GEOLOGICA BALCANICA. 26.3, Sofia, Sept. 1996, p. 53-57

IGCP Contribution to Project 253 "TERMINATION OF PLEISTOCENE"

Neotectonic and geomorphological characteristics of the western part of the Aydemir Lowland, Silistra District

Dora Angelova

Geological Institute, BAS, 1113 Sofia, Acad G. Bonchev St, bL 24

(Submitted 9.03.1994; accepted 06.11.1995)

AIUelloBa, ,[(. - Heome~emoHuatecKilJI u zeoMop¢011ozu­'leCKilJI xapaKmepucmuKa 3anadHOU atacmu A udeMupc­KOU HU3UHbl, CUIIucmpeHcKozo pauoHa. llpeJlCTasnena xapaKTepHCTHKa HeOreHCKHX, 'leTBepTH'IHhiX H COBpe­MeHHbiX JlBHxteneii B lanaJlHOH 'laCTH AMeMapcKoii HH-3HHhl, rJle pacnonoxteHo H 6onoTo "Cpe6LipHa", npeJlC­rasmnomee co6oii 6aoccJ>epnb1H pe3epsaT DOJl JamaTOH opraHH3aQHH IOHECKO, a TaiOICe HX pe3yn&TaHTHIUI -pen&e«t> H cy6crpar. Ha ocnosaHHH JlaTaposox JCoppenJI­THBHhiX OTJIO)l(eHHH 6biJIH yCTaHOBJieHbl pa.3JIH'IHJI B reo­liHRaMH'IeCKOM pa.3BHTHH OTJleJibHhiX 6JIOKOB HCCJie}lye­MOfO paifona. Bnepsble s noM paJione H s lionrapaa 6b1Jla OOHap~eRa naneoceH3MOJlBCJIOUllHJL, Ha3BaRHIUI"Cpe6-blpHa" Ha rpaHBQe WieiCTOQeH-rOJIOQeB B03paCTOM I 0500 ± 250 B.P. Ee JlJIBBa coCTaBJIJieT 2750 m, mapaHa - OT 750 JlO 1000 m H aMilJIBTYJla BepTBltaJlbHOro CMe­UlCHH.A 20 m. Ona pacnonoJKeRa B renoHH'IecxoM pne, o6pa30BaHROM B TO'IKe nepece'leRHJI npOJlOJibROH TeK­TOHH'IeCKOH 30Hbl 1 panra H MepHJlHORaJibHOH TeKTORH­'ICCKOH 30Rbl III panra. On MapupyeT 3DMQeRTpaJibR}'JO o6naCTb JeMJJCTpliCeHH.A. B pe3yn&rare OJlffOaJCTHoro co6-biTH.A C CHJJOH 8-9 CTeneBH H npeJlDOJiaraeMOH rny6HROH O'lara 30-60 Km, OTpbiBaeTCJI 6JJOK, o6e3rJiaBJIJIJOUlHH YCTbe peK Cpe6blpneucKa H KbiJIRe)l(Ka, H 4>opMepyeT 60JIOTO Ra rpaRHQe Me)l(Jly JleCTpyKTHBHOH H UK)'MYJIJI­THBROH 'laCTbJO paBRHRbl, OTJCJIOReRHe BOJlhl peK B OCHO­BC rpaBHTal{HORROrO 6JIOKa H yxOJllliUHX B ero KapCTO­BYJO DOJlOWBy. liCCJJe}lOBaHHe HMeeT npHJCJiaJlROe 3Ha­'ICHHC, TaK xaK sonpoc coxpaneHHJI 6aoc4Jepnoro peJep­saTa H COOTBeTCTBeHHO H npHp0JlHO-reOM0p4JOJIOrH'IeC­KOrO 4JeHOMena .ABJI.AeTCJI aKTYaJibHhiM.

