Carbonate platforms are built mainly by corals living in shallow light-saturated tropical waters. The Saya de Malha Bank (Indian Ocean), one of the world's largest carbonate platforms, lies in the path of the South Equatorial Current. Its reefs do not reach sea level, and all carbonate production is mesophotic to oligophotic. New geological and oceanographic data unravel the evolution and environment of the bank, elucidating the factors determining this exceptional state. There are no nutrient-related limitations for coral growth. A switch from a rimmed atoll to a current-exposed system with only mesophotic coral growth is proposed to have followed the South Equatorial Current development during the late Neogene. Combined current activity and sea-level fluctuations are likely controlling factors of modern platform configuration.Carbonate platforms are edifices kilometers high and hundreds of kilometers wide produced mostly by shallow-water organisms, such as reef-building zooxanthellate corals, and by their detritus. Platforms thrive for millions of years in the tropical belt of the oceans, many isolated from continental areas. Coral reefs reach sea level, mainly along the platform rims, such as, e.g., in the Indo-Pacific biogeographic region. Light availability as well as water temperature, turbidity, salinity, nutrients, and current velocity determine the depths at which corals and their photosynthetic symbionts thrive (Schlager, 2005). Coral reefs, amongst the most productive marine ecosystems, flourish in oligotrophic waters.Sea-level change exerts a fundamental control on reef development at geological time scales (Webster et al., 2018). Reefs migrate sea-ward and platform-ward following falling or rising sea level, whereas a sea-level rise outpacing reef growth interrupts reef development. In the Indo-Pacific biogeographic region, reefs that are now submerged and do not reach sea level are typically structures of Pleistocene age with a thin coralgal cover deposited during a brief episode of recolonization in deglacial time (Montaggioni, 2005). Apart from sites subject to tectonic uplift, incipient buildups that formed before 19 kyr B.P. were drowned. Some reefs were able to keep up with deglacial sea-level rise, but others, for reasons that are not fully understood, were not (Montaggioni, 2005; Woodroffe and Webster, 2014; Webster et al., 2018). The latter are today the sites of many mesophotic coral ecosystems.The Saya de Malha Bank in the Indian Ocean lies in the window of optimal conditions for shallow-water reef development, but the carbonate platform today is mostly populated by mesophotic coral ecosystems. Using geophysical, oceanographical, and sedimentological data, we studied how ocean currents shape this platform and how—along with sea-level changes—they impede shallow-water reef growth. This has implications for other cases of carbonate platforms in the geological record where reefs do or did not grow to sea level, i.e., those that are fully or partially drowned.Indian Ocean Cenozoic isolated carbonate platforms grow on volcanic ridges generated by Indian and African plate drift over the Réunion hotspot (Purdy and Bertram, 1993). The