Virgínio Henrique Neumann

Redescription of Cearadactylus atrox (Pterosauria, Pterodactyloidea) from the Early Cretaceous Romualdo Formation (Santana Group) of the Araripe Basin, Brazil

ABSTRACT Based on one of the first cranial pterosaur specimens unearthed from the Romualdo Formation (Araripe Basin), Cearadactylus atrox has caused disagreement among paleontologists regarding its relationships. Ranging from an ornithocheirid, an indeterminated pterodactyloid, to a ctenochasmatid, some authors even regarded this species as representing a distinct suprageneric clade. Further preparation of the holotype that was transferred to the collections of the Museu Nacional/UFRJ (MN 7019-V) revealed several new features allowing a redescription and reevaluation of the phylogenetic position of this species. Among the new observations, it is clear that the rostral end of this specimen had been glued to the skull, rendering previous anatomical interpretations incorrect. There is no rostral gap, and the expanded rostral end of the premaxillae is larger than the dentary, rather than smaller. Cearadactylus atrox is here considered a valid taxon that can be diagnosed by a dentary groove that bifurcates at the rostral end, orbit and naris in a high position relative to the nasoantorbital fenestra, and a comparatively small number of teeth (32–36 maxillary, 22–26 mandibular), decreasing in size towards the posterior end. Phylogeneticaly, it is placed as the sister group of the Anhangueridae, forming a large clade of Brazilian forms (Tropeognathus and Anhanguera), which has a European taxon (‘Ornithocheirus’ compressirostris) as its sister group. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Carbon isotopes, rare-earth elements and mercury geochemistry across the K–T transition of the Paraíba Basin, northeastern Brazil

Abstract The Paraíba Basin, northeastern Brazil, is divided into three sub-basins: Olinda, Alhandra and Miriri, which encompass the formations Beberibe (Coniacian–Santonian), Itamaracá (Campanian) and Gramame and Maria Farinha (Maastrichtian to Danian, respectively). In the Olinda sub-basin, the Cretaceous–Palaeogene transition (KTB) has been recorded by the carbonates of the Gramame and Maria Farinha formations. This study focus on the behaviour of C and O isotopes, major and rare-earth elements and mercury in carbonates from three drill holes in the Olinda sub-basin. The climate was fairly cold during the marine transgression in which carbonates of the Itamaracá Formation were deposited. A temperature and bioproductivity increase has been registered in the Early Maastrichtian (Gramame Formation), with a gradual fall during the rest of this period. A positive δ13C (+2‰) excursion near the KTB is followed by a drop to values around +1‰ immediately after this transition. In one drill hole, several negative δ13C anomalies predate the KTB, possibly related to either multiple impacts or volcanic activity that preceded this transition. In two of the three drill holes, the total mercury increases immediately after the KTB and, in two of them, mercury spikes (four of them in one case) precede this transition, which has been interpreted as an indication that volcanic activity predated the transition. Rare earth element patterns support a marine origin for the carbonates in the Campanian–Maastrichtian transition and KTB in the Olinda sub-basin. In carbonates from one of the drill holes, absent to weakly positive Ce anomalies (−0.1 and 0.002) in the KTB coincide with a fall in δ13C values, followed by an increase (from 2.3 to 1.8‰ and back to 2.3‰) and in increment in mercury values (from 0.4 to 2.7 ng g−1). The presence of pyrite nodules associated with a weakly negative Eu anomaly point to slightly reducing conditions around the KTB.

Stable isotopes of organics and inorganics, clay mineralogy and chemical environment of an Aptian lacustrine succession in northeastern Brazil

