# Bay of Kiladha 2023

Julien Beck, Patrizia Birchler Emery, Evangelia Manoutsoglou, Alexandre Masselot, Catherine Perlès, Andreas Sotiriou

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Julien Beck, Patrizia Birchler Emery, Evangelia Manoutsoglou, Alexandre Masselot, Catherine Perlès, et al.. Bay of Kiladha 2023. Antike Kunst, 2023, 67, pp.110-116. halshs-05095745

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Distributed under a Creative Commons Attribution 4.0 International License
Bay of Kiladha 2023¹

Julien Beck, Patrizia Birchler Emery, Evangelia Manoutsoglou, Alexandre Masselot, Catherine Perlès, Andreas Sotiriou

Launched in 2012, the Bay of Kiladha project is a joint collaboration between the University of Geneva and the Ephorate of Underwater Antiquities. Its goal is to study submerged prehistoric sites and landscapes in the southern Argolid, close to Franchthi Cave (fig. 1).

In 2014, the submerged architectural remains of an Early Helladic II fortified settlement were found at Lambayanna, a few hundred meters north of the cave. The discovery was followed by a marine survey in 2015, and by underwater excavations in 2016 and 2017, revealing the existence of an earlier, Early Helladic I, and later, Late Roman/Early Byzantine, occupation on the site.

In 2023, research focused on studying more finds from the marine survey and underwater excavations at Lambayanna, on improving underwater mapping techniques in a shallow environment, and on clay analysis linked to experimental archaeology.

*Early Helladic and Late Roman/Early Byzantine activities at Lambayanna*

More evidence surfaced in connection with the Late Roman/Early Byzantine occupation at Lambayanna: roof tiles, including calypters, a few bricks or slabs, one of which is inscribed, a LR 2 amphora (5th-7th c. CE), and a flask (askodabla, attested from the 5th-6th c. CE onwards) (fig. 2).

Regarding Early Helladic II finds, the surprise came from a large pithos fragment with a roller-impressed band (fig. 3), the only one attested at Lambayanna so far, although this type of vessel is found at all the major Early Helladic II sites. The impressed decoration of concentric circles and herringbones is similar to examples from Lerna and Tiryns<fnref n="2" />. In the Southern Argolid, this pattern has only been attested on a hearth rim so far<fnref n="3" />.

Another surprise came from a concentration of sherds made of orange or grey clay, with traces of burnishing and remains of red slip: although they were found on the sea floor, they are very similar to Early Helladic I sherds retrieved from the underwater excavations. If they do belong to Early Helladic I, how could one explain their presence on the sea floor? They were found close to the underwater excavations, which revealed that a vertical pit, dug after the Bronze Age settlement was abandoned, cut through the Early Helladic I and II levels<fnref n="4" />. Could it be that these unusual sherds were extracted from the Early Helladic I level when the pit was dug? They are better preserved than the other objects found on the sea floor, which could be explained if the pit was dug during the Late Roman/Early Byzantine occupation, more than

<footnote n="1">¹ The authors wish to thank the Ephorate of Underwater Antiquities, the University of Geneva, G. Bobov (archaeologist, Sofia), C. Dupont (Directeur de recherches, CNRS), A. Seni (logistics, Kiladha), T. Fourgereau-Socrate (student, University of Geneva), A. Hautier (Prilly), C. Jacquiard (student, University of Geneva), and A. Tsompanidis (Ephorate of Underwater Antiquities) for their contribution and support.</footnote>

<footnote n="2">² Galligan 2013, 313, figs. 7 and 8; CMS V, cat. nos. 133 and 546.</footnote>

<footnote n="3">³ Pullen 1995, 271, no. 650, fig.6.</footnote>

<footnote n="4">⁴ Beck – Koutsoumba 2017.</footnote>
three thousand years after the end of the Early Helladic I occupation. But they also have fewer
marine concretions, which would not be justified in that case...

Underwater photogrammetry

The difficulties involved in mapping submerged architectural remains in a shallow marine
environment have already been addressed<fnref n="5" />. In 2023, further investigations were conducted
with the aim of improving the sea floor reconstruction using photogrammetry. The goal was to
optimize computing time versus model accuracy.

