Landscape Sensitivity to Changing Climate: Plio-Pleistocene Erosion and Sedimentation in SE Arizona

景观对气候变化的敏感性：亚利桑那州东南部上新世-更新世的侵蚀和沉积亚利桑那州立大学Arjun Heimsath-1124460摘要亚利桑那州东南部沉积盆地的残留物是突出的和引人注目的沉积物，因此，从世纪早期到现在，它们吸引了地质学家的注意。 尽管大量的描述性工作捕捉到了它们的视觉显著性，但对这些矿床的年龄或地质起源几乎没有共识。 虽然形成这些地貌的沉积物有明显的源区，可以追踪和绘制地图，但导致这些沉积物被遗弃的构造和气候力量的潜在组合远不清楚，也没有得到很好的研究。松散相关的盆地高位的年龄推断范围从20，000年前到1.0-2.2 Ma，更多的是基于推测而不是定量地质年代学。 该项目将为这些盆地何时被沉积物填满以及盆地随后何时被区域侵蚀事件切割和解剖的最后阶段建立一个绝对的时间轴。 建立这样一个时间轴需要应用和发展宇宙成因核素方法，以扩大其时间范围，并测试多种稳定和放射性核素的创新使用。 采样策略将覆盖亚利桑那州东南部广泛的沉积盆地水平，并将量化沉积物的年龄和源区侵蚀速率。 由于未变形的盆地高位表面和底层盆地填充物可以追溯到该地区活跃的构造强迫停止的时间，因此表面的侵蚀很可能是由气候强迫驱动的。 因此，确定这些特征的年表以及源区的古侵蚀速率有助于在理解构造和气候力量如何塑造地球之间建立一座桥梁。亚利桑那州东南部的这些表面在视觉上引人注目的性质，确保了人们对它们的起源以及它们如何能够洞察构造和气候力量的广泛兴趣。通过建立这种广泛研究和几乎没有日期的景观的地质年代学，我们将扩大这个项目的智力范围远远超出假设的测试。具体来说，天空岛联盟将帮助我们协调如何了解过去气候对景观的影响，这将有助于更好地预测本研究中生态敏感地区的未来变化。 我们正在研究的每一个沉积矿床都起源于源区，现在那里是特有物种和空间孤立的生态系统的家园。 因此，有跨学科的兴趣，定量地了解这些景观如何在不同的气候制度下变化。此外，NSF资助的Jemez河临界区观测站（CZO），由亚利桑那大学的同事运行，在我们的一些现场附近有现场站点。我们正在与他们协调实地工作和约会策略，从而确保具有知识重叠但项目目标非常不同的项目之间的协同作用。我们将与合作者协调本科生和K-12学生的培训和推广，从而进一步扩大该项目的范围。这个项目和伯克利地质年代学中心之间的合作研究将有助于亚利桑那州立大学的设施建设，以及培养研究生。最后，本项目所使用的实地考察有助于开发我们学校教授的本科和研究生课程的实地组成部分和课程。

Landscape sensitivity to changing climate: Plio-Pleistocene erosion and sedimentation in SE ArizonaArjun Heimsath, Arizona State UniversityEAR-1124460ABSTRACTRemnants of sedimentary basin levels in southeastern Arizona are prominent and striking deposits, and as such they have attracted the attention of geologists from the early 20th century through the present. Despite extensive descriptive work capturing their visual conspicuousness, there is little consensus on the ages or geologic origins of these deposits. Although the sediments with which these landforms were built have obvious source areas that can be traced and mapped, the potential combinations of tectonic and climatic forces conspiring to leave such deposits abandoned are far from clear and have not been well examined. The ages inferred for loosely correlative basin high stands have ranged from ~20,000 years ago to 1.0-2.2 Ma and are based more on conjecture than quantitative geochronology. This project will establish an absolute timeline for the final stages of when these basin were filled with sediments, as well as when the basins were subsequently incised and dissected by regional erosional events. Establishing such a timeline requires application and development of cosmogenic nuclide methodology that will extend its temporal reach and test the innovative use of multiple stable and radio-nuclides. The sampling strategy will cover a broad range of sedimentary basin levels across southeast Arizona and will quantify both the ages of the deposits and the source area erosion rates. Because the undeformed basin high stand surfaces and underlying basin fill may date to the time that active tectonic forcing ceased in the region, the erosion of the surfaces is likely to have been driven by climatic forcing. Firmly establishing the chronology of these features, as well as the paleo-erosion rates of the source areas thus helps to build a bridge in understanding between how tectonic and climatic forces shape the Earth?s surface.The visually arresting nature of these surfaces across southeastern Arizona insures broad interest in their origins as well as how they may enable insight into tectonic and climatic forces. By establishing the geochronology of such widely studied and virtually undated landscapes we will expand the intellectual reach of this project well beyond the testing of hypotheses. Specifically, the Sky Island Alliance will help us coordinate how understanding the impacts of past climates on the landscape will help better predict future changes across the ecologically sensitive areas of this study. Each of the sedimentary deposits that we are studying originates in source area that is now home to endemic species and spatially isolated ecosystems. There is, therefore, interdisciplinary interest in quantitatively understanding how these landscapes change under different climate regimes. Additionally, the NSF-funded Jemez River Critical Zone Observatory (CZO), run by colleagues at the University of Arizona, has field sites near some of our field sites. We are coordinating field efforts and dating strategies with them, thus insuring synergy between projects with intellectual overlap, but very different project objectives. We will coordinate training and outreach of undergraduate and K-12 students with both collaborators, thus further widening the reach of the project. Collaborative research between this project and the Berkeley Geochronology Center will help develop facilities at Arizona State University as well as train graduate students. Finally, class trips to the field areas used for this project are helping to develop both the field component and the curriculum of undergraduate and graduate courses taught in our school.