Seismic models of the lower lithosphere beneath the southern Baltic Sea between Sweden and Poland

Tectonophysics,

189 (1991) 219-221

219

Elsevier Science Publishers B.V.. Amsterdam

Seismic models of the lower lithosphere beneath the southern Baltic Sea between Sweden and Poland M. Grad a, A. Guterch

b and C.-E. Lund ’

u Institute of Geophysics, University of Warsaw, Pasteura 7, PL-02-093 Warsaw, Poland h Institute of Geophysics, Polish Academy of Sciences, Ksiqcia Janusza 64, PL-01-452 Warsaw, Poland ’ Department of Geophysics, University of Vppsala, Box 556, S 751 22 Uppsala, Sweden (Received April 7,1989;

revised version accepted December 29. 1989)

ABSTRACT Grad, M., Guterch. A. and Lund, C.-E., 1991. Seismic models of the lower lithosphere beneath the southern Baltic Sea between Sweden and Poland. In: S. Bjiimsson, S. Gregersen, E.S. Husebye, H. Korhonen and C.-E. Lund (Editors), Imaging and Understanding the Lithosphere of Scandinavia and Iceland. Tectonophysics, 189: 219-227.

Based on recordings from the northern part of the Baltic Sea-Black Sea profile and EUGENO-S profile 4, 2-D seismic models have been constructed for a profile across the southwestern part of the East European Platform from southern Sweden to northern Poland. The thickness of the crust along the profile varies from 33 to 47 km. The Moho P-wave velocity is 8.0-8.3 km/s. The uppermost mantle has a fine structure with alternating layers of higher and lower velocities. Down to a depth of about 120 km three alternating high- and low-velocity layers have been modelled. The velocities vary between 8.2 and 8.7 km/s in the high-velocity layers and 8.0 and 8.5 km/s in the low-velocity layers. A tendency of the depth of the Moho and the depth of the uppermost mantle seismic boundaries to increase towards the southeast is observed.

Introduction The first clear indication of an inhomogeneous subcrustal lithosphere in Western Europe was ob-

The lower lithosphere beneath the southern part of the Baltic Shield and the Baltic Sea between Sweden and the coastal area of northern Poland has been investigated using data from two earlier

tained from a profile across the Central Massif in France (Him et al., 1973, 1975; Kind, 1974;

seismic profiles. These two profiles are the Baltic Sea-Black Sea profile (Sollogub et al., l980; Grad

Steinmetz et al., 1974; Ansorge, 1975). These find-

et al., 1986) and the EUGENO-S profile 4 (EUGENO-S Working Group, 1988). In 1979, recordings were made in Poland and the USSR

ings were later confirmed by seismic investigations in Great Britain (Bamford et al., 1976,1978; Faber, 1978; Faber and Bamford, 1979), across the Scandinavian Peninsula (Lund, 1979) and in the Alps (Miller et al., 1978). Similar results have been

along the Baltic Sea-Black Sea profile of shots fired at four shotpoints (Pl to P4) equally spaced along the profile, and of shots fired at Fennolora

obtained in the USSR: at about the same time as in Western Europe, Ryaboy (1966) presented models for the subcrustal lithosphere showing both vertical and lateral inhomogeneities, and later work from the USSR has confirmed these results (Burmakov et al., 1975; Ryaboy, 1977; Yegorkin and Pavlenkova, 1981; Vinnik and Ryaboy, 1981; Pavlenkova and Yegorkin, 1983).

shotpoint B in Sweden. On the map (Fig. 1) only the northern part of the profile with the Polish shotpoints, PI and P2, is shown. During the 1984 EUGENO-S project, recordings were made along profile 4 in Sweden of shots fired at shotpoints 21, 22, 23 and 7 in Sweden, and also of shots fired at shotpoint 30 in Poland. Recordings were also made along the extension of profile 4 in Poland of shots

0040-1951/91/$03.50

0 1991 - Elsevier Science Publishers B.V.

fired at shotpoints 30 in Poland and 7 in Sweden. Profile 4, with its extension into Poland, is seen in

ready been published (Grad, 1987b; Working Group, 1988).

