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河流在洪水期携带大量陆源碎屑,当其入湖或入海后,由于洪水密度大于周围水体的密度,洪水 发生下沉并沿盆地底部长距离运移,形成陆源下潜流或异重流。异重流形成的相关沉积岩被统称为异 重岩。异重岩通常由一个底部的反粒序单元和一个顶部的正粒序单元组成,反粒序单元反映了异重流 能量的逐渐增强,正粒序反映了流体能量的逐渐减弱。异重流以3 种方式搬运碎屑颗粒,即底载搬运、悬浮搬运和漂浮搬运。根据搬运方式的不同,异重岩分为3 类岩相,即底载成因的B 类岩相、悬载成因 的S 类岩相和漂浮物成因的L 类岩相。异重流的沉积充填形成了河道、堤岸和朵叶体3 类微相,内部 岩相变化极为发育。异重岩的沉积特征虽然典型且较易识别,但是常被误认为是砂质碎屑流、滨岸相、三角洲相或河流相沉积。 Flooding river discharges a sediment-water mixture having a bulk density that often exceeds that of the water in the receiving water body. Consequently,when these flows enter a marine or lacustrine basin they plunge and move basinward as a land- derived underflow or hyperpycnal flow. Deposits related to hyperpycnal flows are hyperpycnites. Some fine hyperpycnites are composed of an inversely graded(waxing flow)basal unit,followed in transition by a normally graded(waning flow)unit.Three main facies families related to the three main elements that govern the movement of almost all sustained hyperpycnal discharges in marine settings:bedload,suspended load and lofting. These facies categories are here termed as B(bedload related sedimentary facies),S(suspended- load related sedimentary facies)and L(lofting related sedimentary facies). Hyperpycnites include three kinds of depositional elements:channel fill,lobes and levee deposits. Although hyperpycnites display typical and diagnostic characteristics that allow a clear recognition,these deposits are often misinterpreted in the literature as sandy debrites,shoreface,estuarine of fluvial deposits.
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30 1
2018 2
岩性油气藏
LITHOLOGIC RESERVOIRS Vol. 30 No. 1
Feb. 2018
Carlos 等:异重流成因和异重岩沉积特征
收稿日期:2017-09-18修回日期:2017-12-18
作者简介:Carlos Zavala1964-男,博士,教授,主要从事沉积学方面的教学 和科研 工作地址B8000JSZ阿根廷布宜诺斯艾利斯省
布兰卡港市Bahía BlancaCalle 1320Florida 1600Emailczavala@gcsargentina.com
文章编号:1673-8926201801-0001-18 DOI10.3969/j.issn.1673-8926.2018.01.001
引用:ZAVALA C潘树新 .异重流成因和异重岩沉积特征 .岩性油气藏,20183011-18.
Cite ZAVALA CPAN S X. Hyperpycnal flows and hyperpycnitesOrigin and distinctive characteristics. Lithologic Reservoirs
20183011-18.
异重流成因和异重岩沉积特征
Carlos Zavala12潘树新 3
1. GCS Argentina布兰卡港 B8000JSZ阿根廷;2. 阿根廷国立南方大学 地质学系,
布兰卡港 B8000CPB阿根廷;3. 中国石油勘探开发研究院 西北分院,兰州 730020
摘要:河流在洪水期携带大量陆源碎屑,当其入湖或入海后,由于洪水密度大于周围水体的密度,洪水
发生下沉并沿盆地底部长距离运移,形成陆源下潜流或异重流。异重流形成的相关沉积岩被统称为异
重岩。异重岩通常由一个底部的反粒序单元和一个顶部的正粒序单元组成,反粒序单元反映了异重流
能量的逐渐增强,正粒序反映了流体能量的逐渐减弱。异重流以 3种方式搬运碎屑颗粒即底载搬运、
悬浮搬运和漂浮搬运。根据搬运方式的不同,异重岩分为 3类岩相,即底载成因的 B类岩相、悬载成因
S类岩相和漂浮物成因的 L类岩相。异重流的沉积充填形成了河道、堤岸和朵叶体 3类微相,
岩相变化极为发育。异重岩的沉积特征虽然典型且较易识别,但是常被误认为是砂质碎屑流、滨岸相、
三角洲相或河流相沉积。
关键词:异重流;异重岩;浊流;深水沉积;内乌肯盆地;鄂尔多斯盆地;松辽盆地;西伯利亚盆地
中图分类号:TE121.3 文献标志码:A
Hyperpycnal flows and hyperpycnitesOrigin and
distinctive characteristics
Carlos Zavala12PAN Shuxin 3
1. GCS ArgentinaBahía Blanca B8000 JSZArgentina2. Geology DepartmentNational University of the South
Bahía Blanca B8000CPBArgentina3.PetroChina Research Institute of Petroleum Exploration &
Development-NorthwestLanzhou 730020China
AbstractFlooding river discharges a sediment-water mixture having a bulk density that often exceeds that of
the water in the receiving water body. Consequentlywhen these flows enter a marine or lacustrine basin they
plunge and move basinward as a land-derived underflow or hyperpycnal flow. Deposits related to hyperpycnal
flows are hyperpycnites. Some fine hyperpycnites are composed of an inversely gradedwaxing flowbasal
unitfollowed in transition by a normally gradedwaning flowunit.Three main facies families related to the
three main elements that govern the movement of almost all sustained hyperpycnal discharges in marine settings
bedloadsuspended load and lofting. These facies categories are here termed as Bbedload related sedimentary
2岩性油气藏 第30 1
faciesSsuspended-load related sedimentary faciesand Llofting related sedimentary facies. Hyperpyc-
nites include three kinds of depositional elementschannel filllobes and levee deposits. Although hyperpycnites
display typical and diagnostic characteristics that allow a clear recognitionthese deposits are often misinterpreted
in the literature as sandy debritesshorefaceestuarine of fluvial deposits.
