A few of the samples of chert collected as part of this study, which show some of the common colors of Tallahatta Chert.
| Tallahatta Chert: Sedimentology | ||||||||||
| The Tallahatta Formation consists of several types of siliciclastic sedimentary rocks. The dominant lithology is micaceous sandy claystone. It is thick-bedded, massive, and contains abundant trace fossils and burrows. A study by Schroeder and Harris (2004) in Mississippi determined that the claystone contained significant amounts of opal-CT (essentially non-crystalline quartz) and the zeolite mineral clinoptilolite. The presence of both of these minerals are significant as they are thought to be alteration productions derived from volcanic ash. Indeed, Schroeder and Harris (2004) imply that much of the fine sediment in the Tallahatta Formation in Mississippi was derived from a volcanic source. They also suggested that opal-rich claystone in Alabama might have been derived from more biogenic sources as they contain fewer zeolite minerals and, as observed in this study, more marine indicators (e.g., burrows). Other researchers (e.g., Counts and Savrda, 2004) have suggested that diatoms might have been the source of much of this biogenic silica. | ||||||||||
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A few of the samples of chert collected as part of this study, which show some of the common colors of Tallahatta Chert.
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| Tallahatta Chert is variably colored. The most common color is red-brown, but yellow, colorless, blue-grey and multicolored forms also occur. Most of the knappable-quality material examined in this study is characterized by fine laminations. Some is relatively massive (structureless), and/or weakly mottled. At least some of the chert contains the remains of fossils shells, suggesting that limestone seams within the Tallahatta Formation were preferentially silicified. Chert seams are very common in limestones in other parts of Alabama (e.g., Bangor Formation) and around the world. | ||||||||||