Academic literature on the topic 'Palaeo- Mesoproterozoic'

Rapakivi granites and several small leucogabbroic and gabbroic bodies are located in the Rangnim Massif, North Korea. The largest batholith in the Myohyang Mountains covers an area of 300 km2 and was intruded into Precambrian metamorphosed rocks. It has a SHRIMP U–Pb zircon weighted mean 207Pb/206Pb age of 1861 ± 7 Ma. The country rocks of rapakivi granites are Neoarchaean orthogneisses and Palaeo-Mesoproterozoic graphite-bearing metasedimentary rocks of granulite facies, and they are similar to those of the rapakivi granites and anorthosites exposed in South Korea and in the North China Craton. We conclude that the three massifs in the Korean Peninsula commonly record an identical Palaeo-Mesoproterozoic anorogenic magmatic event, indicating that they have a common Precambrian basement with the North China Craton.

The paper analyses eight silicified Mesoproterozoic microbiotas of peritidal and shallow subtidal settings from Siberia, Ural and India. These microbiotas, subdivided into three main types - Kotuikan, Satka and Kataskin-are characterized by different taxonomic composition of microfossils. Mat-building entophysalidacean algae Eoentophysalis, ellipsoidal akinetes of nostocalean cyanobacteria genus Archaeoellipsoides and spherical large planktic microfossils Myxococcoides grandis of uncertain affinities dominate the Kotuikan-type microbiotas, the short trichomes are a rare but a distinctive element of these assemblages. The Satka type microbiotas are dominated by mat-building hormogonian cyanobacteria of genus Siphonophycus and chroococcacean dwellers genera Gloeodiniopsis, Eosynechococcus, Sphaerophycus, whereas entophysalidacean cyanobacteria are conspicuously missing and akinetes of genus Archaeoellipsoides occur but never abundant. Besides, microbiotas of Satka type include morphologically simple remains of phytoplanktic eukaryotic microorganisms-sphaeromorphic acritarchs genera Satka, Pterospermopsimorpha, Granomarginata? and Leiosphaeridia. The late Mesoproterozoic Kataskin-type microbiotas contain mat-forming entophysalidacean, oscillatoriacean and nostocalean as well as mat-dwelling and planktic chroococcacean cyanobacteria, but the most typical feature of these microfossil assemblages is the presence of a stalked cyanobacterium, Polybessurus bipartitus. Almost all-available data on relevant silicified Mesoproterozoic microbiotas from China, Greenland and North America have been analysed. Further different types of Mesoproterozoic silicified microbiotas have been compared with Palaeo- and Neoproterozoic microbiotas in cherts as well as with the assemblages of organic-walled microfossils throughout the world and explained differences and similarities in their composition. The analysis indicate that the Mesoproterozoic microbiotas have their own specific taxonomic composition and differ from the Palaeo- and Neoproterozoic microfossils occurring in the same and different palaeoenvironmental setting. The presence of newly evolved type of cyanobacteria, red algae and acanthomorphic acritarchs in the Kataskin-type microbiotas and contemporaneous open-shelf facies suggest that the terminal Mesoproterozoic can be separated as an independent biostratigraphical unit.

AbstractThe Neoproterozoic Jiangnan orogenic belt records the accretion and collision between the Yangtze and Cathaysia blocks in South China. The orogen is divisible into three units: a northeastern domain (also referred to as the Huaiyu or Shuangxiwu domain), a central domain (Jiuling domain) and an undifferentiated southwestern domain. Detrital zircons from the oldest sequences (Shuangqiaoshan, Lengjiaxi, Fanjingshan and Sibao groups) in the central and southwest domains yield similar age spectra with major age populations at c. 875–820 Ma, along with minor Palaeo- to Mesoproterozoic and Archaean ages. The dominance of detrital ages close to the deposition ages of the units, along with juvenile zircon Hf isotopic compositions and arc-like whole-rock compositional data, indicate the sedimentary units accumulated adjacent to a convergent plate margin magmatic arc. The presence of Mesoproterozoic and older zircons, both as detritus in the units and as xenocrysts within igneous rocks displaying a subduction-related signature, along with the compositional data, place the magmatic arc along a continental margin. In the northeastern domain, the oldest coeval sequence (Shuangxiwu and Qigong groups) and arc igneous suites are dated at c. 970–850 Ma, and lack older detritus and xenocrysts, indicating they represent an accreted oceanic arc system.

