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首页> 外文期刊>Journal of Biogeography >The maximum age of Hawaiian terrestrial lineages: geological constraints from Koko Seamount
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The maximum age of Hawaiian terrestrial lineages: geological constraints from Koko Seamount

机译：夏威夷陆地谱系的最大年龄：来自Koko Seamount的地质限制

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AimTo determine if Koko Seamount submerged below sea level before Kure Island and Pearl and Hermes Reef formed, resulting in a period in which there were no extant islands. A period with no islands would eliminate prior terrestrial and shallow marine biotas that could migrate from island to island and require a restart of colonization from distant shores to populate the younger islands of the Hawaiian volcanic chain.LocationEmperor Seamount Chain, north-central Pacific Ocean.MethodsWe estimate subsidence rates for Koko Seamount using ages determined from fossil large foraminifera and Sr-isotopes, and maximum depths using palaeodepth estimates based on coralline algae. These data are combined with palaeolatitude changes as the Pacific Plate moved northwards, sea level variations, and sea surface temperature variations at the seamount through time to reconstruct the time and causes of submergence.ResultsRounded carbonate clasts include three facies: zooxanthelate corals, bioclastic packstones to rudstones, and rhodolith floatstones. Two rudstones contain relatively deep-water, coralline algal rhodoliths and large foraminifera indicative of Aquitanian (20.4-20 Ma) and Burdigalian (20-16 Ma) stages of the Early Miocene, consistent with Sr-isotope ages of algae and one sample of large foraminifera. Corals grew on Koko Seamount from c. 50 to 27.1 +/- 0.4 Ma, the youngest Sr-isotope age of a coral sample. These shallow, warm-water coral reefs came under increasing stress as the volcano subsided at 0.012 +/- 0.003 mm yr-1, and migrated northwards, and as global climate cooled. The summit submerged and shallow coral reef growth ceased before 29 Ma, probably around 33 Ma. The volcano continued its slow subsidence, and deep-water carbonates accumulated until they too were unable to keep pace, dying out at c. 16 Ma.Main conclusionsThe final submergence of the summit of Koko Seamount by about 33 Ma confirms that biota on older Hawaiian-Emperor Islands could not have migrated from island to island along the entire chain to eventually colonize the present Hawaiian Islands. There was a period between at least 33 and 29 Ma in which no islands existed, and distant colonization had to repopulate the younger portion of the Hawaiian chain, which began to emerge between about 29 and 23 Ma.
机译：目的是确定在库尔岛，珍珠和爱马仕礁形成之前，科科海山是否沉没在海平面以下，从而导致没有现存岛屿的时期。一个没有岛屿的时期将消除先前可能从一个岛迁移到另一个岛的陆地和浅海生物群系，并需要从遥远的海岸重新开始殖民化，以填充夏威夷火山链的年轻岛屿。位置Emperor Seamount Chain，太平洋中北部。方法我们使用根据化石大型有孔虫和Sr同位素确定的年龄来估算科科海山的沉降速率，并使用基于珊瑚藻类的古深度估算来估算最大深度。这些数据与太平洋板块向北移动时的古纬度变化，海平面变化以及海山随时间的海面温度变化来重建时间和淹没原因相结合。结果圆形碳酸盐岩碎屑包括三个相：黄原珊瑚，生物碎屑结石，鲁斯通石和菱锰矿浮石。两种阶石包含相对较深的水，珊瑚藻藻状红景天和较大的有孔虫，它们指示中新世早期的阿基坦（20.4-20 Ma）和布尔迪加利安（20-16 Ma）阶段，与藻类的Sr同位素年龄相符，并且有一个大样本有孔虫。珊瑚生长于科科海山。 50至27.1 +/- 0.4 Ma，这是珊瑚样品中最年轻的Sr同位素年龄。随着火山在0.012 +/- 0.003 mm yr-1处平息并向北迁移以及全球气候变冷，这些浅水，温水珊瑚礁承受的压力不断增加。山顶被淹没，浅珊瑚礁的生长在29 Ma之前停止，大概在33 Ma左右。火山继续缓慢沉降，深水碳酸盐积累，直到它们也无法跟上步伐，在c处消失。 16 Ma。主要结论科科海山峰的最后淹没大约是33 Ma，这证实了夏威夷帝国皇帝岛上的生物群不可能沿着整个链条从一个岛移到另一个岛，从而最终殖民了现在的夏威夷群岛。在至少33至29 Ma之间的一个时期内，没有任何岛屿存在，并且遥远的殖民化不得不重新填充夏威夷链的年轻部分，该岛开始出现在大约29至23 Ma之间。

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