东北太平洋Cascadia陆缘Orca滑坡触发机理的数值模拟

何雯, 曹运诚, 陈多福

何雯,曹运诚,陈多福. 东北太平洋Cascadia陆缘Orca滑坡触发机理的数值模拟[J]. 海洋地质与第四纪地质,2023,43(1): 180-189. DOI: 10.16562/j.cnki.0256-1492.2022050701
引用本文: 何雯,曹运诚,陈多福. 东北太平洋Cascadia陆缘Orca滑坡触发机理的数值模拟[J]. 海洋地质与第四纪地质,2023,43(1): 180-189. DOI: 10.16562/j.cnki.0256-1492.2022050701
HE Wen,CAO Yuncheng,CHEN Duofu. Modelling of triggering of Orca submarine landslide, Cascadia margin, northeast Pacific[J]. Marine Geology & Quaternary Geology,2023,43(1):180-189. DOI: 10.16562/j.cnki.0256-1492.2022050701
Citation: HE Wen,CAO Yuncheng,CHEN Duofu. Modelling of triggering of Orca submarine landslide, Cascadia margin, northeast Pacific[J]. Marine Geology & Quaternary Geology,2023,43(1):180-189. DOI: 10.16562/j.cnki.0256-1492.2022050701

东北太平洋Cascadia陆缘Orca滑坡触发机理的数值模拟

基金项目: 国家重点研发项目“中国海域冷泉系统演变过程及其机制”(2018YFC0310006);国家自然科学基金项目“南海北部冷泉和天然气水合物发育区海底浅表层沉积物碳循环数值模拟”(41730528),“马里亚纳弧前海底蛇纹岩泥火山无机成因甲烷形成水合物的条件及潜力分析”(41776050),“冲绳海槽海底冷泉-热液系统相互作用及资源效应”(91858208)
详细信息
    作者简介:

    何雯(1997—),女,硕士研究生,主要从事天然气水合物模拟研究,E-mail:m190200563@st.shou.edu.cn

    通讯作者:

    曹运诚(1983—),男,副研究员,主要从事天然气水合物数值模拟研究,E-mail: yccao@shou.edu.cn

  • 中图分类号: P736

Modelling of triggering of Orca submarine landslide, Cascadia margin, northeast Pacific

  • 摘要: 海底温度和海平面变化可以引起海底天然气水合物分解,导致沉积物孔隙内形成超压,改变沉积物有效应力从而触发海底滑坡。本文建立了与此相关的海底滑坡产生的数值模型,并应用于东北太平洋Cascadia陆缘14~9 kaBP期间发生的Orca滑坡形成过程研究。模拟结果显示在最近18 ka海平面逐渐上升的大背景下,18~14 kaBP期间底水温度升高引起其后的天然气水合物稳定带底界快速上移,并在13.7 kaBP达到1.18 m/ka的高底界上移速率,此时Orca地区稳定带底界粗颗粒层内的高饱和度天然气水合物发生分解,产生114 kPa的流体超压,使地层安全系数显著小于1,触发海底滑坡。因此,海底温度升高引起高饱和度天然气水合物分解可能是东北太平洋Cascadia陆缘Orca海底滑坡的主要触发因素。
    Abstract: Bottom-water temperature variations and eustatic sea-level fluctuations may cause decomposition of marine gas hydrate and excess pore pressure in sediment, which leads to a subsequent decrease in effective stress of the sediment, and eventually results in submarine landslides. A numerical modeling of the mechanism of such slope failure was developed herein, and was applied to the study of Orca Slide that occurred between 14 and 9 kaBP on the Cascadia margin in the northeast Pacific. The modeling results show that with the rising sea level in the last 18 ka, the base of hydrate stability zone (BHSZ) experienced a fast upward movement whose rising rate peaked to 1.18 m/ka at 13.7 kaBP due to continuous bottom-water warming during 18~14 kaBP. Meanwhile, an excess pore pressure of 114 kPa was formed in the coarse-grained layers in the BHSZ of Orca Slide as a result of gas hydrate decomposition, which then significantly reduced the factor of safety of the strata to less than 1, thereby triggering the submarine landslides. Therefore, highly saturated hydrate decomposition caused by the bottom-water temperature rise may be the main triggering mechanism of Orca submarine landslide.
  • 东海陆架盆地位于欧亚、太平洋和印度三大板块交汇处,构造演化历史复杂,具有多期次、多类型的构造演化特征[1],是一个中、新生代的非继承性的叠合盆地,面积约46×104 km2,沉积厚度达10 000 m以上。区域上新生代表现为NNE向隆、凹相间的特征,东海陆架盆地南部新生代盆地由6个二级构造单元组成[2-5],从西到东到南分别为:瓯江凹陷、雁荡低凸起、闽江凹陷、台北低凸起、基隆凹陷和观音凸起(图1)。近年来,随着对中生代油气勘探新领域新层系的重视、地震资料采集和处理技术的不断提高以及海陆中生代地层对比研究的不断深入,东海中生代地层和构造单元属性展现出与新生代明显不同的特征[6-12]。地震资料综合解释认为,瓯江凹陷与其东侧的闽江凹陷在中生代地层、构造、沉积、火山岩等方面存在较大差异,而与西侧的浙闽隆起在大地构造背景、白垩纪沉积建造等方面具有较多的相似性。由于不同的构造单元具有不同的油气富集规律,因此,厘清瓯江凹陷构造单元属性具有重要的理论和实际意义。为此,本文通过地震剖面解释、平衡剖面分析、海陆对比等研究手段,探讨东海陆架盆地瓯江凹陷中生代构造单元的属性。

    图  1  东海陆架盆地南部新生代构造区划图(据文献[2])(由西到东到南构造单元为:瓯江凹陷、雁荡低凸起、闽江凹陷、台北低凸起、基隆凹陷及观音凸起)
    Figure  1.  Cenozoic tectonic map of southern East China Sea Shelf Basin(after reference [2])(Note: The tectonic units from west to east and south are: Minjiang Sag, Yandang Low Uplift, Qujiang Sag, Taipei Low Uplift, Jilong Sag and Guanyin Uplift)

