Overview of the Late Cretaceous Biota of the western São Paulo State,Brazil, Bauru Group

The Turonian–Maastrichtian beds of the Bauru Group, western São Paulo State (Brazil), have yielded a diverse biota. The nine species of mesoecrocodilians are all mesosuchians. There is a single frog, a Neubatrachia. The vertebrates include, four types of fishes, a neobatrachian frog, an anilioid snake, two lizard, six species of podocnemid turtles, nine species of mesosuchian mesoecrocodilians three theropods, two birds, five titanosaurid sauropods, and one mammalian. The invertebrates include one cyclo, one cyclophoroid and eight pulmonates. Plants are represented by only two carophyte species. The biota from western São Paulo State is one the most diverse of the Late Cretaceous in Brazil. The biota from this area confirms that Bauru Group was connected to Patagonia and other Gondwanan areas during the Late Cretaceous.     

The upper Maastrichtian dinosaur fossil record from the southern Pyrenees and its contribution to the topic of the Cretaceous–Palaeogene mass extinction event

In the present paper, the fossil record of the archosaurs (dinosaurs, crocodylomorphs and pterosaurs) of the southern Pyrenees before the Cretaceous–Palaeogene (K–Pg) transition is revised. On the basis of this fossil record, a well-dated succession of dinosaurs and other archosaurs is established within polarity magnetochrons C30 and C29r. Almost 150 sites with dinosaur remains have been identified, containing hadrosauroid ornithopods, titanosaur sauropods and theropods, as well as egg sites and tracks. Fossil remains of dinosaurs and other archosaurs are abundant in C29r, disappearing abruptly near the top of the “Lower Red Garumnian” unit of the Tremp Formation. Thus this should be located very close to, or coinciding with the K–Pg boundary. These data suggest that the disappearance of the dinosaurs and other archosaurs was geologically abrupt in the southern Pyrenees, but to date there is no incontrovertible evidence of the presence of the impact level that marks the Cretaceous–Palaeogene boundary. Interestingly, what is highlighted in the southern Pyrenees is that the vertebrate-rich upper Maastrichtian continental sites were replaced by similar sedimentological facies characterized by the virtual absence not only of dinosaurs but also of any vertebrate remain throughout the lower Palaeocene. This could mean that the Danian terrestrial ecosystems of the southern Pyrenees took longer than other areas of the world to recover their biodiversity after the K−Pg extinction event.     

Invertebrate traces in pseudo–coprolites from the upper Cretaceous Marília Formation (Bauru Group), Minas Gerais State,Brazil

Pseudo–coprolites are inorganic structures often confused with fossil faeces. The absence of some diagnostic features, such as inclusions, coprofabrics, grain adhesion, and defined shape, suffices to disregard these structures as coprolites. Herein we revise the so–called “coprolites” from the Serra da Galga Member of the Marília Formation (Maastrichtian of Bauru Group, Paraná Basin), at “Ponto 1 do Price” locality near the town of Peirópolis (Uberaba municipality, Minas Gerais State, Brazil) and conclude that they are, in fact, pseudo–coprolites related to calcretes. These data also agree with the geological setting of “Ponto 1 do Price”, composed mainly of coarse sandstones and conglomerates, in which these pseudo–coprolites were found. In addition, some of these specimens exhibit superficial traces, here described as a new boring ichnospecies, Asthenopodichnium fallax isp. nov., produced by invertebrates in Late Cretaceous fresh–water settings of Brazil.     

