Sedimentary and structural evolution of the northwest Arabian Red Sea margin

13:

~e~t~no~hy~j~, 153 (1988) 137-151 Elsevier Science Publishers B.V.. Amsterdam - Printed in The Netherlands

Sedimentary and structural evolution of the nurthw~st Arabian Red Sea margin H.-J. BAYER, H. HijTZL, AX JADO, B. ROSCHER and W. VQGGENREITER Geobgisches Institut, Uiriuersitsirkkrkruhe, Kaiserstrasse f2, O-7500 Karbuhe (I? R. G.) {Received May 1,1987; revised version acceptedJanuary

4.1988)

Abstract Bayer, H.-J., H5t& H., Jade. AR., Roscher, B. and Voggenreiter, W., 1988. Sedimentary and strnctura1 evotuton of the northwest Arabian Red Sea margin. In: X. Le Pichon and J.R. Co&ran (Editors), The Gulf of Suez and Red Sea Rifting. Tectonophysics, 153: 137-151. An investigation of the northwestern margin of the Arabian peninsufa (Midyan region) provides new insights into the two-stage development of the Red Sea graben system: the early Red Sea-Suez stage and the later Red Sea-Aqaba stage. The early stage is characterized by the passive subsidence of a continental gtaben since the Early Oligocene. kfier a period of enhanced subsidence of the basin in the Early Miocene this stage ended at the Langhian/Serravaiian boundary (14 Ma). The later stage was initiated by a release of stresses by strike-slip movement along the newly formed Aqaba-Levant transform. Creation of the new plate boundary was accompanied by stagnation of extension in the Gulf of Suez branch of the early rift stage. Strike-slip motion on the Aqaba-Levant structure is younger than 14 Ma and is recorded ay the post-Langhian compressional structures in the area of the Midyan peninsula, which developed by transpression along the curved path of a left-lateral strike-slip fault.

IntwhUion

Continental rifting and development of graben structures characterize the initial stage of the Wilson cycle and are essential to the theory of plate tectonics. Recently introduced ideas fcx the evolution of rift systems include the half-graben concept (Bosworth, 1985; Bosworth and Gibbs, 1985; Rosendahl et al., 1986) and the normal simpleshear model (Wernicke, 1985). The Red Sea permits a study of the evolution from a continental rift to a passive continental margin, A joint scientific project between the King Fahd University of Petroleum and Minerals in Dhahran (Saudi Arabia) and the University of Karlsruhe (F.R,G.) offered the possibility to study the Arabian margin of the Red Sea. This paper deals 0040-1951/88/%03.s0

0 1988 Elsevier Science Publishers B.V.

with the sedimentary and tectonic evolution of the Northern Red Sea as well as with the development of the Aqaba-Levant structure. The results are based on field investigations in the Midyan area opposite to the Sinai (Fig. 1) and along the narthwestern part of the Arabian Red Sea margin. Stratigraphy arnd facies of Cenozoic sediments Prior to this ~nves~g~tion limited data were known on the Cenazoic sedimentav sequence along the Saudi Arabian side of the Red Sea. Therefore stratigraphic and facies studies were carried out to aid the tectonic investigations (Dulfo et al., 1983; Bayer et al., 1986; Roscher et al., 1988). The stratigraphic results and a facies model are summarized in Fig. 2. For a detailed deserip-

exposed quence

in

the

Midyan

represents

area.

a generally

of the axial part of the graben

The

Midyan

deeper marine (cf. profile

in Fig. 2). The age of these sediments units

and Hotzl,

can be distinguished

5 and 6

ranges from

34 to 14 Ma (Rupelian-Serravalian). mentary

sef’acies

Four (camp.

sediPurser

this vol.). They are in turn overlain

the Plio-Pleistocene

by

deposits.

Sharik Formation This basal elastic red bed unit is approximately 300 m thick. It is known

from the entire northern

Red Sea area. Its age is still unknown.

Musayr Formation

Fig. 1. Sketch map of the northern I-Precambrian Quatemaq; tion

basement;

4 -Tertiary

Red Sea-Gulf of Suez area.

2-Mesozoic;

J-Neogene

and

to recent volcanics.

of the sedimentary

successions on both sides of the northern Red Sea compare Purser and Hotzl (this vol.), where two lithostratigraphic profiles are presented for this area. Pre-rift succession Cretaceous-Paleogene sediments are both continental and marine. In contrast to the Egyptian margin of the Red Sea, where prerift sediments are widespread, the pre-rift sequence on the Arabian side is confined to tectonically depressed areas (Usfan, Azlam, and Aymmah grabens). A younger Paleocene-Eocene pre-rift succession, comprising the Usfan- and partly the Shumaysi formations signifies the marine facies of a transgression from the Mediterranean Sea. The uppermost part of the Shumaysi formation (Middle Eocene) already shows synsedimemary extensional tectonics. Syn-rift sequence On the Arabian Red Sea margin Ghgocene and Miocene syn-rift sediments are well preserved and

This unit consists mainly of carbonates with a thickness of approximately 60 m, which alternate with sandstone beds. Benthic Foraminifera fauna in the lower limestone beds indicate the pianktonic zone N2 (Blow, 1969). The upper limestone beds are probably equivalent to the planktonic zone N3. The Musayr Formation cmmspnds to the Abu-Zenima Formation of the eastern Gulf of Suez, to which an Oligocene age has been assigned (Stratigraphic Subcommittee of Geologic Sciences -NCSC, 1976). This age assignment for the Musayr Formation is strengthened by the occurrence of reworked Oligocene planktonic foraminifers (Nl/N2) at the base of the Nukhul Formation in a borehole near Hurghad~ Egypt (El Shinnawi, 1975).

