Day 5: EJB and Sage Hen Flat Plutons, White-Inyo Range
Published:January 01, 2005
2005. "Day 5: EJB and Sage Hen Flat Plutons, White-Inyo Range", Incremental assembly and emplacement of Mesozoic plutons in the Sierra Nevada and White and Inyo ranges, California, Drew S. Coleman, John M. Bartley, Allen F. Glazner, Richard D. Law
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In the morning, we will drive to the northern Inyo Mountains to examine ductile deformation of wall rocks and other structures found at the margins of the EJB pluton (Fig. 35). In the afternoon, we will return to Crooked Creek in the White Mountains to examine the Sage Hen Flat pluton. Much of the guide for Day 5 was adapted and modified from Morgan et al. (1998b, 2000) and Nelson (1980).
The central White-Inyo range in eastern California (Figs. 35, 36) is an excellent area to study emplacement of both concordant plutons with deformed aureoles and discordant plutons because the plutons are well exposed at various structural levels, and because the wall rocks belong to a well-mapped sedimentary section (Fig. 37) that underwent regional shortening before the plutons were emplaced but has scarcely been deformed since. Stevens et al. (1997), Dunne et al. (1998) and Stockli et al. (2003) described the Phanerozoic geologic evolution of the eastcentral California region, and Morgan and Law (1998) summarized the regional deformation recorded in the central White-Inyo range.
The EJB composite pluton and the Sage Hen Flat pluton (Figs. 35, 36, 38) are similar in age but differ drastically in the amounts and styles of deformation at their margins. As we will see today, ductile strain is practically absent adjacent to the Sage Hen Flat pluton whereas the contact aureole of the EJB pluton underwent intense emplacement-related ductile deformation that has been interpreted to record outward and downward translation and tilting of sedimentary wall rocks. In addition to examining these contrasting emplacement styles, we will examine and consider the interpretation of magmatic and solid-state foliations related to pluton emplacement.
Figures & Tables
Incremental assembly and emplacement of Mesozoic plutons in the Sierra Nevada and White and Inyo ranges, California
This field guide was created in coordination with the Geological Society of America Field Forum “Rethinking the Assembly and Evolution of Plutons: Field Tests and Perspectives,” held 7-14 October 2005 in the Sierra Nevada and White and Inyo ranges, California. The goal of this five-day field trip was to examine field relations and characteristics of plutons in the central Sierra Nevada and in the White and Inyo ranges as they relate to processes of pluton growth and emplacement and, more particularly, as they relate to the hypothesis that plutons are assembled slowly and incrementally.