A Semi-Quantitative Assessment of Clay Content in Sedimentary Rocks Using Portable X-Ray Fluorescence Spectrometry

This paper deals with assessment of clay content in sedimentary rocks using portable X-ray fluorescence spectrometry. Whilst measuring chemical properties of sedimentary rocks, it was noted a positive, quasi-linear correlation between the rock’s Rb concentration and both percentage of clay fraction, and equally gamma ray emission. Rb is relatively easy to measure and provides a semi-quantitative assessment of a sedimentary rock’s clay content. The measurement error of the tool is less than 10 %. Initial data indicate that the measurement is sensitive to clay mineral composition, given some samples deviate from others showing higher or lower-thanexpected values. In clastic sediments, the Rb-XRF method can be used as an alternative to Gamma-Ray in determining clay content, such as to describe the cleanness of sand. Furthermore in carbonate rocks, the XRFmeasurements can be used to fairly accurately determine the content of clay. In such way, industrial carbonate hardrock’s, clay content can be correlated with rock strength. By using XRF, it was demonstrated in the ‘failed’ Kpg.Opak quarry that the clay content some 20 % in the rock matrix. The high clay content is responsible here for areduced industrial quality of the hard rock. With this method, limestone strength can be estimated on the spot. Withproper calibration, the tool might also be used to detect clay mineral composition semi-quantitatively

Borneo coral reefs subject to high sediment loads show evidence of resilience to various environmental stressors

For reefs in South East Asia the synergistic effects of rapid land development, insufficient environmental policies and a lack of enforcement has led to poor water quality and compromised coral health from increased sediment and pollution. Those inshore turbid coral reefs, subject to significant sediment inputs, may also inherit some resilience to the effects of thermal stress and coral bleaching. We studied the inshore turbid reefs near Miri, in northwest Borneo through a comprehensive assessment of coral cover and health in addition to quantifying sediment-related parameters. Although Miri’s Reefs had comparatively low coral species diversity, dominated by massive and encrusting forms of Diploastrea, Porites, Montipora, Favites, Dipsastrea and Pachyseris, they were characterized by a healthy cover ranging from 22 to 39%. We found a strong inshore to offshore gradient in hard coral cover, diversity and community composition as a direct result of spatial differences in sediment at distances <10 km. As well as distance to shore, we included other environmental variables like reef depth and sediment trap accumulation and particle size that explained 62.5% of variation in benthic composition among sites. Miri’s reefs showed little evidence of coral disease and relatively low prevalence of compromised health signs including bleaching (6.7%), bioerosion (6.6%), pigmentation response (2.2%), scars (1.1%) and excessive mucus production (0.5%). Tagged colonies of Diploastrea and Pachyseris suffering partial bleaching in 2016 had fully (90–100%) recovered the following year. There were, however, seasonal differences in bioerosion rates, which increased five-fold after the 2017 wet season. Differences in measures of coral physiology, like that of symbiont density and chlorophyll a for Montipora, Pachyseris and Acropora, were not detected among sites. We conclude that Miri’s reefs may be in a temporally stable state given minimal recently dead coral and a limited decline in coral cover over the last two decades. This study provides further evidence that turbid coral reefs exposed to seasonally elevated sediment loads can exhibit relatively high coral cover and be resilient to disease and elevated sea surface temperatures

Subsurface Hydrogeochemical Processes in Lower Bhavani River Basin, Tamil Nadu, India

Bhavani River is one of the important tributaries of Cauvery River, and originates in the Silent Valley range of Kerala State, India. The Lower Bhavani River Basin lies between 11 15' N and 11 45' N latitudes and 77 00' E and 77 40' E longitudes with an area of 2,475 km2. Variation of groundwater quality in an area is a function of physical and chemical parameters that are greatly influenced by geological formations, recharge-discharge mechanisms of groundwater and anthropogenic activities. The correlation of groundwater chemistry with hydrologic and geologic environments gives valuable information to understand the effect of these processes and to properly manage aquifer systems. A detailed study has been carried out to understand the subsurface hydrogeochemical processes that are responsible for the quality variation of groundwater. Residence time of groundwater was also considered to be an important parameter to study groundwater evolution. The NETPATH computer code was used to model the major subsurface processes contributing to the evolution of groundwater chemistry. The occurrence of such chemical processes as silicate weathering, carbonate dissolution, ion exchange and dilution due to rain were verified by performing inverse mass balance modeling using the same code. The net geochemical mass balance reactions between initial and final water were identified and quantified based on the flow in selected well pairs. The model output shows that dilution, ion exchange and illite precipitation are the dominant processes that control the chemistry of the groundwater along the flow paths. Calcite and NaCl dissolution are also involved to a certain extent. Reverse ion exchange process is also observed in two models

