Glendonites are carbonate pseudomorphs after ikaite are used as indicators of near-freezing temperatures. We describe the first glendonites of Middle–Late Jurassic to Early Cretaceous age from the Barents Shelf, including the first glendonites of Late Barremian–Early Aptian age ever discovered on Earth and provide the detailed mineralogical-geochemical and isotopic studies. Although Mesozoic glendonites are well-known across the Arctic realm, however the ikaite-calcite transformation and implication of glendonite findings are still debatable. Pseudomorphs are mainly composed of calcite. Cathodoluminescence and scanning electron microscopy studies reveal three types (I-III) of calcite: type I - elongated, rounded and irregular calcite; type II - blocky, fibrous and needle-like calcite/siderite; type III - blocky calcite in pores. Elemental analyses distinguish geochemical differences between the calcite types: type I comprises pure CaCO₃; type II calcite contains Mg and P (in all studied samples), Fe (Bajocian–Callovian), S (Middle Volgian) or Sr (Upper Barremian–Lower Aptian); type III calcite is depleted in Mg, P and Fe. Concentrations of Mn, Fe, Sr and calculated Mn/Ca, Fe/Ca and Sr/Ca ratios are suggestive of diagenetic alteration. Bulk δ¹⁸O values range from −5.39 to −1.71‰ VPDB, supporting overprinting of primary values during burial diagenesis, while bulk δ¹³C values range from −33.3 to −22.6‰ VPDB, providing the influence of organic matter on ikaite-glendonite formation. However, ⁸⁷Sr/⁸⁶Sr values range from 0.7070 to 0.7110, mainly corresponding to Jurassic–Cretaceous seawater. Rare-earth elements characterize porewater REE-patterns, with slight middle REE-enrichment and depletion in light and heavy REE. Weak positive and negative Ce anomalies indicate fluctiating from anoxic to oxic conditions during ikaite-glendonite formation. Our new biostratigraphic data refine the ages of glendonite-bearing horizons in the Barents Shelf region, allowing a more definitive correlation with coeval glendonite occurrences across the Arctic realm and with global climatic changes during the Jurassic–Cretaceous.

Glendonites 是 ikaite 被用作接近冰点温度的指标后的碳酸盐假晶型。我们描述了来自巴伦支陆架的中晚侏罗世至早白垩世时代的第一批菱镁矿，包括地球上发现的第一批晚巴雷姆期至阿普第阶早期的菱镁矿，并提供了详细的矿物地球化学和同位素研究。尽管中生代格陵脱岩在整个北极范围内广为人知，但格陵脱岩发现的ikaite-方解石转变和含义仍然存在争议。伪晶主要由方解石组成。阴极发光和扫描电子显微镜研究揭示了三种类型 (I-III) 的方解石：I 型 - 细长、圆形和不规则方解石；II型——块状、纤维状和针状方解石/菱铁矿；III型 - 孔隙中的块状方解石。₃ ; II 型方解石包含 Mg 和 P（在所有研究样品中）、Fe（Bajocian-Callovian）、S（Middle Volgian）或 Sr（Upper Barremian-Lower Aptian）；III型方解石缺乏Mg、P和Fe。Mn、Fe、Sr 的浓度和计算出的 Mn/Ca、Fe/Ca 和 Sr/Ca 比值暗示了成岩作用。大块 δ ¹⁸ O 值范围为 -5.39 至 -1.71‰ VPDB，支持埋藏成岩过程中原始值的叠加，而大块 δ ¹³ C 值范围为 -33.3 至 -22.6‰ VPDB，提供有机质对辉绿岩的影响形成。然而，⁸⁷ Sr/ ⁸⁶Sr 值范围为 0.7070 至 0.7110，主要对应于侏罗纪-白垩纪海水。稀土元素表征孔隙水 REE 模式，轻、重 REE 中 REE 轻度富集和耗尽。弱的正负 Ce 异常表明在 ikaite-glendonite 形成过程中从缺氧到有氧条件波动。我们的新生物地层数据完善了巴伦支大陆架地区含菱镁矿层位的年龄，从而与整个北极地区的同期菱镁矿分布以及侏罗纪 - 白垩纪期间的全球气候变化建立了更明确的相关性。