Nutaysh Formation This formation is characterized by an a&emating succession of sandstone, marl and s&stone. Its thickness is about 300 m. A coralhne limestone in the central part of the sucxtession has been dated as Burdigalian (planktonic zone N6) by foraminifers. The upper part of the Nutaysh Formation corresponds with the Nukhul and Rudeis formations in the Gulf of Suez (El H&y and Martini, 1981; cf. profiles 3 and 5 in Fig. 2). The lower part of this unit, however, has noequivalent on the western side of the Gulf of Suez. Foraminifera in a local interc&tion of coral lime-

......-..

posfflon

.

dwng

Olfgowne

- Middle Miocene

ttme marker

Fig. 2. Facies patterns in the Gulf of Suez-Northern Red Sea area during the Oligocene and Miocene. Stratigraphic corrt:lation based on the sections: f-Abu Girfan (NCSC 1976), 2-Myos-Hormos well (El-Heiny and Martini, X981), f-GebeI-Zeit well (El Heiny and Martini, 1981), d-Midyan (Bayer et al., 1986). 5-Dhuba (Bayer et al., 1986).

stones have yielded an Aquitanian age for the lower part of the Nutaysh Formation (Dull0 et al., 1983). Bad Formation The Bad Formation is ~h~a~te~d by a cyclic alternation of marl-shale and gypsum-anhydrite beds with a total thickness of about 300 m. In the upper part limestones with corals and limestones with ~~~~~~~~~are inter-bedded. The Gfobigerina fauna of the Bad Formation belongs to the zone of Orbulina suturalis-Globorotulia fahsi peripheromzda in the Gulf of Suez (El Heiny and Martini, 1981) and corresponds to the phurktonic zone N9 (Blow, 1969). The Nulliporu limestone at the top contains Miogypsina cf. antillea, a species confined to the planktonic zone NlQ (Clarke and

Blaw, 1969). A Former age designation of the Nzdlipora limestone as Upper Miocene (Torton&n; Dullo et al., 1983) thus has to be revised. The Bad Formation is equivalent to the Kareem Formation of the Gulf of Suez. With these new stratigraphic results, correlation of the Tertiary Midyan sequence with the sediments of the Gulf of Suez is possible (Fig. 2). Despite local facies variations, a synoptic view of the stratigraphic profiles reveals a distinct trend. By putting individual facies domains into their proper time frame, a reconstruction of the graben sedimentation in time and space is possible, taking into account that several of the facies are diaehronous. For the appropriate reconstruction of the pre-Serravalian facies pattern (Fig. 2) the Saudi Arabian Red Sea coast was moved back to its Middle Miocene position (cf. Fig. 2, Fig. I).

140

Ifal Formation This elastic formation is of Pliocene age and overlies the Miocene sediments of Midyan and the Red Sea coast with an angular unconformity. Particularly on Midyan coarse elastic material with a thickness of more than 2000 m indicates the onset of strong tectonic activity. Further to the south along the coast conglomerates and sandstones are progressively replaced by the calcareous sediments of littoral and near offshore facies. Echinoid assemblages from Midyan indicate a Pliocene age for most of the lower Ifal succession while foraminifers from samples of the middle part of the series indicate Late Pliocene age (Roscher et al., 1988). An age up to Early Pleistocene would therefore be possible for the sequence. Quarternaly Marine and terrestrial terraces at different levels, in general up to elevations of 50 m at the coast site, form the youngest sedimentary sequence. They overlie the sediments of the Ifal Formation in pronounced unconformity. Continuity of tectonic activity is documented by basinward tilting of older terraces and vertical displacement even of the youngest terraces in the Gulf of Aqaba. Structursl development

Pre-rifting (Precambrian-Eocene) The Arabian-Nubian Shield received its main tectonic imprint during Late Precambrian orogenie phases. Dike swarms in the northern part of the shield reflect post-erogenic extension. One of the most important tectonic features generated at that time is the NW-SE &king Najd fault system (McMahon Moore, 1979). During the Paleozoic and Mesozoic the sedimentation on the shield was influenced by a large E-W trend&g antiform (Arabian Homocline) in the central parts of the shield. Folds of the same age displaying long wavelengths and small amplitudes have also been described from North Africa (IUitzsch, 1970). Along the recent margin of the Bed Sea, halfgrabens and grabens trend NW-SE (strike of Najd

fault system) and NNW-SSE. They contain Cretaceous and Eocene pre-rift sediments. Particularly the Azlam half graben fits as counter image of the Duvi half graben on the Egyptian side if the two margins are palinspastically restored to their initial configuration. The existence of such half grabens, slightly oblique to the present Red Sea trend, could indicate a pre-Oligocene tectonic activity along reactivated NW-SE trending basement faults, but could also reflect initial Red Sea-related rifting. This problem is not yet resolved. Rift stage I: Red Sea-Suez cene-Middle Miocene)

stage (Early O&o-

Rift initiation The age of the earliest symift sediments indicates that rifting started in the Early Oligocene. The oldest graben sediments in the Midyan area are older than 31 Ma (Dull0 et al., 1983; Bayer et al., 1986). The early stage of the graben development appears to have been characterized by normal faulting. Individual fault blocks were downwarped and antithetically tilted. The oldest marine strata are limited to the eastern side of the graben and have a Late Oligocene (Chattian) age. They were deposited over fault blocks antithetically tilted to the east (cf. Jabal Hamdza in the Midyan peninsula-Dullo et al., 1983; Jabal Dhaylan-Vasquez et al., 1981). The facies correlation (Fig. 2) indicates a distinctly asymmetric graben development. The first marine ingression in the Gulf of Suez-Northern Red Sea area proceeded from north to south. At the same time lacustrine sediments of the Baid Formation (Oligocene-Earliest Miocene, Schmidt et al., 1982) were deposited along the Arabian margin south of Jeddah. This suggests that the marine ingression during the Oligocene and the Aquitanian probably did not yet reach the southem part of the Red Sea region. Subsidence and uplift in the Lower Miocene In the Aquitanian unconformities and increasing rates of sedimentation suggest a remarkable tectonic accentuation of the graben development.

