劉家瑄Liu, Char-Shine臺灣大學:海洋研究所邱瑞焜Chiu, Jui-KunJui-KunChiu2010-05-062018-06-282010-05-062018-06-282009U0001-0902200918444100http://ntur.lib.ntu.edu.tw//handle/246246/181232本研究利用海底迴聲剖面資料探討台灣海峽以及台灣西南海域的迴聲型態與沈積構造，彙整、分析了海研一、二號共十二個航次在研究地區蒐集之地層剖面資料，剖面總長分別超過兩千公里（台灣海峽）及一萬一千公里（台灣西南海域）。此外，亦結合水深資料及前人之反射震測剖面研究與沈積物的地質、地化分析結果，建構台灣海峽及台灣西南海域淺層沈積物可能的傳輸方式，並比較西南海域被動性與活動性大陸邊緣不同沈積環境的特徵。據海床不同之迴聲特徵，本研究將台灣海峽的迴聲型態分成三大類（平坦型、土堆型、不規則型）及七小類，各類迴聲型態多呈東北－西南走向之狹長型分佈，與潮流橢圓的長軸方向一致，可以看出台灣海峽的沈積物傳輸受到潮流影響很大。台灣西南海域的迴聲型態則可分為四大類（清晰型、濃密型、雙曲線型、不規則型）及八小類，其迴聲型態分布圖清楚顯示被動性與活動性大陸邊緣主要的迴聲型態不一樣：南中國海大陸坡（被動性大陸邊緣）的上部陸坡多為雙曲線型的迴聲型態，代表該區以海底崩移造成的侵蝕作用為主；下部陸坡海床多呈現清晰型迴聲型態，代表穩定的沈積作用；而活動性大陸邊緣（高屏陸坡）的上部斜坡因為有高屏溪等河流帶來大量沈積物在該地區堆積，海床以清晰型迴聲型態為主；下部斜坡之海床則多呈現雙曲線型迴聲型態，推測沈積物供應少，有小規模海底崩移。本研究顯示海床迴聲型態可以用來探討活動性與被動性大陸邊緣不同之沈積環境與沈積作用。據地層迴聲剖面資料，在西彰雲砂脊西側有一條長約一百公里的泥質帶，沿著澎湖水道北延的低凹帶發展。因為泥質帶迴聲剖面顯示其地層面向西傾斜，推測其沈積物來源是台灣西部之河川。台灣海峽北部之觀音凹陷區域有崎嶇的海床，而其東北方有厚度達20公尺的砂質沈積物堆積，參考台灣海峽潮流橢圓資料，本研究認為台灣海峽北部存在一個「觀音凹陷—北台砂脊」潮流沈積體系，為搬運細顆粒沈積物離開台灣海峽的主要營力。台灣西南海域，靠近台灣島一側的南中國海陸坡上可以觀察到牽引式海底崩移現象，在發生海底崩移的海床迴聲剖面上清楚顯示一系列剪力面，而且剪力面附近沈積層有被拉張變薄的情況。本研究認為在此地區發生的牽引式海底崩移主要是受到台灣島荷重的影響，且此作用有從東往西逐漸發展的趨勢。屬於活動性大陸邊緣的上部高屏陸坡，在摺皺及逆衝斷層等構造作用下呈現一系列西北－東南走向之海脊與斜坡間盆地。由於高屏溪提供了大量的沈積物，在上部高屏陸坡地區即呈現出沈積物「填滿及溢出」的沈積與傳輸方式，此作用在海床迴聲剖面資料中亦可清楚顯示。言之，本研究顯示海床迴聲特徵可以用來辨識海床沈積物分布並協助探討研究地區之沈積作用。在台灣海峽之海床迴聲特徵分析結果認為台灣海峽北部存在一個「觀音凹陷—北台砂脊」潮流沈積體系，此為在短時間內搬運細顆粒沈積物離開台灣海峽的主要營力。而在台灣西南海域的研究結果則顯示被動性大陸邊緣與活動性大陸邊緣沈積作用有不同之趨勢，在南中國海大陸邊緣是上部陸坡侵蝕、下部陸坡沈積，在高屏陸坡則相反，為上部陸坡沈積、下部陸坡侵蝕。Chirp sonar profile data have been analyzed and compiled in this study to map the echo character distribution of the sea floor sediments in the Taiwan Strait and in the area offshore Southwestern Taiwan. These chirp sonar profile data were collected from 12 cruises of the Ocean Researcher 1 and Ocean Researcher 2 from 2002 to 2007, with total lengths of over 2,000 km in the Taiwan Strait and over 11,000 km in offshore Southwestern Taiwan area. By integrating the echo character studies with sea floor topography and results of previously published seismic and coring studies, sea floor sedimentary processes and possible sediment transport mechanisms in the study area can be established. ased on the different echo characters, three types of echo character patterns (flat, mound and irregular) and seven sub-types have been recognized in the Taiwan Strait. In general, those patterns are distributed in several NE-SW trending long and narrow zones, parallel to the M2 axis of the local tidal current ellipses, suggesting that sediment transport in the Taiwan Strait is strongly influenced by the tidal