Key wordshyperpycnal flowshyperpycnitesturbulent flowdeep water sedimentaryNeuquén BasinOrdos
BasinSongliao BasinSiberian Basin
0引言
河流是沉积物从源到汇最主要的运地质营
力。据 Syvitski1
的调查和研究洋中超过 90%
的陆源碎屑由陆上河流长距离运输而来,每年输送
250 亿t。传统观点认为:当河流抵达海
岸线后,其流速迅速降低且摆脱了河流堤岸的
束缚,因此河流携带的碎屑物质绝大部分在河口区
发生快速卸载和沉积,然而,越来越多的证据表明,
河流在洪水期所携带的大量沉积物不仅能路过
岸地区,而且所形成的异重流
2
可向盆地方向继续
运移几百公里。河流在洪水期向盆地深水区输
的沉积物量非常大,Mulder
3
记述 Var 河一次
持续 18 个小时的异重流输送到大洋的沉积物量相
当于过去 20 间正常状态下的总和。因此
期性的洪水期,仅有少量河流搬运碎屑堆积在河口
地区,而大部分被运移到了大陆架甚至更远的盆地
深水区。
230 条现代河流的研究表明:大部分河流
84%发育异重流
4
然而,术界对异重流及其形
成的异重岩研究程度仍然不够深入,大量含油气盆
地的异重岩被误判为河流相、三角洲相、暴岩、
岸沉积或砂质碎屑流沉积。因此,深入研究异重流
及其相关沉积物对盆地深水区优质储层的形成机
制和深水油气勘探具有重要意义。
1异重流
Bates2
提出的三角洲分类方案中,考虑了河
流密ρr
与湖或海水密度ρw
之间的关系,将进
入汇水盆地的流体分为 3种,分别称为异轻流、
密度流和异重流1异轻流:河流的水体密
度小于汇水体的密度ρr<ρw
。河流在河口处流速
迅速降低,并且失去河流堤岸的束缚而发生粗粒碎
屑的卸载和沉积。河水中悬浮的细粒碎屑和植
碎片则形成上浮羽流,再搬运一定距离后,这些细
粒物质沉降形成前三角洲沉积。异轻流及其搬
碎屑形成了海相或湖相三角洲,而三角洲的形态则
由滨岸水动力的主控因素河流水动力、波浪或潮
所决定,形成河控、浪控或潮控三角洲5
密度流:河流密度与汇水体密度相近ρr=ρw
。此
时,河流携带的所有碎屑物质包括粗粒底载荷
河口一带迅速沉积,形成陡坡三角洲吉尔伯特型
三角洲此类三角洲经常发生前积层碎屑的滚落
崩塌。必须强调:无底床载荷搬运的河流不
能成为等密度流。异重流:河水密度大于汇水体
密度ρr>ρw
河流流入汇水盆地后,在岸线处产生
了密度差,则形成异重流。异重流在自然界普遍发
育,并能携带陆源碎屑长距离向深水区运移
2
。在
海相环境下,河流悬浮沉积物浓度要达到 35
45 kg/m3才能克服海水的阻滞
6
形成异重流。在
淡水湖盆中,河流浓度只需达到 1 kg/m3可形
异重流1。异重流是一种沉积物重力流,但重
力流不一定是异重流。盆内形成的沉积物重力流,
如块体搬运体、盆内浊积岩、风暴岩及对流不稳定
产生的浊流
7
都不是真正的异重流。
1三角洲的分类据文献2修改
Fig. 1 Classification of deltas according to Bates
c)异重流,海底三角洲
a异轻流,海相滨岸三角洲
b)等密度流,湖相吉尔伯特型三角洲
河口坝
三角洲前缘
粉沙 黏土
上浮羽流
前三角洲
三角洲
前缘
淡水
吉尔伯特三角洲
上浮流
底载荷
悬浮载荷
表层水的牵引、下潜
ρr
ρrρw
ρr=ρw
ρr
ρw
ρw
ρr
ρrρw
ρw
Carlos 等:异重流成因和异重岩沉积特征
2018 3
1河流形成异重流的临界条件据文献3修改
Table 1 Critical sediment concentration in fluvial
inflows required to produce a hyperpycnal flow
异重流可以带动部分环境水体下沉,因此,
潜入区不利于形成上浮羽流1c。当异重流
发生时,河流中相对较轻的物质,如植物碎片、
叶、树干和其他炭质碎屑,可以被异重流裹挟下沉
并向盆地中心长距离运移。按照持续时间长短,
重流可以分为短期和长期性异重流。短期性异
流通常持续几个小时,主要发育在扇三角洲环境,
坡度陡并且汇水区范围小。由于其浓度相对更高
且持续时间短,短期性异重流在盆地中分布的面积
相对有限。因此,本文重点讨论长期性异重流。
2长期性异重流
中型、型河流形成的异重流可以持续几周甚
至几个月,持续时间取决于气候、流域面积以及古
形。性异和盆力流大不
长期性异重流的主要特征2包括:与河流的
沉积卸载直接相关,同时受到流速和浓度的影响;
发育底床载荷包括陆源组分和盆内侵蚀组分
具水流路过引起的剪切作用;内部由河流淡水及
其他陆源轻质悬浮物组分组成,如植物残体、叶片、
树干等。
2长期性异重流的主要特征及其典型沉积
8-10
Fig. 2 Main characteristics of long-lived hyperpycnal flows and their typical deposits
长期性异重流包括 3典型部分注入区、
主干区和前端区
11
。不同于盆内浊流的是,异重流
前端流速慢且不侵蚀
912
主要侵蚀和沉积作用发
生在主干区
913-15
。细粒异重流沉积常由 1个底部
反粒序单元和 1个顶部的正粒序单元组成,下部反
粒序单元反映了异重流能量的逐渐增强,上部正粒
序单元反映了流体能量的逐渐减弱
315-16
。反粒序
形成于异重流前端,底部通常发育爬升波纹层
15
说明前端流速小于 0.2 m/sNakajima17
记述
了距富士港 700 km 处日本海中央的异重流沉积,
估算流 速 为 0.3 m/s能够流动如此远的距离,估计
洪水持续了大约 34周。
只要河流持续补给、环境水体对前端阻滞力
小,异重流就能裹挟淡水和植物碎片等陆源轻组分
长距离搬运
918
3且与环境水体不相混合。该
结论被越来越多的直接测量或观测结果所证实。
Johnson
19
Farnsworth20
均报导1个长达 12
年的观测实例,发育Monterrey 海底峡谷的极端
浊流与附近 Salinas 河的最大洪水事件直接相关,
里的异重流位于距河口 5.222.0 km海水深 230
1 170 m处,在不同观测站都有温淡水携带大量陆源
有机质,并延伸到 1 000 m 水深以下