Our current acquisition setup consists of an 80 x 80 cm raft pushed by a swimmer (fig. 4). At the centre of the raft, a vertical pole holds an EMLID DGPS rover at the top, and a GoPro Hero 8 camera at the bottom, shooting a picture every second. The DGPS rover is coupled to a base station on the beach, providing a position with a 2-3 cm precision. This position is accessible to the swimmer in real-time on a waterproof phone screen, and later inserted in the pictures' metadata at a post-processing stage, based on timestamps.

The accuracy of the camera's position is affected by timestamp error, and by the inclination of
the pole due to wave action and other factors. On a digital camera, a timestamp is attached to
each picture metadata. In the present case, the recorded time is crucial to accurately post-
process the picture shooting positions, by interpolating the recorded DGPS signal. However,
the camera timer is not accurate, and the shutter lag adds another error between the moment
the shot is triggered (and time recorded), and the moment the picture is acquired. Here, a one-
second delay results in a 30 to 60 cm error (when the swimming speed is between 1 and 2 km
per hour, which is typical with our setup), compared to the 2-3 cm actual DGPS precision. By
shooting targets with known positions, it was possible to deduce an 880 ms delay, and thus to
achieve an average position error of 2 cm.

Depending on the sea floor depth, and the picture overlapping required for photogrammetry, a
route and swimming speed are provided to the swimmer, who must follow the path as precisely
as possible. A first lawn mowing route is oriented to the north, while a second one follows at a
30° angle, to lower the bow effect.

The open-source OpenDroneMap software is then used to create a photogrammetry model.

Practically, the lower the distance between the camera and the sea floor, the better the picture
quality, and the richer the reconstruction. Visibility in shallow water is changing and rarely
optimal, which is why getting close to the sea floor is the alternative to waiting for perfect
conditions.

The swimming route is never perfect either, and typically more pictures are shot than
necessary (during the turning phases, and when swimming is too slow). A software was thus
specifically designed to select the closest pictures to the theoretical optimal position.

During two days with different visibility conditions, the same 5 x 5 m area was acquired at
varying distances from the sea floor (1 m, 1.5 m, 2 m). The result is an exponential relation
between the number of pictures and the computation time. Reducing the number of pictures
therefore significantly decreases computation time. When the number of pictures is limited by
selecting only the ones closest to the theoretical optimal positions, the reconstruction quality
is not compromised in the best visibility conditions, except when the distance from the sea floor

<footnote n="5">⁵ See, for instance, Beck *et al.* 2023.</footnote>
is the highest. Moreover, poorer visibility does not only affect reconstruction quality, but also
increases computation time.

These results will be decisive in choosing a mapping strategy for the submerged architectural
remains at Lambayanna.

Experimental archaeology and clay analysis

Since 2015, experimental archaeology has been a regular component of the Bay of Kiladha
project: every summer, pots are made, inspired by the Neolithic pottery from Franchthi Cave.
In 2023, for the first time, clay analysis was included.

The clay used for experimental purposes comes from the marsh at the eastern end of the bay (fig. 1). Two samples were analysed, one from the clay itself (KP), and the other from the same clay after a specific cleaning process (KC), which involved mixing the clay with water, settling the coarser sediments, and gradually removing them.

In an initial attempt to conduct a closer visual observation, the samples were examined using
a Nikon SMZ800 stereo microscope with an attached camera (Tucsen True Chrome HD).
However, due to the significant number of fine sediments in both samples, it proved challenging
to observe even the coarser particles. The presence of biogenic material was nevertheless
detected, aligning with expectations based on the sampling location (fig. 5).

To gain a deeper understanding of the clay's consistency, a grain-size analysis of the two
samples was carried out. In this study, Folk and Ward's<fnref n="6" /> grain-size analysis, a widely adopted
method rooted in the Wentworth<fnref n="7" /> scale, was preferred to categorize sediment particles based
on size. To achieve this, it was necessary to separate the samples' grain-size fractions. For
this process, and due to the fine-grained nature of the material in both samples, the pipette
method was employed and the GRADISTAT package<fnref n="8" /> was used for the calculations and
categorization of the samples. The analysis of the samples was conducted at the Laboratory
of Marine Geology and Sedimentology of the Department of Marine Sciences (University of
the Aegean).

The analysis revealed only minor differences between the samples. Table 1 displays the
percentages of grain-size classes, indicating that the cleaning process mainly eliminated sand,
leading to a 3.2% decrease in the class of sand in KC. This was followed by an increase in the
percentage of mud. The slight increase in the gravel percentage by 0.4% may be attributed to
the random distribution of coarser sediment particles in the matrix material from which the
samples were initially collected.

