The structural and petrologic development of the Sierra Nevada foothills between the Kings and Tule Rivers is summarized in the corresponding article in Part I of the Bulletin. Supporting data and more detailed discussions of the critical points are presented here with the assumption that the reader is familiar with the Summary article. Since the geochronological data reflect numerous Igneous and metamorphic petrogenetic episodes, the reader may find it helpful to refer to Table 1 from the Summary article while reading the in-depth discussions of Part II. The complex history of the region calls for careful consideration of geological relations in order to interpret the geochronological data. For this reason, the first part of this article centers on the geological setting of the isotopic age samples. With this foundation, the geochronological data are then presented and interpreted, and a chronology of structural and petrologic events is developed.

Structural and Petrologic Settings of Geochronological Samples


Igneous and metamorphic rocks of the study region represent a time span of about 200 m.y. during which numerous petrogenetic and deformation processes operated. Thus an informative discussion of the geologic settings of the age samples must include structural and petrologic data. In the discussion that follows, geologic maps, field photographs, photomicrographs, major-element chemical data, and phase chemical data are presented to help elucidate the complex settings of the samples. Map locations, age assignments, and identification numbers are given on the generalized geologic map of Figure 1. Information on the field locations and materials sampled are given in Appendix 1. The rocks studied can be broken into three groups of distinct structure, petrology, and age. The three groups consist of the 200- to 300-m.y. -old Kings-Kaweah ophiolite belt, Jurassic island-arc-type intrusive rocks, and the Cretaceous batholith. Sample collecting was aimed at solving a number of petrogenetic and structural problems dealing with these groups.

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