21
。最近 Gwi-
azda 22
Monterey 海底 水深3 000 m
的沉积物中发现了农用 DDT这些 DDT 1944
1972 年间 使用于州。Salinas Pajaro
发育异重流期间,这种化学物质由峡谷顶部向盆内
运移距离达 250 km因此,它在深海的出现既表明
Monterrey 扇体在目前的高水位期活动,也表明异
重流可长距离输送盆外组分DDT 和淡水到深
水,而且与周围海水的混合很有限;Khripounoff
23
记录了 Zaire 海底峡谷距刚果河口 330 km
4 000 m 处持续了大约 10 天的大型异重流事件,
温暖的湍流速度超过了 1.214 m/s异重流冲断了穿
越峡谷的电缆并向深水输送了大量细粒石英砂和
物碎24
这些件与期的河直
25
Kao
26
观察到 2009 年台风莫拉克过后,
盆地水
体性质
海水
淡水
质量分数/
%
>3.44.7
>0.1
体积分数/
%
>1.31.74
>0.04
平均密度/
kg·m-3
>1 0221 027
>1 000.4
悬浮物密度/
kg·m-3
>3545
>1
底载荷
悬浮物
起源于河流
的直接排放
混合载荷
湍流路过产
生剪切作用
沉积物重力流
内部含淡水
准稳定的波
动性流体
淡水引起的密
度倒置而上浮
缓慢前进的无
侵蚀性前端
4岩性油气藏 第30 1
距台湾岛西南 180 km 远,水深 3 0003 700 m 处,
迅速形成了温暖的低盐度湍流,这说明异重流事件
中淡水可沿海底长距离运移;基于英国 Shetland
Faroes 盆地内硅酸盐岩屑溶解形成的高岭石,Man-
surbeg
27
提出了异重流可以携带淡水到深水区的
认识。
3异重流沉积过程和岩相组合据文献928-29修改
Fig. 3 Main sedimentary processes and related facies families
异重流长距离运移的主控因素有 3方面
主干区流速相对较快,而前端流速慢,因此不会
产生强烈的湍流漩涡,也不会与周围水体大量混
合;前端和两翼的上浮作用尤其在海相环境
碍了水和沉积物重新聚合;持续性洪水为其提供
了充足能量。
3异重岩及其岩相类型
异重流形成的相关沉积岩被统称为异重岩
3
异重岩也被称为盆外成因的浊积岩,是盆内物质与
盆外物质多重相互作用形成的复杂沉积体,具有特
殊的岩相特征12
。异重岩的形成与河流密切相
30
因此其岩相类型、沉积特征与典型的河流相
沉积极为类似如发育底床载荷,弯曲河道等。异
重岩岩相复杂,难以用传统观点解释,也无法使用
生物地层或水深指示矿物,厚层异重岩中通常缺乏
或偶有指示河口环境的指相遗迹化石。对于每
洪水事件中形成的异重岩,粗粒沉积体的位置和厚
度对当时的水下地貌很敏感,常形成很厚的层状或
无层理的砂岩体。
异重岩岩相的复杂性主要取决于重流及其
演化的复杂性。异重流实际上也是一种湍流,由于
含有高密度的悬浮颗粒以细沙、粉沙及黏土为主
而具有较高的浓度。悬浮物中各组分比例变化
大,因此可形成不同岩性和岩相组合。异重流产生
的湍流通常无法支撑和搬运粗粒碎屑物质,但是盆
地底部异重流流体过路产生的剪切力也能以底负
载方式来搬运粗粒碎屑物质。另外,当异重流部分
悬浮载荷沉降而造成其密度降低后,所携淡水产生
的浮力使其与海水密度倒转,头部也能产生上浮羽
流。因此,异重流具有底载搬运、悬浮搬运和漂浮
搬运等 3种碎屑搬运方式,从而形成了 3种主要的
岩相系列4。笔者分别将这 3种岩相命名为底
载成因的 B类岩相、悬载成因的 S类岩相和漂浮物
成因的 L类岩相。
3. 1 底载成因的 B类岩相
粒径变化较大,既有粗碎屑,又有细粒沉积
物。由 2种作用力共同形成:异重流底部的剪切
力使粗粒碎屑以底载荷形式滚动和跳跃搬运;
悬浮载荷中部分细粒物质的重力沉降。因此B
岩相具有双峰结构,反映了底载与悬浮共存的沉积
作用。粗粒物质的滚动除了受颗粒大小的影响,
形也有重要的影响,磨圆好的碎屑不论大小都可以
长距离运移。粗粒碎屑滚动后直接形成了叠瓦
悬浮载荷
床底载荷
漂浮物
B类岩相 S类岩相 L类岩相
Carlos 等:异重流成因和异重岩沉积特征
2018 5
4异重岩的岩相类型及空间演化模式据文献12修改
Fig. 4 Genetic facies tract for the analysis of sustained hyperpycnites
构造,因为磨圆差的颗粒在滚动时容易停留在稳定
的位置5。叠瓦状构造表明,在非黏性异重流
底部,大的碎屑可以自由移动及转动。因此,识别
叠瓦状排列的粗粒物质非常重要,它是非黏性流体
的标志。在 B类岩相中,粗碎屑可以滑动和滚动方
式进行搬运,而作为基质的细粒沉积物,则为浓度
相对较高的水流底部区域以低速悬浮搬运为
31
。底载成因的粗粒碎屑既有来自于盆外的砾
大部分磨圆性较好还有来自盆内或盆外的黏
土条或黏土碎块、盆外的软体动物碎片或其他湖生
或海生动物化石或上述几种物质均有。B岩相
中存在盆外组分,表明底载荷直接由陆地河流注入
而来。砂岩中叠瓦状分布的砾石或泥岩碎块,不应
被误认为是流体内聚作用所形成,如砂质碎屑流或
砂质碎屑岩
32-33
。砂质碎屑流沉积是一种重力流沉
积,但以塑性流为特征,为流体冻结式搬运形成的
块状砂岩
34
。因此,碎屑流搬运机制无法充分地解
释细粒砂岩中呈叠瓦状展布的粗碎屑。据此,鄂尔
多斯盆地上三叠统发现的砂质碎屑流33- 37
部分
段可能是持续性异重流底部所形成的底载沉积。
5湍流底部底载成因和双峰式沉积
Fig. 5 Occurrence of bedload at the base of sustained
turbulent flows often results in bimodal deposits
湍流方向
流体
沉积界面
S
B
早期沉积
砾石质底载荷岩相
异重流通过的速度
B类岩相(底载荷沉积
剪切力增大
淡水上浮(相对于沙、粉沙、植物碎片和云母片)
黏土碎块质底载荷岩相
B1 B2 B3
碎屑支撑砾石
块状基质支撑的砾
叠瓦状排列砾质砂岩,
部收敛沙丘
砾质砂岩
平行层理
B1s B2s B3s
块状沉积,碎屑
支撑黏土碎块 中粗砂岩,底部收敛
沙丘,含黏土碎块
中粗砂岩,黏土
碎块定向排列
悬浮载荷岩相
