本文選題：深水沉積體系 + 底流��； 參考：《中國地質(zhì)大學(xué)》2014年博士論文

【摘要】：深水(水深200m)沉積物中能夠記錄有關(guān)深水動(dòng)力學(xué)、古海洋學(xué)、古氣候?qū)W等方面的豐富信息,“深水沉積體系研究”的相關(guān)領(lǐng)域日益受到全世界范圍沉積學(xué)、海洋學(xué)、氣候?qū)W研究人員的高度關(guān)注。目前,中國南海的深水沉積研究是主要集中在古海洋學(xué)和古氣候?qū)W方面的,但是缺乏對(duì)深水沉積體系(尤其是等深流沉積體系)發(fā)育演化所涉及的地質(zhì)學(xué)、海洋學(xué)等信息的系統(tǒng)分析。本文通過高分辨率二維地震、測(cè)井等地球物理學(xué)資料以及海水電導(dǎo)、溫度、鹽度等物理海洋學(xué)資料,描述南海西北次海盆西北陸緣約700-3500m水深范圍的深水沉積體系特征,總結(jié)不同類型深水沉積體系內(nèi)部構(gòu)成及空間展布規(guī)律,并分析、研究其形成發(fā)育過程中的控制因素和演化機(jī)制。 1.本文研究區(qū)地處海南島以東、西沙群島以北(東經(jīng)113°-114。30'；北緯18°-19°30'),海域面積約1×104km2。研究區(qū)北部為珠江口盆地南部隆起區(qū),西南部是西沙海槽,東南部屬于西北次海盆深海平原。珠江口盆地南部隆起區(qū)出露兩處海山,名為一統(tǒng)暗沙(水深700-1000m)和神狐南海山(水深1100-1300m)。兩處海山相距約50km,出露形態(tài)在平面上均為長軸呈WSW-ENE的橢圓形。神狐南海山長軸方向出露山體規(guī)模約為26.5km,短軸方向約為6km；一統(tǒng)暗沙長軸方向規(guī)模約為16km,短軸方向約為8km。本文所采用的數(shù)據(jù)包括南海西北次海盆西北陸緣-深海平原結(jié)合帶的高分辨率二維地震、測(cè)井等地球物理學(xué)以及海水電導(dǎo)、溫度、鹽度等物理海洋學(xué)資料。 2.描述了在西北次海盆西北陸緣區(qū)陸坡上發(fā)育的不同類型深水等深流和重力流沉積體系特征。高分辨率二維地震資料顯示：(1)一統(tǒng)暗沙和神狐南海山附近的寬緩陸坡上(水深約700-1500m,平均坡度1.2°)發(fā)育獨(dú)具特色的“海山相關(guān)等深流沉積體系”,包括環(huán)槽(moat)、伸長狀-丘狀漂積體(elongated-mounded drifts)、黏附型漂積體(plasterd drifts)、等深流沉積水道(contourite channels)、犁溝(furrows)等。(2)珠江口盆地南部隆起區(qū)以南水深約1500-2500m陡峭陸坡(平均坡度2°)廣泛發(fā)育重力流坡移沉積(mass-wasting deposits),頻繁見垂直陸坡方向展布的深水“無頭型”峽谷,構(gòu)成重力流“坡移沉積體系”和“峽谷沉積體系”。(3)西北次海盆西北陸緣下陸坡區(qū)(水深2500m),坡度稍緩(平均坡度1.5°),坡移現(xiàn)象明顯減少,普遍發(fā)育等深流沉積席狀漂積體(sheeted drift)。該區(qū)主要發(fā)育“等深流沉積體系”和“峽谷體系”。 3.精細(xì)刻畫了“海山相關(guān)等深流沉積體系”中環(huán)槽、伸長狀-丘狀漂積體、黏附型漂積體、等深流沉積水道、犁溝和無沉積區(qū)等沉積／侵蝕單元的外部形態(tài)和內(nèi)部構(gòu)成�！碍h(huán)槽”指底流侵蝕作用下,沿海山／陸坡坡腳形成的下凹地形；研究區(qū)內(nèi)見環(huán)槽沿一統(tǒng)暗沙和神狐南海山北側(cè)坡腳發(fā)育,寬度約2-5km,環(huán)槽底為光滑而平坦的侵蝕(負(fù))地形,深度變化從約15m至超過100m。“伸長狀-丘狀漂積體”指與環(huán)槽共生的、由底流沉積作用形成的伸展?fàn)疃逊e物；研究區(qū)伸長狀-丘狀漂積體主要發(fā)育在環(huán)槽北側(cè)的寬緩陸坡上,其沉積厚度的變化范圍較大(從100ms TWT至超過500ms TWT);地震相主要表現(xiàn)為極連續(xù)、平行-亞平行、中-高振幅的反射特征�！