Olwen Williams-Thorpe, one of the lead authors of the big OU report on the bluestones
I have frequently cited the seminal publication by Thorpe et al in 1991, which was republished online in 2014. I cannot understand why the Proceedings of the Prehistoric Society / Cambridge University Press still have this behind a paywall -- it should be accessible to everybody, given its importance in the bluestone provenancing debate. Anyway, here is the abstract......
It's a very big and impressive piece of work -- more than 50 pages long.
The Geological Sources and Transport of the Bluestones of Stonehenge, Wiltshire, UKProceedings of the Prehistoric Society , Volume 57 , Issue 2 , 1991, pp. 103 - 157
DOI: https://doi.org/10.1017/S0079497X00004527
Published online by Cambridge University Press: 18 February 2014
Richard S. Thorpe ,
Olwen Williams-Thorpe ,
D. Graham Jenkins ,
J. S. Watson ,
R. A. Ixer and
R. G. Thomas
(Note that Rob Ixer is one of the authors -- from a time before he was seduced away by the Pied Piper and his merry gang of storytellers.......)
ABSTRACT
Stonehenge on Salisbury Plain is one of the most impressive British prehistoric (c. 3000–1500 BC) monuments. It is dominated by large upright sarsen stones, some of which are joined by lintels. While these stones are of relatively local derivation, some of the stone settings, termed bluestones, are composed of igneous and minor sedimentary rocks which are foreign to the solid geology of Salisbury Plain and must have been transported to their present location. Following the proposal of an origin in south-west Wales, debate has focused on hypotheses of natural transport by glacial processes, or transport by human agency. This paper reports the results of a programme of sampling and chemical analysis of Stonehenge bluestones and proposed source outcrops in Wales.
Analysis by X-ray-fluorescence of fifteen monolith samples and twenty-two excavated fragments from Stonehenge indicate that the dolerites originated at three sources in a small area in the eastern Preseli Hills, and that the rhyolite monoliths derive from four sources including northern Preseli and other (unidentified) locations in Pembrokeshire, perhaps on the north Pembrokeshire coast. Rhyolite fragments derive from four outcrops (including only one of the monolith sources) over a distance of at least 10 km within Preseli. The Altar Stone and a sandstone fragment (excavated at Stonehenge) are from two sources within the Palaeozoic of south-west Wales. This variety of source suggests that the monoliths were taken from a glacially-mixed deposit, not carefully selected from an in situ source. We then consider whether prehistoric man collected the bluestones from such a deposit in south Wales or whether glacial action could have transported bluestone boulders onto Salisbury Plain. Glacial erratics deposited in south Dyfed (dolerites chemically identical to Stonehenge dolerite monoliths), near Cardiff, on Flatholm and near Bristol indicate glacial action at least as far as the Avon area. There is an apparent absence of erratics east of here, with the possible exception of the Boles Barrow boulder, which may predate the Stonehenge bluestones by as much as 1000 years, and which derived from the same Preseli source as two of the Stonehenge monoliths. However, 18th-century geological accounts describe intensive agricultural clearance of glacial boulders, including igneous rocks, on Salisbury Plain, and contemporary practice was of burial of such boulders in pits. Such erratics could have been transported as ‘free boulders’ from ‘nunataks’ on the top of an extensive, perhaps Anglian or earlier, glacier some 400,000 years ago or more, leaving no trace of fine glacial material in present river gravels. Erratics may be deposited at the margins of ice-sheets in small groups at irregular intervals and with gaps of several kilometres between individual boulders.
‘Bluestone’ fragments are frequently reported on and near Salisbury Plain in archaeological literature, and include a wide range of rock types from monuments of widely differing types and dates, and pieces not directly associated with archaeological structures. Examination of prehistoric stone monuments in south Wales shows no preference for bluestones in this area. The monoliths at Stonehenge include some structurally poor rock types, now completely eroded above ground. We conclude that the builders of the bluestone structures at Stonehenge utilized a heterogeneous deposit of glacial boulders readily available on Salisbury Plain. Remaining erratics are now seen as small fragments sometimes incorporated in a variety of archaeological sites, while others were destroyed and removed in the 18th century. The bluestones were transported to Salisbury Plain from varied sources in south Wales by a glacier rather than human activity.
