Tectonic evolution of the Gulf of Suez and the Gulf of Aqaba

Tectonophysics, 153 (1988) 209-220 Elsevier Science Publishers

209

B.V., Amsterdam

- Printed

in The Netherlands

Tectonic evolution of the Gulf of Suez and the Gulf of Aqaba N. LYBERIS lJniversit6 de Paris VI, DPpartement de GCotectonque, 4, Place Juweu, (Revised

version

accepted

December

75252 Paris, CPdex 05 (France)

12. 1987)

Abstract Lyberis,

N., 1988. Tectonic

(Editors),

evolution

of the Gulf of Suez and the Gulf of Aqaba.

The tectonic

evolution

of the Gulfs of Suez and Aqaba

Suez rift in the lower Miocene

resulted

began in the Late Burdigalian

and were associated

rift. In the Gulf of Aqaba pattern

(040°

between

direction

the Arabian

extension,

from NNE-SSW

the movements of extension a rotation

oblique

with ENE-WSW

and J.R. Co&ran

a 130”

using fault slip data. Early opening to the rift trend. Subsequent

extension

The Late Miocene

with

plate and the Sinai peninsula.

which indicates

can be determined extension,

are younger.

associated

In: X. Le Pichon

Tecfonophysics, 153: 209-220.

The Gulf of Suez and Red Sea Rifting.

compression)

which determined

motion

which

Since the end of the Miocene

of the regional

stress pattern

Introduction

is associated

in the vicinity

produced

the faulting

tectonic

of the events

the shape of the Suez with a strike-slip the left lateral

stress motion

is the result of an E-W

of the transform

fault.

The shoulders of the Suez and Aqaba basins were uplifted in the Late Tertiary (Kohn and Eyal, 1981) and deep erosion has exposed the Pre-

Field studies of the Late Tertiary fault pattern in the Sinai peninsula and the surrounding area indicate that the Neogene movements are com-

cambrian basement of the Arabo-Nubjan shield. The sediments overlying the basement, of

plex. The 150”-trending Red Sea rift opened between Arabia and Africa along a 030” direction

Cambrian

(McKenzie

relative activity Aqaba. that the the Red

1962). The lower part of the platform e:over consists of quartzose continental sands tones, the “Nubian sandstones”, which are poorly. fossiliferous. The upper part of the platform cover, widely exposed, consists of shallow-water marine sediments of Cenomanian to Middle Eocene (or Late

Sea prior to major shear along the Gulf of Aqaba-Dead Sea fault system (e.g. Steckler, 1986). The Suez rift is a 60-80 km wide depression

Eocene in the northern Sinai) age. The younger post-Eocene sediments are of local extent. Their distribution was directly controlled by the rift

and only its central part is below sea level. In contrast, the 30-40 km wide Aqaba rift is mostly a submarine basin where the Tertiary sediments are rarely exposed (Fig. 1). These basins separate the Sinai block or plate (Le Pichon and Francheteau, 1978), from the African and Arabian

shape. Igneous rocks younger than Precambrian in the Sinai and neighbouring areas are predominantly basaltic bodies (dykes and flows) of Mesozoic (Meneisy and Kreuzer, 1974) and Oligocene to lower Miocene age (Siedner, 1973). Their main direction is parallel to the Suez and Red Sea Rift.

et al., 1970; Le Pichon

form

and Franchetau,

1978; Cochran, 1981). The Arabia-Africa motion is also responsible for the tectonic in the Gulf of Suez and the Gulf of Several authors give convincing evidence Suez rift was the northern termination of

plates. 0040-1951/88/$03.50

0 1988 Elsevier Science Publishers

B.V.

to Eocene

deposits

with

age, comprise a wide

lateral

typical extent

plat(Said,

fn the Eastern Desert of Egypt and in the Sinai dyke intrusions of Late Precanxbrian to Early Palaeozoic age are abundant. They strike N-S to NE-SW and NW-SE and are prqsent in the entire Precambrian outcrop (Vail, 1970). However, Ries et al. (1983), who studied. an E-W section across the basement in the Eastern Desert of Egypt, show that- foEatin phmes as well as mineral lineations in the Precambrian bt+sement with

NW-SE strikes indicate the direction of tectonic transport. Thus, the Late Tertiary faults {Fig. 1) are parallel to the basement tectonic features. Age of rifting

Robson (1971) cancluded that the Suez rift was not formed u&f Late Eocene times (40 Ma ago). Garfunkel and 3artov (1977) show that early rifting in the Suez basin must have occurred slightly

211

before the erosional duced the marked Miocene.

pre-Miocene

period.

unconformity

In addition,

basaltic

This pro-

at the base of the igneous

activity

oc-

curred in the Late Oligocene or Early Miocene, just before the deposition of the earliest marine Miocene

sediments

Kreuzer,

1974).

interpreted

(Siedner,

This

as related

1973;

igneous

phase

to initial

faulting

Meneisy

consists and

in the Suez

truncated

Cochran,

vol.).

Cochran

authors

There

is no evidence into

1971;

Steckler,

al. (1970) and Co&ran

on stratigraphic

studies

of the earliest

syn-

In the Aqaba

region

palaeontological

data

are

most

because the rift is mainly below sea level. the oldest movements along the However,

vol.).

