Edward Fleming | The University of Birmingham (original) (raw)

Papers by Edward Fleming

EGU General Assembly Conference Abstracts, Apr 1, 2013

Raw carbon isotope data for construction of Figure 1 and Figure 10.

Precambrian Research, Dec 1, 2018

Journal of Glaciology, Jul 14, 2022

We assess the evolution of glaciological structures during the 2003-05 surge in the Paulabreen gl... more We assess the evolution of glaciological structures during the 2003-05 surge in the Paulabreen glacier system, Svalbard. Glaciological structures on the glacier surface were mapped using aerial photographs captured in the early stages of the surge (2003) and 5 years after surge termination (2011). Three-dimensional measurements of glaciological structures were collected at the tidewater front in 2013. These datasets document the physical changes during (1) the late quiescent phase; (2) the early phase of the surge as the surge front propagated down Skobreen and advanced into Paulabreen and (3) the final stages of the surge following the surge front reaching the glacier terminus. Crevasse patterns and clusters of arcuate shear planes record zones of compressive and extensional flow associated with the downglacier progression of the surge front. The transfer of surging ice from Skobreen into Paulabreen caused lateral displacement of the medial moraines to the northeast. At the ice front, this movement tilted glaciological structures in the same direction. Structures at the southwest margin record strike-slip faulting and the elevation of debris into the ice in a zone of compression and transpression. We summarise these observations in a schematic reconstruction of structural evolution during the surge.

EGU General Assembly Conference Abstracts, Apr 1, 2013

Journal of Glaciology, 2015

Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Lit... more Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Little Ice Age (LIA), demonstrated by prominent ice-cored moraines up to several kilometres beyond present-day margins. The majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds, indicating they are likely to have undergone a thermal transition from a polythermal to a cold-based regime. We present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of Tellbreen, a small cold-based valley glacier in central Spitsbergen, based on its basal sequence and glaciological structures. Within the basal sequence, the underlying matrix-supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed, indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former deforming layer. This is overlain by debris-poor dispersed facies ice, interpreted to have formed through strain-induced metamorphism of englacial ice. The sequential development of structures includes arcuate fracture traces, interpreted as shear planes formed in a compressive/transpressive stress regime; and fracture traces, interpreted as healed extensional crevasses. The formation of these sediment/ice facies and structures is indicative of dynamic, warm-based flow, most likely during the LIA when the glacier was significantly thicker.

Sedimentology, Feb 1, 2016

Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of longstan... more Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of longstanding debate, particularly concerning the interpretation of diamictites. The Wilsonbreen Formation of northeast Svalbard is a 130 to 180 m thick diamictite-dominated glacigenic succession deposited during a late Cryogenian (Marinoan) glaciation. Previous research has highlighted a complex sedimentary architecture with evidence of subaqueous, subglacial and non-glacial conditions. This study combines well-established sedimentological techniques with the first sedimentological application of the anisotropy of magnetic susceptibility (AMS) technique in Neoproterozoic glacial sediments, to investigate the origin and palaeoenvironmental significance of glacigenic sediments within the Wilsonbreen Formation. A range of lithofacies occurs within the succession, dominated by massive diamictites, sandstones and conglomerates. Some of these facies display evidence of primary deformation and can be grouped into a Deformed Facies Association; these are interpreted to have been formed through glacitectonic deformation in a subglacial environment. Fabric investigation reveals that this deformation was associated with glacier flow towards the north. In addition, an Undeformed Facies Association records deposition in ice-proximal Accepted Article This article is protected by copyright. All rights reserved. and ice-distal subaqueous environments. Taken together with intervening non-glacial facies, the glacigenic sediments record a series of advance-retreat cycles, with ice flow involving sliding and sediment shearing below wet-based ice.

