Geology of the Arroio Grande Metamafic-Ultramafic Association, Southeasterh Sul-Rio-Grandense Shield. In Rio Grande do Sul State (southern Brazil) several occurrences of ultramafic rocks are recognized and described in the central and western portions of the Sul-rio-grandense Shield. However, no scientific work referred to this type of rock association for the eastern portion of the Shield. In this paper, a study of a metamafic- ultramafic rock association is shown, located at the southern end of the eastern portion of the Sul-Rio- -Grandense Shield, near the town of Arroio Grande. Through field investigation, petrography, scanning electron microscopy and X-ray diffraction hornblende-plagioclase-epidote rich amphibolites, chromian serpentinites and their metasomatic products (tremolitites, chloritites and talc schists) were identified. Amphibolite facies paragenesis were characterized for both epidote amphibolites and metasomatites. The Arroio Grande rock association was interpreted to represent fragments of an ancient ocean floor obducted during the closure of a paleo-ocean in Neoproterozoic times, possibly due to collision of the Kalahari and Río de La Plata paleoplates in the final stages of Western Gondwana assemblyA reappraisal of the geological basis of a Plate Tectonics model proposed for the tectonic evolution of the Dom Feliciano Belt in the Sul-rio-grandense Shield is presented under the light of a research programme in geology. Folio wing the presentation of a synthesis about the nature and structural characteristics of each geotectonic unit recognised, the main geotectonic models presented for this belt are discussed under the conceptual and substantive point of view. A discussion about the nature and advantages of an atualistic model for this belt is presented, being followed by a criticai evaluation of the geochronological and geophysical data recently obtained, the latter in the second part of this SHIT IN STONE MADE .....GÉOLOGIE DU RIO GRANDE DO SUL - LES MASSIFS ULTRABASIQUES DANS LE SOCLE DE RIO GRANDE DO SUL -FORMATION CAMBAI FORMATION MIGMATISÉE DE BASE EST DISCORDANTE AVEC CELLE ECTINIQUE CARBONATÉE ET SILICICATÉE QUE NOUS APPELONS FORMATION CERRO DO OURO TOUTES DEUX D'ÂGE PRÉCAMBRIEN MASSIFS INTÉNSEMENT TRANSFORMÉES EN SERPENTINES ( ANTIGORITE ALFA UND BETA UND BETO DA GAMA GAY)

Em Arroio Grande, as
reações metassomáticas podem ter ocorrido entre serpentinitos
e litologias do Complexo Pinheiro Machado
e/ou também o granito Três Figueiras, gerando desequilíbrios
químicos durante o metamorfismo regional atuante
naquela porção crustal, formando zonas minerais
de reação (Brady, 1977; Bucher & Frey, 2002; Vernon &
Clarke, 2008) e consequentemente as diferentes rochas
metassomáticas encontradas junto aos serpentinitos
como resposta a esse desequilíbrio. No Escudo Sul-rio-
-grandense, há ocorrência de metassomatitos semelhantes
(clorititos, tremolititos e talco xistos) localizados no
Ofiolito Cerro Mantiqueiras (Hartmann & Remus, 2000)
formados a partir de protólito harzburgítico.
Assembleias minerais contendo tremolita, talco,
clorita e cromita indicam condições de metamorfismo
na fácies anfibolito para rochas ultramáficas (Spear,
1995). Nos anfibolitos de Arroio Grande são também
encontradas paragêneses que indicam metamorfismo
na fácies anfibolito, pela presença de plagioclásio +
hornblenda + quartzo + epidoto (Bucher & Frey, 2002).
Os protólitos dos anfibolitos provavelmente são rochas
básicas, como basaltos e gabros.
Megaspores from coals of the Triunfo Member,
Rio Bonito Formation (Lower Permian),
northeastern Paraná State, Brazil

megaspores occurring in coal seams of the Triunfo
Member, Rio Bonito Formation at Figueira, Paraná State, Brazil. This coal-bearing sequence accumulated
in a marine delta system during the Early Permian.
Four species are described and illustrated: Lagenoisporites triunfensis, L. scutiformis, Sublagenicula cf.
brasiliensis, and Setosisporites cf. furcatus. Of these, the two species of Lagenoisporites are predominant.
Relationships to other megaspore species are discussed; and the temporal and spatial distributions of the four
species in the Paraná Basin are documented.
Key words: megaspores, Permian, Rio Bonito Formation, Paraná Basin.