Late Jurassic paleogeography of the U.S. Cordillera from detrital zircon age and hafnium analysis of the Galice Formation, Klamath Mountains, Oregon and California, USA
Late Jurassic paleogeography of the U.S. Cordillera from detrital zircon age and hafnium analysis of the Galice Formation, Klamath Mountains, Oregon and California, USA
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DOI：
10.1130/b36810.1
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发表时间：
2023-08
影响因子：
4.9
通讯作者：
K. Surpless;Ryan W. Alford;Calvin G. Barnes;A. Yoshinobu;Natalee Weis
中科院分区：
文献类型：
--
作者：
K. Surpless;Ryan W. Alford;Calvin G. Barnes;A. Yoshinobu;Natalee Weis
上侏罗纪Galice组是西克拉马斯山脉的一个变质沉积单元，在内华达造山运动之前和期间形成于弧内盆地内。新的碎屑锆石U-Pb年龄分析（N = 11; n = 2792）产生的最大沉积年龄（MDA）范围从约。160 Ma至151 Ma，跨越牛津至Kimmeridgian时间，并与约开始于约100 Ma的Nevadan收缩变形重叠。157马。锆石年龄表明一个重要的北美大陆物源成分，这与晚侏罗世将西克拉马斯岩置于大陆边缘的构造模型一致。Galice样品中中生代碎屑锆石（n = 603）的Hf同位素分析揭示了侏罗纪和三叠纪颗粒的宽范围εHf值，其中许多不能用克拉马斯山脉的近源来解释，因此指示了一个复杂的物源。克拉马斯山脉内侏罗纪岩体的新U-Pb年龄和Hf数据与Galice组碎屑锆石的一些相匹配，但这些数据不能解释大多数非放射成因的侏罗纪碎屑颗粒。事实上，现场的科迪勒拉弧记录并没有提供一个明确的匹配广泛的同位素签名的三叠纪和侏罗纪颗粒。当编译时，Galice样本表明来源于内华达州前岩基框架和弧后区域，更古老的克拉马斯岩，以及可能来自蓝山和岛上岩的重叠地层。上侏罗统大峡谷群和马里波萨组碎屑锆石年龄谱具有相似的年龄模式，表明它们具有共同的沉积物源。推断Galice物源内的克拉马斯山脉和更远的来源表明，Galice盆地收到silicicicactical浊积岩喂养的河流，横穿克拉马斯-Sierran弧在弧后地区的源头。因此，Galice组包含了活跃的侏罗纪岩浆活动在大陆弧的记录，与大陆沉积物源的活动弧内和东部的显着碎屑输入。这些向西流动的河流系统保持活跃的整个转变，在科迪勒拉弧构造从一个transtensional系统的内华达收缩系统，其特点是沉积物来源于隆起内和东部的弧和推力下的老克拉马斯火山口老Galice沉积物向东。
The Upper Jurassic Galice Formation, a metasedimentary unit in the Western Klamath Mountains, formed within an intra-arc basin prior to and during the Nevadan orogeny. New detrital zircon U-Pb age analyses (N = 11; n = 2792) yield maximum depositional ages (MDA) ranging from ca. 160 Ma to 151 Ma, which span Oxfordian to Kimmeridgian time and overlap Nevadan contractional deformation that began by ca. 157 Ma. Zircon ages indicate a significant North American continental provenance component that is consistent with tectonic models placing the Western Klamath terrane on the continental margin in Late Jurassic time. Hf isotopic analysis of Mesozoic detrital zircon (n = 603) from Galice samples reveals wide-ranging εHf values for Jurassic and Triassic grains, many of which cannot be explained by a proximal source in the Klamath Mountains, thus indicating a complex provenance. New U-Pb ages and Hf data from Jurassic plutons within the Klamath Mountains match some of the Galice Formation detrital zircon, but these data cannot account for the most non-radiogenic Jurassic detrital grains. In fact, the in situ Cordilleran arc record does not provide a clear match for the wide-ranging isotopic signature of Triassic and Jurassic grains. When compiled, Galice samples indicate sources in the Sierra Nevada pre-batholithic framework and retroarc region, older Klamath terranes, and possibly overlap strata from the Blue Mountains and the Insular superterrane. Detrital zircon age spectra from strata of the Upper Jurassic Great Valley Group and Mariposa Formation contain similar age modes, which suggests shared sediment sources. Inferred Galice provenance within the Klamath Mountains and more distal sources suggest that the Galice basin received siliciclastic turbidites fed by rivers that traversed the Klamath-Sierran arc from headwaters in the retroarc region. Thus, the Galice Formation contains a record of active Jurassic magmatism in the continental arc, with significant detrital input from continental sediment sources within and east of the active arc. These westward-flowing river systems remained active throughout the shift in Cordilleran arc tectonics from a transtensional system to the Nevadan contractional system, which is characterized by sediment sourced in uplifts within and east of the arc and the thrusting of older Galice sediments beneath older Klamath terranes to the east.