    瓯江凹陷位于东海陆架盆地南部西侧,总体上为NE—SW向展布,西邻浙闽隆起,东接雁荡低凸起,面积约3.5×104 km2,发育南北2个次凹,为明显的“东断西超”断陷盆地,从北到南中海油称之为椒江凹陷和丽水凹陷,中石化上海分公司称之为钱塘凹陷和瓯江凹陷,本文统称为瓯江凹陷。从穿越东海陆架盆地南部所有构造单元的地震测线CX01和CX02线来看[10]图2图3),瓯江凹陷断陷结构特征明显,主要发育白垩纪地层,沉积中心位于断陷东部,厚达3 000~4 000 m,平均厚度500~1 000 m[13]。从图2图3来看,瓯江凹陷东侧的闽江凹陷除了发育有白垩纪地层以外,还有厚度较大的侏罗纪地层。构造上呈向东倾斜的单斜,中生界向东加厚,沉积中心位于基隆凹陷。

    图  2  CX01地震相解释结果(据文献[10])
    Figure  2.  Seismic facies interpretation results of CX01 line(after reference [10])
    图  3  CX02地震相解释结果(据文献[10])
    Figure  3.  Seismic facies interpretation results of CX01 line(after reference [10])

    根据东海陆架盆地南部地震反射特征和钻井(FZ13-2-1和FZ10-1-1井)揭示的沉积特征,建立了东海陆架盆地南部中生界地震相解释模板(图4),并开展了地震相—沉积相解释。解释结果显示,瓯江凹陷中生界地震反射特征为变振幅较连续—断续的楔状相和充填相,以冲积扇相沉积为主;东部的闽江凹陷和基隆凹陷中生界反射特征主要为中—强振幅较连续—断续的席状相,以滨浅海相沉积为主。由此可见,东海陆架盆地南部侏罗系主要发育浅海相、海陆过渡相以及火山岩相,从NW到SE方向中生代沉积环境逐渐由陆相过渡为海相[10]。同时,从中生代地层的剖面特征和沉积相分布来看,瓯江凹陷与其东侧的其他凹陷具有较大的差异。同时,区内主要发育伸展、挤压及复合3种构造样式[14],属于张扭型盆地[15]

    图  4  东海陆架盆地南部中生界地震相解释模板
    Figure  4.  Mesozoic seismic facies interpretation template for southern East China Sea Shelf Basin

    运用平衡剖面可以获取各构造演化阶段的构造变形和展布特征,对深入分析构造变形演化历史和构造单元的属性具有重要的作用。从穿过新生代各构造单元的CX03线的平衡剖面来看,瓯江凹陷构造演化经历了裂陷阶段、裂后期沉降阶段、抬升阶段和区域沉降阶段[12, 16]。侏罗纪时瓯江凹陷为隆起区,未接受沉积,而东部的闽江和基隆凹陷为一整体,沉积中心位于基隆凹陷,侏罗系最大厚度近2 200 m。白垩纪时瓯江凹陷和闽江凹陷在剖面上表现为一种复式箕状断陷的构造样式,断裂发育,地层向西逐渐减薄乃至尖灭,超覆特征明显,而向东则逐渐加厚。火山活动瓯江凹陷晚,而闽江凹陷早(图5)。

    图  5  东海陆架盆地南部CX03线构造演化剖面图
    Figure  5.  Tectonic evolutionary section along the CX03 line in southern East China Sea Shelf Basin

    另外,前人研究认为[17],东海陆架盆地南部可以划分出4个NE和NNE向火山岩带,他们是:①浙闽隆起区;②中部隆起区;③钓鱼岛隆褶带;④琉球岛弧带。其中,由于瓯江凹陷火山岩与浙闽地区火山岩特征较为一致,火山活动主要在上新世,因此,推测瓯江凹陷火山岩属于浙闽隆起区的一部分,而由渔山凸起、观音凸起等构成的中部隆起区,火山活动主要在白垩纪晚期。

    由此可见,瓯江凹陷与东侧的闽江—基隆凹陷在沉积地层、构造演化以及火山岩发育时间上均存在较大差异,前者以白垩纪地层为主,后者白垩纪和侏罗纪地层兼而有之,且向东有加厚之趋势;前者以断陷为主,后者以凹陷为主;前者火山岩发育晚,后者火山岩发育早。

    闽江凹陷西邻雁荡低凸起,东接台北低凸起,面积约3.7×104 km2,发育南北2个次凹,具明显的“断坳转化”特征。从穿越东海陆架盆地南部构造单元的CX01和CX02地震剖面来看(图2图3),闽江凹陷不仅发育白垩纪地层,而且还沉积了较厚的侏罗纪地层。白垩系由西向东加厚,最大厚度2 500 m,一般厚度为750~2 000 m。侏罗系同样由西向东加厚,最大厚度2 000 m,一般厚度为0~1 900 m。从图2图3中可以看出,NE向的雁荡低凸起分割了闽江凹陷和瓯江凹陷,造成侏罗纪地层只分布在闽江凹陷及以东的区域,且超覆在雁荡低凸起之上[13],具有伸展型盆地的特征[14]。从图中还可以看出,闽江凹陷侏罗纪时断层不发育,白垩纪时断层发育,具有断坳转换的特征。

    另外,闽江凹陷南部有2口井(FZ10-1-1和FZ13-2-1)钻遇较厚的侏罗纪地层,岩心观察发现:中下侏罗统福州组为受海侵影响的半深湖/深湖相沉积环境,沉积了较厚的灰黑、黑色泥岩,而上白垩统为广阔的潮坪环境,沉积了灰白色粉砂岩(表1)。因此,从中生代地层的分布和断裂构造特征来看,闽江凹陷与瓯江凹陷具有较大的差异。