S类岩相(悬浮载荷沉积
L类岩相(漂浮物沉积
S1 S2 S3 S4
块状砂岩 细砂岩
平行层理
细砂岩
爬升波纹层理
块状粉砂岩-泥岩
复合流体作用陆棚异重流
B3h S2h S3w
砾质砂岩
对称丘状交错层理
细砂岩
对称丘状交错层理
水道
细砂岩
波纹层理
朵叶体
沉积岩相
S1L
S2L
S3L
L
块状砂岩含黏土小
碎块和间断粉沙层
层状砂岩、粉砂岩
含植物碎片
层状粉砂岩
爬升波纹层理
水平层理粉砂岩、泥岩
含植物碎片和云母
水道轴部
爬升波纹层理
纹层状砂岩
块状砂岩
羽流沉积韵律
砾石斜列
S1
S2 S3 LP L
B1-B2
B3
底载荷 B类岩相
牵引+自由沉降作用
牵引流+自由沉降作用
S类岩相
上浮羽流(自由沉降作用
L类岩相
b)在横截面上的相变化
a)沿沉积方向的相组合
6岩性油气藏 第30 1
B类岩相进一步可以分为 3种亚岩相,B1
B2 B3 亚岩相4。当砂岩沉积序列中含有大
量黏土碎屑时,3种亚型即为 B1sB2s B3s
岩相4
3. 1. 1 B1 亚岩相
以中细砂岩为基质由块状或略呈层状的砾石
组成,结构上为砂岩基质支撑,也有些为砾质支撑
B1c 微岩相,6c。大的砾石在砂岩基质中呈
“漂浮”状,或呈发散亚平行叠瓦式排列。受控于异
重流能量和持续时间,垂向层序可以为正粒序或反
粒序,或二者的复合变化。野外露头显示 B1c 微岩
相与 B1 亚岩相的垂向变化6c由异重流
路过产生的牵引力逐渐减小所致。在粗粒物质缺
乏的体系中,B1 岩相全部由砂岩组成,或由黏土
碎屑互相支撑组成B1s 微岩相,6d
6 B1 亚岩相露头实例
ab委内瑞拉 Margarita 岛始新统 Pampatar 组深水沉积中
B1 亚岩相,砾石叠瓦状图中用 i表示排列于细粒基质中;
c)内乌肯盆地 Los Molles 组陆架异重流沉积中碎屑支撑的
砾岩B1c 微岩相d内乌肯盆地 Los Molles 组泥岩碎屑
漂浮在细粒的砂质基质中
Fig. 6 Field examples of B1 facies
3. 1. 2 B2 亚岩相
由砂岩、含砾砂岩和细砾岩组成,常发育低
度收敛交错层理和含砾砂丘。交错层理形成于
质紊流的底部,其特征与河流环境或开放河道
常见的沉积特征相同。流体流形成的沙丘或颗粒
流沙丘最主要的标志是流体流动分离形成了高角
度前积层理,即水流在流经底床沙脊部或高点
缘点处产生流动分流现象,高点背水面为“阴影
区”没有层流,水流下部纵向上向下形成一个回流
漩涡7a带动相对较粗碎屑以底载搬运方式
沿河床底部沙丘的背流面向上运动聚集,结果在背
流面反复发生重力崩落,形成向上粒度变细的纹层
7a。因此,形成的交错层理整体为正粒序展
布,底界面突变且角度大,并常见侵蚀面。与此相
反,颗粒沉降沙丘是含有大量悬浮物的流体在沙丘
波缘点向前扩散,由于流速逐渐减小,悬浮物质沿
沙丘背水面逐渐下沉,形成细沙沉积,底部常含大
量植物化石及小的黏土碎屑8bd
物质沿沙丘前部的沉降形成了底部呈渐近收敛的
交错层理8ad。细粒悬浮物在前积层下
7河流底部不同成因的 2类交错层理
Fig. 7 Main differences between cross bedding
generated at the base of a streamflow
8 B2 亚岩相野外露头和岩心典型实例
aMargarita Pampatar 组深水沉积中的低角度底部收敛型交错
层理;b西伯利亚盆地下白垩统浅海水道下部的收敛型交错层
自然光和紫外线下c内乌肯盆地更新统 Huarenchenque
组粗粒湖相沉积中的收敛型交错层理,粒度向上变粗;d图片
a的局部放大;e内乌肯盆地 Huarenchenque 组河流相形
成的交错层理,底界面突变接触,向上粒度变细
Fig. 8 Field and core examples of facies B2
a)颗粒流沙丘
b)颗粒沉降沙丘
B1
B1
B1c
B1
B1s
i
ii
i
i
i
ab
cd
流体
阴影区
颗粒流
底载荷
纹层组
流体分离
流体扩散
悬浮载荷
纹层组
底载荷
沿沉积面粒度递减
15°-30°
B2
B2
B2s
CU
cch
B2s
P
CU
FU
ab
c
de
Carlos 等:异重流成因和异重岩沉积特征
2018 7
部沉积,而粗粒在上部沉积,这种底部收敛的交错
层理主体构成了向上逐层增厚并变粗的沉积序列
7b8bc
B2 亚岩相中大粒径的碎屑常沿前积纹层漂浮
在中粗粒砂岩基质中8c前积纹层斜度通常
小于 20°。当异重流增强且碎屑沉降速率较小时
沙丘的顶界面可发生侵蚀,形成各向异性的丘状交
错层理;沉降速率增大时则渐变为上叠沙丘
30
野外露头观察表明,B2 亚岩相与水道沉积充填
紧密相关。在砾石缺乏的沉积体系中,B2 亚岩相几
乎全由中粗粒砂岩组成8bd在前积层低
部位经常发育大量泥质碎屑和植物残体,这种砂岩
相被称为 B2s 微岩相4。如果黏土含量高且
度偏细,则形成的构造很容易与潮汐环境相混淆。
二者的区别在于前者为细小的黏土碎块,而潮汐环
境中为大面积的席状泥坪。
3. 1. 3 B3 亚岩相
由中砂岩质砂岩组成,发育平行层理及
列的砾石层9ab。砾石或泥砾岩呈叠瓦
状斜列展布,粒度分布为典型的双峰式。大粒径的
砾石或泥砾岩分布在砂岩中,可解释为:当异重流
能量减弱时,悬浮的沙粒发生重力分异沉降形成沙
基质当运力减剪切 法再
9 B3 亚岩相典型实例
a含砾砂岩,砾石斜列图中用 i来标识展布,底载荷与悬浮载荷在加积层
中共同发育,内乌肯盆地更新统 Huarenchenque 组湖相沉积;b)含砾砂岩,
砾石呈叠瓦状排列,Margarita Pampatar 组深水沉积;c西西伯利亚盆
地下白垩统块状砂岩含斜列的黏土碎片B3s 岩相d)泥岩碎屑呈叠瓦
状排列的 B3s 微岩相,内乌肯盆地下白垩统 Rayoso 组湖相沉积;e)砂
岩含斜列的泥岩碎片,内乌肯盆地 Los Molles 组外大陆架沉积
Fig. 9 Field and core examples of facies B3
粒径碎屑滚动时,过路紊流搬运来的砾石将逐个排
列沉积下来。B3 亚岩相呈板状—透镜状沉积体充
填于侵蚀凹槽中。
如果 B3 亚岩相中发育斜列的泥质碎屑并常伴
有植物碎片,则称为 B3s 微岩相。浅水环境下,B3
