Index Of Alteration Research Articles

Biogeochemical responses to global warming during the Paleocene–Eocene Thermal Maximum in the eastern Tethys

The Paleocene–Eocene Thermal Maximum (PETM; ∼56 Ma) represents a rapid and sustained climatic perturbation that lasted for ∼170 kyr and coincided with the emplacement of the North Atlantic Igneous Province (NAIP). Global average temperature increased by 5 to 9 °C, which was likely triggered by a rapid emission of 13C-depleted CO2. Numerous sites from the deep oceans have been studied for the PETM, but subtropical shallow-water eastern Tethys remains poorly understood despite its importance in regulating heat and moisture transport. Prior studies on calcareous nannofossil biostratigraphy and stable isotopes of marine carbonates confirmed the occurrence of the PETM in the Tarim Basin of the eastern Tethys in northwestern China. Here we present new, high–resolution major, trace and rare earth element geochemical data, and clay mineral records at the Kuzigongsu section in the Tarim Basin to assess the biogeochemical responses of the eastern Tethys to climatic forcings across the PETM. Chemical weathering proxies (chemical index of alteration [CIA], chemical index of weathering [CIW], plagioclase index of alteration [PIA], and Rb/Sr) support an enhanced terrestrial input shortly after the PETM onset, possibly due to intensified chemical weathering. Furthermore, clay mineral assemblage is dominated by illite and illite/smectite during the PETM, implying increased physical weathering. The PETM is also characterized by an increase in nutrient-sensitive elements such as P, Ni, and Cu and higher abundance of nutrient–sensitive calcareous nannofossils, suggesting an intensification of marine primary productivity. Meanwhile, the Tarim Basin may have encountered episodic bottom water deoxygenation supported by an increase in the enrichment factor of redox–sensitive elements such as U and V. The integrated geochemical proxy records suggest that the eastern Tethys has encountered profound ecosystem stress imposed by elevated nutrient fluxes and ocean deoxygenation, which may have been amplified by simultaneously intensified chemical and physical weathering during the PETM.

D-shape Optical Fiber Development and Enhancement as a Refractive Indices Sensor Using Surface Plasmon Resonance

This article showcases the development and utilization of a side-polished fiber optic sensor that can identify altered refractive index levels within a glucose solution through the investigation of the surface Plasmon resonance (SPR) effect. The aim was to enhance efficiency by means of the placement of a 50 nm-thick layer of gold at the D-shape fiber sensing area. The detector was fabricated by utilizing a silica optical fiber (SOF), which underwent a cladding stripping process that resulted in three distinct lengths, followed by a polishing method to remove a portion of the fiber diameter and produce a cross-sectional D-shape. During experimentation with glucose solution, the side-polished fiber optic sensor revealed an adept detection sensitivity of 0.2015 au. /RIU. In order to improve sensitivity, a recent sensor was subjected to a coating process utilizing a thin film layer of gold (Au) measuring a thickness of 50 nm. The sensor was subsequently subjected to a series of tests utilizing the same glucose solutions as in previous experiments. A notable enhancement in sensitivity was observed when utilizing gold as the sensing material, with an equivalent maximum sensitivity of 3.101 au. /RIU.

Sea level and East Asian monsoon influenced chemical weathering records in the southern South China Sea over the past 21 ka

High-resolution major element geochemistry of Core MD05–2892 from the lower Sunda Slope was analyzed to investigate the variation of chemical weathering records and its controlling factors in the southern South China Sea since the last glaciation. Chemical index of alteration (CIA) and SiO2/Na2O ratio were selected as chemical weathering proxies. The values of the proxies are higher during the last glaciation than during the Holocene. We attribute this to the provenance shift caused by sea level change. Provenance analysis indicates that the Malay Peninsula and Sumatra were the major sediment sources for the study region during the last glaciation, while the Indochina Peninsula has been the major source since the early Holocene. Accordingly, the weathering evolution analysis reveals increased physical erosion in the Malay Peninsula and Sumatra during enhanced East Asian summer monsoon rainfall, while increased chemical weathering in the Indochina Peninsula during the intensified monsoon rainfall. Therefore, the chemical weathering records of the deep-sea sediments in the southern South China Sea were regulated by monsoon rainfall-driven physical erosion in the Malay Peninsula and Sumatra during the last glaciation, while the records have been influenced by monsoon rainfall-induced chemical weathering in the Indochina Peninsula since the early Holocene. This study emphasizes that higher weathering values of the deep-sea sediments during the last glaciation could be related to the provenance variation driven by sea level change, rather than to enhanced chemical weathering in the same provenance.

