Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajokull region, northwest Iceland

Skafti Brynjólfsson; Anders Schomacker; Ólafur Ingólfsson; Jakob Kløve Keiding

doi:10.1016/j.quascirev.2015.09.001

Cosmogenic ³⁶Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajokull region, northwest Iceland

Skafti Brynjólfsson, Anders Schomacker, Ólafur Ingólfsson, Jakob Kløve Keiding

22 Citations (Scopus)

Abstract

We present twenty-four new cosmogenic isotope (³⁶Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangajökull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfir{eth}ir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice.Old³⁶Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfir{eth}ir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfir{eth}ir peninsula were occupied by warm-based, dynamic ice during the last glaciation.The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfir{eth}ir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP.The outermost moraine at the mouth of Leirufjörour is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjör{eth}ur as well as a 9.4 ka deglaciation age in the coastal area of Reykjarfjör{eth}ur suggest that an extensive ice cap persisted over the eastern Vestfiroir peninsula at least until c. 9 ka BP.

Original language	English
Journal	Quaternary Science Reviews
Volume	126
Pages (from-to)	140-157
Number of pages	18
ISSN	0277-3791
DOIs	https://doi.org/10.1016/j.quascirev.2015.09.001
Publication status	Published - 15 Oct 2015

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Cosmogenic ³⁶Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajokull region, northwest Iceland. / Brynjólfsson, Skafti; Schomacker, Anders; Ingólfsson, Ólafur et al.

In: Quaternary Science Reviews, Vol. 126, 15.10.2015, p. 140-157.

Research output: Contribution to journal › Journal article › Research › peer-review

@article{2e42b20eff4a47c98750d18f0623f530,

title = "Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajokull region, northwest Iceland",

abstract = "We present twenty-four new cosmogenic isotope (36Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangaj{\"o}kull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfir{eth}ir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice.Old36Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfir{eth}ir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfir{eth}ir peninsula were occupied by warm-based, dynamic ice during the last glaciation.The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfir{eth}ir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP.The outermost moraine at the mouth of Leirufj{\"o}rour is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufj{\"o}r{eth}ur as well as a 9.4 ka deglaciation age in the coastal area of Reykjarfj{\"o}r{eth}ur suggest that an extensive ice cap persisted over the eastern Vestfiroir peninsula at least until c. 9 ka BP.",

author = "Skafti Brynj{\'o}lfsson and Anders Schomacker and {\'O}lafur Ing{\'o}lfsson and Keiding, {Jakob Kl{\o}ve}",

year = "2015",

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doi = "10.1016/j.quascirev.2015.09.001",

language = "English",

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pages = "140--157",

journal = "Quaternary Science Reviews",

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T1 - Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajokull region, northwest Iceland

AU - Brynjólfsson, Skafti

AU - Schomacker, Anders

AU - Ingólfsson, Ólafur

AU - Keiding, Jakob Kløve

PY - 2015/10/15

Y1 - 2015/10/15

N2 - We present twenty-four new cosmogenic isotope (36Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangajökull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfir{eth}ir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice.Old36Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfir{eth}ir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfir{eth}ir peninsula were occupied by warm-based, dynamic ice during the last glaciation.The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfir{eth}ir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP.The outermost moraine at the mouth of Leirufjörour is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjör{eth}ur as well as a 9.4 ka deglaciation age in the coastal area of Reykjarfjör{eth}ur suggest that an extensive ice cap persisted over the eastern Vestfiroir peninsula at least until c. 9 ka BP.

AB - We present twenty-four new cosmogenic isotope (36Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangajökull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfir{eth}ir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice.Old36Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfir{eth}ir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfir{eth}ir peninsula were occupied by warm-based, dynamic ice during the last glaciation.The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfir{eth}ir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP.The outermost moraine at the mouth of Leirufjörour is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjör{eth}ur as well as a 9.4 ka deglaciation age in the coastal area of Reykjarfjör{eth}ur suggest that an extensive ice cap persisted over the eastern Vestfiroir peninsula at least until c. 9 ka BP.

U2 - 10.1016/j.quascirev.2015.09.001

DO - 10.1016/j.quascirev.2015.09.001

M3 - Journal article

SN - 0277-3791

VL - 126

SP - 140

EP - 157

JO - Quaternary Science Reviews

JF - Quaternary Science Reviews

ER -