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Wadi Khuda-Wadi Shut area in the South Eastern Desert (SED) of Egypt is mainly made up of gneisses, ophiolitic serpentinites and intermediate schistose metavolcanics. These metamorphic rock units are intruded by syn-late-tectonic diorite, granodiorite, ultramafic-mafic, and monzogranite intrusions. The gneisses comprise biotite hornblende gneiss, hornblende gneiss and migmatites. They are of granodiorite and diorite composition. The ophiolitic serpentinite with talc carbonate rocks were thrusted over the metavolcanics with NW-SE thrust contact. The late tectonic ultramafic-mafic rock units are represented in the study area by Dahanib pluton, which is consisted of layered peridotite-dunite associated with olivine gabrro, normal gabbro and gabbro-norite as well as rare hornblende gabbro. These varieties are related to the layered intrusions rather than Alaskan-types, and formed by magmatic differentiation. The granodiorite and monzogranite represent the youngest basement rock units in the study area. The principal components and band ratios of ASTER and Landsat-8 data were successfully used for the first time in lithological discrimination and geological mapping of the study area. This study concluded that, the interpreted data of ASTER and Landsat-8 combined with field study and petrographic investigation clearly discriminated the exposed rock units. Accordingly, a detailed geological map emphasizing the lithological units in Khuda-Shut area has been presented.

The Chinese North Tianshan (CNTS) in the southern part of the Central Asian Orogenic Belt (CAOB) has undergone multistage accretion-collision processes during Paleozoic time, which remain controversial. This study addresses this issue by tracing the provenance of Late Paleozoic sedimentary successions from the Bogda Mountain in the eastern CNTS through U–Pb dating and Lu–Hf isotopic analyses of detrital zircons. New detrital zircon U–Pb ages (N ​= ​519) from seven samples range from 261 ​± ​4 ​Ma to 2827 ​± ​32 ​Ma. The most prominent age peak is at 313 ​Ma and subordinate ages vary from 441 ​Ma to 601 ​Ma, with some Precambrian detrital zircon ages (~7%) lasting from 694 ​Ma to 1024 ​Ma. The youngest age components in each sample yielded weighted mean ages ranging from 272 ​± ​9 ​Ma to 288 ​± ​5 ​Ma, representing the maximum depositional ages. These and literature data indicate that some previously-assumed “Carboniferous” strata in the Bogda area were deposited in the Early Permian, including the Qijiaojing, Julideneng, Shaleisaierke, Yangbulake, Shamaershayi, Liushugou, Qijiagou, and Aoertu formations. The low maturity of the sandstones, zircon morphology and provenance analyses indicate a proximal sedimentation probably sourced from the East Junggar Arc and the Harlik-Dananhu Arc in the CNTS. The minor Precambrian detrital zircons are interpreted as recycled materials from the older strata in the Harlik-Dananhu Arc. Zircon ɛHf(t) values have increased since ~408 ​Ma, probably reflecting a tectonic transition from regional compression to extension. This event might correspond to the opening of the Bogda intra-arc/back arc rift basin, possibly resulting from a slab rollback during the northward subduction of the North Tianshan Ocean. A decrease of zircon ɛHf(t) values at ~300 ​Ma was likely caused by the cessation of oceanic subduction and subsequent collision, which implies that the North Tianshan Ocean closed at the end of the Late Carboniferous.

A compilation of 178 more precise ages on 10 potential Large Igneous Provinces (LIPs) across southern Africa, is compared to Earth’s supercontinental cycles, where 5 more prominent LIP-events all formed during the assembly of supercontinents, rather than during breakup. This temporal bias is confirmed by a focused review of field relationships, where these syn-assembly LIPs formed behind active continental arcs; whereas, the remaining post-assembly – and likely breakup-related – LIPs never share such associations. Exploring the possibility of two radically different LIP-types, only the two younger breakup events (the Karoo LIP and Gannakouriep Suite) produced basalts with more enriched asthenospheric OIB-signatures; whereas, all assembly LIPs produced basalts with stronger lithospheric, as well as more or less primitive asthenospheric, signatures. A counterintuitive observation of Precambrian breakup LIPs outcropping as smaller fragments that are more peripherally located along craton margins, compared to assembly LIPs as well as the Phanerozoic Karoo breakup LIP, is explained by different preservation potentials during subsequent supercontinental cycles. Thus, further accentuating radical differences between (1) breakup LIPs, preferentially intruding along what evolves to become volcanic rifted margins that are more susceptible to deformation within subsequent orogens, and (2) assembly LIPs, typically emplaced along back-arc rifts within more protected cratonic interiors. A conditioned duality is proposed, where assembly LIPs are primarily sustained by thermal blanketing (as well as local arc hydration and rifting) below assembling supercontinents and breakup LIPs more typically form above impinging mantle plumes. Such a duality is further related to an overall dynamic Earth model whereby predominantly supercontinent-orientated ocean lithospheric subduction establishes/revitalizes large low shear velocity provinces (LLSVPs) during assembly LIP-activity, and heating of such LLSVPs by the Earth’s core subsequently leads to a derivation of mantle plumes during supercontinental breakup.

This chapter covers a lot of territory including the atmosphere and hydrosphere and their interactions with each other through time. It discusses Earth's primitive atmosphere and oceans as well as the post-lunar formation atmosphere, including atmospheric composition and the faint young Sun paradox. It includes a discussion of the carbon and sulfur cycles and carbon and sulfur isotopic anomalies and a discussion of paleoclimates both in the Phanerozoic and in the Precambrian. It summarizes the geologic history of oceans including secular changes in seawater composition and variations in temperature and volume of seawater through time.

The Una and Bambui Groups of northeastern and central Brazil are remnants of a vast intracratonic carbonate platform formed on the Sao Francisco Craton during the Ediacaran Period. Their basal stratigraphic units contain early phosphatic cements and phosphatic intraclasts in association with elongate digitate stromatolites in the more northern Irece and Salitre paleobasins (Salitre Formation), and microbial laminites and aragonite crystal fan pseudomorphs in the more southern Sao Francisco paleobasin (Sete Lagoas Formation). Previous studies have drawn comparisons to other Precambrian phosphorites, as well as modern phosphogenetic environments, suggesting mechanisms of phosphogenesis dependent on the accumulation of porewater phosphate via microbial activity in low flow velocity environments, such as relatively quiescent tidal flats, where an absence of wave-driven advection and porewater refreshment could have allowed oversaturation with respect to carbonate fluorapatite. Here, we present new sedimentological data that characterize the depositional setting of the Salitre and Sete Lagoas formations as a shallow, wave-swept carbonate platform notable for its extensive high-energy lithofacies. In this setting, phosphatic and non-phosphatic stromatolite buildups formed within the same depositional facies, often in close (meter- and decimeter-scale) spatial association with one another. These data suggest that early phosphate mineralization of the Salitre and Sete Lagoas formations was likely not a function of low porewater advection in paleogeographically sheltered regions, but rather highly local processes of phosphate enrichment on a high-energy, wave-swept platform environment.

