Why are archaeologists so scared of glacial erratics?

 King's Quoit, Manorbier -- as ever, made of large stones from the immediate vicinity

This is an interesting chapter in MENGA -- relating to European megalithic structures.  The authors (Scarre, Sanjuan and Wheatley)  make the point that megalithic monuments are preferentially or primarily made from stones gathered up in the locality -- and then they refer to "others brought from more distant sources." Now why did they have to use the term "brought from" when they could have used the phrase "which have come from" instead?  It's true that jadeitite axes might have been traded items, carried over large distances, but it's also true that in many instances axes have simply come from erratics found not far from the find spot -- and this point has been made by Stephen Briggs, Olwen Williams-Thorpe and many others over the years.  Has the term "glacial erratic" been banned within the archaeological community?  The authors go on, referring to these exotic stones:  "These are materials that have been selected and transported........" 

Hang on a bit, chaps.  Sloppy thinking runs through this whole section of the article.  What's the point of making a generalisation about local stones being used whenever possible, and then talking about a gigantic exception to the rule on the basis of no evidence whatsoever?  The quarry myth runs deep, and causes normally rational people to say very irrational things.

EXPLORING TIME AND MATTER IN
PREHISTORIC MONUMENTS: DEBATING
ABSOLUTE CHRONOLOGY AND RARE ROCKS
IN EUROPEAN MEGALITHS
Chris Scarre (Department of Archaeology, Durham University). [ chris.scarre@durham.ac.uk ]
Leonardo García Sanjuán (Department of Prehistory and Archaeology, University of Seville).
[ lgarcia@us.es ]
David Wheatley (Department of Archaeology, University of Southampton).
[ D.W.Wheatley@soton.ac.uk ]
MENGA. REVISTA DE PREHISTORIA DE ANDALUCÍA // MONOGRÁFICO Nº 01. 2011. PP. 11-23. ISBN 978-84-9959-083-7-ISSN 2174-9299 // INTRODUCTION
Proceedings of the 2nd European Megalithic Studies Group Meeting
(Seville, Spain, November 2008)
Menga. Journal of Andalusian Prehistory, Monograph nº 1


Extract:

4. RARE ROCKS

Megalithic monuments consist primarily of
materials derived from the local landscape. The
artefacts associated with them are likewise primarily
of local origin. Alongside these local materials,
however, are others brought from more distant
sources. They include both objects of ‘exotic’ stone
deposited within or around megalithic monuments;
and, in some cases, the megalithic blocks of which
the monuments themselves are built.

These are materials that have been selected and
transported – that have been chosen for some
particular quality that they possess, be it colour,
strength, shape, texture, or indeed the special
significance of their places of origin. Some, for
example, are from relatively remote mountainous
regions: the bluestones from southwest Wales used
in the construction of Stonehenge (Thorpe et al.
1991; Bevins et al. 2011; Darvill 2009; Parker
Pearson et al., this volume), or the jadeitite axes of
western and northern Europe now traced to a
precise place of origin in the western Alps (Pétrequin
et al. 2006).