In addition to representing
omission surfaces important for sequence stratigraphic analyses, paleosols and
subaerial exposure features provide important insights into terrestrial
processes and climate. This study of Miocene paleosols in
the Madrid Basin by Bustillo et al.
addresses the formation of three different uranium-rich calcrete-silcrete
profiles to understand the processes and environments involved in their
formation and the mechanisms involved in the fixation of uranium in surficial
environments. The study integrates macromorphological, micromorphological, and
geochemical observations to demonstrate the importance of roots in the
formation of the profiles and in the concentration of uranium. The data
illustrate interesting processes, such as contemporaneous calcitization and
silicification in the pedogenic vadose environment, intense rhizoturbation and
rooting, and uranium enrichment. These insights provide a conceptual model for
processes in uranium-rich pedogenic and meteoric environments.
Continental carbonates are
markedly influenced by hydrodynamics and geochemistry, like their marine
relatives, but many fundamental dynamics are quite different. In this paper, Gierlowski-Kordesch et al. explore the genesis and depositional
conditions that produce extensive carbonate lakes on siliciclastic floodplains
in the fossil record by a literature review of Phanerozoic river systems and by
examining several Pennsylvanian freshwater limestones of the Appalachian Basin.
The results of the study reveal that climate is not the most important control;
instead, a Ca-rich provenance and hydraulic setting (below the regional spring
line) are most important factors favoring accumulation of thick carbonate lake
successions among distal anastomosed river deposits.
Carbonate mounds occur in
many parts of the stratigraphic record, yet details of their growth dynamics
and resultant depositional geometries commonly are poorly constrained. In this
study, Samankassou et al. focus on
the composition and growth dynamics of two large mound complexes well exposed
in the Cantabrian Mountains, Northern Spain, with the goal of evaluating the
impact of sea level, accommodation, and siliciclastic input on mound growth. The
results of this study reveal how paleohighs, recurrent sea-level fluctuations
(presumably linked to glacio-eustacy) and episodic siliciclastic input
controlled the shape, size, and growth evolution of these mounds. The internal
architecture, a mosaic of juxtaposed small bodies, provides an analog model for
understanding mound growth and for constraining reservoir heterogeneity,
particularly for upper Paleozoic deposits.
Stratigraphically and
geomorphically complex, fluvial systems can be impacted by both bankfull and
overbank stages. In this paper, Ghinassiet al. explore 3D geometries of sandy
deposits accumulated by a fluvial pointbar in the Pleistocene of the Dandiero
Basin (Eritrea), reconstructing the main bar geometry and discuss its
morphodynamic evolution and investigating the role of overbank flow in channel
bend dynamics. The results of this work provide new conceptual depositional
models to explain fluvial pointbar dynamics, and are of interest in terms of
fluvial environment management and exploration of alluvial sandstone bodies.