Abstract: Neogene, Quaternary and recent characteristics of the western part of the Aydemir lowland are presented in this paper. The "Srebarna" swamp is situated in this region being a biosphere reserve under UNESCO protec­tion as well as their results-relief and substrate. There are some· geodynamic development differences of various blocks of the investigated region found on the basis of correlative deposition age determinations. A paleoseismo­dislocation named "Srebarna" bound to the Pleistocene­Holocene boundary and aged 10500 ± 250 yr. has been found for the frrst time. It has a length 2750 m, a width varying from 750 up to 1000 m and a vertical amplitude-20 m. The paleoseismodislocation is situated at a tectonic junction of a first-rank longitudinal tectonic zone and a third-rank meridional tectonic zone. It marks the epicen­tral zone of the earthquake. A block bas been broken ofT as a result of one-act seismic event ( intensity of 8-9 de­gree and supposed depth of 30-60 km). As a result of this event, the Srebarna a.nd .Kalnezhka River mouths have been naturally embanked by the gravitationally subsided block. It has been a natural barrage for the rivers' waters. The block bas caused water baffiing to its base, and thus their loss in the karstic underseams. The investigations presented in this paper are of practical importance due to the value of the biosphere reserve and the respective natural-geo­morphological phenomenon.

Angelova, D. 1996. Neotectonic and geomorphological characteristics of the western parts of the Aydemir lowland, Si!istra District- Geologica Bale., 26, 3; 53-57.

Key words: neotectonics; Srebama Lake; Northern Bulgaria

The region studied covers a part of the Aydemir lowland that includes the Srebarna Lake -an international biosphere reserve (MH'ieB, H.!IHeB,

1982). It is naturally fed by karstic waters and river Danube waters. Because of anthropogenic environmental disturbance (the embankment of

53

Ill f I ...

• J

Fig. I. Pre-Quaternary relief map of the western part of Aydemir lowland: J- "Srebama" swamp area;2- isohypses of absolute elevations; 3 - borehole location; 4.- faults

Danube), Srebarna Lake area continuously de­creases and this process is quite troublesome. The Srebarna Lake is situated entirely in the val-1ey below the confluence ofSrebama and Kaln­ezhka rivers. The lake depth varies between 1,5 and 3 m (Fig.1 ).

The regional neotectonic situation has not been an object of special investigations. The re­gion has been studied in geological respect by HHKOJIOB (1969) (Cretaceous rock complexes), TIOIJOB (1993) (Neogene sediments), <I>HJIHDOB, MHKOBa (1986) and Angelova (1995) (about the Quaternary deposits), and in geomorphologic respect- by MnHKOB (1968) and liO)KHJIOBa et al., (1985). Some data concerning the tectonics of NE Bulgaria are supplied by lleTKOB (1962), Boncev et al. (1982), liyHJ et al. (1982), ToToMaHoB, Bp'h6JI.RHCKH (1980), Mandrescu (1990), KocTa,nHHOB et al. (1992).

According to the existing ideas the valley where the Srebarna Lake has been formed is a result of erosion processes during Early and Mid­dle Pleistocene time (MHmcoB, 1968). Common tectonic processes are a result of positive verti­cal movements to the South of Danube River and negative vertical movements to the North of it. The analysis of the marsh and alluvial sed­iments (lio)KHJIOBa et al., 1985; Angelova, 1995) shows that they have been formed in a situation of block movements with different intensity and they reflect the climatic changes on a planetary scale (Fig.2).

In structural and geomophological respect the region is situated in the Danube epiplatform plain (BannapoB, MHmea, 1977). Concerning its morphostructural features the lake is localized on the boundary between highly fragmented and slightly up-lifted Pre-Pliocene and Pliocene den­udation plains over which a loess accumulative plain and Low-Danube lowland have been formed during Pleistocene. After contemporary

54

geomorphological zoning the region belongs to the Low-Danube intermountain kettle (Ban­napoB et al., 1990).

It inherited a various relief which had been formed during Barremian time (HHKOJIOB et al., 1969). The region has been overflowed by the Pre-Carpathian basin waters during the Upper Pontian- the clays ofSarpovska Formation are their correlate (TionoB, 1993). Several separate shallow freshwater basins have been formed over the whole region as a result of the Pre-Car­pathian basin bottom pulsations as well as its shallowing during the Dacian (a correlate- Ay­demir Formation sands, TionoB, 1993) and the Romanian (correlate - Srebarna Formation limestones, llonoB, 1993). The existing regional geodynamic interpretation (Kojumdjieva, Pop­ov, 1989) is within the framework of the recon­struction made by Balla (1984, 1987) - a de­pression as a result of concentric extension. Be­ing an effect of the crust ~ectonic condition, the geomorphological data show a low amplitude normal fault manifestation (from several meters up to 20-30 m and more rarely 100- 120m) be­tween accumulative and destructive parts of the lowland.