    表  1  东海陆架盆地南部中生代地层厚度及终孔深度(据文献[18-19])
    Table  1.  Mesozoic strata thickness and drilling holes depths in southern East China Sea Shelf Basin(after reference [18-19])
    位置 井号 地层厚度/m 终孔深度/m
    白垩系 侏罗系
    闽江凹陷 FZ13-2-1 909 978 3 523
    FZ10-1-1 451 1 092 3 523
    瓯江凹陷 SMT-1 265 3 353
      注:“−”表示未钻遇
    下载: 导出CSV 
    | 显示表格

    图5可以看出,侏罗纪时闽江凹陷与东部的基隆凹陷连为一体,沉积了较厚的侏罗纪地层,侏罗系最大厚度近2 000 m。白垩纪时闽江凹陷在剖面上表现为一种复式箕状断陷的构造样式,地层向西逐渐减薄乃至尖灭,断裂和火山岩发育,但整个中生代地层向东仍然有逐渐加厚的趋势(图5)。后期构造运动的改造导致闽江凹陷呈现出现今的盆地形态[20]。由此可见,瓯江凹陷与闽江凹陷在平衡剖面特征上存在较大差异,可以认为属于不同的构造单元。

    研究表明[21],浙闽隆起从晚三叠世到侏罗纪一直是隆起区,其上没有沉积,而浙闽隆起西部为河湖相沉积,隆起南部为浅海—滨海相的龙岩海湾沉积。白垩纪时浙闽隆起上沉积有火山岩或非火山岩的红色砂岩、沙砾岩、凝灰质砂砾岩夹中酸性火山岩。

    陆域中生代发生了4次大规模的构造运动:中—晚三叠世之间的印支运动和中—晚侏罗世之间的燕山Ⅰ幕运动在浙闽隆起都表现为隆升作用,未沉积三叠纪—侏罗纪地层;早白垩世早期火山活动相对较弱,浙闽隆起上沉积了巨厚的火山岩;早白垩世中晚期发生燕山Ⅱ幕运动,火山喷发和岩浆侵入强烈,造成十分强烈的褶皱和变形。晚白垩世发生了燕山Ⅲ幕运动,形成NE和NNE断裂带,以断裂变动为主,褶皱变形次之,大规模的火山活动是其最显著的特点。

    前已述及,瓯江凹陷主要发育陆相白垩纪地层,而闽江凹陷除了发育白垩纪地层外,还发育有侏罗纪地层,白垩纪和侏罗纪地层往东增厚,其沉积环境属海陆过渡相—海相。瓯江凹陷为“东断西超”断陷盆地,闽江凹陷为断坳转换盆地。

    从盆地演化历史来看,瓯江凹陷在侏罗纪时为隆起区,与其西侧的浙闽隆起一样缺少沉积;白垩纪时期,瓯江凹陷进入初始开裂阶段[22],火山喷发和岩浆侵入频繁,沉积了一套火山岩—陆相红色碎屑岩,白垩系残留厚度较薄而稳定[23]。闽江凹陷在白垩纪和侏罗纪沉积了较厚地层。其中,雁荡低凸起是侏罗系的西部边界[13],也是闽江凹陷和瓯江凹陷中生界沉积和构造演化的分界线[24-25]

    据分析[22],太平洋板块在1.25~0.7亿年沿亚洲大陆边缘作NWW向俯冲,0.7~0.43亿年转为向N俯冲,0.43亿年之后转为NW向俯冲。在此期间,浙闽隆起上发育了永康型(NNE向坳陷式)火山岩—沉积碎屑岩盆地(K1中晚期—K2),随后在浙西北发育了金衢型(NEE向地堑式)红盆(K1晚期—K2),再后在东面的滨海发育了瓯江型(NE向地堑式)红盆(K2中晚期)。

    由此可见,瓯江凹陷在中生代时与浙闽隆起处于相似的大地构造背景,侏罗纪时均处于隆起剥蚀,白垩纪时均处于断裂拉张[26]。二者具有相似的构造运动特征(断裂为主、褶皱为辅)、相似的断裂方向(主要为NE和NEE),因此,推测瓯江凹陷是浙闽隆起的一部分(表2)。

    表  2  浙闽隆起区、瓯江凹陷及闽江凹陷中生代地层、构造、岩浆活动等对比
    Table  2.  Comparison of Mesozoic strata, tectonics, magmatic activities etc. between Zhejiang-Fujian Uplift Belt, Oujiang Sag and Minjiang Sag
    凹陷/隆起 中生代地层分布 中生界沉积相 侏罗纪时地形 白垩纪岩浆活动时间及强度 白垩纪沉积建造 断裂构造特征
    瓯江凹陷 白垩系 陆相 隆起 晚、弱 火山岩—红色碎屑岩 断陷
    浙闽隆起 白垩系 陆相 隆起 晚、强 火山岩—红色碎屑岩 断裂为主
    闽江凹陷 白垩系+侏罗系 海陆过渡相—海相 沉降 早、强 火山岩—深灰色碎屑岩 断坳转化
    下载: 导出CSV 
    | 显示表格

    东海陆架盆地紧邻西太平洋活动大陆边缘火山岩带的东侧。该大陆边缘形成始自印支期华北与华南板块的拼合,之后,全区规模巨大、时间集中(主要在晚侏罗世—早白垩世)的燕山期陆相火山活动形成了中国东部巨型火山岩带。

    上白垩统在福建地区自下而上包括均口组、沙县组和崇安组[27]。均口组为白垩纪红盆,岩性以浅灰、灰绿、灰黑色粉砂岩、钙质粉砂岩、粉砂质泥岩为主,夹泥灰岩及紫红色粉砂岩。沙县组为内陆盆地紫红色细碎屑沉积,岩性以紫红色粉砂岩、泥岩为主,夹砂砾岩、长石石英砂岩及黄绿色粉砂岩、细砂岩、凝灰岩。崇安组为陆相红盆厚层粗碎屑沉积,岩性为紫红色厚层砂砾岩、砾岩夹中—薄层细砂岩、粉砂岩,风化后常形成丹霞地貌。通过岩性组合特征判断,福建地区晚白垩世主要为干燥炎热氧化环境下形成的河、湖相红色碎屑沉积,后期发育冲积扇粗碎屑沉积。

