Inception of the Modern Colorado River

Map of the Miocene to Pliocene Hualapai – Bouse lake system, showing maximum inferred extent of each lake (modified from Spencer et al., 2008a) and, in red, the locations of the Lawlor tuff where interbedded with Bouse Formation marl. Maximum lake elevations are inferred based on maximum outcrop elevations. The drainage divide that separates Bristol and Blythe basins is also shown, but would have been submerged at maximum fill level. Lake Hualapai was probably not a single lake, and had an ~6 million year, pre-Bouse history of spring-carbonate accumulation, with Sr isotopic characteristics unlike Colorado River water or Bouse Formation carbonates (Lopez Pearce, 2010).