Anomalously high concentrations of lithium in fluviatile-lacustrine sediments near McDermitt, Nevada, may constitute a potential resource. These sediments are associated with a caldera about 45 km in diameter that is a result of volcanic activity, subsidence and sedimentation chiefly of Miocene age. The sediments originally were vitroclastic and now consist chiefly of authigenic zeolites, clay minerals, feldspar and quartz. Calcite occurs as thin beds, nodules and cement Gypsum is presnt but sparse. Most of the clay beds in the caldera contain 0.01-0.1% Li and have well above the average Li concentration for continental clays (0.006%) (Ronov et al.1). Individual smectitic clay samples from the western and southern part of the caldera contain as much as 0.65% Li and are associated with analcime and K-feldspar. Two beds, each 0.6m thick, contain 0.35% Li. Clay samples from the northern part of the caldera contain as much as 0.36% Li, and are associated with clinoptilolite and erionite. The clay beds are thinner in the north; in one section a bed 0.3 m thick contains 0.36% Li, and in another section a bed 0.1 m thick contains 0.30% Li. Lithium is probably derived from volcanic material and then incorporated into the clay beds during alteration. ?? 1978.