A Holocene palaeorecord from Lake Shudu, Yunnan Province, southwestern China is dominated by (1) ... more A Holocene palaeorecord from Lake Shudu, Yunnan Province, southwestern China is dominated by (1) a pronounced basin-wide sedimentary hiatus after ca. 7.2 kcal yr BP, spanning some 4,000 years and (2) significant changes in sediment source/supply and an increase in heavy metal influx coupled with a shift to more eutrophic lake conditions from ca. 0.9 kcal yr BP, lasting *300 years. The hiatus is most likely a due to a significant and abrupt reduction in sedimentation rates, the driver of which is unclear; although it appears likely to have been climatically driven. The environmental changes captured in the Lake Shudu palaeorecord provide unambiguous evidence of late Holocene anthropogenic activity, most likely linked to mining activity.
Submarine mass failures (which include submarine slides or submarine landslides) occur widely on ... more Submarine mass failures (which include submarine slides or submarine landslides) occur widely on open continental margins. Understanding their cause is of great importance in view of the danger that they can pose both to coastal populations through tsunamis and to the exploitation of ocean floor resources through mass movement of the sea floor. Present knowledge of the causes of submarine mass failures is briefly reviewed, focussing on the role of sea level rise, a process which has previously only infrequently been cited as a cause. It is argued that sea level rise could easily have been involved in at least some of these events by contributing to increased overpressure in sediments of the continental margin whilst causing seismic activity. The Holocene Storegga Slide off South West Norway may have been partly caused by the early Holocene sea level rise in the area, accentuated by meltwater flux from the discharges of Lake AgassizeOjibway in North America. Relative sea level rise increased water loading on the Norwegian continental margin, increasing overpressure in the sediments and also causing seismic activity, triggering the Holocene Storegga Slide. Given that some forecasts of future sea level rise are not greatly different from rises which obtained during the early Holocene, the implications of rising sea levels for submarine mass failures in a global warming world are considered.
Temporal and spatial patterns of relative sea level (RSL) change in the North of Britain and Irel... more Temporal and spatial patterns of relative sea level (RSL) change in the North of Britain and Ireland during the Holocene are examined. Four episodes, each defined by marked changes in the RSL trend, are identified. Each episode is marked by a rise to a culminating shoreline followed by a fall. Episode HRSL-1 dates from the Younger Dryas to early in the Holocene; HRSL-2 to HRSL-4 occurred later in the Holocene. There is extensive evidence for each episode, and on this basis the spatial distribution of the altitude data for three culminating shorelines and a shoreline formed at the time of the Holocene Storegga Slide tsunami (ca 8110 AE 100 cal. BP) is analysed. Ordinary Kriging is used to determine the general pattern, following which Gaussian Trend Surface Analysis is employed. Recognising that empirical measurements of RSL change can be unevenly distributed spatially, a new approach is introduced which enables the developing pattern to be identified. The patterns for the most widely occurring shorelines were analysed and found to be similar and common centre and axis models were developed for all shorelines. The analyses described provide models of the spatial pattern of Holocene RSL change in the area between ca 8100 cal. BP and ca 1000 cal. BP based on 2262 high resolution shoreline altitude measurements. These models fit the data closely, no shoreline altitude measurement lying more than À1.70 m or þ1.82 m from the predicted value. The models disclose a similar pattern to a recently published Glacial Isostatic Adjustment model for present RSL change across the area, indicating that the overall spatial pattern of RSL change may not have varied greatly during the last ca 8000 years.
The causes, anatomy and consequences of the early Holocene sea level rise (EHSLR) are reviewed. T... more The causes, anatomy and consequences of the early Holocene sea level rise (EHSLR) are reviewed. The rise, of ca 60m, took place over most of the Earth as the volume of the oceans increased during deglaciation and is dated at 11,650e7000 cal. BP. The EHSLR was largely driven by meltwater release from decaying ice masses and the break up of coastal ice streams. The patterns of ice sheet decay and the evidence for meltwater pulses are reviewed, and it is argued that the EHSLR was a factor in the ca 8470 BP flood from Lake Agassiz-Ojibway. Patterns of relative sea level changes are examined and it is argued that in addition to regional variations, temporal changes are indicated. The impact of the EHSLR on climate is reviewed and it is maintained that the event was a factor in the 8200 BP cooling event, as well as in changes in ocean current patterns and their resultant effects. The EHSLR may also have enhanced volcanic activity, but no clear evidence of a causal link with submarine sliding on continental slopes and shelves can yet be demonstrated. The rise probably influenced rates and patterns of human migrations and cultural changes. It is concluded that the EHSLR was a major event of global significance, knowledge of which is relevant to an understanding of the impacts of global climate change in the future.
