Origin of the Blue Ridge escarpment along the passive margin of Eastern North America
Origin of the Blue Ridge escarpment along the passive margin of Eastern North America
复制标题
北美东部被动边缘蓝岭悬崖的起源
DOI：
10.1111/j.1365-2117.2003.00219.x
复制
发表时间：
2004
期刊：
影响因子：
3.2
通讯作者：
Bill S. Henika
中科院分区：
文献类型：
--
作者：
J. Spotila;G. Bank;P. Reiners;C. Naeser;N. Naeser;Bill S. Henika
蓝岭悬崖是一个位于古老的阿巴拉契亚造山带内的崎岖地貌。虽然在某些方面与其他被动边缘的大悬崖相似，但其年轻的地形表现形式激发了北美东部新生代构造复兴的建议。为了更好地理解被动边缘的后造山和后裂谷地貌演化，我们使用低温热时测定法和地形指数的操作研究了这种地貌的起源。沿断崖横断面的磷灰石(U-Th)/He和裂变径迹分析显示了向海岸年轻化的趋势。这种模式与其他大悬崖一致，符合长期侵蚀演化的解释，没有构造复兴的要求。测量到的年龄也与其他大悬崖上测量到的年龄特别相似，这些悬崖比它年轻100迈。这表明，在裂谷后早期阶段维持崎岖峭壁的侵蚀机制可能在远古被动边缘长期保持活跃。然而，悬崖的精确侵蚀演化尚不清楚，有几个端元模型可以解释这些数据。我们的首选模型与所有的数据都吻合，它涉及到新生代相当程度的侵蚀陡坡退缩。虽然这表明被动边缘演化不需要地形稳定的早期开始，但需要更多的数据来更好地约束悬崖发育的细节。
The Blue Ridge escarpment is a rugged landform situated within the ancient Appalachian orogen. While similar in some respects to the great escarpments along other passive margins, which have evolved by erosion following rifting, its youthful topographic expression has inspired proposals of Cenozoic tectonic rejuvenation in eastern North America. To better understand the post‐orogenic and post‐rift geomorphic evolution of passive margins, we have examined the origin of this landform using low‐temperature thermochronometry and manipulation of topographic indices. Apatite (U–Th)/He and fission‐track analyses along transects across the escarpment reveal a younging trend towards the coast. This pattern is consistent with other great escarpments and fits with an interpretation of having evolved by prolonged erosion, without the requirement of tectonic rejuvenation. Measured ages are also comparable specifically to those measured along other great escarpments that are as much as 100 Myr younger. This suggests that erosional mechanisms that maintain rugged escarpments in the early post‐rift stages may remain active on ancient passive margins for prolonged periods. The precise erosional evolution of the escarpment is less clear, however, and several end‐member models can explain the data. Our preferred model, which fits with all data, involves a significant degree of erosional escarpment retreat in the Cenozoic. Although this suggests that early onset of topographic stability is not required of passive margin evolution, more data are required to better constrain the details of the escarpment's development.