A Slice Through Time: Dendrochronology and Precision Dating

175 Pages·1997·5.453 MB·English

by  M.G.L. Baillie

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A SLICE
THROUGH TIME
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A SLICE
THROUGH TIME
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e Dendrochronology and precision
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M. G. L. Baillie
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~ ~~o~;~;n~~~up
LONDONANDNEWYORK
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a © M. G. L. Baillie 1995
o
l
n
w Firstpublished 1995
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TransferredtoDigitalPrinting2005
Allrightsreserved. Nopartofthispublicationmay
bereproducedinanyform orbyanymeans,without
permissionfrom thePublisher
PublishedbyRoutledge
2ParkSquare,MiltonPark,Abingdon,Oxon,OX144RN
ACIPcataloguerecordforthisbookisavailablefrom
theBritishLibrary
ISBN071347654O(1imp)
Contents
7 List ofillustrations 6
1
0 Preface 9
2
ne Introduction 11
u
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7 1 The tree-ring dating method 16
2
4
4 2 Oak dendrochronology comes
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2 ofage 32
t
a
o] 3 Art-historical dendrochronology
g
e and the limitations ofoak
i
D
n dendrochronology 45
a
S
a, 4 Archaeological dating and some
i
n ultimate chronological truths 57
r
o
f
li 5 Volcanoes and tree-rings 73
a
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of 6 Volcanoes and chronology: the 91
ty AD 540 story
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e
v 7 Volcanoes and chronology: the
i
n
U Bronze Age eruption of
[
y Santorini (Thera) 108
b
d
e 8 Socio-economic information
d
a from tree-rings 122
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9 Environmental reconstruction
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from tree-rings 135
10Problems with dating the Shang
and the New IZingdom 149
Conclusion 159
Bibliography 161
Index 172
5
III ustrations
1.1 Schematicrepresentation ofthe 3.2 Suggestedrelationships oftwo
principle behind dendrochronology 16 Dublinboattimbers 54
1.2 Schematic representation ofthe dat 3.3 Possible 'matching' positions for
7 ingprocess 17 shortsample Q3138a 54
1
0 1.3 Completelyintegrated correlations 3.4 Difficultiesin attemptingto date
2
e between independent chronologies 20 individual samples at a distance 55
n
u 1.4 Sapwood completeness affects exact 4.1 The phantom 'phase' in the samples
J
7 interpretationoffelling phases 22 from Teeshan crannog 58
2
4 1.5 Sapwoodnumbers for oaks from 4.2 Apparentphantomphase(s) in
4 different areas 24 timbers from IslandMacHugh 60
:
0
2 1.6 Hollstein's proposedmethod for 4.3 Howthe IslandMacHughposts
at assessingclosestfelling date 24 were made from riven oak 61
o] 1.7 The Irishmedieval chronology 4.4 Figure 4.2 redrawn to illustrate the
g
e confirmedbyconsistentlinks to two riven-oakhypothesis 62
i
D living-tree chronologies from Britain 26 4.5 The chronological danger associated
n 1.8 The fourteenth-centuryAD depletion with split oaktimbers 63
a
S /regeneration phase and the Black 4.6 Intrinsic datingfails withpost-
a, Death 26 groups from IslandMacHugh 63
i
n
r 1.9 An earlyexample oftertiaryreplica 4.7 Non-random distribution ofdated
o
f tionbetweenindependent Irish archaeological sites 68
i
l
a chronologies 27 4.8 High-precision radiocarbon dating
C
f 1.10 The DarkAge linkexploiting ofArdnagross horizontal mill 69
o
y intermediate Englishmaterial 28 4.9 High-precision radiocarbon dating
it 1.11 Fulltertiaryreplication ofthe ofCaerlaverockPhase 3 bridge 70
s
r
e European oakchronologies for the 4.10 High-precision radiocarbon dating
v
i lasttwo millennia 29 ofwickerhouses at DeerparkFarms 71
n
U 1.12 The individual tree-ringpatterns 5.1 The confirmationofa 1627 BC
[
y makingup the Garry Bog 2 environmental event 76
b
d chronology 30 5.2 Coincidencebetweenice-core acidi
e 1.13 The 1980 status ofthe European ties and narrowestrings inIrish
d
oa longchronologies 30 bogoaks 78
l
n 2.1 The Swan Carrchronologyforms a 5.3 Oak-ringpatterns from four
w
o critical link 34 differentbogs showingthe
D
2.2 The tentative completion ofthe 1159-1141 BC event 82
Belfastchronologyin 1982 36 5.4 Burgess' postulatedpopulation
2.3 The Irish-Germanlinkwhichraised graphfor Britain 88
