Abstract Day 4 of the Field Forum is dedicated entirely to the magmatic evolution of the Tuolumne Intrusive Complex. The Tuolumne Intrusive Complex is mostly located in Yosemite National Park and is superbly exposed due to a series of glaciations that started 2–3 million years ago and ended ca. 10,000 yr B.P. one of the many reasons why it has become one of the most studied intrusions in the world. We will be driving from Mammoth Lakes to Yosemite National Park taking Hwy 395 north and then Hwy 120 west crossing the entire Tuolumne Intrusive Complex before we start off at its western margin. On this side, the Tuolumne Intrusive Complex intruded into the rocks of the Yosemite Valley Intrusive Suite, Sentinel, and Yosemite Creek granitoids (Day 3). Today we will make stops along Hwy 120 while traversing the Tuolumne Intrusive Complex from west to east ( Fig. 4-1) looking at exposures near the road and discussing field data, structural geology, geochronology, and geochemistry from the Tuolumne Intrusive Complex…

Abstract To expand our evaluation of the Mesozoic Sierran arc, we need to consider the volcanic section that overlies the intrusive parts of the arc seen in Days 1–4. While doing so, we can discuss evidence for links between the magmatic and volcanic components of the arc, the nature of regional sedimentation and tectonism that accompanied active volcanism, and the challenges of estimating volume rates of volcanic activity in ancient arc systems. The most complete exposures of the volcanic section of the Mesozoic arc in the central Sierra occur in several pendants near the eastern topographic divide of the Sierra Nevada Mountains. These volcanic sections are exposed in the Saddlebag and Ritter Range pendants. We have completed new 1:24,000–1:10,000 scale mapping in four areas within these eastern pendants, which from north to south are: (1) Eagle Creek pendant around Twin Lakes, (2) the Virginia Canyon area, (3) the Saddlebag Lake pendant, and (4) the northern Ritter Range pendant…

Abstract Much of today will be spent in the plutons that are the principal host rocks of the western margin of the Tuolumne Intrusive Complex ( Fig. 3-1 ). These include the Sentinel and Yosemite Creek granodiorites (Kistler, 1973; Bateman, 1992) and the Yosemite Valley Intrusive Suite ( Bateman, 1992 ). The Sentinel and Yosemite Creek Granodiorites were tentatively included as part of the Tuolumne by Kistler and Fleck (1994) and Bateman (1992), but assignment of these plutons to the Tuolumne has been hampered by lack of detailed study. We and our students and colleagues have been mapping and conducting focused studies on the petrology, geochemistry, and structure of both plutons recently, but the results are presently only in theses and abstracts (Petsche, 2008; Fulmer and Kruijer, 2009; Bliekendaal, 2012; van der Linde, 2012; Johnson, 2013). Reasonably accessible exposures of these units can be seen along Highway 120 within Yosemite National Park