Permo-Carboniferous Climate Change: Geochemical Evidences from Lower Gondwana Glacial Sediments, Rangit Valley, Sikkim Lesser Himalaya, India

2021 ◽  
Vol 7 (1) ◽  
pp. 1-11
Author(s):  
Raj Kumar Priya ◽  
Vinod Chandra Tewari ◽  
Rakesh Kumar Ranjan
Keyword(s):  
Climate Change ◽  
Chemical Weathering ◽  
Depositional Environment ◽  
Lesser Himalaya ◽  
Glacial Sediments ◽  
Source Areas ◽  
Chemical Index ◽  
Chemical Index Of Alteration ◽  
Compositional Variability ◽  
Stratigraphic Sequences

The Rangit Gondwana Basin of Sikkim in the lesser Himalaya witnessed a wide span of climate change during the Permo-Carboniferous period. The principal objective of the present study is to document this Permo-Carboniferous climate change in the form of a geochemical signature preserved in the siliciclastic facies of the Rangit Pebble Slate Formation. The stratigraphic sequences of the Rangit Gondwana Basin are categorically well defined and subdivided into upper and lower sequences on the basis of their depositional environment. The lower sequences of the Rangit Gondwana basin are comprised of massive diamictite with large stromatolitic dolomite boulders and dropstone embedded in the coarser sandstone which indicate the cold glaciomarine environment of deposition, whereas upper sequences consist of repeated alternate beds of sandstone, black shale and coal seam with a regular interval depicting the fluvial and deltaic environment of deposition. The enrichment of SiO2, Al2O3, TiO2, MnO, MgO, and K2O indicates that these sediments were mostly derived from felsic rock source areas. Chemical Index of Alteration (CIA) and Index of Compositional Variability (ICV) CaO + Na2O + K2O/Al2O3, and SiO2 vs. (Al2O3 + K2O + Na2O) values suggest that the sediments maturity and paleoclimatic environment deposition of the sediments of lower sequences was cold and semi-humid whereas the deposition of sediments of upper sequences was warm and humid. The A-CN-K ternary plot and CIA vs ICV binary plot also indicate and verify that the source areas were subjected to prolonged intense chemical weathering from low to high grade due to shifting of cold to warm humid paleo-climatic condition.

Reconstructing chemical weathering during the Lower Mesozoic in the Western-Central Mediterranean area: a review of geochemical proxies

2017 ◽  
Vol 155 (4) ◽  
pp. 944-954 ◽  
Author(s):  
FRANCESCO PERRI
Keyword(s):  
Rift Valley ◽  
Chemical Weathering ◽  
Mineralogical Composition ◽  
Mediterranean Area ◽  
Climatic Changes ◽  
Central Mediterranean ◽  
Geochemical Proxies ◽  
Chemical Index ◽  
Chemical Index Of Alteration ◽  
Mineralogical Compositions

AbstractThe Triassic–Jurassic rift-valley stage of Tethyan rifting in the Western-Central Mediterranean area is characterized by a development of a puzzle of plates and microplates with the deposition of continental redbeds (in the internal domains of the Gibraltar Arc and Calabria–Peloritani Arc) that can be considered a regional lithosome. This paper aims to reconstruct the chemical weathering conditions of the Triassic–Jurassic boundary in the Western-Central Mediterranean area using the geochemical and mineralogical composition of continental redbed mudrocks of Mesozoic age. The mudrocks from the Calabria–Peloritani Arc show higher values of weathering (mobility) indices (αMg=(Al/Mg)sed/(Al/Mg)UCC;αK=(Th/K)sed/(Th/K)UCC;αBa=(Th/Ba)sed/(Th/Ba)UCC) than the Gibraltar Arc samples. Furthermore, the CIA (Chemical Index of Alteration) and MIA (Mineralogical Index of Alteration) values and the ‘Rb-type indices’ (e.g. Rb/Sr and Rb/K ratios) are higher for the Calabria–Peloritani Arc mudrocks than the Gibraltar Arc samples. All these geochemical proxies closely resemble each other and show similar variations suggesting climatic changes towards humid conditions through the Uppermost Triassic to Lowermost Jurassic that favoured chemical weathering conditions. This period is probably characterized by seasonal climate alternations corresponding to an increase in palaeoclimatic humidity. The mineralogical compositions of the Mesozoic mudrocks further confirm these indications as shown by a higher abundance of kaolinite, related to warm–humid conditions, in the Calabria–Peloritani Arc mudrocks than in those of the Gibraltar Arc.

