The Chisana Formation consists of Lower Cretaceous volcanic rocks that occur in the Nutzotin Mountains of eastern Alaska. New stratigraphic analysis indicates that the volcanic succession is >2 km thick at the Bonanza Creek type section. We present stratigraphic, geochemical, Sr‐Nd‐Pb isotope, and U‐Pb age data from samples collected from various stratigraphic levels of the Chisana Formation. We demonstrate that the Chisana Formation can be divided into a lower subaqueous unit, a middle transitional unit, and an upper subaerial unit. Chisana Formation lavas range from transitional to subalkaline basalts through andesites. Trace element geochemistry shows high field strength element depletions relative to large ion lithophile elements and hydrous mineral assemblages with calc‐alkaline to tholeiitic chemistries, all consistent with a magmatic arc origin. Chisana lavas yield geochemical compositions and isotope characteristics that overlap with magmas from volcanic suites formed within juvenile continental crust and immature island arcs. Volcanism occurred between ~131 and 117 Ma judging from previously reported lava ages and new U‐Pb ages of detrital zircons recovered from sandstones that conformably underlie the lowermost Chisana Formation lavas. Our results support existing tectonic models in which an east dipping subduction zone existed beneath Wrangellia during Early Cretaceous time. The upsection shift from marine to terrestrial depositional conditions in the Chisana Formation and the overlying ~117–93 Ma Beaver Lake Formation was coincident with regional shortening. Together, the geologic evidence for shortening and terrestrial deposition are interpreted to reflect accretion/suturing of Wrangellia against inboard terranes.

中文翻译：

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阿拉斯加东部兰吉利亚地带Chisana组的地球化学和地层分析：对北山脉山脉边缘的早白垩世岩浆作用和构造的认识

Chisana组由位于阿拉斯加东部努特佐丁山脉的下白垩纪火山岩组成。新的地层分析表明，Bonanza Creek型断面的火山演替厚度大于2 km。我们提供了从Chisana组不同地层水平收集的样品中的地层，地球化学，Sr-Nd-Pb同位素和U-Pb年龄数据。我们证明了Chisana地层可以分为下部水下单元，中间过渡单元和上部空中单元。Chisana组熔岩范围从安山岩到过渡玄武岩到亚碱性玄武岩。痕量元素地球化学显示，相对于大型离子亲石元素和含水钙矿物质组合物（钙碱性至可渗透性化学物）而言，场强元素耗竭较高，全部与岩浆弧原点一致。Chisana熔岩的地球化学成分和同位素特征与来自幼年大陆壳和不成熟岛屿弧内形成的火山岩浆的岩浆重叠。从先前报道的熔岩时代和从碎屑锆石中发现的碎屑锆石的新的U-Pb年龄来看，火山活动发生在大约131至117 Ma之间。我们的研究结果支持了现有的构造模型，其中早白垩世时期在兰吉利​​亚下存在一个东倾俯冲带。Chisana组和上覆的〜117-93 Ma Beaver Lake组从海相到陆相沉积条件的上移转变与区域缩短一致。一起，