EUGENE-S

Fig. 1. In this study, recordings made along the Polish part of the Baltic Sea-Black fired at shotpoint

Geology

and crustal

stmmcture along the profile

Sea profile of shots

7 in Sweden, and recordings

The

entire

profile

made along the Swedish part of profile 4 of shots

European

fired at shotpoint

area on the western

30 in Poland have also been

Platform.

is situated

on

the

East

Starting in the Baltic Shield Swedish

formation about the lower lithosphere in the area.

southern part of Sweden, the Baltic Sea and the

cover a

total profile length of about 1000 km. The locations of the two profiles and the main geological units in the area are seen in Fig. 1. The two lower lithospheric profiles are situated on the East European Platform and run nearly parallel to the Teisseyre-Tomquist Zone in Poland and its northwestern continuation, the Tomquist Zone. Interpretations of the crustal structure yielded by the data recorded along these profiles have al-

BALTIC

Fig. 1. Location map of the EUGENE-S Baltic !%a, between European crystalline

northeastern

direction

the profile

extends

The recordings used in this investigation

in a southeasterly

coast

used. These recordings provide data yielding in-

across

the

part of Poland, ending at the Soviet

border. In Poland the profile is made up of two branches. The Baltic Shield forms the northwestern part of the East European Platform. The southeastern edge of the Baltic Shield is defined where the crystalline basement dips below the sedimentary cover of the East European Platform. In southeastern Sweden where the profile crosses the transition between the shield area and the sedimentary

SHIELD

profile 4 and the northern part of the Baltic Sea-Black

Sweden and Poland.

I = J%@eof the B&c

Shield;

2 = Tomquist

Sea p&k

in the mgiotxof the south

Line; 3 = so@hw&em

edge of the E?aat

in Poland determined from shallow seismic refraction; I- main faults; 5 = depth contours (km) of the and shotpoints. Compiled using data from Winterhalter et al. basemen t; 6 = deep seismic sounding (kmg+range) profii (1981) and Skompa (1974). Platform

SEISMIC

MODELS

OF THE

LOWER

LITHOSPHERE

area of the East European approximately In

coincides

Sweden

basement

the

mostly

profile

over

(granitoid

the southeastern

reworking

orogeny

(1200-900

Models along

and

the

of the sedimentary

the

profiles Syneclise

and

have

compiled

from

been

sections

the already

1974; Guterch

Sea,

the

Elevation,

published

re-

et al., 1975, 1986;

et al., 1981; Dadlez

1986; Grad,

showing

of the crust

Baltic

the Mazury

1976; Winterhalter

al., 1980; Grad,

Sveconorwegian

part

crossing

Peri-Baltic

Dadlez,

strong

from 0.5 to 6 km in thick-

1974).

sults (Skorupa,

and

The whole area, except for during

cover varying

ness (Skorupa,

part of

coastal part, has undergone

ensialic

mentary

Ga old

coastal

221

BALTIC

crystalline

crosses an area of granitic

composition.

SOUTHERN

coast.

gneisses

In the southeastern

the profile

gneissose

runs

THE

this border

up of 1.15-1.75

gneisses

orthogneisses). Sweden

Platform,

with the Swedish

made

polymetamorphic

BENEATH

1987a,b).

the structure

et

Generalized

of the sedimentary

crust along the profiles

are seen in Figs

The profile crosses the Baltic Sea between southeastern Sweden and northern Poland. The maximum water depth along the profile is about 100 m. The crystalline basement across the Baltic

The

layered

of the sedimentary

and

the velocities

Sea is covered

form. To the southeast, across the Baltic Sea, the thickness of the sediments increases to about 3 km

Ma).

