Eastern Branches Research Articles

Investigation of geothermal structure of the Sulawesi, using gravity and magnetic method

The Sulawesi Sea and Sulawesi Island are located in the western Pacific area where volcanic activity, plate subduction, and seismic activity are very active. The Sulawesi basin formed during the Middle Eocene-Late Eocene and nearly half of the Eocene oceanic crust has subducted below the North Sulawesi Trench. The Sulawesi Island was spliced and finalized in the Early Pliocene-Pleistocene during volcanic activity and is recently very active. This area is an optimal location to study volcanic geothermal conditions and subduction initiation mechanisms in the southern part of the western Pacific plate margin, which are important in geothermal and geodynamic research. In this study, we combined 133 heat flow data with gravity and magnetic data to calculate the Moho structure and Curie point depth of the Sulawesi Sea and periphery of the Sulawesi Island, and analyze the distribution characteristics of the geothermal gradient and thermal conductivity. The results show that the average depths of the Moho and Curie surfaces in this area are 18.4 and 14.3 km, respectively, which is consistent with the crustal velocity layer structure in the Sulawesi Basin previously determined by seismic refraction. The average geothermal gradient is 4.96°C (100 m)−1. The oceanic area shows a high geothermal gradient and low thermal conductivity, whereas the land area shows a low geothermal gradient and high thermal conductivity, both of which are consistent with statistical results of the geothermal gradient at the measured heat flow points. The highest geothermal gradient zone occurs in the transition zone from the Sulawesi Sea to Sulawesi Island, corresponding to the spreading ridge of the southward-moving Sulawesi Basin. Comprehensive gravity, magnetic, and geothermal studies have shown a high crustal geothermal gradient in the study area, which is conducive to the subduction initiation. The northern part of the Palu-koro fault on the western side of Sulawesi is likely the location where subduction initiation is occurring. During the process of moving northwest, the northern and eastern branches of Sulawesi Island have different speeds; the former is slow and the latter is fast. These branches also show different deep tectonic dynamic directions; the northern branch tilts north-up and the eastern branch tilts north-down.

Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift

The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In striking contrast to its neighboring plates, Victoria rotates counterclockwise with respect to Nubia. The underlying cause of this distinctive rotation has remained elusive so far. Using 3D numerical models, we investigate the role of pre-existing lithospheric heterogeneities in continental microplate rotation. We find that Victoria’s rotation is primarily controlled by the distribution of rheologically stronger zones that transmit the drag of the major plates to the microplate and of the mechanically weaker mobile belts surrounding Victoria that facilitate rotation. Our models reproduce Victoria’s GPS-derived counterclockwise rotation as well as key complexities of the regional tectonic stress field. These results reconcile competing ideas on the opening of the rift system by highlighting differences in orientation of the far-field divergence, local extension, and the minimum horizontal stress.

Large shift of the Pacific Walker Circulation across the Cenozoic.

Fluctuations in the Pacific Walker Circulation (PWC), a zonally oriented overturning cell across the tropical Pacific, can cause widespread climatic and biogeochemical perturbations. It remains unknown how the PWC developed during the Cenozoic era, with its substantial changes in greenhouse gases and continental positions. Through a suite of coupled model simulations on tectonic timescales, we demonstrate that the PWC was ∼38° broader and ∼5% more intense during the Early Eocene relative to present. As the climate cooled from the Early Eocene to the Late Miocene, the width of the PWC shrank, accompanied by an increase in intensity that was tied to the enhanced Pacific zonal temperature gradient. However, the locations of the western and eastern branches behave differently from the Early Eocene to the Late Miocene, with the western edge remaining steady with time due to the relatively stable geography of the western tropical Pacific; the eastern edge migrates westward with time as the South American continent moves northwest. A transition occurs in the PWC between the Late Miocene and Late Pliocene, manifested by an eastward shift (both the western and eastern edges migrate eastward by >12°) and weakening (by ∼22%), which we show here is linked with the closure of the tropical seaways. Moreover, our results suggest that rising CO2 favors a weaker PWC under the same land-sea configurations, a robust feature across the large spread of Cenozoic climates considered here, supporting a weakening of the PWC in a warmer future.

