The discovery of deep-sea hydrothermal vents in 1977 revealed an ecosystem supported by chemosynthesis with a rich diversity of invertebrates, Archaea and Bacteria. While the invertebrate vent communities are largely composed of endemic species and exist in different biogeographical provinces, the possible factors influencing the distribution patterns of free-living Archaea and Bacteria are still being explored. In particular, how differences in the geologic setting of vent fields influence microbial communities and populations associated with active vent deposits remains largely unknown. The overall goal of the studies presented in this dissertation was to examine the links between the geologic setting of hydrothermal vent fields and microorganisms associated with actively venting mineral deposits at two levels of biological organization. At the community level, bar-coded pyrosequencing of a segment of the archaeal and bacterial 16S rRNA gene was employed to characterize and compare the microbial communities associated with numerous deposits from several geochemically different vent fields. Results from these studies suggest that factors influencing end-member fluid chemistry, such as host-rock composition and degassing of magmatic volatiles, help to structure the microbial communities at the vent field scale. At the population level, targeted cultivation-dependent and -independent studies were conducted in order to expand our understanding of thermoacidophily in diverse hydrothermal environments. Results of these studies expanded the phylogenetic and physiological diversity of thermoacidophiles in deep-sea vent environments and provided clues to factors that are influencing the biogeography of an important thermoacidophilic archaeal lineage. Overall, these studies have increased our understanding of the interplay between geologic processes and microorganisms in deep-sea hydrothermal environments.

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Yes / Local scour around submarine pipelines can affect the stability of the pipeline. The accurate estimation of the scour around submarine pipelines has been a hot topic of research among marine engineers. This paper presents results from a numerical study of clear-water scour depth below a submarine pipeline for a range of the steady flow conditions. The flow field around the pipeline under scour equilibrium condition is numerically simulated by solving the Reynolds-Averaged Navier-Stokes (RANS) equations with the standard k-ε turbulence closure. The flow discharge through the scour hole for various flow conditions is investigated. The results are used to establish the relationship between the flow discharge and the maximum scour depth. Incorporated with the Colebrook-White equation, the bed shear stress is obtained and an iterative method is proposed to predict the scour depth around the submarine pipeline. The calculated scour depths using the present method agree well with the laboratory measurements, with the average absolute relative error being smaller than that using previous methods, indicating that the proposed method can be used to predict the clear-water scour around the submarine pipeline with satisfactory accuracy. / National Nature Science Fund of China (Grant No.50879084, 51279189), the Open Fund from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1302),China Scholarship Council, Public Projects of Zhejiang Province (2016C33095) and the Natural Science Fund of Zhejiang Province (LQ16E090004).

