Multiple Miocene block rotation in the Bakony Mountains, Transdanubian Central Range, Hungary

93

Tecto?mphysics, 199 (1991) 93-108

Elsevier Science Publishers B.V., Amsterdam

Multiple Miocene block rotation in the Bakony Mountains, Transdanubian Central Range, Hungary

Department of Geology, E&I& University, Mtizeum krt. 4/A.

1083 Budapest, Hungary

(Received March 14,199l; revised version accepted March 28,1991)

ABSTRACT Tari, G., 1991 Multiple Miocene block rotation in the Bakony Mountains,

Transdanubian

Central Range, Hungary.

Tectonophysics, 199: 93-108.

The Bakony Mountains of the Transdanubian Central Range, Hungary, are located in the western part of the Pannonian basin. Their Neogene structure is dominated by right-lateral strike-slip faults, with offsets of up to 5 km. These faults are organized in two sets. The older one, trending WNW, is offset by the younger NW-lending set. Neither set of faults, i.e. the NE-trending left-lateral RBba and Balaton major strike-slip faults, extends across the boundary faults. It is proposed here that the late Miocene structural evolution of the Bakony Mountains can be best explained in terms of multiple block rotation. On the basis of this simple geometric model a 15’ counterclockwise rotation is suggested as a working hypothesis for the entire tectonic unit. Previous paleomagnetic measurements conform well to the block rotation predicted by the model. The proposed detachment for the rotated rigid upper-crustal blocks is a regional decoupling surface at an average depth of 10 km. This surface probably emanated from a nappe system of Cretaceous age.

Mmluction

The importance of strike-slip faulting during the Late Cenozoic evolution of the Pannonian basin system was recognized in the early 1980s (Horvath and Royden, 1981, Royden et al., 1982). The “back-arc” extension of the entire region occurred along a conjugate system of strike-slip faults (Royden et al., 1983) that connected areas of coeval extension and compression within the Carpathian thrust belt (Royden, 1988). Wrench faulting culminated during the middle to late Miocene and formed deep tr~stension~ sedimentary basins (Horvath et al., 1987b). The Neogene tectonic structure of the area (Fig. 1) is dominated by NE-ENE-trending leftlateral and NW-WNW-trending right-lateral

’ Present address: Department of Geology and Geophysics, Rice University, Houston, TX 77251-1892, U.S.A. DO-1951/91/$03.50

faults. This implies a strike-slip stress regime during the middle to late Miocene characterized by roughly N-S-directed maximum (a,) and E-Woriented minimum (0,) principal stresses. This stress orientation is also supported by microtectonic observations in the “island mountains” of the Pannonian basin (Bergerat, 1989; Csontos et al., this issue). The well-defined strike-slip zones can be traced for a considerable distance, in some cases for some hundreds of kilometers. In many strike-slip tectonic regions of the world, parallel and contemporaneous faults occur in domains that contain either only left-lateral or rightlateral faults (Ron et al., 1984). Detailed paleomagnetic and structural evidence shows that many of these structural domains rotated about vertical axes relative to boundaries of the fault domain (for a suck, see Nur et al., 1989). Simple geometric considerations (Freund, 1974, Garfunkel and Ron, 1985) shows that the amount of rotation can be quantitatively related to the

0 1991 - Elsevier Science Publishers B.V. AI1 rights reserved

::::: *..:. +:.. 0 :?j$ ..,*.p :: .:. 2. u)

in UI

MULTIPLE

MIOCENE

BLOCK

ROTATION

IN BAKONY

MOUNTAINS,

slip, spacing and orientation of faults. Strike-slip induced rotations of rigid blocks have been identified in Iran (Freund, 1970), in the western U.S. (Garfunkel, 1974; Luyendyk et al., 1980, 1985; Hornafius et al., 1986; Carter et al., 1987), in the Near East (Ron et al., 1984; Ron and Eyal, 1985; Ron, 1987) and elsewhere. A recent review of the block rotation and distributed deformation of the continental crust can be found in Kissel and Laj (1989). The purpose of this paper is to describe strikeslip deformational structures in the Bakony Mountains (Transdanubian Central Range, Hungary) which I believe can be best understood in terms of multiple Neogene block rotation, and to discuss the implications of block rotation on the structural development of the Pannonian basin. Geologic setting The Bakony Mountains are an elongated Mesozoic range located in the western part of the Pannonian basin (Fig. 1). A general review of the sedimentary and structural evolution of this area, which is the best known part of the Transdanubian Central Range (TCR), is given by Gal&z et al. (1985). According to their facies analyses and interpretations the Triassic through early Cretaceous of this area is interpreted as a passive continental margin. Paleogeographic reconstruction shows that the Bakony Mountains belonged to the Periadriatic region of the Tethys and developed in close association with the Southern Alpine paleotectonic realm. The almost complete Mesozoic sedimentary sequence which crops out in the Bakony Mountains constitutes the “basement ” of the surrounding Neogene basins. Neogene and Paleogene sediments are restricted only to certain areas in the Bakony Mountains as thin sedimentary cover.

HUNGARY

95

The tectonic unit of the Bakony Mountains is bound by the left-lateral Raba line to the northwest and the left-lateral Balaton line to the southeast (Fig. 1). Both lines are fund~ental strike-slip faults in the sense of Reading (1980), since crustal reflection seismic profiles suggest that they penetrate the entire crust (Posgay et al., 1981), and they have a long history of transcurrent movements. K&zmCr and Kovacs (1985) suggest a 450 km Oligocene right-slip along the Balaton line associated with the eastward-directed continental escape of the “Bakony” unit from the Alpine domain. The “exotic” origin of the Bakony is inferred from the Permian-Paleogene paleogeography and is also supported by crustal thickness data. Between the boundary faults the crust is remarkably thicker under the Bakony Mountains (35-40 km, Posgay et al., 1981) than in the basins both in the north and south (25 km on average). This anomalous crustal thickness may suggest that the Bakony Mountains including its Paleozoic basement, may be an Alpine nappe thrust onto Penmnic or lower Austroalpine units (Horvath and Rumpler, 1984). This interpretation is supported by recent reflection seismic data (Rumpler and Horvath, 1988) and by the presence of a magnetotellurically determined high-conductivity layer at mid-crustal (5-15 km) depths (Adam et al., 1981; Adam, 1985). This conductivity anomaly can be found only between the Balaton and Raba lines, and probably marks the decoupling surface of the Paleoalpine nappe system (Horvath et al., 1987a, their model I). This middle Cretaceous nappe formation did not lead to a strong deformation in higher crustal levels. The only Cretaceous-age structures observed are a large syncline of the pre-Senonian strata with a NE-directed long axis (e.g. Balla, 1988), a few reverse faults (e.g., the Liter fault; Kbkay, 1976) and strike-slip faults (Meszaros,

Fig. 1. Tectonic map of the Pannonian basin and surrounding regions, showing the main Neogene faults and folds (from Rumpler and Horvath, 1988). I = Molasse foredeep; 2 = Alpine-Carpathian flysch belt; 3n = Inner Alpine-Carpathian Mountain belt and the Dinarides; 3h = outcrops of Neogene calc-alkaline volcanic rocks; 4 = strike-slip faults-the sense (and usually the amount) of displacement is well constrained (thick arrows) or unconstrained (thin arrows); 5 = normal fault, thrust fault and fold; 6 = areas of major crustal extension and subsidence. The inset indicates the location of the Bakony Mountains (see Fig. 2).