by Cambro-Silurian

sediments

been

3 km

(Winterhalter

in the

coastal

area

in-

the two branches

of the profile

= u

Poland

Baltic

of various

from seismic

cover

ages have

measurements

and

data in the Polish part of the plat-

the thickness of the sediments decreases to about 0.5 km in the Mazury Elevation. Along the exten-

run over a sedi-

Baltic Shield SPB

of rocks

2a and b.

in thecoastal area of Poland. Along the northern part of the Baltic Sea-Black Sea profile in Poland

of Poland

et al., 1981). In northeastern

determined

from borehole

creasing in thickness from the outcropping basement in the coastal region of southeastern Sweden to about

structure

Sea

Pen-Baltic

Syneclise

Mazury Elevation

SP Pl

SP P?

[al

DiSTANCC Baltic Shield SP23 SP22

iN KM Pen-Baltic

Baltic Sea SP 21

Syneclise SP30

SP 7

lb1

I00

0

200

300

DISTANCE Fig. 2.Generalized

600

500

IN KM

sections showing the structure of the sedimentary layers along (a) the northern part of the Baltic Sea-Black

profile and (b) the EUGENO-S

profile 4 extension in Poland. I = Water (velocity of P-wave 1.5 km/s);

sediments (mean layer velocity 2.2-2.5 (mean layer

400

velocity 4.2-4.5 km/s);

km/s);

3 = Permian sediments (velocity 5.1-5.2

5 = crystalline basement (velocity 6.0-6.2

km/s).

km/s);

Sea

2 = Cainozoic and Mesozoic

4 = Lower Palaeozoic sediments

Compiled from Winterhalter et al. (1981).

Dadla (1976), Dadlez et al. (1980), Skorupa (1974), Grad 1987a), and EUGENO-S

Working Group (1988).

22’

sion of EUGENO-S ness

increases

Syneclise.

profile

to about

The velocity

varies from 1.8 km/s layer to 4.5 km/s the sequences. good marker The rocks Polish

part

4 in Poland

the thick-

6 km in the Peri-Baltic in the sedimentary

in the uppermost Permian

km/s.

sequence. basement

East

European

in the

Platform

he

beneath the sedimentary cover at depths varying from 200-500 m in the area of the Mazury Elevation to about

8-9 km in the marginal

down

of 7.1-7.4

from

part,

of 6.6-6.8

the crust

part of

of the crystalline

km. The middle

velocities

layer acts as a

in the sedimentary of the

cover

Cainozoic

in the lower Palaeozoic

A 5.2 km/s

18-25

has a velocity

to 42-47

the Moho)

km/s. velocity

The mean velocity

down

km/s.

to 30 -36 km,

The lower part of

km is characterized

by

The Pn-wave

(refracted

varies

8.1 to 8.3

from

of the crystalline

part of

the crust is about 6.6 km/s. The mean velocity for the whole crust varies with the thickness of the sediments.

For a 3-6 km thick sedimentary

the velocity

varies

km/s

1986).

(Grad,

respectively

from

cover

6.3 to 6.1

zone of the

platform (Teisseyre-Tomquist Zone). The crystalline basement has been formed under the in-

Interpretation

fluence

of several

Karelian

granitoid

Models of the crystalline part of the crust down to the Moho along the whole profile have been

tectonic massif

zones of pre-Karelian

cycles, separates

and Karelian

and

the pre-

a number

of

metamorphic

rocks (Ryka, 1984). In Sweden, along profile 4 the crustal thickness varies between 32 and 47 km; the crust is at its thickest beneath the central part of the profile. The upper crust varies in thickness from 11 km in the northwest to 20 km along the southeastern part of the profile. The velocity varies from about 6 km/s near the surface to, in the deepest part of the profile, about 7.2 above the Moho. The mean crustal velocity is about 6.6 km/s (EUGENO-S Working

Group,

1988).

