Geosystems and Geoenvironment最新文献

This study aims to assess the pollution levels and sources of heavy metals (Al, Mn, Co, Ni, Sc and V) and radionuclides (Th and U) in sediments of Lékié Watershed in Cameroon. Surface sediment samples were collected from 14 stations across different areas of the Lékié Watershed. The heavy metal and radionuclide analysis on sediments were carried out and pollution indices such as enrichment factor (EF), contamination factor (CF), degree of contamination (DC), pollution load index (PLI), potential ecological risk assessment and multivariate statistical methods were utilized to evaluate the degree of contamination and estimate the source of metals in the sediments of Lékié Watershed. The results show that the mean concentrations are lower than those of the upper continental crust (UCC) reference values except those of Mn, Co, Ni, and V. The values of EF varied from moderate to severe enrichments (from 4 to 44). The contamination factor (1 < CF < 3), potential ecological risk (<40) and degree of contamination (<8) revealed a low to moderate degree of contamination. The majority of stations have PLI > 1, indicating pollution. The application of multivariate analysis to these metallic elements reveals contaminations attributed to anthropogenic activities, including the release of domestic, artisanal mining, and industrial effluents, as well as natural sources originating from the leaching of local surrounding soils and geological factors. To mitigate more pollution in this watershed which is closed from urbanization, it is crucial for local authorities to implement wastewater treatment measures.

Natural arch is one of the most fascinating geomorphological features formed by erosional process and many of them are formed within gently dipping sandstone. A natural arch (Location: 21°54′32.20″ N, 83°43′46.20″ E, RL: ∼370 m) of such type is present in the rocks of Upper Kamthi Formation of Middle Jurassic age (160–184 Ma), Upper Gondwana Group, Ib River Coalfield within dense Chhengapahar Reserve Forest near Brahmani Village, Sundargarh District, Odisha. This oval shaped natural arch with a maximum length and height of ∼30 m at the base and ∼12 m respectively. The alcove of the natural arch has maximum height and width of ∼7 m and ∼15 m respectively, is opened along NE-SW direction on the top of the hill. Flesh red colored, ripple topped, trough to planar cross stratified, coarse to gritty, texturally and mineralogically immature, ferruginous sandstone of Upper Kamthi Formation forms the hill. Kaolinisation of feldspathic members makes the sandstone loose and porous. Two orthogonal set of faults-joints (130°/60°W and 40°/60°E) initiated the formation of natural arch while the porosity of the immature, arkosic sandstone accelerate the process through subaerial weathering where surface/rain water percolation–temperature fluctuation played effective roles. Therefore, the formation of natural arch is a result of structurally triggered weathering and erosion. Efforts have already been taken to preserve this place as national geo-heritage site by Geological Survey of India, Government of India.

The integration of remote sensing data, machine learning and geographic information system in managing and analysing spatial data helps in generating maps showing groundwater potential. These maps are important tools for aiding stakeholders and decision-makers in groundwater resources to make informed decisions during groundwater development and management; to ensure the reliability of these maps, validation with the field data is conducted. This study analysed 125 scientific articles spanning the period from 2002 to 2023. The results show that around 85% of articles contain validated maps, indicating a significant number of researchers adhere to validate the remote sensing and GIS-based maps with field data, which is crucial in scientific research. However, 15% of articles contain non-validated maps. This is an alarming figure; therefore, journals should be strict in ensuring that validation is adhered to. In the reviewed articles, a total of 10 methods were used to validate groundwater potential maps using various parameters such as well yield, well/spring discharge rate, aquifer transmissivity, well specific capacity, and presence of wells/springs. This study will also add to the knowledge of selecting appropriate methods for validating remote sensing and GIS-based groundwater potential maps. The use of field data reflecting aquifer productivity is more appropriate for validation of groundwater potential maps.

Beaches form one of the most contaminated sedimentary environments by a myriad variety of anthropogenic activities, including tourism and recreational activities. The concentrations of metals and their pollution levels were studied for four tropical tourist beaches in Kerala state, Southern India. Bulk geochemical and mineralogical analyses of 16 sediment samples were performed to determine the environmental status and the environmental risk level using various geochemical indices. Based on the enrichment of TiO₂ and SiO₂ concentrations, the samples were grouped into ilmenite-rich samples (IRS) and quartz-rich samples (QRS) respectively and the geochemical signatures are significantly different. Mineralogically, the IRS group is dominated by ilmenite, quartz, sillimanite, zircon and rutile while the QRS group consists of quartz, spinel and calcite and garnets are common in both groups of sediments. Despite the variation in the trends of pollution indices, it has been found that Kovalam beach sediments are enriched with W, Th and U where, IRS with enrichment of W, U and Th while QRS only enriched with W and Th and not U. The mineralogical affinity of W with secondary tungsten-bearing minerals has been documented by the XRD analysis and these metals are mainly controlled by the geogenic sourced minerals. However, in terms of ecological risk, Pb, As and Cu have a considerable to moderate risk in both groups of sediments. Overall, both group of sediments shows a moderate risk. Based on the biological effect assessment the elements of concern are Pb and Zn in IRS and possible effect by the Cr, Cu and As in IRS and only by Cu in QRS. Though the prevalence of geogenic and anthropogenic processes and influences of metal enrichments are documented by the study, their relative influences, mobility and bioavailability need to be systematically studied.