Precambrian Research, Aug 1, 2016

The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates presumed... more The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates presumed representatives of the Sturtian and Marinoan panglaciations. Its duration is poorly constrained radiometrically and its deposits are relatively poorly known in most geographic regions. This paper aims to constrain the duration, palaeoenvironments and petrogenesis of such deposits in the classic region of NE Spitsbergen, Svalbard. The succession comprises a 200-205 m dolomitic shale (Macdonaldryggen Member, known as E3, of the Elbobreen Formation) overlain by oolitic dolomite Slangen Member (E4), 15-25 m thick, with limestone developed at top and base of E3 in the south of the area. The assumed age context of the succession has been confirmed by the presence of a typical Sturtian cap carbonate profile of negative to positive δ 13 C, and primary Sr isotope compositions of basal E3 limestones <0.7072 and of upper E3 limestones of 0.7076. At the base of E3, interstratification of cap carbonate with ice-rafted and redeposited glacial sediments occurs. Early diagenetic stabilization of carbonate mineralogy from a precursor, possibly ikaite, to calcite or dolomite is inferred. E3 is predominantly dolomitic silt-shale, with sub-millimetre lamination, lacking sand or current-related sedimentary structures. Thin fine laminae are partly pyritized and interpreted as microbial mats. Dolomite content is 25-50%, with δ 13 C values consistently around +4‰, a value attributed to buffering by dissolution of a precursor metastable carbonate phase. Local calcite cement associates with low δ 13 C values. The carbonates form silt-sized, chemically zoned rhombic crystals from an environment with dynamically changing Fe and Mn. Three-dimensional reconstructions of cm-scale disturbance structures indicate that they represent horizontally directed sock-like folds, developed by release of overpressure into thin surficial sediment overlying an early-cemented layer. A shoaling upwards unit near the top of E3 displays calcium sulphate pseudomorphs in dolomite in the north, but storm-dominated limestones in the south, both being overlain by peritidal oolitic dolomites, exposed under the succeeding Wilsonbreen glacial deposits. There is no Trezona δ 13 C anomaly, possibly implying top-truncation of the succession. Regular 0.5 m-scale sedimentary rhythms, reflecting subtle variations in sediment texture or composition occur throughout E3 and are interpreted as allocyclic. They are thought to be mainly primary in origin, locally modified slightly during early diagenetic cementation. Rhythms are proposed to represent ca. 18 kyr precession cycles, implying 6-8 Myr deposition between glaciations.

Journal of Glaciology

We assess the evolution of glaciological structures during the 2003–05 surge in the Paulabreen gl... more We assess the evolution of glaciological structures during the 2003–05 surge in the Paulabreen glacier system, Svalbard. Glaciological structures on the glacier surface were mapped using aerial photographs captured in the early stages of the surge (2003) and 5 years after surge termination (2011). Three-dimensional measurements of glaciological structures were collected at the tidewater front in 2013. These datasets document the physical changes during (1) the late quiescent phase; (2) the early phase of the surge as the surge front propagated down Skobreen and advanced into Paulabreen and (3) the final stages of the surge following the surge front reaching the glacier terminus. Crevasse patterns and clusters of arcuate shear planes record zones of compressive and extensional flow associated with the downglacier progression of the surge front. The transfer of surging ice from Skobreen into Paulabreen caused lateral displacement of the medial moraines to the northeast. At the ice fro...

20 21 The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates pr... more 20 21 The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates presumed 22 representatives of the Sturtian and Marinoan panglaciations. Its duration is poorly constrained 23 radiometrically and its deposits are relatively poorly known in most geographic regions. This paper aims to 24 constrain the duration, palaeoenvironments and petrogenesis of such deposits in the classic region of NE 25 Spitsbergen, Svalbard. The succession comprises a 200-205 m dolomitic shale (Macdonaldryggen Member, 26 known as E3, of the Elbobreen Formation) overlain by oolitic dolomite Slangen Member (E4), 15-25 m thick, 27 with limestone developed at top and base of E3 in the south of the area. The assumed age context of the 28 succession has been confirmed by the presence of a typical Sturtian cap carbonate profile of negative to 29 positive C, and primary Sr isotope compositions of basal E3 limestones <0.7072 and of upper E3 30 limestones of 0.7076. 31 At the base of E3...

