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Transcript of Van Helmond BA Thesis 2008
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Forum Hadriani: A dendrochronological study to determine theage and origin of wood from a Roman quay and landing stage.
A sculpture of the Roman emperor Hadrian,the founder of Forum Hadriani.
(www.romancoins.info)
N.A.G.M. van HelmondProf. dr. E. JansmaApril - July 2008
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List of contents
Abstract 3
Introduction 4
Research question & Hypothesis 7
Materials & Methods 9
Results 20
Interpretation 25
Discussion 36
Conclusions 38
Acknowledgements 39
References 40
Appendix 1: Shapes of the studied cross sections of the wood (scale 1 : 5) 42
Appendix 2: Photos of the excavation 47
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Abstract
We determined the age and origin of the wooden remains of a Roman harbour. The remains
of the harbour were found on the archeological site of the ancient Roman city of Forum
Hadriani. Archeologists assume that the wooden remains are parts of a Roman quay andlanding stage.
The wooden remains can be classified in two groups, based on their dating. One group dates
around AD 159. Another group dates around AD 218. when we plot the dating of the wood
samples on the excavation map, it becomes clear that the harbour was constructed during
(at least) two phases.
The origin of the timber is diverse. One group matches against a regional calendar built out
of the growth patterns of southern German oak. A second group corresponds with a regional
calendar from the Saar-Mosel region in central western Germany. Because the object and
site calendars used to construct the regional Saar-Mosel calendar are known, we can make
a more detailed prediction. The wood shows high correlations with wood used in a Roman
bridge in Koblenz, a Roman bridge in Trier and wood found during an excavation near Mainz,
which points at a wood provenance between the Mosel and Rhine, South of the Mosel and
East of the Rhine. A third group of timbers correlates with domestic calendars from the
Netherlands and represents indigenous oak.
Comparison with wood from an earlier studied water well, found in Forum Hadriani, points
out that the youngest phase of the harbour may have been built simultaneously with this
water well. The likelihood that these structures were related in terms of the organization of
their construction is strengthened by the fact that the wood of the water well shows a strong
similarity with the wood used for the harbour.
The dimensions of the studied wood reveal that the timber from southern Germany and the
Saar-Mosel region, used for the harbour in Forum Hadriani, was derived from dense forests.
The wood that correlates with domestic calendars originates from trees that probably grew in
a more open landscape.
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Introduction
Biogeology is the field of science that studies the interactions between Earths biosphere and
lithosphere. Traditionally, geologists deal with time spans of millions of years, whereas
biologists deal with time spans of days to years. Biogeologists complement both, by studyingprocesses in the past in extreme detail and by looking at contemporary and future processes
at intermediate time scales of decades and centuries. Biogeology examines biotic,
hydrological and terrestrial systems in relation to each other, to help understand Earths
climate, oceans and other effects on geological systems.
Biogeology consists of several sub disciplines like palaeoclimatology, microbiology, systems
ecology, landscape ecology, biogeochemistry, organic chemistry and palaeoecology.
Dendrochronology can be placed in several sub disciplines of biogeology, depending on its
usage. Dendrochronology can be used to study present climate and reconstruct past climate
(palaeoclimatology). But it can also be used to study factors that affect Earths ecosystems
(systems ecology). There are several other usages of dendrochronology (see e.g.
Schweingruber 1996).
Dendrochronology is an interesting branch of science as it forms the link between biogeology
and cultural studies, like archeology. Trees are part of the biosphere and therefore part of a
field studied by biogeologists. When a tree is felled and used by humans it enters the study
field of archeologists. Now we have a link between biogeology and archeology. The tree is a
source of natural data, but the data are influenced by humans. When we study trees (or the
remains of trees) felled or/and used by humans we use a biogeological branch of science to
deduct human activity in the past.
In this study we use the science of dendrochronology to determine the age and origin of
wooden remains of a harbour excavated at the archeological site of the ancient Roman city
of Forum Hadriani.
Fig.1) The arrow indicates the location of ForumHadriani (Kosian, 2008)
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Forum Hadriani is situated in todays Voorburg (fig. 1). It was the most northern city of the
ancient Romans on the European continent. Forum Hadriani is the second oldest city of The
Netherlands after the ancient city of Noviomagus, todays Nijmegen (Buijtendorp, 2006).
The city was located in the centre of the civitas of the Cananefates, an ancient Germanic
tribe, which lived in the Rhine-delta, situated in the western part of the Roman province
Inferior Germania (Bazelmans & De Jonge, 2006).
The first settlement, which formed the basis for Forum Hadriani, was a small native village of
the Cananefates. They built their village along the Fossa Corbulonis or Corbulo-canal. This
waterway was constructed by the Roman general Corbulo around AD 47. The canal formed
an important economical connection between the two major rivers Rhine and Meuse. After
the Revolt of the Batavi (AD 69-70) the Cananefates became loyal allies of the Romans.
Afterwards the settlement, which we know today as Forum Hadriani, started to play a central
role in the region (Buijtendorp, 2006).
In AD 121 and/or 122 the Roman emperor of that time, Hadrian, made a voyage along the
northwestern border of the Roman Empire. During his voyage Hadrian visited the former
native settlement of the Cananefates, located at todays Voorburg. The emperor gave his
own name to the town, after which it which was rebuilt in Roman style. In a few years Forum
Hadriani developed into a flourishing market city. During the reign of Antoninus Pius,
between AD 138 and 151, Forum Hadriani acquired town rights. The official name of the city
then changed into Municipium Aelium Cananefatium (Aelius was the family-name of Hadrian)
shortly written as MAC (Buijtendorp, 2006).