Paleoweathering and Detrital Provenance of Balangbaru Shale, in South Sulawesi

Sulawesi Island, known for its geological complexity, offers a unique opportunity for researchers to investigate further into sedimentary basins particularly in South Sulawesi area. The Cretaceous Balangbaru Shale is one of the rocks that has an extensive distribution in South Sulawesi especially in the western part. Due to limitation of geological information related to this formation we performed the paleodepositional investigation to elucidate the paleoweathering, geochemistry characterization, and detrital provenance of the Balangbaru Shale. Indeed, previous studies have demonstrated that fine-grained sedimentary rocks can serve as valuable archives of geochemical information, enabling the reconstruction of paleoclimate evolution during the deposition period. Employing XRF quantitative analysis, we examine the dispersion of major elements within eight distinct layers of the Shale. Additionally, comprehensive whole-rock analyses enable us to ascertain the abundance of major elements and subsequently deduce detrital SiO2 and biogenic SiO2 content, thereby comprehending the inorganic geochemical composition of the Balangbaru Shale.The present study seeks to address the limited understanding of the geochemical properties of the Balangbaru Shale, specifically pertaining to paleoweathering intensity and detrital provenance. Acknowledging the scarcity of recent data available on the subject matter, this research aims to bridge the limitation data gap by conducting an in-depth investigation into the geochemical characteristics of the Balangbaru Shale by employing major oxides concentrations (SiO2, Al2O3, Fe2O3, K2O, P2O5, MgO, CaO, Na2O, MnO, TiO2, Cr2O3) and trace elements (Sr, Cu, Ba, Th, Ni, V, Th, U) into the equations such as C-value, chemical index alteration (CIA), plagioclase index of alteration (PIA), weathering index of parker (WIP) and ratio of Rb/Sr, U/Th, Sr/Cu, Sr/Ba. Furthermore, the major oxides ratio of Al2O3/TiO2 and TiO2/Zr were performed to specify the sediment provenance and the source-area rock compositions of the Balangbaru Shale. The obtained data reveals a moderate to high degree of weathering intensity in the detrital source environment of the Balangbaru Shale, suggesting warm to humid climate conditions in the source region. Additionally, the analysis of the detrital fraction indicates the possible origin of the Balangbaru Shale from felsic rocks. Overall, these findings contribute significantly to the understanding of paleoenvironmental conditions associated with the Balangbaru Shale, shedding light on its geological history.

Geochemical Compositions of Size‐Fractioned Sediment Samples From the Yangtze and Yellow Rivers: Implications for Chemical Weathering, Fractionation Behavior of Provenance Tracers, and Sources of Radial Sand Ridges

