Palaeosurfaces and palaeovalleys are landforms under destruction in the present climate and/or tectonic regime, and thus mainly reflect processes not active today. Uplifted palaeosurfaces exist along the formerly glaciated passive continental margins around the North Atlantic. Large-scale landform development has recently become a matter of interest also for geologists and geophysicists as the result of an increasing awareness that a thorough knowledge of uplift, erosion, deposition and development of landforms along continental margins can only be accomplished by combined studies using independent data from different scientific disciplines. The present study focuses on one of these above data sets; the landform record. Two uplifted areas, southern Norway and central West Greenland, were selected for landform analysis of high resolution digital elevation models, aerial photographs, relation between landforms in basement and cover rocks, offshore seismic lines and X-ray diffraction of clay minerals in saprolites. In southern Norway, analysis of slope angles within the range of pediment slopes was combined with analysis of main valley incision. This resulted in the identification of three main planation surfaces in a stepped sequence formed along the main valleys as a consequence of tectonic uplift events, maybe in the Palaeogene, (in total >1000 m). Two phases of late uplift (~900 m), probably in the Neogene, triggered incision of deep fluvial valleys, later reshaped by glacial erosion (up to 300 m). In central West Greenland palaeosurfaces were analysed in relation to cover rock of different age. An exhumed etch surface, characterized by a typical hilly relief, occurs on Disko and south of Disko Bugt, and are by the presence of cover rocks shown to be sub-Palaeocene in origin. To the north, a post-Eocene erosion surface on Nuussuaq, cuts across basement and basalt and was probably formed close to sea level. Uplift in two phases elevated this surface up to 2000 m above present sea level and broke it in differently tilted tectonic blocks. South of Disko Bugt, a planation surface, of probably the same age as the one on Nuussuaq, cuts the tilted etch surface, and also cuts across different bedrock types. The planation surface rises towards the south and splits in two surfaces, separated in altitude up to 300 m, within two highly elevated areas. The separation into two surfaces indicate two uplift events: A first minor event of a few hundred metres in the uplift centres resulted in incision of the lower planation surface. This event was later followed by a major uplift event amounting to >1000 m. Correlation with the offshore sedimentary record suggests that both uplift events occurred in the Neogene. The erosion pattern calculated from one reconstructed palaeosurface to present topography shows large spatial variations. This is interpreted as an effect of differential bedrock resistance and local variations of glacial erosion (400–1300 m in low areas). The results presented in this thesis demonstrate the usefulness of palaeosurfaces and palaeovalleys as tools for deciphering magnitude of uplift events, establishing relative event chronologies and for calculation of erosion. Moreover integrated studies of palaeolandforms, offshore geology and thermal chronologies, are shown to be invaluable when used to solve the spatial and temporal patterns of uplift, erosion and deposition.

The quantification and prediction of soil properties is fundamental to further understanding the Critical Zone (CZ). In this study we aim to quantify and predict soil properties within a forested catchment, Marshall Gulch, AZ. Input layers of soil depth (modeled), slope, Saga wetness index, remotely sensed normalized difference vegetation index (NDVI) and national agriculture imagery program (NAIP) bands 3/2 were determined to account for 95% of landscape variance and used as model predictors. Target variables including soil depth (cm), carbon (kg/m²), clay (%), Na flux (kg/m²), pH, and strain are predicted using multivariate linear step-wise regression models. Our results show strong correlations of soil properties with the drainage systems in the MG catchment. We observe deeper soils, higher clay content, higher carbon content, and more Na loss within the drainages of the catchment in contrast to the adjacent slopes and ridgelines.