International audience; This database is a geological and geochronological compilation made to study a small Archean/Paleoproterozoic block located in the centre of the Precambrian rock exposition of Uruguay. Petrographic and field outcrops data supporting the samples from which the zircons for textural analysis and U-Pb dating (LA-ICP-MS) come are presented at first with their descriptions. The first table (1) contains the new U-Pb isotopic data. The second table (2) presents a correlation of textures from different zircon samples. The last table (3) contains an inventory of different U-Pb ages found in antecedents. All these data are associated with the paper entitled: "The Archean Pavas Block in Uruguay: extension and tectonic evolution based on LA-ICP-MS U-Pb ages and airborne geophysics".

The Precambrian basement of the Gyeonggi Massif in the central Korean Peninsula consists mainly of Paleoproterozoic (2.0–1.8 Ga) gneisses. In this study, we present petrological, zircon U–Pb age and Hf isotope, and whole-rock geochemical and Sr–Nd–Pb isotope data for late Paleoproterozoic (ca. 1.7 Ga) granitic gneisses and anatectic granites from the southwestern Gyeonggi Massif. Zircon U–Pb dating of two granitic gneisses and three anatectic granites yielded ages of 1685 ± 14, 1693 ± 8, 1683 ± 18, 1690 ± 6, and 1706 ± 17 Ma, respectively. The samples exhibit LILE enrichment, negative Nb–Ta anomalies, high Ga/Al ratios and HFSE contents, similar to A-type granites. Compared with typical anorogenic intra-continental rift-related granites (A1-type), Y/Nb and Ce/Nb ratios of the samples are much higher, and similar to those of post-collisional granites (A2-type). The eHf(t) values of late Paleoproterozoic zircons from the granitic gneisses and anatectic granites range from –17.8 to –7.0 and –15.3 to –9.7, respectively, indicating derivation from ancient crustal sources. The zircon U–Pb ages of the anatectic granites show that some of the late Paleoproterozoic intrusions underwent re-melting (i.e., anatexis) in the Late Triassic (ca. 230 Ma). Whole-rock initial eNd (230 Ma) values of the anatectic granites (–29.4 to –28.1) and granitic gneisses (–26.3 to –24.3) are similar, indicating that the anatectic granites were sourced from the granitic gneisses. Late Paleoproterozoic igneous activity in the southwestern Gyeonggi Massif can be correlated with post-collisional activity in North China Craton, and was distinct from the coeval rift-related magmatism in South China Craton.

At present, deep and ultra-deep oil and gas have become the research and exploration hotspots. With little drilling data available, the geological understanding on deep formations is still in the exploratory stage, but most petroleum geologists have universally acknowledged that the deeply-buried strata of Chinese marine craton basins are equipped with the conditions for abundant oil and gas resources. A series of discoveries have been made in the Ordovician and Cambrian strata. For Precambrian strata, besides breakthroughs in the Sichuan Basin, a lot of research or drilling work has been initiated in other basins. In the Tarim Basin, the current burial depth of the Lower Paleozoic and the Precambrian mainly ranges from 5000 to 12000 m. This is attributed to rapid subsidence and deposition since the Neogene. A large number of exploration discoveries have been made, and commercial productivity projects have been constructed at the depth less than 8000 m. Strata more than 8000 m deep will be a significant major prospecting exploration field in the future. The analyses of hydrocarbon accumulation conditions of the ultra-deep layers of the Tarim Basin provide theoretical guidance for ultra-deep oil and gas exploration. This research is based on source rocks in the Cambrian, Sinian, and Nanhua System, formation and preservation of ultra-deep carbonate reservoirs, phase of petroleum and accumulation assemblages in ultra-deep strata, the exploration fields deeper than 8000 m were also evaluated to sort out the most favorable areas and, future exploration focuses on the Ordovician, Cambrian, and Sinian strata are pointed out. Keywords: Ultra-deep, Neoproterozoic, Phase of petroleum, Cambrian, Craton basin, Tarim Basin

In the modern ocean, U reduction and incorporation into anoxic sediments imparts a large isotopic fractionation of approximately +0.6‰ that shifts the seawater δ238U value (238U/235U, expressed as δ238U per mil deviation relative to CRM-112a) relative to continental runoff. Given the long residence time of U in the modern oceans (∼400 kyr), the isotopic composition of carbonates (taken as a proxy for seawater) reflects the global balance between anoxic and other sinks. The U isotopic composition of open-marine carbonates has thus emerged as a proxy for reconstructing past changes in the redox state of the global ocean. A tenet of this approach is that the δ 238U values of seawater and anoxic sediments should always be fractionated by the same amount. In order to test this hypothesis, we have measured the U concentrations and isotopic compositions of carbonates spanning ages from 3250 Ma to present. A first-order expectation for the Archean and possibly Proterozoic is that near-quantitative U removal to extensive anoxic sediments should have shifted the uranium isotopic composition of seawater and carbonates towards lower values. Instead, the measurements reveal that many Archean and Proterozoic carbonates have unfractionated δ238U values similar to those of continents and riverine runoff. These results are inconsistent with the view that the U isotopic composition of seawater simply reflects the areal extent of anoxic sediments in the past. We consider two plausible explanations for why the U isotopic composition of Archean and Proterozoic carbonates is not fractionated from the crustal and riverine composition: (1) the residence time of U could have been much shorter in the Precambrian oceans when anoxic settings were much more extensive, and (2) the process of incorporation of U into anoxic sediments in the Precambrian imparted a smaller U isotopic fractionation than in the modern because of differences in the efficiency or mechanism of uranium removal. This study highlights the challenges inherent to applying knowledge of the modern marine U isotopic cycle to periods of Earth’s history when ocean-floor anoxia was much more extended, anoxic basins were ferruginous, and atmospheric oxygen content was significantly lower than present.