Aqaba-Dead

that

Sea

fault

zone

are younger

than

those in the Suez basin (Eyal et al., 1981). A set of 18-22 Ma old NW-SE-trending dykes has been identified

in southeastern

Sinai

(Steinitz

et al.,

1978). Faults belonging to the Aqaba system in the eastern Sinai area which cut these dykes are therefore younger than 18 Ma. To the southeast of the Gulf of Aqaba, in the Midyan area, Bayer et al. (this vol.) show that the first Neogene tectonics began after 14 Ma and prior to the Pliocene. Thus, an Upper Miocene age for the Aqaba rift seems likely, while the Suez rift has been active since at least the Early Miocene. Tectonic setting The Suez rift The Suez rift is an asymmetric graben. Moustafa (1976) and Abdine (1982) distinguish the northern, central and southern basins (Fig. 1). Each basin corresponds to a main half graben with an average tilt of 20 O, limited by a major 150 O-trending fault. Numerous smaller faults affect each half graben. The basins are separated by NNE-SSW to NE-SW fault zones (Fig. 1). On either side of these fault zones the direction of tilt is reversed. Moreover, the southern edge of the Gulf of Suez is bordered by N-S faults which mark the transition between the shallow-water Suez basin and the deep (> 1 km) northern Red Sea basin. The Gulf of Suez structure can be compared with the northern Red Sea margins. Geophysical data show that the continental crust of the northern Red Sea

and

recent

subsidence

scarce

Martinez,

this

a half graben

the Suez structure total

Bartov

(1977)

calculations

for 15-20

based

the present

of historical tectonic

along the southern the junction

et km km.

orI tectonic et al., this

earthquakes

activity

of

Yreund

(1981) argue for :!5-30

studies yield 34 km (Steckler

The distribution

(Rob-

a:nount

of the Suez rift is still debated.

and Garfunkel The

fault

(Martinez

Mediterranean

1986). The

opening

rift sediments.

that

the Eastern

cene age of the early opening based

and

also propose

rift. Bayer et al. (this vol.) argue for a Late Oligoof the Red Sea basin

features

for the early Red Sea rifting.

continues son,

of 150”-trending

by transverse 1988;

These

structure

and

is generally

of a succession

blocks

shows

is concentrated

edge of the Gulf of !iuez, near

between

the Suez rift and the north-

ern Red Sea. There is no evidence for significant seismicity in the northern and central part of the Gulf of Suez (Daggett

et al., 1986).

The Aqaba fault system In the region of the Gulf of Aqaba the main faults trend N-S to NNE-SSW. They are found on the Sinai and Arabian deformed coastal areas as well as within the Gulf (Ben Avraham et al.. 1979; Ben Avraham, 1985). On the Arabian side of the Gulf of Aqaba, analysis of Land:jat images shows that the deformed zone, which is 60 km wide in the Midyan area, narrows to the north. Thus, in the Wadi Arava area the deformed zone is

only

20

km

wide

(Fig.

1).

The

Gulf

of

Aqaba-Dead Sea fault system is a left lateral transform fault linking the Zagros-Taurus area of plate convergence, with the Red Sea opening. Quennel (1959) and Freund et al. (1968, 1970) argue for a 105 km left-lateral movement between Arabia and Sinai. The 1800 m deep Gulf of Aqaba is considered to be a succession of NNE-SSW pull-apart basins by Garfunkel (1981). Narrow graben are present in the eastern Sinai area. At present, the seismic activity is confined to the Dead Sea area. The Arava fault, which connects the Gulf of Aqaba and the Dead Sea, has been active throughout the Quaternary

(Garfunkel

and Freund,

1981).

212

Fault mechanisms

Analysis of fault planes and slickenside lineations from field measurements of strike, dip and pitch have enabled the orientations of the principal stress axes that prevailed during the faulting to be reconstructed (maximum compressional stress ul, intermediate stress a, and minimum stress u3). The methods used have already been published by Carey and Brunier (1974) and described in detail by Angelier (1979). They include geometrical analysis of fault slickensides using the method of right dihedra and determination of stress tensors. Control of the age of fault movements is difficult to obtain in the study area. It is suggested that the clustering of stress directions reflects the regional stress pattern. These clusters were dated using the few sites where dating was possible. Tectonics of the Gutf of Suez area

Pre-Miocene tectonics The earliest Cenozoic deformations identified in the pre-rift sedimentary cover of the Egyptian coast of the Red Sea correspond to strike-slip faults. The Cretaceous and Eocene sediments, as well as the underlying basement and the Nubian sandstones westward of Safaga, form three adjacent tilted blocks (Fig. 2), cut by numerous small conjugate strike-slip faults. The N-S faults are left lateral and the ESE-WNW faults are right lateral. The corresponding stress tensor has a NW-SE direction for the maximum principal stress axis (parallel to the Red Sea axis) and the NE-SW direction for the minimum principal stress axis

(perpendicular to the rift axis) (Fig. 3). The faulting occurred prior to the deposits of the first syn-rift sediments of Miocene age and might be related to the main folding phase of the Syrian Arc. A similar phase of strike-slip tectonics has been observed during the early rifting in other areas. For instance, the first deformation in the Rhine graben, which preceded the opening, was associated with a strike-slip stress pattern, with the axis of shortening parallel to the future rift (Bergerat, 1987). On the western side of the Sinai peninsula, compressive structures (mainly folds) are observed. Folding, with locally overturned folds and overthrusts, affected the pre-rift as well as the Lower Miocene pre-evaporite sediments_ Letouzey and ChCnet (1984) and Chorowicz et al. (1987) argued that the apparent compression observed is due to gravity phenomena, during rapid subsidence, on the walls of steep scarps of the rift. In the area investigated, no evidence for a compressive stress pattern (a, horizontal and Us vertical) of Late Tertiary age has been recorded. The NNE-SS