Abstract The studied Aptian lacustrine succession of the continental Jatobá Rift Basin varies mainly between pure carbonates (predominantly laminated limestones), marls and shales, with some intercalations of presumably deltaic sandstone complexes. In accordance with geochemical data, the occurrence of dolomite indicates intensive microbial activity in a stratified water column with slightly enhanced salinity. Petrographic data prove mild weathering conditions. Aggregates of authigenic smectite observed in sandstones, probably representing transformed volcanogenic glass particles, strongly indicate explosive volcanic activity. Occasionally occurring dolomite seems to have been formed due to intensive microbial activity under moderately increased salinity conditions. Potential hydrocarbon source rocks containing Type I organic matter (OM) were deposited during various phases of the Aptian. Enhanced biological productivity is indicated by bulk organic geochemical data (Corg, hydrogen index, extraction yield) and δ13C values of carbonates within peletoidal and laminated limestone layers. Carbon-isotope ratios of carbonates argue for OM cycling and remineralization. High δ18O values of carbonates are attributed to periods of lower lake levels. A major contribution of aquatic organisms (green algae, microalgae, zooplankton) and minor input from macrophytes and land plants to OM accumulation is indicated by n-alkane distributions, steroid composition and δ13C values of individual biomarkers. Microbial communities included heterotrophic bacteria and cyanobacteria, as well as purple and green sulphur bacteria. The sediments were deposited in an alkaline palaeolake. Highly reducing (saline) bottom water conditions and a stratified water column existed during OM accumulation of the Crato Formation. This is indicated by low pristane/phytane, gammacerane index, and the presence of β-carotane and aryl isoprenoids. Differences in OM composition and stable isotope data reflect the evolution of the basin from a stratified saline lake to a freshwater environment with limited potential for OM preservation.

Estratigrafia, arquitetura deposicional e faciologia da formação Missão Velha (Neojurássico-Eocretáceo) na área-tipo, bacia do Araripe, nordeste do Brasil: exemplo de sedimentação de estágio de início de rifte a clímax de rifte

Este trabalho enfoca revisao da Formacao Missao Velha na area-tipo (Bacia do Araripe, Nordeste do Brasil), atraves de analises de facies, elementos arquitetonicos, sistemas deposicionais e paleocorrentes. As principais facies reconhecidas foram: 1. conglomerados de seixos e grânulos, com abundantes troncos fosseis silicificados, formando ciclos granodecrescentes, estratificacoes cruzadas acanaladas e tabulares, de pequeno e medio portes e geometria predominantemente lenticular; 2. arenitos grossos a medios, conglomeraticos, com grânulos, quartzosos, com troncos fosseis silicificados, com estratificacoes cruzadas acanaladas de medio e grande porte e geometria lenticular; 3. conglomerados e arenitos medios com seixos esparsos, mal selecionados, com estratificacao plano-paralela; 4. arenitos finos a muito finos, silticos, tabulares, laminados, intercalados com 5. camadas decimetricas de horizontes peliticos com estratificacao plano-paralela e laminacoes cruzadas cavalgantes. Dez elementos arquitetonicos foram reconhecidos: CH: canais, GB: formas de leito cascalhosas, SG: barras, SB: formas de leitos arenosos, SB(p): formas de leitos arenosos com estratificacao cruzada tabular (p), OFch: depositos de transbordamento (overbank) como diques, crevasse e channel splays, DA: macroformas de acrescimo para jusante, LS: lencois de areia laminada, LA: deposito de acrescimo lateral e FF: depositos finos de planicie de inundacao. Nem todos esses elementos foram observados em cada afloramento. Estes elementos, definidos pela geometria e superficies delimitantes, formam a base para interpretacao dos ambientes deposicionais. A Formacao Missao Velha foi interpretada como: a. sistemas fluviais entrelacados de alta energia com as seguintes caracteristicas: ciclos granodecrescentes, estratificacoes cruzadas tabulares e acanaladas, truncamentos entre estratos cruzados, geometria lenticular, feicoes canalizadas, seixos esparsos e b. sistemas fluviais meandrantes pela presenca de depositos de planicie de inundacao, crevasse splays e barras em pontal. Ocorrem tambem depositos eolicos.

