Palaeobotanical evidence of wildfires in the Late Palaeozoic of South America – Early Permian, Rio Bonito Formation, Paraná Basin, Rio Grande do Sul, Brazil

Fossil charcoal, as direct evidence of palaeowildfires, has repeatedly been reported from several plant-bearing deposits from the Late Palaeozoic of the Northern Hemisphere. In contrast charcoal reports from the Late Palaeozoic deposits of the Southern Hemisphere are relatively rare in comparison to the Northern Hemisphere. Although the presence of pyrogenic coal macerals has repeatedly been reported from Late Palaeozoic coals from South America, no detailed anatomical investigations of such material have been published so far. Here is presented an anatomical analysis of charcoal originating from Early Permian sediments of the Quitéria Outcrop, Rio Bonito Formation, Paraná Basin, located in the central-eastern portion of Rio Grande do Sul, Brazil. This charcoal comes from two different coaly facies, and it was possible to scrutinize between three types, based on anatomical characters of the charcoal. Two of these charcoal types can be correlated to gymnosperm woods, and the other type corresponds to strongly permineralized bark with characteristic features of lycopsids. The presence of charcoal in different facies, ranging from parautochtonous to allochtonous origin, indicates that different vegetation types, i.e. plants which grew under wet conditions in the lowland as well as in the more dry hinterland, have experienced wildfires. Taking into account previous petrographic and lithological analyses from the facies in which the charcoal occurs and from the conditions of the wood and bark fragments, it was possible to speculate that the intensity of such wildfires most probably corresponds to forest-crown fires. Moreover, it is possible to state that wildfires have been a more or less common element in distinct Late Palaeozoic terrestrial ecosystems in the South American part of Gondwana. The data support previous assumptions on the occurrence of wildfires in the Early Permian of the Paraná Basin which were based solely on coal-petrographic data.     

Deglaciation sequences in the Permo-Carboniferous Itararé Group, Paraná Basin, southern Brazil

The Late Carboniferous–Early Permian Itararé Group is a thick glacial unit of the Paraná Basin. Five unconformity-bounded sequences have been defined in the eastern outcrop belt and recognized in well logs along 400 km across the central portion of the basin. Deglaciation sequences are present in the whole succession and represent the bulk of the stratigraphic record. The fining-upward vertical facies succession is characteristic of a retrogradational stacking pattern and corresponds to the stratigraphic record of major ice-retreat phases. Laterally discontinuous subglacial tillites and boulder beds occur at the base of the sequences. When these subglacial facies are absent, deglaciation sequences lie directly on the basal disconformities. Commonly present in the lowermost portions of the deglaciation sequences, polymictic conglomerates and cross-bedded sandstones are generated in subaqueous proximal outwash fans in front of retreating glaciers. The overlying assemblage of diamictites, parallel-bedded and rippled sandstones, and Bouma-like facies sequences are interpreted as deposits of distal outwash fan lobes. The tops of the deglaciation sequences are positioned in clay-rich marine horizons that show little (fine-laminated facies with dropstones) or no evidence of glacial influence on the deposition and likely represent periods of maximum ice retreat.     

Catastrophic floods as a possible cause of organic matter accumulation giving rise to coal, Paraná Basin, Brazil