The critical zone is the interface between abiotic and biotic constituents that spans from the vegetation canopy through the groundwater and represents an open system shaped by the climate, topography, and vegetation communities of a given environment. Four studies were completed to examine soil development, specifically mineral weathering and soil carbon storage, across semiarid sites spanning the Santa Catalina Mountain Critical Zone Observatory (SCM-CZO). The Santa Catalina Mountain Critical Zone Observatory is located along an environmental gradient in southern Arizona where co-varying climate and vegetation community properties have generated distinct changes in soil development across a relatively short distance (<20 miles). Soil, saprock, and parent rock were sampled on north-facing slopes from five climate-vegetation zones spanning desert scrub to mixed conifer forest. Within each climate-vegetation zone, samples were collected from two divergent summit and two convergent footslope landscape positions to account for topographic controls on mineral transformation. In the first study, the soil morphologic, physical, and chemical properties collected for all samples were combined with profile development indices to quantify soil variation with landscape position across the SCM-CZO. The results of this research demonstrated that climate and landscape position exert significant control on soil development in semiarid ecosystems, and that the profile development index is an effective tool for detecting these regional to hillslope scale variations in soil properties. The second study consisted of a cross-scale analysis of feldspar mineral transformation across the selected research sites to connect measures of pedon-scale soil development, depletions of feldspar and sodium in bulk soil, and elemental losses across feldspar grains at the microscale. Results indicated that greater soil development in the mixed conifer pedons corresponded to increased total feldspar and sodium losses. Desert scrub soils presented less evidence for feldspar transformation including lower profile development indices, gains in total feldspar percentages attributed to dust deposition, and less Na chemical depletion at the microscale. Greater soil development in convergent positions relative to adjacent divergent sites was consistent across all sites, with the highest degree of total feldspar depletion occurring in the conifer convergent locations. The third study focused on the physical distribution and mean residence time of soil organic carbon (SOC) in the SCM-CZO soils described for the first two studies. Surface (0-10 cm) and subsurface (30-40 cm) samples were collected from the aforementioned granitic regolith profiles. The soils were characterized using total C and N, δ¹³C, Δ¹⁴C, and radiocarbon derived mean residence time (MRT) estimates of bulk soil and physically separated C fractions to quantify SOC change with climate, vegetation, and landscape position. The results document a shift in SOC stabilization mechanisms across bioclimatically distinct ecosystems from mineral-associated SOC in the desert scrub soils to a mixture of mineral and occluded SOC in the conifer soils. Soils in the convergent landscapes concentrated the most SOC and typically exhibited the longest residence times across all locations. The fourth study examined the geochemical and mineralogical properties of the SCM-CZO soils across regional and hillslope scales of study to quantify soil development in semiarid environments. X-ray fluorescence and x-ray diffraction were used to characterize the elemental and mineralogical properties of the soils and parent material. Desert scrub dust samples were analyzed using x-ray fluorescence. The results indicate that mineral and base cation depletion were greatest in the convergent landscape positions at both sites and increased from the hot, moisture-limited desert scrub sites to the wetter, more productive conifer ecosystems. Enrichments in mica and select elements (i.e., Fe, Mg) suggested that dust deposition was a significant contributor to soil development across all sites. Geochemical estimates of dust fraction inputs confirmed this finding with dust composing up to 35% of the regolith material in the mixed conifer convergent soils. Clay mineral assemblage was dominated by halloysite and smectite minerals in the desert scrub site, reflecting complex climatic and mineral microtextural interactions in the dry, silica-rich desert environment. Clay minerals at the mixed conifer site exhibited the greatest degree of mineral transformation in the SCM, consisting of vermiculite, illite, kaolinite, and minor amounts of smectite and gibbsite. These findings confirm the interactive role of climate, vegetation, and landscape position in shaping the critical zone, where greater moisture availability and biological production are likely driving increased soil organic carbon storage and mineral weathering across various scales of study.

Inverse geochemical modelling has been used frequently in groundwater systems between wells along a known flowpath and between precipitation and stream waters in catchments. This research expands the use of inverse geochemical modelling through a reaction path model (RPM) between waters in an alpine catchment to determine the geochemical connections and disconnections within the catchment. The data for this study are from the Green Lake 4 catchment in the Colorado Front Range during the 1996 snowmelt season, which has been divided into discrete time intervals based on snowmelt hydrology. Unique combinations of geochemical connections occur during these time intervals, and they show a dynamic hydrologic system. RPM results show notable disconnections; soil water is not geochemically connected to any other end member. These changes reflect changes in weathering reactions in the catchment that are dependent on the duration and timing of snowmelt. Previously end-member mixture analysis (EMMA) models have been used to discern the water sources in catchments. The combination of RPM and EMMA approaches offers the opportunity to connect the source of water to the internal hydrologic structure of the catchment, to better understand how catchments might respond to changes in climate or atmospheric deposition.

No description available.

No description available.

