As low-lying areas, deltas are sensitive to changes associated with advance taking place on the land and in the ocean. The pattern of change in shoreline positions over time can be used as an indicator of changes in land and/or ocean environments. Land development and rapid population and economic growth can cause subsidence due to excess groundwater extraction, reduction of river sediment supply by dams, and floodplain engineering. Global eustatic and local relative sea-level changes can also significantly affect the coastline of the lowland area. The main purpose of this study is to investigate the causes of shoreline change in the Chao Phraya (CPY) River delta in Thailand, which is a coastal region dominated by intertidal mudflats. This study focuses on river sediment supply, relative sea level change, and mangrove deforestation. Long-term historical data coupled with field observation were used to determine how these factors are related to shoreline retreat of the delta coastline. Shoreline change evaluation for the Upper Gulf of Thailand, including the Chao Phraya estuary between 1954 and 2013, are based on a series of aerial photographs and satellite imagery. This data set represents historical shoreline positions with time intervals ranging from 2 years to 24 years. The shoreline data were converted into vectorized ArcGIS shapefiles and analyzed using the USGS Digital Shoreline Analysis System ArcGIS extension. River survey data collected during the period 2011-2013 were used for studying the characteristics of river flow and sediment transport in the river system. During the period 2011-2013, the flow and sediment characteristics of rivers were measured 9 times at 8 stations in the Ping, Wang, Yom, Nan, and Chao Phraya rivers. The data cover wet season and dry season flow conditions, including the extreme flood event during 2011. Additionally, sediment deposition rates at the Chao Phraya River mouth were estimated from two sediment cores taken from the Chao Phraya River mouth using 210Pb radiometric dating. The results of this study indicate that relative sea-level rise due to the extremely high rate of land subsidence is the major cause of rapid shoreline change in the CPY Delta, and is responsible for 56 and 63 percent of shoreline retreat in the western and eastern portions of the Chao Phraya Delta, respectively. Unlike other major deltas in the southeast and east Asia, the severe shoreline recession during the period 1954-2013 is not strongly related to sediment supply reduction associated with large dam impoundments. Conversely, sediment deposition rates at the CPY Delta tended to increase after 1994 (30 and 22 years after construction of the Bhumibol and Sirikit Dams, respectively). However, the observed average rate of sediment deposition (8-10 mm/year) is less than the average rate of relative sea-level rise (17 mm/year), and the sediment supply from the CPY is not sufficient to balance land loss due to the rise of sea-level during the past six decades. For land-use changes, most of the vegetation areas, especially mangrove forest bounding along the edge of the shoreline, have been converted into aquacultural farmland by 1994. Results from mangrove area analysis over the period 1954-2013 reveal that the reduction of shoreline retreat rates in the eastern CPY was not directly associated with an increase in mangrove areas undergoing reforestation, and mangrove reforestation could not be cited as a shoreline builder or effective measure for coastal protection for coastlines that are rapidly retreating due to land subsidence. However, conversion of mangrove areas into aquaculture farmland can magnify shoreline retreat caused by relative sea-level rise. Results of this study may provide a useful analog for other coastal regimes of the Earth that may experience the effect of the predicted 1-2 meter rise over the next century associated with global warming. / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2016. / June 7, 2016. / muddy coast, relative sea-level change, Sedimentation, sediment supply, sediment transport, shoreline change / Includes bibliographical references. / Stephen A. Kish, Professor Co-Directing Dissertation; Joseph F. Donoghue, Professor Co-Directing Dissertation; James B. Elsner, University Representative; William C. Burnett, Committee Member; William C. Parker, Committee Member.