    上白垩统在福建以北的浙江南部地区为衢江群,自下而上划分为中戴组、金华组和衢县组。中戴组岩性为紫红色厚层块状砾岩、砂砾岩、细砂岩、粉砂岩夹粉砂质泥岩,下部偶夹火山岩。金华组岩性为浅灰紫色薄层粉砂质泥岩(图6)、泥质粉砂岩、粉砂岩夹细砂岩及灰绿、浅灰、灰黑色泥岩。衢县组岩性为棕褐、棕红色厚层至块状砂岩、粉砂岩、含砾砂岩、砂砾岩及砾岩。通过岩性组合特征判断,浙江南部地区上白垩统主要为河流相沉积。

    图  6  浙江省龙游县高仙塘上白垩统金华组紫红色含砾粗砂岩
    Figure  6.  Purple red pebbly coarse sandstone of the Upper Cretaceous Jinhua Formation in Gaoxiantang, Longyou County, Zhejiang Province

    上白垩统在福建以南的粤东地区自下而上为优胜组和叶塘组。优胜组由流纹质凝灰岩、流纹岩、流纹—英安质熔岩等组成,以流纹岩分布最广。叶塘组岩性以紫红色粉砂岩、钙质粉砂岩、粉砂质泥岩夹灰绿或深灰色钙质泥岩、粉砂质泥质灰岩和石膏薄层为主。通过岩性组合特征判断,粤东地区在晚白垩世早期,仍然受到火山活动影响,发育火山喷发相沉积,至晚白垩世晚期,发育一套湖泊相碎屑岩沉积。

    总体看来,浙闽陆区晚白垩世仍受到火山活动影响,属于白垩系陆相红色沉积,沉积物以紫红色—红色为主。

    目前,瓯江凹陷钻遇白垩系的钻井只有几口。其中,位于瓯江凹陷北部的FY1井,自下而上钻遇了下白垩统渔山组、上白垩统闽江组和石门潭组。渔山组厚约600 m,上部为棕红、棕褐色泥岩夹灰色粉砂岩,下部为厚层状浅灰色、灰白色砂砾岩夹棕红色泥岩。闽江组和石门潭组厚约2 000 m,总体表现为大段的褐色、棕红色泥岩、粉砂质泥岩与灰色含砾岩屑中砂岩互层,局部含杂色砂砾岩。砂砾岩成分为石英、岩屑,砾石成分主要为火山岩屑,颜色有肉红色、灰白色、灰黑色等,分选差,次棱角状,泥质胶结,较致密。含砾岩屑砂岩中,岩屑有霏细岩、流纹岩、英安岩、安山岩、千枚岩、晶屑凝灰岩,砾径最大10 mm,胶结物为高岭土及少量铁白云石,致密。泥岩质不纯,局部含岩屑斑块及石英斑晶,岩屑有千枚岩、安山岩、英安岩等中酸性火山岩。而位于瓯江凹陷南部的石门潭1井钻遇一套杂色的上白垩统石门潭组碎屑岩,由棕红色泥岩夹灰白色砂岩组成,厚265 m[18-19]

    瓯江凹陷的火山岩主要为喷出岩与侵入岩[28]。推测闽江组发育的沉积体系类型为扇三角洲或者近岸水下扇,整体表现为一套陆相红色碎屑岩沉积,夹有火山喷发岩及火山碎屑岩。与浙闽隆起带上白垩统沉积较为类似。同时,也有学者对瓯江凹陷物源开展分析认为,物源主要来自邻近的华南[29-30]

    FZ13-2-1井位于闽江凹陷南部,在上白垩统闽江组钻取了6 m岩心。岩心总体为灰白色粉砂岩系,局部有很薄的灰黑、黑色泥质纹层,另外有2~3个中粗砂的滞留沉积。其中粉砂岩粒度细而颜色浅,肉眼观察岩性纯,石英含量高,长石、岩屑含量低。沉积构造多见冲刷面、波状槽状层理、前积纹层、虫孔发育、局部见双向泥纹层和非对称羽状交错层理。同时可以在岩心上观察到海相矿物海绿石及海相微体古生物丁丁虫,综合判定,当时的沉积环境为滨浅海环境(图7[31]

    图  7  闽江凹陷FZ13-2-1井白垩系海绿石显微照片(据文献[31])
    Figure  7.  Photomicrograph of Cretaceous glauconite from Well FZ13-2-1 in Minjiang Sag(after reference [31])

    镜鉴结果表明,闽江组岩心火山碎屑物质含量为30%。岩屑类型主要是火山岩岩屑和少量变质岩岩屑。火山碎屑以中酸性喷出岩为主,包括酸性喷出岩—流纹岩岩屑、中性喷出岩—安山岩岩屑、基性喷出岩—玄武岩岩屑和一些塑性变形岩屑。变质岩岩屑包括热变质岩屑—石英岩岩屑,浅动力变质岩—云母片岩岩屑。

    通过FZ13-2-1井观察到的大量的火山变质岩岩屑和长石石英晶屑,说明闽江凹陷中生界白垩系闽江组受火山作用影响,且FZ13-2-1井矿物颗粒分选中—差,次棱角—次圆,说明距离物源很近。因此,FZ13-2-1井在沉积时应该受到两方面物源的影响,一部分来自于正常的浅水碎屑物质,另一部分来自于火山喷发形成的火山碎屑物质,很少有来自于浙闽隆起带的物源供给。

    综上,瓯江凹陷晚白垩世沉积环境与浙闽隆起带相似,均属于陆相红层沉积和火山岩沉积,而闽江凹陷则属于滨浅海环境下的水下含火山岩岩屑的碎屑沉积,从而推测,瓯江凹陷白垩纪时期可能属于浙闽隆起带的一部分,而有别于东部的中生代闽江凹陷(表2)。由于闽江凹陷发育侏罗纪的烃源岩,因此,推测闽江凹陷中生代的油气资源潜力好于瓯江凹陷[26, 32-34]

