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Abstract

Badwater Basin salt pan, Death Valley, California, occupies the bottom of a large, enclosed basin and is the lowest elevation land surface in the Western Hemisphere. Its location, at the end point of regional drainage, makes the sediments collected in the valley of special interest for long-term paleoclimate study. This paper describes the bottom half of a 185 m-long core taken from the salt pan in 1993.

Four facies, deposited in a changing saline lacustrine system, appear in the core. (1) Massive black mud and layered, mostly cumulate-textured, halite settled to the bottom of a perennial lake. (2) Layered halite, with distinctive vertical and horizontal dissolution and cementation fabrics, is similar to salt layers that form in the modern salt pan/shallow ephemeral saline lake cycles at Badwater Basin and is interpreted to represent the same or a very similar environment. (3) Brown silty mud with displacively grown salts was deposited in a saline mudflat. (4) Laminated silty mud displays sedimentary structures that reflect desiccation and exposure on a dry mudflat.

The succession of facies in the lower 90+ m of the Death Valley core is dominated by the development and eventual desiccation of a perennial lake, which was saline during all or most of its long existence. The oldest sediments in the core record a saline mudflat in transition upward to a salt pan/shallow ephemeral saline lake, probably in response to increased inflow to the basin. After accumulating more than 20 m of halite and mud, the salt pan/ephemeral saline lake system experienced another period of increased inflow and made the transition to a more persistent shallow saline lake. The lake deepened and freshened, and more than 30 m of black mud accumulated at the quiet bottom. The lake occasionally evaporated to halite supersaturation and experienced one longer episode of halite precipitation. The top 18 m of perennial lake sediments record increased halite precipitation, probably during a period of increasing regional aridity. Dry mudflat sediments that cap the perennial lake sequence may record the most arid time, and they are overlain by saline mudflat sediments that signal the beginning of another episode of increasing inflow.

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