OR/17/042 Conceptual geological model - Revision history

Ajhil at 14:30, 3 December 2019

2019-12-03T14:30:54Z

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Ajhil at 14:29, 3 December 2019

2019-12-03T14:29:37Z

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Ajhil: /* Glacitectonic structures (folds and thrusts) */

2019-12-03T14:28:38Z

Glacitectonic structures (folds and thrusts)

← Older revision		Revision as of 15:28, 3 December 2019
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	[[Image:OR17042fig4.5.jpg\|thumb\|center\|700px\| '''Figure 4.5'''    Structural interpretation of deformed bedrock and superficial sequences at Møens Klint, Denmark (from Lee and Phillips, 2013<ref name="Lee 2013">LEE, J R, and PHILLIPS, E. 2013. Glacitectonics — a key approach to examining ice dynamics, substrate rheology and ice‐bed coupling. ''Proceedings of the Geologists' Association'', Vol. 124, 731–737. </ref>). ]]		[[Image:OR17042fig4.5.jpg\|thumb\|center\|700px\| '''Figure 4.5'''    Structural interpretation of deformed bedrock and superficial sequences at Møens Klint, Denmark (from Lee and Phillips, 2013<ref name="Lee 2013">LEE, J R, and PHILLIPS, E. 2013. Glacitectonics — a key approach to examining ice dynamics, substrate rheology and ice‐bed coupling. ''Proceedings of the Geologists' Association'', Vol. 124, 731–737. </ref>). ]]

	Within the Cheshire Basin (CB), a tripartite glacigenic sequence comprising two tills and intervening outwash deposits has been described (Worsley, 1991; Crofts ''et al''., 2005). They were laid‐down in association with a lobe of wet‐based Irish Sea Ice that extended across the Cheshire/Shropshire lowlands reaching as far south and west as the West Midlands. Evidence from both modern glacial environments and the geological record suggests that key controls on ice‐bed interactions and in‐turn glacier behaviour is meltwater availability (Eyles, 2006<ref name="Eyles 2006">EYLES, N. 2006. The role of meltwater in glacial processes. ''Sedimentary Geology'', Vol. 190, 257–268. </ref>; Bell, 2008<ref name="Bell 2008">BELL, R E. 2008. The role of subglacial water in ice‐sheet mass balance. ''Nature Geoscience'', Vol. 1, 297–304. </ref>). Within the CB, given the lateral continuity of the major till facies, it suggests that ice‐bed traction was largely limited with a meltwater‐enhanced substrate zone effectively decoupling the glacier from its bed. This would have limited the transmission of strain into the substrate. Reducing and/or varying the availability of meltwater within the substrate typically has the effect of enhancing ice‐bed traction enabling the transmission of strain into the glacier bed (Lee ''et al''., 2017<ref name="Lee 2017">LEE, J R, PHILLIPS, E, ROSE, J, and VAUGHAN‐HIRSCH, D. 2017. The Middle Pleistocene glacial evolution of northern East Anglia, UK: a dynamic tectonostratigraphic‐parasequence approach. ''Journal of Quaternary Science'', Vol. 32, 231–260.</ref>). This dramatically increases the potential for larger‐scale deformation of the substrate including the development of glacitectonic folds, faults and bedrock rafts. Therefore, during collapse of the Irish Sea Ice and progressive northwards retreat of the ice margin across the CB, temporal and spatial variations in substrate water availability may have led to enhanced ice‐bed traction and in‐turn substrate deformation by glacitectonic processes. This effect of often amplified where the substrate is dominated by permeable lithologies (e.g. SSG) which act as meltwater sinks and/or where seasonal freezing of the glacier snout to its bed occurs (e.g. Hiemstra ''et al''., 2007<ref name="Hiemstra 2007">HIEMSTRA, J F, EVANS, D J A, and COFAIGH, C Ó. 2007. The role of glacitectonic rafting and comminution in the production of subglacial tills: Examples from southwest Ireland and Antarctica. ''Boreas'', Vol. 36, 386–399. </ref>; Lee ''et al''., 2013, 2017<ref name="Lee 2013"></ref>).		Within the Cheshire Basin (CB), a tripartite glacigenic sequence comprising two tills and intervening outwash deposits has been described (Worsley, 1991; Crofts ''et al''., 2005). They were laid‐down in association with a lobe of wet‐based Irish Sea Ice that extended across the Cheshire/Shropshire lowlands reaching as far south and west as the West Midlands. Evidence from both modern glacial environments and the geological record suggests that key controls on ice‐bed interactions and in‐turn glacier behaviour is meltwater availability (Eyles, 2006<ref name="Eyles 2006">EYLES, N. 2006. The role of meltwater in glacial processes. ''Sedimentary Geology'', Vol. 190, 257–268. </ref>; Bell, 2008<ref name="Bell 2008">BELL, R E. 2008. The role of subglacial water in ice‐sheet mass balance. ''Nature Geoscience'', Vol. 1, 297–304. </ref>). Within the CB, given the lateral continuity of the major till facies, it suggests that ice‐bed traction was largely limited with a meltwater‐enhanced substrate zone effectively decoupling the glacier from its bed. This would have limited the transmission of strain into the substrate. Reducing and/or varying the availability of meltwater within the substrate typically has the effect of enhancing ice‐bed traction enabling the transmission of strain into the glacier bed (Lee ''et al''., 2017<ref name="Lee 2017"></ref>). This dramatically increases the potential for larger‐scale deformation of the substrate including the development of glacitectonic folds, faults and bedrock rafts. Therefore, during collapse of the Irish Sea Ice and progressive northwards retreat of the ice margin across the CB, temporal and spatial variations in substrate water availability may have led to enhanced ice‐bed traction and in‐turn substrate deformation by glacitectonic processes. This effect of often amplified where the substrate is dominated by permeable lithologies (e.g. SSG) which act as meltwater sinks and/or where seasonal freezing of the glacier snout to its bed occurs (e.g. Hiemstra ''et al''., 2007<ref name="Hiemstra 2007">HIEMSTRA, J F, EVANS, D J A, and COFAIGH, C Ó. 2007. The role of glacitectonic rafting and comminution in the production of subglacial tills: Examples from southwest Ireland and Antarctica. ''Boreas'', Vol. 36, 386–399. </ref>; Lee ''et al''., 2013, 2017<ref name="Lee 2013"></ref>).