It is certain that Forum Hadriani was an important local city. This is proven by the major
Roman road (about 6 metres wide), which was found by archeologists in the area near
Forum Hadriani. This road was already known because it appeared on the Tabula
Pautingeriana, an old Roman route map (Waasdorp, 2006).
It is sure that Forum Hadriani flourished up to AD 160, when the high days of the Romans
came to an end. But archaeological research does not show an obvious decrease in Roman
activity in the Netherlands after AD 160.In the third century the Roman Empire collapsed, thats why Forum Hadriani was largely
abandoned between AD 250 and 275. Although the Roman Empire partly redeveloped again
after the big collapse, Forum Hadriani didnt revive its glory days ( De Jonge, 2006).
The first archeological excavations on the site of Forum Hadriani were done by C.J.C.
Reuvens (1793-1835) between 1827 and 1834. Reuvens was the first professor in
archeology worldwide. Unfortunately he died before he was able to publish his findings ( Van
Es, 2006).
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Almost a century later J.H. Holwerda (1873-1951) continued the excavation started by
Reuvens. Holwerda published about his excavation, but he interpreted his findings as a
Roman naval base instead of a Roman city (Van Es, 2006).
In 1960 J.E.A.Th. Bogaers (1926-1996) was the first archeologist to recognize that he was
dealing with the remains of Forum Hadriani. His conclusion was based on analysis of several
inscriptions and did not lead to any comprehensive fieldwork (Van Es, 2006).
Since the excavation of Bogaers several excavations took place on the site of Forum
Hadriani. The material used for the current study represents the harbour of Forum Hadriani
and was collected during the most recent excavation, in 2007-2008, Amsterdams
Archeologisch Centrum (AAC, University of Amsterdam).
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Research question & Hypothesis
Research question
The aim of this study is to determine the age and origin of the wooden remains of the
harbour excavated at the archeological site of the ancient Roman city of Forum Hadriani.For the archeologists it is very important to know the age of the harbour. The harbour could
be the start of the city, because it would be the perfect manner to bring in the building
materials the city required. Therefore we need the oldest date. But the youngest date is also
very interesting, because this would represent the year during which the harbour was
maintained for the last time. This year might also indicate at what time big economical
investments in this part of the Roman Empire came to an end
Hypothesis a: the age of the structure
Since we know that Forum Hadriani started to flourish after the visit of the Roman emperor
Hadrian, somewhere around AD 121/122 (Buijtendorp, 2006), we can predict that the
construction of the harbour took place after this event. Therefore we assume that the
construction of the harbour had a military background, meaning that the construction of the
harbour was a military action.
We know that the high days of the Roman Empire, and therefore Forum Hadriani, came to an
end somewhere between AD 151 and 160 (De Jonge, 2006). Therefore we may expect that
the harbour was built somewhere between these two events. This means it would be built
between AD 121 and 160. We can even focus on a smaller interval. It is known that Forum
Hadriani acquired town rights between AD 138 and 151 (Buijtendorp, 2006). We expect that
the construction of the harbour took place after the city acquired town rights. Our hypothesis
is therefore that that the construction of the harbour started after AD 138 and was finished in
the period between AD 138 and 160. We furthermore assume that the wood used for each
separate construction phase was felled simultaneously (i.e., in the same year). From a
logistical point of view, it would be logical that the used wood was felled at the same time.
Hypothesis b: the provenance of the wood
We know from other dendrochronological studies on Roman wood found in the Netherlands
that Roman wood in part did originate from domestic forests. This is for instance the case
with the construction timbers of the Roman river barges De Meern 1 (built around AD 148)
and De Meern 4 (AD 100; Jansma, 2007a, 2007b). But in the second century, the Romans
also used oak from German forests for building activities in the Netherlands. This was the
case with the river barge De Woerden 7, which was built from a mix of oaks from the
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catchment basin of the river Mosel and oaks that grew in the vicinity of the Dutch town of
Zwolle (Vorst, 2005).
When we take a look at Roman wood provenance from a logistical point of view, we would
expect the use of domestic wood. Transport of wood from Germany to the Dutch coast would
have cost lots of effort. It is much easier to use wood from locations near the construction
site. But this raises the question whether enough domestic wood was available at the time of
the construction of the studied structures at Forum Hadriani. The answer is: probably not. We
know from several locations near the limes1 that around AD 100 and AD 125 a new wooden
road, quay, and shore sheets were placed (Enckevort & Vos, 2006). It is unlikely that in the
following decennia local forests had recovered sufficiently from this period of extensive wood
use and we therefore expect that construction timber in Forum Hadriani was derived from
forests further away.
We also assume that per construction phase the wood originates from the same region
and/or forest stand, because in terms of logistics it is much easier to coordinate transport of
wood from one single region and/or forest stand, than it would be to organize several
transports from a variety of regions.
Hypothesis c: different phases of construction
Archeologists think they have excavated a minimum of two construction phases (Koot,
written communication, June 21st, 2008). The oldest phase (fig.6, materials & methods)
consists of the two eastern rows of posts in trench 2. The row of posts to the western part of
trench 2 belongs to a younger phase. It is thought that the posts in trench 1 have the same
age as the posts in the western part of trench 2 .