AbstractThe North Qilian Orogenic Belt is surrounded by the Tarim Craton to the NW and the North China Craton to the NE. The Precambrian continental crust remnants that are distributed in the North Qilian Orogenic Belt are termed the North Qilian Block (NQB), and their tectonic evolution has profound implications for the evolution of the Columbia Supercontinent. Here we present major- and trace-element and Sr–Nd–Hf isotope data for (meta-) basalts from the Beidahe Group (BDHG) and Zhulongguan Group (ZLGG) in the western North Qilian Orogenic Belt, to investigate the tectonic evolution of the NQB during the Proterozoic Eon. The protoliths of Palaeoproterozoic amphibole gneisses and plagioclase amphibolites from the BDHG are calc-alkaline series basalts. These metabasalts show island-arc-basalt affinities with variable Nd and Hf isotopes (ϵNd(t) = −5.0–0.6 and 2.7–4.3; ϵHf(t) = −14.2–2.0 and 6.9–8.8) and were generated by partial melting of the asthenospheric mantle that was metasomatized by aqueous fluid and sediment melt in a continental-arc setting. The early Mesoproterozoic ZLGG basalts show features of shoshonite-series basalts and are geochemically similar to ocean-island basalts. These basalts show variable (87Sr/86Sr)i, ϵNd(t) and ϵHf(t) values of 0.70464–0.70699, −1–2.6 and −1.5–5.7, and are products of mantle plume magmatism that participated with subducted oceanic crust in an intracontinental rift setting. This study suggests that the NQB underwent tectonic evolution from palaeo-oceanic subduction to intracontinental rifting during the Palaeoproterozoic–Mesoproterozoic eras. Furthermore, the above tectonomagmatic events were in response to convergence–splitting events of the Columbia Supercontinent during the Palaeoproterozoic–Mesoproterozoic eras.

The Tsodilo Hills Group strata exposed in the Tsodilo Hills are an association of meta-arenites, meta-conglomerates, quartz-mica schists, sandstone, red siltstone and sedimentary breccia deposited on an open siliciclastic marine shelf between the Late Palaeoproterozic and Late Mesoproterozoic, and outcropping in NW Botswana. The succession is dominated by three micaceous quartzite units interlayered with subordinate lenses and wedges of other rock types. Facies gradients from S to N are expressed by decreasing content of muscovite at all levels of metasediment organisation from thin wedge-shaped units to thick quartzite complexes, as well as a decrease in pebble content and increase in the arenaceous matrix in some metal conglomerate beds, matching regional palaeotransport direction. Well-rounded pebbles of rocks are flat, suggesting redeposition from a beach environment. Lenticular conglomeratic bodies with erosional lower boundaries represent infills of local incisions in the sandy bottom sediments. The abundance of laterally discontinuous lithological units reflects shelf palaeotopography controlled and modified by deposition and migration of large bed forms, ranging from megaripple marks (or submarine dunes) to sand waves. Deposition was influenced by tides and two regressive events. The older regression resulted in a marker unit of tidal mudflat-related red-bed facies: mudstone, siltstone, channel-fill sandstone and sedimentary breccia. The second regression is indicated by a tabular conglomerate marker reflect-ing increased input of coarse terrigenous material.

