Journal of African Earth Sciences 38 (2004) 449–460
www.elsevier.com/locate/jafrearsci
Paleostress analysis of the Cretaceous rocks in the easternmargin of the Dead Sea transform, Jordan
Abdullah A. Diabat a, Mohammad Atallah b,*, Mustafa R. Salih c
a Institute of Earth and Environmental Sciences, Al al-Bayt University, Al Mafraq, Jordanb Department of Earth and Environmental Sciences, Yarmouk University, Irbid, Jordan
c Department of Geology, Sana’a University, Sana’a, Yemen
Received 14 August 2002; accepted 22 April 2004
Available online 17 June 2004
Abstract
This paper presents the first paleostress results from fault-slip data on Cretaceous limestone at the eastern rim of the Dead Sea
transform (DST) in Jordan. Stress inversion of fault-slip data is performed using an improved right dieder method, followed by
rotational optimization (Delvaux, TENSOR Program). The orientation of the principal stress axes (r1, r2 and r3) and the ratio of the
principal stress differences (R) show two main paleostress fields marking two main stress regimes, strike-slip and extensional. The first
is characterized by NNW–SSE compression and ENE–WSW extension and related to Middle Miocene-Recent sinistral movement
along the Dead Sea transform and the opening of the Red Sea. The second paleostress field is a WNW–ESE compression and NNE–
SSW extension restricted to the northern part of the investigated area. This stress field could be associated with the development of the
Syrian Arc fold belt which started during the Turonian, or it may be due to an anticlockwise rotation of the first stress field.
� 2004 Elsevier Ltd. All rights reserved.
Keywords: Paleostress; Tensor; Dead Sea transform; Syrian Arc
1. Introduction
The Dead Sea transform (DST) is one of the major
morphotectonic features of the Middle East and is the
source for most historical and recent earthquakes. It
represents the boundary between the Sinai micro plate
and the Arabian plate (Fig. 1). In Jordan, the transform
consists of three morphotectonic segments: Wadi Araba
in the south, Dead Sea in the middle and Jordan Valleyin the north. Though it has many features of an exten-
sional rift, many evidences indicate that it is a transform
linking the Red Sea, where sea floor spreading takes
place to the south, with a continental collision zone
in the Taurus-Zagros mountain belt in the north
(Garfunkel et al., 1981).
The tectonic stress field due to the regional driving
forces acting on a portion of the lithosphere is modifiedby the deformational processes that take place within
the lithosphere. Thus, the observed tectonic stress field
* Corresponding author.
E-mail address: [email protected] (M. Atallah).
0899-5362/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jafrearsci.2004.04.002
reflects the dynamic conditions existing now, but someof its characteristics are also inherited from conditions
created by earlier tectonic evolution, in particular lateral
heterogeneities and zones of weakness (Delouis et al.,
1993). During the last few decades, several techniques
for paleostress analysis have been devised and modified
using both numerical and graphical methods. Such
methods are based on the stress–shear relationship
described by Wallace (1951) and Bott (1959).The displacement along the DST has probably been
the major source for the stress stored in the rocks along
this transform, resulting in seismic activity and internal
deformation of plates adjacent to it (Garfunkel, 1981;
Eyal, 1996). East of the DST paleostresses were deduced
from the general orientation of folds and faults (Burdon,
1959; Mikbel and Zacher, 1981; Atallah, 1992) and by
tectonic stylolite (e.g. Salameh and Zacher, 1982), whilewest of the DST, paleostresses were deduced from the
analysis of the mesostructures (Eyal and Reches, 1983;
Eyal, 1996; Eyal et al., 2001). The latter proved the
existence of two stress fields since the Late Cretaceous,
one is responsible for the formation of the Syrian
Arc (Syrian Arc Stress field, SAS), and the other is
Fig. 1. (a) Plate tectonic setting of the Dead Sea transform. (b) General geological and structural map of the area east of the DST (simplified after
Bender, 1968).
