## 2 Materials and Methods  
### Samples  
The samples considered in the present study were collected during a series of investigation campaigns during which outcropping substrate rocks were collected both on the top of Serravuda Hill and along the slopes of the hill itself, as well as fragmented material accumulated on the top of the hill itself and showing evidence of having undergone pyrometamorphism and vitrification.  
Previously published work by [PERSON] et al. (2021) provided detailed descriptions and general data, including location, quantitative X-ray mineral analysis, and petrographic attributions of the individual samples collected [12].  
Among these samples, fourteen rock fragment samples from the vitrified structure, which showed evidence of prometamorphism, were selected for thermoluminescence (TL) dating. Such evidence consists of reddening, macro- and micro-fracturing, and, above all, the presence of a vitreous component testifying the material underwent partial melting with consequent formation of liquids able to percolate throughout rock fragments.  
In addition, a sample of substrate rock (named sample SE 9) was collected from the Serravuda hill. This sample was not affected by the heating event that caused the vitrification, thus serving as a crucial confirmation for the method employed.  
The selection of samples for analysis was initially guided by their mineralogy, with a preference for granitoid samples rich in quartz and feldspars and poor in Fe-rich phases. These samples were considered more suitable for conventional TL methodologies, as confirmed by previous research [21]. Based on their mineralogy, glass phase content, and location, they can be classified into distinct groups (see Table 1).  
Although gramitoid pyrometamorphites are a relatively minor component (<5% volume) within the vitrified structure, they typically occur as small, rounded pebbles of about 10 cm. They exhibit pronounced macro- and micro-deformation, with only slight indications of partial melting.  
The metamorphic pyrometamorphite fragments (85% volume) consist of kinzigitic gneisses or their retro-metamorphic counterparts. Morphologically distinct from gramitoids, these fragments exhibit elongated shapes and sharp edges, often accompanied by an amorphous component. These characteristics imply significant involvement in the partial melting process during the heating event.  
The term \"vitreous cements\" includes all pyrometamorphic products in which optical microscopy reveals a predominant amorphous component. A portion of amorphous liquid has managed to flow between the un-melted rock fragments, effectively binding them together. These cements appear as thin glassy crusts enclosing the rock fragments (e.g., samples SV 1-4 and SV4-V), as veins of dense material without bubbles (SV 1-A), or as accumulations within pockets containing dense black glass (sample SV 1-3V) or considerably vesicular pumice glass (SV1-B).  
For the preparation of thermoluminescence measurements of samples, an extensive granulometric grinding process was carried out using a stainless-steel mortar to prepare the sample to the measurement. This entire procedure was executed in the dim red laboratory light. The selection of particle size was necessary, considering the instrument's irradiation and measurement requirements, and it included grain sizes within the intervals of <125, 125-250, and 250-500. Macroscopically ground samples exhibit varying colors and aspects, with many of them appearing very dark.