Indian plate platforms are the Maldives, the Laccadive Islands, and the Chagos Archipelago. On the African plate, the Mascarene Plateau, with the Saya de Malha Bank and Nazareth Bank, is located between 4°S and 20°S (Fig. 1A). Saya de Malha Bank covers an area of 40,000 km2 and consists of the smaller North Bank and the larger South Bank, the latter of which is the focus of this study.The South Bank has a west-east extent of 230 km and a north-south extent of 290 km. It is fringed by a horseshoe-shaped submerged reef rim, which lies at a minimum water depth of 8 m and opens to the south (Fig. 1B) (Fedorov et al., 1980). In petroleum well SM-1 (3264 m depth; Fig. 1B), Paleocene to Quaternary neritic to shallow-water carbonates overlie 45 Ma basalts (Meyerhoff and Kamen-Kaye, 1981). The subsidence of the region is thermally controlled (Fig. 1B), as determined based on backtracking Ocean Drilling Program sites using an Airy isostatic model (Coffin, 1992). Through use of a low-resolution seismic line (Purdy and Bertram, 1993), the bank's succession was interpreted as an atoll, which eventually drowned.Saya de Malha Bank lies in the direct path of the South Equatorial Current, which between 10°S and 16°S flows at 0.3–0.7 m s−1 (Fig. 1B) (New et al., 2007). Barotropic tidal currents can add 0.35 m s−1 in the east-west direction during spring tides. The main flow of the South Equatorial Current is diverted north and south of the bank, and is strongest between 11°S and 13°S where it is funneled between Saya de Malha and Nazareth Banks (Fig. 1). The current transports ∼50 Sv (sverdrup; 50 × 106 m3 s–1), primarily driven by the strong southeast trade winds. In the upper well-mixed layer (50–100 m), the currents are nearly uniform and weaken toward water depths of 500–1000 m.We acquired seismic reflection data using a 144-channel 600 m digital Hydroscience Technologies Inc. streamer. The Ocean Floor Observation System (OFOS) video sled was equipped with a photo and a video camera. The water column was measured by a SeaBird SBE911plus conductivity, temperature, and depth (CTD) meter with O2 sensors. Rosette water samples for nutrient analyses were filtered through disposable syringe filters and immediately analyzed using a continuous flow injection system (SKALAR SANplus System/08529). For further details on methods, see Lindhorst et al. (2019).The seismic data we collected in 2019 allow a subdivision of the Saya de Malha Bank succession into three units (Fig. 2). The base of the lowermost unit 1 is not imaged in the profiles; at the top, it is delimited by an unconformity at 0.9–1.2 s two-way traveltime, which corresponds to a depth of 1.3–1.6 km below seafloor, using International Ocean Discovery Program (IODP) data from seismically comparable Maldives carbonates (Lüdmann et al., 2013; Betzler et al., 2018). The nature of unit 1 is not fully interpretable with the available data because the reflection pattern is mainly chaotic.In unit 2, a basin was imaged, which was laterally infilled by progradational clinoform strata (Figs. 2A and 2B). Clinoform bottomsets pass into subhorizontal and subparallel layering. In the topset, layering is subhorizontal and laterally