Cosmogenic 10Be-Derived Sediment Yields to the Western Gulf of Mexico Over Multiple Glacial-Interglacial Cycles

Terrestrial cosmogenic ¹⁰Be is being used to measure sediment yields from two non-glaciated and tectonically quiescent river systems (Colorado and Trinity Rivers) draining into the western Gulf of Mexico. The goal of this study is to establish the magnitude of sediment flux variability over the past 5 million years and to quantify the response of non-glaciated catchments to glacial-interglacial climate change.

Deposits already associated with specific glacial or interglacial intervals in the past 200 ka (Blum and Aslan, 2006) are the main focus of the climate-response portion of this study, but older (Pliocene) deposits are also being analyzed. In the Colorado River catchment, sediment yields of 7.1 ± 1.5 Mt a^-1 (averaged) and 4.7 ± 0.4 Mt a^-1 have already been measured from channelbelt sand packages in the Lissie Fm. (ca. 640 ka from appearance of Lava Creek “B” ash) and Beaumont Fm. (155 ka, TL, Blum and Price, 1998), respectively. These values are of the same order of magnitude as other sediment yield estimates for the modern pre-dam Colorado River (e.g., Kanes 1970).

In the Colorado River catchment, additional sediment yield samples from modern pre-dam sediment, Columbus Bend Alloformation-3 (CBA-3) (14 – 5 ka, ¹⁴C in buried soil, Blum and Valestro, 1994), and an earlier deposit in the Beaumont Fm. (119 ka, TL, Blum and Price, 1998) have been collected. In the Trinity River catchment, sediment yield samples from i) a modern pre-dam deposit, ii) the Low, Middle, and High Deweyville terraces, iii) the Beaumont Fm., and iv) the Lissie Fm. have also been collected. Results from these samples, along with exposure ages for each deposit determined via cosmogenic ¹⁰Be depth profiles, are pending; these data will be obtained prior to October 2008 and presented at this conference.