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This study is the first contribution towards the estimation of paleoatmospheric carbon dioxide concentration (p CO 2) from the paleoequatorial late Aptian Crato Formation (Santana Group, Araripe Basin, NE Brazil) based on stomatal numbers. Cuticular and epidermal silicon replicas of Pseudofrenelopsis capillata Sucerquia, Bernardes-de-Oliveira & Mohr (Cheirolepidiaceae, Coniferales) were observed under scanning electron microscopy to analyze their stomatal frequency and distribution for paleoatmospheric and paleoenvironmental inferences. Stomatal counting yielded a mean stomatal density (SD) and stomatal index (SI) of 68.8 mm−2 and 6.7. Based on the mean SI value of four modern nearest living equivalent (NLE) conifer species, the stomatal ratio (SR) was calculated to be 1.4. The paleoatmospheric p CO 2 range was estimated to be between 514.9 ppmv (Recent standardization) and 1029.8 ppmv (Carboniferous standardization). These values were found to be consistent with results from the literature based on other latitudes in the Early Cretaceous and were discussed in the light of the paleoenvironmental context that prevailed around the peri-equatorial Crato paleolake, including the occurrence of stomatal clustering in the leaves of P. capillata. • Paleoatmospheric CO 2 results ranged between 515 ± 79 and 1029.8 ± 158 ppmv. • Calculated paleoatmospheric CO 2 was relatively low among late Aptian findings. • Low stomatal density could be indicative of freshwater environment. • Stomatal clustering suggested high evaporative demand. • Low paleo-CO 2 could be correlated with low temperature in the late Aptian. [ABSTRACT FROM AUTHOR]

A Brazilian glossopterid species is reassigned and redescribed based on cuticular analysis. The original name (Guerra-Sommer, 1992) is illegitimate because it is a later homonym of Glossopteris papillosa Srivastava (1969). Thus, the new name Glossopteris pubescens is erected as a replacement for G. papillosa Guerra-Sommer. The leaf adpressions come from a tonstein layer within a Sakmarian coal seam (U/Pb age 291 ± 1.3 Ma) of the Faxinal Coalfield, southern Paraná Basin, Brazil (Rio Bonito Formation). Leaf fragments macerated in Schulze's solution yielded larger cuticle fragments than those previously described, totaling over 100 analyzed leaves. The unique ornamentation of the lower side of the lamina comprises simple trichomes and trichome base complexes densely concentrated on the venation system. These epidermal structures are interpreted under the light of new paleoecological data for the Faxinal Coalfield which include humidity oscillations, wildfire occurrences and influence of volcanic activity. These paleoenvironmental factors are suggested to have played a main role in the development of the xeromorphic cuticle structures which possibly had a multitask function during both dry and wet cycles, mainly as protection of stomata against excessive humidity and air dust. [ABSTRACT FROM AUTHOR]

The presence of the fern Weichselia in a restricted sedimentary interval of a drilling core in the Parnaíba Basin (Brazil) was used as a lead for paleoenvironmental interpretation integrating paleobotanical, palynofacies, palynological, organic petrography and clay mineralogy analyses. The fern paleobiogeography was amplified and its association with terrestrial bryophyte gametophytes (Muscites) indicated depositional conditions corresponding to marginal areas of freshwater bodies subjected to frequent flooding under the general fluvial-deltaic conditions so far accepted for the intermediary portion of the Codó Formation. The high dominance of non-opaque phytoclasts and very scarce autochthonous non-marine palynomorphs pointed to a shallow water body linked to marginal areas of fluvial systems in the river outlets, channel margins in estuarine systems, and/or shallow floodplain lakes connected/open to fluvial canals. The very scarce marine palynomorphs (dinoflagellate cysts) suggest a limited influence from unstable environments on coastal margins or estuarine canals. The terrestrial vegetation surrounding the depositional setting, deciphered by palynological analysis, reflected distinct environmental conditions prevailing simultaneously in 1) humid areas dominated by fern communities, and 2) dry-xerophytic areas dominated mainly by Araucariaceae and Cheirolepidiaceae gymnosperms, both as components of a wider Aptian paleoenvironment within the periequatorial latitudes in South America. The results were supported by clay mineralogy that showed abundance of detrital kaolinite over montmorillonite and suggest the dominance of a climatic humidification process and a less expressive semiarid climate in a regional context. • The paleobiogeography of Weichselia is amplified for the Aptian. • Weichselia and Muscites imply freshwater marginal areas under frequent flooding. • Multi proxies imply fluvial/estuarine systems margins and/or shallow floodplain lakes. • Rare marine plankton imply unstable environments on coastal margins/estuarine canals. • A climatic humidification and less expressive semiarid conditions in regional context. [ABSTRACT FROM AUTHOR]