W extension

The faults under study are located along the Egyptian coast, from Hurgada to Suez, and along the western side of the Sinai peninsula. The faults cut through both the Neogene sediments and the pre-rift sequence (Fig. 1). Most the Late Cenozoic faults trend NW-SE and N-S. They control the structure and the morphology of the Suez rift. The chronology of faulting has been established by taking into account stratigraphic data and field evidence for successive fault motions, as well as geometrical and mechanical compatibility (Fig. 4).

ENE

wsw Mine of phofphatas

Mine of phosphates

I

lkm

5km

Fig. 2. Schematic gdogical

section across the northemmsst

Red Sea coast, south of Waga.

For location

of sect&n line see Fig. 1.

213

Fig.

3. Examples

analysed

cene sediments. planes

of fault

in the Safaga are shown

centrifugal

Schmidt (normal

or centripetal the direction

(centrifugal

arrows)

(centripetal

arrows).

of tension

slickenside motion),

arrows

ding planes are represented indicate

of pre-Miocene

lower-hemisphere

as curves,

arrows

motion)

populations,

age,

area. The faults cut the Cretaceous-Eo-

double

(reverse

arrows

motion).

Fault

as dots with (strike-slip)

Poles to bed-

as open circles. Large black arrows

of the minimum and

projections. lineation

maximum

principal principal

The open squares

stress axis es stress

correspond

axis

et

to the poles

gashes.

Slickenside lineations on Neogene fault planes in the Gulf of Suez area distinguish movements that _ . .. . occurred before and after the upper tiarandhal sediments of mid-Miocene (16.5 Ma) (Garfunkel

Fig. 5. Palaeostress

and Bartov, 1977; Webster and Ritson, 1982) age were deposited. The most precise information on the age of faulting has been obtained in the Safaga and Abu

(us) with a vertical

results

are summarized

in Fig.

maximum

principal

stress (at).

movement along NW-SE-trending normal faults. This tectonic event is dated by the synsedimentary faulting in the Lower Rudeis sediments (Fig. 5. sites 2 and 3) and by the faulting at site 10. located in the area of the Wadi Taiba border fault. on the eastern side of the Suez rift (Fig. 1). There.

5.

Abu

the Suez rift during

Thus, there is sinistral-extensional motion along the N-S-trending faults and oblique extensional

mid-clysmic event (16.5 Ma ago). Synsedimentary faults have been also found in the Abu Zenima sequence (Fig. 4A and Fig. 5, site 9) of assumed Late Oligocene age. main

along

Early Miocene faulting is characterized by a NNE-SSW (030 o ) minimum principal stress axis

Zenima areas. Synsedimentary structures in the Lower Rudeis conglomerates (e.g., Fig. 5, site 3) provide good evidence for faulting before the

The

reconstruction

the Early Miocene.

Alaqa

formation

Sandstones

Fig. 4. Examples Formation

of Early Miocene

faulting.

A. The Wadi Taiba

(site 9, Fig. 5). For the legend see Fig. 3.

border

fault (site 10, Fig. 5). B. Faults

within

the Wadi Gharandal

214

the fault zone between the Eocene rocks and the Nubian sandstones is unconformably covered by the Lower Abu Alaqa (Upper Rudeis equivalent) of Late Burdigalian age (Fig. 4B). Subsidence studies show that the Lower Miocene is characterized by an increase in the rate of subsidence, which reaches a maximum during the mid-clysmic event (Steckler et al., this vol.). Unpublished well and seismic reflection data show an “en echelon” shape for the Lower Miocene Gulf of Suez basin compatible with a 030” extension. Scattered observations of the Red Sea faults, along the Egyptian coast from 24O N to 26 o N, suggest that faulting is due to a single tectonic event. The available data (from eight sites) show a consistent NNE-SSW (020 “-045 o ) direction of the minimum principal stress (u3). This stress pattern is in agreement with the 030“ direction of North Red Sea opening (Le Pichon and Gaulier, this vol.; Steckler et al., this vol.). In the small island of Zabargad located on the Egyptian side of the Red Sea, at 23”27’N, outcrops of fresh peridotite bodies are considered to represent fragments from the mantle (Bonatti et al., 1983, 1986). Nicolas et al. (1985, 1987) argue that mantle upwelling occurred in the Lower Miocene during the early rifting of the Red Sea. The kinematics of mantle emplacement (120°trending foliation planes, dipping at 85 O, with 55 o W mineral lineations) is in agreement with the 030 ’ extension demonstrated by faulting. ENE- WS W extension

During the Late Burdigalian, strong subsidence occurred in the Suez rift, prior to evaporite deposition, and corresponds to the “mid-clysmic

