Constraints on Miocene Uplift of the Central Cascade Range, Oregon

摘要山脉和高原的地形隆升与各种构造过程引起的岩石圈密度变化密切相关。在俄勒冈州喀斯喀特山脉，现有的对中新世以来地形历史的解释是相互矛盾的，一种结论是抬升在20 Ma至晚中新世之间是渐进的，另一种结论是抬升直到晚中新世才开始。相应的构造推断是，与俯冲相关的密度变化（持续数千万年）是负责任的过程，或者是滑脱断裂等短期强迫因素是原因。该项目将通过使用氧同位素代用品来测试这些假设，该代用品与记录在哺乳草食动物中的山地雨影效应相关。预期的数据应该能够区分竞争假设的模型预测中的强烈差异。研究结果将对喀斯喀特的构造史具有重要意义，而且该方法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.