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<p>St. Joseph peninsula is situated on the panhandle of Florida west coast in the northeastern Gulf of Mexico at N29°50‘ and W85°20‘ and is located at the west edge of the westernmost portion of the Apalachicola Barrier Island Complex (ABIC) on the Gulf of Mexico shoreline. Three vibra-cores were collected on Saint Joseph Bay side of Cape San Blas which is part of St. Joseph peninsula to determine its evolution in context of previous work by Rink and Lopez (2010). The study uses detailed textural analysis (PSD - Particle Size Distribution plots), multivariate statistics on the PSDs (Q-mode cluster analysis) and organic matter geochemistry (C/N and δ13C). In addition, Ground Penetrating Radar (GPR) profiles are used to provide broader stratigraphic context.</p> <p>The stratigraphic analysis found that CSB has an older nucleus of strandplain deposits dating to >12 Ka that were subsequently flooded and modified through Holocene sea-level rise at ≈ 2.2 Ka. Actual barrier formation began sometime between 2.2. Ka and 0.6 Ka which is the oldest beach ridge measured by Rink and Lopez (2010). Progradation of the barrier on the St Joseph Bay side began at least by 0.3 Ka and likely earlier. There is no evidence to indicate a higher than present sea-level in our core data and our data follows that of other sea-level studies using submerged offshore samples</p> / Master of Science (MSc)

Submarine Groundwater Discharge (SGD) through seafloor sediments is gaining recognition as an important component of coastal water quality. Stratigraphic features creating geologic heterogeneity, such as incised paleochannels, may influence preferential pathways for SGD. The central Mississippi Sound is underlain by paleochannels that were incised into Pleistocene sediments while the area was subaerially exposed during the last glacial maximum and are now buried by transgressive Holocene deposits. In this thesis, newly collected chirp, previously published seismic reflection, and sediment core data are used to characterize the three-dimensional structure of the Holocene-Pleistocene contact. Results indicate that Pleistocene paleochannels cross-cut the study area, exhibiting depths from 7.3–23.4 m, widths from 0.2–2.5 km, infilling with higher acoustic impedance fluvial sediments, and burial by transgressive Holocene sediments. Results suggest that this shallow subsurface stratigraphy may mediate locations of SGD and aid in predicting SGD pathways and associated contaminant loading into the coastal ocean.

The disintegration of the Classic Maya throughout the Terminal Classic (750-900 C.E.) is a complex loss of human population that has presented many questions about climate change and its impact on humanity. With droughts proposed as a prominent cause, understanding the quality and availability of groundwater resources at the time is pivotal to further determining the spatial and temporal distributions of population deterioration. The Yucatan aquifer consists of karstic cave systems, with a small number of inland lakes, which have previously been termed closed to the aquifer. It is important to understand how both of these types of water bodies react to long- and short-term forcing mechanisms such drying climate, sea-level rise and precipitation events. Using a variety of spatial and temporal records to determine aquifer evolution, changes and connectivity throughout the Holocene it will further understanding of how the aquifer reacts to changes in climate and the implications this may have had on the Classic Maya. Four sediment cores from Pac Chen Lake and two sediment cores from Carwash Cenote were collected to investigate Holocene paleoclimatic trends on the Yucatan Peninsula in Mexico. Records of past climate, groundwater conditions and flooding history at both sites were determined through microfossil and micro X-Ray fluorescence data. In Pac Chen Lake, elevation and timing of flooding of the lake coincided with sea-level rise. Using Ti, Fe and K records to determine wet vs dry conditions, dry periods through the terminal classic coincided with other paleoclimate records, but with no evidence of draw-down within the lake. Both of these observations imply connection of the lake to the aquifer. The Cl record from Carwash was used alongside a core from the Yax Chen cave system to observe spatial and temporal potability of the aquifer. An overall freshening trend in the coastal groundwater occurred throughout the Holocene. The largest amount of this freshening transpired through the Terminal Classic. At this time, populations inland were experiencing deterioration, while coastal populations along the coast continued to survive. Comparing Cl records at various depths and distances from the coast proved that Cl is impacted by proximity to the halocline. / Thesis / Master of Science (MSc)