Gondwana coals of the Rio Bonito Formation (Paraná Basin) in Southern Brazil have generally large ash yields, so they could be better called coaly siltstones than coal. In addition, hummocky cross stratification (HCS) was found in several coal beds of the Rio Bonito Formation throughout the basin. In this formation, the frequent and close relationship between facies involving rocks generated by subaqueous gravity flows (diamictites) and coal itself provides an excellent depositional model based on resedimentary processes acting during deposition, as well as a stratigraphic rearrangement of the present units.In the State of Rio Grande do Sul (southern part of Paraná Basin), coals are actually prodelta deposits related to delta-front diamictite and conglomeratic sandstone with sigmoidal bedding. Coal-forming organic sediments would come from trees plucked by the floods, as indicated by the wood logs floating in the diamictite, and reworking of previous peat accumulations. Every coal layer is covered generally by paleosoil siltstones, which represent colonization at the top of the catastrophic flood deposit, ending a sedimentary cycle.In case of Brazilian coal settings, several authors recognized deltas (fan deltas or braid deltas). Here is particularly considered the general environment as a salted interior sea (lago mare, Hsü et al. sense).The present study will refer to three important lithostratigraphic units in the Carboniferous–Early Triassic cycle: the Itararé Group, the Rio Bonito Formation, and the Palermo Formation.Although the preferential mode of occurrence of HCS in shallow marine environments indicates a genesis attributed to storm action, other causes, such as catastrophic flooding, have been advanced. Mutti et al. [Mem. Sci. Geol. 48 (1996) 233] described flood-dominated deltaic systems with thick conglomerate, sandstone, and pelitic deposits, derived from small- to medium-scale fluvial systems and mountain-bordered drainage basins adjacent to the sea. In such settings, seaward sediment flow can increase dramatically when weather conditions can supply water in such amounts to produce catastrophic floods. Thick and laterally extensive sandstone lobes with HCS are the fundamental depositional elements of fan deltas and other river-dominated delta systems.Diamictites and coal together could be a result from Jökullhlaups—an Icelandic term for glacial outburst flood—in case of catastrophic floods coming from a melting mountain glacier, similar to the Columbia River Valley Scablands (15,000 BP) and in modern Iceland examples.     

Coal petrology of coal seams from the Leão-Butiá Coalfield, Lower Permian of the Paraná Basin, Brazil — Implications for coal facies interpretations

In the Leão-Butiá Coalfield, Rio Grande do Sul the coal seams occur in the Rio Bonito Formation, Guatá Group, Tubarão Supergroup of the Paraná Basin, Brazil and are of Permian (Artinskian–Kungurian) age.This study is the first detailed investigation on the coal petrographic characterization of the coal-bearing sequence in relation to the depositional settings of the precursor mires, both in terms of whole seam characterization and in-seam variations. The study is based on the analyses of nine coal seams (I2, CI, L4, L3, L2, L1, S3, S2, S1), which were selected from core of borehole D-193, Leão-Butiá and represent the entire coal-bearing sequence.The interpretation of coal facies and depositional environment is based on lithotype, maceral and microlithotype analyses using different facies-critical petrographic indices, which were displayed in coal facies diagrams. The seams are characterized by the predominance of dull lithotypes (dull, banded dull). The dullness of the coal is attributed to relatively high mineral matter, inertinite and liptinite contents. The petrographic composition is dominated by vitrinite (28–70 vol.% mmf) and inertinite (> 30 vol.% mmf) groups. Liptinite contents range from 7 to 30 vol.% (mmf) and mineral matter from 4–30 vol.%. Microlithotypes associations are dominated by vitrite, duroclarite, carbominerite and inertite. It is suggested that the observed vertical variations in petrographic characteristics (lithotypes, microlithotypes, macerals, vitrinite reflectance) were controlled by groundwater level fluctuations in the ancient mires due to different accommodation/peat accumulation rates.Correlation of the borehole strata with the general sequence-stratigraphical setting suggests that the alluvial fan system and the coal-bearing mudstone succession are linked to a late transgressive systems tract of sequence 2. Based on average compositional values obtained from coal facies diagrams, a deposition in a limno-telmatic to limnic coal facies is suggested.     

Ice flow direction during late Paleozoic glaciation in western Paraná Basin, Brazil

The recent discovery of ice-striated surfaces associated with the late Paleozoic Aquidauana Formation suggests that glaciers coming from southwest Africa reached westernmost parts of the Paraná Basin in central Brazil. Abrasion features were developed by glaciers moving from SSE towards NNW, mainly on an unconsolidated bed. These records expand to about 1,050,000 km², the coverage of the late Paleozoic glaciation in the region of the Paraná Basin in Western Gondwana.