Based on Folk and Ward's classification (fig. 6), both samples are categorized as “slightly
gravelly mud” in terms of texture. They are characterized as “very fine silt” and “very poorly
sorted” based on their mean size (table 1). Poorly sorted sediments have a wide range of
particle sizes, indicating a lack of uniformity. Particle sizes vary significantly not only among
sediment classes (gravel, sand, and mud) but also within their individual fractions (i.e., fine
sand). Both samples exhibit a “coarse skewed” distribution, indicating the presence of coarser
particles within their fractions (table 1). Despite the notable percentage of mud, a significant
portion of the samples contains coarser particles, contributing to the observed distribution. In

<footnote n="6">⁶ Folk – Ward 1957.</footnote>

<footnote n="7">⁷ Wentworth 1922.</footnote>

<footnote n="8">⁸ Blott – Pye 2001.</footnote>
terms of kurtosis, both samples display a platykurtic distribution, indicating a broader range of
particle sizes and less sorting, as confirmed previously.

Upon comparing the percentage distribution of grain size classes, and the statistical
parameters of the two samples, it appears that their differences are small, and their
characteristics identical. However, the statistical parameters, skewness, and kurtosis, are
significant only for the original sample (KP). Together with the mean size and sorting, they
provide information about the way and environment of deposition. The fine-grained material
concentration near the marsh where the clay was collected suggests that it was deposited in
an earlier period, possibly as an alluvial deposit.

The "very poorly sorted" sediments indicate environments with fluctuating or low-energy conditions. The "coarse skewness" suggests a prevalence of larger particles in comparison to smaller ones. This could be associated with erosional processes or selective transport, where larger particles are preferentially transported. The platykurtic distribution implies a wider range of particle sizes and less sorting, possibly connected to a more varied or turbulent sedimentary environment. All the above results are confirmed by observations that when the sea level was lower, this area was a small coastal plain traversed by a river<fnref n="9" />.

The primary aim of analyzing the two samples (KP, KC) was to understand the behavior of the clay in relation to pottery production within the context of experimental archaeology. Drawing on examples of analyses for this purpose<fnref n="10" />, the composition, addressing the distinct distribution of grain-size classes (sand, silt, clay), as well as the physicochemical characteristics of the clay, can govern its behavior during firing and temperature development.

To achieve a good clay body, it is common for the clay percentage to be higher than that of silt, while the amount of sand varies proportionally and acts as temper, like other materials such as crushed calcite<fnref n="11" />. Here, a preliminary step was taken in this direction by providing the composition of each sample, with the silt-clay ratio being nearly equivalent in the original material (KP), and lower in the cleaned one (KC). Since the alteration of these ratios is distinct for each type of material, and is primarily empirical, extending from prehistory to the present day, there is significant potential for conducting more experimental studies to understand the details of clay behavior in the Neolithic pottery from Franchthi Cave.

At the experimental level, both the original clay from the marsh, and the cleaned one, were
used by Georgi Bobov (Sofia) to produce simple cups, with different kinds of temper (grass,
sand, and crushed shells). Interestingly enough, once fired, the cups made of the original clay
could always hold liquids, whereas the cups made of filtered clay were invariably porous,
regardless of the type of temper involved.

Hexaplex Trunculus

During the underwater excavations at Lambayanna, a significant amount of *Hexaplex trunculus*
(murex shells) was found in the Early Helladic I level<fnref n="12" />. The shells were later examined by
David Reese (Yale University), who concluded that they were intentionally selected<fnref n="13" />. From
the start, the question arose as to whether they were used to produce purple dye: the stakes

<footnote n="9">⁹ Beck et al. 2021.</footnote>

<footnote n="10">¹⁰ See, for instance, Martineau et al. 2007.</footnote>

<footnote n="11">¹¹ Milošević – Logar – Djordjević 2020.</footnote>

<footnote n="12">¹² Beck – Koutsoumba 2018.</footnote>

<footnote n="13">¹³ Beck – Sotiriou 2020.</footnote>
are high, as this could currently be the oldest known workshop, in an area that was famous in antiquity for the quality of its purple production.