450 A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460
responsible for the formation of the DST (Dead Sea
Stress field, DSS). There are no previous studies based
on the analysis of fault-slip data in Jordan, except for
Zain Eldeen et al. (2002). The aim of this study is
reconstructing the first paleostress results in 12 stations
(Fig. 2) at the eastern margin of the DST. The basic
assumption of the paleostress analysis is that any planar
discontinuity in a rock may be activated as a faultregardless of its origin.
2. Geological setting
The study area is located at the eastern rim of the
Dead Sea transform. It comprises 12 sites concentratedin three areas, NW Jordan, east of the Dead Sea, and
NE of Aqaba (Fig. 1). Cretaceous rocks cover more
than 60% of Jordanian land (Bender, 1968). The thick-
ness decreases from north to south and from west to
east. Two different facies of Cretaceous sedimentation
are recognized in Jordan: Lower Cretaceous composed
mainly of sandstone, and Upper Cretaceous consisting
mainly of limestone. The Lower Cretaceous sandstone
unconformably overlies older strata (Jurassic and Tri-
assic in north and central Jordan and Silurian, Ordovi-
cian and Cambrian in south Jordan). Upper Cretaceouscarbonaceous rocks are composed mainly of alternating
beds of limestone, marl, marly limestone, chalk, chert
and phosphate. Few normal and strike-slip faults cut the
area east of the DST (Fig. 1).
3. Faults and slickensides
In this study the term slickenside was used for the
polished surface formed by frictional sliding and the
Fig. 2. Location of the fault-slip data measurements east of the DST (1, 2, etc. are station numbers).
A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460 451
groove lineations (striations or scratches) on the slic-
kensides are called lineated slickensides or slickenlines.445 fault planes with their slickenlines were measured
east of the DST (Al-Diabat, 1999). The measured faults
have various lengths (i.e. few centimeters up to 100 m).
Strike-slip faults represent more than 60% of the total
measured faults. The major trends of these faults are
WNW–ESE and NNE–SSW. The dip angle ranges from
65� to 90� (Fig. 3a). Normal faults have shorter traces in
the field and they are less abundant than strike-slipfaults. They represent about 30% of the total measured
faults and trend WNW–ESE and NW–SE. Their dip
angle ranges from 60� to 90� (Fig. 3b). Reverse faults are
generally rare and do not exceed 10% of the total mea-
sured faults. They trend ENE–WSW with two minor
sets trending ENE–WSW and WNW–ESE. There are
two dip group values: 70–90� and 40� (Fig. 3c).The measured faults have slickenlines on their sur-
faces; the strongest and most clear being horizontal, on
the sub-vertical strike-slip faults. Some of the slickenside
on a few slickolite faint oblique slickenlines were ob-
served superimposed on previously formed horizontal
slickenlines. Vertical slickenlines were also observed on
many slickenside surfaces. In some cases they aresuperimposed on horizontal slickenlines. A convenient
way to determine the slip orientation on faults is pro-
vided by the observation of slickenlines on slickenside
surfaces. The attitude of slickenlines in addition to
associated features as mineral steps and tension gashes
have been used to determine the orientation of slip and
the sense of relative motion allowing the reconstruction
of the paleostress in the area under investigation.
4. Paleostress analysis
4.1. Field measurements
The fault-slip data were collected by measuring fault
planes and slickenlines on these fault planes at 12 sta-
tions (Al-Diabat, 1999). The measurements at eachstation included the attitude of the fault plane, trend and
plunge of slickenlines, motion along these planes (Fig.
4). 445 fault-slip data were collected from sub-horizontal
Fig. 4. Plunge and azimuth of the measured slickenlines (A: 250 lines
on strike-slip faults, B: 130 lines on normal faults and, C: 30 lines on
reverse faults).
Fig. 3. Dip (left) and strike (right) of (a) 271 strike-slip faults; (b) 137
normal faults and; (c) 37 reverse faults in the study area.