梆じ叫推e體”指受低速率水流活動(dòng)控制的、通常發(fā)育在較緩陸坡上的堆積體；研究區(qū)內(nèi)在神狐南海山北壁和一統(tǒng)暗沙南壁上分別發(fā)育一套黏附型漂積體,沉積厚度分別為200ms TWT左右和100ms TWT;其地震相表現(xiàn)出低振幅、連續(xù)性較弱、平行-亞平行的反射特征。“等深流沉積水道”指由底流侵蝕作用產(chǎn)生的、平行于陸坡方向展布的下凹地形；研究區(qū)內(nèi)所發(fā)現(xiàn)的等深流沉積水道主要發(fā)育在神狐南海山以北(環(huán)槽北側(cè))的伸長狀-丘狀漂積體沉積中,以及神狐南海山以東的寬緩陸坡上；水道寬度約2-10km,下切深度變化范圍從10m至60m不等。“犁溝”特指由底流侵蝕作用形成的、沿陸坡方向展布的、下切深度小于10m的侵蝕地形；研究區(qū)內(nèi)所見的犁溝主要發(fā)育在神狐南海山北側(cè)(環(huán)槽北側(cè))的伸長狀-丘狀漂積體沉積中�！盁o沉積區(qū)”指在穩(wěn)定底流活動(dòng)作用下的“過路不沉積”區(qū)域,主要在神狐南海山以東的寬緩陸坡上出現(xiàn)。 4.分析了研究區(qū)海山附近等深流沉積/侵蝕單元的形成發(fā)育與南海中層水(反氣旋式環(huán)流,水深范圍從約350m至1500m或更深,水溫約5℃)底流活動(dòng)之間的關(guān)系。北半球海山地形附近(即本文中水深范圍約700-1000m的一統(tǒng)暗沙和約1200-1400m的神狐南海山),自西向東的水流(即南海中層水底流)受科氏力右轉(zhuǎn)作用,在海山北側(cè)受到地形限制,水流速度大幅增加,發(fā)生侵蝕作用；海山南側(cè)區(qū)域受到山體地形的“遮擋”,水流速度漸漸減小,發(fā)生沉積作用。由此可知,海山北側(cè)水流侵蝕能力強(qiáng),可沿海山北緣山腳形成環(huán)槽；環(huán)槽北側(cè)的陸坡則接受沉積,發(fā)育伸長狀-丘狀漂積體；環(huán)槽中水流隨地形變化而速度減緩時(shí),可在環(huán)槽南側(cè)(神狐南海山北緣)發(fā)育黏附型漂積體；同一側(cè)(海山以北)遠(yuǎn)離海山的底流活動(dòng)未受到地形限制,可在環(huán)槽北側(cè)的伸長狀-丘狀漂積體沉積中形成常規(guī)的等深流沉積水道或犁溝。海山南側(cè)區(qū)域主要接受底流活動(dòng)的沉積作用,形成沉積區(qū)；一統(tǒng)暗沙南壁上可見黏附型漂積體。隨著底流經(jīng)過并離開海山區(qū)的隆起地形,底流活動(dòng)的能量、速度逐漸恢復(fù)至常態(tài),環(huán)槽逐漸消失；至神狐南海山東側(cè)寬緩陸坡(水深約1100-1300m)處主要發(fā)育常規(guī)的等深流沉積水道,以及“過路不沉積”的特征。 5.通過海底地形和二維地震測(cè)線等資料,在研究區(qū)識(shí)別出10條陸坡限制型(無頭型)峽谷后對(duì)其編號(hào),并且詳細(xì)描述其外觀形態(tài)和內(nèi)部結(jié)構(gòu)特征。除下部陸坡(水深約3000m)處的兩條峽谷(峽谷9和10)以外,其它峽谷均呈NNW-SSE方向展布,延伸長度超過20km,峽谷寬度約2-30km,最大下切深度變化范圍從十幾米至超過900m不等。峽谷9和10延伸長度較短(約3km),寬度較窄(6km),但下切深度均超過200m。深水無頭型峽谷形成過程中,受到低位體系域和陸架邊緣下切谷侵蝕影響的可能性極�。黄涑梢驒C(jī)制更可能受“退后型滑移/滑塌”作用或與斷層相關(guān)的構(gòu)造活動(dòng)所控制。