Influence of Roller Ball Tool in Single Point Incremental Forming of Polymers

Polymers defend the metals in making complex geometries because of their strength to weight ratio. Utilizing the conventional process has become a challenge in manufacturing customized products. Increase in demand of tailored products in minimum quantities with preferred quality creates the need for developing new techniques. Incremental forming process is an emerging flexible technology that can obtain pre-defined profiles through deformation of metals and polymers in desired thickness at a reasonable cost. In this work, single point incremental forming (SPIF) of different polymer materials is done using roller ball tool and modest fixture system. Materials such as polyvinyl chloride (PVC), polypropylene (PP), polycarbonate (PC), high density poly ethylene (HDPE) are considered for this investigation due to high applications in automobile and biomedical area. The experiments are designed to analyse the influence of variable process parameters such as tool diameter, step size, spindle speed and sheet thickness. The analysis is carried out by characterizing the formability with depth of failure, thickness distribution, surface roughness and microstructure evaluation. Based on the result, the spindle speed and sheet thickness show high response in formability, surface roughness and depth of failure. The tool diameter has a significant effect on the surface roughness. PVC shows the springback resistance and cracks are observed in the circumferential route on the transition area among the bottom and side wall portion

Interpretation of paleoenvironment using benthic foraminifera from Tertiary rocks, northern Sarawak

In this work, we collected and examined three samples from an exposed 50 cm thick fossiliferous bed and prepared thin and polished sections for petrographic analysis. The benthic foraminifera assemblages and other marine fossils are studied to infer the paleo depositional environment. Based on the benthic foraminifera and their common ecological preferences, it is inferred that this layer has deposited between the intertidal and neritic zones, and within the photic zone, they are under oxygenated conditions. In addition, the presence of the glauconite mineral also supported the neritic environment interpretation, suggesting a water depth of less than 300 metres during the deposition, denoting shallow water conditions. Even though the results presented in this paper are at an elementary level, this could serve as additional information to develop a better understanding of the geology on a much larger scale

Geochemistry of Neoproterozoic limestones of the Shahabad Formation, Bhima Basin, Karnataka, Southern India

Major, trace and rare earth element (REE) geochemistry of carbonate rocks of the Neoproterozoic Shahabad Formation, Southern India were studied in order to investigate the depositional environment and source for the REEs. The PAAS (Post Archaean Australian Shale) normalized REE + Y pattern of Shahabad limestones have consistent seawater-like pattern i.e., i) LREE depletion (average (Nd/Yb)SN = 0.64 ± 0.08), ii) negative Ce anomaly, iii) positive Gd anomaly (average GdSN/Gd* = 1.05 ± 0.16), iv) superchondritic Y/Ho ratio (average Y/Ho = 38.13 ± 21.35). The depletion of LREE and enrichment of HREE are clearly indicated by the (La/Yb)SN, (Dy/Yb)SN and (Nd/Yb)SN ratios, which suggest the retention of seawater characteristics in these limestones. The negative Ce anomaly reflects the incorporation of REE directly from seawater or from the pore water under oxic condition, and also reveals the mixing of two-component systems with terrigenous clay (detrital) in the marine sediments. The terrigenous input in these limestones is confirmed by positive correlation of ΣREE with Al2O3, negative correlation of ΣREE with CaO and differences in Y/Ho ratios. V, Cr, and Sc, are positively correlated with Ti, and strong positive correlation of ΣREE with Fe2O3, Ni, Cr, Sc, and Y also indicate the presence of terrigenous materials in the Shahabad limestones

Epiphreatic caves in Niah karst tower (NW Borneo): occurrence, morphology and hydrogeochemistry

Epiphreatic caves develop close to the water table at the boundary between vadose and phreatic karst zones. The recognition of their former existence and position in uplifted limestone regions can inform on phases of uplift, base level lowering and rate of vertical deepening of the karst. Hence, epiphreatic caves and the karst processes that form them are of specific interest. Although the large and spectacular caves of Niah have been subject of much research and interest, the existence of small epiphreatic caves at the foot of the karst towers has not previously been documented in this region of NW Borneo. The study documents and reports an epiphreatic cave passage at water table elevation in the Painted Cave karst tower where several large caves are also known. The semi-flooded passage is over 480 m long and traverses the tower from east to west, intersecting other much larger vadose caves. The epiphreatic flow path is characterized by a number of sinking streams and resurgences as well as several sharp bends in the passage indicating joint control. As an initial attempt this study was undertaken to correlate the water chemistry along the cave path to understand the geomorphological controls. A preliminary campaign of water sampling was carried out with samples collected at ten locations along the path of the cave stream and analyzed for pH, EC, TDS, DO, Eh, major ions, nutrients and trace metals. The results show that dissolution of host rock and leaching of organic matter are the dominant controlling factors for the geochemistry of surface water along the cave stream passage. During dry conditions the water was under-saturated for carbonate minerals but not aggressive suggesting that most dissolution and erosion occurs during flood conditions. This is supported by the morphology of the passages and features of the rock wall both inside the caves and at the foot of the karst tower. Key words: Karst, Niah cave, Epiphreatic, Hydrogeochemistry, water table.Jame epifreatične cone v kraškem stolpu Niah (severozahodni Borneo): pojavnost, morfologija in hidrogeokemija Epifratične jame nastajajo na meji med vadozno in freatično cono. Prepoznavanje epifreatičnih elementov v bloku dvignjenega masiva nam omogoča razbrati faze dvigovanja masiva oz. spuščanja erozijske baze, zato so epifreatične jame in procesi še posebno zanimivi. Čeprav so o jamah stolpa Niah opravili številne študije, nobena od teh ne obravnava epifreatičnih jam ob vznožju kraškega stolpa. Ta študija obravnava epifreatične rove na ravni vodne gladine v stolpu Painted Cave v severozahodnem Borneu, kjer sicer poznamo več velikih jam. Delno potopljen rov je dolg več kot 480 m in preči stolp od vzhoda proti zahodu ter pri tem seka še več drugih, veliko večjih vadoznih jam. Epifreatični tok je povezan z več ponikalnicami in izviri, zanj so značilne nagle spremembe smeri, ki sledi vodilnim razpokam. Namen študije je povezati kemijo vode vzdolž toka in aktivne geomorfološke dejavnike. Vzorčenje in analize vode na desetih lokacijah so dali podatke o pH, električni prevodnosti, skupni raztopljeni snovi (TDS), raztopljenem kisiku, Eh ter o koncentraciji glavnih ionov, hranil in kovin v sledeh. Rezultati so pokazali, da sta raztapljanje matične kamnine in izpiranje organskih snovi prevladujoča dejavnika geokemije vode v kanalu. V sušnem obdobju je voda rahlo nenasičena na kalcit, a je agresivnost majhna, kar kaže na to, da glavna faza razvoja poteka v poplavnih obdobjih. To potrjujejo tudi morfologija rova in jamske skalne oblike v jami in ob vznožju kraškega stolpa.Ključne besede: kras, jama Niah, epifreatična cona, hidrogeokemija, vodna površina.

