GEOLOGICA BALCANICA. 26. 2, Sofia, Jun. 1996, p. 63-80 Tectonic Sites of Special Scientific Importance (TSSSI) in tbe Mid -Cretaceous Strouma Superunit, Southwest Bulgaria Jl·an S. Zagorchev Geologica/Institute, Bulgarian Academy of Sciences, Acad G.Bonche~ St. build. 24. 11/3 Sofw. Bulgaria Ja~op'U!e- Te~emOHU'4eCICUe o6&eiC111bl cne&~UaAbHO ­ Abstract. The Mid-Cretaceous tectonic structure of ~ IUJY~Utozo 3Ha'4eHwr e cpedHeMeAoeou CmpyMciCou Southwest Bulgaria consists of the parautochthonous ~.JOzo-JanadHa.Ji E011zapwr. Cpe.llHeMenoaoe Te&­ Strouma Superunit and the allochthonous Morava ecaoe CTJ)OCHHe 10r0-3808,1lHOI Jio.nrapHH COCTO­ Superunit. Five sections represent excellent exposures of :U 10 napaaTOXTOHHol Crp)'Mcaoll e.llBRHilW H aJIJIOX- unique tectonic features. They should be protected by the A Mopaacaol e.llHHHUbl. IbTb p83peJoB BbiJIBnll- State, and conserved in a manner suitable for preservation 11:7 )'Blll:&nbHble TeKTORH'IeCa:He OC06tHHOCTH. 0HH as well as for educational and scientific purposes . .JOID"Hbl 6b1Tb DOCT&BneHbl DO.ll JllU.lHTOA rocy.llapcna, • cepsHpOBaHiol Taa:HM cnoco6oM 'ITOObl o6ecne'tHTb toXpaHeHlle .11M H8}"1HWX Hccne,nOBaHHA H ,lleMOHCT­ C yqe6Hol uenbiO. b:gorchev, I. - Tectonic Sites of Special Scientific Importance (TSSSI) in the Mid-Cretaceous uma Superunit, Southwest Bulgaria. - Geologica Bale., 26, 2; 63-80. ~· words: geological heritage; Southwest Bulgaria; tectonic sites Introduction Geological setting present paper aims to draw the attention Strouma Superunit ds five geological sites that should be "dered as Sites of Special Scientific The Strouma Superunit (Strumicum; Trun­ portance (SSSI) and placed under the VIahina structural zone - Zagorchev, 1984, ection of the State. They have a complex 1990) is a parautochthonous element (Fig. I) of mostly tectonic character, and exhibit the Mid-Cretaceous ("Austrian") structure of rtant relations between different geological Bulgaria that has been included in the Late ·es being also (in some cases) stratotypes of Cretaceous Morava-Rhodope structural zone al lithostratigraphic units. These sites are (Boyanov et al., 1989). After the main Mid­ tg. 1): I. Road cut south of the village of Cretaceous folding, the formations of the .urvodol; 2. Road cut near the village of Superunit have been covered in Mid-Cretaceous Gurbino; 3. Road cut west of the village of time by the thrust sheets of the Morava yantsi; 4. Ravine near the village ofPoletintsi, Superunit, and furthermore, folded together in confluent of the river Poletinski-dol; 5. Road Late Cretaceous time, and covered (sealed) by near the village of Tsurvishte. Paleogene sedimentary and volcano-sedimen­ These sites should certainly be included in tary formations. · e Bulgarian Geological Heritage List (Bulg The pre-Permian basement of the Strouma (jlfl.) and the Balkan GHL. Some of them may Superunit is of Vlahina type. It is built up of considered as candidates for the European biotite and two-mica gneisses and migmatites GHL, and even for the World GHL. interlayered by amphibolites and quartzo- 63 i~- · ~- .1,. ..... -., j _l ,. ....- · Fig. 1. Sketch map for the position of the tectonic SSSI in the Strouma Superunit. 1 -Alpine plutons; 2- Hercynian granitoid plutons; 3- 5 - southern part of the Srednogorie Superunit: 3 - Melovete (MU) and Radomir (RU) units, 4 - Lyubash and Golo-Burdo units, 5 - Viskyar-Vitosha part; 6 - Louzhnitsa-Trun Unit of the Strouma Superunit; 7 - Osogovo-Vlahina Unit of the Strouma Superunit; 8 - diabase-phyllitoid complexes (mainly Frolosb Formation) of the pre-Alpine basement; 9- Rhodopian Supergroup from the Pirin Unit; 10 - Rhodopian Supergroup of the West-Rita Unit; 11- Ograzhdenian Supergroup from the ~, Kapatnik Unit; 12- Osogovo Formation of the Osogovo l£:3z Subunit, Osogovo-Vlahina Unit; 13 - 14 - Morava Superunit: 13-external thrust units with Paleozoic section ~3 [q:@~f), ~II of Kouchay type (SK- Strumolska klippe, VK- Vlashki­ ~' ~. ~12 ,,.:-, 15 kamak klippe, RN - Rizovtsi thrust sheet), 14- internal thrust units with high-grade metamorphic formations; 15 ~s !lmmg§3r3~r5 - Poletintsi-Skrino fold-thrust zone; 16 -thrusts (a) and ~6 ~.,E:J" ,TS 11 faults (b); 17- tectonic SSSI: SR- section Rayantsi, GT 0 5 1P 15 20km - Gurbino thrust, SP - Section Poletinski-dol, MA­ Murvodol anticlinaloid, TS - Tsurvishte thrust feldspathic gneisses. They are referred to the of the Petrohan Terrigenous Group. The next Precambrian Ograzhdenian Supergroup. This lskur Carbonate Group (Tronkov, 1983) covers amphibolite-facies basement is covered with a the interval from the Spathian (uppermost Lower primary depositional contact (primary uncon­ Triassic) to the Norian, and consists mainly of formity later reworked both tectonically and limestones and