Scaling laws are ubiquitous in modern biological systems. However, whether such patterns existed in deep-time biological systems is less investigated; the best-known example is the scaling law between the frequency and size of extinction events. Here, I show that the variation rates of biodiversity, origination intensity, extinction intensity, and body size of marine animals during the last 540 million years exhibited scaling laws. I then derive a general form of these scaling laws from a conceptual model with some principles of thermodynamics and assumptions about the global biological system. The results in this study suggest that the scaling laws systematically appearing in the biological metrics characterizing different aspects of the evolutionary processes of marine animals likely belong to the same universality class and probably derived from a set of common factors.

This paper presents an up-to-date review of Nigerian geological evolution during the Upper Cretaceous to treat with in-depth knowledge gathered from previous literature, field geological mapping and 2D seismic interpretation, the contentions concerning possible pathways of entrance throughout transgressive episodes that guide the initiation of the Trans-Saharan seaway. Assessment of the economic potency of this portion, inclusive of the petroleum system and coal (fossil fuel) deposits, groundwater, and mineral resources. Two episodes of transgression connected large number of Upper Cretaceous basins of Nigeria. The first Trans-Saharan seaway between the South Atlantic and the Tethys was confirmed during the Turonian time and started flooding southwards from the Cenomanian, of which the first transgression was entrenched in the Bida and Yola Sub-basins. The connection pathway was probably east and westward, linking Tethys with the Gulf of Guinea along the Benue Trough and Bida Basin. These resulted in extensive marginal marine conditions in the Campanian-Maastrichtian favored the deposition of coal, ironstone, and clay of great economic value. This connection was put to a standstill by the Santonian epeirogenic event (inversion, reversal, etc.) made distinctive by folding, faulting, uplift, and intrusions. A second transgression, beginning in the Campanian to Maastrichtian, re-confirmed the Trans-Saharan seaway through a westward Bida Basin path in the Maastrichtian, coming to a climax globally. Mainly marginal marine environments in Benin, Anambra, Sokoto, and Bida basins as established in this paper. The inundation of oceanic waters from the Tethys, restricted in expanse by the edified region of the southern Benue Trough brought about marginal marine conditions in the northern, central Benue Trough, and Chad Basin. Extensive deposition of clay, coal, ironstone. Also, good to prolific aquiferous units occurred during this time.

Calculating and analyzing ecological efficiency of forestry carbon sink is key to develop China's forestry carbon sink effectively. This paper utilized super-efficiency stochastic frontier model (SBM) to measure ecological efficiency of forestry carbon sink of 30 provinces (municipalities and autonomous regions) in China from 2000 to 2017. In addition, this study calculated and analyzed convergence trend by constructing β convergence model under consideration of spatial conditions. Study results were revealed as follows. Firstly, ecological efficiency of China's forestry carbon sink presented a "double peak" distribution characteristic of a steady rise with fluctuations. However, overall level was not high, and large room still existed for improvement. Secondly, a significant spatial convergence existed in ecological efficiency of forestry carbon sink in China. Spatial factors had an accelerating effect on convergence trend, making spatial differences in ecological efficiency of forestry carbon sink among regions further narrowed over time. Thirdly, five major forest regions possessed significant spatial convergence, and convergence rates were higher than national average level. The southwest forest region had the highest convergence rate, followed by the northeast, south, northwest and the North China forest regions. Spatial convergence speeds of two periods from 2000 to 2010 and 2011 to 2017 were higher than classical convergence speed, and shown a decreasing change process. Due to existing of spatial convergence, different regions should explore value realization mechanism of forestry carbon sink, clarify regional positioning, and formulate measures based on local conditions to develop forestry carbon sink.

