- Email: [email protected]
Genesis and significance of the MIS 2 Kirkham moraine
Abstracts / Quaternary International 279-280 (2012) 9–120
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records suggest a regional decline in Casuarina and increases in Eucalyptus associated with European settlement, but few other consistent or substantial changes in vegetation communities over time. Sediment geochemistry varied between frequently connected and less frequently connected billabongs, but there was no apparent influence from European settlement. In contrast, diatom assemblages varied substantially both spatially and temporally. Records from each billabong show that epiphytes were more abundant during the pre-European period. Around the point of the first evidence of European occupation the abundance of planktonic diatoms increases and that of epiphytic diatoms is reduced. Plankton dominance or co-dominance extends through the post-European periods of two of the deeper billabongs (>1 m); however, the abundance of planktonic diatoms declines in the remaining two shallower billabongs (<1 m) where epipelic diatoms predominate. This variation in response did not correlate with hydrological connectivity, suggesting that depth is the critical factor influencing diatom assemblages and hence the structure of billabong ecosystems.
assemblages reflect rapidly changing erosional and depositional conditions during retreat of ice margins across lowland Lancashire. From the inner sectors the landform assemblages range outwards, from a subglacial depositional assemblage, characterised by drumlin swarms through a diamict plain of basal ice lodgement till to a large ice-marginal assemblage, the Kirkham moraine. The moraine displays a complex polygenetic morphology of glaciotectonised ridges, intervening margin-parallel sandur troughs and an ice disintegration of ridges and kettle-hole basins. The sequence reflects the progressive unzipping of former ice streams, the oscillatory movement (still-stand) probably forced by ice-sheet dynamics rather than large scale climatic variation, and then rapid wastage or disintegration of the ice mass. Optical stimulated luminescence dating is in progress to secure a timeframe for ice-parallel sandur deposits during the still-stand phase of the Kirkham moraine.
LAKE - CATCHMENT RESPONSES TO HUMAN AND CLIMATE FORCING
E-mail address: [email protected]
Richard C. Chiverrell. University of Liverpool, United Kingdom
The Korean Peninsula has generally been considered as a tectonically stable region that is not earthquake-prone because it is located in the Eurasian intraplate region. However, more than 20 Quaternary faults and historical records of damage by earthquakes have recently been reported in the area around the Yangsan and Ulsan faults, SE Korean. The Quaternary Eupcheon fault and its northern extent were exposed in an area close to a nuclear power plant. We analyzed slip data in fault zone and trench excavated across the Eupcheon fault with the aim of understanding its movement history and kinematics. The fault gouge zone is composed of several different colored gouge bands. For the purpose of understanding the transport direction during fault movement, we analyzed cleavages, slickenlines, shear fabrics, and intersection lineations. These data indicate that fault zone experienced repeated movements including early normal slip under SE extension and was later reactivated under NNW compression resulting in inversion tectonics. In the trench analysis, it shows a reverse fault (strike/dip: N20E/40SE) that records 6–7 m of displacement (3–4 m vertical separation). We identified four or five Quaternary faulting events upon the fault based on an interpretation of the trench logs including an analysis of colluvial wedges, and measurements of displacement–distance (d–x) relationships along the fault. We used a quantitative analysis of d–x relationships, commonly used for consolidated sedimentary rocks, to interpret the deformation history of the fault. From this we estimated the amount of slip in the range of 0.7–1.8 m for each of the five identified faulting events and the earthquake magnitude in the range of Mw 5.4–7.4. We propose a tectonic evolution model for the area around this fault. This approach may be applicable to analyses of earthquake hazards and studies of fault evolution elsewhere.
THE EVOLUTION OF THE QUATERNARY EUPCHEON FAULT, SE KOREA Jin-Hyuck Choi. Pukyong National University, Korea
E-mail address: [email protected]
Fluvial catchments in the English Lake District have responded to human loading with increases in sediment flux driven by human-mediated changes in land cover and practice, e.g. those associated with phases of extensive gullying after 2200, between 1250 and 700, and after 500 BP. Overprinting this punctuated trend towards a sediment-rich fluvial system, shorter duration high magnitude flow events (floods) have impacted on both people and the landscape. Sediment archives from lakes with differing catchment/lake area configuration reveals the impacts of drivers of environmental changes to varying degrees. For small lakes (e.g. Brotherswater) with large catchments, high catchment to lake area (C/L) ratios and limited capacity for storage in the catchment, the sediment record appears strongly coupled with flow processes and reflects variations in flood frequency and magnitude: e.g. Brotherswater shows a flood laminated stratigraphy that persists through the last 2000 years. For other lakes, e.g. Crummock Water, with smaller effective C/L ratios this process coupling breaks down and the sediment record is more reflective of longer-term variations in sediment supply. At Crummock Water a suite of changes in magnetic and geochemical parameters corresponds with the regional onset of human activity after 3000 BP, and particularly to the intensification of human activity in the last 1000 years. The character of sediment records in lakes appears governed in part by the efficiency of coupling of catchment and lake, which affects whether these sediment archives are tuned to better reflect variations supply (instability) or carrying capacity (discharge) of sediment. This distinction is a little arbitrary and high magnitude floods, like those that affected Cumbria in 2009 and 2005, clearly have exceeded process coupling thresholds and left a clear imprint of high magnitude flows in the sediment columns of supply dominated lakes, e.g. Crummock Water.
