Viés Analítico em Estudos Tafonômicos com Macroinvertebrados: Implicações (Paleo)Ambientais e (Paleo)Ecológicas

A review of recent literature shows that most taphonomic studies of Holocene and fossil macrovertebrates are not methodologically standardized. Hence, results from distinct studies are not comparable, even among researches sharing virtually identical goals, targeting the same biological group of similar age and depositional environment. The effects of the shell size in the taphonomic analysis are still poorly understood. In order to study this issue, the taphonomic signatures (articulation, valve type, fragmentation, abrasion, corrosion, edge modification, color alteration, bioerosion and encrustation) of brachiopod shells (Bouchardia rosea (Mawe)), from Ubatuba Bay in the northern coast of São Paulo State, were investigated according to the sieve sizes. In the study area, 14 collecting stations were sampled via Van Veen grab sampler, along a bathymetric gradient, ranging from 0 to 35 m of depth. Bulk samples were sieved through 8 mm, 6 mm, and 2 mm mesh sizes, yielding a total of 5.204 shells. The results indicate that, when taphonomic signatures were independently analyzed per size classes (8 mm, 6 mm, and 2 mm), the taphonomic signatures are recorded in a complex and random way. Additionally, cluster analysis showed that the similarity among the clusters vary according to the considered sieve size. Thus, the sieve size plays an important role in the distribution of taphonomic signatures in shells of distinct sizes. These results suggest that the concentration of the taphonomic analysis on one class (e.g., the largest sieve size, 8 mm) is not always the best method. Rather, the total data (all sieves included) seems more accurate in recording the whole spectrum of taphonomic processes recorded in shells of a given assemblage.

Tafonomia de tempestitos conchíferos amalgamados da formação Teresina em Rio Preto (Estado do Paraná, permiano médio, bacia do Paraná) e suas implicações paleoambientais

The deposits of the Permian Teresina Formation are mainly characterized by fi ne-grained siliciclastic rocks and centimetric intercalations of tempestites (bioclastic sandstones and coquinas). Despite the relevance of the bivalve-rich carbonate beds of the Teresina Formation to paleoenvironmental studies, their taphonomy is still poorly studied. The fossil concentration studied in this work was found in a quarry in the city of Irati, Rio Preto district, Parana State. The fossil concentration is located in the middle/upper portion of the unit, far from the top. The studied bed is a bioclastic, intraclastic, peloidal, grainstone/ packstone, with abundant bivalve shell fragments, pelitic and micritic intraclasts, peloids, rare ooids and oncoids, as well as permineralized of Lycophyta microphylles and fish scales. The grains of this carbonate concentration show: high degree of time-averaging, variable degree of packing (dense to disperse), no sorting and chaotic orientation. Notably, the concentration includes a mixture of elements which are indicative of: a) restrictive, low energy, carbonate environment (peloids, ooids and oncoids); b) subaerial environment surrounding the main body of water (Lycophyta microphylles) and c) quiet-water environment punctuated by storm events, where the suspension-feeding bivalves thrived. At least four depositional events caused by storm fl ows were recorded. The amalgamated nature of the bed is a result of storm events in an intracratonic basin with very low seafl oor slope and low rates of sedimentation and subsidence.

Tafonomia de biválvios em calcários oolíticos da formação Teresina (Bacia do Paraná, Permiano Médio, Prudentópolis, PR)

Herein, it is presented the first detailed taphonomic study on bivalve mollusk shells preserved in the oolitic limestones of the Teresina Formation (probably Kungurian-Roadian, Lower-Middle Permian) in the eastern margin of the Parana basin. The selected beds are located in two quarries (informally named PRU 1 and PRU 2) in Prudentopolis municipality (Center-South Parana State), and positioned approximately in the middle of the formation and probably in the Pinzonella illusa Zone. The PRU 1 limestone ([approximately]30 cm thick), which is partially silicified and intercalated with predominantly pelitic rocks, is classified as a bivalve oolitic grainstone. The basal contact is erosive and the top shows symmetrical ripple marks, which are draped by shale with mud cracks. There are two fining-upwards successions characterized by dense to dispersed packing of the shells, which are usually disarticulated, randomly oriented (many nested/stacked) and mixed with some Formapelitic intraclasts. Microhummocky cross-stratification occurs a little below the top of the bed. The PRU2 bed is classified as ooidbivalve rudstone[approximately] (~5 cm thick), where all shells are disarticulated and fragmented, showing dense packing. The bivalves probably inhabited a muddy substrate and were mixed (as parautochtonous and allochthonous bioclasts) with ooids during high-energy storm events, including posterior shell displacement as a result of bioturbation. Thus, the calcareous beds represent amalgamated proximal tempestites with a complex taphonomic history, strong temporal/spatial mixing of bioclasts and limited paleoecological resolution. They are a typical example of shell beds generated in a huge epeiric sea, which was not necessarily connected to the ocean and where very low depositional-slope gradient, very slow subsidence and minimum sediment accommodation space caused frequent sediment reworking by storm related processes.

