کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6431780 | 1635399 | 2015 | 6 صفحه PDF | دانلود رایگان |
- Eccentricity and precession can drive landscape evolution in continental interiors.
- Eccentricity and precession impact modeled summer runoff in northeastern Wyoming.
- Precipitation may be the dominant geomorphic driver in some intermontane basins.
While climate has long been implicated in the extensive erosion of Eocene through Miocene-aged basin fills in the Rocky Mountains, lack of precise, high temporal-density datasets of landform ages has made it difficult to detail the mechanisms by which climate increased relief. A dense dataset of (U-Th)/He dates from the Powder River Basin, Wyoming and Montana, USA, indicates correspondence between elevated exhumation and peaks in orbital eccentricity. Here we use an atmospheric general circulation model to investigate the potential role of eccentricity in enhancing erosion in the Rocky Mountains. We find that with high orbital eccentricity (0.05767), elevated seasonality (the moving vernal equinox of perihelion [MVELP] = 270°) results in 10-100% more summer precipitation and surface runoff than low seasonality (MVELP = 90°). Under low orbital eccentricity (0.0034), precipitation and runoff changes across a precession cycle are negligible. These results suggest that elevated eccentricity could, indeed, be associated with more intense summer precipitation and runoff, which could then drive higher landscape erosion rates. This finding could explain the occurrence of ~ 100-kyr cyclicity in Powder River Basin landform ages and provides a clear, non-glacial, link between climate variability and landscape evolution in the Rocky Mountains. In this, and other low-to-mid-latitude sedimentary basins, runoff volume and not glacier dynamics may be the variable that exerts primary control on landscape evolution.
Journal: Geomorphology - Volume 250, 1 December 2015, Pages 89-94