	Evidence for these glacitectonic processes occurring in the CB is indicated by the development of terminal moraine complexes (Boulton and Worsley, 1965<ref name="Boulton 1965"></ref>; Thomas, 1989<ref name="Thomas 1989"></ref>; Price ''et al''., 2007<ref name="Price 2007">PRICE, S J, BRIDGE D, KESSLER, H K, and TERRINGTON, R. 2007. The Manchester and Salford 3D Superficial Deposits Model: a guide to the model and its applications. British Geological Survey Internal Report IR/07/001, 19pp.</ref>; Parkes ''et al''., 2009<ref name="Parkes 2009">PARKES, A A, WALLER, R I, KNIGHT, P G, STIMPSON, I G, SCHOFIELD, D I, and MASON, K T. 2009. A morphological, sedimentological and geophysical investigation of the Woore Moraine, Shropshire, England. ''Proceedings of the Geologists' Association'', Vol. 120, 233–244. </ref>; Clark ''et al''., 2012<ref name="Clark 2012">CLARK, C D, HUGHES, A L, GREENWOOD, S L, JORDAN, C, and SEJRUP, H P. 2012. Pattern and timing of retreat of the last British‐Irish Ice Sheet. ''Quaternary Science Reviews'', Vol. 44, 112–146. </ref>; Crofts ''et al''., 2012<ref name="Crofts 2012">CROFTS, R G, HOUGH, E, HUMPAGE, A J, and REEVES, H J. 2012. Geology of the Manchester district: a brief explanation of the geological map. (1:50 000 Sheet 85 Liverpool (England and Wales): Sheet Explanation of the British Geological Survey.): Nottingham, British Geological Survey.</ref>). To date, no glacitectonic rafts have been identified within the Cheshire Basin. However, the style of deglaciation coupled with the prevailing climatic conditions and hydrogeological properties of the SSG make it particularly susceptible to the development of these structures. The likely occurrence of these features beneath the study site is ‘about as likely as not’ ([[OR/17/042 Conceptual geological model#Table 4.1\|Table 4.1]]).		Evidence for these glacitectonic processes occurring in the CB is indicated by the development of terminal moraine complexes (Boulton and Worsley, 1965<ref name="Boulton 1965"></ref>; Thomas, 1989<ref name="Thomas 1989"></ref>; Price ''et al''., 2007<ref name="Price 2007">PRICE, S J, BRIDGE D, KESSLER, H K, and TERRINGTON, R. 2007. The Manchester and Salford 3D Superficial Deposits Model: a guide to the model and its applications. British Geological Survey Internal Report IR/07/001, 19pp.</ref>; Parkes ''et al''., 2009<ref name="Parkes 2009">PARKES, A A, WALLER, R I, KNIGHT, P G, STIMPSON, I G, SCHOFIELD, D I, and MASON, K T. 2009. A morphological, sedimentological and geophysical investigation of the Woore Moraine, Shropshire, England. ''Proceedings of the Geologists' Association'', Vol. 120, 233–244. </ref>; Clark ''et al''., 2012<ref name="Clark 2012">CLARK, C D, HUGHES, A L, GREENWOOD, S L, JORDAN, C, and SEJRUP, H P. 2012. Pattern and timing of retreat of the last British‐Irish Ice Sheet. ''Quaternary Science Reviews'', Vol. 44, 112–146. </ref>; Crofts ''et al''., 2012<ref name="Crofts 2012">CROFTS, R G, HOUGH, E, HUMPAGE, A J, and REEVES, H J. 2012. Geology of the Manchester district: a brief explanation of the geological map. (1:50 000 Sheet 85 Liverpool (England and Wales): Sheet Explanation of the British Geological Survey.): Nottingham, British Geological Survey.</ref>). To date, no glacitectonic rafts have been identified within the Cheshire Basin. However, the style of deglaciation coupled with the prevailing climatic conditions and hydrogeological properties of the SSG make it particularly susceptible to the development of these structures. The likely occurrence of these features beneath the study site is ‘about as likely as not’ ([[OR/17/042 Conceptual geological model#Table 4.1\|Table 4.1]]).

Ajhil at 14:27, 3 December 2019

2019-12-03T14:27:49Z

← Older revision		Revision as of 15:27, 3 December 2019
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	The rockhead surface model provides a valuable insight into the nature of the rockhead surface beneath the study area. However, it only provides a generalisation of the rockhead surface with local variation also influenced by relative borehole density. The model shows a radial arrangement of buried valleys fanning outwards from the Liverpool‐Skelmersdale area southwards and eastwards beneath the Cheshire/north Shropshire lowlands (Figure 4.1). The radial pattern conforms to the geometry of the hydraulic gradient that would generate perpendicular to the margins of a piedmont‐style glacier lobe that fanned outwards across the Cheshire lowlands towards the west, south and east. This style of glacier geometry has previously been inferred for the Late Devensian ice lobe based upon the mapped distribution morainic landforms around the region (Boulton and Worsley, 1965<ref name="Boulton 1965">BOULTON, G, and WORSLEY, P. 1965. Late Weichselian glaciation in the Cheshire‐Shropshire basin. ''Nature'', Vol. 207, 704–706.</ref>; Yates, 1967<ref name="Yates 1967">YATES, E. 1967. A contribution to the glacial geomorphology of the Cheshire Plain. ''Transactions of the Institute of British Geographers'', 107–125.</ref>; Thomas, 1989<ref name="Thomas 1989"></ref>).		The rockhead surface model provides a valuable insight into the nature of the rockhead surface beneath the study area. However, it only provides a generalisation of the rockhead surface with local variation also influenced by relative borehole density. The model shows a radial arrangement of buried valleys fanning outwards from the Liverpool‐Skelmersdale area southwards and eastwards beneath the Cheshire/north Shropshire lowlands (Figure 4.1). The radial pattern conforms to the geometry of the hydraulic gradient that would generate perpendicular to the margins of a piedmont‐style glacier lobe that fanned outwards across the Cheshire lowlands towards the west, south and east. This style of glacier geometry has previously been inferred for the Late Devensian ice lobe based upon the mapped distribution morainic landforms around the region (Boulton and Worsley, 1965<ref name="Boulton 1965">BOULTON, G, and WORSLEY, P. 1965. Late Weichselian glaciation in the Cheshire‐Shropshire basin. ''Nature'', Vol. 207, 704–706.</ref>; Yates, 1967<ref name="Yates 1967">YATES, E. 1967. A contribution to the glacial geomorphology of the Cheshire Plain. ''Transactions of the Institute of British Geographers'', 107–125.</ref>; Thomas, 1989<ref name="Thomas 1989"></ref>).

	Whilst a glacial origin for several of the larger buried channels is logical, some channels may have existed in the landscape prior to the Late Devensian glaciation and originally be of fluvial origin. For example, Worsley ''et al''. (1983)<ref name="Worsley 1983">WORSLEY, P, COOPE, G R, GOOD, T R, HOLYOAK, D T,and ROBINSON, J E. 1983. A Pleistocene succession from beneath Chelford Sands at Oakwood Quarry, Chelford, Cheshire. ''Geological Journal'', Vol. 18, 307–324. </ref> describes a buried channel that contains preglacial organic sediments overlain by glacial till and meltwater sediments. Of particular relevance to the study area is the existence of a major buried channel beneath the modern River Mersey (Figure 4.2). Small, broadly north‐south trending offshoots of this buried valley occur to the west and east of Thornton‐le‐Moors. However, the resolution of the rockhead model mean that the true geometry of these buried valleys remains poorly constrained. Therefore, the presence of a buried valley beneath the Cheshire Energy Research Field Site is ‘about as likely as not’ ([[OR/17/042 Methodology#Table 2.1\|Table 2.1]]). Local perturbations in the rockhead surface up to 47 m below OD, some likely associated with buried channels, have been identified to the east of the village of Elton, beneath Ince Marshes and are described by Burke ''et al''. (2016)<ref name="Burke 2016"></ref>.		Whilst a glacial origin for several of the larger buried channels is logical, some channels may have existed in the landscape prior to the Late Devensian glaciation and originally be of fluvial origin. For example, Worsley ''et al''. (1983)<ref name="Worsley 1983"></ref> describes a buried channel that contains preglacial organic sediments overlain by glacial till and meltwater sediments. Of particular relevance to the study area is the existence of a major buried channel beneath the modern River Mersey (Figure 4.2). Small, broadly north‐south trending offshoots of this buried valley occur to the west and east of Thornton‐le‐Moors. However, the resolution of the rockhead model mean that the true geometry of these buried valleys remains poorly constrained. Therefore, the presence of a buried valley beneath the Cheshire Energy Research Field Site is ‘about as likely as not’ ([[OR/17/042 Methodology#Table 2.1\|Table 2.1]]). Local perturbations in the rockhead surface up to 47 m below OD, some likely associated with buried channels, have been identified to the east of the village of Elton, beneath Ince Marshes and are described by Burke ''et al''. (2016)<ref name="Burke 2016"></ref>.

