ABSTRACT The impact-generated hydrothermal system at Vargeão Dome, Brazil, is a unique potential analogue for impact-generated hydrothermal systems on Mars. Its evolution can be understood through thermodynamic modeling, for which one of the necessary parameters is the composition of the involved water. The exact water composition for Vargeão at the time of the impact is unknown, and, moreover, the effect of this uncertainty is often underestimated in thermodynamic modeling. Here, the effect of initial water composition was tested by using a randomized set of initial solutions for thermodynamic modeling of the evolution of the Vargeão Dome impact-generated hydrothermal system. It was found that even small changes in composition could affect the precipitation of common minerals like calcite and quartz. Therefore, it is necessary to perform a sensitivity analysis for any thermodynamic model in which the initial solution is poorly constrained. Subsequently, the found effects were used to constrain water compositions for the Vargeão Dome system at the time of the impact, by eliminating randomized solutions of models precipitating different minerals from those observed in reality. Using a simple set of rules, it was possible to constrain the total amount of dissolved solids between 6 and 2000 mg/L, as well as provide approximate boundaries for all individual elements present in the solution.

Although the evolution of Brazilian coastal depositional systems in the Quaternary has been studied in past decades, it is only in the last couple of years that it has been possible to incorporate the latest remote sensing databases available to help understand their development. In comparison to other freely accessible imagery, high-resolution images available on Google Earth are advantageous when undertaking local coastal analysis. In some instances, it is possible to differentiate geomorphologic features such as tidal deltas, beach ridges, and dunes. Also, the monitoring of small-scale features allows evaluation of the sensitivity of coastal zones to high-frequency and low-intensity processes. Thus, the downscaling description of coastal zones is now easily accessible, permitting the analysis of the extensive Brazilian coastal depositional systems. On the regional scale, a quick glance of a coastal setting may help frame the sedimentary characteristics of the depositional system. Coastal areas in the States of Santa Catarina and São Paulo are taken into consideration in this study. These areas illustrate representative prograded barrier formations from Middle to Late Holocene with dunes formed at a later development stage. A comparison is made in the use of Google Earth and its historic images with aerial photographs and Landsat images. In the past, small-scale features of these regions were evaluated in aerial photographs, while regional features were studied by low-resolution satellite images. Accordingly, integration of these two products was difficult. In this work, we show that Google Earth facilitates the analysis as a whole. Furthermore, comparison of Google Earth images with aerial photographs from 1938 onward allowed the study of short-term migration and deflation of the dunefields probably accelerated in recent years by human interference. In addition, Keyhole Markup Language (KML) files were saved from Google Earth placemarks to facilitate georeferencing raster images on GIS programs. Finally, information available from previous local studies, such as luminescence dating, geomorphology of the costal system, grain size, heavy minerals, pollen, and carbon isotope analyses, was gathered into a Google Fusion Table database making data retrieval and parsing easily accessible. This database provides information that can be shared with other researchers and may be used to address important questions about the development of Brazil's coastal system in the past, present, and future.

The Bashkirian to Sakmarian-Artinskian Itararé subgroup provides a record of the evolution of the Permian-Carboniferous glaciation in the Paraná Basin (Brazil). The glaciogenic succession was deposited under the influence of glaciers incoming from southwestern Africa. This paper presents an overview of the third-order sequence stratigraphy of that succession and a biostratigraphic summary, showing that: (1) the most complete and thick outcrop portion of the glaciogenic succession occurs in the northeastern part of the Paraná Basin, where several (at least nine) major cycles of ice advance and retreat can be recognized during the development of the Itararé subgroup; (2) biostratigraphically, two well-defined stratigraphic gaps within the Permian-Carboniferous succession are recognized, one within the Itararé subgroup, related to the Lapa–Vila Velha incised valley fill, and another at the Itararé–Rio Bonito boundary, both of which represent regional sequence boundaries; and (3) the transition between palynozones Crucisaccites monoletus and Vittatina costabilis is associated with the maximum flooding surface represented by the marine Lontras Shale, a regional marker bed located in the upper third of the glaciogenic succession.