Changes in relative sea level (RSL) and their effect on the distribution of human activity in the... more Changes in relative sea level (RSL) and their effect on the distribution of human activity in the Forth lowland, Scotland, UK between ca 11,700 and ca 2000 calibrated years before present (BP) are examined. Block uplift of shorelines occurred over a longer period than previously thought, continuing to at least around 4700 BP. New graphs of RSL change, based upon an analysis of previous work and evidence from new sites using standard morphological and stratigraphical analyses, support a fall in RSL in the early Holocene during which buried estuarine surfaces were formed, followed by a marked reversal on a centennial, perhaps even decadal, scale sometime around 9900e9500 BP from a falling sequence to a rising one. There may have been a short-lived fluctuation in the rising RSL ca 8300 BP, and the Holocene Storegga Slide tsunami of ca 8100 BP was widespread in the lowland. The rising RSL culminated at the Main Postglacial Shoreline, reached ca 7800 BP, when Mean High Water Spring Tides (MHWS) lay within the range 14.6e16.5 m British Ordnance Datum (OD) in the western lowland. This is the highest published Holocene RSL in Britain and Ireland. The subsequent fall in RSL stabilised at a second shoreline, the Blairdrummond Shoreline, from which regression was occurring at ca 4700 BP. RSL later fell to a lower shoreline at ca 3900 BP before reaching present levels within the last three millennia. Comparison between the empirical evidence for RSL change in this area and glacial isostatic adjustment models indicates both similarities and differences. Records of archaeological sites and artefacts in the lowland and surrounding areas are discussed. Maps showing the evolution of the estuary are compared with the distribution of Mesolithic, Neolithic, Bronze Age and Iron Age activity. Evidence for Mesolithic people indicates the opportunistic use of available resources as RSL rose and the estuary expanded to its maximum extent. Neolithic people were also attracted to the estuary, building at least one platform from which to exploit resources and accumulating middens along the shoreline for over 2000 years. Bronze Age people were present across the emerging saltmarshes and mudflats before raised peat mosses, already extensive at the head of the lowland, developed more widely. In the Iron Age, the area could be accessed both between the peat mosses of the western lowland and across newly emergent land in the east as RSL continued to fall.
This paper contributes to knowledge of Holocene relative sea level change along the mainland Ayrs... more This paper contributes to knowledge of Holocene relative sea level change along the mainland Ayrshire coast and offshore Isle of Bute, SW Scotland, UK, where few such studies have previously been undertaken. Morphological studies (mapping and altitude survey), together with stratigraphical and biostratigraphical studies (pollen and diatom analyses and radiocarbon dating) disclose evidence for mid and late Holocene relative sea level changes. The Main Postglacial and Blairdrummond displaced shorelines, previously identified widely in mainland Scotland, are dated in the area at c. 6800 calibrated years (c. 6000 14 C years) and c. 4200 calibrated years (c. 3800 14 C years) BP respectively. This information is compared with previously published information for Scotland against the classical theoretical model of relative sea level change in areas of glacio-isostasy. For the mid and late Holocene, in conformity with the model, a falling sequence of relative sea level changes near the centre of uplift is replaced by a rising sequence towards the periphery, in which later shorelines overlap earlier ones. In particular, the Blairdrummond Shoreline, which overlaps the earlier Main Postglacial Shoreline, is identified as the highest Holocene shoreline over much of the coastline of Scotland.