current. Offshore southwestern Taiwan, four types of echo character patterns (distinct, indistinct, hyperbolic and irregular) and eight sub-types have been identified. The echo character distribution patterns reveal that there are district sedimentary processes in the upper and lower continental slopes of the passive South China Sea continental margin, and in the active orogenic margin of the Kaoping slope area. The upper continental slope of the South China Sea continental margin presents hyperbolic echo characters which suggests that the submarine landslides is the dominative processes here, while most chirp profiles show distinct echo characters in the lower South China Sea continental slope, implies a more stable depositional environment. On the contrary, the distinct echo character patterns are prevailing in the upper Kaoping Slope, reflecting a depositional environment here due to the huge influx of the orogenic sediments from Taiwan. In the lower Kaoping Slope, sea floor echo characters appear to be most hyperbolic, suggesting the sedimentary environment is less depositional and many submarine landslides occurred here.n the Taiwan Strait, the chirp sonar data show that a mud belt extending northward from the north end of the Penghu Channel along the western flank of the Yun-Chang Ridge for over 100 km. The westward dipping reflectors and acoustic blanking caused by shallow gas in the chirp sonar profiles suggest that the mud should come from Taiwan. In the northern Taiwan Strait, the rugged sea-floor in the Kuayin Depression and the presence of a 20-m thick sand ridge suggests that there is a tidal deposition system here which plays a key role in transporting fine grain sediments from the Taiwan Strait eastward to the Okinawa Trough.n the passive South China Sea continental margin near Taiwan, retrogressive failures have been observed. There are many shear planes on the sub-bottom profiles where the submarine slides occurred and the sediment layers near the shear plane were stretched, bended and thinned. We suggest that the retrogressive failure processes are mainly caused by the loading of the Taiwan mountain belt as this process is well developed on the South China Sea continental slope near Taiwan while is less developed westward along the continental margin. n the active margin of the Kaoping Slope, folds and thrusts are the dominative structure features which form a series of submarine ridges and intra-slope basins. In the upper Kaoping Slope region, the “fill and