In order to improve the understanding of how the high northern latitudes responded to the escalating warming which led to the middle Cretaceous super greenhouse climate, more temperature proxy records from the High Arctic are needed. One of the current obstacles in obtaining such records is poor age control on the Lower Cretaceous strata in the Boreal region. Here, we provide a biostratigraphic framework for the Rurikfjellet and Helvetiafjellet formations representing the lower part of the Lower Cretaceous succession on Spitsbergen. We also attempt to date the boundary between the Agardhfjellet and the Rurikfjellet formations. This study is based on dinoflagellate cysts (dinocysts) from three onshore cores (DH1, DH2 and DH5R) and three outcrop sections (Bohemanflya, Myklegardfjellet and Ullaberget). Relatively abundant and well-preserved dinocyst assemblages from the Rurikfjellet Formation date this unit as early Valanginian – early Barremian. The dinocyst assemblages from the Helvetiafjellet Formation are significantly impoverished and are characterized by reworking, but collectively indicate a Barremian–Aptian age for this formation.

中文翻译：

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挪威北极斯匹次卑尔根的 Valanginian-Aptian Rurikfjellet 和 Helvetiafjellet 地层的恐龙囊地层学

为了更好地理解北高纬度地区如何应对导致中白垩纪超级温室气候的不断升级的变暖，需要更多来自北极高纬度地区的温度代理记录。目前获得此类记录的障碍之一是北方地区下白垩统地层的年龄控制不佳。在这里，我们为代表斯匹次卑尔根下白垩统序列下部的 Rurikfjellet 和 Helvetiafjellet 地层提供了生物地层框架。我们还尝试确定 Agardhfjellet 和 Rurikfjellet 地层之间的边界。本研究基于来自三个陆上岩心（DH1、DH2 和 DH5R）和三个露头部分（Bohemanflya、Myklegardfjellet 和 Ullaberget）的甲藻包囊（dinocysts）。来自 Rurikfjellet 组的相对丰富和保存完好的恐龙囊组合将该单元确定为早期 Valanginian - 早期 Barremian。Helvetiafjellet 组的恐龙囊组合明显贫瘠，并以返工为特征，但共同表明该地层的 Barremian-Aptian 时代。