FOSSILS, STRATIGRAPHY, AND STRUCTURE OF THE ALWAYS WELCOME INN OUTCROP, BAKER CITY, OREGON

Terry Frest, a malacologist from Seattle, discovered fossils in the early Pliocene sediments (Brooks and others, 1976, Oregon DOGAMI GMS-7) behind the Always Welcome Inn in Baker City, Oregon, in May 2002. The fossils in the sequence include fish, gastropods (Gyraulus, Pisidium, Sphaerium, lymnaeids, and possibly, Drepatoma), ostracods, charophytes, diatoms (including the freshwater planktic diatoms Aulacoseira and Cyclotella, and the benthic diatoms Anomoeneis, Cocconeis, Epithemia, Fragilaria, Navicula, Nitzchia, and Rhopaloidia), freshwater sponge spicules (Ephydatia fluviatilis), a bird bone, and a small rodent(?) tooth. The Always Welcome Inn sequence consists of an ~10 m-thick section composed of diatomites, massive and laminated silts (some of which contain significant amounts of volcanic ash), and fine sands. The lower 7 meters of the sequence includes three units of diatom- and sponge-rich shallow lake and lake margin sediments alternating with laminated and massive silts. These sediments contain spines, vertebrae, skull bones, and other fragments of a new species of the sunfish, Archoplites, which most closely resembles the Archoplites species in the Ringold Formation of Washington. The percentages of diatoms and sponge spicules decrease upward, suggesting that the water depth may have become shallower with time. The upper part of the sequence includes stream channel and floodplain deposits consisting of trough cross-bedded sands and the sandy silt unit in which the rodent (?) tooth was found. A silt unit that contains diatoms and sponge spicules, plus the bones of a large minnow similar to Gila and fragments of a smaller minnow, caps these units. The Always Welcome Inn fossil sequence dips ~10-20 degrees toward the southwest, is crosscut by ~9 normal faults with a total throw of ~7 m, and is overlain unconformably by a northwest-dipping sequence of imbricated pebble gravels that contains clasts of argillite and chert derived from the Elkhorn Mountains to the west.