Thursday, February 27, 2014

Highlights—Rooting for U

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.

Monday, February 10, 2014

Highlights—The Source of Continental Carbonates

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 lake deposits associated with distalsiliciclastic perennial-river systems by Elizabeth Gierlowski-Kordesch, David B. Finkelstein, Jessie J. Truchan Holland, and Kevin D. Kallini

Thursday, February 6, 2014

Highlights—Complex Mound Complexes

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.

Monday, February 3, 2014

Highlights—Accumulations of Banks and Overflow

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.