Main Geological Units Research Articles

Geoheritage of the Sila National Park and surrounding areas (Northern Calabria, Italy)

ABSTRACT This paper introduces a geological map of the Sila mountain block (Northern Calabria, Italy), realized as a tool to promote knowledge of this geological landscape uniqueness and to develop effective geoheritage management and enhancement strategies, also from a geotouristic and geoeducational perspective. The Sila block is defined as a plateau whose morphology is deeply connected to its lithological characteristics and tectonic evolution that combined with exogenous processes over time has conditioned the landscape. The 1:60,000 scale map provides an overall scheme of the main geological units and tectonic elements constituting the study area, as a synthesis of thematic cartography existing in the literature coupled to targeted investigations and field surveys. It also displays the main geosites and geosite systems, identified with the purpose of communicating geoheritage processes/products, which favour an understanding of the surrounding environment, and for tourist purposes.

An integrated geological characterization of the Mid‐Pleistocene to Holocene geology of the Sørlige Nordsjø II offshore wind site, southern North Sea

Subsurface deposits in recently glaciated marine areas are highly heterogeneous, representing a range of glacial and postglacial environments and processes including glacitectonism, overconsolidation, fluvial and lacustrine deposition, and transgression. These heterogeneities are often linked to variations in engineering properties, with important implications for the design and installation of offshore wind infrastructure. In this study we present an integrated geological characterization of the Sørlige Nordsjø II offshore wind site, located in waters of 50–70 m depth along the southern border of the Norwegian North Sea, focusing on the evolution of the area's depositional setting during the late Quaternary period and its implications for offshore wind development. We integrate interpretations from a marine geological data set acquired in 2022 with legacy 3D seismic data and a review of the current understanding of the southern North Sea's complex glacial history. A preliminary ground model and accompanying risk map for the site is presented with five main geological units: (i) homogeneous and layered marine sands covering most of the site, with patchy distribution and coarser‐grained deposits in the east; (ii) buried, layered channel deposits containing organic material and possible associated shallow gas; (iii) buried, stiff glacilacustrine clay deposits; (iv) a buried, layered, glacitectonized unit incised by tunnel valleys, with a sandy marine infill; and (v) mounded tills and glacitectonized deposits containing boulders, exposed to shallowly buried in the east. Salt diapirism and gas migration were also found to be important potential geohazards at the site. Three‐dimensional seismic attribute maps were found to be a powerful aid to understanding the distribution and genesis of seismic facies identified on 2D high‐resolution sub‐bottom profiles. This type of data integration is an under‐utilized methodology for generating detailed preliminary ground models, which can inform more cost‐effective site survey and early foundation concept planning at geologically complex offshore wind sites.

Messinian canyons morphology of the Rhône and Ardèche rivers (south-east France): new insights from seismic profiles

Twelve available two-way time high-resolution seismic reflection profiles located in the central part of the middle Rhône valley are interpreted. In addition, one of the profiles was reprocessed to determine the P-wave velocities of the main geological units and to convert this profile into a depth cross section. The Lower and Upper Cretaceous units are clearly identifiable on all the profiles, along with the Messinian Erosion Surface (MES) carved out during the Messinian Salinity Crisis (MSC) by the paleo-Rhône and its western tributaries, the Ardèche and Cèze paleo-canyons. The Plio-Quaternary fill of these paleo-canyons shows at least 4 main units with an overall transgression. The combination of geological data from geological maps, geological field surveys and borehole data made it possible to model the MES in 3D at the scale of the region, and to produce depth/elevation model. From a geological point of view, the interpretation of the seismic profiles enabled us to reconstruct the stages in the sub-aquatic filling of the Messinian-Pliocene aggradation of the paleo-river. Several Mass Transport Deposits (MTDs) were identified both during the drop and during the rise in the Mediterranean Sea level. From a geomorphological point of view, this study provides new insights in the route and longitudinal profile of paleo-rivers and, in particular, it deepens the profile of the Paleo-Rhône at the latitude of the Tricastin region (up to −700 m b.s.l.) and significantly modifies the course and depth of the Ardèche proposed in previous studies. The N-Ardèche river, known to develop a karstic system during the MSC, is connected to a deep canyon, most likely through a karstic pocket valley, as suggested by the very steep longitudinal profile of the MES. Finally, from a structural point of view, our interpretation of the seismic profiles shows a broad ENE-trending anticline structure associated with a normal fault which apparently did not affect the Mio-Pliocene fill. In the southern part of the area, near the Uchaux anticline, the imaged structures suggest the presence of a recent (syn- to post-Pliocene) fault propagation fold. In addition to all the new information on the geology, morphology and methods of excavation and filling of the Messinian paleo-canyon, the proposed topographic model of the paleo-canyon is crucial for modelling seismic movement in the context of a basin with a complex geometry and, in particular, for the numerical assessment of site effects in a context of low seismicity.