In Poland the total crustal thickness varies from 42 to 47 km. The crystalline part of the crust comprises a three-layer structure. The upper part, with velocities of 6.1-6.4 km/s, reaches a depth of

. . Baltic

460

Sea - Black

Sea

480

Profile,

compiled based on the EUGENO-S model (EUGENO-S Working Group,

profile 4 1988) and

the Baltic Sea-Black Sea model (Grad, 198723). The modelling of the lower lithosphere has been carried the northern

out using recordings in Poland along part of the Baltic Sea-Black Sea

profile from SP B in Sweden and recordings along the EUGENO-S profile 4 in Sweden from SP 30 in Poland. The two record sections are seen in Figs. 3 and 4. A number of phases have been correlated in the record sections. phase denoted Pd and connected most part

of the upper

mantle

In addition to a with the upper(below

the Moho

boundary), three other phases denoted P’, P2 and P3 have also been correlated. These phases are interpreted as reflections or diving waves from

SP 6

500

520 DISTAKCE

540

560

KM

Fig. 3. Record section from SP B recorded along the northern part of the Baltic Sea-Bleck

Sea profile. Lines indicate th~retiutl

traveltime curves for lithospheric waves P’, Pz and P3 computed for a 2-D model. Reduction velocity 8 km/s.

SEISMIC

MODELS

OF THE

12

LOWER

EUGENO-S,

LITHOSPHERE

BENEATH

THE SOUTHERN

223

BALTIC

Profile 4. SP 30

(a)

10

Fig. 4. Record

sections

from SP 30 recorded traveltimes

within

layers

with

higher

FROM

along EUGENO-S

in the lower

lithosphere. For the record section of EUGENO-S profile 4 (Fig. 4) recorded in Sweden from SP 30 in Poland, the various correlated phases may be seen. The phases can only be correlated as first arrivals over distances of 50-300 km. The time delays between the different phases indicate the existence of zones of lower velocity. In addition to phases Pi-P3 one more phase has also been correlated

in the record

recorded about distance interval The

depth

section

(Fig. 4). This phase

is

2 s later than phase P3 in the 480-650 km from the shotpoint.

to the

SHOT

POINT.

reflecting

boundry

has

been

estimated at about 140-145 km. It is not possible to correlate the phase in the section in Fig. 3. In the record section from the northern part of the Baltic Sea-Black Sea profile recorded in Poland from SP B the three phases (P’, P2 and P3) have been correlated in the distance range 460-560 from the shotpoint. The various refracted

km and

reflected waves have been recorded with a relatively large amount of background noise. It would be very difficult or even impossible to separate these waves if only single-channel stations had been used: the use of multichannel stations, with a channel separation of 200 m, makes separation of

650

km

profile 4. (a) Without

interpretation.

of waves Pd, P’, P* and P3 for a 2-D model. Reduction

velocities

600

550

450 DISTANCE

velocity

With computed

ard interpreted

8 km/s.

the various arrivals possible, even when their amplitudes are small. Even though the recording layout for the section was not particularly dense, envelope lines can nevertheless be correlated for the refracted phase P’ and for the groups of reflected waves P2 and P3. In the two sections (Figs. 3 and 4) the phases P’, P2 and P3 are all connected with high-velocity layers in the lower lithosphere. In Fig. 3, phase P’ represents a diving wave from within the first high-velocity layer. The two following

phases,

P2 and

P3, represent

re-

flected waves from the top of the second and third high-velocity layers. In Fig. 4, phases P’ and P2 represent diving waves and P3 a reflected The crustal models briefly explained

wave. in the

previous section were used in the input model. The 2-D models of the lower lithosphere were developed using the ray tracing package RAY81 (cerveny and PSenEik, 1981). The depths of boundaries and the velocity distribution were chosen and corrected by comparing the experimental and calculated traveltimes of the waves P’, P* and P3. Theoretical traveltimes were recalculated for several succesive versions of the models until good agreement, of the order of 0.1-0.2 s, between the traveltimes was obtained. The depths to the top of

224

c 120

EUGENO-S, Fig. 5. Ekmple

of modetig

PROFILE 4, SP 30

of the lower lithosphere

Baltic Shield

on EUGENO-S profile 4. Ray diagrams for waves P’, P2 and P3 from SP 30. L VL = bw-W&xity layer.