All matter has a specific magnetic signal , due to their magnetic properties. These range from a high susceptibility to become magnetised (ferrimagnetic) to a low ability to be magnetised (diamagnetic). Magnetic susceptibility measures the degree to which a substance can be magnetised, and this can be used to identi fy minerals within material and used as an indicator for processes Le., erosion. Therefore magnetic susceptibility has been widely used to investigate soil related research as the values obtained correspond with the types of magnetic mineral s in the soil, mainly the iron oxides such as magnetite and maghaemite (higher MS), and haematite and goethite (lower MS). Thus MS acts as a signature for different types of soils allowing them to be categorised. The amount of magnetic minerals present in the soil is largely dependent on soil processes active in the profile and external factors, such as parent material. Soil processes influence the type or amount of magnetic mineral in the soil, or the strength of the magnetic signal. Lower MS values are associated with horizons that have undergone gleying, eluviation, leaching and reductive weathering. Higher MS values are found in horizons that have undergone illuviation, and hydrolytic and oxidative weathering. Diamagnetic materials, such as calcium carbonate, decrease the magnetic susceptibility by diluting the magnetic signal. The relationship between MS and iron in soil is influenced by both external factors such as parent material ; climate; topography; land use history of the area and time. Similarly these factors significantly contribute to soil genesis and are highly interactive. Parent materials that are igneous are found to form soil with higher magnetic susceptibility, and sedimentary and metamorphic rocks form less magnetic soils. However, it has also been found that materials such as slate are related to soil with high susceptibility, which is argued to result from more rapid weathering and the release of iron in the ionic form. Climate has a direct affect on the soil processes that drive magnetic susceptibility, thus in warm tropical climates magnetic susceptibility is expected to have higher values . Topography has been shown to alter magnetic susceptibility values , and generall y the top and foot of the slope have higher values than the slopes. Land-use history influences magnetic susceptibility as cultivation is likely to disturb the soil causing magnetic susceptibility values to be lower due to mixing of the upper and lower soil layers. Time relates to the age of the soil and older soil either has large magnetic susceptibility values due to more prolonged pedogenesis, or the magnetic particles have weathered out of the profile and magnetic susceptibility is lowered. Past research has found topsoil to have higher frequency dependent magnetic susceptibility than lower soil horizons. Frequency dependent magnetic susceptibility measures fine-grained ferrimagnetic particles with grain sizes between 0.013 and O.027f.lm. Two measurements at low and high frequency (0.46 and 46 kHz respectively) are used to calculate frequency dependent magnetic susceptibility. These are measured using a Bartington MS2B sensor and certain measures need to be taken in order to obtain an accurate measurements of magnetic susceptibility. Frequency dependent magnetic susceptibility values are influenced by factors including burning, organic matter and pedogenesis. However, the nature of contribution of these is still highly debated. Many South African soils are considered to be old soils and the amount of magnetic minerals in these is unknown. It has been found that magnetic minerals such as maghaemite have been depleted due to erosion cycles. Very little research has been undertaken regarding the applicability of magnetic susceptibility for South African soils as most of the research on magnetic susceptibility in soils has been carried out in countries of the northern hemisphere, where soil materials are much younger than in South Africa. The ability of frequency dependent magnetic susceptibility to differentiate between topsoil and subsoil allows it to be used as a method of assessing topsoil erosion. Topsoil erosion has a detrimental effect on the environment and it is vital a rapid field indicator is developed to assess erosion in order to curb the process. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.

As an abundant sedimentary rock, shale is widely used as construction material around the world. However, shale is a fissile and laminated material and is therefore subject to deterioration due to environmental and chemical forces (i.e., weathering), which is possible to cause high maintenance cost on associated structures and failures of earth slopes and embankments. However, currently, there is lack of efficient method to monitor the weathering process of shale. This thesis uses several shale samples collected from the commonwealth of Kentucky to study the deformation and shear behaviors of weathered compacted shale. A new electrical approach was developed to access the deformation behavior of shale. The long term deformation behaviors, such as collapse and swell can be predicted from specific electrical parameters. The critical state theory was used to describe the shear behavior of weathered compacted shale. Some findings observed by previous researchers were confirmed, and new empirical equations were provided to estimate the shear strength parameters of weathered compacted shale.

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 1994.