The tectonic phase preceding the Quaterna­ry is characterized by vertical tectonic deforma­tions. These deformations have a negative sign in the Sub-Carpathian region and exceed 2000 m (BannapoB, 1990), and on the Bulgarian ter­ritory they have a positive sign (+50 m ).

The Quaternary and recent tectonic evolu­tion controlled by the regional tectonic setting on the boundary between North Bulgarian Swell and Lower Danube Lowland as well as by the local development of separate blocks that build the Aydemir lowland and the northern parts of Dobrudzha massif.

The beginning of the Quaternary tectonic movements is marked by Villafranchian erosion and erosion - accumulative surfaces situated at a relative altitude 70 - 100 m (EsnorHeB, 1988). Their absolute elevations in the region are +60 and + 100 m, respectively (Fig.l ). The correlates are fluvial and alluvial deposits: clays, pebbles, gravel sands. Their thickness vary from several centimeters up to 10 m. The age is proved by vertebrate fauna (<I>HJIBDOB, Mmcosa, 1986). These sediments are not established in the base of the bottoms of Danube River and Srebarna Lake. This fact proves their young age.

Pleistocene movements are marked by a com­plex of river terraces. After accomplished in­vestigations it was found that the rivers valleys in the region (Danube, Srebarna and Karlezhka rivers) have been formed as a result of erosion­tectonic processes which have begun during

~rotigrophic -~ i! Strat9qtlic -on ~ v ..c: Climatic o- S , .,..,. ,.... · · Oa. c: L ' th 1 v• 1100 o u B.P ~Subdivisl- -0c: 1S e Lithology V emf ~)'IIQr sUuuiVISI- ·;:;c: _,., e I o ogy em year l ~ periods f---- ons 11?~1£ o s ons lf~l~ ll 30 so ~~+-+-----~ ot-----i=~~~~~·~i-~-4~-----f~3~iO~~~~~MI~~~~~

>-Sub-

a: Atlantic I.U w

<( .... <(

z ..... Sub-z Boreal

a: w

w u

.... 0 Atlantic

:>...

<( ..... ..... a:

:::> 0 <(

Bore a I Ul

0 :X:

Pre-Bor&al

NEOGENE

IJ.III 2000- Todoranko

lllllllll -· - - -

-------Forma- 0; -=-=-=------...:--.---

E 5,30 - =-=-=-tion a -------• ------= ----- -----

11m-

"' -=-=-=-- - - -'lODO-

:-=-=-=-11000

,_ _____ _ - - - ----

11m-

!OOOG

Torl i tso

Forma­

t i on

c::3, b·-±J . . -:- . 5

~\\\k

~0 t"' _;_ . ..:_ . .:.. . ,_ _____ _

0 6.0 r-_-___ _

~-=-=-=

E-81 auun3 -~ ~ 7 ~ 8

§§§_, IW"-"1,,

Fig. 2. Correlation scheme of Todoranka Clayey Formation and Tarlica Pebble-sand-clayey Formation and their sedimentation velocity: 1 - soil; 2 - clays; 3 - peat; 4 - goethite; 5 - sandy clay; 6 - sands; 7 -pebble gravel; 8 -boulders; 9- re-deposited loess; 10- Neogene sediments; 11 - wash-out

Early Pleistocene time and continued till the end of the Pleistocene.

The value of the total tectonic movements in the western part of Aydemir lowland is estimat­ed at 55-60 m. The Holocene has begun by clear and differentiated vertical movements which determine the specificity of recent tectonic de-elopment of the local structures. The latter are

differentiated to a high degree due to tectonic neterogeneity of the investigated region. Their structure has originated as a result of a long dif-erentiation, and this process is still not com-leted. That fact could be well-illustrated by

recent and contemporary geodynamic process­es. Their sediment correlates are: Todoranka Clayey Formation (swamp sediments) which has

thickness from 4 up to 20 m and Tarlica Peb­le-Sand-Clayey Formation (alluvial sediments) 'th a thickness from 1 up to 30m (Angelova,

1995) (Fig. 2). The swamp sediments fill up old karst forms in some localities (Fig.l ). That karst forms are developed in the limestones of the Russe Formation (Nikolov, 1969).