Fission track and U–Pb in situ dating applied to detrital zircon from the Vale do Rio do Peixe Formation,Bauru Group,Brazil

Combined methods of fission track (FTM) and U–Pb in situ zircon dating were applied to sedimentary samples from the Vale do Rio do Peixe Formation, Bauru Basin, Brazil. Detrital zircons of nine samples were determined by the FTM, and the obtained ages varied from 239 Ma–825 Ma, which can be grouped into four main populations as the 230–300 Ma, 460–490 Ma, 500–650 Ma and 696–825 Ma groups. The U–Pb data show two clear source areas: the Early Paleozoic to Neoproterozoic zircons, ranging from 445 ± 14 to 708 ± 18 Ma, and the Paleoproterozoic zircons, ranging from 1879 ± 23 to 2085 ± 27 Ma. Subordinate occurrences of Early Neoproterozoic to Mesoproterozoic zircons (836 ± 15 and 1780 ± 38 Ma) were identified. The combined information allows us to characterize Early Brazilian, Brazilian and Rhyacian material as the main source for the zircons, which are areas situated to west of the Bauru Basin (e.g., Goiás Massif) that have been incorporated into the sedimentary cycles in the Phanerozoic (mainly in the Paraná Basin). FT zircon ages reflect the main denudation processes of the South American Plate from Neoproterozoic to Early Triassic as those related to orogenic cycles of Early Brazilian, Brazilian, Famatinian/Cuyanian and Gondwanide.     

Multicusped crocodyliform teeth from the Upper Cretaceous (São José do Rio Preto Formation,Bauru Group) of São Paulo,Brazil

The six peculiar multicusped teeth described here were collected from sediments of the Upper Cretaceous of São José do Rio Preto Formation, near Ibirá (northeastern São Paulo, Brazil). Their bulbous crowns are slightly labio-lingual compressed, and bear a main plus two accessory cusps, which conceal a well developed cingulum. Wear facets are seen on the main and distal accessory cusps. Comparison to the known Crocodyliformes with multicusped teeth show that the new material is not referable to “protosuchians” or eusuchians, nor related to two unnamed forms from Morocco and “notosuchians” such as Uruguaysuchus, Chiamaerasuchus, and Simosuchus. On the other hand, possible affinities with Candidodon and Malawisuchus were maintained based on shared traits. This includes teeth with the main cusp and some accessory cusps arranged in more than one axis, a previously defined unambiguous apomorphy of the putative clade composed of Candidodon plus Malawisuchus. The term Candidodontidae can be applied to this group, and defined as all taxa closer to Candidodon itapecuruensis than to Notosuchus terrestris, Uruguaysuchus aznarezi, Comahuesuchus brachybuccalis, Sphagesaurus huenei, Baurusuchus pachecoi, and Crocodylus niloticus.     

Dinosaur ichnofauna of the Upper Jurassic/Lower Cretaceous of the Paraná Basin (Brazil and Uruguay)

Upper Jurassic and Lower Cretaceous sedimentary layers are represented in the Brazilian Paraná Basin by the fluvio–aeolian Guará Formation and the Botucatu Formation palaeoerg, respectively, overlapped by the volcanic Serra Geral Formation. In Uruguay, the corresponding sedimentary units are named Batoví and Rivera Members (both from the Tacuarembó Formation), and the lava flows constitute the Arapey Formation (also in Paraná Basin). Despite the lack of body fossils in the mentioned Brazilian formations, Guará/Batoví dinosaur fauna is composed of theropod, ornithopod and wide–gauge sauropod tracks and isolated footprints, as well as theropod teeth. In turn, the Botucatu/Rivera dinosaur fauna is represented by theropod and ornithopod ichnofossils smaller than those from the underlying units. The analysis of these dinosaur ichnological records and comparisons with other global Mesozoic ichnofauna indicates that there is a size reduction in dinosaur fauna in the more arid Botucatu/Rivera environment, which is dominated by aeolian dunes. The absence of sauropod trackways in the Botucatu Sandstone fits with the increasingly arid conditions because it is difficult for heavy animals to walk on sandy dunes, as well as to obtain the required amount of food resources. This comparison between the Upper Jurassic and Lower Cretaceous dinosaur fauna in south Brazil and Uruguay demonstrates the influence of aridization on the size of animals occupying each habitat.     