Recent Surge Behavior of Walsh Glacier Revealed by Remote Sensing Data.

Many surge-type glaciers are present on the St. Elias Mountains, but a detailed study on the surge behavior of the glaciers is still missing. In this study, we used remote sensing data to reveal detailed glacier surge behavior, focusing on the recent surge at Walsh Glacier, which was reported to have surged once in the 1960s. Glacial velocities were derived using a cross-correlation algorithm, and changes in the medial moraines were interpreted based on Landsat images. The digital elevation model (DEM) difference method was applied to Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEMs to evaluate the surface elevation of the glacier. The results showed that the surge initiated near the conjunction of the eastern and northern branches, and then quickly spread downward. The surge period was almost three years, with an active phase of less than two years. The advancing speed of the surge front was much large than the maximum ice velocity of ≈14 m/d observed during the active phase. Summer speed-ups and a winter speed-up in ice velocity were observed from velocity data, with the speed-ups being more obvious during the active phase. Changes in the glacier velocity and the medial moraines suggested that the eastern branch was more affected by the surge. The DEM differencing results showed that the receiving zone thickened up to about 140 m, and the upstream reservoir zone became thinner. These surge behaviors, as characterized by remote sensing data, gave us more detailed insights into the surge dynamics of Walsh Glacier.

Phenology and potential reproduction of turi (Sesbania grandiflora) at Cibinong, Bogor, Indonesia

Abstract. Syamsuwida D, Aminah A. 2020. Phenology and potential reproduction of turi (Sesbania grandiflora) at Cibinong, Bogor, Indonesia. Nusantara Bioscience 12: 13-20. Turi (Sesbania grandiflora (L.) Pers.) is one of a prospectus energy woody species to be developed in establishing renewable energy base forest plantation. The development of this species cannot be separated from the basic information of its reproductive biology. The study was aimed to evaluate flowering phenology and reproductive potency of S. grandiflora so that information could be elaborated to estimate the fruit production potential produced. The research method was carried out by direct observation of samples of flowering trees. Data were analyzed descriptively. The number of tree samples observed for flower and fruit development and reproductive success of 10 trees, from each tree were observed three flowering branches distinguished from the west and east branches. The results showed that S. grandiflora did not experience generative bud dormancy so that flower initiation was thought to occur throughout the year and could flower and bear fruit throughout the year. S. grandiflora at the observation location has a flowering-fruiting development cycle of about 3-4 months which begins with the emergence of generative bud at the time of the observation in April and developed into flower shoot in the same month. Blooming flower (anthesis) in May, develop into young fruit in June. Mature fruits can be harvested in June-July. The reproductive potency of S. grandiflora was low with a value of fruit set (fruit/flower ratio) at the eastern and western branches were 19% ± 0.07 and 17%±0.06 and seed set (seed/ovule ratio) of 87% ± 0.12 and 83% ± 0.16, respectively. Reproductive success was 18% ± 0.07 for the eastern branches and 17% ± 0.05 for the western branches. Most reproductive variables of S. grandiflora did not show a significant difference between the eastern and western branches (P>0.05), except for fruit number (P<0.05).

Восточные ветви российской диаспоры – 2020

The article provides an overview of the reports of the 11th Annual Scientific Inter-Institutional Conference "Eastern Branches of the Russian Diaspora", which was held in absentia on May 21, 2020. In the conference organized by the Center for Southeast Asia, Australia and Oceania of the IOS RAS, was attended by scientists, as well as applicants and graduate students from various institutes not only from Moscow, but also from other cities of Russia.