	[[Image:OR17042fig4.2.jpg\|thumb\|center\|500px\| '''Figure 4.2'''    Rockhead (geological) surface model adjacent to the Cheshire Energy Research Field Site (green dot) showing a major buried valley (pale yellow to pale green) to the west extending northwards to Ellesmere Port joining an assumed valley that extends beneath the Mersey Estuary. Borehole locations are indicated by small black dots. Includes Ordnance Survey data © Crown copyright and database rights [2017] Ordnance Survey [100021290 EUL]. ]]		[[Image:OR17042fig4.2.jpg\|thumb\|center\|500px\| '''Figure 4.2'''    Rockhead (geological) surface model adjacent to the Cheshire Energy Research Field Site (green dot) showing a major buried valley (pale yellow to pale green) to the west extending northwards to Ellesmere Port joining an assumed valley that extends beneath the Mersey Estuary. Borehole locations are indicated by small black dots. Includes Ordnance Survey data © Crown copyright and database rights [2017] Ordnance Survey [100021290 EUL]. ]]

Ajhil: /* Buried valleys (meltwater erosion) */

2019-12-03T14:27:16Z

Buried valleys (meltwater erosion)

← Older revision		Revision as of 15:27, 3 December 2019
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	[[Image:OR17042fig4.1.jpg\|thumb\|center\|500px\| '''Figure 4.1'''    A rockhead (geological) relief model for the northern Cheshire Basin including the study area (green dot). Pale yellow and pale green areas of shading correspond to areas of lowest rockhead relief and, where connected, the location of major buried valleys. Includes Ordnance Survey data © Crown copyright and database rights [2017] Ordnance Survey [100021290 EUL]. ]]		[[Image:OR17042fig4.1.jpg\|thumb\|center\|500px\| '''Figure 4.1'''    A rockhead (geological) relief model for the northern Cheshire Basin including the study area (green dot). Pale yellow and pale green areas of shading correspond to areas of lowest rockhead relief and, where connected, the location of major buried valleys. Includes Ordnance Survey data © Crown copyright and database rights [2017] Ordnance Survey [100021290 EUL]. ]]

	The consensus within the literature is that these buried valleys were produced by glacial over‐deepening (subglacial erosion) and/or subglacial meltwater incision (Gresswell, 1964<ref name="Gresswell 1964">~~GRESSWELL, R K. 1964. The origin of the Mersey and Dee Estuaries. ''Geological Journal'', Vol. 4, 77–86.~~</ref>; Howell, 1973<ref name="Howell 1973"></ref>). Buried valleys produced by subglacial meltwater incision are commonly called tunnel valleys (or tunnel channels in North America) and occur widely around former glacier margins (Ó Cofaigh, 1996<ref name="Ó Cofaigh 1996">Ó COFAIGH, C. 1996. Tunnel valley genesis. ''Progress in Physical Geography'', Vol. 20, 1–19. </ref>; Piotrowski, 1997<ref name="Piotrowski 1997">KRISTENSEN, T B, PIOTROWSKI, J A, HUUSE, M, CLAUSEN, O R, and HAMBERG, L. 2008. Time‐transgressive tunnel valley formation indicated by infill sediment structure, North Sea — The role of glaciohydraulic supercooling. ''Earth Surface Processes and Landforms'', Vol. 33, 546–559. </ref>; Dürst Stucki ''et al''., 2010<ref name="Dürst 2010">DÜRST STUCKI, M, REBER, R, and SCHLUNEGGER, F. 2010. Subglacial tunnel valleys in the Alpine foreland: an example from Bern, Switzerland. ''Swiss Journal of Geosciences'', Vol. 103, 363–374. </ref>; Kehew ''et al''., 2012<ref name="Kehew 2012">KEHEW, A E, PIOTROWSKI, J A, and JØRGENSEN, F. 2012. Tunnel valleys: Concepts and controversies — A review. ''Earth‐Science Reviews'', Vol. 113, 33–58.</ref>). Incision of tunnel valleys occurs under immense hydraulic gradients with flow regimes constrained by channel morphology and the thickness of overlying ice. A common characteristic of tunnel valleys is that their bases (referred to as the thalweg) are often undulating with significant normal and reverse changes in gradient developed along their long‐profile. Infills to buried valleys tend to be highly‐chaotic encompassing intercalated beds of till, glaciolacustrine (silt and clay) and glaciofluvial (sand and gravel) sediment that typically give‐rise to chaotic and unpredictable hydrogeological behaviour.		The consensus within the literature is that these buried valleys were produced by glacial over‐deepening (subglacial erosion) and/or subglacial meltwater incision (Gresswell, 1964<ref name="Gresswell 1964"></ref>; Howell, 1973<ref name="Howell 1973"></ref>). Buried valleys produced by subglacial meltwater incision are commonly called tunnel valleys (or tunnel channels in North America) and occur widely around former glacier margins (Ó Cofaigh, 1996<ref name="Ó Cofaigh 1996">Ó COFAIGH, C. 1996. Tunnel valley genesis. ''Progress in Physical Geography'', Vol. 20, 1–19. </ref>; Piotrowski, 1997<ref name="Piotrowski 1997">KRISTENSEN, T B, PIOTROWSKI, J A, HUUSE, M, CLAUSEN, O R, and HAMBERG, L. 2008. Time‐transgressive tunnel valley formation indicated by infill sediment structure, North Sea — The role of glaciohydraulic supercooling. ''Earth Surface Processes and Landforms'', Vol. 33, 546–559. </ref>; Dürst Stucki ''et al''., 2010<ref name="Dürst 2010">DÜRST STUCKI, M, REBER, R, and SCHLUNEGGER, F. 2010. Subglacial tunnel valleys in the Alpine foreland: an example from Bern, Switzerland. ''Swiss Journal of Geosciences'', Vol. 103, 363–374. </ref>; Kehew ''et al''., 2012<ref name="Kehew 2012">KEHEW, A E, PIOTROWSKI, J A, and JØRGENSEN, F. 2012. Tunnel valleys: Concepts and controversies — A review. ''Earth‐Science Reviews'', Vol. 113, 33–58.</ref>). Incision of tunnel valleys occurs under immense hydraulic gradients with flow regimes constrained by channel morphology and the thickness of overlying ice. A common characteristic of tunnel valleys is that their bases (referred to as the thalweg) are often undulating with significant normal and reverse changes in gradient developed along their long‐profile. Infills to buried valleys tend to be highly‐chaotic encompassing intercalated beds of till, glaciolacustrine (silt and clay) and glaciofluvial (sand and gravel) sediment that typically give‐rise to chaotic and unpredictable hydrogeological behaviour.

	The rockhead surface model provides a valuable insight into the nature of the rockhead surface beneath the study area. However, it only provides a generalisation of the rockhead surface with local variation also influenced by relative borehole density. The model shows a radial arrangement of buried valleys fanning outwards from the Liverpool‐Skelmersdale area southwards and eastwards beneath the Cheshire/north Shropshire lowlands (Figure 4.1). The radial pattern conforms to the geometry of the hydraulic gradient that would generate perpendicular to the margins of a piedmont‐style glacier lobe that fanned outwards across the Cheshire lowlands towards the west, south and east. This style of glacier geometry has previously been inferred for the Late Devensian ice lobe based upon the mapped distribution morainic landforms around the region (Boulton and Worsley, 1965<ref name="Boulton 1965">BOULTON, G, and WORSLEY, P. 1965. Late Weichselian glaciation in the Cheshire‐Shropshire basin. ''Nature'', Vol. 207, 704–706.</ref>; Yates, 1967<ref name="Yates 1967">YATES, E. 1967. A contribution to the glacial geomorphology of the Cheshire Plain. ''Transactions of the Institute of British Geographers'', 107–125.</ref>; Thomas, 1989<ref name="Thomas 1989"></ref>).		The rockhead surface model provides a valuable insight into the nature of the rockhead surface beneath the study area. However, it only provides a generalisation of the rockhead surface with local variation also influenced by relative borehole density. The model shows a radial arrangement of buried valleys fanning outwards from the Liverpool‐Skelmersdale area southwards and eastwards beneath the Cheshire/north Shropshire lowlands (Figure 4.1). The radial pattern conforms to the geometry of the hydraulic gradient that would generate perpendicular to the margins of a piedmont‐style glacier lobe that fanned outwards across the Cheshire lowlands towards the west, south and east. This style of glacier geometry has previously been inferred for the Late Devensian ice lobe based upon the mapped distribution morainic landforms around the region (Boulton and Worsley, 1965<ref name="Boulton 1965">BOULTON, G, and WORSLEY, P. 1965. Late Weichselian glaciation in the Cheshire‐Shropshire basin. ''Nature'', Vol. 207, 704–706.</ref>; Yates, 1967<ref name="Yates 1967">YATES, E. 1967. A contribution to the glacial geomorphology of the Cheshire Plain. ''Transactions of the Institute of British Geographers'', 107–125.</ref>; Thomas, 1989<ref name="Thomas 1989"></ref>).