Mantle-derived magmatism provides important insights for understanding the mechanism of lithospheric thinning. Here we report the results of an integrated geochronological and geochemical study of Late Triassic mafic dykes in Eastern Hebei, northern North China Craton. In situ zircon U-Pb dating shows that the dykes were emplaced between 238 and 223 Ma; the coeval Gaojiadian and Mataizi dykes intruded Precambrian basement at 238–234 Ma and the Saheqiao dyke was emplaced into Neoarchean supracrustal rocks later at 223 ± 4 Ma (2s). Bulk-rock geochemistry indicates that the Late Triassic dykes in Eastern Hebei were produced by melting of ancient lithospheric mantle within the garnet-spinel transition zone (~70–80 km), heated by upwelling asthenosphere. This ancient lithospheric mantle had been metasomatized during previous subduction events. The Gaojiadian and Mataizi dykes resulted from higher degrees of partial melting at slightly lower pressures than the Saheqiao dyke. The melting depth of Late Triassic dykes in Eastern Hebei indicates that the intact ancient lithospheric mantle had been at least locally modified/thinned to ~70–80 km by the Late Triassic. The intrusion of these Late Triassic dykes took place at the onset of the lithospheric thinning of the North China Craton, caused by post-collisional extension after subduction and collision of neighboring blocks with the North China Craton.

The different image attribute extracting techniques, spectral enhancement ability, pixel classification methods have been applied on the Landsat 8 OLI satellite image data to map geological features and spatial distribution of hydrothermal alteration zones, which have been recorded to be associated with gold mineralization in the Pala, Mayo Kebbi region of southwestern Chad. Radiometric calibrated, noise filtered and image enhanced Landsat 8 OLI data were subjected to colour composite, band rationing and crosta analyses in order to enhance spectral reflectance and compositional information, create colourful multispectral images which enable the mapping of desired spectral bands into principal component images for the purpose of accentuating salient information needful to delineate hydrothermal alteration zones within the study area.Composite ratios 4/2-6/7-6/5 indicate relative spatial distribution of iron-oxide in the southeast while clays and hydroxyl minerals occur in the west and northwestern part of the study area. The eigenvectors and eigenvalues for hydroxyl minerals from the crosta analysis indicate highest loadings of opposite signs (-0.721498 & 0.649465; bands 6 & 7) in PC3, representing ‘’H’’ image. The eigenvectors and eigenvalues for iron-oxides on the other hand present highest loading of opposite signs (0.895721 & -0.443283; bands 2 & 4) in PC4, representing the “F” image. The white coloured pixels within the bright reflections generated from Crosta composite image of H, H+F & F in RGB delineate hydrothermal alteration zones. The plot of delineated zones of hydrothermal alteration on the Landsat 8 true colour indicate spatial distribution of the alteration areas within the host greenstone belt belonging to the Precambrian Goueygoudoum series and they plot mainly along major structural features, suggesting structural control. Field control revealed that some areas delineated by band rationing as hydrothermal alteration zones appear to be the result of intense weathering. Accordingly, we recommend that remote sensing delineation of hydrothermal alteration zones should be checked by a relevant ground-observation based control procedure.

This chapter summarizes the key aspects of Precambrian geomagnetic field in three successive time intervals (pre-1880 Ma, 1190–1880 Ma, and post-1190 Ma) representing hypothesized supercontinents Kenorland, Nuna, and Rodinia. Our analyses of inclination frequency, reversal asymmetry, paleointensity, and paleosecular variation are generally in favor of Geocentric Axial Dipole as the time-averaged Precambrian geomagnetic field. However, in the Nuna supercontinent phase, the field was weaker, less reversing, and biased toward low inclinations, suggesting the presence of considerable (23%) octupole component or more likely that Nuna occupied shallow latitudes as evidenced by paleoclimate indicators. Another paradoxial result emerges from paleosecular variation data, which suggests a field with quadrupolar characteristics while the inclination analysis favors the presence of an octupolar field in the Mid-Proterozoic. Despite these exceptions, the existence of a stable dipole field gives us a solid ground for paleogeography studies beyond the Phanerozoic.

We present a compilation of reliable Precambrian paleomagnetic poles from three successive international workshops (in years 2009, 2014, 2017), comprising paleomagnetists specializing in Precambrian tectonic reconstructions. The working groups compiled lists of two global classes of poles, published through the end of 2017. “Grade-A” results are judged to provide essential constraints on tectonic reconstructions; “Grade-B” poles are judged to be suggestive of high-quality, but not yet demonstrated to be primary, or perhaps lacking precise geochronologic or other constraints. Our catalog documents a resurgence of high-quality data acquisition in recent years, and highlights specific cratons and time intervals that are most lacking in the data needed to reconstruct those blocks through supercontinental cycles.

The Sveconorwegian orogen represents a branch of Grenville-age (~1250–950 Ma) orogenic belts that formed during the construction of the supercontinent Rodinia. This study traces the Sveconorwegian records from its type-area in the Baltic Shield of South Norway into basement windows underneath Caledonian nappes, by combining zircon U–Pb geochronology and Hf–O isotopes. Samples along a N-S trending transect reveal multiple magmatic episodes during Gothian (ca. 1650 Ma), Telemarkian (ca. 1500 Ma) and Sveconorwegian (1050–1020 Ma vs. 980–930 Ma) orogenesis as well as Sveconorwegian migmatization (1050–950 Ma). Newly documented 1050–1020 Ma magmatism and migmatization extend the Sirdal Magmatic Belt to a 300 km-long, NNW-SSE trending crustal domain, with the northern boundary corresponding to the gradual transition from Telemarkian to Gothian crust. These Precambrian crustal heterogeneities largely controlled the development of Caledonian shear zones. The ca. 1050–1040 Ma granitic and mafic magmas show similar isotopic signatures with slightly negative or positive εHf(t) and moderate δ18O values (6–7‰), which indicates that crustal reworking was more dominant than juvenile inputs during their genesis. The generation of leucosomes and leucogranites at ca. 1030–1020 Ma, which have a more evolved Hf isotopic composition, probably reflects an even higher degree of remelting of older crust. The Hf–O isotopic patterns show that Sveconorwegian magmas differ from typical arc magmas by lower involvement of sedimentary components and juvenile material. This makes the 1050–930 Ma magmatism incompatible with a long-term subduction setting. The ca. 1650–1500 Ma samples, in contrast, generally have juvenile Hf isotopic compositions associated with varying δ18O values of 4.5–9‰, consistent with subduction-accretion processes involving significant sedimentary recycling. This accretionary margin was most likely transformed into the Sveconorwegian orogen through collisional interactions of Baltica, Laurentia and Amazonia in the context of Rodinia amalgamation. publishedVersion

