The Twyfelfountein Formation in Namibia and the Botucatu Formation in East South America represent a single dune-field separated through rifting of Gondwana during the Cretaceous. The Early Cretaceous Botucatu desert was the last depositional system operating in the Gondwanan heartland prior to continental drift initiated by the Paraná-Etendeka large igneous province. The dry-aeolian dunes, draas and sandsheet deposits of the Botucatu Formation are also present in the Twyfelfountein Formation. We aim to test whether the two formations had a similar provenance. The provenance of the Twyfelfountein is established using a multiproxy dataset including petrography, grain-size, heavy mineral composition and geochemistry, and detrital zircon U-Pb dating (16 samples from 5 sites in the Huab Basin, Namibia). Results indicate dominantly fine-to-medium feldspatho-quartose sands, rich in resistate minerals such as tourmaline, garnet and Fe-Ti oxides. Detrital zircon ages yielded mostly Cambrian-Neoproterozoic (450 to 650 Ma) ages. The geochemistry of garnet and tourmalines shows that these grains are originally sourced from amphibolite-facies metasedimentary rocks and acidic granitoids. The Botucatu Formation typically comprises sands that are quartzose, fine-medium sized, ZTR-rich with a predominance of Neoproterozoic detrital zircon ages. Based in this work and previously published data, the Twyfelfountein Formation sands are considered very similar to those of the Botucatu Formation, demonstrating a similar provenance for, and supporting the correlation of both units. The sands of the palaeodesert were derived from reworking of underlying strata from the Paraná and Huab basins. Furthermore, comparison of the datasets for both the Twyfelfountein and Botucatu formations shows a trend from SW to SE in sand composition due to the changes in the composition of the underlying pre-desert strata.

Grain size distribution in deserts is driven by a combination of autogenic controls suchas grain abrasion and sorting due to wind transport and allogenic controls such asprovenance and spatial changes in wind-direction. Downwind grain-size trends inpresent day sand seas display contrasting results. For example, the Namib and HexiCorridor sand seas show broad downwind fining and sorting trends which are notpresent in the Ténére, Australian and Sinai sand seas. This study examines the grainsize distribution along the margins of the Cretaceous Botucatu paleodesert across anarea of >1,000,000 km2 to determine the relative importance of autogenic and allogeniccontrols on sand distribution. A comparison between the spatial distribution of grainsize metrics with detrital zircon geochronology as a provenance test, paleowindpatterns as a wind-regime test and 3 transects along the basin paleomargins as adownwind abrasion test, are used to quantify the main controls on Botucatupaleodesert grain-size distribution. Grain size dispersion shows an E to W finingpattern, which agrees with provenance control - in contrast to a N-S trend expected forthe predominant wind-regime control. In the NE region there is good evidence fordownwind fining due to aeolian abrasion – of about 0.4 μm by km, indicating that whilstdownwind fining due to abrasion does occur, but that it is limited by the rounded natureof available sands for Botucatu desert and possibly by mix of different provenancesources. The results suggests that the provenance of the available sand is the primarycontrol on the grain-size distribution in the Botucatu sand sea and potentially in mostlarge-scale dune fields.