Ajhil: /* Sea‐level change */

2019-12-03T14:26:56Z

Sea‐level change

← Older revision		Revision as of 15:26, 3 December 2019
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	Following the retreat and melting of the glaciers at the end of the Late Devensian glaciation global sea‐levels rose drowning previously exposed (and glaciated) areas of continental shelf and basinal areas including the Irish Sea. Immediately following deglaciation, a new drainage system became established including the River Mersey with a major period of sedimentation and stabilisation during the early Holocene (c.9,600–8,000 yrs BP) (Tooley, 1974<ref name="Tooley 1974">TOOLEY, M J. 1974. Sea‐level changes during the last 9000 years in north‐west England. ''Geographical Journal'', 18–42. </ref>; Macklin ''et al''., 2010<ref name="Macklin 2010">MACKLIN, M G, JONES, A F, and LEWIN, J. 2010. River response to rapid Holocene environmental change: evidence and explanation in British catchments. ''Quaternary Science Reviews'', Vol. 29, 1555–1576. </ref>; Roberts ''et al''., 2011<ref name="Roberts 2011">ROBERTS, M J, SCOURSE, J D, BENNELL, J D, HUWS, D G, JAGO, C F, and LONG, B T. 2011. Late Devensian and Holocene relative sea‐level change in North Wales, UK. ''Journal of Quaternary Science'', Vol. 26, 141–155. </ref>). Continued sea‐level rise during the Holocene is likely to have resulted in the transition from terrestrial (fluvial?) to estuarine (proximal) and finally estuarine (distal) as continued sedimentation led to emergence of the coastal plain. Regional sea‐level rise around the Mersey Estuary is ‘very likely’ to have led to saline groundwater incursion into the SSG depending on the hydraulic connectivity between the bedrock, overlying superficial deposits and seabed.		Following the retreat and melting of the glaciers at the end of the Late Devensian glaciation global sea‐levels rose drowning previously exposed (and glaciated) areas of continental shelf and basinal areas including the Irish Sea. Immediately following deglaciation, a new drainage system became established including the River Mersey with a major period of sedimentation and stabilisation during the early Holocene (c.9,600–8,000 yrs BP) (Tooley, 1974<ref name="Tooley 1974">TOOLEY, M J. 1974. Sea‐level changes during the last 9000 years in north‐west England. ''Geographical Journal'', 18–42. </ref>; Macklin ''et al''., 2010<ref name="Macklin 2010">MACKLIN, M G, JONES, A F, and LEWIN, J. 2010. River response to rapid Holocene environmental change: evidence and explanation in British catchments. ''Quaternary Science Reviews'', Vol. 29, 1555–1576. </ref>; Roberts ''et al''., 2011<ref name="Roberts 2011">ROBERTS, M J, SCOURSE, J D, BENNELL, J D, HUWS, D G, JAGO, C F, and LONG, B T. 2011. Late Devensian and Holocene relative sea‐level change in North Wales, UK. ''Journal of Quaternary Science'', Vol. 26, 141–155. </ref>). Continued sea‐level rise during the Holocene is likely to have resulted in the transition from terrestrial (fluvial?) to estuarine (proximal) and finally estuarine (distal) as continued sedimentation led to emergence of the coastal plain. Regional sea‐level rise around the Mersey Estuary is ‘very likely’ to have led to saline groundwater incursion into the SSG depending on the hydraulic connectivity between the bedrock, overlying superficial deposits and seabed.

	Additional geological features that may occur beneath the Cheshire Energy Research Field Site are aeolian sediments and inter‐stratified peat horizons. Aeolian activity adjacent to the Irish Sea Basin was widespread following the end of the last glaciation because of the high‐availability of suitable sediment (pre‐existing glacifluvial deposits) and the prevailing climatic conditions (Wilson ''et al''., 1981<ref name="Wilson 1981">WILSON, P, BATEMAN, R M, and CATT, J A. 1981. Petrography, origin and environment of deposition of the Shirdley Hill Sand of southwest Lancashire, England. ''Proceedings of the Geologists' Association'', Vol. 92, 211–229.</ref>). Extensive sand dune systems are present in coastal areas of Cheshire and Lancashire (Gresswell, 1937<ref name="Gresswell 1937">GRESSWELL, R K. 1937. The geomorphology of the south‐west Lancashire coast‐line. ''Geographical Journal'', 335–349. </ref>; Pye and Neal, 1994<ref name="Pye 1994">PYE, K, and NEAL, A. 1994. Coastal dune erosion at Formby Point, north Merseyside, England: causes and mechanisms. ''Marine Geology'', Vol. 119, 39–56. </ref>), North Wales and Anglesey (Greenly, 1919<ref name="Greenly 1919">GREENLY, E. 1919. ''The Geology of Anglesey, Memoirs of the Geological Survey of Great Britain''. (HMSO, London.) </ref>; Ranwell, 1959<ref name="Ranwell 1959">RANWELL, D. 1959. Newborough Warren, Anglesey: I. The dune system and dune slack habitat. ''The Journal of Ecology'', 571–601. </ref>; Bailey and Bristow, 2004<ref name="Bailey 2004">BAILEY, S, and BRISTOW, C. 2004. Migration of parabolic dunes at Aberffraw, Anglesey, north Wales. ''Geomorphology'', Vol. 59, 165–174. </ref>) and an aeolian coversand (the Shirley Hill Sand Formation) has also been recognised in parts of the region (Wilson ''et al''., 1981<ref name="Wilson 1981">WILSON, P, BATEMAN, R M, and CATT, J A. 1981. Petrography, origin and environment of deposition of the Shirdley Hill Sand of southwest Lancashire, England. ''Proceedings of the Geologists' Association'', Vol. 92, 211–229.</ref>; Howard ''et al.'', 2007<ref name="Howard 2007">		Additional geological features that may occur beneath the Cheshire Energy Research Field Site are aeolian sediments and inter‐stratified peat horizons. Aeolian activity adjacent to the Irish Sea Basin was widespread following the end of the last glaciation because of the high‐availability of suitable sediment (pre‐existing glacifluvial deposits) and the prevailing climatic conditions (Wilson ''et al''., 1981<ref name="Wilson 1981">WILSON, P, BATEMAN, R M, and CATT, J A. 1981. Petrography, origin and environment of deposition of the Shirdley Hill Sand of southwest Lancashire, England. ''Proceedings of the Geologists' Association'', Vol. 92, 211–229.</ref>). Extensive sand dune systems are present in coastal areas of Cheshire and Lancashire (Gresswell, 1937<ref name="Gresswell 1937">GRESSWELL, R K. 1937. The geomorphology of the south‐west Lancashire coast‐line. ''Geographical Journal'', 335–349.</ref>; Pye and Neal, 1994<ref name="Pye 1994">PYE, K, and NEAL, A. 1994. Coastal dune erosion at Formby Point, north Merseyside, England: causes and mechanisms. ''Marine Geology'', Vol. 119, 39–56.</ref>), North Wales and Anglesey (Greenly, 1919<ref name="Greenly 1919">GREENLY, E. 1919. ''The Geology of Anglesey, Memoirs of the Geological Survey of Great Britain''. (HMSO, London.)</ref>; Ranwell, 1959<ref name="Ranwell 1959">RANWELL, D. 1959. Newborough Warren, Anglesey: I. The dune system and dune slack habitat. ''The Journal of Ecology'', 571–601.</ref>; Bailey and Bristow, 2004<ref name="Bailey 2004">BAILEY, S, and BRISTOW, C. 2004. Migration of parabolic dunes at Aberffraw, Anglesey, north Wales. ''Geomorphology'', Vol. 59, 165–174. </ref>) and an aeolian coversand (the Shirley Hill Sand Formation) has also been recognised in parts of the region (Wilson ''et al''., 1981<ref name="Wilson 1981">WILSON, P, BATEMAN, R M, and CATT, J A. 1981. Petrography, origin and environment of deposition of the Shirdley Hill Sand of southwest Lancashire, England. ''Proceedings of the Geologists' Association'', Vol. 92, 211–229.</ref>; Howard ''et al.'', 2007<ref name="Howard 2007"></ref>). Commonly associated with coversand and dune systems are thin discontinuous horizons or beds of peat. These typically form as thin immature soils or peat development within localised poorly‐drained inter‐dune areas. The presence of aeolian deposits of variable thickness beneath the study area, including sand (coversand) or loess (silt), is ‘about as likely as not’. Accumulations of peat have also been identified offshore of the Wirral (Innes et al., 1990<ref name="Innes 1990">INNES, J B, BEDLINGTON, D J, KENNA, R J B, and COWELL, R W. 1990. A preliminary investigation of coastal deposits at Newton Carr, Wirral, Merseyside. ''Quaternary Newsletter'', 62, 5–13.</ref>; Kenna, 1986<ref name="Kenna 1986">KENNA, R J B. 1986. The Flandrian sequence of north Wiral (NW England). ''Geological Journal'', Vol. 21 pt. 1, 1–27.</ref>) and some of these may be contemporaneous with peat units identified by Burke et al. (2016) within coastal deposits. Peats can acts as local aquitards and give rise to compressible ground conditions when loaded. Their presence within coastal deposits is ‘very likely’.