Baftic Sea

0

30

s

DlSTANCE

(KM)

SEISMIC

MODELS

OF THE

the low-velocity points

LOWER

zones

BENEATH

were determined

of the deepest

diagrams.

LITHOSPHERE

northern

beneath

using

EUGENO-S

ray

profile

4 and the Sea profile

determined

in the lower lithosphere

from refracted

of

which are

or reflected

of the lithosphere

has been

carried

Both the velocities

and the depth given for the different boundaries are distorted and exceed the true values for the Earth

(Hill,

1972).

For

depths

sponding to the lower lithosphere these of the order of 1 km for any given 0.1-0.15 km/s for any given velocity. the velocities corrected for the spherical

corre-

errors are depth and In Fig. 6, Earth are

given in parentheses. In the two models shown in Figs. 6a and b, the two points marked SP B and SP 7 are the same point. From the Moho down to a depth of about 120 km, three layers with higher velocities separated

by zones

modelled.

of lower

The thickness

the profiles P-wave

ing, models

velocities

have

been

of the high-velocity

is about lo-20 km, and for the low-velocity about IO-30 km. The high-velocity layers

been

from the

Sea Profile

is greater

Sweden

of

from 33 to 47 than

From long-range

The data

of the

The thickness

varies

of the lower lithosphere

constructed.

plained mantle.

data

4, 2-D models

velocity

in the two profiles.

ern Baltic Sea between

out using the flat Earth model.

spherical

profile

have been presented. along

km. The Moho

waves are

with heavy lines.

Modelling

lithosphere the crust km/s

sounding

part of the Baltic Sea-Black

and the EUGENO-S

of the lower

are shown in Fig. 6. In both cases the segments

marked

Based on deep seismic northern

part of the Baltic Sea-Black

the boundaries

225

BALTIC

Conclusion

for waves P’, P2 and

P3 from SP 30 is shown in Fig. 5. The main elements of the models lithosphere

SOUTHERN

from the

ray penetration

The ray diagram

THE

8

record-

for the south-

and Poland

observed

have

can be ex-

by a nearly hor~ontally strati?ied upper From the Moho down to a depth of about

120 km, three alternating high- and lclw-velocity layers have been modelled. The thickness of the high-velocity layers is about lo-20 km, and for the low-velocity layers about lo-30 km. The velocities vary with depth between 8.2 and km/s in the high-velocity layers and between and 8.5 km/s in the low-velocity layers. The results

obtained

for northeastern

can be compared with the results ern part of the Baltic Sea-Black P4) (Grad et al., 1986; Grad, study too the lower lithosphere

layers

135 km consists

layers in the

low-velocity

of three wave

field

Poland

from the southSea profile (SP

198713): In Grad’s down to a depth of

alternating

layers with thicknesses

In the observed

8.7 8.0

high-

and

of lo-25

km.

from

shot-

recorded

lower lithosphere have been modelled in the depth intervals 33-50, 55-75 and SO-105 km. The Pwave velocities found and corrected to the spheri-

point P4 in the distance interval 600-900 km and 0.3-0.5 s after the first arrivals, an extended group of reflected waves lasting LO-l.2 s occurs. At-

cal Earth

tempts at explaining such a compleu reflected wave group suggest the possibility of the existence of an alternating series of high- and low-velocity

are 8.15, 8.37 and 8.69 km/s

and 8.04,

8.26 and 8.46 km/s for high- and low-velocity layers respectively. The two models indicate a southeasterly downdip for the lower lithosphere structures. In general, the lower lithospheric boundaries in northeastern Poland are about lo30 km deeper than in southern Sweden.