The lower Proterozoic Fern Creek Formation, northern Michigan: mineral and bulk geochemical evidence for its glaciogenic origin

2002 ◽  
Vol 39 (4) ◽  
pp. 481-492 ◽  
Author(s):  
Anne Argast
Keyword(s):  
Rare Earth ◽  
Chemical Weathering ◽  
Chemical Index ◽  
Quartz Arenite ◽  
Bulk Chemical ◽  
Chemical Index Of Alteration ◽  
Rare Earth Mineral ◽  
Chemical Trends ◽  
Northern Michigan ◽  
Bulk Chemistry

Bulk chemical data indicate the Fern Creek Formation (Early Proterozoic, Marquette Range Supergroup, Lower Chocolay Group) originated as a glacial till, resolving an old argument about the correct interpretation for diamictite-containing units within the formation. There are poor correlations among SiO2, Al2O3, and K2O, and the chemical index of alteration averages 55. These are qualities characteristic of tills and other sediments accumulated in the absence of chemical weathering and transport-induced sorting and inconsistent with an origin as a fluvial deposit (the principal alternate hypothesis). The Archean Carney Lake Gneiss might be the source for at least the lower portions of the Fern Creek Formation. Compositions are similar, and rare earth element trends in the Fern Creek Formation are consistent with derivation from an Archean high-grade terrane. Pegmatites in the gneiss could be the source for monazite, huttonite, and an unnamed fluor-hydroxy-rare earth mineral that occurs in the midsection of the Fern Creek Formation. In addition, mineral and bulk chemical trends are consistent with models involving deep erosion of a complex Archean source, similar to models previously developed for Gowganda tills in the Huronian Supergroup. Samples of the Sturgeon River Quartzite occurring above the Fern Creek Formation were also analyzed. The bulk chemistry is consistent with a well-sorted, supermature quartz arenite.

scholarly journals Assessing sediment pollution by applying some geochemical indices for Al-Wind River banks/ East of Iraq

2019 ◽  
pp. 1711-1719
Author(s):  
Iman A. Al-Ali
Keyword(s):  
Enrichment Factor ◽  
Chemical Weathering ◽  
Contamination Factor ◽  
Anthropogenic Pollution ◽  
Sediment Pollution ◽  
Pollution Indices ◽  
Polluted Sediments ◽  
Chemical Index ◽  
Chemical Index Of Alteration ◽  
Cu And Zn

15 sediment samples were collected; 8 samples from the eastern bank, and 7 samples from the western bank of Al-Wind River in Diyala governorate to assess the sediment pollution in some trace elements such as Fe, Ni, Cd, Zr, Zn and Cu in addition to some oxides such as Al2O3, CaO, Na2O and K2O to find the effect of anthropogenic pollution and the industrial production on the sediment closed especially Naftkhana by using some geochemical pollution indices such as: geoaccumulation factor (I-geo), enrichment factor (EF),contamination factor (CF), pollution loud index (PLI) and to evaluate the degree of weathering by Applying the Chemical Index of Alteration (CIA)in both banks of Al-Wind River. The results of general contamination factors indicate that the eastern bank of Al-Wind River especially that closed by Naftkhana area having quite more concentrations of trace element and oxides from the western bank. The results of I-geo presents unpolluted sediment with Pb and Fe and slightly polluted with Zn, Cu, and Ni in both banks, while the western bank in some locations recorded of moderately polluted sediments with Ni and slightly to moderately polluted sediments with Cu and Zn and reach moderately severely polluted in the eastern bank. The contamination factor (CF) for Ni and Zr classified as class 2 which indicate moderately contamination to severely pollute in both banks, while Fe, Pb, Cu and Zn conbankred unpolluted in both banks. Enrichment factor (EF) for Fe, Pb, Zr and Cu are conbankred deficiency to low enrichment the range of natural variability, while Ni record  high values reached to 6.4 indication of anthropogenic inputs. Pollution load Index (PLI) is perfection and classified as class 0 in both banks. Chemical index of alteration (CIA) reflecting the chemical weathering intensity especially for the western bank.