亚岩相发育低角度纹层,与砾质丘状交错层理4
B3h 微岩相很相似。Mutti
38
认为陆源成因的重
力流向下游流动并经过浅水区时,浅水区水体本身
的动荡会对重力流流体产生同样的震荡作用,此时
也有利于形成 B3h 微岩相。因为有“漂浮”的泥岩
碎块,该岩相常被误解释为砂质碎屑流。
3. 2 悬载成因的 S类岩相
异重流能量较弱时悬载颗粒会发生重力沉降
并形S类岩相。岩石类型主要为包括细砂和粉
砂在内的细粒沉积,可发育块状或牵引流成因的沉
积构造。
3. 2. 1 S1 亚岩相
是异重岩中最常见的一种岩相。通常由单一的
厚层砂体序列构成,岩性为块状中细砂岩10
有时发育正粒[图 10d常见黏土碎“漂浮”
10 S1 亚岩相典型实例
a)西伯利亚盆地 YK 油田白垩系块状细砂岩;b鄂尔多斯盆地
上三叠统湖相块状砂岩中发育的泥砾;cColumbus 盆地中新统
朵叶体块状细砂岩含 phiomorpha nodosa 遗迹;dMargarita
Pampatar 组深水朵叶体板状砂岩;e阿根廷火地岛始新统深
水沉积块状砂岩中保存了完整的叶片;f火地岛始新统的
深水沉积块状砂岩中含完整叶片和炭质碎屑
Fig. 10 Field and core examples of facies S1
B3
B3s
i
i
B3
iB3s
i
B3s
5 cm
ab
cd
e
S1
S1
S1
S1
S1
S1
S1
2 cm 1 cm
ab
c
d
e) (f
cch
Oph
ch
叶片
ch
叶片
斜列黏土碎片
斜列泥岩碎片
8岩性油气藏 第30 1
在砂岩中,或由于异重流上部流体浓度降低,黏土
在层 [图 10b形成 S2
相。在 S1 亚岩相中,块状砂岩中常见炭化物、炭屑
和木质碎片甚至完整的树叶10e。在印尼
Kutei 盆地的块状砂岩中,叶片的含量非常高,可作
为生烃物质
39
S1 亚岩相一般不发育生物扰动
造,偶见孤立的 Ophiomorpha10cThalas-
si-noides 等遗迹化石,他们是由异重流从浅水区携
带而来的甲壳类
40
S1 亚岩相为异重流从底到顶逐渐加积而成
41-43
11这种加积作用继承了底层原始沉积物的构
造特征。因此,块状砂岩内部没有清晰的界限。实
验研究表明
44-46
S1 亚岩相形成条件是紊流的沉降
率大0.44 mm/s如果速不变、沉积 率小
0.44 mm/s会形类似 S2 的纹 砂岩
异重流携带的沙质成分快速沉降使得植物碎片
被卷入砂粒中11快速沉降产生的块状砂岩因
充填疏松而具有很高的原始孔隙度S1 亚岩相分
选性很好,但部分颗粒间隙通常有粉砂、黏土等细
粒物质充填。12 Trinidad 岛块状细粒砂岩显
微照片和激光粒度统计的例子,显示分选相对好的
细砂岩中含有大量的植物碎屑。
11 块状砂岩及植物碎片的沉积过程
据文献4247修改
C. 流体浓度;u. 流速
Fig. 11 Diagram showing the accumulation of massive
sandstone deposits with plant debris at the base
of a long lived and waning turbulent flow
12 Trinidad 岛上新统块状细砂岩显微照片及粒度分析
Fig. 12 Microphotography and laser grain size analysis of massive sandstones of Pliocene turbidites
在断陷盆地中,于断裂形成的次凹会影响异
重流及异重岩的分布13因此块状砂岩单层厚
度会增加很快
48
甚至有时会大45 m49-50
。流动
慢的引导流流势更地方
果被沉积中心拦截,会减速并沉积形成透镜状厚层
砂岩
9
3. 2. 2 S2 亚岩相
主要由细砂岩组成,发育亚平行层理14或低
角度纹415d底界面为突变面或过渡面,
个纹层厚度有时仅有几毫米,界面含大量云母、
物 残 片[图 15cfg及 炭 屑[图 15e
S2 亚岩相与发育爬升层理的 S3 亚岩相常常紧密
共生。
纹层状细砂岩在浊积岩中也很常见
51
但仍未
形成统一的成因认识
52
Sanders41
指出,湍流形成
的平行层理常在侧向上渐变为爬升纹层,说明兼有
牵引与重力沉降的形成机制。该结论 与 Arnott
45
Sumner 46
做的 致,S2
S1 亚岩相常呈互层共生这一现象所证实15c
e。在异重岩中纹层状细砂岩相S2是块状砂
岩相S1与爬升层理砂岩相S3的过渡岩相。从
块状砂岩相S1过渡到纹层状砂岩相S2流体流
速变化不大,但是沉积速率减小0.44 mm/s46
层状亚岩相S2转变为爬升层理亚岩相S3是由
水流速度减小而引起沉降速率增大所致41
(图
14
。因此,异重流能量的波FF引起沉降速率
b)激光粒度分析
a)显微照片
Z
CU
Cu
植物碎片
岩心数量:1
样品数量:1-5
样品深度:1 257.15 m
0.5 mm
岩心数量:1
样品数量:1-5
样品深度:1 257.15 m
2.000 00
1.000 00
0.500 00
0.250 00
0.125 00
0.062 50
0.031 25
0.015 63
0.007 81
0.003 91
0.001 95
0.000 98
0.000 49
0.000 24
0.000 12
0.000 06
0.000 03
Carlos 等:异重流成因和异重岩沉积特征
2018 9
13 厚层块状砂岩沉积过程示意图据文献9修改
Fig. 13 Accumulation of very thick massive sandstone bodies in structurally confined depocenters
14 异重流沉降速率及流速减小形成的块状、纹层及爬升沙纹层理
Fig. 14 Origin of massiveS1laminatedS2and climbing rippledS3sandstones as related to changes
in the rate of sediment fallout and decrease in flow velocity of sustained turbulent suspensions