The Kaladgi Basin, one of the important Proterozoic Sedimentary basins of Peninsular India, exposes a thick sequence of Proterozoic succession composed of a variety of lithologies with predominance of arenaceous rocks interrupted with Carbonate sediments at different stratigraphic levels. The present work focuses mainly on understanding the Sedimentological nature and diagenetic character of the Lower part of the Lokapur sub-group rocks that are exposed in and around Savadatti Town, Belagavi District of Karnataka. These rocks are mainly composed of Arenite sequences of varying grain size. The clastic succession comprises lithologies Sandstones with minor conglomeratic facies at the lower regimes. An attempt is made to identify the detailed petrographic character of the sandstones to understand the provenance and depositional environments based on the detailed petrographic observation. The study suggests that the coarse clastic conglomerates are essentially polymictic types and the sandstones are sub-mature to mature (mineralogically), medium to coarse grained and can be categorized mainly into lithic/feldspathic and quartz arenites. Minor occurance of feldspars as the framework constituent also suggests that the rock have undergone considerable transport. However with their variable degree of alteration (from fresh to partially alter to completely altered grains) associated with textural maturity and nature of Quartz point towards the possibility of derivation of these sediments from two different sources. Palaeocurrent data that indicate a NW palaeoslope suggest the derivation of sediments from a variety of granitic and gnesssic crystalline complexes occurring along the basin margin. The maturity of the sandstones (Quartz Arenites) is attributed to the recycling and re-working of the older sediments. Analysis of Textural parameters of these rocks pointed towards deposition under beach environments. The lack in preservation of much amount of feldspar in these sandstones is indicates a remote source and relatively dry-arid climate of the source area.

Este trabalho caracteriza a evolucao tectónica, identificando a cronologia dos principais eventos tectono-magmáticos do Pré-Cambriano Boliviano. A complexa evolucao geológica do Oriente da Bolívia se estende desde o Paleo a Mesoproterozoico compreendendo as provincias Rio Negro Juruena, Rondoniana San Ignacio e Sunsás na regiao conhecida como Bloco Paragua. Diversos métodos de estudo foram adotados na pesquisa tendo em vista tratar-se de um terreno com evolução policíclica e incluiram, alem do mapeamento geológico e petrografía dos principais tipos de rocha, a metodologia U-Pb para determinação da idade de corpos graníticos e a metodologia Sm-Nd na estimativa de idade das fontes destes corpos plutônicos e inferências de ordem petrogenética, bem como dados geoquímicos obtidos para detalhamento das interpretações petrogenéticas. Nas interpretações houve ainda a avaliação critica da literatura recente, a integração de dados de campo, aeromagnéticos e aero-radiométricos, inclusive embasadas na experiência profissional do autor. Os dados obtidos na última década modificaram substancialmente a concepcao do Pré-Cambriano Boliviano, tendo sido caracterizados tres conjuntos litológicos temporalmente distintos antecedendo a orogenia San Ignacio. O granito Correreca na parte meridional da area possui idade 207Pb-206Pb de 1,92 1,89 Ga, com modelo de idades TDM de 2,8 a 2,9 Ga e valores de Nd(t) de -8,5 e -9,4. A Suite Yarituses composta pelos granitos La Cruz, Refugio e San Pablo possui quimismo calcio-alcalino. Os dados U-Pb SHRIMP, TIMS e abrasão por laser-ICPMS indicam a formação desta suíte no lapso temporal entre 1673 a 1621 Ma. A idade de cristalização U-Pb SHRIMP do granito La Cruz é de 1673 ± 21 Ma, idade modelo TDM de 1,83 Ga e valor de Nd(t) de + 2.1 indicativo de derivação mantélica. O granito Refugio tem idade U-Pb TIMS de 1673 ± 25 Ma e o pluton San Pablo idade ICPMS por laser ablasion de 1621 ± 80 Ma (idade TDM de 1,7 Ga e valor de Nd(t) de + 3,5). Este conjunto de dados sugere uma derivação mantelica principal para a suite Yarituses. O granodiorito San Ramón possui uma idade de cristalização de 1429 ± 4 Ma (SHRIMP), TDM de 1,7 Ga, e Hf(t) entre + 3,49 e +5,47 e representa um evento de geração da crosta, a partir de material juvenil. O magmatismo, deformação e metamorfismo da orogênese San Ignácio constitui o principal evento representado na área de estudo, cujo maior representante é o Complexo Granitoide Pensamiento com seus plutons sin a tardi-cinemáticos e tardi a pos-cinemáticos. Os