Hypothesis d: chronological and organizational relationship with existing data
One last research question regards the relationship of the studied timbers (age and
provenance) with earlier dendrochronological results from the same site. Earlier
dendrochronological research had focused on a water well from Forum Hadriani (RINGReport 1988001). This material was shown to date in ca. AD 220, which is later than the
predicted age of the quay and landing stage. We therefore expect no chronological and
organizational relationship between the construction of the water well and the construction of
the quay and landing stage at Forum Hadriani.
1Limesis the Latin word for frontier. The limeswas the fortified frontier of the Roman Empire.
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Materials & Methods
Dendrochronology
The term dendrochronology is derived from three Greek words. These are dendron, which
means tree, chronos, which means time and logos, which means the study or science of.
Dendrochronology is the science that uses the growth rings in trees to date their exact year
of formation and to study environmental phenomena that are recorded in their growth
patterns. Chronological information derived from tree rings can be used to analyze temporal
and spatial patterns of processes in the physical and cultural sciences (Grissino-Mayer,
1996).
Fig. 2) Schematicrepresentation of theprinciple of cross-dating
in dendrochronology.(Baillie, 1982)
In temperate climates a living tree produces one growth ring every year. Ring formation takes
place during the growing season, between the months of March/April and October. If one
takes a sample from a living tree, the year of sampling coincides with the calendar year in
which the outer ring in the tree (and in the sample) was formed. The growth patterns of living
trees can be matched to the ring patterns of trees used for instance as beams in historic
buildings (fig. 2). This process of cross dating is carried on using the patterns of successively
older timbers from buildings, archeological sites and, ultimately, from natural vegetation
remains buried in situ(in lakes, peat and swampy areas) or imbedded in river sediments. As
a result ultra-long master chronologies can be constructed, with lengths up to nine millennia.
These master chronologies are not built out of single trees, but out of the average of
hundreds or even thousands of trees from the same species (mostly oak and coniferous
species). Master chronologies are based on data that represent single species from well-
defined regions with comparable environmental characteristics (soil, hydrology, climate;
Baillie, 1995). Once master chronologies are available for a given region, it becomes
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possible to determine the age and origin of a random sample of wood that originated from
(grew in) this region.
Samples
The research was done on cross sections of wooden posts. The wood comes from oaks
(Quercus). It is easy to recognize wood of oaks because the wood has very broad pith rays
and a simple ring porosity (Brinkkemper et al., 2007). With a microscope it is not possible to
determine which Quercusspecies it is. We assume that we are dealing with either the
pedunculate oak (Quercus robur) or the sessile oak (Quercus petraea). Today these two
species are most abundant in Northwestern Europe. We know that nowadays the
pedunculate oak (Quercus robur) is highly abundant in the Netherlands, while the sessile oak
(Quercus petraea) is rare (Brinkkemper, written communication, June18th, 2008). But the
environmental conditions during the Roman era differ from todays conditions. Therefore it is
not possible to say anything useful about the species of oak used for the construction of the
harbour.
Archeologists provided samples of different sizes for dendrochronological research. After
they had excavated the wood, they cut cross sections from the timbers, which they wrapped
in foil to prevent them from drying out. All samples were labeled with cards. These cards
contained basic information like the code of the excavation, the number of the found object,
the feature number, the date of excavation and the person responsible for the excavation of
the object.
The smallest samples are cross sections of about 15 x 15 cm. The biggest samples are
about 35 x 35 cm (Appendix 1). Most of the cross sections of the timbers have a rectangular
or square shape. But we also found some trapezium-shaped cross sections. Some samples
appear to have had an octahedral shape. A few samples had been broken into pieces,
therefore it was impossible to identify the original shape of these samples.
PreparationBefore one starts measuring the tree-ring pattern of a sample, it is necessary to prepare a
fresh radius. This is done with different tools. It starts with the soft parts of the wood.
Especially the outside of water-logged wood is very soft as a result of century-long direct
contact with the groundwater. These soft parts are prepared with fresh (unused)
razorblades (Gillette Blue Extra). For the harder parts we applied razorblades that had
already been used and were somewhat blunter. Because the wood had been buried in sand,
lots of sand grains were attached to the samples and were on occasion engrained in the
wood. Therefore the blades got blunt after a while and needed to be replaced. When
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preparing large hard surfaces we used the scalpel. Samples that were to wet for preparation,
were dried with water absorbing tissues before treatment..
We prepared and measured two radii per sample and used these to calculate the average
annual tree growth. Average series are better suited than single series to approach the
overall annual growth of a tree. In addition, using multiple measurement series per sample
has the advantage that the number of measured rings can be maximized. It is very important
to measure as many rings as possible per sample, because every measured ring means
extra information. Therefore it is important to start the measurement as close as possible to
the pith up to the ring which is closest to the bark of the tree.
Measuring
Measuring starts with the oldest ring and ends with the youngest. An oak tree ring is
characterized by a layer of big vessels (spring wood), which are built by the tree in early
spring (March and April), and smaller cells (summer wood) which represent the remaining
growing season (April to October). The next ring of big vessels in the wood represents the
next new growing season. Ring boundaries in oak are easily discerned using a microscope
Measuring was done using a binocular with different magnifications (6.4x, 10x or 16x). The
thickness of the tree rings determines which magnification is used. The sample is placed on
a measuring platform, which has an internal measuring device with a precision of 0.01 mm.