PETROPHYSICAL CHARACTERIZATION BY 3D MODEL OF ZONES 4 AND 3 OF THE TURONIAN RESERVOIR OF THE KINKASI FIELD IN THE D.R. CONGO COASTAL BASIN

Kinkasi is one of the oil fields of the DR Congo Coastal Basin. It is essentially formed of two main geological units (A and B) in the Turonian, each composed of a succession of different horizons (Zones) according to the type of siltstone. These two main units contain 6 Zones. Unit A consists of Z6 and Z5 of Coniacian age, while the rest of the reservoir (Z4, Z3, Z2 and Z1) is of Turonian age which is characteristic of Unit B. Indeed, the present study is devoted to the petrophysical characterization of the two zones Z4 and Z3 of the unit B in order to locate the interesting zones to develop this oil field. For this fire, we used the data of 11 wells having the geographical coordinates, the porosity, the permeability as well as the water saturation. The processing and interpretation of these data using the Kriging method allowed us to deduce from the scale of appreciation the areas that contain high values of porosity, permeability and water saturation. Porosity in zones 4 and 3 varies from good to very good, saturation 3 to 59% for zone 4 and 32 to 53% for zone 3 as well as permeability from poor to low for both zones. The combined interpretation of these three properties allowed us to find an interesting zone located towards the east of zones 4 and 3 with high porosity and permeability values and low water saturation values.

Геоэкологические проблемы излива термальных вод скважины 9-Т Каргалинская

Based on stock materials on the Kargalinskoye thermal water deposit and field studies in the area of the geothermal well 9-T Kargalinskaya (Chechen Republic), mapping of the area of impact of the outflowing waters of this well was carried out and a comprehensive geoecological assessment of their impact on the landscape and land use was given. At the mesolevel, an assessment was made of the integration of the well into the regional landscape structure (a profile was built on which the main geological and geographical boundaries and units of physical and geographical differentiation are indicated: types and groups of landscapes). At a large-scale level, a comprehensive mapping of landscapes and land use was carried out on a scale of 1:10 000. In the field, characteristics were given to natural complexes of the rank of tracts and facies (with a description of vegetation, soils and actual use), water temperatures were measured, and water samples were taken for chemical analysis from a well and a groundwater basin used for drip irrigation of agricultural land. Geobotanical studies of the flora were carried out with the identification of the main phytocenoses, at some points of which transects (1 m2) were laid, dominant associations, the number of dominants, and the total projective cover were determined.

Obtaining the hydraulic and thermal properties of the main hydrostratigraphic units surrounding a standing column well using a thermal response test

In general, classical interpretation of pumping tests assume homogeneous hydraulic properties and cannot characterize aquifer heterogeneity in the form of a profile. In this work, a thermal response test, which is routinely performed prior to the design of ground source heat pump systems, is conducted on an open-walled borehole to identify the hydraulic conductivity profile and thermal properties of the main geological units. Parameter identification and uncertainty quantification are performed in a Bayesian framework and rely on a neural network and a spectral method to speed up the solution of the direct problem. The analysis of a data set from field testing showed that the use of temperature measurements alone provided a hydraulic conductivity profile, with an average value close to that provided by a conventional pumping test. For the specific conditions observed on the field, it was also possible to precisely identify the thermal properties, as was the case for the main geologic unit, but not for the thin geologic units whose distributions were similar to the priors used for inference. This indicates that in some geologic settings, a thermal response test could fail to provide the thermal properties of some units. The approach, however, paves the way for new characterization techniques.

