SGER: The Owens River as a TIltmeter for Long Valley Caldera: Exploratory Dating of its Oxbow Sediments Using Tephrochronology

朗谷的欧文斯河沿着火山口的护城河环绕着复兴的圆顶的北侧和东侧，并显示出地貌证据表明，在比过去十年长得多的一段时间里，圆顶的抬升改变了它的航道。在其下方15公里的大部分地区，这条河由两个平行的曲流带组成，中间隔着一个几乎平坦的河流间面(200-300米宽)，没有显示出最近河流活动的痕迹。这两条带的曲流幅度和波长基本相同，但年龄不同。较老的曲流带，现在携带着一条不适合的小溪，总是比新的舷外航道的主流更接近穹顶，海拔高出约30-60厘米。经过一段时间的横向倾斜后，这条河显然跳入了新的航道。河流间面向某些地块轴线的投影表明，可能发生了15至35米的总隆升。在其航道的最下面六公里处，欧文斯河泛滥平原显示了多达六个不同时代的可识别的曲流带(一些位于现代航道的外侧，另一些位于船内)，似乎记录了下沉和复活的事件。知道这条河占据每一条曲流带的绝对年龄，可能会为我们提供一个圆顶重新抬升和下沉的时间估计。我们特别感兴趣的是，火山口以北的Mono陨石坑和Inyo陨石坑的喷发活动是否在时间上与欧文斯河航道的迁移行为有关，从而可能与板条箱底部的回升和下沉有关。

The Owens River at Long Valley follows the caldera's moat around the N and E sides of the resurgent dome and shows geomorphic evidence that its course has been modified by uplift of the dome over a period of time considerably longer than the last ten years. In most of its lower 15km, the river consists of two parallel meander belts separated by a nearly planar interfluvial surface (200-300m wide) that shows no trace of recent river activity. The two belts display essentially identical meander amplitude and wavelength, but are not the same age. The older meander belt, now carrying a small underfit stream, invariably lies closer to the dome than the main flow in the new outboard channel, and sits some 30-60 cm higher in elevation. The river apparently jumped into the new channel after some period of lateral tilting. Projection of the interfluvial surface to the axis of the some suggests that total uplift of 15 to 35 meters may have occurred. In the lowermost six km of its course, the Owens River floodplain shows as many as six identifiable meander belts of different age (some lying outboard and other lying well inboard of the modern channel) that appear to record events of subsidence as well as resurgence. Knowing the absolute ages of the river's occupancy of each of these meander belts may provide us an estimate of the timing of the resurgence and subsidence of the dome. We are particularly interested to know whether eruptive activity in the Mono Craters and Inyo Craters north of the caldera has been tied in a temporal way to the migratory behavior of the Owens River channel, and thus possible to the resurgence and subsidence of the crate floor.