Evidence for relative sea-level changes during the middle and late Holocene is examined from two ... more Evidence for relative sea-level changes during the middle and late Holocene is examined from two locations on the Atlantic coast of Harris, Outer Hebrides, Scotland, using morphological mapping and survey, stratigraphical, grain size and diatom analysis, and radiocarbon dating. The earliest event identified is a marine flood, which occurred after 7982-8348 cal. a (7370 AE 80 14 C a) BP, when the sea crossed a threshold lying at À0.08 m Ordnance Datum Newlyn (OD) (À2.17 m mean high water springs (MHWS)) before withdrawing. This could have been due to a storm or to the Holocene Storegga Slide tsunami. By 6407-6122 cal. a (5500 AE 60 14 C a) BP, relative sea levels had begun to fall from a sandflat surface with an indicated MHWS level of between 0.08 and À1.96 m (À2.01 to À4.05 m). This fall reached between À0.30 and À2.35 m (À2.39 to À4.44 m) after 5841-5050 cal. a (4760 AE 130 14 C a) BP, but was succeeded by a relative sea-level rise which reached between 0.54 and À1.57 m (À1.55 to À3.66 m) by 5450-4861 cal. a (4500 AE 100 14 C a) BP. This rise continued, possibly with an interruption, until a second sandflat surface was reached between 2.34 and À0.26 m (0.25 to À2.35 m) between 2952-3375 cal. a (3000 AE 80 14 C a) and 1948-2325 cal. a (2130 AE 70 14 C a) BP, before present levels were reached. The regressive episode from the earliest sandflat is correlated with the abandonment of the Main Postglacial Shoreline. It is maintained that the fluctuations in relative sea level recorded can be correlated with similar events elsewhere on the periphery of the glacio-isostatic centre and may therefore reflect secular changes in nearshore sea surface levels. Despite published evidence from trim lines of differential ice sheet loading across the area, no evidence of variations in uplift between the locations concerned could be found.
Lithostratigraphical and biostratigraphical investigation of coastal marshes along the Atlantic c... more Lithostratigraphical and biostratigraphical investigation of coastal marshes along the Atlantic coast of the Outer Hebrides from Lewis in the north to Barra in the south discloses inland-tapering sand units within marshland areas. The inland extent of each sand unit has been radiometrically dated and the units have been collectively interpreted as a proxy for past coastal storminess. The data appear to indicate that for the study sites investigated, the majority of the sand units were produced during episodes of climate deterioration both prior to and after the well-known period of Medieval warmth (MWP). Many were produced after ca. AD 1400. It is argued that the episodes of sand blow indicated by the deposits may reflect periods of increased cyclogenesis in the Atlantic associated with increased sea ice cover and an increase in the thermal gradient across the North Atlantic region. D
A Holocene palaeorecord from Lake Shudu, Yunnan Province, southwestern China is dominated by (1) ... more A Holocene palaeorecord from Lake Shudu, Yunnan Province, southwestern China is dominated by (1) a pronounced basin-wide sedimentary hiatus after ca. 7.2 kcal yr BP, spanning some 4,000 years and (2) significant changes in sediment source/supply and an increase in heavy metal influx coupled with a shift to more eutrophic lake conditions from ca. 0.9 kcal yr BP, lasting *300 years. The hiatus is most likely a due to a significant and abrupt reduction in sedimentation rates, the driver of which is unclear; although it appears likely to have been climatically driven. The environmental changes captured in the Lake Shudu palaeorecord provide unambiguous evidence of late Holocene anthropogenic activity, most likely linked to mining activity.
Submarine mass failures (which include submarine slides or submarine landslides) occur widely on ... more Submarine mass failures (which include submarine slides or submarine landslides) occur widely on open continental margins. Understanding their cause is of great importance in view of the danger that they can pose both to coastal populations through tsunamis and to the exploitation of ocean floor resources through mass movement of the sea floor. Present knowledge of the causes of submarine mass failures is briefly reviewed, focussing on the role of sea level rise, a process which has previously only infrequently been cited as a cause. It is argued that sea level rise could easily have been involved in at least some of these events by contributing to increased overpressure in sediments of the continental margin whilst causing seismic activity. The Holocene Storegga Slide off South West Norway may have been partly caused by the early Holocene sea level rise in the area, accentuated by meltwater flux from the discharges of Lake AgassizeOjibway in North America. Relative sea level rise increased water loading on the Norwegian continental margin, increasing overpressure in the sediments and also causing seismic activity, triggering the Holocene Storegga Slide. Given that some forecasts of future sea level rise are not greatly different from rises which obtained during the early Holocene, the implications of rising sea levels for submarine mass failures in a global warming world are considered.
