南海北部珠江口盆地重力流与等深流交互作用沉积特征、过程及沉积模式

通过地震及钻孔资料对南海北部珠江口盆地重力流及等深流沉积进行了研究。南海北部重力流及等深流沉积类型多样,包括峡谷、单向迁移水道、堤岸、朵叶及漂积体。单向迁移水道迁移方向分别为北东向和南西西向,为重力流与等深流交互作用形成。漂积体有大型长条状漂积体、限制型漂积体和陆坡席状漂积体,岩性为粘土、泥质粉沙。南海北部陆坡水深200~1200m范围内发育北东向迁移水道及小规模的漂积体,而水深约1200~3000m内则以朵叶及大规模的漂积体为主,见少量南西西向迁移水道。其中,漂积体多分布于峡谷、水道及朵叶的两侧,为等深流改造堤岸、朵叶等"细粒"沉积物而成。     

东沙隆起南缘第四系等深流沉积特征及成因机制

珠江口盆地东沙隆起南缘深水陆坡区（水深约900~2 600 m）是西北太平洋和南海水体交换的活跃区域,发育了类型丰富的等深流沉积体,但等深流沉积特征和成因机制尚不明确,相关研究仍缺乏足够证据。通过区域地震资料和ODP1144站钻井数据分析发现,该区第四系地层中可识别5种深水底流成因的等深流沉积:涂抹形漂积体、伸长形-丘形漂积体、限制形漂积体、沉积物波以及席状漂积体。根据等深流沉积特征、发育类型以及分布范围,从陆坡到深海平原大致依次出现涂抹形漂积体、伸长形-丘形漂积体、限制形漂积体和席状漂积体,而具有波状沉积底形的沉积物波主要发育于陆坡区。东沙隆起南缘第四系等深流沉积的形成、演化受控于多种因素,其中主控因素包括:西北太平洋与南海中-深层水体的"双层"环流结构、科里奥利力的"右偏"效应、冰期-间冰期海平面升降所诱导的底流与重力流交互作用机制以及新构造运动时期火山活动对海底地貌的改造。     

南海西北陆缘深水沉积体系内部构成特征

深水沉积是近年来我国海域油气勘探重点之一,利用高精度二维和三维地震剖面的精细解剖,揭示了南海西北陆缘区深水沉积体系类型及其内部构成特征.这些深水地区除堆积正常深海-半深海泥岩外,还发育大量深水重力流沉积,包括块体流沉积、深水峡谷、沉积物波等大型沉积体.研究表明,南海西北陆缘区发育4类陆坡, 即进积型、滑塌型、水道化型、宽缓渐变型陆坡.不同陆坡类型具有不同地貌形态,发育不同的沉积体类型.大型块体流沉积主要发育于滑塌型和水道化型陆坡,沉积物波主要发育于宽缓渐变型陆坡下部及深海中央峡谷长昌段的周缘地区.由于南海西北陆缘自晚中新世以来形成向东开口的喇叭形变深的地貌形态,导致在盆地中央形成了独特的与陆坡走向一致的深海峡谷体系——中央峡谷.该峡谷的沉积充填不仅包括来自于西部峡谷头部的浊积水道沉积,还包括来自于北部陆坡的块体流沉积,特别是来自于滑塌型陆坡的块体流沉积.中央峡谷体系构成了西北陆缘区多源汇聚的深水沉积物输送系统,同时也是南海西北陆缘深水区重要的油气储层发育层系.      

南海北缘一统暗沙附近深水等深流沉积体系特征

利用高分辨率2D地震资料揭示南海北缘一统暗沙附近(水深700~1 000 m)发育海山相关的深水等深流沉积体系, 为南海北部陆缘深水洋流循环和深海动力学研究, 以及深水油气矿产资源勘探提供了新的资料.一统暗沙南、北两侧发育边缘侵蚀槽沟, 其中北缘的边缘槽沟可称为"环槽", 反映底流(可能属于南海中层水循环体系)自西向东流经海山.一套等深流沉积的伸长状-丘状漂积体沿环槽北岸发育.一统暗沙南侧和背侧还发育黏附型漂积体、南侧沉积区和补丁型漂积体.地震沉积记录显示该区稳定底流侵蚀-沉积活动可追溯至晚中新世早期.      