	HOWARD, A S, HOUGH, E, CROFTS, R G, REEVES, H J, and EVANS, D J. 2007. ''Geology of the Liverpool district — a brief explanation of the geological map''. (1:50 000 Sheet 96 Liverpool (England and Wales): Sheet Explanation of the British Geological Survey.): Nottingham, British Geological Survey.</ref>). Commonly associated with coversand and dune systems are thin discontinuous horizons or beds of peat. These typically form as thin immature soils or peat development within localised poorly‐drained inter‐dune areas. The presence of aeolian deposits of variable thickness beneath the study area, including sand (coversand) or loess (silt), is ‘about as likely as not’. Accumulations of peat have also been identified offshore of the Wirral (Innes et al., 1990<ref name="Innes 1990">INNES, J B, BEDLINGTON, D J, KENNA, R J B, and COWELL, R W. 1990. A preliminary investigation of coastal deposits at Newton Carr, Wirral, Merseyside. ''Quaternary Newsletter'', 62, 5–13.</ref>; Kenna, 1986<ref name="Kenna 1986">KENNA, R J B. 1986. The Flandrian sequence of north Wiral (NW England). ''Geological Journal'', Vol. 21 pt. 1, 1–27.</ref>) and some of these may be contemporaneous with peat units identified by Burke et al. (2016) within coastal deposits. Peats can acts as local aquitards and give rise to compressible ground conditions when loaded. Their presence within coastal deposits is ‘very likely’.

	==Conceptual geological model of the study area==		==Conceptual geological model of the study area==

Ajhil at 14:26, 3 December 2019

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	The consensus within the literature is that these buried valleys were produced by glacial over‐deepening (subglacial erosion) and/or subglacial meltwater incision (Gresswell, 1964<ref name="Gresswell 1964">GRESSWELL, R K. 1964. The origin of the Mersey and Dee Estuaries. ''Geological Journal'', Vol. 4, 77–86.</ref>; Howell, 1973<ref name="Howell 1973"></ref>). Buried valleys produced by subglacial meltwater incision are commonly called tunnel valleys (or tunnel channels in North America) and occur widely around former glacier margins (Ó Cofaigh, 1996<ref name="Ó Cofaigh 1996">Ó COFAIGH, C. 1996. Tunnel valley genesis. ''Progress in Physical Geography'', Vol. 20, 1–19. </ref>; Piotrowski, 1997<ref name="Piotrowski 1997">KRISTENSEN, T B, PIOTROWSKI, J A, HUUSE, M, CLAUSEN, O R, and HAMBERG, L. 2008. Time‐transgressive tunnel valley formation indicated by infill sediment structure, North Sea — The role of glaciohydraulic supercooling. ''Earth Surface Processes and Landforms'', Vol. 33, 546–559. </ref>; Dürst Stucki ''et al''., 2010<ref name="Dürst 2010">DÜRST STUCKI, M, REBER, R, and SCHLUNEGGER, F. 2010. Subglacial tunnel valleys in the Alpine foreland: an example from Bern, Switzerland. ''Swiss Journal of Geosciences'', Vol. 103, 363–374. </ref>; Kehew ''et al''., 2012<ref name="Kehew 2012">KEHEW, A E, PIOTROWSKI, J A, and JØRGENSEN, F. 2012. Tunnel valleys: Concepts and controversies — A review. ''Earth‐Science Reviews'', Vol. 113, 33–58.</ref>). Incision of tunnel valleys occurs under immense hydraulic gradients with flow regimes constrained by channel morphology and the thickness of overlying ice. A common characteristic of tunnel valleys is that their bases (referred to as the thalweg) are often undulating with significant normal and reverse changes in gradient developed along their long‐profile. Infills to buried valleys tend to be highly‐chaotic encompassing intercalated beds of till, glaciolacustrine (silt and clay) and glaciofluvial (sand and gravel) sediment that typically give‐rise to chaotic and unpredictable hydrogeological behaviour.		The consensus within the literature is that these buried valleys were produced by glacial over‐deepening (subglacial erosion) and/or subglacial meltwater incision (Gresswell, 1964<ref name="Gresswell 1964">GRESSWELL, R K. 1964. The origin of the Mersey and Dee Estuaries. ''Geological Journal'', Vol. 4, 77–86.</ref>; Howell, 1973<ref name="Howell 1973"></ref>). Buried valleys produced by subglacial meltwater incision are commonly called tunnel valleys (or tunnel channels in North America) and occur widely around former glacier margins (Ó Cofaigh, 1996<ref name="Ó Cofaigh 1996">Ó COFAIGH, C. 1996. Tunnel valley genesis. ''Progress in Physical Geography'', Vol. 20, 1–19. </ref>; Piotrowski, 1997<ref name="Piotrowski 1997">KRISTENSEN, T B, PIOTROWSKI, J A, HUUSE, M, CLAUSEN, O R, and HAMBERG, L. 2008. Time‐transgressive tunnel valley formation indicated by infill sediment structure, North Sea — The role of glaciohydraulic supercooling. ''Earth Surface Processes and Landforms'', Vol. 33, 546–559. </ref>; Dürst Stucki ''et al''., 2010<ref name="Dürst 2010">DÜRST STUCKI, M, REBER, R, and SCHLUNEGGER, F. 2010. Subglacial tunnel valleys in the Alpine foreland: an example from Bern, Switzerland. ''Swiss Journal of Geosciences'', Vol. 103, 363–374. </ref>; Kehew ''et al''., 2012<ref name="Kehew 2012">KEHEW, A E, PIOTROWSKI, J A, and JØRGENSEN, F. 2012. Tunnel valleys: Concepts and controversies — A review. ''Earth‐Science Reviews'', Vol. 113, 33–58.</ref>). Incision of tunnel valleys occurs under immense hydraulic gradients with flow regimes constrained by channel morphology and the thickness of overlying ice. A common characteristic of tunnel valleys is that their bases (referred to as the thalweg) are often undulating with significant normal and reverse changes in gradient developed along their long‐profile. Infills to buried valleys tend to be highly‐chaotic encompassing intercalated beds of till, glaciolacustrine (silt and clay) and glaciofluvial (sand and gravel) sediment that typically give‐rise to chaotic and unpredictable hydrogeological behaviour.

	The rockhead surface model provides a valuable insight into the nature of the rockhead surface beneath the study area. However, it only provides a generalisation of the rockhead surface with local variation also influenced by relative borehole density. The model shows a radial arrangement of buried valleys fanning outwards from the Liverpool‐Skelmersdale area southwards and eastwards beneath the Cheshire/north Shropshire lowlands (Figure 4.1). The radial pattern conforms to the geometry of the hydraulic gradient that would generate perpendicular to the margins of a piedmont‐style glacier lobe that fanned outwards across the Cheshire lowlands towards the west, south and east. This style of glacier geometry has previously been inferred for the Late Devensian ice lobe based upon the mapped distribution morainic landforms around the region (Boulton and Worsley, 1965<ref name="Boulton 1965">BOULTON, G, and WORSLEY, P. 1965. Late Weichselian glaciation in the Cheshire‐Shropshire basin. ''Nature'', Vol. 207, 704–706.</ref>; Yates, 1967<ref name="Yates 1967">YATES, E. 1967. A contribution to the glacial geomorphology of the Cheshire Plain. ''Transactions of the Institute of British Geographers'', 107–125.</ref>; Thomas, 1989<ref name="Thomas 1989">~~THOMAS, G S P. 1989. The Late Devensian glaciation along the western margin of the Cheshire‐ Shroshire Iowland. ''Journal of Quaternary Science'', Vol. 4, 167–181.~~</ref>).		The rockhead surface model provides a valuable insight into the nature of the rockhead surface beneath the study area. However, it only provides a generalisation of the rockhead surface with local variation also influenced by relative borehole density. The model shows a radial arrangement of buried valleys fanning outwards from the Liverpool‐Skelmersdale area southwards and eastwards beneath the Cheshire/north Shropshire lowlands (Figure 4.1). The radial pattern conforms to the geometry of the hydraulic gradient that would generate perpendicular to the margins of a piedmont‐style glacier lobe that fanned outwards across the Cheshire lowlands towards the west, south and east. This style of glacier geometry has previously been inferred for the Late Devensian ice lobe based upon the mapped distribution morainic landforms around the region (Boulton and Worsley, 1965<ref name="Boulton 1965">BOULTON, G, and WORSLEY, P. 1965. Late Weichselian glaciation in the Cheshire‐Shropshire basin. ''Nature'', Vol. 207, 704–706.</ref>; Yates, 1967<ref name="Yates 1967">YATES, E. 1967. A contribution to the glacial geomorphology of the Cheshire Plain. ''Transactions of the Institute of British Geographers'', 107–125.</ref>; Thomas, 1989<ref name="Thomas 1989"></ref>).