Fig. 6. Fault populations

event” (Garfunkel and Bartov, 1977). Pelagic sedimentation took place in the deeper part of the basin, while on border slopes and structural highs, reefal build-ups were developed. The reefs are present on the eastern and southern slopes of the Gebel Esh el Mellaha and. farther south, they cover the Safaga 150” faults (Fig. 2). The reefs were built, during the Langhian, on the major 150”-trending normal fault scarps which bound some of the main tilted blocks (Rouchy et al., 1983). The reefs are themselves faulted. Thus, the movement along the major scarps is of Langhian age or younger. The stress pattern calculated from fault-slip data correspond to an extension with a 060” mean orientation of the minimum principal stress axis (perpendicular to the rift trend) (Figs. 6 and 7). On the east side of the rift a similar stress pattern was found (Fig. 7). At two sites, the NE-SW extension (Fig. 6A) followed the NNE-SSW Lower Miocene extension (site 5 of Fig. 7), as shown by the relationship of superposed slickenside lineations in the same fault planes. The NNE-SSW extension is younger than Late Burdigalian (16.5 Ma). In addition, the Abu Rudeis N-S major fault presents slickensides showing left lateral motion followed by normal faulting. This fault cuts both the pre-Miocene series and the 16-12 Ma old Upper Rudeis formation. This ENE-WSW extension was previously assumed to be the only one present during the Suez rift opening (e.g. Angelier, 1985). Strike-slip tectonics in the Gulf of Aqaba area

On the western side of the Gulf of Aqaba where the Neogene outcrops are almost absent,

of Middle to Late Miocene age. A. The Abu Rudks

N-S

border fault and associated

fault pIaws

Fig. 7). B. The Safaga border fault. C. Faulting from the Gebel Esh el Mellaba area (site 3, Fig. 7). For legend see Fig. 3.

(site 8,

215

southwestern

part

of the Aqaba-Dead

Sea shear

zone. The observed into sinistral trend,

and

dextral

fault planes

conjugate

extension in

the

(Fig.

assumed main

slip

several

along

the Middle

the fault pattern affects mainly rocks and their Mesozoic-Lower mentary cover. Numerous N-S have produced

rotation

the Gulf of Suez and

to Late Miocene.

the Precambrian Tertiary sedistrike-slip faults

of the minor

blocks

(Eyal

and Raham

age (Garfunkel event

et al.,

pre-dates in the

movements

area, along

kilometers

strike-slip

reconstruction

are

sediments

extension

tectonic

sinistral

the investigated

during

faults

the

Gulf

of

are recorded

in

fault system.

(70-90” ) dipping single faults range

Fig. 7. Palaeostress

from

8). The

basement,

Miocene

submeridian

Large-scale

the Gulf of Aqaba

E-W

(Fig, 7, site 9 and Fig. f(B) of an

Middle

strike

Some resulting

Cretaceous-Eocene

1974). This Aqaba

organized to the Gulf

faults. motion

(Fig. 8A), the Precambrian conglomerates

is mainly

faults, parallel

show a normal

submeridian observed

fault network

strike-slip

faults

N-S

trending

steeply

faults. The displacements on from a few hundred meters to (Eyal cross

et al., 1981). The major the

zone

from

south

to

north with a prolongation towards the north in the Wadi Arava-Dead Sea area (Fig. 1). The strike-slip faults correspond to a homogeneous stress pattern for the whole area, which is summarized on Fig. 7. Numerous major faults, parallel to the Gulf, show a sinistral movement associated with dextral conjugate

faults

strike

slip stress

(Fig.

9). The faults pattern

indicate

(CT, and

a clear

u7 horizontal)

Eyal and Reches (1983) have proposed a deformation pattern of this area using mesostructures measurements. Our field data, which mainly con-

with a NE-SW minimum principal stress axis and a NW-SE maximum principal stress axis. The submeridian extension, as well as the strike-slip tectonic events, correspond to the first stage of deformation of the Aqaba shear zone.

sist of fault planes and slickenside analysis, provide an additional view of the deformation in the

This deformation occurred prior to the Pliocene and produced the deep pull-apart basin in the

et al., 1986).

Fig. 8. Examples Cretaceous-Eocene

of faults

of the N-S

sediments.

which cut conglomerates

B. Faults

attributed

extensional

event in the Gulf

in the southernmost

to the Middle

Miocene.

of Aqaba.

Sinai within

A. Fault

sediments

population

of assumed

from

the Taba

Oligocene-Miocene

area within

age. C. Faults

Fig. 9. Examples of the Late Miocene main tectonic phase of the Aqaba fault system. A. Mechanism of a major N-S sinistral fault and the associated dextral faults. B. The site of the Fig. 8A faults second motion (site 10, Fig. 7). C. N-S fault through the basement.

Gulf of Aqaba. In the Midyan area of the Arabian coast of the Gulf of Aqaba, Bayer et al. (this vol.) show a younger than 14 Ma NW-SE compression associated with a NE-SW extension. The similarity between the Midyan and the eastern Sinai deformation leads one to propose a Late Miocene age for the strike-slip tectonics in the Aqaba shear zone.