峽谷5在水深約1350坡度約1°處呈NNW-SSE走向,寬度約6.5km,下切形態(tài)呈不對(duì)稱V型,下切深度約140m；在峽谷內(nèi)部沉積結(jié)構(gòu)中可識(shí)別出晚中新世(T4,11.5Ma)以來連續(xù)發(fā)育的峽谷侵蝕界面,表現(xiàn)為連續(xù)、高振幅的地震反射特征；晚中新世以來的峽谷侵蝕界面具有明顯向ENE方向的遷移特征,指示該峽谷體系可能受持續(xù)的、較強(qiáng)烈的、自西向東的底流活動(dòng)的改造作用,從而導(dǎo)致峽谷體系強(qiáng)制性向東遷移；上述自西向東的底流活動(dòng)與附近深度范圍內(nèi)形成“海山相關(guān)等深流沉積體系”的水流活動(dòng)方向一致,很可能同屬南海中層水循環(huán)。峽谷5以西約15km處的中部陸坡(水深約1500-2500m)上發(fā)育峽谷6,該峽谷在水深約1790m、坡度約2°的位置表現(xiàn)出具有平坦峽谷底的U型下切形態(tài)(下切深度約135m,峽谷寬度約4km)；峽谷兩側(cè)發(fā)育丘狀天然堤沉積,沉積物表現(xiàn)出高振幅且相當(dāng)連續(xù)的地震反射特征,且晚中新世以來自下而上表現(xiàn)出加積型的沉積序列;峽谷ENE一側(cè)的天然堤沉積表現(xiàn)出平行-亞平行的地震反射特征,而WSW一側(cè)的天然堤沉積中出現(xiàn)明顯的波狀沉積特征。波狀沉積物表現(xiàn)出波狀、極連續(xù)且相互平行、中-高振幅的地震反射特征；波形完整,具有中等尺度規(guī)模(波長小于2km而波高小于60m)；各波形之間具有相似的內(nèi)部反射特征,整體表現(xiàn)出沿陸坡方向向上(NNW方向)的遷移現(xiàn)象；根據(jù)所上述波狀沉積物的發(fā)育位置和沉積特征,推測(cè)其屬于濁流沉積物波。 6.揭示了研究區(qū)水深約1500-2500m范圍內(nèi),陡峭陸坡(平均坡度2°)處沉積過程與重力流作用的關(guān)系。該范圍坡度大,沉積環(huán)境不穩(wěn)定,廣泛發(fā)育重力流坡移沉積和無頭型峽谷沉積。鮮見等深流沉積,一方面可能因底流活動(dòng)弱,不足以造成沉積／侵蝕記錄；另一方面可能因頻繁的重力流活動(dòng)對(duì)底流沉積記錄反復(fù)破壞,以至于無法通過二維地震資料識(shí)別。通過地震沉積學(xué)記錄,在該范圍內(nèi)的坡移沉積區(qū)中可識(shí)別出連續(xù)疊加滑塌體、失穩(wěn)滑動(dòng)面、滑移痕和分離滑塌體等沉積單元。而且本區(qū)罕有地震活動(dòng),未現(xiàn)天燃?xì)馑衔锘蛴蜌鈴?qiáng)烈富集,故推測(cè)“陡峭陸坡”很可能是誘發(fā)大規(guī)模陸坡失穩(wěn),進(jìn)而發(fā)生坡移的決定性因素。 8.查明了西北次海盆西北陸緣研究區(qū)深水沉積體系發(fā)育演化的重要控制因素。研究區(qū)陸坡形態(tài)自東向西的明顯變化(逐漸變陡),以及不同深度范圍南海洋流活動(dòng)方向、強(qiáng)度的差異,都是控制該區(qū)深水沉積體系發(fā)育演化的重要因素。研究區(qū)東部陸坡形態(tài)表現(xiàn)出三級(jí)“分階”的輪廓,上部Ⅰ型階(水深1500m)和下部Ⅲ型(水深2500m)均為坡度較緩的陸坡(平均坡度小于1.5°),主要發(fā)育等深流沉積/侵蝕單元；中部Ⅱ型階坡度大(平均坡度2°),主要發(fā)育峽谷沉積和坡移沉積。三級(jí)分階狀的輪廓向西逐漸消失,變?yōu)椤阿窬?Ⅱ陡“的二級(jí)分階；上部Ⅰ型階主要發(fā)育等深流沉積水道以及底流“過路不沉積”的無沉積區(qū)；下部Ⅱ型階主要發(fā)育坡移沉積和峽谷沉積；不發(fā)育Ⅲ型階及相關(guān)等深流席狀漂積體沉積。最終在研究區(qū)西部陸坡,陸坡輪廓演變?yōu)闊o分階、整體陡峭的單一Ⅱ型陸坡；水深1500m以上為神狐南海山南壁,水深2500m及以下為西沙海槽北壁),至此深水沉積體系僅發(fā)育坡移沉積和峽谷沉積。 9.根據(jù)精細(xì)的地震沉積學(xué)記錄,針對(duì)本文研究區(qū)水深1500m之上陸坡處所發(fā)育的等深流沉積／侵蝕特征,提出了“西北次海盆西北陸緣區(qū)深水等深流沉積的發(fā)育演化最早可追溯至晚中新世早期”。從不整合界面T4(11.5Ma)自下而上至現(xiàn)今海底沉積物中,利用地震相差異特征識(shí)別出六個(gè)地震沉積單元(沉積單元1-6)。