The Hell Creek Formation and its contribution to the Cretaceous–Paleogene extinction: A short primer

Although it represents but one geographic data point, the uppermost Maastrichtian Hell Creek Formation (HCF), exposed in the upper Great Plains of the North American craton, remains the most studied source for understanding the final ∼1.5 Myr of the Mesozoic Era in the terrestrial realm. Because it lies conformably below the earliest Paleocene Fort Union Formation, and together these two units preserve a rich fauna and flora, much of what is understood about the terrestrial Cretaceous–Paleogene (K–Pg) boundary comes from this sequence.The HCF has been reconstructed as an expansive, fluvially drained, low coastal plain, built out, to the west, against the Laramide Orogen, and to the east, against the ultimate transgression (Cannonball) of the Western Interior Sea. Its meandering rivers and moist soils supported a multi-tiered angiosperm-dominated flora and rich insect and vertebrate faunas, including dinosaurs, crocodilians, squamates, turtles, and mammals. A dramatic facies change representing the initiation of catastrophic flooding is preserved, within available levels precision, at the K–Pg boundary.High-precision stratigraphy has proven difficult in this lenticular fluvial system. Where present, the boundary can be recognized by the bipartite boundary claystone; otherwise, palynostratigraphy has proven a powerful tool. Numerical dates have been successfully obtained from in tonsteins at the boundary and above, in the Fort Union; however, these have proven elusive below the boundary within the HCF. The K–Pg boundary in this region is dated at 66.043 Ma (Renne et al., 2013). Magnetostratigraphic studies have been carried out in the HCF; although all but one have lacked numerical dates, these have been used for correlations of widespread, disjunct exposures and for the estimation of sedimentation rates.The palynoflora is largely homogenous through the HCF; at the K–Pg boundary, it shows an abrupt ∼30% extinction. This makes it a powerful tool for identification of the K–Pg boundary, although because the boundary is identified on absence of Cretaceous taxa rather than presence of earliest Paleocene taxa, several competing methods have been applied to identifying the K–Pg boundary using pollen.The macroflora, consisting largely of leaves, consists of three successive floras, showing increasing diversity through the HCF. The ultimate of these three floras undergoes an abrupt 57% extinction; taken as a whole, however, the macroflora undergoes a 78% extinction at the K–Pg boundary.The best data available for dinosaurs – including archaic Aves – show an abrupt extinction. By contrast, salamanders and other lissamphibians, as well as chelonians, cross the boundary virtually without perturbation. Squamates appear to have suffered significant extinctions at the K–Pg boundary, as did euselachians (elasmobranchs) and insects. Mammals suffered a 75% extinction; however, some of this figure cannot be shown to have occurred in less than the last 500 kyr of the Cretaceous, and thus has been potentially attributable to causes other than a bolide impact. Taken together, the survivorship patterns are concordant with the catastrophic inception of ubiquitous flooding characterizing the K–Pg boundary.While the key K–Pg boundary question in the HCF was once the rate of the biotic extinction, it has moved to the distinction between single-cause scenarios, with the Chicxulub bolide as agent of extinction, and multi-cause scenarios, uniting habitat partitioning, Deccan flood-basalt volcanism, climate change, competition, and bolide impact. Not every potential environmental perturbation need be a mechanism for the extinction: parsimony and the data continue to be concordant with a bolide impact as the single agent of the terrestrial K–Pg mass extinction.     

Petrology of the Colíder Group volcanic successions in the northernmost Mato Grosso,Brazil: A contribution to the knowledge of the felsic volcanism of the Alta Floresta Gold Province

