Abstract

The mechanisms of pluton emplacement into continental crust have long been debated in igneous geology, with early models emphasizing forceful processes such as ballooning, later contrasted by alternative emplacement mechanisms including diapirism, incremental assembly, stoping and, emplacement by sheets and dikes. These contrasting perspectives highlight the complexity of the construction of mid-crustal intrusions and the need for case studies that integrate multiple datasets. The Box Springs Plutonic Complex (BSPC) in the northern Peninsular Ranges Batholith (PRB) preserves structural, textural, and compositional features that record its emplacement and internal construction. Although its lithology, structure, and geochemistry have been described, an integrated analysis combining field, petrographic, geochemical, isotopic, and geochronological data is lacking. This study reconstructs the BSPC’s emplacement history by addressing its lithologic framework, magmatic processes, and emplacement timing from U-Pb zircon dating. Beyond characterizing a single pluton, this work refines models of crustal growth and contributes to the broader debate on pluton emplacement and magma chamber evolution in continental arcs. The thesis is organized such that it will first review background and theoretical models of pluton emplacement, then present the results of field, petrographic, and geochemical analyses, which are followed by interpretations of magmatic and tectonic processes, and concludes with broader implications.

The findings, presented in this study, demonstrate that the BSPC was emplaced incrementally over approximately four million years from a vertically stratified magma chamber. The BSPC displays reverse zoning from felsic margins to a more mafic core, supported by petrographic, geochemical, isotopic, and structural data. Accommodation of magma occurred through a combination of magma wedging, lateral shortening, and floor subsidence, resulting in the construction of a funnel-shaped pluton. These results challenge earlier ballooning interpretations and provide a refined model for the assembly of mid-crustal intrusions in arc environments.

LLU Discipline

Geology

Department

Geology

School

School of Medicine

First Advisor

Ana María Martínez Ardila

Second Advisor

Ben Clausen

Third Advisor

Vali Memeti

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2026

Date (Title Page)

12-2025

Language

English

Library of Congress/MESH Subject Headings

Geology, Structural—California—Riverside County; Intrusions (Geology)—California—Riverside County; Geochemistry—California—Riverside County; Zircon—Geology—California—Riverside County—Dating

Type

Thesis

Page Count

xvi, 96 p.

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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