Geochemical mapping by stream sediments of the NW portion of Quadrilátero Ferrífero, Brazil: Application of the exploratory data analysis (EDA) and a proposal for generation of new gold targets in Pitangui gold district

Quadrilátero Ferrífero (QF) is a worldwide known metallogenetic province and has in its NW portion the Pitangui greenstone belt, one of the new frontiers for gold exploration in that region, presenting important gold deposits, such as Turmalina and São Sebastião. Among several actions of the geological and mineral resources projects carried out by Geological Survey of Brazil (SGB/CPRM) in the QF region, a high-density geochemical survey (1 sample/4 km2) by stream sediments was accomplished in its NW portion to better understand the behavior and distribution of chemical elements along the main geological units, especially those related to gold mineralization (Au, As, Sb, Bi, etc.). The exploratory data analysis (EDA), regarding uni-, bi-, and multivariate analyses, point to an important chemical control of the stream sediments by the geological units and help to describe some lithological features and to understand the behavior and distribution of hydrothermal processes and gold mineralization. This procedure defined the main geochemical associations, including the association As, Sb, Cu and Bi linked to Ni, Cr and Co, interpreted as gold mineralization hosted in the metavolcanosedimentary lithotypes. The staged factor analysis (SFA) considering compositional data (CoDa), logistic function, and fractal model approaches provided the generation of the geochemical mineralization probability index (GMPI), which produce a GMPI map for gold mineralization. The calculations did not take into account the gold concentrations but only the pathfinder elements and the model validation by the prediction-area plot, confirm the high performance of this approach. The gold mineralization map, in addiction to satisfactorily predicting the location of most known gold occurrences, was able to indicate new potential targets for prospecting new gold deposits.

Geological, compositional and crystallinity analysis of the Melkart impact crater, Ganymede

In this work, we analyze the ∼103 km-diameter Melkart impact crater on the surface of Ganymede, which is a ∼ 103 km impact crater located at the boundary between the two main geological units of the satellite, the light and dark terrains. Such crater is covered both by Galileo SSI and NIMS datasets allowing inference of any possible correlation between its geology and composition, as well as to investigate the evolution of the substrate units. We provide a geomorphological characterization of the crater by creating a high-resolution geological map, investigating the DTM and performing a strain analysis to infer its deformation. We find that the Melkart dome underwent strike-slip deformation with right-lateral kinematics. Moreover, this crater is a low strain end member with subtle deformation, which has been formed in an area of gradual transition between light and dark terrains. The results obtained through band depth and crystallinity maps of the study area do not reflect the evolutionary history of the crater, instead, they are representative of the different geological terrains affecting the subsurface of Melkart. Such result implies that the possible compositional differences between the crater's units might have been obliterated through time. Our analysis supports the interpretation that the material constituting the substrate of the crater might be heterogeneous suggesting that: (i) the transition between the two geological units might be gradual or ii) the dark material located over the study area only represents a thin layer draping the icy crust.

Geochemical features and seismic imaging of the tectonic zone between the Tibetan Plateau and Ordos Block, central northern China

The Tibetan Plateau is growing by both vertical uplift and horizontal extension. It is a continuing debate how the Tibetan Plateau interacts with its surrounding plates and blocks. Due to intense tectonic activity, which produced catastrophic earthquakes, the tectonic zone between the northeast margin of the horizontal extending Tibetan Plateau and the stable Ordos Block has garnered considerable interest. This study investigated the spatial distribution of gas geochemical anomalies (e.g., high flux of CO2 in correspondence of the main faults) at regional scale together with the seismic tomography in correspondence of this tectonic zone with the aim to figure out the domain of convergent boundary between the Ordos block and Tibetan plateau, and trace the tectonic discontinuities which are able to transfer fluids through the crustal layers between the two main geological units. From northwest to southeast, obvious difference of spatial distributions of geochemical and geophysical features in the tectonic zone between the northeast margin of the Tibetan Plateau and the Ordos Block is inferred. The northeast area (Zone A) is dominated by thrust and strike-slip faults with clear velocity boundary underneath, where low crack density (ε), saturation rate (ξ) and Poisson’ ratio (σ) in the middle-lower crust coincided with the low values of heat flow and CO2 emissions, tectonic compression and regional locked-fault can be inducements. The southeast area (Zone C) is dominated by extensional tectonics with roughly E-W fast-velocity direction (FVD) of P-wave azimuthal anisotropy, where high permeability and porosity can be deduced from crustal high ε, ξ and relatively high σ anomalies, resulting in high heat flow, CO2 concentrations and fluxes at the surface, and predominantly crustal-derived gases. The intermediate area (Zone B) also dominated by thrust and strike-slip faults is an extraordinary zone, where intensely locked-fault were clearly revealed, while the predominant anisotropic FVDs in the middle crust changed obviously, more contribution of shallow gas component was detected, and CO2 flux, heat flow, and regional ε, ξ, and σ in the upper crust were higher, compared with those in Zone A, which indicated the regional crushing fragmentation underneath Zone B. The adopted multidisciplinary approach demonstrated that Zone B is the convergent boundary between the Tibetan Plateau and the Ordos Block.