questions aboutthe integrityofthe 5.5 The dates ofvolcanic effects and
German chronology 37 archaeological sites in Ireland 90
2.4 The weaklinkin the 1982 German 6.1 RestrictedgrowthinIrishand
prehistoric complex 38 Scottishchronologies atAD 540 95
2.5 New chronologies reinforce the orig 6.2 Fennoscandinaviansummer
inal Irish chronology 40 temperatures 96
2.6 CrostonMoss illustrates the power 6.3 Meangrowthindices for fifteen
ofrandom sampling 42 European oaksites 96
6
3.1 Increasingcorrelations eastward 6.4 Comparison oftree-ringeffects at
across Europe indicate importation 48 theAD 536-45 event 97
6.5 Archaeological change in Germany 8.3 The 'missinggeneration' ofIrish
and Ireland atAD 536-45 99 oaks 126
6.6 Archaeological change inEurope 8.4 Tree-ringsuggestions ofclimate
andAmerica atAD 536-45 100 changeAD 800-1000 127
6.7 A sixth-centuryAD unfinished 8.5 Hiatus in site constructioninIreland
dug-out 103 AD 648-720 128
6.8 Comparison oftree-ringeffects at 8.6 Evidence for medieval tradefrom
the AD 1815 Tambora event 105 tree-ringsourcing 131
6.9 Summaryofphenomena related to 8.7 Correlations showingIrish origin of
7 the AD 536-45 event 107 Roskilde boattimbers 132
1 7.1 Radiocarbon dating ofthe Bronze 9.1 Temperature records from American
0
2 Age eruption ofSantorini 110 and Fennoscandinaviantree-rings 140
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n 7.2 The impossibility ofdating 9.2 Hemispheric pressure patterns for AD
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J Santorinibysingle-sample 1816from tree-rings 141
7
2 radiocarbon dates 110 9.3 GarryBogtree-ringgap and dated
4 7.3 Acid layers inthe Camp Century archaeological sites 143
4
0: core 119 9.4 The 200-13 Be gap in the Irishbog-
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t 7.4 Correlationbetweenthe Camp oakchronology 144
a
] Century and Dye 3ice-cores 120 9.5 Tail-offinNeolithic radiocarbon
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g 8.1 Buildingphases in seventeenth- dates in the BritishIsles 146
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i centuryUlster 123 9.6 Environmental effects atthe start of
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n 8.2 European buildinghiatus atthe time the Neolithic 147
a ofthe BlackDeath 124
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7
Preface
During the 1970s and 1980s I had the great will be left out and to them I apologize in
good fortune to be heavily involved in the con advance.
7 struction ofsome ofthe Old World's first long The Tree-Ring Laboratory at Queen's
1 tree-ring chronologies. These year-by-year University, Belfast, has always been closely asso
0
2 records of mean oak growth, stretching back ciatedwithQueen'sRadiocarbonLaboratoryand
e
n some sevenmillennia, offernot justthe opportu much ofthe driving force behind the construc
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J nityto date some ancient sites and artefactsvery tion of the oak chronologies came from
7
2 precisely, but additional opportunities to inves involvementwithDrG.W. Pearsonandtheradio
4 tigate the stored information within a parallel carbon calibration work in Belfast. The tree-ring
4
0: biological system, parallel, that is, to the human work was greatly facilitated by generous grants
2
t populations who inhabited the earth over the from the Science-Based Archaeology Committee
a
] same period. The environmental potential of ofthe ScienceandEngineeringResearchCouncil
o
g these tree-ring chronologies is immense and I in Britain and latterly by support from The
e
i have been lucky enough to be one ofthe first WolfsonFoundation. Itwouldnothavebeenpos
D
n workers to have an opportunity to look into sible without the involvement ofa whole list of
a some ofthesepastrecords. Havingwitnessedthe research assistants, though for brevity I shall
S
a, large and expanding literature on den mention only the last four: Ms Elizabeth
ni drochronology, and its related disciplines, Halliday, Dr Martin Munro, Mr Andrew
r
o dendroecology and dendroclimatology, I feel McLawrence and most importantly Mr David
f
li that there is room for someone to draw together Brown whose measurement and organizational
a
C some ofthe disparate sources andproduce atext abilities underpin the Belfasttree-ring operation.
