The International Open Workshop “Insights into temporal and spatial variability of environmental conditions during deposition and organic matter transformation into Tertiary Bulgarian coal basins of different rank“, held on June 03, 2024, Sofia was organized in the frame of project KP-06-H64/5 funded by the Bulgarian National Science Fund by Organizing committee of the project members Z. Milakovska. A. Zdravkov and M. Stefanova. Scientists and PhD students from the hosting Geological Institute, Institute of Mineralogy and crystallography and Institute of organic chemistry with centre of phytochemistry at the Bulgarian Academy of Sciences, Mining university “St. Ivan Rilski”, Sofia University “St. Kl. Ohridski”, University “Prof. dr. A. Zlatarov”- Burgas, Bulgarian Humus Substances Society, and Mini Maritsa Iztok EAD participated at the workshop. The foreign members of the project team Prof. K. Stojanovič and Dr. I. Kojič (Belgrade University, Serbia), Assoc. Prof. M. Misz-Kennan (University of Silesia in Katowice, Poland), Dr. A. Bechtel (Montanuniversitaet Leoben, Austria), and the invited lecturers Prof. D. Zivotič (Serbia) and Prof. R. Sachsenhofer (Austria) were the prominent scientists that stand out among the participants.

The Director of the Geological Institute, Assoc. Prof. Dr. Svetoslav Georgiev, welcomed the participants and officially opened the workshop. The workshop proceeded with 12 presentations. The new petrological and geochemical data on coal basins in Bulgaria, Serbia, and Indonesia intrigued the participants. The results submitted for the environmental conditions during coal and carbonaceous sediment deposition, the topics related to weathering of carbonaceous dump materials and to different lithotypes pyrolysis from Maritsa Iztok Basin, as well as to the reclamation achievements in the coal mining areas in Bulgaria and South Wales, United kingdom and North Ireland came up to long fruitful discussions. Very interesting were the reviews concerning the environmental aspects of the polyaromatic hydrocarbons in airborne particulate matter and their potential health risks, the floral changes during the Tertiary Era and their climatic implications based on biomarker and isotopic methods, as well as the Re-Os isotopic studies of carbonaceous sediments. New strategies for further research collaborations were developed as a result of the high scientific level of the presentations and friendly atmosphere during the lively discussions, and, also, after a visit to the Geochemical laboratory for elemental analyses and Laboratory for LA-MS-ICP at the Geological Institute. The presentations submitted, reviewed and accepted were published in a Special chapter of the Review of the Bulgarian Geological Society, official Journal of the Bulgarian Geological Society, https://bgd.bg/review-bgs. During the day after the International Open Workshop a field-trip to the Pernik coal basin was organized. The scientists visited and sampled a geological section from the north-eastern coastal area and the dump of the open-pit Republika Mine at the Mini Pernik AD.