141

Synthetic

downwarping

of blocks

for this time. In connection sion, subsidence the graben ing

of the graben

shoulders

erosion

and

account

of tilted

facies

of tilted types.

disappeared Miocene

fault

1975) blocks,

had been eroded

The pattern verse

The

with

fringing

exten-

and uplift

of

by increasfaulting.

Re-

fauna at the base of Burdigalian

(El Shinawy,

sediments

basin

was accompanied synsedimentary

worked Oligocene sediments

can be inferred

with increasing

indicate,

that

previous

on

graben

blocks

time.

led to highly

di-

subsequently

Widespread

Lower

reefs, often with strong sedimen-

tary dipping of the talus regime and accretion to fault planes mark an increase of sealevel up to the Early

Langhian

(-16

Ma). In general

fault block

geometry was governed by new normal faults parallel to the graben and reactivated NW-SE to N-S trending basement faults. While the northern part of the Red Sea graben shows more or less symmetric tectonic block development at both sides of the graben, an asymmetric block rotation to the west must be considered for the southern part of the Red Sea. This asymmetric development in the south supports a Wemicke type-model for the evolution of the southern Red Sea (Voggenreiter

opment

event.

et al., 1988).

Sedimentary overlap during the Middle Miocene Until the Middle Miocene, all features typical of graben tectonics, such as small scale antithetic faults related to synthetic normal faults and splays related to reactived faults, were well developed. Caused by an eustatic sealevel rise the Miocene sea reached its largest extension in late Burdigalian to Langhian time (18-15 Ma). Subsequently a main phase of regression followed. Marls and evaporites related to the transgression conformably overlie medium to fine-grained

Subsequently

try. While the eastern yan

area

erable

reached

length

(Hurghada,

segment

above

offshore

sediments

probably

related

on

the

of

missing

eastern

to a major

Red

to

Upper

side

and

rearrangement

in the Red Sea-Gulf

Rift stage II: Miocene-Recent)

of

about

(cf. Fig. 2) appears

consequence

Miocene kinematics

deposition

et al., 1986). The resulting

facies pattern a

area

a new phase of subsidence

12 Ma ago (Colletta mainly

the Mid-

for a consid-

of time, the Egyptian

during

by asymme-

including

sea level

Jebel Zeit) saw renewed

evaporites

be

the facies devel-

once again was characterized

asymmetric

and redeposited.

differences

post-Kareem

is of

of Aden area.

Sea-Aqaba

stage

(Late

Initiation In the Late Miocene the kinematics of the Red Sea area changed from passive rifting with extension in a WSW-ENE direction to sinistral shear along the NNE

trending

Aqaba-Levant

transform

(Fig. 3) and accompanying opening of the Red Sea due to the oblique drift of the Arabian plate. This rearrangement

led to stagnation

of extension

and subsidence in the Gulf of Suez and. created a new plate-boundary, the Aqaba-Levant structure. The beginning of strike-slip movement along the Aqaba-Levant

structure

postdates

the Lan-

ghian (ca. 14 Ma) sediments of Midyan. On the other hand the sedimentation of the Plocene Ifal Formation was influenced by sinistral strike-slip faulting. It is likely that the evolution of the Aqaba-Levant transform is the result of the interaction of several processes. The Red Sea-Suez graben at its northern tip interacted with the Mediterranean margin. Vink et al. (1984) have

elastics of the Lower Miocene. The earlier tectonic relief became more and more subdued. In the Middle Langhian (15 Ma) the facies patterns pro-

suggested that because the strength of oceanic lithosphere exceeds that of continental lithosphere, strain rates are expected to be significantly

graded offshore and extensive precipitation basin.

higher in continental than in oceanic lithospheres. Thus, strain rates at the northern end of the Gulf of Suez were not intense enough for a complete release of the extensional stresses associated with the Red Sea rifting (Steckler and Ten Brink, 1986). The increasing stresses in the Gulf of Suez area

a general regression led to of gypsum in the graben

Near the Langhian-Serravalian boundary (14 Ma) this regression reached the deeper parts of the graben,

described

by Colletta

et al. (1986) as the

142

Red

0

Quaternary

B

Cretaceous

m

Tertiary

/3$&g Cambrian-Jurassic

E

Barali~c dtkes

Sea

tb%tamorphwd

Precambrian: m

Granilotd

@g

Weakly rocks

m%G

rocks

(1985),

map of

Eyal et at. (1980,

the

1

md u’trsbasic

mtamrphossd 0

10

M

GnTwan.

Fig. 3. Gdogic

I, I

rocks

30 H-J &“U

40

Cartog@”

Northem Red Sea-G&f ef Aqaba rcgism, compiled from Bawkr (1968). Fhmkamp 1: 500,000) and field imesti~~s of tih3authors.

1 Xlb”

A RLIB

et d. (1%3), Ckk

Sinai Map

were finally releasedby a shear zone in the weakest part of the surround&g liw. The path of this new fracture possibly was guided by a pre-ex-

isting structural element in the Wadi Araba-Dead sea area. This stlllcturd lilxmmt, an OkIezhalf graben or graben has been mentioned by various

GLIGOCENE

_ MIOCENE

PRECAMBRIAN

&

-

L

_

4

c

IIAJOf4

ANTICLINAL

AXIS

MAJOR

SYNCLINAL

AXIS

AWTICLINES

_X_&4VNCLINES MAJOR /STRIKE

STRIKE* SLIP

STRIKE

AND

SLIP

FAULT

FAULT

DIP

OF

STAATA

c Y

01466f6 irtkrn Fig. 4. Teetonic map of the Midyan petist.t~a. rotated crystalline Plio-Pleistocene

bIo&s.

-

The central part is occupied by an at~ticlinal updoming, built up by ix&ted

These bfocks are surrounded by an Oligocene-Miocene

and

sedimentarycover. East of the anticline the

sediments of the Ifal basin show folding and faulting caused by the narrowing of the basin.

