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Drilling during ODP Leg 133 offshore Cairns, northeast Queensland, provided a unique opportunity to document carbonate production and facies development on a mixed carbonate-siliciclastic margin. Recent studies have shown that variations in the sedimentology of Late Quaternary and Pliocene periplatform sediments (Schlager and James, 1978), deposited on continental slopes and in deep basins surrounding shallow carbonate platforms, are linked to changes in sea-level (Droxler et al., 1993; Schlager et al., 1994). However, considerable debate has arisen to the timing of the production and export of shallow water carbonate material, with respect to sea level change. Two main hypotheses have been proposed to explain the response of shallow water carbonate platforms to variation in Late Quaternary sea level: I) 'highstand shedding' and 2) 'lowstand shedding'. Proponents of highstand shedding argue that depositional systems shed most of its carbonate sediments onto the platform slopes during highstands of sea level. Conversely, during lowstands of sea level bank top production and export of carbonate material is restricted, and platform slopes are largely starved of bank derived carbonate (Schlager, 1992; Schlager et al., 1994 ). Supporters of lowstand shedding maintain that significant carbonate production and export of shallow water carbonate material occurs during lowstands (and highstands) of sea level (Bosellini, 1989; Goldhammer and Harris. 1989; Grammer and Ginsburg. 1992). In order to investigate the response of mixed carbonate-siliciclastic systems to variations in Late Quaternary sea level and climate change, core material was collected from Ocean Drilling Program (ODP) Leg 133, Sites 819 and 823 (northeast Australian margin). These two sites form part of an eastward extending transect of drill localities, offshore Cairns, Queensland, from the outershelf/upper-slope of the Great Barrier Reef (Sites 821 /820/819), into the Queensland Trough (Site 823) and ultimately onto the flanks of the Queensland Plateau (Sites 824 and 811 /825). Pelagic to hemipelagic sediments collected from these two sites were examined for the downcore distribution of grain size, magnetic susceptibility, carbonate content, variations in carbonate mineralogy (XRD), and major and minor element (XRF) geochemistry. Using high resolution foraminiferal stable oxygen isotopes, coupled with biostratigraphic and magnetostratigraphic datums, well defined age models for Hole 819A and Hole 823A have been constructed, although it was not an easy task as hiatuses occur in these records. Age models for the sequences recovered from Hole 819A and Hole 823A have been further refined using correlation with existing isotopic stratigraphies in the Pacific Ocean (ODP Hole 677, Raymo et al., 1989), and comparison with high resolution sedimentologic records from other ODP Leg 133 marine sequences. Analysis of the mineralogical, sedimentological and geochemical records from Holes 819A and 823A indicate that, over the last 1.1 million years, highstands of sea level (and during the early regression) are characterized by increased shallow water carbonate production, and deposition on the upper slope. This pattern of carbonate deposition is consistent with the highstand carbonate shedding scenario outlined by Schlager et al. (1992), and Schlager et al. ( 1994 ). Lowstands of sea level (and particularly the early transgression) are characterized by increased deposition of non-carbonate (mainly terrigenous) material and/or were not diluted by shallow water carbonate platform material. During the lowstands of sea level the shallow water carbonate factories were switched off. Therefore, the sediments deposited during lowstands of sea level tend to record the greater influence of pelagic driven carbonate. Although the above mentioned scenario of highstand shedding applies to the entire record of 1.1 million years. mineralogical and geochemical data indicate that shallow burial diagenesis, and dissolution of solution sensitive carbonate, occurred in the lower part of the records. The diagenesis and dissolution, however, have played only a minor role in determining the composition of the Queensland margin sediments. Variations in the terrigenous input (Cr/Al and Ti/AI ratios) in Queensland margin sediments indicate that interglacial periods were generally wetter than corresponding glacials or lowstands of sea level, during the Late Quaternary.

