In Memoriam Academician Todor G. Nikolov (26.02.1931, Varana, Pleven District – 26.03.2021, Sofia) Academician Todor Georgiev Nikolov left us on 26 March 2021, only a month after his 90th birthday. This sudden death is a heavy blow for the scientific community and an irreparable loss for the Bulgarian Academy of Sciences. It ended a remarkable life’s path of work and endeavors of a scientist, university professor, organizer and popularizer of science, editor and author. Born in a small village in Central North Bulgaria, young Todor lived in a rural family whose father used to find additional income as a seasonal construc- tion worker in different parts of the country. After primary school he had to walk 6 km daily to attend secondary school at a neighbouring village. At that time, he was under the influence of his godfather – the poet Ivan Krastev, and also tried himself in the poetical field but soon discovered that this was not his field and life’s path. Nevertheless, his whole life he kept the intimate love of poetry and the fluent style so impressive in the numerous books written in his mature academic years. The odyssey of his life is vividly described in his auto- biographic book “Outlines of a Life’s Path” printed on the occasion of his 85th birthday. After finishing high school in the small town of Levski, Nikolov applied for studentship on “Natural Sciences” at Sofia University – the oldest and most renowned university of Bulgaria. During his studentship, the speciality split into “Biology” and “Geology”, and Todor chose the second one although he remained always attracted to biology and the great achievements in the fields of its capital problems as the origins and evolution of life. Due to the very good background obtained at high school by high-class teach- ers and to his talents and love of Nature, Todor had a remarkable scientific ca- reer. He graduated “Geology” with honours in 1955, worked for two years in i the Balkan Coal Basin as mine geologist, and then became research scientist at the Geological Institute of the Bulgarian Academy of Sciences. His professional path in geosciences has been greatly influenced by the specializations in the for- mer Soviet Union (1960) and France (1968). These two scholarships gave him the opportunity to acquaint himself with some of the leading paleontologists and stratigraphers in the fields of Lower Cretaceous as well as with the classical sec- tions of the world’s Lower Cretaceous in Southern France. In the meantime, he obtained his PhD (“kandidat na naukite”, 1967) degree and became Senior Research Associate (1968) at the Geological Institute. In the fall of 1970, Todor Nikolov applied to a lecturer’s position at Sofia University, where he was consecutively elected Associate Professor (1970) and full Professor (1979), Head of the Chair of Paleontology (1973; later Chair of Geology and Paleontology, 1991) up to his retirement as Professor Emeritus in 1996. During his tenure of academic positions at the University, he held also the responsibilities of Deputy Dean (1972–1979) and Dean (1979–1980) of the Faculty of Geology and Geography, Vice-Rector of the Sofia University (1980– 1987), and Member of the Academic Council of the Sofia University (1979–1989). An impressive list of his positions in different scientific bodies includes Member- ship (since 1973; President 1992–2009) in the National Committee of Geology, in the National Committee for the International Programme for Geocorrelations (1975–1989), in the Scientific Council of the Geological Institute (1968–1993; 1995–2010; Chairman 2004–2010), participation in the governing bodies of the Higher Testimony Commission at the Council of Ministers (member of the Scien- tific Commission for Geological and Geographical Sciences, 1980–1987; President of the Presidium of the Commission, 1987–1990; President of the Specialized Scientific Council of Geological Sciences, 1995–1998; Member of the Presidium, 2006–2011), and many others. He has also been editor and Chief Editor of a number of national and international scientific journals and books, member of sci- entific societies, international commissions and workgroups, of five international scientific projects, of eight international congresses, symposia and workshops, nu- merous travels and workshops abroad (with reports at Lyon, Moscow, M¨unster, Dubrovnik, Vladikavkaz, T¨ubingen, Wellington, and Naples, and lecturing in Di- jon, Toulouse, Athens, T¨ubingen, Paris, Moscow, and Leningrad). During his work at the University of Sofia, T. Nikolov initiated several im- portant projects which had long-term effects on the development of geosciences at the University and contributed much to the international image and recognition of Bulgaria. His beloved child is the Teaching Base of the Faculty