452 A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460
strata of the Upper Cretaceous limestone (Wadi As Sir
Formation). This formation was selected because it was
affected by the stress system responsible for the forma-
tion of the Syrian Arc and the DST and post-date
known older stress regimes (Paleozoic and Pre-
cambrian). Furthermore, it is exposed along the DST
from north to south and can be documented in detail in
quarries (fresh slickensides). The term station in thisstudy means a group of quarries, valley sides or road
cuts located at different sites ranging in area from 1 to
10 km2.
4.2. Stress inversion method
Fault plane and slickenline orientations, including
slip senses are used to compute the reduced paleostress
tensors (r1, r2, r3 and R): the principal stress axis r1
(maximum compression), r2 (intermediate compression)
and r3 (minimum compression) and the ratio of prin-
cipal stress differences R ¼ ðr2 � r3Þ=ðr1 � r3Þ. Thesefour parameters are determined using successively an
improved version of the Right Dihedron method of
Angelier and Mechler (1977), and a rotational optimi-
zation method, using the TENSOR computer program
developed by Delvaux (1993). For faults, the angular
deviation between observed slickenlines and computed
shears is minimized, together with the maximization of
friction coefficients for each fault plane (for detailssee Delvaux, 1993; Delvaux et al., 1995, 1997).
4.3. Stress tensor determination
A total of 445 fault-slip data were measured in the
field, out of which 330 measurements found to be usefulin stress determination. The computed stress tensors in
this study explained 74% of the numerous striations
observed. According to the slip deviation angle between
A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460 453
theoretical striations derived from the computed meanstress tensor, homogeneous populations of faults have
been obtained from each station separately. All the
WNW–ESE compression trends are compatible with the
Syrian Arc stress field (SAS), and those trending NNW–
SSE are compatible with Dead Sea stress field (DSS).
The following is a representation of the results in each
station.
4.3.1. Station 1
Seventy-eight measurements were carried out inquarries located NNW of Irbid (Fig. 2). Fifty fault
planes with their slickenlines have been used in com-
putation. Three stress tensors were obtained from the
whole fault population: the first stress tensor gives the
maximum principal stress axis (r1) 08/118, the interme-
diate principal stress axis (r2) 78/349, and the minimum
principal stress axis (r3) 09/210; with stress ratio (R)
equals 0.30. The tensor belongs to the pure strike-slipsystem. It indicates a WNW–ESE compression and
NNE–SSW extension. The second stress tensor is char-
acterized by r1: 60/314, r2: 30/142 and r3: 04/050 with
R ¼ 0:27. This tensor belongs to pure extension system,
and indicates ENE extension. The third stress tensor is
characterized by r1: 39/209, r2: 40/076 and r3: 26/323
with R ¼ 0:75. It indicates NNW–SSE extension with
oblique principal stress axes.
4.3.2. Station 2
Eighty fault-slip measurements were used in com-
puting 108 measurements from quarries located SSW of
Irbid (Fig. 2). The movements along the measured faults
are of strike-slip (dominant) and dip-slip nature. The
sense of motion is determined based on calcite steps,
tension gashes on fault planes and stratigraphic sepa-
ration. We observed vertical and oblique striationssuperimposed on horizontal striations in the area. Five
stress tensors were separated from the total fault pop-
ulation: the first one is characterized by r1: 07/140, r2:
77/018, and r3: 11/232 with R ¼ 0:37. It belongs to a
pure strike-slip system and indicates NNW–SSE com-
pression and ENE–WSW extension. The second one is
characterized by r1: 07/294, r2: 83/106 and r3: 01/204
with R ¼ 0:50. It belongs to pure strike-slip system (asthe first one), indicating WNW–ESE compression and
NNE–SSW extension. The third tensor is characterized
by r1: 60/145, r2: 26/297 and r3: 12/034 with R ¼ 0:75.It belongs to an extension system, and indicates NNE–
SSW extension. The fourth tensor is characterized by r1:
52/035, r2: 29/260 and r3: 22/157 with R ¼ 0:56. It
belongs to a pure extension (as the third one), but
indicates NNW–SSE extension. The last one, is char-acterized by r1: 22/275, r2: 16/012 and r3: 62/135 with
R ¼ 0:5. This tensor indicates WNW–ESE compression,
and belongs to a pure compressive system.