The platform is linked to a computer. Using the software PAST4 (Bernhard Knibbe, 1995-
1999; Bernhard Knibbe and SCIEM, 1999-2005) all ring widths were registered, and
diagrams of tree-ring patterns were constructed. Subsequent statistical analyses also were
performed with PAST4.
Fig.3) The photo shows a microscopic image of sometree rings of an oak. (www.microscopy-uk.org)
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Dating
The next objective was to date the samples. Since we know the wood is from the Roman era,
we needed to compare the measured tree-ring patterns of the individual samples with the
available master chronologies that represent this time interval (1st to 4th century AD; see
paragraph below). When the measured patterns match the master chronology it is possible
to date them to(Fig. 4).
Fig. 4) Schematic representation of the dating process. (Baillie, 1995)
A dendrochronological match is calculated using various variables: visual comparison, the
percentage of parallel variation (%PV) with probability of exceedence (P) and cross-
correlation and Students t-values.
The most important cross dating technique is visual comparison of the plotted curves
(Jansma, 1995). This can be done with the computer program PAST4. The computer
program shifts the two curves for a proper match, after which comparison is easy.
PV (%) expresses the percentage of ring widths that at a given position simultaneously show
an increase or decrease relative to the preceding width (Jansma, 1995). The probability of
exceedence (P) is the probability that the obtained result is accidental. A high PV(%)
combined with a low P-value are indicators for a good dendrochronological match.
A Students t-value is based on the coefficient of (cross)correlation. Students t-value is a
measure for the correlation between two series at each position of overlap.
In dendrochronological dating a Students t-value of less than three is meaningless and a
value over six almost always indicates that two patterns can be matched visually (Jansma,
2005).
In dendrochronology it is allowed to say that two pieces of wood represent the same tree if
the patterns of two pieces of archaeological wood match with a t > 10.
To make sure we are dealing with two pieces of wood from the same tree we also use visual
comparison of the tree ring patterns.
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For the samples with sapwood we can calculate the estimated felling date of the tree. If a
sample contains sapwood we can predict the total number of tree-rings (from germination till
felling). Therefore we can make an approximation (with help of a computer program) for the
total number of sapwood rings in the tree. With this approximation we can give a felling date
for the tree a margin. The margin is added because the number of sapwood rings differs
per tree. The used program gives a minimum and a maximum number of sapwood rings
belonging to the total number of tree-rings in the sample.
For the samples without sapwood we can only give a later then prediction for the felling
date. We know or we can estimate the number of tree-rings to the pith. With this number of
tree-rings we can calculate a minimum number of sapwood rings belonging to this tree. This
means we can give the date after which the tree was felled. So the tree was felled later
then this date. In dendrochronology this is called a terminus post quemdating.
Position of a studied sample
The highest age of wood in a tree can be found just above the roots (this is the position in the
tree where we can find the highest number of tree-rings). The number of tree-rings
decreases when we move to a higher position in the tree (fig. 5), this decrease in tree-rings is
in proportion with the yearly length growth of the tree. An archeological dating of wood
therefore usually represents a minimum age, which is based on an observation (sample)
higher in the tree (Jansma, 2007).
Fig. 5) The figure shows the effect of the position of a sample on the age of the sample.
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Calendars
The calendars we used are listed in table 1. They represent tree growth in various regions in
Germany and the Netherlands.
Lab code Region 1st
year Last year Author Lit.
DECENT01V West Germany, average ofothers, includingDERHMA01 andDESAMO03
-690 1975 Hollstein, 1980 1
DEOFRI01V East Friesland (Germany) -441 1991 Leuschner,unpublished
n.p.
DERHMA01 Germany; catchment basisof the rivers Rhine andMain
-201 198 Hollstein, 1980
1
DESAMO03 Germany, catchmentbasins of the rivers Saarand Mosel
-201 198 Hollstein, 1980 1
DESUDE01V South Germany -361 1950 Becker, 1995 n.p.
EUDLIM01 Wood used in Limburg andcentral/southern part ofGermany
-971 1995 EU Contractnr. ENV4-CT95-0127
n.p.
NLBRUG01 Brugge and surroundingarea
-217 128 RING data n.p.
NLROMR1 Central Netherlands,combination of bog oaksand archaeology
-325 563 Jansma 1995 2
NLVEEN05 Bog oaks from Abcoude,Weesp, Diemen andVinkeveen (NL)
-940 227 Jansma 1995, RINGdata
2 andn.p.
NLVEEN06 Bog areas in theNetherlands
-168 210 Visser, 2005 3
NLVLAA01 Netherlands and Flanders -211 1104 Jansma & Hanraets2004
4
Table 1) The major regional calendars of EIKVROEG.
n.p. = not published
1 = Hollstein, E., 1980: Mitteleuropische Eichenchronologie, Mainz.
2 = Jansma, E., 1995: RemembeRINGs. The development and Application of Local and
Regional Tree-Ring Chronologies of Oak for the Purposes of Archaeological and HistoricalResearch in the Netherlands. Nederlandse Archeologische Rapporten 19 (dissertation),Amersfoort.
