Glaciotectonic Processes Associated with the Central Alpine Fault: A Gravity Study of the Central West Coast, South Island, New Zealand

<p>The rugged topographic relief of the central West Coast reflects ongoing interplay between active tectonic and climatic processes. Major geomorphological features have formed in response to convergence between the Pacific and Australian continental plates, and the principal locus of this collision is the transpressive Alpine Fault. This thesis describes a gravity study of glaciotectonic structures in the footwall of the central Alpine Fault and the processes responsible for their formation. During this study 361 new gravity observations were collected in the Wanganui, Whataroa, Waiho, and Fox river flood plains on the western (footwall) side of the Alpine Fault. When combined with existing gravity observations, the available database comprises 932 measurements over the four catchments. These gravity data are used to produce detailed gravity maps and 2-3/4D gravity models of the subsurface structure below the flood plains. Models reveal extensive glacial erosion focused within the flood plains, with individual glacial channels reaching depths of ~ 800 m. Based on fault-perpendicular models, it is proposed that the South Westland Fault is a transition between a thrust-driven monocline structure in South Westland and the steeply dipping Hohonu reverse fault in North Westland. Using gravity data, dextral off sets on the Alpine Fault since the Last Glacial Maximum have been determined by examining the structure and geomorphology of deeply incised glacial erosional channels. By studying how the lower reaches of the Wanganui, Whataroa, and Fox rivers have been translated with respect to their channels on the eastern (hanging wall) side of the Alpine Fault, horizontal fault displacements have been determined in three of the four catchments. Fault offsets of 383 ± 388 m, 372 ± 88 m, and 450 ± 99 m are estimated for the Wanganui, Whataroa, and Fox River valleys respectively. A range of possible channel formation ages are used to estimate dextral strike-slip movement rates, with the preferred formation age of 19 ± 1 ka yielding rates of 20.2 ± 24.0 mm/yr, 19.6 ± 6.0 mm/yr and 23.7 ± 8.5 mm/yr for the Wanganui, Whataroa, and Fox river valleys respectively.</p>

Glaciotectonic Processes Associated with the Central Alpine Fault: A Gravity Study of the Central West Coast, South Island, New Zealand

<p>The rugged topographic relief of the central West Coast reflects ongoing interplay between active tectonic and climatic processes. Major geomorphological features have formed in response to convergence between the Pacific and Australian continental plates, and the principal locus of this collision is the transpressive Alpine Fault. This thesis describes a gravity study of glaciotectonic structures in the footwall of the central Alpine Fault and the processes responsible for their formation. During this study 361 new gravity observations were collected in the Wanganui, Whataroa, Waiho, and Fox river flood plains on the western (footwall) side of the Alpine Fault. When combined with existing gravity observations, the available database comprises 932 measurements over the four catchments. These gravity data are used to produce detailed gravity maps and 2-3/4D gravity models of the subsurface structure below the flood plains. Models reveal extensive glacial erosion focused within the flood plains, with individual glacial channels reaching depths of ~ 800 m. Based on fault-perpendicular models, it is proposed that the South Westland Fault is a transition between a thrust-driven monocline structure in South Westland and the steeply dipping Hohonu reverse fault in North Westland. Using gravity data, dextral off sets on the Alpine Fault since the Last Glacial Maximum have been determined by examining the structure and geomorphology of deeply incised glacial erosional channels. By studying how the lower reaches of the Wanganui, Whataroa, and Fox rivers have been translated with respect to their channels on the eastern (hanging wall) side of the Alpine Fault, horizontal fault displacements have been determined in three of the four catchments. Fault offsets of 383 ± 388 m, 372 ± 88 m, and 450 ± 99 m are estimated for the Wanganui, Whataroa, and Fox River valleys respectively. A range of possible channel formation ages are used to estimate dextral strike-slip movement rates, with the preferred formation age of 19 ± 1 ka yielding rates of 20.2 ± 24.0 mm/yr, 19.6 ± 6.0 mm/yr and 23.7 ± 8.5 mm/yr for the Wanganui, Whataroa, and Fox river valleys respectively.</p>

Trace element content in alluvial soils landscape of the flood plains of the Iput river