scholarly journals Geochemistry of Selected Kaolins from Cameroon and Nigeria

2017 ◽  
Vol 9 (1) ◽  
Author(s):  
Nenita N. Bukalo ◽  
Georges-Ivo E. Ekosse ◽  
John O. Odiyo ◽  
Jason S. Ogola
Keyword(s):  
Source Rock ◽  
Industrial Applications ◽  
Factor Analyses ◽  
Major Phase ◽  
Rock Types ◽  
Major Oxides ◽  
Chemical Index ◽  
Geochemical Indices ◽  
Chemical Index Of Alteration ◽  
Compositional Variability

AbstractThe geochemical characteristics of selected kaolins from Cameroon and Nigeria are presented, with an attempt to elucidate on their possible industrial applications by comparing them to world-known kaolin deposits. Major oxides concentrations were subjected to factor analyses in interpreting their relationships. Geochemical indices, including chemical index of alteration (CIA), chemical index of weathering (CIW) and the index of compositional variability (ICV) were computed and plotted on binary and ternary diagrams to determine the intensity of weathering of the kaolins and discriminate their different source rock types. Kaolinite was the major phase, followed by quartz, illite and goethite as minor phases. Minerals in trace phases included smectite, anatase, muscovite, gibbsite, microcline, palygorskite and calcite. Mean abundances of major oxides in wt% were: SiO

scholarly journals Potassium-metasomatism in Anthracite: A Cluster of Geochemical Evidences

2021 ◽  
Author(s):  
Santanu Ghosh ◽  
Anwita Ojha ◽  
Atul Kumar Varma
Keyword(s):  
Source Rock ◽  
Chemical Weathering ◽  
Bituminous Coal ◽  
Climatic Conditions ◽  
Rock Composition ◽  
Thrust Belts ◽  
Chemical Index ◽  
Parent Rocks ◽  
Chemical Index Of Alteration ◽  
The Fourier Transform

Abstract The present study focuses on the inorganic geochemical features of the bituminous coal samples from the Raniganj and the Jharia Basin, as well as the anthracite samples from the Himalayan fold-thrust belts of Sikkim, India. The SiO2 content (48.05 to 65.09 wt% in the ash yield of the bituminous coal samples and 35.92 to 50.11 wt% in the ash yield of the anthracite samples) and the ratio of Al2O3/TiO2 (6.97 to 17.03 in the bituminous coal samples and 10.34 to 20.07 in the anthracite samples) reveal the intermediate igneous source rock composition of the minerals. The ratio of the K2O/Al2O3 in the ash yield of the bituminous coal samples (0.03 to 0.09) may suggest the presence of kaolinite mixed with montmorillonite, while its range in the ash yield of the anthracite samples (0.16 to 0.27) may imply the presence of illite mixed with kaolinite. The chemical index of alteration values may suggest the moderate to strong chemical weathering of the source rock under sub-humid to humid climatic conditions. The plot of the bituminous coal samples in the A-CN-K diagram depicts the traditional weathering trend of parent rocks, but the anthracite samples plot near the illite field and are a bit offset from the weathering trend. This may imply the plausible influences of the potassium-metasomatism at post coalification stages. The Fourier transform infrared spectra further reveal the hydroxyl stretching intensity of the illite in the anthracite samples substantiating the effect of the epigenetic potassium-metasomatism. The decrease in total kaolinite intensity/compound intensity of quartz and feldspar may provide additional evidence towards this epigenetic event.