Located in the far western equatorial Pacific, the Western Pacific Warm Pool (WPWP) is a greater than 10 million km² area of the warmest water on the planet. The WPWP therefore facilitates intense atmospheric convection and participates in coupled ocean-atmosphere climate phenomena such as El Niño Southern Oscillation, regional monsoons, and the shifting Intertropical Convergence Zone. The WPWP is also a water mass crossroads where thermocline-depth western boundary currents (WBCs) such as the New Guinea Coastal Undercurrent (NGCUC) facilitate the transfer of mass, heat, and nutrients vertically, zonally, and meridionally in the ocean. In this dissertation I focus mostly on reconstructing WPWP upper ocean temperature, salinity, nutrient, and productivity dynamics via a suite of physical and geochemical paleoclimate proxies. I apply these proxies in bulk sediments and planktic foraminifera from International Ocean Discovery Program (IODP) Site U1486 over the Pleistocene (2580 ka to 11.7 ka) and Holocene (11.7 ka to present). Site U1486 is located at 2°22’S, 144°36’E in the Bismarck Sea north of New Guinea in the southern WPWP, and is ideally situated to track changes to the WPWP upper water column forced by the South Pacific. The presence of glacial-interglacial (G-IG) variability within WPWP records is particularly important for determining local versus high-latitude climatic influences on the WPWP – with climate shifts such as the mid-Pleistocene Transition (MPT; ~1250 – 700 ka) and mid-Brunhes Event (MBE; ~430 ka) of particular interest in the long-term records I present. In chapter 1, I explore the paleoceanography of the low-latitude Pacific via upper ocean nitrate dynamics. I present a new bulk sediment ẟ¹⁵N record from Site U1486 that spans from 1420 to 0.67 ka – over a million years longer than any nearby records. Via analysis of orbital variability and secular trends at Site U1486 and in records directly along the equator in the Pacific, I find that nitrate dynamics were largely unrelated in the two regions in the Middle and Late Pleistocene. Whereas ẟ¹⁵N at Site U1486 is in line with patterns of eastern Pacific denitrification, increasing ẟ¹⁵N after the MPT at sites located directly along the equator appears linked to increasing Southern Ocean nitrate utilization. Enhanced nitrate utilization is an indicator of a strengthened biological pump – a major contributor to the reduction of atmospheric 𝑝CO₂ during the last glacial. A post-MPT increase in nitrate utilization may therefore point to the Southern Ocean biological pump as a driver for the deeper and longer glacial periods of the 100-kyr world after the MPT. In Chapter 2, I investigate changes in the vertical temperature and salinity structure of the southern sector of the WPWP in relation to the upper ocean’s response to climate change. When combined with Mg/Ca paleotemperatures and δ¹⁸O_sw, my 670-kyr record of Δẟ¹⁸O between the surface-dwelling foraminifera Globigerinoides ruber (sensu stricto) and the thermocline-dwelling foraminifera Pulleniatina obliquiloculata and Globorotalia tumida suggests enhanced thermocline shoaling and a progressively increasing vertical salinity gradient commencing near 240 ka. This secular change in upper water column dynamics does not appear to be associated with previously documented changes in G-IG variability such as the MPT or MBE. Via comparison to other records, I identify widespread cooling of the thermocline in the equatorial Pacific after ~240 ka. After combining these reconstructions with ²³⁰Th-derived focusing factors I validate previous model results indicating obliquity-driven strengthening of low-latitude ocean currents and extend this to imply the periodic increased transport of high-salinity thermocline water masses. These results strengthen previous evidence that the structure of the WPWP thermocline is relatively independent from the drivers of climate at the surface and support that variability in WPWP thermocline circulation is substantially influenced by obliquity. Because of the nitrate dynamics in the Bismarck Sea, bulk sediment ẟ¹⁵N cannot be used to reconstruct productivity. However, chapter 3 constrains variability in productivity via the analysis of new ²³⁰Th-normalized records of preserved biogenic flux and its components at Site U1486 over the last 138 kyr. Here, I assess the drivers of variability in paleo-productivity by reconstructing paleo-stratification, as in the modern Bismarck Sea productivity is stimulated by the delivery of nutrients to the surface during increased upwelling (reduced