Front where slopes are often steeper than 0.1 (rise over run). Oard frequently makes the comparison of Lake Bonneville with Hopi Lake, saying that Hopi Lake has “no evidence for the lakes,” “no lake-bottom sediments,” “no tufa” and “no shorelines” (Oard 2010, 2016, 2021). Similarly, Tim Clarey dismisses Hopi Lake which he regards as one of those “fictional lakes that some creation geologists propose emptied in a catastrophic manner to carve Grand Canyon but are based on little if any geological evidence” (Clarey 2018). The way that Hopi Lake critics argue seems to imply that they are extremely familiar with Bidahochi Basin landforms. That allows them to toss out freely universal negatives, statements we believe are unworthy of good science publications. Michael Oard (2021) makes a lengthy argument claiming “no tufa” at Hopi Lake as described in Austin et al. (2020). Oard discusses tufa, travertine and speleothems, then concludes, “So, tufa, or the interpretation of tufa, is not necessarily a positive indicator of a shoreline.…” (Oard, 2021, p. 217). Algal-secreted, laminated, cool-water carbonate coatings (“tufa”) are a very prominent feature along the high shorelines of Lake Bonneville (Felton et al., 2006; Vennin et al., 2018). Because Oard believes in shorelines of Pleistocene Lake Bonneville and modern Great Salt Lake, he should tell us why Bonneville and Salt Lake tufa “…is not necessarily a positive indicator of a shoreline” at these lakes. Notice, Oard can elaborately convolute the definition of “tufa,” but we have in modern times witnessed deposition of an analogous cool-water, calcareous encrustation at the shore of the modern Great Salt Lake! Just because terminology can be controversial, that does not require interpretations to be (Cappezzuoli et al., 2013). What was the final volume of the paleolake? If the basin structure that impounded the lake is older than the lake, then Bidahochi Basin’s structure can be used to estimate the volume of the 300-kilometerlong paleolake. Because tufa deposits indicate that the final filling of Bidahochi Basin was to present elevation of 1860 meters (6100 feet), the present topographic depression could have filled with approximately 4700 cubic kilometers (1130 cubic miles) of water. We estimated paleolake volume from topographic cross-sections of the basin. However, our topographic-basin estimate of Hopi Lake is almost certainly an underestimate as illustrated by better-studied Pleistocene Lake Bonneville in the Great Basin of Utah, Nevada and Idaho. O’Connor (1993, 2016) estimated the volume of the Lake Bonneville Flood into the Snake River to be 4750 cubic kilometers from analysis of Great Basin topography. O’Connor (1993) assumed, Figure 21. Map of putative lakes associated with erosion of eastern Grand Canyon (from Austin et al., 2020). Lakes on southern Colorado Plateau are understood to be successive and temporary, not simultaneous and enduring. Upstream basins initiated the fill-and-spill process. Canyonlands Lake formed first, then failed by spillover at Lees Ferry into Bidahochi Basin that was vacant of a big lake. Hopi Lake rose rapidly and overtopped East Kaibab Monocline. Then, rapid drainage of Hopi Lake caused Lake Toroweap to fill abruptly and breach Uinkaret Plateau at Toroweap. After drainage of lakes and erosion of canyons, plateaus and basin continued to be tilted, down on the north side, up on the south side. AUSTIN, HOLROYD, FOLKS, AND LOPER Shoreline Transgressive Terraces 2023 ICC 359
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