The average sedimentation velocity in there­gion could be seen on the fig. 2. The sedimenta­tion changes are controlled by a transition from peristrative to constrative lithodynamic phase. The total value of the negative Holocene move­ments is from -20 m to -40 m (Fig.l ), and those of the positive ones, from 4 up to 5 m.

The problem of the Srebama lake origin has not been seriously discussed up to now. The

model proposed in this paper is a result of the evidence found about a paleoseismodislocation. It is named after the name of the Srebama vil­lage where a residual relief deformation has been caused by one-act event at the Holocene-Pleis­tocene boundary. It has caused a bifurcation of Srebarna and Karlezhka rivers mouths and for­mation of the swamp (Fig.3). An arch-bent struc­ture (river terrace) has been uplifted 10m over the contemporary swamp level. Its Pebble-sand alluvial deposits are deformed in such a man­ner that they form a pocket with a depth of 10-12 m near the normal fault. That fact as well as the presence of a gravitational deformation in front of the pocket have to be considered as an evidence about a sudden displacement on the fault plane with a short-term fault opening ac­companied simultaneously by a subsidence or abatement of the superficial alluvium deposits, i. e. all these are evidences about seismogenic character of the considered rupture. The known maximum paleoseismodislocation dimensions are: length- 2 750 m, width- from 750 up to 1000 m and vertical displacement - 20 m. The paleoseismodislocation age is determined on the basis of analogies with rock units (Angelova, 1995) - I 0 500 ± 250 years (Figs. 2 and 3).

The "Srebarna" seismodislocation is localized within the confines of a big longitudinal first­rank tectonic zone which has an ESE strike, that includes also the Danube River delta {HHKoHOB, HHKOHOBa, 1990). It reflects the complex con-

55

N s ~swamp Slllstro -1

Fig. 3. Geological-geomorphological profile of the "Srebarna" paleoseismodislocation: I- Tarlica Pebble-sand-clayey Formation (Upper Holocene); 2- Todoranka Clayey Formation (Lower-Upper Holocene); 3 -undivided Lower Holocene alluvial deposits; 4- Russe Formation (Baremian-Aptian); 5- accumulative pockets; 6- relief deforma­tion; 7 - paleoseismodislocation area; 8 - boreholes locations; 9 - block displacement orientation; 10 - event localisation; II - earthquake influence area

figuration of longitudinal ( regional) and me­ridional (local) structures. The formed tectonic junction marks the epicentral area of the earth­quake.

The geological structure of the shifted block, its geomorphological features, the one-act phe­nomenon as well as the gravitational deforma­tion are controlled by the local tectonic activity with a possible intensity of 8-9 degree accord­ing to Solonenko classification. The problem about the focus depth remains open. This depth can be estimated at 30 - 60 km on the basis of the rupture length, vertical block displacement and the presumable intensity.

According to instrumental data, the region has been reactivated in 1864, 1892 and 1893 (rpuropoaa, rpuropoB, 1962; HHKOHOB, HHKO­HOBa, 1990). Mter data published by HHKOHOB, HuKoHoBa (1990), an earthquake on 14 October 1892 which occurred in the Danube River delta had an intensity of VII - VIII degree, energy class of 9 degree and foci depth 60 ± 10 km.

According to geodetic data on the recent ver­tical displacements surveyed on a regional scale, the region belongs to a stable area having a dis­placement velocity of 0 mmfyr. (ToToMaHOB et al., 1978). The recent vertical local displacements of the smaller blocks show a differentiated char­acter with different signs: Silistra + 0.10 mm/yr, Aydemir + 0.80 mmfyr, Popina + 0.40 mmfyr, etc. Recent swamping in the investigated region indicates in most cases a local tectonic subsid­ence.

The investigated region belongs to a low-seis­micity zone of NE Bulgaria after different au­thors who have carried out seismotectonic zon­ing in this area (Oenos, 1962 - 4-5 degree; Bonchev et al., 1982 - 4- 5 degree; liYH3 et al.,

56

1982 - 5-6 degree; KocTa,nnHOB et al., 1992 -4-5 degree). The mentioned prognostic estima­tions are a result of mathematic modelling, and they do not reflect the actual Neogene-Quater­nary geological and geomorphological situation. An attention has to be paid in this case to the geodynamic processes and phenomena zoning made by Manadrescu (1990). According to this author, the Aydemir lowland belongs to a re­gion of high geodynamic activity potential.