G. TAR1

96

According to Meszaros (1983), two major phases of wrench faulting can be distinguished, a Cretaceous phase and a Neogene phase (Fig. 2). The second phase culminated during the late Miocene (in the Sarmatian, 11.5-13.6 Ma). For a correlation of the Central Paratethys local stages with the Mediterranean ones, the reader is referred to Steininger et al. (1988). The general characteristics of the Neogene strike-slip faults are as follows (Meszaros, 1983): (1) All of these strike-slip faults are rightlateral, and the amount of horizontal displacements on individual faults varies from a few meters to up to 5 km. (2) The fault traces are rather long, for example the Telegdi-Roth line (Fig. 2) is in excess of 40 km long. (3) The fault traces are slightly curved and are convex to the southwest (Fig. 2). (4) The individual strike-slip faults are organized in sets with different strikes, repre-

1982, 1983, 1986). The pervasive Neogene strikeslip tectonics associated with the formation of the Pannonian basin are supe~mpos~ on this preTertiary structural pattern. In this paper, attention will be focused on the strike-slip structures. Strike-slip structures in the Bakony Mountains

L&y (1917) was the first to emphasize the importance of strike-slip tectonics in the Bakony Mountains. Telegdi-Roth (1935) recognized one of the most spectacular faults of this type, which was recently called the Telegdi-Roth line. Systematic investigation of strike-slip features in the area was carried out by Meszaros (1980a,b, 1982, 1983, 1985, 1986), in the course of geological mapping on a 1 : 10,000 scale. He also considered the structural data obtained in the course of extensive exploration for economic deposits of Jurassic manganese, Cretaceous coal and bauxite, and Miocene coal.

_f:

Fig. 2. Sketch of the strike-slip

faults in the Bakony

indicated

on Fig. 1. I = Intra-Sarmatian

Miocene

normal

faults;

4 = the Liter

7 = intra-Cretaceous

strike-slip

Beds; IO = reflection

seismic profites.

Telegdi-Roth

(11.5-13.6

faults;

line after Telegdi-Roth

reverse

Mountains

(original

Ma) right-lateral

fault;

figure from MCszaros,

strike-slip

5 = the southern

faults;

boundary

B = T~assic-Jur~sic-Noons-Aptian The intra-Sarmatian

strike-slip

(1935), who first recognized

its strike-slip

of Eocene

Figs. 4 and 5 respectively.

between

character.

1983). The location

of this area is

2 = zones of local compression;

syncline; fault running

SB”“‘“‘“fl~

formations;

6 = I’-T,

9 = strike of the upper Papa and Varpalota Insets

3 = middle boundary;

Triassic

Kossen

has been named

A and B indicate

the locations

the of

MULTIPLE

MIOCENE

BLOCK

ROTATION

IN BAKONY

MOUNTAINS,

senting different tectonic phases during the Sarmatian. The first is a WNW-trending set characterized by the largest offsets. The Telegdi-Roth line has 4.7 km of displacement, the DevecserBalatonftired line has 2 km and the Stimeg-Zanka line has 4-5 km (Fig. 2). It should be noted that all of these faults produce pronounced lineaments in remote sensing data. Interpreting Landsat images, Marsi and Sikhegyi (1985) have found that these lines dominate the lineament map of the area (Fig. 3). Comparing Fig. 3 with Fig. 2 one can speculate that there may be more WNW-striking right-lateral faults than Meszaros (1983) observed. The next fault sets generated by younger tectonic activity are characterized by more northward-trending strike directions. The NW-striking set is represented, for example, by the Csehbanya-Herend line with 600 m, and the Ugod-Vilonya line with 500 m of right-lateral offset, respectively (Fig. 2). This set of faults systematically offset the WNW-trending set. The superposition is best documented in the Bakonyjak&BakonybCl area (Fig. 4). MCszaros (1986)

Fig. 3. Lineaments

interpreted

from remotely

sensed images

91

HUNGARY

contructed this map in order to delineate prospective areas for bauxite exploration. There is a third set of right-lateral faults with a strike of NNW and N, but they are too small to map. This set may represent the final stage in the strike-slip structural development of the Bakony Mountains. Post-strike-slip normal faulting dominated the area during Pliocene time. (5) The strike-slip fault traces of the same set are parallel, in some cases for more than 10 km (Fig. 2). (6) However, there is also evidence for the bifurcation of strike-slip faults. For instance, in the vicinity of Bakonybel the Telegdi-Roth line bifurcates. The right-lateral offset on the northern strand was found to be 2.8 km, while on the sourthem one it is 1.9 km. The sum equals the total offset (4.7 km) measured to the east, where the fault has a single trace. (7) Structural markers can be used to determine the amount of horizontal displacement on Neogene strike-slip faults: (a) Steeply dipping, pre-Senonian wrench zones (to be discussed later), associated with redeposited

in the Bakony

Mountains

shown in the same as in Fig. 2.

(after

Marsi

and Sikhegyi,

1985). The area

G. TAR1

Fig.

4. Tectonic

area (original

sketch-map

the area see Fig. 2, inset (1986) constructed areas

for

dolomite; Neogene

bauxite strike-slip

1986). For the location

A. It is to be noted

this map in order exploration.

2 = Jurassic

displacement,

of the Bakonyjitko-Bakonybel

figure from Mdszaros,

to middle faults

with

(a) identified

Cretaceous

4 = Cretaceous

(pre-Senonian)

section;

normal

IO = proposed

3=

and (b) supposed;

5 = Cretaceous

8 = early Miocene

and

formations;

of right-lateral

reverse fault, (a) identified Csehbanya

prospective

limestone

the amount

(pre-Senonian) (pre-Senonian)

that Mtszaros

to delineate

I = Triassic

of

strike-slip fault;

fault;

Herend area (Fig. 5) the lower Badenian (16.5-15.5 Ma) coal seam is displaced by the NW-striking Csehbarrya-Herend line. Taking into consideration the general SE-directed dip of the Miocene strata and the normal component of displacement along the fault (determined by drillhole data) the apparent 2.8 km offset represents only 600 m of actual right slip. (8) The fault traces are usually not associated with consistent topographic features. (9) The strike-slip faults die out in the southeastern part of the Bakony Mountains in local zones of compression (Fig. 2). A good example is the Devecser-Balatonfiired line, along which the 2 km right-lateral offset decreases to zero in a few kilometers, near Balatonfured. Shortening on the northeast side of the fault was accommodated by local thrusts and folds (Fig. 6). (10) The downthrown sides alternate along the faults. (11) Narrow and elongate, downdropped blocks can be found along the fault traces, due to local releasing bends. This phenomenon is well known in the Halimba bauxite mines, where strike-slip faults often juxtapose the barren Eocene strata with the Cretaceous bauxite.

and (b) supposed: fault;

7 = Pliocene

6 = Cretaceous normal

fault;

9 = trace of geological

cross-

drilling sites for bauxite

exploration.

manganese deposits (Meszbros, 1980a) are offset. The Cretaceous Liter reverse fault is also offset, and thus may be used to determine the right-lateral offset on several Neogene faults. (b) Some fold axes of Cretaceous age were displaced in a right-lateral sense. (c) The disrupted outline of any mappable pre-Neogene unit, which cannot be interpreted in terms of pure vertical movements, is inferred to be offset by strike-slip motion. For example, in the

3km

Fig. 5. The trace of the CsehbAnya-Herend of Herend

(original

right-lateral

strike-slip

of the normal sandstone;

figure from Mtszkos,

fault, with the direction

component

3 = trace

line in the vicinity 1983). I = Neogene

of faulting

of the lower

coal seam; 4 = upper Badenian

indicated; Badenian (15.5-13.6

and the amount 2 = Oligocene (16.5-15.5 Ma) marl.