The Gulf of Aqaba Most of the major N-S faults on the eastern side of the Sinai peninsula show at least two successive motions. The last motion is normal and postdates the Late Miocene left-lateral slip. Several narrow grabens in the investigated area, where Cretaceous-Eocene and Miocene rocks outcrop, may result from normal faulting along the N-S

The E-W extension The GulfofSuez There is now strong evidence that the Suez rift has been inactive during the last 5 Ma (Steckler et al., this vol.) although several Plio-Quatemary sedimentary basins can be identified (Berthelot, 1986; Moretti and Colletta, 1986). The formation of the basins is then attributed to the thermal cooling following the crustal thinning of the Miocene rift, and not to a presently occurring phase or significant tectonic activity, although Courtillot et al. (1987) have argued that the Suez rift is still active. It has been pointed out that in some places fault planes are reactivated by E-W extension after the mid-Miocene (Fig. 10). The E-W extension is dated according to a relationship of successive motions or fault planes. A F~o-Quatema~ age for this second order tectonic activity in the Suez rift is suggested, since it is similar to the Plio-Quaternary Aqaba tectonics. The Plio-Quaternary kinematics of the Gulf of Suez are discussed in detail by Steckler et al. (this vol.).

Fig. 10. Palacostress reconstruction pIoBB the G&f of Suez and the Gulf of Aqaba during the Plio-Quaternary.

211 Cretaceous

Nubian

0

Fig. 11. Geological

Sandstones

50m

section of normal fault on the western side of the Gulf of Aqaba (for location see Fig. 1).

faults. The field observations show an E-W extension for the youngest movement of the Aqaba fault system (Fig. 10). The E-W extension, during the Quaternary, has also been found in the Dead Sea area (Z. Reches, pers. commun. 1986). The northern segment of the Nueiba fault, close to the shore line, has an important offset (several hundred meters) (Fig. 11). The last motion of the fault plane results from the E-W extension (Fig. 12A). The folds of the Cretaceous-Eocene rocks are unconformably overlain by the Raham conglomerates and are due to gravity. The E-W extension, perpendicular to the Aqaba trend,

suggests

Gulf of Aqaba The formation

series

that a part

of the opening

of the

is induced by extensional tectonics. of the pull-apart Aqaba basins

related to the strike-slip motion, as proposed by Garfunkel (1981) and Ben Avraham (1985), had a Late Miocene age. Then, an E-W extension occurred in the Aqaba structure during the PlioQuaternary. The interpretation of the Gulf of Aqaba as a simple E-W opening (Mart, 1982; Mart and Hall, 1984) corresponds

Fig. 12. Examples of the Plio-Quatemary

only to the last

stage of movement. This E-W extension affects an area 70-80 km wide, extending on both sides of the Gulf of Aqaba. The analysis presented above confirms the presence of two principal stages for the Aqaba faulting (Garfunkel, 1981; Le Pichon and Gaulier. this

vol.).

The

Miocene

Arabian plate corresponds pattern shown by faulting

020”

motion

of

the

to the strike-slip stress (040” extension associ-

ated with 130’ compression). On the other hand, the E-W extension of the Plio-Quarternary reflects a local stress field near the Aqaba fault zone, which Arabian produce

is undergoing

a 030”

motion

of the

plate. The E-W extensional tectonics the N-S-trending narrow grabens of the

eastern Sinai by normal motion, as well as left lateral movements on the NE-SW trending faults. For example, the 040 O-trending basin located near the

southeast

Sinai

coast

(Pautot

et al., 1986),

along the junction between the northern Red Sea and the Gulf of Aqaba-Dead Sea fault system, can be considered as a pull-apart basin over 040 o left-lateral faults.

faulting in the Gulf of Aqaba. A. Last motion of the site of the Fig. 8A faults. B. Faults

which cut the basement near Taba. C. Fault population

of the Oligocene-Miocene

sediments

of southern Sinai.

Discussion and conclusions

Figure 13 summarizes the Neogene stress pattern of the northern extension of the Red Sea basin. The Gulf of Suez was the northern extension of the Red Sea until the Late Burdigalian, before any motion had taken place along the Aqaba fault system. The Arabia-Africa motion since the Oligocene yields a 030” extension common to the Suez rift and the northwest part of the Red Sea. The NNE extension, oblique to the Suez rift, created the early Suez basin shaped by N-S- and NW-SEtrending faults. The next stage began in the Late Burdigalian with the 16.5 Ma old “mid-clysmic event” (Garfunkel and Bartov, 1977), marked by a rapid tectonic subsidence (Steckler et al., this vol.). Then, the tectonic subsidence of the Suez Rift slowed down during the Middle and Late Miocene. In the Middle to Late Miocene, 060’ extension in the Suez rift is clear established (e.g. Angelier, 1985). The Suez rift has been shaped by this 060 o extension, which created important normal offsets along the 150 O-trending faults.

r

-

AGE -

RED SEA

SUEZ RIFT ?. 090'

5

d=+

0300

ODOR

0350 u3

u3 Ul

/

060

125O J 015"

a3

/

12

0300

16.5

0304

(13 /

(13 /

24 Ma

Fig. 13. Suxnmay

of the tectonic

whole area investigated.