    (1)地震剖面上,瓯江凹陷为以白垩系为主体的陆相断陷盆地,具有“东断西超”的特征,沉积地层以陆相红层为主;而闽江凹陷除了白垩系外,还有厚度较大的侏罗系,构造上具有“断坳转换”的特征,与其东侧的基隆凹陷构成一个整体,沉积环境为海陆过渡相和海相。

    (2)平衡剖面上,侏罗纪瓯江凹陷为隆起区,缺少沉积,而闽江凹陷为凹陷区,沉积了较厚的侏罗系;白垩纪瓯江凹陷断裂发育,闽江凹陷及其东侧的基隆凹陷断裂和火山活动同时发育。

    (3)海陆对比显示,瓯江凹陷在中生代时与浙闽隆起处于相似的大地构造背景,侏罗纪时均处于隆升剥蚀,白垩纪时均处于断裂拉张。二者具有相似的构造运动特征(断裂为主、褶皱为辅)、相似的断裂方向(主要为NE和NEE),相似的沉积建造(火山岩—红色碎屑岩)。

    (4)沉积特征对比结果显示,瓯江凹陷与浙闽隆起在白垩纪时期均属陆相红层沉积和火山岩沉积,而闽江凹陷属于滨浅海环境下的水下含火山岩岩屑的碎屑沉积。

    (5)综上所述,推测瓯江凹陷属于浙闽隆起带的一部分。

  • 图  1   海底斜坡受力示意图

    Figure  1.   Stresses on a submarine slope

    图  2   东北太平洋Cascadia北部陆缘Orca地区的地质背景和U1326站位地质特征

    a: Orca滑坡地理位置,其中北太平洋深层水(NPDW)的分布据文献[50] ;b: Orca滑坡水深图据文献[36],黄色点为U1326站位,下方为Orca滑坡; c: U1326站位地层岩性[45]显示了很好的层状和透镜状的砂体与粉砂质黏土的互层; d: U1326站位水合物饱和度随深度分布,其中高饱和度水合物发育在底部、中部和顶部,达0.4以上[47]。GHOZ:水合物赋存区; GHSZ:水合物稳定带。

    Figure  2.   Geological setting of the Orca area in the northern continental margin of Cascadia in northeast Pacific and geological characteristics of the site U1326

    a: Location of the Orca Slide and the distribution of NPDW [50]; b: bathymetry of the Orca Ridge [36]. Yellow dot indicates the location of the site U1326, below which southward is the Orca Slide; c: stratigraphic lithology at the site U1326 showing intercalation between silty clay layers and lenticular sand layers [45]; d: the distribution of hydrate saturation with depth at the site U1326 and high-saturation hydrate formation at the bottom, middle, and top of GHOZ and reaches more than 0.4[47] . GHOZ: gas hydrate occurrence zone, GHSZ: gas hydrate stability zone.

    图  3   东北太平洋Cascadia北部陆缘Orca地区18 ka以来水合物稳定带底界变化

    a: 相对海平面[54](以现今海平面高度为0),b: 底水温度和275 mbsf的稳定带底界温度,c: 以水合物饱和度为0.056和0.4模拟计算的稳定带底界深度。灰色区域为主要稳定带底界上移时期。

    Figure  3.   The dynamic changes of BHSZ in the Orca area over the last 18 ka

    a: Relative sea level curve [54] (the present-day sea level is considered to be zero), b: the time record of the bottom-water temperature and sediment temperature at 275mbsf, c: the modeled depth of BHSZ at Sh=0.056 and Sh=0.4 respectively. The grey area illustrates the time span of upward movement of BHSZ.

    图  4   东北太平洋Cascadia北部陆缘Orca地区不同水合物饱和度条件下的底界移动速率(a)、 超压(b)和地层安全系数(c)

    底界移动速率<0代表水合物分解,稳定带向上移动;底界移动速率>0代表水合物生成,稳定带向下移动灰色区域为定年确定的滑坡发生时间(14~9 kaBP)[48]

    Figure  4.   a: The movement rate of BHSZ; b: excess pore pressure; c: factor of safety under different hydrate saturation conditions in the Orca area, the northern continental margin of Cascadia in northeast Pacific

    A movement rate of BHSZ less than zero suggests hydrate decomposition and an upward moving trend of the depth of BHSZ. In the contrary, a movement rate of BHSZ greater than 0 means hydrate formation and a downward moving trend of the depth of BHSZ. The grey area represents the Orca Slide age estimated by radiocarbon dating (14~9 kaBP) [48].

    表  1   模型使用的地质参数及其取值

    Table  1   Geological parameters and their values used in the model

    符号参数名称参数取值
    Sh水合物饱和度0.056[47]
    α热扩散系数1×10−6 m2/s[51]
    S海水盐度33 PSU[52]
    ZBHSZ水合物稳定带底界深度275 mbsf[45]
    $ {\mu _{\text{f}}} $流体粘度8.87×10−4 Pa·s[34]
    $ \phi $沉积物孔隙度0.54[45]
    $ k $沉积层渗透率1.0×10−17 m2[36]
    G地温梯度0.06℃/m[52]
    θ滑坡前地层倾角20°[35]
    C内聚力105 kPa[53]
    φ摩擦角18°[53]
    下载: 导出CSV
  • [1]

    Nisbet E G, Piper D J W. Giant submarine landslides [J]. Nature, 1998, 392(6674): 329-330. doi: 10.1038/32765

    [2]

    Luo M, Torres M E, Kasten S, et al. Constraining the age and evolution of the Tuaheni landslide complex, Hikurangi Margin, New Zealand, using pore-water geochemistry and numerical modeling [J]. Geophysical Research Letters, 2020, 47(11): e2020GL087243.