Ma)

MULTIPLE

MIOCENE

BLOCK

ROTATION

IN BAKONY

MOUNTAINS,

99

HUNGARY

It is important offset

of 4.7 km

Mesozoic line

to note

(1935) though

its reactivation

age; Eocene

The Cretaceous important displacementsbn

Fig. 6. The right-lateral accommodated

by local folds and thrusts

side of the fault (after sistent local

Neogene

MtszAros,

traces

near

1985).

Note

with the block rotation compression

along

on the northeastern

to their termination that

to the SW

this phenomenon

is con-

model (Fig. 9) which predicts

the boundary

geometric

faults were

faults,

in the

same

position.

tion of manganese by

ples, the presence of wrenching is shown by subhorizontal slickenside striations. It is also supported by detailed microtectonic measurements (Bergerat, 1989; Csontos et al., this issue). There is another feature, which I believe

is

strike-slip

during

exploration

and bauxite shear

point deposits

Kijssen rocks

horizontal

of these

the upper

Tri-

by

km

8

Triassic-Jurassic-Neoco-

are strongly movements,

is strongly

One

right-laterally

The

of view.

the distribu-

zones.

near SzBc (Fig. 2) displaced 1982).

are also very

that

assic

Beds

to

movements

faults

concluded

these

into

the Miocene.

faults

(Meszlros,

mines and even on core sam-

an

taking

he supposed

times. According

strike-slip

(1980a,b)

controlled

mian (12) In outcrops,

from

MCszaros

fault was essen-

terranes,

all of the

along this fault occurred

Telegdi-Roth

however,

in post-Eocene

(1985),

by displaced

Originally,

that this strike-slip

displaced

Kokay

determined

1983).

of Cretaceous

account

the right-lateral

in the case of the Telegdi-Roth

(Meszaros,

tially

was

terranes

that

deformed while

due

to these

the Barremian-Ap-

tian strata are seemingly not influenced by this tectonic phase. On the basis of these observations, MCsziros (1982, 1983) concluded that the age of the Cretaceous wrench faulting was late Neocomian. The trends of these fault zones are at

characteristic for the evolution of Neogene strikeslip faults. At the eastern end of the Telegdi-Roth

present usually northwest or north-northwest and after the restoration of the Neogene horizontal

line,

movements

Meszaros

distribution

of the Cretaceous

fault,

in the well-studied trending

east,

Bantapuszta

is at present

basin,

this

a high-angle

reverse fault (Kokay, 1985). On the basis of numerous borehole data, the apparent “compres-

regular

sive”

early

lateral

that the coal seam

faults.

deformation

Sarmatian.

Taking

occurred into account

during

the

(1983) pointed

as the Neogene

additional

difference

strike-slip

is that both

faults can be found

out that the

fault

among

set is not as fault. set. An

left- and rightthe Cretaceous

of lowermost upper Badenian age shows a pronounced bending along the fault trace, significant

Paleomagnetic

right-slip can be assumed during the late Badenian. From the bending Kokay (1985) calculated l-2 km right-lateral offset for the master fault. The observed strikes of normal faults (trending north-

Paleomagnetic measurements on the Mesozoic of the Transdanubian Central Range (TCR) were carried out by Marton and Marton (1981, 1983,

west) and compressional features (trending northeast) are in good agreement with the inferred

1989). The obtained counterclockwise rotated clinations within this region are not uniform:

right-lateral

angle of the rotation

E-W-trending

simple shear along the

Telegdi-Roth line. In general, tion occurred not only during MCszaros (1983) pointed out, Badenian. At present there strike slip movements during (pre-Badenian) in the Bakony

strike-slip deformathe Sarmatian, as but also during the is no evidence for older Miocene time Mountains.

data

differs depending

dethe

on age and,

to a lesser extent, on the sample location (Fig. 7). Marton and Marton (1981) constructed an apparent polar wander curve for most of the Mesozoic. This curve and its refined version (Marton and Marton, 1983) clearly displays a characteristic clockwise loop, which resembles the inferred polar

100

wandering for Africa. The curves can be brought practically into correspondence by a 35 D clockwise rotation of the measured paleodeclinations of the TCR. This means that the block of the TCR (and thus the Bakony Mountains) was decoupled from the African plate in post-Cretaceous times and was rotated 35” counterclockwise during the Tertiary (M&ton and M&ton, 1981, 1983). Since paleodeclinations obtained from upper Eocene volcanic rocks in the Velence Mountains (Fig. 7) also show countercl~k~se rotation of about 30 ‘, the decoupling definitely postdates 30 Ma (K/Ar age) in the TCR (M&ton, 1986). On the other hand, this counterclockwise rotation predates the Pliocene basalt volcanism (K/Ar age 5-2 Ma, Balogh et al., 1982) in the Bakony Mountains, since their declinations do not show si~fi~nt co~terclock~se rotation (M~ton, 1985).

G. TARI

~n~~~~tion of the Neogene strike-dip faults in terms of multiple block rotation The geometric model of strike-slip induced block rotation is shown in Fig, 8a and b (Ron et al., 1984). In this model, which was originally proposed by Freund (1970, 1974) and Garfunkel (1974), the external simple shear on boundary faults is accommodated by rotation of the internal rigid blocks. The sense of rotation must be opposite to the sense of the fault slip, within the deforming zone with left-lateral slip associated with clockwise rotation, and right-lateral slip with counterclockwise rotation. Similarly, the sense of strike-slip movements on the boundary faults is opposite to those within the fault domain (Fig. 9). The geometric relationship (inset in Fig, 8) between the displacement along a fault d (positive when right-lateral) the width of the fault block w,

Fig. 7. Some representative paIeomagne& data for the Bakony Mountains. Shaded regions indicate outcropping Mesozoic-Paleozoic formations. Neogen right-lateral strike-slip faults from Fig. 2 are also shown. Arrows indicate paleodeclinations, with a 95% confidence interval. I = Velence Mountains, upper Eocene andesite; 2 = Bakonyjti6, Senonian grey marl; 3 = MagyarpolBny, Senonian grey marl; 4 = Halimba, Senonian red marl and bauxite; 5 = Jasd, Albian grey limestone; 6 = Olaszfalu, Albian grey limestone; 7 = Grktit, Albian grey limestone; 8 = Borzav&r I, Aptian grey limestone; 9 = Borzav&r II, Aptian grey limestone; IO = Siimeg, Tithonian grey limestone; I I = L6kU, Tithonian grey limestone; 22 = H&k&, Tithonian grey limestone. All paleomagnetic data from M&on and M&on (1983, 1989).

