Engineering Geology

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Sanyog Shelar — 2023-01-12

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris imperdiet sapien vel justo tempor fringilla. Nam rhoncus condimentum mauris in maximus. Aenean vestibulum, nunc vel feugiat tincidunt, ligula turpis viverra magna, quis auctor quam leo ut nibh. Sed accumsan est quis arcu euismod vulputate. Vivamus dapibus molestie augue, ut viverra neque. Sed a ligula non justo dictum cursus. Vestibulum tincidunt nisl ut vehicula fringilla. Nullam lectus mi, mollis ac enim quis, convallis commodo ipsum. Suspendisse sit amet elit congue nisl sagittis efficitur.

Integer rhoncus neque fringilla, lobortis mauris eu, hendrerit enim. Proin porta odio non volutpat euismod. Proin id justo a orci elementum condimentum vitae et ex. Aliquam quis ante porta, ultricies nisl a, auctor nisl. Phasellus laoreet ipsum at interdum suscipit. Nunc et ex ut dui tincidunt congue. Sed arcu nulla, lacinia at massa sed, cursus rutrum justo. Morbi pellentesque venenatis massa eu fermentum. Sed suscipit lectus non ante venenatis, vel vulputate neque porttitor. Nunc vestibulum eros nunc. Proin cursus, magna quis congue cursus, ligula mauris ornare quam, sed iaculis massa lectus non sem. Aliquam nec volutpat leo, id fermentum libero. Donec vulputate mattis velit, in tempor libero consectetur vitae. Fusce euismod arcu ut nibh sodales gravida. In imperdiet lectus at turpis dictum hendrerit. Quisque eu dui a nisl venenatis euismod.

Pellentesque id mauris aliquam, sagittis libero vel, cursus ex. Donec sagittis vitae elit nec tempor. Nunc sed turpis eu tellus semper volutpat faucibus ut quam. Etiam in nibh sit amet metus eleifend mattis. Suspendisse nec interdum mi, sit amet congue elit. Nam lectus lacus, cursus eu facilisis id, sollicitudin a leo. Interdum et malesuada fames ac ante ipsum primis in faucibus.

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Vestibulum sagittis eleifend dui a tempor. Maecenas blandit cursus ullamcorper. Cras ac justo non quam aliquam ornare eu nec nunc. Nulla ipsum neque, rhoncus a odio ultrices, suscipit bibendum lectus. In mattis metus ante, eget feugiat velit accumsan in. Donec venenatis, urna in tincidunt faucibus, augue purus cursus tellus, nec vulputate orci dolor ac nisl. Nullam nunc orci, blandit in nibh at, interdum lacinia mi. Fusce hendrerit ante eros, eget ultrices nunc accumsan sed. Nunc non magna vel ex egestas dapibus. Quisque ut sodales magna, ut laoreet dolor. Praesent a consequat erat. Cras rutrum nisi sed aliquet dignissim.

The Stress changes during exhumation of a high-pressure nappe

Arvind Baraskar — 2023-01-05

Highlights

•: Different quartz generations formed within the SGR field.
•: Grain-size statistics revealed mainly bimodal distributions.
•: Multimodal distributions reflect episodic stress increase.
•: Stress increase occurred at the early exhumation stages.
•: Stress increase lasted less than 0.5 Myr followed by stress drop.

Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.

In this study, we carried out microstructural and grain size analysis of recrystallized quartz in quartz-rich samples collected from different structural levels of a 1.5–2.0 km thick high-pressure nappe (Phyllite-Quartzite unit, Greece). Exhumation-related deformation led to the recrystallization of quartz by subgrain rotation (SGR) and the formation of different generations of recrystallized quartz with different grain sizes. Applying a new, fully automated histogram-based method, we reconstructed the “hidden” empirical probability density functions included in the histograms of the initial grain size distributions. Statistical analysis showed that most grain-size histograms display bimodal distributions with mean grain sizes in cluster A ranging from 46 to 48 μm, and a cluster B with mean grain sizes between 81 and 93 μm. Few grain size histograms display trimodal distributions and show an additional cluster C with mean grain sizes ranging from 100 to 115 μm. Microstructural observations indicate that the grains of cluster C are the oldest whereas those of cluster A are the youngest. Bimodal and trimodal distributions may reflect an episodic increase in the differential stress from 17 to 19 MPa and then to 31 MPa during exhumation, accompanied by a strain rate increase of at least one order of magnitude (from 10⁻¹³s⁻¹ to 10⁻¹² s⁻¹). This stress increase likely occurred at the early stages of the exhumation and may have lasted less than 0.5 Myr. Stress increase was followed by a stress drop expressed by partial foam structures of quartz in a few samples.

21st Century Earth science is computer intensive and data driven

Vinayak Vinayak — 2023-01-07

Advanced computing techniques have completely transformed the Earth sciences, affecting not only how the field’s scientists and students acquire their data, but also how that data is processed, modeled, and analyzed. “We finally have the ability to explore Earth in its real complexity,” says Eric Dunham, an associate professor of geophysics.

A Geochemical Analysis of the Eocene Tallahatta Formation in Northern Mississippi

James Paul — 2023-01-04

The Eocene Tallahatta Formation forms part of the Tallahatta-Winona aquifer, which is part of the lower Claiborne confining unit of the Mississippi Embayment. A thorough understanding of the distribution of natural resources within the Tallahatta is limited by a lack of detailed studies at the outcrop and pore scales. In this study, we integrate particle size, petrographic, lithofacies, and geochemical analyses to interpret depositional environments, sequence stratigraphy, provenance, and diagenetic history from outcrops in Grenada County, Mississippi. Lithofacies include unprotected sand flat, tidal channel, open tidal mudflat, protected tidal flat, lower and middle shoreface, offshore transition, and offshore shelf settings. Lithofacies associations indicate that the Tallahatta consists of at least two parasequences within a falling stage systems tract (FSST). This is the first report on FSST strata from the Tallahatta Formation. Petrographic and geochemical results show that sediments were sourced from Precambrian Laurentian basement, recycled Appalachian basin sediment, and the Appalachian hinterland. Upsection changes in geochemistry represent an increase in contributions from recycled Appalachian basin sediment and progressive weathering of Acadian orogeny elements. Geochemistry also suggests that potentially economically important Ti-rich minerals are concentrated in tidal flat facies and scarce in shoreface facies. Primary porosity and bioturbation exert the greatest influence on the high porosity within many lithofacies. Early diagenesis also included detrital clay coating of framework grains, deposition of fecal pellets, minor chemical weathering, and hematite precipitation. Fecal pellets were altered to glauconite and opal cement was precipitated shortly after deposition or during early burial. Shrinkage of fecal pellets during glauconitization introduced minor moldic porosity. Limited burial produced minor physical compaction and only slightly reduced porosity. Abundant hematite precipitation during exhumation greatly decreased porosity locally.