的周期性变 化,形成了 S1S2 互层,流速的周期性
变化形成了 S2S3亚岩相互层14S1S3
直接互层转换,在水力学上是不可能的。当流体流
速和沉降速率在平面上具有各向异性时,流体非均
性形成了低角度侧向发散的纹层,内部以不连续的
侵蚀面为界称为 S2h微岩相,参见图 4a其特征
与各向同性的丘状交错层理类似
3853-56
3. 2. 3 S3 亚岩相
由发育爬升波纹层理的板状或不则的细砂
岩所构 成16单层厚度可达 5 cm同时前积层
底部具收敛趋势,底部常见云母片和细小植物碎片
16bd。如果层理的爬升角度长时间保持
异轻流三角洲
巨厚层块状砂岩
低地
主干
前端
下冲区
B
B
B
B
S
BS
S
1
3
2
异重流
流体波动 流体波动
沉降速率减小 流速减小
S1
S2
S1
S2
S2
S3
S2
S3
S1 S2 S3
10 岩性油气藏 第30 1
15 S2 亚岩相的岩心和露头典型实例
aColumbus 盆地上中新统陆架朵叶体沉积中纹层状细砂岩;
bMargarita Pampatar 组块状砂岩S1 亚岩相)顶上发育纹层
状砂岩S2 亚岩相c内乌肯盆地下白垩统 Centenario 组陆架
砂岩朵叶体沉积,纹层状砂岩S2 亚岩相与块状砂岩互层,显示
了沉降速率的快慢循环变化,图上箭头所指的黑线是植物残留;
d内乌肯盆地 Rayoso 组湖相朵叶体沉积;eColumbus 盆地上
新统 Mayaro 组陆架砂岩朵叶体沉积,纹层状细粒砂岩S2 亚岩
与块状细粒砂岩互层,箭头所指为炭屑;f鄂尔多斯盆地三
叠系朵叶体块状和纹层状细粒砂岩,箭头所指为植物残体;g
尔多斯盆地三叠系朵叶体沉积,层状砂岩中富含植物碎片
Fig. 15 Core and field selected examples of facies S2
一致,整套沉积会呈“假交错层理现象 16a
水槽实验表明,波纹交错层理形成于低流速
0.10.4 m/s且下伏为具有稳定的底形的砂质
57
。波纹层理并不单由沉积作用形成,侵蚀作用
和沉积环境的转变都可形成该类层理。波纹层
形成的关键是纹层爬升角度
53-54
理爬升角度与
沉降速率成正比,高角度爬升层理临界或超临界
爬升沙纹层
58
意味着前积层沉积物并非来自于对
迎流面的侵蚀,而是由衰减的流体路过卸载而成。
此,爬升波纹层是高砂质悬浮载荷湍流的标志性沉
积构造
164659-61
。另外,S3 亚岩相在垂向上和平面
上可逐渐转变为 S2 亚岩相
2841
这也证明了湍流流
速波动能形成 S3 S2 互层沉积16b。受浅
水水体的影响,爬升层理也可以表现为加积的波状
构造S3w微岩相,16e表明单向水流到震
水流可以形成更复杂的沉积组合。
3. 2. 4 S4 亚岩相
由块状或粒序层理粉砂岩及泥岩组成,底界面
16 S3 亚岩相露头和岩心实例
a)内乌肯盆地 Rayoso 组,发育爬升波纹层理的细砂岩S3 亚岩
与纹层状砂岩互层,高角度爬升层理的相似于“假交错层理”
bMargarita Pampatar 组,沙纹交错层理砂岩S3 亚岩相和纹
层状砂岩S2 亚岩相互层,代表了当时水流速度的波动;c西伯
利亚盆地下白垩统 Vikulovskaya 爬升波纹层理砂岩向上转变
为泥质沉积;d鄂尔多斯盆地上三叠统湖相沉积,爬升波纹层
理,上面黑色线是植物碎片;eTrinidad 岛和 Tobago 上新统
Morne LEnfer 组,变化型爬升波纹层理,含大量植物残片
Fig. 16 Selected field and core examples of facies S3
为突变面或侵蚀面,该岩相是异重流输送来的最细
粒物质在水流彻底停止时沉降而成的沉积。因此,
S4 亚岩相可用来确定不同期次异重流之间的边
界。S4 亚岩相与前三角洲或深水泥岩沉积很难区
分,S4 常含有陆相或浅水生物物种,因此,可通
过对微体古生物的识别来判断是否S4 亚岩相。
在海相粗粒含沙质或砾质异重流沉积体系中,S4
亚岩相不发育,细粒物质由内部淡水形成的漂浮羽
流裹挟而形成 L类岩17ab海相
质异重流是粉沙和泥浆的混合物,沉积物浓度所形
成的负荷量并非直接由流速决定,上浮羽流不发
育,因此 S4 亚岩相非常发育17c
质异重流最终形成几厘米至几米厚的正粒序
泥岩层,内部可混有盆内外生物化石18d与下
伏地层突变或侵蚀接触 19。与 L相不同,
质异重岩中植物碎屑通常分散在泥岩中19。泥
质异重流即属于高动力流体,表现在底界的侵蚀面、
火焰状 构造及正 粒序经常 重复发育19又是长
时间持续的脉动性流体,表现在内部粒序层理周期
性变化。泥质异重流具有较强的侵蚀性和搬运
力,尤其是将大量的盆外有机质搬运到盆内深水区
而成为优质烃源岩。
S2 S2
S2
S2h
S1
S1
S1
S2
S2
S1
S2
PR
S1
S2
S1
S2
S1
2 cm
ab
c
d
e
fg
ch
S2
S2
S3
S2
S2 S3
S3
S3
FF
S3
S3
2 mm
S2 S3
S2 S1
S3w
L
ab
cd
e
流向
Carlos 等:异重流成因和异重岩沉积特征
2018 11
17 海相环境中异重流的类型及其沉积特征据文献12修改
a)发育砂质底载荷的异重流,流体中含较多的粉砂/黏土组分,漂浮羽流的上升速度比较低;b不发育砂质底载荷的异重流,粉砂/黏土含量
较低形成高速的上浮羽流;c泥质异重流,由于流体密度不随流速减小而降低,泥质异重流一般不能产生上浮羽流
Fig. 17 Composition of hyperpycnal flows and their resulting deposits in marine settings
18 内乌肯盆地 Los Molles 组泥质异重流沉积
S4 亚岩相露头据文献12修改
a三层粒序层理的划线追踪,2底界发育侵蚀面,1
顶部发育火焰状构造,侵蚀面表明泥质异重流从左向右
运动侵蚀;b)露头全貌及显微照片 abc位置,显微
照片 abc中均含有大量植物化石
Fig. 18 Example of deposits related to muddy
hyperpycnal flowsFacies S4
19 内乌肯盆地上侏罗统—下白垩统 Vaca Muerta
S4 亚岩相岩心实例
ac)泥质异重流形成的沉积层,底部侵蚀接触和整体沉积