The Bells Creek catchment covers an area of 100 km2 in the northern part of the Pumicestone Passage region of southeast Queensland. This catchment is an example of a low-lying sub-tropical coastal plain including both freshwater and estuarine settings. The main creeks drain into Pumicestone Passage, a large shallow estuary, which is a declared marine habitat and a Ramsar listed wading bird location. The Bells Creek catchment has undergone land-use change from bushland to grazing to pine plantations and is now coming under pressure for urban development. Quaternary age unconsolidated sediments are the dominant surface material in this area and formed during the last marine transgression. Of significance for such a setting is that estuarine sediments can retain metals mobilised as a result of natural processes (e.g. weathering) and anthropogenic activities (e.g. land-use disturbance). As trace metals can also occur naturally in rocks and their weathered products, it is of value to clearly distinguish natural and anthropogenic controls over metal source, distribution and mobility. To achieve this aim two approaches were taken: 1) to determine the factors controlling the geochemistry of weathered profiles, unconsolidated sediments, soils and natural waters, and 2) to identify the most effective analytical and numerical methods for evaluating metal concentration in different solid materials. This investigation is structured around four linked papers. The influence of mineralogy, geological setting, location of water table and depth of burial on the geochemistry of weathered profile are assessed in Paper 1. The second paper is an investigation of different analytical approaches for studying weathered sedimentary rocks, as well as the testing of several numerical methods for evaluating geochemical data from weathered profiles. In paper 3, a large heterogeneous geochemical data set including trace metals, total organic carbon and sulfur content, in addition to mineralogy and land use practices are integrated to enable evaluation of geochemical and anthropogenic processes controlling metal distribution. The fourth paper considers the distribution of iron and its transport as well as variations in size and morphology of different forms of framboidal pyrite within a smaller sub-catchment in the southern part of the study area. The labile and heterogeneous nature of the bedrock of the region, the Landsborough Sandstone, along with the sub-tropical climate of the area have resulted in weathering profiles up to 26 m deep. Due to the absence of industrial activity in the Bells Creek catchment, such weathering of the bedrock constitutes the major process governing metal distribution throughout the area. Analysis by X-ray diffraction (XRD) shows that the primary minerals occurring in the weathered profiles are quartz, plagioclase and K-feldspars while kaolinite is the most dominant secondary mineral present. Overall, parent rock silicates have been extensively replaced by clay minerals and Fe oxides. The relative influence of mineralogy, geological setting and groundwater over chemical weathering and geochemical cycling of metals can be summarised as follows: Mineralogy>geological setting>watertable position>depth of profile burial As the relationship between the total metal composition and the extractable and mobile component has environmental significance, a comparison was made between these forms of metals in weathered material. This comparison shows that metals such as V, Cr and Fe are part of the aluminosilicate matrix and remain largely in primary mineral structures. The retention of these metals may lead to their future release to the environment during on-going weathering. Other elements such as Cu, Zn, Pb, however, are found to be primarily adsorbed to sediment particles and therefore, easily releasable to the environment. As limited information on weathering of sedimentary rocks is reported in the literature, a variety of chemical analysis and numerical assessment methods were used to understand the geochemical processes involved in trace metal mobility in the weathered profiles. Two analytical methods of digestion, hydrofluoric acid and x-ray fluorescence were tested and found to be highly comparable except for refractory elements such as V and Cr. Among the numerical methods applied to the dataset were "chemical and mineralogical indices", "weight loss factor" and "immobile element approach". The "immobile element approach" was found to be the most appropriate method to characterise the weathering profiles typical of the catchment. This method considers a weathering system to be open and transforms the absolute values of trace metals enabling a quantitative evaluation of metal mobility. The following sequence of mobility was determined after applying this method to the data generated in this study: Zn>Pb>Cu>Cr>V The above sequence of mobility is supported by the comparison between extractable and total metal concentrations where Cr and V were identified as being part of aluminosilicate matrix and less mobile. On the other hand, Zn, Pb and Cu were found to exist in adsorbed form and to be readily released to the environment. Trace elements released through weathering and erosion of the bedrock can accumulate in estuarine and coastal sediments. Therefore, both the lateral and vertical distribution of trace metals within sediments and soils of Bells Creek catchment were investigated. Natural and anthropogenic factors controlling metal distribution were compared and it was concluded that the natural sediment character such as its mineral content is more significant than anthropogenic influences in controlling lateral and vertical metal distribution. Further, due to varying degrees of weathering and the heterogeneous nature of soils and sediments, the data were normalised. After testing several methods, it was concluded that calculation of an enrichment factor was the most appropriate. The enrichment factor revealed that elevated trace metal concentrations at some sites are due to bedrock weathering. Due to the environmental persistence of iron, excess of this common metal has always been of environmental concern in many coastal settings. In the small Halls Creek sub-catchment, for example, iron anomalies were detected in bottom sediments (Fe up to 14%). This finding has significance in the area, as iron has been identified as one of the major contributors in the growth of the toxic cyanobacteria "Lyngbya majuscula" which can negatively impact on aquatic fauna. Iron concentrations were also shown to be high in natural stream waters of this coastal zone (up to 16 mg/L); in the bottom sediments of the creek, iron occurs as hematite (freshwater section) or pyrite (estuarine section). A variety of pyrite morphologies were identified in both bottom sediments and particulate matter samples including spherical closely packed framboids, and the rare form of euhedra which indicates slow crystallisation. The different components of this investigation have: 1) established the order and extent to which natural factors control weathering, 2) tested a number of analytical and numerical methods in evaluating weathering profiles, 3) assessed natural and anthropogenic factors and established the mobility sequence for trace metals in weathered profiles and, 4) determined the iron mineral speciation and established morphological variations of pyrite. As the area of Bells Creek catchment will be under development pressure in the future, findings of this study represent a baseline of comparison for environmental assessment and are of importance for environmental management.