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The Trabancos is a river in Spain that flows between the Zapardiel and the Guareña rivers, and is a tributary of the Duero river. The source of the Trabancos is in Moraña, a region in the north of the province of Ávila, near Blascomillán. The Trabancos is at an elevation of approximately , is approximately long and, although its river bed is stable, only has a constant water flow during and immediately after torrential rains. ==Fluvial geomorphology== From its source in the province of Ávila, to its mouth in the village of Pollos ''("Village of Chickens" in Spanish)'' in the Vallisoletana (''"confluence of waters"'') region, the course of the Trabancos is markedly affected by a geologic fault originating in the Tertiary era—likely pre-Pliocene that, like most of the observed faults of that geological era, follows a NNE-SSW direction. As shown in the graph below, the fault separates material laid down during the Oligocene epoch on the right margin, from material laid down during the Miocene epoch on the left margin. The surface level represents material deposited during the Quaternary period. Archeological research in areas that surround the Trabancos River, between the villages of Castrejón and Pollos (Valladolid province) have been compared with the specialized bibliography and the published geological charts (''infra''). This produced identified a sequence of river terraces as follows, on the left hand margin of the chart: TT-1 platform (the most ancient, at +35/40 meters over the flood plain); the TT-2 platform (the second one at +25/30 meters); the TT-3 platform (at +15 meters over the floodplain); and the TT-4 platform (at +10 meters, the last and most recent). The right hand margin of the designated chart depicts a ''gravel plateau'' present along the middle and final courses of the Trabancos River. The scientist Alfredo Pérez-Gonzalez named this formation ''"Superficie de Alaejos"'' ("The Plateau of Alaejos", after a nearby village). The Alaejos Plateau incorporates a number of different types of materials, including red argillic soil and a colluvium buildup of gravels with rounded stones of quartz and quartzite. The terraces of the Trabancos River only occur on the left hand side of the valley. Their sediments overlie Miocene sediments. This is the result of a hard slope in the opposite margin, where the terrain is heavily eroded, which renders the formation and maintenance of river terraces impossible. Of the previously mentioned river terraces, the one known as TT-4 is only visible near ''Narros del Castillo'' (Ávila). Terrace TT-3 is the best preserved of the lot; although its height on the bed of the stream is not constant, it clearly stands out on the floodplain. Terrace TT-2 is quite well preserved as well, although it has been more heavily sculptured by other small tributaries of the Trabancos River. By contrast, terrace TT-1 is greatly eroded; although some sections survive to the south of the municipality of ''Alaejos'' (Valladolid), they are very difficult to differentiate from the colluvium floor that covers the ''Superficie de Alaejos''. Entering into land in the municipality of ''Pollos'', the stream stops to form river terraces, cutting traversely and lowering enough (between 40 and 60 meters) to meet the terrace deposits of the Duero River. The TT-3 platform features a very compact and thick Miocene epoch conglomerate formed of river-smoothed pebbles of quartzite, most likely cut by the Trabancos River ages ago, and cemented together by chalk and sandstone materials. While this Miocene conglomerate emerges from the banks of each river terrace, the quartzite in the conglomerate on the TT-2 platform, just northwest of the municipality of Siete Iglesias de Trabancos, likely derives from the action of the Duero River rather than the Trabancos River, as a slope in the terrain is thought to have caused the formation of an alluvial fan that deposited quartzite on the fluvial fossil river bed of the Trabancos. The fact that the river terraces of the Trabancos River cut and cross some terraces of the Duero River indicates the affected Duero River terraces are younger than those not formed from activity of the waters of this river. The ''"superficie de Alaejos"'' carve-out intrudes 4 to 6 meters into the Duero River terrace designated TD-7 (+74/80 m) to the northwest of Siete Iglesias de Trabancos village. Likewise, the TT-2 fluvial terrace of Trabancos cuts some Duero River terraces. Since the previously mentioned Duero River terrace named TD-7 has been dated by Alfredo Pérez-González (op.cit.) to the beginning of the Middle Pleistocene, meaning the river terraces of Trabancos River are younger than the "Superficie de Alaejos", it appears plausible that this postdates the creation of Trabancos valley: the proposed date could, thus, be halfway through the Middle Pleistocene or later. 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「Trabancos (river)」の詳細全文を読む スポンサード リンク
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