granitos San Martín, La Junta e Diamantina possuem idades de cristalizacao de 1373- 1340 Ma, idades modelo TDM de 1,6 a 2,0 Ga, com valores de Nd(t) de + 2.0 ate -4,0. Os granitos Las Maras, Talcoso, Limonal e San Andrés produziram idades de cristalização de 1347 a 1275 Ma. As idades TDM dos granitos Limonal e San Andrés correspondem a 1,9 e 1,8 e Nd(t) de -1,4 e 1,6 respectivamente. A geoquímica em rocha total indica uma composição compatível com arco magmático, corroborando a assinatura acima dos parâmetros petrogeneticos. Em suma, a orogênese San Ignácio representa um arco acrescionário de natureza continental que construiu a arquitetura final da província Rondoniana-San Ignacio pela colisão entre o Bloco Paraguá e a província Rio Negro-Juruena. A evolução mesoproterozoica finaliza com a formação da faixa colisional Sunsás. Esta orogênese produziu plutonismo sin a tardi cinematico e tardi a cinemático marcando o limite com o bloco Paragua. A natureza alóctone e colisional do orogeno Sunsás como o evento mais jovem do Cráton Amazônico é marcada por frentes tectônicos, bem definidos de sentido sinistral, convergentes para o Bloco Paragua.
This work characterizes the tectonic and magmatic evolution of the Precambrian shield of Bolivia. The complex geological evolution of the eastern Bolivia extends from the Paleo- to Mesoproterozoic, and can be related with the magmatic and metamorphic events that are ascribed to the Rio Negro - Juruena (1.78-1.60 Ga), Rondonian - San Ignacio (1.56-1.30 Ga) and Sunsás Aguapei (1.25-1.00 Ga) provinces, known in Bolivia as the Paragua block. Several methods of study were adopted in the research with the scope that this is a land with polycyclic evolution. As such our study included, besides the geological mapping and petrography of major rock types, the U-Pb age determinations of granitoid rocks, Sm-Nd and Rb-Sr isotopic analyses, as well as geochemical data. At the interpretation there was the critical evaluation of recent papers, the integration of field data, aeromagnetic and aero-radiometric, including the field experience of the author. The data obtained in the last decade have substantially changed the geology of the Bolivian Precambrian shield. It has been characterized three temporally distinct granite suites preceding the San Ignacio orogeny (1.37-1.30 Ga): the Correreca granite in the southern part of the area has 207Pb/206Pb age from 1.92 to 1.89 Ga, with TDM model ages of 2.8 to 2.9 Ga and values of Nd(t) of -8.5 and -9.4; the Yarituses suite (La Cruz, Refugio and San Pablo granites) shows calc-alkaline signature. Data U-Pb SHRIMP, TIMS and ICPMS laser ablation indicate the formation of this suite between 1673 to 1621 Ma. The U-Pb SHRIMP crystallization age of La Cruz granite is 1673 ± 21 Ma, TDM model age of 1.83 Ga and Nd(t) of +2.1 indicative of a predominantly mantle source. The Refugio granite has U-Pb TIMS age of 1673 ± 25 Ma and the San Pablo pluton yields a ICPMS Laser ablation age of 1621 ± 80 Ma (TDM age of 1.7 Ga and Nd(t) +3.5). These data suggest again a mantle source for the Yarituses suite. The San Ramon granodiorite event has a crystallization age of 1429 ± 4 Ma (SHRIMP), TDM of 1.7 Ga, and Hf(t) between +3.49 and +5.47 and represents a juvenile accreted episode. The magmatism, deformation and metamorphism of San Ignacio orogeny is the main event of the study area, represented by the Pensamiento Granitoid Complex with sin to late-kinematic and late to post-kinematic plutons. The San Martín, La Junta and Diamantina granites have crystallization ages of 1373 - 1340 Ma, TDM model ages from 1.6 to 2.0 Ga, with values of Nd(t) from 2.0 up to -4.0. The Las Maras, Talcoso, Limonal and San Andrés granites yielded crystallization ages of 1347-1275 Ma. The TDM ages of Limonal and San Andrés granites are between 1.9 and 1.8 Ga and the Nd(t) values of -1.4 and +1.6 respectively. The whole rock geochemistry of these granites indicates a composition consistent with the magmatic arc. Thus the San Ignacio orogeny represents a continental accretionary arc that built the final architecture of the Rondonian-San Ignacio province (1.56-1.30 Ga) by the collision between the Paragua block and the Rio Negro -Juruena province (1.78-1.60 Ga). The Mesoproterozoic evolution of the SW margin of the Amazonian craton ends with the formation of the Sunsás collisional belt that produced sin to-late and late topost- kinematic plutonism. The allochthonous and collisional nature of the Sunsás orogeny is marked by tectonic fronts, with well-defined sinistral sense, converging towards the Paragua block.