spill” processes are observed, and echo character patterns also support this process here. n summary, this study has demonstrated that sea floor echo characters can be used to identify the sediment distribution patterns and to reveal the sedimentary processes involved. In the northern Taiwan Strait, the existence of a tidal deposition system, named the “Kuayin Depression and North-Taiwan Sand Ridge system”, has been suggested which is the driving force for transporting fine grain sediments from Taiwan Strait to deep sea in a short period. In the passive continental margin offshore Southwestern Taiwan, sea floor erosion caused by submarine slides is widespread on the upper South China Sea continental slope, while the lower South China Sea continental slope is a stable depositional environment. In contrast, huge amount of sediments are deposited on the upper Kaoping Slope, while rugged sea floor topography and submarine landslides are the main features in the lower Kaoping Slope.口試審定書 I謝 II要 IIIbstract V錄 VIII目錄 XIII目錄 XVI一章 緒論 1.1前言 1.2淺層沈積作用研究 2.3大陸棚上的淺層沈積研究 3.4大陸斜坡上的淺層沈積研究 5.5研究目的與重要性 7.5.1 台灣海峽值得研究之處 7.5.2 台灣西南海域值得研究之處 8.5.3 本研究的重要性 9二章 研究背景 11.1 地層剖面資料於淺層沈積學之應用 11.1.1 地層剖面儀的原理 12.1.2地層剖面儀的發展歷史 14.1.3新舊地層剖面儀的差異 15.1.4地層剖面與迴聲型態分類 16.2台灣海峽的研究背景 20.2.1台灣海峽的區域地質 21.2.2台灣海峽的海洋地質 21.2.3台灣海峽的水文與氣候概況 24.3台灣西南海域的研究背景 27.3.1台灣西南海域的區域地質 28.3.2台灣西南海域的海洋地質 29.3.3台灣西南海域的水文概況 30三章 研究方法 32.1資料收集 32.1.1地層剖面資料 32.1.2水深資料 39.1.3反射震測剖面 39.2資料處理 40.2.1地層剖面資料的處理 40.2.2反射震測剖面 43四章 台灣海峽的研究結果 44.1台灣海峽迴聲型態分佈 44.2地層剖面資料描述 49.2.1觀音凹陷及其以北區域 50.2.2彰雲砂脊區域 52.2.3烏坵凹陷及台灣海峽西側區域 55.3颱風造成的短期泥質沈積作用 58.4討論 59.4.1 台灣海峽泥質沈積物的分佈與傳輸 59.4.2 颱風時期的沈積物傳輸 61.4.3 地層剖面資料與沈積物分析結果的對比 63.4.4沈積物等厚度圖及可能的傳輸途徑 65.5小結 70五章 台灣西南海域的研究結果 71.1西南海域的水深與坡度 71.1.1被動性大陸邊緣的水深與坡度 71.1.2活動性大陸邊緣的水深與坡度 73.2台灣西南海域的迴聲型態及其分佈 75.3地層剖面資料描述 80.3.1被動性大陸邊緣 80.3.2活動性大陸邊緣 86.4討論 91.4.1牽引式海底崩移 91.4.2碎屑流沈積 96.4.3迴聲型態與沈積速率的關連 98.5小結 101六章 綜合討論 102.1台灣海峽泥質帶所代表的意義 102.1.1 泥質帶的來源 102.1.2泥質帶的形貌與水文狀況 102.1.3台灣海峽泥質帶跟長江以南大陸沿岸泥質帶的比較 103.2觀音凹陷潮流沈積體系 107.2.1水文資料 107.2.2海床形貌與沈積物 107.3台灣海峽與東海陸棚在沈積環境上的比較 113.3.1 地理位置與海底形貌 113.3.2水文狀態 113.3.3沈積物分佈與傳輸 113.4台灣西南海域被動性與活動性大陸邊緣沈積作用的比較 117.4.1海底形貌與坡度 117.4.2沈積物地質地化分析結果 117.4.3 迴聲型態 117.4.4沈積物傳輸方式 118七章 結論 121考文獻 123錄一 邱瑞焜歷年著作 132application/pdf12442842 bytesapplication/pdfen-US台灣海峽活動性與被動性大陸邊緣地層剖面資料潮流沈積體系牽引式海底崩移Taiwan StraitActive and Passive Continental MarginSub-bottom ProfileTidal Deposition SystemRetrogressive Failure[SDGs]SDG14[SDGs]SDG15thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/181232/1/ntu-98-D92241006-1.pdf