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New data about the fossil macroflora from Blagoevgrad Graben (SW Bulgaria)Нови данни относно фосилната макрофлора от Благоевградския грабен (ЮЗ България)Miroslav Ivanov1, Vladimir Bozukov2, Konstantin Tyufekchiev1

Мирослав Иванов1, Владимир Бозуков2, Константин Тюфекчиев1

1 South-West University “Neofit Rilski”, 66 Ivan Mihailov str., 2700 Blagoevgrad; Е-mails: m_ivanov@swu.bg; konstantinat@abv.bg2 Institute of Biodiversity and Ecosystem Research, BAS, Acad. G. Bonchev str., bl. 23, 1113 Sofia; E-mail: vladimir_bozukov@yahoo.com

Keywords: Blagoevgrad Graben, Upper Neogene sediments, fossil macroflora, stratigraphy.

IntroductionDuring field investigations undertaken in 2016, a new fossil site that is situated inside the Blagoevgrad Graben near the town of Boboshevo and contain-ing presumably Late Pontian–Early Dacian macro-flora was found by M. Ivanov and determined by V. Bozukov. The fossils are found in situ 10 m below the surface inside the sediment outcrop considered as a part of the Pokrovnik Formation (Bakalov, 1978; Zagorchev, 1992; Ivanov, Bozukov, 2017). The site contains mainly arctotertiary species found in various habitats. Until now trees, bushes, lianas and semi-par-asitic bushes that belongs to 12 taxa were registered (Ivanov, Bozukov, 2017).

Stratigraphy of Blagoevgrad GrabenAccording the Geological Map of Bulgaria (Mari-nova, Zagorchev, 1991) the Neogene sediments in Bla goevgrad Graben are separated in two main strati-graphic formations – Dzerman (Meotian) and Ba ra-kovo (Pontian–Pliocene).

Zagorchev (1992) proposed a new stratigraphic scheme of the Neogene sediments inside the Bla-goevgrad Basin that consists of four stratigraphic units: Pokrovnik, Dzerman, Barakovo and Badino Formations. Pokrovnik Formation is the oldest with probable Meotian–Pontian age and it is built mainly of proluvial yellowish polymictic conglomerates and interbeds of sands and sandy clays (Zagorchev, 1992). Dzerman Formation interfingers with the Pokrovnik Formation and it consists of predominantly alluvial deposits: greenish, whitish or yellowish sands and clays interbedded with whitish or yellowish pebble gravel. The age of Dzerman Formation is Meotian

probably continuing into Pontian (Zagorchev, 1992). Barakovo Formation (Pontian–Pliocene) – aluvial sediments and Badino Formation (Pleistocne) – pro-luvial sediments, overlap the Dzerman and Pokrovnik Formations (Zagorchev, 1992).

Ivanov (2016, 2018) and Ivanov and Bozukov (2017) confirmed the presents of the four main litho-stratigraphic units determined by Zagorchev (1992), but based on the newly discovered fossil site near the town of Boboshevo the authors corrected the stratigraphic positions of Pokrovnik and Dzerman Formations. According Ivanov and Bozukov (2017) Pokrovnik Formation (Upper Pontian–Lower Dacian) is younger than Dzerman Formation (Meotian) and has complex lateral relationships with the last.

New data about the fossil macroflora from Blagoevgrad GrabenAs a result of the ongoing in 2018 studies of the sedi-ments from Pokrovnik Formation were established: one species of gymnosperms – Tsuga europaea Menz. and 15 angiosperm taxa. Of the last mentioned Potamogeton praenatans Knoll, Cyperus sp. and Typha latisima A. Braun possess cosmopolitan near-est living relatives (Fig. 1). In this case, the cosmo-politan distribution of these three taxa is presumed by its water-related lifestyle. Six angiosperm taxa are representatives of the arctotertiary type of vegetation: Alnus ducalis (Gaud.) Knobl., A. incana (L.) Moench, Carpinus betulus L. foss., Sorbus aff. aria (L.) Crantz, Ulmus pyramidalis Goepp. and Viburnum aff. nudum L. The species Tsuga europaea belongs to the arc-totertiary type too (Fig. 1). Five angiosperm taxa are representatives of the paleotropical type of vegetation: Caesalpinites inaequalis Palam. et Petkova, Laurus