discontinuous. In view of the isolated nature of Saya de Malha Bank without any siliciclastic input, the architecture is interpreted to reflect a flat-topped carbonate platform (Eberli and Ginsburg, 1987). Such platforms have an edge formed by reefs or shoals, inclined slopes, and flat-lying inner platform deposits. The carbonate edifice enclosed a basin several tens to hundreds of meters deep and at least 60 km wide (Figs. 2A and 2B). Locally in the basin, there are isolated buildups as much as 5 km wide, which rest on the unconformity separating units 1 and 2. The progradation of the inner platform edge toward the inner basin was not controlled by margin orientation (Figs. 2A–2C), which favors the interpretation that Saya de Malha Bank was an atoll at the time of unit 2 deposition (Purdy and Bertram, 1993).The growth mode illustrated by unit 2 terminated at a pronounced and platform-wide seismic reflection (drowning unconformity, DU) (Fig. 2). Above horizon DU, the succession is layered (unit 3), reaching up to the seafloor and thinning out toward the south. In northeast-southwest–oriented sections, unit 3 has a backstepping carbonate ramp–like geometry (Fig. 2C). The layered sedimentation pattern of unit 3 is interrupted by flat-topped minor bodies as much as 12 km wide, which reach up to a water depth of 20 m (Fig. 2A). These bodies are wide near the bank margins and narrow in the bank interior. Some show an internal stratification (Fig. 2A), with a succession of parallel to subparallel strata in the center and some inclined and prograding strata toward the margins. At present, the surfaces of the bodies are populated by mesophotic coral ecosystems with red algae, corals, and green algae (Fig. 2D). The rims of the marginal bodies facing the open sea are located farther platform-inward compared to the outer platform margins of unit 2; i.e., the edges of these relict banks stepped back over time.The establishment of the horseshoe-shaped bank rim appears to correlate with changes in the stratal patterns above horizon DU. In northeast-southwest–oriented seismic lines (Fig. 2C), it is apparent that horizon DU crops out at the seafloor as a hardground dissected by fissures (Fig. 2E), in parts infilled by soft sediment. The hardground has a local cover of submarine dune fields (Fig. 2C). The surface also displays large and scattered circular to subcircular depressions (Fig. 2C) as much as 1 km wide and as much as 160 m deep, which are interpreted as karst features.Temperature, salinity, and oxygen concentrations over the Saya de Malha Bank indicate tropical surface waters of low salinity, and more saline water of Arabian Sea provenance near the surface (Fig. 3A). Salt-rich subtropical surface water and Indonesian Throughflow water that is low in oxygen mix at ∼200 m water depth (Figs. 3A and 3B). Below, there is the relatively oxygen-rich Southern Indian Central Water (300–500 m water depth), in turn underlain by oxygen-poor Red Sea–Persian Gulf Intermediate Water. In October 2019, during R/V SONNE cruise SO270 (Lindhorst et al., 2019), the mean sea-surface temperature was 26.9 °C. This temperature, and the mean salinity of 34.8 psu (practical salinity