Fig. 6. Models

of the lithosphere

I = sediments;

2 = upper

km/s); boundary; reflected

along

the northern

4 = lower part of the crust (velocity 7 = low-velocity or refracted

part

part of the crust with P-wave 6.9-7.2

waves. Values in lower lithospheric

of the Baltic

velocities

km/s);

zones in the lower lithosphere;

layers of the order of a few kilometres in thickness at a depth of 110-135 km (Grad et al.. 1986). Regarding southern Sweden, in general our results agree with earlier findings from the Baltic

Sea-Black

of 6.0-6.4

5 = low-veIocity 8 = sections

km/s;

3 = middle

(a) and EUGENO-S part of the crust

zones in the upper crust (velocity

of the boundaries

layers are P-wave velocities

are for spherical

Sea profile

Earth models.

(km/s)

profile (velocity

6.1 km/s);

in the lower lithosphere for flat Earth models;

4 (b). 6.6-6.8

6 = Moho

determined

from

those parentheses

Shield (Lund, gisberg,

1979; Cassel and Fuchs,

1986; Luosto,

1986; Clowes

1979; Guget al.. 1987).

In particular,

our model can be compared

results

from

the

Fennolora

profile

in the

around

SP 7. The Fennolora

profile

and EUGE-

NO-S profile on

4 cross each other

Fennolora).

In

that

along the two profiles profiles

down to a depth

the

Moho

has been layered

of about

depth

33 km. Along

the lower lithosphere

as a high- and low-velocity

area

at SP 7 (= SP B

area,

is about

with the

both

modelled

upper

mantle

120 km.

Dadlez,

R.. Deczkowski,

of structural

versus its basement, EUGENO-S

Working

tectonic

evolution

and the North ject).

Faber,

work

German

S., 1978.

Lithosphke

was carried

out

within

the

framework

of

exchange between the two academies. The data were recorded during the international EGT EUGENO-S project and during various and international projects in Poland.

national

und dem mittleren

sis, Univ. Karlsruhe, Bamford,

D., Faber,

Prodehl, Geophys. Bamford,

S., Jacob,

B., Kaminski,

seismic profile in Britain, J.R. Astron. Crustal

J.R. Astron. Burmakov,

Prodebl,

structure

K.,

P., 1976. A

I. Preliminary

results.

Grad,

of Northern

Jacob, Britain.

European Grad,

Platform.

from

seismic

data.

Dokl.

Akad.

Grad,

M., Guterch,

Seismic

model

84-87.

subcrustal

lithosphere

beneath

Fennoscandia.

of the

J. Geophys.,

Cervenh

V. and PSentik,

S., 1987. Lithosphere from physics, South

The

In:

European

SEIS81. Prague.

E., Demartin,

structure

FENNOLORA.

(Editors), Dadlez,

I., 1981. Program in southern R. Freeman Geotraverse,

M. and Saxov, Sweden-results

Baltic

Platform.

Acta Geophys.

Pol.,

T. and

the

Baltic

Schield.

Erdmantels

Sea-Black

Sea

unter

mantle

NOLORA

data. In: D.A. Gabon

under

Workshop,

Strasbourg,

Struktur

Fennoscandischen

southern

Scandinavia

of

from FEN-

and St. Mueller (Editors),

the Northern

Segment.

R., Pajchel,

Eur.

J. and Perch&,

from deep seismic sounding VII on the territory

(Editor),

(Trieste

dem

Sci.

pp. 49-52.

A., Materzok,

Guterch,

Refractionsseis-

J. and Mueller, St., 1984. Structure

the upper

Found.,

profile.

ETH, Zurich.

B., Ansorge,

EGT

E., 1986. European

der Geschwindigkeits-Tiefen

Ph.D. Thesis,

Guggisberg,

First

Perch&,,

of the East

Gen.