Accelerating sea-level rise (SLR) poses an imminent threat to salt marshes, which sit within meters of mean sea level. In order to assess marsh vulnerability to SLR, we must first understand the fundamental processes governing marsh response to SLR. The objective of this dissertation work is to examine how marsh sedimentation and erosion affect the morphological development of marshes as sea level rises, over a broad range of spatial and temporal scales. At the smallest scale, the effects of bioturbation by Sesarma reticulatum crabs on sediment erodibility are examined using a laboratory flume. Measurements of surface elevation, erosion, and turbidity show that S. reticulatum bioturbation repackages formerly compacted sediment and deposits it above the surface, decreasing the threshold velocity for erosion and increasing eroded volume. S. reticulatum-induced sediment erosion can have broader impacts on creek development and marsh morphology. S. reticulatum has facilitated drainage network expansion in salt marshes at Sapelo Island, GA and Cape Romain, SC in response to local SLR. Burrowing by this crab directly adjacent to tidal creeks at these locations leads to rapid headward growth. The effects of site-specific conditions on creek expansion are examined through comparison of sediment properties, surface elevations, and historical rates of creek growth at each site. Results suggest that while similar processes are occurring at both locations, the higher elevation of the marsh in GA leads to greater shear strength and a larger volume of material to be eroded by creeks. These combined effects have led to slower creek growth compared to SC. At the largest spatial scale, and projecting forward over a 100-year period, a model for marsh response to SLR at the Great Marsh in Massachusetts is developed. This model takes into account limitations imposed by both low sediment availability and steep topography in the surrounding uplands. Results indicate that while the marsh may persist for several decades, it undergoes a dramatic shift in ecology and hydrology. As the rate of SLR accelerates, marsh loss increases due to the lack of sediment available for accretion and the physical barriers to migration presented by surrounding topography.

Deteriorating climate in the period leading up to the Last Glacial Maximum (LGM) 20,000 years ago caused global sea levels to fall to a lowstand of 125m below modern levels. This resulted in the recession of the Sicilian palaeoshoreline by up to 150km and the emergence of vast tracts of coastal lowland. Following climate amelioration and deglaciation, rising sea levels inundated these formerly exposed areas. The earliest indication of a modern human presence on Sicily comes from Fontana Nuova, in the southeast of the island. The timing of this occupation, on the basis of cross-dating of Aurignacian lithic typology, is about 37,000 BP – a time when sea levels around the Sicilian coastline were some 40-80m lower than at present. The oldest scientifically-dated human remains come from Addaura Caprara, dated to 15,643–15,177 cal BP. Some archaeologists interpret the evidence as suggesting a brief, solitary visit to the island at around 37,000 BP followed by a gap of some 20,000 years before the establishment of a permanent presence during the 16th millennium BP. Others dismiss the veracity of the evidence from Fontana Nuova and hold that Sicily was never settled until some considerable time after the LGM. Until late 20th-century studies demonstrated the attractions of coastal ecotones, absence of evidence was sometimes interpreted as a rejection of coastal landscapes by Upper Palaeolithic and Mesolithic hunter-gatherers. My thesis will argue that Sicily was not uninhabited for 20,000 years or more but that any evidence for human coastal presence throughout prehistory is potentially submerged. I consider the attractions of coastlands for early modern humans. I discuss the physical background to glaciation and deglaciation resulting in sea-level change. By combining data on absolute sea-level change with evidence for terrestrial displacement resulting from tectonic forces, I have determined relative sea-level change affecting the coastlines of Sicily from 37,000 BP until the Iron Age (ending c750 BC). The results have been combined with digital bathymetric data within an ESRI ArcMap GIS program to produce a series of maps at archaeologically-significant dates. The very areas that are now recognised as being attractive to modern humans will be shown to be submerged today. With reference to modern scientific techniques and their application by specialists in a variety of locations, I shall demonstrate that the successful recovery of submerged archaeological evidence is achievable. I shall also consider a number of phenomena revealed by my field observations that have conspired to conceal or destroy the coastal archaeological record, the absence of such evidence being used illegitimately to support claims for an unpopulated island. These phenomena include natural catastrophes such as earthquakes and related tsunamis, volcanic activity and landslides. Additionally, coastline modification resulting from river estuary migration, and anthropogenic impacts will be considered.

Post-seismic deformation and glacial isostatic adjustment are two processes by which the Earth deforms viscoelastically. In both cases, the details of the deformation depend on the rheological structure of the Earth as well as the forcing, which is the earthquake and further movement on the fault in the case of post-seismic deformation, and the change in load on the surface of the Earth due to the redistribution of water and ice mass in the case of glacial isostatic adjustment. It is therefore possible to learn about the Earth's rheological structure and the processes' respective forcings from measurements of the deformation. In order to use measurements in this way, it is first necessary to have a method of forward modelling the processes, that is, calculating the deformation due to a given forcing and in an earth model with a given structure. Given this, a way of calculating derivatives of measurements of the deformation with respect to the parameters of interest is then desirable. In this dissertation, the adjoint method is used. This, for the first time, enables efficient calculation of continuous derivatives, which have many potential applications. Firstly, they can be used within a gradient-based optimisation method to find a model which minimises some data misfit function. The derivatives can also be used to quantify the uncertainty in such a model and hence to provide understanding of which parts of the model are well constrained. Finally, they enable construction of measurements which provide sensitivity to a particular part of the model space. In this dissertation, new methods for forward modelling both post-seismic deformation and glacial isostatic adjustment are presented. The adjoint method is also applied to both problems. Numerical examples are presented in spherically symmetric earth models and, in the case of glacial isostatic adjustment, models with laterally varying rheological structure. Such examples are used to illustrate the potential applications of the developments made within this dissertation.