stratification). Paleo-stratification is approximated by calculating upper ocean density gradients between the calcification depths of G. ruber, P. obliquiloculata, and G. tumida using Mg/Ca temperatures and δ¹⁸O_sw-estimated salinity. Decreased paleo-stratification (a reduced vertical density gradient) was associated with increased productivity and is generally in phase with maximum orbital precession. Paleo-productivity therefore appears to respond to monsoonal increases in coastal upwelling when the Intertropical Convergence Zone (ITCZ) was at its southernmost extent. This illustrates that the unique and more direct method of constraining stratification presented here, which is subject to greater uncertainty, yields results consistent with our current understanding of upper ocean dynamics. I also identify a period between 100 and 60 ka during a potential reorganization of the upper water column in which variability in productivity occurs at a higher frequency than that of precession. Finally, while also related to ITCZ shifts, a nearby record closer to the equator is phase-lagged from Site U1486 – emphasizing the fine-scale regional differences in the drivers of primary productivity in the WPWP.

[EN] The understanding of the mechanical behaviour of natural intact soils is central to engineers when designing new structures. The research carried in this thesis focused on investigating the effects of the naturally occurring in-situ structure on the mechanical behaviour of two shallow recently deposited Holocene alluvial materials, the Bormida River silts (BRS) from Italy and the Valencia silty soils (VSS) from the alluvial plains of the Turia River, Spain. These types of deposits are frequently characterised by highly heterogeneous in-situ structures. A large range of soils with different size distributions from sands to silty clays were investigated. Oedometer and triaxial tests were carried out on intact, slurry and compacted samples. The first step was to characterise the behaviour of the materials at their reconstituted state to define the reference framework for investigating the effect of the in-situ structure of the intact specimens. The effects of the sample preparation technique on the mechanical behaviour were examined, in particular its influence on the uniqueness of the normal compression line and critical state line. The initial structure created during the preparation of the specimens was totally removed after compression and shearing regardless of the sample preparation method. Only one soil displayed a clear effect of the sample preparation technique, the oedometer compression lines of which remained parallel to each other even at a very high stress levels for the case of the slurry samples. This result showed that contrary to what is stated in the literature the sample preparation technique can created very robust initial structures resulting in a transitional behaviour. Clears effects of the in-situ structure of the intact samples of the BRS and VSS were observed on the oedometer compression behaviour even at very high stress levels with stress sensitivity values still larger than unity at the end of the tests. It appeared that the effects were more noticeable as the degree of heterogeneity inside the specimens increased at a meso-structure level as it was the case of some samples of the VSS materials which exhibited a certain layering. Small effects of the in-situ structure were seen at large shearing strains and only on the wet side of the critical state. / [ES] El conocimiento del comportamiento mecánico de los suelos en su estado natural es de importancia capital para los ingenieros a la hora de diseñar nuevas obras. La investigación desarrollada en esta Tesis se centra en descubrir los efectos que tiene la estructura del suelo en su estado natural en la respuesta mecánica de dos suelos aluviales holocenos, depositados superficialmente: los limos del río Bormida (BRS) en Italia y los suelos limosos provenientes de la llanura aluvial del río Turia (VSS) en España. Este tipo de suelos se caracterizan frecuentemente por una estructura inicial altamente heterogénea. Se ha ensayado una gran variedad de muestras con diferentes granulometrías, desde arenas a arcillas limosas en las que se han realizado ensayos edométricos y triaxiales en muestras intactas, compactadas y en muestras reconstituidas (slurry). En una primera etapa de la investigación se caracterizó la respuesta del material en su estado reconstituido para definir un marco de referencia con el que poder comparar la respuesta de las muestras intactas tomadas in situ y que preservan su estructura natural (inalteradas). Se ha analizado la influencia del modo de preparación de las muestras en