The Silurian was a period characterized by rapidly fluctuating climate, multiple biotic turnover events, and eustatic sea-level variability. The Homerian Mulde biotic event (late Wenlock), ~428Ma, lies between the Sheinwoodian (early Wenlock) Ireviken and late Ludlow (mid- Ludfordian) Lau extinction events. It is characterized by a near complete extinction (95% loss) in graptolites, a severe drop (~80%) in diversity in conodonts, and a 50% loss in acritarchs (organic-walled phytoplankton groups), collectively known as the Wenlock ‘Big Crisis’. Previous studies have aligned the various Big Crisis extinctions to a double peaked carbon isotope excursion (CIE), known as the Mulde CIE, and inferred this to be a major change in the global carbon cycle. However, causal mechanisms that link the Mulde CIE to the ‘Big Crisis’ remain poorly constrained. In this thesis, two carbonate-bearing sequences connected to separate paleobasins, the shallow shelf carbonate sequence at McCrory Lane, TN and upper slope mixed siliclastic-marl sequence at Coal Canyon, Simpson Park Range, NV have been analyzed for multiproxy investigations. I present new δ13C, δ34S, I/(Ca+Mg), pyrite framboid, and carbonate microfacies data from these two successions spanning the Mulde CIE and Big Crisis interval. I document for the first time a positive ~10‰ shift in δ34SCAS during the Big Crisis extinction interval and first peak of the Mulde CIE. This suggests an expansion of reducing conditions globally; triggering enhanced organic matter and pyrite burial during a eustatic sea-level rise. At McCrory Lane, TN, local pyrite sulfur, I/(Ca+Mg), and microfacies fauna analysis support enhanced pyrite burial, and indicate the temporary contraction of reducing conditions during the Big Crisis survival and recovery intervals and protracted eustatic high stand. During the recovery interval of the Big Crisis the second Mulde CIE peak occurs and new δ34SCAS data suggest a second smaller expansion of reducing conditions in the late Wenlock oceans occurred. Interestingly, there is no documented no biotic turnover that occurs in concert with the second Mulde CIE peak suggesting a smaller and limited nature of this second expansion of marine reducing conditions. Statistical thin section analyses of fauna grain composition and niche replacement and near ubiquitous presence of pyrite framboids further support the notion that global oxygen content and bioavailability is still playing a major role in the evolution of biosphere and oceanic redox conditions through the mid-Paleozoic. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / 2019 / August 28, 2019. / Extinction, Late Wenlock, Mulde, Paleozoic, Redox, Silurian / Includes bibliographical references. / Seth A. Young, Professor Directing Thesis; Jeremy D. Owens, Committee Member; Yang Wang, Committee Member.

published_or_final_version / Applied Geosciences / Master / Master of Science

Graduation date: 1968

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 87-91).

Thesis (Ph. D. Geology)--University of Southern California. / Includes bibliographical references (leaves 236-242).

Thesis (Ph. D. in Oceanography)--A. & M. College of Texas. / Ozalid process.

Thesis (M.S. in Geophysics)--A. & M. College of Texas.

Thesis (Ph.D.) - University of St Andrews, January 2009.

This project aimed to constrain the interpretation uncertainties associated with reflection seismic data of deep-water slope deposits.  The basic premise of the project is that seismic data is affected by small-scale architectural elements and even conventional low-frequency data may contain clues of the sub-seismic geometries.  These can be decoded by understanding the interaction between internal elements and the seismic wavelet.  A series of outcrop-derived forward seismic models was created, representing different types of outcrop based slope deposits.  The seismic interpretation of the forward models was based on amplitude analysis supplemented by instantaneous attributes and spectral decomposition. In order to create realistic synthetic seismograms, input models included geometries whose thickness was as low as 1% of the resolution limit.  By revealing the influence of small-scale structures on synthetic seismic data at the high end of the spectrum (70Hz to 100Hz), the knowledge of tuning effects and the interaction between interfering reflections at lower frequencies (i.e. 20, 40 and 60Hz) could potentially be significantly improved. The gained experience was then applied to real seismic data.  It was proven that small-scale geometries have an additional, highly significant effect on the composite reflection. Because of the inherent non-uniqueness in seismic reflection, the specific seismic forward models of particular outcrop analogues can only be used as guides to the seismic interpretation of the particular architectural elements of a subsurface deposit and not as definite models against which one can definitely pattern match real and modelled seismic data.  as burial depth increases, so does the non-uniqueness of the seismic interpretation of seismic data from deposits whose internal geometries are around/below the tuning thickness.