Abstract Neoproterozoic spessartitic lamprophyres are linked to the Lavras do Sul Shoshonitic Association in the Sul-Riograndense Shield, southernmost Brazil. Bodies of intrusive spessartitic lamprophyres occur in trachyandesites of this association in the Cerro Tupanci region. There, Neoproterozoic igneous and metamorphic complexes are covered by volcanic-sedimentary Ediacaran sequences of the Camaquã Basin that include trachyandesites, conglomerates, sandstones, and spessartitic lamprophyre dikes of which a spessartitic lapilli tuff N-NE oriented is the main occurrence. Gamma spectrometric and gravimetric data for the lapilli tuff allowed definition of its occurrence as a dike elongated N-S, bearing low values for gamma spectrometry and a strong negative gravimetric anomaly approximately 450 m long and 70 m wide. Two-dimensional modeling of this anomaly suggests that the dike is subvertical to vertical. Magnetometry did not provide significant data regarding the lamprophyre but did show a normal dipolar anomaly to the west, suggesting the presence of a non-outcropping cylindrical intrusion in the area.

Abstract The Santa Vitória Formation is a lithostratigraphic unit known for its fossil assemblage of Pleistocene mammals, established in 1973 from sediments exposed along the banks of Chuí Creek, in the southern coastal plain of the state of Rio Grande do Sul (CPRS), Brazil. The original description was presented in a Masters’ dissertation and never formally described in a peer-reviewed publication. Moreover, surveys and fossil collecting efforts developed in the last decade have led to a better understanding of its origin and nature. An updated description of this unit is presented here, which outcrops in areas occupied by barrier-lagoon depositional systems originated by eustatic oscillations. The formation encompasses Middle-Upper Pleistocene fluvial and eolian depositional systems and paleosols formed chiefly of fine to medium quartz sand, with subordinate clay, concentrations of iron and manganese oxides, and caliche nodules of pedogenic origin. It conformably overlies upper shoreface-foreshore marine deposits, and is overlain by loess deposited during the last glacial period. Here is proposed to re-define it as Santa Vitória Alloformation, considering that the use of an allostratigraphic framework to characterize this unit has the practical purpose of grouping depositional systems genetically unrelated to the barrier-lagoon systems.

Abstract Mineralogical evolution of ophiolites is significant to understand paleo-oceanic crust and mantle requiring multi-proxy techniques to identify steps in the processes. We studied the Bossoroca ophiolite from the southern Brasiliano Orogen, a prime example of Tonian accretion to an oceanic island arc. Integration of field geology, aeromagnetometry, aerogamaspectrometry, electron microprobe analyses, and compositional maps of minerals led to the decoding of oceanic and continental processes. The ophiolite is highly magnetic and low-K and is positioned at the base of the superstructure. We studied amphibolite, tourmalinite, and chromite-talc-magnesite granofels from the ophiolite, Capivaras diorite from the Cambaí Complex infrastructure and one metavolcanoclastic rock from the Vacacaí Group superstructure. Honblende is zoned in all rock types. Low-Ti hornblende is compatible with medium-pressure metamorphism at 7 kbar. This M1 to M2 amphibolite facies resulted in the widespread association of olivine + talc in metaserpentinite. Dravite is similar to tourmaline from the Ibaré ophiolite. Andesine and oligoclase are dominant and albite minor. Cr-spinel in granofels recrystallized in greenschist facies; host rock originated by carbonatization of serpentinite formed in the oceanic crust along with chloritite and tourmalinite. Serpentinite rare earth elements (REE) suggest origin in depleted mantle peridotite. The ophiolite evolved in the Adamastor Ocean until incorporation into the island arc.

Neste trabalho apresentamos uma análise das variações geomagnéticas e contagem de raios cósmicos (muons) detectados no Observatório Espacial do Sul - OES/CRS/INPE - MCT (29.43ºS, 53.80ºW), em São Martinho da Serra, RS, durante o mês de Novembro de 2004. As medidas das variações geomagnéticas são realizadas através de um magnetômetro fluxgate de três componentes e baixo ruído, e as contagens de muons são obtidas através de um detector de muons multi-direcional, ambos instrumentos instalados no Observatório. O magnetômetro fluxgate detecta variações nas três componentes ortogonais do campo magnético Terrestre, H (Norte-Sul), D (Leste-Oeste) e Z (Vertical), com uma taxa de aquisição de 0.5 Hz. O Telescópio Cintilador de Muons realiza contagens horárias. A chegada de um distúrbio solar é identificada observando-se o decréscimo na contagem de muons. O objetivo deste trabalho é fazer uma descrição da morfologia e fenomenologia física observada durante a tempestade geomagnética de Novembro de 2004, usando a componente H do campo geomagnético e o canal vertical V do Telescópio Cintilador de Muons no Sul do Brasil.

An analysis of geomagnetic storm variations and the count rate of cosmic ray muons recorded at the Brazilian Southern Space Observatory -OES/CRS/INPE-MCT, in São Martinho da Serra, RS during the month of November 2004, is presented in this paper. The geomagnetic measurements are done by a three component low noise fluxgate magnetometer and the count rates of cosmic ray muons are recorded by a Muon Scintilator Telescope - MST, both instruments installed at the Observatory. The fluxgate magnetometer measures variations in the three orthogonal components of Earth magnetic field, H (North-South), D (East-West) and Z (Vertical), with data sampling rate of 0.5 Hz. The Muon Scintilator Telescope records hourly count rates. The arrival of a solar disturbance can be identified by observing the decrease in the muon count rate. The goal of this work is to describe the physical morphology and phenomenology observed during the geomagnetic storm of November 2004, using the H component of the geomagnetic field and vertical channel V of the multi-directional muon detector in South of Brazil.