Temporal and spatial patterns of relative sea level (RSL) change in the North of Britain and Irel... more Temporal and spatial patterns of relative sea level (RSL) change in the North of Britain and Ireland during the Holocene are examined. Four episodes, each defined by marked changes in the RSL trend, are identified. Each episode is marked by a rise to a culminating shoreline followed by a fall. Episode HRSL-1 dates from the Younger Dryas to early in the Holocene; HRSL-2 to HRSL-4 occurred later in the Holocene. There is extensive evidence for each episode, and on this basis the spatial distribution of the altitude data for three culminating shorelines and a shoreline formed at the time of the Holocene Storegga Slide tsunami (ca 8110 AE 100 cal. BP) is analysed. Ordinary Kriging is used to determine the general pattern, following which Gaussian Trend Surface Analysis is employed. Recognising that empirical measurements of RSL change can be unevenly distributed spatially, a new approach is introduced which enables the developing pattern to be identified. The patterns for the most widely occurring shorelines were analysed and found to be similar and common centre and axis models were developed for all shorelines. The analyses described provide models of the spatial pattern of Holocene RSL change in the area between ca 8100 cal. BP and ca 1000 cal. BP based on 2262 high resolution shoreline altitude measurements. These models fit the data closely, no shoreline altitude measurement lying more than À1.70 m or þ1.82 m from the predicted value. The models disclose a similar pattern to a recently published Glacial Isostatic Adjustment model for present RSL change across the area, indicating that the overall spatial pattern of RSL change may not have varied greatly during the last ca 8000 years.
The causes, anatomy and consequences of the early Holocene sea level rise (EHSLR) are reviewed. T... more The causes, anatomy and consequences of the early Holocene sea level rise (EHSLR) are reviewed. The rise, of ca 60m, took place over most of the Earth as the volume of the oceans increased during deglaciation and is dated at 11,650e7000 cal. BP. The EHSLR was largely driven by meltwater release from decaying ice masses and the break up of coastal ice streams. The patterns of ice sheet decay and the evidence for meltwater pulses are reviewed, and it is argued that the EHSLR was a factor in the ca 8470 BP flood from Lake Agassiz-Ojibway. Patterns of relative sea level changes are examined and it is argued that in addition to regional variations, temporal changes are indicated. The impact of the EHSLR on climate is reviewed and it is maintained that the event was a factor in the 8200 BP cooling event, as well as in changes in ocean current patterns and their resultant effects. The EHSLR may also have enhanced volcanic activity, but no clear evidence of a causal link with submarine sliding on continental slopes and shelves can yet be demonstrated. The rise probably influenced rates and patterns of human migrations and cultural changes. It is concluded that the EHSLR was a major event of global significance, knowledge of which is relevant to an understanding of the impacts of global climate change in the future.
Changes in relative sea level (RSL) and their effect on the distribution of human activity in the... more Changes in relative sea level (RSL) and their effect on the distribution of human activity in the Forth lowland, Scotland, UK between ca 11,700 and ca 2000 calibrated years before present (BP) are examined. Block uplift of shorelines occurred over a longer period than previously thought, continuing to at least around 4700 BP. New graphs of RSL change, based upon an analysis of previous work and evidence from new sites using standard morphological and stratigraphical analyses, support a fall in RSL in the early Holocene during which buried estuarine surfaces were formed, followed by a marked reversal on a centennial, perhaps even decadal, scale sometime around 9900e9500 BP from a falling sequence to a rising one. There may have been a short-lived fluctuation in the rising RSL ca 8300 BP, and the Holocene Storegga Slide tsunami of ca 8100 BP was widespread in the lowland. The rising RSL culminated at the Main Postglacial Shoreline, reached ca 7800 BP, when Mean High Water Spring Tides (MHWS) lay within the range 14.6e16.5 m British Ordnance Datum (OD) in the western lowland. This is the highest published Holocene RSL in Britain and Ireland. The subsequent fall in RSL stabilised at a second shoreline, the Blairdrummond Shoreline, from which regression was occurring at ca 4700 BP. RSL later fell to a lower shoreline at ca 3900 BP before reaching present levels within the last three millennia. Comparison between the empirical evidence for RSL change in this area and glacial isostatic adjustment models indicates both similarities and differences. Records of archaeological sites and artefacts in the lowland and surrounding areas are discussed. Maps showing the evolution of the estuary are compared with the distribution of Mesolithic, Neolithic, Bronze Age and Iron Age activity. Evidence for Mesolithic people indicates the opportunistic use of available resources as RSL rose and the estuary expanded to its maximum extent. Neolithic people were also attracted to the estuary, building at least one platform from which to exploit resources and accumulating middens along the shoreline for over 2000 years. Bronze Age people were present across the emerging saltmarshes and mudflats before raised peat mosses, already extensive at the head of the lowland, developed more widely. In the Iron Age, the area could be accessed both between the peat mosses of the western lowland and across newly emergent land in the east as RSL continued to fall.