Proterozoic crustal provinces that underlie much of the United States record prolonged southward growth of the North American craton (Laurentia) between ca. 1.8 and 1.0 Ga. Exposures throughout central Arizona's Tonto Basin represent multiple generations of sedimentary basins formed during Proterozoic accretion. Metasedimentary rocks sampled across Tonto Basin resulted have identified remnants of a previously undated but potentially widespread Mesoproterozoic basin called the Yankee Joe Basin. Sediments of Yankee Joe Basin are particularly interesting because they have depositional age's ca. 200 m.y. younger than previously thought and because they are rich in detrital zircons with ages between 1.6-1.48 Ga, a time period not widely represented in the igneous record of Laurentia. Metasedimentary rocks with similar age and provenance are found in northern New Mexico and in the lower parts of the Belt Supergroup in northern Idaho, Montana, and Canada. Zircon ages and Hf isotopic characteristics suggest the distinctive 1.6-1.48 Ga grains might have been derived from non-Laurentian sources, most likely one or more formerly adjacent cratons such as north Australia. Circa 1.48-1.43 Ga units in the Yankee Joe Basin rest disconformably on Paleoproterozoic quartzite, and all were deformed together during northwest-directed foreland-style thrusting. This event was previously interpreted to represent the ca. 1.66-1.60 Ga Mazatzal orogeny. However, new findings challenge this view and suggest a major deformation event occurred ca. 1.47-1.45 Ga, possibly representing the Picuris orogeny as recently described in northern New Mexico. Regional thrust faulting during the Mesoproterozoic might have unroofed and removed significant portions of the Yankee Joe section, potentially shedding detritus north from the thrust front into the upper parts of the Belt-Purcell basin.

Detrital zircon ages and hafnium isotope compositions provide a critical test of sediment provenance and depositional age and were used to reassess sedimentary age and sources multiple Proterozoic unconformity-bound metasedimentary successions exposed across Arizona. These successions represent a series of ca. 1.75 to 1.3 Ga basins that span the Proterozoic accretionary provinces of southwestern Laurentia, representing key elements in the tectonic evolution of the continental margin. The ca. 1.75 Ga Vishnu Schist contains a bimodal detrital zircon age distribution with prominent Archean (2.5 Ga) and Early Paleoproterozoic (1.8 Ga) populations and minor juvenile 1.75 Ga input. The predominance of 3.3-1.8 Ga detrital zircon ages and initial epsilon Hf (ϵHf) values of +4 to -13 in both detrital grains of the Vishnu Schist and xenocrystic grains in plutons from cross-cutting plutons suggests the Vishnu Schist was derived primarily from recycling of the Mojave and other older basement provinces, possibly including one or more outboard cratons. In contrast, the ca. 1.74-1.72 Ga Jerome and ca. 1.72 Ga Alder successions of central Arizona, show a marked shift to strongly unimodal detrital zircon age distributions with initial ϵHf values ranging from +13 to -5, generally more positive and near-juvenile. Cross-cutting ca. 1.74-1.72 Ga plutons that intrude these rocks also have largely juvenile Hf isotopic signatures. The prominent ca. 1.73 Ga age peaks and relatively juvenile ϵHf values of detrital grains and plutons are consistent with first-cycle sediment derived from local arc systems formed during progressive assembly of the Yavapai province with the older Mojave province. The ca.1.66-1.63 Ga Mazatzal succession is more compositionally mature and contains broader unimodal detrital zircon age spectra, interpreted to represent increasing regional crustal recycling following the culmination of the Yavapai orogeny.