units), the low productivity, and the phosphate concentration of 0.11 µM (Figs. 3C and 3D) are well within the tolerance limits of coral reefs.Zones of the Saya de Malha Bank impacted by the highest current velocities (Fig. 1B) coincide with the areas where horizon DU is at the seafloor (Figs. 2C and 2E). In spite of the blocking position of the bank in the massive South Equatorial Current water flow, there is no indication of topographic upwelling of nutrient-rich sub-thermocline waters into the euphotic zone (Figs. 3C and 3D). Instead, low phosphate and chlorophyll-alpha concentrations in the waters over the bank mark the region as being nutrient limited, with only low levels of pelagic productivity.The depositional geometries (Fig. 2) of the Saya de Malha Bank indicate that the present-day platform state of partial drowning was established during the younger Neogene. The platform factory eventually changed from shallow-water carbonate growth—with the platform top at or near sea level—to a mode with carbonate producers unable to fill the available accommodation at any location of the platform.Because no rock or well data are available, age interpretation for horizon DU formation relies on indirect evidence. The thermally controlled subsidence rate for this part of the Mascarene Plateau was ∼0.1 m k.y.−1 for the past 7 m.y. (Coffin, 1992) (Fig. 1B). Assuming that horizon DU traces the pre-drowning top of the shallow-water carbonate platform, the surface thus would have formed during the Pliocene. This is endorsed by data from the conjugate margin (Indian plate) with a similar thermal history. Industry well NMA1, located in the Maldives at a depth of 300–330 m below sea level, recovered a facies of an early Pliocene drowning event (Aubert and Droxler, 1992). Correlation with seismic horizons and ages of sediments recovered during IODP Expedition 359 (Lüdmann et al., 2013) delimits this interval with sequence boundaries formed at 2.1 and 3.0 Ma (Betzler et al., 2018).The most straightforward explanation for the Saya de Malha Bank drowning thus appears to be the response to a sea-level rise. Other isolated carbonate platforms such as the Bahamas, the Maldives, or the platforms off northeastern Australia also record this episode of high Pliocene eustatic sea level (Eberli and Ginsburg, 1987; Aubert and Droxler, 1992; Betzler et al., 2000; McNeill et al., 2001; Reijmer et al., 2002). Subsequent recovery of these platforms with recent shallow-water carbonate sedimentation, however, indicates that in addition to sea-level fluctuations, other factors controlled Saya de Malha Bank drowning.Nutrient injection into shallow water has been invoked as a drowning trigger (Hallock and Schlager, 1986), but it has also been shown that coral reefs adapt to changes in trophic state (Morgan et al., 2016). At present, the low phosphate and chlorophyll-alpha concentrations in the water column on and around the bank (Fig. 3) are not indicative of nutrient control. Conditions of low productivity in the Indian Ocean can also be traced back for the past ∼4 m.y. by carbonate mass accumulation rates (Dickens and Owen, 1999). For the period before 4 Ma, the same data indicate more