4.3.3. Station 3
Sixty measurements were carried out in the quarries
west of station 2 (Fig. 2), including 44 fault-slip mea-
surements of both strike-slip and normal faults. Two
stress tensors were separated from the total fault pop-
ulation: the first is characterized by r1: 01/335, r2: 80/
241 and r3: 10/065 with R ¼ 0:33. It belongs to a pure
strike-slip system, and indicates NNW–SSE compres-
sion and ENE–WSW extension. The second tensor ischaracterized by r1: 80/102, r2: 10/282 and r3: 00/012
with R ¼ 0:1. This stress subset indicates a major NNE–
SSW extension and a minor WNW–ESE extension, so
it belongs to a radial extension system.
4.3.4. Station 4
Thirty-nine measurements were carried out in the
quarries NNW of Ajlun (Fig. 2). The movements along
fault planes are of both strike-slip and dip-slip nature.
Thirty-four measurements were used during computa-
tion. As a result, four stress tensors were separated from
the total fault population. The first one is characterizedby r1: 00/107, r2: 86/014 and r3: 04/196 with R ¼ 0:5. Itindicates WNW–ESE compression and NNE–SSW
extension, and thus belongs to a pure strike-slip system.
The second tensor is characterized by r1: 08/335, r2: 80/
121 and r3: 05/244 with R ¼ 0:88. It indicates ENE–
WSW extension and minor NNW–SSE compression.
This tensor belongs to an extensional strike-slip system.
The third tensor is characterized by r1: 60/192, r2: 19/318 and r3: 22/056 with R ¼ 0:55. It indicates ENE–
WSW extension, and belongs to a pure extension
system. The last one is characterized by r1: 29/129, r2:
29/237 and r3: 47/003 with R ¼ 0:63. It indicates
WNW–ESE compression, and belongs to an oblique
compressive system.
4.3.5. Station 5
Eighteen fault-slip measurements were carried out in
the quarries and in road cut north of Jerash along
Amman–Irbid highway (Fig. 2). Fourteen measure-ments of strike-slip faults were included in the compu-
tation and separated from the total fault population.
The stress tensor which has been obtained is character-
ized by r1: 01/326, r2: 84/228 and r3: 06/056 with
R ¼ 0:25. It indicates NNW–SSE compression and
ENE–WSW extension and belongs to the compressive
strike-slip system.
4.3.6. Stations 2, 3, 4 and 5
These stations display similar stress tensors and thus
the data were grouped to test the whole fault population
data and compare the results with the tensors obtainedfor each of the primary subsets. The obtained stress
tensor is characterized by r1: 03/336, r2: 87/174 and r3:
01/066 with R ¼ 0:33. It belongs to the pure strike-slip
454 A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460
system, and indicates NNW–SSW compression andENE–WSW extension (Fig. 5).
4.3.7. Stations 1, 2 and 4
These stations indicate the same stress tensors, thusthey are grouped and tested for new stress tensor. The
new tensor is characterized by r1: 02/119, r2: 83/009 and
r3: 07/210 with R ¼ 0:34. It belongs to the pure strike-
slip system, and indicates WNW–ESE compression and
NNE–SSW extension.
4.3.8. Stations 1 and 4
A new stress tensor has been obtained from grouping
similar stress subsets of two stations 1 and 4. It is
characterized by r1: 70/313, r2: 20/141 and r3: 02/050
with R ¼ 0:35. It indicates ENE–WSW extension andbelongs to the pure extension system.
4.3.9. Stations 1 and 2
The similar stress tensors of these stations have beengrouped, and tested for a new stress tensor. This stress
tensor is characterized by r1: 81/317, r2: 02/058 and r3:
09/148 with R ¼ 0:31. It indicates NNW–SSE extension,
and belongs to the pure extension system.
