A Northeast-Propagating Wave of Topographic Uplift and Subsidence of the Cordilleran Orogenic Plateau, Late Cretaceous through Late Tertiary Time
Abstract
Low-temperature thermochronological data from the Grand Canyon region suggest that c. 1.5 km of uplift of the SW Colorado Plateau occurred in Late K-early T time (Flowers et al., 2008), mainly during carving of Grand Canyon in the Campanian (80-70 Ma; Wernicke, 2011). Other, as-yet unpublished thermochronological data have been cited as a basis to discredit its Cretaceous formation age, interpreting them instead as supporting a young age (<6 Ma) for the formation of Grand Canyon (e.g., Karlstrom et al., 2012). Serious difficulties exist with this interpretation, in particular it does not appear to account for the marked dependence of (U-Th)/He ages in apatite on U concentration that is well documented for these rocks (Flowers et al., 2007, 2008). This dependence makes them particularly useful for tightly constraining the unroofing history, which precludes a late Cenozoic age for the carving of Grand Canyon. Also during Campanian time, arc zircons from coastal California were being deposited on the Colorado Plateau in Utah, requiring transport through the uplifting SW margin of the plateau via a "California River." By early T time, drainage had reversed owing to the Laramide uplift of the plateau interior, and the simultaneous collapse of the former Cordilleran uplands along the southern California coast. In mid-T time, gravel clasts coastal basins were being derived from as far NE as central and northern Arizona, indicating migration of the Tertiary drainage divide hundreds of km inland from its K position near the coast, with dimensions similar for drainages documented further north at the latitude of the northern Sierra Nevada. In mid- to late T time, formation of the southern and central Basin and Range promoted further topographic collapse of the K uplands. Also in late T time, an increasingly wet climate promoted spillover of drainages in the plateau interior southwestward into the Basin and Range, resulting the establishment of the modern Colorado River drainage basin. Flowers, R. M., Shuster, D. L., Wernicke, B.P. and Farley, K. A., 2007, Radiation damage control on apatite (U-Th)/He dates from the Grand Canyon region, Colorado Plateau: Geology, v. 35, n. 5, p. 447-450; doi:10.1130/G23471A.1. Flowers, R. M., Wernicke, B.P., and Farley, K.A., 2008, Unroofing, incision and uplift history of the southwestern Colorado Plateau from apatite (U-Th)/He thermochronometry, Geological Society of America Bulletin v. 120, p. 571-587, doi: 10.1130/B26231.1. Karlstrom, K.E., Lee, J.P., Kelley, S.A., Crow, R., 2012, Evaluating the evidence: The California/Arizona paleoriver model for an old Grand Canyon: Geological Society of America Abstracts with Programs, v. 44, No. 6, p. 80. Wernicke, B., 2011, The California River and its role in carving Grand Canyon, Geological Society of America Bulletin, v. 123, p. 1288-1316, doi: 10.1130/B30274.1.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.T31F..02W
- Keywords:
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- 1824 HYDROLOGY / Geomorphology: general;
- 8175 TECTONOPHYSICS / Tectonics and landscape evolution;
- 8177 TECTONOPHYSICS / Tectonics and climatic interactions