This paper contributes to knowledge of Holocene relative sea level change along the mainland Ayrs... more This paper contributes to knowledge of Holocene relative sea level change along the mainland Ayrshire coast and offshore Isle of Bute, SW Scotland, UK, where few such studies have previously been undertaken. Morphological studies (mapping and altitude survey), together with stratigraphical and biostratigraphical studies (pollen and diatom analyses and radiocarbon dating) disclose evidence for mid and late Holocene relative sea level changes. The Main Postglacial and Blairdrummond displaced shorelines, previously identified widely in mainland Scotland, are dated in the area at c. 6800 calibrated years (c. 6000 14 C years) and c. 4200 calibrated years (c. 3800 14 C years) BP respectively. This information is compared with previously published information for Scotland against the classical theoretical model of relative sea level change in areas of glacio-isostasy. For the mid and late Holocene, in conformity with the model, a falling sequence of relative sea level changes near the centre of uplift is replaced by a rising sequence towards the periphery, in which later shorelines overlap earlier ones. In particular, the Blairdrummond Shoreline, which overlaps the earlier Main Postglacial Shoreline, is identified as the highest Holocene shoreline over much of the coastline of Scotland.
Evidence for relative sea-level changes during the middle and late Holocene is examined from two ... more Evidence for relative sea-level changes during the middle and late Holocene is examined from two locations on the Atlantic coast of Harris, Outer Hebrides, Scotland, using morphological mapping and survey, stratigraphical, grain size and diatom analysis, and radiocarbon dating. The earliest event identified is a marine flood, which occurred after 7982-8348 cal. a (7370 AE 80 14 C a) BP, when the sea crossed a threshold lying at À0.08 m Ordnance Datum Newlyn (OD) (À2.17 m mean high water springs (MHWS)) before withdrawing. This could have been due to a storm or to the Holocene Storegga Slide tsunami. By 6407-6122 cal. a (5500 AE 60 14 C a) BP, relative sea levels had begun to fall from a sandflat surface with an indicated MHWS level of between 0.08 and À1.96 m (À2.01 to À4.05 m). This fall reached between À0.30 and À2.35 m (À2.39 to À4.44 m) after 5841-5050 cal. a (4760 AE 130 14 C a) BP, but was succeeded by a relative sea-level rise which reached between 0.54 and À1.57 m (À1.55 to À3.66 m) by 5450-4861 cal. a (4500 AE 100 14 C a) BP. This rise continued, possibly with an interruption, until a second sandflat surface was reached between 2.34 and À0.26 m (0.25 to À2.35 m) between 2952-3375 cal. a (3000 AE 80 14 C a) and 1948-2325 cal. a (2130 AE 70 14 C a) BP, before present levels were reached. The regressive episode from the earliest sandflat is correlated with the abandonment of the Main Postglacial Shoreline. It is maintained that the fluctuations in relative sea level recorded can be correlated with similar events elsewhere on the periphery of the glacio-isostatic centre and may therefore reflect secular changes in nearshore sea surface levels. Despite published evidence from trim lines of differential ice sheet loading across the area, no evidence of variations in uplift between the locations concerned could be found.
Lithostratigraphical and biostratigraphical investigation of coastal marshes along the Atlantic c... more Lithostratigraphical and biostratigraphical investigation of coastal marshes along the Atlantic coast of the Outer Hebrides from Lewis in the north to Barra in the south discloses inland-tapering sand units within marshland areas. The inland extent of each sand unit has been radiometrically dated and the units have been collectively interpreted as a proxy for past coastal storminess. The data appear to indicate that for the study sites investigated, the majority of the sand units were produced during episodes of climate deterioration both prior to and after the well-known period of Medieval warmth (MWP). Many were produced after ca. AD 1400. It is argued that the episodes of sand blow indicated by the deposits may reflect periods of increased cyclogenesis in the Atlantic associated with increased sea ice cover and an increase in the thermal gradient across the North Atlantic region. D
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