We review models of the Precambrian supercontinent Nuna (c.1.80–1.20 Ga) and present a new model of the Nuna life-cycle. We explore the option where Amazonia−West Africa and Congo−Sao Francisco cratons were not a part of Nuna but form a cluster of cratons named Atlantica. Nuna was finally assembled at c.1.65 Ga, encompassing Laurentia, Baltica, Siberia, proto-Australia, North China, and India. The break up of Nuna is here suggested to have started at c.1.3 Ga with Australian cratons moving away from Laurentia. Varying drift rates and length between coeval poles from separate cratons support the operation of modern style plate tectonics during the Nuna supercycle. Moreover, if there was no link between Nuna and the Atlantica cratons, the size of Nuna might not meet the criteria for a supercontinent, but should be regarded as a huge landmass.

Laurentia is the craton that forms the Precambrian core of North America and was a major continent throughout the majority of the Proterozoic following its amalgamation 1.8 billion years ago. The paleogeographic position of Laurentia is key to the development of reconstructions of Proterozoic paleogeography including the Paleoproterozoic to Mesoproterozoic supercontinent Nuna and latest Mesoproterozoic to Neoproterozoic supercontinent Rodinia. There is a rich record of Precambrian paleomagnetic poles from Laurentia, as well as an extensive and well-documented geologic history of tectonism. These geologic and paleomagnetic records are increasingly better constrained geochronologically and are both key to evaluating and developing paleogeographic models. These data from Laurentia provide strong support for mobile lid plate tectonic processes operating continuously over the past 2.2 billion years.

There is ample evidence that supercontinent cycles on Earth have been operating since the Late Paleoproterozoic. Evidence for the supercontinent cyclicity arises from multidisciplinary observations from geology, geochronology, geophysics (e.g., paleomagnetism, seismology, heat flow), isotope geology, and geochemistry. This overview summarizes current views of Precambrian supercontinent episodicity or cyclicity. In addition, paleogeographic reconstructions based on global key paleomagnetic poles and kinematic models of Paleo-Mesoproterozoic Nuna supercycle, Meso-Neoproterozoic Rodinia supercycle, and the Phanerozoic Gondwana/Pangea supercycle are explored. The lifecycle of supercontinents is tested by geological, geophysical, and geochemical data coupled with secular evolution trends of Earth. Results suggest that (1) supercontinent cyclicity has a characteristic (quasi-) period of ~700–500 million years, supported by planetary secular evolutionary trends, but other periods are also present; (2) supercontinents Nuna, Rodinia, and Gondwana/Pangea have different configurations and secular evolutionary trends possibly due to different tectonic styles of assembly; (3) globally averaged plate velocity during the Precambrian reveals a wave-like pattern with peaks and lows corresponding with features in several secular evolution indices including the distribution of U−Pb ages, passive margins, metamorphic events, tectonic proxies, and magmatic activity; (4) the data suggest three tectonomagmatic lulls during the Proterozoic, but the proposed Mesoproterozoic quiescent period, coined as “boring billion” years of Earth history (1.8–0.8 Ga) appears to be seen mainly by atmospheric and biospheric data rather than tectonomagmatic activity; and (5) tectonic processes driving supercontinent cyclicity are interactive, with feedbacks from all six spheres of the Earth—the geosphere, cryosphere, hydrosphere, biosphere, atmosphere, and magnetosphere.

This chapter reviews the Precambrian paleogeography of West African Craton (WAC), which is critical for understanding the plate tectonics on early Earth and the configurations of Proterozoic supercontinents. We have summarized the geological history and paleoclimate indicators of WAC, and thoroughly evaluated the available paleomagnetic data. Although we found that WAC has essentially no highly reliable paleomagnetic data of pre-Ediacaran age, ubiquitous mafic dyke swarms could be promising targets for paleomagnetism. In this context, we compiled all high-precision ages pertaining to the mafic intrusions recognized in WAC, and constructed a magmatic barcode for global comparisons. Finally, various paleogeographic reconstruction models regarding the position of WAC in supercontinents Nuna/Columbia and Rodinia were presented and discussed. Because of the lack of robust data, WAC is poorly constrained paleogeographically in Proterozoic supercontinents. We hope this review can provide a basic introduction with regard to the paleogeography of WAC in the Precambrian and advocate future studies.

We review paleomagnetic data and paleoclimatological indicators of Baltica and its subcratons. Between Neoarchean and middle Mesoproterozoic Karelia and Kola, and later the united Baltica were located mostly at the latitudes between 35°N and 35°S. Location of Baltica oscillated between high latitudes and the equator at late Mesoproterozic–Neoproterozoic. Drift velocities of the separate cratons between Neoarchean and middle Proterozoic are lower than the velocities of the united Baltica at late Paleoproterozoic–middle Mesoproterozoic. At Late Mesoproterozoic–Neoproterozoic Baltica shows high velocity peaks, which correlate temporarily with the ones obtained for Laurentia and can be ascribed to true polar wander. Increase in drift rates correlate temporarily with orogenies related to the formation of the supercontinents Nuna and Rodinia and in smaller scale to the crustal growth of Baltica. Based on the results, we review possible nearest neighbors for the Kola and Karelia in the Superia supercraton and for Baltica in the Nuna and Rodinia supercontinents.

Congo and Sao Francisco cratons are made of several Archean and Paleoproterozoic nuclei welded together by Paleoproterozoic belts. The pair is considered to be a stable lithospheric entity by ~2.0 Ga and hosts fissural mafic magmatism at 2.7–2.6, 1.71, 1.50, and 0.92 Ga; magmatic events at 1.38 and 1.10 Ga are restricted to Africa. Some of these dike swarms and also younger sedimentary units have been targeted for paleomagnetic studies, but the paleomagnetic data for the Congo−Sao Francisco craton is still scarce. Here we review the available data for both cratons. A total of 21 paleomagnetic poles was selected for paleogeographic reconstructions, 11 of them with Q-index higher than 4. Segments of apparent wander paths were drawn for 1.1–0.92, 0.79–0.74, and 0.57–0.52 Ga. Tentative reconstructions are proposed to place Congo−Sao Francisco into the context of supercontinents Columbia, Rodinia, and Gondwana.

