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E. Lodolo, Z. Ben-Avraham / Journal of Archaeological Science: Reports 3 (2015) 398–407 399
separated from the North African coastline by less than 50 km. The grad- cover of the bedrock is composed of coarse organogenic sands with
ual increase of the sea level caused the flooding of most of the peninsula, thickness ranging from a few decimetres to a few metres (Stanley
with the exception of some morphological highs that, until at least the et al., 1975; Colantoni et al., 1985). This bank is located in a sector of
Early Holocene, formed an archipelago of several islands separated by the Adventure Plateau dominated by NW-trending, high-angle normal
stretches of extremely shallow sea, as shown by the analysis of swath faults related to the continental rifting phase that produced the Pantel-
bathymetric mapping and high-resolution seismic profiles (Lodolo, leria graben (Civile et al., 2010). Compressional structures, generated by
2012; Civile et al., 2015). Today, the Adventure Plateau is morphologi- a Late Miocene compressional phase (Argnani et al., 1986; Lentini et al.,
cally separated from Sicily by the Mazara del Vallo Channel (depth of 1996), have been also recognized in this sector.
about 120 m), and from Tunisia by the Pantelleria graben (depth of The high-resolution map focussing on the area between the two
about 1300 m). shoals (Fig. 2) shows that the most evident morphological feature is
It is well known that the Mediterranean Sea is a unique basin an 820 m long, rectilinear ridge connecting the two shoals and enclosing
from a historical and archaeological perspective, since it was an im- an embayment. The base of this ridge lies at water depths ranging from
portant means of communication among human communities living 43.1 to 44.4 m while its summit lies between 35.1 and 36.8 m below sea
on its shores. These ancient civilizations have left numerous imprints level. The ridge is characterized by a flat top and a regular slope ranging
along the former coasts, such as production and town structures, from 16° to 20°. A parallel, but less continuous, segment of ridge is locat-
landing places, and ports. Some structures that are today submerged ed 80 m inward of the main outer one and rises about 2 m above the sur-
can provide fundamental information to support the reconstruction rounding sea-floor. Underwater surveys were made throughout the
of the ancient coastlines (Auriemma and Solinas, 2009). Conversely, entire length of the outer ridge and part of the inner one, in order to ob-
in shallow water areas distant from the coastline, the information on tain photographs and video images, and to collect rock samples. The
possible ancient permanent human settlements are scarce, and there slopes of the ridge are devoid of sedimentation due to a relatively strong
are no traces to date found in the Mediterranean Basin mainly be- and constant bottom current with velocity varying between 2 and 3
cause the lack of detailed and extensive bathymetric mapping, and knots. The entire ridge is composed of rock blocks generally with a rect-
the presence of a variably thick sedimentary cover masking any sub- angular shape in plain view lying in close contact to each other. Such a
merged structure. geometric arrangement is particularly evident in the central part of
Here we present the results of high-resolution bathymetric surveys the ridge. About 100 m seawards from the southern termination of
performed on the Pantelleria Vecchia Bank (PVB), a submerged shallow the outer ridge, an elongated rectangular flat top ridge extends 82 m to-
relief of the Adventure Plateau, located 40 km north of the volcanic is- wards the open sea and rises ~2 m from the surrounding sea-floor. To
land of Pantelleria, as well as underwater visual observations by divers, the north of the rectilinear ridge, other important morphological ele-
analyses of some rock samples collected in several locations of the bank, ments seen on the map are at least three concentric, semi-circular
and radiocarbon dating. These data provide evidence for an unique and ridges, and regularly spaced by 60 m. Between the two southern ridges
significant structure of anthropogenic origin. the almost flat sea-floor lies at 36÷38 m below sea level. The water
depth of the annular areas between the northern semi-circular ridges
2. Methods ranges from 32 to 34 m. At ~15 m from the base of the southern semi-
circular ridge, an important morphological element, easily recognizable
Detailed sea-floor surveys were conducted in November 2012 from the bathymetric maps (Fig. 3), is an elongated monolith laying on
using a hull-mounted multi-beam sonar system with the R/V OGS- the sea-floor, isolated from the rest of the outcrops, and broken in half,
Explora. Subsequently, in December 2012, a high-resolution survey as appears from inspections carried out by divers (Fig. 4). The good
was focused on a specificarea ofthe PVB, whichwas mapped with match between the two adjacent parts suggests that it was originally a
a portable multi-beam sonar system. These surveys provided a context single block. Its length is 12 m, with a recognizable squared section of
for direct sea-floor observation made by divers, who recorded high- about 2 m, particularly regular in its southern half. The longitudinal
definition video (for a total of approximately 8 h of registration) and axis of the monolith is oriented N50°E. A rounded hole with a diameter
photos, and collected several rock samples. In addition, radiocarbon of about 60 cm passes right through the monolith, at 50 cm from one
measurements were made on small, intact shells extracted from 4 dif- end. Another hole of the same diameter, but not crossing the whole
ferent rock samples, applying the Talma and Vogel (1993) calibration monolith, is present in one of its sides. It is about 40 cm deep and is lo-
method. Because the obtained ages are close to the limit for 14 Cdating, cated midway in the monolith, at a right angle with respect to the first
the measurements were performed in two different laboratories in USA hole. Another hole, but less regular, with a diameter of about 50 cm, is
(Lawrence Livermore National Laboratory, and Beta Analytic Inc., found along the other side of the monolith. Also this hole is located
Miami) to verify the goodness of the data. midway in the monolith.
These activities, carried out in various phases from August 2013 to
September 2014, were supported by the Italian Arma dei Carabinieri, 3.2. Macroscopic and microscopic analyses on rock samples
who made available their boat and a group of divers. Francesco
Spaggiari and Fabio Leonardi (Global Underwater Explorers)contribut- Here we present analyses of rock samples recovered in some loca-
ed with rock samplings and underwater videos. More details on ac- tions of the PVB (Fig. 5). Samples 1, 2, 3, 1A, 2A, 4A, 5A, 6A and 7A
quisition parameters and processing of high-resolution bathymetric have been grouped together because these all correspond to a bioclastic
data can be found in the Supplementary Material. calcirudite. Samples 1, 2, 3, 4A and 6A have been taken by divers at var-
ious water depths from the blocks composing the outer rectilinear ridge,
3. Results and sample 7A was taken at the top of the inner ridge. Samples 1A, 2A
and 5A have been taken by divers from the monolith described above.
3.1. High-resolution bathymetric maps and underwater surveys The macroscopic analysis shows that about 95% of the clasts consist of
fragments of shells, red algae and corals, with rare, well rounded
The bathymetric map (Fig. 1) reveals that the PVB is made up of two lithoclasts (generally between 0.5–4 mm in size), embedded in a thin
main shoals, intersected by fractures and steep valleys, and a number of layer of calcite. A photomicrograph of a thin section (transmitted
2
smaller isolated bathymetric highs, covering a total area of 5.2 km ,with light) shows that the coarse-grained, rounded bioclasts (red algae) are
little or no sedimentary cover. The present depth of the two main shoals surrounded by an isopachous fringe of calcite, indicative of precipitation
varies from 16 to 24 m, while the surrounding areas are located at in marine phreatic zones where all pores are filled with water (typical
depths ranging from 46 to 60 m. Here, the unconsolidated sedimentary feature of low-intertidal and sub-tidal cements). In this case, bridging