4.3.10. Station 6
Sixteen measurements from this station were col-
lected along a monoclinal structure dipping 65� WNW
east of Dead Sea (Fig. 2). Despite the scarcity of data,
two stress tensors were separated from the whole fault
population. The first tensor is characterized by r1: 54/
359, r2: 27/134 and r3: 22/235 with R ¼ 0:57. Thisindicates ENE–WSW extension, and it belongs to a pure
extension system. The second is characterized by r1: 22/
Fig. 5. Example of stress inversion results in north Jordan (stations 1,
2, 3, 4 and 5).
344, r2: 26/086 and r3: 55/220 with R ¼ 0:56. It indicatesNNW–SSE compression and belongs to a pure com-
pressive system.
Since the limestone bedding is steep in this area, it has
been rotated to a horizontal position. As a consequence
the new orientation of the principal stresses become as
follows: the first has r1: 09/332, r2: 76/204 and r3: 06/
062. The second has r1: 22/165, r2: 57/030 and r3: 20/
264. The two tensors belong to the strike-slip system,but the compressional and extensional directions remain
in the same orientation before and after rotation (cor-
rection). Because there are no sufficient evidences on the
timing of the tilting and the slip, the two probabilities
are presented.
4.3.11. Station 7
Eleven measurements were carried out in quarries
northwest of Karak, east of Dead Sea (Fig. 2). The
fault-slip data show an oblique stress tensor. This may
be due to block rotation or to error in the measurement.
So it is excluded from the analysis.
4.3.12. Station 8
Nine fault-slip measurements were carried out north
of Karak (Fig. 2). The stress tensor is characterized by
r1: 02/097, r2: 83/200 and r3: 07/007 with R ¼ 0:46. Itbelongs to a pure strike-slip system, and indicates E–W
to WNW–ESE compression and N–S to NNE–SSWextension.
4.3.13. Station 9
Only nine measurements of strike-slip faults have
been carried out SSE of Petra (Fig. 2). They give a stress
tensor characterized by r1: 17/334, r2: 66/201 and r3: 17/069, with R ¼ 0:50. It indicates NNW–SSE compression
and ENE–WSW extension, and it belongs to a pure
strike-slip system.
4.3.14. Station 10
Thirty-nine fault-slip data of this station were carriedout in south of Gharandal, east of Wadi Araba (Fig. 2).
Twenty-six measurements of strike-slip faults have been
used in the computation of the stress tensor. This stress
tensor is characterized by r1: 27/324, r2: 63/154 and r3:
04/056 with R ¼ 0:50. It belongs to pure strike-slip and
indicates NW–SE compression and NE–SW extension.
4.3.15. Station 11
Fifty fault-slip data of this station were carried out
NNW of Quweira (Fig. 2). Thirty-five fault-slip mea-
surements of both strike-slip (dominant) and dip-slip
(rare) faults were included in the computation. Four
stress tensors were deduced from the whole fault pop-ulation. The first tensor is characterized by r1: 35/120,
r2: 55/311 and r3: 05/213 with R ¼ 0:53. It belongs to
pure strike-slip, and indicates WNW–ESE compression
Fig. 6. Example of stress inversion results in south Jordan (stations 9,
10, 11 and 12).Fig. 7. Representative paleostress tensor east of the DST.