Submarine channel-levee systems represent one of the most significant features of sediment transfer on Earth and one of the final segments in source-to-sink routing systems. As such, they serve as conduits as well as intermediate or final storage for large volumes of sediment, paleoenvironmental signals, and pollutants on their way to the deep ocean. Over the years, these systems have been studied through a variety of methods, including: (i) outcropping analogs; (ii) seismic data, occasionally integrated with core analysis; (iii) numerical modeling and physical experiments, and more recently; (iv) repeated multibeam bathymetry and (v) direct measurement of sediment gravity flows. However, as we are able to show in this study, there are still questions about the inherent evolution of these systems that need to be addressed. In this study, we focus on the sedimentary processes and depositional products of submarine channel-levee systems through the characterization, analysis and interpretation at different scales of outcropping analog systems of the Upper Cretaceous Tres Pasos and Cerro Toro Formations in the Magallanes-Austral Basin. In the first research-chapter, Chapter 2, we analyze the transition between laterally offset and vertically stacked channels on a previously undocumented, seismic-scale outcrop of the Tres Pasos Formation. This change in stacking pattern has been widely recognized in submarine channel systems, however, the stratigraphic and sedimentologic details and implications to general conceptual models have not been addressed in the past. Our observations indicate that in between these two depositional architecture styles there is a significant phase of erosion and bypass at a complex-scale (or larger) and that the relief achieved via this deep incision of one or multiple simultaneously active conduits was the necessary condition to promote flow stripping processes and associated overbank deposition. In addition, we discuss the presence of an unusual intra-channel lithofacies association observed directly overlying one of these incisions, which we interpret to represent the along-strike expression of bedforms associated with supercritical flow processes that are found in modern channels and some ancient channel-fill successions. In the next research chapter, Chapter 3, we characterize a 500 m thick fine-grained dominated sedimentary succession interpreted as overbank deposits of the Cerro Toro Formation that have been affected by synsedimentary faulting and crosscut by an extensive injectite network. The scale of this outcrop allows us to resolve the relationship between sedimentary packages and structural features that are commonly overlooked or beyond the resolution of datasets derived from other sources by using high-resolution measurements and quantitative analysis at a cm scale. The orientation of synsedimentary normal faults, paleocurrent directions, and characteristics of 10-36 m thick sandstone-prone intervals suggest a model of overspilling turbidity currents (from the main axial channel belt to the west) on a large levee-slope that might share deformational mechanisms with other depositional slopes. Finally, in Chapter 4, we use detrital zircon U-Pb geochronology to determine maximum depositional ages of seven sandstone samples attributed to the axial channel-belt of the Cerro Toro Formation and shallow-marine deposits of the Dorotea Formation, which extend the chronostratigraphic framework for Ultima Esperanza 55 km southward to help reduce the gap between field sites in the Ultima Esperanza and Magallanes provinces. Based on these new data, we hypothesize that the conglomeratic-rich deposits at this location, which have generally similar lithofacies and large-scale stratigraphic architecture to the Cerro Toro Formation, are unlikely to represent the southward extension of the well-studied axial channel belt deposits to the north, and therefore they potentially represent their own sediment routing system emanating from erosional catchments in the fold-thrust belt to the west. This chapter highlights the value of establishing a chronostratigraphic framework to reconstruct ancient paleogeography in addition to interpretation based purely on observable sedimentary parameters. / Doctor of Philosophy / Turbidity currents are one of the most common processes in in deep-marine environments, they are sediment-laden flows that move downslope due to an excess of density caused by the sediment they carry. They occur under a wide range of geomorphologic configurations, one of such are submarine channel-levees systems. A submarine channel-levee system is a composite geomorphologic feature in the ocean floor consisting of a concave, long-lived sedimentary conduit flanked by parallel depositional highs that is orders of magnitude longer in its downslope longitude than its width. These systems have a worldwide distribution and can be found in every tectonic setting. They represent one of the final segments in sedimentary routing systems and their study is of great importance for numerous reasons, including (i) as hydrocarbon reservoirs, (ii) to mitigate submarine geological hazards that might affect human infrastructure, (iii) their role in the carbon cycle as they transport and bury organic carbon, (iv) their impact to the marine environment as they disperse human-sourced pollutants, and (v) their capacity to preserve geochemical proxies that record past climate and tectonic history. This dissertation is divided in three research chapters focused on different aspects of the processes and depositional products of submarine channel-levee systems through the characterization, analysis and interpretation at different scales of analog ancient systems now exposed in the mountains of Southern Chile. The use of outcropping sedimentary successions is a common practice to characterize and understand modern environments, as they provide an accessible record of their evolution through temporal scales of hundreds of thousands or even millions of years. From a geologic point of view, this study is located in the Chilean part of the Magallanes-Austral Basin, which in the past was an ocean that reached paleowater depths of ~2,000 m during the Late Cretaceous and that was subsequently filled with sediments that form the different geologic units of the area. Here, we focus on two geologic units that represent deep-marine sedimentation in this ancient ocean, known as the Tres Pasos and the Cerro Toro formations. Our study ranges from the detailed stratigraphic characterization of the transition between two different styles of stacking patterns widely recognized in submarine channel systems and its implications, to the influence of sedimentary structures on hundreds of meters of fine-grained sediments deposited in a large levee subjected to failure, and the use of tiny minerals known as zircons to constrain the depositional age and paleogeography associated to coarse-grained deposits historically attributed to a >150 km long axial channel-belt. The results presented here do not only serve to better understand the configuration of ancient deep-marine deposits in this part of the world, but also have implications to improve our understanding of the fundamental sedimentary processes and the depositional products in deep-marine environments worldwide.

Architecture exists through human experience. As the product of the relationship between a building and a person, architecture gains meaning when it is viewed and contemplated by an individual moving throughout a building. Architecture simultaneously engages the body and mind of one who experiences it, and its intentions become visible through a continuous weaving of motion through situations that constitute a place. My thesis examines the interplay between architecture and human action. Manifest in the following thesis are explorations of the institution of the museum. From its earliest forms to its present day forms, the museum has undergone many changes due to a number of influences. In this thesis I will look at the cultural dynamics that shape museums. Specifically, my critique will be through the lens of its cultural history, my own culturally based observations, and through a design: the demonstration. One objective of this thesis is to revive the idea of the museum as a place of the muses, where the muses inspire those people who experience the place. I have selected Charleston and its historic setting for the project location of a Museum. This is a place where one might participate in a journey of initiation, education, and cultivation. Through design, I demonstrate a museum, which aims to initiate and encourage self-cultivation by one's experience of the objects in the museum and the space that surrounds the objects. It is perhaps through a perusal of objects contained without authoritative concepts applied that one may acquire knowledge and become inspired. / Master of Architecture

