Lower Permian stems as fluvial paleocurrent indicators of the Parnaíba Basin, northern Brazil

A comprehensive biostratinomic study was carried out with abundant stems from the Lower Permian Motuca Formation of the intracratonic Parnaíba Basin, central-north Brazil. The fossils represent a rare tropical to subtropical paleofloristic record in north Gondwana. Tree ferns dominate the assemblages (mainly Tietea, secondarily Psaronius), followed by gymnosperms, sphenophytes, other ferns and rare lycophytes. They are silica-permineralized, commonly reach 4 m length (exceptionally more than 10 m), lie loosely on the ground or are embedded in the original sandstone or siltstone matrix, and attract particular attention because of their frequent parallel attitudes. Many tree fern stems present the original straight cylindrical to slightly conical forms, other are somewhat flattened, and the gymnosperm stems are usually more irregular. Measurements of stem orientations and dimensions were made in three sites approximately aligned in a W-E direction in a distance of 27.3 km at the conservation unit Tocantins Fossil Trees Natural Monument In the eastern site, rose diagrams for 54 stems indicate a relatively narrow azimuthal range to SE. These stems commonly present attached basal bulbous root mantles and thin cylindrical sandstone envelopes, which sometimes hold, almost adjacent to the lateral stem surface, permineralized fern pinnae and other small plant fragments. In the more central site, 82 measured stems are preferentially oriented in the SW-NE direction, the proportion of gymnosperms is higher and cross-stratification sets of sandstones indicate paleocurrents mainly to NE and secondarily to SE. In the western site, most of the 42 measured stems lie in E-W positions. The predominantly sandy succession, where the fossil stems are best represented, evidences a braided fluvial system under semiarid conditions. The low plant diversity, some xeromorphic features and the supposedly almost syndepositional silica impregnation of the plants are coherent with marked dry seasons. Thick mudstones and some coquinites below and above the sandy interval may represent lacustrine facies formed in probably more humid conditions. The taphonomic history of the preserved plants began with exceptional storms that caused fast-flowing high water in channels and far into the floodplains. In the eastern site region, many tree ferns only fell, thus sometimes covering and protecting plant litter and leaves from further fragmentation. Assemblages of the central and western sites suggest that the trees were uprooted and transported in suspension (floating) parallel to the flow. Heavier ends of stems (according to their form or because of attached basal bulbous root mantle or large apical fronds) were oriented to upstream because of inertial forces. During falling water stage, the stems were stranded on riverbanks, usually maintaining the previous transport orientation, and were slightly buried. The perpendicular or oblique positions of some stems may have been caused by interference with other stems or shallow bars. Rare observed stems were apparently waterlogged before the final depositional process and transported as bedload. The differences of interpreted channel orientations between the three sites are expected in a braided fluvial system, considering the very low gradients of the basin and the work scale in the order of tens of kilometers. The mean direction of the drainage probably was to east and the flows apparently became weaker downstream. This study seems to provide reliable data for paleocurrent interpretations, especially considering areas with scarce preserved sedimentary structures. © 2013 Elsevier Ltd.

A new mid-Cretaceous Neomeris (dasycladacean alga) from the Potiguar Basin, Brazil

Neomeris (Lamouroux, 1816) is an extant taxon, the origin of which can be tracked back into Early Cretaceous times. The introduction of a new mid-Cretaceous species from Brazil, i.e., Neomeris srivastavai n. sp., offers the opportunity to review the subdivision of the genus into three subgenera, to complete the catalogue of the fossil calcareous algae of Brazil, and to point out the huge stratigraphic gap and lack of documentation between the first occurrence of the dasycladacean model of reproduction, i.e., choristospory, and the oldest record so far known of an undescribed fossil Neomeris (from Portugal). © Springer-Verlag Berlin Heidelberg 2012.