The Eastern Highlands of Myanmar are characterized by Precambrian to Mesozoic rock formations, with Carboniferous-Permian sequences prominently present in the Shan Scarp and Shan Plateau zones. These sequences are particularly concentrated in the western margin of the Sibumasu Block. Although Permian sequences are abundant in this region, they are complicated by geological faults. Consequently, a lithostratigraphic study was conducted to establish correlations across an extensive area spanning 1200 km from Mandalay City in the north to Kawthaung City in the south and 250 km wide, bordered by the Sagaing Fault to the west and Inle Lake to the east. The Permian sequences can be categorized into lower siliciclastic units and upper carbonate units. These siliciclastic units encompass the Mergui Group, locally referred to as the Lebyin Group, Mawchi Series, Taungnyo Group, and Mergui Group, as well as the Yinyaw Formation. Additionally, there is a carbonate unit known as the Moulmein Formation in the Thaton, Hpa-an, and Mawlamyine areas, and the Tenasserim Formation in the Myeik and Bokepyin areas within the Shan Scarp zone. In the late Lower Permian sequences, the Mwedaw Beds are exclusively found in the Linwe area. However, the Thitsipin Formation, which is an equivalent of the Moulmein Formation, and the Nwabangyi Formation are also exposed in the Shan Plateau zone. Lower Carboniferous sequences, such as the Loikaw Beds, are sporadically visible in the Loikaw area but are overlain by the Thitsipin Formation. This study elucidates the presence of a diamictite unit (Mergui Group) and its associated units (Yinyaw and Thitsipin/Moulmein Formations) in the geo-structurally complex zones of the Shan Plateau and Shan Scarp through lateral lithostratigraphic correlation, shedding light on the Carboniferous-Permian period at the western margin of the Sibumasu Block.

The Banyo area is situated in the west Cameroon domain of the Central African Fold Belt. In this study, field data and remote sensing conventional mapping techniques including Red-Green-Blue (RGB) colour combination, principal component analysis (PCA), Crosta-PCA, Band Ratios (BR), Constrained Energy Minimization (CEM), Minimum Noise Fraction (MNF), Spectral Angle Mapper (SAM) classification and Linear Spectral Unmixing (LSU) algorithms were used to process Landsat 9 OLI and ASTER data in order to discriminate various rock units such as biotite-amphibole granites, hornblende-biotite orthogneiss and map associated mineral deposits (e.g., iron-oxide, hydroxyl and corundum minerals). In addition, it was found that RGB combination (743) of OLI bands, PCA of OLI bands (PC123), BR of OLI bands (4/2, 6/7, 6/5), BR of ASTER (4/2, 7/6, 8/9), Crosta-PCA of OLI bands, MNF (123) of OLI bands, SAM, and LSU techniques applied to ASTER bands ascertain potential locations of granitoids and gneisses bearing iron and hydroxyl minerals. On the other hand, this study also revealed that corundum deposits are detected by applying the CEM method to OLI band ratio 6/7 highlighting red tones and processing SAM classification algorithm both using laboratory reference spectra. Automatic (using PCI Geomatica line tool) and manual extractions of lineaments revealed three major trends (N-S, E-W, and WNW-ESE to NW-SE) and an accessory trend (NE-SW to ENE-WSW) that surround hydrothermally altered rocks recognized as containing iron oxide, hydroxyl, and corundum mineral deposits. In the field, these lineaments may group to the tree deformation phases. The D₁ phase (NW-SE); the D₂ phase (NE-SW to ENE-WSW) and the D₃ phase (N-S). Maximum Likelihood Calssification (MLC) and SAM classification methods showed to be more effective in discriminating rocks bearing Iron-oxide, hydroxyl and corundum minerals in the study area.

This result permits to confirm that, the combination of remote sensing (Landsat 9 OLI and ASTER data in this case) and field data constitute a useful tool for mineral exploration in the shear zone. However, the accuracy assessment was relied on comparing the different maps produced from Landsat 9 OLI and ASTER data with the ground truth sample points and also, with the earliest geological map of Banyo area. Thus, quantitatively the results were accurate at 99%.

Complications of interpretations of geochemical proxies used for paleoclimatic constructions, including proxies which may be interpreted as evidence of former glaciations, are more fundamental than is commonly acknowledged. Recent advancements have shown a much larger variation in the geochemical data than expected, and there may be a connection to local geological environments and processes rather than paleoclimate. The data has often been overinterpreted in paleoclimatic models and studies, and more caution is justified when interpreting ancient climates from geochemical proxies. A broader range of reasons for geochemical variations, additional to climate (e.g., source and paleotransport which may help in discovering provenance), should be considered.

Isotopes of carbon, oxygen and strontium, weathering (CIA), ikaites and banded iron formations are reviewed and discussed. Cap carbonates are considered as evidence for warm climate and are commonly covering diamictites that have been interpreted to be glaciogenic, and these are therefore relevant and discussed.