Subduction zones, where one tectonic plate descends beneath another, are the most seismically active regions on Earth and have produced the largest earthquakes and some of the most destructive tsunamis ever recorded. Significant questions remain regarding the roles both the downgoing and overriding plates play in contributing to varying styles of rupture along the main seismogenic contact between the two plates, or megathrust, where such great (Mw > 8) earthquakes are generated. In the last few decades, the scientific community has recognized how different structural and compositional properties of both plates, and in particular the hydration state of the incoming plate can contribute to variations in megathrust slip behaviors. In this thesis, I show how marine multichannel seismic (MCS) and ocean-bottom seismometer (OBS) data can be used to investigate structural controls on megathrust slip behavior including the different styles of great earthquakes and/or the generation of slow slip events. Offshore Alaska and Sumatra, we used long-streamer multichannel seismic data to create a high-resolution P-wave velocity (Vp) model of the upper oceanic crust prior to subduction. Using a differential effective medium theory, we place the first constraints on the amounts pore (free) water contained therein. Our results indicate that the uppermost oceanic crust of the incoming plates in both regions is significantly hydrated. Offshore Alaska, we show that pervasive faulting in the bending area allows seawater to penetrate into the uppermost crust. We propose that high water content in uppermost crust might contribute to observations of low coupling along the shallow plate interface in this area through the expulsion of pore fluids. Geochemical analyses of arc lavas in this segment of the Alaska subduction zone suggests significant fluid release from the downgoing crust compared to adjacent segments. Thus, we propose that during subduction, additional bending and high-temperature circulation of remaining pore fluids could further alter the upper oceanic crust that dehydrates around sub-arc depths. Offshore Sumatra, few bending-related faults are observed; however, evidence for significant and homogeneous hydration within the the uppermost crustal layer 2A (extrusives) suggests that plate bending plays a role in the shallow reopening cracks, facilitating the shallow penetration of seawater. In layer 2B (sheeted dikes) just below, our results suggest heterogeneous, yet significant, hydration that we attribute to the slow and diffuse deformation taking place in the Wharton Basin. We speculate that the large amounts of upper-crustal water carried into the Sumatra subduction zone can influence shallow slip behavior, as evidenced by recent records of a long-lasting slow slip event in the area. To further explore potential structural and compositional controls on spatial varia- tions in megathrust slip behavior in Alaska, we use OBS data to create a 3D Vp model of the Alaska Peninsula Subduction zone within a 500-by-400 km wide area with good resolution down to 20-25 km depths in both the incoming and overriding plates. Our model samples two subduction zone segments that exhibit differences in history and style of megathrust rupture. We interpret reductions in seismic velocities within the incoming plate as evidence for modest hydration of the Pacific oceanic plate resulting from a series of fracture zones and the formation of large seamounts and an associated basement swell, or platform. The bathymetry of the seamounts and platform in part modulates the distribution and lithology of subducting sediments across the margin that we propose might influence shallow slip behavior. Within the overriding North American plate, we see evidence for contrasting styles of deformation and variations in composition (i.e., rigidity) that agrees well with observed changes in plate coupling and great earthquake history. These results emphasize the importance of considering not only one, but several factors related to both the incoming and overriding plates which collectively contribute to along-strike and downdip variations in megathrust slip behavior between segments. Our final study looks at the incoming Cocos plate just before it subducts offshore Mexico beneath the North American plate. Here we jointly inverted 2D OBS and long-offset MCS data acquired parallel to the trench to derive a 270 km-long, high-resolution Vp model of the entire oceanic crust and uppermost mantle. We provide the first constraints on the quantities of both free and structural (i.e., mineral-bound) water contained within the Cocos plate outboard of the Guerrero Gap and adjacent segments of the Mexican subduction zone. The Guerrero gap hosts large slow slip events that are commonly explained through the release of water through the dehydration of altered sediments and upper oceanic crust downdip. Strikingly, our results show that while the Cocos plate is hydrated offshore Mexico, nearly all of the water is contained within the upper oceanic crust. Moreover, we see that most of the water by weight is present as free fluids in the pores and that the upper oceanic crust is only moderately altered (0.3-1.3 wt.%) compared to global averages (> 1.5-3 wt.%). While the upper crust appears hydrated everywhere across our profile, we find that ∼30% more water is subducting outboard the Guerrero seismic gap where large seamounts contribute to a thicker extrusive layer and more alteration. This, along with evidence for the subduction of seamounts in Guerrero might help explain observations of weak shallow plate coupling and a greater propensity for slow slip at greater seismogenic depths compared to adjacent segments. These results provide important new constraints on how much pore and structural water is carried in the Cocos plate offshore Mexico. We propose that global estimates of incoming structural water content are not applicable everywhere, as is commonly assumed by petrologic and thermal models. Much less structural water may be needed within the upper oceanic crust just before subduction to explain the occurrence of slow-slip events downdip in some subduction zones.