Foot-trembling behavior in Semipalmated Plover Charadrius semipalmatus reveals prey on surface of Brazilian beaches

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Contribuição para o conhecimento da biologia de Cynoscion jamaicensis (Vaillant & Bocourt, 1883), na área entre Cabo de São Tomé (22º04's) e Torres (29º21'S), Brasil

Este trabalho baseia-se na análise de dados obtidos de 1891 exemplares de Cynoscion jamaicensis coletados durante quatro cruzeiros oceanográficos realizados por intermédio do N/Oc. Prof. W. Besnard, na área entre Cabo de Sao Tomé (22º04'S) e Torres (29º30'S), até a isóbata de 200 m, dentro do programa FAUNEC. A espécie distribui-se ao longo da plataforma continental, preferencialmente na região banhada pela agua costeira, com temperaturas entre 27ºC e 18ºC. Ocorrem concentrações de jovens e adultos, indiscriminadamente da distância da costa; os jovens ocorreram, em fevereiro-março, entre 22ºS e 27ºS e, nos demais períodos, entre 23º20'S e 27º30'S, enquanto os adultos distribulram-se, em fevereiro-março e maio, entre 26ºS e 27º30'S e, em setembro e novembro, entre 23ºS e 29º30'S. A desova ocorre entre as latitudes 24º30'S e 26º30'S, durante o fim do inverno-primavera (setembro-novembro). Concordando com o ciclo reprodutivo, o fator de condição mostrou variações cíclicas, com valor mais baixo durante setembro, período de desova. O pico de recrutamento verificou-se em maio, quando ocorreram indivíduos com comprimento total entre 70 e 90 mm, provenientes da desova do ano anterior, que ainda nao completaram um ano de idade. 0 comprimento médio de início da primeira maturação sexual é de 154 mm, sendo que aos 200 mm todos os indivíduos estão aptos para a reprodução. A relação peso total/comprimento total apresentou diferenças estatisticamente significativas entre sexos, com α = 3,25 para machos e 3,10 para fêmeas.

Food resource utilization of the skates Rioraja agassizii (Müller & Henle, 1841) and Psammobatis extenta (Garman, 1913) on the continental shelf off Ubatuba, South-eastern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Tectonics and paleogeography of the Marajó Basin, northern Brazil

A área da Bacia do Marajó apresenta feições geológicas e geomorfológicas devidas principamente à distensão Mesozóica e à neotectônica pós-miocênica. O evento de distensão, com fases do Cretáceo Inferior e Superior, originou quatro sub-bacias que contituem a Bacia do Marajó, com uma espessa seqüência clástica continental mostrando influência marinha. Falhas normais NW e NNW e direcionais NE e ENE controlaram a geometria da bacia. A distensão, relacionada com a abertura do Atlântico Equatorial, propagou-se continente adentro ao longo de zonas de fraqueza crustal dos cinturões orogênicos pré-cambrianos Tumucumaque, Amapá e Araguaia. O evento neotectônico é um regime transcorrente que desenvolveu bacias transtensivas preenchidas por sedimentos marinhos rasos (Formação Pirabas) e seqüências transicionais (Grupo Barreiras) do Terciário Superior, seguidos por depósitos fluviais e seqüências transicionais do Quaternário, derivadas dos rios Amazoans e Tocantins e do estuário do Marajó. A paisagem atual tem morfologia tipicamente estuarina. A morfologia costeira apresenta escarpas em seqüências transicionais do Terciário Superior, enquanto no interior dominam elevações sustentadas por crosta laterítica do Pleistoceno Médio, aparadas por superfície erosiva a 70 m. No leste da Ilha do Marajó são reconhecidas várias gerações de paleocanais com seqüências estuarinas associadas, enquanto no lado oeste predomina uma planície flúvio-marinha.

