Detrital-zircon U–Pb geochronology has revolutionized sediment provenance studies over the last two decades, and zircon has been successfully analyzed from nearly all sedimentary lithologies, depositional environments, and sediment grain sizes. However, despite the ubiquity of this method and the far-reaching interpretations supported by detrital-zircon data, few studies have investigated the potential role of zircon grain size on age spectra and provenance interpretation. In this study, we investigate the connections between sample grain size, zircon grain size, U–Pb age spectra, and interpreted provenance using 18 detrital-zircon samples (4999 individual grains) collected from Pennsylvanian–Permian strata in central and southern Arizona, USA. In these samples, there is no clear correlation between sample grain size and zircon grain size and no clear correlation between sample grain size and age spectra. However, when all grains are grouped by zircon minimum long-axis dimension, the abundance of some age groups is correlated to zircon grain size. In Pennsylvanian samples, < 400 Ma grains and 2500–3000 Ma zircons are more abundant in the finer fractions, and 1400–1900 Ma zircons are more abundant in coarser fractions of both Pennsylvanian and Permian samples. In Permian samples, 500–800 Ma zircons are most abundant in the finer fractions, and 2500–3000 Ma grains are concentrated in the coarser fractions. Based on changes in abundance and grain-size distribution of 500–800 Ma grains, we interpret a change in zircon provenance across the Pennsylvanian–Permian boundary that reflects regional climate and paleogeographic changes driven in part by the northward drift of Laurentia across the equator. Specifically, we interpret the concentration of 500–800 Ma zircons in Permian samples in central and southern Arizona to indicate that these grains were: 1) sourced from Gondwana, 2) deposited in, and subsequently eroded (recycled) from, Mississippian–Pennsylvanian strata in the Arkoma, Anadarko, and Fort Worth basins at the margins of Laurentia, and 3) finally transported into the Arizona study area as loess by easterly trade winds. This study serves as a case study in the value and interpretive power of basic grain-size characterization of detrital-geochronology datasets.

中文翻译：

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美国晚古生代亚利桑那陆架和 Pedregosa 盆地的混合风成-沿岸沉积物输送：碎屑-锆石数据集粒度分析的案例研究

在过去的二十年里，碎屑锆石 U-Pb 地质年代学彻底改变了沉积物物源研究，并且已经成功地分析了几乎所有沉积岩性、沉积环境和沉积物粒度的锆石。然而，尽管这种方法无处不在，并且碎屑锆石数据支持深远的解释，但很少有研究调查锆石粒度对年龄谱和物源解释的潜在作用。在这项研究中，我们使用从美国亚利桑那州中部和南部宾夕法尼亚-二叠纪地层收集的 18 个碎屑锆石样品（4999 个单个晶粒）研究样品粒度、锆石粒度、U-Pb 年龄光谱和解释来源之间的联系. 在这些样本中，样品粒度和锆石粒度之间没有明确的相关性，样品粒度和年龄光谱之间没有明确的相关性。然而，当所有晶粒按锆石最小长轴尺寸分组时，某些年龄组的丰度与锆石粒度相关。在宾夕法尼亚州样品中，<400 Ma 晶粒和 2500-3000 Ma 锆石在较细的部分中更丰富，而 1400-1900 Ma 锆石在宾夕法尼亚和二叠纪样品的较粗部分中更丰富。在二叠纪样品中，500-800 Ma 的锆石在较细的部分中最为丰富，2500-3000 Ma 的晶粒集中在较粗的部分中。根据 500~800 Ma 晶粒的丰度和粒度分布变化，我们解释了宾夕法尼亚-二叠纪边界上锆石来源的变化，这反映了区域气候和古地理变化，部分原因是 Laurentia 向北漂移穿过赤道。具体来说，我们解释了亚利桑那州中部和南部二叠纪样品中 500-800 Ma 锆石的浓度，以表明这些晶粒是：1）来自冈瓦纳，2）沉积在密西西比 - 宾夕法尼亚地层中，随后被侵蚀（回收）在 Laurentia 边缘的 Arkoma、Anadarko 和 Fort Worth 盆地中，3) 最终被东风信风作为黄土输送到亚利桑那州研究区。本研究作为碎屑地质年代学数据集基本粒度表征的价值和解释能力的案例研究。