坦桑尼亚滨海盆地陆坡峡谷沉积特征及其控制因素*

东非陆缘深水盆地具有巨大油气资源潜力,但对陆坡峡谷沉积特征研究较少,制约有利储集层预测。本研究利用三维地震资料,对东非坦桑尼亚滨海盆地陆坡峡谷开展精细研究。结果表明:(1)研究区陆坡发育多条大型海底峡谷;上陆坡处,坡度较陡,峡谷内以侵蚀作用为主,沉积物主要局限在褶皱推覆带的翼部;褶皱推覆带之外的下陆坡区,坡度变缓,峡谷末端发育席状砂质沉积及砂泥混杂的碎屑流沉积,同时在峡谷北侧发育向北延伸的泥质漂积体;在陆坡边缘,发育海底滑塌,形成块体搬运沉积。(2)峡谷沉积受陆源物质供给、褶皱推覆带、北大西洋底流以及陆坡边界断层等因素控制。受东非裂谷海域分支活动影响,研究区陆架窄、陆坡陡,陆源物质可迅速通过陆架,进入陆坡峡谷:与河流相连的峡谷,物源充足、规模较大,有沉积物发育而没有与河流直接相连的峡谷物源有限、规模较小,峡谷内无明显沉积;褶皱推覆带通过改变海底地形来控制峡谷内沉积分布,褶皱翼部发育沉积,核部则以侵蚀为主;褶皱推覆带外,北大西洋底流与峡谷末端重力流发生交互作用,细粒物质被搬运至峡谷北岸形成漂积体;陆坡边缘断层活跃,峡谷被断层切割,形成断崖,并引发海底滑塌,陆坡处不发育水道及朵体沉积,陆源物质通过峡谷被搬运至更深的深海盆地内。     

深水单向迁移水道-堤岸沉积体系特征及形成过程

南海珠江口盆地白云深水区及西非下刚果盆地发育一种深水单向迁移水道-堤岸沉积体系,主要包括轴部沉积、侧积体沉积、滑塌/块状搬运复合体沉积、堤岸沉积,另见阶地。该沉积体系水道整体具有单向迁移特征,为重力流和等深流共同作用而成,水道迁移方向与等深流运动方向大致相同。其影响因素包括重力流及等深流相对能量的大小、物源、海平面升降、气候、地形、科氏力及陆架宽度等。阶地成因可分为3种,即重力流侵蚀侧积体成因、沉积失衡滑塌或断层作用成因和重力流在水道内部的差异侵蚀成因。对该沉积体系的研究不仅能加深深水沉积的认识,还可为油气进一步勘探服务。     

西非科特迪瓦盆地深水底形样式及成因分析

通过三维地震资料海底平面成像和浅层地震剖面解释、分析,识别和描述了西非科特迪瓦盆地深水底形类型。研究区发育下切水道、侵蚀冲坑、周期阶坎、小型沉积物波、大型沉积物波多种深水底形。下切水道表现为直线型,地形坡度从上斜坡5°过渡到下斜坡1.9°,水道历经多次合并,合并后水道内部起伏地貌指示侵蚀—沉积交互作用;识别出孤立状、串珠状和猫爪状三种类型侵蚀冲坑;在斜坡限制性水道内部地形坡度1.9°～3.1°之间识别出8个不同波长和波高的“周期阶坎”底形,周期阶坎具有剖面上向上游方向迁移、平面上呈新月形态的特征,从上游到下游波长有逐渐变短的趋势。小型沉积物波发育于水道内和水道外两种环境,其中限定性环境小型沉积物波发育在周期阶坎上游方向,非限定环境小型沉积物波发育地形坡度为1°左右,具有加积或轻微向下迁移的内部反射结构。大型沉积物波发育在非限定环境中,显示为长波长、低幅度浅层构造特征,分析认为早期滑塌地貌对晚期大型沉积物波的形成具有重要的控制作用。在现象描述基础上,对不同底形的成因、形成过程、控制因素和其发育的深水动力学背景与环境展开探讨,加深了对西非赤道段科特迪瓦盆地深水底形成因的认识,可对未来深水区...     

