鹿野溪與卑南溪的河階地與其新構造運動意義

River Terraces and Their Neotectonic Implications of Luye and Beinan River, Taidong

齊士崢(Shyh-Jeng Chyi) ； 陳文山(Wen-Shan Chen) ； 龔琪嵐(Chi-Lan Kung)

《環境與世界》 8期 (2003/12) Pp. 1-23

https://doi.org/10.6304/EAW.2003.8.1

摘要

鹿野溪河口與匯流後的卑南溪至利吉村之間，分布四階河階地。鹿野溪的四階河階地，是河口沖積扇在河川下切後受切割形成的，卑南溪的四階河階地均分布於河川東岸，是鹿野溪沖積扇發育時，迫使卑南溪向東側遷移，強烈的側蝕作用形成的侵蝕面，在後期河川下切後形成的。這些河階地受南北延伸的四條主要活動構造線影響而發生變形，自西而東分別是鹿野逆斷層、背斜、向斜和利吉斷層（縱谷斷層）。整體而言，它們屬於海岸山脈持續向西擠壓，形成的縱谷斷層和伴生的局部的構造。大致上，區域自更新世末期的平均上升速率是中央山脈邊緣區最慢，大約僅每年1至3公釐，鹿野斷層東側的背斜軸部與向斜構造東側，也就是背斜構造的中南段最快，可能接近每年1公分，向南、北再逐漸降低，其他區域大約每年5公釐左右，海岸山脈西緣又可能稍高於每年5公釐。雖然這些活動構造在最近的活動跡象不明顯，不過很可能是持續活動的。因此，目前附近居住、活動的人，都有非常高的危險性，這些活動構造值得進一步詳細研究。

關鍵字

卑南溪 ； 鹿野溪 ； 河階地 ； 沖積扇 ； 新構造運動

並列摘要

Four levels of terraces were developed in the area from the interflow of Luye and Beinan River to Lichi village. In Luye River, the alluvial fans were incised by the main stream as terraces. The highest two levels of terraces in altitude have been deformed by active faults and folds. Field investigation shows the highest surface is covered by lateritic soils. In Beinan River, there are strath terraces developed. The formation of Luye fans cause eastward shift of Beinan Rive. The strath surface developed by lateral erosion was subsequently incised and distributed along the eastern side of the Hua-Dong valley. These river terraces were displaced by a series of N-S trending faults and folds that resulting from ongoing collision of Coastal Range and Central Mountain Range. The uplifting of this area is estimate about 5mm/yr of in average. The highest rate is observed from the south central part of the anticline axis at about 1cm/yr since late Pleistocene. The proximal fan area gives the lowest rate ranged 1 to 3mm/yr. This study shows the Luye fans were formed during late Pleistocene to early Holocene. Whether or not they are influenced by active folds and faults in this period of time needs future studies. In addition, the age dating for the terraces, the distribution and activity of those folds and faults, and the hazard potentials of this area are worthy of further studies in detail.

並列關鍵字

Beinan River ； Luye River ； river terrace ； alluvial fan ； neotectonic