MULTIPLE

MIOCENE

BLOCK

ROTATION

IN BAKONY

MOUNTAINS,

101

HUNGARY

A Inltlal

conflguratlon

c Lockad

fikt

Ht

Active

Amnd

sat

Fig. 8. Geometric model of multiple block rotation (after Nur et al., 1986). (A) The initial configuration, where the fault set is optimally oriented (4) relative to the stress field. (B) Due to tectonic shearing of ihe fault domain, distributed fault slip and block rotation occur. The rotation can be described by geometric parameters (see inset, after Ron et al., 1984). (C) Mechanical considerations of stress, strenght and friction reveal that after a certain amount of rotation the first set of faults lock, and a new, mechanically more favourable second set forms to accommodate the rotational deformation. Qc is the critical angle between the two sets of faults.

the initial angle ru between the faults and the boundary of the domain, and the angle of rotation S (positive when counterclockwise) is given by (Ron et al., 1984): K=d/w=

sin6 sin (y sin(cr-6)

=

cot(ff-q-cot

ar

(1) The rotation of the fault blocks and of the faults themselves can be measured relative to a boundary fault across which the faults do not extend (that is, not parallel to the faults) which is called a “reference boundary” (Garfunkel and Ron, 1985). In the idealized case of rigid blocks and straight parallel faults with a variable spacing

Fig. 9. The geometry of rotating blocks requires a specific pattern of deformation around their edges (from Biddle and Christie-Blick, 1985; after Nicholson, 1986a,b). I = Areas in extension; 2 = areas in compression.

that terminate on a straight reference boundary, fault displacements are proportional to the width of the blocks, i.e. to fault spacing. Therefore the ratio K = d/w is constant throughout the domain. On the basis of the geometric model of rigidbody rotation, a specific pattern of deformation can be predicted around the fault block edges (Fig. 9). Evidence for alternating transtensional and transpressional features along the strike of the boundary faults was found by Nicholson et al. (1986a,b) within the San Andreas fault system. The kinematic model of Nur et al. (1986) takes into consideration the mechanical condition of faulting. If one considers a fault set originally formed at the optimal direction of failure 0, relative to the maximum stress shown in Fig. 8a as the deformation and rotation proceed, the shear stress acting on the fault plane decreases and the normal stress increases. Beyond a critical angle of rotation the fault becomes locked and a new mechanically more favourable fault forms in the intact rock mass, optimally oriented relative to the stationary direction of the maximum principal stress (q) (Figs. 8b and c). The critical angle QC is given by (Nur et al., 1986):

(2)

102

where s,, and S, are the cohesive strengths of the virgin rock mass and the pre-existing fracture respectively, p is the coefficient of friction, and u. is the effective overburden pressure. Using reasonable values of these parameters, Nur et al. (1986) concluded that the angle to which a fault set can rotate before a new set must appear to accommodate further block rotation is in the range of 20-45 O. Recently, Scotti et al. (in press) generalized the block rotation model in three dimensions. This 3-D model quantitatively explains why reactivated faults inherited from previous structural phases can rotate even if they are not optimally oriented relative to the stress field. 1 consider the block rotation model to be a plausible explanation of the observed Neogene deformations in the Bakony Mountains (Tari, 1989) because: (I) All strike-slip faults are organized in subparallel sets that moved simultaneously. (2) Only right-lateral, map scale-faults can be found in the whole area, so the whole of the Bakony Mountains is a single fault domain. (3) These strike-slip faults do not extend across the boundary faults (Balaton and Raba lines, Fig. 1). (4) The counterclockwise-rotated paleomagnetic declinations are in accordance with the right-lateral slip on the faults. (5) The observed local compressiop on the northeaster sides of the fault traces near to their terminations in the southeast (Figs. 2 and 6) is in good agreement with the expected pattern of deformation at the block edges (Fig. 9) (6) The second fault set is superimposed on the first set, and the characteristic angle between them is that expected in the case of multiple block rotation. The fault traces (Fig. 2) are slightly curved and the fault blocks must have been deformed internally to have remained in mutual contact. This internal deformation, however, was not large, so the Neogene structural pattern of the Bakony Mountains can be approximated by the idealized geometric model. The tectonic map of the Bakonyjako-Bakonybe1 area (Fig. 4) is sufficiently detailed to enable

G TARI

estimation of the geometric parameters of block rotation. The presence of two fault sets indicates multiple rotation; therefore of the younger, NWtrending set should be determined first. At present, this set has a strike of about 131”. The southeastern boundary fault, the Balaton line (Fig. l), strikes approximately 57 o and can be used as a reference boundary for the analysis. The displacement-to-width ratio (K) for the fault set is about K = 0.2. Since (Y,- 6, = 74”, then eqn. (1) gives at = 85=‘, indicating that the faults rotated counterclockwise by 8, = 85” - 74” = 11”. Hence their original strike was about 142’. This original 142O strike implies 38” initial angle relative to the N-S-oriented (J,. It is to be noted, that this value is very close to the expected angle of about 35”. as suggested by brittle-failure theory and laboratory experiments (e.g. Paterson, 1978). The older, right-lateral fault set presently has a strike of about 105 ‘. Adding the rotation found on the younger set (St = ll” ) its trend was originally 116O. K is estimated at 0.1, and since (Y*S, = 59” using eqn. (1) cy2= 63’ and then a2 = 4”. This is a quite small rotation; however, the total amount of counterclockwise rotation on the two set of faults is 6, i- 6, = 15O. Ignoring the proposed multiple rotation, the general structural map of the Bakony Mountains (Fig. 2) can be used to estimate the amount of counterclockwise rotation of the entire area. For example, the trace of the Cretaceous Liter reverse fault is displaced about 12 km in a 40-km wide belt between the Telegdi-Roth and the DevecserBalatonftired lines, so by simple division K = 0.3. The present strike of the Liter fault is 50”, hence eqn. (1) gives 6 = 12’ counterclockwise rotation. Similarly, displaced structural markers between the Telegdi-Roth and the Stimeg-Zanka lines give an estimation for the displacement-to-width ratio as K = 0.5, and then S = 20”. However, this approach is not correct, since the trace of the Liter reverse fault and, for example, the Y&-T, boundary indicated in Fig. 2, might also have been displaced by the Cretaceous wrench faults, not just by the Miocene ones. The supe~osition of the two structural phases is poorly known. Since the details are not so well documented as in the

MULTIPLE

MIOCENE

BLOCK

ROTATION

IN BAKONY

MOUNTAINS.

