. Acta Academiae Aboensis. Science; Mathematics. 82 SIERRA DE UMANGO At the southern end of the Sierra de Umango ridge the „inter- montane zone" shows a remarkable virgation. The western half of the zone bends into a sharp curve to the west along the sout- hern head of the „crystalline" mountain block, while the eastern half continues in southerly direction to the Precordillera of Guanda- col, here passing over into the tertiary structure. Between these two branches lies the tectonical throw of Nacimientos — Zapallar, filled out by dislocated, young tertiary gravels. The eastern bran
. Acta Academiae Aboensis. Science; Mathematics. 82 SIERRA DE UMANGO At the southern end of the Sierra de Umango ridge the „inter- montane zone" shows a remarkable virgation. The western half of the zone bends into a sharp curve to the west along the sout- hern head of the „crystalline" mountain block, while the eastern half continues in southerly direction to the Precordillera of Guanda- col, here passing over into the tertiary structure. Between these two branches lies the tectonical throw of Nacimientos — Zapallar, filled out by dislocated, young tertiary gravels. The eastern branch has entirely the same appearance as the just described ridge between the Vinchina valley and the Jaguel de-. Fig. 13. Tertiary arenaceous strata dipping W to the N from Sierra de Umango, at the E border of the Jaguel bolson. S. U. in the distance. Z = intermontane zone with folded sandstones. C = young conglomerate in horizontal position. pression. The Cerros de San Antonio, as this southern ridge has been named, forms too a high bluff of several hundred meters to the east running SSW and also almost S, at the same time bordering the Zapallar depression from the Carrizal valley train to the east. The strata here show, like these in the northern ridge, a generally increasing dip towards the west, while the lithological character of the strata changes getting a softer consistence and a paler colour. The bluff on the eastern side shows the same brown, slightly dis- turbed layers as in the ridge to the north of the mountains (the stratigraphy of this bluff has been already more closely described on page 81). A good cut through the whole ridge can be obtai-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Åbo akademi (1918- ). Åbo : Åbo akademi
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectm, booksubjectscience
