598 SENCINDIVER & AMMONS
<br />al., 1980; Sencindiver, 1977). Many of these mottles and mixed colors are related
<br />to parent material deposition (relic) or may be the result of parent material weath-
<br />ering and/or chemical reactions related to the process of sulfuricization (pyrite
<br />oxidation) (Fanning & Fanning, 1989; Fanning et al., 1993). Dark colors of sur-
<br />face horizons normally result from recent organic matter accumulation and
<br />decomposition. The presence of coal fines or high -C rock fragments produces
<br />dark colors in some subsurface horizons. These materials often result in erratic
<br />distribution of organic C with depth because of the backfilling and topsoiling
<br />processes (Ciolkosz et al., 1985; Smith & Sobek, 1978). In situations where soils
<br />are replaced, such as prime farmlands, gray colors from pre - existing soils with
<br />drainage problems are possible. These replaced soils may no longer be in poorly
<br />drained landscape positions so that higher chromas may develop with time.
<br />VI. STRUCTURE
<br />Most minesoils, even those that are 1 or 2 yr old, have weak to moderate
<br />structure that has developed in their surface horizons. This structure is primarily
<br />granular or subangular blocky (Ciolkosz et al., 1985; Daniels & Amos, 1981;
<br />Roberts et al., 1988b; Thomas & Jansen, 1985), but sometimes it is platy (Bus -
<br />sler et al., 1984; Schafer et al., 1980). The platy structure often results from
<br />machinery compaction during minesoil construction. Structure developed since
<br />the placement of earth materials by mining equipment also has been observed in
<br />some subsurface horizons of older minesoils (Ciolkosz et al., 1985; Daniels &
<br />Amos, 1981; DeMent et al., 1992; Schafer et al., 1980; Thomas & Jansen, 1985).
<br />McSweeney and Jansen (1984) described a new type of structure in Illinois
<br />minesoils, which they called " fritted." This structure has a similar appearance to
<br />semifused spheres and consists of rounded aggregates loosely compressed
<br />together. Size classes are similar to blocky. Fritted structure is formed in materi-
<br />als excavated by a bucket -wheel excavator and transported on a conveyor belt.
<br />Plant root systems were more extensive in the Illinois minesoils with fritted struc-
<br />ture in the subsoil than in scraper constructed minesoil subsurface horizons that
<br />were massive and compact.
<br />VII. BULK DENSITY AND POROSITY
<br />Numerous investigators have reported minesoil bulk density values to be
<br />higher than contiguous native soils (Bussler et al., 1984; Dunker & Barnhisel, 1997;
<br />Potter et al., 1988; Schafer et al., 1980; Smith et al., 1971; Thurman & Sencindiver,
<br />1986). Some of these authors reported only total bulk density, whereas others
<br />reported bulk density adjusted for rock fragments, as well as total bulk density.
<br />Thurman and Sencindiver (1986) reported that adjusted bulk densities of surface
<br />horizons from 25 -yr -old minesoils were higher than the native soils, but the bulk
<br />densities of minesoil subsurface horizons were similar to the unmined soil.
<br />In a study comparing minesoils of different ages (Schafer et al., 1980), bulk
<br />density of the old minesoils ( -50 yr) was equal to or less than the native soil. New
<br />41INKSOIL GENESIS AND CLASSIFI
<br />nmie.oils had a slightly higher b
<br />,cm ubuted the differences to minis
<br />t'he old minesoil had been dump
<br />new minesoils were constructed w
<br />diIl'erent -aged lignite minesoils in
<br />minesoils to be significantly lowe
<br />1990). These bulk density differe
<br />meanie inputs on older sites.
<br />In a study of topsoiled and
<br />.ullusted bulk density values were
<br />that had been topsoiled. Equipmei
<br />soul. Most studies have shown tha'
<br />soil hulk density (Short et al., 198
<br />Varela et al., 1993). The lower del
<br />logical activity, organic matter inc
<br />cycles.
<br />Compaction of minesoils n
<br />plant root extension. Minesoil c
<br />major limiting factor to successl
<br />However, some investigators (S
<br />Bested that minesoils with no ph
<br />compacted layers, extremely ac
<br />monly deeper than native soils d
<br />soils have a greater depth for 1
<br />capacity. Texas studies (Bearden
<br />dactvlon (L.) Pers.] roots extent
<br />sediments of the Wilcox Group,
<br />of the area.
<br />VII
<br />On undisturbed landscapes
<br />isms, relief or topography, paren
<br />factors of soil formation (Jenny,
<br />and Jansen (1981) have observe(
<br />does little to help perceive the sI
<br />active factors of soil formation
<br />mation. Parent material variabili
<br />morphic models. Grube et al. (1
<br />pedologic, and chemical inform
<br />of soils that form in specific roc
<br />solution, leaching, oxidation, o
<br />and aggregation of soil particles
<br />ferentiate minesoil properties a
<br />al., 1988a).
<br />
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