The Colider Group ignimbrites and rhyolites, located between Guarantã do Norte and Serra do Cachimbo, Brazil derives from a felsic magmatism with a wide spatial distribution at the Alta Floresta Gold Province (AFGP). The geological mapping and petrographic studies allow distinguishing three volcanic successions of the Colider Group at the study area, named Lower (LS), Intermediate (IS) and Upper (US). The LS characterizes by its abundance in pyroclastic density current deposits, such as ignimbrites and surge deposits, with subordinated effusive rocks. The US consists of effusive rhyolites and trachytes and, subordinately, rheomorphic ignimbrites. The magmas that generated the volcanic rocks of the LS is of a subsolvus character. The US rocks present, dominantly, a mineralogy indicating a hypersolvus character. This characteristic can be indicating a variation of the fluid pressure conditions within the magma chambers that generated this magmatism. Regarding the chemical composition of the volcanic rocks from the two successions, we can point out that both have a metaluminous to slightly peraluminous character and affinity with A2-type magmas. The zircon U-Pb LA-ICPMS isotopic data of a LS rhyolite indicate a crystallization age of 1810 ± 9 Ma, interpreted as the Lower Succession age. One of the hypotheses that may be suggested to the generation of the volcanic successions is that the petrographic, lithochemical, and geochronological contrasts indicate the occurrence of two distinct magmatic events, one of ∼1.80 Ga and another of ∼1.76 Ga. The second hypothesis is that both successions belong to the same magmatic event, which occurred from 1.81 Ga to 1.76 Ga.     

Cretaceous–Tertiary structures and kinematics of the Serbomacedonian metamorphic rocks and their relation to the exhumation of the Hellenic hinterland (Macedonia, Greece)

 The kinematic pattern and associated metamorphism of the predominant ductile deformation and the subsequent deformational stages of the Serbomacedonian metamorphic rocks and granitoids are presented in terms of peri-Tethyan tectonics. A systematic record of structural and metamorphic data gives evidence of a main top-to-ENE to ESE ductile flow of Cretaceous age (120–90 Ma) associated with a crustal stretching and unroofing. A subordinate WSW to WNW antithetic sense of movement of the tectonic top is observed in places. The associated metamorphic conditions are estimated at 4.5–7.5 kbar and 510–580  °C. During Eocene to Miocene times these fabrics were successively deformed by low-angle extensional D_e ductile shear zones with top-to-NE and SW sense of movement and brittle shear zones of similar kinematic pattern, suggesting a transition from ductile to brittle deformation. D_e deformation was accompanied during its later stages by NW/SE-directed shortening. We also discuss the relation of this Cretaceous–Tertiary deformation of the Serbomacedonian metamorphic rocks with the Eocene to Miocene ductile, top-to-southwestward crustal shear of the adjacent Rhodope crystalline rocks. We regard the Serbomacedonian and the Rhodope metamorphic rocks to represent related metamorphic provinces, the most recent exhumation and cooling history of which is bracketed between the Eocene and Neogene. Received: 8 December 1998 / Accepted: 19 April 1999     

Vulnerability and resistance to neoliberal environmental changes: An assessment of agriculture and forestry in the Biobio region of Chile (1974–2014)

This article examines the dynamics of double exposure, vulnerability, and resistance to neoliberal globalization and environmental change in the Chilean agricultural region of Biobio. By using climatic models and secondary Agricultural Census data from 1997 and 2007, we assess how Chilean neoliberal reforms have, since 1974, facilitated land use changes and forestry investments. We demonstrate that policy changes which incentivize forestry investments have reduced cultivated agricultural lands and native forest, and concentrated land in the hands of global agribusiness corporations. Compounding these issues, Biobio shows a climatic trend towards aridity coupled with an increasing demand for irrigation. Analyzing these conditions, we argue that the neoliberal globalization of regional agriculture under the context of climatic changes has produced a regional space of increasing vulnerabilities and uneven geographical development in Biobio. We particularly demonstrate that the Chilean mode of agricultural neoliberalization has been conducive to land dispossession—to the detriment of traditional agriculture —and has homogenized the biophysical landscape, replacing traditional crops and native forests with exotic species like pines and eucalyptus. We also examine how local producers are using resistance movements to cope with and contest neoliberal environmental changes. We conclude by evaluating the implications of these spaces of agricultural vulnerabilities and local resistances in the context of uneven geographical development at a regional and global scale.     