elevated surface-water productivity.Ocean currents can trigger drowning (Isern et al., 2004; John and Mutti, 2005; Betzler et al., 2009; Eberli et al., 2010; Purkis et al., 2014; Reolid et al., 2020; Ling et al., 2021), and the present-day oceanographic conditions around Saya de Malha Bank introduce the South Equatorial Current as a major player in platform evolution. Today, the bank is sculpted by the current, with sediment winnowing at its southern tip (Figs. 2C and 2E). The South Equatorial Current established at 3.3 Ma (Auer et al., 2019), and accelerated currents through trade-wind intensification started at ca. 3 Ma as documented in upwelling records of the Benguela Current (Marlow et al., 2000), which is connected to the South Equatorial Current through the Agulhas leakage (Durgadoo et al., 2017).Whether a shallow-water carbonate factory keeps up with sea-level rise depends on the amplitudes and frequencies of sea-level changes, but also on the antecedent topography. Coral colonization of a substrate during a rapid sea-level rise is possible only when there is substrate for corals to grow in the upper photic zone, as documented by many backstepping and submerged reef terraces around modern carbonate platforms (Woodroffe and Webster, 2014). Flat-topped platforms do not provide these conditions, and thus, under elevated rates of sea-level rise as high as 19 mm yr−1 (Montaggioni and Martin-Garin, 2020), can drown if the sediment production rate of the carbonate factory is too low to infill accommodation. The seismic evidence of relict banks with margin progradation (Fig. 2A) in this context reflects ephemeral past stages with bank-top carbonate production and export; i.e., short episodes when the bank tops were at sea level.The onset of eccentricity-driven sea-level fluctuations at ca. 3 Ma resulted in high amplitudes and rates of change, which later during the Pleistocene became even more pronounced. This induced a change from flat-topped banks to atolls on many Pacific and Indian Ocean carbonate platforms (Droxler and Jorry, 2021). In the case of Saya de Malha Bank, however, the South Equatorial Current prevented the reefs from forming a closed rim, thus drowning the bank, which from then on was populated only by shallow-water reefs during short periods of lowered sea level.The Saya de Malha Bank drowning is therefore not attributed to one factor alone. It was rather a combination of two processes, i.e., sea-level change and current intensification, which were the reasons that the reef systems, although situated in a suitable setting, did not produce sufficient sediment to infill the available accommodation. These findings are applicable to other drowned Tertiary platforms in the Indo-Pacific region, such as, e.g., in the South China Sea. Nutrient injection into shallow waters, a process invoked as a platform-drowning trigger elsewhere, is not seen as relevant in the case of the Saya de Malha Bank drowning.The German Federal Ministry of Education and Research (BMBF) is funding the project MASCARA (grants 03G0270A and 03G0270B). We are grateful to Captain Mallon, the officers, and crew of R/V SONNE for their excellent support. Many thanks to the technicians