NUMERICAL MODELLING OF SEDIMENT DEFORMATION BY GLACIAL STRESS Anders D. Christensen. University of Aarhus, Denmark
GENESIS AND SIGNIFICANCE OF THE MIS 2 KIRKHAM MORAINE
E-mail address: [email protected]
Richard C. Chiverrell. University of Liverpool, United Kingdom
Numerical simulation of subglacial sediment deformation on micro- to intermediate scale offers insight into the origin of structural and textural features related to progressive shear strain. Numerical simulations complement analogue experiments by allowing complete control of physical variables involved in the experiments, which in turn facilitates a targeted study of mutual relationships and feedbacks of parameters controlling subglacial deformation. The Discrete Element Method (DEM) is a numerical formulation applicable for simulating the mechanical behaviour of granular material under certain boundary conditions. Each particle is an unbreakable spherical entity with spatial and rotational degrees of freedom and inertia. Inter-particle contact forces are approximated by treating the particles as elastic bodies with friction at contact surfaces. The resulting movement is calculated by integration of Newton's second law of motion. The particle assemblage is subjected to gravity and forced by a set of walls, moving in a shearing fashion with periodic lateral boundaries. A setup corresponding to a soft, granular sediment with realistic physical parameters is created, and the response of the virtual particle assemblage
E-mail address: [email protected]
The glacial sediments and landforms of lowland Lancashire reflect the advance, coalescence and subsequent retreat and uncoupling of several regional ice-masses during the MIS 2 de-glaciation. These ice-masses issued from source areas in the eastern Lake District and central Pennines and interacted with a larger eastern Irish Sea ice-stream that at its maximum bifurcated following a southerly path across lowland Cheshire into the English Midlands and further west southwards down the Irish Sea basin as part of the Irish Sea ice stream. The smaller dimensions and restricted source areas in the upper Ribble valley and in the Eastern Lake District led to a more rapid decline and retreat than Irish Sea ice after the late glacial maximum (LGM). Irish Sea ice appears to have acted as a dam confining a large lake in the space vacated by ice in the lower Ribble valley, with glaci-lacustrine sediments extending through the lower Ribble and into the Calder and Hodder tributaries. The sediment–landform
89
records suggest a regional decline in Casuarina and increases in Eucalyptus associated with European settlement, but few other consistent or substantial changes in vegetation communities over time. Sediment geochemistry varied between frequently connected and less frequently connected billabongs, but there was no apparent influence from European settlement. In contrast, diatom assemblages varied substantially both spatially and temporally. Records from each billabong show that epiphytes were more abundant during the pre-European period. Around the point of the first evidence of European occupation the abundance of planktonic diatoms increases and that of epiphytic diatoms is reduced. Plankton dominance or co-dominance extends through the post-European periods of two of the deeper billabongs (>1 m); however, the abundance of planktonic diatoms declines in the remaining two shallower billabongs (<1 m) where epipelic diatoms predominate. This variation in response did not correlate with hydrological connectivity, suggesting that depth is the critical factor influencing diatom assemblages and hence the structure of billabong ecosystems.
assemblages reflect rapidly changing erosional and depositional conditions during retreat of ice margins across lowland Lancashire. From the inner sectors the landform assemblages range outwards, from a subglacial depositional assemblage, characterised by drumlin swarms through a diamict plain of basal ice lodgement till to a large ice-marginal assemblage, the Kirkham moraine. The moraine displays a complex polygenetic morphology of glaciotectonised ridges, intervening margin-parallel sandur troughs and an ice disintegration of ridges and kettle-hole basins. The sequence reflects the progressive unzipping of former ice streams, the oscillatory movement (still-stand) probably forced by ice-sheet dynamics rather than large scale climatic variation, and then rapid wastage or disintegration of the ice mass. Optical stimulated luminescence dating is in progress to secure a timeframe for ice-parallel sandur deposits during the still-stand phase of the Kirkham moraine.
