Physical Sciences and Mathematics Commons^™

Tracing Sediment Erosion In The Yangtze River Subaqueous Delta Using Magnetic Methods, Can Ge, Weiguo Zhang, Chenyin Dong, Feng Wang, Huan Feng, Jianguo Qu, Lizhong Yu

Department of Earth and Environmental Studies Faculty Scholarship and Creative Works

We assessed the usefulness of magnetic properties for tracing sediment erosion in a deltaic environment. Surface and core sediments from the Yangtze River subaqueous delta were subjected to magnetic, granulometric, geochemical, and radionuclide analyses. Based on magnetic properties and particle size, the surface sediments can be divided into three groups. Groups I and II have a similar particle size distribution and geochemical composition, but the former has higher values of magnetic susceptibility (χ) and saturation isothermal remanent magnetization (SIRM). We interpret Group I as consisting of modern sediments, while Group II represents previously buried sediments that have undergone significant reductive …

East African Weathering Dynamics Controlled By Vegetation-Climate Feedbacks, Sarah J. Ivory, Michael M. Mcglue, Geoffrey S. Ellis, Adam Boehlke, Anne-Marie Lézine, Annie Vincens, Andrew S. Cohen

Earth and Environmental Sciences Faculty Publications

Tropical weathering has important linkages to global biogeochemistry and landscape evolution in the East African rift. We disentangle the influences of climate and terrestrial vegetation on chemical weathering intensity and erosion at Lake Malawi using a long sediment record. Fossil pollen, microcharcoal, particle size, and mineralogy data affirm that the detrital clays accumulating in deep water within the lake are controlled by feedbacks between climate and hinterland forest composition. Particle-size patterns are also best explained by vegetation, through feedbacks with lake levels, wildfires, and erosion. We develop a new source-to-sink framework that links lacustrine sedimentation to hinterland vegetation in tropical …

Geophysical Investigations Of Pyroclastic Density Current Processes And Deposit Properties At Mount St. Helens, Washington (Usa), Andrew Cleveland Gase

Boise State University Theses and Dissertations

Geophysical imaging has the potential to significantly improve investigations in pyroclastic deposits, either as a means of in situ property estimation or to provide geologic context where exposures do not exist. I perform two geophysical studies set in the deposits of the 1980 eruption at Mount St. Helens, Washington (USA); the aim is to investigate the physical properties and geology of pyroclastic deposits.

Joint petrophysical modeling reveals the dependence of seismic and electromagnetic velocities in pyroclastic deposits on two-phase porosity (vesicularity and inter- granular porosity) and water-saturation. Seismic first arrival travel-time tomography, multi-channel analysis of surface waves, and multi-offset GPR …

Using Survey Data And Hec-Ras Modeling To Assess A Riffle-Remediation Structure On The Big River, Bonne Terre, Missouri, Nichole Renee Weedman

MSU Graduate Theses

Sediment transport and deposition in river channels can vary for many reasons including flooding, dredging, channel velocity, and grain size. On the Big River, the Army Corps of Engineers constructed a riffle ramp structure to trap and remediate lead-contaminated sediments. The performance of the structure is unknown. The goal of this study is to evaluate the storage capabilities of the riffle structure. To do this, survey data was collected to analyze sediment storage and entered into the HEC-RAS 5.0 to model the hydraulics of the channel before and after the riffle installation. Samples were collected to assess the level of …

Evidence Of Erosional Self-Channelization Of Pyroclastic Density Currents Revealed By Ground-Penetrating Radar Imaging At Mount St. Helens, Washington (Usa), Andrew C. Gase, Brittany D. Brand, John H. Bradford

Geosciences Faculty Publications and Presentations

The causes and effects of erosion are among the least understood aspects of pyroclastic density current (PDC) dynamics. Evidence is especially limited for erosional self-channelization, a process whereby PDCs erode a channel that confines the body of the eroding flow or subsequent flows. We use ground-penetrating radar imaging to trace a large PDC scour and fill from outcrop to its point of inception and discover a second, larger PDC scour and fill. The scours are among the largest PDC erosional features on record, at >200 m wide and at least 500 m long; estimated eroded volumes are on the order …

Effects Of Habitat Restoration On Soil Retention On Santa Rosa Island, Michael Perez, Kathryn Mceachern, Ken Niessen

STAR Program Research Presentations

Ranching began on Santa Rosa Island in the 1840’s, consequently introducing nonnative megafauna that put novel selective grazing pressures on endemic plant species. Their movement patterns also altered substrate integrity as the land became denuded of any stabilizing vegetation. Dense groves of island oak (Q. tomentella) are known to aid in sediment deposition and retention. The groves also function to collect water during periods of intense fog common to the island. This experiment sought to determine whether sediment is being lost or deposited on a ridge in the middle of the island containing a grove of Q. tomentella …

Weathering And Erosion Of Fractured Bedrock Systems, Marina I. Lebedeva, Susan L. Brantley

United States Geological Survey: Staff Publications

We explore the contribution of fractures (joints) in controlling the rate of weathering advance for a low-porosity rock by using methods of homogenization to create averaged weathering equations. The rate of advance of the weathering front can be expressed as the same rate observed in non-fractured media (or in an individual block) divided by the volume fraction of nonfractured blocks in the fractured parent material. In the model, the parent has fractures that are filled with a more porous material that contains only inert or completely weathered material. The low-porosity rock weathers by reaction-transport processes. As observed in field systems, …

Quaternary River Erosion, Provenance, And Climate Variability In The Nw Himalaya And Vietnam, Tara Nicole Jonell

LSU Doctoral Dissertations

The influence of Quaternary climate variation on sediment generation, storage, and transport in two mountainous Asian river basin was examined in the largest tributary to the upper Indus River in the Himalayan rain shadow, the Zanskar River basin (~15,000 km²), and the smaller, subtropical Song Gianh basin (<3,500 km²) of central Vietnam. Spatial patterns of erosion in the Zanskar River Basin were established to quantify the dominant controls on Quaternary sedimentation in the Himalayan rain shadow on the edge of the Tibetan Plateau. Glacial erosion and precipitation along the High Himalaya together dominate sediment production and transport …