Grain size of granite and derived grus, Enchanted Rock pluton, Texas

Strath development in small arid watersheds: Case study of South Mountain, Sonoran Desert, Arizona

“…The results of this research in small ephemeral granitic watersheds provide additional support for an "asymmetry in bedrock erodibility" (p. 464) facilitating strath development. Granite's tendency to break down into grus through biotite decay (Isherwood and Street, 1976;Hoskin and Sundeen, 1985), discongruent dissolution ( fig. 6), and biotic processes ( fig.…”

“…The premise is that the lack of grain-to-grain attachment promotes granular disintegration or grussification (Isherwood and Street, 1976;Hoskin and Sundeen, 1985). For each cobble studied, 100 sequential perimeter mineral grains were "cut out" digitally from the backscattered electron microscope (BSE) imagery of polished cross-sections.…”

An overview of the role of weathering in the production of quartz silt

“…This results in the development of microsheeting joints which run parallel to the weathering surface and cut indiscriminately across minerals causing grain-grain disaggregation. Subsequent observations by Hoskin and Sundeen (1985) have provided some support for this idea. Pye (1985) suggested that the first step in the breakdown of a granitoid rock mass would be granular disintegration due to the exploitation of weaknesses along mineral boundaries.…”

“…The presence of these 'Moss Defects' within granitic quartz and their subsequent exploitation during the breakdown of granitoid parent rocks into grus may, at least partially, explain the lack of correspondence which Hoskin and Sundeen (1985) observed between the texture of parent granites and the grain size of the grus at Enchanted Rock, Texas. However, Power et al (1990) investigated the possibility that certain weathering processes may be sufficiently energetic to, not only exploit pre-existing structural flaws such as 'Moss Defects', but also initiate microfractures in previously sound quartz.…”

“…They, and the soils derived from them, can contain substantial quantities of quartz silt. Hoskin and Sundeen (1985) noted a mean silt content of 35% for grus samples collected from vegetated weathering pits on Enchanted Rock Batholith, Texas. This silt is often attributed to the exploitation of pre-existing partial fractures by pedogenic processes (e.g.…”