Constraints on Miocene Uplift of the Central Cascade Range, Oregon

山脉和高原的地形隆起与各种构造作用引起的岩石圈密度变化密切相关。在俄勒冈州的喀斯特山脉，现有的对中新世以来地貌历史的解释是相互矛盾的，一种认为隆升是从20 Ma到晚中新世，另一种认为隆升直到中新世晚期才开始。相应的构造推断是与俯冲有关的密度变化，作用时间超过数千万年是负责的过程，或短期的强迫因素，如拆离断层作用，分别是原因。这个项目将通过使用氧同位素替代物来检验这些假设，这些变化与哺乳动物草食动物中记录的与山雨阴影效应有关的海拔-同位素比变化。预期的数据应该能够区分相互竞争的假设在模型预测中的巨大差异。结果将对喀斯喀德的构造历史具有重要意义，该方法很可能适用于其他地方。

ABSTRACT9909568KohnTopographic uplift of mountain ranges and plateaus is intimately related to lithospheric density changes caused by various tectonic processes. In the Cascade Ranges of Oregon existing interpretations of topographic history since the Miocene are in conflict, with one concluding that uplift was progressive between 20 Ma until Late Miocene and the other concluding that uplift did not start until the Late Miocene. The corresponding tectonic inferences are that subduction-related density changes, acting over tens of millions of years was the responsible process or that a short-term forcing factor such as detachment faulting was the cause, respectively. This project will test these hypotheses by using an oxygen isotopic proxy for elevation - isotopic ratio variation associated with mountain rain shadow effect as recorded in mammalian herbivores. The intended data should be able to differentiate between the strong differences in model predictions of the competing hypotheses. Results will be important to the tectonic history of the Cascades and the methodology will likely be applicable elsewhere.