The thermal and compositional structure of lithospheric keels underlying cratons, which are stable continental cores formed during the Precambrian, is still an enigma. Mapping lithospheric temperatures and compositional heterogeneities is essential to better understand geodynamic processes that control craton formation and evolution. Here we investigate the northeastern part of North America which comprises the Superior Craton, the largest Archean craton in the world, and surrounding Proterozoic belts. We model Rayleigh-wave dispersion curves from a previous study, which were regionalised based on cluster analysis. Next, we perform a grid search for sub-crustal thermal and compositional structures that are consistent with the average dispersion curve for each cluster. We apply constraints on crustal structure and use thermodynamic methods to map thermo-compositional structures into seismic velocity. In agreement with previous studies, most regions require concentrations of metasomatic minerals over certain depth intervals to fit the seismic profiles. Our results further require vertical as well as lateral variations in compositional and thermal structures, which appear to reflect different stages of formation and modification of the lithosphere below the region, with distinct structures found under Archean cores, Archean/Paleoproterozoic collision belts, mid-late Proterozoic collision belts, and zones affected by rifting.

We use heavy minerals and rutile and garnet chemical compositions to constrain the provenance of two glaciogenic sandstone formations that build up the Palaeozoic succession in Ethiopia. The heavy mineral assemblage of the Upper Ordovician–Lower Silurian Enticho Sandstone is dominated by ultra-stable minerals, implying high maturity of the sediment. Variable amounts of garnet are present as well. The Carboniferous–Permian Edaga Arbi Glacials contain mainly less stable heavy minerals, such as garnet and apatite, suggesting little chemical alteration. A combination of magmatic and metamorphic source rocks is likely for both formations. Rutile and garnet chemistry point to mainly amphibolite-facies and to a lesser extent granulite-facies metamorphic source rocks with generally slightly higher metamorphic temperatures for detrital heavy minerals in the Enticho Sandstone. We conclude that the Enticho Sandstone is mainly the product of reworked mature Cambrian–Ordovician sediment, which may have been supplied via the Gondwana super-fan system. Locally, glaciers of the Late Ordovician glaciation eroded fresh basement material, delivering the garnet. For the Edaga Arbi Glacials, a rather proximal provenance is likely. The potential source area is the southern hinterland, where Precambrian low-to higher grade metamorphic rocks of the Arabian–Nubian Shield occur at the transition to the Mozambique Belt.

Due to the paucity of exposure, the formation and evolution of the Precambrian basement of the Lhasa terrane remain poorly known. Here we report zircon and titanite in situ U–Pb ages, bulk-rock geochemical and zircon Hf isotopic data on the orthogneisses from the Dongjiu area of the southern Lhasa subterrane (SLT), southern Tibet. Geochemical data suggest that the protoliths of the biotite-amphibole gneiss and biotite gneiss are granodiorite and granite, respectively. Inherited magmatic zircon cores from these orthogneisses give protolith crystalline ages of 1520–1506 Ma, whereas the overgrown zircon rims give metamorphic ages of 605–590 Ma. The Mesoproterozoic granitic rocks have bulk-rock eNd(t) values of -3.6 to +0.1 and zircon core eHf(t) values of -4.5 to +2.6, which give similar TDM2 ages of 2.35–2.05 Ga and 2.54–2.10 Ga respectively, suggesting their derivation from partial melting of Paleoproterozoic crustal material. The granitic rocks are also local provenance for the Mesoproterozoic detrital zircons in the Paleozoic strata in the Lhasa terrane. Titanite in situ U–Pb ages further indicate that the Dongjiu orthogneiss experienced more recent metamorphism at ∼ 26 Ma. The mineral assemblage and thermobarometry calculations indicate that the Oligocene metamorphism occurred under medium-pressure (MP) amphibolite-facies conditions (5.4–7.2 kbar, 691–765 °C). We propose that the Dongjiu gneisses represent the Precambrian metamorphic basement of the Lhasa terrane, but have been intensively reworked by metamorphism in the SLT in response to the continued India-Asia convergence since the collision.

Knowledge of the Precambrian history of the Earth between the birth of the Solar System (c. 4.567 Ga) and the end of the Mesoproterozoic (1.0 Ga) has improved dramatically as a result of the acquisition of a range of isotopic and geochemical data and new fossil discoveries. None the less, subdivision of the Precambrian in a comparable manner to that achieved for the Phanerozoic continues to be extremely challenging. Global Standard Stratigraphic Ages (GSSAs) have long been used to subdivide the Precambrian into eons, eras, and periods. It accepted that there are shortcomings in this approach and a move toward a revised time scale based as closely as possible around geobiological events would be desirable. However, development of such a “naturalistic” time scale is still a “work in progress” as shown by the state of flux in the understanding of particular biogeochemical events and the extent to which they are globally synchronous given the fragmentary state of the preserved rock record. Until these issues are resolved (if at all possible) the GSSA approach continues to serve geoscientists well in broadly delimiting major parts of the Earth’s history that are characterized by particular tectonic and biogeochemical regimes.

The data presented in this article are related to research to the research article entitled ‘Petrology and Geochemistry Data of the Precambrian granitoids from the Hyderabad part of Eastern Dharwar Craton, Telangana state, India’. The granitoids from the Hyderabad area of the Telangana State are confined to the Precambrian gneissic complex of the northern-eastern part of Eastern Dharwar Craton. They cover 7760 Sq. km of the study area and fall between latitudes 16° 52′–17°42′ N and between East longitudes 77° 21′–77° 51′ E. The granitoids are mainly classified into grey and pink granites, granodiorites and aplites. The field studies are understood they occasionally contain older mafic enclaves in the form of lensoid bodies and thin bands and cut by younger dolerite dykes, pegmatite and quartz veins and laboratory investigations resolved the classification of the granitods and their chemical histories. Keywords: Precambrian gneisses, Granitoids, Mafic enclave, Dolerite dykes and chemical histories