su comportamiento mecánico, y, en particular, en la unicidad de las curvas de compresión noval y de estado critico. Se ha comprobado que la estructura inicial inducida durante el proceso de preparación desaparece completamente tras someter la muestra a compresión y corte, independientemente del método de preparación utilizado. Únicamente un suelo mostró, de un modo nítido, el efecto de la técnica de preparación, de modo que las líneas de compresión edométrica se mantuvieron paralelas incluso a niveles de tensión elevados en el caso de muestras reconstituidas (slurry). Este resultado demostró, contrariamente a la opinión aceptada en la bibliografía, que el sistema de preparación de la muestra puede crear una potente estructura inicial dando lugar a un comportamiento de tipo transicional. En los ensayos de compresión edométrica se ha podido comprobar un claro efecto positivo de la estructura inicial de las muestras intactas, incluso a niveles altos de tensión, observándose índices de sensitividad tensional superiores a uno al final de los ensayos, de modo que para igualdad de índice de huecos, la tensión efectiva vertical de la muestra intacta es superior a la correspondiente en la muestra reconstituida. Aparentemente, este efecto es tanto más significativo cuanto mayor es el grado de heterogeneidad interno de la muestra a nivel de meso-estructura, como se pudo observar en algunas muestras de los suelos (VSS) que presentaban niveles de laminación horizontal. En los ensayos de corte la influencia de la estructura intacta fue relativamente pequeña y únicamente en el lado húmedo del estado critico. / [CA] Conèixer el comportament mecànic dels sòls en el seu estat natural és d'importància capital per als enginyers a l'hora de dissenyar noves obres. La investigació desenvolupada en aquesta Tesi se centra a descobrir els efectes de l'estructura del sòl en el seu estat natural en la resposta mecànica de dos sòls al¿luvials holocens, dipositats superficialment: els llims del riu Bormida (BRS) a Itàlia i els sòls llimosos provinents de la plana al¿luvial del riu Túria (VSS) a Espanya. Aquests tipus de sòls es caracteritzen sovint per una estructura inicial altament heterogènia. S'ha assajat una gran varietat de mostres amb diferents granulometries, des d'arenes fins a argiles llimoses amb les quals s'han realitzat assajos edomètrics i triaxials en mostres intactes, compactades i en mostres reconstituïdes (slurry). En una primera etapa de la investigació es va caracteritzar la resposta del material en el seu estat reconstituït per a definir un marc de referència amb el qual poder comparar la resposta de les mostres intactes preses in situ i que preserven la seua estructura natural (inalterades). S'ha analitzat la influència del mètode de preparació de les mostres en el seu comportament mecànic i en particular, en la unicitat de les corbes de compressió noval i d'estat crític. S'ha comprovat que l'estructura inicial induïda al llarg del procés de preparació desapareix completament després de sotmetre la mostra a compressió i tall, independentment del mètode de preparació utilitzat. Únicament un sòl va mostrar clarament l'efecte de la tècnica de preparació, de manera que les línies de compressió edomètrica es van mantenir paral¿leles fins i tot a nivells de tensió elevats en el cas de mostres reconstituïdes (slurry). Aquest resultat va demostrar, contràriament a l'opinió acceptada en la bibliografia, que el sistema de preparació de la mostra pot crear una potent estructura inicial donant lloc a un comportament de tipus transicional. Als assajos de compressió edomètrica s'ha pogut comprovar un clar efecte positiu de l'estructura inicial de les mostres intactes, inclús a nivells alts de tensió, observant-se índexs de sensitivitat tensional superiors a la unitat al final dels assajos, de manera que per a igualtat d'índex de buits, la tensió efectiva vertical de la mostra intacta és superior a la corresponent en la mostra reconstituïda. Aparentment, aquest efecte és més significatiu quant major és el grau d'heterogeneïtat intern de la mostra a nivell de meso-estructura, com es va poder observar en algunes mostres dels sòls (VSS) que presentaven nivells de laminació horitzontal. Als assajos de tall la influència de l'estructura intacta va ser relativament petita i únicament en el costat humit de l'estat crític." / Carrión Carmona, MÁ. (2016). The effects of the structure on the mechanical behaviour of young Holocene alluvial materials from the Bormida River (Italy) and Turia River (Spain) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63470