呈正粒序;d层内植物化石黄色箭头)
Fig. 19 Selected core examples of S4 facies in cores of
the Upper Jurassic-Lower Cretaceous Vaca Muerta
FormationNeuquén BasinArgentina
流体类型及组分 流体状态及其典型沉积相 沉积
悬浮载荷
悬浮载荷
悬浮载荷
上浮羽流
上浮羽流更轻
无上浮羽流
砂质异重流
泥质异重流
粉沙/黏土 淡水 碎屑 叶片
底载荷
岩相类型:B1B2B3S1S2S3L
岩相类型:B1sB2sB3sS1L
岩相类型:S4
a
b
c
a
b
2 cm
2 cm
2 cm 2 cm
c
ab2 mm 2 mm
2 mm
2 mm
abc
d
12 岩性油气藏 第30 1
3. 3 漂浮物成因的 L类岩相
由粉砂岩与极细砂岩组成,单层厚度仅几毫米
1 cm平面上呈席状大面积展布,界面上有大量
植物碎片和云母片20并发育丰富的小型重力
负载构造,常与收缩缝与菱铁矿结核伴生。遗迹化
石少见,通常只有一些古藻类,这种纹层可叠置成
厚达 0.5 m 的层组称为漂浮羽流沉积韵律
62-63
在空间分布上,L类岩相与陆架页岩或深海页岩呈
互层状 ,更多的是与块状砂岩S1 亚岩相)相伴
[参见图 420cd。植物碎片是河流体
系与海/湖体系之间存在直接联系的证据
4764-65
。砂
岩中不发育流水成因的构造,表明为悬浮漂浮物在
正常重力沉降作用下形成。
韵律性发育的 L类岩相是异重岩的典型特
征。异重流是由不同密度组分形成的紊流,相对于
海水密度(平均表层密度1.025 g/cm3
度为 1.0 g/cm3
炭 质密度为 0.208 g/cm3
和植物碎
密度为 0.090.55 g/cm3
等均属于漂浮组分或轻
组分21而沙密度为 2.22.8 g/cm3
粉沙
度为 2.42.8 g/cm3
和黏土密度为 2.72.8 g/cm3
等属于负载组分或重组分。在一定的速度条件下,
湍流将这些组分以不同比例进行混合,如果密度大
于海水,流体就会潜入海底流动。在此过程中,
果高密度流体在运动过程中部分负载组分如沙或
粉沙发生沉降,密度降低后的流体会在浮力作用
下形成上浮羽流
66-70
这些上升流体将携带细粒沉
积物、植物碎片和云母片向上运动,最终沉降后形
成漂浮物及其相关的沉积。
20 L 类岩相岩心和露头实例
aL类岩相与深海泥岩M岩相)互层,内乌肯盆地 Los Molles 组陆架内沉积;b)图a中植物碎片全貌;cd西伯利亚盆地白垩系,
浮物及其相关岩相L类岩相与块状砂岩S1 亚岩相互层,图中 P表示黑色植物化石;ed中的植物遗体化石,同时层面富含云母片
Fig. 20 Field and core examples of facies L
L类岩相主要发育在异重流边部
9
主体
积分布更广4762
L类岩相与 S类岩相在垂向和横
向上形成过渡接触关系,而不是突变接触参见图 4
b分别称作 S1/L块状砂岩层与连续的粉砂岩
层转换,22S2/L纹层状砂岩与大量植物碎片
及云母片转换S3/L粉砂岩与发育低角度小型爬
ab
cde
M
M
L
L
L
L
P
S1
S1
Carlos 等:异重流成因和异重岩沉积特征
2018 13
升波纹层理的砂岩互层
21 异重流中的漂浮和负载组分据文献9修改
Fig. 21 Buoyant and load components as the basic
constituents of a turbulent hyperpycnal flow
22 内乌肯盆Los Molles SL类岩相的接触关
Fig. 22 Outcrop showing the lateral relationship between
massive sandstonesfacies S1and loftingfacies L
微观薄片分析23为正确鉴定 L类岩相提
供了可靠的证据
4763
漂浮成因的细粒物质分选非
常好,整体具有正粒序特征,沉降遵循斯托克定律,
23 Trinidad Tobago Columbus 盆地上新统 L类岩相据文献47修改
Fig. 23 Thin sectionaand grain-size analysisbof lofting deposits in the Pliocene
of the Columbus BasinTrinidad & Tobago
同时植物化石和植物碎片在泥岩中也非常富集,
沿层呈分散状展布。
24 L类岩相的韵律因作了详细图解。
首先,异重流在流体的侧面形成了分选性极差的漂
浮或悬浮物云24a随后当异重流衰减时,
同粒度的碎屑物质自由沉降形成了正粒序层,顶部为
24 L 类岩相沉积演化过程据文献4763修改
a)羽流带来悬浮组分,未分选,悬浮物沉降遵循斯托克斯定律;b多数叶片和植物碎片仍为悬浮状态,悬浮物自由沉降沙—粉沙
正粒序层;c羽流带来悬浮组分,为分选,大粒径沙粒自由沉降,并推动叶片一起沉降;d粒序砂岩层之间发育炭质薄层。
Fig. 24 Lofting rhythmites are the result of the repeated aggradation of fine grained materials from suspension clouds
related to the buoyant inversion of hyperpycnal flows at flow margin areas
载荷组分
飘浮组分
a)岩石薄片 b粒度分析
悬浮物质
黏土质
沙/粉沙质
淡水
S1
S1
S1
S1/L
L
岩心数量:3
样品数量:3-20
样品深度:1 288.97 m 岩心数量:3
样品数量:3-20
样品深度:1 288.97 m
碎屑下沉推动
植物碎片沉积
正粒序
叶片和植
物碎片
0.5 mm
abcd
2.000 00
1.000 00
0.500 00
0.250 00
0.125 00
0.062 50
0.031 25
0.015 63
0.007 81
0.003 91
0.001 95
0.000 98
0.000 49
0.000 24
0.000 12
0.000 06
0.000 03
14 岩性油气藏 第30 1