Precambrian Research, 2018

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Sedimentology, 2016

The Marinoan panglaciation (ca 650 to 635 Ma) is represented in north‐east Svalbard by the 130 to... more The Marinoan panglaciation (ca 650 to 635 Ma) is represented in north‐east Svalbard by the 130 to 175 m thick Wilsonbreen Formation which contains syn‐glacial carbonates in its upper 100 m. These sediments are now known to have been deposited under a CO2‐rich atmosphere, late in the glaciation, and global climate models facilitate testing of proposed analogues. Precipitated carbonates occur in four of the seven facies associations identified: Fluvial Channel (including stromatolitic and intraclastic limestones in ephemeral stream deposits); Dolomitic Floodplain (dolomite‐cemented sand and siltstones, and microbial dolomites); Calcareous Lake Margin (intraclastic dolomite and wave‐rippled or aeolian siliciclastic facies); and Calcareous Lake (slump‐folded and locally re‐sedimented rhythmic/stromatolitic limestones and dolomites associated with ice‐rafted sediment). There is no strong cyclicity, and modern analogues suggest that sudden changes in lake level may exert a strong control ...

Sedimentology, 2016

Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of long‐sta... more Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of long‐standing debate, particularly concerning the interpretation of diamictites. The Wilsonbreen Formation of north‐east Svalbard is a 130 to 180 m thick diamictite‐dominated glacigenic succession deposited during a late Cryogenian (Marinoan) glaciation. Previous research has highlighted a complex sedimentary architecture with evidence of subaqueous, subglacial and non‐glacial conditions. This study combines well‐established sedimentological techniques with the first sedimentological application of the anisotropy of magnetic susceptibility technique in Neoproterozoic glacial sediments, to investigate the origin and palaeoenvironmental significance of glacigenic sediments within the Wilsonbreen Formation. A range of lithofacies occurs within the succession, dominated by massive diamictites, sandstones and conglomerates. Some of these facies display evidence of primary deformation and can be group...

Journal of Geophysical Research: Earth Surface, 2015

The englacial entrainment of basal debris during surges presents an opportunity to investigate pr... more The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt‐out of debris‐rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge‐type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris‐poor dispersed facies ice is the result of strain‐induced metamorphism of meteoric ice near the bed. Debris‐rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squ...

Proceedings of the Geologists' Association, 2013

North Norfolk is a classic area for the study of glacial sediments with a complex glaciotectonic ... more North Norfolk is a classic area for the study of glacial sediments with a complex glaciotectonic deformational history, but the processes leading to the formation of some structures can be ambiguous. Anisotropy of magnetic susceptibility (AMS) analyses, providing quantitative fabric data, have been combined with the analysis of visible structures and applied to the Bacton Green Till Member, exposed at Bacton, Norfolk. Thermomagnetic curves, low temperature susceptibility and acquisition of isothermal remanent magnetism (IRM) reveal that the magnetic mineralogy is dominated by paramagnetic phases. The magnetic foliation is parallel to fold axial planes and weakly inclined to bedding, whilst the magnetic lineation is orientated parallel to stretching, indicated by the presence of stretching lineations and the trend of sheath folds. Variations in the orientation of the magnetic lineation suggest that the Bacton section has been subject to polyphase deformation. After subaqueous deposition, the sequence was overridden by ice and glaciotectonically deformed which involved stretching initially north-south, then east-west. These results show that AMS can be used to detect strain in three dimensions through a glaciotectonite where paramagnetic mineralogy is dominant. This approach therefore provides further support to the use of AMS as a fast, objective and accurate method of examining strain within deformed glacial sediments.

Journal of Glaciology, 2015

Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Lit... more Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Little Ice Age (LIA), demonstrated by prominent ice-cored moraines up to several kilometres beyond present-day margins. The majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds, indicating they are likely to have undergone a thermal transition from a polythermal to a cold-based regime. We present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of Tellbreen, a small cold-based valley glacier in central Spitsbergen, based on its basal sequence and glaciological structures. Within the basal sequence, the underlying matrix-supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed, indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former...