Climatología de las granizadas en Colombia

A partir de datos históricos de registros de periódicos nacionales, regionales, de archivos y bases de datos especializadas, se identificaron 468 granizadas en diferentes regiones del país. Se analizó el comportamiento de diferentes variables (índices de inestabilidad, viento, humedad relativa, la altura de la isoterma de 0 °C y precipitación) de simulaciones horarias generadas por el modelo Weather & Research Forecasting (WRF) en cada evento de granizada, estableciendo umbrales en los que tales granizadas ocurrieron para tener un elemento de estimación de probabilidad de granizada. Se ajustaron los datos por orografía, pendiente, altitud a nivel del mar y la dirección del viento, y se generaron series de probables granizadas para una grilla de 10x10 km, las cuales se validaron frente a las registradas. Con estas series se establecieron los patrones espaciales y el ciclo anual de las granizadas para construir la climatología de este fenómeno en Colombia. Se obtuvo que las zonas con mayor probabilidad de granizadas se encuentran en zonas montañosas (cordillera Occidental, cordillera Central y cordillera Oriental) y en la Sierra Nevada de Santa Marta, especialmente en los departamentos de Antioquia, Caldas, Quindío, Valle del Cauca, Cauca, Norte de Santander, Santander, Cundinamarca y Boyacá.Ideas destacadas: artículo de investigación que aborda cómo las granizadas en diferentes regiones de Colombia generan diversos impactos negativos a cultivos, edificaciones, infraestructura vial y redes de comunicaciones. Por la necesidad de información sobre estos eventos meteorológicos extremos, se elaboró una climatología de las granizadas para Colombia basada en el análisis de datos observados y modelados.

The Intra-Pontide ophiolites in Northern Turkey revisited: From birth to death of a Neotethyan oceanic domain

The Anatolian peninsula is a key location to study the central portion of the Neotethys Ocean(s) and to understand how its western and eastern branches were connected. One of the lesser known branches of the Mesozoic ocean(s) is preserved in the northern ophiolite suture zone exposed in Turkey, namely, the Intra-Pontide suture zone. It is located between the Sakarya terrane and the Eurasian margin (i.e., Istanbul-Zonguldak terrane) and consists of several metamorphic and non-metamorphic units containing ophiolites produced in supra-subduction settings from the Late Triassic to the Early Cretaceous. Ophiolites preserved in the metamorphic units recorded pervasive deformations and peak metamorphic conditions ranging from blueschist to eclogite facies. In the non-metamorphic units, the complete oceanic crust sequence is preserved in tectonic units or as olistoliths in sedimentary mélanges. Geochemical, structural, metamorphic and geochronological investigations performed on ophiolite-bearing units allowed the formulation of a new geodynamic model of the entire “life” of the Intra-Pontide oceanic basin(s). The reconstruction starts with the opening of the Intra-Pontide oceanic basins during the Late Triassic between the Sakarya and Istanbul-Zonguldak continental microplates and ends with its closure caused by two different subductions events that occurred during the upper Early Jurassic and Middle Jurassic. The continental collision between the Sakarya continental microplate and the Eurasian margin developed from the upper Early Cretaceous to the Palaeocene. The presented reconstruction is an alternative model to explain the complex and articulate geodynamic evolution that characterizes the southern margin of Eurasia during the Mesozoic era.

High-resolution 3D crustal S-wave velocity structure of the Middle-Lower Yangtze River Metallogenic Belt and implications for its deep geodynamic setting

