Characterisation and Spatial Variability of the Magnetic and Electrical Resistivity Geophysical Properties of the Soils of Counties Kildare and Wicklow, Eastern Ireland.

The magnetic characteristics (low and high frequency mass specific magnetic susceptibility [χ], volume susceptibility [K] and K-T data) and electrical resistivity characteristics were obtained for the soils of Co. Kildare and Co. Wicklow, eastern Ireland (an area of 3688 km2). Spatially, the magnetic susceptibility shows a general pattern of values increasing from the northwest to the southeast over a two orders of magnitude range. A northeast trending broad zone of high resistivity with values 1-2 orders of magnitude higher than background corresponds spatially with the Wicklow Mountains. Analysis of a 17 variable GIS database shows that lf has a high positive correlation with soil iron content and weaker positive ones with copper, lithium, tin, lead, mercury and uranium and a weak negative correlation with nickel and zinc. There is a high positive correlation between lf and frequency dependent susceptibility (fd%). The correlation between lf and resistivity, between fd% and resistivity and between lf and topography is statistically virtually zero. The correlation between lf and geology and glacial sediments is very weak (0.08). There is however, a good correlation between lf and soils. A strong positive correlation exists between resistivity and topography and soils. Correlation between resistivity and geology and glacial sediments is close to zero. The magnetic properties of the soils in the study area depend greatly on the formation of superparamagnetic (SP) secondary ferrimagnetic minerals (almost exclusively magnetite). 80% of the study area soils are characterised by a high degree of secondary enrichment. For 89% of the acquired magnetic data, the greater the amount of SP grains, the higher the susceptibility. A well drained soil environment which undergoes fluctuating reducing and oxidising conditions facilitates the formation of SP grains and in this study was best achieved by Acid Deep Well Drained Mineral (ADWDM) and Acid Shallow Well Drained Mineral (ASWDM) soils (highest lf and fd% values). Poorly drained soils have a low lf and a low fd%. A small percentage of soils have a high lf but a low fd%. Such frequency independent soils tend to have an anthropogenic origin and are located around Avoca, a site of former industrial activity. Using averaged values at the soil type level, a strong positive correlation between magnetic susceptibility and resistivity values for the topmost soil layer was determined.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

National University of Ireland Maynooth

Year dc:date.issued

2018

Author dc:creator

• Alduraibi, Samar

Language dc:language

en