粉泥和定向排列的云母片,多数植物叶片和碎片仍
为悬浮状态24b当另一期异重流形成新的悬
浮云后,大粒径沙粒自由沉降并推动植物叶片一起
发生沉降24c。如此不断重复,则在块状砂
岩及粉砂岩层之间形成了大量具韵律性L类岩相
4单元水道堤岸和朵叶体
与盆内浊积岩不同长期性异重流入盆后形成
了动力很强的喷射流
71
在平缓的盆地斜坡可以长
距离向前流动,能量来自于河流持续输送补给的洪
水。因此,异重流的流动距离受控于其洪水持续时
和盆形。前端爬升层理
测其平均流速为 20 cm/s爬升沙纹层理形成于流
1525 cm/s的水体环境
60
。如果持续时间为 2
个月、平均流速为 20 cm/s异重流会沿海底延伸
1 000 km。据沉积构造与内部侵蚀面发育特征推
测,相比前端,主干流速更高。异重流在盆地内的
演化过程是理解水道充填和朵叶体沉积几何形态
的关键。在向盆地流动过程中,由于沉降速率快,
靠近异重流的构造低洼地会首先截获流体,从而沉
积厚层连续的块状砂岩体。在底形平坦的地方,
干的喷射流会产生侵蚀和下切作用。异重流水
的沉积充填演化过程分 3个阶段:初始沉积;
侵蚀和路过;水道充填25
25 异重流成因水道的演化和沉积过程据文献63修改
Fig. 25 Depositional schema showing the step by step origin of hyperpycnal channel fill deposits
在初始沉积阶段,流体前端加速到达后
S3S2 岩相堤岸沉积L类岩相)25a
随后流速逐渐再增大,在喷射区和主干区形成湍
流,一旦流速超过侵蚀临界速度25b河床底
部将产生线形沟槽状冲刷
71
并在两侧形成规模更
大的堤岸沉积L岩相这一阶段侵蚀临时
和路间相用,水道形成
B1B2 B3 浮载 S1 亚岩
相)常伴
Rayoso 组露头26该露头剖面垂直于流向,
道充填形成了多期侧向加积沉积。
在水道最终形成和充填阶段异重流呈波动式
衰减25c砂质颗粒持续从湍流中沉降出来,
形成 S1S2 S3 亚岩相,同时伴生边部堤岸沉积
初期沉积
时间
排放量
时间
排放量
侵蚀和路过
1
1
2
时间
排放量
水道充填
12
3
加速期
滨外沉积
持续性湍流喷射流
高峰期
1
2
3水道充填堤岸
侵蚀面 漂浮物岩相堤岸
内部侵蚀面 黏土碎块
衰减期
流向
Carlos 等:异重流成因和异重岩沉积特征
2018 15
26 异重流水道中的侧向加积现象
63
Fig. 26 Field example of lacustrine hyperpycnal
channel fill with lateral accretion
L岩相与河流相河道充填不同的是重流
水道充填后在海底形成了正向地形,控制后期水道
分布,形成沉积补偿循环
68
使得砂体之间的关系
变得非常复杂。当异重流流速减小并失去了对
床的侵蚀能力后,水道末端的异重流会逐渐演化为
朵叶体沉积。
湖盆古底形和盆内断裂对异重流分布有着
重要的控制作用。在墨西哥湾陆坡和阿尔卑斯
地的古近系,盆地古底形起伏大,异重流“充填与溢
出”的过程至少包括 4个阶段
72-74
异重流注入
洼地,所有注入水流都被截获并沉积了厚层毯状砂
泥层。水流分流,低密度的异重流从低洼分流出
来,在别处低洼地沉积。水流路过,流体穿过蓄
满水的凹地,把沉积物搬运到更远的地方。最后
形成低砂/泥比值的弯曲水道-堤岸沉
73
27。在
断陷盆地中,异重流沿凹陷中心轴部推进时,常形成
厚层块状砂岩与纹层状砂岩的互层沉积28
27 Columbus 盆地充填和溢出三维模型及其沉积序列
Fig. 27 3D model showing the progressive infill and spill of Columbus basin and its control in the
stacking pattern of the associated reservoirs
4 m
侧向加积
S1 S1
S1 S1
b)跨越凹陷向其他洼地沉积
a)洼地轴部发育厚层砂岩
垂向层序模式
异重流水道
上浮羽流
流体轴部
断裂控制的
沉积中心
沉积路过区
异重流主体路过时
产生的漂浮物沉积
断凹内部的主
体充填沉积
3 800
4 000
4 200
4 400
4 600
埋深/m
0120
GR/API 岩相
埋深/m
0GR/API 岩相
120
3 800
4 000
4 200
4 400
4 600
B1
B2
B1
A3
A2
A1
A2
B1
B2
B1
B2
B1
A3
A2
A1
A2
B1
B2
2
1
2
1
1
2
16 岩性油气藏 第30 1
28 Columbus 盆地上新统 Mayaro 组块状砂岩体
Fig. 28 Thick massive sandstone bodies in the Pliocene
Mayaro FormationColumbus Basin
在湖盆底形极为平缓的盆地异重流成因的水
通常几十百公末端
朵叶体或湖底扇沉积。如松辽盆地嫩江组,发源于
盆地北部的异重流
75
途经北部三角洲后在深水区
形成完整的水道-湖底扇系统29自北向南依
发育水道曲水河道伸距
80 km度为 100900 m水道末端发育湖底扇,
单个面积可达 20 km2
29 松辽盆地嫩江组均方根地震属性
75
Fig. 29 RMS of Late Cretaceous shallow to deep water
lacustrine deposits of the Nengjiang Formation
in Songliao Basin
5结论与讨论
异重流是一种重要的将浅水沉积向深水盆
地大规模搬运的地质营力,但这种流体类型、搬运
机制及形成的深水砂体等方面的研究却未受到足
够的重视,本文只讨论了异重流的成因及其沉积物
的主要特征。对现今碎屑岩沉积环境尤其是水下
环境认识不全面,对异重流的认识仍很有限,这些
都限制了对深水砂体成因的正确认识。大量含
气盆地的异重岩被误判为河流相、三角洲相、风暴
岩、滨岸沉积或砂质碎屑流沉积,正确认识这些沉
积体系还需要进一步深化研究,以期对异重流及其
沉积物有更为系统的认识。
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