The Qilian block is a Precambrian block in the Qilian Orogen, which marks the junction of the North China, South China and Tarim cratons. The mechanism of continental growth for the Qilian block remains unclear and several models have been proposed. We present a systematic study of petrology, geochemistry and geochronology of paragneisses and intermediate to basic intrusions from the Hualong Group, which represents the lower part of Precambrian basement of the block. The protoliths of paragneisses are wackes with a maximum deposition age of ca. 900 Ma formed at an active continental margin during assembly of the Rodinia supercontinent. Their clastic input was derived from a single source granitic material of ca. 922 Ma and the magmas of their source rocks mainly came from reworked Paleoproterozoic crustal sources. The sediments were deposited close to source with a minor degree of weathering and limited sorting. Cooling after amphibolite facies metamorphism affected the paragneisses at 439.6 ± 4.9 Ma as suggested by a biotite 40Ar/39Ar age. Lenticular quartz diorites with a LA-ICPMS zircon U-Pb age of 900 ± 22 Ma are adakitic rocks formed by partial melting of lower crustal material. The quasi-lamellar hornblendites have a zircon U-Pb age of 469 ± 2 Ma and a biotite 40Ar/39Ar age of 465.4 ± 3.1 Ma. They were derived from a subduction-related metasomatic mantle and underwent fast cooling during their ascent. It is inferred that the Qilian block is a continental fragment that rifted from the South China craton during break-up of the Rodinia supercontinent, which resulted in formation of the North Qilian ocean and the South Qilian ocean as two branches of the global early Paleozoic ocean. The Hualong block, represented by the Hualong Group, is a fragment broken away from the Qilian block during this stage and situated in the South Qilian ocean. Combining our results with existing data, we identify a sequence of seafloor spreading related to a mantle plume activity (ca. 600–500 Ma), northward intra-oceanic subduction (ca. 540–469 Ma), oceanic crust-continent subduction (ca. 470–446 Ma) and continent-continent collision (ca. 446–440 Ma) between the Qilian block and the Qaidam block.

The Wutai greenstone belt in central North China Craton (NCC) hosts a number of Precambrian gold deposits and ore occurrences. Based on the host rock association, these can be divided into Banded Iron Formation (BIF), meta-volcano-sedimentary and meta-conglomerate types. The two former types formed during ∼2.5–2.3 Ga and the third one at ∼1.85 Ga. The characteristics of these Precambrian gold deposits are broadly similar with those of the orogenic gold deposits. Based on available geochronological data, here we reconstruct the major tectonic events and their relationship with gold mineralization in the Wutai-Hengshan-Fuping region during Neoarchean to Paleoproterozoic as follows. (1) ∼2.6–2.5 Ga: widespread intrusion of tonalite-trondhjemite-granodiorite (TTG) magmas in the Hengshan terrane and Fuping continental arc, formation of the Wutai volcanic arc in the southern margin of Hengshan terrane with granitoids emplacement, and the Hengshan-Wutai intra-oceanic arc accretion to the Fuping arc at the end of Neoarchean. (2) ∼2.5–2.3 Ga: the subduction of Hengshan arc from north leading to persistent magmatism and orogenic gold mineralization. (3) ∼2.2–2.1 Ga: extension leading to the formation of graben structure in the Wutai and Fuping region, deposition of the Hutuo and Wanzi Group sediments, formation of placer gold through erosion of the orogenic gold deposits. (4) ∼2.2–2.0 Ga: widespread magmatism in the Wutai-Hengshan-Fuping region. (5) ∼1.95–1.8 Ga: regional metamorphism associated with collision of the Western and Eastern Blocks of the NCC and associated orogenic gold deposits. The multiple subduction-accretion-collision history and subsequent deep erosion has significantly affected most of the Precambrian gold deposits in the Wutai greenstone belt.

Although Plate Tectonics cannot be effectively tested by palaeomagnetism in the Precambrian aeon due to the paucity of high precision poles spanning such a long time period, the possibility of Lid Tectonics is eminently testable because it seeks accordance of the wider dataset over prolonged intervals of time; deficiencies and complexities in the data merely contribute to dispersion. Accordance of palaeomagnetic poles across a quasi-integral continental crust for time periods of up to thousands of millions of years, together with recognition of very long intervals characterised by minimal polar motions (∼2.6–2.0, ∼1.5–1.25 and ∼0.75–0.6 Ga) has been used to demonstrate that Lid Tectonics dominated this aeon. The new PALEOMAGIA database is used to refine a model for the Precambrian lid incorporating a large quasi-integral crescentric core running from South-Central Africa through Laurentia to Siberia with peripheral cratons subject to reorganisation at ∼2.1, ∼1.6 and ∼1.1 Ga. The model explains low levels of tidal friction, reduced heat balance, unique petrologic and isotopic signatures, and the prolonged crustal stability of Earth's “Middle Age”, whilst density concentrations of the palaeomagnetic poles show that the centre of the continental lid was persistently focussed near Earth's rotation axis from ∼2.8 to 0.6 Ga. The exception was the ∼2.7–2.2 Ga interval defined by ∼90° polar movements which translated the periphery of the lid to the rotation pole for this quasi-static period, a time characterised by glaciation and low levels of magmatic activity; the ∼2.7 Ga shift correlates with key interval of mid-Archaean crustal growth to some 60–70% of the present volume and REE signatures whilst the ∼2.2 Ga shift correlates with the Lomagundi δ13 C and Great Oxygenation events. The palaeomagnetic signature of breakup of the lid at ∼0.6 Ga is recorded by the world-wide Ediacaran development of passive margins and associated environmental signatures of new ocean basins. This event defined the end of a dominant Lid Tectonic phase in the history of Earth's continental lithosphere recorded by the quasi-integral Precambrian supercontinent Palaeopangaea and the beginning of the comprehensive Plate Tectonics which has characterised the Phanerozoic aeon. Peripheral modifications to the lid achieved a symmetrical and hemispheric shape in Neoproterozoic times comparable to the familiar short-lived supercontinent (Neo)Pangaea (∼350–150 Ma) and this appears to be the sole supercontinent cycle recorded by the palaeomagnetic record. Prolonged integrity of a large continental nucleus accompanied by periodic readjustments of peripheral shields can reconcile divergent tectonic analyses of Precambrian times which on the one hand propose multiple Wilson Cycles to explain some signatures of Plate Tectonics, and alternative interpretations which consider that Plate Tectonics did not commence until the end of the Neoproterozoic.