AbstractRiver sediments are valuable archives of the environmental conditions within their catchments. The Yangtze and Yellow Rivers are the most active fluvial systems for sediment transport in East Asia, and they are regarded as potential sediment sources for the radial sand ridges (RSRs) in the southwestern Yellow Sea. We used the geochemical compositions of size‐fractioned sediment samples from the Yangtze and Yellow Rivers to characterize chemical weathering, the fractionation behavior of provenance tracers, and the sources of RSRs. For the Yangtze and Yellow River sediments, the (Rb + Sr)/Ti ratio is a reliable chemical weathering proxy that is grain‐size independent. The chemical indices of Chemical Index of Alteration, Rb/Sr, (Rb + Sr)/Ti, and acid‐leached elements from common grain‐size fractions together reveal that the Yangtze River basin undergoes stronger chemical weathering than the Yellow River basin, indicating that the chemical weathering is dominated by latitudinally‐dependent climatic variations. The dissolution and precipitation of amorphous Fe‐Mn oxides can result in the significant fractionation of La/Y, La/Sc, Nb/Co, La/Co, (La/Sm)N, (La/Yb)N, Ti/Sc, Zr/Y, Zr/Co, and Cr/Ta, whereas Zr/Ti and Zr/Nb are largely unaffected. Based on the robust provenance tracers of Zr/La, La/Hf, (La/Yb)N, Zr/Nb, Ti/Zr, and Hf/Ta, we conclude that the RSRs in the southwestern Yellow Sea are mainly derived from Yangtze River sediments, and that part of the clay fraction is from the Yellow River. In future research, we suggest that established geochemical indicators of chemical weathering and sediment provenance can be applied to the deposits of the Yangtze and Yellow River Deltas, the Yellow Sea, and the East China Sea.

Exploring climate variability during the Marinoan glaciation: A study of black shale geochemistry

The Marinoan glaciation is the younger of the two extraordinary glaciations during the Cryogenian Period. It has been debated whether the glacial world was featured by a complete ice cover or if parts of the oceans remained ice free. Here, we present petrographic and geochemical data of two black shale units found within diamictites of the Marinoan-aged Nantuo Formation in South China. The lower black shales exhibit low values of the chemical index of alteration (CIA) and muted enrichments of uranium, while the upper black shales show elevated CIA and uranium concentrations. These distinct geochemical signals are best explained by intensified chemical weathering and terrestrial runoff, which might be linked to global/local temperature changes. Our study is consistent with the notion that significant climate variations occurred during the Marinoan glaciation. The cyclic isolation and expansion of habitable areas might have acted as a biodiversity pump, contributing to the rapid radiation of eukaryotic life in the aftermath of the glaciation.

Changes of sediment provenance driven by the sea level and Indian summer monsoon in the northern Ninetyeast Ridge over the past 50 kyr

The Ninetyeast Ridge is situated within the world's largest sediment “source-sink” system, which extends from the Tibetan Plateau to the Bay of Bengal (BoB). Modest and stable sedimentation rate makes it a suitable region for studying long-term land-sea interaction. Recent research has primarily focused on the northern Bengal Fan, leaving limited knowledge about sedimentary processes on the distant Ninetyeast Ridge. This study aims to address this gap by investigating sediment transport pattern and its response to climatic and environmental changes since the last glacial period, using the gravity core (CJ04–50) selected from the northern Ninetyeast Ridge. The provenance discrimination based on δEu-(Gd/Yb)N revealed that the Irrawaddy (Irr) River, along with the Ganges-Brahmaputra (G-B) Rivers, represented the primary sources of the study area. Quantitative analysis equations indicated that the contribution of the G-B Rivers decreased from the last glacial period (22%) to the Holocene period (16%), while that of the Irr River increased (from 78% to 84%). Chemical index of alteration (CIA*) values, and terrigenous input proxy indicators (Ti/Ca, Rb/Sr) were used to indicate the changes of weathering and terrigenous input over the past 50 kyr. During the last glacial period, CIA*, Ti/Ca and Rb/Sr revealed significantly millennial-scale periodic changes, including the distinct declining trend during the Last Glacial Maximum (LGM) and Heinrich 2–4 (H2-H4) periods, followed by recovery trend during subsequent warm periods. During these cold periods of LGM and H2–H4, weakened Indian monsoon condition, reduced precipitation, cold climate, and expanding ice sheets, adversely affected physical erosion and chemical weathering in the source area, and the reduced river runoff impeded sediment transport. Conversely, these environmental factors reversed during relatively warm periods. Since the Holocene, CIA*, Ti/Ca and Rb/Sr declined, which was contrast to the climate change, and the sea level changes became the dominant factor. The rapidly rising sea level submerged the main terrigenous input channel (the Swatch of No Ground) of the G-B Rivers, made the depositional center shift from the Bengal Fan to the continental shelf, causing the decline of terrigenous input and lower CIA* values.