Assem.

E., 1975.

along

of Poland.

Eur. Seismol.

interIn:

Comm.,

H. 15th

and Berlin). pp. 281-293. A., Grad,

M., Materzok,

Deep structure

of the Earth’s

and

Precambrian

quist-Teisseyre

zone).

(Editors),

European

The

In:

R. and Perch&, crust in contact Platforms

D.A.

E., 1986. zone of the

in Poland

Gabon

Geotraverse,

and Part

(Tom-

St. Mueller 2. Tectono-

128: 251-279.

Hill, D.P., 1972. An earth-flattening

transformation

for waves

from a point source. Bull. Seismol. Sot. Am., 62: 1195-1210. Him,

A., Steinmetz,

St. Mueller

range profiles

Part

3. Tectono-

lower

L., Kind,

in Western

lithosphere

R. and Fuchs, Europe.

in France

II-fine

(southern

K.. 1973. Long structure

Brittany).

of the J. Geo-

phys., 39: 363-384.

Outline

Basin.

(in Polish,

and Russian).

128: 281-288.

Oberen

and

142: 1-14.

R., 1976.

of the East

31: 97-114

B., 1986. Eine zweidimensionale

physics,

R.M., Gens-Lenartowicz,

Pol., 34: 21-29.

Gcolog.,

A., Janik,

beneath

Palaeozoic

B.R. and Fuchs, K., 1979. Seismic investigations

con-

Britain.

in sediments

of the lithosphere

profile

46: 369-384. Clowes,

Kwart.

of the East European

national

USSR.,

crustal

Northern

35: 121-155.

Geophys.

*‘auk.

der

M., 1987b. Seismic model of the Earth’s crust and upper

mantle

structure

V.Z.,

of

velocities

in English

Crustal

European

Untersuchungen

Inseln. Ph.D. Thesis, Univ.

Acta Geophys.

Seismic

with summary

Stiller in north-eastern

Part 4. Tectonophysics,

Caledonides

in Poland.

B., 1978.

A.V. Popov, E.A. and Ryaboy,

(Edi-

59: 17-30.

M.. 1987a.

Guterch,

C. and

Sot., 54: 43-60.

B.R., Ego&in,

224(l): Cassell,

W., Nunn,

Sot., 44: 145-160.

K.,

1975. The upper mantle structure platform

Ph.D. The-

K., King, R. and Willmore,

D., Nunn,

LISB-IV.

Erdmantels

111 pp.

C., Fuchs,

lithospheric

des obersten

Pro-

and St. Mueller

M., 1986. Seismic P-wave velocities of the East European

Platform

Nordametika,

(the EUGENO-S

D., 1979. Lithospheric

the

mische Interpretation

J., 1975. Die Feinstruktur

and

the Baltic Shield

Caledonides Geotraverse,

Bamford,

across

Guggisberg,

tuner Europa

structure

132 pp.

S. and

des Ansorge,

between

Refraktionsseismische

Tectonophysics,

References

Geol..

Crustal

A. Berthelsen

unter den britischen

Karlsruhe,

Platform

Academy of Sciences (contract CPBP 03.02) and by the Royal Swedish Academy of Sciences. The

Warsaw.

Wydawn.

1988.

of the transition

Tectonophysics,

by the Polish

1:1,000,000. Group,

150: 253-348.

Grad,

supported

map

complex

tors), The European

trasts

This work was partly

S., 1980. Sketch

of the Zechstein-Mezozoic

In: R. Freeman,

Faber,

Akxwledgements

Z. and Marek,

units

of sub-Cainozoic

Biul. Inst. Geol.

(in Polish, with summary

in English

geology

Warsaw,

in the

285: 21-50

and Russian).