Stratigraphy of the Post-Rift Sequences of the Jatobá Basin, Northeastern Brazil

The sedimentary infill of the Jatoba Basin is not well known, belying its importance in relation to other interior rift basins of northeastern Brazil. In its northern portion, and particularly in the middle to the top of Serra Negra and the Periquito hills, outcrops of laminated limestones interbedded with terrigenous sediments are found, which have been correlated by da Rocha and Leite (1999) with the Aptian laminated limestones of the Crato Formation (Santana Group, Araripe Basin) (Neumann and Cabrera 1999). Among the intracratonic basins of northeastern Brazil, the Jatoba Basin presents a succession of lacustrine sediments with pronounced phases of deltaic siliciclastic influence similar to the Aptian lacustrine phase of the Araripe Basin (Neumann et al. 2003). The Crato Formation of Jatoba Basin presents very similar lithology, fossil content, age, and depositional environment to those of the Paracuru (Ceara Basin; Neumann et al. 2009), Codo (Paranaiba Basin; Bruni et al. 1976), and Crato (Araripe Basin; Neumann et al. 2009) formations. The Aptian lacustrine infill is both a generator and reservoir of oil in the Atum and Xareu oilfields in the Ceara Basin. Given these various points, it is important to determine the geological evolution of the post-rift stratigraphic sequence of the Jatoba Basin. Therefore, the main objective of this work is investigate the post-rift sequence of the Jatoba Basin, focusing on its subdivision into two units: post-rift I (Marizal, Crato, and Romualdo formations), and post-rift II (Exu Formation). The results will contribute to establishing a new lithostratigraphic scheme for the Jatoba Basin, and will also inform studies of other lacustrine systems of intracratonic basins in northeastern Brazil.

Análise estratigráfica da Formação Brejo Santo, Bacia do Araripe, Nordeste do Brasil: implicações paleogeográficas

A Bacia do Araripe tem sido objeto de varias publicacoes nos ultimos anos, notadamente a respeito do rico acervo paleontologico das formacoes Brejo Santo, Crato e Romualdo. Entretanto, trabalhos que abordem em detalhe a Formacao Brejo Santo, do ponto de vista estratigrafico, sao escassos. A Formacao Brejo Santo, de idade mesozoica (Andar Dom Joao), e representada por espessa sucessao (ate 450 m) predominantemente pelitica aflorante na porcao leste da bacia. A Formacao Brejo Santo repousa discordantemente sobre a Formacao Cariri, de idade presumivelmente paleozoica, e faz contato gradacional com a sobrejacente Formacao Missao Velha. Constitui-se de pelitos, tais como argilitos e folhelhos calciferos -castanho-avermelhados, macicos a laminados, com intercalacoes decimetricas de siltitos argilosos cinza-esbranquicados a esverdeados e camadas centimetricas de folhelhos avermelhados mosqueados com nodulos calcarios e, subordinadamente, arenitos finos calciferos, abundantemente fossiliferos, e arenitos finos brancos com estratificacao cruzada tabular. Paleocorrentes medidas possuem padrao de dispersao consistente para SE, SW e S, coerente com a instalacao de ampla bacia aberta nesta direcao. As facies e associacoes de facies descritas foram interpretadas como geradas por (i) sistemas lacustres nos quais periodicamente o nivel dos lagos e/ou lagoas sofriam variacoes bruscas, cujas variacoes de coloracao acham-se relacionadas as sazonalidades do nivel do lago (periodos de exposicao subaerea) e por (ii) sistemas fluviais efemeros que alimentavam esses lagos. A ocorrencia disseminada de organismos fosseis, tais como ostracodes nao marinhos e conchostraceos, sugere que os sedimentos da Formacao Brejo Santo teriam sido depositados em sistemas lacustres favoraveis a formacao de camadas de red beds sob condicoes climaticas quentes e de estacao seca bem definida, corroborando a interpretacao deposicional.

Characteristics, distribution and diagenetic stages of chert in the La Silla Formation (Lower Ordovician), Argentine Precordillera

The late Cambrian – late Tremadocian La Silla Formation is a carbonate unit of the eastern Precordillera in Argentina whose facies indicate a shallow platform environment. Until this moment, there were no studies that referred to the diagenetic evolution of these rocks. The present study involves the characteristics and distribution of the silicification that affects this unit and determines its different diagenetic stages through petrographic (with cathodoluminescence support) and stratigraphic analyses. An early diagenetic chert, in a stage previous to the compactation, was observed. This chert is related to silica-rich seawater in contact with permeable and porous sediments. A later pulse of chert, associated with fracturing, also occurs. The knowledge provided by the characteristics and distribution of chert in these carbonates is significant, especially when considering that the La Silla Formation in San Juan province is the most quarried unit for the elaboration of lime.