Geochronology, provenance, and tectonic setting of the meta-sedimentary rocks from the North Shahrekord metamorphic Complex, Iran

ABSTRACT The meta-sedimentary rocks from the North Shahrekord metamorphic Complex (NSMC) comprise micaschists, paragneisses, quartz-feldspathic schists, and marbles. Detrital zircons from the paragneisses yield ages of ca. 2811–507 Ma with most of the dated grains belonging to the Late Neoproterozoic to Cambrian, suggesting a maximum depositional age of the sedimentary protolith during the Late Ediacaran to the Early Cambrian times (543 ± 12 Ma). In contrast, detrital zircons from the quartz-feldspathic schists are mostly dominantly 692–577 Ma and a few at ca. 2369–703 Ma, suggesting that the maximum depositional age of 577 ± 9 Ma, Late Neoproterozoic. The age distribution of detrital zircons suggests that their main provenance was located within the Arabian-Nubian Shield and adjacent terranes. Rutiles from a paragneiss give a U-Pb lower-intercept age of 181 ± 3 Ma, indicating the occurrence of a high-pressure metamorphic event during the Early Jurassic. The trace element contents of the two rock units show enrichment in LREE relative to HREE and negative Eu anomalies, indicating upper continental crustal sources. The geochemical evidence (e.g. low to moderate Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration, high Index of Compositional Variability (PIA), and low Th/U) suggests that the quartz-feldspathic schists and paragneisses originated from an immature, and immature to less mature, respectively, intermediate-felsic igneous source and their protolith experienced a simple sedimentary recycling history with relatively weak to moderate chemical weathering. Geochemical and petrographic data also suggest that the precursor to the quartz-feldspathic schists and paragneisses were deposited in a continental island arc and a back-arc basin setting, respectively. Our new data, including depositional age, provenance, and geochemical evidence, provide perspectives on palaeogeographic affinities (provenance of sediments with different weathering and recycling materials), and paleotectonic reconstructions (from arc to back-arc) of the Iranian basement, exposed in the Sanandaj-Sirjan Zone, during Ediacaran.

Evaluation of the Genotoxic and Histological Effects in Neotropical Fish Prochilodus Lacustris (Pisces, Prochilodontidae) in Conservation Area of the Brazilian Northeast.

Human activities significantly impact the aquatic biota in lacustrine environments, leading to negative environmental consequences. Due to this, this study was carried out to evaluate the genotoxic and histological biomarkers in the gills and kidneys of Prochilodus lacustris. The collection of fish and water was conducted in three distinct stations (S1, S2, S3) in an international protected area in northeast Brazil. The histological alterations index was used to assess changes in the gills and kidneys at a histological level. In addition, micronucleus and nuclear abnormalities tests were employed to examine damage to the genetic material. According to the frequency of Micronucleus, nuclear injuries, and the histopathology of gills and kidneys, it can be inferred that station S1 had the highest impact on the fish, causing significant harm. Based on our findings, the organisms residing in Lake Açu are adversely affected by the poor environmental conditions. This raises doubts about the effectiveness of the Protection Area by Humid Zone of International Interest in Northeast Brazil.