In the northern Tonto Basin, detrital zircon age populations from similar looking quartzite and shale successions were used to develop new regional correlations. First, the Houdon Quartzite of the Alder Group was correlated to the Pine Creek Conglomerate. Second, the Mazatzal Group that unconformably overlies the Alder Group, was found to be deposited ca. 1631 ± 22 Ma, consistent with the White Ledges Formation and the quartzite succession at Four Peaks. Third, a new detrial zircon population collected from the upper part of the argillaceous section in the core of the Four Peaks synform yield ages between 1591-1560 Ma suggesting this section is correlative to the Yankee Joe Formation. (Abstract shortened by UMI.)

The Gawler Craton, South Australia, consists of late Archaean to early Mesoproterozoic igneous and supracrustal lithologies which preserve a deformation history lasting the duration of the Palaeoproterozoic. Understanding the evolution of the Gawler Craton is of significance in global supercontient reconstructions as it preserves evidence for earliest Palaeoproterozoic collisional orogenesis (c. 2460-2430 Ma) and, in conjunction with the North Australian Craton and Antarctica, has often been correlated to the western margin of Laurentia. In addition, the Gawler Craton is also host to the world-class Olympic Dam Fe-oxide-Cu-Au-U type-deposit (world's fourth largest Cu and largest U deposit) and related Fe-oxide-Cu-Au-U and Cu-Au mineralising systems. Despite the various geologically and economically important characteristics of the Gawler Craton there has traditionally been a poor understanding of the tectonothermal evolution of the Gawler Craton, in particular for the Palaeoproterozoic. This study addresses and refines the Palaeo-to Mesoproterozoic tectonothermal evolution of the Gawler Craton. This is done using geochemical, geochronological and isotopic analytical techniques to better understand selected supracrustal and igneous lithologies in the Gawler Craton and the orogenic events which have affected them. Largely unexposed metasedimentary lithologies of the northern Gawler Craton record multiple deformation events but have previously been virtually unconstrained with respect to their timing of protolith deposition and the age of deformation/metamorphism. New geochronological data demonstrate these metasedimentary lithologies were deposited during the time period -1750-1730 Ma before being metamorphosed and deformed during the Kimban (1730-1690 Ma) and Kararan (1570-1545 Ma) Orogenies. Detrital zircon geochronology and isotopic and geochemical characteristics of the sampled metasedimentary lithologies suggest a relatively similar protolith sedimentary succession was deposited across a large extent of the northern Gawler Craton. Detritus for the sedimentary protolith does not appear to have been sourced from the Gawler Craton. Instead the protolith it is more consistent with a North Australian Craton provenance suggesting a proximity between the northern Gawler Craton and North Australian Craton at the time of protolith deposition. The newly defined presence of the Palaeoproterozoic Kimban Orogeny in the northern Gawler Craton demonstrates the Kimban Orogeny to be a major, high-grade, craton-wide orogenic event. This finding contradicts previous suggestions that the northern Gawler Craton was accreted to the proto-Gawler Craton during the later Mesoproterozoic Kararan Orogeny. In addition, previous reconstruction models for the Palaeo-to early Mesoproterozoic often cite the felsic Tunkillia Suite (1690-1670 Ma), western and central Gawler Craton, as representing arc magmatism prior to the subsequent amalgamation of the Gawler Craton during the Kararan Orogeny. New geochemical and isotopic data for the Tunkillia Suite have allowed for re-examination of the tectonic setting for the petrogenesis of the Tunkillia Suite. Contrary to previous suggestions (based upon discrimination diagrams), the mineralogy, geochemistry and isotopic characteristics of the Tunkillia Suite are not consistent with arc-magmatism. Instead the Tunkillia Suite is interpreted to represent a late-to post-tectonic