    [3]

    Wharton W J L, Geikie A, Perry P, et al. Sub-oceanic changes: discussion [J]. The Geographical Journal, 1897, 10(3): 285-289. doi: 10.2307/1774772

    [4]

    Herzer R H. Uneven submarine topography south of Mernoo Gap—the result of volcanism and submarine sliding [J]. New Zealand Journal of Geology and Geophysics, 1975, 18(1): 183-188. doi: 10.1080/00288306.1975.10426354

    [5]

    Barrier A, Bischoff A, Nicol A, et al. Relationships between volcanism and plate tectonics: a case-study from the Canterbury Basin, New Zealand [J]. Marine Geology, 2021, 433: 106397. doi: 10.1016/j.margeo.2020.106397

    [6]

    McIver R D. Role of naturally occurring gas hydrates in sediment transport [J]. AAPG Bulletin, 1982, 66(6): 789-792.

    [7]

    Elger J, Berndt C, Rüpke L, et al. Submarine slope failures due to pipe structure formation [J]. Nature Communications, 2018, 9(1): 715. doi: 10.1038/s41467-018-03176-1

    [8] 唐常锐, 徐秀刚, 孙秉才, 等. 天然气水合物分解诱发海底滑坡影响因素分析及致灾风险评价[J]. 海洋地质前沿, 2021, 37(5):14-21 doi: 10.16028/j.1009-2722.2021.021

    TANG Changrui, XU Xiugang, SUN Bingcai, et al. Influence factors and risk assessment for seabed landslides induced by natural gas hydrate decomposition [J]. Marine Geology Frontiers, 2021, 37(5): 14-21. doi: 10.16028/j.1009-2722.2021.021

    [9]

    Hance J J. Development of a database and assessment of seafloor slope stability based on published literature[D]. Doctor Dissertation of University of Texas, 2003.

    [10]

    Mulder T, Cochonat P. Classification of offshore mass movements [J]. Journal of Sedimentary Research, 1996, 66(1): 43-57.

    [11]

    Locat J, Lee H, Kayen R, et al. Shear strength development with burial in eel river margin slope sediments [J]. Marine Georesources & Geotechnology, 2002, 20(2): 111-135.

    [12] 秦志亮, 孙思军, 谭骏, 等. 西沙群岛海域海洋地质灾害现状与对策[J]. 海洋开发与管理, 2014, 31(9):12-16 doi: 10.3969/j.issn.1005-9857.2014.09.03t

    QIN Zhiliang, SUN Sijun, TAN Jun, et al. Current situation and countermeasures of marine geological disasters in the Xisha Paracel Islands [J]. Ocean Development and Management, 2014, 31(9): 12-16. doi: 10.3969/j.issn.1005-9857.2014.09.03t

    [13]

    Chen Y M, Zhang L L, Liao C C, et al. A two-stage probabilistic approach for the risk assessment of submarine landslides induced by gas hydrate exploitation [J]. Applied Ocean Research, 2020, 99: 102158. doi: 10.1016/j.apor.2020.102158

    [14] 陈泓君, 黄磊, 彭学超, 等. 南海西北陆坡天然气水合物调查区滑坡带特征及成因探讨[J]. 热带海洋学报, 2012, 31(5):18-25 doi: 10.3969/j.issn.1009-5470.2012.05.004

    CHEN Hongjun, HUANG Lei, PENG Xuechao, et al. Discussion of characteristics and formation of landslide zones in the gas hydrate survey area of northwest continental slope, the South China Sea [J]. Journal of Tropical Oceanography, 2012, 31(5): 18-25. doi: 10.3969/j.issn.1009-5470.2012.05.004

    [15]

    Yang L L, Wang J, Jiang Y H. Experimental study and numerical simulation of overlying layer soil failure caused by hydrate decomposition [J]. ACS Omega, 2020, 5(48): 31244-31253. doi: 10.1021/acsomega.0c04619

    [16]

    Dickens G R. The potential volume of oceanic methane hydrates with variable external conditions [J]. Organic Geochemistry, 2001, 32(10): 1179-1193. doi: 10.1016/S0146-6380(01)00086-9

    [17] 陈多福, 姚伯初, 赵振华, 等. 珠江口和琼东南盆地天然气水合物形成和稳定分布的地球化学边界条件及其分布区[J]. 海洋地质与第四纪地质, 2001, 21(4):73-78 doi: 10.16562/j.cnki.0256-1492.2001.04.014

    CHEN Duofu, YAO Bochu, ZHAO Zhenhua, et al. Geochemical constraints and potential distributions of gas hydrates in Pearl River Mouth Basin and Qiongdongnan Basin in the northern margin of the South China Sea [J]. Marine Geology & Quaternary Geology, 2001, 21(4): 73-78. doi: 10.16562/j.cnki.0256-1492.2001.04.014

    [18] 刘杰, 刘丽华, 吴能友, 等. 南海东沙海域深水区末次冰期以来天然气水合物稳定带演化[J]. 海洋地质与第四纪地质, 2021, 41(2):146-155 doi: 10.16562/j.cnki.0256-1492.2020061801

    LIU Jie, LIU Lihua, WU Nengyou, et al. Evolution of gas hydrate stability zone in the deep water of Dongsha sea area since the Last Glaciation Maximum [J]. Marine Geology & Quaternary Geology, 2021, 41(2): 146-155. doi: 10.16562/j.cnki.0256-1492.2020061801

    [19]

    Sultan N, Cochonat P, Foucher J P, et al. Effect of gas hydrates melting on seafloor slope instability [J]. Marine Geology, 2004, 213(1-4): 379-401. doi: 10.1016/j.margeo.2004.10.015

    [20]

    Sultan N, Marsset B, Ker S, et al. Hydrate dissolution as a potential mechanism for pockmark formation in the Niger delta [J]. Journal of Geophysical Research:Solid Earth, 2010, 115(B8): B08101.