Bakon~~~-B~onyb~l area, it is not possible to obtain a correct estimate for Neogene block rotation in the southern part of the Bakony Mountains. Therefore, as a working hypothesis, I suggest that the 15” counterclockwise rotation obtained from inspection of Fig. 4 can be extrapolated for the whole Bakony Mountains as a reasonable estimate of multiple block rotation. At this point an apparent discrepancy arises. Nur et al. (1986) concluded, on the basis of mechanical consid~ations, that block rotations that are larger than 40’ or 45 O require multiple fault sets to accommodate the rotation. A compilation on examples of multiple sets (Nur et al., 1989) also support this statement. If the presence of a multiple set is indicative of a minimum of 40 ’ rotation, in the case of the Bakony Mountains the calculated X0 ~unterclockwise rotation seems to be too small. This dilemma may be solved by relaxing the assumption that the older set of faults formed not in a virgin rock mass but along pre-existing zones of weakness that were reactivated during the first phase of block rotation. Recently, Scotti et al. (in

103

HUNGARY

press) investigated the mechanics of the reactivated, not optimally oriented faults during rotation. Based mainly on their results, the development of the muhiple sets’ in the Bakony Mountains can be explained as follows. The rotation history is shown in Fig. 10, on the conventional 2 D Mohr circle. I assume that the axis of the maximum principal stress was oriented N-S during the rotation of both sets. The validity of this assumption is discussed by Csontos et al. (this issue). An additional assumption is that the magnitude of the mean stress (q,) remains constant in the consecutive rotational phases. In order to initiate slip along a pre-existing fault set, the stress magnitudes must change from point I to point 2. The Byerlee criterion for sliding along pre-existing faults states that at point 2 there must be sufficient shear stress to overcome friction and thus for fault slip to occur. In this case, faults and blocks rotate even if they were not optimally oriented with respect to the maximum stress (2a0 = 120 O, instead of the expected 70” ). The rotation path from point 2 to point 3 reflects the strain hardening of the fault domain in

I SHEARSTRESS

BAKONY MOUNTAINS

NORMAL

STRESS

Fig. 10. Mohr circle representation of the history of multiple block rotation in the Bakony Mountains, based mainly on the concepts of Nur et al. (1989) and Scotti et al. (in press}. A stationary N-S-oriented maximum principal stress is assumed throughout the whole process, and all changes of stress take place by keeping the mean stress q-, constant. During the late Miocene a Cretaceous fault set striking 120° was reactivated due to the increasing ol (from point I to point 2). Upon reaching point 2 right-slip initiated along these inherited fault planes, in accordance with the Byerlee criterion for sliding, although they were not optimally oriented relative to the stress field. After a rotation of 4O (8,) from point 2 to point 3, this fault set locked, since the state of stress had increased such that a new optimally oriented (@a= 36O) set of faults formed at point 4 in accordance with the Coulomb criterion for fracturing of intact rock mass. The critical angle between the two sets of faults is about 26 “.

G. TAR1

104

the sense of Nur et al. (1989), i.e. larger shear stress increments were required per increment of strain as the blocks rotated. It is important to note that the rotation of faults with respect to the boundary faults occurred in a “domino style” in the sense of Mandl(1987). Upon reaching point 3 the fault set became locked after only a small rotation (S = 4 o ), since the state of stress was such that a new fracture set formed at point 4, to accommodate further rotation. The new, nearly optimally oriented (ZQi, = 76“) fault set developed in accordance with the Coulomb criterion for fracturing of intact rock mass. The critical angle between the two sets of faults is about 26 *, well within the range of 2045” given by Nur et al. (1986) for multiple sets. The new fault set rotated 11’ counterclockwise before the rotation stopped, most probably in association with the major change of the stressfield in the Pannonian basin at the end of Sarmatian time (cf. Bergerat, 1989). Unfortunately, the paleomagnetic data cannot be used directly at present to support the model of multiple block rotation in the Bakony Mountains. The 35 o countercl~kwise rotation with respect to Africa obtained from the Mesozoic strata can hardly be related to the calculated 15’ of rotation of the same sense, since many other units in the Central Mediterranean show similar counterclockwise paleodeclinations (e.g., Umbria, Southern Alps and Istria). This may reflect a fundamental change in the Tertiary g~dyn~c evolution of the whole area (Marton, 1987). However, a small, but significant difference was found in the Cretaceous paleodeclinations between Umbria and the TCR (Mkton et al., 1987). These units moved in close coordination from the Jurassic onwards (Marton and Marton, 1983), as also supported by the coincident paleo~titudes of these units for the Mesozoic (M&on and M&on, 1985). The minor relative rotation between these units might have resulted from the Cenozoic collision process of Africa with stable Europe (M&on et al., 1987). This extra counterclockwise rotation of the TCR relative to Umbria is of the order what would be expected on the basis of the block rotation model (i.e. - 15 ” ). Therefore I suggest that from the observed 35’ counterclockwise rotation of paleo-

declinations in the Bakony Mountains only 20* can be attributed to the decoupling of this unit from stable Europe, and the remaining 15” reflects multiple block rotation. Discussion

The regional consistency of the paleomagnetic results from the Mesozoic of Bakony Mountains was demonstrated even for the entire TCR by the grouping of the sample locality mean directions of magnetization of the same age (Marton and Marton, 1985). As a consequence, the counterclockwise-rotated paleodeclinations may also reflect block rotation in the northeastern part of the TCR. However, very little is known at present about the strike-slip features in that area (e.g., Balla and Dudko, 1989), so the geometric parameters of the block rotation model cannot be calculated properly. I speculate that the Neogene domain of right-lateral faults does not extend beyond the Danube river in the northeast (Fig. I), since Miocene volcanic rocks in that area do not show any significant rotation (Marton, 1981). The extension of the fault domain to the southwest is not constrained by any paleomagnetic data. Another closely related problem is the depth of the lower boundary of the fault domain. This boundary might be expected to occur at the brittle-ductile transition, where shear deformation is essentially accommodated by creep. Here, rotating rigid blocks of the upper crust might have detached from the ductile lower crust. On the basis of seismicity patterns, Nicholson et al. (1986a,b) have found such a detachment level at a depth of 10 km within the San Andreas fault system. A recent review of deep-seismic reflection profiles in strike-slip zones (Lemiszki and Brown, 1988) supports the existence of a detac~ent of this type. In the case of the Bakony Mountains the base of the Cretaceous Paleo-Alpine nappe system (Horvath et al., 1987) might have provided the detachment surface during Neogene block rotation (Fig. 11). The average depth of this surface is about 10 km. However, magnetotelluric data (Adam, 1985) indicate that this detachment dips gently to the southeast about 8”. The right-lateral strike-slip faults sets probably penetrate the upper crust down to