Stratigraphic Relations of the Ipubi Formation: Siliciclastic-Evaporitic Succession of the Araripe Basin

The Ipubi Formation represents the Aptian-Albian siliciclastic-evaporitic succession of Araripe Basin, NE Brazil. This succession comprises siliciclastic rocks (bituminous shales and claystones) and evaporites (gypsum and secondary anhydrite) and represents part of the lacustrine-shallow marine post-rift phase I. This study used sequence stratigraphy concepts to define the relations between changes in the relative lake level and the formation of Ipubi deposits. Results show that the organic-rich shales of the Ipubi Formation formed during a transgressive pulse that covered large areas of the proximal domains. These deposits overlie a regional unconformity that marks the end of the deposition of the underlying Crato Formation. A High Stand stage that followed the transgression influenced the formation of evaporitic deposits. Climate conditions played a major role in influencing the triggering and stopping of evaporite deposition. Thus, a new relative lake level fall event caused the exposure of the Ipubi Formation deposits, and created another regional subaerial unconformity accompanied by widespread karstification of evaporite beds. A posterior transgression caused the deposition of siliciclastic rocks of the Romualdo Formation over the Ipubi Formation strata, and also promoted a new event of karstification of the Ipubi upper evaporite beds.

MAPEAMENTO GEOLÓGICO DA PORÇÃO SUDOESTE DA FOLHA AIRI, BACIA DE JATOBÁ, NORDESTE DO BRASIL

A area de estudo esta inserida no Dominio Pernambuco-Alagoas da Provincia Borborema, onde ocorre embasamento Paleoproterozoico (Complexo Belem do Sao Francisco – ortognaisses graniticos migmatizados) e uma Suite Granitica Neoproterozoica (Alcalifeldspato granitos a sienogranitos) e rochas sedimentares (arenitos, siltitos, folhelhos e argilitos) da Bacia do Jatoba. Foi realizado mapeamento geologico na escala de 1:50.000, em uma area com 250 km2, que abrange os litotipos do embasamento cristalino e da Bacia de Jatoba. Na Bacia de Jatoba, a Fase Pre-Rifte de idade Jurassica (Tithoniana), e representada pela Formacao Alianca (folhelhos e siltitos avermelhados e esverdeados – redbeds – com niveis areniticos, por vezes calciferos) e pela Formacao Sergi (arenitos quartzosos finos a grossos, alem da presenca de troncos fosseis silicificados caracteristicos dessa unidade). A Fase Rifte e caracterizada por arenitos esbranquicados que variam de finos a grossos e folhelhos e siltitos da Formacao Candeias (Berriasiano), caracterizando um ambiente fluviolacustre, e o ambiente fluvial de alta energia com retrabalhamento eolico da Formacao Sao Sebastiao (arenitos finos a medios com niveis grossos na base). Alem das rochas sedimentares de idade mesozoica, encontram-se depositos coluvio-eluviais que representam o Cenozoico.

Geochemical Signatures of Recent Holocene Estuarine Sediments of the Jaboatão River, Pernambuco, Brazil

The Jaboatao River Basin, northeastern Brazil, is characterized by urban and industrial land uses, although it includes extensive sugarcane plantations with a marked deterioration of the native forests. Heavy metal (HM) concentrations in estuarine sediments of the river have been measured to assess possible historical sources of pollution. The trace metals were investigated based on samples from a drill core taken 4 km from the mouth of the river. The sediments of the core were analysed for chemistry, particle size, and organic matter (OM) content. The chemical species analysed (As, Cr, Pb, Hg, Ni, and Zn) show higher concentrations in the 30–35 cm interval of the core. This indicates that the accumulation of HMs has been constant over the last few decades and confirms the existence of two well-differentiated compartments, one above and one below the 30–35 cm horizon. The partitioning of the sedimentary and geochemical profiles highlights varying environmental conditions in the estuary. This behaviour is marked by a conspicuous dichotomy in the C/N ratio, specifying signatures dependent on the geochemistry of the sediments and on hydrodynamic variations, in an essentially organo–siliciclastic depositional context. The OM present in the sediments indicates a progressive evolution of continental environment conditions at the bottom to more estuarine conditions at the top, which could indicate a small and progressive drowning of the Jaboatao River mouth, probably related to sea-level rise in the range considered.