3D thermal model of Sicily (Southern Italy) and perspectives for new exploration campaigns for geothermal resources

Quantification of the subsurface geothermal potential primarily relies on the assessment of the thermal and mechanical configuration of the lithosphere. Such investigations require a detailed knowledge of the geological and tectonic forcing on the regional thermal, stress and hydraulic regimes and their counter feedback mechanisms. This approach becomes even more relevant in complex and active tectonic settings. In this regard, the Sicily region, which is located in the Central-Western Mediterranean, is an exceptional case study due to its almost unexplored geothermal potential hosted in a complex geodynamic setting. The present-day geological configuration resulted from the collision between the African and European plates, which led to the coexistence of compressional phases, beginning with the Oligocene-Miocene clockwise rotation of Corsica-Sardinia and alternated extensional phases in the Tyrrhenian basin due to the southward progression of the Sicilian-Maghrebian chain towards areas of the internal foreland (Hyblean domain). In this study, we attempt a reconstruction of the present-day lithospheric state of Sicily to quantify its thermal regime at shallow and intermediate depths. We have carried out a 3D lithospheric-scale gravity modelling in order to define the main geological units and their lithology-dependent rock properties, then integrated into a 3D geological model consistent with available borehole and seismic datasets. We have used the constructed geological model with its lithology-dependent density, thermal conductivity, and radiogenic heat production to derive the present-day conductive thermal field as a whole and for individual tectonic or geological units, thereby considering different boundary conditions. We have finally validated results of the modelling against a shallow temperature dataset derived from hydrocarbon explorations. Our results indicate that the thermal field at depths shallower than 10 km is largely controlled by variability in sedimentary thickness in the foreland and the orogen, while deeper temperatures are primarily controlled by the distribution of the heat transferred from the mantle together with the radiogenic contribution of the shallow crystalline basement rocks and deeper crustal layers. The thermal modelling portrays a rather heterogenous Moho heat flow, locally higher than 80 mW/m2, revealing a particular geodynamic setting with specific areas characterized by high-to-medium enthalpy geothermal potential. As such, our modelling provides new perspectives for the exploration of geothermal resources in Sicily and helps to better constrain the thermal structure of the complex Sicilian collisional setting.

English

2D electrical resistivity imaging technique has been used to investigate the nature and dimensions of the fracture prone zones in Isu-Awaa, Enugu State, Nigeria. The study area lies within Latitude 06° 14I 0II N to 06° 17I 0II N and Longitudes 007° 23I 0II E to 007° 28I 0II E, with an area extent of about 51 Km2. The area is underlain by three main geological units (Enugu Shale, Owelli Sandstone and Mamu Formation). The study area is topographically undulating with high ridges surrounding the area. 2D electrical resistivity data was acquired with Wenner configuration, employing the roll-along technique to image the subsurface. A total of four (4) number 2D electrical resistivity imaging traverses were carried out. Data was processed and interpreted using RES2DINV. Measured and calculated apparent resistivity pseudo sections were convolved to generate the inverse model resistivity section, which was the diagnostic interpretative model used. Discontinuities in the layering are possible fracture zones. Major discontinuities were observed at distances of 48 and 87, 52.5, 106, 8.0 and 26 m at traverses A, B, C and D respectively. Fracture trend azimuth rose diagram, shows pre-dominant trend to the SE direction with minority to the SW and NW, and relicts to the NE directions. This conforms to the regional lineaments map of Nigeria. The use of 2D electrical resistivity imaging tool has proved useful in the mapping of fracture prone zones in the study area. Key words: Electrical resistivity imaging, fracture lineaments, Rose diagram.