珠江口盆地白云凹陷陆坡限制型海底峡谷群成因机制探讨

珠江口盆地白云凹陷北部陆坡发育着17条近似NNW-SSE走向的海底峡谷,构成了区域内的陆坡限制型海底峡谷群。基于研究区内高密度覆盖的2D地震资料,通过外部形态、内部结构等反射特征的描述和刻画,建立了第四纪以来的高精度层序地层格架,将沉积充填序列划分为三个体系域,即低位体系域（LST）、海侵体系域（TST）和高位体系域（HST）。根据陆坡进积特征、垂向地层叠加样式、侵蚀特征变化、连续性强振幅同相轴的识别和空间追踪,将高位体系域进一步划分为两个沉积旋回单元,HST-I和HST-II。研究表明,白云凹陷陆坡限制型海底峡谷群发育在高位体系域晚期沉积旋回（HST-II）中。在此基础上,分别讨论了沉积物供给、沉积物失稳作用、限制型地形和流体渗漏作用对峡谷群形成和演化的影响。第四纪以来珠江水系携带的大量沉积物经由陆架进入到陆坡区域,为海底峡谷群的发育和演化提供了充足的沉积物来源。在第四纪高位体系域早期水道形成的限制型“负地形”基础上,大量的沉积物在沿着陆坡坡降方向自北向南的输送过程中发生向下的侵蚀、沉积物失稳,导致了陆坡限制型海底峡谷群的发育。研究区内广泛分布的气烟囱构造,暗示了含气流体的垂向运移和渗漏,可能促进了海底峡谷群的进一步演化。     

中建海底峡谷地貌及沉积特征的分段性

中建海底峡谷具有分段性,但分段的关键地貌特征、各段沉积充填及其控制因素缺乏精细描述和系统论证.综合利用高分辨率二维和三维地震资料,结合水深地貌数据,对中建海底峡谷地貌及沉积特征进行了详细分析,总结了其南北段沉积过程的主控因素.中建海底峡谷呈NW向顺直展布于广乐隆起与西沙隆起之间,以华光礁附近的地貌高点为拐点被分为南北两段.中建海底峡谷北段沉积体系包括重力流沉积（水道、席状沉积、滑塌体）和底流沉积（漂积体、环槽、谷槽）,南段以重力流水道和海底扇为主.北段沉积体系受底流和重力流交互作用控制,底流自中中新世开始出现,改造重力流水道,使其出现侧向迁移或翼部不对称现象,上新世以后重力流作用减弱,底流作用增强,沉积物波和漂积体广泛发育;峡谷南段水道表现出侵蚀-沉积-废弃的沉积旋回,未见底流沉积现象.相对海平面变化导致碳酸盐生产率变化影响物源供应,从而控制水道沉积演化,碳酸盐台地的“高位溢流”作用决定水道在高水位时发育.      

等深流沉积研究进展

等深流沉积研究已有约50年的历史,其研究成果极为丰富。近10余年,随着科学技术的发展和海洋意识的提高,等深流沉积研究工作开展迅速,涌现出了大量的新成果。简要回顾了等深流沉积研究的历程,结合最新研究成果,对其进展及认识进行了总结。等深流沉积以细粒沉积为主,沉积构造及生物扰动发育,多呈细-粗-细沉积序列。其类型可分为长条形丘状漂积体、水道型漂积体、补丁型漂积体等7类。沉积模式根据地形、水动力、路径等可分为简单路径模式、复杂路径模式以及等深流与重力流交互作用模式。等深流与重力流交互作用是深水沉积研究热点之一。等深流沉积研究面临的问题及发展方向主要有三方面,即,1）完善识别标志,推广研究成果;2）综合运用多种手段和理论,探讨沉积过程与构造演化、古海洋及气候变化的耦合关系;3）加大油气勘探潜力研究力度。     

Contour current imprints and contourite drifts in the Bahamian archipelago

New data collected along the slopes of Little and Great Bahama Bank and the abyssal plain of the Bahama Escarpment provides new insights about contour current‐related erosive structures and associated deposits. The Bahamian slope shows abundant evidence of bottom current activity such as furrows, comet‐like structures, sediment waves and drifts. At a seismic scale, large erosion surfaces and main periods of drift growth resulted from current acceleration related to plate tectonic processes and progressive opening and closure of gateways and long‐term palaeoclimate evolution. At present‐day, erosion features and contourite drifts are either related to relatively shallow currents (<1000 m water depth) or to deep currents (>2500 m water depth). It appears that the carbonate nature of the drifts does not impact the drift morphology at the resolution addressed in the present study. Classical drift morphologies defined in siliciclastic environments are found, such as mounded, plastered and separated drifts. In core, contourite sequences show a bi‐gradational trend that resembles classical contourite sequences in siliciclastic deposits showing a direct relationship with a change in current velocity at the sea floor. However, in a carbonate system the peak in grain size is associated with increased winnowing rather than increased sediment supply as in siliciclastic environments. In addition, the carbonate contourite sequence is usually thinner than in siliciclastics because of lower sediment supply rates. Little Bahama Bank and Great Bahama Bank contourites contain open‐ocean input and slope‐derived debris from glacial episodes. Inner platform, platform edge and open ocean pelagic input characterize the classical periplatform ooze during interglacials. In all studied examples, the drift composition depends on the sea floor topography surrounding the drift location and the type of sediment supply. Carbonate particles are derived from either the slope or the platform in slope and toe of slope drifts, very deep contourites have distant siliciclastic sources of sediment supply. The recent discovery of the importance of a large downslope gravitary system along Bahamian slopes suggests frequent interactions between downslope and along‐slope (contour currents) processes. The interlayering of mass flow deposits and contourites at a seismic scale or the presence of surface structures associated with both contour currents and mass flow processes shows that both processes act at the same location. Finally, contour currents have an important impact on the repartition of deep‐water coral mounds. Currents can actively interact with mounds as a nutrient and oxygen supplier or have a passive interaction, with mounds solely being obstacles orienting erosion and deposition.     