3 = Visser, R.M., 2005: Houtvoorziening in het gebied van de Nedergermaanse Limes. Eenhistorisch en dendrochronologisch perspectief op Romeinse import en/of export van hout,(thesis Vrije Universiteit), Amsterdam.
4 = Jansma, E., & E. Hanreats 2004: Dating Flanders. Towards a Flemish tree-ringchronology of oak, in: E. Jansma, A. Brauning, H. Grtner & G. Schleser (eds.), Tree-rings inarchaeology, climatology andecology (TRACE) 2, Proceedings of the Dendrosymposium2003, Jlich (Schriften des,Forschungszentrum Jlich, Reihe Umwelt 44), 131-138.
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Most regional calendars are built up out of a collection of object and site calendars from that
region. These object and site calendars are digitized individually for the regional calendar
DESAMO03. The object and site calendars are listed in table 2.
Lab code Object 1st year Last year Author Lit.holkoble Koblenz, Roman Mosel bridge -110 203 Hollstein, 1980 1
holmbran Mainz, excavation near Brand -79 253 Hollstein, 1980 1holmbrom Mainz, Brand, Roman wells 7 259 Hollstein, 1980 1
holtmos1 Trier, Roman Mosel bridge -34 140 Hollstein, 1980 1
Table 2) Site and object calendars where regional calendar DESAMO03 was built out of. Thetable only shows the site and object calendars which show high correlations with the maincurve of group B (see results and interpretation).
1 = Hollstein, E., 1980: Mitteleuropische Eichenchronologie, Mainz.Digitized by Vorst, Y.E., in 2005
Determining the origin of timber
The calendars are not only used for dating, but also for the determination of the origin of
timber. The calendar that shows the best match with a timber represents the origin of the
timber. For some of the timbers only the region of origin can be predicted, because there is
a lack of individually digitized site and object calendars. When there are individually digitized
site and object calendars available we can give a more precise prediction for the origin of the
timber.
Groups
When we apply dendrochronology on samples found in archeological excavations we can
identify groups of samples with the same origin.
First we can recognize groups by the regional calendars they date with. But the best way to
identify groups is by mutual comparison between the samples. High correlations (Students t-
values above eight) between two or more samples indicate that we are dealing with samples
with a similar origin, and therefore they belong to the same group. Out of the samples, with
high mutual correlations, a main curve is constructed. All the samples which do not yet
belong to the group are compared with that main curve. When there are samples that show
high correlations with the main curve these can be added to the group. Afterwards a new
main curve is constructed, then another round of comparisons is done. This method is
rehearsed until there are no samples left anymore that show a high correlation with the main
curve.
Circumference
To calculate the circumference of the tree this formula is used: circumference = 2 radius .
To use this formula it is presumed that the stems are circular
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Excavation
Information obtained from written correspondence with C.W. Koot (2008).Photos (with description) of the excavation are shown in Appendix 2.
Fig.6 ) Positions of the trencheswhere the wooden remains of the
wpp harbour were found.The grey areas are the trialtrenches. The black dots indicatethe locations of the wooden postsand beams. The black linesindicate the location and shape ofthe wooden quays and landing-stages. (Koot, 2008)
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The wooden remains of the harbour of Forum Hadriani were excavated by the Amsterdams
Archeologisch Centrum (AAC).2 The project was directed at the so called villas II, III an IV.
These so called villas are apartment complexes. The villas are situated between the
contours of the wrecked buildings of the health establishment Effatha, namely Aula (trench
1), LTS/Nieuwe School (trench 2) and Meisjespaviljoen (trench 3) (fig. 6).
The wooden remains of the harbour, which is the topic of the current study, are derived from
trench 1 and trench 2.
The trenches are situated on the eastern flank of the shoreline/bank Voorburg-Voorschoten.
The flank of the shoreline descends in the direction of De Vliet, towards the south. This
means that trench 2 is located in the south and trench 1 in the north. The flank of the
shoreline was covered by peat and drift-sand deposits (dune formation), after which it was
covered by a thick layer of clay. The clay dates from around 400 BC, and is a coating
deposition from the Gantel, originated during the Duinkerke 1 transgression phase. The
Gantel is a creek that stretches itself out from the mouth of the Meuse in a northward
direction. Near the height off Rijswijk the creek deflects to the west and furcates (branches
off) in all kinds of creeks and brooks, which we know today as Midden-Delfland. It is known
that some creeks originate in the first part of the Gantel too. One of those creeks reaches
Voorburg. In trench 1 the archeologists identified the western bank of this creek. They
identified the eastern bank in trench 2. This is one of the main reasons why clay
sedimentation took place on the flank of the shoreline. The archeologists presume that
during the habitation of Forum Hadriani sedimentation of clay occurred even in the urban
area. The open creek in the centre of Forum Hadriani is an astonishing discovery. The
archeologists did not find any close-packed wooden sheetings. But they did find massive
squared driven posts.
The channel bed of the creek is filled with fine clay. In the clay packet no stratification was
recognized, which means that we are dealing with a constant grain size. The fine clay is a
marine sediment, probably coming from the mouth of the Meuse. The channel bed of the
creek is covered by litter: bones, potsherds, bricks, stones, leather, metal, glass and wood.Regarding the wood, the archeologists found sharpened stakes, planks, spars, staves,
branches, twigs and also some chips, but no big quantities and certainly no concentrations of
chips. This means that the wood used for the harbour mainly was worked somewhere else.