The compilation of stratigraphic, sedimentologic, paleontologic and geochronological data allows the proposal of a regional stratigraphic framework for the Late Permian to Lower Cretaceous succession of the Paraná Basin. Each unit is characterized in terms of sedimentological and stratigraphic characteristics, ages (fossils and radiometric dating) and regional correlation, allowing the construction of an integrated stratigraphic chart. The Permo-Mesozoic sedimentary succession is mostly characterized by fluvial and/or aeolian systems that can be subdivided into eight distinct depositional sequences limited by unconformities of tectonic origin. These sequences correspond to the following stratigraphic units: Rio do Rasto, Buena Vista, Sanga do Cabral, Santa-Maria-Caturrita, Piramboia, Guará, Pedreira and Serra Geral. The Paraná Basin sedimentary record is marked by a very complex tectono-stratigraphic evolution, characterized by sedimentary units accumulating in different depocenters and with a highly fragmented preservation, reflecting regional tectonic events of Gondwana. Despite the incomplete record, a general evolutionary scenario can be reconstructed where the paleoclimates and wind regimes of western Gondwana are inferred. The Middle to Late Permian is characterized by a progressive aridization, evidenced by the presence of distributive fluvial systems (Rio do Rasto Formation) overlain by extensive aeolian dune deposits (Buena Vista Formation). The Triassic Period (Sanga do Cabral, Santa Maria and Caturrita formations) is marked by an essentially fluvial sedimentation indicative of relatively wetter climate conditions, with a well-marked peak of humidity in the Carnian Age. The Jurassic Period is characterized by fluvio-aeolian systems of the Piramboia Formation, Guará Formation and Pedreira Sandstone, indicating a semi-arid setting. The Lower Cretaceous (Valanginian-Hauterivian) is characterized by the development of an extensive paleoerg (Botucatu Formation) denoting hyperarid climatic conditions, which later switches to wetter conditions during the volcanic events of the Serra Geral Group. Despite these climatic variations during the Permo-Mesozoic, the wind regime from Permian to Lower Cretaceous remained dominated by westerly winds in the mid-latitudes and monsoonal winds in the mid-to-low latitudes of Gondwana.

The Cr-rich Jacurici Complex is located at the limit between the Serrinha Block and the Salvador-Curaca Belt, Northeastern Sao Francisco Craton. In order to better understand the age span of magmatism and tectonism, we have studied a basement high-grade charnockite orthogneiss, a metanorite of the Complex and a crosscuting undeformed quartz-feldspar pegmatite. For the orthogneiss, SHRIMP U-Pb ages of zircon cores and overgrowth rims yielded, 2966 +/- 9 Ma for crystallization and 2091 +/- 10 Ma for metamorphism, respectively. Zircons from the metanorite show internal textures consistent with high grade metamorphism. The U-Pb LA-ICP-MS age determination provided a 2099 +/- 6 Ma metamorphic age for the Jacurici Complex, indicating it was already emplaced during amalgamation around 2.1 Ga. Zircons from the undeformed quartz-feldspar pegmatite provided a LA-ICP-MS U-Pb age of 2083 +/- 11Ma, marking the end of the N-S transcurrence. The magmatic Jacurici Complex age remains undefined, but is equal to, or older than, 2.1 Ga. Therefore, possible correlations with other mafic-ultramafic intrusions, such as the Cu-rich Caraiba Complex, should be reassessed. Our results indicate that the N-S transcurrence ended earlier in the Jacurici Complex region than in the northwestern area of the Salvador-Curaca belt.

The Early Cretaceous volcanic Jaguarão Formation formed duringthe early stages of Gondwana breakup. These felsic rocks characteristically enclose numerous crustal xenoliths. Fieldwork, petrographic studies, and laser ablation multicollector ion coupled plasma mass spectrometer (LA-ICP-MS) U-Pb analyses were carried out to evaluate the xenoliths of the Jaguarão Formation. A base-to-top distribution of xenoliths in the different flows of the volcanic pile indicates that earlier flows incorporated centimeter-sized fragments of local underlying gneiss, granite, and quartz veins, with limited assimilation. In the middle part of the volcanic pile, the size of the xenoliths is smaller and assimilation textures are more frequent. At this same level, reequilibrated orthopyroxene and plagioclase antecrysts were recognized, suggesting fractionation coeval with assimilation in a lower magmatic chamber prior to extrusion. At the top, no visible xenoliths occur. U-Pb ages of the zircon xenocrysts served as a proxy for assessing the crust underlying the volcanic rocks. Most of the ages obtained are similar to the ages of the Eastern Dom Feliciano Belt cropping out nearby, ranging from 680 to 620 Ma, with a subordinate group ranging from 580 to 570 Ma, suggesting a shallow crust contribution. The presence of few Paleoproterozoic and Mesoproterozoic (1.0-1.2 Ma) zircons, however, suggeststhat the underlying terrain may be more complex..