Him, A., Prodehl,

C. and Steinmetz,

L., 1975. An experimental

test of models of the lower lithosphere (1) (2). Ann. G&ophys.,

31: 517-530.

in Brittany

(France)

SEISMIC

Kind,

MODELS

OF THE

LOWER

R., 1974. Long-range

the lower lithosphere. Lund, In:

K. Fuchs

and

Compositional

M.H.P.

Variation

NOLORA

profile.

H.. Ansorge,

liminary

results

structure

Hellenides. Pavlenkova.

K. Schmidt

Planet

33: 180-193.

deep waves associated Dagh-Arab Ryaboy,

593-610.

by explosion

Platform

seismic

J., 1974. Seismic

longitu-

1983.

part of Eurasia.

Steinmetz,

mantle

Phys. Earth

characteristics

in the profile

of

Kopet

2 (5): 3-13 L., Him,

seismiques

of the structure

of the lower litho-

in USSR. J. Geophys..

Yu. K., Guterch, O.M.,

R., Pajchel,

and the first results

geotraverse

of the deep

J. and

of intemastructure

in south-eastern

of

Europe.

J.

(in Russian).

A. and

Perrier,

G.,

a Ia base de I’asthenosphere.

L.P. and

East

European

Earth

Planet.

1974.

Reflextions

Ann. Geophys.,

43:

Yegorkin, structure

V.Z., 1981. Deep structure

Platfoorm according Inter..

30:

T.,

L., 1981. Geology

Ignatius,

files. Phys. Earth

Phys.

H., Ax>erg,

S. and

Oceanography

Ser., 30.)

pp. I- 121.

and Pavlenkova,

of U.S.S.R.

of the

data.

of the Baltic Sea. In: A. Voipio

The Baltic Sea. (Elsevier A.V.

to seismic

25: 27-37.

B., Floden,

Nietnisto, (Editor),

Ryaboy,

Elsevier, Amsterdam,

Phys., 3: 74-82.

seismology

Wydawn.

V.P., Khariionov,

M., Materrok.

investigation

along

Winterhalter, and dynamic

A.V., Shchukin,

E., 1980. Project

geophysical

Geophys.,

Vinnik,

Upper

of

173-180.

Apennines,

pp. 33-39.

A.V..

basement

Publ. Inst. Geophys.

map of Poland.

N.V., Sidorov.

V.I., Grad,

lithosphere

In: M. Gloss,

Afps,

Khomenko, PerchuC,

Pre-

velocity

V.B., Chekunov,

tional

refraction

Alpine

of the crystalline in Poland.

Geol., Warsaw. Sollogub,

FEN-

G., 1978.

to Hungary.

with boundaries

Sea. Izv. Earth

V.Z.. 1977. Study

sphere

Perrier,

Stuttgart,

V.Z., 1966. Kinematic

the northern

(Editors),

Yergorkin,

in the northern

Inter.,

and

Rep. S-13. 19 pp,

K. and

heterogeneity Ryaboy.

Structure

Res.. 35: 195-206.

of the iithospheric

and

W., 1984. Deep structure

Pal. Acad. Sci.. A-13 (160): 47-61.

and Asthenophere.

along

Univ. Helsinki,

Schweizerbart, N.I.

Ryka,

Skorupa.

Scandinavia.

of Sylen-Porvoo

J.. Aric,

and

221

BALTIC

A., Kondorskaya,

1975, from France

R. Roeoler

in

of the lower lithosphere

of Lithosphere

Precambrian

Inst. Seismol..

dinal profile,

energy

SOUTHERN

the Precambrian

in northern

Bott (Editors),

U., 1986. Reinte~retation

data.

of seismic

THE

56: 111-122.

C.-E., 1987. Crustal

Luosto,

BENFATH

4: 189-202.

the BIue Road profile

T~tonophysi~s~

Miller,

propagation J. Geophys.,

C.-E., 1979. The fine structure

underneath

Lund.

LITHOSPHERE

territory

Planet

N.I., 1981. Studies on long-range

Inter.. 25: 12-26.

of mantle

seismic

pro-