Long‐Term Lithospheric Strength and Upper‐Plate Seismicity in the Southern Central Andes, 29°–39°S

AbstractWe examined the relationship between the mechanical strength of the lithosphere and the distribution of seismicity within the overriding continental plate of the southern Central Andes (SCA, 29°–39°S), where the oceanic Nazca Plate changes its subduction angle between 33°S and 35°S, from subhorizontal in the north (<5°) to steep in the south (∼30°). We computed the long‐term lithospheric strength based on an existing 3D model describing variations in thickness, density, and temperature of the main geological units forming the lithosphere of the SCA and adjacent forearc and foreland regions. The comparison between our results and seismicity within the overriding plate (upper‐plate seismicity) shows that most of the events occur within the modeled brittle domain of the lithosphere. The depth where the deformation mode switches from brittle frictional to thermally activated ductile creep provides a conservative lower bound to the seismogenic zone in the overriding plate of the study area. We also found that the majority of upper‐plate earthquakes occurs within the realm of first‐order contrasts in integrated strength (12.7–13.3 log Pam in the Andean orogen vs. 13.5–13.9 log Pam in the forearc and the foreland). Specific conditions characterize the mechanically strong northern foreland of the Andes, where seismicity is likely explained by the effects of slab steepening.

Climate change and groundwater resources availability in the Great Limpopo National Park (Mozambique): the current state of knowledge

This work outlines a comprehensive study of groundwater resources supply in Mozambique’s Great Limpopo National Park buffer zone in Southern Africa. To protect biological diversity and the water resources supply of dispersed communities of the buffer zone is a crucial problem to fix people in the region and, in the meantime, to boost the development of the Limpopo National Park. This work shows the current state of knowledge about this topic and try to point out some suggestions on technical solutions. Some previous studies concluded that two different main factors make a complex water supply in this area: (i) the rainwater distribution, it is hard to transform the rainwater into groundwater resources available for exploitation, and (ii) the common groundwater resources, rich in elements such as Boron (B), Mercury (Hg), Uranium (U), Zinc (Zn) and Lead (Pb). The occurrence of these elements is linked to the presence of groundwater with long residence times, unsafe for people’s health. The methodological approach adopted has been to assess the potential infiltration, applying the inverse hydrogeological budget technique, starting from the main outcropping geological units, in the study area. Due to the lack of meteorological data referred to Limpopo National Park, the gauge stations located in the Kruger National Park during the last 64 years have been, on the whole, considered. The target of the study has been to assess the trend of meteorological data and understand how precipitations could affect groundwater recharge and their availability. Without a strategy of biodiversity conservation and sustainable water resources management, they cannot be reached and guaranteed healthy conditions for local dispersed communities. A hydrogeoethical responsible approach is essential to protect biological diversity and hydrosocial cycle framework with integrative ecosystem services and nature-based solutions.

Gravity for Lithosphere Architecture Determination and Analysis: the Central Eastern Mediterranean case study

ABSTRACTThe Central‐Eastern Mediterranean region is known to be a complex area due to the interaction of four tectonic plates, namely Arabia, Africa, Anatolia and Eurasia, and by the presence of an ancient oceanic crust in the Herodotus and Ionian Basins. The analysis of the available literature highlights that the distribution of the freely available geophysical data (i.e. seismic, gravity and magnetic observations) is quite disparate. In this framework, high‐resolution global gravity field models, such as XGM2019e, mainly based (offshore) on satellite data, can be profitably used as a uniform dataset to study, in a coherent way, large regions.In the current work, we exploit the XGM2019e model, together with a set of a priori information, derived mainly from geophysical data retrieved from the literature, to study the structure of the crust in the Central‐Eastern Mediterranean area. The study is organized in three different phases: in the first one, we enhanced the map of geological crustal provinces by means of an automatic Bayesian classification algorithm applied to the second radial derivatives of the gravitational potential. In the second phase, using as observation a grid of gravity anomalies, we applied a full three‐dimensional inversion procedure (always based on a Bayesian paradigm) to estimate the mass density variations and the geometries of the main geological units in the whole study area. Finally, in the third phase, we performed a refined three‐dimensional local inversion on the Cyprus area to improve the modelling of the shallowest layers. The main results of this study, carried out in the framework of the European Space Agency GIADA project, are freely available, upon request, at https://www.g‐red.eu/geophysics/.

