Geofísica

The development of a seismic network in Uruguay in recent years has enabled studies of crustal structure in a region with few seismological studies of this type. In this work, we update the crustal thicknesses and Vp/Vs ratios calculated by H-k stack and present S-wave velocity models based on joint inversion of receiver functions and Rayleigh wave group velocity dispersion curves.

At least 10 global digital elevation models (DEMs) at one-arc-second resolution now cover Earth. Comparing derived grids, like slope or curvature, preserves surface spatial relationships, and can be more important than just elevation values. Such comparisons provide more nuanced DEM rankings than just elevation root mean square error (RMSE) for a small number of points.

The São Francisco River in Northeast Brazil has seen hydrological and morphological changes due to extensive damming and climate change over the past century. In this study, we examine the influence of human activities and natural fluctuations in precipitation on the hydrological patterns of the basin and the morphological responses of the lower course of the river (LOW-SF) to these alterations over a span of several decades. The findings indicate a decrease in water release by 41% from 1995 to 2013 and 54% from 2013 to 2018, solely attributed to human actions.

Understanding the extent and implications of microplastic (MP) pollution along the São Paulo State coastline in southeastern Brazil is crucial, considering the significant environmental burden imposed by industrial and port activities in this region. This research aims to understand the complex dynamics of MP deposition on sandy beaches, which poses severe environmental risks to coastal ecosystems, marine organisms, and humans.

The amalgamation and breakup of the West Gondwana shaped the South American platform. The dynamics during the processes can be reflected by crust anisotropy of the platform, but there are no specialized crustal anisotropic measurements yet. Splitting analysis of Moho-converted shear waves in P-wave receiver functions (Pms) can reveal crustal-scale anisotropy, which is important for understanding the dynamic evolution of the crust and for the interpretation of mantle anisotropy from splitting analysis of core–mantle refracted shear waves (XKS phases).

The Caiuá and Bauru Groups of Cretaceous age, represent the post-volcanic sedimentation in the Paraná Basin. Under dry conditions, extensive dunes (Draa) were formed with depocenter in the southern area. Later, under more humid conditions, the fluvial-aeolian processes reworked the dunes, forming a landscape with small dunes and river channels. The Caiuá Group comprises, in ascending stratigraphic order, the Goio Erê Formation (margins of Draa), the Rio Paraná Formation (inner Draa) and the Santo Anastácio Formation (Paleosols).

Speleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high-resolution paleomagnetic records of short-term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10⁻¹¹ Am²), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm³, averaging tens to hundreds of years of magnetic variation.

The recording of planetary magnetic fields is often attributed to uniformly-magnetised nanoscopic iron oxides, called single-domain. Yet, the main magnetic constituents of rocks are more complex, non-uniformly magnetised grains in single or multi-vortex states. We know little about their behaviour due to limitations in defining their precise shape and internal magnetic structure. Here we combine non-destructive Ptychographic X-ray Computed Nano-tomography with micromagnetic modelling to explore the magnetic stability of remanence-bearing minerals.

The Neoproterozoic carbonate rocks of the Araras Group (Amazon Craton) and the Sete-Lagoas and Salitre Formations (São Francisco Craton) share a statistically indistinguishable single-polarity (reversed) characteristic direction. This direction is associated with paleomagnetic poles that do not align with the expected directions for primary detrital remanence. We employ a combination of classical rock magnetic properties and micro imaging/chemical analysis (in thin sections) using synchrotron radiation to examine these remagnetized carbonate rocks.

During the Precambrian − Cambrian transition, the occurrence of phosphogenesis and the rise in atmospheric oxygen levels are closely linked to the proliferation of life. However, the mechanisms associated with these phenomena and their underlying causes are not well understood. The Irecê Basin represents the remnants of intracratonic marine environments that document the Neoproterozoic sea flooding of West Gondwana.