GEOLOGICA BALCAN I CA, 18. 2, Sofia, April. 1988 p. 61-66. Sedimentation cycles in the Neogene grabens along the Struma valley 1 1 P . .\'edjo/ko u , £ . 1\o jumdgieva-t , I . Bo'J.kou 1 Entreprise " Rare metals", u. Buhouo 2 Geologico[ l n~titute , 1113 Sofia (A ccepted for publicatio '1 , orember 3, 19.\7) n. H eaH..lKOB , F.. }\o,u,ua)((ueoa , 11. bO:'If.KOO - CeaulltCHI/laljUOHHble ljU K:Ibl 0 HCOZL'HOtJbiX z pa6t!Hax (J ao ­ .1/4 11(; peKu C111py.ua. Bb! ;J.eJJ SJIOTCSI TP H cc:tHMi!IITliUIIOHHbiX UHK.n<: n HeoreH OBbiX riJa6 Hax B:lOJJ b peKu (TpyMa, KOTOpt..!e CKOp)Je.1H)JO il3J.bl H ,!l,aTII)JOBalibl !Ia OCIIOBaHHH B33liMOOTIIO Well llii Me>KI\Y OT.10JI\elii!SIM II H 110 u axo;tKaM M.'l ei<OIIHTa JOW,IlX. I Ull K.1 (cpe.'I.Ht' MH OUeuo ao-sa:Ie :JH~I CKII ii ) - TO.%KO B Ca zi AaHcl OM rp a6CIJC, aKTIIBIIble pa3JJ0Mbl C <jlaur.n o IepaTa,\HJ- neTpvBCKIIii II lOiK1111!1 '!aCTb 3ana,il.ltO-fl Hp11lit"K0fO pa 3JJOAJOil. II UHKJJ (~I.~ OTH •I ecKHH=H H >f\H e - cpe .'\ tieTy!J O JJ IIH CKIIii) - a CaH JtaHCKOM, CTpyMewJtHWK OM, CHMHT<illliCKO~I I! GJJarocerpa.lCKOM rpa!"ieuax , aKfltBH bl e pa3JJO ~Ibl c <jlaHrJJOMepanMH ·- no,!l,r OpCK Hii, Oc!pouciOi H, KpyiiHIIWKIIii 11 3anaAHO-P!i.1CKHii pa 3 .~0~I bl. Ill UIIK.1 (nOJtTll4eCKI1ii=cp~: ;tnenepx iH: Ty­ ponuiicKHH 11 ocpo!ITIIO IIHiKHeiiJJIIOUe iWBblii) - · ll CaH .:J. aHCKOM, CTpyMeWJI HWKOM, OwTaBCKOM, ( HMH T· .1HllcKOM II J):taroeor pa.lCK OM rpnGcuax, 3KTHB Hble pa3.10M bl c !paur.noMeparaM JJ - n o.'lrOpCKHll, MeJI. liJIKCK IIH, 3ana;\II O-fiHpH1iCJ\IIii H 3ana."l. fltJ -Pli.1CKHH pa :i:IOMU . fl oc.1 t TpeTbero UHK;;a (eepO!!ThO D eonJJefl croneu.:) nu;ttiSI"r lle 3ana;tllbi X ropCTOil II IIIITeHCHDIIOe pa3.~aMbi B 8 11H e C<jlOIJ~Uip0113.111 6JJOK I1 C MOIIOK.11111 <1Jl bllblM YKJJOH0~1 JleOrt'hOBWX c. IOC D I( BOCTvKy, IIJJ0111D !jJliUH<IJlbliOJJ 30113 .1 bii00.:TI1 . fl O:l· ropomii, n e l pOB ~ KIIi'l, 3ana.:tH0- 011 p1111CJ\ 11JI, KpyniiiiKCKHH 113aua;III•> -PH JJCI\HH pa3 .'10Mbl CHO!la aK nt· UII311PYI01Cll Ab ~ lr acf. Three so.:d imentalion cycles have been differen tial din the Neogene grabens aloug the v alley of the Struma river, correl ated aJHI dated after the re!ati n s bct w ten th e e dim ~n t a11 d after M ammab finds. I cycle (Mi ddl e Miocene- Vallo:! ~i an)- only i n Sandanshi Graben, adi vc f aults with [arglomerates - Pctrovo and sou thern par t of the \\ es:-Pirin faults. II cycle (Maeotian=Lo­ w i-J\'\iudl e Turo!idu)- i n Sandan5ki. Strumesu ica, Simitli and Bl ag oe,·grad Grab ns, acti ve f aults with fa1 glomeratcs- Podgolie, Pet rovo, Krupuik and West- Rila faults. Ill cycle (Pc·n ti an=Middle­ U pper T urolian an d pr obably also L ower Pli ocene)- in Sandan ·ki, Strumesn ica, O ~tava , Simitli <~li d Blagoe \·g:ad Grabens, active f au lts wi h far.gl ur t:mates- P odgorie, .M e!Hik, \Ves t-Pirin and we ~ t - Ril a f ault ~. Iter the third cycle (probabl y in Eopleist oc.n e) ! he uplifting of the w r s!ern h or sts and ihc in ten ive faul !ing hav f ormed block with a m onoc!inal di p of th e Neogme beds toward th e E as t, oppo, it(;; to the f acies zonali ty. The P odgori e, Petrovo, \\'est-Pirin, K rupn ik nr: d \\' est­ Rit a raul t wc1 e al so reac tivated . The principal grabens along the valley of the river Struma in Bulgarian territory are: Sandanski Graben with the dependent, secondary Strumesnica and Ostava Grabens, Simitli Graben and Blagoevgrad Graben. The great and complex Lower Strimon Gra­ ben in Greece is not treated, because of lack of personal observations. Three sedimentation cycles have been differentiated in these grabens, correlated and dated after Mammals and following the relations between the sediments. The first cycle sedimentation occurred onl y in Sandanski Graben (Fig. 1). It is represented by Del cevo and Katunci Formations (K o j u m d g i e v a et al., 1982; He .n. 5I JI K o a H .n. p., 1986). Delcevo Formation is extended in the wes tern and cen­ tral parts of Sandanski Graben and is represented by alluvial and fine proluvial sedi- 61 \ ' l ) > I \ .. · •. ! \ . \ \ \ ~. 1 I \ . \ I J I • I / :* .. ·. ( \ : ~ . :l-·' \ : I .' t ·.