According to the characteristics of Neogene­Quaternary and recent activity obtained it can be concluded that:

-the "Srebarna" "Lake" has to be regarded as a typical swamp;

- its origin is defined as a result of an one­act event that has occurred at the Pleistocene­Holocene boundary;

- as a result of this event, the Srebarna and Kalnezhka rivers mouths have been naturally embanked by a gravitationally subsided block. It has been a natural barrage for rivers waters. The block has caused waters baffiing to its base and thus their loss in the karstic underseams.

- "Srebarna" swamp marks a tectonic junc­tion which reflects a complex configuration be­tween a longitudinal ( regional) first-rank tec­tonic zone and a meridional (local) tectonic zone. That junction marks the earthquake epi­central area as well;

- a paleoseismodislocation has been found in Bulgaria and described in this paper for the first time as an event which has occurred at the Pleistocene-Holocene boundary on the basis of dated sediments and significant relief deforma­tion;

- the region could be used as a reference region for the geodynamic Holocene history of

Europe because of its strategic situation and dated sediments;

- the swamp should be considered not only as a biosphere phenomenon but also as an geo­logical and geomorphological phenomenon;

- an additional study of the Neogene-Qua­ternary and recent structures as well as their movements lead to a new geodynamic concept, more realistic seismic risk estimations, a new seismotectonic zoning in the investigated region, and preservation of the natural phenomenon "Srebarna".

References Angelova, D. 1995. Stratigraphy of Holocene sediments

in the western part of the Ajdemir valley - Geologica Bale .. 25, I; 21-26

Balla, Z. 1984. The Carpathian loop and the Panonian basin- a kinematic analysis- Geophys. trans., 30, 4; 313-353.

Balla, z. 1987. Neogene kinematics of the Carpatho­Panonian region - Ann. Inst. Geo/. Pub/. Hung., 10; 193-199.

Boncev, E., Bune, I., Christoskov, L., Karagjuleva, J., Kostadinov, V., Reisner, 1., Rizhikova, S., Sebalin, N., Sholpo, N., Sokerova, D. 1982. A method for compilation of seismic zoning prognostic maps for the territory of Bulgaria - Geologica Bale., 12, 2; 3-48.

Kojumdgieva, E., Popov, N. 1989. Paleogeographie et evolution geodynamique de Ia Bulgarie Septentrionale au Neogene- Geologica Bale., 19, l; 73-92.

Mandrescu, N . 1990. Data concerning seismic risk evolution in Romania. - GAPG Int. Symp. for Natural Disasters Reduction, Sofia, 2-3 June.

EiOJI<HJlOBa, E .• JlaJapooa, M ., CTpaweocKa, K. 1985. re­OMOp$onorH'feCKHe OCOfieHHOCTH H pa3BHTHe paCTH· TeJlbHOCTH B paMOHe OJepo Cpe6hlpHa- roo. Co¢. YHU6., btA0/1. if>aK., 19; 99- l 09.

EiyH3, B., fHTHC, B., MHpouoo, M . 1982. llpHMeueuHe MeTO.ll8 anpOKCHMBQHif HHTepBaJibHLlX 3KCnepTHbiX Ol.leHOK K DOCTpOeHHlO JCapTbl JeMJlJITpJICeHHH Bonra­pHH- Geologica Bale., 12, 2; 49-70.

Banuapoo, H ., MHwe8, K. 1977. OcuosHH JaKOHOMep­HOCTH 8 p83BHTHCTO Ha MOp$OCTJ>YIC1)'PHTe 8 fi"Lnra­pHJI- B: Ilpo611. Ha 2eo2p., 1; 12-25.

Banuapo8, H. 1990. K8aTepuepua TeKTOHHKa s ,llonuo­.nyHaBcKaTa enHnnaT$opMeua paBHHHa - B: AEL( .. EieJieHe" , HJCJie06aHuJI u cmaH06UU1e Ha EiAH. C., lh.n. BAH; 283-288.

8

BanQapos, 11., KoCTeHKO, H., KpbiCTeB, T., ,lzyHaeo, H . 1990. FeOJ102U'leCKaJI 360/IIOI,#UJI 3ana0HOU llacmu l{epHOMopcKoii KOmii06UHbl 6 He02eH-'lem6epmu~oe 6peMJJ. C. 6AH; 34-40;

fpHroposa, E., fpHropos, 6 . 1964. Enu14eHmpume u ce­U3MU'lHUme JIUHUU 6 HP EiM2apUJJ. lh.n. BAH, C.; 81 c.

