Van Helmond BA Thesis 2008

7/29/2019 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

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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.

Van Helmond BA Thesis 2008

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