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ResumoO evento anóxico global do Frasniano está bem caracterizado na Bacia do Paraná na porção superior da Formação Ponta Grossa por folhelhos escuros carbonosos ricos em matéria orgânica. Esses folhelhos são encontrados em uma seção da Formação Ponta Grossa de idade Meso-Neodevoniana, onde os folhelhos apresentam a assinatura da transição Givetiano-Frasniano e, também, o progressivo afogamento da sequência devoniana na bacia. Por meio dos dados geoquímicos e bioestratigráficos obtidos da seção acima referida, foi possível reconhecer as superfícies de inundação e a superfície de inundação máxima da seção e também o progressivo afogamento da sequência devoniana na bacia que atingiu o seu ápice no Frasniano. Esses folhelhos, que representam a assinatura da transição Givetiano-Frasniano, e a superfície de inundação máxima ocorrida no Frasniano, podem ser usados como um marco cronoestratigráfico, como também, são objeto de interesse para a exploração de hidrocarbonetos. Foram identificadas duas assembléias de miósporos pertencentes ao Givetiano e ao Frasniano e algumas formas de algas do gênero Maranhites, assim como, acritarcos. Palavras-chave: Devoniano; Formação Ponta Grossa; Bacia do Paraná AbstractThe global anoxic event in the Frasnian is well characterized in the Paraná Basin, in the upper portion of the Ponta Grossa Formation, by dark carbonaceous shales rich in organic matter. These shales are found in a section of the Ponta Grossa Formation of Meso and Neo-Devonian age, where the shales correspond to the signature of the GivetianFrasnian transition-and, also, to the progressive drowning of the Devonian sequence in the basin. Through geochemical and biostratigraphic data obtained from the section mentioned above, it was possible to recognize flood surfaces and the maximum flooding surface in the section and, also, the progressive drowning of the Devonian sequence in the basin that reached its maximum in the Frasnian. These shales, which represent the signature of the Givetian-Frasnian transition and the maximum flooding surface, occurred in Frasnian, can be used as a chronostratigraphic marker and are also the object of interest for hydrocarbon exploration. Two miospore assemblages related to the Givetian and Frasnian and some algae of the genus Maranhites were recognized as well as acritarchs.

O objectivo deste trabalho era caracterizar as propriedades físicas do solo da área da mata da galeria na sub-bacia hidrográfica da Mariana. Os atributos físicos avaliados foram: densidade aparente, humidade gravimétrica, porosidade do solo e resistência mecânica à penetração. O trabalho de campo foi levado a cabo em Alta Floresta-MT, Brasil. Nove parcelas de 20 m x 50 m de superfície foram marcadas ao longo das zonas do curso superior e médio do rio de tal forma que eram representativas de toda a extensão da sub-bacia hidrográfica. O desenho experimental foi completamente aleatório. A densidade do solo da área da mata de galeria era superior à da floresta nativa, de modo a que o desenvolvimento do sistema radicular das árvores pudesse mesmo ser restringido. Verificou-se que a humidade gravimétrica era homogénea quando diferentes áreas ou diferentes profundidades eram comparadas. Verificou-se que a porosidade do solo era adequada para as matas de galeria nativas. A resistência média à penetração a 0-0,25 m de profundidade foi classificada como moderada, sobre as áreas do curso superior e médio dos rios.

