New technologies are continuously being developed that can aid us in archaeological research. The purpose of this project is to revisit an area containing Late Iron Age (LIA) Stone Walled Structures (SWS) that have received sporadic archaeological research over time, and employ new techniques and technologies to test/re-evaluate previous findings. This involves developing new mapping techniques, which involve the use of Geographical Positioning Systems (GPS), which allowed for a wide survey/mapping exercise in a time effective and budget conscious manner. From these data, a new typology was created in order to reflect new types as well as further segregate exiting types. The resulting data was analysed in a Geographic Information Systems (GIS) environment, allowing us to tackle issues such as spatial distribution and landscape patterns in a digital environment. This analysis allowed us to re-evaluate the original spatial distribution, looking at possible reasons for the inaccuracies in the original study. We then explore the implications of these new data. We tested the results of these analyses based on proposed scenarios for the location of these sites, in order to try better understand the positioning, as we as identify possible diagnostic sites that can undergo further examination.

Cette thèse est focalisée sur la contribution de l'étude couplée de l’organisation multi-échelle et de la composition isotopique de C et N des carbones de météorites différenciées (acapulcoites – lodranites (A-L)), pour mieux comprendre l’histoire de leur corps-parent. Nous avons systématiquement combiné observations des carbones de ces météorites avec des analogues expérimentaux. Nous avons développé une méthodologie originale couplant l'étude de l'organisation des échelles micrométriques à nanométriques (par Microscopie Electronique par Transmission et Microspectrométrie Raman) et l'analyse isotopique des carbones (par SIMS) sur rigoureusement les mêmes plages de dimensions micrométriques. La comparaison avec les mélanges expérimentaux indique que le graphite d’Acapulco s’est formé par un mode de graphitisation "catalysée par le fer". L’absence de graphitisation des carbones de Lodran dans un environnement riche en fer et chaud est apparemment paradoxale. Toutes nos observations peuvent être réconciliées si nous considérons une collision tardive du corps-parent des A-L avec un corps chondritique apportant matière organique insoluble et chaleur d'impact. Ce scénario est conforté par les analyses isotopiques qui indiquent une formation des carbones des A-L par carbonisation d’un précurseur chondritique et une migration d’effluents carbonés au sein du corps-parent / This thesis is focused on the contribution of the coupling of multi-scale organization and C, N isotopic composition of carbons in differentiated meteorites (acapulcoites – lodranites (A-L)), in order to better understand the history of their parent body. We systematically combined observations of carbons from these meteorites with experimental analogues. We developed an original methodology associating the study of the organization at the micrometre to nanometre scales (by Transmission Electron Microscopy and by Raman Microspectrometry), and the analysis of the isotopic composition of carbons (by SIMS) on strictly the same areas of micrometre dimensions. The comparison with experimental analogues indicates that the Acapulco graphite was formed by a "catalytic" graphitization mode. The absence of graphite in Lodran, in an iron-rich and hot environment, is apparently paradoxical. All our observations can be reconciled if we consider a late collision of the A-L parent body with a chondritic body bringing insoluble organic matter and impact heat. This scenario is strengthened by isotopic analyses, which indicate formation of A-L carbons by carbonization of a chondritic precursor and migration of carbonaceous effluents within the parent-body