SIMS zircon U–Pb dating of the Late Cretaceous dinosaur egg-bearing red deposits in the Tiantai Basin,southeastern China

Dinosaur eggs or fragments are abundant and extensively distributed in China. They can be very informative in biostratigraphic division and correlation of continental strata where other fossils are relatively lacking. Despite remarkable discoveries of vertebrate fossils, particularly dinosaur eggs and skeletons from the middle and Late Cretaceous of both northern and southern China, there is hardly any direct evidence for the ages of the vertebrate-bearing terrestrial deposits. To constrain their depositional ages, here we have obtained SIMS U–Pb zircon ages from the tuffs interbedded with dinosaur egg-bearing sediments from the Laijia and Chichengshan formations of the terrestrial red deposits of the Late Cretaceous in the Tiantai Basin, Zhejiang Province, southeastern China. The SIMS zircon U–Pb ages from the Laijia and Chichengshan formations are about 96–99 Ma (Cenomanian) and 91–94 Ma (Turonian), respectively, providing direct time constraints on the vertebrate and dinosaur egg evolution in the Late Cretaceous as well as a basis for correlation with terrestrial Cretaceous deposits in other regions of southern and northern China.     

Paleoenvironmental framework of dinosaur tracksites and other ichnofossils in Early Cretaceous mixed siliciclastic-carbonate deposits in the Neuquén Basin,northern Patagonia (Argentina)

The study of the uppermost section of the Early Cretaceous Agrio Formation in northern Patagonia (Neuquén Basin) where dinosaur tracks assigned to cf. Therangospodus pandemicus are exposed (tracksites I and II) evidence mixed marginal marine siliciclastic-carbonate deposits. The succession was divided in two intervals. A lower one containing theropod tracks, recorded on top of subtidal oolithic limestones with tiny wave ripples suggesting shoreline fluctuations and subaerial exposure. Tidal influence is recognised by fining upward and prograding cycles starting with subtidal carbonates and ending with fine-grained siliciclastic deposits at the top, or rarely laminites. Dolomitization affects subtidal deposits generated in an alkaline media stressful for tracemakers. Intertidal facies include abundant heterolithic deposits, coquinas composed of gastropods encrusted by multilayered bryozoans and muddy levels with incipient mud cracking. Invertebrate ichnofossils recognized from tidally dominated deposits include Arenicolites, Kouphichnium, and Rhizocorallium. The upper interval is a transgressive–regressive cycle that starts with dark shales, deficiently oxygenated, and covered by prograding sandstones and finally sand flat deposits. This interval contains Gyrochorte, Hillichnus, and Ophiomorpha documented in wave-influenced sandstones. Dinosaur tracks as well as Hillichnus, attributed to tellinoid bivalves, and Kouphichnium assigned to xiphosurans, imply the activity of producers rarely recorded previously as body fossils in marginal marine deposits of southern South America. Previous paleogeographic schemes are questioned by our analysis, which shows evidence of extremely shallow and tide-controlled sedimentation, sometimes with subaerial exposure, with high cyclicity related to a marginal marine depositional setting and lack of significant erosion by the overlying unit, as traditionally was suggested.     

Evolution of Jurassic–Cretaceous magmatism in the Khambin volcanotectonic complex (western Transbaikalia)

The Khambin volcanotectonic complex is a horst framing the Late Cretaceous Lake Gusinoe basin in the northwest. This complex is due to the intracontinental rift conditions which existed in western Transbaikalia in the Late Mesozoic. They gave rise to a system of subparallel grabens and horsts in present-day topography. The magmatic evolution of this complex spans from 159 to 117 Ma and is divided into three stages. The first stage (159–156 Ma) witnessed the formation of thick (up to 1500 m) volcanic masses of trachybasalts, basaltic trachyandesites, trachytes, trachydacites, trachyrhyolites, and pantellerites. The next two stages were the formation of isolated ancient volcanoes (127–124 Ma) composed of trachybasalts, basaltic trachyandesites, phonotephrites, tephriphonolites, and alkali trachytes and the formation of the Murtoi (Lake Gusinoe) essexite dike (122–117 Ma). The main trends for igneous associations from early to late stages are reduced magmatism and reduced rock diversity because of the decreasing portion of felsic volcanic rocks. Mafic rocks show an increase in total alkalinity, the content of incompatible elements (Th, U, K, Rb, Pb, Nb, Ta, Zr, Hf), total REE content, and the LREE/HREE ratio. The Sr–Nd isotopic composition of these rocks remained nearly constant and corresponds to that of OIB-EMII mantle sources. Compositional variations are attributed to a time-dependent decrease in the degree of partial melting of a similar magma source.     