Provenance and geochemical variations across the Ediacaran–Cambrian transition in the Soltanieh Formation, Alborz Mountains, Iran

2018 ◽  
Vol 156 (07) ◽  
pp. 1157-1174 ◽  
Author(s):  
NAJMEH ETEMAD-SAEED ◽  
MAHDI NAJAFI
Keyword(s):  
Chemical Weathering ◽  
Tectonic Setting ◽  
Geochemical Data ◽  
Remarkable Change ◽  
Northern Iran ◽  
Magmatic Arc ◽  
Chemical Index ◽  
Geochemical Variations ◽  
Chemical Index Of Alteration ◽  
Mountain Belts

AbstractThe Soltanieh Formation in the Alborz Mountains of northern Iran is not only a key lithostratigraphic unit for reconstruction of the Iranian geological history, but also a globally outstanding succession to reveal variations in seawater composition across the Precambrian–Cambrian (PC–C) transition. Mineralogical and geochemical data from a continuous stratigraphic record of Lower and Upper Shale members of the Soltanieh Formation are used to define their provenance, tectonic setting as well as geochemical variations during the PC–C transition. The Soltanieh mudrocks are composed of quartz and plagioclase, with minor constituents of illite, chlorite and montmorillonite. The chemical index of alteration, A-CN-K (Al2O3 – CaO + Na2O – K2O) relations, index of compositional variability, and Th/Sc versus Zr/Sc ratios indicate low chemical weathering in source areas, compositionally immature and first-cycle sediments. Immobile trace-element ratios and discrimination diagrams, chondrite-normalized rare Earth element (REE) patterns and negative Eu anomaly, along with low total REE abundances and negligible Ce anomalies, demonstrate that the Soltanieh Formation was mainly derived from proximal felsic-intermediate Cadomian magmatic arc sources and deposited in a continental-arc-related basin on the proto-Tethyan active margin of Gondwana. The palaeoredox indicators exhibit a remarkable change in environmental condition from a suboxic to an oxic state across the PC–C transition from the Kahar Formation to the Upper Shale Member of the Soltanieh Formation. Moreover, a significant upwards increase of P, Ba, and Ca is likely associated with enhanced fluxes of nutrient elements during the PC–C transition, coeval with the building of collisional mountain belts during the amalgamation of Gondwana.

Neoproterozoic Blaini Formation of Lesser Himalaya, India: Fiction and Fact

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2267-2281
Author(s):  
Sumit Dey ◽  
Prabir Dasgupta ◽  
Kaushik Das ◽  
Abdul Matin
Keyword(s):  
Snowball Earth ◽  
Turbidity Currents ◽  
Rift System ◽  
Lesser Himalaya ◽  
Glacial Origin ◽  
Chemical Index ◽  
The Matrix ◽  
Chemical Index Of Alteration ◽  
Fault Scarps ◽  
Different Levels

Abstract The long-conceived idea of the glacial origin of Blaini diamictite of Lesser Himalayan Neoproterozoic succession reached its maxima when the diamictites and capping pink limestone were attributed to the Neoproterozoic Snowball Earth event and its aftermath, respectively. Occurrences of diamictite-limestone association in two different levels have also been correlated with the Sturtian and Marinoan glaciations. Critical review, however, reveals that the interpretations of the glacial origin of diamictites are not well founded. The diamictite-limestone association, which occurs at the lower part of a thick, light brown shale unit and laterally grades into light brown shale, primarily indicates episodic surge events in an otherwise tranquil condition favorable for hemipelagic sedimentation. The lithology, bed geometry, internal organization, and disposition of the diamictite bodies suggest deposition of debris flow fan lobes along fault scarps in a rift setting. Emplacement of subaqueous debris flows is indicated by the associated deposits of entrained turbidity currents. The limestone also bears the signature of claciturbidites. The appearance of diamictite bodies and associated limestone in two distinct levels is not a stratigraphic disposition; on the contrary, the deposits were dislocated and repeated by two successive regional thrust faults. The Chemical Index of Alteration (CIA) values of the light brown shale and the matrix of the diamictites indicate that these sediments formed through prolonged subaerial weathering. The events leading up to development of the rift system and evidence of prolonged weathering within the basin-fill sediments are consistent with supercontinental break up, the prologue of Snowball Earth.

scholarly journals Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation

2020 ◽  
Vol 133 (1-2) ◽  
pp. 379-392 ◽  
Author(s):  
Lily S. Pfeifer ◽  
Gerilyn S. Soreghan ◽  
Stéphane Pochat ◽  
Jean Van Den Driessche
Keyword(s):  
Chemical Weathering ◽  
Ice Age ◽  
Coarse Grained ◽  
Mean Annual Temperature ◽  
Fine Grained ◽  
Chemical Index ◽  
Low Degree ◽  
Low Latitudes ◽  
Chemical Index Of Alteration ◽  
Unique Distribution