This paper deals with borehole data from 1.587,80-1.660,75 m interval of the well 1-AM-1-AM, which represents the most complete section of the Silurian in Amazon basin. Pitinga and Lower Manacupuru formations occurring in Petrobras cores T-40 to T-47 and in Eletronorte shallow boreholes SM 1015, SM 1016, SM-1018, SM-1047 and SM 10-48 were analysed. Besides Acritarch, Chitinozoa, Criptospores, Escolecodontia and amorphous organic matter were also recorded. The Silurian section is rich in well-preserved Acritarchs and prasinophytes, exhibiting a great diversity, mainly in the Pitinga Formation. Forty and eight species were classified. For each well, the Acritarch vertical distribution was done, the asociations age was discussed and the Chitinozoa-based dating, as established by (Grahn and Melo 1990), was compared. The informal division of the Pitinga Formation in lower and upper members was kept. The lower member (Telychian to Sheinwoodian) is represented mainly by Domasia limaciforme, D. Canadensis, D. trispinosa, D. amphora, D. rochesterensis, Dateriocradus monterrosae e Salopidium granuliferum, Cymbosphaeridium pilar, Dactylofusa tenuistriata, D. cucurbita, Deunffia furcata, Baltisphaeridium capillatum, Vibysphaera erratica, Micrhystridium intonsurans. The upper member (Gorstian) is separated from the lower by a hiatus, and is well defined by the following species: Deunffia furcata, D. brevispinosa, D. ramusculosa, Tyrannus giganteus, Eisenackidium ramiformis, Gorgonisphaeridium bringewoodense, Domasia bispinosa, D. trispinosa, Helios aranaides, Micrhystridium stellatum, Neoveryhachium carminae, Multiplicisphaeridium caperoradiola, Leiofusa kryanovii, Leiofusa filifera, Oppilatala insolita, Pterospermopsis marysae, Veryhachium rhomboidium, Cymbosphaeridium pilar, Cymbosphaeridium cf. ravum, Multiplicisphaeridium fisheri, Dactylofusa striatifera, Polysphaeritae, Visbysphaera microspinosa, Visbysphaera dilatispinosa, Salopidium wenlockensis and Veryhachium europaeum. According to Molyneux et al., 1996, most of the referred species such as Tyrannus giganteus and Perforela perforata are indigenous forms that were described in Upper Silurian from Spain and North Africa. Although these species could be excellent biostratigraphic markers, some of them still need a graptolitic correlation. For the basal Manacupuru formation, separated from Pitinga formation by a hiatus, the following species could be noted: Balthisphaeridium pilar, B. cariniosum, Multipliscisphaeridum saharicum, M. scaber, Domasia rochesterensis, Dateriocradus monterrosae, Neoveryhachium carminae and Perforela perorata. This association is considered to be Pridoli in age, which agrees with the Chitinozoa-based dating of Grahn & Melo (1990). Deunffia and Domasia are important taxa defining the Llandovery-Wenlock interval, of incontestable chronostratigraphic value, since they are restricted globally to the Silurian. According to (Cramer, 1970a; Le Hérissé, 1989; Molyneux et al., 1996) these taxa increase in number near the boundary between Llandovery-Wenlock, what is also confirmed in the present paper.

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Acritarchs are known to be related to cysts of marine microphytoplankton, and are reliable indicators of marine paleoenvironments. The acritarch genus Veryhachium was erected by Deunff (1954) to encompass an entire plexus of microfossils first recorded in Paleozoic strata of England and France. It includes a variety of organic-walled microphytoplanktonic organisms consisting of a smooth or granulated, hollow vesicle with triangular to polygonal shape. The vesicle is provided with up to eight, tapered and long, often bent, unbranched processes, which are hollow and present either smooth or granulated walls. The oldest known representatives of Veryhachium are from the Upper Cambrian, but the genus becomes most abundant and diversified in succeeding Paleozoic intervals. By contrast, post-Paleozoic records include only two species from the Cretaceous, and three Tertiary species which Stancliffe & Sarjeant (1994) regard as anomalous forms. The occurrence of Veryhachium in recent sediments of Bolivia has been attributed by several authors to the reworking of Paleozoic strata. Due to the long stratigraphic range of most of its species, the genus has generally played a secondary role in biostratigraphic zonations. Our palynological study of the Trombetas Group (Amazonas basin, northern Brazil), based on numerous outcrops and Eletronorte shallow core-drills, together with core samples of a single Petrobras well, has recorded such Silurian species as Veryhachium owensii, V. oklahomense, V. pertonense, V. longispinosu, V. rhomboidium and V. lairdii. They occur together with more age-diagnostic Silurian species belonging to the genera Deunffia and Domasia. The diversity of Veryhachium in the Trombetas Group highlights not only its importance as a paleoenvironmental indicator, but also its usefulness in characterizing regional palynomorphs assemblages in Paleozoic basins of Western Gondwana.