    [21] 宋海斌. 天然气水合物体系动态演化研究(Ⅱ): 海底滑坡[J]. 地球物理学进展, 2003, 18(3):503-511 doi: 10.3969/j.issn.1004-2903.2003.03.028

    SONG Haibin. Researches on dynamic evolution of gas hydrate system (Ⅱ): submarine slides [J]. Progress in Geophysics, 2003, 18(3): 503-511. doi: 10.3969/j.issn.1004-2903.2003.03.028

    [22]

    Kayen R E, Lee H J. Pleistocene slope instability of gas hydrate-laden sediment on the Beaufort sea margin [J]. Marine Geotechnology, 1991, 10(1-2): 125-141. doi: 10.1080/10641199109379886

    [23]

    Hornbach M J, Lavier L L, Ruppel C D. Triggering mechanism and tsunamogenic potential of the Cape Fear Slide complex, U. S. Atlantic margin [J]. Geochemistry, Geophysics, Geosystems, 2007, 8(12): Q12008.

    [24]

    Leslie S C, Mann P. Giant submarine landslides on the Colombian margin and tsunami risk in the Caribbean Sea [J]. Earth and Planetary Science Letters, 2016, 449: 382-394. doi: 10.1016/j.jpgl.2016.05.040

    [25] 倪玉根, 夏真, 马胜中. 与天然气水合物分解有关的海底滑坡和气候突变事件[J]. 南海地质研究, 2013(1):73-81

    NI Yugen, XIA Zhen, MA Shengzhong. The submarine landslides and climate change events related to gas hydrate dissociation [J]. Gresearch of Eological South China Sea, 2013(1): 73-81.

    [26]

    Mienert J, Vanneste M, Bünz S, et al. Ocean warming and gas hydrate stability on the mid-Norwegian margin at the Storegga Slide [J]. Marine and Petroleum Geology, 2005, 22(1-2): 233-244. doi: 10.1016/j.marpetgeo.2004.10.018

    [27]

    Guan H X, Liu L, Hu Y, et al. Rising bottom-water temperatures induced methane release during the middle Holocene in the Okinawa Trough, East China Sea [J]. Chemical Geology, 2022, 590: 120707. doi: 10.1016/j.chemgeo.2022.120707

    [28] 李天赐, 孔亮, 赵新波, 等. 考虑超孔压影响的海底能源土斜坡稳定性数值模拟和评价[J]. 科学技术与工程, 2019, 19(5):253-260 doi: 10.3969/j.issn.1671-1815.2019.05.039

    LI Tianci, KONG Liang, ZHAO Xinbo, et al. Numerical simulation and evaluation of the stability of submarine energy soil slope considering the effect of the excess pore pressure [J]. Science Technology and Engineering, 2019, 19(5): 253-260. doi: 10.3969/j.issn.1671-1815.2019.05.039

    [29]

    Grozic J L H. Interplay between gas hydrates and submarine slope failure[M]//Mosher D C, Shipp R C, Moscardelli L, et al. Submarine Mass Movements and Their Consequences. Dordrecht: Springer, 2010: 11-30.

    [30] 宋晓帅, 孙志文, 朱超祁, 等. 深海滑坡研究进展[J]. 海洋地质与第四纪地质, 2022, 42(1):222-235 doi: 10.16562/j.cnki.0256-1492.2021062701

    SONG Xiaoshuai, SUN Zhiwen, ZHU Chaoqi, et al. A review on deepwater landslide [J]. Marine Geology & Quaternary Geology, 2022, 42(1): 222-235. doi: 10.16562/j.cnki.0256-1492.2021062701

    [31]

    Grozic J L H, Kvalstad T J. Effect of gas on deepwater marine sediments[C]//Proceedings of the International Conference on Soil Mechanics and Geotechnical Engineering. 2001: 2289-2294.

    [32]

    Kwon T H, Cho G C, Santamarina J C. Gas hydrate dissociation in sediments: pressure-temperature evolution [J]. Geochemistry, Geophysics, Geosystems, 2008, 9(3): Q03019.

    [33]

    Nixon M F, Grozic J L H. Submarine slope failure due to gas hydrate dissociation: a preliminary quantification [J]. Canadian Geotechnical Journal, 2007, 44(3): 314-325. doi: 10.1139/t06-121

    [34]

    Xu W Y, Germanovich L N. Excess pore pressure resulting from methane hydrate dissociation in marine sediments: a theoretical approach [J]. Journal of Geophysical Research:Solid Earth, 2006, 111(B1): B01104.

    [35]

    López C, Spence G, Hyndman R, et al. Frontal ridge slope failure at the northern Cascadia margin: margin-normal fault and gas hydrate control [J]. Geology, 2010, 38(11): 967-970. doi: 10.1130/G31136.1

    [36]

    Scholz N A. Submarine landslides offshore Vancouver Island, British Columbia and the possible role of gas hydrates in slope stability[D]. Doctor Dissertation of University of Victoria, 2014.

    [37] 苏正. 海洋天然气水合物分布及渗漏动力学数值模拟[D]. 中国科学院大学博士学位论文, 2008.

    SU Zheng. Numerical computation on gas hydrate distribution and gas venting dynamics in marine environment[D]. Doctor Dissertation of Chinese Academy of Sciences, 2008.

    [38]

    Sun S C, Zhao J, Yu D J. Dissociation enthalpy of methane hydrate in salt solution [J]. Fluid Phase Equilibria, 2018, 456: 92-97. doi: 10.1016/j.fluid.2017.10.013

    [39]

    Tishchenko P, Hensen C, Wallmann K, et al. Calculation of the stability and solubility of methane hydrate in seawater [J]. Chemical Geology, 2005, 219(1-4): 37-52. doi: 10.1016/j.chemgeo.2005.02.008

    [40] 王淑红, 宋海斌, 颜文. 天然气水合物稳定带的计算方法与参数选择探讨[J]. 现代地质, 2005, 19(1):101-107 doi: 10.3969/j.issn.1000-8527.2005.01.015

    WANG Shuhong, SONG Haibin, YAN Wen. Discussion of the calculation methods and selection of parameters of the gas hydrate stability zone [J]. Geoscience, 2005, 19(1): 101-107. doi: 10.3969/j.issn.1000-8527.2005.01.015

    [41]

    Kaul N, Rosenberger A, Villinger H. Comparison of measured and BSR-derived heat flow values, Makran accretionary prism, Pakistan [J]. Marine Geology, 2000, 164(1-2): 37-51. doi: 10.1016/S0025-3227(99)00125-5

    [42]

    Waite W F, Santamarina J C, Cortes D D, et al. Physical properties of hydrate-bearing sediments [J]. Reviews of Geophysics, 2009, 47(4): RG4003.

