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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.

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.

Acknowledgements The authors gratefully acknowledge support from Shell Brasil through the ‘BG05: UoA‐UFRGS‐SWB Sedimentary Basins’ project at UFRGS and the strategic importance given by ANP through the R&D levy regulation. The authors would like to thank Renan Guilherme de Souza and Adriano Reis for help in Tacuarembo/Uy Field Trip. This work is part of the current dual‐degree PhD from Gabriel Bertolini at Universidade Federal do Rio Grande do Sul and University of Aberdeen. We thank the editors, and Dr Eduardo Garzanti, Dr Luca Caracciolo and Dr Sebastian Oriolo for their kind and constructive reviews. We thank to Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) by the financial support (Grant: 203786/2017‐3).

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 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 Q91F6L2, 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.