Spatiotemporal variation in global floods with different affected areas and the contribution of influencing factors to flood-induced mortality (1985–2019)

Natural Hazards - Floods are great threats to human life and property. Extensive research has investigated the spatiotemporal variation in flood occurrence, while few have studied the heterogeneity...     

Interhemispheric radio-astrochronological calibration of the time scales from the Andean and the Tethyan areas in the Valanginian–Hauterivian (Early Cretaceous)

An integrated radio-astrochronological framework of the Agrio Formation in the Andean Neuquén Basin of west-central Argentina provides new constraints on the age and the duration of the late Valanginian through Hauterivian stratigraphic interval. A CA-ID TIMS U-Pb age of 126.97 ± 0.04(0.07)[0.15] Ma is presented here from the upper Hauterivian Agua de la Mula Member of the Agrio Formation. Biostratigraphic data from ammonoids and calcareous nannofossils and this high precision new radioisotopic age, together with three former ones from the same Agrio Formation are combined with new astrochronological data in the Andes. These are correlated with modern cyclostratigraphic studies in the classical sections of the Mediterranean Province of the Tethys, supporting detailed interhemispheric correlations for the Early Cretaceous. We also provide new δ¹³C data from the Agrio Formation which are compared with records from the classic Tethyan sections. According to our calibration, the minimum in the values in the mid-Hauterivian appears to be synchronous and, thus, another important stratigraphic marker for global correlation. A new duration of 5.21 ± 0.08 myr is calculated for the Hauterivian Stage, starting at 131.29 ± 0.19 Ma and ending at 126.08 ± 0.19 Ma. The difference between the duration of the Hauterivian in GTS2016 and in this study is 1.32 myr while the base and top of the GTS2016 Hauterivian differ respectively by 3.40 and 4.69 myr.     

Energetic and spatial characterization of seismicity in the Algeria–Morocco region

We estimate the energetic and spatial characteristics of seismicity in the Algeria–Morocco region using a variety of seismic and statistical parameters, as a first step in a detailed investigation of regional seismic hazard. We divide the region into five seismotectonic regions, comprising the most important tectonic domains in the studied area: the Moroccan Meseta, the Rif, the Tell, the High Plateau, and the Atlas. Characteristic seismic hazard parameters, including the Gutenberg–Richter b-value, mean seismic activity rate, and maximum possible earthquake magnitude, were computed using an extension of the Aki–Utsu procedure for incomplete earthquake catalogs for each domain, based on recent earthquake catalogs compiled for northern Morocco and northern Algeria. Gutenberg–Richter b-values for each zone were initially estimated using the approach of Weichert (Bull Seismol Soc Am 70:1337–1346, 1980): the estimated b-values are 1.04 ± 0.04, 0.93 ± 0.10, 0.72 ± 0.03, 0.87 ± 0.02, and 0.77 ± 0.02 for the Atlas, Meseta, High Plateau, Rif, and Tell seismogenic zones, respectively. The fractal dimension D ₂ was also estimated for each zone. From the ratio D ₂/b, it appears that the Tell and Rif zones, with ratios of 2.09 and 2.12, respectively, have the highest potential earthquake hazard in the region. The Gutenberg–Richter relationship analysis allows us to derive that in the Tell and Rif, the number of earthquake with magnitude above Mw 4.0, since 1925 normalized to decade and to square cell with 100-km sides is equal to 2.6 and 1.91, respectively. This study provides the first detailed information about the potential seismicity of these large domains, including maximum regional magnitudes, characteristics of spatial clustering, and distribution of seismic energy release.