Field Guide to Pleistocene Lakes Thatcher and Bonneville and the Bonneville Flood, Southeastern Idaho

Link, P.K., Kaufman, D.S., and Thackray, G.D., 1999, Field Guide to Pleistocene Lakes Thatcher and Bonneville and the Bonneville Flood, southeastern Idaho, in Hughes, S.S., and Thackray, G.D., eds., Guidebook to the Geology of Eastern Idaho: Idaho Museum of Natural History, p. 251-266. INTRODUCTION This field guide is designed to summarize and describe field trip stops that illustrate the rise of Lakes Thatcher and Bonneville and the Bonneville Flood in southeastern Idaho (Figs. 1 and 2). The Bonneville events were sufficiently recent that their effects are well-preserved in the landscape, and easily discerned by all. Shoreline and scabland remnants are easy to see in portions of Gentile, Cache, Marsh and Portneuf valleys southeast and in the vicinity of Pocatello, Idaho. Further, the history of Lake Bonneville and its flood record interaction of climate change, basaltic volcanic activity, and drainage capture caused by detumescence after the passage of the Yellowstone hot spot (Fig. 3). All of this information has been previously published. The primary sources are Gilbert (1890), Bright and Ore (1987), O’Connor (1993), Link and Phoenix (1996), Bouchard et al. (1998), Anderson (1998), and Anderson and Link (1998). An essay by H. T. Ore (written communication, 1995) relates the framework of topographic and geomorphic change in southeastern Idaho over the last ten million years. Segments of that essay are quoted in a text box on the fourth and fifth pages of this article. Tom Ore’s big-picture wisdom molded the academic tradition from which PKL and GDT have approached southeast Idaho geology.