中国科学院地质与地球物理研究所Ross N. Mitchell团队揭示了冰岛的格陵兰碎片可能与黑暗时代的邦德事件1漂流有关。2025年4月8日出版的《地质学》杂志发表了这项最新研究成果。

研究组报告了在冰岛北部Breiðavík附近的凸起海滩沉积物中发现的外来火成岩、变质岩和沉积卵石。这些沉积物由交替的卵石、砂和粉砂为主的相组成。附近的一组沙子和淤泥，可追溯到古小冰河时代晚期（LALIA；约536-660 CE），为凸起的阶地提供了年龄限制。虽然上阶地仅由当地玄武岩材料组成，但最下阶地（高潮以上约2米）含有玄武岩和非玄武岩卵石的混合物，包括石英长石片麻岩、花岗岩、流纹岩、砂岩和蛇纹岩。

锆石的U-Pb年代学分析揭示了约2800、1150、500和240 Ma的主要年龄模式，Lu-Hf同位素组成表明其起源于格陵兰的北大西洋克拉通和加里东褶皱带。LALIA的较冷条件，加上格陵兰冰盖冰山崩裂的增加，将导致冰块漂流碎片（IRD）向格陵兰岛南部和东部不同地区的运输增加。东格陵兰和东冰岛洋流将这种IRD从格陵兰岛运送过来，随着冰山融化，沿着冰岛海岸发生沉积。该IRD可能是在邦德事件1期间横跨北大西洋运输的。这一过程，以及其他瞬态冷却事件中的过程，可能解释了北极当地基岩和碎屑锆石之间的年龄差异。

附：英文原文

Title: Greenlandic debris in Iceland likely tied to Bond event 1 ice rafting in the Dark Ages

Author: Christopher J. Spencer, Thomas M. Gernon, Ross N. Mitchell

Issue&Volume: 2025-04-08

Abstract: We report the discovery of exotic igneous, metamorphic, and sedimentary cobbles in raised beach deposits near Breieavík, northern Iceland. These deposits consist of alternating cobble-, sand-, and silt-dominated facies. A nearby package of sands and silts, dated to the Late Antique Little Ice Age (LALIA; ca. 536660 CE), provides age constraints for the raised terraces. While the upper terraces are composed exclusively of local basaltic material, the lowermost terraces (～2 m above high tide) contain a mix of basaltic and nonbasaltic cobbles, including quartzofeldspathic gneiss, granitoid, rhyolite, sandstone, and serpentinite. U-Pb geochronologic analysis of zircon revealed dominant age modes of ca. 2800, 1150, 500, and 240 Ma with Lu-Hf isotopic compositions suggesting derivation from Greenland’s North Atlantic craton and Caledonian fold belt. The colder conditions of the LALIA, coupled with increased iceberg calving from the Greenland ice sheet, would have led to enhanced ice-rafted debris (IRD) transport to disparate areas south and east of Greenland. The East Greenland and East Iceland currents transported this IRD from Greenland, with deposition occurring along the Icelandic coast as the icebergs melted. This IRD was likely transported across the North Atlantic during Bond event 1. This process, along with those during other transient cooling events, may explain the age discrepancies between local bedrock and detrital zircons in the Arctic.

DOI: 10.1130/G53168.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G53168.1/653479/Greenlandic-debris-in-Iceland-likely-tied-to-BondredirectedFrom=fulltext