f
o which is narrative in character and which will I have been greatly assisted by interchange of
y serve to draw the student, or the interested lay data and information, particularly from Ms
t
i
rs reader, into the subject. Jennifer Hillam and Ms Cathy Groves, at the
e
v Inevitably, I have drawn heavily on work with Sheffield Tree-Ring Laboratory; Mr Ian Tyers at
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n which I have been personally involved. Much of London; Dr Ann Crone at Edinburgh; Dr Keith
U
[ the information has been published in separate Briffa at Norwich; the late Dr Bernd Becker at
y
b articles overtheyears, andthisbookis anoppor Stuttgart; Dr Burghart Schmidt at Kaln;
d tunity to draw elements from several of these Professor Dieter Eckstein at Hamburg and Dr
e
d together into a single text. However, as will Hubert Leuschner at Gattingen, though many
a
o
l become clear to the reader,' there is nothing others could be mentioned. Important wood
n
w insular about Irish dendrochronology. samples have been supplied by many workers in
o
D Information from tree-ring work is inherently differentgeographical areas andinnumerous dif
internationalincharacter. This isbecause, being ferent disciplines, and I must acknowledge their
underpinned by precise calendrical dating, tree generosity. OfparticularimportanceareMrMike
ring studies allow real-time comparisons from Harvey who introduced us to Croston Moss,
one region to many others; lessons learned in Lancashire; Dr Malcolm Hughes and Dr Pat
one area are often universally applicable. Leggett who donated their Lancashire sub-fossil
Indeed, the range ofinformation covered in the collection; Mr Richard Parr and the staffat the
following text would not have been possible Godwin Laboratory, Cambridge, for supplying
without the efforts of many other individuals their East Anglian sub-fossil collection and the
around the world. I would like to acknowledge Staffat the Nottingham Tree-Ring Laboratory
the debt lowe to the many scholars who have for the original river gravel oaks from the River
helped make this text possible. Inevitably some Trent. 9
Preface
As will be evident in the following text, my Finally,thisbookisabouthardinformationand
excursionsinto thepossible environmentaleffects soft information. Hard information is that which
ofsome major, ancient, volcanic dust-veil events is precisely dated and where relationships can be
have led to interchange ofinformation and ideas worked out with some confidence. Soft informa
with awide range ofscholars in other disciplines. tion is more or less everything else which is not
Among others I would like to thank Dr Sturt preciselydated- much ancienthistory, almostall
Manning, Dr Mike Rampino, Dr Steve Self, Dr prehistoric archaeology, quite a lot ofvolcanolo
Kevin Pang, Dr Greg Zielinski, Mr Richard gy. This realization, based on chasing the past
7 Warner, Mr Leroy Ellenburger and Mr Don effectsofancienteruptions,bringsonetothecon
1 Carleton. Ihaveenjoyedmanyhours ofusefuldis clusion that, in reality, we know almost nothing
0
2 cussion with my colleagues ProfessorJon Pilcher, aboutthepast- almostnothing, thatis, atannual
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n Dr Jim Mallory, Dr Valerie Hall and Dr Gerry resolution. To takebutone example:
u
J McCormac. Much ofthe content ofChapter 9 is
7
2 taken from Dendrochronology and Past TheGreatCycleoftheMaya Calendarwhich
4 EnvironmentalChange, read inFebruary 1991 at a beganin darkness on 13 August 3114 BC will
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0: joint symposium of the Royal Society and the cometo anend... on23 DecemberAD 2012
2
t British Academy, published in Proceedings ofthe ... on that day, the ancient Maya scribes
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] British Academy, vol. 77, New Developments in would say, it will be 13 cycles, 0 katuns, 0
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g ArchaeologicalScience and I am grateful for their tuns, 0 uinals and 0 kins since the Beginning
e
i permission to reproduce it here. Similarly, I ofthe Great Cycle. (Coe 1992)
D
n would like to thank the Ulster Museum for their
Sa permissionto re-publishFigure 1. So what happened in 3114 BC to start off a
a, I cannotleave these acknowledgementswithout GreatCyclefortheMaya?Wasitadatepulledout
ni reference to the late Professor Valmore C. ofthe air purely by retro-calculation? Was there
r
o LaMarche Jnr of the Laboratory of Tree-Ring anykind ofnaturaleventwhichactedas atrigger?