144

geologists of the Middle East (compiled by Bender, 1968; 1974). Another tectonic process which might have influenced the change in the Red Sea area was the beginning seafloor spreading south of the Arabian plate. Oceanic accretion in the Gulf of Aden started approximately lo-12 Ma (Cochran, 1983) ago. The resulting northward drift of the Arabian plate possibly initiated the strike-slip motion along the Aqaba-Levant transform. The synchronism of both events can hardly be considered as simple coincident.

Midyan transpression Although a connection between an ENE-WSW striking transform fault in the Red Sea and a NNE-SSW striking tensional segment in the Wadi Araba-Dead Sea region provided a means of movement of the Arabian plate, it caused much deformation in the local frame between southern Sinai and the Midyan peninsula (Figs, 3 and 4). It was necessary for the connecting fractures to follow a curved path between the Red Sea transform and the northern structure (Fig. 5). The triangular shape of the Midyan peninsula was the result of this newly formed plate boundary between SinaiPalestine and Arabia. During northward motion of the Arabian plate the Midyan peninsula was pressed against southern Sinai due to the curved line of separation (Fig. 5-l). The Midyan peninsula was the mechanically less resistant part during this transpression. Compressional structures in several outcrops of the Midyan peninsula indicate multiple deformations. The tectonic map of the Midyan peninsula (Fig. 4) shows two large fold structures approximately parallel to the Aqaba system, the West Midyan anticline and the Ifal syncline. With a total amplitude of about 4000 m they correspond to a shortening of Midyan by about 2 km in an E-W direction. In addition the transpression along the convergent part of the major strik&ip fault caused a shear fracturation of the Precambrian basement of Midyan. Shear deformation with important dextral strike-slip movements along E-W fractures and sinistral shear along N-S fractures, which

Fig. 5. Evolutionary scheme for the tectonic development of the southern extent of the Aqaba-Levant strike-slip zone (Midyan-Sinai area) for the last 14 Ma. Special emphasis is drawn on transpressional deformations of Midyan along the curved path of the strike-slip fault. 1. Initial fracturation along a curved path. 2. Intense- deformation. ‘Ibe West Midyan anticline and the Ifal syncline, E-W trending strike-slip faults, rotation of crystalline blocks and small-scale thrusts are formed. 3. Continued deformation with block rotations and the formation of a secondary shear pattern. 4. Late stage of transpression. Only southwest Midyan with Tiran and Sinafra islands are affected; at the same tune opening of rhombed shaped segments (pull-apart basins) north of the curved fault-bend.

also effected the Tertiary sediments, can be observed (Fig. 5-2). The original& antithetically tilted crystalline blocks were rotated counterclockwise partly up to 70 o (Fig. 5). AI&ough most of the compressional structures are hidden below the plastically deformed evaporitic cover, they are clearly visible in erosional cuttings on the central part of West

145

Midyan.

Typical

cataclasites, the western

for the edges of the blocks

like those found

vicinity

of the cataclasite

sedimentary

4). Along

small-scale Museir

zones, minor

eastern

tensional

downfaulting

patterns

between

side

features Jabal

in the continuation

in the

folds in the

faults are typi-

side of the Midyan

the

and

and Jabal Amrah

fracture

cover and local thrust

cal for the western (Fig.

at the northern

sides of Jabal Tayran

block (Fig. 5). Small-scale

are

Hamdza

and

sedimentary

intercalated

From

the very young

in the southwest position

comer

(together

with

compressional of Midyan Tiran

re-

part

(e.g.,

north

of Tiran,

Jabal

leased faulting

Recently by

pure

strike-slip

structures and its close

island)

curved

and

layers

acted plastically.

form.

Tayran

fill was partly

gypsum

of the stronger

of the blocks,

of Jabal

out and

seems that this part is just passing

anticline

developed

the Ifal basin the young squeezed

to Sinai

the eastern

of the Aqaba stresses

movements.

occurs along the opening

it end

transare

re-

Normal

pull-apart

basins

Jabal Amrah).

of the Gulf of Aqaba.

Along the western side of the peninsula SEand E-vergent thrusts, locally with displacements in excess of several hundreds of metres, were

yan area are summarized in Fig. 5 as an evolutionary scheme. Figure 5-l shows the breakthrough of

related

to the

prominent of Jabal Magna,

overall

transpression.

The

most

thrust fault exists along the eastern side Faydah (south of the coastal village Fig. 4). Here

the Precambrian

rocks

of

Jabal Faydah were thrusted over Lower Miocene sediments of the Nutaysh Formation. As the shear pattern indicates, in a later stage of the transpression, the small southwestern part of Midyan had to pass along the curved fault line. This was achieved along new strike-slip faults. During this process, the distance between Midyan and Tiran was tilted

Island (Fig. 5-4) increased and Tiran and uplifted. North of the transpres-

sional zone the main strike-slip fault became so that rhombed shaped graben segments Avraham,

1985) were

formed.

These

leaky (Ben

pull-aparts

developed by extension in a N-S direction between individual branches of the main transcurrent fault. Subsequently the connection of three pull-apart basins (Fig. 3) and ingression of seawater from the south formed the Gulf of Aqaba. The irregular deformation of the Ifal sequence in the vicinity of the West Midyan anticline (Fig. 4) confirms the continuation of the compressional deformation at least up to the latest Pliocene. Some authors (Bokhari, 1981; Clark, 1985) suggest, that these structures are due to salt diapirism. But neither the known facies distribution nor two deep wells south of the Ifal basin (Bokhari, 1981) suggest the existence of subsurface salt there. Folds and faults within the Pliocene sediments fit into the general compressive deformation pattern of this area. It seems that by further shortening of

The transpressional

a new fracture in the northern

deformations

of the Mid-

system between a transform Red Sea and a preexisting

ture in the Wadi Araba area. Fault-bounded of central Midyan (Tayran-Hamzda, Tiran)

are restored

to their original

fault strucblocks Amrah,

position.