MULTIPLE

MIOCENE

BLOCK

ROTATION

IN BAKONY

MOUNTAINS,

this boundary surface, which might have coincided with the brittle-ductile transition during the late Miocene. The mechanical behaviour of the rigid upper crust can be estimated using eqn. (2), since the critical angle between the sets is known. However, at present the other mechanical parameters are not sufficiently constrained to make any definitive statement. Similarly, the quantitative application of the 3-D block rotation model of Scotti et al. (in press) needs further systematic investigation in the case of the Bakony Mountains. In the model suggested by McKenzie and Jackson (1983, 1986) and Lamb (1987), the brittle crustal blocks rotate above a viscous material. Since the deforming continental zone in the case of the Bakony Mountains is about 100 km wide and the spacing between individual faults within the zone is of the order of a few kilometers, the “floating” model of McKenzie and Jackson (1983) seems to be appropriate to describe the distributed deformation in the area. On the other hand, some of the faults (e.g. the Telegdi-Roth line) seem to cross the entire deformed zone, lending support to the “pinned” model of McKenzie and Jackson

HUNGARY

105

(1983). Unfortunately, at present too little is known about the late Miocene velocity field of defo~ation to apply their “vorticity” model to the Bakony Mountains. An important consequence of the block rotation model is the elongation and narrowing of the deforming zone (Fig. 8). In the case of the Bakony Mountains this implies E-W elongation and N-S shortening. If this process is extrapolated for the conjugate set of Neogene strike-slip faults of the Carpatho-Pannonian region (Fig. l), a significant amount of E-W elongation can be expected across the entire area. In the Dead Sea area of the Near East, such an elongation was found to be much more effective during the phase of strike-slip faulting compared to that due to the subsequent phase of normal faulting (Ron and Eyal, 1985). Similarly, in the Basin and Range area of the western U.S. Ron et al. (1986) and Hudson and Geissman (1987) suggested that the extentional strain accommodated by strike-slip faulting and block rotation should be incorporated into the regional extension of the region. In the Neogene ~tra-ca~at~~ basins

Fig. 11. Block diagram illustrating the proposed allochtbonous structure of the B&cony Mountains (modified from Horvath et al., 1987a; crustal thickness data is from Posgay et al., 1981). It is suggested here that the base of the Cretaceous nappe system (heavy line) acted as the required basal detachement surface for the rotation of the upper-crustal rigid blocks. Since its depth (10 km on average) is close to the inferred brittle-ductile transition during the middle to late Miocene, the regional left-lateral shear might have been accommodated by creep below this surface (shaded) in the lower crust.

G. TAR1

106

the total extension was estimated at about 100 km in the E-W direction by Royden et al. (1982), while in the East Carpathian thrust and fold belt Burchfiel(l980) calculated a ~~rnurn of 116 km of shortening for the same time interval. Therefore it is suggested here that as the strike-slip faults of the Pannonian region rotated away from the NS-oriented principal axis of shortening this might have contributed significantly to the E-W elongation of the whole area, and this component is responsible for the missing part of the extension. Finally, I would like to emphasize the importance of distinguishing surficial, areally restricted tectonic processes, such as block rotation, from fundamental, regional geodynamic changes, both of which could cause anomalous paleomagnetic data in the Central Mediterranean (Marton, 1987). Anomalous paleodeclinations do not necessarily reflect the rotation of large tectonic units (cf. MacDonald, 1980), and the validity of a 100’ clockwise rotated microcontinent within the Carpathian loop (e.g., Balla, 1984, 1987) should be reviewed in the light of local block rotation. The case of the Bakony Mountains as the first example of block rotation in the whole ~a~atho-Pannonian region indicates that this tectonic process might also have significantly influenced the paleomagnetic declinations in other intra-Carpathian areas. Conclusions

Using the multiple block rotation model as a working hypothesis, the Neogene structural development of the Bakony Mountains of the Transdanubian Central Range can be summarized as follows. Due to the increasing N-S-oriented maximum principal stress in the Carpatho-Pannonian region during the upper Miocene (15.5-11.5 Ma), pre-existing zones of weakness were reactivated in the Bakony Mountains. Right-slip occurred along the reactivated Cretaceous fault planes, which rotated 4O counterclockwise. When the maximum principal stress reached the critical value of Coulomb fracturing for intact rock mass, a new set of right-lateral faults formed in an optimal direction relative to the regional strike-slip stress regime. This set of faults offset the older set, and the 26” angle between them conforms well to the

multiple block rotation model predictions. Since the younger set rotated 11” counterclockwise before the rotation stopped, the total amount of count~cl~k~se rotation due to block rotation is 15O. On the basis of previous paleomagnetic measurements, a similar amount of relative counterclockwise rotation was found between the Transdanubian Central Range (and thus the Bakony Mountains) and Umbria during the Tertiary. This finding indirectly supports the block rotation model. The rest of the approximately 20” counterclockwise Tertiary rotation determined by paleomagnetic data is due to regional geodynamic processes. Since the Mesozoic rocks of the Bakony Mountains and their Paleozoic basement are supposed to be a large Paleoalpine nappe, it is suggested here that this thrust belt and the rotated upper crustal blocks share a common detachment surface at a depth of about 10 km. Acknowledgments

I would like to thank Albert Bally, Frank Horvath and Emil Marton for suggesting improvements to the manuscript, I appreciate the reviews of Clark Burchfiel and Amos Nur. I also thank Cynthia Blankenship for correcting the English. Oona Scotti, Emil Marton and Zoltan Balla kindly provided their papers prior to publication. This work is dedicated to the memory of Jbzsef Mtszaros (1936-1985).

Adam, A., 1985. Electric conductivity increases in the Earth’s crust in Transdanubia (W-Hungary). Acta Geod. Geophys. Mont. Hung., 20: 173-182. Adam, A. and Wallner, A., 1981. Information from electromagnetic induction data on Carpatho-Pannonian geodynamics. Earth Evol. Sci., 1: 280-284. Balia, Z., 1984. The Carpahtian loop and the Pannonian basin: a kinematic analysis. Geophys. Trans., 30: 313-353. Balla, Z., 1987. Tertiary paleomagnetic data for the CarpathoPannonian region in the light of the Miocene rotation kinematics. In: D.V. Kent and M. Km (Editors), Laurasian Paleomagnetism and Tectonics. Tectonophysics, 139: 6798.

MULTIPLE

MIOCENE

BLOCK

ROTATION

Balla, Z., 1988. Clockwise

paleomagnetic

in the light of the structural Range (Hungary). displacements Balogh,

recorded

in

Geophys.

K., Jamhor,

danubia.

Hungary.

243-260 Bergerat,

Annu.

(in Hungarian

structure

the

Trans-

Rep.;

hung.

with English pull-apart

L. and

rocks

in Trans-

Geol.

Inst.

1980:

basin.

process:

the

Tectonophysics,

157:

Burchfiel,

B.C..

Carpathian

1980.

Eastern

orocline

Tectonophysics, clockwise

tectonic

California,

Alpine

as an example

system

and

of collision

the

tectonics.

B.P. and Terres, rotation

suggested

R.R., 1987. Neogene

of the eastern

Transverse

by paleomagnetic

vectors.

Range,

Geol. Sot.

N. and

basin formation

(Editors),

and

Mineral.,

and

faults. In: K.T. Biddle and

Strike-slip

Sedimentation.

Deformation,

Sot.

Econ.

Basin

Paleontol.

faults in Sistan, south-

Iran. J. Geol., 78: 188-200.