of the cruise SO270 scientific party. The Joint Commission of the Extended Continental Shelf, Mascarene Plateau Region, is thanked for allowing work in the Joint Management Area between Mauritius and Seychelles; and the Department for Continental Shelf, Maritime Zones Administration and Exploration (Mauritius) allowed work in the Republic of Mauritius Exclusive Economic Zone. Schlumberger is thanked for the grant to use Petrel software. We thank Sam Purkis, an anonymous reviewer, and editor Kathleen Benison for insightful and constructive comments.

中文翻译：

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洋流和海平面控制着热带海岸浅层碳酸盐生产的消亡（Saya de Malha Bank，印度洋）

碳酸盐平台主要由生活在浅光饱和热带水域的珊瑚建造。Saya de Malha Bank（印度洋）是世界上最大的碳酸盐岩台地之一，位于南赤道洋流的路径上。它的珊瑚礁没有达到海平面，所有的碳酸盐生产都是中光到寡光的。新的地质和海洋学数据揭示了银行的演变和环境，阐明了决定这种特殊状态的因素。珊瑚生长没有与营养相关的限制。新近纪晚期南赤道洋流的发展，提出了从边缘环礁到只有中光珊瑚生长的暴露系统的转变。当前活动和海平面波动的组合可能是现代平台配置的控制因素。碳酸盐平台是高数公里、宽数百公里的建筑物，主要由浅水生物（如造礁虫黄藻珊瑚）及其碎屑产生。平台在热带海洋带中繁衍生息数百万年，其中许多与大陆地区隔离。珊瑚礁主要沿着平台边缘到达海平面，例如在印度-太平洋生物地理区域。光照以及水温、浊度、盐度、养分和流速决定了珊瑚及其光合共生体的繁盛深度（Schlager，2005）。珊瑚礁是生产力最高的海洋生态系统之一，在贫营养水域蓬勃发展。海平面变化在地质时间尺度上对珊瑚礁的发育产生根本性的控制（Webster 等，2018）。珊瑚礁在海平面下降或上升后向海面和平台移动，而海平面上升超过珊瑚礁生长会中断珊瑚礁发育。在印度太平洋生物地理区域，现在被淹没且未达到海平面的珊瑚礁通常是更新世时代的结构，在冰消期的短暂重新殖民化过程中沉积了薄薄的珊瑚覆盖物（Montaggioni，2005）。除了受构造抬升影响的地点外，在 19 kyr BP 之前形成的初期堆积物也被淹没了。一些珊瑚礁能够跟上冰消期海平面上升，但其他珊瑚礁由于尚未完全了解的原因而无法跟上（Montaggioni，2005；Woodroffe 和 Webster，2014；Webster 等，2018）。后者是今天许多中光珊瑚生态系统的所在地。印度洋的 Saya de Malha Bank 处于浅水珊瑚礁开发的最佳条件窗口，但如今的碳酸盐平台主要由中光珊瑚生态系统组成。利用地球物理、海洋学和沉积学数据，我们研究了洋流如何塑造这个平台，以及它们如何——连同海平面变化——阻碍浅水珊瑚礁的生长。这对地质记录中的其他碳酸盐平台案例有影响，其中珊瑚礁生长或没有生长到海平面，即完全或部分淹没的那些。印度洋新生代孤立的碳酸盐平台生长在印度和非洲板块产生的火山脊上飘过留尼汪热点（Purdy 和 Bertram，1993 年）。印度板块平台是马尔代夫、拉卡代夫群岛和查戈斯群岛。在非洲板块，马斯卡林高原与 Saya de Malha Bank 和 Nazareth Bank 位于 4°S 和 20°S 之间（图 1A）。Saya de Malha 银行占地 40,000 平方公里，由较小的北岸和较大的南岸组成，后者是本研究的重点。南岸东西宽 230 公里，北岸南边290公里。它被马蹄形的暗礁边缘环绕，其最小水深为 8 m，向南开放（图 1B）（Fedorov 等，1980）。在 SM-1 油井（3264 m 深；图 1B）中，古新世到第四纪浅海到浅水碳酸盐岩覆盖在 45 Ma 玄武岩上（Meyerhoff 和 Kamen-Kaye，1981）。该区域的下沉受热控制（图 1B），根据使用艾里等静压模型（Coffin，1992）回溯海洋钻探计划站点确定的。通过使用低分辨率地震测线（Purdy 和 Bertram，1993），该银行的演替被解释为一个最终淹没的环礁。Saya de Malha 银行位于南赤道洋流的直接路径，在 10°S 之间和 16°S 在 0.3–0.7 ms-1 处流动（图 1B）（New 等人，2007 年）。在大潮期间，正压潮汐流可以在东西方向上增加 0.35 ms-1。南赤道洋流的主要流动向北和南岸分流，在 11°S 和 13°S 之间最强，在 Saya de Malha 和 Nazareth Banks 之间汇合（图 1）。当前输送 ∼50 Sv (sverdrup; 50 × 106 m3 s-1)，主要受强东南信风驱动。在上部混合良好的层（50-100 m）中，水流几乎均匀并在水深 500-1000 m 处减弱。我们使用 144 通道 600 m 数字 Hydroscience Technologies Inc. 拖缆获取地震反射数据。海底观测系统 (OFOS) 视频雪橇配备了照片和摄像机。水柱由带有 O2 传感器的 SeaBird SBE911plus 电导率、温度和深度 (CTD) 计测量。用于营养分析的 Rosette 水样通过一次性注射器过滤器过滤，并立即使用连续流动注射系统 (SKALAR SANplus System/08529) 进行分析。有关方法的更多详细信息，请参阅 Lindhorst 等人。(2019)。我们在 2019 年收集的地震数据允许将 Saya de Malha Bank 序列细分为三个单元（图 2）。最下方单元 1 的底部未在轮廓中成像；在顶部，它由 0.9-1.2 秒双向走时的不整合面划定，对应于海底以下 1.3-1.6 公里的深度，使用来自地震可比的马尔代夫碳酸盐岩的国际海洋发现计划 (IODP) 数据（Lüdmann 等al.，2013 年；Betzler 等人，2018 年）。单元 1 的性质不能用现有数据完全解释，因为反射模式主要是混沌的。在单元 2 中，成像了一个盆地，该盆地被前积的倾斜地层横向填充（图 2A 和 2B）。Clinoform 底部设置进入次水平和次平行分层。在顶部，分层是近水平的和横向不连续的。鉴于 Saya de Malha 银行的孤立性质，没有任何硅质碎屑输入，该架构被解释为反映了一个平顶的碳酸盐平台（Eberli 和 Ginsburg，1987）。此类台地的边缘由暗礁或浅滩、倾斜的斜坡和平坦的内台地沉积物形成。碳酸盐岩建筑物包围着一个深达数十至数百米、宽至少 60 公里的盆地（图 2A 和 2B）。在盆地局部，有多达 5 公里宽的孤立堆积物，位于不整合分离单元 1 和 2 上。内台地边缘向内盆地的进积不受边缘方向的控制（图 2A-2C） )，这支持 Saya de Malha Bank 在 2 号机组沉积时是一个环礁的解释 (Purdy and Bertram, 1993)。 