The bottom of the channel-bed deposits already contains some material from the Roman
age. Archeologists think that the channel bed of the creek may have been dredged.
2AAC is responsible for the archeological survey of the new construction project New Hadriani in Voorburg. AAC
was hired by building company BAM Vastgoed b.v.. The building company was obliged to let carry out an
archeological survey by an acknowledged archeological company, because the new construction project is partlysituated between the contours of the protected monument Forum Hadriani.
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In trench 1 one row of posts was found, Viewed from above this row makes an angle just
within the entrance of the excavation. This is the end of the creek. To the west there are
some other posts. One of them (dendrocodeVFH00010) was dated 212 6 AD.3
In trench 2, the archeologists were able to study the bank of the creek as a whole. Here three
rows of posts can be discerned. The most western row (the posts that were placed in the
creek) consists of posts that are conserved up to an average height of 2 m. These posts
were sharpened along a length of some 1,7 m. At the top end they had six sides, but in the
direction of the bottom they had 4 sides. The squared posts have an identical shape, with
average sides, these sides all have a width of 27 cm. A part of the construction is damaged.
some posts had fallen into the creek a long time ago. The two rows of posts to the east stand
in line with each other. Between these rows some smaller posts were placed, with lengths up
to 0,8 m. The two eastern rows of posts are shorter than the posts in the western row. They
have an average height of 1,6 m. The sharpenings are four-sided or, less often, two-sided,
and have a maximum length of 0,8 m. Some of these posts are massive, the sides are up to
35 cm width.
All posts are driven and stand in clay. The posts in trench 1 have been driven while there
was clay in the channel bed. They are probably the remains of a quay. The eastern rows of
posts in trench 2 are also interpreted as the remains of a quay. The archeologists interpret
the western row of posts on the eastern bank (trench 2) as a landing stage, because the
posts stand in the creek instead of directly along the bank (Koot, written communication,
June 21st, 2008).
The wood samples
The archeologists provided us with 58 wood samples taken from posts that belonged to the
harbour construction. For this study, 46 samples were prepared and measured. The current
report deals with 30 of these samples (table 3). The remaining 16 samples were not used
because of measurement errors and growth anomalies like reaction wood and double piths.
3Ring Report number 2007082
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SampleCode
Featurenumber
Objectnumber
Function
VFH00021 2284 6518 Fallen post in the middle structure of trench 2VFH00031 2194 6480 Post in the most eastern structure (quay) of trench 2VFH00041 2292 6576 Post near the most eastern structure (quay) of trench 2VFH00050 2264 6478 Post of the quay in the middle structure of trench 2
VFH00061 2301 6510 Post in the most eastern structure (quay) of trench 2
VFH00070 368 5914 Post that is part of the most northern part of the quay in trench 1VFH00090 2304 6460 Fallen post in the most northeastern part of trench 2VFH00100 2288 6461 Post of the quay in the middle structure of trench 2VFH00110 2258 6316 Post of the quay in the middle structure of trench 2
VFH00120 2282 6511 Post of the quay in the northern part of the structure in the middle of trench2VFH00130 362 6431 Sharpened wooden post (35 x 35 cm) part of the quay in trench 1
VFH00140 2252 6481 Post of the quay in the middle structure of trench 2VFH00150 373 5913 Post that is part of the most northern part of the quay in trench 1VFH00160 2101 3798 dupl. Fallen side straightened post of the landing stage (western part trench 2)VFH00220 2239 6319 Post of the quay in the middle structure of trench 2
VFH00230 2104 3371 dupl.Massive sharpened and side straightened post, still standing (near fallenposts) most southwestern post in trench 2, part of the landing stage.
VFH00250 2295 6517Post with squared hole in the middle, possible reused wood, in the middlestructure of trench 2
VFH00270 2271 6306 Post of the landing stage in the western part of trench 2VFH00340 2296 6476 Is a smaller post near post 2295VFH00350 400 6555 Part of the quay in the northwest corner of trench 1
VFH00360 3612 6432 -VFH00380 371 5932 Post that is part of the most northern part of the quay in trench 1VFH00400 2265 6311 Post of the quay in the middle structure of trench 2VFH00410 54 6459 Sharpened wooden post (35 x 35 cm) part of the quay in trench 1VFH00420 2150 6313 Post of the quay in the middle structure of trench 2
VFH00430 2274 6303 Post of the landing stage in the western part of trench 2VFH00440 2270 6307 Post of the landing stage in the western part of trench 2VFH00450 2242 6436 Belongs to the most western posts of the quay in the eastern part of trench 2VFH00461 2254 6479 Post of the quay in the middle structure of trench 2VFH00470 363 6430 Sharpened wooden post (35 x 35 cm) part of the quay in trench 1
Table 3) The table contains some general information of the samples used in this study. SeeAppendix 1 for information on size and shape of the samples.
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Results
Dating results
In table 4the dating report for the 30 used samples is shown.
RINGlaboratorycode
Ringstopith
Ringsofsap-wood
Ringstobark
Nr. ofrings
Dateoffirstring
Dateof lastring
Date offelling(AD)
THO %PV P 10, can not be used in every situation.