Resumen

A recente descoberta de superfícies estriadas associadas à Formação Aquidauana, de idade permocarbonífera, sugere que as geleiras provenientes do sudoeste da África alcançaram as porções ocidentais da Bacia do Paraná, na região central do Brasil. As feições de abrasão foram geradas pelo deslocamento de geleiras de SSE para NNW, principalmente sobre substrato inconsolidado. Estes novos registros evidenciam que a glaciação neopaleozóica cobriu uma área de pelo menos de 1.050.000 km² na região ocupada pela Bacia do Paraná no Gondwana Ocidental.     

New chondrichthyans from the Irati Formation (Early Permian,Paraná Basin), Brazil: origin,paleoenvironmental and paleogeographical considerations

Three genera, known by dorsal finspine, are reported from conglomeratic sandstone at the base of the Lower Permian (Kungurian) Irati Formation (Paraná Basin) near Rio Claro, São Paulo State, Brazil, noteworthy for the great richness of vertebrate fossils. The fossils include: (1) the previously known Sphenacanthus with the species Sphenacanthus sanpauloensis and an indeterminate species; (2) the Permian – Carboniferous genus Amelacanthus; (3) a new indeterminate Chondrichthyes. These fossils are found together with: continental, fresh-water and salt-water vertebrates. The analysis of this assemblage allows inference about the origin of Paraná Basin Chondrichthyes as well as reconstruction of the paleoenvironment and the possible geographic isolation of these fishes during the Permian in Brazil.     

Tectonic Control of the Triassic Santa Maria Supersequence of the Paraná Basin, Southernmost Brazil, and its Correlation to the Waterberg Basin, Namibia

The Middle and Late Triassic Santa Maria Basin, exposed in southernmost Brazil, and Waterberg Basin, in Namibia, are herein interpreted as part of en échelon small basins in southern West Gondwana. The main structures are the Waterberg-Omaruru Fault which can be connected to a NW-strike anastomosed fault zone in Brazil. Based on field structural and stratigraphic analysis two populations of NW-strike fractures, named A-type and B-type, are recognized. A-type fractures (Az = 280°-290°) occur in the Sanga do Cabral Supersequence, underlying units of Santa Maria Basin, as extension of the Waterberg-Omaruru Fault during the Early Triassic. B-type fractures (Az = 295°-345°) are observed in all studied stratigraphic units, from the Triassic Sanga do Cabral Supersequence to the Early Cretaceous Botucatu/Serra Geral formations. Based on the structural analysis we propose that NNE-SSW extension reactivated structures of the Damara Belt, Namibia, with a propagation towards Rio Grande do Sul State forming an anastomosing normal fault system and related-rift basin by Early-Middle Triassic time. The A-type fractures were preferentially active by this phase and the B-type ones are interpreted as secondary link segments within the anastomosing system. During the Gondwana break-up and South Atlantic opening (rift to proto-oceanic phase, Aptian) the B-type fractures were reactivated as normal faults by N50°E-S50°W extension.     

The application of FAMM (Fluorescence Alteration of Multiple Macerals) analyses for evaluating rank of Paraná Basin coals, Brazil

Combining vitrinite reflectance (VR) and fluorescence alteration of multiple macerals (FAMM) analyses provide insights into the chemical nature of vitrinites (i.e., perhydrous vs. orthohydrous vs. subhydrous compositions) in Permian Gondwana coals of the Paraná Basin, Brazil. The FAMM-derived equivalent VR (EqVR) values and relationships with VR can be determined according to calibration curves based largely on Permian Gondwana coals of eastern Australia.The analytical results indicate that vitrinites in the Paraná Basin coals studied generally range from orthohydrous to perhydrous, with interpreted VR suppression ranging up to 0.2% absolute for the most perhydrous case. The EqVR values of the Santa Catarina coals, which range from about 0.85% to 0.95% differ from VR values by about 0.10–0.15% absolute, potentially having significant implications on coal utilization.The causes of vitrinite reflectance suppression in the Paraná Basin coals are as yet poorly understood, but are likely to be related to a combination of factors.     