The results of research on the content and distribution of trace elements in alluvial soils of various elements of the floodplain landscape, and their relationship with fertility indicators are presented. It has been found that the maximum concentrations of most trace elements (Ni, Zn, Mn, Cr, Co, Mo, As) are characteristic of the alluvial overhanging-marsh heavy-coal pristine subsystem of the floodplain landscape. In the riverine and perish subsystems of the floodplain landscape in individual layers of the corresponding soils, an excess of clark was found: in the alluvial sour acid layered primitive shortened sandy loam Cu by 1.5; Zn in 1.1; Cd 9.2 times, in alluvial chilli-marsh heavy-coal Cu 1.05; Zn in 1.4; Mn in 1.01; Cr in 1,2; Cd 3.2 times. For the riverine and perch subsystems, the excess of Cu, Mn and Cr was observed in the soil layer 0-5 cm, the remaining exceedances are characteristic of deeper layers. Decreasing rows of trace elements in alluvial soils have a similar structure. The microelements in question, in the soils of the floodplain landscape of the Iput River, in terms of clark concentration, belong to the group of dispersing. There is no significant correlation between micronutrient content and fertility of the alluvial soils under consideration.

Evaluation of geohazards in the Cape Girardeau area using LiDAR and GIS, Southeast Missouri, USA

The New Madrid Seismic Zone (NMSZ) has historically recorded some of the largest intensity earthquakes in North America, including significant earth movements that resulted in about 2000 felt earthquakes during 1811–1812. The region continues to experience mass wasting due to earth movements. The aim of this study is to understand the influence of geologic variables on mass wasting processes in the greater Cape Girardeau area, which forms the commercial center of Missouri's fertile "Bootheel" region. Earth movement susceptibility was evaluated in Cape Girardeau and Bollinger counties and portions of Stoddard and Scott counties by mapping potential landslide features on topographic maps, field verification of such features, and geospatial analysis of recent LiDAR imagery. In order to evaluate the changes in surface morphology, slope inclination, hillshade aspect, hydrology, lithology, faults, precipitation, seismicity, sinkholes, and geohydrology were considered. Geographically weighted analysis of the geomorphologic variables identified zones of relative risk. In addition, data were evaluated for oil and gas pipelines, bridges, utilities, and open pit mines associated with mass wasting on public and economic infrastructure. The results suggest that anthropogenic changes commonly associated with urban development impact land use, runoff, infiltration, and slope failures, while sustained precipitation and seismic ground shaking tend to trigger landslides. The scale of mass wasting in the study area was robust, varying from as small as one-half hectare to as much as 67 km2. The vulnerability of the population in susceptible areas tends to increase at the lower elevations and on alluvial flood plains. Thus, hazard susceptibility evaluation can be useful in both community planning as well as emergency preparedness.

Application of 3D Laser Image Scanning Technology and Cellular Automata Model in the Prediction of the Dynamic Process of Rill Erosion

Black soil areas are strongly affected by rill erosion due to the geomorphic characteristics of flood plains and heavy rainfall. To study the problem of rill erosion in black soil areas and achieve ecological restoration, based on the method of artificially simulated rainfall, the effects of rainfall intensity and slope on the characteristics of flow and sand production on the slope surface of black soil areas were studied, and the erosion pattern of the slope surface after rainfall was monitored by a 3D laser scanner to analyze the erosion of the soil on the slope surface. The slope erosion model was constructed on the basis of the cellular automata (CA) method, and the results of the model’s operation were compared with actual rainfall measurement results to deepen research on the slope erosion mechanism in black soil areas. By analyzing the slope erosion pattern after rainfall, it was found that the surface area and erosion volume of serious slope erosion areas increased with increases in slope gradient. Based on the physical model test results combined with the CA model to simulate flow and sand production on bare slopes under different rainfall intensities, comparison showed that the CA model can accurately simulate flow and sand production on a slope where the Ens coefficient of the flow production rate is between 0.70 and 0.97, thus theoretically verifying the reliability of the model, and on this basis, the erosion pattern of the slope after rainfall was predicted to explore the evolution and development law of erosion.