John Boyle - Academia.edu (original) (raw)

Papers by John Boyle

Research paper thumbnail of Late Pleistocene and Holocene drought events at Lake Tana, the source of the Blue Nile

Magnetic and geochemical core data spanning the last 17,000 years are correlated with new seismic... more Magnetic and geochemical core data spanning the last 17,000 years are correlated with new seismic stratigraphy from Lake Tana, Ethiopia, to infer past lake-level change and hence effective precipitation. The data confirm that low lake-level coincides with Heinrich Event 1 (H1) in the North Atlantic, as previously shown from diatom and pollen evidence . The lake deepened at 15.3 cal kyr BP and abruptly returned to freshwater conditions, when the lake overflowed into the Blue Nile. Low runoff and lake levels and therefore rainfall are inferred between 13.0 and 12.5 cal kyr BP and may represent southerly suppression of the ITCZ and the associated monsoon front at the time of the Younger Dryas. Two drought episodes occurred at 8.4 and 7.5 cal kyr BP, and are also interpreted as a southward shift in the monsoon front. The first of these events appears to have preceded and been more significant than the 8.2 cal kyr BP. Precipitation declined after 6.8 cal kyr BP, although we do not see an abrupt end to the African Humid Period. This period culminated in a dry episode at~4.2 cal kyr BP, supporting the view that reduced Nile flow was a contributing factor to the demise of the Egyptian Old Kingdom.

Research paper thumbnail of Geomorphology and Sedimentology of Lakes and Reser Voirs edited by J. McManus and RW Duck, Wiley, Chichester, 1993. No. of pages: 278. Price: $60.00 (hardback). ISBN 0 471 93773 8

Research paper thumbnail of Pb isotope ratios of lake sediments in West Greenland: inferences on pollution sources

Lead (Pb), like many other pollutants, is carried into the Arctic by long-range atmospheric trans... more Lead (Pb), like many other pollutants, is carried into the Arctic by long-range atmospheric transport from industrial centers at lower latitudes. Unlike other pollutants, Pb can be used to assess emission source regions through the use of stable Pb isotope analyses. Using sediment cores from 17 lakes (three profiles and 14 top/bottom sample pairs) in the Sndre Strmfjord (Kangerlussuaq) region, West Greenland (678N), this study assesses the extent and origin of Pb pollution along a 150 km transect between the Inland Ice and Davis Strait. Like ice core analyses from the interior of Greenland, the isotope analyses suggest pre-industrial contamination, although significant concentration changes in the lake sediments do not occur until the 18th/19th centuries, with the maximum concentrations occurring about 1970. Compared to the background, the Pb concentrations in recent sediments have increased about 2.5-fold, with slightly higher enrichments towards the coast, where annual precipitation is highest. For all of the lakes, there is a major decline in the 206 Pb/ 207 Pb ratio in the recent sediments (mean 1.218 AE 0.030) as compared to deeper sediments (mean 1.365 AE 0.084). Using a Pb isotope mixing model, we calculated an excess Pb isotope ratio, i.e. the isotope ratio necessary to produce the observed declines in recent sediments. While studies of atmospheric aerosols in the high Arctic ( 206 Pb/ 207 Pb ratio 1.16)haveindicatedthatRussianemissions(206Pb/207Pbratio1.16) have indicated that Russian emissions ( 206 Pb/ 207 Pb ratio 1.16)haveindicatedthatRussianemissions(206Pb/207Pbratio1.15-1.16) are a dominant source of arctic pollution, the excess Pb ratios of the lake sediments in the Sndre Strmfjord region ( 206 Pb/ 207 Pb ratio 1.14−1.15),inthelowArctic,suggestthatWEurope(206Pb/207Pbratio1.14-1.15), in the low Arctic, suggest that W Europe ( 206 Pb/ 207 Pb ratio 1.14−1.15),inthelowArctic,suggestthatWEurope(206Pb/207Pbratio1.14) is also a major emission source for this region. #

Research paper thumbnail of The late-Holocene history of Gormire Lake (NE England) and its catchment: a multiproxy reconstruction of past human impact

DOI: 10.1191/0959683603hl654rp 2003 13: 677 The Holocene Fisher and George Wolff ... Frank Oldfie... more DOI: 10.1191/0959683603hl654rp 2003 13: 677 The Holocene Fisher and George Wolff ... Frank Oldfield, Rebecca Wake, John Boyle, Richard Jones, Steve Nolan, Zoe Gibbs, Peter Appleby, Elizabeth reconstruction of past human impact The late-Holocene history of ...

Research paper thumbnail of Association between magnetic properties and element concentrations of Liverpool street dust and its implications

... Boyle (2000) reported that total concentrations of 15 elements can be determined in soils and... more ... Boyle (2000) reported that total concentrations of 15 elements can be determined in soils and sediments with sufficient accuracy using isotope source X-ray fluorescence (XRF) analysis with a Metorex oy (Finland) XMET920 system, which was used to measure total ...