Table 1
Results of the reduced Paleostress tensors from fault-slip data of the studied stations
Station N Nt. R (a) Principal stress axes Q R0 Shmax Tensor type
r1 r2 r3
1 12 78 0.30 8.93 08/118 78/349 09/210 B 1.70 118 Pure strike-slip
22 0.27 11.36 60/314 30/142 04/050 B 0.27 142 Pure extension
16 0.75 6.0 39/209 40/076 26/323 A 0.75 Oblique extension
2 31 108 0.37 10.75 07/140 77/018 11/232 A 1.63 140 Pure strike-slip
19 0.50 11.37 07/294 83/106 01/204 B 1.5 294 Pure strike-slip
9 0.75 12.66 60/145 26/297 12/034 B 0.75 297 Pure extension
15 0.56 6.95 52/035 29/260 22/157 A 0.56 260 Pure extension
5 0.50 1.5 22/275 16/012 62/135 C 2.5 275 Pure compression
3 14 60 0.33 10.17 01/335 80/241 10/065 B 1.67 335 Pure strike-slip
7 0.32 7.29 52/028 14/278 34/179 B 0.32 278 Pure extension
8 0.35 15.05 55/127 27/264 20/005 C 0.35 264 Pure extension
15 0.10 15.76 80/102 10/282 00/012 B 1.10 282 Radial extension
4 10 39 0.88 9.15 08/335 80/121 05/244 B 1.12 335 Extension strike-slip
10 0.50 9.17 00/107 86/014 04/196 B 1.50 107 Pure strike-slip
9 0.55 4.8 60/192 19/318 22/056 B 0.55 318 Pure extension
5 14 18 0.25 7.37 01/326 84/228 06/056 B 1.75 326 Compression strike-slip
2, 3, 4, 5 68 0.33 9.23 03/336 87/174 01/066 A 1.67 336 Pure strike-slip
1, 2, 4 38 0.34 12.08 02/119 83/009 07/210 A 1.66 119 Pure strike-slip
1, 4 31 0.35 13.72 70/313 20/141 02/050 A 0.35 141 Pure extension
1, 2 34 0.31 15.56 81/317 02/058 09/148 A 0.31 058 Pure extension
6 7 16 0.57 5.67 54/359 27/134 22/235 0.57 134 Pure extension
5 0.56 3.32 22/344 26/086 55/220 B 2.56 344 Pure compression
8 8 9 0.46 1.14 02/097 83/200 07/007 A 1.54 097 Pure strike-slip
9 9 9 0.50 6.4 17/334 66/201 17/069 B 1.50 334 Pure strike-slip
10 26 39 0.50 11.2 27/324 63/154 04/056 A 1.50 324 Pure strike-slip
11 18 50 0.64 10.63 22/357 60/130 19/258 B 1.36 357 Pure strike-slip
9 0.53 9.78 35/120 55/311 05/213 B 1.47 120 Pure strike-slip
4 0.40 6.09 58/148 32/324 02/056 C 0.40 324 Pure extension
4 0.30 7.74 01/132 04/222 86/028 C 2.30 132 Pure compression
12 12 17 0.10 7.46 25/148 65/317 05/056 B 1.90 148 Compression strike-slip
9, 10, 11, 12 66 0.37 12.33 13/328 75/176 07/060 A 1.63 328 Pure strike-slip
All 127 0.37 11.43 04/330 84/202 05/061 A 1.63 330 Pure strike-slip
N ¼ net data number representing the tensor; Nt.¼ total data measured; R¼ stress ratio ðr2 � r3Þ=ðr1 � r3Þ; a¼mean slip deviation angle;
Q¼ quality ranking (as defined by Delvaux et al., 1997); R0 ¼ tensor type index (as defined by Delvaux et al., 1997); Shmax ¼maximum horizontal
shear.
A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460 455
Fig. 8. Distribution of the stress field that is characterized by NNW–SSE compression (black arrow¼r1) and ENE–WSW extension (white
arrow¼r3) in the study area.
456 A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460
and NNE–SSW extension. The second is characterized
by r1: 22/357, r2: 60/130 and r3: 19/258 with R ¼ 0:64.It belongs to the same system as the previous one, but
indicates NNW–SSE compression and ENE–WSWextension. The third tensor is characterized by r1: 58/
148, r2: 32/324 and r3: 02/056 with R ¼ 0:4. It indicatesENE–WSW extension and belongs to a pure extension
system. The last one is characterized by r1: 01/132, r2:
04/222 and r3: 86/028 with R ¼ 0:3. It indicates NW–SE
compression, and it belongs to a pure compression
system.
4.3.16. Station 12
Seventeen measurements were carried out at the
eastern edge of Wadi Araba, about 30 km north of
Aqaba (Fig. 2). Twelve fault-slip measurements of
strike-slip faults at this station have been extracted from
the whole fault population. The only stress tensor is
characterized by r1: 25/148, r2: 65/317 and r3: 05/056with R ¼ 0:1. It indicates NNW–SSE compression and
ENE–WSW extension and thus belongs to a compres-
sional strike-slip system.