	Whilst a glacial origin for several of the larger buried channels is logical, some channels may have existed in the landscape prior to the Late Devensian glaciation and originally be of fluvial origin. For example, Worsley ''et al''. (1983)<ref name="Worsley 1983">WORSLEY, P, COOPE, G R, GOOD, T R, HOLYOAK, D T,and ROBINSON, J E. 1983. A Pleistocene succession from beneath Chelford Sands at Oakwood Quarry, Chelford, Cheshire. ''Geological Journal'', Vol. 18, 307–324. </ref> describes a buried channel that contains preglacial organic sediments overlain by glacial till and meltwater sediments. Of particular relevance to the study area is the existence of a major buried channel beneath the modern River Mersey (Figure 4.2). Small, broadly north‐south trending offshoots of this buried valley occur to the west and east of Thornton‐le‐Moors. However, the resolution of the rockhead model mean that the true geometry of these buried valleys remains poorly constrained. Therefore, the presence of a buried valley beneath the Cheshire Energy Research Field Site is ‘about as likely as not’ ([[OR/17/042 Methodology#Table 2.1\|Table 2.1]]). Local perturbations in the rockhead surface up to 47 m below OD, some likely associated with buried channels, have been identified to the east of the village of Elton, beneath Ince Marshes and are described by Burke ''et al''. (2016)<ref name="Burke 2016"></ref>.		Whilst a glacial origin for several of the larger buried channels is logical, some channels may have existed in the landscape prior to the Late Devensian glaciation and originally be of fluvial origin. For example, Worsley ''et al''. (1983)<ref name="Worsley 1983">WORSLEY, P, COOPE, G R, GOOD, T R, HOLYOAK, D T,and ROBINSON, J E. 1983. A Pleistocene succession from beneath Chelford Sands at Oakwood Quarry, Chelford, Cheshire. ''Geological Journal'', Vol. 18, 307–324. </ref> describes a buried channel that contains preglacial organic sediments overlain by glacial till and meltwater sediments. Of particular relevance to the study area is the existence of a major buried channel beneath the modern River Mersey (Figure 4.2). Small, broadly north‐south trending offshoots of this buried valley occur to the west and east of Thornton‐le‐Moors. However, the resolution of the rockhead model mean that the true geometry of these buried valleys remains poorly constrained. Therefore, the presence of a buried valley beneath the Cheshire Energy Research Field Site is ‘about as likely as not’ ([[OR/17/042 Methodology#Table 2.1\|Table 2.1]]). Local perturbations in the rockhead surface up to 47 m below OD, some likely associated with buried channels, have been identified to the east of the village of Elton, beneath Ince Marshes and are described by Burke ''et al''. (2016)<ref name="Burke 2016"></ref>.