f
li Research in the University ofArizona at Tucson. Ancienthistory, archaeology and even Greenland
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C Val, together with Dr Kathy Hirschboeck, first ice-core records can't help: in terms ofconven
f
o drew attention to the date 1627 BC and suggested tional study there is absolutely no information
y thatthe tree-ringeffectsinthatyearmightbe due available about that year. The only real informa
t
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rs to the Bronze Age eruption ofSantorini in the tionabout3114BC islockedup inthe cellulose of
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v Aegean. The fall-out from that story occupies the tree-ringswhichgrewinthatyear. Thatinfor
i
n almost halfofthis book. Ifwe think oftheir date mationis available inthe form ofbristleconepine
U
[ as asolitarysignpost, pointingbackinto themists samples, from thewesternUnited States, andoak
y
b oftime, it was that signpost which set me offon rings from Ireland, England, Germany and
d the strangebutfascinating journeyinto aspects of Switzerland. Ifwe want to study the past in real
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d archaeology, volcanology and ancient history detail, tree-rings arethe essentialstartingpoint.
a
o
l whichI describe in Chapter5 andthereafter.
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10
Introduction
During the 1980s the science ofdendrochronol nologists in the United States he could be sup
7 ogy came of age in Europe. Long reference plied with samples ofbristlecone pine or foxtail
1 chronologies for oak were completed for most of pinewhichgrewinNevadain that sameyear.
0
2 the later Holocene and, as a result, for the first Such precisely dated samples have already
e
n time precise calendrical dating became available been used to duplicate the calibration of the
u
J across a swath ofthe OldWorld. radiocarbon timescale by providing samples of
7
2 The implications ofthat success are only now cellulose, ofpreciselyknown age, for the analysis
4 beginning to dawn on the scientific community. ofits residual radiocarbon content; so the scien
4
0: The work has been well known to archaeologists tific community already has a continuous
2
t and to people working in the field ofradiocar measure ofvariation in the amount ofradiocar
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] bon; however, there are still surprisingly large boninthe atmosphereinthe past. Moreover, not
o
g numbers of people who have never heard the only has this work been done, it has also been
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i term 'dendrochronology' and their reaction on duplicated using wood samples supplied by
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n having it explained tends to be at the level differentworkers andtheradiocarbonconcentra
a 'wouldn't it be nice ifsuch a method could be tions have been measured In different
S
a, produced but have you thought ofthe following laboratories- sothe calibrationisalreadyarepli
ni problems ...'. Frequentlyit is an uphill battle to catedsystem. The radiocarbon calibrationcurve,
r
o explain that, yes, ofcourse there were problems produced primarily with the view of allowing
f
li and chronologies took many years to build but archaeologists to refine their understanding of
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C they are here, they are completed and replicated chronology, also forms one of the best proxy
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o and producing precise dates for a range ofboth records ofvariation in solar activity with time;
y archaeological and naturally preserved timbers. itselfa fundamentally important parameter in
t
i
rs On occasion this message is best driven home by anystudyofpastvariations in earth climate.
e
v pointing out that, ifthe reader cares to give any Now obviously, for someone who has only just
i
n calendar date in the last seven millennia, den been introduced to the concept of den
U
[ drochronologists can now supply a sample of drochronology, the astonishing fact is the
y
b wood which grew in thatyear- a time capsule of discovery that it is more than just a concept - it
d biological material. Indeed, dendrochronologists already exists. Intuitively a method which offers
e
d cansupplynotonebutmanybiologicaltime cap calendrically precise dating should always have
a
o
l sules for any year in the last seven millennia. been a 'holy grail' for both archaeological and
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w Moreover,formanyperiodsthesepreciselydated environmental dating - something to be striven
o
D time capsules exist over a wide geographical area towards. Instead, in a single leap, in the mid
and for avarietyofsubstrates. 1980s, the grailwas reached inEurope.
Take as an exampletheyear 1492Be. Aworker One irony is that dendrochronology, aimed at
interested in studying cell size or cell density or the calibration ofthe radiocarbon timescale, has
isotopic compositionortrace elementconcentra tended to expose the limitations ofradiocarbon
tions in thatyear could be suppliedwith samples dating. Tree-ring dates have started to accumu
ofoak wood which grew in northern or southern late for historic and prehistoric sites and
Ireland, in western oreasternEngland, in north structures and have shed a new hard light on
ern or southern Germany and in Switzerland. If chronological issues. Moreover, ancient history
there was necessity, samples could be supplied which had regarded itselfas possessed ofa supe
from 10 different trees in each ofthese areas. If rior chronological system, for the Mediterranean
that worker was willing to contact dendrochro- at least, suddenly has a competitor. The hard 11