A Hybrid Quantitative Framework for the Chronological Reclassification of Indeterminate Ceramic Assemblages

The chronological classification of ceramic assemblages is frequently limited by the presence of large groups of fragments lacking secure phase attribution. These residual categories, often labelled as “indeterminate”, “no phase” or “SIN_INFO” (“no information”), distort phase distributions, weaken diversity and equitability indices, and reduce the interpretative coherence of archaeological datasets. This study develops a hybrid and fully traceable quantitative framework for the chronological reclassification of indeterminate ceramic materials, applied to the Neolithic assemblage from Tossal de les Basses / Cerro de las Balsas (Alicante, Spain). The initial dataset comprised 7,507 ceramic fragments and 387 stratigraphic units, with approximately 47% of fragments (NTE) and 52% of minimum number of individuals (MNI) lacking chronological attribution. The proposed protocol combines three complementary procedures: cosine similarity between techno-decorative profiles and phase centroids, supervised classification through Random Forest, and proportional/profile-based imputation. These outputs were integrated through a hierarchical decision model that prioritised agreement between methods, high-probability predictions and controlled similarity thresholds, while reserving lower-confidence profile-based assignment for unresolved cases. Rather than eliminating uncertainty, the framework transforms it into explicit, ranked and reproducible decision rules. The results enabled the formal reintegration of previously indeterminate materials into the chronological sequence of the site, improving stratigraphic consistency, phase comparability and the interpretative use of ceramic diversity indicators. The complete workflow was implemented through Python scripts, structured matrices and documented procedures, ensuring replicability, auditability and transferability to other archaeological contexts affected by high levels of ceramic indeterminacy.