An Investigation of The Effect of Low Impact Shock Processes on Breakdown of Sandstone at Meteor Crater
Notice bibliographique
Résumé
Impact cratering is one of the most common geologic processes shaping all the terrestrial planetary bodies and moons in our solar system. The widespread presence of craters on terrestrial planets and moon in the inner solar system shows that impact cratering was a dominant process during the early history of the solar system. Asteroid and comet impacts can influence the geologic and climatic history of terrestrial planets and impact processes can also play a significant role in subsequent rock breakdown on planetary bodies. The formation of impact craters has a catastrophic effect on target lithology, producing a range of heterogeneities and deformation features in rocks. Recognising how these heterogeneities and deformation features affect the mechanisms and kinetics of rock weathering provides a framework for understanding impact inheritance in rock breakdown. \nResearch within the past few decades has revealed extensive shock related features and deformations in rocks in the impact craters. In recent years, stress history and rock control are recognised important in controlling the rate and nature of breakdown. This thesis is the first detailed and comprehensive investigation of the effect of impact metamorphism processes on subsequent rock breakdown. \nThe focus of this thesis is to understand how the inheritance from low impact shock (<10 GPa) deformations and heterogeneities affects subsequent rock breakdown. This is achieved through a combined field and laboratory approaches that examined rock breakdown on impacted, and non-impacted rocks of the same lithology that are exposed at Meteor Crater site, Arizona. Rock hardness data and topographic data using a Structure from Motion (SfM) photogrammetry-based method developed in this thesis was used to compare rock breakdown between impacted and non-impacted sandstone outcrops at Meteor Crater site. The topographic data collected in the field was analysed using a range of roughness and morphometric parameters. The rock samples collected from the Meteor Crater and additional small number of impactite samples from West Clearwater Impact Structure (Canada) and Ries Crater (Germany) were characterised and assigned a shock level in the laboratory using different analytical techniques (petrographic microscopy, powder X-ray diffraction, scanning electron microscopy, X-ray computed tomography). Further, these samples were used in a physical weathering simulation in semi-arid conditions. The rock samples were analysed before and after the experiments to identify and quantify changes. This research advanced the field of rock breakdown by providing insight into the influence of impact processes on subsequent rock breakdown processes.\nThis thesis has revealed the following new insights: (1) The low impact shocked sedimentary rocks show a decrease in porosity. (2) Macrofracturing and microfracturing caused by low impact shock occur in all types of impactites. Macrofracturs of 0.1-0.2 mm and microfractures 0.1-5 µm in aperture are observed in all types of impactites. (3) The rock breakdown experiment results showed that impactites exhibit an accelerated decline in strength compared to non-impacted control samples. (4) Rock type and impact deformation history are important in controlling the rate of deterioration. (5) Close-range Structure from Motion (SfM) photogrammetry can be used to collect sub-mm resolution topographic data on rock surfaces in the field. (6) Rock hardness, rock surface roughness and morphometric analysis revealed no substantial difference in terms of nature of breakdown between low shocked and ushocked Moenkopi Sandstone at Meteor Crater site. (7) Aspect related microclimate within Meteor Crater affects the nature of rock breakdown on different crater sidewalls. \nThis thesis has improved the understanding of low shock deformed sandstones in impact craters and provided an insight into the role of low shock inheritance on subsequent rock breakdown. This research also advances the data collection methods on rock breakdown in field and laboratory settings by developing and applying novel SfM photogrammetry and X-ray computed tomography (CT) techniques.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».