Collaborative Research: Timing and Controls on Plio-Pleistocene Erosion in the Eastern Peninsular Ranges, Southern California

合作研究：南加州东部半岛山脉上皮奥-更新世侵蚀的时间和控制

• 批准号: 0710988
• 负责人: Bernard Housen
• 金额: $ 2.75万
• 依托单位: Western Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0710988&HistoricalAwards=false
• 关键词: Collaborative; Research; Timing; Controls; Plio

A research team from the University of North Carolina, University of Oregon, and Western Washington University is conducting a multi-disciplinary examination of a remarkably complete and well exposed archive of late Pliocene to modern paleo-erosion rates preserved in the Fish Creek - Vallecito basin in southern California. Erosion rates in the source are determined from cosmogenic nuclide concentrations in detrital quartz, with corrections for minimal post-depositional nuclide in-growth during rapid burial and exhumation of basinal sediments. Relief production in the source areas are assessed by comparison of (U-Th)/He cooling ages in modern bedrock exposures to detrital minerals in basinal sediments. Depositional ages and sedimentation rates are calibrated with high-precision magnetic reversal and paleointensity stratigraphy. These data yield a high resolution time series of cosmogenic nuclide in-growth of alluvial sediments, which record important changes in catchment-averaged erosion rates through time. Temporal changes in source-area erosion rate are compared to the stratigraphic record of changes in facies architecture and sediment accumulation rates in the basin, allowing assessment of the process-response functions that link erosional forcing to stratigraphic outcomes. Using these approaches, the team is testing hypotheses for tectonic - versus climate driven changes in erosion of the bedrock source: (1) a shift into cooler and more temporally variable climate conditions at the onset of northern hemisphere glaciation approximately 2.5 to 3.0 million years ago caused increased erosion and pronounced progradation of locally derived sediment; and (2) significant, upper mantle-driven uplift lead to relief production and enhanced erosion in the Peninsular Ranges beginning at about 1.0 to 1.3 million years ago.It is well documented that rates of bedrock erosion and sediment production are closely linked to climate forcing and tectonic construction of topographic relief, though the exact nature and feedback dynamics of those controls remain incompletely understood. Detrital cosmogenic nuclide concentrations in modern stream sediments are widely used for quantifying short-term catchment erosion rates, and for assessing the role of tectonic forcing, lithology, and erosion processes on sediment production rates. While this method is common in studies of modern sediment-catchment systems, its application to ancient sediments is relatively rare, and its use in continuous sedimentary sequences is rarer still. This study is charting new ground through the application of these methods to older sediments. If successful, geologists will have new tools to distinguish the role of climate versus tectonics in landscape evolution.

北卡罗来纳大学，俄勒冈大学和西华盛顿大学的一个研究团队正在对上新世晚期的非常完整且暴露得很好的档案进行多学科检查，以保存在菲什克里克（Fish Creek） - 南加州的Vallecito Basin中。来源中的侵蚀率是由碎屑石英中宇宙基因核素浓度确定的，在快速埋葬期间，校正了最小的沉积后核素内生长和盆地沉积物的挖掘。通过比较（u-th）/He冷却年龄在现代基岩暴露于盆地沉积物中的碎屑矿物质中，评估了源区域的浮雕生产。用高精度磁反转和古显着地层学校准沉积年龄和沉积速率。这些数据产生了高分辨率时间序列的宇宙核素内增长的增长，这些核素沉积物的增长记录了随着时间的推移流域平均侵蚀速率的重要变化。将源区域侵蚀率的时间变化与盆地相结构和沉积物积累速率变化的地层记录进行了比较，从而评估了将侵蚀强迫与地层结构联系起来的过程 - 反应函数。使用这些方法，该团队正在测试构造的假设 - 与气候驱动的基础侵蚀的变化相对于气候驱动的变化：（1）在北半球冰川发病的一开始，转向较酷且更具时间变化的气候条件，大约2.5亿年前，大约2.500万年前，导致了局部侵蚀和发音的销量增加； （2）重要的，上地幔驱动的隆升导致半岛范围内的缓解生产和增强的侵蚀，从大约1.0至130万年前开始。有充分的文献证明，基岩侵蚀和沉积物的生产速率与气候强迫和构造的强迫和反馈的动力保持不变，这与气候强迫和反馈的动力保持不变，这与气候强迫和构造的构造保持不变。现代溪流沉积物中的碎屑宇宙核素浓度广泛用于量化短期流域侵蚀率，并评估构造强迫，岩性和侵蚀过程对沉积物产量的作用。尽管这种方法在现代沉积系统的研究中很常见，但其在古代沉积物中的应用相对较少，并且在连续沉积序列中的使用仍然很少。这项研究是通过将这些方法应用于较旧的沉积物来绘制新的基础。如果成功的话，地质学家将拥有新的工具来区分气候与构造在景观进化中的作用。