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194 F. Pepe et al. / Geomorphology 303 (2018) 191–209
3.3. Bulk density measurement and mass estimation of boulder 3.4. AMS 14 Canalysis

Determination of bulk density was carried out on 7 rock samples col- Four radiocarbon analyses were carried out on biogenic encrusta-
lected in the studied area. The volume of rock samples was determined tions of Vermetid sp. found on boulder surfaces. The samples were first
by the “Instantaneous Water Immersion Method”. Rock samples were subjected to a chemical treatment with hydrogen peroxide to remove
coated with a thin layer of silicone grease in order to prevent that the the external layer and were then converted, under vacuum, into carbon
water flowed into the sample during water immersion. Subsequently, dioxide through acid hydrolysis with H 3 PO 4 . The extracted CO 2 was af-
their volume was calculated by taking the difference between the vol- terwards cryogenically purified, and converted into graphite through a
umes of water after and before immersion of the rock sample into a catalytic reaction at 600 °C by using ultrapure hydrogen as a reducing
1000 ml cylinder, graduated in 20 ml divisions, partly filled by distilled agent and iron powder as a catalyst (D'Elia et al., 2004). The extracted
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water at room temperature. The rock masses were measured by using a graphite was then used to measure the 14 C/ C ratio by an Accelerator
precision balance with a readability scale of 0.1 g. The bulk density for Mass Spectrometry (AMS) system (Calcagnile et al., 2005). The mea-
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each rock sample was then calculated as the ratio of the measured sured 14 C/ C isotopic ratio was corrected for machine and sample pro-
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mass to volume. cessing background and for isotopic fractionation by using the δ Cterm
The mass of each boulder was estimated as the product of boulder's measured with the AMS system. Measurement uncertainty was esti-
density and volume. Density was assigned to each boulder on the basis mated as the largest between the radiocarbon counting statistics and
of results of bulk density measurements as well as by considering its the scattering of the data for the ten repeated measurements performed
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thickness and lithology. The volume was calculated for each boulder on the sample. Finally, the Δ C value was calculated according to
by multiplying the values of the A, B and C axes. Stuiver and Polach (1977).

Fig. 2. Boulders and sockets characteristics in the Punta Faraglione coastal area. a) Boulder axes (A, B and C); b) seaward imbricated accumulation of tabular boulders; c) view of a boulder
berm. A-sector is the area corresponding to the berm that extends parallel to the coastline; IE: inner edge of the berm; OE: outer edge of the berm; d) example of biogenic encrustations of
Vermetid sp. detected on boulder surfaces used for radiocarbon analysis; e) boulders with sharp edges and pieces of wood embedded in the deposit; f) striae on thesurface of aboulder
(~80 × 40 × 30 cm) due to recent impact; g) underwater free boulders with sharp edges; h) sockets carved out in the submerged platform edge; i) block not yet detached from the host
rock (predicted boulders) as well as joint-defined sockets (indicated using different colors); l) joint-defined sockets formed at different layers along the platform edges; m) socket axes
(A, B and C); n) boulder with angulated edges.