Due

to the strike-slip movement along the curved fault, transpressional deformation began (Fig. 5-2). The further development is sketched in Fig. 5-3 and 5-4. These figures represent the time period about Early Pliocene to Middle Pleistocene. the whole

period

the regional

stress

pattern

from For re-

mained more or less constant. The schematic drawings in Fig. 5 do not include the deformations of Sinai. As the more resistant counterpart of this transpression

Sinai was uplifted

(Kohn

and

Eyal, 1985). Feather faults opened in a NNW direction (according to local shear-stress patterns) and NNE-trending strike-slip faults were generated on the eastern side of Sinai (cp. Fig. 3). Small elongated crustal slices were sheared along each other following the sense of the mair. strike-slip fault (Eyal et al., 1981). These segments form a wide shear zone with decreasing rates of displacement to the west. A reconstruction of the graben the previous Red Sea-Suez rift further details for the understanding

margin during stage provides of the defor-

mation pattern observed in Midyan. Figure 6 shows the coastal section between Yanbu and Sinai as well as the main fault pattern of that area. The previous coast is delineated by the Lower Miocene fringing reefs, indicating the early morphologic expression of the graben margin. The

NE-F?f#3 SEA 4#iMRZiN Miocene and rfmmt situation

m

Coastal

a

Mafic Metavolcanics

-

Fault

-H+-

Tertiary

m

Ciraben feature

114 -.-----: -..__..:

Miocene CWsg&f_

plain

hssslt dike

fringing

reef

&&&

Fig. 6. Tectordc setting at the northeast Red Sea mergh.~with major basement faults (Bramkamp et at. 1%3) and Tertiary basaltie dikes(Eyal et at., f980,1981; Cfmk, l9IkS).Lower hdiaccnt reefs delixmte the former ca&gur&w of the gnibkm margia. L)Aiaiions in fault trends in Midyamare cmsed by drag along the skdstral transform accomwed by &em&g of the bas&meat(cf. the two enhmced cuttings). By the mxmstruction of the Lower Miocene the,mm~t u.n& NE-trending border line of the cqstdiim. block, north of Maqna proves to be a part of an old NW-strikingfault.

rec;til,inear trend of the graben margin to the north-northwest is interrupted by trmsverse faults (Yanbq south of Al Wab, A&in, Aymm&& foIlowing E-W and ESE-WNW trends of basement faults. Together with displacements atong smth-

ward j&r&g grabens, tremIing NNW, t&y may indicate a greater opening rate to the so&. Restoring Mdyan ~~~~~a~y by about 100 km along the Aqaba-Levant transform, not c&y the coast Iine of Arabia and Snai, but alsa a zone

147

of

basic

metamorphic

cambrian

rocks

within

as well as Lower Miocene

(Bran&

et al., 1963;

Sinai as 18-21

Clark,

the

basaltic

1985)

Predikes

dated

on

Ma (Eyal et al., 19981) fit together

Due to sinistral

basement

ward, so that originally faults

was dragged

WNW-trending

and metamorphic

zones

(cf. upper

lower

westerly Further

and

bending

boundary

now trend inset

to the north NW-trending

show a gradual

south-

to western

south-

in Fig.

basement

6).

faults

and southwest-

ern directions by approaching the Aqaba shear zone. A dragging effect for this bending was already

For

suggested

by Clark

(1985)

while

the

spreading

the two

southern

(Voggenreiter

and Styles, propagation

from

several

magnetic

anomalies. of

troughs

In contrary 24” N.

with

associated are

(1383)

(1985) suggest

tinental

crust for this area. only injected Geochemical

1980).

such features

Cochran

thinned

1975;

can be deduced

Bonatti intrusions.

seafloor

15 O30’ N to

1974; Styles and Hall, and

al.,

spreading.

active

from about

of spreading

deeps

north

oceanic Sea

et

N for the last 5 m.y. (Roeser,

Axial

missing

Red

is documented

21°00’

Girdler

shear along the Aqaba-Levant

the Midyan

convection

1988), which may have induced

about

(Fig. 6). system

asthenospheric

and

and stretshed

studies

con-

by basaltic

of basalts

from

the northern Red Sea also suggest the absence typical oceanic crust (Altherr et al., 1988).

of

western most crystalline blocks (cf. small lower inset of Fig. 6) are completely separated and displaced

in a sinistral

Transform

sense.

North Rifting and spreading

The development

of the Red Sea graben

during

the second stage of rifting was less dramatical than the development of the Midyan area with its superimposed convergent shear movement. In contrast to the Gulf of Suez, which now was decoupled proceeded

from the main graben, the in a more or less continous

The widening Miocene was

Red Sea opening.

of the graben during the Late above all directly related to the

oblique strike-slip movement of the Arabian plate along the Aqaba-Levant structure. The calculated lateral displacement of 107 km (Quennell, along the Aqaba-Levant transform resulted

1959) in an

additional extension of about 70 km perpendicular to the axis of the Red Sea. This opening led to gravitational sliding along listric normal faults, synsedimentary tilting and development of angular unconformities within the Plio-Pleistocene sedimentary sequence. The Island of Hasani, west of Umm Lajj, is a typical example, where a listric normal fault caused an antithetic tilting of a Plio-Pleistocene reef platform which forms a steep ridge emerging more than 100 m above sea-level. Stretching of the lithosphere probably led to a passive upwelling of the asthenosphere. The decompression and juxtaposition of hot asthenosphere against cold lithosphere possibly triggered

movement

of the Arabian

of Sinai/Midyan,

the main

plhte

strike-slip

fault probably used (Wadi Araba-Jordan

a pre-existing graben zone valley). The main strike-slip

fault, striking

to this graben

oblique

became

twice

displaced so that pull-apart basins could develop (the Dead Sea basin and the Lake Tiberias basin -Garfunkel et al., 1981; Bayer et al., 1986). The Aqaba-Levant zone connects the tensional setting of the Red Sea with the zone of convergence at the northern part of the Arabian plate and in the Anatolian chains. Collision between Eurasia and Arabia took place during the Middle and Late Miocene and resulted in final closure at the end of the Miocene. During the Middle Pleistocene bending (mega-kink) in the Lebanon

a huge fault region erected

the Lebanon and Antilebanon mountains; zoic folds in the Palmyra belt (southern

MesoSyria)

became compressed and steeply refolded (Wolfart, 1967). Intense basaltic volcanism in the AS Shamah plateau accompanied this process (Barheri et al.. 1980). Internal shear movements in the Anatolian plate (Sengor, 1979) released compressional stresses in the north, however, a high Imount of compressive stress also affected the northern part of the Arabian plate. In the area around Damascus and Amman, continuous compressional superpositioning of former E-W trending normal faults determine the tectonics there, since Late Pleistocene time (Beynon and Donahue, 1982).