Choques interplanetários do tipo frontal rápido (FFS) são caracterizados por uma descontinuidade súbita positiva em todos os parâmetros de plasma interplanetário (velocidade, temperatura e densidade do vento solar) e campo magnético interplanetário. Os choques do tipo reverso rápido (FRS) possuem descontinuidade súbita negativa em todos os parâmetros exceto a velocidade do vento solar. Observa-se que os FFS causam impulsos súbitos (SI) positivos e os FRS causam SI negativos na componente H do campo magnético terrestre. Neste trabalho realizou-se um estudo destes impulsos súbitos, causados por choques interplanetários. Utilizaram-se os parâmetros de plasma, antes e depois do choque, para calcular a variação da pressão dinâmica. Observou-se que os SIs são maiores quando causados por FFS que quando formados por FRS, isto porque os FFS possuem maior variação na pressão dinâmica que os FRS.

Fast forward interplanetary shocks (FFS) are characterized by positive jump in all interplanetary plasma parameters (solar wind speed, temperature and density) and interplanetary magnetic field. However the fast reverse interplanetary shocks (FRS) are characterized by negative jump in all mentioned parameters except solar wind speed. Observations show that FFS cause positive sudden impulses (SI) while FRS cause negative SI in the H-component of the geomagnetic field. In this work we investigate the SI caused by interplanetary shocks. We use the observed plasma parameters, upstream and downstream, to calculate the variation of dynamic pressure. We observe that the SI amplitude is larger for positive SI than for negative ones, as a consequence of the fact that FFS have larger dynamic pressure variations as compared to FRS.

Neste artigo nós estudamos a relação entre as Ejeções Coronais de Massa Interplanetárias (ICMEs) e o decréscimo na contagem de muons observada pela Rede Internacional de Detectores de Muons no período de 6 a 12 de novembro de 2004. A Rede Internacional de Detectores de Muons é composta pelos detectores instalados em Nagoya (Japão), Hobart (Austrália) e o detector protótipo instalado no Observatório Espacial do Sul OES/CRSPE/INPE - MCT, situado em São Martinho da Serra, RS, Brasil. Com o decréscimo na contagem de muons observado pela Rede Internacional de Detectores de Muons podemos determinar a direção em que a ICME se move, e com isso, nós poderemos calcular o ângulo que elas chegam à Terra. Também, com esta rede de detectores de muons, poderemos dar um alerta de até 12 horas antes da chegada de um choque ou uma ICME. O método de previsão do Clima Espacial que usa raios cósmicos será uma ferramenta muito importante porque proporciona uma previsão com boa antecedência.

In this paper we study the relationship between Interplanetary Coronal Mass Ejections (ICMEs) and the muon count rate decreases detected of the Muon Detector Network on November 6-12, 2004. The Muon Detector Network is composed by the detectors installed at Nagoya (Japan), Hobart (Australia) and the prototype detector installed at the "Observatório Espacial do Sul - OES/CRSPE/INPE-MCT", located in São Martinho da Serra, RS, Brazil. With the muon count rate observed by the Muon Detector Network, we will be able to observe, in the future, the direction in which a given ICME moves, and with that, we will be able to calculate their angle of incidence on the Earth. Also, with this muon network, we will be able to send alerts of up to 12 hours before the arrival of a shock or an ICME. The Space Weather forecast method using cosmic rays will be a very important tool because it provides a forecast with good antecedence.

Acredita-se que o mecanismo físico responsável pela transferência de energia do vento solar para a magnetosfera terrestre seja a reconexão entre o campo magnético interplanetário e o campo magnético terrestre (Tsurutani & Gonzalez, 1997). O critério necessário para que ocorra uma Tempestade Geomagnética Intensa, Dst < -100nT, é o de haver um campo elétrico interplanetário, na direção do anoitecer, maior que 5 mV/m, por um período maior que 3 horas. Raios cósmicos são fenômenos naturais que podem nos ensinar muito tanto sobre o espaço vizinho à Terra, quanto sobre processos astrofísicos distantes (Jokipii, 2000). As estruturas solares que se propagam no meio interplanetário afetam a população pré-existente de raios cósmicos galácticos de várias maneiras. A mais conhecida é o chamado "decréscimo de Forbush", que é uma diminuição das contagens de raios cósmicos observados na superfície durante distúrbios Geomagnéticos. O objetivo deste trabalho é estudar a resposta das observações do Telescópio Cintilador Multidirecional de Muons do Observatório Espacial do Sul - OES/CRSPE/INPE-MCT, instalado em São Martinho da Serra, RS, Brasil, a 3 Tempestades Geomagnéticas Super Intensas, combinando observações feitas por satélites localizados no ponto Lagrangeano L1, e detectores de superfície.

It is believed that the physical mechanism responsible for the transference of energy from the solar wind to the Earth magnetosphere is the reconnection between the interplanetary magnetic field and the terrestrial magnetic field (Tsurutani & Gonzalez, 1997). The necessary criterion for a Intense Geomagnetic Storms to occur, Dst < -100nT, is the existence of a dawn-dusk interplanetary electric field larger than 5 mV/m, for a period larger than 3 hours. Cosmic rays have been studied as a natural phenomenon that can tell us much about both Earth's environment in space and distant astrophysical processes (Jokipii, 2000). A solar disturbance propagating away from the Sun affects the pre-existing population of galactic cosmic rays in a number of ways. The most famous one is known as the "Forbush decrease", which is a supression of ground cosmic-ray counts observed during Geomagnetic Disturbances. The objective of this work is to study the response of the Southern Space Observatory - SSO ground Muon Telescope observations, installed in São Martinho da Serra, RS, Brazil, to 3 super intense geomagnetic storms, combining observation provided by L1 satellites and ground detectors.