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摘要
The Brazos, Colorado, and Trinity rivers of Texas drain a tectonically quiescent, non-glaciated, and low-relief landscape inland from the Gulf of Mexico, where long-term [10(3)-10(5) a] changes in denudation rates are probably driven largely by climate change. Here, we use cosmogenic Be-10 to obtain spatially averaged denudation rates for these river catchments, primarily from terrace deposits associated with glacial or interglacial intervals over the past half million years. The denudation rates are similar to 30-35% higher during interglacial periods than during glacial periods, and correlate broadly with temperature. The results are consistent with predictions from the BQART sediment flux model, and support the hypothesis that increased weathering rates associated with warmer climates will accelerate landscape erosion. Furthermore, by analyzing Al-26/(10) Be in these deposits, we can estimate the bed load sourced from up-catchment surfaces. The stored coastal plain fraction varies from similar to 10% to 30%, and is greater during times of relatively lower sea level. The results indicate that although sediment flux is moderated by coastal-plain storage, increased up-catchment flux during warmer interglacial periods outpaces evacuation of stored sediment during glacial periods, resulting in a net increase in sediment flux to the ocean during warm intervals. If this temperature-sediment flux relationship is valid beyond the Plio-Pleistocene transition, then global sediment flux to the ocean from passive, non-glaciated, and low-relief landscapes would have been greater during the Pliocene than in the cooler Quaternary.
- 出版日期2014-3-15