Ajhil: /* Cenozoic weathering */

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Cenozoic weathering

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	The bedrock geology beneath the study area is likely to have been subaerially exposed for several millions of years during the Cenozoic — possibly for much of the Neogene extending back in time to the Palaeogene. This restriction on ‘accommodation space’ limited where sediments could be deposited and critically their preservation. Palaeogene deposits occur discontinuously across southern East Anglia, the Thames Valley and southern England (Gale ''et al''., 2006<ref name="Gale 2006">GALE, A S, HUGGETT, H, PALIKE, E, LAURIE, E, HAILWOOD, E A, and HARDEBOL, N. 2006. Correlation of Eocene–Oligocene marine and continental records: orbital cyclicity, magnetostratigraphy and sequence stratigraphy of the Solent Group, Isle of Wight, UK. ''Journal of the Geological Society'', Vol. 163, 401–415. </ref>). Collectively, these support global records (Figure 3.3; Zachos ''et al''., 2001<ref name="Zachos 2001">ZACHOS, J C, PAGANI, M, SLOAN, L, THOMAS, E, and BILLIPS, K. 2001. Trends, Rhythms and Aberrations in Global Climate 65 Ma to Present. ''Science'', Vol. 27, 686–693.</ref>, 2008<ref name="Zachos 2008">ZACHOS, J C, DICKENS, G R, and ZEEBE, R E, 2008. An early Cenozoic perspective on greenhouse warming and carbon‐cycle dynamics. ''Nature'', Vol. 451, 279–283.</ref>) in demonstrating that so‐called ‘greenhouse climates’ dominated and were generally much warmer and wetter than during later parts of the Cenozoic with several pronounced climatic optima (Westerhold et al., 2009<ref name="Westerhold 2009">WESTERHOLD, T, RÖHL, U, MCCARREN, H K, and ZACHOS, J C. 2009. Latest on the absolute age of the Paleocene–Eocene Thermal Maximum (PETM): New insights from exact stratigraphic position of key ash layers + 19 and -17. ''Earth and Planetary Science Letters'', Vol. 287, 412–419.</ref>) and cooling events (Hooker ''et al''., 2004<ref name="Hooker 2004">HOOKER, J J, COLLINSON, M E, and SILLE, N P. 2004. Eocene–Oligocene mammalian faunal turnover in the Hampshire Basin, UK: calibration to the global time scale and the major cooling event. ''Journal of the Geological Society'', Vol. 161, 161–172.</ref>). Limited geological evidence exists for the Neogene within the UK. Heavily‐degraded Miocene deposits crop‐out within the Peak District and reveal a transition from sub‐tropical, seasonally wet conifer‐dominated forest to sub‐tropical mixed forest (Pound and Riding, 2016<ref name="Pound 2016">POUND, M J, and RIDING, J B, 2016. Palaeoenvironment, palaeoclimate and age of the Brassington Formation (Miocene) of Derbyshire, UK. ''Journal of the Geological Society of London'', Vol. 173, 306–319.</ref>). Pliocene‐age deposits occur principally in southern East Anglia and whilst deposited against a backdrop of progressive global cooling are still considered to reflect climates that were probably warmer than the present day (Haywood ''et al''., 2000<ref name="Haywood 2000">HAYWOOD, A, SELLWOOD, B, and VALDES, P. 2000. Regional warming: Pliocene (3 Ma) paleoclimate of Europe and the Mediterranean. ''Geology'', Vol. 28, 1063–1066.</ref>; Johnson et al., 2000<ref name="Johnson 2000">JOHNSON, A L A, HICKSON, J A, SWAN, J, BROWN, M R, HEATON, T H E, CHENERY, S, and BALSON, P S. 2000. The queen scallop ''Aequipecten opercularis'': a new source of information on Late Cenozoic marine environments in Europe. 425–439 in ''The evolutionary biology of the Bivalve''. HARPER, E M, TAYLOR, J D, and CRAME, J A. (editors). (London: Geological Society). </ref>; Williams et al., 2009<ref name="Williams 2009">WILLIAMS, M, HAYWOOD, A M, HARPER, E M, JOHNSON, A L A, KNOWLES, T, LENG, M J, LUNT, D J, OKAMURA, B, TAYLOR, P D, and ZALASIEWICZ, J. 2009. Pliocene climate and seasonality in North Atlantic shelf seas. ''Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences'', Vol. 367, 85–108.</ref>). Collectively, the prevailing tropical to temperate climatic conditions that prevailed during the Palaeogene and Neogene would have led to enhanced rates of chemical (e.g. saline water incursion, groundwater dissolution, soil development) and biological (e.g. root penetration, organisms) weathering (Huggett, 2011<ref name="Huggett 2011">Hugget, R J. 2011. ''Fundamentals of Geomorphology, Third Edition''. Routledge Fundamentals of Physical Science, New York.</ref>).		The bedrock geology beneath the study area is likely to have been subaerially exposed for several millions of years during the Cenozoic — possibly for much of the Neogene extending back in time to the Palaeogene. This restriction on ‘accommodation space’ limited where sediments could be deposited and critically their preservation. Palaeogene deposits occur discontinuously across southern East Anglia, the Thames Valley and southern England (Gale ''et al''., 2006<ref name="Gale 2006">GALE, A S, HUGGETT, H, PALIKE, E, LAURIE, E, HAILWOOD, E A, and HARDEBOL, N. 2006. Correlation of Eocene–Oligocene marine and continental records: orbital cyclicity, magnetostratigraphy and sequence stratigraphy of the Solent Group, Isle of Wight, UK. ''Journal of the Geological Society'', Vol. 163, 401–415. </ref>). Collectively, these support global records (Figure 3.3; Zachos ''et al''., 2001<ref name="Zachos 2001">ZACHOS, J C, PAGANI, M, SLOAN, L, THOMAS, E, and BILLIPS, K. 2001. Trends, Rhythms and Aberrations in Global Climate 65 Ma to Present. ''Science'', Vol. 27, 686–693.</ref>, 2008<ref name="Zachos 2008">ZACHOS, J C, DICKENS, G R, and ZEEBE, R E, 2008. An early Cenozoic perspective on greenhouse warming and carbon‐cycle dynamics. ''Nature'', Vol. 451, 279–283.</ref>) in demonstrating that so‐called ‘greenhouse climates’ dominated and were generally much warmer and wetter than during later parts of the Cenozoic with several pronounced climatic optima (Westerhold et al., 2009<ref name="Westerhold 2009">WESTERHOLD, T, RÖHL, U, MCCARREN, H K, and ZACHOS, J C. 2009. Latest on the absolute age of the Paleocene–Eocene Thermal Maximum (PETM): New insights from exact stratigraphic position of key ash layers + 19 and -17. ''Earth and Planetary Science Letters'', Vol. 287, 412–419.</ref>) and cooling events (Hooker ''et al''., 2004<ref name="Hooker 2004">HOOKER, J J, COLLINSON, M E, and SILLE, N P. 2004. Eocene–Oligocene mammalian faunal turnover in the Hampshire Basin, UK: calibration to the global time scale and the major cooling event. ''Journal of the Geological Society'', Vol. 161, 161–172.</ref>). Limited geological evidence exists for the Neogene within the UK. Heavily‐degraded Miocene deposits crop‐out within the Peak District and reveal a transition from sub‐tropical, seasonally wet conifer‐dominated forest to sub‐tropical mixed forest (Pound and Riding, 2016<ref name="Pound 2016">POUND, M J, and RIDING, J B, 2016. Palaeoenvironment, palaeoclimate and age of the Brassington Formation (Miocene) of Derbyshire, UK. ''Journal of the Geological Society of London'', Vol. 173, 306–319.</ref>). Pliocene‐age deposits occur principally in southern East Anglia and whilst deposited against a backdrop of progressive global cooling are still considered to reflect climates that were probably warmer than the present day (Haywood ''et al''., 2000<ref name="Haywood 2000">HAYWOOD, A, SELLWOOD, B, and VALDES, P. 2000. Regional warming: Pliocene (3 Ma) paleoclimate of Europe and the Mediterranean. ''Geology'', Vol. 28, 1063–1066.</ref>; Johnson et al., 2000<ref name="Johnson 2000">JOHNSON, A L A, HICKSON, J A, SWAN, J, BROWN, M R, HEATON, T H E, CHENERY, S, and BALSON, P S. 2000. The queen scallop ''Aequipecten opercularis'': a new source of information on Late Cenozoic marine environments in Europe. 425–439 in ''The evolutionary biology of the Bivalve''. HARPER, E M, TAYLOR, J D, and CRAME, J A. (editors). (London: Geological Society). </ref>; Williams et al., 2009<ref name="Williams 2009">WILLIAMS, M, HAYWOOD, A M, HARPER, E M, JOHNSON, A L A, KNOWLES, T, LENG, M J, LUNT, D J, OKAMURA, B, TAYLOR, P D, and ZALASIEWICZ, J. 2009. Pliocene climate and seasonality in North Atlantic shelf seas. ''Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences'', Vol. 367, 85–108.</ref>). Collectively, the prevailing tropical to temperate climatic conditions that prevailed during the Palaeogene and Neogene would have led to enhanced rates of chemical (e.g. saline water incursion, groundwater dissolution, soil development) and biological (e.g. root penetration, organisms) weathering (Huggett, 2011<ref name="Huggett 2011">Hugget, R J. 2011. ''Fundamentals of Geomorphology, Third Edition''. Routledge Fundamentals of Physical Science, New York.</ref>).