Conclusions

Table 1 summarizes the development of the northern Red Sea area which is also shown in Fig. 7 as an evolutionary scheme. For the evolution of the southern Red Sea, especially for the kinematic development of the southwestern Arabian continental margin we elaborated on the Wemicketype model of simple-shear (Fig. 7a, b) (Voggenreiter et al., 1988). According to this model the Red Sea rift could be originated by extension along a low-angle detachment plane dipping to the northeast. This part of the Arabian margin is characterized by a basic dike swarm, several generations of normal faults and a monoclinal downwarping towards the Red Sea. Only a young set of

normal faults, which accomplishes the uplift of the escarpment dips towards the Red Sea. Along the northwestern Arabian margin the oldest extensional features during the Oligocene were mainly E-dipping normal faults. These faults were subsequently overprinted by west-dipping normal faults. The similarity suggests that the simple shear mechanism of rifting probably was also acting in the Gulf of Suez-northern Red Sea area (see Perry and Schamel, 1985). However, there seems to be a discrepancy in the timing of the shoulder uplift, which probably occurred earlier in the north than in the south. More recently models with alternating dips of detachment zones have been discussed for the Gulf of Suez (Perry and Schamel, 1985) and the

Fig. 7. Evolutionary scheme for the ttctogic development of the Nor&em Sea-Suez rift stage (Oligocene-Miocene). transcurrent

Hypotktical

movement aiong the Aqaba-L.evant

left-lateral displaoement along the Aqaba-Levant

low-at@

Rad Sea, Gulf of Suez and Gulf of Aqaba area. a, b. Red

shear zone after Vogsenreiter et al. (1988). c. Initiation of the

system (Middle Miocene).

d-f.

Various stages with increasing akounts

fault. The southern extent of the fault (southern Sinai and Mdyan

shows transpressional tectonics (Middle Miocene-Pliocene,

of

peninsula)

in the soutbwestem part of Midyan up to the younger Pkistocene.

149

TABLE Tectonic

Acknowledgements

1 evolution

the northwest

of the Red Sea deduced

Arabian

from evidence

of

We wish to acknowledge

margin.

Foundation, Age

Events

part

(Ma) - 42

movements

(Shumaysi - 34 31

Oldest

in

pre-rift

sity of Karlsruhe

sediments

University

Formation)

syn-rift

for

deposits

First

marine

ingression

part

of the Red

in the central

Sea graben

and eastern

(Musayr

18 or 15 14

Increased

tectonic

rapid extension

sidence of the graben,

uplift of the graben

intense

and tilting

blockfaulting

Mid-clysmic

on the Arabian

Post-Kareem

event:

of Midyan

shoulders,

side, until now

of the

regression.

Red

Sea

Continuation

transpression

onset of strike-slip

Begin of active

reading

transform

seafloor

movement and

along

beginning

to

Altherr,

for

spreading

Sea; enlargement development - 2-l

Formation the northern pressional in northern

spreading

in the Gulf

in the southern

of the Aqaba-Levant

of pull apart

of

all

for their was pro-

SFB 108, ccntribution

zone with

of E-W

F., Puchelt,

activity

H. and Haumann,

A.,

in the Red Sea axial trougl-evi-

large

mantle and

diapir?

In:

the Red

E. Bonatti

Sea Rift.

(Editor).

Te:tonophysics,

150: 121-133. Barberi,

F. et al., 1980. Recent its implications

Dead

Sea shear

Bayer,

basaltic

volcannm

on the Geodynamic

zone.

In: Geodynamic

Rift System-Int.

of Jordan

h story

of the

Evolution

of the

Meet. Atti Convemi

Lincei,

Naz. Lincei, 47: 667-683.

H.-J.,

Ostsaum

1985. Kollisions-

und Kompressionstektonik

am

des

Aqaba.

74:

Golfes

von

Geol.

R undsch.,

599-610.

part of the Aqaba-Levant Jordan

Red

basins

of the Lebanon-Antilebanon overprinting

Sea group”

of the manuscript

Island

Afro-Arabian of seafloor

providing

and their help in the

Eisbacher.

R., Henjes-Kunst,

Acad. Begin

Dhahran,

and

References

and

peninsula

Aden -5

Fahd

also like to thank

of the “Red

field. Critical

Zabargad

of the Midyan

studies

in discussions

by G.H.

as and

King

and Minerals,

field

contributions

dence

Aqaba-Levant

We thank

We would

1988. Volcanic

event.

Midyan-event:

support.

vided

Ma and pre-5 Ma:

Post-14 the

and sub-

side

termination

widespread

the

project “Stress

no. 231.

event on the Egyptian

no indications

Suez rift-stage;

10-12

activity:

logistic

Project

(SFB 108) at the Univer-

of Petroleum

sponsoring

Research

the research

Research (F.R.G.).

our colleagues

Formation,

Midyan) 23

which funded

of the Special

strain in the lithosphere” Syntectonic

the German

-striking

bending

in

Bayer,

H.-J.

et al., 1986.