It is strange that Group B shows a stronger correlation with DECENT01V (THO of 18,1, the
%PV is 78,8 and the P < 0,0001), compared to the correlation with Holkoble (THO of 13,1,
the %PV is 73,0 and the P < 0,0001). We assumed that the wood of Group B originates from
the same forest as the wood of Holkoble. The stronger match with DECENT01V undermines
this assumption. But DECENT01V is a calendar that is compiled from many smaller
calendars. Therefore DECENT01V represents an average. When this averaged calendar is
compared with a main curve (also an average), it is reasonable that a high correlation
appears.Since only ten of the studied samples contain sapwood, only ten estimated felling dates can
be derived (the other dates are terminus post quemdates). This may simplify our image of
the chronological phasing of the studied structures; possibly the actual chronological phasing
of the structures is more complicated than the image we presented.
For the calculated circumferences it is important to know that this is the minimum
circumference of the stem since we do not know the position of the studied sample in the
stem (see materials & methods).
Determinations of the origin of wood are highly dependant on the quality of the chronologies
used for dating and provenancing. The dendrochronologist Hollstein assumed that the
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archaeological wood he used for his chronologies, actually grew in the region where the
wood was put to use. His assumption was, of course, incorrect; already in the Roman Period
people transported wood over quite large distances. However, the Roman object
chronologies from the Saar-Mosel region most likely will represent local growth conditions;
this region was forested in Roman times. Part of the wood used in the harbour of Forum
Hadriani correlates very well with these object chronologies, which implies that it was derived
from the same area. With southern German material the situation is much more complicated.
The components of chronology DESUDE02V are not published and therefore cannot be
assessed. We do not know in which part of southern Germany the trees grew, and the
geographical definition the author used when he defined his calendar as representing South
Germany.
Recommendations
It would be interesting to compare the results of this study with results from other
dendrochronological studies on wood from the same time interval. We assume that the
construction of the harbour had a military background, meaning that the construction of the
harbour was a military action.
There have been some excavations near the site of Forum Hadriani where Roman soldiers
were encamped. These military vici(military villages) were found near several castella
(military fortresses for reinforcement troops). These viciand castella(Valkenburg-Veldzicht
and Leiden-Roomburg) may have been the bases for the soldiers who built the harbour.Therefore it might be interesting to look for possible clues that link the soldiers of the viciand
castellato the harbour of Forum Hadriani.
It would also be interesting to investigate if the wood used for renovations of the Roman road
near Valkenburg and Vleuten-De Meern matches the wood in one of the construction phases
of the harbour in Forum Hadriani. Independent of the results it will increase our knowledge.
We know that a part of the wood used in the construction of the harbour of Forum Hadriani is
similar to wood used in Roman structures in the Mosel-Rhine area. Therefore we might be
able to link these construction activities to a certain group of Roman soldiers.
In the Roman era a command to built bridges and harbors was given by a Roman
commander or even by an emperor. It is interesting to search for a link between the
construction activities and a certain Roman commander or emperor.
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Conclusion
On the site of the ancient Roman city of Forum Hadriani the wooden remains of a harbour
were found. These wooden remains comprise parts of a quay and landing stage.
Dendrochronological research has shown that the wooden remains of the harbour can beplaced into two chronologically coherent groups. The oldest group of timbers was cut from
trees that were felled around AD 159. The youngest group dates around AD 218. The
difference in dating indicates a phasing in the construction of the harbour.
In terms of origin there are three distinct groups of timber. One group correlates with a
regional calendar from South Germany and represents oak collected high upstream the Rhine
in southern Germany. A second group correlates with a regional calendar from the Saar-
Mosel area, especially with an object chronology of a Roman bridge in Koblenz, which is one
of the building blocks of the Saar-Mosel chronology. This wood was derived from the region
between the Mosel and Rhine (South of the Mosel, West of the Rhine). The last groupcorrelates with domestic calendars and represents oaks from locations in the current
Netherlands.Comparison with wood from an earlier studied water well, found in Forum Hadriani, points
out that the youngest phase of the harbour may have been built simultaneously with this
water well. The likelihood that these structures were related in terms of the organization of
their construction is strengthened by the fact that the wood of the water well shows a strong
similarity with the wood used for the harbour.
The wood of the group that correlates with the regional calendar from South Germany and
the wood of the group that correlates with the Saar-Mosel chronology originates from trees
that grew in closed-canopy forests. The wood that correlates with domestic calendars
originates from trees that probably grew in a more open landscape.
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Acknowledgements
I want to thank Hennie Sloots for some translations of passages out Mitteleuropische
Eichenchronologie(Hollstein, 1980), Geert Hoefnagels for reviewing my writing skills, and
Menne Kosian (RACM) for the help he provided with the scanning of the samples. Menne
Kosian also helped me to digitalize the sketches of the trenches. I am grateful for the
information of the excavation provided by Kees Koot and Mark Driessen (UvA). Kees Koot
also delivered the photos of the excavation. I also want to thank Ronald Visser (VU and
RACM). He helped me with different questions and problems, which came up during the
project.
My special thanks go to Martha Dominguez Delmas (the RING Foundation) and Esther
Jansma. Martha Dominguez Delmas helped me with the lab work and the structuring and
interpretation of the results. Esther Jansma planned and supervised the project and
improved the current report with her comments.
