About 70 fossil and live-collected specimens of Desmophyllum dianthus were collected from steep rocky surfaces and time-averaged assemblages at their base (“coral graveyards”) in the southern Labrador Sea at depths ranging from ~1700 m (Orphan Knoll) to ~2200 m (Flemish Cap). Aside from stable isotope and mineralogical analysis, U-series and ¹⁴C age determinations were performed on the samples. Fossil corals from the coral graveyards display two principal age clusters corresponding respectively to the Holocene and Marine Isotope Stage (MIS) 5c intervals. Three samples lay outside these clusters, at ~13.5 ka (Bølling-Allerød), ~ 64 ka (MIS 3) and at ~181 ka (MIS 7a). The clusters are thought to record intervals with both i) high food availability, either through pelagic primary production in the overlying water column or more effectively in relation with particulate and dissolved organic carbon transport via an active Western Boundary Undercurrent (WBUC), and ii) high carbonate micrite advection by this current from more open North Atlantic coccolithophorid production areas, maintaining an aragonite saturation horizon (now at 2300 m) slightly deeper than the coral habitat (~ 2200 m). Attempts at estimating ventilation ages from ²³⁰Th vs ¹⁴C age offsets in Holocene samples failed. This is due to uncertainties about the initial ¹⁴C-apparent age of coral skeletons and to their high initial excesses in ²³⁰Th. This initial excess relates mostly to the scavenging of ²³⁰Th produced by the dissolved marine U by the coral-feeding organic matter carried along the WBUC trajectory. In addition, discrete diagenetic U-fluxes can be documented in fossil samples. They are well illustrated in specimens from MIS 5c age, which depict variable excesses in ²³⁴U vs ²³⁸U, but similar ²³⁰Th/²³⁸U activity ratios, pointing to a recent but fractionating redistribution of uranium in the samples. These are also documented by the development of FeMn coatings of specimens exposed at the sea floor, due to the winnowing of embedding slope sediments, with the mid- to late Holocene intensified WBUC. Such diagenetic processes are to be notably taken into consideration for the dating of pre-Holocene samples. Thus, both the initial isotopic properties of corals from this WBUC-influenced, mid-continental slope, and subsequent diagenetic effects impact their calculated ages, and blur estimates of “ventilation ages” based on their ¹⁴C vs ²³⁰Th-ages offsets.

在南拉布拉多海的基部（“珊瑚墓地”）的陡峭岩石表面和时间平均组合中，收集了约70个石竹和活体标本，深度约为〜1700 m（孤峰）至〜2200。 m（佛兰芒帽）。除了稳定的同位素和矿物学分析外，U系列和¹⁴对样品进行了年龄确定。来自珊瑚墓地的化石珊瑚显示出两个主要的年龄群，分别与全新世和海洋同位素阶段（MIS）的5c间隔相对应。三个样本位于这些星团之外，分别为〜13.5 ka（Bølling-Allerød），〜64 ka（MIS 3）和〜181 ka（MIS 7a）。人们认为这些集群记录了以下时间间隔：i）较高的食物供应量，要么是通过上覆水柱中的浮游初级生产，要么是通过活跃的西部边界暗流（WBUC）更有效地与颗粒物和溶解的有机碳输送有关，以及ii）这种高碳酸盐微晶对流来自更开放的北大西洋球藻类产区，保持文石饱和层（现在为2300 m）比珊瑚生境（〜2200 m）略深。全新世样品的²³⁰ Th vs ¹⁴ C年龄偏移失败。这是由于对珊瑚骨骼的初始¹⁴ C表观年龄和其²³⁰ Th的初始高度过高的不确定性。最初的过量主要与溶解的海洋U沿WBUC轨迹携带的以珊瑚为食的有机物产生的²³⁰ Th清除有关。此外，化石样品中可以记录不连续的成岩U型通量。它们在MIS 5c年龄的样本中得到了很好的说明，该样本描绘了²³⁴ U和²³⁸ U中的变量过量，但相似的是²³⁰ Th / ²³⁸U活度比，指出了样品中铀的近期但不连续的重新分布。由于埋藏斜坡沉积物的风吹以及全新世中期至晚期WBUC的强化，在海底暴露的标本的Fe Mn涂层的发展也记录了这些情况。全新茂前样品的年代测定应特别考虑到此类成岩过程。因此，受该WBUC影响的大陆中陆斜坡的珊瑚的初始同位素特征以及随后的成岩作用都会影响其计算的年龄，并基于其¹⁴ C对²³⁰ Th年龄的偏移模糊了“通风年龄”的估计。