深水牵引流形成的床形单元组合

海底上发育深水牵引流形成的各种床形单元,包括等深岩丘及大型沉积物波在内的不同床形单元有规律地组合在一起,对于此类床形组合的确切形成机理,目前仍在探讨之中。本文经详细研究得出以下几点进展：① 运用内波理论可对海底上大型沉积物波各组成单元的成因作出较为合理的解释,向深海方向传播的内波可形成向上坡方向迁移的大型沉积物波;② 在等深流与上覆低密度水体之间的界面上具备产生大规模界面内波的条件;③ 某些底流成因的床形单元组合属于等深流与等深流所引发内波的联合作用的产物,首次提出了等深流－内波沉积组合的概念;④ 在现代海底上及古代地层记录中均发现了等深流－内波沉积组合的实例;⑤ 建立了一个古代地层记录中的深水牵引流沉积组合综合模式。     

Characteristics of modern carbonate contourite drifts

Carbonate environments inhabit the realm of the surface, intermediate and deep currents of the ocean circulation where they produce and continuously deliver material which is potentially deposited into contourite drifts. In the tropical realm, fine‐grained particles produced in shallow water and transported off‐bank by tidal, wind‐driven, and cascading density currents are a major source for transport and deposition by currents. Sediment production is especially high during interglacial times when sea level is high and is greatly reduced during glacial times of sea‐level lowstands. Reduced sedimentation on carbonate contourite drifts leads to early marine cementation and hardened surfaces, which are often reworked when current strength increases. As a result, reworked lithoclasts are a common component in carbonate drifts. In areas of temperate and cool water carbonates, currents are able to flow across carbonate producing areas and incorporate sediment directly to the current. The entrained skeletal carbonate particles have variable bulk density and shapes that lower the prediction of transport rates in energy‐based transport models, as well as prediction of current velocity based on grain size. All types of contourite drifts known in clastic environments are found in carbonate environments, but three additional drift types occur in carbonates because of local sources and current flow diversion in the complicated topography inherent to carbonate systems. The periplatform drift is a carbonate‐specific plastered drift that is nearly exclusively made of periplatform ooze. Its geometry is built by the interaction of along‐slope currents and downslope currents, which deliver sediment from the adjacent shallow‐water carbonate realm to the contour current via a line source. Because the periplatform drift is plastered on the slopes of the platforms it is also subject to mass gravity flow and large slope failures. At platform edges, a special type of patch drift develops. These hemiconal platform‐edge drifts also contain exclusively periplatform ooze but their geometry is controlled by the current around the corner of the platform. At the north‐western end of Little and Great Bahama Bank are platform‐edge drifts that are over 100 km long and up to 600 m thick. A special type of channel‐related drift forms when passages between carbonate buildups or channels within a platform open into deeper water. A current flowing in these channels will entrain material shed from the sediment producing areas. At the channel mouth, the sediment‐charged current deposits its sediment load into the deeper basin. With continuous flow, a submarine delta drift is built that progrades into the deep water. The strongly focused current forming the delta drift, is able to rework coarse skeletal grains and clasts, making this type of carbonate drift the coarsest drift type.     

