Open AccessDifferential tectonic movements in the confluence area of the H uang S hui and H uang H e rivers ( Y ellow R iver), NE T ibetan P lateau, as inferred from fluvial terrace positions
Author(s) -
Wang Xianyan,
Balen Ronald,
Yi Shuangwen,
Vandenberghe Jef,
Lu Huayu
Publication year - 2014
Publication title -
boreas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 74
eISSN - 1502-3885
pISSN - 0300-9483
DOI - 10.1111/bor.12054
Subject(s) - terrace (agriculture) , geology , confluence , tectonics , fluvial , geomorphology , block (permutation group theory) , paleontology , geometry , archaeology , geography , structural basin , mathematics , computer science , programming language
In the N ortheastern T ibetan P lateau ( NETP ), the courses of the H uang S hui and H uang H e near their confluence are characterized by alternating gorges and wide depressions, segmenting the fluvial systems. The river valleys have developed terrace staircases, which are used to infer relative tectonic motions between the segments. The terrace staircases are correlated by means of relative height and optically stimulated luminescence ( OSL ) dating. At least eight terraces are present, two of which have been dated by OSL (the sixth and the third ones; c. 70 and c. 24 ka, respectively). The correlated longitudinal terrace profiles show no distinct relative tectonic movements within the confluence area, demonstrating that this area behaved as one tectonic block. The correlation of the terrace staircase of this block with areas upstream ( X ining area) and downstream (eastern L anzhou area) indicates relative tectonic movements, which therefore represent different tectonic blocks. The fluvial incision rate since c. 70 ka was much higher in the confluence area than in the blocks upstream and downstream, possibly indicating relative uplift. This relatively strong uplift provided more space for differentiation within the terrace staircase as a result of climatic changes, leading to six terraces formed as a response to minor climatic fluctuations (10 3 –10 4 year timescale) since the last interglacial. This may indicate that the stronger the tectonic movement the better the climatic imprint as expressed in the form of terrace development. Over a shorter timescale, two accumulation terraces with thick stacked deposits (>18 m) may indicate relative subsidence in the confluence, occurring sometime between 20 and 70 ka. This indicates changes in relative vertical crustal motions at timescales of tens of thousands of years. We speculate that the inferred tectonic motions are related to transpression movements in the NETP as a result of the collision of the Indian and Asian plates.