A new species of Cycloramphus Tschudi (Anura: Cycloramphidae) from the Parque Nacional da Serra dos Orgaos, Southeastern Brazil

We report here the discovery of a new species of frog associated to the open areas of the highlands of the Parque Nacional da Serra dos Orgaos. The new species, Cycloramphus organensis is characterized by a unique skin texture, medium size ( maximum male and female SVL 26.4 mm and 33.3 mm respectively), dorsal surfaces uniformly brick red colored, uniformly areolate skin on dorsum, pupil horizontal, iris with a menisc on upper margin; no fleshy tubercles on eyelid, tympanic annulus concealed beneath skin, macroglands not visible externally, fingers and toes without fringes and webs; supernumerary palmar and plantar tubercles absent, nuptial spines absent. Despite the presence of an iris menisc, a character shared by frogs of both genera Cycloramphus and Zachaenus Cope, the combination of morphological characters is so unique that the allocation of the species to any of these genera remains ambiguous. Consequently, we used additional molecular-based phylogenetic analyses to ascertain the position of the new taxon. The new species proved to be embedded within the genus Cycloramphus.

Boron isotope composition of tourmalinite and vein tourmalines associated with gold mineralization, Serra do Itaberaba Group, central Ribeira Belt, SE Brazil

Important concentrations of tourmaline occur as gold-bearing stratiform tourmalinites and in mineralized quartz-tourmaline veins at the Tapera Grande and Quartzito gold prospects in the Mesoproterozoic Serra do Itaberaba Group, central Ribeira Belt (Sao Paulo State, SE Brazil). The main rock types in both prospects constitute the volcanic-sedimentary Morro da Pedra Preta Formation, which formed in a submarine back-arc setting. At Tapera Grande, the volcanic-sedimentary sequence is composed of metabasic and metavolcaniclastic rocks, graphitic and sulfur-rich metapelites, banded iron formation, metandesite, metarhyolite, calcsilicates, tourmalinites and metahydrothermalites derived from mafic and felsic rocks. The Mesoproterozoic rocks at Quartzito prospect are lithologically similar but they have been affected by Neoproterozoic faulting and shearing and by the emplacement of granitic rocks, resulting in the formation of tourmaline-rich quartz-carbonate veins with gold and base metal mineralization. We conducted a chemical and B-isotope study of tourmalines in order to better understand the origin of the stratiform tourmalinites in the Morro da Pedra Preta Formation and their relationship with gold mineralization. The overall range of delta(11)B values obtained for the tourmalinite and vein tourmalines is between - 15%. and -5 parts per thousand, with the tourmalinites failing at the low end of this range (-15 to -8 parts per thousand). Such values are typical for continental crust and inconsistent with a primary marine boron signature as expected from the submarine-exhalative model for the gold prospects. We conclude from this that tourmaline formed or recrystallized from crustal fluids related to the amphibolite-grade metamorphism which affected the Serra do Itaberaba Group and that gold deposition occurred syn- to post-peak metamorphism by phase immiscibility, as attested by fluid inclusions in Tapera Grande tourmalinite tourmaline and quartz. The vein-hosted tourmalines at Quartzito have isotopically variable boron signatures, with heavier delta(11)B values of -5 parts per thousand to -8 parts per thousand for acicular green tourmalines and lighter values (-15 parts per thousand to -7 parts per thousand for light blue, Ti-firee tourmaline from quartz-carbonate veins). We attribute the heavier boron to fluids derived from the volcano-sedimentary rocks of marine affinity whereas the lighter boron was contributed by crustal fluids related to the granitoids or metasediments in the continental crust. (c) 2009 Elsevier B.V. All rights reserved.

Denudation history of the Bocaina Plateau, Serra do Mar, southeastern Brazil: Relationships to Gondwana breakup and passive margin development

The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 +/- 32 and 46 +/- 5 Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 +/- 1.51 to 11.1 +/- 1.48 mu m, with standard deviations between 1.16 and 1.83 mu m. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (>200 Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Parana, Bauru, and Santos basins. (C) 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.