The equatorial Pacific is a dynamic region, characterized by zonal and meridional asymmetries in both the ocean and the atmosphere. The asymmetries in the eastern equatorial Pacific (EEP) reach a maximum in northern hemisphere fall, when southern hemisphere trade winds cross the equator and drive the upwelling of cold, CO₂ and nutrient-rich waters along a shallow thermocline, fueling marine primary production. Interannual perturbations in ocean heat content also result in El Niño or La Niña events, which diminish or amplify these asymmetries. In this dissertation, multi-proxy paleo-records derived from marine sediment cores are used to reconstruct fundamental aspects of the coupled ocean-atmosphere system in the EEP and to evaluate the hypothesis that changes in the seasonal distribution of equatorial insolation, which were primarily controlled by Earth’s precession, influenced the mean state and variability of the EEP in the late Pleistocene. EEP thermocline depth, reconstructed from the δ18O of multiple species of planktic foraminifera that lived at different depths in the water column, was found to oscillate between a La Niña-like and an El Niño-like state on precession timescales, in close phase with equatorial insolation during northern hemisphere late summer/early fall. EEP export production, reflected in sedimentary 231Pa/230Th, was influenced by changes in high latitude nutrient leakage and upwelling and, at times, varied on precession timescales. Glacial increases in EEP deep ocean carbon storage, reconstructed from sedimentary authigenic 238U, occurred independently of changes in local export production. Individual δ18O analyses of the surface-dwelling foraminifera Globigerinoides ruber were used to reconstruct EEP sea-surface variability during the last interglacial and penultimate glacial period. While sea-surface variance was not significantly different from that of the late Holocene, the paleo-record suggests that the strength and frequency of ENSO events varied with changes in equatorial insolation during northern hemisphere late summer/early fall and with EEP thermocline depth.

No / Concepts of residential and logistic mobility are applied to survey assemblages from multiple decades of research along the interior drainages of central lower Michigan. Drawing on the ethnographic record of boreal hunter-gatherers and archaeological interpretations of long-distance logistic mobility from the Mesolithic of northern England and continental Europe, it is argued that the importance of logistic mobility is underrepresented in summaries of northern hemisphere hunter-gatherers. Reconstruction of Middle Holocene environments suggests that the resource structure of the central Michigan uplands was one that fostered use of logistic mobility, and that interior Middle Archaic assemblages and site structures reveal special function activities systemically tied to residential and other special function sites at lower coastal elevations, as well as currently submerged under Lake Huron. We conclude that rising levels of Lake Huron ca. 4500 B.P. resulted in decreased land area, population packing, and a consequent shift to residential mobility by the Late Archaic. Further, the results of this analysis can serve as a comparative framework for recognizing the role of logistic mobility in the evolution of hunter-gatherer adaptive strategies in other regions.

Investigating the archaeology of submerged landscapes beneath many metres of sea and buried under modern sands requires an understanding of the terrestrial surface as it may have been prior to the inundation. To do this, environmental evidence is required from contextualised in-situ locations and the best material evidence for preservation of archaeology, organic remains, dating proxies, pollen, diatoms, microfossils, coleoptera etc. is peat. This research supports the search for peat in submarine environments by interpreting seismic surveys of the sub-sea floor and analysing reflective signals for distinctive organic responses. By means of sedimental analysis and ground observation, the research sets out to differentiate between organic signals, to allow for the identification and location of shallow peat beds within features of a palaeolandscape. Using these results should provide an opportunity to target such peat beds in an archaeologically focused coring programme. The research also examines ways in which organic responses may be mapped over larger areas in order to integrate the results into a wider scale landscape model identifying potential peatland, marsh, valley fen and lowland areas. Finally, the research introduces an artificial intelligence neural networking technology for the identification of organic interfaces in seismic surveys, examining three different ways in which this could be accomplished using specialist computer tools and software.