Page 69 - TINA Dergi Sayi 11

TINA

Maritime Archaeology Periodical

This data reveals that volcanic material, which has the current elevation, we estimate the relative sea level
been interpreted as hydraulic mortar (pozzolana?), was rise as 2.5±0.3 m. Maximum 1.0 m of this value is
used in the construction of the mole. This material was related to global sea level rise due to glacier melt . If
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frequently used in harbor construction during antiqui- we remove this value, the rest of the 1.5±0.3 m can be
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ty . The Bodrum peninsula has a volcanic structure . explained by the vertical tectonic movements related
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However, detailed analysis in further studies is needed to earthquakes. This means that 1.5±0.3 m of tectonic
to understand whether the material is local or imported. subsidence took place in the last 2,400 years, in other
The mole is highly significant for the history of mari- words 0.62±0.3 m during the last 1,000 years with a
time technology. Therefore, an excavation is also nec- rate of tectonic subsidence at 0.62±0.3 mm/year. Our
essary to reveal the architectural features of the mole. results are relevant to geoarchaeological studies on the
5.2. Sea Level Changes submerged harbor structures dated to the Hellenistic
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Eustatic – isostatic sea level rise that resulted from period along the coast of the Bozburun peninsula .
the melting of a glacier did not exceed 1 m over 2,500 The submerged structure measured in the second
years. In addition, it is clear that the inundation of the study area, which was interpreted as the shipshed in
Aegean coasts is associated with ongoing tectonic ac- question, was formed by cutting bedrock having a dis-
tivity. In particular, the earthquake activity that took tinguished ramp. Since the hull of the ship should re-
place in mid 6 century CE caused subsidence of the main dry, the shipshed should be located above the sea
th
coasts, which gave rise to submersion of harbor struc- level at the time of construction. Therefore, shipsheds
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tures, making them useless . are indicators for sea level change. A well-preserved
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According to Flemming , relative sea level change shipshed can be used for sea level estimation with
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for the Bodrum peninsula reached 1.2 m over the last ±0.25 m certainty . However, there is still a question
2,000 years in Myndus (0.6 mm/year), 1 m in the last of the original level of the ramp’s lower part . A 30 m
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2,400 years in Halicarnassus (0.4 mm/year), and 1 m long shipshed in the study area, which begins from the
in the last 1,500 years in Loryma (0.7 mm/year), while shore and reaches a depth of -3.1±0.1 m with an 8° of
sea level was stable in Knidus over the last 2,300 ye- slope, has the ideal dimensions and ramp for dragging
ars. a ship. Nevertheless, it does not provide precise infor-
The mole in the Halicarnassus harbor consists of two mation for sea level estimation, since both the bottom
sections in parallel, and there is an elevation difference is completely filled with pebbles and rubble stones,
between them. The wider section to the east lies at 0.5- and the original base level of the ramp is questionable.
0.9±0.1 m below the modern sea level. The relatively However, from the fact that the structure is entirely
narrower section to the west is located in deeper water, submerged today, it is obvious that it has been under
and its upper level is at -1.7±0.1 m. Although we have the effect of vertical tectonic movements since the time
no evidence on height difference, it may be assumed of construction.
that the wider section was raised in the later periods by Similarly, the submerged tidal notches in the same
repairs or additional construction. However, both sec- location of the shipshed also support this tectonic mo-
tions of the mole must have been built above sea level. vement. A lateral depth of 0.3 m and a height of 0.4 m
Therefore, we will consider for geoarchaeological that are compatible with the local tidal range suggest
interpretation just the narrow section that is located in that the paleo sea level stayed at this level for a long
deeper water at -1.7±0.1 m. period and submerged following a sudden tectonic
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The upper surface of the mole must have been subsidence . In addition, a possible notch formation
0.8±0.2 m above the mean sea level at the time of was also observed below the distinctive notch, which
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th
construction (4 century BCE). Adding this value to indicates older sea level stability.
36 VITRUVIUS, II.6.1.
37 ULUSOY et al. 2004, 73.
38 PIRAZZOLI et al. 1996.
39 FLEMMING 1978, 412.
40 See Chapter 3.2.c: Margin of error ±0.2 m for the minimum original elevation determined for the structure.
41 Studies performed in tectonically stable regions (i.e. Sardinia island) revealed that the amount of submersion of archaeological
structures is only due to eustatic and isostatic sea level changes (ANTONIOLI et al. 2007, 2480). Although researchers suggest
different values, we considered the eustatic-isostatic sea level rose of ~1 m in the last 2,500 years for our calculations, suggested by
Vacchi et al. (2017, 782).
42 KIZILDAĞ et al. 2012, 227.
43 EVELPIDOU – PIRAZZOLI 2013, 5.
44 It is questionable how far the shipshed’s ramp would have continued into the sea, in other words, what the water level in the base
should be. Blackman (1973, 128) answered this question as “deep enough for ships to be able to float into the base of ramp, which is
maximum 1 m”.
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