Pedogenic Siliceous Features

Gutiérrez-Castorena, Ma. del Carmen

doi:10.1016/b978-0-444-63522-8.00006-1

Cited by 12 publications

(2 citation statements)

References 146 publications

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“…According to Frianeza and Adajar [8], the presence of kaolinite in both soil types from the XRD analysis agrees with the highly plastic USCS classification of both soil types. In addition, quartz, which is present in both soil types, is a parent material inherited by sand and silt, which also agrees with the USCS classification of both soil types [11].…”

Section: Xrd Analysissupporting

confidence: 84%

Lateral Shrinkage of Compacted Polyurethane-Clay Subjected to a Single Wet-Dry Cycle

Frianeza

2024

GEOMATE

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Compacted clay is often used as a sanitary landfill liner due to its impermeable characteristics. However, compacted clay is susceptible to shrinkage as the temperature changes, which may affect the permeability due to the development of shrinkage cracks. Thus, clay was mixed with polyurethane, a stable polymer, once the reaction was completed. The polyurethane-clay mixture was compacted wet of the optimum moisture content and monitored through several moisture contents using direct measurement of the specimen diameter by Vernier caliper. The study inferred that the ratio of the lateral shrinkage of the compacted polyurethane-clay mixture is significantly less than that of the clay specimen with the same initial void ratio. Hence, the changes in the soil structure induced by the addition of polyurethane into the compacted mixture increased the resistance of the soil mass from lateral shrinkage quantified using the free shrinkage ratio. Furthermore, the regression model of the free shrinkage ratio for a wide variety of moisture content was also presented for the compacted polyurethane clay and compacted clay.

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Section: Xrd Analysissupporting

confidence: 84%

Lateral Shrinkage of Compacted Polyurethane-Clay Subjected to a Single Wet-Dry Cycle

Frianeza

2024

GEOMATE

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“…Opal is a common product of the weathering of volcanic glass 57,58 and precipitates from an aqueous gel 9 . Opal precipitation could originate from the weathering of volcanic rocks deposited later, rather than occurring simultaneously with zeolite crystallization, as demonstrated for both precious opal formation [3][4][5][6] and fossils replaced by silica in various location 7,8,20 .…”

Section: Discussionmentioning

confidence: 99%

Arthropod entombment in weathering-formed opal: new horizons for recording life in rocks

Chauviré

Houadria

Donini

et al. 2020

Sci Rep

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Animal fossils preserved in various geological materials, such as limestone, claystone, or amber, provide detailed information on extinct species that is indispensable for retracing the evolution of terrestrial life. Here, we present the first record of an animal fossil preserved in opal formed by weathering with such high-resolution details that even individual cuticle hairs are observed. the fossil consists of the exoskeleton of a nymphal insect belonging to the order Hemiptera and either the family Tettigarctidae or the Cicadidae. This identification is based on anatomical details such as the tibial and femoral morphology of the forelegs. the exoskeleton of the insect was primarily zeolitized during the alteration of the host rocks and later sealed in opal deposited by silica-rich fluids derived from the continental weathering of the volcanic host rocks. organic matter is preserved in the form of amorphous carbon. This finding makes opal formed by rocks weathering a new, complementary source of animal fossils, offering new prospects for the search for ancient life in the early history of Earth and possibly other terrestrial planets such as Mars, where weathering-formed opal occurs. Most invertebrate fossil records where anatomical details are well preserved are from amber or lacustrine or fluvial sedimentary rocks 1. These fossils have provided evolutionary evidence of ancestral traits and extinct species, retracing the evolution of life. Here, we describe an insect fossil in opal-a variety of silica-in which the degree of preservation is comparable (Fig. 1) 2. Silica minerals exist in various species ranging in structure from amorphous to crystalline. Opal is the main species of amorphous silica that precipitates from saturated or near-saturated silica-rich aqueous fluids produced by the alteration of the earth's crust. One of the main sources of silica for opal formation (and hence the eventual silicification of fossils) are volcanic rocks, especially volcanic ashes due to their inherent porosity and glass abundance 3-8. Among opals, the most sought-after type is precious opal, which differs from common opal only by the presence of colored patches (called play-of-color) that appear to move as the stone is viewed from different angles, an optical phenomenon attributed to the diffraction of visible light by a regular arrangement of silica spheres 9,10. Both precious and common opal form mainly in two geological settings: (1) hydrothermal alteration occurring when hot water circulates underground and precipitates opal when the temperature drops, e.g., as siliceous sinter (a hard incrustation around hot springs); and (2) continental weathering that occurs when meteoric waters percolate, hydrolyzing silicate while transforming the rock into a soil. In both contexts, the dissolved silica exists as silicic acid (H 4 SiO 2) in aqueous solution. Silicic acid will polymerize into silica during a variation in physical or chemical conditions, primarily pH and temperature 11. The degradation of organic matter may favor t...

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