L'élucidation du mécanisme de formation de divers verres naturels peut aider à comprendre la dynamique de la Terre car ces matériaux retiennent l'état de formation dans leurs structures. La spectroscopie XAFS appliquée aux matériaux amorphes issue des météorites fournit des informations sur les changements structuraux locaux des éléments présents. En effectuant des analyses dans la phase de verre des météorites et dans les verres issus de l'impact météoritiques des informations sur les conditions de formation des ces matériaux peuvent être obtenues. Dans cette thèse, l'analyse de la structure locale d’éléments de transition (Ti, Zr) dans les minéraux et les verres naturels a été réalisée par la XAFS. Des expériences de chauffage au laser à haute température et de flux gazeux sur zircon ont également été effectuées pour observer les changements structuraux à haute température dans les phases cristallines qui accompagnent le verre météoritique. La structure locale de ces matériaux est semblable à celle du Zr dans les sédiments de la limite Crétacé – Paléogène (K-Pg). Ce dernier ne montre aucune influence de diagenèse ou d'altération, ce qui suggère que les sédiments Cependant, l'abondance de Zr dans les sédiments n'est pas toujours suffisante pour obtenir des informations fiables sur la structure locale du Zr. Nous nous sommes ainsi intéressés à la structure local du Ti, qui appartient au même groupe que le Zr. Les conditions d'impact des météorites sur Mars et du passage des météorites à travers l'atmosphère peuvent être estimées par l'analyse de la structure locale de Zr dans la partie vitrifiée des météorites. L'analyse de la structure locale du Zr dans la météorite martienne de Tissint montre la croûte de fusion de cette météorite est semblable à celle des tectites et du verre d'impact qui les accompagne, alors que la partie intérieure vitreuse de Tissint est similaire à celle de la baddeleyite et de la fulgurite. Cette dernière aurait subi une vitrification pendant le passage à travers l'atmosphère. Afin de confirmer le changement structurel de Zr à haute température, nous avons effectué des expériences de chauffage du zircon, ainsi qu’une expérience de diffraction des rayons X sur poudre pendant le chauffage. L'analyse chimique dans le MEB a montré l'évaporation de la composante SiO2. Nous avons aussi obtenu un nouveau digramme de phase ZrO2-SiO2 dans lequel la région d’immiscibilité liquide proposée auparavant n’a pas pu être confirmée / Elucidation of the formation mechanism of various natural glasses can help to understand the dynamics of the Earth because these materials record the formation condition in their structures. XAFS applied to natural meteorite-related glasses provides information about the local structural changes of elements therein. By performing high-accuracy XAFS analyses for trace elements and their local structure in sedimentary rocks, in the glass phase of meteorites and in the meteorite impact-related glasses such as tektite and impact glass, information on the formation condition of these materials can be obtained. We have performed local structure analysis of IVb transition metal elements (Ti, Zr) in natural minerals and glasses K-edge XANES and EXAFS as well as high-temperature laser heating and gas flow experiments on zircon, to observe structural changes at high temperature in the crystalline phases that accompany the meteoric glass. The local structure of these materials is similar to that of of Zr in K-Pg sediments, which do not show any influence from diagenesis and weathering, suggesting that K-Pg sediments maintain the thermal quenching history of the meteorite impact. However, the low abundance of Zr in sediments prompted us to study Ti, which belongs to the same group as Zr and is much more abundant. Combination of the information about the local structures of Ti and Zr allows a higher reliability for the estimation of meteorite impact event. The local structure of Zr in the fusion crust and inner glassy part of the Martian meteorite of Tissint are similar, respectively, to that in tektite and accompanying impact glass and to that in baddeleyite and fulgurite. The latter was likely vitrified part during the passage through the atmosphere. It should be possible to estimate the conditions of meteorite impact on Mars and the passage of meteorites through the Earth’s atmosphere through the analysis of the local structure of Zr in the glassy part of meteorites. In order to confirm this hypothesis, we performed heating experiments of zircon with in-situ powder X-ray diffraction experiment was performed for ZrSiO4 and ZrO2. SEM analysis confirmed evaporation of the SiO2 component. We have obtained a new ZrO2-SiO2 phase diagram where the liquid-immiscible region proposed earlier does not appear.

Thesis (doctoral)--University of Tartu, 2006. / Vita. Includes bibliographical references. Also available on the Internet.

<p>Meteorites fallen from the sky and surface particles of the moon gathered by lunar space missions, have distinct microstructure and properties that can provide unique insights on the origins and processes for the evolution of our solar system. These extraterrestrial materials contain highly complex microstructures due to the formation and structure evolution events spanning long periods of time. The comprehensive characterization on these samples, to extract multi-scale structural information, is especially crucial to support formation theories, understand material utilization possibility, and preparation for potential hazard mitigation. In addition to the microstructure, an understanding of the mechanical properties of these materials is also vital. Hence, an in-depth investigation on how microstructural phase distribution and their respective mechanical properties connect to macroscopic deformation behavior is required.</p> <p>In this study, a correlative microscopy-based methodology was used to study several celestial samples; meteorite Aba Panu (L3), meteorite Tamdakht (H5), and a lunar dust grain from mature sample 10084 returned by the Apollo 11 mission. X-ray microcomputed tomography (XCT) was utilized to acquire inherent 3D structural details from samples non-destructively. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) was used to further resolve finer structural features and compositional information to complete the correlative described above.</p> <p>Both ex situ and in situ compression experiments, in the XCT, were performed on machined cylindrical samples of Aba Panu meteorite. Structure development including crack initiation, propagation, and failure states were analyzed and correlated to the macroscopic stress-strain behavior. Direct 3D correlation on ex situ and in situ images of crack growth were used to obtain a comprehensive mechanistic understanding of crack development and deformation. Finally, nanoindentation was used to complement the 3D microstructural study, by acquiring mechanical properties of individual constituent phases.</p> <p><br></p>