,llOH'IeB, n ., E8JlOrHe8, H., MHHICOB, M. 1985 fpaHHQ8Ta ueoreu-K8aTepuep H crpaTHrpa$HJI ua J:BaTepuepa 8 PyceHcKo_. - Cn. liM2. 2e0J1. 0-60, 46, 3; 325-334.

E8norHeB, li. 1988. EonneiicToueH"bT 8 llpH.nyua8cKa Ce8epHa B1>nrapHJ1 H rpaHHI..IaTa My c HeoreHa - Cn. b"b/12. 2€0/1. 0-60, 49, 2; 37-44.

Kaues, ,n., Mna.neuoBCKH, M. 1969. C"bspeMeHHH sepTH­KaJIHH .ll8HJKeHHJI ua JeMHaTa Kopa B B"b.JlrapHJI- H36. EiM2. 2eo2p. 0-60, 9; 17-25.

KocTa.llHHOB, R., Ulauoo, CT., Kapanoneoa, 10., 1992. CeAcMoTeKTOHH'feCKoe npOilfOJHpOBaHHe H paAouu­pooaHHe Ceoepo-BoCTO<~Hoii lionrapHH - Geologica Bale., 22, l; 83-104.

MHHKOB, M . 1968.JlbOCt>m e CeeepHa EiM2apUJ1. C., liAH; 202 c.

MH'IeB, T ., H.nHeB, P. 1982.IleJIUKaHu, mp-z,cmu~eu, xopa. C ., 3eMHJ.llaT.

HHKonoo, T. 1969. CTpaTHrpB$HJI na .nonnan JCpe.na o CeoepOHJTO'IHa li"b.JlrapHJI - H36. reoJI. UHcm .• cep. cmpamu2p. u JtumoJt., 18; 31 -71.

HuKOHOB, A., HHKOHOBa, K. 1990. 0 ceACMH'feCKoA onac­nocTH .nen&Tbl p . )lynu no .llBHHYM o6 HCTOPH'ICCKHX JeMJlJITpJICeHIUIX - Bonp. UHX. ceiicMOA02UU, Bbln. 31, M ., HaYJCa; 126-134.

nenos, .11. 1962. KopenaQHJI na reocjlHJH'fHHTe noneTa c oco6ennoCTHTe B ceHJMH'fHHJI pe)((HM B CesepoHnoq­na Ei"bJlrapH.R H qaCT OT ,llo6py.n)((a c orne.n aa ceHJ­M.H'IHOTO paHOHHpaHe- H36. reo¢u3. UHCm. EiAH, 3; 221 -229.

nooos, H . 1993. JluTocTpaTHrpa«tJcKH e.nHHHU.H na ue­orena B CHnHCTpeHCKO- Cn. li"ll/12. zeoJI. o-so, 51, l; 65-70.

ConoueHKO, B. n. 1962. Onpe.neneHHe 30Hl.leHTpaJIHhiX 30H 3CMneTp.RCeHHH DO reOJlOfH'ICCKHM npH3HaKBM -H 36. AH CCCP, cep. 2eo11., 11; 58-83.

ToToMaHoB, .11., Bp"L6n.RHCKH, 6., M.na.neHOBCKH, M . 1970. .11JCJle,llBaHe H KapTHpaHe Ha C1>BpeMCHHHTe 8CpTH­KaJIHH .llBHX<eHHJI aa JeMHaTa Kopa B li"Lnrapni - B: Ilpo6JI. Ha zeo2p., 3; 68-74.

ToToMaHoB, H ., Bp"b6JlJIHCKH, li. 1980. C"LopeMeHHHTe BepTHICaJIHH .llBH)((CHHJI H8 3CMHBTB KOpa B fi"bJlTapHll H npHJleJKaW.HTe JCMH- B: reoOUHOMUICa Ha EiaJIKa ­HUme. C.; 165 c.

Cl>HnHnos, Jl., MnKooa, Jl. 1986. KoaTepnepHHTe o6paJy-88HHll B Jly.noropneTo- Cn. Ei"bll2. zeoJI. 0 -6o, 47, 2; 140-149.

57