Ichthyofauna of the rio Itatinga in the Parque das Neblinas, Bertioga, São Paulo State: composition and biogeography

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

O uso de praias arenosas com diferentes concentrações humanas por espécies de aves limícolas (Charadriidae e Scolopacidae) neárticas no sudeste do Brasil

As aves migratórias podem reconhecer humanos e animais domésticos como possíveis predadores, alterando seus padrões de abundância e comportamento de formação de bandos. O objetivo do presente estudo foi comparar a abundância de aves migratórias neárticas, a freqüência de bandos e o número médio de aves por bando em áreas com alta e baixa concentração humana em uma região costeira de praia arenosa no sudeste do Brasil. As aves, pessoas e cães foram contados mensalmente entre novembro de 2006 a abril de 2007. Foram registradas seis espécies de aves (Arenaria interpres, Calidris alba, Calidris canutus, Calidris pusilla, Charadrius semipalmatus, Pluvialis dominica) nas duas áreas, no entanto somente C. canutus foi registrado exclusivamente na área com baixa concentração humana. Houve diferença significativa no número médio de pessoas e cães entre as áreas, mas não no número médio de aves. Não houve correlação entre o número de humanos e aves, e entre cães e aves. Adicionalmente, não houve diferença significativa na freqüência de bandos e número de indivíduos por bando entre as áreas. Os resultados deste estudo destacaram a sensibilidade de C. canutus na área com alta concentração humana e a necessidade de futuras investigações que determinem os limites máximos de concentração de pessoas e cães domésticos que as aves migratórias neárticas podem tolerar para a tomada de ações de proteção em áreas costeiras com ocupação humana.

Análise dos atributos físico-ambientais do município de Praia Grande-SP

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Prospecção geofísica em ocorrência de cobre localizada na bacia sedimentar do Camaquã (RS)

Estudos de pesquisa mineral são fundamentais para o reconhecimento e a incorporação de novas reservas. Esse trabalho apresenta os resultados de aplicação do método geofísico da eletrorresistividade numa ocorrência mineralizada em carbonatos de cobre, por meio da técnica de caminhamento elétrico em arranjo azimutal. A área de estudos está inserida na bacia sedimentar do Camaquã, formada por um conjunto de unidades estratigráficas sedimentares e vulcanogênicas, onde são descritas diversas ocorrências cupríferas. A presença de azurita e malaquita em fraturas e zonas de maior porosidade em arenito encaixante define a geologia local. Os modelos de inversão revelam anomalias circulares de resistividade moderada para até 25m abaixo da ocorrência aflorante e anomalias de baixa resistividade em profundidades abaixo de 25m, além de áreas adjacentes com alta resistividade. Indicadores de mineralização descritos para ocorrências de cobre estudadas, no âmbito da bacia sedimentar do Camaquã, ocorrem na área de estudos e permitem caracterização em termos de resistividade elétrica. Áreas com silicificação apresentam alta resistividade, enquanto que valores intermediários são atribuídos a zonas com carbonatação e, finalmente, áreas de baixa resistividade, provavelmente, indicam concentrações de sulfetos disseminados.

Othonella araguaiana (Bivalvia, Megadesmidae) from the Corumbatai Formation (Midlle [Middle] Permian), Eastern Margin of the Parana Basin: systematic, evolutionary and biostratigraphic significances.

In this study, the occurrence of Othonella araguaiana Mendes, a rare bivalve species is reported for the first time in the Pinzonella illusa biozone, Middle Permian Corumbatai Formation, in the State of São Paulo. This species was originally described in coeval rocks of the Estrada Nova Formation (= Corumbatai) from the Alto Araguaia and Alto Garcas regions, State of Mato Grosso. The specimens of O. araguaiana were found in the base of a bioclastic sandstone bed, a proximal tempestite, in the middle of the Corumbatai Formation, in the city of Rio Claro, São Paulo State. The silicified shells and internal molds are well preserved, showing impressions of muscle scars and other internal anatomic characters (e.g., hinge), never illustrated by previous authors. In his original description, Mendes (1963) called attention to the similarity between O. araguaiana and Terraia aequilateralis, a common veneroid of the Corumbatai Formation. Conversely, Runnegar and Newell (1971) suggested that O. araguaiana belongs to Megadesmidae, being a junior synonym of Plesiocyprinella carinata (the commonest megadesmid of the Passa Dois Group). Our study indicates that O. araguaiana is indeed a megadesmid, but is distinct from the P. carinata. The new occurrence of O. araguaiana demonstrates that a) the paleobiogeographic distribution of this species is wider than previously thought (that it was restricted to the northern part of Parana Basin, Mato Grosso State); b) the molluscan fauna of the Corumbatai Formation (P. illusa biozone) in the State of São Paulo is more diverse and dominated by megadesmids; and c) the composition of the molluscan fauna of the Corumbatai Formation in Alto GarYas, State of Mato Grosso, is essentially the same as that of the P. illusa biozone of the eastern margin of the Parana Basin.