Sediment&e

zone; com-

wicklung

fault zones

band

1984-1986,

und

Spannungsumwandlung

and in Syria

des nijrdlichen

Karlsruhe,

und Meer

stnkturelle Grabens.

Sonderforschungsbereich in

der

Ent-

Berichts-

108: Spannung Lithosphlre,

Univ.

pp. 893-918.

Ben-Avraham, Elat

Roten

Z., 1985. Structural

(Aqaba,

Northern

Red

framework

of the Gulf

of

Sea). J. Geoplys.

Res.,

90:

Z., 1986. Character

of trans-

703-726. Ben-Avraham,

northern Red Sea basin (Martinez and Cochran, 1988). Since there is no evidence for bipolar asymmetries in the southern and central parts of the Red Sea, it is possible that opposing sets of half grabens are only associated with immature rifts (e.g., East African Rift, Gulf of Suez). With increasing rates of extension one system may prevail for reasons not yet known and a unipolar mechanism of simple-shear might take over. Traces of the formerly opposing sets of detachments could become obscured by further development (subsidence, sedimentation).

verse

Z. and Garfunkel,

faults

in the

Elat

pull-apart

basin.

Tectonics,

5:

1161-1169. Bender,

F., 1968. Geologic

(Editor),

Beitrage

Bomtraeger, Bender,

von Jordanien.

zur Regionalen

the Wadi Araba, D.E.

Donahue, Progr.,

B., Dercourt, ocean

Map of

BlO: 11-62.

J., 1982.

Tectocic

effects

Dead Sea plain, Jordan.

14, 1982-7:

of the western

Paris, pp. 143-164.

on

Geol.

443.

J. and Le Pichon,

to the Mediterranean

model of the evolution tions Technip,

Geol. Jahrb.,

sites, southeast

Sot. Am., Abstr. Tethys

Notes on the Geological

Jordan.

and

archaeological Biju-Duval,

Martini

der Erde, Vol. 7.

Berlin, 230 pp.

F., 1974. Explanatory

Beynon,

In: H.-J.

Geologie

X., 1977. From the

seas: a plate Alpine

tectonic

system.

Edi-

Blow, W.H., 1969. Late Middle Eocene to Recent planktonic foraminiferal biostratigraphy. In: P. Briinmmann and H.H. Renz (Editors), Int. Conf. Plankt. Microfoss. Proc., Geneva. 1967. Brill, Leiden, 199 pp. Bokhari, M.M.A., 1981. Explanatory notes to the reconnaissance geologic map of the Maqna quadrangle, sheet 28/34D. Open-file Rep. DMGR-OF-01-16/Jiddah, Kingdom of Saudi Arabia. Bonatti, E., 1985. Punctiform initiation of seafloor spreading in the Red Sea during transition from a continental to an oceanic rift. Nature, 316: 33. Bosworth, W., 1985. Geometry of propagating continental rifts. Nature, 316: 625. Bosworth, W. and Gibbs, A.D., 1985. Discussion of the structural evolution of extensional basin margins. J. Geol. Sot. London, 142: 939-942. Bran-&, R.A., Brown, G.F., Holm, D.A. and Layne, N.M., 1963. Geologic map of the Wadi as Sirhan Quadrangle, Kingdom of Saudi Arabia, Map I-2OOA. 1: 500,000.U.S. Geological Survey, Washington, D.C. Clark, D.M., 1985. Late Proterozoic crustal evolution of the Midyan region, Northwestern Saudi Arabia. Geology, 13: 611-615. Clarke, W.J. and Blow, W.H., 1969. The inter-relationships of some late Eocene, Oligocene and Miocene larger foraminifera and planktonic biostratigraphic indices. Proc. 1st Planktonic Conf., Geneva, 1968: 82-97. Co&ran, J.R., 1983. A model for the development of the Red Sea. Am. Assoc. Pet. Geol. Bull., 67 (1): 41-69. Coleman, R.G., 1984. The Red Sea: a small ocean basin formed by continental extension and sea floor spreading. Proc. Int. Geol. Congr., 27th, Moscow, 23: 93-121. Colletta, B. et al., 1986. The structure of the Gebel Zeit area: a field example of tilted block crest in the Suez rift. 8th E.G.P.C. Conf., Cairo, 14 pp. Dullo, WC., Hi%l, H. and Jado, A.R., 1983. New stratigraphical results from the Tertiary sequence of the Midyan area, NW Saudi Arabia. Newslett. Stratigr., 12 (2): 75-83. El-Heiny, I. and Martini, E., 1981. Miocene foraminiferal and calcareous nannoplancton assemblages from the Gulf of Suez region and correlations. Geol. Mediterr., 8: 101-108. El-Shinnawi, M.A., 1975. Planctonic foraminifera from the Miocene Globigerina Marl of Hurgada-well-134, Eastern Desert, Egypt. Proc. 4th Afr. Coll. Micropal., Addis Abeba, 1972: 199-224. Eyal, M., Bartov, Y., Shimron, A.E. and Bentor, Y.K.. 1980. Sinai-Geological map, 1: 500,000. Eyal, M., Eyal, Y., Bartov, Y. and Steinitz, G., 1981. The tectonic development of the Western margin of the Gulf of Elat (Aqaba) rift. Tectonophysics, 80: 39-66. Fairhead, J.D., 1973. Crustal structure of the Gulf of Aden and the Red Sea. Tectonophysics, 20: 261-267. Francheteau, J. and Le Pichon, X., 1976. Plate tectonics of the Levant Red Sea-Gulf of Aden area. Int. Symp. Struct. Tectonics East. Me&err-Jordan Rift valley-Red Sea, Tel Shikmona.