New gymnospermous woods from the Permian of the Parnaíba Basin, Northeastern Brazil, Part II: Damudoxylon, Kaokoxylon and Taeniopitys

This is the second contribution on the Permian permineralized flora of the Parnaíba Basin, NE Brazil that focuses on the gymnosperm woods from the Motuca Formation. We describe five new species of gymnospermous woods Damudoxylon buritiranaense sp. nov., Damudoxylon humile sp. nov., Damudoxylon roessleri sp. nov., Kaokoxylon punctatum sp. nov. and Taeniopitys tocantinensis sp. nov., and one new form, Taeniopitys sp. 1. The woods vary widely in their anatomy, mainly in their pith features, from simple parenchymatic to solenoid piths with canals and ducts, as well as different cells, such as secretory and sclerenchymatic ones. However, they have one characteristic in common - araucarian pitting in the radial walls of the tracheids. © 2013 Elsevier B.V.

Estrategia para el desarrollo y manejo de la región andina: una propuesta de acción a nivel de cuenca hidrográfica = Strategy for the development and management of the Andean region: a proposal for action at the river-basin level

Incluye Bibliografía

Integrated assessment for establishing an oil environmental vulnerability map: Case study for the Santos Basin region, Brazil

The growth of maritime transport and oil exploitation activities may increase the risk of oil spills. Thus, plans and actions to prevent or mitigate impacts are needed to minimize the effects caused by oil. However, tools used worldwide to support contingency plans have not been integrated, thus leading to failure in establishing priority areas. This investigation aimed to develop indices of environmental vulnerability to oil (IEVO), by combining information about environmental sensibility to oil and results of numerical modeling of spilled oil. To achieve that, a case study concerning to oil spills scenarios in a subtropical coastal area was designed, and IEVOs were calculated and presented in maps, in order to make the information about the areas' vulnerability more easily visualized. For summer, the extension of coastline potentially affected by oil was approximately 150. km, and most of the coastline presented medium to high vulnerability. For winter, 230. km coastline would be affected, from which 75% were classified as medium to high vulnerability. Thus, IEVO maps allowed a rapid and clearer interpretation of the vulnerability of the mapped region, facilitating the planning process and the actions in response to an oil spill. © 2013 Elsevier Ltd.

Evidence for euphotic zone anoxia during the deposition of Aptian source rocks based on aryl isoprenoids in petroleum, Sergipe-Alagoas Basin, northeastern Brazil

Four crude oil samples from the Sergipe-Alagoas Basin, northeastern Brazil, were analyzed using full scan gas chromatography-quadrupole mass spectrometry (GC-qMS) for biomarkers, in order to correlate them using aromatic carotenoids thereby enhancing knowledge about the depositional environment of their source rocks. The geochemical parameters derived from saturated fractions of the oils show evidence of little or no biodegradation and similar thermal maturation (Ts/(Ts+Tm) for terpanes, C29 αββ/(αββ+ααα), C27, and C29 20S/(20S+20R) for steranes). Low pristane/phytane ratios and the abundance of gammacerane and β-carotane are indicative of an anoxic and saline depositional environment for the source rocks. Moreover, we identified a large range of diagenetic and catagenetic products of the aromatic carotenoid isorenieratene, including C40, C33, and C32 diaryl isoprenoids and aryl isoprenoid derivatives with short side chains and/or additional rings. These results indicate anoxia in the photic zone during the deposition of the source rocks. © 2013 The Authors.

Sharing responsibility for river basin management

Includes bibliography

Privatization of services in the Great Lakes basin

Includes bibliography

Informe del II Taller de Gerentes de Organismos de Cuenca en América Latina y el Caribe = Report on the Second Workshop for Managers of River Basin Authorities in Latin America and the Caribbean

Incluye Bibliografía

Deforestation in the Amazon Basin: magnitude, dynamics and soil resource effects

Includes bibliography

Agroforestry in the Amazon Basin: practice, theory and limits of a promising land use

Includes bibliography

Port planning parameters of the Caribbean Basin

Includes bibliography