R., 1974. Kinematics A., Horvath.

structural

Central

cations. Garfunkel, history

and

transcurrent

of

the

Range,

Bakony

Hungary):

Mountains

28: 85-100.

Z., 1974.

for the late

of the Mojave

tion to adjacent

Desert,

regions.

impli-

Cenozoic

tectonic

macroscopic

faults

M.J., 1986. Timing in the western

Amsterdam, of the Bakony

Ranges,

F. and Royden,

line. Acta Geol. Hung.,

R.R. and Kamerling, tectonic

California.

rotation Geol

Sot.

basins:

a review.

Earth

Evol.

Sci., 1: 307-316. extension Hung., Horvath,

J., 1984. The Pannonian

and subsidence

of an Alpine orogene.

basement: Acta Geol.

27: 229-235. F., Adam,

physical

data:

danubian

A. and Stanley,

evidence

Central

Transtensional

W.D.,

1987a.

for the allochthony

New geo-

of the Trans-

Range. Rend. Sot. Geol. Ital., 9: 123-130.

F., Rumpler,

J., Pogacsh,

origin

dence and interpretation.

geomechanical

G. and Tari,

of the Pannonian

basin:

Terra Cognita,

7: 201.

G., 1987b. new evi-

studies

in the

(Varpalota,

Bakony

Mountains).

Rep.

Geol.

Inst.

43-50

(in Hungarian

English

S.H.,

Lemiszki,

1983:

Annu. with

summary).

vertical

1987.

A model

axis. Earth

for tectonic

Planet.

P.J. and Brown,

rotations

about

L.D.,

1988. Variable

crustal

struc-

fault zones as observed

reflection

Bull. Geol. See. Am., 100: 665-676.

profiles.

L. Jr., 1917. Structure

vicinity

Annu.

B.P., Kamerling,

Mandl,

Simple

crustal

Inst.

R.R., 1980. Geo-

rotations

M.J., Terres,

shear

times suggested

in southern

of

R.R. and Homafius,

southern

California

by paleomagnetic

during

declinations.

J.

Res., 90: 12,454-12,466.

studies.

J. Geophys.

G., 1987. Tectonic

faults:

in the

Geol.

Bull. Geol. Sot. Am., 91: 211-217.

1985.

Geophys.

Highland

Hung.

M.J. and Terres,

for Neogene

B.P., Kamerling,

J.S.,

Rep.

(in Hungarian).

model

Luyendyk,

on deep seismic

of the Balaton

of Balatonfured.

California.

a

Sci. Lett., 84: 75-86.

ture of strike-slip

the “bookshelf”

rotation, tilt

apparent

correction

in

Res., 85: 3659-3669.

deformation

by rotating

mechanism.

Tectonophysics,

parallel 141:

277-316. I. and Sikhegyi,

imagery Foldt.

and

F., 1985. Possibilities

areal

Kutatas,

photographs

28: 65-70.

for using

in bauxite

space

exploration.

(in Hungarian

with

English

summary). E., 1981. Tectonic

implication

for the Carpatho-Pannonian

of paleomagnetic

region.

Earth

Evol.

data Sci., 1:

257-264. Marton,

F. and Rumpler,

and

basin

Marton, for the forma-

of the southern

Bantapuszta Hung.

and

Studies,

20: 245-257.

J., 1985. Tectonic

tectonic

L., 1981. Mechanism

tion of the intra-Carpathian

investigation

structural

Res.,

Rotations

Mts. and the age of the Liter fault

Net

J. Geophys.

28:

516 pp.

the

of

the continental

Advanced

and

and extent of Neogene

Transverse

NATO

1980.

Am. Bull., 97: 1476-1487.

Horvath,

Deformation.

J., 1976. Geomechanical

margin

Marsi, B.P., Terres,

for

unit. Acta Geol. Hung.,

D.W.,

of a type

Permian-Paleogene

evidence

rotation,

deformation.

J.s., Luyendyk,

system:

tectonic

and deforma-

west-central

part of the Insubri-Peri-

MacDonald,

90: 8589-8602. Hornafius,

1985.

and for its rela-

2. The properties

discontinous

S.,

Sot. Am., 85: 1931-

Z. and Ron, H., 1985. Block rotation

tion by strike-slip

region,

Laj, C., 1989. Palaeomagnetic

paleomagnetic

Garfunkel.

Horvath,

Kluwer,

Neogene

California,

Bull. Geol.

and

1944.

Horvith,

C. and

Continental

Luyendyk,

(Trans-

paleogeographic

Acta Geol. Hung., Model

Kovacs,

along the eastern

lineament

metric

F. and V&i%, A., 1985. Sedimentary

evolution

danubian

of transform

Valley

15: 638-642.

and

1916: 353-388

21: 93-134.

Dixie

and

counterclockwise

71-84.

Lbczy,

of strike-slip

faults. Tectonophysics, Galacz,

1985. Deformation

Spec. Publ., 37: l-34.

R., 1970. Rotation

eastern

K.T.,

along strike-slip

N. Christie-Blick Formation,

Biddle,

in the

Tertiary

escape of the Bakony-Drauzug

Lamb,

Am. Bull., 98: 199-206. Christie-Blick,

Freund,

adriatic

J.W., 1987. Paleomagnetic

for middle

Geology, M.

Kokay,

63: 31-62.

J.N., Luyendyk,

Freund,

K&mu+,

Kokay,

271-280.

Carter,

rotation

Nevada.

Kissel,

summary).

to the rifting

of the Pannonian

evidence

paleogeography

35: 3-63.

of basaltic

M.R. and Geissman,

structural

strike-slip

of

Hudson, block

Tertiary

Z:, Ravasz-Baranyai,

dating

F., 1989. From

formation

the

A., Partenyi,

Solti, G., 1982. K/Ar

in the Alps

145: 277-292.

Trans.,

107

HUNGARY

of the Transdanubian

A., 1989. Large-scale

Range.

MOUNTAINS,

rotations

pattern

Tectonophysics,

Balla Z., and Dudko, danubian

IN BAKONY

E., 1985. Tying

Central

Mountains

scale. In: M. Kretzoi the Neogene pp. 99-108. Marton,

the basahs

(Hungary)

from the Transdanubian

to the standard

polarity

and M. Pecsi (Editors),

and Qutemary.

E.. 1986. Palaeomagnetism

Velence hills and Mecsek

Akadtmiai

Kiadb,

of igneous

Mountains.

Problems

time of

Budapest,

rocks from the

Geophys.

Trans.,

32:

83-145. Marton,

E., 1987. Palaeomagnetism

terranean

region.

J. Geodyn.,

and tectonics 7: 33-57.

in the Medi-

G. TAR1

108

Marton,

E., and Maton,

P., 1981. Mesozoic

of the Transdanubian

Central

nics of tectonic

palaeomagnetism

Mountains.

Vanicek

Tectonophysics,

E. and Marton,

P., 1983. A refined polar wander

for the Transdanubian

Central

on the Mediterranean Marton,

E. and M&on,

of palaeomagnetism

Central

Mountains. E.

and

studies

paleomagnetic

P.,

results from Hungary.

of

Trans.,

35:

117-133. M&on,

E., Marton,

of tectonic

P. and D’Andrea,

implications

M., 1987. Some aspects

of Mediterranean

palaeomagne-

D. and Jackson,

strain

rates,

crustal

J., 1983. The relationship

thickening.

strain, and fault movements Planet.

between

palaeomagnetism,

within a deforming

finite

zone. Earth

Sci. Lett., 65: 182-202.