	During the Quaternary, the prevailing climate changed significantly with a progressive intensification of the global climate signal and development of regular cold (‘glacial stages’) and warm (‘interglacial stages’) climatic cycles. Within the Early Pleistocene (c.2.58–1.2 Ma), major climate changes occurred with moderate frequency (approximately every 41 000 years) but their magnitude and influence on geological systems was relatively modest (Rose, 2010<ref name="Rose 2010">ROSE, J. 2010. The Quaternary of the British Isles: factors forcing environmental change. ''Journal of Quaternary Science'', Vol. 25, 399–418. </ref>). Thus, whilst chemical and biological weathering was still active they were by no means the dominant geological agents. A globally‐recognised interval, referred to as the Mid‐Pleistocene Transition (1.2–0.6 Ma), records the amplification of glacial‐interglacial cyclicity and switch to high‐magnitude and low‐frequency (approximately every 100 000 years) climatic oscillations. These acted to drive regular switches between extreme climatic regimes even in mid‐latitude regions like Britain. During the optima of several interglacial events for example, palaeontological evidence demonstrate the presence of Mediterranean‐style climates (i.e. high seasonal soil‐moisture deficit) within Southern and Central Britain (Candy ''et al''., 2010<ref name="Candy 2010">CANDY, I, COOPE, G, LEE, J, PARFITT, S, PREECE, R, ROSE, J, and SCHREVE, D. 2010. Pronounced warmth during early Middle Pleistocene interglacials: Investigating the Mid‐Brunhes Event in the British terrestrial sequence. ''Earth‐Science Reviews'', Vol. 103, 183–196. </ref>; Schreve and Candy, 2010<ref name="Schreve 2010">SCHREVE, D, and CANDY, I. 2010. Interglacial climates: Advances in our understanding of warm climate episodes. ''Progress in Physical Geography'', Vol. 34, 845–856. </ref>). Geological evidence for temperate climate weathering includes the development of a range of soil types and chemical precipitates such as iron‐pan and calcrete (Weil ''et al''., 2016<ref name="Weil 2016">WEIL, R R, and BRADY, N C. 2016. ''The Nature and Properties of Soils, Fifteenth Edition''. Pearson: Columbus.</ref>). By contrast, colder climates within Britain have supported the repeated development of permafrost (ground that occurs beneath the 0°c isotherm for over 2 years) and periglacial processes (Boardman, 2011<ref name="Boardman 2011">BOARDMAN, J E. 2011. ''Periglacial processes and landforms in Britain and Ireland''. (Cambridge: Cambridge University Press.) ISBN 0521169127</ref>; Busby ''et al''., 2015<ref name="Busby 2015">BUSBY, J P, LEE, J R, KENDER, S, WILLIAMSON, P, and NORRIS, S. 2015. Regional modelling of permafrost thicknesses over the past 130 ka: implications for permafrost development in Great Britain. ''Boreas'', Vol. 45, 45–60.</ref>). Simple conductive air‐ground heat exchange modelling has demonstrated that permafrost thicknesses during the past 130 ka have within major cold stages exceeded over 100 metres depth (Busby ''et al''., 2015<ref name="Busby 2015"></ref>). The combined effect of these warm‐ and cold‐climate processes has, over the past one million years, led to dramatic increases in the mechanical (e.g. freeze‐thaw, frost action), chemical (e.g. salt water incursion, groundwater dissolution, soil development) and biological weathering (e.g. root penetration, organisms) of materials exposed at or near to the surface (Rose, 2010<ref name="Rose 2010">~~ROSE, J. 2010. The Quaternary of the British Isles: factors forcing environmental change. ''Journal of Quaternary Science'', Vol. 25, 399–418.~~</ref>).		During the Quaternary, the prevailing climate changed significantly with a progressive intensification of the global climate signal and development of regular cold (‘glacial stages’) and warm (‘interglacial stages’) climatic cycles. Within the Early Pleistocene (c.2.58–1.2 Ma), major climate changes occurred with moderate frequency (approximately every 41 000 years) but their magnitude and influence on geological systems was relatively modest (Rose, 2010<ref name="Rose 2010">ROSE, J. 2010. The Quaternary of the British Isles: factors forcing environmental change. ''Journal of Quaternary Science'', Vol. 25, 399–418. </ref>). Thus, whilst chemical and biological weathering was still active they were by no means the dominant geological agents. A globally‐recognised interval, referred to as the Mid‐Pleistocene Transition (1.2–0.6 Ma), records the amplification of glacial‐interglacial cyclicity and switch to high‐magnitude and low‐frequency (approximately every 100 000 years) climatic oscillations. These acted to drive regular switches between extreme climatic regimes even in mid‐latitude regions like Britain. During the optima of several interglacial events for example, palaeontological evidence demonstrate the presence of Mediterranean‐style climates (i.e. high seasonal soil‐moisture deficit) within Southern and Central Britain (Candy ''et al''., 2010<ref name="Candy 2010">CANDY, I, COOPE, G, LEE, J, PARFITT, S, PREECE, R, ROSE, J, and SCHREVE, D. 2010. Pronounced warmth during early Middle Pleistocene interglacials: Investigating the Mid‐Brunhes Event in the British terrestrial sequence. ''Earth‐Science Reviews'', Vol. 103, 183–196. </ref>; Schreve and Candy, 2010<ref name="Schreve 2010">SCHREVE, D, and CANDY, I. 2010. Interglacial climates: Advances in our understanding of warm climate episodes. ''Progress in Physical Geography'', Vol. 34, 845–856. </ref>). Geological evidence for temperate climate weathering includes the development of a range of soil types and chemical precipitates such as iron‐pan and calcrete (Weil ''et al''., 2016<ref name="Weil 2016">WEIL, R R, and BRADY, N C. 2016. ''The Nature and Properties of Soils, Fifteenth Edition''. Pearson: Columbus.</ref>). By contrast, colder climates within Britain have supported the repeated development of permafrost (ground that occurs beneath the 0°c isotherm for over 2 years) and periglacial processes (Boardman, 2011<ref name="Boardman 2011">BOARDMAN, J E. 2011. ''Periglacial processes and landforms in Britain and Ireland''. (Cambridge: Cambridge University Press.) ISBN 0521169127</ref>; Busby ''et al''., 2015<ref name="Busby 2015">BUSBY, J P, LEE, J R, KENDER, S, WILLIAMSON, P, and NORRIS, S. 2015. Regional modelling of permafrost thicknesses over the past 130 ka: implications for permafrost development in Great Britain. ''Boreas'', Vol. 45, 45–60.</ref>). Simple conductive air‐ground heat exchange modelling has demonstrated that permafrost thicknesses during the past 130 ka have within major cold stages exceeded over 100 metres depth (Busby ''et al''., 2015<ref name="Busby 2015"></ref>). The combined effect of these warm‐ and cold‐climate processes has, over the past one million years, led to dramatic increases in the mechanical (e.g. freeze‐thaw, frost action), chemical (e.g. salt water incursion, groundwater dissolution, soil development) and biological weathering (e.g. root penetration, organisms) of materials exposed at or near to the surface (Rose, 2010<ref name="Rose 2010"></ref>).

	Because of its lithological and textural properties, with poorly‐cemented porous and permeable units, bedding discontinuities, fractures and faults, the SSG is highly‐susceptible to '''chemical '''and '''biological weathering '''associated with glacial and post‐glacial processes and weathering (Yates, 1992<ref name="Yates 1992">YATES, P. 1992. The material strength of sandstones of the Sherwood Sandstone Group of north Staffordshire with reference to microfabric. ''Quarterly Journal of Engineering Geology and Hydrogeology'', Vol. 25, 107–113. </ref>). Indeed, a study by Mottershead ''et al''. (2003)<ref name="Mottershead 2003">MOTTERSHEAD, D, GORBUSHINA, A, LUCAS, G, and WRIGHT, J. 2003. The influence of marine salts, aspect and microbes in the weathering of sandstone in two historic structures. ''Building and environment'', Vol. 38, 1193–1204. </ref> highlights the role of chemical and biological weathering and specifically the influence of marine salt crystallisation on weathering rates. Their study concluded, for example, that the presence of marine salts resulted in the acceleration of weathering rates by a factor of 1.59 (Mottershead ''et al''., 2003<ref name="Mottershead 2003"></ref>). Thus, saline water incursion into the SSG during successive global marine high‐stands throughout the Cenozoic would have likely‐resulted in enhanced salt weathering rates (Trenhaile and Mercan, 1984<ref name="Trenhaile 1984">TRENHAILE, A, and MERCAN, D. 1984. Frost weathering and the saturation of coastal rocks. ''Earth Surface Processes and Landforms'', Vol. 9, 321–331.</ref>; Williams and Robinson, 2001<ref name="Williams 2001">WILLIAMS, R B G, and ROBINSON, D A. 2001. Experimental frost weathering of sandstone by various combinations of salts. ''Earth Surface Processes and Landforms'', Vol. 26, 811–818.</ref>). Weathering under longer‐term cold climates is likely to include carbonate dissolution (greater at lower temperatures), salt weathering and frost weathering (mechanical weathering).		Because of its lithological and textural properties, with poorly‐cemented porous and permeable units, bedding discontinuities, fractures and faults, the SSG is highly‐susceptible to '''chemical '''and '''biological weathering '''associated with glacial and post‐glacial processes and weathering (Yates, 1992<ref name="Yates 1992">YATES, P. 1992. The material strength of sandstones of the Sherwood Sandstone Group of north Staffordshire with reference to microfabric. ''Quarterly Journal of Engineering Geology and Hydrogeology'', Vol. 25, 107–113. </ref>). Indeed, a study by Mottershead ''et al''. (2003)<ref name="Mottershead 2003">MOTTERSHEAD, D, GORBUSHINA, A, LUCAS, G, and WRIGHT, J. 2003. The influence of marine salts, aspect and microbes in the weathering of sandstone in two historic structures. ''Building and environment'', Vol. 38, 1193–1204. </ref> highlights the role of chemical and biological weathering and specifically the influence of marine salt crystallisation on weathering rates. Their study concluded, for example, that the presence of marine salts resulted in the acceleration of weathering rates by a factor of 1.59 (Mottershead ''et al''., 2003<ref name="Mottershead 2003"></ref>). Thus, saline water incursion into the SSG during successive global marine high‐stands throughout the Cenozoic would have likely‐resulted in enhanced salt weathering rates (Trenhaile and Mercan, 1984<ref name="Trenhaile 1984">TRENHAILE, A, and MERCAN, D. 1984. Frost weathering and the saturation of coastal rocks. ''Earth Surface Processes and Landforms'', Vol. 9, 321–331.</ref>; Williams and Robinson, 2001<ref name="Williams 2001">WILLIAMS, R B G, and ROBINSON, D A. 2001. Experimental frost weathering of sandstone by various combinations of salts. ''Earth Surface Processes and Landforms'', Vol. 26, 811–818.</ref>). Weathering under longer‐term cold climates is likely to include carbonate dissolution (greater at lower temperatures), salt weathering and frost weathering (mechanical weathering).

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Glacitectonic structures (folds and thrusts)

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