Garfunkel, Z.. Zak. I. and Freund, R.. 1981. Active faulting in the Dead Sea rift. Tectonophysics. 80: l-76. Girdler, R.W. and Styles, P.. 1974. Two stage Red Sea floor spreading. Nature, 247 (5435): 7-11. Hosney, H.M., 1985. Geophysical investigations of the Gulf of Suez-Consequence for the tectonic evolution of the Northern Red Sea. Diss. Univ. Kiel, Kiel, 188 pp. Izzeldin, A.Y., 1982. On the structure and evolution of the Red Sea based on geophysical data from the central and northem parts. Diss. Univ. Strassbourg, Strassbourg, 163 pp. Kohn, B.P. and Eyal, M.. 1981. History of uplift of the crystalline basement of Sinai and its relation to opening of the Red Sea as revealed by fission track dating of apatites. Earth Planet. Sci. Lett., 52: 129-141. Klitzsch, E. 1970. Die Strukturgeschichte der Zentralsahara. Geol. Rundsch. 59: 459-527. Le Pichon, X. and Francheteau, J., 1978. A plate-tectonic analysis of the Red Sea-Gulf of Aden area. Tectonophysics, 46: 369-406. Mart, Y. and Hall, J.K., 1984. Structural trends in the Northem Red Sea. J. Geophys. Res., 89 (B13): 11.352-11.364. Martinez, F. and Co&ran, J.R.. 1988. Structure and tectonics of the Northern Red Sea: catching a continental margin between rifting and drifting. In: E. Bonatti (Editor), Zabargad Island and the Red Sea Rift. Tectonophysics, 150: l-32. McMahon Moore, J., 1979. Tectonics of the Najd tramcurrent fault system, Saudi Arabia. J. Geol. Sot. London, 136: 441-454. Moretti, I., 1987. Modelisation de l’extension intracontinentale -exemple du Golfe de Suez. Diss. Univ. Paris-&d, Grsay. Moretti, I. and Froidevaux, C., 1986. Thermomechanical models of active rifting. Tectonics, 5: 501-511. Perry, S.K. and Schamel, S., 1985. Low-angle normal faulting and isostatic response in the Gulf of Suez: evidence from seismic interpretation and geometric reconstruction. Papers presented to the conference on Heat and Detachment in Crustal Extension on Continents and Planets, Houston, 106-110. Purser, B. and Hotzl, H., 1987. The sedimentary evolution of the Red Sea rift: a comparison of the NW (Egyptian) and the NE (Saudi Arabian) margins. Tectonophysics, 153 (this vol.): 193-208 Quermell, A.M., 1959. Tectonics of the Dead Sea rift. Proc. 20th Int. Geol. Congr., 20th. Mexico-Assoc. Serv. Geol. Afr., Actas Trab., 385-405. Reches, Z. and Hoexter, D.F., 1981. Holocene seismic and tectonic activity in the Dead Sea area. Tectonophysics, 80: 235-254. Roeser, H.A., 1975. A detailed magnetic survey of the southern Red Sea. Geol. Jahrb., 13: 131-153. Roscher, B., Hatzl, H. and Jado, A.R., 1988. Stratigraphy of the Tertiary and Quaternary sediments along the Arabian Red Sea margin. In prep. Rosendahl, B.R. et al., 1986. Structural expression of rifting: Lessons from Lake Tanganyika. Geol. Sot. London, Spec. Pap., 25: 29-43.

151 Schmidt.

D.L., Hadley,

Tertiary

ssouth-western A.M.C.,

Arabia.

Deputy

USGS-OF-03-6,

56 pp.

1979. The North

its age.

offset

London,

136: 269-282.

Steckler,

and Brown,

and

tectonic

1982. Middle

of the Red Sea in Mini&.

Anatolian

Miner.

transform

significance.

Refault:

J. Geol.

Sot.

of induced

mantle

at the Gulf of Suez:

convection.

Nature,

317:

M.S. and Ten Brink, U.S., 1986. Lithospheric

variations

as a control

from the Northern

on new plate boundaries:

Stratigraphic

Red Sea region.

Earth Planet,

Sciences,

of the National

strength

Morgan,

rifting

related

spreading

1976.

histories

Miocene

of the western

Red Sea. Acad.

Vasquez-Lopez,

early

Voggenreiter,

rock

of

stratigraphy

of

R. and

Gulf

of the seafloor of Aden

and

the

E., 1981.

Prospecting

in the

coast

between

Saudi-Arab.

De-

Tech. Rec., BRGM-TR-01-l:

a source

H&J.

W.L., 1984. Preferential of displaced

H. and Jado,

of extension

and

Saudi Arabia): Red

origin

(Editor),

Tectonophysics,

Sea

A.R..

terraines.

J.

1988. Red Sea

magmatism indication

rifting.

in the Jizan

for simple-shear

Geol.

for the Red Zabargad

Rund!ch..

Sea Rift

Island

77(l):

System?

In: E.

and the Red Sea Rift.

150: 51-75.

B., 1985. Uniform-sense

continental Wolfart,

Sea

W.R., Hotzl, H. and Mechie, J., 1988 Low angle

lithosphere. (Editor),

Erde, 6. Bomtraeger,

normal

simple :;hear of the

Can. J. Sci., 22: 108-1::5.

R., 1967. Geologie

H.J. Martini

Naz. Lincei, 47: 585-606.

Motti,

Bonatti Wemicke,

Resour.,

W.J. and Zhao,

W.R., history

during

Red

1986-1979.

Res., 89 (B12): 10072-10076.

Voggenreiter,

Sci. Lett.,

Committee

of the

Maqna

of continents:

257-274.

Egypt. J. Geol., 18: l-69.

P. and Hall, S.A., 1980. A comparison

Central

77 PP. Vink, G.E.,

and

Miner.

detachment

Subcommittee

Geological Styles,

puty Minist.

examples

79: 120-132.

Egypt.

formations

al Bahr

area (Southwest

135-139. Steckler,

sedimentary Yanbu

Geophys.

M.S., 1985. Uplift and extension

indications

G.F.,

rift and evolution

Saudi

sour., Jeddah, Senglir,

D.G.

continental

von Syrien und dem Libanon.

Beitrage Berlin.

zur Regionalen

Geologic

In: der