The Lower Cretaceous Botucatu Formation comprises a dry-aeolian system developed in western Gondwana and preserved within the Parana Basin of central South America. Multiproxy provenance analysis (detrital zircon U-Pb dating, heavy mineral, petrographic and granulometric analysis) was undertaken along two 500 km transects of the northern Parana Basin (NW and NE transects). To assess the provenance variation within the aeolian stratigraphy, samples were taken from the base and top of the Botucatu Formation and from sandstones interbedded with volcanics in the overlying Serra Geral Formation. Granulometric analysis shows a mean fine- to very fine-grained sand. The bulk petrography yields an average composition of Q(91)F(6)L(2), and heavy mineral analysis gives a mean of 86% of zircon-tourmaline-rutile, demonstrating the overall polycyclic nature of the sediment. The discrete occurrence of garnet, apatite and epidote indicates local sediment input points, providing indirect evidence for point-sourced fluvial input into an overall dry aeolian system. Detrital zircon U-Pb LA-ICP-MS dating demonstrates a dominant Cambrian to Late Neoproterozoic (520-750 Ma) population with subsidiary Tonian-Stenian (0.9-1.2 Ga) and Orosirian-Rhyacian (1.9-2.3 Ga) contributions. The Botucatu Formation along the northern basin margin displays similar provenance to the southern part of the basin, pointing to a predominance of recycling processes within the basin. Statistical plots illustrate the detrital zircon age variability recording an upward decrease in the age proportion of Permian and Tonian-Stenian populations and an increase in Cambrian-Late Neoproterozoic dates towards the top. Such variability can be related to the recycling of distinct Parana Basin strata. The proportion of Cambrian-Late Neoproterozoic dates increases in the NE, indicating a possible input from the Ribeira Belt granitoids. Similar to major-scale dune-fields, Botucatu erg register variable sand sources there are possibly linked with coexisting depositional systems. In summary, the northern Botucatu erg is mostly fed by local sources reworked from underlying Parana Basin units, with little direct input from basement sources and limited impact of regional wind-pattern variability. (C) 2021 Elsevier B.V. All rights reserved.

Aeolian desert systems were widely distributed in South China during the Late Cretaceous. These systems developed under the control of subtropical highs and a monsoon climate. They reveal the evolution of palaeoclimate and palaeogeography and the regional palaeowind pattern in the South China interior during this period. Based on the analyses of sedimentology and facies architecture, this study examines and reassesses the aeolian succession of the Upper Cretaceous Daijiaping Formation in the southern Liyou Basin of southeast China. This aeolian desert succession records aeolian dune, dry and damp interdune and aeolian sandsheet sedimentation in streamflow, fluvial channel and overbank settings. Aeolian dune deposits comprise low-angle dune plinth strata and superimposed sets of cross-strata bounded by a hierarchy of bounding surfaces. The deposits record two morphological types of compound crescentic dunes and complex linear dunes. Palaeowind direction in the Liyou desert agrees with the subtropical high-pressure westerly and northeasterly wind pattern that existed in the mid to low latitudes of the Northern Hemisphere, in conjunction with possible monsoon climate conditions during the Late Cretaceous. The fault-bounded basin in which the succession accumulated experienced a high subsidence rate and a high supply and availability of windblown sand, which ensured hundreds of metres of thick accumulation of the dune field system. The occurrence of a near-surface water table and soft-sediment deformation in the aeolian dune foresets indicates that the monsoon rains could have recharged the groundwater system and resulted in episodes of relative water-table rise, which played an important role in the accumulation and preservation of aeolian systems in the Liyou desert basin. Gradual and progressive subsidence of the aeolian succession combined with water-table fluctuations allowed the preservation of the aeolian accumulation system.

The Jacurici mafic-ultramafic Complex hosts the largest chrome deposit in Brazil. This deposit is characterized by the presence of a massive chromitite layer that occurs in a single intrusion tectonically fragmented that, currently, outcrops in different segments along an N-S belt. The present work investigates the characteristics of these bodies through remote sensing techniques and airborne geophysical surveys, describing the geophysical and landform responses of economic targets. The study area presents magnetic anomalies when using 1 derivative filters and tilt derivative of the total magnetic field, whereas eU/K and eTh/K ratios define the best delimitations of igneous bodies using the gamma-spectrometric method. The information presented serves as a prospective parameter in the discovery of new lateral bodies in order to provide a guide for the discovery and analysis of similar deposits by Brazil.

