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Stratigraphy and structure of Mesozoic metavolcanic rocks in the vicinity of Mt. Dana, Yosemite National Park, California.
Mt. Dana is one of several high peaks along the Sierra Nevada crest on the eastern boundary of Yosemite National Park (Fig. 1). The mountain is underlain by metamorphic rocks which form the northern extension of the Ritter Range roof pendant, an elongate belt of metamorphozed sedimentary and volcanic rocks assigned to the Paleozoic and Hesozoic respectively (Fig. 2). Kistler (1966b) subdivided that portion of the pendant exposed around Mt. Dana into three rock "Sequences"—a term introduced by Sloss and others (1949) to define stratigraphic units bounded by major unconformities. In this instance, two proposed angular unconformities (one forming the contact between metavolcanic and metasediirientary rocks, and the other contained within the metavolcanic section) were used to distinguish between Late Paleozoic sedimentary rocks of the Lewis Sequence, PermoTriassic volcanic and sedimentary rocks of the Koip Sequence, and Lower Jurassic volcanic and sedimentary rocks of the Dana Sequence (Fig. 3). In recent years tnis interpretation has generated some concern, especially with regard to (1) the type of contact separating metasediraentary and metavolcanic portions of the pendant, (2) the existence of uwo sequences in the metavolcanic section, and (3) the overall extent of deformation.