LAKE - CATCHMENT RESPONSES TO HUMAN AND CLIMATE FORCING
E-mail address: [email protected]
Richard C. Chiverrell. University of Liverpool, United Kingdom
The Korean Peninsula has generally been considered as a tectonically stable region that is not earthquake-prone because it is located in the Eurasian intraplate region. However, more than 20 Quaternary faults and historical records of damage by earthquakes have recently been reported in the area around the Yangsan and Ulsan faults, SE Korean. The Quaternary Eupcheon fault and its northern extent were exposed in an area close to a nuclear power plant. We analyzed slip data in fault zone and trench excavated across the Eupcheon fault with the aim of understanding its movement history and kinematics. The fault gouge zone is composed of several different colored gouge bands. For the purpose of understanding the transport direction during fault movement, we analyzed cleavages, slickenlines, shear fabrics, and intersection lineations. These data indicate that fault zone experienced repeated movements including early normal slip under SE extension and was later reactivated under NNW compression resulting in inversion tectonics. In the trench analysis, it shows a reverse fault (strike/dip: N20E/40SE) that records 6–7 m of displacement (3–4 m vertical separation). We identified four or five Quaternary faulting events upon the fault based on an interpretation of the trench logs including an analysis of colluvial wedges, and measurements of displacement–distance (d–x) relationships along the fault. We used a quantitative analysis of d–x relationships, commonly used for consolidated sedimentary rocks, to interpret the deformation history of the fault. From this we estimated the amount of slip in the range of 0.7–1.8 m for each of the five identified faulting events and the earthquake magnitude in the range of Mw 5.4–7.4. We propose a tectonic evolution model for the area around this fault. This approach may be applicable to analyses of earthquake hazards and studies of fault evolution elsewhere.
THE EVOLUTION OF THE QUATERNARY EUPCHEON FAULT, SE KOREA Jin-Hyuck Choi. Pukyong National University, Korea
E-mail address: [email protected]
Fluvial catchments in the English Lake District have responded to human loading with increases in sediment flux driven by human-mediated changes in land cover and practice, e.g. those associated with phases of extensive gullying after 2200, between 1250 and 700, and after 500 BP. Overprinting this punctuated trend towards a sediment-rich fluvial system, shorter duration high magnitude flow events (floods) have impacted on both people and the landscape. Sediment archives from lakes with differing catchment/lake area configuration reveals the impacts of drivers of environmental changes to varying degrees. For small lakes (e.g. Brotherswater) with large catchments, high catchment to lake area (C/L) ratios and limited capacity for storage in the catchment, the sediment record appears strongly coupled with flow processes and reflects variations in flood frequency and magnitude: e.g. Brotherswater shows a flood laminated stratigraphy that persists through the last 2000 years. For other lakes, e.g. Crummock Water, with smaller effective C/L ratios this process coupling breaks down and the sediment record is more reflective of longer-term variations in sediment supply. At Crummock Water a suite of changes in magnetic and geochemical parameters corresponds with the regional onset of human activity after 3000 BP, and particularly to the intensification of human activity in the last 1000 years. The character of sediment records in lakes appears governed in part by the efficiency of coupling of catchment and lake, which affects whether these sediment archives are tuned to better reflect variations supply (instability) or carrying capacity (discharge) of sediment. This distinction is a little arbitrary and high magnitude floods, like those that affected Cumbria in 2009 and 2005, clearly have exceeded process coupling thresholds and left a clear imprint of high magnitude flows in the sediment columns of supply dominated lakes, e.g. Crummock Water.
NUMERICAL MODELLING OF SEDIMENT DEFORMATION BY GLACIAL STRESS Anders D. Christensen. University of Aarhus, Denmark
GENESIS AND SIGNIFICANCE OF THE MIS 2 KIRKHAM MORAINE
E-mail address: [email protected]
Richard C. Chiverrell. University of Liverpool, United Kingdom
Numerical simulation of subglacial sediment deformation on micro- to intermediate scale offers insight into the origin of structural and textural features related to progressive shear strain. Numerical simulations complement analogue experiments by allowing complete control of physical variables involved in the experiments, which in turn facilitates a targeted study of mutual relationships and feedbacks of parameters controlling subglacial deformation. The Discrete Element Method (DEM) is a numerical formulation applicable for simulating the mechanical behaviour of granular material under certain boundary conditions. Each particle is an unbreakable spherical entity with spatial and rotational degrees of freedom and inertia. Inter-particle contact forces are approximated by treating the particles as elastic bodies with friction at contact surfaces. The resulting movement is calculated by integration of Newton's second law of motion. The particle assemblage is subjected to gravity and forced by a set of walls, moving in a shearing fashion with periodic lateral boundaries. A setup corresponding to a soft, granular sediment with realistic physical parameters is created, and the response of the virtual particle assemblage
E-mail address: [email protected]
The glacial sediments and landforms of lowland Lancashire reflect the advance, coalescence and subsequent retreat and uncoupling of several regional ice-masses during the MIS 2 de-glaciation. These ice-masses issued from source areas in the eastern Lake District and central Pennines and interacted with a larger eastern Irish Sea ice-stream that at its maximum bifurcated following a southerly path across lowland Cheshire into the English Midlands and further west southwards down the Irish Sea basin as part of the Irish Sea ice stream. The smaller dimensions and restricted source areas in the upper Ribble valley and in the Eastern Lake District led to a more rapid decline and retreat than Irish Sea ice after the late glacial maximum (LGM). Irish Sea ice appears to have acted as a dam confining a large lake in the space vacated by ice in the lower Ribble valley, with glaci-lacustrine sediments extending through the lower Ribble and into the Calder and Hodder tributaries. The sediment–landform