<p>Magnetic surveys are one of the principal geophysical methods employed to map the structure of basement rocks deeply buried below cover strata. In resource studies, aeromagnetic surveys are commonly acquired at regional scales (100-1000’s km2) while very few studies have attempted to resolve basement structures at site-scale (<10 >km2). In this study, high-resolution lake-based magnetic survey methods were evaluated for mapping of deeply-buried basement faults (Küçükçekmece Lagoon, Turkey; 6 km2) and a suspected meteorite impact crater (Charity Shoal, Lake Ontario; 9 km2). Total magnetic intensity (TMI) surveys were acquired using a single Overhauser magnetometer with 50-150 m line spacing. Interpretation of the magnetic data was aided by forward modelling of TMI data and depth to basement estimates using Euler and analytic signal methods. Total magnetic intensity (TMI) maps of Küçükçekmece Lagoon identify several north-northwest trending (340-350°) magnetic lineaments that are aligned with strike-slip faults mapped from offshore seismic data. The pattern of magnetic anomalies in the lagoon is consistent with extensional normal faulting of bedrock and lake sediments. Magnetic results from Charity Shoal reveal a large (>1400 nT) parabolic-shaped magnetic anomaly centered over the crater basin and an annular magnetic high (40-50 nT) corresponding with the basin rim. Modelling results exclude the origin of the CSS as a shallow glacial erosional or karst sinkhole feature and are most consistent with a pre-Paleozoic meteorite impact in the Precambrian basement.</p> / Master of Science (MSc)

In the northern part of Swedish Caledonides, north of Lake Torneträsk is a 7 km long exposure of a breccia layer. The layer thins westwards and eastwards from the central part where it is up to 27 m thick. It is called the Vakkejokk Breccia after the type section. The breccia has been described in literature since about a century, but its origin is enigmatic. The breccia layer is since the summer of 2012 investigated by three geologists specialized in impact craters, Paleozoic sediments, and the Caledonian orogeny. They put forward evidence for the breccia being formed by a hypervelocity impact during the Lower Cambrian at approximately 520 Ma (Ormö et al. 2017). At that time the target area was a shallow epicontinental sea that surrounded the mainly peneplanized continent Baltica. An impact into the sea is known to generate tsunami waves as well as resurge deposits when the water brings ejected and rip-up material back into the crater. Ormö et al. (2017) suggest the top part of the Vakkejokk Breccia to include such resurge deposits. The depositional marine environment is also known to rapidly protect an impact crater from further erosion. It is possible that only the topographic rim of the Vakkejokk crater was eroded during the millions of years it may have taken before the crater was covered by younger sediments. About 100 m.y. after the formation, it was completely covered by overthrust nappes during the Caledonian orogeny, when Baltica and Laurentia collided. The crater itself is not exposed today, merely parts of what is thought to be the ejecta layer and resurge deposits. This Bachelor of Science project aimed to investigate the putative resurge deposits to learn more about the process of formation and the provenance in the target of the clasts in the deposits. This was carried out by three short drillcores through the resurge deposit part of the Vakkejokk Breccia layer. The place to drill the boreholes was chosen at an outcrop which is proximal to the putative hidden crater. The retrieved drillcores were cut longitudinally, then polished and photographed in high resolution. Each core was then analyzed in an image analysis software with respect to clast granulometry and lithology. To the results are presented as graphs showing clast size, size sorting, clast shape, of the relative amounts of different lithologies and the matrix content. The results are discussed with respect to well-documented analogue marine-target craters

ELEMENTAL AND ISOTOPIC STUDY OF DIFFERENTIATED METEORITES AND IMPLICATIONS FOR THE ORIGIN AND EVOLUTION OF THEIR PARENT BODIES Iron meteorites are differentiated meteorites composed largely of Fe-Ni alloys. The metallic phase of many iron meteorites shows a texture called the Widmanstätten pattern, which develops as a two-phase intergrowth of kamacite (α-bcc, ferrite) and taenite (γ-fcc, austenite), and forms by nucleation and growth of kamacite from taenite during slow cooling of the parent body. Selected iron meteorites - octahedrites of different structural and chemical groups (Canyon Diablo, Toluca, Bohumilitz, Horh Uul, Alt Biela, Nelson County, Gibeon and Joe Wright Mountain) were studied with intention to evaluate the scale and extent of Fe isotopic heterogeneities in iron meteorites and to find the possible link between the isotopic variations and thermal histories of the respective meteorite parent bodies. The Fe isotopic compositions of kamacite and taenite in the studied meteorites, obtained by three independent analytical techniques with different spatial resolution capabilities (laser ablation and solution MC ICP-MS and SIMS) show significant variations of up to ~4.5‰ in δ56 Fe. The taenite is isotopically heavier compared to kamacite in all studied meteorites. There is no correlation...