dolomites with local marly and metamorphically) by the so-called diabase­ shaly interbeds. The Moesian Group (Norian) phyllitoid complex (Frolosh Formation) built up is represented by marine red beds : shales with of metadiabases, green rocks, actinolite and infrequent limestone interbeds (with Norian chlorite schists, metakeratophyres, etc. that foraminifers) and irregular bodies of underwent a greenschist-facies metamorphism. conglomerates built up predominantly by The rocks of the Frolosh Formation are intruded pebbles of Triassic limestones and dolomites. by the rocks of the Strouma diorite formation, Jurassic formations occur only in the northern with a probable early Paleozoic age. parts (Louzhnitsa- Trun Unit) of the Strouma Permian red beds of the Skrino and Eroul Superunit, to the North of the Poletintsi - Formations (Zagorchev, 1980, 1995) cover with Skrino fold-thrust zone. The usual development unconformable depositional contact all pre­ (Sapunov et al., 1983, 1985; Dodekova et al., Permian rocks and formations listed. The basal 1984) consists of a continental Zhablyano conglomerates contain pebbles of the pre­ Formation (shales, oligomictic quartz sand­ Permian rocks. The thickness is irregular. In stones, conglomerates, with interbeds of black some parts of the superunit, the Permian coal) of Lower Pliensbachian age, followed by deposits are lacking most probably due to the marine Ozirovo Formation (sandy biodetrital primary causes (non-deposition), and the pre­ limestones and calcareous sandstones; Permian basement is covered directly by the Pliensbachian - Lower Toarcian), Gradets basal conglomerates of the Lower Triassic. The Formation (oligomictic quartz sandstones; Lower Triassic is represented mostly by red beds Upper Toarcian -Bajocian), Polaten Formation 64 (biodetrital and oolithic limestones; Aalenian - greenschtst-facies metamorphism; intruding pre­ Lower Bathonian), Yavorets Formation (micritic Permian basic and granitoid rocks; ii) Vlasina and biodetrital limestones with flint nodules; type: amphibolite-facies metamorphic rocks of Middle Callovian - Oxfordian), Gintsi the Dragoychintsi Formation covered by Formation (nodular limestones, often of the metapsammites, metapelites, marbles and "ammonitico rosso" type; Lower Oxfordian - metaphosphorites (Cheshlyantsi Formation) of Lower Kimmeridgian), Neshkovtsi Formation Ordovician age; and iii) Eleshnitsa type: (calcareous shales and marls with some Precambrian? amphibolite-facies metamorphic limestones and sandstones) and Kostel For­ rocks covered by metadiabases, metatuffs and mation (coarse flysch in transition to sandy metaterrigeneous rocks (Zhdrapanitsa Forma­ flysch). The section is ending with a calcareous tion) of Vendian - Early Paleozoic age, and post-flysch with Lower to Middle Berriasian age. graphite-bearing micaschists, quartzous schists, A specific development in a part of the superunit quartzites and limestones (Ruzhcha Formation) is represented by limestone breccia and with recently proven Silurian to Early Devonian conglomerate and micritic limestone (Lobosh age. Formation) in lateral interfingering with the The rocks of the Morava Superunit repre­ limestones of the Y avorets and Gintsi sented the basement of an Early Alpine (Triassic Formations. -Jurassic to Early Cretaceous?) sedimentation Another and very specific Jurassic section zone that possibly was a part of the continental (Treklyano Group) crops out only in the slope towards the Vardar ocean or a very deep westernmost parts of the Louzhnitsa-Trun Unit, gulf of that ocean (Zagorchev, 1986). It has been beneath the thrust sheets (Penkyovtsi and folded and thrusted to the north-east over the Poletintsi thrusts) of the Morava Superunit. The folded Strouma Superunit in Mid-Cretaceous Treklyano Group consists of polymictic time. conglomerates, olistostromes and sandstones (at the base) and interbedding of slates and Murvodol anticlinaloid (MA) radiolarites. Laterally they pass into a shaly formation with sandstone and limestone The Murvodol anticlinaloid (Figs. 2 - 7) is a interbeds. The beds of the Treklyano Group striking example of antiformal syncline cover with depositional contact and (anticlinaloid). It is situated South of the village unconformity the Norian red beds (Komshtitsa of Murvodol, the core cropping out in the stream Formation), and are covered by the flysch of and its eastern bank. The southern limb of the the Kostel Formation. structure is well exposed along the country-road The whole Mesozoic section of the Strouma towards the hamlet Vodenicharska-mahala of Superunit has been folded in Mid -Cretaceous the village of Pastouh, and is covered near that time, and different levels of the eroded section hamlet by the thrust sheet of the Skrino thrust built