McKenzie,

D. and Jackson,

uted deformation

J., 1986. A block model of distrib-

by faulting.

J. Geol.

Sot. London,

143:

J., 1980a. Structural

exploration Kutatas, Mtszaros,

(the Halimba-Herend-Csehb&nya 23: 9-12.

23: 13-16. M&&OS,

for manganese

and geophysical

methods.

Annu.

Hungarian

prospecting

Rep.

cance of strike-slip

tectonic

Kutatas,

dislocations

in the western

Hung.

with English

Rep. Hung.

Geol.

Inst.

Bakony

1980:

as a Moun-

517-526

(in

and economic-geological

faults in the Bakony

signifi-

Mountains.

displacements

Szerkezetfoldtani Budapest,

(in Hungarian)

Vizsgalatok.

pp. 59-88

AMU. Rep. Hung.

erations. Hungarian Nicholson,

with English C., Seeber,

1986a. Seismicity Transverse faulting

H., 1987.

straining

area: Geol.

Inst.

consid-

1984: 95-102

(in

summary).

L., Williams, California:

and low-angle

in the

tectonic

block

thrusts.

and

Earth

and recognition

Ballance

Evol.

northern

Israel. Tectonics,

netic evidence. Ron, H., Aydin,

Zones.

the Yammuneh,

the re-

paleomagnetic

Tectonics,

6: 653-666.

deformation

by block

along the Dead Sea transform, 4: 85-105.

R., Garftmkel,

by strike-slip

Reading

Mobile

Sea transform:

implications.

and mesostructures

of strike-

H.G.

4: 7-26.

along

rotation

Ron, H., Freund,

and

in Oblique-slip

of the Dead

data and kinematic

Z. and Nur, A., 1984. Block

faulting:

J. Geophys.

structural

and paleomag-

Res., 89: 6256-6270.

A. and Nur, A., 1986. Strike-slip

faulting

and

in the Lake Mead fault system. Geology,

14:

1020-1023. Royden,

L.H., 1988. Late Cenozoic system.

In: L.H.

the Pannonian

Basin-a

tectonics

Royden

of the Pannonian

and F. Horvath

Study

in Basin

(Editors),

Evolution.

Am.

Assoc. Pet. Geol., Mem., 45: 27-48. Royden,

L.H.,

Horvath,

faulting,

F. and Burchfiel,

extension

pathian-Pannonian

and

region.

L.H. Horvath,

Rumpler,

B.C., 1982. Trans-

subduction

in

the

Car-

Geol. Sot. Am. Bull., 93: 717-

F. and Rumpler,

basin

system,

J. and Horvath,

reflection

J., 1983. Evolution

1. Tectonics.

of

Tectonics,

2:

basin.

Scotti,

In: L.H. Royden

O., Nur,

through

the eastern

central

rotation,

strike-slip

5908.

interpretation

Basin-a

seismic

from the Pan-

and F. Horvath

Study

in Basin

(Editors),

evolution.

Am.

Assoc. Pet. Geol. Mem., 45: 153-169.

Steininger,

Res., 91: 4891-

F., 1988. Some representative

lines and structural

The Pannonian

L.R.,

J. Geophys.

Sykes,

P.f.

Deformation

bend

deformation P.L.

In:

Ron. H. and Eyal, Y., 1985. Intraplate

nonian

and fault kinematics

Ranges,

In: Gyakorlati

explorations

on the basis of

63-90.

Spec. Publ. Hung. Geol. Inst., of bauxite

mantle

Spec. Publ. Int. Assoc. Sedimentol.,

725.

(in Hungarian).

J., 1986. Prospects

Deformation-the

in Hungary.

1980. Characteristics Sedimentation

Royden,

guide to the determination

Csehbanya-Bakonyj&%BakonybU

A. and

Estevez,

R., in press.

and block rotation

Distributed

in 3D. J. Geophys.

Res.

F.F., Mtiller, C. and Rogl, F., 1988. Correlation Paratethys,

Neogene

eastern

Paratethys,

stages. In: L.H. Royden

The Pannonian

Basin-a

and F. Horvath

Study

of

and Mediterranean

in Basin

(Editors),

Evolution.

Am.

Assoc. Pet. Geol. Mem., 45: 79-87. C., Seeber, L., Williams,

Seismic within

H.G.,

the Pannonian

J., 1985. Methodological

Monogr.,

I. and R&ner, G., 1981. Char-

measurements

(Editors),

with

summary).

Rock

crust and upper

systems.

Annu.

(in Hungarian

P. of

New York, 254 pp.

slip fault

form

summary).

Geol. Inst. 1981: 485-502

of strike-slip

Nicholson,

Reading,

basin

M&~&OS, J., 1983. Structural

MCszaros,

FBldt.

(in Hungarian).

guide to mineral

Meszaros,

ore by struct-

and

Vol. 4. Geophys.

I., Petrovics,

block rotation

J., 1982. Major horizontal

English

area). Fiildt.

(in Hungarian).

J., 1980b. Exploration

ural geological

tains.

geology in the service of bauxite

S.C. Cohen

and Transmission

49: 31-46.

Experimental

reflection

rotation

349-353. Mtszaros,

1978.

K., Albu,

In:

Sci., 1: 272-279.

Ron,

tism. Rend. Sot. Geol. Ital., 9: 137-142. McKenzie,

M.S.,

seismic

compilation

Geophys.

I.U.G.G.

Union,

acter of the earth’s

28: 59-70. A

Paterson, Posgay,

and palaeochmatic

1989.

Am. Geophys.

Brittle Field. Springer,

98: 43-57.

in the Transdanubian

Acta Geol. Hung.,

Marton,

and its bearing

Tectonophysics,

P., 1985. Tectonic

aspects Marton,

Mountains

history.

curve

rotations.

Slow Deformation

Stress in the Earth.

72: 129-140. Marton,

block

(Editors),

evidence

for

the San Andreas

Tectonics,

conjugate

P. and Sykes, L.R., 1986b. slip

fault system,

and

block

southern

danubian

California.

Telegdi-Roth,

5: 629-648.

Gebirge

Nur, A., Ron, H. and Scotti, O., 1986. Fault mechanics kinematics

of block rotations.

Tari, G. 1989. Multiple

rotation

Geology,

and the

14: 746-749.

Nur, A., Ron, H. and Scotti, O., 1989. Kinematics

and mecha-

Central

block rotations

Hungary.

K., 1935. Daten Zwischenmasse”. Ertesitb,

man summary).

in the Trans-

Terra Abstr.,

1: 52.

aus dem Nordlichen

zur Jungmesozoischen

“Ungarischen tudomanyi

Neogene

Range,

52: 205-252

Bakony

Entwicklungsgeschichte Matematikai

der

es Termeszet-

(in Hungarian

with Ger-