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The Lowe sequence describes a set of sedimentary structures in turbidite sandstone beds that are deposited by high-density turbidity currents. It is intended to complement, not replace, the better known Bouma sequence, which applies primarily to turbidites deposited by low-density (i.e., low-sand concentration) turbidity currents. ==Description== The Lowe sequence adds three layers labelled S1 through S3 to Bouma's terminology, with S1 being at the bottom and S3 at the top of a sandy turbidite bed. As with the Bouma sequence, each layer has a specific set of sedimentary structures and lithology. And like the Bouma sequence, the layers become finer grained from bottom to top. The layers are described as follows.〔 * S3 - Massive to graded, fine- to coarse-grained sandstones that overlie the S2 layer represent deposition from a turbulent suspension. Sometimes dish structures and dewatering pipes are present. This layer is essentially the same as the Bouma A layer. * S2 - Inverse (reverse) graded, fine- to coarse-grained sandstone layers that overlie the S1 layer represent deposition as traction carpets, where grain-to-grain collisions are an important process. * S1 - Sandstone to conglomerate that are at the base of the turbidite and display parallel-laminated to cross-laminated beds that indicate traction deposition, wherein the current moves grains, pebbles and large clasts by rolling and sliding them across the surface beneath the flow. As previously mentioned, the Lowe sequence is intended to complement, not replace the Bouma sequence. Fine-grained turbidites resulting from low-density turbidity currents, in which the Bouma A through Bouma E terminology applies, are referred to in the Lowe classification as Ta through Te, in which the T acronym derives from "Traction". By contrast, because the S1-S3 terminology describes sand-rich turbidites deposited by high-density turbidity currents, the S acronym derives from "Sandstone". Lastly, R1-R3, which uses the same descriptive criteria as S1-S3, applies to conglomerates, wherein the R acronym derives from "Rubble". In practice, the S1-S3 terminology is widely used, Ta-Te, is used sometimes, and R1-R3 is seldom used. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lowe sequence」の詳細全文を読む スポンサード リンク
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