Evaluation of contaminants retention in soils from Viamão District, Rio Grande do Sul State, Brazil

Adsorption is one of the most significant processes in the mobility of soluble pollutants in soils. The aim of this work is to characterize and evaluate the adsorption capacity of soils from Viamão District, Brazil. The studied ions were lead_total, copper_total, sulfate, phosphate, and potassium. The soils were mapped by remote sensing and characterized by granulometrical and mineralogical techniques. The adsorption tests were made by the contact of soil samples with aqueous solutions. The soils adsorption capacity presented the following trend: Pb_total>Cu_total≈PO ₄ ³⁻ >K⁺ ≈SO ₄ ²⁺ . Adsorption in the soils is strongly influenced by clay content. The adsorption of phosphate, copper, and lead was accentuated by the presence of organic matter. Phosphate adsorption was controlled by oxides and organic matter. Both potassium and sulfate showed insignificant adsorption in the studied soils.     

黑龙江三江盆地晚白垩世海浪组孢粉组合

依据东基三井1 226. 0～1 538. 0 m井段的孢粉鉴定结果,结合前人资料,首次将该井段孢粉组合命名为Cyathidites-Taxodiaceaepolleni-Aquilapollenites组合。其组合特征为:裸子植物花粉占48. 10%～78. 58%,蕨类孢子占2. 44%～34. 18%,被子植物花粉占0%～28. 26%;蕨类孢子中Cyathidites百分含量最高(0. 79%～37. 50%),其次是Cicatricosisporites (0%～12. 50%)和Leiotriletes (0%～10. 00%),重要分子有Appendicisporites、Schizaeoisporites、Lygodiumsporites和Lygodioisporites;裸子植物花粉中Inaperturopllenites的百分含量最高(11. 29%～38. 83%),其次是Taxodiaceaepollenites (12. 66%～28. 57%),重要分子有Tsugaepollenites、Parcisporites、Parvisaccites、Ephedripites和Classopollis等;被子植物花粉中Tricolpites的百分含量最高(0%～16. 46%),其次是Betulaepollenites (0%～15. 22%),含量较高的还有Momipites和Tricolporopollenites,重要分子有Aquilapollenites、Fibulapollis和Proteacidites等。该组合可以与松辽盆地嫩江组孢粉组合对比,地质时代为晚白垩世Santonian-Campanian期。鉴于宁安市南团子山、高家等露头区海浪组所产Estherites mitsuishii、E. liuxinensis、Tylestheria cf. shanhoensis、Halysestheria yui、Calestherites sp.和Brachygrapta? sp.等叶肢介化石群,系松辽盆地嫩江组常见分子,故将东基三井1 226. 0～1 538. 0 m井段划归为海浪组,废弃"七星河组"一名。     

Stratigraphical correlation of the Late Jurassic Lourinhã Formation in the Consolação Sub‐basin (Lusitanian Basin), Portugal

The c. 700 m thick succession of continental–brackish‐marine deposits forming the Lourinhã Formation, cropping out along the coast of western Portugal between Baleal and Santa Cruz, has been correlated using laterally persistent shelly marker beds. Three shelly units record the episodic establishment of relatively short‐lived, brackish‐marine embayments, transgressing from the southwest, onto a low‐lying coastal plain. The succession displays systematic changes in facies types and stacking patterns reflecting differences in fluvial style, bedload character and palaeontological content. Based on these observations, four new members for the Lourinhã Formation are proposed: the Sáo Bernardino, Porto de Barças, Areia Branca and Ferrel members. New biostratigraphical data indicate that the Lourinhã Formation is Late Kimmeridgian to earliest Early Tithonian in age. This age has also been obtained from the underlying mixed carbonate and clastic deposits of the Abadia Formation at Consolação. As a result, these latter sediments are now re‐assigned to the Alcobaça Formation, a lithostratigraphical term currently in use in other areas of the Lusitanian Basin. Improved regional mapping of the Lourinhã Formation has established a new sub‐basin within the western parts of the Lusitanian Basin. This sub‐basin, now named the Consolação Sub‐basin, is bounded to the east by the Lourinhã–Caldas de Rainha (L–C) fault zone and to the west by the Berlengas Horst. Copyright © 2013 John Wiley & Sons, Ltd.     