Evaluating indicators of hydrologic alteration to demonstrate the impact of open-pit lignite mining on the flow regimes of small and medium-sized rivers

Our study provides a retrospective evaluation of the perturbances of the opencast mining on the small river. Based on a standard 'before-after-control-impact' approach, we assess the impact of disturbances on aquatic ecosystems. For this purpose, we used IHA (Index of Hydrological Alteration) statistics to fully quantify the impact of open-pit mine on flow regimes of small-to-medium-size rivers. The analysis results in flow data captured in the 33 parameters of the range variability approach (RVA) and five ecological flow components (EFC). This approach helped us comprehensively evaluate the alteration in the flow regime in areas of open-pit mining on the example of the Noteć River, a typical lowland river. We conclude that the level integrated hydrologic alterations to this river under the influence of the groundwater depression cone and water from the mine dewatering are high, as assessed by the RVA and EFC methods. Specifically, this work uses the IHA framework to verify the necessity of including a specific group of indicators. Our analysis shows that for the post-impact period on the investigated river, the functioning of the river ecosystem was degraded. One of the EFC components completely disappeared at both water gauge stations. There were also profound hydrologic alterations, such as increased frequency or duration of “extreme low flows” at one station; at the second station, “high flow pulses” occurred more frequently. More than 65 % of the altered parameters in five IHA groups were modified drastically. In the river section affected by the groundwater depression cone, both the minimum and maximum flows decreased by 20 % to 55 %. In the section where water from the mine dewatering is fed in, the minimum flows changed by + 170 to + 230 %. The use of the IHA tool provides an opportunity for environmental flow restoration of water conditions in degraded post-mining areas.

Influence of micro-scale factors in weathering and elements mobility: Evidence from a comparative study of granite and basalt weathering profiles across India

In an attempt to constrain the micro-scale factors during weathering, large number of samples from four weathering profiles developed on granite and basalt rocks under different climatic conditions from western (Gujarat, GJ) and central (Bundelkhand, BK) India are reported in this study and compared these profiles with profiles from north eastern (Arunachal Pradesh, Lesser Himalaya, AP) India. In granitic profiles, the chemical index of alteration (CIA) values ranges from 50 to 85 whereas 42–90 CIA values are observed for basalt profiles. This highlights the significance of climate conditions (i.e., precipitation) over lithology in controlling weathering advancement. The results of the mass-transfer coefficient (τ) of major oxides significantly vary among the three granite and basalt profiles. The trace elements distribution in weathering profiles seems to be strongly controlled by the degree of weathering and formation of secondary minerals. Regardless of the nature of parent rocks, HFSEs (high field strength elements) tend to be enriched in the upper portion of all the weathering profiles; whereas REEs (rare earth elements) display variable behavior in each profile. The principal component analysis (PCA) reveals that three components are accounted for 89.14% of the variance. PC1 is attributed to weathering intensity and formation of secondary minerals, PC2 can be related to the lithology of parent material, and PC3 might be a location-specific factors. The present study shows that the geochemical characteristics of weathering profiles cannot be explained by the influence of a single weathering agent rather, there seems to be a significant role of local (or micro-scale) factors that controls the weathering and soil formation.

Crude glycerin in feed for Colossoma macropomum fish: evaluation of histopathological effects on the liver and kidney

The present study aimed to verify whether the use of crude glycerin in the diet of juvenile Colossoma macropomum could promote histopathological changes in the liver and kidneys. 150 juveniles were used, divided into 15 tanks of 1000 liters (five treatments and three repetitions, n = 10). Five different diets with inclusion of crude glycerin (0%; 7.5%; 10%; 12.5%; 15%) were used in exchange for soybean oil and partial replacement of corn bran. The animals were fed to satiation for 60 days. After this period, liver and kidney samples from each group were submitted to histological processing and histopathological analysis. The semi-quantitative method was used to assess the lesions: calculation of Mean Alteration Values (MVA), which assess the occurrence of the lesion, and the Histopathological Alterations Index (HAI), which allows assessing the severity of the lesions. The results indicated significant non-harmful effects, but adaptive responses to the diet. In conclusion, the inclusion of up to 15% crude glycerin can be used without causing significant liver and kidney changes in C. macropomum juveniles.