magmatic suite generated during the waning stages of the Kimban Orogeny. This petrogenesis further highlights the importance of the Kimban Orogeny as a fundamental tectonothermal event in the evolution of the Gawler Craton. Subsequent to the Kimban Orogeny, the Gawler Craton was thought to undergo a period of subduction-related magmatism (St Peter Suite) prior to the anorogenic magmatism of the voluminous felsic Gawler Range Volcanic (GRV) and Hiltaba Suite magmatism (1595-1575 Ma). New geochronological data for the ms-bi-gt-bearing peraluminous Munjeela Suite (1590-1580 Ma) have demonstrated the Hiltaba/GRV event was accompanied by significant crustal anatexis not associated with the Hiltaba/GRV magmatism. The Munjeela Suite and metasedimentary enclaves within it demonstrate that the Gawler Craton was likely to be undergoing compressive deformation and crustal thickening sometime during the petrogenesis of the Hiltaba/GRV magmatism. This suggests the Hiltaba/GRV magmatism did not occur in an anorogenic setting as previously proposed. The findings of this study are incorporated into a revised tectonothermal evolution of the Gawler Craton. This is used to discuss previous reconstruction models for Proterozoic Australia and provide a new reconstruction model of Australia and Antarctica during the Palaeoproterozoic. Important facets of the proposed model are links to the Archaean-Early Palaeoproterozoic Sask Craton in the Trans-Hudson Orogen, Laurentia, and the joint evolution of the North Australian and Gawler Cratons throughout the entire Palaeoproterozoic.
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Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2008

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The Palaeo- to Mesoproterozoic Cuddapah Supergroup was deposited in the Cuddapah Basin, which is one of a number of Proterozoic volcano-sedimentary basins that overlie the Indian Shield. On the south-western margin of the basin, the stratigraphic succession in the basal Papaghni and Chitravati groups is initially composed of gravelly fluvial deposits with dominant sediment input coming from the western foreland. These are succeeded by shallow-water stromatolitic dolomite and shale with a significantly reduced siliciclastic component, and finally by sub-tidal laminated silt and sand. A detailed facies analysis of these rocks suggests that deposition occurred initially in an active extensional setting which subsequently developed into a passive extensional setting. Stable isotope geochemistry of dolomites in the Vempalle Formation of the Papaghni Group indicates that deposition of the formation may initially have occurred in a restricted setting where δ13C varied according to fractionation via environmental processes. Whether the Vempalle Formation was deposited in a shallow marine or lacustrine milieu is equivocal; δ13C values may correlate with the conclusion of the global oceanic “Lomagundi” positive δ13C excursion around 2100 Ma, however, this inference requires the carbonates to have been precipitated in oceanic water, and have retained their primary isotopic signature during pervasive dolomitisation. U-Pb dating of detrital zircon grains from the Gandikota Formation – previously thought to be the uppermost formation of the Chitravati Group – yields a maximum depositional age of 1207 ± 22 Ma. This is significantly younger than intrusive igneous rocks within the Cuddapah Supergroup and it is therefore likely that the Gandikota Formation is part of the overlying Meso- to Neoproterozoic Kurnool Group. The detrital zircon age spectrum of the Gandikota Formation indicates significant sediment input from the east, which is likely to be a result of the thrusting of the Eastern Ghats Belt onto the Eastern Dharwar Craton and a reversal of the prevailing extensional regime in the Cuddapah Basin. A number of authors have proposed a genetic link between the Cuddapah Basin and several other Proterozoic basins of the Indian Shield. This study provides no reason to directly correlate the temporally and spatially distinct basins.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2011