晚古生代—中三叠世右江盆地的格局和转换

晚古生代—中三叠世右江盆地是在夷平的南华加里东造山带基础上再生裂陷的大陆边缘盆地,该盆地的形成与金沙江—哀牢山古特提斯洋盆关系密切,是一个具有台地与台间海槽相间结构的大陆边缘裂谷盆地。右江盆地自早泥盆世埃姆斯晚期开始裂陷,到石炭纪盆地与越北地块之间出现一个与古特提斯洋相关的局限小洋盆或深海盆。至二叠纪,该洋盆开始向西南俯冲于越北地块之下,形成活动大陆边缘。早三叠世晚期以后,随着该洋盆的闭合和碰撞造山,在凭祥、那坡等地出现同碰撞型的火山活动,右江盆地也于中三叠世转变为以复理石为特征的前陆盆地。因此右江盆地经历了裂谷盆地(早泥盆世晚期—晚泥盆世)、被动大陆边缘(早石炭世—早三叠世)、前陆盆地(中三叠世)的构造演化阶段。     

Santa Bárbara Formation (Early Paleozoic, Caçapava do Sul, southern Brazil): Petrographic and Sm–Nd isotopic provenance parameters

Integrated petrographic and Sm–Nd isotopic data were applied in order to constrain the provenance of the Early Paleozoic Santa Bárbara Formation, Sul-rio-grandense Shield, southern Brazil. This unit comprises continental sandstones, conglomerates and siltstones deposited under semi-arid climate in a rift or pull-apart basin. Samples were collected within a stratigraphic framework composed of three sequences, in which the two basal ones present northeastwards paleoflow, and the third one marks the inversion of basin filling. Samples from sequence I show, in the south, a strong influence of intermediate volcanic (Hilário Formation) sources, and a significant increase in quartz and metamorphic fragments upsection. In the northern deposits, there is a possible influence of juvenile units (Cambaí/Vacacaí), and a more significant input of Paleoproterozoic-sourced sedimentary rocks (e.g. Maricá Formation) upsection. Samples collected from the topmost deposits of sequence II present a clear increase in the amount of volcanic fragments (mostly acidic), reflecting denudation of the “Caçapava high”. Data obtained in sequence III (Pedra do Segredo) show a progressive decrease in quartz content and a significant increase in feldspathic, plutonic fragments. A more evolved phase of denudation of the “Caçapava high”, exposing leucogranitoids of the Caçapava do Sul complex, is proposed for this interval.     

Genesis of Polyhalite in the Halite in Jialingjiang Formation of Triassic,Eastern Sichuan Basin,China

正Polyhalite generally formed in the early diagenetic stage.It is formed by the brine which rich in K+and Mg2+and adverse reaction with the gypsum,anhydrite,glauberite(Pierre,1985;Peryt et al.,2005;Leitner et al.,     

藏北羌塘盆地上三叠统那底岗日组与下伏地层沉积间断的确立及意义

藏北羌塘盆地上三叠统那底岗日组呈近东西带状展布，下部主要为凝灰岩、凝灰质砂岩夹流纹岩、玄武岩，上部主要为含砾砂岩、泥质粉砂岩和生物碎屑泥灰岩。笔者等野外调查中首次在下伏的上三叠统肖茶卡组顶部发现古风化壳，结合在那底岗日组底部识别出来的不同底界类型和底砾岩特征，证实那底岗日组与下伏地层之间存在沉积间断。早期磁性地层研究中也曾发现了该沉积间断的存在，间断时间被认为约2Ma。运用已有的生物地层资料确定肖茶卡组地层的沉积时间（晚三叠世诺利期一瑞替期），从而推测那底岗日组火山岩形成时代略晚于这个时间，很可能早于前人关于该套地层的时代认识。那底岗日组火山岩可能对研究东特提斯地区的晚三叠世生物绝灭、气候变化以及海退事件有重要意义。     

The Triassic Santa Juana Formation at the lower Biobío River, south central Chile

