Resumo em Inglês:
Abstract We combined detailed field work with whole-rock geochemistry of samples from both surface exposures and rock chips from a ~300 m pile of basalt retrieved from a groundwater borehole in the Jaú region (central part of the state of São Paulo) to contribute to the stratigraphic knowledge of the northern Paraná Magmatic Province. The P2O5 content was used as the first guide to flow identification, always combined with other minor and trace elements (mostly Ti, Zr, Sr, and Cu). This approach allowed the establishment of a stratigraphic column with 16 flows, which were tentatively divided into three sequences. Regional correlations show that the lower portion of these basalt flows (Sequence 1) has good correspondence with the flow-by-flow succession identified at the border of the Paraná Basin by previous regional works. The upper eight flows, occurring at the top of the plateau where the thickness of basalt reaches up to 300 m, should have their continuity westward (toward the center of the Paraná Basin), where the volcanic pile thickens. The local preservation of these upper flows may result from significant (up to 170 m) displacements along the ENE-directed Jaú fault, identified from stratigraphic relations here defined in the basalt pile.Resumo em Inglês:
Abstract In the Carajás Province, many Au and Cu deposits are hosted in Archean metabasic rocks belonging to the Itacaiúnas Supergroup. These metabasic rocks underwent seawater metamorphism of greenschist facies concomitantly to the volcanic activity and banded iron deposition. In the Carajás Province, synkinematic granite magmatism occurred at ca. 2.75 Ga as represented by the Estrela, Serra do Rabo, Planalto, and Igarapé Gelado granites. Emplacement at relatively shallow levels created thermal aureoles of albite-epidote hornfels to hornblende hornfels facies. Metabasic xenoliths show assemblages of hornblende hornfels. Regional stresses and lateral expansion of the syntectonic granites promoted high-temperature low-pressure metamorphism and ductile deformation in the host metabasic rocks. Dehydration reactions increased the fluid pressure permitting hydraulic fracturing and veining in the metabasaltic rocks. These conditions increased the kinetic energy of minerals so that pressure solution and dissolution of minerals were enhanced. The material transfer caused by the advective flow of supersaturated fluids leads to the formation of amphibole-bearing veins and subordinate quartz-bearing and plagioclase-bearing veins. Progressive reactions during thermal metamorphism promoted the replacement of actinolite to ferropargasite/edenite and Na-plagioclase to Ca-plagioclase. Silica produced in these reactions was transported by fluids and deposited in veins that crosscut the amphibolites.Resumo em Inglês:
Abstract In February 2023, anomalously heavy rainfall caused widespread landslides in the coastal city of São Sebastião (Southeastern Brazil). This report describes the first version of a landslide inventory dataset for this event. The inventory is primarily based on the analysis of aerial images with 10 cm spatial resolution acquired immediately after the event, as well as archive images from Google Earth and PlanetScope. Delimitation of the landslides relied on a comparison of the images along with the area’s Digital Surface Model (DSM) and hydrography. The spatial vector dataset (shapefile and geopackage) contains points representing the landslide’s crowns and polygons indicating the affected area and is openly available in Zenodo.Resumo em Inglês:
Abstract Net erosion recorded in lithological columns of hundreds of wells from the proximal domain of the Sergipe–Alagoas Basin was quantified through palaeoburial indicators: transit time sonic logs (DT) and vitrinite reflectance profiles (VRe). The preferred determinations with DT logs of pelitic rocks compound a large database and are less subject to variations in sampling and laboratory procedures. The sonic log profiles of 485 wells have been used for the calculation of the net erosion grid, while just 60 VRe profiles have been used for this purpose. Net erosion varies typically from 100 to 700 m in the Sergipe Sub-basin to the south, probably as a result of isostatic compensation to the sedimentary loads of the post-rift stratigraphic sequences. The Alagoas Sub-basin to the north stands as the most eroded. The average net erosion in the Alagoas SB is around 750 m but reaches more than 1,200 m in the north. The main cause of the erosion of the syn-rift strata in the Alagoas SB is probably the long-time sub-aerial exposure of uplifted rift flanks. Late Albian tectonic inversion, focused on northern Alagoas SB, enhanced erosion as evidenced in seismic sections, especially those parallel to the coast.Resumo em Inglês:
Abstract Conulariids are extinct scyphozoans, have benthic and sessile life modes, and inhabited shallow marine platforms. Taphonomic studies of these animals from the Parnaíba Basin are scarce, distinctly from the Paraná Basin. The present work seeks to analyze the taphonomic characteristics of Conularia quichua from the Pimenteira Formation, Parnaíba Basin, and infer deposition events that influenced this fossiliferous concentration. The material is housed at Laboratório de Paleontologia de Macroinvertebrados (LAPALMA) and consists of 43 specimens. The taphonomic signatures used in the analyses were orientation in relation to the bedding plane, concentration, degree of preservation, and theca filling. The cluster and correspondence analyses evidenced two taphonomic classes for single-unit, fragile skeletons of conulariids from Pimenteira Formation: the taphonomic class 1 comprehends obliquely, filled, and complete skeletons; the taphonomic class 2 comprehends concordantly, fragmented, flattened, grouped, and isolated skeletons. A high-stand system tract, after the maximum transgressive surface of the Pimenteira Formation, is interpreted to be the depositional environment of this concentration, where an episodic high-energy event was responsible for the fossiliferous lens. In addition, the lack of preserved calcium carbonate shells suggests acidic conditions, assuming that diagenetic control occurred in this accumulation.