Geological History of Southeastern Gorgonum Chaos, Mars: A Story of Water and Wind

AbstractGorgonum Chaos is part of the Eridania paleolake in Terra Sirenum and displays a number of prominent light‐toned morphological features that bear a record of the regional climatic conditions throughout most of Martian history. Based on an intergrated analysis of orbital data, we mapped a 1,500 km2 area in the southeast of Gorgonum Chaos. Morphologic, spectroscopic, and stratigraphic analyses were used to determine age and composition of the main geological units in the area. We identified four major geological units with decreasing content of hydrated minerals from the oldest to the youngest units, which were completely free of hydrated minerals. In the study area, phyllosilicate‐rich Noachian units compose the majority of the basin floor. Deposits enriched with evaporites were formed around the Noachian/Hesperian transition and erosion created prominent inverted morphologies. Loess‐like material without significant amounts of hydrated minerals was deposited until the late Hesperian. The youngest unit is an Amazonian layer free of hydrated minerals that originated from volcanic activities. This succession of minerals reflects the transition from more humid climatic conditions with the ability to sustain liquid water on the planet's surface during the Noachian to the hyper‐arid Amazonian environment we observe currently on Mars.

A multi-scale 3-D crust velocity model in the Hefei-Chao Lake area around the southern segment of Tanlu Fault Zone

Regional high-precision velocity models of the crust are an important foundation for examining seismic activity, seismogenic environments, and disaster distribution characteristics. The Hefei-Chao Lake area contains the main geological units of Hefei Basin, with thick sediments and the Chao Lake depression. Several major concealed faults of the southern NNE-trending Tanlu Fault Zone cross this area. To further explore the underground distribution characteristics of the faults and their tectonic evolutionary relationship with adjacent tectonic units, this study used ambient noise data recorded by a seismic array deployed in Hefei City and Chao Lake, constructing a 3-D velocity model at the depth of 1–8 km. Then a multi-scale high-resolution 3-D velocity model of this area was constructed by this new upper crustal velocity model with the previous middle and lower crustal model. The new model reveals that a high-velocity belt is highly consistent with the strike of the Tanlu Fault Zone, and a low-velocity sedimentary characteristic is consistent with the Hefei Basin and Chao Lake depression. The distribution morphology of high and low velocity bodies shows that the sedimentary pattern of Hefei-Chao Lake area is closely related to the tectonic evolution of the Tanlu Fault Zone since the Mesozoic. This study also identifies multiple low-velocity anomalies in the southeastern Hefei City. We speculate that strong ground motion during the 2009 Feidong earthquake (magnitude of 3.5) was related to amplification by the thick sediments in the Hefei Basin. We also discuss further applications of multi-scale high-resolution models of the shallow layer to strong ground motion simulations in cities and for earthquake disaster assessments.

Characterization of the Candidate Landing Region for Tianwen‐1—China's First Mission to Mars

AbstractThis paper presents our efforts to characterize the candidate landing region (109°–133°E, 23°–30°N) for Tianwen‐1, China's first mission to Mars, in terms of engineering safety and scientific significance. Topographic analysis reveals that the region has a low elevation around −4,230 m, and 98% of the region have slopes smaller than 8°. The geomorphological mapping and analysis show that the region has an average crater density of about 28 craters (≥200 m in diameter) per 100 square kilometers, with several clusters of high crater densities distributed around the center of the region. There are also pitted cones distributed mainly in the southern part of the region, with a density of approximately 6.6 cones per 100 square kilometers in specific local areas. The region has rock abundances ranging from 1% to 23%, with local clusters of low and high rock abundances. The region comprises four main geological units, including a lowland unit formed in the Late Hesperian and a volcanic unit formed in the Amazonian and Hesperian period. Their specific surface ages are estimated through the analysis of crater size‐frequency distribution. Combining the engineering constraints on surface slopes, crater density, cone density, and rock abundance, a hazard map of the candidate landing region is generated for landing site evaluation and safety assessment. Based on the results, we further discuss the potential scientific outcomes from the exploration in this region. The findings will be helpful for the mission planning and maximization of the scientific return from Tianwen‐1, and complement existing Martian scientific research.

