A number of signs that are hard to decipher have been found inscribed on blocks of tuff on stretches of walls in Pompeii. They include asterisks, opposing triangles, and short lines that intersect to form tridents. These are quarry logos, consisting of incomprehensible graphic symbols that do not correspond to the letters of any alphabets known to be used at the time. So, if we are to interpret them, we need to find an alternative code in order to build up a separate semantic system. One possible interpretation of these signs that has been put forward associates the quarry logos with the stylised shape of the tools used by the various workers. In this case, the symbol would be like a company advertisement that, instead of using names, initials, or monograms, summed up the shape of the tools in a simple form, instantly recalling the activities involved in building. Something not that dissimilar from a modern logo, portraying the work tools of stonecutters and masons. The asterisk seems to refer to the groma, a surveying instrument with plumb lines, and the trident shape to various types of lewis, while the double opposed triangle logo would represent a double axe. These signs evoke everyday scenes of a hard-working Pompeii, where construction work was on the cutting edge: the first known dome in opus caementicium is that of the Stabian Baths, dating from the second decade of the first century BC, while opus craticium, – wattlework – an early example of an anti-seismic construction system, had been commonly used ever since the end of the third century BC. Opus craticium was a forerunner of the casa baraccata, consisting of a wooden frame with vertical posts and supporting beams or horizontal stringers with a filling of opus incertum. In 1784 the Bourbon government issued its “Royal Instructions”. These were anti-seismic building regulations applicable to all new buildings in southern Italy, and they were directly inspired by the construction system that had been used centuries earlier, in Pompeii. 

From a geological point of view, the 0009 core sampling site is located at the overlap between the western remains of the Civita volcano caldera and the edge of the volcanic edifice of Via Stabia. 

From an archaeological point of view, the core sampling area is located outside the northern walls, to the north-east of Tower XI on the city walls, also known as the Tower of Mercury, in a sector where archaeological excavation has not been carried out.

The Tower of Mercury, which dates from the age of Silla, is a quadrangular structure on three floors, crenelated at the top. Significant stratigraphic investigations in this area have examined the various stages of construction of the walls and, in particular, they have identified the archaic period of the fortifications of Pompeii built in “pappamonte” (tuff).

The uppermost portion of the stratigraphy of the 0009 core shows a layer about 1.5 m thick of material accumulated in recent times.

Below this layer is a sequence of archaeological layers with some compacted, relatively thin surfaces. In particular, compacted layers are reported at -1.5 (US 2), -2.15 (US 4), -2.7 (US 6), -3.25 (US 8) and -4 m (US 11). The layers of soil compacted either by human transit or by exposure to surface waters have no archaeological elements to allow them to be dated. They are interspersed with artificial accumulations containing non-datable materials, mainly in the form of remains of ruined buildings. The only exception is that of the accumulation of soil at between 1.6 and 2.15 m (US 3) containing a fragment of a Dressel 2/4, generically datable to between the first century. BC and the first century AD. 

The sequence of natural and artificial accumulations reaches down to -6 m (US 15) from the current ground level: the considerable depth of the archaeological layers suggests the presence of a moat, which might have been part of one of the periods of Pompeii’s defensive system.

Below this, between -6 and -6.4 m below ground level, grey cinerites are found with black scoria from a prehistoric eruption of Vesuvius, resting on a paleosol with white pumice at the end of the core.