acase@tulane.edu / Relative Sea-Level (RSL) change influences surface processes and stratigraphic architecture of deltaic systems and has been studied extensively for decades. However, we still lack a quantitative framework to define what constitutes a small vs. large or short vs. long RSL cycle. We explore these questions with a suite of physical experiments that shared identical forcing conditions with the exception of sea-level. We utilize two non-dimensional numbers that characterize the magnitude and period of RSL cycles. Magnitude is defined with respect to the maximum autogenic channel depth, while the periodicity is defined with respect to the time required to deposit one channel depth of sediment, on average, everywhere in the basin. The experiments include: 1) a control experiment lacking RSL cycles, used to define autogenic scales, 2) a low magnitude, long period (LMLP) stage, and 3) a high magnitude, short period (HMSP) stage. We observe clear differences in the response of deltas to the forcing in each experiment. The RSL cycles in the HMSP stage induce allogenic surface processes and stratigraphic products with scales that exceed the stochastic variability found in the control stage. These include the generation of rough shorelines and large temporal gaps in the stratigraphy. In contrast, the imprint of LMLP cycles on surface processes and stratigraphy is found in properties that define the mean state of a system. These include the mean shoreline location and extraction of sediment inbound of the mean shoreline. This work demonstrates the effectiveness of defining RSL cycle magnitude and period through autogenic scales and provides insights for generation of forward stratigraphic models influenced by RSL change. / 1 / Lizhu Yu

Climate change is one of the factors that pose new challenges to the sustainability of the capture fishery and aquaculture sector around the world. As concerns over the impacts of climate change on ecosystems have been increasing over the last few decades, this study investigated how anticipated changes in climatic conditions would affect Manila Clams and Pacific Oysters bottom culture in British Columbia (BC) and assessed the extent to which the environmental databases that have been assembled by various agencies and institutions in BC could support this type of analysis. This study examined changes in sea surface salinity (SSS) and sea surface temperature (SST) developed scenarios of these changes and analyzed the trends based on projections of SST and SSS of open ocean adjacent waters of BC’s coast. In addition, this study quantified beach exposure/inundation as result of sea level rise (SLR). Moreover, this study identified areas along the Strait of Georgia (SoG) that have capability for shellfish culture and defined capability indices for Manila Clams and Pacific Oysters bottom culture based on the physical conditions that characterize existing commercial aquaculture operations. Finally, this study assessed how bottom shellfish culture sites’ capability in the SoG will be affected by changes in SST, SSS and beach exposure/inundation associated with SLR. Results of the analysis indicate that the annual average projections of SST of open ocean adjacent waters of BC’s coast will increase approximately 10C between 2012 and 2050 at a rate of 0.1110C/year, and between 2051 and 2100 the SST will increase approximately 20C at a rate of 0.0330C/year. The annual average projections of SSS of open ocean adjacent waters of BC’s coast will decrease approximately 0.2 ppt between 2012 and 2050 at a rate of 0.0055 ppt/year. Furthermore, projections from 2051 to 2100 indicate that SST will decrease approximately 0.5 ppt at a rate of 0.0088 ppt/year. In addition to the performed analysis, this study selected and simulated SLR on three sites (Buckley Bay and Fanny Bay in Baynes Sound, and Henry Bay on Texada Island). The results indicate that an increase of 1.2 m in sea level will inundate 121 ha of Buckley Bay and Fanny Bay combined and 37 ha of Henry Bay. An increase of 2 m in sea level will inundate 195.2 ha of Buckley Bay and Fanny Bay, and, 51.4 ha of Henry Bay. Capability indices’ classes defined and mapped in this study for Manila Clams bottom culture are: Not advisable, Poor, Medium and Good; and Not Advisable, Medium and Good for Pacific Oysters. This study concluded that the existing datasets provided by various agencies and institutions are accessible, and can be used to investigate the impacts of climate change on coastal aquaculture in BC, although there is lack of some datasets as well as there is a need to improve some available datasets. This study also demonstrated and concluded that site capabilities to support Manila Clams and Pacific Oysters culture in the SoG will not be affected by the expected changes of SST, SSS. Changes in SST and SSS associated with SLR will not adversely affect shellfish bottom culture in the SoG. In contrary, SLR will have a negative impact on shellfish bottom culture. / Graduate

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No description available.