents the initial destabilization of the continental lithosphere as a precursor of rift development. The Flood Phonolite Phase (ca. 16–12 Ma) was most pronounced in regions south of those impacted by the prior Samburu Phase, and likely represent the continued southward expansion of lithospheric destabilization. The Mid-Miocene Resurgence Phase (ca. 12–9 Ma) is poorly represented in the Southern Kenya Rift, though magmatic activity is recorded in the Western Branch of the EARS at Kivu during this time. In contrast, the Early Rift Development Phase (ca. 9–4 Ma) is particularly well-represented in the Kenya Rift. Large-scale magmatic events include: commencement of activity in the Northern Tanzania Divergence (NTD) and Mt. Kenya, Rungwe Volcanic Province, and the Southern Kenya Rift. The Stratoid Phase (ca. 4 Ma – 0.5 Ma) commences with significant magmatic events at ca. 3 to 2.5 Ma within the Southern Kenya Rift and NTD. This phase manifests as basalts and trachytes that flood the newly formed graben in the Southern Kenya Rift. This phase also correlates with the main phase of magmatism in the NTD, the commencement of volcanism at Virunga, and the intermediate shield phase in the Rungwe Volcanic Province. The Axial Phase (0.5 Ma to present) is defined by narrow axial grabens in the Kenya Rift with central volcanoes and interposing basaltic cinder cones. In the less mature regions of the EARS, alkaline volcanoes dominate. Three distinct pulses of magmatism and extension initiated in Turkana commencing at ca. 23 Ma, 12 Ma, and 4 Ma; the consistent temporal lag in magmatic activity in the Southern EARS following each pulse reveals the southward expansion of these extensional events. Lavas at any given location within the rift exhibit a consistent temporal sequence characterized by a shift from Type II lavas (lithospheric mantle derived) to Type IV lavas (hybrid lithospheric mantle – sub-lithosphere derived) to Type III lavas (sub-lithosphere derived), requiring a progressive change in the reservoirs contributing to rift magmatism from lithospheric to sub-lithospheric. When examined in aggregate, these data paint a picture of progressive rift development and attendant lithospheric thinning, mediated by pulses of extension originating in Turkana.

Influence of Strategic Communication on Growth of Students’ Population in Selected Private Universities in Kenya

The study sought to investigate the influence of strategic communication on the growth of students’ population in selected private universities in Kenya. The study was guided by resource-based theory. The study utilized descriptive research design. Random sampling technique was used to select research respondents. The study targeted private universities in north rift, south rift and Nyanza region of Kenya. The unit of observations was staff and students in various departments and faculties existing in the institutions. The study used purposive sampling to select research respondents. Questionnaire was the main instrument for data collection. Descriptive and inferential statistics with the aid of SPSS version 23.0 were used to analyze collected data and presented using frequency distribution tables and bar graphs. The findings indicated that if strategic communication is changed by one unit, the growth of student population will increase by a margin of 0.440. The study concludes that strategic communication plays a critical role in growing students’ population in private universities. It is also recommended that private universities should consider using professional bloggers to build the publicity of the institution. Top management of the private universities will get insight on various strategic issues with regard to student population through the recommendations of the study. Scholars in the field of strategic management will find the study useful as it will form basis of future references.

Vegetation change in the Baringo Basin, East Africa across the onset of Northern Hemisphere glaciation 3.3–2.6 Ma