自沉積單元2底界面向上至現(xiàn)今海底,可見持續(xù)、穩(wěn)定發(fā)育的等深流沉積／侵蝕特征(加積型序列),暗示南海西北次海盆西北緣陸坡區(qū)的穩(wěn)定底流作用可追溯至晚中新世早期。通過分析、對(duì)比神狐南海山附近晚中新世以來沉積物的地震相特征,發(fā)現(xiàn)隨著海山逐漸被掩埋,海山地形對(duì)水流的限制、加速作用也逐漸消失；之后底流活動(dòng)將呈常規(guī)狀態(tài)持續(xù)作用于海底,早期所發(fā)育的、極具特色的環(huán)槽逐漸被常規(guī)的等深流沉積水道取代。海山出露-被掩埋的過程明顯控制了其周緣等深流沉積的發(fā)育類型；反之,等深流沉積的內(nèi)部構(gòu)成也反映了海底地形——特別是海山地貌由出露向被掩埋消失的變化過程。 綜上,深水沉積體系研究為物理海洋學(xué)和海洋沉積學(xué)之間的學(xué)科交叉研究搭建了新的橋梁,更為南海新生代古海洋學(xué)和深海動(dòng)力學(xué)研究提供了新資料。
[Abstract]:Deep water (water depth 200m) deposits can record abundant information about deep water dynamics, paleoceanography, paleoclimatology and so on. The related fields of "deep water depositional system research" are increasingly concerned with the worldwide sedimentology, oceanography and Climatology researchers. At present, the study of deep water deposits in the South China Sea is the main focus. In the field of paleoceanography and paleoclimatology, there is a lack of systematic analysis of geology, oceanography, and other information about the development and evolution of the deep-water depositional system (especially the sedimentary system). In this paper, geophysical data such as high resolution two-dimensional earthquakes, logging, and other physical oceanographic data, such as seawater conductivity, temperature, salinity and so on, are used in this paper. The characteristics of the deep water depositional system of the northwest continental margin of the northwest sub sea basin of the South China Sea are described in the depth of 700-3500m water depth. The internal structure and spatial distribution of different types of deep-water sedimentary systems are summarized, and the control factors and evolution mechanisms in the process of formation and development are analyzed.