The Middle-Lower Yangtze River Metallogenic Belt (MLYMB) is an important mineral resource region in China. High-resolution crustal models can provide crucial constraints to understand the ore-forming processes and geodynamic setting in this region. Using ambient seismic noise from 107 permanent and 82 portable stations in the MLYMB and the adjacent area, we present a new high-resolution 3D S-wave velocity model of this region. We first extract 5–50 s Rayleigh wave phase velocity dispersion data by calculating ambient noise cross-correlation functions (CFs) and then use the surface wave direct inversion method to invert the mixed path travel times for the 3D S-wave velocity structure. Checkerboard tests show that the horizontal resolution of the 3D S-wave velocity model is approximately 0.5°–1.0° and that the vertical resolution decreases with increasing noise and depth. Our high-resolution 3D S-wave velocity model reveals: (1) A V-shaped high-velocity zone (HVZ) is located in the lower crust and the uppermost mantle in the study region. The western branch of the HVZ passes through the Jianghan Basin, the Qinling-Dabie orogenic belt and the Nanxiang Basin. The eastern branch, which almost completely covers the main body of the MLYMB, is located near the Tanlu Fault. The low-velocity anomalies between the western and eastern branches are located in the area of the Qinling-Dabie orogenic belt. (2) High-velocity uplifts (HVUs) are common in the crust of the MLYMB, especially in the areas near the Tanlu Fault, the Changjiang Fault and the Yangxin-Changzhou Fault. The intensities of the HVUs gradually weaken from west to east. The V-shaped HVZ in the lower crust and uppermost mantle and the HVUs in the middle and lower crust likely represent cooled mantle intrusive rocks. During the Yanshanian period, fault systems formed in the MLYMB due to the convergence between the South China Plate and the North China Plate, the multiple-direction drifting of the Paleo-Pacific Plate and its subduction beneath the Eurasian Plate. The dehydration of the cold oceanic crust led to partial melting in the upper mantle. Temperature differences caused strong convection of the upper mantle material that underplated the lower crust and rose to near the surface along the deep fault systems. After mixing with the crustal materials, mineralization processes, such as assimilation and fractional crystallization, occurred in the MLYMB.

Characteristics of Tidal Discharge and Phase Difference at a Tidal Channel Junction Investigated Using the Fluvial Acoustic Tomography System

This study investigates the tidal discharge division and phase difference at branches connected to a channel junction. The tidal discharge at three branches (eastern, western, and northern branches) was continuously collected using the fluvial acoustic tomography system (FATS). The discharge asymmetry index was used to quantify the flow division between two seaward branches (eastern and western branches). The cross-wavelet method was applied to calculate the phase difference between the tidal discharge and water level. The discharge asymmetry index shows that the inequality of flow division is obviously prominent during the spring tide duration, where the eastern branch has the capability to deliver greater amounts of subtidal discharge, approximately 55–63%, compared with the western branch. However, the equality of flow division between the eastern and western channels can be observed clearly during the neap tide period. The wavelet analysis shows that the phase difference at the western branch is higher than at the eastern branch, because the geometry of the western branch is more convergent than that of the eastern branch. Accordingly, the amplitude of the tidal wave at the western branch is more magnified compared with that at the eastern branch. Moreover, the phase difference at the northern branch is greater than at the two seaward branches, implying that the phase difference is slightly increased after passing through the junction into the northern branch.

Summer Mesozooplankton Biomass Distribution in the West Spitsbergen Current (2001–2014)

Marine ecosystems in Arctic regions are expected to undergo large changes, driven by sea ice retreat and increasing influence of warmer and saline waters. We examined changes in the hydrography and mesozooplankton from a 14-year long time series in the West Spitsbergen Current during the summer period. The aim was to provide a contemporary description of spatial and temporal variations in the zooplankton community inhabiting the surface layer (0-60 m), over an area extending 6 latitudinal degrees and nearly 20 longitudinal degrees. A total of 296 samples were partitioned into three groups, based on salinity and temperature signatures, representing the western, eastern and coastal branches of the West Spitsbergen Current. Only the waters of the eastern branch, influenced by north-flowing Atlantic water, showed significant temporal trend in salinity, whereas no significant time trend was found for temperature in any of the three branches in the surface layer studied. Zooplankton biomass generally decreased from south to north in the western and eastern branches, suggesting poleward net loss of zooplankton, whereas relatively constant biomass in the coastal branch was likely sustained by higher production at the shelf break. The biomass remained constant over the study period for all three branches. Four species (Calanus finmarchicus, C. glacialis, C. hyperboreus, and Eukrohnia hamata) contributed almost 90% of the mesozooplankton biomass in all branches, with C. hyperboreus and C. glacialis being relatively important in the western and coastal branches, respectively. C. finmarchicus became increasingly important over time in the eastern branch, almost doubling its biomass and contributing more than 50% of the total biomass at the end of the study period. This increase was not associated with a general tendency towards more mature stages. C. finmarchicus copepodid CV and adults constituted >80 % of this species biomass in the western and eastern branches. In general, the relatively long time series, for Arctic standards, could not confirm expected drastic trends, but showed subtle changes over time overlaid by considerable interannual variability. Given the large inherent variability in zooplankton data, time series extending more than 14 years are needed for assessing trends in the West Spitsbergen Current.