ABSTRACT
Stonehenge on Salisbury Plain is one of the most impressive British prehistoric (c. 3000–1500 BC) monuments. It is dominated by large upright sarsen stones, some of which are joined by lintels. While these stones are of relatively local derivation, some of the stone settings, termed bluestones, are composed of igneous and minor sedimentary rocks which are foreign to the solid geology of Salisbury Plain and must have been transported to their present location. Following the proposal of an origin in south-west Wales, debate has focused on hypotheses of natural transport by glacial processes, or transport by human agency. This paper reports the results of a programme of sampling and chemical analysis of Stonehenge bluestones and proposed source outcrops in Wales.
Analysis by X-ray-fluorescence of fifteen monolith samples and twenty-two excavated fragments from Stonehenge indicate that the dolerites originated at three sources in a small area in the eastern Preseli Hills, and that the rhyolite monoliths derive from four sources including northern Preseli and other (unidentified) locations in Pembrokeshire, perhaps on the north Pembrokeshire coast. Rhyolite fragments derive from four outcrops (including only one of the monolith sources) over a distance of at least 10 km within Preseli. The Altar Stone and a sandstone fragment (excavated at Stonehenge) are from two sources within the Palaeozoic of south-west Wales. This variety of source suggests that the monoliths were taken from a glacially-mixed deposit, not carefully selected from an in situ source. We then consider whether prehistoric man collected the bluestones from such a deposit in south Wales or whether glacial action could have transported bluestone boulders onto Salisbury Plain. Glacial erratics deposited in south Dyfed (dolerites chemically identical to Stonehenge dolerite monoliths), near Cardiff, on Flatholm and near Bristol indicate glacial action at least as far as the Avon area. There is an apparent absence of erratics east of here, with the possible exception of the Boles Barrow boulder, which may predate the Stonehenge bluestones by as much as 1000 years, and which derived from the same Preseli source as two of the Stonehenge monoliths. However, 18th-century geological accounts describe intensive agricultural clearance of glacial boulders, including igneous rocks, on Salisbury Plain, and contemporary practice was of burial of such boulders in pits. Such erratics could have been transported as ‘free boulders’ from ‘nunataks’ on the top of an extensive, perhaps Anglian or earlier, glacier some 400,000 years ago or more, leaving no trace of fine glacial material in present river gravels. Erratics may be deposited at the margins of ice-sheets in small groups at irregular intervals and with gaps of several kilometres between individual boulders.
‘Bluestone’ fragments are frequently reported on and near Salisbury Plain in archaeological literature, and include a wide range of rock types from monuments of widely differing types and dates, and pieces not directly associated with archaeological structures. Examination of prehistoric stone monuments in south Wales shows no preference for bluestones in this area. The monoliths at Stonehenge include some structurally poor rock types, now completely eroded above ground. We conclude that the builders of the bluestone structures at Stonehenge utilized a heterogeneous deposit of glacial boulders readily available on Salisbury Plain. Remaining erratics are now seen as small fragments sometimes incorporated in a variety of archaeological sites, while others were destroyed and removed in the 18th century. The bluestones were transported to Salisbury Plain from varied sources in south Wales by a glacier rather than human activity.
Thanks to Tim Daw for drawing attention to this shorter version of the big study:
http://publications.thebritishacademy.ac.uk/.../77p133.pdf
Williams-Thorpe, O. and Thorpe, R.S. 1991 Geochemistry, sources and transport of the Stonehenge Bluestones. Proc Br Acad. 77, pp 133-161
6 comments:
Why is this glacial transportation study still behind a Paywall? As a former Chartered Librarian ( trained at Aberystwyth, by the way!) I conclude that The Prehistoric Society is involved in virtual CENSORSHIP. This paywall should be withdrawn FORTHWITH.
Tony Hinchliffe BA(Hons) Geography,Durham, Dip Lib (University of Wales)
I have just found out that Dr Mike Allen is a significant person on the board of The Prehistoric Society. He was a key member of Parker Pearson's Stonehenge Riverside Project, and lives near the river Wylye not that far from Stonehenge. We ought to contact him as his role is connected to research publications.
Mike Allen was involved in the "periglacial stripes" saga at Stonehenge -- and I was mystified that somebody referred to as a geomorphologist might really have signed up to MPP's extremely wacky hypothesis......... I think he refers to himself as an "environmental archaeologist".........
No, he ain't no geomorphologist. He's, amongst other things, an expert on prehistoric snails. It's a that chap called Charly French who says he's a a geomorphologist ( Cambridge)
As regards then periglacial stripes, I heard that editor, Mike Pitts, express some scepticism about these in the last 12 months.
Pitts seems to be demonstrating he is capable of independent thought from Pearson. Maybe they are not joined at the hip....
Geomorphologist? Ah -- French and Allen. Sorry -- my mistake.
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