An analysis of the petrophysical and diagenetic effects of the emplacement of Cretaceous basaltic lava flows (Serra Geral Formation) on aeolian sandstones (Botucatu Formation) has been undertaken on core samples from the Paraná Basin, Brazil. Between 0.1 and 1 m from the contact zone, acoustic wave velocities and porosities in sandstones show a significantly wider scatter than those located >1 m away from the lava contact. Higher P-wave values (average 3759.3 m s −1 ) occur between 0.1 and 1 m from the lava contact in contrast to those areas >1 m away (average 3376.8 m s −1 ), whilst the average porosity is 6.5% near the contact (0.1–1 m) and 10.7% away from the contact (>1 m). Petrographical evaluation reveals two diagenetic pathways responsible for modification of the petrophysical properties: early hydrothermal Mg-rich authigenesis (Type 1) and early chemical dissolution (Type 2). Type 3 diagenesis occurs away from the lava–sediment contact (>1 m), with the appearance of poikilitic calcite and smectite. The sandstone samples associated with Type 1 and Type 2 diagenesis display a decrease in porosity and increased acoustic velocities in relation to Type 3, while Type 3 samples show little or no variation in reservoir properties. The lava-induced diagenetic effects at the sandstone–lava contacts (0.1–1 m) may form a baffle or seal to fluids around the margins of the sandstone bodies. Therefore, whilst diagenesis associated with lava emplacement may hinder reservoir quality around the margins, the original reservoir properties are preserved within these large sandstone bodies. Supplementary material: Petrophysical and petrographical data are available at https://doi.org/10.6084/m9.figshare.c.5244473

Os corpos ígneos do Vale Jacurici hospedam o maior depósito de Cromo do Brasil. Esse depósito é caracterizado pela presença de uma camada maciça de minério que ocorrem em diversos corpos, segmentos de um possível corpo único fragmentado. O presente trabalho analisa as características desses corpos através de técnicas de sensoriamento remoto e levantamentos aerogeofísicos, descrevendo as respostas geofísicas e de relevo dos alvos econômicos. A área de estudo apresenta anomalias magnéticas quando utilizando-se filtros de 1ª derivada e tilt derivativo do campo magnético total, ao passo que razões eU/K e eTh/K definem as melhores delimitações dos corpos ígneos utilizando o método gamaespectrométrico. As informações apresentadas servem como parâmetro prospectivo na descoberta de novos corpos laterais a fim prover guia para a descoberta e análise de depósitos similares pelo Brasil.

The Lower Cretaceous Botucatu Formation records the development of widespread dry-aeolian desert sedimentation throughout the Parana Basin in south-west Gondwana. To reconstruct the provenance of the aeolian sediment, petrography, granulometric analysis, U-Pb detrital zircon ages have been determined from along the southern basin margin in Rio Grande do Sul state (southern Brazil) and Uruguay (Tacuarembo region). The dataset reveals a mean composition Qt(89)F(8)L(3), comprising very fine to medium-grained quartozose and feldspatho-quartzose framework. Heavy mineral analysis reveals an overall dominance of zircon, tourmaline and rutile grains (mean ZTR(0.84)) with sporadic garnet, epidote and pyrolusite occurrences. The detrital zircon U-Pb ages are dominated by Cambrian to Neoproterozoic (515 to 650 Ma), Tonian to Stenian (900 to 1250 Ma) and Orosirian to Rhyacian (1.8 to 2.2 Ga) material. The detrital zircon dataset demonstrates a significant lateral variation in sediment provenance: Cambrian to Neoproterozoic detrital zircons dominate in the east, while Tonian to Stenian and Orosirian to Rhyacian ages predominate in the west of the study area. Sandstones are quartz-rich with dominantly durable zircon, tourmaline and rutile heavy mineral suite, with subtle but statistically significant along-strike differences in heavy mineral populations and detrital mineralogy which are thought to record local sediment input points into the aeolian system. The similar age spectra of Botucatu desert with proximal Parana Basin units, the predominance of quartzose, and zircon, tourmaline and rutile components, suggests that recycling is the mechanism responsible for the erg feeding.