ABSTRACT The mechanisms controlling the incorporation of large volumes of debris into glacier ice... more ABSTRACT The mechanisms controlling the incorporation of large volumes of debris into glacier ice during High-Arctic surges are important for a number of reasons. Firstly, they may provide an indication of basal conditions beneath the glacier. Secondly, the relationship between debris layers and ice can present evidence of the tectonic regime active during a surge. Thirdly, assessing the manner in which debris is entrained, transported and deposited may help to improve our understanding of the formation of ice-sediment-landform assemblages associated with surging. Collectively, these three points may provide an insight into surge mechanisms and the palaeo-record produced by surges. We present initial fieldwork results from Tunabreen, a 35 km-long tidewater glacier in central Spitsbergen which surged in the 1930s, 1970s and 2003-2005. During the most-recent surge the glacier advanced c. 2 km into Tempelfjorden. Since surge termination Tunabreen has calved back c. 1 km, revealing evidence of englacial debris inclusions and debris-rich ice. These are best exposed in two sections in the tidewater ice cliff, located at the NW and SE margins of the glacier front and thought to delimit the lateral extents of active ice during the surge. Both sections contain debris-rich structures, including both up- and downglacier dipping and near-vertical features. Large volumes of debris can often be seen at the base of these, particularly at the SE section. The debris within the structures at both sections is a matrix-supported, muddy diamicton containing predominantly sub-angular to sub-rounded clasts displaying evidence for subglacial transport (striations, grooves, gouges and facets). Both sections are also characterised by complex layering of debris-rich and debris-poor ice units as a result of deformation. We offer some preliminary interpretations of this evidence and its links to surge dynamics. This work forms part of a wider project investigating the ice-debris-landform signature of surging glaciers in Svalbard.

EGU General Assembly Conference Abstracts, Apr 1, 2013

Raw carbon isotope data for construction of Figure 1 and Figure 10.

Precambrian Research, Dec 1, 2018

Journal of Glaciology, Jul 14, 2022

We assess the evolution of glaciological structures during the 2003-05 surge in the Paulabreen gl... more We assess the evolution of glaciological structures during the 2003-05 surge in the Paulabreen glacier system, Svalbard. Glaciological structures on the glacier surface were mapped using aerial photographs captured in the early stages of the surge (2003) and 5 years after surge termination (2011). Three-dimensional measurements of glaciological structures were collected at the tidewater front in 2013. These datasets document the physical changes during (1) the late quiescent phase; (2) the early phase of the surge as the surge front propagated down Skobreen and advanced into Paulabreen and (3) the final stages of the surge following the surge front reaching the glacier terminus. Crevasse patterns and clusters of arcuate shear planes record zones of compressive and extensional flow associated with the downglacier progression of the surge front. The transfer of surging ice from Skobreen into Paulabreen caused lateral displacement of the medial moraines to the northeast. At the ice front, this movement tilted glaciological structures in the same direction. Structures at the southwest margin record strike-slip faulting and the elevation of debris into the ice in a zone of compression and transpression. We summarise these observations in a schematic reconstruction of structural evolution during the surge.

EGU General Assembly Conference Abstracts, Apr 1, 2013

Journal of Glaciology, 2015

Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Lit... more Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Little Ice Age (LIA), demonstrated by prominent ice-cored moraines up to several kilometres beyond present-day margins. The majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds, indicating they are likely to have undergone a thermal transition from a polythermal to a cold-based regime. We present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of Tellbreen, a small cold-based valley glacier in central Spitsbergen, based on its basal sequence and glaciological structures. Within the basal sequence, the underlying matrix-supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed, indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former deforming layer. This is overlain by debris-poor dispersed facies ice, interpreted to have formed through strain-induced metamorphism of englacial ice. The sequential development of structures includes arcuate fracture traces, interpreted as shear planes formed in a compressive/transpressive stress regime; and fracture traces, interpreted as healed extensional crevasses. The formation of these sediment/ice facies and structures is indicative of dynamic, warm-based flow, most likely during the LIA when the glacier was significantly thicker.