Submarine slope failure releases sediments; it is an important mechanism that changes the Earth surface morphology and builds sedimentary records. I study the mechanics of submarine slope failure in sediment that dilates under shear (dilative slope failure). Dilation drops pore pressure and increases the strength of the deposit during slope failure. Dilation should be common in the clean sand and silty sand deposits on the continental shelf, making it an important mechanism in transferring sand and silt into deep sea. Flume experiments show there are two types of dilative slope failure: pure breaching and dual-mode slope failure. Pure breaching is a style of retrogressive subaqueous slope failure characterized by a relatively slow (mm/s) and steady retreat of a near vertical failure front. The retreating rate, or the erosion rate, of breaching is proportional to the coefficient of consolidation of the deposit due to an equilibrium between pore pressure drop from erosion and pore pressure dissipation. The equilibrium creates a steady state pore pressure that is less than hydrostatic and is able to keep the deposit stable during pure breaching. Dual-mode slope failure is a combination of breaching and episodic sliding; during sliding a triangular wedge of sediment falls and causes the failure front to step back at a speed much faster than that from the breaching period. The pore pressure fluctuates periodically in dual-mode slope failure. Pore pressure rises during breaching period, weakens the deposit and leads to sliding when the deposit is unstable. Sliding drops the pore pressure, stabilizes the deposit and resumes breaching. The frequency of sliding is proportional to the coefficient of consolidation of the deposit because dissipation of pore pressure causes sliding. Numerical model results show that more dilation or higher friction angle in the deposit leads to pure breaching while less dilation or lower friction angle leads to dual-mode slope failure. As a consequence, pure breaching is limited to thinner deposits and deposits have higher relative density. / text

Submarine topographic features of the channels, sounds, fiords, and bays can best be explained as the products of extensive glacial excavation of a pre-existing drainage system. Troughs, hanging troughs, strings of deeps or basins, terminal sills, linear rises and depressions, and oversteepened deltas are considered direct or indirect evidence of glacial scour. Following glaciation, a negative movement of the Sverdrup Basin was accompanied by flooding of the northern part of the Archipelago. Only the upper portions of former interfluvial areas remained above sea level. These topographic highs are the present-day islands of the Canadian Arctic Archipelago. Statistical analyses of beach, fluvial, deltaic, and offshore marine sediments reveal characteristics that may be unique to polar deserts and ice-covered seas. Textures of beach and fluvial sediments are a function of associated relief and parent material. The deltaic environment is defined as that portion of the sea floor extending from the mouth of a river to approximately 3,200 feet from shore. Deltaic sediments show a progressive decrease in grain size seaward. Size distribution is related to the settling velocities of particles of different diameters. Offshore sediments have uniform textural properties. They are a combination of silt and clay (settled from suspension), and a minor but significant portion of sand- to granule-sized sediment (ice-rafted). An increase in mean grain size on the crests of submarine topographic highs suggests that winnowing by currents is taking place over these features. Two large areas of the sea floor lack a cover of Recent sediment. Organic carbon constitutes 0.84 to 2.14% of the offshore sediments. A dual source, terrigenous and phytoplanktonic, may explain the relatively high percentage of organic carbon. There is a positive correlation between percent organic carbon and amount of clay in the samples. Results of semiquantitative clay-mineral analyses of source rock, fluvial, deltaic, and offshore marine sediments indicate that montmorillonite, kaolinite, and illite are the dominant clay minerals. In this northern region, there is no change in clay mineralogy during weathering and transport. It is suggested that this may be characteristic of weathering under polar desert conditions. The mineralogy of parent materials on the islands controls the clay mineral distribution in offshore areas. In Louise Fiord, well-crystallized kaolinite is differentially flocculated close to shore. A study of the roundness of quartz grains of sand, silt, and clay size reveals that the distribution of this property is bimodal. Coarse and medium sands are well rounded, fine sands through coarse silts are angular, and fine silt and clay-sized particles are well rounded. High roundness of grains in the medium to coarse sand grades is attributed to abrasion. Well rounded quartz in the silt-clay size range is considered to be a product of solution. / text

Call number: LD2668 .T4 1986 M63 / Master of Arts / History