Stratigraphy and sedimentology of the northern part of the upper Gazelle Formation, eastern Klamath Mountains, northern California

The Gazelle Formation of the eastern Klamath Mountains constitutes a large part of the fragmentary record of Devonian paleogeography in northern California and is the only record of Devonian tectonics and sedimentation in the Yreka Terrane. The upper Gazelle, which overlies melange, is at least 1000 feet thick and composed of four laterally continuous sandstone units that are interbedded with shale, siltstone, siliceous mudstone, and chert. Very fine-grained sandstones, siltstones, and mudstones exhibit a progressive sequence of sedimentary structures indicative of deposition by low-density turbidity currents. The sandstones are green lithic graywackes composed of approximately 15% quartz, 30% plagioclase, and 55% volcanic lithic fragments. Geochemical analyses indicate that the sandstones were derived from an Ordovician-Silurian volcanoplutonic terrane located near an active continental margin. A retroarc successor basin model and a trench slope basin model are proposed to explain the tectonic setting of the Gazelle Formation