For the first time, this study describes the dynamics of white rot fungal decay in a petrified conifer branch with clear araucarian affinity from the late Aptian Crato Lagerstätte (Santana Formation, Araripe Basin, northeastern Brazil). High resolution optical microscopy was used to identify tridimensional chemical and anatomical evidence in different regions of the bark and xylem tissues of permineralized shoots, and results support the hypothesis that the host responded to disease that may have started when it was still alive. The wood decay pattern was strongly indicative of the selective decay by white rot. The general pattern of interaction is consistent with pathogenic rather than saprophytic fungal activity. Analysis of fungus–plant interactions associated with growth ring patterns imply intermittent periods of favorable temperature-moisture inputs that were crucial for fungal activity during the deposition of the Crato fossil Lagerstätte included in the Tropical Equatorial Hot arid belt. • Decay by white rot occurred in a late Aptian araucarian branch from the Crato Member. • Selective delignification dominated the decay process. • Cell wall apposition, barrier and reaction zones imply attack in living plant. • Favorable temperature-moisture inputs occurred in Tropical Equatorial Hot arid belt. [ABSTRACT FROM AUTHOR]

A gelified wood from the late Aptian Maceió Formation (Sergipe–Alagoas Basin, northeastern Brazil) was studied under scanning electron microscopy and organic petrography allowing for the record of the fossil-species Brachyoxylon patagonicum , likely belonging to the Cheirolepidiaceae family. The anatomical structure of the secondary xylem is characterized by mixed type of radial tracheary pitting, composed exclusively by uniseriate bordered pits, in separated, contiguous and compressed arrangements. Cross-field pits are of the araucarioid type, xylem rays are uniseriate or rarely partially biseriate, and probable sporadic traumatic resin canals are present. The present record expands the paleobiogeographic distribution of the fossil-genus in South America and amplifies its climatic tolerance, since the parent plants lived in the Aptian Tropical Equatorial Hot arid belt. The presence of fungal remains within the wood tissue, and the absence of signs of plant defense against fungal decay suggest saprophytic fungus–wood interactions that likely occurred during a stage of aerobic exposure before burial. • A record of cheirolepidiacean wood for the Brazilian Aptian. • Wood preservation by gelification was determined by organic petrography. • Periquatorial occurrence of Brachyoxylon amplified its climatic tolerance. [ABSTRACT FROM AUTHOR]

This paper presents preliminary results of paleoclimatic signatures of conifer woods during the deposition of the basal Crato and topmost Romualdo members of the Santana Formation within the Tropical Equatorial Hot Arid Belt (late Aptian, Araripe Basin, Brazil). Analysis was carried out using standard thin sections, and the anatomical details were studied in transmitted light. The wood growth pattern from the lowermost laminated lacustrine carbonate level of the Crato Member was characterized by the absence of true growth rings and the common presence of wood growth interruptions, and could be linked to a tropical, equable but erratically humid environment. In an interlayered fine-to-coarse sandstone level attributed to a fluvio-deltaic interval, the wood growth pattern was homogeneous, lacking true growth rings, with weakly delineated growth interruptions over long radial distances. In this level the growth pattern could be related with a transition to a more equable tropical climate during a relatively humid period. In contrast, the wood pattern from the carbonate succession of the uppermost Romualdo Member, interpreted as a lagoon area with marine influence, showed true growth rings with abrupt ring boundaries and rings of variable width, also including frequent growth interruptions. This pattern could be linked to a monsoonal-like climate, subjected to distinct cyclical conditions and periodical droughts during the growing season. • Preliminary wood growth data showed changing climate along the Santana Formation. • A tropical, erratically humid climate was inferred for the lacustrine Crato Member. • Equable humid conditions occurred in the fluvio-deltaic Crato Member. • A tropical monsoon-like climate was inferred for Romualdo Member. [ABSTRACT FROM AUTHOR]

