Publication Date

8-2024

Advisor(s) - Committee Chair

Patricia Kambesis, Jason Polk, Michael May, John Tinsley, Joel Despain

Degree Program

Department of Earth, Environmental, and Atmospheric Sciences

Degree Type

Master of Science

Abstract

Caves in the Permian-aged, McCloud Limestone of the Klamath Mountains of Northern California preserve a diverse range of clastic sediments that represent broad-scale variations in paleo-hydrologic conditions and transport mechanisms that hint at varied modes of speleogenesis through local landscape development. Caves in the McCloud Limestone exhibit a range of cave passage geometries and arrangements that suggests periods of both hypogene and epigene cave development through temporal and spatial scales. This study evaluates the variability in the distribution, mineralogy, and transport mechanisms of clastic-cave sediments in seven hydrologically-distinct caves in the McCloud Limestone to establish relationships between clastic-cave sedimentation and modes of cave genesis and paleo-hydrologic conditions. This study utilizes a combination of detailed cave mapping, sediment facies relationships, particlesize distribution statistics, and mineralogical analysis to differentiate depositional conditions, sediment provenance, and hydrologic control on the deposition of clastic material in a range of suspected polygenetic cave environments. Quantitative techniques such as particle-size statistics, X-ray powder diffraction, scanning electron microscopy, and electron dispersion spectrometry were employed to evaluate sedimentary textures and constituent mineralogy. Samples were collected using percussion-driven core-sampling techniques and grab-sampling. Three primary facies associations are observed that aid in distinguishing depositional and paleo-hydrologic conditions in a polygenetic setting: epikarst-dominated, fluvially-dominated, and autogenic dominated. Relationships between cave genesis and sedimentation are present that elucidate the speleogenetic and geomorphic history of the McCloud Limestone and relationships with regional volcanism occurring since the Miocene. Multi-stage polygenetic hypogene and epigene cave development is evident along with periods of significant sedimentation, erosion, and extensive in-situ weathering. Correlation of cave sediments with regional stratigraphic markers has yielded a minimum age of cave development at Lake Shasta Caverns of 2.5 to 3.5 Ma. Evaluating sedimentation patterns in a set of seven, hydrologically distinct hypogene and epigene caves has provided insight into the nature of polygenetic cave development and sedimentation. Evaluation of cave sedimentation through facies relationships and mineralogical and grain size trends could be used as a framework for further study on polygenetic karst regions elsewhere.

Disciplines

Earth Sciences | Geology | Geomorphology | Physical Sciences and Mathematics | Sedimentology | Speleology | Stratigraphy

Download

Share

COinS