207Pb*/206Pb* chronometry was used to obtain the ages of Ca,Al-rich inclusions (CAIs) and chondrules found in ancient meteorites. Assuming a 238U/235U=137.88, Pb/Pb ages of chondrules in NWA801 (a CR2 meteorite) are 4564.6±1.0 Ma, chondrules in Mokoia (a CV3 chondrite) are 4564.2±1.1Ma, and CAIs in Mokoia are 4567.9±5.4 Ma. The Pb/Pb age of NWA801 chondrules is concordant with 26Al/26Mg ages of CR chondrules. However if a 238U/235U < 137.88 is used, the age for NWA801 chondrules becomes younger by ~1Ma and discordant with 26Al/26Mg ages of CR chondrules. This suggests either a discrepancy with the U compositions or the initial Mg isotopic compositions of NWA801 chondrules. The shapes of NWA801 chondrules, and blebs of FeNi metal in the meteorite matrix, were further studied by 3D X-ray micro-computed tomography (CT). Most chondrules (92%) were ‘armoured’ with one discontinuous layer of FeNi metal. Two layers of FeNi metal (one on the exterior and one concentric through the interior separated by silicate) were rare <8%. Chondrules and matrix blebs occur as oblates, prolate, spheres and triaxial spheroids. It is proposed that the shapes were made free-floating in the nebula likely by flash-melting precursors into molten droplets that were vibrating as harmonic oscillators that ‘froze-in’ their shapes during cooling. Parent-body metamorphism and shock are not likely processes affecting the matrix-bleb and chondrule shapes. Chondrules with ≥2 FeNi metal layers were likely formed by mergers and not by successive deposition and annealing of metal in multiple flash-melting events. Attempts to obtain 207Pb*/206Pb* ages from chondrules and CAIs by thermal extraction (TE)- TIMS were unsuccessful. However LA-ICP-MS was shown to be useful for rapidly determining Pb isotopic trends in meteorites and unknown objects. In particular, it was shown that 137La (T1/2=60ky) should be detectable in recently fallen meteorites using LaF−4 to suppress the 137Ba isobar during tandem accelerator mass spectrometry combined with a novel instrumental technique for isobar separation.

207Pb*/206Pb* chronometry was used to obtain the ages of Ca,Al-rich inclusions (CAIs) and chondrules found in ancient meteorites. Assuming a 238U/235U=137.88, Pb/Pb ages of chondrules in NWA801 (a CR2 meteorite) are 4564.6±1.0 Ma, chondrules in Mokoia (a CV3 chondrite) are 4564.2±1.1Ma, and CAIs in Mokoia are 4567.9±5.4 Ma. The Pb/Pb age of NWA801 chondrules is concordant with 26Al/26Mg ages of CR chondrules. However if a 238U/235U < 137.88 is used, the age for NWA801 chondrules becomes younger by ~1Ma and discordant with 26Al/26Mg ages of CR chondrules. This suggests either a discrepancy with the U compositions or the initial Mg isotopic compositions of NWA801 chondrules. The shapes of NWA801 chondrules, and blebs of FeNi metal in the meteorite matrix, were further studied by 3D X-ray micro-computed tomography (CT). Most chondrules (92%) were ‘armoured’ with one discontinuous layer of FeNi metal. Two layers of FeNi metal (one on the exterior and one concentric through the interior separated by silicate) were rare <8%. Chondrules and matrix blebs occur as oblates, prolate, spheres and triaxial spheroids. It is proposed that the shapes were made free-floating in the nebula likely by flash-melting precursors into molten droplets that were vibrating as harmonic oscillators that ‘froze-in’ their shapes during cooling. Parent-body metamorphism and shock are not likely processes affecting the matrix-bleb and chondrule shapes. Chondrules with ≥2 FeNi metal layers were likely formed by mergers and not by successive deposition and annealing of metal in multiple flash-melting events. Attempts to obtain 207Pb*/206Pb* ages from chondrules and CAIs by thermal extraction (TE)- TIMS were unsuccessful. However LA-ICP-MS was shown to be useful for rapidly determining Pb isotopic trends in meteorites and unknown objects. In particular, it was shown that 137La (T1/2=60ky) should be detectable in recently fallen meteorites using LaF−4 to suppress the 137Ba isobar during tandem accelerator mass spectrometry combined with a novel instrumental technique for isobar separation.