The Bashkirian to Sakmarian-Artinskian Itararé subgroup provides a record of the evolution of the Permian-Carboniferous glaciation in the Paraná Basin (Brazil). The glaciogenic succession was deposited under the influence of glaciers incoming from southwestern Africa. This paper presents an overview of the third-order sequence stratigraphy of that succession and a biostratigraphic summary, showing that: (1) the most complete and thick outcrop portion of the glaciogenic succession occurs in the northeastern part of the Paraná Basin, where several (at least nine) major cycles of ice advance and retreat can be recognized during the development of the Itararé subgroup; (2) biostratigraphically, two well-defined stratigraphic gaps within the Permian-Carboniferous succession are recognized, one within the Itararé subgroup, related to the Lapa–Vila Velha incised valley fill, and another at the Itararé–Rio Bonito boundary, both of which represent regional sequence boundaries; and (3) the transition between palynozones Crucisaccites monoletus and Vittatina costabilis is associated with the maximum flooding surface represented by the marine Lontras Shale, a regional marker bed located in the upper third of the glaciogenic succession.

ABSTRACT Explorers found a total of 82 giant conventional discoveries over the decade, defined as fields holding most likely resources of at least 500 million barrels of oil equivalent (BOE). Collectively, these giants hold total resource volumes of 129 billion BOE, representing 53% of all new field resource adds over the decade. Without these giants, the recent recovery in exploration’s fortunes would have been a quite different story. Giant oil and gas discoveries were at the heart of key exploration trends over the decade 2010–2019. The middle years of the decade were a period of profound change for the industry. Sharp falls in oil prices led to a broad reduction in the scale of the exploration business. Well completions and investment fell by more than half and look unlikely to recover. This smaller industry has become profitable again. Toward the end of the decade, a partial recovery in oil prices combined with a broad rebasing of the industry’s costs led to much improved full-cycle exploration returns. These giant discoveries are widely distributed. There are important clusters in deep-water regions of Brazil, East Africa, and the eastern Mediterranean. Frontier and early-stage exploration is the other common theme among these giant discoveries. By contrast, only 11 giants were found in mature plays, mainly in the super basins of the Middle East, West Siberia, and China.

Abstract The Pennsylvanian on the western rim of Gondwana can be considered a time of significant contrasts in terms of environments, revealing a unique translatitudinal disposition of the South American continent, where glaciomarine deposits and peat-forming environments, situated further south, coexisted with marine carbonate platforms and aeolian dune fields, in terrains further north. This peculiar record creates an opportunity to better understand the teleconnections of glaciation and deglaciation during the Late Paleozoic Ice Age (LPIA) between mid and low latitude regions. In the last decade, radiometric dating together with marine microfossils (mostly conodonts) has enabled a better understanding of the timing and duration of deposition of different sedimentary environments found in the climate belts that originated from a global ice-house regime. These advances in the chronostratigraphical positioning of sedimentary deposits also allow a more precise correlation between them, making it possible to estimate cause–effect patterns arising from the growth and decay of glaciers in this portion of Gondwana. This contribution aims to present an overview of the main climatic–environmental events that took place during the Pennsylvanian and to associate them with the floristic changes that occurred in the emergent lands based on palaeobotanic and palynological information. The record from the west rim of Gondwana could be roughly divided into Early, Middle and Late Pennsylvanian, exactly as proposed in the geological time-scale.

Abstract Provenance studies on metasedimentary rocks of the Baixo Araguaia Supergroup of the Brasiliano Araguaia Belt, central Brazil, yield 207 Pb/ 206 Pb zircon evaporation ages for detrital zircons from quartzites concentrated around 1000–1200 Ma and 2800–2900 Ma; Sm–Nd T DM model ages of schists and phyllites scatter around 1600–1700 Ma. Facies analysis of low-grade metasedimentary rocks from drill cores suggests a sedimentary environment of basin floor and lower- to upper-slope turbidites. Nearby sources are indicated by the textural and mineralogical immaturity; together with structural geological data indicating tectonic transport of the supracrustal pile towards the NW, this suggests probable provenance from the southeastern portion of the Araguaia Belt and not from the Amazonian Craton as usually believed. The Goiás Massif, Goiás Magmatic Arc, São Francisco Craton and Paranapanema block are considered to be the best candidates. They may have formed a larger continental mass during West Gondwana amalgamation, prior to their collision with the Amazonian Craton to form the Araguaia Belt. Final timing of this collision is constrained by c . 550 Ma syntectonic granites. Similar ages for high-grade gneisses in the Rokelide Belt suggest coeval collision and coetaneous metamorphism of the Araguaia and Rokelide belts, but more geological and geophysical data are required for a decisive correlation between these belts.

