10 EXPLORING THE CAVES OF AGION OROS: A COMPREHENSIVE GEOLOGICAL SYNTHESIS OF FIELD-WORK DATA Georgios Lazaridis 1 , Alexey Zhalov 2 , Aikaterini Panora 1 , Despoina Dora 1 , Athanasios Dimou 3 , Konstantinos P. Trimmis 4 , Konstantinos Vouvalidis 1 1 Aristotle University of Thessaloniki, School of Geology, Thessaloniki, 54124, Greece, geolaz@geo.auth.gr, despdora@geo.auth.gr, kate.panora@gmail.com, vouval@geo.auth.gr 2 Bulgarian Caving Society, azhalov@gmail.com 3 University of Aegean, Cultural technology and communication dpt., Lesvos, Mytilene, 81100 Greece, a.dimou@aegean.gr 4 University of Bristol, Department of Anthropology and Archaeology, Bristol, BS8 1TH, England, kostas.trimmis@bristol.ac.uk Abstract More than 220 caves and underground artificial constructions have been explored and documented during international expeditions to Agion Oros (Holy Mount Athos) under the patronage of the European Speleological Federation as the International project ―The caves of Holy Mount Athos, Greece‖ (more information about the project in Zhalov et al., 2011). All the caves have been surveyed, photographed, and documented. Certain speleothems found in these caves have been analyzed and identified as rare silicate speleo- thems (Lazaridis et al., 2022) or as evidence of hydrothermal speleogenesis (Lazaridis et al., 2014). This work classifies all the rec- ords into three categories 1. natural caves; 2. natural caves with artificial modifications, such as building or curving, and 3. artificial constructions. The third type of record is excluded by cave definition (Lazaridis, 2022) as artificial in origin. Caves of Agion Oros are formed in diverse locations, altitudes, and lithology, comprising carbonate and non -carbonate rocks. The analysis of various data is conducted, encompassing the qualitative classification of cave patterns in ground plan (Palmer, 1991), along with the examination of the meso- and micro-scale morphological features of these caves and the distribution of caves in the Agion Oros peninsula. The results of these analyses are forming the framework for the solid qualitative and quantitative ongoing study of the Agion Oros caves. Keywords Cave, cave morphometry, cave distribution, cave expedition, Serbo-Macedonian Massif, Agion Oros, Athos, Chalkidiki. SOFIA 2023 - PROCEEDINGS OF BALKAN SPELEOLOGICAL CONFERENCE - SOFIA - BULGARIA , OCTOBER 19-22 2023 1. Introduction The Peninsula of Agion Oros is currently the focus of systematic exploration within the scope of the international project ―The caves of Holy Mountain Athos‖ (Alexey et al., 2011) under the patronage of the European Speleological Federation. Over 220 caves and underground artificial constructions have been ex- plored and documented. These data are being collated and ana- lyzed for the first time in terms of geology and speleogenesis. The results of these analyses are forming the framework for the solid qualitative and quantitative ongoing study of the Agion Oros caves. 2. Geological setting The Chalkidiki Peninsula is located in Central Macedonia, Greece, and is divided into 3 smaller peninsulas: Sithonia, Kas- sandra and Mount Athos. The latter, differs from the other two morphologically and geologically, and constitutes the study area. The peninsula of Athos has a NW-SE direction and 50 km length. Its main body is a mountainous ridge that gradually in- creases in altitude, forming the top of Mount Athos at 2030 m (Georgiadis, 2007). Mount Athos (Figure 1) consists of the Serbo-Macedonian Massif (SMM), which is the central part of Internal Hellinides crystalline basement (Kockel et al., 1977). Two units of SMM are forming the Mt Athos Peninsula. Ver- tiskos unit in the west, which is the upper and newer unit of the SMM, covers part of the north peninsula and extends north to the country‘s borders. It consists of a sequence of green shales, gneisses, and other ultramafic rocks, interrupted by thin marble horizons, and Kerdillion unit in the east, which is the lower unit of the SMM and consists of marbles and biotic gneisses, which alternate by depth (Burg et al.,1996). Between Vertiskos and Kerdillion units there is a zone of ophiolitic mélange that consists of mafic and ultra-mafic rocks, gneiss, and metasediments (Himmerkus et al., 2003). More specifically, the rocks that are mapped on the Athos penin- sula (IGME, 1978) are (from the upper to lower layers): Quater- nary and Neogenic post-alpine sediments, recrystallized lime- stones and marbles of the Aspri Vrysi -Chortiati section, biotitic and two-mica gneisses of the Vertiskos unit, marbles of the Ker- dillion unit and, finally, the Paleozoic basement of SMM (amphibolites, gneisses, etc.). Igneous rocks are also present, covering a large part of the peninsula. Grigoriou granite is the most significant, followed by a granodiorite and granitic dykes intruding in metasediments. 3. Methods This work classifies all the records into three categories: natural caves, natural caves with artificial modifications, such as building or curving, and artificial constructions. The third type of record is excluded by cave definition (Lazaridis, 2022) as artificial in origin. All caves with artificial modifications are also excluded from further analysis. In order to analyze the field work data from the Agion Oros area the follow- ing parameters have been considered: cave entrance location, lithology and cave entrance altitude. In addition, morphologically the caves are classified according to their pattern in ground plan and longitudinal sections in categories that have been used in other works about Greek caves (Lazaridis et al., 2022) such as 1. vertical shaft and complex vertical structure; 2. horizontal single passage; 3. chamber; 4. horizontal with multiple passages/ chambers; 5. combination of single vertical and horizontal pas- sage; 6. complex caves of multiple horizontal and vertical pas- sages; 7. sinkhole; 8. complex branchwork. Some quantitative data measured from cave maps and are statistically analyzed. These are the following parameters maximum cave width, cave length, cave height, cave area, cave perimeter. The area to perim-