Combustion features are routinely studied using micro-geoarchaeology in prehistoric sites, providing information on human social life. In submerged prehistory such features have not been studied from the microscopic perspective, and here we present a study of three combustion features from two submerged Neolithic sites from the southeastern Mediterranean: Atlit-Yam (ninth-millennium cal BP) and Neve Yam (eighth-millennium cal BP). Mineralogical analyses were utilized to detect heated clay while quantification of phytoliths, ash pseudomorphs, and dung spherulites allowed determination of fuel sources. Micromorphology was deployed to determine whether or not the features represent in situ combustion activities and to understand formation processes. Two installations from Atlit-Yam contain evidence for short in situ fire events that were fueled by wood and reached 700–900 °C. One installation from Neve Yam contains reworked deposits that bear evidence for combustion at 500–700 °C, includes remains of wood ash and livestock dung. However, this feature cannot be identified with certainty as an in situ combustion feature. This research shows that pyrotechnological, functional, and social information can be gleaned from underwater combustion features using a micro-geoarchaeological approach and techniques.

Fourier transform infrared (FTIR) spectroscopy is frequently used for archaeological studies related to fire, allowing, among other things, researchers to distinguish between unheated and heated clay minerals. However, heat signatures are not always clear‐cut in infrared spectra of bulk sediments, as spectra occasionally appear with ambiguous absorbance bands attributed to hydroxyl (OH) in clay minerals. This paper presents an experimental study addressing this interpretational problem by considering the effect of mixtures of heated and unheated clay, a phenomenon expected in archaeological sites. After creating experimental mixtures and testing them using bulk FTIR spectroscopy, our results indicate that even a relatively small amount of unheated clay—only ca. 5%–10% mixed into a fully heated deposit—will result in ambiguous infrared spectra that are difficult to interpret. For comparison, ambiguous bulk FTIR spectra from two archaeological contexts—an ashy fill within a pit installation and a hearth—were studied with FTIR microspectroscopy, which demonstrated the presence of unheated clay within a largely heated deposit. Micromorphological observations explain the mixed nature of the investigated archaeological contexts, in this case, primarily via bioturbation. Our results thus emphasize the importance of microcontextual analysis of clay minerals. Furthermore, these results indicate that heated deposits are likely missed altogether in some archaeological contexts where only bulk FTIR analyses have been conducted.

The investigation of submerged archaeological sites faces numerous logistical challenges in the recovery of stratigraphic sequences and, as a result, is often restricted to surface deposits limiting the application of geoarchaeology. This paper outlines a new integrated field and microanalytical methodological protocol to investigate deep stratigraphic sequences (up to 2 m) within the submerged Pre‐Pottery Neolithic (PPN) site of Atlit‐Yam (9267–7970 cal. B.P. [calibrated years before the present]). A new coring method for the extraction of deep underwater stratigraphy was developed to extract three cores: two between architectural remains within the site and one outside the site. The cores were analysed using Fourier‐transform infrared spectroscopy, phytolith and pollen analysis and archaeological micromorphology to detect anthropogenic signals and undertake paleoenvironmental reconstruction. Our results indicate anthropogenic evidence at 95 cm depth based on the presence of heat‐altered sediments, high phytolith concentrations and micromorphological observations of archaeological remains. Radiocarbon analysis indicates the oldest anthropogenic layers date to the Mid Pre‐Pottery Neolithic B (PPNB) and Late PPNB (9859–9323 cal. B.P.), bearing implications for reassessing the emergence of the first coastal Neolithic villages in the Mediterranean. Our integrated field and multiproxy micro‐geoarchaeological protocol offers a new approach to detecting and studying submerged archaeological sites worldwide.

Underwater excavations require an immense amount of logistics and have inherent time limitations. Underwater challenges such as nitrogen toxicity, underwater color change, and dive time limits increase with working depths, affecting the interpretation of archaeological contexts. Thus, underwater excavations involve methods and approaches to extract the maximum information from small areas while providing a comprehensive understanding of the archaeological record. Here, we present the benefits of using an on-site laboratory comprising a microscope, binocular microscope, Fourier transform infrared spectrometer and blue light inspection device. Three case studies are presented, focusing on the identification of stratigraphic boundaries, as well as the preservation and identification of archaeological materials. The results show a complex stratigraphic sequence containing seven layers divided into four mineralogical units: (1) Calcite, (2) Calcite and aragonite, (3) Aragonite, and (4) Dolomite. Additionally, the use of an on-site laboratory is effective in preventing the misidentification of archaeological materials, which could affect the final interpretation of the archaeological site (e.g., glass, lead, bone), and enabling the identification of materials invisible to the naked eye, such as opaline phytoliths. In the case of the Antikythera shipwreck, the on-site laboratory facilitated the examination of stratigraphy and quality of the archaeological context while streamlining excavation practices and documentation. Furthermore, the on-site laboratory allowed for the assessment of material preservation and provide crucial insights to inform post-excavation treatments and analysis of artifacts.

In submerged landscapes, distinguishing anthropogenic features versus natural ones is often challenging. We have developed a set of criteria to validate the identification of submerged anthropogenic remains that include examining the geological context, sea-level considerations, associated archaeological finds (including coastal survey), and documenting the broader archaeological context. Furthermore, our experience demonstrates that, while progress has been made in applying remote-sensing technologies to detect anthropogenic features on the seabed, there is no substitute for direct, visual assessment by an underwater archaeologist for verification of their anthropogenic status. We have applied these criteria to examine two published case studies detailing suspected anthropogenic stone features on the seabed in the Sicilian Channel. Our examination has led us to conclude that both localities are not anthropogenic features. The Pantelleria Vecchia Bank features represent natural outcrops on a submerged paleo-landscape that were shaped by depositional and erosional processes during transgression and regression periods. The suspected Lampedusa cultic site comprises natural features that are located on a submerged neo-landscape formed due to erosion and retreat of the coastal cliff since the mid-Holocene, when the sea level reached its present level.