Research paper thumbnail of Late Pleistocene and Holocene drought events at Lake Tana, the source of the Blue Nile

Magnetic and geochemical core data spanning the last 17,000 years are correlated with new seismic... more Magnetic and geochemical core data spanning the last 17,000 years are correlated with new seismic stratigraphy from Lake Tana, Ethiopia, to infer past lake-level change and hence effective precipitation. The data confirm that low lake-level coincides with Heinrich Event 1 (H1) in the North Atlantic, as previously shown from diatom and pollen evidence . The lake deepened at 15.3 cal kyr BP and abruptly returned to freshwater conditions, when the lake overflowed into the Blue Nile. Low runoff and lake levels and therefore rainfall are inferred between 13.0 and 12.5 cal kyr BP and may represent southerly suppression of the ITCZ and the associated monsoon front at the time of the Younger Dryas. Two drought episodes occurred at 8.4 and 7.5 cal kyr BP, and are also interpreted as a southward shift in the monsoon front. The first of these events appears to have preceded and been more significant than the 8.2 cal kyr BP. Precipitation declined after 6.8 cal kyr BP, although we do not see an abrupt end to the African Humid Period. This period culminated in a dry episode at~4.2 cal kyr BP, supporting the view that reduced Nile flow was a contributing factor to the demise of the Egyptian Old Kingdom.

Research paper thumbnail of Geomorphology and Sedimentology of Lakes and Reser Voirs edited by J. McManus and RW Duck, Wiley, Chichester, 1993. No. of pages: 278. Price: $60.00 (hardback). ISBN 0 471 93773 8

Research paper thumbnail of Pb isotope ratios of lake sediments in West Greenland: inferences on pollution sources

Lead (Pb), like many other pollutants, is carried into the Arctic by long-range atmospheric trans... more Lead (Pb), like many other pollutants, is carried into the Arctic by long-range atmospheric transport from industrial centers at lower latitudes. Unlike other pollutants, Pb can be used to assess emission source regions through the use of stable Pb isotope analyses. Using sediment cores from 17 lakes (three profiles and 14 top/bottom sample pairs) in the Sndre Strmfjord (Kangerlussuaq) region, West Greenland (678N), this study assesses the extent and origin of Pb pollution along a 150 km transect between the Inland Ice and Davis Strait. Like ice core analyses from the interior of Greenland, the isotope analyses suggest pre-industrial contamination, although significant concentration changes in the lake sediments do not occur until the 18th/19th centuries, with the maximum concentrations occurring about 1970. Compared to the background, the Pb concentrations in recent sediments have increased about 2.5-fold, with slightly higher enrichments towards the coast, where annual precipitation is highest. For all of the lakes, there is a major decline in the 206 Pb/ 207 Pb ratio in the recent sediments (mean 1.218 AE 0.030) as compared to deeper sediments (mean 1.365 AE 0.084). Using a Pb isotope mixing model, we calculated an excess Pb isotope ratio, i.e. the isotope ratio necessary to produce the observed declines in recent sediments. While studies of atmospheric aerosols in the high Arctic ( 206 Pb/ 207 Pb ratio 1.16)haveindicatedthatRussianemissions(206Pb/207Pbratio1.16) have indicated that Russian emissions ( 206 Pb/ 207 Pb ratio 1.16)haveindicatedthatRussianemissions(206Pb/207Pbratio1.15-1.16) are a dominant source of arctic pollution, the excess Pb ratios of the lake sediments in the Sndre Strmfjord region ( 206 Pb/ 207 Pb ratio 1.14−1.15),inthelowArctic,suggestthatWEurope(206Pb/207Pbratio1.14-1.15), in the low Arctic, suggest that W Europe ( 206 Pb/ 207 Pb ratio 1.14−1.15),inthelowArctic,suggestthatWEurope(206Pb/207Pbratio1.14) is also a major emission source for this region. #

Research paper thumbnail of The late-Holocene history of Gormire Lake (NE England) and its catchment: a multiproxy reconstruction of past human impact

DOI: 10.1191/0959683603hl654rp 2003 13: 677 The Holocene Fisher and George Wolff ... Frank Oldfie... more DOI: 10.1191/0959683603hl654rp 2003 13: 677 The Holocene Fisher and George Wolff ... Frank Oldfield, Rebecca Wake, John Boyle, Richard Jones, Steve Nolan, Zoe Gibbs, Peter Appleby, Elizabeth reconstruction of past human impact The late-Holocene history of ...

Research paper thumbnail of Association between magnetic properties and element concentrations of Liverpool street dust and its implications

... Boyle (2000) reported that total concentrations of 15 elements can be determined in soils and... more ... Boyle (2000) reported that total concentrations of 15 elements can be determined in soils and sediments with sufficient accuracy using isotope source X-ray fluorescence (XRF) analysis with a Metorex oy (Finland) XMET920 system, which was used to measure total ...