Bouse Formation in the Bristol basin near Amboy, California, USA

Abstract

Limestone beds underlain and overlain by alluvial fan conglomerate near Amboy, California, are very similar in many respects to parts of the Bouse Formation, suggesting that an arm of the Pliocene Bouse water body extended across a wide part of the southern Mojave Desert. The deposits are north of the town of Amboy at and below an elevation of 290 m, along the northern piedmont of the Bristol "dry" Lake basin. The Amboy outcrops contain the Lawlor Tuff (4.83 Ma), which is also found in an outcrop of the Bouse Formation in the Blythe basin near Buzzards Peak in the Chocolate Mountains, 180 km southeast of Amboy. Bouse exposures near Amboy are ~3.4 m thick, white, distinctly bedded, with limestone and calcareous sandstone as well as stromatolite mounds; we interpret these as nearshore deposits. The Bouse at Amboy contains ostracodes, diatoms, and mollusks that indicate saline lake or estuarine environments with an admixture of fresh-water forms. Along with wading bird tracks and a spine from a marine fi sh, these fossils suggest that the deposits formed in saline waters near a fresh-water source such as a perennial stream. Beds of the outcrop dip southward and are 113 m above the surface of Bristol Playa, where similar age sediments are buried 270+ m deep, indicating signifi cant faulting and vertical tectonics in this part of the Eastern California Shear Zone during the past 5 m.y. Confi rmation of the Bouse Formation at Amboy strengthens previous assignments to the Bouse Formation for mudstones in driller logs at Danby "dry" Lake, California, and suggests that areally extensive arms of the Bouse water body were west of the Blythe basin. The Bristol basin arm of the lower Bouse basin probably was restricted from the main water body by narrow passages, but Bouse sediment there is similar to that in the Blythe basin, suggesting generally similar water chemistry and environmental conditions. Examining the degree to which Bouse deposits in the western arms differed from Bouse deposits in the Blythe basin offers an approach to test whether the southernmost Bouse water body was deposited in an estuarine or lacustrine setting.

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

“…Second, simple calculations based on measurements of possible annual varves in Bouse marl suggest that Bouse deposition could have lasted anywhere from 10 to 300 ka (Homan and Dorsey, 2013). Third, there is well-documented post-Bouse movement on some basin-bounding faults at the divides (Miller et al, 2014;Seixas et al, 2015) and within Bouse basins (Metzger et al, 1973;Miller et al, 2014), suggesting that the original extent and distribution of lakes cannot be precisely reconstructed by contouring the modern elevation of the highest Bouse outcrops (Fig. 1).…”

“…Previous workers have stressed that 87 Sr/ 86 Sr ratios in carbonates of the southern Blythe basin (0.710-0.711) are significantly more radiogenic than seawater (0.709) and therefore refute a marine influence on Bouse depositional environments (Spencer and Patchett, 1997;Roskowski et al, 2010). To address this question, model 4 in Figure 14 explores the possibility that 87 Sr/ 86 Sr ratios in Bouse carbonates could reflect mixing of "Bouse waters" with seawater in a marineestuary environment McDougall Miranda Martinez, 2014;Miller et al, 2014). If [Sr] in the arriving Bouse water was significantly lower than seawater (~1-2 ppm for Bouse water, compared to 8 ppm for seawater), a mixture with 85%-95% Bouse water and 5%-15% seawater would produce the observed southern Bouse values of 0.710-0.711 (4A, Fig.…”

“…Elevations of the highest outcrops are interpreted to record lake highstands, which differ from lake to lake across bedrock divides as shown in Figure 1 and the inset to cer et al, 2013;Miller et al, 2014), and Blythe basin (330 m), which extended to the Chocolate Mountains divide; and (6) Yuma basin, where the top of the inferred Bouse Formation is as much as 1 km below sea level (Olmsted et al, 1973). The Imperial Formation (Fish CreekVallecito basin and SM in Fig.…”

“…5-6 Ma (Spencer et al, 2013). There is ongoing debate, however, regarding the exact age and early history of the Colorado River (Dorsey et al, 2007House et al, 2008;Aslan et al, 2010;Spencer et al, 2013;Miller et al, 2014;Pearthree and House, 2014;McDougall and Miranda Martinez, 2014;Harvey, 2014). In this paper, we adopt the view that the first Colorado River waters reached the western edge of the Colorado Plateau after 6 Ma (e.g., the age of upper Hualapai Limestone; Spencer et al, 2001) and before the ca.…”

Punctuated Sediment Discharge During Early Pliocene Birth of the Colorado River: Evidence from Regional Stratigraphy, Sedimentology, and Paleontology

“…Imperial Formation marine deposits in the northern Indio Hills (Dibblee, 1997) may have formed during initial marine incursion, and/or early Pliocene time . A rise in relative sea level caused deepening-up from intertidal to subtidal conditions over a large area from Parker, Ariz., south to Cibola and Milpitas Wash, possibly inundating areas a far west as Amboy in a tideswept shallow marine embayment or saline lakes (Miller et al, 2014). Areas north of Parker may have experienced carbonate deposition in one or more lakes during this period Pearthree and House, 2014), though the timing of deposition in the northern lakes remains uncertain.…”