The Kap Stewart Group (Rhaetian-Sinemurian, Triassic–Early Jurassic) of the Jameson Land Basin in central East Greenland has traditionally been regarded as a strictly continental unit with delta and perennial lake sediments. New finds of plesiosaur bone remain in a thin storm deposited sandstone bed in the middle part of the Rhætelv Formation of the Kap Stewart Group, however, indicates a likely period of marine influence. At the study area at the eastern margin of the basin, the Rhætelv Formation is 300-m thick and overlies unconformably the Norian Fleming Fjord Group. The bone-bearing sandstone occurs 190 m above the base of the group and is closely associated with black laminated mudstones; palynological investigation of three samples from these mudstones indicates that they are of a younger Hettangian age. The Hettangian was a relatively short stage (201.3–199.5 Ma) and elsewhere characterized by two episodes of sea-level highstands. Assuming that the marine incursion in the Jameson land Basin evidenced by the plesiosaur fossil remains took place during the youngest of these sea-level highstands, the bone-bearing bed of the Rhætelv Formation can be dated to 200 Ma and thereby gives the first numerical age constraint of this hitherto poorly dated succession.

中文翻译：

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格陵兰岛东部中部 Rhætelv 组（Kap Stewart Group）的新脊椎动物化石层：Hettangian 海洋侵入大陆詹姆逊陆盆地的证据

位于东格陵兰岛中部的詹姆逊陆盆地的卡普斯图尔特群（Rhaetian-Sinemurian，三叠纪-早侏罗世）传统上被视为具有三角洲和多年生湖泊沉积物的严格大陆单元。然而，在 Kap Stewart 组 Rhætelv 组中部的一个薄薄的风暴沉积砂岩床中发现了新的蛇颈龙骨，这表明可能存在海洋影响时期。在盆地东缘研究区，Rhætelv 组厚 300 米，不整合地覆盖在 Norian Fleming Fjord 群上。含骨砂岩产于群基部以上190 m，与黑色层状泥岩密切伴生；对来自这些泥岩的三个样品的孢粉学研究表明，它们属于较年轻的赫坦阶时代。Hettangian 阶段是一个相对较短的阶段（201.3-199.5 Ma），在其他地方以两次海平面高位为特征。假设蛇颈龙化石所证明的詹姆逊陆盆地的海洋入侵发生在这些海平面高位中最年轻的时期，Rhætelv 组的含骨床可以追溯到 200 Ma，从而给出了第一个数字年龄迄今为止，这种陈旧过时的继承受到了限制。