· v I . " i i I o SA"-'OANSI< I 1 I I * • " I * \ I 'i Fig. I. Tectonic-sedtmen tological skekh-map of th e S truma a! ley during the firs t s dimtntol o­ gical cycle (Mi ddle Mi ocene- Valle ian) I- Neogene sediment · , examin ed in outcrops or in L>or hole;'!- Delcevo f- ormati on; 3 - Kalunci Formati on; 4 - Paleogene ·cdimen t<; 5 - granite. : 6 - m tamorphic r oc h!'; 7 - active faul t;;; 8- in active faul ts. F:l:J!t ·: I. Pdr vo.>; 2. \ e·t-Pi rill" .3. \\'';.t· Rila ments with predominating red coloration and a thickne s from 150-200 to 300- 400 m. The age after Mammal finds is Middle Miocene and aile ian. l(atunci Formation near the eastern boundary of the graben i represented by "eakly cemented conglomerates and breccia-conglomerate (fanglomerates) more of 400 m thick (up to 500-600 m after geophysical data). Their upper part is Vallesian in age, the lower parts being probably Middle Miocene, as thei r lateral correlate ­ Delee o Formation. The fanglomerates of Katunci Formation are bound to the Petro o fault and to the southern part of the West-Pirin fault proving the dominant acti ity along this faults. The others faults were inactive, or more exact! lacking important vertical movements (Fig. 1). The second cycle is represented in all grabens except for Ostava Graben (Fig. 2). The sediments are of two types: alluvial (alluvial-lacustrine) and prolu ial (fanglo­ merates) . The alluvial-lacustrine and fine-prolu ial facies of the second cycle included the lower part of Sandanski Formation in Sandanski and Strumesnica Grabens, and the alluvial-fineproluvial facies, - Simitli Formation in Simitli Graben and Dzerman Formation in Blagoevgrad Graben. The fanglomerates of the second cycle included the lower part of l(alimanci Formation in Sandanski and Strumesnica Grabens, Cer­ nicevo Formation in Simitli Graben, and the lower part of Barako o Formation in Blagoevgrad Graben. The correlation of all these Formations is based as well on trac- 62 Fi g. 2. Tectonic sed i m en tologic<~l ke tch -map of the S tr uma valley during the .econ tl sedimentol o­ gical cycl e ( \ aeo<ian ) I - Dzer rnan For ma~io : 1 ; 2- Simi ll i Formalio1;; 3- S andan ki Formati on; 4- t.ernicevo Forma­ tion; 5 ·- Barakovo ~ormat i o n; 6 - Kal!manci Formation; 7 -- P a!eogenc sed imen t <>; 8- gra­ nites; 9- metamorphic r ock; 10- active faults; II - inac ti\•e [au!! ~. r:aulb: I . Podgorie; 2. Pe t­ ro,·o; 3. We t- Pirin; 4 . 1\ru pn i l<; 5. \\·es!-Rila ing their horisontal relations, as on the Mammal find . The Mammal prouved the LO\ver-Middle Turolian (Maeotian) age of the sediments of the second cycle (K o j u m­ d g i eva et al., 1982; K o 10M p., >t< 11 e sa H ,11.p ., 1984; He p., n n K o s H p.,p ., 1986; H e ,11. H J1 K 0 B H p.,p . , 1988) . The most active faults (\dth fault-bound thick fanglomerates) during the second cycle have been Petro o (including the southern part of the West-Pirin), Podgorie, Krupnik, and West Rila faults . The corresponding sediments are 300-700 m thick, and together with the alluvial and alluvial-lacustrine sediments, also accumulated in the grabens, their thickness reaches up to 1 000 m . Normal faults striking 60-90° formed Strumesnica and Simitli Grabens, thus be- ginning to play an important role together with the W-SSE faults of the Struma set, forming the Sandanski and Blagoevgrad Grabens (Fig. 2). At the midst of the second cycle, fanglomerates have been formed in the northern part of Sandanski Graben (Jlindenci Member of Kalimanci Formation) and in the sou­ thern part of Simitli Graben (Gradevo Member of Cernicevo Formation) (K o 10M­ p., >t< He sa H p.,p ., 1984; He p., H n K o s H p.,p., 1986). Their formation has been bound to local elevation of the horsts between them. The third cycle is represented in all grabens, including Ostava Graben (Fig. 3~­ The sediments of this cycle are strong! y erroded (the thickness of the preserved sedt- 63 Fig. 3. Tecto.d c- sed i1 11e.t!ologica! . kclch-m aiJ o! the S!r u m~ ,·alley during the third sedimen tolo­ gical cycle (Po,, tian-Lower Pli ocene) I -Sandanski fo•mati o1 : :! - Kalimanci f o rm ~l i O!l; 3 - Barakovo Formation; 4- eogene sedi men t from the I anrl II ~.:y cl e . ; 5 - P aleogene sed ime n t ~; 6 -- g ra n i t e ~ ; 7 - metamorphic.