Red clays indicate sub-aerial exposure of the Rio Grande Rise during the Eocene volcanic episode

Autonomous underwater vehicle (AUV) mapping of the western Rio Grande Rise (RGR), South Atlantic, and subsequent exploration and photography of horizontal lava flows exposed in near vertical, faulted escarpments, showed occurrences of red clays/weathered volcanic tops trapped between successive alkaline lava flows. These red clays indicate a hiatus in successive volcanic eruptions. Here, we report detailed mineralogical, geochemical, and rock magnetic characteristics of one such distinct red clay dredged from ~ 650 m water depth in the western RGR. The mineral constituents of the red clay are kaolinite, magnetite, oxidized magnetite (/maghemite), hematite, and goethite, with biogenic calcite and halite occupying voids or precipitated on the surface of the red clay. The chemical index of alteration (CIA) has a value of 93, showing that red clay is a product of extreme chemical weathering of the lava flows. The alkaline volcanic rocks recovered from nearby show an age of ~ 44 Ma, indicating an Eocene age for the volcanism. We show that the red clays are a product of sub-aerial chemical weathering of these Eocene volcanic rocks, in a warm-wet climate, before the thermal subsidence of the RGR to its modern-day bathymetric depth.

Early Oligocene marine transgression and organic matter accumulation recorded in the upper Eocene to lower Oligocene Enping Formation of the Baiyun Sag, Pearl River Mouth Basin, South China Sea

The upper Eocene to lower Oligocene Enping Formation provides the primary source rocks for hydrocarbon accumulation in the Baiyun Sag, Pearl River Mouth Basin, South China Sea. Nevertheless, the depositional environment of this formation has been a subject of debate. This study confirms that the lower to middle members of the Enping Formation predominantly consist of lacustrine deposits, and a marine transgression occurred during the deposition of the Enping Formation’s upper member in the Early Oligocene period. This transgression is supported by an increase in paleosalinity proxies (B/Ga, Sr/Ba), greater negative S isotopic values of pyrite, and an increase in triaromatic dinosteroid concentrations in the upper member samples. A series of indicators (chemical alteration index, V/Cr and Ni/Co ratios) suggest that mudstones from the lower–middle member and the upper member were all deposited under warm-humid climate with the dysoxic-oxic water conditions. The mudstones from the lower–middle member and upper member were formed with low-to-moderate primary productivity under relatively strong dilution condition. The paleoredox and paleoproductivity were minimally influenced by marine transgression. Additionally, there is a weak correlation between the total organic carbon content and indicators of these depositional conditions. The input of terrigenous organic matter is a pivotal factor in regulating the accumulation of organic material within the Enping Formation. The multi-stage deltas likely played a significant role in supplying terrigenous organic matter, thereby influencing the distribution of organic-rich mudstone in the Baiyun Sag.

Physiological mechanism of action and partial separation of herbicide–active compounds from the Diaporthe sp. extract on Amaranthus tricolor L.

Thirteen fungi that produce compounds with herbicidal activities were isolated, identified, and extracted under the assumption that the mechanism of action occurs during seed exposure to the extract. The extracts from all the fungal strains considerably decreased the growth parameters of Amaranthus tricolor L. The EC010 strain extracts showed the greatest effect. Through ITS region gene sequencing methods, the isolated EC010 was identified as a genus of Diaporthe. The results showed a significant (p < 0.05) inhibitory effect of 91.25% on germination and a decrease in shoot and root length by 91.28% and 95.30%, respectively. The mycelium of Diaporthe sp. was extracted using sequential extraction techniques for the partial separation of the herbicidal fraction. According to the bioassay activities, the EtOAc fraction showed the highest inhibitory activity. The osmotic stress of the A. tricolor seeds was studied. Although the extract increased the accumulation of proline and soluble protein, the treated seeds showed lower imbibition. While the activity of α-amylase was dramatically decreased after treatment. A cytogenetic assay in the treated Allium cepa L. root revealed a decrease in the mitotic index, an altered mitotic phase index, and a promotion of mitotic abnormalities. Accordingly, the Diaporthe sp. may serve as a potential herbicidal compound resource.