Evidences for Extreme Wave Events in Velanganni Coast, Southeast of India

The present study focuses on sediment grain size, microfossil content and heavy minerals present in the sediments collected from a trench in the southeast coast of India in order to identify the frequent extreme wave events (e.g. storm surge, cyclone, tsunami, etc.). Two different depositional events were identified at different depths with distinct sedimentological, mineralogical and microfossil characteristics. These geological features further improve the understanding of depositional sequences in this region

Carbon, oxygen, and strontium isotope geochemistry of the Proterozoic carbonate rocks, Bhima basin, south India: Implication for diagenesis

A carbonate dominated shallow marine Proterozoic Bhima basin consists of carbonates and clastic rocks, and is widely distributed in the northern part of the Karnataka state, south India. Limestones of the Shahabad Formation have been selected for this study and secular variations in C, O, and Sr isotope compositions are reported. δ13C values are varying from +3.50 to -1.38‰PDB. Similarly, the δ18O values recorded a range between -5.76 and -12.93‰PDB 87Sr/86Sr ratio for these limestones is varying between 0.70699 and 0.7117. Higher burial rate of organic matter could have been responsible for the positive δ13C values, which is common in the Proterozoic carbonate rocks. The δ18O values in most of the samples are similar to the average value of the Proterozoic carbonate rocks. Albeit some of the samples are modified in their original isotopic signature, which shows high negative δ18O values 1.5 and a negative trend between δ18O and 87Sr/86Sr, suggesting that the δ18O and 87Sr/86Sr isotopic signatures of Bhima carbonates have been altered by diagenesis. The post depositional diagenetic alteration is also supported by the petrographic characters of these carbonates

Groundwater Geochemistry of Neyveli Lignite Mine-Industrial Complex, Tamil Nadu, India and Its Suitability for Irrigation

This study was undertaken to assess the quality of groundwater for irrigation and level of trace metal concentration in the surface and groundwater bodies from Neyveli lignite mine-industrial complex which is located in Cuddalore district, Tamil Nadu, India. The hydrogeology of the Neyveli groundwater basin is extremely complex, consisting of a series of productive, confined aquifers below the lignite seam in both Mine I and II areas, while a semi-confined aquifer lies above the seam and occurs only in the Mine II area. The suitability of groundwater quality for agricultural purposes in and around Neyveli lignite mine-industrial complex was assessed by measuring physicochemical parameters, including major cation and anion compositions, pH, total dissolved solids, electrical conductivity, and trace metals. The results of the chemical analysis of the groundwater showed that concentrations of ions vary widely and the most prevalent water type is mixed CaNaHCO3, followed by other water types: mixed CaMgCl types and NaCl which is in relation with their interactions with the geological formations of the basin, dissolution of feldspars and chloride and bicarbonate minerals, and anthropogenic activities. The most dominant class is C1-S1, C2-S1 (85% PRM and 74% POM) in the study area, indicating that sodicity is very low and salinity is medium, and that these waters are suitable for irrigation in almost all soils.Based on sodium absorption ratio the groundwater of the study area is suitable for all types of crops and soil except for those crops sensitive to Na and based RSC values of the groundwater, considered safe. Based on the parameters such as TDS, EC, SO4, Cl and Wilcox diagram about 99% of samples are suitable for irrigation. The average concentration of trace metals (Fe, Mn, Cr, Zn, Pb, and Cu) in groundwater samples fall within the permissible limit, with the exception of Ni which is recorded higher than the permissible limit which may retard growth and metabolic activities while the groundwater used for irrigation