Abstract The Araguaia Belt, the northern branch of Neoproterozoic Tocantins tectonic province, developed during West Gondwana amalgamation as a result of collision between the Amazon and West African and/or São Francisco/Congo cratons. The external zone of the belt consists of ophiolitic slices and fragments, sedimentary rocks derived from magmatic arc sources, volcanic rocks, and part of a passive continental margin with low-grade metamorphic rocks, while the internal zone corresponds to a pile of low- to medium-grade metasedimentary rocks. The largest and best preserved ophiolitic bodies occur in the southern part of the belt, where the Quatipuru and Morro do Agostinho ophiolites are composed predominantly of mantle peridotites (mainly residual harzburgite) representing the base of the Moho transition zone. They contain chromitite pods, dunitic lensoid bodies and a suite of mafic–ultramafic dykes and/or sills resulting from partial melting, magma impregnation and diapiric up-rise. A Sm–Nd isochron age of 757±49 Ma indicates oceanic crust formation during the Early Neoproterozoic. NW African correlatives of the Araguaia Belt, the Mauritanide–Bassaride–Rokelide belt, show similarities with respect to lithostratigraphic units, the ages of basement and supracrustal rocks, the presence of Neoproterozoic ophiolitic slices and fragments, suture zones characterized by high gravity anomalies and centrifugal tectonic vergence. We conclude that these belts were probably formed around the same Neoproterozoic ocean or several small coeval oceans.

Abstract Nickel laterites are thick weathering profiles derived by leaching of ultramafic rocks by meteoric water. Olivine or derived serpentine provides the nickel. Profiles with economically significant deposits derive their Ni from 40-m (15−100 m, 10 th −90 th percentile range) thicknesses of protolith grading 0.16 to 0.3 percent Ni and 5.5 to 10.5 percent Fe. The profiles may be preserved in situ or transported to form a sedimentary unit that may be buried, lithified, and metamorphosed. From bottom upward, in situ nickel laterites may be comprised of silicate saprolite, a nontronite clay zone, high Co and Mn limonite or ferruginous saprolite, low Co and Mn limonite, and allocthonous cover. Any of these units may be absent due to erosion or nondeposition and, importantly, one or all may be siliceous, usually due to quartz precipitation in the saprolite zone. Nickel is leached downward from the limonite zone, added to the saprolite and nontronite zones, and left residually enriched in limonite. Strong supergene enrichment requires downward leaching into saprolite and fractured rock above a deep water table. Zones of strong passive jointing and pre- or synweathering fracture zones all may lead to an order of magnitude increase in the rate of advance of the weathering front. The rate of advance of the weathering front in tropical rain forest covered highlands is about 50m/m.y., regardless of whether the bed rock is ultramafic, dioritic, or felsic. Weathering fronts advance at progressively slower rates in terranes with less relief. Nickel laterite deposits accumulate on terraces or plateau landforms in karstlike basins or under semiarid peneplains. The topographic controls of in situ nickel laterite deposits can be understood in terms of structural controls and three long-term climatic and topographic scenarios. The scenarios include: (1) permanently wet rain- forest setting in tectonically active terrane with moderate relief, (2) a formerly wet peneplain that has evolved toward aridity, and (3) a formerly arid peneplain setting that has evolved into a permanently wet environment.

Abstract Icehouses are the less common climate state on Earth, and thus it is notable that the longest-lived ( c. 370 to 260 Ma) and possibly most extensive and intense of icehouse periods spanned the Carboniferous Period. Mid- to high-latitude glaciogenic deposits reveal a dynamic glaciation–deglaciation history with ice waxing and waning from multiple ice centres and possible transcontinental ice sheets during the apex of glaciation. New high-precision U–Pb ages confirm a hypothesized west-to-east progression of glaciation through the icehouse, but reveal that its demise occurred as a series of synchronous and widespread deglaciations. The dynamic glaciation history, along with repeated perturbations to Earth System components, are archived in the low-latitude stratigraphic record, revealing similarities to the Cenozoic icehouse. Further assessing the phasing between climate, oceanographic, and biotic changes during the icehouse requires additional chronostratigraphic constraints. Astrochronology permits the deciphering of time, at high resolution, in the late Paleozoic record as has been demonstrated in deep- and quiet-water deposits. Rigorous testing for astronomical forcing in low-latitude cyclothemic successions, which have a direct link to higher-latitude glaciogenic records through inferred glacioeustasy, however, will require a comprehensive approach that integrates new techniques with further optimization and additional independent age constraints given challenges associated with shallow-marine to terrestrial records.