A family of geophysical lineaments have been identified in ∼15,000 km 2 in central Kerala between 9°30′N to 10°45′N and 76°00′E to 77°30′E, integrating geophysical data with geological and geomorphological features. The characteristics of these lineaments in the magnetic and gravity fields and their derivatives have been analysed. The evolution of the lineaments has been traced to the temporal phases of global evolution of the region. A group of these faults have formed by reactivation of the deep-seated distensional fractures associated with and accompanying dyke emplacements during the episodic breakup of Gondwana at ∼90 and 65 Ma under distinctive mantle thermal regimes. It is possible that reactivation of these distensional faults may have started during the cooling interval of time between the two distensions in the 90 and 65 Ma and post 65 Ma periods and later in the Cenozoic, when the lineaments were enlarged to their present dimension, possibly under the influence of forces that led to the uplift of the western Ghats. These may extend down to the crust-mantle interface. A cluster of younger geophysical lineaments has been generated by reactivation along the weak planes of transformation of the charnockitic rocks of the Precambrian. They seem to have a strike-slip character. They are devoid of any dyke association and were formed on a cold crust. They may be confined to the upper-middle crust. They were generated in the high intensity intra-plate palaeo-stress fields of the triple forces arising from (1) the back-thrust from the Himalayan Collision; (2) the impact of epeirogenic forces and related isostatic uplift of the Western Ghats and (3) the flexural isostatic uplifts due to surface loads of late Mesozoic basaltic lavas and Cenozoic sedimentation in the coastal rifted basins in late Cenozoic, probably in the time span of 20 Ma to the present, when the palaeostress fields were most intense.

New versions of the universal Jd-Di exchange clinopyroxene barometer for peridotites, pyroxenites and eclogites, and also garnet barometer for eclogites and peridotites were developed. They were checked using large experimental data sets for eclogitic (∼530) and peridotitic systems (>650). The precision of the universal Cpx barometer for peridotites based on Jd-Di exchange is close to Cr-Tschermakite method produced by Nimis and Taylor (2000). Cpx barometer was transformed by the substitution of major multiplier for KD by the equations dependent from Al-Na-Fe. Obtained equation in combination with the thermometer of Nimis and Taylor (2000) allow to reconstruct position of the magma feeder systems of the alkali basaltic magma within the mantle diapirs in modern platforms like in Vitim plateau and other Southern Siberia localities and several localities worldwide showing good agreement of pressure ranges for black and green suites. These equations allow construct PTX diagrams for the kimberlite localities in Siberia and worldwide calculating simultaneously the PT parameters for different groups of mantle rocks. They give very good results for the concentrates from kimberlite lamproites and placers with mantle minerals. They are useful for PT estimates for diamond inclusions. The positions of eclogite groups in mantle sections are similar to those determined with new Gar–Cpx barometer produced by C. Beyer et al. (2015). The Fe rich eclogites commonly trace the boundary between the lower upper parts of subcontinental lithospheric mantle (SCLM) at 3–4 GPa marking pyroxenite eclogites layer. Ca-rich eclogites and especially grospydites in SCLM beneath Precambrian kimberlites occurs near pyroxenite layer but in younger mantle sections they became common in the lower parts. The diamondiferous Mg Cr-less group eclogites referring to the ancient island arc complexes are also common in the middle part of mantle sections and near 5–6 GPa. Commonly eclogites in lower apart of mantle sections are remelted and trace the high temperature convective branch. The Mg- and Fe-rich pyroxenites also show the extending in pressure trends which suggest the anatexic melting under the influence of volatiles or under the interaction with plums.

Brazil is a natural laboratory for the application of isotope stratigraphy tools on the study of Precambrian sedimentary successions, with excellent registers of Archean, Paleo, Meso, and Neoproterozoic age. Those successions witnessed the most extreme and unidirectional events in Earth's history, such as the Paleoproterozoic and Neoproterozoic oxygenation events (GOE and NOE), the main stages of iron formation deposition, the global Cryogenian glaciations and the explosive diversification of metazoans near the Precambrian/Cambrian border. Chemical sedimentary rocks such as carbonates, iron formations and evaporites that can act as natural recorders of seawater composition are present in all of those successions and furnish important pieces of evidence in order to reconstruct the chemostratigraphic record. The field of isotope stratigraphy keeps expanding in Brazil and novel information from developing isotopic systems will surely add to the growing database and provide important information on Earth's ancient biogeochemical cycles in the years to come.

The Muju area, located on the north–central margin of the Yeongnam Massif, mainly consists of Precambrian orthogneisses (granitic, leucogranitic, augen and dioritic gneisses) with minor migmatite. Zircon U–Pb dating indicates that the protoliths of the orthogneisses intruded at ca. 2.00–1.97 Ga and were metamorphosed at ca. 1.87–1.86 Ga. Magmatic zircon grains within the orthogneisses have positive to negative eHf(t) values (−7.63 to +3.3) and a Neoarchean two-stage model age (TDM2 = 2.78 Ga), indicating that the protoliths of most of the orthogneisses may have been derived from Archean crustal material. The results of geochemical analysis indicate that the protoliths of the orthogneisses formed by partial melting of metagraywacke and mafic igneous rocks in an arc-related tectonic setting. The intrusion ages and geochemical data of the Paleoproterozoic orthogneisses in the study area match well with those of Paleoproterozoic (ca. 2.00–1.97 Ga) orthogneisses in the northeastern Yeongnam Massif, indicating the presence of regional Paleoproterozoic subduction zones along the northern margin of the Yeongnam Massif at ca. 2.00–1.97 Ga. Meanwhile, ca. 2.00–1.97 Ga subduction-related magmatism has not been reported from the northern Gyeonggi and Nangrim Massifs in the Korean Peninsula or the Jiao–Liao–Ji belt in the eastern North China Craton, indicating that the Yeongnam Massif may not be correlatable with the northern Gyeonggi and Nangrim Massifs or the Jiao–Liao–Ji belt. The Yeongnam Massif may be correlated with the Cathaysia Block in the South China Craton and may have been located near Laurentia and the Siberian Craton within the Columbia supercontinent.