1. the study area is located in the east of Hainan Island, north of Paracel Islands (113 degree -114.30'of Dongjing and 18 -19 30' in north latitude), the north of the study area about 1 x 104km2. area is the southern uplift area of the Pearl River Mouth Basin, the southwest is the trough, the southeast belongs to the northwest Basin deep sea plain, and the southern uplift area of the Pearl River Mouth Basin shows two seamounts. It is named as 700-1000m and Shenhu Nanhai mountain (water depth 1100-1300m). The two seamounts are about 50km, and the outcropping form is WSW-ENE oval on the long axis. The long axis of the Shenhu Nanhai mountain is about 26.5km and the short axis is about 6km; the direction of the dark sand long axis is about 16km, and the short axis is about 8km. Ben. The data used in this paper include the high resolution two-dimensional earthquake of the northwest continental margin of the northwest sub sea basin of the South China Sea, the geophysics such as logging, and the physical oceanographic data of sea water conductivity, temperature, salinity and so on.
2. the characteristics of deep and gravity flow depositional systems of different types of deep water developed on the continental slope of the northwest continental margin of the northwest sub sea basin were described. The high resolution two-dimensional seismic data showed that (1) the wide slow continental slope in the vicinity of the unified dark sand and the Shenhu Nanhai mountain (the depth of water depth is about 700-1500m, the average slope 1.2 degrees) developed unique "sea mountain related deep flow". The depositional system includes moat, elongated-mounded drifts, plasterd drifts, contourite channels, furrows, etc. (furrows). (2) the slope of the southern uplift of the Pearl River Mouth Basin is widely developed by the deep slope of a steep slope of 2 degrees in the southern water depth of the Pearl River Mouth Basin (the average slope of the slope). Mass-wasting deposits, frequently seen the deep water "no head" Canyon in the direction of vertical slope, constitutes the gravity flow "slope shifting depositional system" and "Canyon depositional system". (3) the northwestern sub basin northwest continental margin lower continental slope area (water depth 2500m), the slope is slightly slow (flat gradient 1.5 degrees), the slope shift phenomenon is obviously reduced, widespread development and so on deep flow sedimentation Sheeted drift. The area mainly develops "equal deep flow depositional system" and "Canyon system".