Abstract Carboniferous–Permian strata in basins within the Central Pangean Mountains in France archive regional paleoequatorial climate during a unique interval in geological history (Pangea assembly, ice-age collapse, megamonsoon inception). The voluminous (∼1.5 km) succession of exclusively fine-grained red beds that comprises the Permian Salagou Formation (Lodève Basin, France) has long been interpreted to record either lacustrine or fluvial deposition, primarily based on a local emphasis of subaqueous features in the upper ∼25% of the section. In contrast, data presented here indicate that the lower-middle Salagou Formation is dominated by up to 15-m-thick beds of internally massive red mudstone with abundant pedogenic features (microscale) and no evidence of channeling. Up-section, limited occurrences of ripple and hummocky cross-stratification, and mudcracks record the intermittent influence of shallow water, but with no channeling nor units with grain sizes exceeding coarse silt. These data suggest that the most parsimonious interpretation for the Salagou Formation involves eolian transport of the sediment and ultimate deposition as loess in shallow, ephemeral lacustrine environments. Provenance analyses of the Salagou Formation indicate coarse-grained protoliths and, together with geochemical proxies (chemical index of alteration [CIA] and τNa) that correspond respectively to a low degree of chemical weathering and a mean annual temperature of ∼4 °C, suggest that silt generation in this case is most consistent with cold-weathering (glacial and associated periglacial) processes in the Variscan highlands. Together with previous studies that detailed voluminous Permian loess in western equatorial Pangea, this work shows a globally unique distribution of dust at low latitudes that can be linked either directly to glaciated alpine terranes or to reworked and deflated deposits of other types (e.g., fluvial outwash) where fine-grained material was originally generated from glacial grinding in alpine systems. These results further support a revised model for early Permian climate, in which extratropical ice sheets coexisted with a semiarid tropics that may have hosted significant ice at moderate elevation.

Chemical weathering and physical erosion rates along a vegetation and climate gradient, Chilean Coastal Cordillera (26° – 38°S)

2020 ◽  
Author(s):  
Mirjam Schaller ◽  
Todd A. Ehlers
Keyword(s):  
Chemical Weathering ◽  
Annual Precipitation ◽  
Mean Annual Precipitation ◽  
Weathering Rates ◽  
Coastal Cordillera ◽  
Erosion Rates ◽  
Denudation Rates ◽  
Chemical Index ◽  
Chemical Index Of Alteration ◽  
Physical Erosion

<p>Chemical weathering and physical erosion are important processes shaping topography, producing soils, and providing nutrients for life.  The rates of these processes are influenced not only by tectonics, but also by climate and biota.  The Chilean Coastal Cordillera from 26° to 38°S is a natural laboratory to investigate chemical weathering and physical erosion rates over different climatic settings.  From North to South, climate changes from arid (Pan de Azúcar), semi-arid (Santa Gracia), Mediterranean (La Campana) to temperate humid (Nahuelbuta).  Here we present chemical weathering and physical erosion rates based on published and new in situ-produced cosmogenic nuclides and immobile elements published from soil pedon depth profiles in the four study areas.</p><p>Calculated chemical weathering rates range from zero in Pan de Azúcar to an high value of 211 t/(km<sup>2</sup> yr) in La Campana.  Chemical weathering rates are comparable in Santa Gracia and Nahuelbuta (~20 t/(km<sup>2</sup> yr).  Physical erosion rates are low in Pan de Azúcar (~11 t/(km<sup>2</sup> yr)) and increase towards the South (~ 40 t/(km<sup>2</sup> yr)).  Combined chemical weathering and physical erosion rates indicate that denudation rates are lowest in Pan de Azúcar and highest in La Campana.  The contribution of chemical weathering to total denudation rates is increasing and then decreasing with increasing mean annual precipitation from North to South.  The observation that the calculated chemical weathering rates in the southernmost location with the highest mean annual precipitation and the highest chemical index of alteration are not the highest of all four study areas is evaluated and discussed.   We investigate possible influence of precipitation and vegetation on chemical weathering and physical erosion rates.</p>

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