Citation
Parra, Sergio Alexander (2025) Location, Location, Location: Insights from Spatially-Resolved Observations of Marine Seep Carbonate Ecosystems and Carbonaceous Chondrite Surfaces. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/c0w0-ns76. https://resolver.caltech.edu/CaltechTHESIS:03052025-175659528
Abstract
Spatially heterogeneous, multi-component systems are prevalent topics of study in geobiology and planetary science. However, previous studies of these systems often represent limited measurements that abstract or separate the sample from its localized context, thereby obscuring or precluding insights into the drivers ultimately shaping these systems. This challenge motivates the work presented in this thesis, where we provide an extensive and spatially-resolved examination of two complex, heterogeneous systems in geobiology and planetary science: marine seep carbonates and carbonaceous chondrite surfaces, respectively. In marine seep systems worldwide, seep carbonates are a mineral byproduct of a microbial metabolism (the anaerobic oxidation of methane, or AOM) and can continue hosting metabolically active microbial communities, including methane-oxidizing microbes. However, much of our understanding of these endolithic microbial communities stems from bulk, centimeter-scale evaluations of microbial identity and/or metabolic activity across a limited number of samples. As such, the range of structural and environmental conditions that ultimately shape the degree and extent of microbial activity in seep carbonates, including AOM, remains relatively under-constrained. To address this gap, Chapters 1-3 investigate carbonate-hosted microbial communities at a methane seep site in Santa Monica. In Chapter 1, we explore carbonate ‘nodules’ from methane seep sediments at and below the sulfate-methane transition zone (SMTZ), analyzing their mineral composition, internal structures, and hosted microbial communities compared to their host sediment communities and porewater chemistry. We also discuss key implications of the connectivity of seep sediments to nodules over geologic timescales and the preservation of microbial ‘thumbprints’. Chapter 2 describes rare tripartite associations between two groups of anaerobic methanotrophic archaea (ANME-1 and ANME-2) and a bacterial partner within seep carbonate crusts and other substrates at the seafloor, with implications towards understudied diversity in the syntrophic interactions governing AOM beyond seep carbonates. Chapter 3 examines the impact of seep carbonate internal structure on endolithic communities from various carbonate crusts, revealing similarities and differences between surface and interior communities that may reflect the importance of pore networks in maintaining favorable local environments. In Chapter 4, we pivot to an extensive analysis of spectra from carbonaceous chondrite surfaces. Carbonaceous chondrites (CCs) are a group of meteorites that represent the oldest materials in the solar system, whose mineralogy preserves a record of early alteration processes thought to be shared with certain asteroids. However, most studies connecting specific CCs to specific asteroids have relied on spectroscopic measurements of bulk powder CCs, which are spatially unresolved and destroy textures, thereby hindering tying shared spectral features to particular phases, petrologic contexts, and alteration histories. As such, Chapter 4 presents an analysis of CCs measured using microimaging hyperspectral visible-and-shortwave-infrared (VSWIR) spectroscopy, where we capture chondrite surfaces features at high spatial resolution. We also compare CC spectral features with asteroids using the Expanded Bus-DeMeo taxonomy, which provides a systematic framework to examine and identify shared drivers of spectral diversity within this spectral range, including Fe-bearing minerals from both original and terrestrial alteration processes. Together, these studies emphasize the importance of spatially-resolved sampling across disciplines, specifically in geobiology and planetary science, thereby capturing and highlighting the heterogenous nature of key systems in these fields and bettering our understanding of the factors shaping them.
| Item Type: | Thesis (Dissertation (Ph.D.)) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Subject Keywords: | methane seeps, seep carbonates, AOM, ANME, methanogenesis, carbonaceous chondrites, microimaging spectroscopy | ||||||||||||
| Degree Grantor: | California Institute of Technology | ||||||||||||
| Division: | Geological and Planetary Sciences | ||||||||||||
| Major Option: | Geobiology | ||||||||||||
| Thesis Availability: | Not set | ||||||||||||
| Research Advisor(s): |
| ||||||||||||
| Thesis Committee: |
| ||||||||||||
| Defense Date: | 4 December 2024 | ||||||||||||
| Funders: |
| ||||||||||||
| Record Number: | CaltechTHESIS:03052025-175659528 | ||||||||||||
| Persistent URL: | https://resolver.caltech.edu/CaltechTHESIS:03052025-175659528 | ||||||||||||
| DOI: | 10.7907/c0w0-ns76 | ||||||||||||
| Related URLs: |
| ||||||||||||
| ORCID: |
| ||||||||||||
| Default Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||||||||
| ID Code: | 17045 | ||||||||||||
| Collection: | CaltechTHESIS | ||||||||||||
| Deposited By: | Sergio Parra | ||||||||||||
| Deposited On: | 14 Mar 2025 20:26 | ||||||||||||
| Last Modified: | 14 Mar 2025 20:26 |
Full text not available from this repository.
Repository Staff Only: item control page