Mineralogy and Provenance of Iron Sand Deposits from Cipatujah and Cikalong, Tasikmalaya, West Java, Indonesia

Provenance, paleoweathering, and tectonic environment were studied on the iron sand samples taken from Cipatujah and Cikalong areas in Tasikmalaya, West Java, Indonesia using their mineralogical and geochemical data. These data were obtained from mineralogy grain analysis, X-ray fluorescence, dan ICP MS. From this study, iron sand deposits in both areas vary in grain sizes from very coarse to fine sand. Various minerals, such as magnetite, ilmenite, hematite, pyroxene, amphibole, garnet, quartz, ankerite, plagioclase, and zircon were identified. In addition, rock fragments, fossils, and clay are also found. In term of grain size, the placer deposit is geochemically classified as Fe shale (clay-silt grain size). The provenance shows that the basic rocks act as the source rock based on REE values, heavy mineral assemblage, and elemental ratios. Based on the provenance characteristics, regional geological framework, and catchment area pattern, the Jampang Formation and Young Formation of Mount Cikuray are the most possible sources of iron sand. The chemical index of alteration calculated from major oxide values indicates that the source area had intense chemical weathering. Heavy minerals contained in iron sand deposits reveal a low maturity based on compositional variability (16.58–36.55). Both iron sand deposits from Cipatujah and Cikalong originated in a continental arc setting, which coincides with the current tectonic setting of western Java.

Pedogenic processes and climatic conditions from Cretaceous (Albian) tropical paleosols of the Itapecuru Formation, Parnaíba Basin, northeast Brazil

Paleosols are an under-utilized tool for paleoenvironmental and paleoclimatic reconstruction in Brazilian intracontinental basins. The Itapecuru Formation, from the Lower Cretaceous of the Parnaíba Basin, consists of a 600-m-thick succession of interbedded very fine-to-fine-grained sandstone, mudstone, and paleosols containing rich fossil assemblages. This paper provides a detailed description of the macro and microscopic pedogenic features of a hydromorphic paleosol profile whithin the Itapecuru Formation. Analyses of clay mineralogy and whole-rock geochemistry in the hydromorphic paleosols at the Prata locality are used to infer pedogenic processes, paleoclimate, paleohumidity and paleovegetation. Estimates of paleoprecipitation and paleotemperature using climofunctions, chemical index of alteration without potassium, and paleosol weathering index proxies (PWIs) show values ranging from 810 to 1042 mm/yr (SE = ±78.1 mm/yr) and 10.9 to 11.8 °C (SE = ±0.23 °C), respectively. Climofunction values (MAP and MAT), paleohumidity, Kӧppen aridity index, and pedogenic clay mineral content suggest a humid paleoclimate during soil-forming and weathering processes. Based on these climate data and previously published paleogeographic and palynological studies, the Cretaceous (Albian) Prata pedotype was formed within the equatorial humid belt with vegetation of wet tropical forests.

Reinterpreting glacial deposits as a MTD ponding sediment gravity flows in the upper Mojón de Hierro Formation (Tepuel–Genoa Basin, Argentina)