中国南海西北次海盆西北陆缘洋陆过渡区深水沉积体系特征

高分辨率二维地震资料显示中国南海西北次海盆西北陆缘（水深1 000 m及以下）发育如下深水沉积体系:珠江口盆地南部隆起区缓坡带（水深约1 000~1 500 m、坡度<1.2°）出露神狐南海山,该海山附近发育“海山相关等深流沉积体系”,可能受南海中层水循环（自西向东）底流控制;神狐南海山以南水深约1 500~2 500 m的陆坡区（坡度>2°）普遍发生坡移,发育“重力流滑塌体系”和“峡谷体系”,鲜见等深流沉积;下陆坡区（水深>2 500 m,坡度稍缓<2°）滑塌现象明显减少,主要发育“峡谷体系”以及“席状等深流沉积体系”,席状等深流沉积体系可能受分散的、流速较低的南海深层水循环底流控制。地震沉积记录显示,神狐南海山附近等深流侵蚀特征最早出现于晚中新世早期,其后至现今该区较稳定发育等深流沉积/侵蚀的加积序列,说明南海西北次海盆西北陆缘的稳定底流沉积/侵蚀可追溯至晚中新世早期。     

Occurrence of submarine canyons,sediment waves and mass movements along the northern continental slope of the South China Sea

In this study, we reveal a series of newly discovered submarine canyons, sediment waves, and mass movements on a flat and smooth seafloor using high-resolution, multi-beam bathymetry and shallow seismic surveys along the northern slope of the South China Sea. We also describe their geomorphology and seismic stratigraphy characteristics in detail. These canyons display U-shaped cross sections and are roughly elongated in the NNW–SSE direction; they are typically 8–25 km long, 1.2–7 km wide, and form incisions up to 175 m into Pliocene–Quaternary slope deposits at water depths of 400–1000 m. Slide complexes and the sediment wave field are oriented in the NE–SW direction and cover areas of approximately 1790 and 926 \(\hbox {km}^{2}\), respectively. Debris/turbidity flows are present within these canyons and along their lower slopes. Detailed analysis of seismic facies indicates the presence of six seismic facies, in which Cenozoic strata located above the acoustic basement in the study area can be roughly subdivided into three sequences (1–3), which are separated by regional unconformities (Tg, T4, and T3). By combining these data with the regional geological setting and the results of previous studies, we are able to determine the genetic mechanisms used to create these canyons, sediment wave field, and mass movements. For example, frontally confined slide complexes could have been influenced by high sedimentation rates and high pore pressures. A series of very large subaqueous sediment waves, which record wavelengths of 1.4–2 km and wave heights of 30–50 m, were likely produced by interactions between internal solitary waves and along-slope bottom (contour) currents. Canyons were likely initially created by landslides and then widened laterally by the processes of downcutting, headward erosion, and active bottom currents and debris/turbidity flows on canyon floors. We therefore propose a three-dimensional model to describe the development of these mass movements, the sediment wave field, and canyons. The four stages of this model include a stable stage, followed by the failure of the slope, and subsequent formations of the sediment wave field and canyons.     

内波单独作用形成的深水沉积物波

深水沉积物波是一种海底普遍发育、规模较大的波状沉积体,大多数学者将它们解释为等深流沉积或浊流沉积。本文结合内波理论的研究进展，考虑内波沉积作用的水动力学特征，探讨了深水沉积物波的内波成因机制。得出以下几点认识：①海底流动单独作用无法满足沉积物波形成所需的流动层厚度及流动速度，较难解释沉积物波的迁移方向及规则的内部及外部形态。②内波可以引起海底流动，内波比表面波更容易形成更大规模范围内的沉积床形。③内波可以形成大型沉积物波，用内波可以较合理地解释内波的对称波形单元、非对称波形单元及上攀波形单元的成因。波动面离海底距离较大的行进内波及内驻波可以形成对称波形的沉积物波；波动面离海底距离较近的行进内波及内孤立波可以形成非对称波形的沉积物波；内波引起的海底流动进一步增强时，可形成上攀波形沉积物波。④行进内波可以形成向内波传播相反方向迁移的沉积物波，向海盆内部传播的内波可以形成向上坡方向迁移的沉积物波。     