Whether swarms of preferentially oriented dykes are controlled by regional stress fields, or passively exploit basement structural fabric, is a much debated question, with support for either scenario in individual case studies. The Sarnu-Dandali alkaline complex, near the northwestern limit of the Deccan Traps continental flood basalt province, contains mafic to felsic alkaline volcano-plutonic rocks and carbonatites. The complex is situated near the northern end of the 600 km long, NNW–SSE-trending Barmer-Cambay rift. Mafic enclave swarms in the syenites suggest synplutonic mafic dykes injected into a largely liquid felsic magma chamber. Later coherent dykes in the complex, of all compositions and sizes, dominantly strike NNW–SSE, parallel to the Barmer-Cambay rift. The rift formed during two distinct episodes of extension, NW–SE in the early Cretaceous and NE–SW in the late Cretaceous. Control of the southern Indian Dharwar structural fabric on the rift trend, as speculated previously, is untenable, whereas the regional Precambrian basement trends (Aravalli and Malani) run NE–SW and NNE–SSW. We therefore suggest that the small-scale Sarnu-Dandali dykes and the much larger-scale Barmer-Cambay rift were not controlled by basement structure, but related to contemporaneous, late Cretaceous regional ENE–WSW extension, for which there is varied independent evidence.

Moghra territory is one of the most encouraging regions for watered farming and development in the northern part of Western Desert. To achieve that development groundwater is considered the most favorable tool. Geophysical survey in terms of geoelectrical resistivity sounding has been conducted using the Schlumberger array – eleven vertical electrical soundings (VES’s) were measured on the study area. The aim of this study was to investigate the hydrogeological condition at the area under investigation. Three geoelectric sections are prepared; each of them is composed of four units. The first layer has resistivity ranging from 58 to 2029 ohm.m and thicknesses from 0.46 to 10.7 m characterizing a gravely sand facies of Quaternary age (Pleistocene to Holocene). The second geoelectrical layer has resistivity values ranging between 188 and 518 ohm.m which are comparatively high, with various depths varying between 14.7 and 25.8 m from Lower Miocene age. It is formed of sand and gravel. The third geoelectrical layer is considered the aquifer for the area under investigation with moderate electrical resistivity values (17–111 ohm.m), and could be recognized sometimes as the most extreme depth of penetration. At the maximum depth of penetration of this area, the lower layer (fourth layer) was recognized with the highest electrical resistivity values (1227–8935 ohm.m) of basaltic sheet (Precambrian age). Structurally, the study area is influenced by three faults two of them are geological/geoelectrical faults forming a graben structure at the central part; the third fault is a geoelectrical fault and is located to the west of the graben structure forming a horest structure.

The chemical evolution of anoxic seawater is chronicled in part by the abundance of sedimentary Fe minerals. Our view of the chemical state of the oceans throughout much of Earth's history, therefore, hinges on understanding the behaviour of Fe2+ in seawater and sedimentary pore water. However, the formation pathways and precipitation rates of a number of sedimentary Fe(II)-minerals are poorly understood. For example, because siderite is widely distributed in Precambrian rocks, it is frequently assumed that seawater Fe2+ concentrations would have been poised at siderite equilibrium. Yet a variety of studies indicate that siderite precipitation would have been strongly controlled by kinetic processes rather than equilibrium behaviour, prompting a reconsideration of the Precambrian Fe cycle and those element cycles to which it was connected. To address this issue, we experimentally investigated spontaneous (or homogeneous) precipitation of Fe(II)-carbonate across a range of pH and pCO2 conditions, and in the presence/absence of SiO 2 ( a q ) . Our data show that the formation of siderite directly from seawater is initiated by the formation of precursor amorphous Fe carbonate (AFC). The precursor, once formed, rapidly transforms into either siderite or chukanovite (Fe2CO3(OH)2; metastable with respect to siderite), dependent on the availability of carbonate ions. Precipitation rates estimated from our experiments reveal a strong exponential dependence on the saturation state of the solution, consistent with theoretical predictions. This relationship, in turn, delineates a critical supersaturation threshold for homogeneous Fe(II)-carbonate precipitation from anoxic and ferruginous water. Incorporation of our experimental data with constraints on the ocean–atmosphere carbon system shows that significant accumulations of siderite in Precambrian sedimentary rocks require an origin from fluids that were distinct from seawater in equilibrium with the ocean–atmosphere inorganic carbon reservoir. In addition, these data show that the maximum Fe2+ concentration in Precambrian oceans was controlled by Fe(II)-silicate precipitation and not by Fe(II)-carbonate, consistent with the sedimentary record of Fe-rich Precambrian rocks. More broadly, these results contribute to a quantitative framework that underpins the utility of Fe(II)-carbonate as a sensitive palaeo-environmental proxy for ferruginous systems where CO2 may have been present.

The Indian Subcontinent constitutes a distinctive geographic entity that can be divided into three geomorphic provinces: (a) the Indian Peninsula, (b) the Himalayas, and (c) the Indo-Gangetic Alluvial Plains. The Indian Peninsula is a triangular-shaped landscape of ancient landmass with record of a prolonged history of erosion, denudation, and resurgent tectonic activities. The present-day geomorphic characteristics of the entire terrain have resulted because of more recent block uplift-type tectonic activities. Evidence of ancient gently rolling, almost featureless ‘peneplain’ surfaces marking the top of upland areas like plateaus and mountains provides proofs of a prolonged period of denudation reaching the base level of erosion much before its elevation to the mountainous height. The Indo-Gangetic Alluvial Plains are the youngest geomorphic unit that evolved as a foreland basin in the frontal region of the rising Himalayas. The Himalayan mountain range is divided axially into six morphotectonic units, each showing a distinctive lithostratigraphic, tectonic, and geomorphic (mainly topographic) characteristics and evolutionary history. The geophysical characteristics of the Indian Subcontinent provide clear evidences of reconstitution of the Indian Shield simultaneously with the pruning of the pristine Precambrian Indian Shield with the formation of the present-day Indian Subcontinent.

Traditionally, the triangular-shaped Peninsular India is described as the Indian Shield. Geological information, however, suggests that the Precambrian terrane of Peninsular India once constituted a part of much larger crustal block described as the ‘Greater India’. The pristine size of the Indian Shield is difficult to ascertain, but surely, it extended considerably in the north, as also in the southeast into Antarctica and in the southwest into Madagascar and Seychelles. The geological and geophysical data indicate that much of the Himalayan edifice is made of components sliced off from the Indian Shield during the late Cenozoic. Apart from that, the slicing of the Indian Shield due to the separation of Antarctica, Madagascar, and Seychelles during the late Phanerozoic helped in pruning the pristine size of the Indian Shield to that of Indian Subcontinent. Further, the process of fragmentation of the pristine Indian Shield into the shape and size of Indian Subcontinent during the different Phanerozoic (post-Precambrian) events has also grossly altered the geological, geomorphic, and geophysical characters of the terrain known to us as Indian Subcontinent.