Indian Monsoonal Variations During the Past 80 Kyr Recorded in NGHP‐02 Hole 19B, Western Bay of Bengal: Implications From Chemical and Mineral Properties

AbstractDetailed reconstruction of Indian summer monsoons is necessary to better understand the late Quaternary climate history of the Bay of Bengal and Indian peninsula. We established a chronostratigraphy for a sediment core from Hole 19B in the western Bay of Bengal, extending to approximately 80 kyr BP and examined major and trace element compositions and clay mineral components of the sediments. Higher δ18O values, lower TiO2 contents, and weaker weathering in the sediment source area during marine isotope stages (MIS) 2 and 4 compared to MIS 1, 3, and 5 are explained by increased Indian summer monsoonal precipitation and river discharge around the western Bay of Bengal. Clay mineral and chemical components indicate a felsic sediment source, suggesting the Precambrian gneissic complex of the eastern Indian peninsula as the dominant sediment source at this site since 80 kyr. Trace element ratios (Cr/Th, Th/Sc, Th/Co, La/Cr, and Eu/Eu*) indicate increased sediment contributions from mafic rocks during MIS 2 and 4. We interpret these results as reflecting the changing influences of the eastern and western branches of the Indian summer monsoon and a greater decrease in rainfall in the eastern and northeastern parts of the Indian peninsula than in the western part during MIS 2 and 4.

ПОСЛЕПОЖАРНАЯ СУКЦЕССИЯ В ЛЕСОБОЛОТНЫХ КОМПЛЕКСАХ

The article is devoted to the study of post-pyrogenic successional changes of plant matter in the forest-mire complexes in the eastern branches of the Great Vasyugan Mire. The aim of the study was to obtain and analyze the data characterizing the post-fire dynamics of plant matter for an objective environmental assessment of the current state of forest-mire landscapes. The objects of the study were ryam communities situated between the Iksa and Bakchar rivers of the Tomsk Region and characterized by varying degrees of post-fire disturbance, which were exposed to catastrophic pyrogenic impact. Studies on the dynamics of vegetation community and plant matter at sites with varying degree of peat fire intensity were carried out for ten years. At sites with a low fire intensity, the degree of disturbance of vegetation cover was 40 – 50 %. At a mire which was exposed to the pyrogenic influence of a moderate degree, small islands with individual specimens of shrubs (Ericaceae) and small islands of Sphagnum mosses have been preserved. Mire ecosystems that have undergone a fire of the greatest intensity, are represented by burned to mineral soil depressions with islands of burnt peat. After ten years of succession in the most disturbed mire ecosystems, the percentage ratio of the above-ground phytomass to that in control sites varied within 10 % of the control phytomass. The amount of live below-ground plant matter increased very slowly, and by the tenth year of recovery, it was only 3.5 % of the stock of control underground living phytomass. The living plant matter stock at sites with moderate fire disturbance was 50 % of the control stock both in above-ground and below-ground areas. At sites of low fire intensity by the tenth year of succession, the amount of live plant matter ranged from 70–80 % of the above-ground control phytomass, and as for below-ground phytomass, the amount of living roots and rhizomes exceeded the control ones by 11 %.