中国油气勘探的一个新领域——深水牵引流沉积

深水牵引流沉积主要分为等深流沉积和内波内潮汐沉积两类。前者可形成巨大的堆积体——等深积岩丘,其规模可与海底扇相比拟。现代海洋大陆坡及陆隆地带等深积岩丘非常发育;古代地层记录中也有等深积岩丘,如已开采数十年的阿拉伯克拉通白垩系等深积岩丘油田。后者则不仅可形成分选极好的砂级沉积物,而且可形成规模巨大的“沉积物波”,并成群成带地出现。海洋中沉积物波的迁移可形成巨大的沉积体。在世界各大洋深盆海底,均有大范围分布的现代大型沉积物波。中国地层记录中的大型沉积物波,首先在塔里木盆地塔中地区中一上奥陶统中被识别出来,并有良好油气显示。认为中国的广大地区发育有多个时代的海相深水沉积,深水牵引流沉积储集层是中国21世纪油气勘探具巨大潜力和现实可行性的新领域。其油气勘探首选地区是塔里木盆地、扬子地台南缘和鄂尔多斯西缘。     

Contourite drifts, moats and channels in the Upper Cretaceous chalk of the Danish Basin

During the Late Cretaceous, high global sea‐level meant that most of the NW European craton was flooded by the deep epeiric ‘chalk sea’. The classical paradigm for chalk deposition envisages a quiet rain of minute skeletal debris of coccolithophorid algae and other pelagic organisms deposited as horizontal, flat‐lying pelagic oozes with local redeposition by slumps, slides and debris flows along faults and other structural features. Seismic data from the Danish Basin and elsewhere necessitate a revision of this paradigm. These demonstrate that the chalk sea floor had a considerable relief, commonly of more than a hundred metres amplitude, comprising moats, drifts, mounds and channels. Seismic sections from the Kattegat sea illustrate the development in the Maastrichtian of a deep moat adjacent to a topographic ridge formed over the inverted NW–SE‐trending Sorgenfrei–Tornquist Zone. The moat was up to 120 m deeper than its SW flank which was formed by an internally complex elongate drift, up to 20 km wide with an estimated length of ca 200 km. Smaller mound‐like features, channels and clinoform beds are superimposed on the large‐scale relief. The sea floor relief is interpreted to have formed in response to persistent bottom currents, flowing parallel to bathymetric contours. The initial build‐up of the broad, gently convex‐up sheeted drift was controlled by relatively low‐velocity bottom currents. The region of highest current velocity was gradually shifted NE‐wards towards the inversion zone ridge, resulting in the formation of the deep moat flanked by the elongate drift. The current is interpreted to have flowed from the SE towards NW on the basis of the internal architecture of the elongate drift and the NW‐ward branching and decrease in moat relief. The architecture and morphology of the moat drift and other features of the chalk sea floor are in all aspects similar to contourite systems of modern continental margins. It is accordingly proposed that the fundamental physical oceanographic concept – contour currents and their resulting contourite drifts – is extended to include the deep epeiric seas which covered NW Europe during the Late Cretaceous.     

Neogene palaeoceanographic changes recorded in a carbonate contourite drift (Santaren Channel,Bahamas)

The Santaren Drift between the Great Bahama Bank and Cay Sal Bank (Bahamas) is closely linked to the development of the Gulf Stream and its shape and geometry record the local to global oceanographic, climatic and tectonic events since the Miocene. High‐resolution multichannel seismic data from the Santaren Channel allow detailed insight into the growth phases of the contourite drift, and by using the stratigraphic information from Ocean Drilling Program Site 1006 to infer its sedimentation rates. The results bring new understanding to this region and to interpretation of carbonate drifts. The data document that the signatures of a bottom current flow in the Santaren Channel initiated about 12·3 Ma, as indicated by the first occurrence of sheeted drifts and moat development at the northern part of the Santaren Channel. Narrowing and steepening of moat flanks as well as the pronounced upslope migration of the moat reflects a sustained current acceleration of the bottom currents until 5·5 Ma, associated with a transformation into mounded elongated drifts. Between 5·5 Ma and 3·1 Ma, bottom current intensity reached its maximum probably caused by the final closure of the Central American Seaway. The last 3·1 Myr were characterized by a marked increase in volume through flow reaching a maximum during the past 900 kyr. Drift growth was driven by the combined sources of export from the shallow‐water carbonate factory and by pelagic rain. The Middle Miocene channel‐related sheeted drift of the inner Santaren Channel is characterized by low accumulation rates, but a rapid increase of accumulation rates occurred during the Early Pliocene. The contourite drift buildup was disturbed by minor erosional phases with narrow moats in the Late Pliocene due to increasing bottom‐current velocities forced by strengthened Atlantic Ocean ventilation. The Early Pleistocene was dominated by increased periplatform sedimentation and margin progradation facilitated by a reduction in along‐slope current flow speed and a concurrent widening and flattening of the moats.