The Late Paleozoic Ice Age (LPIA) was the longest and most extensive glacial interval during the Phanerozoic, lasting from the Late Devonian to the late Permian (362–254 Ma). Numerous questions remain on the spatial and temporal extent of the ice centers, the timing of expansion and contraction of the ice sheets, and the distribution of ice across Gondwana through time. The Tepuel–Genoa Basin, in Patagonia (Argentina) was situated within the paleo South Polar Circle and contains a nearly continuous lower Carboniferous (Tournasian) to lower Permian (Artinskian) succession. The Mojón de Hierro Formation has been described as both non-glacial and glacial in origin, but lacks detailed sedimentological descriptions. This research investigates a ∼50 m succession with sedimentological and geochemical analysis within strata in the upper portion of the Mojón de Hierro Formation at Arroyo Garrido (Chubut Province). Five stratigraphic sections were measured and the strata were categorized into five lithofacies: 1) deformed sandstones, 2) thin-bedded diamictites, 3) graded rhythmites, 4) laminated mudstones with dispersed clasts, and 5) laminated mudstones. Deposition occurred in a slope environment from debris flows, turbidity currents, mass-movements, hemipelagic sedimentation, and ice rafting. The Chemical Index of Alteration (CIA) indicates values similar to average marine shales, which suggests that the muds were supplied from temperate terrestrial sediment sources. This indicates that icebergs from a distant source transited the basin and grounded glaciers were not present in the catchment area. Vanadium/chromium ratios (V/Cr) indicate dysoxic (restricted water circulation) values in samples between the mass-transported blocks and oxic values (well circulated water) in samples stratigraphically above the filled/leveled ponded mini basin. These oxygenation conditions suggest that the mass-transport deposit formed a topography on the sea floor, resulting in a mini basin that ponded sediments within the blocks. A local glacial source was not substantiated for the upper Mojón de Hierro Formation at Arroyo Garrido neither through the detailed facies analysis nor through geochemical proxies.

Significance of conodont data for explaining geosystem perturbations during the Middle Devonian Kačák Episode

The present review of published data as well as the new results demonstrate the versatility of conodonts in documenting and explaining global environmental fluctuations related to the Kačák Episode (KE) in the latest Eifelian. Although the conodont zonation of the KE interval is ambiguous and requires revision, the compilation of conodont stratigraphic ranges shows their potential for a precise worldwide correlation of relevant marine strata. Conodont biofacies may serve to document environmental changes connected with KE, in particular the sealevel rise at its beginning, followed by a regressive trend. Nevertheless, the familiar Icriodus/Polygnathus ratio should be carefully applied as an indication of water depth and nearshore vs. offshore position, being controlled also by other factors, such as paleolatitude and/or climate. Oxygen isotopes in conodont apatite, studied using secondary ion mass spectrometry technique evidence a warming at the onset of KE, based on the new data from the open marine facies of the Prague Basin. At the same time, they indicated climate-controlled salinity fluctuations in the epeiric Belarusian Basin. The present investigations as well as previous results suggest caution when analyzing thermally altered conodonts which may result in biased oxygen isotope signatures. The present experience suggests the conodont colour alteration index CAI 3 as a boundary value above which the caution is necessary.

Biomarcadores branquiais e hepáticos para monitoramento da sanidade de duas espécies de peixes neotropicais em área lacustre maranhense, Maranhão

The aim of the current study is to histologically assess two Neotropical fish species (Hoplerythrinus unitaeniatus and Cichlasoma bimaculatum) to monitor the health of a lake zone in Maranhão State. Forty-two (42) adult fish specimens - 21 belonged to species H. unitaeniatus and 21 to species C. Bimaculatum - were captured, euthanized and had their second right gill arch and liver fragments removed for histological analysis. Histological changes in specimens’ gill and liver were semi-quantitatively assessed by calculating the histological alterations index (HAI) based on the severity of each lesion established as stages I, II and III. Results recorded for both species were presented together; they evidenced that both assessed organs have shown changes associated with all three severity stages. Gill changes mostly observed through the analysis comprised total (85.71%) and partial (85.71%) fusion of several lamellae, epithelial lifting (80.95%), congested blood vessels (76.19%), disorganized lamellae, (76.19%) and lamellar epithelial hyperplasia (76.19%) - stage I alterations. The most common liver changes comprised vacuolization (90.48%), melanomacrophage centers (78.57%), cellular contour deformation (66.67%) and nucleus at cell periphery (52.38%), stage I alterations and hyperemia (45.24%) and cytoplasmic degeneration (40.48%) - stage II. Unlike the HAI indices recorded for gills, liver HAI values presented better distributed rates among severity classifications; therefore, it has evidenced a more severe condition. Thus, both organs analyzed in the investigated species have shown several histological changes that may have resulted from specimens interactions with stressors capable of affecting their health.