analysis

rest&s

from the

Since the end of the Miocene the motion has shifted from the Suez rift to the .4qaba fault system. The origin of this jump has been explained by the impossibility for the Suez rift to propagate farther to the north through the oceanic crust of the Mediterranean basin (Steckler, 1985; Steckler and Ten Brink, 1986). The Plio-Quaternary E-W-oriented minimum principal stress axis in the Gulf of Suez is more difficult to interpret, as it cannot be the result of a significant tectonic extension because there is no evidence for tectonic subsidence of PlioQuatemary age (Steckler et al., this vol.). It might possibly be related to thermal subsidence following the Miocene extension (Steckler et al., this vol.). The Aqaba structure as well as the southern edge of the Suez rift are still active (Ben Menahem and Abodi, 1971; Daggett et al., 1986). I assume, with Le Pichon and Gamier (this vol.), that the southern part of the Gulf of Suez is related to the Aqaba motion. Focal mechanism analysis of the few recorded earthquakes in the southern Gulf of Suez (Ben Menahem and Abodi, 1971; Huang and Solomon, 1987) indicates a NNE-SSW slip direction on the fault planes, in good agreement with a 030 o motion of the Arabian plate with respect to Africa. I consider the E-W extension as a local stress field directly associated with the Levant transform fault zone. It appeared in the Arabia-Sinai boundary at a late stage of the Aqaba-Dead Sea activity in a 70-80 km wide zone centred on the Aqaba structure. The kinematics of the Sinai triple junction show that the direction of motion along Aqaba cannot be parallel to the E-W extensional stress (Steckler et al., this vol.). If the transform is a zone of weakness, shaped during the Late Miocene leftlateral motion, the minimum principal stress axis would be expected to rotate to a direction which is perpendicular to the fault zone. If we accept this rotation for the Plio-Quaternary stress field near the Gulf of Aqaba, then we must consider whether it also affects the Gulf of Suez stress patterns, as suggested by Steclrler et al. (this vol.). The ENE-WSW extensional stress of the Gulf of Suez could be considered as a rotation

219

of

the

earlier

principal

NNE-SSW

oriented

stress axis (u3) which

Angelier,

minimum

initiated

the rift-

J., 1979. Determination

of the mean principal

tions of stresses of a given fault population.

direc-

Tecionophysics.

56: T17-T26.

ing.

Angelier,

An rected could

alternative extensional be related

crust.

Arabia-Sinai

1981;

Steckler

the

Gulf

Le Pichon

E-W

di-

of Aqaba

stress pattern occurred

as suggested

of

in the

by kinematics this

stress

field

of a stress field with similar

char-

also be expected

vol.),

the

to change.

acteristics

can be found

Oligocene

deformation

in the

Late

intraplate

to Africa-Eurasia

Bayer,

H.J..

motion,

Eocene

to

Platform.

compression, has been

E-W extension (Bergerat, produced the opening of the

duced an extensional motion between west and central Eurasia (Le Pichon et al., 1986). The post-Miocene stress in the Gulf of Aqaba fault system, like the Oligocene extension in the West European rift, is perpendicular to the rift orientation. In both cases, the extension occurred

Ben-Avraham,

J.K.,

Arabian

northern Z.O.,

Gulf of Elat (Aqaba). Ben-Menahem,

Bergerat,

I am most grateful to Xavier Le Pichon for suggestions. I thank discussions and valuable Michael Steckler, Gerard Stampfli and James Cochran for helpful comments, and Jean Francheteau for useful remarks. Financial support by the GIS-GENEbenefitted from loCompany.

Berthelot.

Red

Bonatti,

E., Clocchiatti. Ottonello.

Island:

an uplifted

Bonatti,

J. Geophys.

the

patterns

in

F:es. 76 (II):

for

R, Colantoni, fragment

E.. Ottonello,

P.. Gelmini.

of sub-Red

R.. Marinelli, (St. John’s)

I thosphere.

Sea

J.

140: 677-690. P.R., 1985. Peridotites

(St. John),

J. Geophys.

C.R.

539-631.

theorique

Cltmentaire

failles.

Red Sea: petrology

Res.. 9 (Bl):

B., 1974. Analyse

modele mtcanique de

tie Suez dam

Univ. Paris 6. 200 pp.

G. and Hamlyn,

Carey, E. and Brunier, population

du Golfe

These.

at the

61 (2): 99-132.

G. et al.. 1983. Zabargad

and geochemistry. dun

pl.uform

Tectonics.

thermique

from the island of Zabargad

applique

Acad.

et numerique B I’etude d’une

Sci..

Paris.

279,

D:

891-894. P.Y. and

comprise

Letouzey,

entre

Egypte)

dans

Abu

J., 1983. Tectonique

Durba

le contexte

et Gebel

J., Henry,

superposees

C. and

ocean

Res. 86 (Bl);

J.R.

7: 201-215.

N.. 1987. Tectoniques

des secteurs

des golfes

de

Bull. Sot. GCol. Fr.. 8, III: 223-234.

J.R., 1981. The Gulf

transition

(Sina:,

du rift de Suez.

ELF-Aquitain:.

Lyberis.

synddimentaires

of a young

Cochran,

de la zone

Me;zazat

de l’kolution

Bull. Cent. Rech. Explor.-Prod.

and

of Aden:

basin

and

Structure

and evolu-

continental

margin.

J.

263-287.

Martinez,

F.,

from continental

1988.

Evidence

to oceanic

rifting

from

the

Tectonophy-

sits, 153 (this vol.): 25-53. Courtillot,

V., Armijo,

triple junction Daggett.

P.. Morgan,

El-Sayeda,

Basta,

active electronics northern

Sea

R. and Tapponnier,

revisited.

P., Boulos,

rift

of the Egyptian

Red Sea margin

since

mesostructures.Tectonics,

the

and the

foraminiferal from

GCol. Mediterr..

Z., 1983. Tectonic

A., and

125: 313--324.

assemblages

and correlations.