3. a fine depiction of the slots, elongate collucreting collucreting bodies, adhesion type drifting bodies, and the external morphology and internal composition of the sedimentary / erosion units such as ploughing and non depositional areas are carefully depicted in the "seamount related equal deep flow depositional system". In the study area, the width of the slots and the north side slope of the South China Sea Mountain of Shenhu is about 2-5km, and the bottom of the ring groove is smooth and flat erosion (negative) topography. The depth changes from about 15m to more than 100m. "extensional collucret", which refers to the extensional deposits formed by the bottom flow deposition with the ring trough, and the extensional hillock in the study area. The drifting bodies are mainly developed on a wide slow continental slope north of the ring trough, with a large range of variation in sedimentary thickness (from 100ms TWT to more than 500ms TWT), and the seismic facies are characterized by very continuous, parallel subparallel, medium to high amplitude reflection characteristics. "Adhesive type drifting" refers to low rate flow activity, usually developed on a slower slope. A set of adherent drifting bodies developed separately in the north wall of the South China Sea and the southern wall of the yunu Sands of Shenhu, respectively. The sedimentary thickness is about 200ms TWT and 100ms TWT, respectively, and the seismic facies show low amplitude, weak continuity and parallel subparallel reflection characteristics. In the study area, the equal deep flow sedimentary waterways found in the study area are mainly developed in the elongate collucret deposits of the north side of the South China Sea (the north side of the ring trough) and on the broad gentle slope east of the South Sea Mountain of Shenhu; the width of the waterway is about 2-10km and the range of the lower cutting depth varies from 10m to 60m. " The gully is mainly formed by the erosion of the bottom flow, along the slope direction, the erosion terrain is less than 10m, and the furrows in the study area are mainly developed in the elongated Qiu Zhuangpiao's deposit on the north side of the South China Sea Mountain (the north side of the ring trough). "No sedimentary area" refers to "no deposition" under the action of stable underflow. The area appears mainly on the wide slope of the east of Shenhu Nanhai mountain.
4. the relationship between the formation and development of the deep stream deposition / erosion unit near the seamount in the study area and the bottom flow of the South China Sea middle layer water (anti cyclonic circulation, water depth range from about 350m to 1500m or deeper, and water temperature about 5 degrees C). Nan Haishan), the flow of water from the west to the East (that is, the middle sea bottom flow in the South China Sea) is affected by the Coriolis force, which is restricted by the terrain on the northern side of the seamount, and the velocity of the flow is greatly increased and the erosion action occurs. The southern region of the seamount is "blocked" by the terrain of the mountain, and the velocity of the flow is gradually diminished and deposited. Thus, the erosion of the north side of the seamount can be seen. With strong force, the ring groove can be formed along the foot of the northern margin of the seamount; the continental slope on the north side of the ring groove is deposited and develops the elongate - collucreting body. When the velocity of the water flow in the ring groove slows down with the terrain, the adhesive type drifting body can be developed on the south side of the ring trough (the northern margin of the South China Sea, the South China Sea), and the undercurrent activity far away from the seamount on the same side (north of the seamount) has not been subjected to the topography. Limiting the formation of conventional equal deep flow sedimentary waterways or ploughs in the elongated collucret deposits on the north side of the ring trough. The southern region of the seamount mainly receives sediment from the undercurrent activity and forms a sedimentary area. The energy is gradually restored to normal, and the ring groove is gradually disappearing, and to the slow continental slope of the Shandong side of the South China Sea in the South China Sea (the depth of water is about 1100-1300m), the conventional equal deep flow sedimentary waterways are mainly developed and the characteristics of "non deposition".