A sequence of Triassic rocks is exposed near the town of Concepción, Chile. These clastic strata are interpreted as the deposits of rivers, lakes, playas, and alluvial fans. The deposits comprise conglomerates, arkosic sandstones, and sand-, silt- and mudstones. Four facies associations comprising eight sedimentary facies can be distinguished. Plant fossils from the sedimentary sequence of the Santa Juana Formation indicate a Carnian age. The flora includes ferns (Gleichenites, Cladophlebis, Dictyophyllum, Thaumatopteris, Asterotheca, Saportaea) and seed ferns (Kurtziana, Antevsia, Dicroidium), ginkgophytes (Sphenobaiera), cycads (Pseudoctenis), conifers (Heidiphyllum, Telemachus, Rissikia), and gymnosperms of uncertain affinities (Linguifolium, Gontriglossa). Two new species are presented: Pseudoctenis santajuanensis and Gontriglossa reinerae.     

云南楚雄盆地西缘晚三叠世地震软沉积变形及灾变事件分析

震积岩是古地震事件的重要记录,笔者在滇西楚雄盆地西缘斜坡浊流相罗家大山组中识别出震积岩体系。通过对罗家大山组剖面宏观露头和岩石薄片微观构造观察,总结了楚雄盆地西缘晚三叠世震积岩的识别标志,分为原地相脆性震积构造和软沉积变形震积构造,包括固结层脆性变形和疏松层软沉积变形,以及微断层、褶皱组合形成脆韧性构造、撕裂构造、自碎角砾岩、混滑层、液化卷曲变形、枕状构造、碟状构造、液化（角）砾岩、液化脉、沙火山、火焰状构造、负载构造、串珠状构造等。根据罗家大山组的震积岩特征,建立了斜坡相地震-海啸沉积序列。对这些震积岩的研究有利于对楚雄盆地西侧断陷盆地形成大地构造背景、活动时限的约束,并且可以指导在楚雄盆地内开展油气勘查。     

Shrimp U–Pb zircon dating and palynology of bentonitic layers from the Permian Irati Formation, Paraná Basin, Brazil

This paper presents the first SHRIMP zircon age data from bentonitic ash fall layers intercalated with the Irati sedimentary rocks, as well as palynofossils retrieved from the PETROBRAS-Six mine, Paraná State, southern Brazil. The Permian Irati Formation is one the most important oil source horizons within the Paraná Basin, and consists mainly of siltstones, gray claystones, as well as organic-rich claystones intercalated with limestones. Zircon morphology based on cathodoluminescence images includes two different populations: a dominant population of euhedral, prismatic, elongate to acicular grains which are most likely related to an ash fall volcanism; and a population of rounded to large prismatic grains, that were interpreted as detrital grains. SHRIMP analysis performed on the euhedral and prismatic grains revealed an age of ca. 278.4 ± 2.2 Ma (7 points with 95% confidence) interpreted as the crystallization age of the volcanic eruption. Based on this new dating, the Irati Formation should be placed on the Lower Permian (Cisuralian), Artinskian in age, modifying substantially the traditional ages previously attributed to this unit. The palynofossils from this level include key species of the Lueckisporites virkkiae Zone (such as L. virkkiae, L. densicorpus, L. stenotaeniatus, Weylandites lucifer, Alisporites splendens). Typical species of this zone also occur in African and other South American (Argentina) Permian strata, allowing stratigraphical correlations. The origin of the ash falls is not clearly defined. It may be related either to calc-alkaline arc magmatism associated to the Sanrafaelica Orogeny (275 and 250 Ma) or to bimodal volcanic events associated to an early intracontinental rift developed within southwestern Gondwana at ca. 278 My. The dating of this unit is significative to calibrate biostratigraphic schemes along the Paraná Basin, as well as equivalent zones in Gondwana areas, mainly in its Occidental portion.     

西藏申扎地区晚三叠世多布日组地层剖面的启示——对冈底斯印支运动的地层学制约

冈底斯地区古生代台地之上上叠一个重要的沉积地层单元——上三叠统多布日组。其层序特征及底部不整合界面性质的研究,确认了该区在早中生代曾发生过强烈的褶皱运动,随后为一次重要的拉伸事件所更替,从而进一步证实了印支运动对冈底斯地区产生过深刻的影响。