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Cementstone Group
The Ballagan Formation is a geologic formation in Scotland and England. It preserves fossils dating back to the early part of the Carboniferous period (Tournaisian – early Visean). Its name comes from the "Ballagan Beds" of Ballagan Glen, near Strathblane, which has a good example of this geological formation. The Ballagan Formation was historically known as the Cementstone Group, but more recently it has been placed as the middle formation of the Inverclyde Group. This change was motivated by the recognition that the youngest parts of the Devonian Upper Old Red Sandstone (now known as the Kinnesswood Formation) were geologically continuous with the lowest parts of the Lower Carboniferous Calciferous Sandstone Measures (now known as the Ballagan and Clyde Sandstone formations). This interval of Devonian-Carboniferous overlap was named the Inverclyde Group, and the cementstone-rich "drab beds" in the middle of the group were renamed to the Ballagan Formation. In Lothian, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeability and porosity is relatively low, siltstone is sometimes a tight gas reservoir rock, an unconventional reservoir for natural gas that requires hydraulic fracturing for economic gas production. Siltstone was prized in ancient Egypt for manufacturing statuary and cosmetic palettes. The siltstone quarried at Wadi Hammamat was a hard, fine-grained siltstone that resisted flaking and was almost ideal for such uses. Description There is not complete agreement on the definition of siltstone. One definition is that siltstone is mudrock (clastic sedimentary rock containing at least 50% clay and silt) in which at least 2/3 of the clay and silt fraction is composed of silt-sized particles. Silt is defined as grains 2–62 μm in diam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