5. through the data of the seabed terrain and the two-dimensional seismic survey lines, the number is numbered after identifying 10 continental slope restricted canyons, and its appearance and internal structure characteristics are described in detail. Except for the two canyons (Canyon 9 and 10) at the lower slope (water depth about 3000m), the other canyons are distributed in the direction of NNW-SSE and extend long. The width of the canyon is about 2-30km, the width of the maximum cutting depth varies from more than 10 meters to more than 900m. The 9 and 10 Canyon length of the canyon is short (about 3km) and the width is narrower (6km), but the depth of the cutting is more than in the formation process of 200m. deep water Canyon, and the possibility is very little by the low body region and the erosion of the grain cutting under the continental shelf. Its genetic mechanism is more likely to be controlled by the "backward slip / slide" or the tectonic activity associated with the fault. The canyon 5 has a NNW-SSE direction at about 1350 slope at about 1 degrees, the width of which is about 6.5km, the undercut form is asymmetrical V, and the lower cutting depth is about 140m; in the inner sedimentary structure of the canyon, the late Miocene (T4,11.5Ma) can be identified. The continuous development of the canyon erosion interface is characterized by continuous and high amplitude seismic reflection, and the erosion interface of the canyon since the late Miocene has a distinct migration characteristic to the ENE direction, indicating that the canyon system may be sustained, stronger, from west to East, thus leading to the mandatory eastward migration of the Canyon system. The movement of the bottom flow from the west to the East is consistent with the flow direction of the "seamount related deep flow depositional system" in the vicinity of the depth range. It is likely to be the same as the middle sea water cycle in the South China Sea. The central slope (about 1500-2500m depth of water depth about 15km) at the 5 West of the canyon is developed in the canyon, and the canyon is about 1790m in depth and about 2 degrees in the slope. U undercut forms with flat Canyon bottom (lower cutting depth is about 135m and Canyon width about 4km); both sides of the canyon are deposited with a hilly natural embankment, and the sediments show high amplitude and quite continuous seismic reflection characteristics, and the late Miocene epoch shows a sedimentary sequence from lower up and up, and a natural dike deposit table on the side of the canyon's ENE side The seismic reflection characteristics of parallel sub parallel are present, and there are obvious wave depositional features in the natural dike deposits on one side of the WSW. The wavy sediments are wavy, very continuous and parallel to each other, with medium and high amplitude seismic reflection characteristics; the wave form is complete, with a medium scale scale (the wave length is less than 2km and the wave height is less than 60m); the waveforms are between the waveforms. With similar internal reflection characteristics, the migration in the direction of the slope upward (NNW direction) is shown as a whole. According to the development position and sedimentary characteristics of the above wavy sediments, it is presumed to belong to the turbidite sediment wave.
6. the relationship between the sedimentation process and the action of gravity flow in the steep slope (average slope 2 degrees) is revealed in the area of the study area. The slope is large, the sedimentary environment is not stable, the gravity flow slope deposit and the no head Canyon deposit are widely developed. There are few deep current deposits. On the one hand, it may be weak and not enough to cause deposition. On the other hand, the sedimentary records of undercurrent deposits may be repeatedly destroyed by frequent gravity flow activities so that it can not be identified by two-dimensional seismic data. Through seismic sedimentology records, continuous superposition slip bodies, unstable sliding surfaces, slip marks and separate slide bodies can be identified in the sedimentary area of this range. In addition, there are few seismic activities in this area, and the gas hydrate or oil and gas enrichment is not very strong in the present day. Therefore, it is presumed that the "steep slope" may be the decisive factor to induce the instability of the large scale slope and then the slope shift.
8. the important control factors for the development and evolution of the deep-water depositional system in the northwest continental margin research area of the northwest sub sea basin are identified. The obvious change (gradually steepening) from east to West in the study area and the direction of the South China Sea flow in different depths and the difference in intensity are important factors for controlling the development and evolution of the deep water depositional system in this area. The eastern slope of the region shows the outline of three grade "sub order". The upper part I (water depth 1500m) and the lower third type (water depth 2500m) are both gentle slope of the slope (the average slope is less than 1.5 degrees), the main development equal deep flow deposition / erosion unit, the middle grade II order slope is large (the average slope 2 degree), the main development Canyon deposition and slope migration deposit. Three grade. The outline of the fractional order gradually vanished westward to the two order of "I slow - II steepness"; the main development of the upper part I was the main development of the deep flow sedimentary waterway and the undeposited undeposited region of the underflow, and the lower stage II type was mainly developed by slope deposits and Canyon deposits; Finally, in the western slope of the study area, the silhouette of the continental slope evolved into an undivided, unitary and steep single type of continental slope; the depth of water was more than 1500m of the south south wall of the Shenhu Nanhai mountain, and the depth of water was 2500m and below the north wall of the Xisha trough. At this point only the sedimentary and Canyon deposits were developed in the deep water system.
9. according to the fine seismic sedimentology records, the deep deep flow sedimentation in the northwest continental margin of the northwest sub basin was put forward in view of the characteristics of the equal deep flow deposition and erosion developed on the slope above the water depth of 1500m in this study area.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：P736.21

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