Sedimentology, Feb 1, 2016

Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of longstan... more Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of longstanding debate, particularly concerning the interpretation of diamictites. The Wilsonbreen Formation of northeast Svalbard is a 130 to 180 m thick diamictite-dominated glacigenic succession deposited during a late Cryogenian (Marinoan) glaciation. Previous research has highlighted a complex sedimentary architecture with evidence of subaqueous, subglacial and non-glacial conditions. This study combines well-established sedimentological techniques with the first sedimentological application of the anisotropy of magnetic susceptibility (AMS) technique in Neoproterozoic glacial sediments, to investigate the origin and palaeoenvironmental significance of glacigenic sediments within the Wilsonbreen Formation. A range of lithofacies occurs within the succession, dominated by massive diamictites, sandstones and conglomerates. Some of these facies display evidence of primary deformation and can be grouped into a Deformed Facies Association; these are interpreted to have been formed through glacitectonic deformation in a subglacial environment. Fabric investigation reveals that this deformation was associated with glacier flow towards the north. In addition, an Undeformed Facies Association records deposition in ice-proximal Accepted Article This article is protected by copyright. All rights reserved. and ice-distal subaqueous environments. Taken together with intervening non-glacial facies, the glacigenic sediments record a series of advance-retreat cycles, with ice flow involving sliding and sediment shearing below wet-based ice.

Precambrian Research, Aug 1, 2016

The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates presumed... more The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates presumed representatives of the Sturtian and Marinoan panglaciations. Its duration is poorly constrained radiometrically and its deposits are relatively poorly known in most geographic regions. This paper aims to constrain the duration, palaeoenvironments and petrogenesis of such deposits in the classic region of NE Spitsbergen, Svalbard. The succession comprises a 200-205 m dolomitic shale (Macdonaldryggen Member, known as E3, of the Elbobreen Formation) overlain by oolitic dolomite Slangen Member (E4), 15-25 m thick, with limestone developed at top and base of E3 in the south of the area. The assumed age context of the succession has been confirmed by the presence of a typical Sturtian cap carbonate profile of negative to positive δ 13 C, and primary Sr isotope compositions of basal E3 limestones <0.7072 and of upper E3 limestones of 0.7076. At the base of E3, interstratification of cap carbonate with ice-rafted and redeposited glacial sediments occurs. Early diagenetic stabilization of carbonate mineralogy from a precursor, possibly ikaite, to calcite or dolomite is inferred. E3 is predominantly dolomitic silt-shale, with sub-millimetre lamination, lacking sand or current-related sedimentary structures. Thin fine laminae are partly pyritized and interpreted as microbial mats. Dolomite content is 25-50%, with δ 13 C values consistently around +4‰, a value attributed to buffering by dissolution of a precursor metastable carbonate phase. Local calcite cement associates with low δ 13 C values. The carbonates form silt-sized, chemically zoned rhombic crystals from an environment with dynamically changing Fe and Mn. Three-dimensional reconstructions of cm-scale disturbance structures indicate that they represent horizontally directed sock-like folds, developed by release of overpressure into thin surficial sediment overlying an early-cemented layer. A shoaling upwards unit near the top of E3 displays calcium sulphate pseudomorphs in dolomite in the north, but storm-dominated limestones in the south, both being overlain by peritidal oolitic dolomites, exposed under the succeeding Wilsonbreen glacial deposits. There is no Trezona δ 13 C anomaly, possibly implying top-truncation of the succession. Regular 0.5 m-scale sedimentary rhythms, reflecting subtle variations in sediment texture or composition occur throughout E3 and are interpreted as allocyclic. They are thought to be mainly primary in origin, locally modified slightly during early diagenetic cementation. Rhythms are proposed to represent ca. 18 kyr precession cycles, implying 6-8 Myr deposition between glaciations.

