Beidellite in E Horizons of Northern Idaho Spodosols Formed in Volcanic Ash

Abstract

Abstract--While soils formed in tephra are typically dominated by poorly crystalline clay minerals, the occurrence of smectite in E horizons of podzolized soils (Spodosols) has been well-documented. We have observed a well-crystallized smectite mineral dominating the clay fraction of E horizons in tephra-derived soils of northern Idaho. This study was initiated to examine properties and distribution of this mineral along a developmental sequence of high-elevation, forested Spodosols formed in 6800-yr-old Mazama tephra. Three soils exhibiting strong, moderate, and weak E horizon development were sampled along an elevational and climatic gradient. The smectite mineral was identified as beidellite based on expansion and layer charge characteristics. Heated, Li-saturated samples from the most strongly developed E horizon exhibited relatively complete expansion to 1.8 nm with glycerol solvation and mean layer charge was calculated to be 0.44 mole/formula unit using sorption characteristics of alkylammonium ions. Apparent crystallinity and relative abundance of the beidellite in clay fractions decrease with decreasing E horizon development. The more poorly crystalline beidellite is associated with a non-expansive 1.4-nm mineral with considerable Al-hydroxy interlayering. Beidellite was not detected in underlying glacial drift or in a thin layer of 200-yr-old ash that mantles these soils, suggesting it is not inherited from these materials. Rather, our results indicate that beidellite forms in these soils in an environment characterized by low pH and a large flux of organic metal-complexing agents.

The origin and formation of clay minerals in soils: past, present and future perspectives

“…The albic horizon in Spodosols is the site of intense weathering and numerous studies have demonstrated that it is dominantly smectitic and related to the weathering of mica and sometimes chlorite. Ross & Mortland (1966) first showed that such smectite was beidellitic, a finding since confirmed by others (Churchman, 1980;McDaniel et al, 1995). The aluminous nature of these clays, as well as the detailed study of Kodama & Brydon (1966) which showed that the smectite mineral in albic horizons is a three-component random interstratification of mica, vermiculite and smectite, represents convincing evidence that the smectite originates through transformation of the mica.…”

Electron Microscopy Study of Volcanic Tuff Alteration to Illite-Smectite Under Hydrothermal Conditions

“…Hofmann and Jager (1959) found that glass of basaltic composition favors the formarion of saponite, whereas Banfield and Barker (1998) reported the formation of zeolite from alkalibearing tuff. Caballero (1985) found that hydrothermal solutions of granitic composition favored smectite formarion, and McDaniel et al (1995) reported beidellite from tephra in the presence of water with low pH and with organic metal-complexing agents. Berkgaut et al (1994) found illite-smectite (I-S) in soils developed on pyroclasrics where there was an alternation of humid and dry seasons.…”

Methods for Performing Atomic Force Microscopy Imaging of Clay Minerals in Aqueous Solutions

“…However, none of the above real-time, in situ studies involved clay minerals because the standard sample preparation techniques used to fix clay particles for AFM characterization in air are inadequate for fluid-cell applications (Dove and Chermak, 1994). Therefore, AFM work on clays is concentrated on observations of microtopography of clay mineral surfaces and the morphology of clay particles, as measured in air (Lindgreen et al, 1991;Blum and Eberl, 1992;Garnaes et aL, 1992;Johnsson et al, 1992;Sharp et al, 1992;Gaber and Brandow, 1993;Blum, 1994;Nagy, 1994;McDaniel et al, 1995;Brady et al, 1996;Zbik and Smart, 1998). The application of AFM techniques to the study of clay-mineral surface reactivity has mainly involved inferences made from these ex situ observations (Dove and Chermak, 1994;Nagy, 1994).…”