Conchostráceos com linhas de crescimento recurvadas junto à margem dorsal (famílias Palaeolimnadiopseidae e Perilimnadiidae) da formação rio do rasto, Permiano superior, bacia do Paraná, Brasil

Some Upper Permian conchostracans from the Rio do Rasto Formation (Parana Basin, South Brazil) have very characteristic recurved growth lines at the dorsal margin. All previously described specimens were classified as Palaeolimnadiopsis subalata (Reed) Raymond. However, a re-analysis of these fossils and of additional recently- collected specimens demonstrated that not all can be included in a single species, nor only in the Family Palaeolimnadiopseidae. According to their shape and the size of the umbo, they are classified into three species. The sub-elliptic carapaces with small anterior umbo are maintained in Palaeolimnadiopsis subalata (Reed, 1929) Raymond, 1946. The sub-circular carapaces with small sub-central umbo correspond to the new species Palaeolimnadiopsis riorastensis. The small size of the umbo is a character of the Family Palaeolimnadiopseidae. The small elliptic valves with large anterior umbo are assigned to the new species Falsisca brasiliensis of the Family Perilimnadiidae, which is characterized by large umbos. Palaeolimnadiopsis has a wide chronostratigraphic distribution, but Falsisca is restricted to the Upper Permian-Lower Triassic of Europe and Asia. This interval is in agreement with the probable Late Permian age of the respective strata of the Rio do Rasto formation. Falsisca was not previously recorded in Gondwana.

Isotopic characterization of the metabasites and amphibolites of the Acungui and Setuva Groups of the Ribeira Belt

Pb, Rb, Sr, Sm and Nd isotope analyses were carried out on amphibolitic rocks from Campo Largo (PR), Rio Branco do Sul (PR) and Adrianópolis (PR) and for the metabasite from Adrianópolis and Apiai (SP), all belonging to the Açungui and Setuva Groups, southern portion of the Ribeira Belt. These occurrences were chosen because each exhibits geochemical data indicative of a mantle source, having different signatures. Geochronologic determinations are available only for the Apiai metagabbro with Neoproterozoic ages of 617 ± 4 Ma (U/Pb in zircon) and 839 ± 85 Ma (Rb/Sr, whole rock). Age determinations by Sm/Nd mineral isochron using whole rock, plagioclase and pyroxene yield values of 885 ± 53 Ma for the Apiai metagabbro and 820 ± 84 Ma for the Adrianópolis metabasite. These results agree within error with the Rb/Sr isochron of 839 ± 85 Ma may possibly be interpreted as the time of extraction of the magma from the mantle, as suggested by positive εNd(850) values (+2,76) from an Adrianópolis sample. An εNd values versus 87Sr/86Sr diagram shows that each studied occurrence plots in a different position, following approximately the mantle array trend, the most primitive being the metabasite of Adrian-acopolis, near the MORB field, and the most enriched being the amphibolite from the same region, near the enriched mantle and or crustal contamination field. The distinct difference in isotopic signatures between the amphibolite and metabasite suggests derivation from different mantle sources, as supported by available geochemical data. Nevertheless, some of the samples show isotopic evidence of the action of metamorphism, crustal contamination and weathering.

Sm-Nd system in total rock open versus closed isotopic composition in zones of high deformation

High strain shear zones of Brasiliano age, developed in Paleoproterozoic basement gneiss of the Caicó region, Borborema Province, NE Brazil, were associated with medium- to low-grade metamorphism and deformational processes that transformed porphyritic augen gneiss into muscovite quartzite, modifying their original mineralogy and chemical properties. During the last hydrothermal event mobility of major, minor and trace elements was great, whereas the pattern of Rare Earth Elements was not changed. We carried out a Sm-Nd isotopic study in these rocks in order to understand the behavior of Nd isotopes during mylonite generation. TDM model ages at around 2.6 Ga and εNd (t) values for both protolith and transformed rock suggest that the Nd isotopic system remained closed, recording the original source rock signature, despite undergoing two superposed metamorphic events. These new Sm-Nd results provide important information on the geologic evolution of basement rocks in the central Rio Grande do Norte Terrane of the Borborema Province, NE Brazil.