Yasuhara Moriaki, Ando Atsushi, Iba Yasuhiro
School of Biological Sciences, Swire Institute of Marine Science, and Department of Earth Sciences, the University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong, SAR, China.
Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, MRC 121, Washington, DC 20013-7012, USA.
Sci Rep. 2017 Nov 13;7(1):15423. doi: 10.1038/s41598-017-15684-z.
The Cretaceous Period stands out in Earth's geologic history by ubiquitous and sustained massive eruption of lava, forming several enormous igneous plateaus in the ocean basins worldwide. It has been proposed that the subaerial phases of Cretaceous oceanic plateau formation spurred the global environmental deterioration, yet this view is supported by patchy fossil and/or rock evidence for uplifting of the plateau summits above the sea level. Reported here is by far the most comprehensive case of Cretaceous plateau emergence at northern Shatsky Rise, Northwest Pacific, based on the integration of unique micropalaeontological and seismic evidence. From just above the flat-topped igneous edifice, recent Integrated Ocean Drilling Program (at Site U1346) recovered early Cretaceous (Hauterivian) ostracod and foraminiferal assemblages showing marked shallow-marine preferences. Most intriguing discovery is an ostracod taxon with well-developed eye tubercles, which serves as compelling palaeobiological evidence for a very shallow, euphotic setting. By linking the nearshore biofacies (<20 m water depth) to the basement topography undoubtedly shaped by subaerial weathering and/or erosion, it is obvious that northern Shatsky Rise was remarkably emergent during its final emplacement phase. We suggest that early Cretaceous surface environments might have been affected, at least in part, by Shatsky Rise subaerial volcanism.
白垩纪在地球地质历史中格外突出，因为当时全球范围内普遍且持续地大规模喷发熔岩，在各大洋盆地形成了几个巨大的火成岩高原。有人提出，白垩纪海洋高原形成的陆相阶段促使了全球环境恶化，但这一观点仅得到零星的化石和/或岩石证据的支持，这些证据表明高原顶部海拔高于海平面。本文报道了迄今为止基于独特的微古生物学和地震证据，在西北太平洋 Shatsky 海隆北部发现的最全面的白垩纪高原露出海面的案例。在平顶火成岩构造上方，最近的综合大洋钻探计划（在 U1346 站点）采集到了早白垩世（豪特里维阶）介形虫和有孔虫组合，这些组合显示出明显的浅海偏好。最引人注目的发现是一个具有发育良好眼瘤的介形虫分类单元，这是浅海、透光环境的有力古生物学证据。通过将近岸生物相（水深<20 米）与无疑是由陆相风化和/或侵蚀塑造的基底地形联系起来，可以明显看出 Shatsky 海隆北部在其最终就位阶段显著露出海面。我们认为，早白垩世的地表环境可能至少部分受到了 Shatsky 海隆陆相火山活动的影响。