DU）（图2）。在地平线 DU 之上，序列是分层的（单元 3），一直延伸到海底并向南逐渐变薄。在东北-西南方向的剖面中，单元 3 具有类似碳酸盐斜坡的倒退几何形状（图 2C）。单元 3 的层状沉积模式被宽达 12 km 的平顶小体中断，其水深可达 20 m（图 2A）。这些主体在靠近堤岸边缘处较宽，而在堤岸内部较窄。一些显示内部分层（图 2A），在中心有一系列平行于次平行的地层，一些向边缘倾斜和前移的地层。目前，身体表面是由红藻、珊瑚和绿藻组成的中光珊瑚生态系统（图 2D）。与单元 2 的外部平台边缘相比，面向公海的边缘体的边缘位于更远的平台向内；即，这些残存河岸的边缘随着时间的推移而后退。马蹄形河岸边缘的建立似乎与 DU 地层以上地层模式的变化有关。在东北-西南方向的地震测线（图 2C）中，很明显 DU 层在海底露出为被裂缝分割的硬地（图 2E），部分被软沉积物填充。硬地局部覆盖有海底沙丘（图 2C）。地表还显示出大而分散的圆形至亚圆形凹陷（图 2C），宽达 1 公里，深达 160 米，被解释为岩溶特征。温度、盐度、Saya de Malha Bank 上空的氧气浓度和氧气浓度表明热带地表水盐度较低，而地表附近阿拉伯海来源的咸水较多（图 3A）。富含盐分的亚热带地表水和含氧量低的印度尼西亚通流水在约 200 米水深混合（图 3A 和 3B）。下面是相对富氧的南印度中部水域（水深 300-500 米），下面是缺氧的红海-波斯湾中水。2019 年 10 月，R/V SONNE 巡航 SO270（Lindhorst 等，2019）期间，平均海面温度为 26.9 °C。这个温度和 34.8 psu（实际盐度单位）的平均盐度、低生产力和 0.11 µM 的磷酸盐浓度（图 3C 和 3D）完全在珊瑚礁的容许范围内。Saya de Malha Bank 受最高流速影响的区域（图 1B）与地平线 DU 位于海底的区域重合（图 2C 和 2E）。尽管在巨大的南赤道洋流水流中堤坝的位置被阻挡，但没有迹象表明富含营养的次温跃层水在地形上涌入透光区（图 3C 和 3D）。相反，河岸水域中磷酸盐和叶绿素-α 浓度低表明该地区营养有限，只有低水平的远洋生产力。 Saya de Malha 河岸的沉积几何结构（图 2）表明，目前-部分溺水的天台状态是在新近纪较年轻的时期建立的。平台工厂最终从浅水碳酸盐生长——平台顶部处于或接近海平面——转变为碳酸盐生产商无法填补平台任何位置可用空间的模式。 由于没有岩石或井数据可用，地平线 DU 形成的年龄解释依赖于间接证据。在过去的 7 年（Coffin，1992 年）（图 1B）中，Mascarene 高原这部分的热控制下沉率约为 0.1 m ky-1。假设地平线 DU 追踪浅水碳酸盐台地淹没前的顶部，则表面将在上新世期间形成。来自具有类似热历史的共轭边缘（印度板块）的数据证实了这一点。工业井 NMA1，位于马尔代夫海平面以下 300-330 m 深处，恢复了上新世早期溺水事件的相貌（Aubert 和 Droxler，1992 年）。在 IODP 远征 359（Lüdmann 等人，2013 年）期间与地震层和沉积物年龄的相关性用形成于 2.1 和 3.0 Ma 的层序边界划定了该区间（Betzler 等人，2018 年）。对 Saya de 的最直接解释因此，Malha Bank 溺水事件似乎是对海平面上升的反应。其他孤立的碳酸盐平台，如巴哈马、马尔代夫或澳大利亚东北部的平台也记录了上新世高海平面的这一事件（Eberli 和 Ginsburg，1987 年；Aubert 和 Droxler，1992 年；Betzler 等人，2000 年；McNeill 等人al., 2001; Reijmer et al., 2002)。然而，随着最近的浅水碳酸盐沉积物对这些平台的后续恢复，表明除了海平面波动之外，其他因素控制了 Saya de Malha Bank 溺水。向浅水中注入营养已被称为溺水触发因素（Hallock 和 Schlager，1986），但也表明珊瑚礁适应营养状态的变化（摩根等，2016）。目前，堤岸及其周围水体中磷酸盐和叶绿素-α 浓度较低（图 3）并不能说明营养物控制情况。印度洋低生产力的条件也可以通过碳酸盐质量积累率追溯到过去 4 年（Dickens 和 Owen，1999）。对于 4 Ma 之前的时期，相同的数据表明地表水生产力更高。洋流可以引发溺水（Isern 等人，2004 年；John 和 Mutti，2005 年；Betzler 等人，2009 年；Eberli 等人，2010 年） ; Purkis 等人，2014 年；Reolid 等人，2020 年；Ling 等人，2021 年）以及 Saya de Malha 银行周围的当今海洋条件将南赤道流作为平台演化的主要参与者。今天，河岸被水流雕刻，在其南端有沉积物风选（图 2C 和 2E）。南赤道洋流在 3.3 Ma 建立（Auer 等人，2019 年），并且通过信风增强的加速洋流开始于约 3.3 Ma。本格拉洋流的上升流记录（Marlow 等人，2000 年）记录了 3 Ma，该洋流通过 Agulhas 泄漏与南赤道洋流相连（Durgadoo 等人，2017 年）。浅水碳酸盐工厂是否跟上海平面上升取决于海平面变化的幅度和频率，也取决于先前的地形。正如现代碳酸盐台地周围的许多后退和水下珊瑚礁阶地所记录的那样，只有当珊瑚在上光带生长时才有可能在海平面快速上升期间进行珊瑚殖民（Woodroffe 和 Webster，2014）。平顶平台不提供这些条件，因此，在海平面上升速度高达 19 毫米 yr−1 的情况下（Montaggioni 和 Martin-Garin，2020），如果碳酸盐工厂的沉积物生产率降低，则可能会淹死太低，无法填充住宿。在这种情况下，边缘进积的残存堤岸的地震证据（图 2A）反映了岸顶碳酸盐生产和出口的短暂过去阶段；即，当岸顶处于海平面时的短暂发作。3 Ma 导致高振幅和变化率，在更新世后期变得更加明显。这导致许多太平洋和印度洋碳酸盐平台上从平顶河岸变为环礁（Droxler 和 Jorry，2021 年）。然而，在 Saya de Malha Bank 的情况下，南赤道洋流阻止了珊瑚礁形成一个封闭的边缘，从而淹没了银行，从那时起，在海平面下降的短时间内，只有浅水珊瑚礁居住。因此，Saya de Malha Bank 溺水事件不仅仅归因于一个因素。它是两个过程的结合，即海平面变化和海流强化，这就是珊瑚礁系统虽然位于合适的环境中，但没有产生足够的沉积物来填充可用住宿的原因。这些发现适用于印度-太平洋地区的其他淹没第三纪平台，例如在南海。将营养注入浅水区，这一过程在其他地方被称为平台溺水的触发因素，与 Saya de Malha 银行溺水案无关。德国联邦教育和研究部 (BMBF) 正在资助 MASCARA 项目（ 03G0270A 和 03G0270B）。我们感谢 Mallon 船长、R/V SONNE 的军官和船员的大力支持。非常感谢巡航 SO270 科学派对的技术人员。感谢马斯卡林高原地区扩展大陆架联合委员会允许在毛里求斯和塞舌尔之间的联合管理区开展工作；和大陆架部，海区管理和勘探（毛里求斯）允许在毛里求斯共和国专属经济区工作。感谢 Schlumberger 授予使用 Petrel 软件的资助。我们感谢匿名审稿人 Sam Purkis 和编辑 Kathleen Benison 提出的富有洞察力和建设性的意见。