Isotopic and geochemical evidence of palaeoclimate changes in Salton Basin, California, during the past 20 kyr: 2. 87Sr/86Sr ratio in lake tufa as an indicator of connection between Colorado River and Salton Basin

Importance of groundwater in propagating downward integration of the 6–5 Ma Colorado River system: Geochemistry of springs, travertines, and lacustrine carbonates of the Grand Canyon region over the past 12 Ma

“…However, we also note two significant caveats and potential problems with using 87 Sr/ 86 Sr as a single tracer without other information: (1) Addition of a small volume of high-87 Sr/ 86 Sr, high-[Sr] water to low-[Sr] water can have strong leverage on Sr isotope composition; and (2) well-mixed waters should have relatively narrow ranges of 87 Sr/ 86 Sr (0.0002 for Salton Sea; Li et al, 2008b), whereas lake and river systems with distinct subbasins and substantial input from different source waters often show greater variation; for example, Great Salt Lake waters vary by 0.006 (Fig. 2;Hart et al, 2004) and the San Francisco Bay estuary system varies by 0.004 (Ingram and Sloan, 1992;Ingram and DePaolo, 1993).…”

“…Evaporative lake waters can have similar [Sr] to the mean of river inflow (e.g., 1.6 and 2.0 ppm for Great Salt Lake and river values, respectively; Hart et al, 2004). However, there is often significant [Sr] enrichment in some saline lakes, for example, ~24 ppm for modern Salton Sea water, which formed in 1905 when Colorado River water with a mean river input = 2.7 ppm entered the basin (Li et al, 2008b). Geothermal spring inputs also can have very high [Sr]: ~600 ppm in the Salton Sea (Doe et al, 1966).…”

“…Geothermal spring inputs also can have very high [Sr]: ~600 ppm in the Salton Sea (Doe et al, 1966). Carbonates that form from saline lake waters can be significantly enriched in [Sr]; for example, Lake Cahuilla tufas that were deposited between 400 and 20 ka by waters dominated by Colorado River input have a mean of ~2300 ppm, with shells approaching [Sr] = 6000 ppm (Li et al, 2008b). The modern Gulf of California seawater has [Sr] = 8.4 ppm; San Francisco Bay marine-estuary waters are variable with mean [Sr] = ~4 ppm (Ingram and DePaolo, 1993).…”

“…In the 1:1 model, 2A values would be explained by ~40% early Hualapai water mixing with 60% arriving Colorado Plateau groundwater and 2B by ~10% early Hualapai water mixing with 90% arriving Colorado Plateau groundwater at the very top of the section. Alternatively, if [Sr] values in the early Grand Wash lake/marsh were 4-10 times higher than arriving groundwater, for example, due to evaporative concentration (Li et al, 2008b), a mix of 5%-15% early Hualapai water and 85%-95% Colorado Plateau groundwater would be needed to explain late Hualapai 87 Sr/ 86 Sr values of 0.712-0.715 (2C in Fig. 14).…”

Channel incision by headcut migration: Reconnection of the Colorado River to its estuary and the Gulf of California during the floods of 1979–1988

“…The estuary of the Colorado River became disconnected from its fluvial supply following installation of upstream dams and diversions in the mid‐20th century (Carriquiry & Sánchez, 1999; Glenn, Lee, Felger, & Zengel, 1996; Gugliotta & Saito, 2019). These Anthropocene diversions were predated by extended periods of reduced fluvial supply occasioned by Late Pleistocene and Holocene diversions into Salton Sink, when a succession of Colorado River‐supplied lakes occupied the Sink during periods of unusually wet regional hydroclimate (Li, Xu et al, 2008; Li, You et al, 2008). The most recent occurrence of such a lake (Ancient Lake Cahuilla, dark grey shading Figure 1) ended in the first half of the 18th century (Rockwell, Meltzner, & Haaker, 2018).…”