181-190.

S., El-Sherif,

T., 1986. Seismicity

E., 1981. Miocene

nannoplankton

region

141

F., Henmn.

N. and Melek,

I. and Martini,

P. 1987. The Sinai

Tectonophysics.

Red Sea. Tectonophysics,

Eyal, Y. and Reches, Oil,: 99-12.

Hall.

206: 214-216.

collision.

Geol. Sot. London,

Suez region

World

CI. and

E., 1971. Tectonic,

gtodynamique.

G. and

El-Meiny,

References

optimism.

Res.. 90 (Bl):

by a leaky tmnsform:

Sea region.

F.. 1986. Etude

son contexte

calcareous

grounds

o‘ the Gulf of

F., 1987. Stress fields in the European

Geophys.

geology:

Vog-

evolution

Tectonophysics.

Z.. Almagor.

Science,

time of Africa-Eurasia

tion

petroleum

B. and

framework

breakup

A. and Abodi,

the northern

Cochran,

S.A., 1981. Egypt’s

Red Sea margin.

Garfunkel,

Suez et d’Aqaba.

weakness.

Acknowledgements

Abdine,

Rocher.

and structural

Red Sea. J. Geophys.

1979. Continental

Chorowicz,

Orient

A.R.,

703-726.

assume a multidirectional horizontal extension (when u2 = a,), prevailing direction of opening is expected to be perpendicular to major zones of

by Total Proche

Jado,

Z.O.. 1985. Structural

Elat (Aqaba),

Chtnet,

gistic support

H..

W.. 1988. Sedimentary

of the northwest

after a compressional or strike-slip stress pattern (during which u1 is horizontal), then the maximum principal stress axis (a,) became vertical. If we

for the research was provided BAS project. The field-work

the Zeit region, Gulf

2674-2689.

fol-

West European rift. The Oligocene extensional phase is related to the movement of the Africa-Eurasia rotation pole. This movement pro-

crustal

and rifting:

Geol. 7(5): 605-612.

H&J,

genreiter,

Ben-Avraham,

of the European

Late Eocene N-S-directed lowed by Oligocene 1987). This extension

and

J.. 1985. Extension

of Suez. J. Struct.

153 (this vol.): 137-151.

Gaulier,

et al., this

An example

parallel

in the

If a change

motion,

(Garfunkel, would

stress

for

to the regional

the continental

vol.;

explanation

analysis

Late-Cretaceous

2(2): 167-185.

the Gulf

and of

8: 101-108. of the Dead based

on

220

Eyal, M., Bartov,

Y., Shimron.

Sinai-Geological Eyal,

M., Eyal,

tectonic

Y., Bartov,

development

Elat (Aqaba)

Y. and

Freund, Freund,

Nature,

tectonics

1981. The

Nicolas,

of the Gulf of

not,

G. and Folkman, rhomb-shaped

Y..

graben.

of the Red

Sea and

East

2.. 1968. Age and rate of the Dead

Sea Rift. Nature,

220: 253-255. Freund,

R., Garfunkel,

Z., Zak,

I., Goldberg,

B., 1970. The shear along

Philos. Trans.

R. Sot. London,

Z., 1981. Internal

transform

Sea leaky

kinematics.

Tectono-

Z. and Bartov,

Y., 1977. The tectonics

Rift. lsr., Geol. Surv.,Bull., Garfunkel,

Z., Barton,

Raham

in the southern

of the Suez

Y. and

new evidence

Steinitz,

G.,

for Neogene

1974.

tectonism

part of the Dead Sea Rift. Geol. Mag. 111:

Z., Zak, I. and Freund,

R., 1981. Active faulting

the Dead Sea rift. Tectonophysics, P.Y., and Solomon, of mid-ocean

Ocean Gulf

of Aden,

depths and in the Indian

Red Sea. J. Geophys.

Res., 92

B.P.

and

crystalline

Eyal,

basement

M.,

Le Pichon, analysis

X. and

1981.

History

of uplift

of Sinai and its relation

the Red Sea as revealed

to opening

by fission track dating

Francheteau,

of the Red Sea-Gulf

J., 1978.

of the of

of apatltes.

Le Pichon,

X. and Gamier, fault

J.M., 1988. The rotation

of Arabia

system.

153 (this

Tectonophysics,

A new analysis. J. Rodgers,

leading

Roulet,

M.J.,

to Alpine

spreading

Red Sea. Earth.

Red Sea. J. Geophys. Y. and Rabinowitz, F. and Co&ran,

of the northern

Planet.

center

of

Sci., Lett., 60: 117-126. trends in the northern

Red

Red Sea

and tectonics

a continental

margin

A.M.,

dontrees

P., Davies, P. and Molnar, P., 1970. Plate tectonics M.Y. and Kreuzer, H., 1974. Potassium-argon

ages

of Egyptian basaltic rocks. Geol. Jahrb. D9: p. 21-31. Moretti, I. and Colletta, B., 1987. Spatial and temporal evoluGeodyn.,

submitted,

N., 1986. La

nord Mer Rouge (de 25 o N a

gdologiques

de la campagne

et geophysiques

TRANSMEROU

1959. Tectonics

Congr.,

ob-

83. Bull.

20th.

of the Dead

Mexico-Assoc.

Sea Rift.

Surv.

lnt.

Geol.