This study deals with the Piscina Outcrop, a Rhaetic reddish conglomeratic sandstone containing silicified logs which corresponds to the Mata Sequence in the southernmost Brazilian Paraná Basin. We performed ground-penetrating radar (GPR) analysis and the results ratified previous sequence stratigraphy analysis indicating that these deposits correspond to architectural elements exclusively related with the filling processes of fluvial channels. The erosive unconformity identified at the boundary between the Mata Sequence and the underlying rock packages could represent a considerable depositional hiatus. The integration of the GPR results with sedimentological and paleovertebrate data from a nearby outcrop at slightly lower topographic level indicated that the layer with the fossil woods is superimposed through an erosive unconformity to the stratigraphic levels corresponding to the Hyperodapedon Assemblage Zone of Carnian age from the basal portion of the Candelária Sequence. The wood assemblage was composed exclusively of araucarian coniferous stems identified as Agathoxylon (cf. Agathoxylon). The wood growth patterns were mainly characterized by woods showing indistinct growth rings, with latewood mostly restricted to one cell in each ring, suggesting weak seasonality and short-term, periodic droughts. Rare specimens with absent growth rings were also present. Oscillations in growth ring width and the common occurrence of false rings were likely linked to plant exposure to climatic instability. Anatomical evidence pointed to active biochemical responses to intense and extensive biological attack of fungi and arthropods. The dominant presence of carbon in the elemental composition of a dark substance filling many tracheid lumens suggested a very likely affinity with polyphenol remnants in biochemical barriers. The set of wood signatures seems to be linked to regional stressing conditions rather than to the paleolatitudinal location when compared to other key South American basins during the Rhaetic. An allochthonous taphocoenosis is the most likely taphonomic interpretation for this wood assemblage. The logs were probably incorporated into the stream through the collapse of riparian areas and buried in the fluvial channel by high-energy flows after biotic and abiotic decay processes during lifetime and secondarily through exposition before entombment in a river channel. • Mata Sequence with silicified woods occurs discordantly over Triassic layers. • Fossil woods may be much younger than underlying Carnian Hyperodapedon Zone. • Deposition by high-energy flows in fluvial channel under subhumid/arid climate. • Stressing environmental conditions revealed by araucarian wood anatomical patterns. • Conspicuous anatomical and biochemical plant responses to biological attack. [ABSTRACT FROM AUTHOR]

Abstract: The radiometric age of 291 ± 1.2 Ma obtained through single-crystal zircon U–Pb ages (Sensitive High Resolution Ion MicroProbe – SHRIMP II) of tonsteins from the Leão-Butiá Coalfield, southern Paraná Basin (Rio Grande do Sul state), associated with previous SHRIMP II radiometric data obtained from tonsteins from the western (Candiota Coalfield) and eastern (Faxinal and Leão-Butiá coalfields) borders of the basin indicate that the mean age of the main peat-forming interval is 291.0 ± 1.3 Ma. In a regional context, the mean age represents a consistent geochronological correlation for the uppermost and more important coal seams in southern Brazilian coalfields, but this assumption does not establish an ash fall origin from a single volcanic event. According to the International Stratigraphic Chart, the interval is dated as middle Sakmarian. The coal palynofloras are included in the Protohaploxypinus goraiensis Subzone within the palynostratigraphic framework for the Brazilian Paraná Basin. Formal relationships are also established with the Glossopteris–Rhodeopteridium Zone within the phytostratigraphic chart for the Lower Permian of southern Brazilian Paraná Basin. [Copyright &y& Elsevier]

The study of a petrified twig under high-resolution optical microscopy allowed for the first formal record of the morphogenus Agathoxylon for the late Aptian Crato Member (Santana Formation, Araripe Basin, northeastern Brazil) and the description of a new species, Agathoxylon santanensis. The wood is characterized by mostly (95%) araucarian triseriate alternate bordered pits with hexagonal boundaries in a compact arrangement, and cross-field pits with araucarioid organization. In addition to Agathoxyon -type of xylem, the preservation of a belt of stone cells and axial resin ducts in the non-functional phloem, and an attached leaf with parallel venation showing longitudinally oriented stomata point to a probable Araucariaceae affinity. The presence of Agathoxylon xylem associated with phloem of Araucariaceae affinity in the Tropical-Equatorial Hot Arid belt indicate that the parent plants survived in different climatic zones in the Early Cretaceous of Western Gondwana, from periequatorial to warm and cool-temperate belts. The general growth pattern suggests that the growth interruptions zones were caused by temporary water stress, which was the limiting factor for favorable growing. • Agathoxylon is reported for the first time for the Aptian Equatorial Arid belt. • Agathoxylon santanensis amplifies the paleobiogeography of the genus. • Bark and leaf patterns indicate probable Araucariaceae affinity. [ABSTRACT FROM AUTHOR]