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References
- Baillie, M.G.L., A slice through time; dendrochronology and precision dating, Routledge(pp. 16-18),Batsford Ltd., London, 1995
- Bazelmans, J. and De Jonge, W., Wie waren de Cananefaten?, In: Forum Hadriani; VanRomeinse stad tot monument, Stichting Matrijs, Utrecht, 2006
- Brinkkemper, O., Koehler, L. and Nientker J., Houtdeterminatie en houtgebruik, In:Raportage ArcheologischeMonumentenzorg 144, Amersfoort, 2007
- Brinkkemper, written communication, 18th June, 2008
- Buijtendorp, T., Lugdunum bij Katwijk. Een voorstedelijke nederzetting uit de eerste eeuwin Cananefaats gebied, In: Forum Hadriani; Van Romeinse stad tot monument, StichtingMatrijs, Utrecht, 2006
- Buijtendorp, T., De voorganger van Forum Hadriani. Van inheemse nederzetting totcentrale plaats, In: Forum Hadriani; Van Romeinse stad tot monument, Stichting Matrijs,Utrecht, 2006
- Buijtendorp, T., Bouw en groei. De bloeiperiode van Forum Hadriani, In: Forum Hadriani;Van Romeinse stad tot monument, Stichting Matrijs, Utrecht, 2006
- Buijtendorp, T. and Waasdorp, A., Romeins Voorburg. Keizer Hadrianus en de status vande stad, In: Forum Hadriani; Van Romeinse stad tot monument, Stichting Matrijs, Utrecht2006
- Enckevort, H. van, and Vos, W.K., De limes: een natte grens dwars door Nederland, In:Nationale Onderzoeksagenda Archeologie (pp. 25 & 26), 2006
- Es, W. van, Woord vooraf, In: Forum Hadriani; Van Romeinse stad tot monument,Stichting Matrijs, Utrecht 2006
- Grissino-Mayer, H.D., Principles of Dendrochronology, Ultimate Tree-Ring Web Pages,1996
- Hollstein, E., Mitteleuropische Eichenchronologie, Mainz, 1980
- Jansma, E., RemembeRINGs. The development and Application of Local and RegionalTree-Ring Chronologies of Oak for the Purposes of Archaeological and Historical Researchin the Netherlands. Nederlandse Archeologische Rapporten 19 (dissertation), Amersfoort,1995
- Jansma, E., Jaarringonderzoek van het scheepshout en meubelonderdelen:bouwtechnische aspecten, datering en herkomst van het hout, In: RaportageArcheologischeMonumentenzorg 144, Amersfoort, 2007
- Jansma, E., Datering, herkomst en bouwvolgorde van De Meern 4, In: RapportageArcheologische Monumentenzorg 147, Amersfoort, 2007
- Jonge, W. de, Ondergang. De crisis in het rijk en de teloorgang van Forum Hadriani, In:Forum Hadriani; Van Romeinse stad tot monument, Stichting Matrijs, Utrecht, 2006
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- Koot, C.W., written communication, 2008- Schweingruber, F.H., Tree Rings and Environment Dendroecology, Swiss FederalInstitute for Forest, Snow and Landscape Research andPaul Haupt Verlag, Switzerland,1996
- Vorst, Y.E., De constructie en herkomst van de Romeinse platbodem Woerden7; eenstudie van jaarringpatronen en bewerkingsporen, Master thesis UvA, 2005
- Waasdorp, A., Romeinse infrastructuur. De ontsluiting van het Cananefaatse gebied In:Forum Hadriani; Van Romeinse stad tot monument, Stichting Matrijs, Utrecht, 2006
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Appendix 1: Shapes of the studied cross sections of the wood(scale 1 : 5)
VFH00021 VFH00031 VFH00041
VFH00051/2 VFH00061 VFH00081
VFH00071/2 VFH00091/2 VFH00110
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VFH00101/2 VFH00121/2
VFH00131/2 VFH00141/2 VFH00151/2
VFH00161/2 VFH00171/2 VFH00180
VFH00191/2 VFH00201/2 VFH00211/2
VFH00221/2 VFH00231/2 VFH00241/2
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VFH00251/2 VFH00261/2 VFH00271/2 VFH00291/2
VFH00281/2 VFH00301/2 VFH00341/2
VFH00311/2 VFH00321/2 VFH00331/2
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VFH00351/2 VFH00371/2 VFH00381/2
VFH00361/2 VFH00391/2 VFH00401/2
VFH00411/2 VFH00421/2 VFH00431/2
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VFH00441/2 VFH00451/2 VFH00461/2
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Appendix 2: Photos of the excavation
Photo 1.) Two examples of postsbelonging to a quay of the easternbank (trench 2) of the harbour inForum Hadriani. The posts belong tothe quay that has the most forwardedposition towards the waterfront. Thatis why the excavators expect them tobe part of the youngest construction.
Photo 2.) This post, belonging to the
older phase of a quay, marks the
transition from the channel to the
bank. The brown layer of peat behind
the post has not been eroded by the
streambed of the creek. The
streambed has found its way through
the tidal flats, marshes and dunesaround 400 BC. Later on it served as
a harbour for Forum Hadriani.
Photo 3.) A post belonging to the older phase of the quay.
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Photos 4. & 5.) The older phase of the quay is probably constructed by pairs of posts. Inbetween the posts are smaller posts in an irregular interval. The larger posts of the western
row of this construction phase were connected by a plank.
Photo 6.) In the southern part (trench 2) of the younger phase of the construction, a few ofthe posts have been fallen in the water.
Photo 7.) Overview on the excavation of the eastern bank of the harbour.