Afr.,

385-405. Ries,

A.C.,

Shackleton,

in the Eastern

R.M.,

Robson,

Graham,

structures,

desert of Egypt:

R.H.

and

ophiolites

traverse

Fitches,

and melange

26 o N. J. Geol. Sot.

140: 75-95.

A., 1971. The structure

rift, with special

reference

of the Gulf of Suer (Clysmic) to the eastern

side. J. Geol. Sot.

127: 247-276. J.M., Bernet-Rollande,

C., 1983. aux

Signification

tvaporites

Mellaha

du

MC., Maurin,

A.F. and Monty,

sedimentologique

Miocene

(Egypte).

C.R.

moyen

Acad.

et pal&&ogra-

bio-construits prb

Sci.

du

Paris.

associes Gebel

296,

Esh

Ser.

11:

457-462. R., 1962. The Geology

of Egypt.

Elsevier,

Amsterdam,

377 pp. Siedner, from

G.,

1973.

K-Ar

northern

chronology

Israel

and

M., 1986. Uplift

of Cenozoic

Sinai.

Forts&r.

volcanics

Mineral.,

50:

and extension

of induced

mantle

at the Gulf of Suer.

convection.

Nature,

317:

135-139. Steckler,

M.S. and Ten Brink, U.S., 1986. Lithospheric as a control

from the northern Steckler,

on new plate boundaries:

Red Sea region.

M.S., Berthelot, Subsidence

F., Lyberis,

in the Gulf

rifting and plate kinematics. 249-270. Steinitz, G., Bartov,

Earth

strength examples

Planet.

Sci. Lett.,

N. and Le Pichon,

of Suez:

Y. and Hunziher, to the tectonics

X.,

implications

Tectonophysics,

for

153 (this vol.):

J.C., 1978. K-Ar

of some Miocene-Pliocene

their significance

Vail, J.R., 1970. Tectonic rocks

in eastern

(Editors),

150: l-32.

of the Red Sea and East Africa. Nature, 226(5242): 243-248.

tion of the Suez rift subsidence.

of

baa&s

age

in Israel:

of the rift valley.

Geol.

Mag., 115: 329-340.

124: 85-113.

J.R., 1988. Structure Sea: catching

R., 1987. Structure

of the Red Sea. J. Geo-

A. and Lyberis,

axiale du segment

determinations

Res. 89: 11352-11364. P.D., 1986. The northern

Sci..

79: 120-132.

in the Gulf of Elat,

between rifting and drifting. Tectonophysics,

Meneisy,

Quennell,

1988.

and the Dead Sea Rift.Tectonophysics,

McKenzie,

Plate

Geol. Sot. Am. Bull., spec. vol. in honor

Mart, Y. and Hall, J.K., 1984. Structural

Martinez.

1988.

belt formation:

Spec. Pap., 218: 111-131.

Y., 1982. Incipient

northern

F. and

and tectonics

Temoin-clP

C. R. Acad.

46-474.

P., Coutelle,

28 o N). Nouvelles

variations

X., Bergerat,

kinematics

Mart,

dkpression

Steckler,

of Aden area. Tectonophysics,

vol.): 271-294. Le Pichon,

and early rifting

G., Guennoc,

Indications

the Levant

F. and Montigny,

island

R. and Guen-

Jean):

129-130.

A plate-tectonic

46: 369-406.

Mart,

A., Boudier.

phys. Res., 92 (Bl):

Said,

(B2): 1361-1382.

and

Nicolas,

(Saint

phique des divers types de carbonates

ridge earthquakes

and

in

80: l-26.

S.C., 1987. Centroid

mechanisms

Kahn,

1063-1068.

Rouchy,

55-64. Garfunkel, Huang,

Paris, 301(4):

London,

71: l-44.

J., Eyal,

conglomerate,

N.. Montigny.

en Mer Rouge.

W.R., 1983. Pan-African

80: 81-108.

Garfunkel,

precoce

Geol.

of the Dead

to place

F., Lyberis.

Sot. G&o]. Fr., 8, II: 381-399.

M., Weissbrod, the Dead Sea rift.

267: 107-130.

structure

(rift) in relation

physics,

A., Boudier,

in the Gulf of Suer. Proc.

Cairo

R., 1985. LCle de Zabargad

tenues au tours

T. and Derin, Garfunkel,

Sem.. E.G.P.C.,

de l’expansion

Pautot,

along

A.M., 1976. Block faulting

Zabargad

228: 453.

movement

Moustafa,

5th Explor.

5(2): 267-277.

R., Zak, E. and Garfunkel,

the sinistral

1980.

80: 39-66.

of the Bir Zreir

R., 1970. Plate

Y.K.,

G.,

margin

Y., Stein&,

Sinai. Tectonics.

Africa.

Steinitz,

rift. Tectonophysics,

1986. The origin

Bentor.

Geol. Surv. Israel.

of the Western

Eyal, Y., Eyal, M., Bartov, Eastern

A.E. and

map, l/500,000.

African

control

Africa.

of Sykes and related irruptive

In: I.N. Clifford

Magmatiam

and

and Tectonics,

I.G. Gass vol. A. pp.

337-354. Webster,

D.J. and R&on,

N., 1982. Post-Eocene

of the Suez Rift in South-West Sem.. 1: 276.

Sinal, Bgypt.

stratigraphy 6th E.G.P.C.