In 2023, Catherine Dupont (CNRS), a specialist in the various forms of purple dye production in protohistory and antiquity, analyzed more than 15 shell samples from the 2017 excavations. The analysis was carried out at various levels, with the aim of verifying whether the shells had been collected alive or in the state in which they were found, and thus to start by validating the anthropic origin of the assemblage. The proportions of murexes were also assessed in relation to the other species present at each level, and the majority species noted, to determine whether *Hexaplex trunculus* was voluntarily exploited along with other species.

Catherine Dupont has previously shown that strategies for collecting mollusks and processing them for purple vary according to the intensity of production. This should normally result in different dimensional profiles, as well as different fracturing methods. Various measurements were taken on all the murex shells and fragments to reconstruct the original lengths of the broken murexes and, if possible, obtain size profiles of the gastropods collected at different levels. All the murex fragments were classified according to their state of fragmentation. To achieve this, an existing shell fragment classification grid for other species used for purple production on the European Atlantic coast was adapted. This adaptation was linked to the larger dimensions of *Hexaplex trunculus*, and to the possibility of including other recurring types of shell fragments. All mollusks were examined, to compare their fracturing method and state of preservation. These observations will be used to determine the rate of broken murexes, the origin (anthropogenic or natural) of these fractures, their proportions in relation to other species and, in the case of natural fractures, the way(s) in which they were broken.

Preliminary results show a complex situation. The murex shells were individually selected for their large size. Some of them do show the typical stigma of manual fracturing, with the removal of a subcircular flake at the level of the hypobranchial gland, at the top of the shell's final whorl. However, many shells (the MNIs for each category have not yet been calculated) are intensely fractured, to the point of being reduced to the columella and numerous fragments. Such fracturing is not justified for the extraction of the gland, particularly when the selection of individuals and the characteristic stigmata of manual processing show that there is no mass crushing. Alternatively, it may correspond to the extraction of the flesh from the living animal. The purpose could have been for personal consumption, but this is unlikely: these gastropods are eaten cooked, which again does not require for them to be fractured. On the other hand, since *Hexaplex trunculus* are carnivores, their flesh could be used as bait to catch others. This last possibility will have to be tested in the future. It would also be interesting to compare the breakage of murex shells with that of *Terebralia palustris*, which has no dyeing properties but may have been used as bait.

There are three possible explanations to account for these observations: either the flesh, and not the gland for purple production, was sought after, or both were sought after, or the purple production was carried out by non-specialists. To distinguish between the first two alternatives, *Hexaplex trunculus* fished in the Bay of Kiladha were used to check whether it was possible to extract the flesh by pressing on an opening such as the one produced to extract the gland. This proved strictly impossible: the flesh of the animal is wrapped around the columella and strongly tied to it by muscular attachments. In the case of specimens having only a flake removed at the level of the gland, it was therefore the gland and only the gland that was sought after. These experiments, like the ones carried out in previous years, also clearly showed that it is by no means necessary to break the entire shell to extract the gland. This leads one to think the flesh was also sought for. However, another hypothesis could perhaps be put forward to explain these different breaking methods: if the activity was not standardized, and was the work of non-specialists, it is possible that the two processes observed along the French Atlantic
coast were used. One involves tapping at the level of the gland with a pebble, while the other involves crushing the shells with a pestle. A more in-depth analysis of the observations made in 2023, as well as the continuation of the experiments, should provide a clearer picture of the nature of the activities behind this unique find.

Julien Beck

Département des sciences de l'Antiquité

Université de Genève, Faculté des Lettres

5, rue de Candolle

CH-1211 Genève 4

Julien.Beck@unige.ch

Patrizia Birchler Emery

Département des sciences de l'Antiquité

Université de Genève, Faculté des Lettres

5, rue de Candolle

CH-1211 Genève 4

Julien.Beck@unige.ch

Evangelia Manoutsoglou

Coastal Morphodynamics-Management & Marine Geology Lab

Department of Marine Sciences - School of the Environment

University of the Aegean, Lesvos, Greece

eman@marine.aegean.gr

Alexandre Masselot

alexandre.masselot@gmail.com

Catherine Perlès

Université Paris X Nanterre

catherine.perles@cnrs.fr

Andreas Sotiriou
Ephorate of Underwater Antiquities

30 Kallisperi Str.

GR-11742 Athens

asotiriou@culture.gr

BIBLIOGRAPHY

Beck – Koutsoumba 2017

J. Beck – D. Koutsoumba, Baie de Kiladha 2016, AntK 60, 2017, 164 –167

Beck – Koutsoumba 2018

J. Beck – D. Koutsoumba, Baie de Kiladha 2017, AntK 61, 2018, 138 –142

Beck – Sotiriou 2020

J. Beck – A. Sotiriou, Baie de Kiladha 2019, AntK 63, 2020, 120 –123

Beck et al. 2021

J. Beck et al., Searching for Neolithic sites in the Bay of Kiladha, Greece, Quaternary International 584, 2021, 129 –140