    [43]

    Hyndman R D, Wang K. The rupture zone of Cascadia great earthquakes from current deformation and the thermal regime [J]. Journal of Geophysical Research:Solid Earth, 1995, 100(B11): 22133-22154. doi: 10.1029/95JB01970

    [44]

    Currie C A, Cassidy J F, Hyndman R D. A regional study of shear wave splitting above the Cascadia Subduction Zone: margin-parallel crustal stress [J]. Geophysical Research Letters, 2001, 28(4): 659-662. doi: 10.1029/2000GL011978

    [45]

    Riedel M, Collett T S, Malone M J, et al. Site U1326[R]. Proceedings of the Integrated Ocean Drilling Program, 2005: 311.

    [46]

    Expedition 311 Scientists. Expedition 311 summary[C]//Proceedings of the Integrated Ocean Drilling Program. Washington: Integrated Ocean Drilling Program Management International, Inc. , 2006: 1-68.

    [47]

    Malinverno A, Kastner M, Torres M E, et al. Gas hydrate occurrence from pore water chlorinity and downhole logs in a transect across the northern Cascadia margin (Integrated Ocean Drilling Program Expedition 311) [J]. Journal of Geophysical Research:Solid Earth, 2008, 113(B8): B08103.

    [48]

    Hamilton T S, Enkin R J, Riedel M, et al. Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications [J]. Canadian Journal of Earth Sciences, 2015, 52(6): 405-430. doi: 10.1139/cjes-2014-0131

    [49]

    Scholz N A, Riedel M, Urlaub M, et al. Submarine landslides offshore Vancouver Island along the northern Cascadia margin, British Columbia: why preconditioning is likely required to trigger slope failure [J]. Geo-Marine Letters, 2016, 36(5): 323-337. doi: 10.1007/s00367-016-0452-8

    [50]

    Wan S, Jian Z M, Dang H W. Deep hydrography of the South China Sea and deep water circulation in the pacific since the last glacial maximum [J]. Geochemistry, Geophysics, Geosystems, 2018, 19(5): 1447-1463. doi: 10.1029/2017GC007377

    [51]

    Fowler C M R. The Solid Earth[M]. Cambridge: Cambridge University Press, 2005.

    [52]

    Riedel M, Novosel I, Spence G D, et al. Geophysical and geochemical signatures associated with gas hydrate-related venting in the northern Cascadia margin [J]. GSA Bulletin, 2006, 118(1-2): 23-38. doi: 10.1130/B25720.1

    [53]

    Geotechdata. Info[EB/OL]. http://geotechdata.info/parameter.html.

    [54]

    Waelbroeck C, Labeyrie L, Michel E, et al. Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records [J]. Quaternary Science Reviews, 2002, 21(1-3): 295-305. doi: 10.1016/S0277-3791(01)00101-9

    [55]

    Praetorius S K, Mix A C, Walczak M H, et al. North Pacific deglacial hypoxic events linked to abrupt ocean warming [J]. Nature, 2015, 527(7578): 362-366. doi: 10.1038/nature15753

    [56]

    Craig H, Gordon L I. Deuterium and oxygen 18 variations in the ocean and marine atmosphere[C]//Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Palaeo Temperatures. Spoleto Italy, 1965: 9-130.

    [57]

    Shackleton N J. Attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina: isotopic changes in the ocean during the last glacial [J]. Colloques Internationaux du C. N. R. S., 1974, 219: 203-209.

    [58]

    Elderfield H, Greaves M, Barker S, et al. A record of bottom water temperature and seawater δ18O for the Southern Ocean over the past 440kyr based on Mg/Ca of benthic foraminiferal Uvigerina spp [J]. Quaternary Science Reviews, 2010, 29(1-2): 160-169. doi: 10.1016/j.quascirev.2009.07.013

    [59]

    Vogt P R, Jung W Y. Holocene mass wasting on upper non-Polar continental slopes-due to post-Glacial ocean warming and hydrate dissociation? [J]. Geophysical Research Letters, 2002, 29(9): 1341.

    [60]

    Torres M E, Tréhu A M, Cespedes N, et al. Methane hydrate formation in turbidite sediments of northern Cascadia, IODP Expedition 311 [J]. Earth and Planetary Science Letters, 2008, 271(1-4): 170-180. doi: 10.1016/j.jpgl.2008.03.061

    [61]

    Handwerger A L, Rempel A W, Skarbek R M. Submarine landslides triggered by destabilization of high-saturation hydrate anomalies [J]. Geochemistry, Geophysics, Geosystems, 2017, 18(7): 2429-2445. doi: 10.1002/2016GC006706

    [62]

    Yelisetti S, Spence G D, Riedel M. Role of gas hydrates in slope failure on frontal ridge of northern Cascadia margin [J]. Geophysical Journal International, 2014, 199(1): 441-458. doi: 10.1093/gji/ggu254

    [63]

    Goldfinger C, Nelson C H, Johnson J E. Deep-water turbidites as Holocene earthquake proxies: the Cascadia subduction zone and Northern San Andreas Fault systems [J]. Annals of Geophysics, 2003, 46(5): 1169-1194.

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出版历程
  • 收稿日期:  2022-05-06
  • 修回日期:  2022-05-30
  • 录用日期:  2022-05-06
  • 网络出版日期:  2022-11-29
  • 刊出日期:  2023-02-27

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