4.3.17. Stations 9, 10, 11 and 12
Grouping the similar stress tensors of these stations
gives a more consistent new tensor. This tensor ischaracterized by r1: 13/328, r2: 75/176 and r3: 07/060
with R ¼ 0:37. It indicates NNW–SSE compression and
ENE–WSW extension and thus belongs to a pure strike-
A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460 457
slip system (Fig. 6). The above results with all parame-ters of the reduced stress tensors are provided in Table 1.
5. Discussion and conclusions
Stress tensor of the various stations along the whole
length of the DST with relatively similar deviation an-
gles were grouped with each other and new representa-tive stress tensor was obtained (Fig. 7).
To interpret the results easily, the reduced stress
tensors are displayed with the orientation of both hori-
zontal maximum principal stress (Shmax) and horizontal
minimum stress axes (Shmin) on maps (Figs. 8 and 9). As
a result, two main paleostress fields since Late Creta-
ceous are identified. The first is characterized by WNW–
ESE compression and NNE–SSW extension. It includestwo paleostress regimes, one with predominantly strike-
slip faulting (strike-slip regime) and the other with
predominantly dip-slip normal faulting (extensional
regime) which corresponds to S1 and n1, respectively
Fig. 9. Distribution of the stress field that is characterized by WNW–ES
arrow¼r3) in the study area.
(Fig. 10, Table 2). The second paleostress field is char-acterized by NNW–SSE compression and ENE–WSW
extension; it includes two stress regimes, one with
dominating strike-slip faulting and the other with nor-
mal faulting, which corresponds to S2 and n2, respec-tively (Fig. 10 and Table 2). The first paleostress field
is restricted mainly to north Jordan (east of Jordan
Valley), while the other paleostress field is found in all
other stations (Table 2). This may be due to scarcity ofdata collected from the south. This means that the SAS
could be found in southern Jordan, as recognized by
Eyal and Reches (1983) and Eyal (1996) west of the
DST. It is also noted that both normal and strike-slip
faulting of each paleostress field have nearly the same
orientation of r3 axis, while r1 and r2 axes change
according to the stress regime. Associations of stress
regimes of each stress field, which is frequent, can beexplained by stress axes permutation. Permutation of
stress axes r1 and r2 or r2 and r3 commonly occur
during tectonic events. Fig. 10 shows such changes from
predominantly strike-slip to predominantly normal
E compression (black arrow¼ r1) and NNE–SSW extension (white
458 A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460
faulting modes (r1=r2 permutation), for a single stage(i.e. S1=n1 and S2=n2), and a distinct stress field. This
figure also shows local permutations of r2 and r3 from
predominantly strike-slip to reverse faulting mode (i.e
S1=I1 and S2=I1) for both stress fields. It is also clear that
permutation of r2 and r3 for the same normal faulting
mode is possible (e.g. n2=n3; Fig. 10), such permutation
is of local effect (Table 2).
The stress field characterized by NNW–SSE com-pression and ENE–WSW extension is associated with
the 105 km sinistral displacement along the DST and the
opening of the Red Sea since Early Miocene to Recent.
The stress field characterized by WNW–ESE compres-
sion and NNE–SSW extension could be associated with
the formation of the Syrian Arc fold belt that started
during the Turonian or it may be due to an anticlock-
Fig. 10. The mean orientation of the principal stresses of the main stress reg
strike-slip regime belongs to DSS, n1: extensional regime belongs to SAS, n2unknown stress field, I1: compressional regime belongs to the both stress fie
wise rotation of the first stress field. Eyal and Reches(1983) suggested that: (1) the NNW–SSE (DSS) field is a
younger stress field and responsible for the formation
of the Dead Sea transform and (2) the WNW–ESE trend
(SAS) field is older and responsible for the formation of
the Syrian Arc.
