RECONSTRUCTING LATE PLIOCENE TO MIDDLE PLEISTOCENE DEATH VALLEY LAKES AND RIVER SYSTEMS AS A TEST OF PUPFISH (CYPRINODONTIDAE) DISPERSAL HYPOTHESES

Present hypotheses suggest that during glacial periods, Death Valley was the episodic terminus for the Amargosa, Owens and Mojave Rivers. Geological and biological studies tend to support this hypothesis along with a hydrologic link to the Colorado River. This hydrologically linked system allowed pupfish (Cyprinodontidae) and other species to disperse throughout southeastern California and western Nevada. Mitochondrial DNA studies support a common ancestry for pupfish in the region with genetic divergence beginning ca. 3-2 Ma. To test the paleohydrologic connections with respect to Death Valley during (1) the late Pliocene to early Pleistocene, (2) early-middle Pleistocene, and (3) middle to late Pleistocene glacial periods we used tephrochronologic and paleomagnetic data to identify and date lacustrine and non-lacustrine sediments. We conclude that 3-2 Ma a narrow lake occupied the ancient Furnace Creek basin and that Death Valley was not hydrologically connected with the Amargosa or Mojave Rivers. Paucity of data does not allow us to evaluate an Owens River connection to Death Valley 3-2 Ma. Our observations, combined with previous studies, show that Death Valley was not hydrologically linked to the Amargosa, Owens or Mojave Rivers 1.2-0.5 Ma. No evidence was found that Lake Manly backflooded up the Mojave River 0.18-0.12 Ma, although surface water flowed from the Amargosa and Owens Rivers to Death Valley at this time. Thus, a hydrologic link between Death Valley and the Owens River system occurred 0.18-0.12 Ma, and possibly earlier, however, no connection to the Colorado River in the last 3-2 m.y. was not found. Therefore, the hypothesis that pupfish dispersed or were isolated by severed paleohydrologic connections is not supported by the geologic data we have compiled; however, sparse and disputed data suggest a fluvial system connected Panamint (Owens River), Death, and Amargosa valleys before 3 m.y. ago.