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nobilis L. foss., Myrica lignitum (Ung.) Sap., Persea pliocenica (Laur.) Kolak. and Pterocarya paradisia-ca (Ung.) Iljinsk (Fig. 1). The fossil species Quercus cardanii A. Massal (Fig. 1), which is related to the endemic species for the Black Sea region Q. hartwissi-ana Stev., has also been established. The new paleo-floristic data are in line with what has been established so far. They reaffirm the relative young age of the flo-rabearing sediments. Of the newly find out taxa, only Caesalpinites inaequalis has Middle Miocene as a stratigraphic distribution (Palamarev, Petkova, 1987). Taking into account all 28 species that have been es-tablished so far, the following result will be reached: 11 taxa are registered in Bulgarian fossil sites aged as Late Pontian–Early Dacian, 13 taxa are found in fossil sites aged in an interval of Middle Miocene to Late Pontian–Early Dacian, and 2 taxa (Caesalpinites inaequalis and Sapindus falcifolius) are registered in Middle Miocene deposits as upper limit of their stratigraphic distribution. The taxon Alnus aff. viri-dis (Chaix.) D.C. is registered for the first time in Bulgarian paleoflora.

ConclusionsThe studied paleoflora from Pokrovnik Formation is closest to those from Garmen (18 common species) and the Sofia Basin (16 common species). In turn, the paleofloras from Garmen (Kitanov, 1984) and Sofia Basin (Stojanoff, Stefanoff, 1929; Stefanoff, Jordanoff, 1935) have established a Late Pontian–Early Dacian age. On this basis, it could be assumed a similar age of Pokrovnik Formation.

ReferencesBakalov, P. 1978. Litho-stratigraphic division of Blagoevgrad

sediment system in Blagoevgrad Graben I. – Paleontol., Stratigr., Lithol., 9, 79–95 (in Bulgarian with an English abstract).

Ivanov, M. 2016. Evidence for Late Neogene braided rivers in Blagoevgrad Graben. – In: Proceeding of the National Conference “GEOSCIENCES 2016”. Sofia, BGS, 117–118.

Ivanov, M. 2018. Neogene-Quaternary Evolution of the Relief Along Middle Struma River Valley Between Skrino and Oranovo Gorges. PhD Thesis. Blagoevgrad, South-West University “Neofit Rilski”, 197 p. (in Bulgarian).

Ivanov, M., V. Bozukov. 2017. Late Neogene braided rivers in the Blagoevgrad Graben: the first stages of the Late Miocene orthoplen destruction. – Rev. Bulg. Geol. Soc., 78, 1–3, 39–55.

Kitanov, G. 1984. Phytogeographic and ecological character-istics and age of the fossil flora of the vicinity of Gotse Delchev town and evolutionary trends in Pliocene floras in Bulgaria. – Fitologiya, 27, 40–53 (in Bulgarian with an English abstract).

Marinova, R., I. Zagorchev. 1991. Geological Map of Bulgaria on Scale 1:100 000. Blagoevgrad Map Sheet. Geological Institute of BAS, Enterprise of Geophysical Surveys and Geological Mapping.

Palamarev, E., A. Petkova. 1987. La macroflore du Sarmatien. – In: Tzankov, V. (Ed.). Les fossiles de Bulgarie, 8, 1, 3–275. Sofia, Bulg. Acad. Sci. (in Bulgarian with a French abstract).

Stefanoff, B., D. Jordanoff. 1935. Studies upon the Pliocene Flora of the Plain of Sofia (Bulgaria). – Abh. Bulg. Akad. Wiss., 29, 3–150.

Stojanoff, N., B. Stefanoff. 1929. Beitrag zur Kenntnis der Pliozänflora der Ebene von Sofia. – Rev. Bulg. Geol. Soc., 1, 3, 4–120.

Zagorchev, I. 1992. Neotectonic development of Struma (Kraishtid) Lineament, southwest Bulgaria and northen Greece. – Geol. Mag., 129, 2, 197–222.

Fig. 1. Fossil photographs: a, Alnus ducalis; b, A. incana; c, Caesapinites inaequalis; d, Carpinus betulus foss.; e, Cyperus sp.; f, Laurus nobilis foss.; g, Myrica lignitum; h, Persea pliocenica; i, Pterocarya paradisiaca; j, Quer-cus cardanii; k, Ulmus pyramidalis; l, Sorbus aff. aria; m, Tsuga europaea; n, Potamogeton praenatans; o, Typha latissima; p, Viburnum aff. nudum (measuring bar – 1 cm)