Britain, China and Colonial Australia, by Benjamin Mountford

Writing about Britain’s imperial involvement with China has a long history. Over the past decade and more, Australian historians have become increasingly interested in Australia’s relationship with China, and, as Australia grapples with the challenges of a rising China, the generally forgotten fact that Australia has been involved with China virtually from the first establishment of European settlement in 1788 is gaining greater attention. Histories of Australia’s relationship with the Mother Country, throughout the imperial era and beyond, also abound. Benjamin Mountford, in this tightly packed and well-argued monograph, offers us a different perspective, and in doing so breaks what (at least to this reviewer) is new ground, triangulating the British, Chinese and Australian stories. He demonstrates how this three-way relationship impacted on each country and its interests, with significant implications for each, including on broader thinking about the meaning and future of the British Empire, not to mention the growing divergence, within this general imperial identity, of Australian and British (using the word narrowly and anachronistically) ideas about Australia’s role and identity. The book anchors this story in a series of regional, transnational and global developments between the 1780s and the early twentieth century. In his own words, ‘By reintegrating the histories of the Far Eastern and Australian branches of the British Empire, it brings to the fore a series of bilateral and triangular relationships linking Britain, colonial Australia, and China and considers the wider imperial significance of those engagements.’

CОТРУДНИЧЕСТВО ТИХООКЕАНСКОЙ РОССИИ И СТРАН АСЕАН: ЭКОНОМИЧЕСКИЕ АСПЕКТЫ

The Far East holds key positions in the modern Oriental track of the Russian policy. This region is prioritized as a leading actor of Russian expansion and economic integration into the Asia Pacific Region. However, at present the Far East can’t cope with the assigned objective which requires reliable and efficient ties with all the major actors of the Asia Pacific involving ASEAN countries as well. There is still no meaningful progress in the trade and economic relations of the Pacific Russia and ASEAN, and some figures altogether show a steady decline. The analysis of goods’ turnover between the Russian Far East and ASEAN countries (2006-2016) shows a considerable decrease in the volume of trade over the last 5 years. The stake of the Far Eastern Federal District in the total Russian trade with the Southeast Asia states has been reduced accordingly. In 2013-2016 the Far East had the smallest share among all federal districts in the volume of trade with ASEAN participants – just 2–3%. The negative trend is registered amid rather benign figures of the Russian overall goods turnover with ASEAN. There has been some progress in the investment ties of the Pacific Russia and ASEAN countries. Although there are very few investment projects which the Southeast Asia investors have implemented on the Far Eastern territory by now, their interest in the Pacific Russia remains. The cooperation in the investment sphere can be improved provided that the barriers preventing trade and economic ties are eliminated. Such barriers comprise narrowness of the local markets, poorly developed infrastructure, uncompetitive workforce market, often incompetent and indifferent administration that is not interested in developing relations with ASEAN. The fact that the range of the effective interaction of the Pacific Russia and ASEAN is pretty narrow creates considerable challenges. The most prospective are fuel-related (mainly hydrocarbon production) and defense-related industries (aircraft and shipbuilding). In the meantime, there are good chances for extending cooperation with ASEAN countries through establishing new industries based on the traditional Far Eastern branches, namely deep processing of row hydrocarbons as well as modernization of the manufacturing facilities on this territory.&nbsp

Roman Catholicism and Eastern Orthodoxy: Can linguistic and semiotic analysis clarify their contrasts?

The western and eastern branches of Christianity, broadly speaking Roman Catholicism (RC) and Eastern Orthodoxy (EO), have been formally separate for almost a millennium. Yet they share the fundamental dogmas laid down by the first ecumenical councils. History and politics are entwined in the disputes since the Great Schism of 1054, but even earlier there was controversy over basic dogmatic questions and other doctrinal matters. Some, like using leavened or unleavened bread for Consecration, are now considered “matters of custom,” not requiring argument. Other matters are said to block reunification. One of these is Purgatory, for which EO does not even have a term, making a direct comparison difficult. We begin our analysis with the RC teachings on Purgatory, its locus, characteristics, and functions, and provide a simple relational network that shows Purgatory in relation to the afterlife, in particular to Heaven and Hell. With EO we begin with the teachings about life after death and provide a first approximation of Heaven and Hell and their relation to Paradise and Hades, both in characteristics and functions. Again, a simple relational network is enlightening. A surface comparison between the two networks distinguishes between those beliefs about the afterlife that are shared between RC and EO and those parts which house differences. It is these differences that must be subject to careful semiotic analysis to discover whether they are etic and possibly serious but not grounds for mutual excommunication or emic and a true barrier to reunification. We leave the possibly lengthy semiotic analysis for a subsequent study.