Journal of Glaciology

We assess the evolution of glaciological structures during the 2003–05 surge in the Paulabreen gl... more We assess the evolution of glaciological structures during the 2003–05 surge in the Paulabreen glacier system, Svalbard. Glaciological structures on the glacier surface were mapped using aerial photographs captured in the early stages of the surge (2003) and 5 years after surge termination (2011). Three-dimensional measurements of glaciological structures were collected at the tidewater front in 2013. These datasets document the physical changes during (1) the late quiescent phase; (2) the early phase of the surge as the surge front propagated down Skobreen and advanced into Paulabreen and (3) the final stages of the surge following the surge front reaching the glacier terminus. Crevasse patterns and clusters of arcuate shear planes record zones of compressive and extensional flow associated with the downglacier progression of the surge front. The transfer of surging ice from Skobreen into Paulabreen caused lateral displacement of the medial moraines to the northeast. At the ice fro...

20 21 The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates pr... more 20 21 The Late Cryogenian Warm Interval (LCWI) refers to a non-glacial interval that separates presumed 22 representatives of the Sturtian and Marinoan panglaciations. Its duration is poorly constrained 23 radiometrically and its deposits are relatively poorly known in most geographic regions. This paper aims to 24 constrain the duration, palaeoenvironments and petrogenesis of such deposits in the classic region of NE 25 Spitsbergen, Svalbard. The succession comprises a 200-205 m dolomitic shale (Macdonaldryggen Member, 26 known as E3, of the Elbobreen Formation) overlain by oolitic dolomite Slangen Member (E4), 15-25 m thick, 27 with limestone developed at top and base of E3 in the south of the area. The assumed age context of the 28 succession has been confirmed by the presence of a typical Sturtian cap carbonate profile of negative to 29 positive C, and primary Sr isotope compositions of basal E3 limestones <0.7072 and of upper E3 30 limestones of 0.7076. 31 At the base of E3...

Precambrian Research, 2018

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Sedimentology, 2016

The Marinoan panglaciation (ca 650 to 635 Ma) is represented in north‐east Svalbard by the 130 to... more The Marinoan panglaciation (ca 650 to 635 Ma) is represented in north‐east Svalbard by the 130 to 175 m thick Wilsonbreen Formation which contains syn‐glacial carbonates in its upper 100 m. These sediments are now known to have been deposited under a CO2‐rich atmosphere, late in the glaciation, and global climate models facilitate testing of proposed analogues. Precipitated carbonates occur in four of the seven facies associations identified: Fluvial Channel (including stromatolitic and intraclastic limestones in ephemeral stream deposits); Dolomitic Floodplain (dolomite‐cemented sand and siltstones, and microbial dolomites); Calcareous Lake Margin (intraclastic dolomite and wave‐rippled or aeolian siliciclastic facies); and Calcareous Lake (slump‐folded and locally re‐sedimented rhythmic/stromatolitic limestones and dolomites associated with ice‐rafted sediment). There is no strong cyclicity, and modern analogues suggest that sudden changes in lake level may exert a strong control ...

Sedimentology, 2016

Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of long‐sta... more Palaeoenvironmental reconstruction of Neoproterozoic successions has been the subject of long‐standing debate, particularly concerning the interpretation of diamictites. The Wilsonbreen Formation of north‐east Svalbard is a 130 to 180 m thick diamictite‐dominated glacigenic succession deposited during a late Cryogenian (Marinoan) glaciation. Previous research has highlighted a complex sedimentary architecture with evidence of subaqueous, subglacial and non‐glacial conditions. This study combines well‐established sedimentological techniques with the first sedimentological application of the anisotropy of magnetic susceptibility technique in Neoproterozoic glacial sediments, to investigate the origin and palaeoenvironmental significance of glacigenic sediments within the Wilsonbreen Formation. A range of lithofacies occurs within the succession, dominated by massive diamictites, sandstones and conglomerates. Some of these facies display evidence of primary deformation and can be group...

Journal of Geophysical Research: Earth Surface, 2015

The englacial entrainment of basal debris during surges presents an opportunity to investigate pr... more The englacial entrainment of basal debris during surges presents an opportunity to investigate processes acting at the glacier bed. The subsequent melt‐out of debris‐rich englacial structures during the quiescent phase produces geometrical ridge networks on glacier forelands that are diagnostic of surge activity. We investigate the link between debris entrainment and proglacial geomorphology by analyzing basal ice, englacial structures, and ridge networks exposed at the margins of Tunabreen, a tidewater surge‐type glacier in Svalbard. The basal ice facies display clear evidence for brittle and ductile tectonic deformation, resulting in overall thickening of the basal ice sequence. The formation of debris‐poor dispersed facies ice is the result of strain‐induced metamorphism of meteoric ice near the bed. Debris‐rich englacial structures display a variety of characteristics and morphologies and are interpreted to represent the incorporation and elevation of subglacial till via the squ...

