三叉山地區第四紀冰川後退研究初探

Quaternary Glacier Retreat in the Sancha Shan Area of the Southern Taiwan a Preliminary Results

何立德(Lih-Der Ho) ； 王子揚(Tzu-Yang Wang)

《地理學報》 61期 (2011/04) Pp. 105-122

https://doi.org/10.6161/jgs.2011.61.05

摘要

對於臺灣第四紀高山冰川後退的過程，何立德、陳淑樺、齊士崢(2010)提出兩種不同的模式，一為「直接消融」型，主要發育於向陽的南向坡，冰川後退方式是快速向冰斗底部退卻；另一為「後退偏轉」型，主要分布在背陽的北向坡，受太陽熱力的影響，冰川會逐漸往冰斗後壁高處退卻、縮小，侵蝕修飾舊的冰斗，造成冰斗開口偏轉的現象。本研究選擇三叉山為研究區，利用航照分析與野外調查，繪製研究區一帶的冰川地貌，應用風化環相對定年法探討兩種冰川後退模式的正確性。從冰川地貌的特徵研判，三叉山東南坡的嘉明湖屬於「直接消融型」，冰川在後退的過程中會往湖盆底部快速消融，理論上冰磧物的風化環厚度會隨高度遞增而加厚。三叉山西北坡的冰斗則屬於「後退偏轉」型，冰川消融的過程將從低處往山頂退卻，留下了堆積堤與冰水扇，理論上冰磧物的風化環厚度會隨高度遞增而變薄。初步調查的結果發現，嘉明湖3處冰磧堤的風化環平均厚度，由低至高分別為1.65±0.9mm、1.8±0.5mm、2.0±0.3mm，而三叉山西北坡上的冰磧堤，其風化環平均厚度由低向高分別為1.7±0.6mm、1.5±0.5mm、0.9±0.4mm。本研究初步支持「直接消融型」與「後退偏轉型」冰川後退模式的可能性，但未來仍須更精細的測量與分析方法來加以確認。

關鍵字

冰川地形 ； 冰川後退模式 ； 風化環 ； 相對定年法

並列摘要

This study aims to apply geomorphological techniques and rock weathering rind dating to investigate the glacial landforms in the Sancha Shan area of southern Taiwan. Our approach was to test two feasible models for Quaternary glacier retreat in Taiwan's mountain areas, namely the ”retreat and turn” and ”rapid meltdown” models, recently proposed by Ho, Chen, and Chyi (2010). Based on the characteristics of glacial landform assemblage, we considered that the cirque development of Chiaming Lake could be accounted for by the ”rapid meltdown” model, and consequently hypothesized that the weathering rinds of moraines here should thicken as the altitudes of moraines rise. On the other hand, the cirque development on the northwestern slope of Sancha Shan could be explained by the ”retreat and turn” model, so that the weathering rinds of moraines should thin down as the altitudes of moraines rise. As a matter of fact, we found a bottom-up increase in the weathering rind thickness of Chiaming Lake moraines, ranging from 1.65±0.9 mm, 1.8±0.5 mm to 2.0±0.3 mm. Meanwhile, the weathering rind thickness of moraines on the northwestern slope of Sancha Shan decreases bottom-up from 1.7±0.6 mm to 1.5±0.5 mm to 0.9±0.4 mm. Although these preliminary results support the hypotheses statistically, more data is needed in the future to confirm the models for Quaternary glacier retreat.

並列關鍵字

glacial landforms ； glacier retreat models ； weathering rinds ； relative dating

參考文獻

何立德、陳淑樺、齊士崢(2010)。臺灣第四紀高山冰川的後退模式。地理學報。59，19-38。

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