Lithological and Topographic Impact on Soil Nutrient Distributions in Tectonic Landscapes: Implications for Pleistocene Human-Landscape Interactions in the Southern Kenya Rift

Tectonically active regions are characterized by complex landscapes comprising soils with heterogeneous physicochemical properties. Spatial variability of nutrient sources enhances landscape biodiversity and creates heterogeneous habitats potentially attractive for animals and humans. In this study, we analyze the role of geological processes in the distributions of soil nutrients in the southern Kenya Rift, a key region in the interpretation of early human-landscape interactions. Our aim is to determine how spatial variations in rock chemistry, as well as topographic gradients and localized zones of rock fracturing from tectonic faulting determine the distributions of plant-available soil nutrients in soils. We hypothesize that present-day soil nutrient levels reflect the long-term chemical and geomorphological characteristics of the landscape and underlying parent material, and that regions with high nutrient availability occur along pathways correlating with locations of hominin fossil sites. Analyses of 91 topsoil samples from the main geological units show that Calcium (Ca) deficiencies predominately occur in shallow soils developed on trachytic volcanic rocks and granitic gneisses, while high Ca levels are associated with basaltic parent material and sedimentary deposits of mixed sources. XRF analysis of rock samples confirms that CaO levels in trachyte rocks are significantly lower than those in basalts, and Ca mobilization in basalt is more effective than in trachyte. Along two toposequences in densely faulted basaltic and trachytic rocks, we observed slope dependent soil nutritional gradients and a systematic increase of the concentrations of Ca, Mg and SOC in topsoils of colluvial sediments downslope of active normal faults. Known hominin sites in the region are located either along corridors of long-term Ca availability or at short-term nutrient hotspots potentially related to active CO2 degassing along active fault zones. This implies a strategic advantage of Ca-rich regions for hominin subsistence strategies, such as provision of predictable constraints on the distribution and mobility of grazing animals in complex tectonic landscapes. Our study implies that geological processes impact nutrient distributions in the southern Kenya Rift. Results of this study have further implications for understanding the role of soils in the interpretation of hominin-landscape interactions in the early stages of human evolution.

Occurrence, source identification and potential risk evaluation of heavy metals in sediments of the Hunza River and its tributaries, Gilgit-Baltistan

Abstract The present study examined heavy metals concentrations in sediments of the Hunza River and its tributaries, Gilgit-Baltistan, Pakistan. For this purpose, surface sediments were sampled from the Hunza River and its tributaries along with the three main geological units i.e. Wakhan Block (upstream), Karakoram Block (midstream) and Kohistan Block (downstream). Heavy metals concentrations in each sample were analyzed using the atomic absorption spectrometry (AAnalyst 700, PerkinElmer, USA). Results showed the highest mean concentration for iron (Fe, 44400 mg/kg) and the lowest was observed for cadmium (Cd, 0.62 mg/kg). Heavy metals concentration showed an increasing trend in sediments with the downward flow and resulted in higher values along the Kohistan Block (downstream) and lowest in the Wakhan Block (upstream). Determined heavy metals concentration were evaluated for the pollution quantification factors. The values of contamination factor (CF) and pollution load index (PLI) showed heavy metals contaminations in the sediment of the Hunza River and its tributaries. The highest (175) values of ecological risk index (ERI) were observed for Cd and classified at a moderate-risk level to the aquatic ecosystem. Statistical analyses revealed that natural denudation of bedrock and mineralized zone led to heavy metal contamination in sediments of the Hunza River and its tributaries with lesser input from anthropogenic activities.

Geophysical reconstruction of buried geological features and site effects estimation of the Middle Valle Umbra basin (central Italy)

The Middle Valle Umbra (central Italy) is a NW-SE 20 km long and 10 km wide Quaternary extensional basin located in the internal sector of the Apennine chain. This area historically experienced strong earthquakes that caused significant damages to the outstanding historical heritage. The same area has been recently hit by the 2016 seismic sequence of Amatrice-Visso-Norcia.With the aim to reconstruct the buried geological structures of the basin, a multi-technique geophysical approach was performed. An extended campaign of ambient noise measurements was carried out to investigate the subsurface setting, and to identify the main geological units. We performed three 2D passive arrays to analyze two different sites within the basin; their aperture was between 150 and 752 m for one site and of 48 m for the other site, to characterize the geological units in terms of sediment thickness and shear-wave velocity profile. Data collected were processed with f-k and MSPAC analysis to extract dispersion curves with good resolution in a frequency range of 0.5–10 Hz and 4.5–18 Hz for the two sites respectively. Spectral ratios were computed for every single station ambient noise measurement performed and for all the stations of the bigger array. Our final target is to extend these results to the whole valley, in order to retrieve the attitude of the main geological units and propose a reliable reconstruction of the subsurface geometry of the basin. Another point of this work is to evaluate the site response in the middle of the valley through the analysis of the earthquakes recorded by the accelerometric station IT.CSA (belonging to the Italian Civil Protection) and the corresponding recordings of the nearby rock station IT.ASS.