Proceedings of the Geologists' Association, 2013

North Norfolk is a classic area for the study of glacial sediments with a complex glaciotectonic ... more North Norfolk is a classic area for the study of glacial sediments with a complex glaciotectonic deformational history, but the processes leading to the formation of some structures can be ambiguous. Anisotropy of magnetic susceptibility (AMS) analyses, providing quantitative fabric data, have been combined with the analysis of visible structures and applied to the Bacton Green Till Member, exposed at Bacton, Norfolk. Thermomagnetic curves, low temperature susceptibility and acquisition of isothermal remanent magnetism (IRM) reveal that the magnetic mineralogy is dominated by paramagnetic phases. The magnetic foliation is parallel to fold axial planes and weakly inclined to bedding, whilst the magnetic lineation is orientated parallel to stretching, indicated by the presence of stretching lineations and the trend of sheath folds. Variations in the orientation of the magnetic lineation suggest that the Bacton section has been subject to polyphase deformation. After subaqueous deposition, the sequence was overridden by ice and glaciotectonically deformed which involved stretching initially north-south, then east-west. These results show that AMS can be used to detect strain in three dimensions through a glaciotectonite where paramagnetic mineralogy is dominant. This approach therefore provides further support to the use of AMS as a fast, objective and accurate method of examining strain within deformed glacial sediments.

Journal of Glaciology, 2015

Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Lit... more Large numbers of small valley glaciers on Svalbard were thicker and more extensive during the Little Ice Age (LIA), demonstrated by prominent ice-cored moraines up to several kilometres beyond present-day margins. The majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds, indicating they are likely to have undergone a thermal transition from a polythermal to a cold-based regime. We present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of Tellbreen, a small cold-based valley glacier in central Spitsbergen, based on its basal sequence and glaciological structures. Within the basal sequence, the underlying matrix-supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed, indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former...

ABSTRACT The mechanisms controlling the incorporation of large volumes of debris into glacier ice... more ABSTRACT The mechanisms controlling the incorporation of large volumes of debris into glacier ice during High-Arctic surges are important for a number of reasons. Firstly, they may provide an indication of basal conditions beneath the glacier. Secondly, the relationship between debris layers and ice can present evidence of the tectonic regime active during a surge. Thirdly, assessing the manner in which debris is entrained, transported and deposited may help to improve our understanding of the formation of ice-sediment-landform assemblages associated with surging. Collectively, these three points may provide an insight into surge mechanisms and the palaeo-record produced by surges. We present initial fieldwork results from Tunabreen, a 35 km-long tidewater glacier in central Spitsbergen which surged in the 1930s, 1970s and 2003-2005. During the most-recent surge the glacier advanced c. 2 km into Tempelfjorden. Since surge termination Tunabreen has calved back c. 1 km, revealing evidence of englacial debris inclusions and debris-rich ice. These are best exposed in two sections in the tidewater ice cliff, located at the NW and SE margins of the glacier front and thought to delimit the lateral extents of active ice during the surge. Both sections contain debris-rich structures, including both up- and downglacier dipping and near-vertical features. Large volumes of debris can often be seen at the base of these, particularly at the SE section. The debris within the structures at both sections is a matrix-supported, muddy diamicton containing predominantly sub-angular to sub-rounded clasts displaying evidence for subglacial transport (striations, grooves, gouges and facets). Both sections are also characterised by complex layering of debris-rich and debris-poor ice units as a result of deformation. We offer some preliminary interpretations of this evidence and its links to surge dynamics. This work forms part of a wider project investigating the ice-debris-landform signature of surging glaciers in Svalbard.