Receiver Function Imaging of Mantle Transition Zone Discontinuities Beneath the Tanzania Craton and Adjacent Segments of the East African Rift System

AbstractThe mantle transition zone (MTZ) discontinuities beneath the Tanzania Craton and the Eastern and Western Branches of the East African Rift System are imaged by stacking over 7,100 receiver functions. The mean thickness of the MTZ beneath the Western Branch and Tanzania Craton is about 252 km, which is comparable to the global average and is inconsistent with the existence of present‐day thermal upwelling originating from the lower mantle. In contrast, beneath the Eastern Branch, an up to 30 km thinning of the MTZ is observed and is attributable to upwelling of higher temperature materials from either the upper MTZ or the lower mantle. The observations are in agreement with the hypothesis that rifting in Africa is primarily driven by gradients of gravitational potential energy and lateral variations of basal traction force along zones of significant changes of lithospheric thickness such as the edges of the Tanzania Craton.

Reconstruction of Late Pleistocene Paleoenvironments Using Bulk Geochemistry of Paleosols from the Lake Victoria Region

The impact of changing environments on the evolution and dispersal of Homo sapiens is highly debated, but few data are available from equatorial Africa. Lake Victoria is the largest freshwater lake in the tropics and is currently a biogeographic barrier between the eastern and western branches of the East African Rift. The lake has previously desiccated at ~17 ka and again at ~15 ka, but little is known from this region prior to the Last Glacial Maximum. The Pleistocene terrestrial deposits on the northeast coast of Lake Victoria (94 to 36 ka) are ideal for paleoenvironmental reconstructions where volcaniclastic deposits (tuffs), fluvial deposits, tufa, and paleosols are exposed, which can be used to reconstruct Critical Zones (CZ) of the past (paleo-CZs). The paleo-CZ is a holistic concept that reconstructs the entire landscape using geologic records of the atmosphere, hydrosphere, lithosphere, biosphere, and pedosphere (the focus of this study). New paleosol-based mean annual precipitation (MAP) proxies from Karungu, Rusinga Island, and Mfangano Island indicate an average MAP of 750108 mm yr-1 (CALMAG), 800182 mm yr-1 (CIA-K), and 1010228 mm yr-1 (PPM1.0) with no statistical difference throughout the 11 m thick sequence. This corresponds to between 54 and 72% of modern precipitation. Tephras bracketing these paleosols have been correlated across seven sites, and sample a regional paleo-CZ across a ~55 km transect along the eastern shoreline of the modern lake. Given the sensitivity of Lake Victoria to precipitation, it is likely that the lake was significantly smaller than modern between 94 ka and 36 ka. This would have removed a major barrier for the movement of fauna (including early modern humans) and provided a dispersal corridor across the equator and between the rifts. It is also consistent with the associated fossil faunal assemblage indicative of semi-arid grasslands. During the Late Pleistocene, the combined geologic and paleontological evidence suggests a seasonally dry, open grassland environment for the Lake Victoria region that is significantly drier than today, which may have facilitated human and faunal dispersals across equatorial East Africa.

Geothermal asymmetry in transform faults of the equatorial Atlantic Ocean

Statistical analysis of heat flow values measured in transform faults of the equatorial part of the Atlantic Ocean has been performed. Owing to the calculation using the Cramer–Welch criterion, it was established that not only is there an already known statistically significant difference between heat flow in active and passive zones of transform faults, but there is also an asymmetry in heat flow distribution between the western and eastern branches of passive zones of the fault zones. The western zones in all structures studied are characterized by higher average heat flow values. Two models are proposed to explain this phenomenon.

Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS)

The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics.Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE–SW striking transfer fault parallel to and along strike of the onshore Karoo (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip.To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10–100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalization due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings.