Miocene rejuvenation of topographic relief in the southern Appalachians

[摘要] Conventional wisdom holds that the southern Appalachian Mountainshave not experienced a significant phase of tectonic forcing for >200 myr; yet,they share many characteristics with tectonically active settings, including locallyhigh topographic relief, steep slopes, incised river gorges, and frequent mass-wastingevents. Two competing hypotheses are commonly used to explain their modern topographicexpression. One suggests that relief is largely controlled by variable lithologicresistance to weathering and that their modern form has long persisted in a dynamicequilibrium. The second postulates that their relief is a product of recent rejuvenation,driven either by climate change or the epeirogenic uplift of the land surface drivenby mantle forcing. Within portions of the Cullasaja River basin of the southernAppalachians, we show that relief has increased by >150% since the Miocene. Evidentwithin the basin are a set of retreating knickpoints that delineate a rugged, activelyincising landscape from lower-relief relict topography. Constraints on the timingof knickpoint entry into the basin suggest that the process of landscape rejuvenationbegan well prior to the late Cenozoic (<4 myr) transition to a more oscillatory(glacial-interglacial) climate regime. Furthermore, the geomorphology of the CullasajaRiver basin is difficult to reconcile in the context of a transition to a more erosiveclimatic regime but is consistent with an epeirogenically uplifted landscape. Consequently,these observations lend new support to the idea that the rugged topography of thesouthern Appalachians has developed in response to post-orogenic regional upliftin the Miocene.

[学科分类] 地质学

[关键词] Fire safety;fatal fires;smoke alarms