Vegetation in East Africa is generally thought to have shifted from forests to more open grasslands and savannas as global climate cooled and high-latitude ice sheets expanded during the Plio-Pleistocene. Such a shift would have greatly influenced landscape resources, and potentially hominin evolution as well. Existing records of African vegetation spanning these time-scales are generally derived from offshore marine records that record continental-scale changes, or paleosol carbonate records that record very local vegetation changes during the short time intervals of soil carbonate formation. Here we present a new record of basin-scale vegetation change from the late Pliocene (~3.3–2.6 Ma) derived from a drill core from the Chemeron Formation, located in the Baringo Basin/Tugen Hills region of the Kenya Rift Valley. Specifically, we present a new record of the relative abundance of C4 grasses and C3 vegetation based on the carbon isotopic composition of leaf wax biomarkers (δ13Cwax), which captures a signal of regional vegetation change. These data demonstrate that vegetation in the Baringo Basin varied greatly between C3 forests and C4 grasslands, and that vegetation exhibits both long-term (secular) trends and orbital-scale variations. The contribution of C3 plants was lower than estimates based on low-resolution carbon isotope data from paleosol carbonates and organic matter in the basin. C3 plants averaged ~53% of the vegetation during the late Pliocene, from ~3.3 to ~3.04 Ma, after which time δ13Cwax indicates more open vegetation and ~41% C3 plants. This transition may have been driven by changes in basin geomorphology, but also possibly occurred as part of larger-scale drying and expansion of C4 vegetation in East Africa. In addition to this secular change, we observe high amplitude variability in the δ13Cwax record including oscillations between ~80 and ~0% C3 plants. These vegetation changes are correlated with changes in precipitation inferred from δ2Hwax and lake level oscillations inferred from sedimentary facies, implying that high-amplitude, orbital-scale variations in precipitation drove significant changes in vegetation resources during the late Pliocene in the Baringo Basin. These variations have important implications for changes in terrestrial resources in light of the evolutionary innovations in the hominin fossil record related to changes in foraging strategies.

The Cenozoic magmatism of East Africa: Part II – Rifting of the mobile belt

Despite the foundational role East Africa has played in the advancement of our understanding of continental rifting, there remains substantial ambiguity as to how magmatism has evolved during progressive rift development. This contribution is a comparative study that explores the temporal development of magmatism in both rifts, and within the interposing Turkana Depression. Notwithstanding the independent evolution of the Main Ethiopian Rift and Kenya Rift prior to their Quaternary linkage, magmatic events within them show remarkable parallelism. Following an initial pulse of basaltic magmatism ca. 20 Ma, more evolved compositions (flood phonolites in Kenya, rhyolites in Ethiopia) dominated the landscape until ca. 12 Ma. From ca. 12 Ma to 9 Ma, a renewed phase of widespread basaltic volcanism (Mid-Miocene Resurgence Phase) impacted the entire region from the Afar margin to Kenya, though activity in the south slightly predates equivalent basaltic events to the north. Following this widespread basaltic event, silicic magmatism again dominated the now nascent rifts until a renewed phase of basaltic activity commenced ca. 4 to 1.6 Ma termed the ‘Stratoid Phase’. Following the termination of the Stratoid Phase, the modern expression of volcanism in both rifts has been dominated by central silicic volcanoes. Magmatic activity within the Turkana Depression broadly parallels that in both rifts – basaltic events are evident at ca. 20 Ma, 12 Ma, and 4 Ma, however the silicic interludes that are evident within the rifts, are generally absent. Moreover, from 4 Ma to present, there is a progressive decrease in magmatic activity from an initial fissural basalt, to a series of large shield volcanoes, to modern belts of cinder cones. The results of this synthesis suggest widespread pulsed basaltic events precede silicic flare-ups throughout the East African Rift System, and the lack of such flare-ups in Turkana may relate to the Mesozoic rifting that modified the continental lithosphere in that region.

A high-resolution climate history of geochemical and biological proxies from a tropical freshwater wetland located in the Kenyan Rift Valley

The sedimentary and biological material preserved in wetlands in semi-arid regions provide a rich repository of paleoclimate and paleoecological archives. These records reflect an underutilized, but typically ignored paleoenvironmental resource in semi-arid settings. The results presented here demonstrate that groundwater-fed wetlands constitute a valuable record of environmental change that not only complement reconstructions from lacustrine settings, but also contribute unique data and insights into climate and landscape change.We use data obtained from sediment cores collected from Loboi wetland, a groundwater-fed wetland located in the Equatorial East African Rift Valley of Kenya, to demonstrate the value of paleoenvironmental datasets extracted from wetland archives. This article relates surficial sedimentary geochemical data (TOC, δ13C, δ15N, C:N, and %C3) at Loboi to the extant macrophytic vegetation. The surficial data are used as an analog to interpret the geochemical signature of three sediment cores and a soil pit. The stratigraphic records show significant variation along a north to south transect through the wetland. The geochemistry indicates that papyrus wetland records are distinctly different from Typha dominated wetland sedimentary signatures. The interpretation of the stratigraphic material is further improved by the inclusion of sub-fossil macrophyte and testate amoebae remains. The extraction and identification of seeds of wetland plants from the sedimentary archive provide invaluable genus to species specific details of wetland ecology. Further, the inclusion of testate amoebae as an indicator of surface hydrological conditions has significantly improved interpretation of the hydrological history of Loboi wetland.The stratigraphic record from Loboi indicates that between ~1100 and 1470 C.E. (Medieval Climatic Anomaly) dry conditions dominated the Loboi region, except for a brief period of wetter conditions between ~1275 and 1345 C.E. Seasonally wetter conditions began to persist between ~1470 and 1630 C.E. Wetland sediments developed after this time as reflected by the sequestration of carbon in the sedimentary record. Recent historic biological and sedimentary proxies reflect increased agrarian impacts on the landscape surrounding Loboi.

Continental rifting at magmatic centres: structural implications from the Late Quaternary Menengai Caldera, central Kenya Rift

The structural evolution of calderas in rifts helps to characterize the spatiotemporal relationships between magmatism, long wavelength crustal deformation and the formation of tectonic deformation zones along the rift axis. We document the structural characteristics of the c. 36 ka old Menengai Caldera located within a young zone of extension in the central Kenya Rift. Field mapping and high-resolution digital surface models show that NNE-striking Holocene normal faults perpendicular to the regional ESE–WNW extension direction dominate the interior sectors of the rift. Inside the caldera, these structures are overprinted by post-collapse doming and faulting of the magmatic centre, resulting in obliquely slipping normal faults bounding a resurgence horst. Radiocarbon dating of faulted units as young as 5 ka cal BP and the palaeo-shorelines of a lake formed during the African Humid Period in the Nakuru Basin indicate that volcanism and fault activity inside and in the vicinity of Menengai must have been sustained during the Holocene. Our analysis confirms that the caldera is located at the centre of an extending rift segment and suggests that other magmatic centres and young zones of faulting along the volcano-tectonic axis of the Kenya Rift may constitute nucleation points of faulting that ultimately foster future continental break-up. Supplementary material: 40 Ar/ 39 Ar radiometric dating data table is available at: https://doi.org/10.6084/m9.figshare.c.4647818

Groundwater Evolutionary Processes and Quality Characterization: A Case of Olbanita Aquifer System, Lower Baringo Basin, Kenya Rift

A hydro-geochemical relation has been hypothesized through the analyses of physico-chemical data of a fractured volcanic rock aquifer located in the Lower Baringo Basin, Kenyan Rift. Datasets included 15 individual metrics determined in forty-two dry and wet season water samples obtained from six boreholes in the area.

Drainage incision, tectonic uplift, magmatic activity, and paleo-environmental changes in the Kenya Rift, East African Rift System: A morpho-tectonic analysis

We examined average drainage incision in the northern, central, and southern Kenya Rift (NKR, CKR, and SKR) of the East African Rift System (EARS) in relation to tectonic uplift, magmatic activity, and paleo-environmental changes by: (1) Mapping Eocene to Holocene volcanic units using published geological and geochronological data; (2) Calculating the average incision rate (AIR) on the rift flanks by obtaining the difference between paleo-datum and modern topography and dividing the resulting regional incision by the age of volcanic units; (3) Calculating the total amount of incision (TAI) on the rift flank from stream longitudinal profiles using the normalized steepness index (Ksn) and concavity (θ); and (4) correlating the spatial and temporal drainage incision patterns with tectonic, magmatic, and climatic events. Our analysis showed higher AIR (maximum of ~250 mm/kyr) and higher TAI (maximum of ~1200 m) in the CKR after ~4.5 Ma. Pliocene increase in the AIR and TAI is also observed in other parts of the EARS and this has been attributed to increase in tectonic uplift rate. We found that the spatial and temporal patterns of the tectonic uplift inferred from the drainage incision to be well-correlated with known phases of magmatic activity. Moreover, we found that the increase in the AIR and TAI after ~4.5 Ma to be well-correlated with changes in vegetation from woodland to grassland. This suggests that the tectonic uplift coupled with magmatic activity are probably caused by major shifts in ecosystem in the study area.

Cooperation in the midst of violence: land deals and cattle raids in Narok and Laikipia, Kenya

AbstractWhat drives the formation of ties and networks in ethnically hybrid spaces despite the occurrence of conflict? We approach this question by examining the actors involved, the institutions affected, and the economic and environmental contexts surrounding such tendencies. This study explores socially thick arrangements between Maasai and Kikuyu in Narok and their role in the non-violent use of formerly contested lands. In Laikipia, we examine how young Samburu and Kikuyu cooperate in a dangerous yet economically beneficial network involving cattle-rustling ventures. We revisit the history of land settlement in Kenya's Rift Valley, particularly in the study areas of Narok and Laikipia, and show how access and settlement rights to land are negotiated peacefully, encouraging ethnic assimilation and cooperative social and economic relations. Based on this context and the exploration of our case studies, we argue that the formation of alliances in multi-ethnic settings tends to override other identities when mutual benefits drive such associations.

Rifting of the northern margin of the Indian craton in the Early Cretaceous: Insight from the Aulis Trachyte of the Lesser Himalaya (Nepal)

Abstract To reconstruct the early tectonic history of the Himalayan orogen before final India-Asia collision, we carried out geochemical and geochronological studies on the Early Cretaceous Aulis Trachyte of the Lesser Himalaya. The trace-element geochemistry of the trachytic lava flows suggests formation in a rift setting, and zircon U-Pb ages indicate that volcanism occurred in Early Cretaceous time. The felsic volcanics show enrichment of more incompatible elements and rare earth elements, a pattern that is identical to the trachyte from the East African Rift (Kenya rift), with conspicuous negative anomalies of Nb, P, and Ti. Although much of the zircon age data are discordant, they strongly suggest an Early Cretaceous eruption age, which is in agreement with the fossil age of intravolcanic siltstones. The Aulis Trachyte provides the first corroboration of Cretaceous rifting in the Lesser Himalaya as suggested by paleomagnetic data associated with the concept that the northern margin of India separated as a microcontinent and drifted north in the Neo-Tethys before terminal collision of India with Asia.

Agricultural Monitoring, an Automatic Procedure for Crop Mapping and Yield Estimation: The Great Rift Valley of Kenya Case

Agricultural activities conducted in the Great Rift Valley of Kenya show a significant decline of productivity levels. This phenomenon is mainly related to limited availability of water resources, lack of supporting irrigation, and harvesting techniques ineffectiveness. Production risks reduction is closely related with a better use of water resources and a better understanding of the effects resulting from the multiple interactions between climate, agricultural vegetation, soil type, and crops management techniques. In this paper, a remote and automatic agricultural monitoring system is presented as an effective alternative to the most traditional in situ measurements and observations. We investigated the use of phenological information extracted from satellite imagery combined with crop calendar and supported by agro-ecological zoning (AEZ) in accurate crop classification and monitoring. Vegetation indices extracted from Landsat 8 imagery are capable to track the vegetation development through the year, then phenological profiles can be extracted and implemented into a multitemporal automatic classification process to detect agricultural areas and to discriminate among different crop species. The phenological profiles extracted by satellite imagery are compared with crop calendar data compiled by FAO for the area of interest. The classification procedure is supported by AEZs based on crop modeling and environmental matching procedures in order to identify crop-specific environmental limitations under assumed levels of inputs and management conditions. The FAO crop water productivity model AquaCrop is calibrated for wheat and maize yield mapping in the central highland of Kenya, handling both environmental and phenological data. The combined use of phenological data and AEZs results in a robust methodology with a classification overall accuracy of 91.35%. A good model performance is obtained relative to yield predictions, with R of 0.69 and 0.72.