Beck et al. 2023

J. Beck et al., Bay of Kiladha 2022, AntK 66, 2023, 105 –109

Blott – Pye 2001

S. J. Blott – K. Pye, GRADISTAT: a grain size distribution and statistics package for the analysis of unconsolidated sediments, Earth surface processes and Landforms 26.11, 2001, 1237-1248

Folk – Ward 1957

R. L. Folk – W. C. Ward, Brazos River bar: a study in the significance of grain size parameters, Journal of Sedimentary Petrology 27, 1957, 3-26

Galligan 2013

E. E. Galligan, Early Helladic Decorated Ceramic Hearths, Diss. University of North Carolina (2013)

Martineau et al. 2007

R. Martineau et al., Clay resources and technical choices for Neolithic pottery (Chalain, Jura, France): chemical, mineralogical and grain-size analyses, Archaeometry 49.1, 2007, 23-52

Milošević – Logar – Djordjević 2020

M. Milošević – M. Logar – B. Djordjević, Mineralogical analysis of a clay body from Zlakusa, Serbia, used in the manufacture of traditional pottery, Clay Minerals 55.2, 2020, 142-149

Pullen 1995
D. J. Pullen, The Pottery of the Neolithic, Early Helladic I, and Early Helladic II Periods, in C. Runnels – D. J. Pullen – S. Langdon (ed.), *Artifact and Assemblage: The Finds from a Regional Survey of the Southern Argolid, Greece. Vol. 1: The Prehistoric and Early Iron Age Pottery and the Lithic Artifacts* (1995), 6-42

Wentworth 1922

C. K. Wentworth, A scale of grade and class terms for clastic sediments, *Journal of Geology* 30, 1922, 377-392

## LIST OF FIGURES

Fig. 1

Plan of the Bay of Kiladha.

Fig. 2

Early Byzantine flask-askodabla, sections a and b.

Fig. 3

Pithos fragment with roller-impressed band.

Fig. 4

Raft with vertical pole holding an EMLID DGPS rover at the top.

Fig. 5

Snapshot of KC sample from stereo microscope view, showing a specimen resembling a gastropod larva.

Fig. 6

KP (red) and KC (green) on Folk and Ward's classification diagram, both characterized as "Slightly Gravelly Mud".

## Table 1

The grain-size class percentage distribution, statistics, and sediment characterizations of the KP and KC samples.
<figure><img src="image_2.png" /><figcaption>Fig. 1</figcaption></figure>

<figure><img src="image_3.png" /><figcaption>Fig. 2</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>Fig. 3</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>Fig. 4</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Fig. 5</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Fig. 6</figcaption></figure>

<table><caption>Table 1</caption><thead><tr><th>FOLK & WARD (φ)</th><th>KP</th><th>KC</th><th>Text. Group: Slightly Gravelly Mud</th></tr></thead><tbody><tr><td>Mean (M<sub>z</sub>):</td><td>8.311</td><td>8.569</td><td>Very Fine Silt</td></tr><tr><td>Sorting (σ<sub>z</sub>):</td><td>2.796</td><td>2.555</td><td>Very Poorly Sorted</td></tr><tr><td>Skewness (Sk<sub>z</sub>):</td><td>-0.197</td><td>-0.221</td><td>Coarse Skewed</td></tr><tr><td>Kurtosis (K<sub>σ</sub>):</td><td>0.742</td><td>0.726</td><td>Platykurtic</td></tr><tr><td>% GRAIN-SIZE CLASSES</td><td></td><td></td><td></td></tr><tr><td>% Gravel:</td><td>0.7%</td><td>1.1%</td><td></td></tr><tr><td>% Sand</td><td>6.1%</td><td>2.9%</td><td></td></tr><tr><td>% Mud:</td><td>93.2%</td><td>96.0%</td><td></td></tr><tr><td>% Silt:</td><td>46.7%</td><td>46.8%</td><td></td></tr><tr><td>% Clay:</td><td>46.5%</td><td>49.2%</td><td></td></tr></tbody></table>