In addition to the above main stress fields, a local
paleostress tensor characterized by vertical r1 and nearly
N–S oriented r3 is responsible for the formation of E–Wtrending normal faults and N–S elongation at station 3.
This is the youngest event as these faults cut the previous
ones, and it may have been active since the post-Middle
Pliocene (Ron and Eyal, 1985). Another local paleo-
stress tensor was found east of the Dead Sea at station 7.
This is characterized by oblique stress axes, possibly due
to tilting of fault blocks. East of Wadi Araba (station
imes in the study area, where S1: strike-slip regime belongs to SAS, S2:: extensional regime belongs to DSS, n3: extensional regime belongs to
lds.
Table 2
Average results of paleostress tensors
Tensor
symbol
Stress field Axis r1 Axis r2 Axis r3 Station Nt.
Trend Plunge Trend Plunge Trend Plunge
S1 SAS 110 03 015 85 018 04 1, 2, 4, 8 50
S2 DSS 150 05 016 84 060 05 2, 3, 4, 5,
6,9,10 12
147
n1 SAS 295 83 114 07 023 02 1, 2, 3 40
n2 DSS 320 70 140 20 050 01 1, 2, 3, 4, 6,
11
38
I1 Both 125 12 036 05 150 75 2, 4, 11 20
n3 Unknown 317 81 058 02 148 09 1, 2 34
S1 � S2: predominantly strike-slip fault sets; n1 � n3: predominantly normal fault sets; I1: predominantly reverse fault sets; 1, 2: station number as
defined in text; Nt.: number of fault-slip data representing the tensor; SAS: Syrian Arc stress; DSS: Dead Sea stress.
Fig. 11. Stress trajectory map of the dominant stress field east of the
DST (i.e. DSS).
A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460 459
11), a stress tensor with N–S compression and E–W
extension of pure strike-slip type has been identified.
This may be due to clockwise rotation of the regional
stress tensor as a result of continuous compressional
stresses. The stress tensor marked by NNW–SSE
extension with r1 vertical in north Jordan can be ex-plained by the reactivation of the dextral faults or it
belongs to unknown stress field (Table 1). To interpret
results of paleostress analysis on a regional scale, it is
necessary to compare paleostress tensors of a single
tectonic event or a distinct paleostress field. To achieve
this a map of stress trajectories is produced based on
maximum horizontal shears (Fig. 11). This map shows a
general NNW–SSE compression and ENE–WSWextension with slight rotation along some stations of the
study area.
The trend of compressional stresses (r1 ¼ 150�) is
responsible for the development of conjugate strike-slip
faults, and the northward movement of the Arabian
plate since the Oligocene (i.e. since the first opening of
the Red Sea). One set of these faults is parallel to the
western Arabian plate margin namely the major sinistralfaults, while the other set makes an acute angle with
the plate margin (Al-Diabat, 1999).
As a result of these compressional stresses and the
continuous sinistral movement, extensional stresses were
formed during the relaxation period or during reacti-
vation of stresses, they mainly affected the dextral set.
Reactivation of stresses caused vertical movement on
the preexisting dextral faults, as indicated from thesuperimposed of new vertical slickenlines on the older
horizontal slickenlines of the dextral strike-slip faults.
In conclusion, the current results are compatible with
the previous paleostress results, especially those at the
western margin of the DST (e.g. Eyal and Reches, 1983;
Eyal, 1996) defining two distinct stress fields. The older
one (SAS) is characterized by E–W to ESE–WNW
compression, whereas the younger stress field (DSS) ischaracterized by N–S to NNW–SSE compression. Our
results are also compatible to some extent with the
paleostress results based on tectonic stylolites carried
460 A.A. Diabat et al. / Journal of African Earth Sciences 38 (2004) 449–460
out in Jordan by Salameh and Zacher (1982), indicatingtwo dominant paleostress directions; the older Shmax
trends 130–140�, whereas the younger Shmax trends 170�.
Acknowledgements
The authors would like to thank Mrs. Julia Sahawneh
for drafting the figures. We thank two anonymousreviewers for their comments and improvement of the
manuscript.
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