Provenance of Loessite in Equatorial Pangea: Implications for Paleoclimatic Reconstructions

两种环流模式和一些地质资料都表明，季风环流是盘古超大陆的特征。 然而，季风开始的时间以及关于古赤道纬度风向、强度和季节性的数据仍然缺乏约束。 本研究的目的是描述北美西部（西赤道盘古大陆）的古代风成粉砂岩的来源，以描绘paleodisperation，从而在晚古生代的古大气环流。 为了实现这一目标，PLS和学生将结合岩相学为基础的框架矿物学和粒度分析与锆石年龄测定，以精确地建立淤泥来源和粒度谱，从而确定表面风向和强度。 碎屑锆石年龄谱应反映其源区的年龄谱，即，晚古生代/早中生代出露的基底碎屑岩和/或含粉砂地层。 我们将利用现有的碎屑锆石参考剖面发表的北美，补充关键的纬向参考sections.Preliminary结果表明，碎屑锆石和粒度数据可以用来约束主导和次要风向和强度，并提供季节性的信息，淤泥循环的可能性和影响。 碎屑锆石地质年代学的结果，特别是表明，这项工作可能还有助于改善目标红层和晚古生代阶段边界的最大年龄的限制。 最终，研究结果还应有助于（1）提高对晚古生代西盘古大陆低纬度古气候和潜在古构造作用的理解，以及（2）我们对气候变化的理解，以及一般气候模型的校准。

Both circulation models and some geologic data suggest that monsoonal circulation characterized the Pangean supercontinent. The timing of monsoon onset, however, and data on wind directions, intensities and seasonality at paleoequatorial latitudes, remain poorly constrained. The objective of this study is to characterize the provenance of ancient eolian siltstones of western North America (western equatorial Pangea) to delineate paleodispersal and thereby paleoatmospheric circulation in late Paleozoic time. To achieve the objective, the Pls and students will integrate petrographically based framework mineralogy and grain-size analyses with singlecrystal detrital zircon age dating to precisely establish both silt provenance and size spectra, and thereby identify surface wind directions and strengths. The detrital zircon age spectra should reflect the age spectra of their sources, i.e., basement terranes and/or silt-bearing strata exposed in late Paleozoic/earliest Mesozoic time. We will address the possibility and implications of silt recycling by using existing detlital zircon reference sections published for North America, supplemented by key cratonal reference sections.Preliminary results indicate that detrital zircon and grain-size data can be used to constrain prevailing and subordinate wind directions and strengths, and provide information on seasonality. Results of detrital zircon geochronology in particular suggest that this work may additionally contribute to improvements in constraints on maximum ages of the target redbeds and of late Paleozoic stage boundaries. Ultimately, study results should also contribute to (1) an improved understanding of the low-latitude paleoclimate and potentially paleotectonism of late Paleozoic western Pangea, and (2) our understanding of climate change, and calibration of climate models in general.