of Geology and Geography in the beautiful Balkan town of Elena, and the Museum of Paleontol- ogy in the same town. He became deeply acquainted with this beautiful town, its geology, ancient architecture, and remarkable inhabitants and their ancestry as early as during his field work in 1966–1967, and began organizing the field work with the geology students in 1975. Known from the archives since 1340, this small town has always been a cultural and spiritual centre which gave to Bulgaria a number of outstanding politicians, military, clerical, cultural, and scientific lead- ers. Todor Nikolov has fully appreciated not only the high educational potential of Elena and its surroundings but also the goodwill and human power of the inhabi- ii tants and local authorities who answered with full understanding and generously helped his efforts. In 1983 his efforts were crowned with the opening of the Base in the old restored Popnikolov House, and in 1996 (the year of retirement of Pro- fessor Emeritus Nikolov), with the opening of the Museum of Paleontology at the same house. The second field of fruitful initiatives of Professor Nikolov has been the start of extensive collaboration with the French universities. Due to his good knowledge of the French language and to his achievements in the fields of Lower Cretaceous, Nikolov has been highly appreciated in France during his specializa- tion and first visits there. These links have been further improved and tightened, and enlarged with common projects between the Bulgarian and the French geo- logical societies and the academies of sciences of the two countries. The role of Academician Nikolov in these relations has been highly evaluated with his election as Doctor honoris causa (and golden medal) of the University of Toulouse “Paul Sabatier” (1994) and as Chevalier dans l’Ordre de Palmes Acad´emiques (1998) for his services to the French culture. The third great achievement of Academi- cian Nikolov when at the Sofia University was his substantial contribution to the organization of the first Bulgarian Antarctic Expedition (headed by his student, later Professor Christo Pimpirev) and the foundation of the Bulgarian base on the “Ice Continent”. These efforts have been recognized by naming the Nikolov Cove on Smith Island, South Shetland Islands, Antarctica. Besides the recognition by the international and Bulgarian geocommunities and authorities, Academician Nikolov found the greatest satisfaction to leave generations of talented and highly educated followers and pupils many of whom became outstanding scientists and professors in the fields of geology and paleon- tology. Still being at leading academic position at the University, Professor T. Nikolov has found the recognition of his scientific achievements by the Bulgarian Academy of Sciences. He has been elected Corresponding Member (14.11.1984) and Full Member (Academician; 4.06.1997), and has been Member of the Presidium of the Academy (1988–1991), and Chairman of the Department of Natural, Math- ematical and Engineering Sciences (2001–2009). After his retirement from the university position, he became acting Professor at the Geological Institute (1996– 2003) and Guest Professor at the Geographical Institute (2004–2009). During all these years and up to his last days, he continued with enthusiasm to summarize his enormous knowledge and expertise in a number of remarkable books, some of them enlisted at the end of these notes. The scientific interests and achievements of Academician Nikolov are sum- marized by himself as follows: “1. Paleontology and stratigraphy (am- monitic taxonomy and evolution; Jurassic/Cretaceous boundary; Lower Cre- taceous stratigraphy and ammonitic paleontology; stratigraphic principles and methods; sequential and event stratigraphy); 2. Theory of evolution (factors, laws and key moments in the organic evolution; ecosystems evolution, behavioural evolution; adaptation; crises and catastrophic events in evolution; influence of or- bital factors on the geological anals); 3. Regional geology (geological structure of regions of Bulgaria and other European countries; Tethyan mobile zones and orogenic events; field geology of oil and gas); 4. Sedimentology (catastrophic iii events and cyclicity in the geologic anals); 5. Paleoclimatology and paleo- geography.” The sheer numbering of these items demonstrates the wideness of interests, and the contributions of Academician Nikolov in these fields are embod- ied in more than 27 books and textbooks, more than 180 scientific articles and more than 120 articles in popular science journals, reviews, etc. An impressive sci- entific production written with highest respect to scientific precision in methods applied, science ethics, and language style! Among his greatest achievements, we