高雄北部海岸平原區末次冰期沉積環境分析－探討褶皺-逆衝斷層帶前緣之滑移速率

The Postglacial Marine Environment of the Northern Kaohsiung Coastal Plain－its implications for slip rate of the frontal fold-and-thrust belt

陳志壕(Chih-Hao Chen)

指導教授 ： 陳文山

國立臺灣大學/理學院/地質科學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.01846

摘要

高雄北部海岸平原區位屬台灣造山帶前緣之褶皺-逆衝斷層帶，前人在此地區以重力及反射震測調查，以及航照圖判識，判斷的構造有大灣向斜、岡山向斜、中洲背斜、半屏山背斜、小岡山斷層、右昌斷層和中洲斷層。本研究以中洲斷層及小岡山斷層將此區域劃分為四個構造區塊，由西向東分別為濱海平原區(大灣低地)、中洲台地(中洲背斜)、岡山低地(岡山向斜)及西部麓山帶。
　　為瞭解此區域褶皺-逆衝斷層帶之構造特性，本研究針對中央地調所在二仁溪以南之平原區鑽井17口，其中包含資源地質組在此區所鑽探之成功井等250公尺岩芯13口，以及構造與地震地質組針對小岡山斷層所鑽之四口岩芯(70~200公尺)，重新做岩芯紀錄。透過沉積構造的判釋、岩相分類、岩相組合…等進行沉積環境及沉積層序的判釋。可得知末次冰期以來之沉積物厚度於各構造地形分區上相異之分布，及18,000年來海岸線的變遷和沉積環境的演化。
　　再藉由古環境沉積深度、碳十四定年年代、以及當時全球海水面變化高度，推估此區之地殼變動速率。結果顯示，濱海平原區為沉降區，平均沉降速率為-4.3±0.7 mm/yr；中洲台地(中洲背斜)為抬升區，其抬升速率從背斜軸部的3.0±0.9 mm/yr往兩翼遞減為-0.2±0.9 mm/yr；岡山低地(岡山向斜)為沉降區，沉降速率為-3.5±0.6 mm/yr；西部麓山帶前緣為抬升區，平均抬升速率為1.5±0.9 mm/yr。中洲斷層的活動導致中洲背斜的形成，其地下構造可能為斷層擴展褶皺的模式。小岡山斷層並未明顯的截穿覆蓋於其上之全新世沉積層，僅造成沉積層褶曲變形，根據其相異的抬升速率可將之分為南北兩段，小崗山斷層北段變形帶上垂直錯移速率>3.2±1.6 mm/yr，其淨滑移速率>4.0±2.3 mm/yr；而小崗山斷層南段的垂直錯移速率<5.0±1.5 mm/yr，淨滑移速率<6.1±2.4 mm/yr。

關鍵字

小崗山斷層 ； 斷層滑移速率 ； 中洲斷層

並列摘要

The northern part of the Kaohsiung coastal-plain is an ongoing fold-and-thrust belt in the frontal orogenic belt. Previous studies concerning gravity and seismic profiles has shown that the structural framework in the study area is controlled by several NE trending thrust faults and folds, namely the Panpingshan anticline, Yuchang fault, Hsiaokangshan fault, Kangshan syncline, Chungchou anticline, Chungchou fault and Tawan syncline from east to west. The study aera can be divided into four tectonic domains by the Chungchou fault and the Hsiaokangshan fault ,including the coastal plain (Tawan syncline), the Chungchou tableland (Chungchou anticline), the Kangshan lowland (Kangshan syncline) and the western Foothills from west to east.
　　Based on the structural characteristics of the frontal fold-and-thrust belt, the borehole logging drilled by Central Geological Survey was rechecked in order to estimate the deformation rate through analysis of paleo-depositional environment, sequence stratigraphy, and radiocarbon dating. The result shows that subsidence rate of the Tawan syncline is -4.3±0.7 mm/yr, uplift rate of the Chungchou anticline is 3.0±0.9 mm/yr in axis and -0.2±0.9 mm/yr in limb, subsidence rate of the Kangshan syncline is -3.5±0.6 mm/yr, and uplift rate of the western Foothills is 1.5±0.9 mm/yr. The fault-propagation folding is proposed for which the Chungchou fault propagated and caused forming of the Chungchou anticline, and resulted into the Chungchou tableland. Hsiaokangshan fault deformed the overlying Holocene deposits but doesn’t cut the latter through. In addition, the Hsiaokangshan fault can be divided into two segments for different uplift rates, the northern segment has the vertical slip rate more than 3.2±1.6 mm/yr and its net slip rate probably more than 4.0±2.3 mm/yr, while the southern segment has the vertical slip rate less than 5.0±1.5 mm/yr and its net slip rate probably less than 6.1±2.4 mm/yr.

並列關鍵字

Hsiaokangshan fault ； Chungchou fault ； fold-and-thrust belt ； net slip rate

參考文獻

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