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structure and Sedimentary History of Southeastern{Mediterranean Sea-Nile Cone Area^DAVID A. ROSS2 and ELAZAR U CH UP I'

Abstract A detailed seismic, magnetic, and sono-buoy study of the southeastern Mediterranean and Nilecone area shows the details of recent sedimentationand tectonic activity, and especially the effects of saltdeformation due to movement of a late Miocene evap-orite sequen ce. The co ntinental rise in this area can bedivided into tvio major sub provinces: the Nile cone andthe Levant platform. The name Levant platform is applied to the rough topography extending northwardfrom the Sinai that separates the essentially smoothNile cone on the west from the Cyprus basin on theeast. The previously reported suggestion of two off-shore fans (the Rosetta and Damietta) off the presentmouths of the Nile is not confirmed; rather, one majorfeature is present the Nile cone . Both the Levant platform and Nile cone have considerable thicknesses ofNile-derived sediment, but the topographic irregularities of the Levant platform result from greater verticaland hoh zontal flow of evaporites than on the Nile cone .The movements of evaporites have resulted in largenumbers of collapse structures and a 100 k m-long saltridge at the northern edge ot the Levant platform.The offshore Miocene evaporites are acousticallydetectable (reflector M) and have been mapped. Theyare perhaps correlative with a nearshore reflector (P)that underlies much of the Nile cone area. Reflector Pis either a middle to late Miocene carbonate sequence

that prograded eastward during the Messinian regression or an erosional surface cut into pre-Messinianstrata. This reflector marks the top of a broad anticlinalstructure off the Nile delta and Sinai Peninsula.The volume of post-Messinian sediment (essentiallyall is Nile derived) is about 387,000 cu km (assumingan average sediment velocity of 2 km/s ec) , or an average sediment thickness of 1.89 km for the area and anaverage sedimentation rate of 37 cm/1,000 years.

INTRO DUCTIO NThe Mediterranean Sea is geologically one of

the most complex of the world's marginal seas. Inspite of numerous geologic and geophysical studies, the southeastern Mediterranean and especially the Nile cone, a major feature of the area, isvirtually unexplored (see, for example. Carter etal, 1972, Figs. 1, 2). Our principal objective instudying the southeastern Mediterranean was todetermine its structural framework and the depo-sitional history of the Nile cone.Our field work was done during two legsaboard R/V Chain (Cruise 119, February-April1975). On the first leg, which is the subject of this

paper, we made 32 seismic, magnetic, and 3.5-kHz echo-sounding profiles; 27 sonobuoy stations; and collected surface suspended matter. Onthe second leg, we collected sediment cores, echo-sounding profiles, and suspended matter, and

made hydrographic observat ions (C. P. Summer-hayes et al, in prep.).PREVIOUS WORK

A recent summary of geophysical data by theCooperative Investigations in the MediterraneanGroup (CIM) showed that relatively litt le workhas been done in the southea stern M editerrane anin general and over the Nile cone in particular.Bathymetric data from the area have been compiled by Pfannenstiel (1960), Mikhaklov (1965),Emery et al (1966). Ryan et al (1970), Allan andMorelli (1971), and Carter et al (1972). A recentstudy of shallow faults and other features on theLevant platform has been made by Kenyon et al(1975) using a long-range (13 km) side-scan sona r.

A detailed geophysical study of the entire Mediterranean is being made by the OsservatorioGeofisico Sperimentale (OGS) of Trieste University and the Saclant ASW Research Center of La5 Cop yright 1977. The America n Association of Petroleu m

Geologists, All rights reserved.Woods Hole Oceanographic Institution Contribution No.3806. .Manuscript received. July 16. 1976: accepted. November17. 1976.2Woods Hole OceanDgraphic Institution. Woods Hole.Massachusetts 02543.We wish to give special appreciation to the many people whohelped in planning and implementing Chain Cruise 119 to thesoutheastern Mediterranean. In particular, the officers and crewof the R./V Chain and Don Koelsch who supervised the seismicsystem. Mark Flora who handled the sonobuoy operation anddata reduction, and Bob Groman who ran the shipboardcom puter system. Said Ali. Jeff Ellis. Franc y F orrestel. Joh n

Forrestel. C. W. (Butch) Grant. Kurt Holmes, Robert McGirr,and Lois Toner assisted in data collection and maintenance ofequipment. Four Egyptian scientists also participated in theexpedition: A. A. Ammar of the Egyptian .atomic EnergyCommission: N. M. H. Ali of Ain Shams University; R. M.Kebeasy. Helwan Observatory: and R. A. Shereef. MansuraUniversity.Ibrahim Naguib Mahmoud was of invaluable help in guidingus and our equipment through official channels.Our most important acknowledgment is reserved for E. M. ElShazly, President of the National Committee on GeologicalScience, of the Egyptian Academy of Scientific Research andTechnology, without whose help, assistance, and guidance thiscruise would not have been possible.Drumm Matthews and John Woodside of the Department of

Geodesy and Geophysics at Cambridge have allowed us to seesome seismic data they had collected from the easternMediterranean.This research was supported by National Science FoundationGrants DES 74-13212 and OIP 75-02.M6. K. O. Emery. Colin P.Summerhaves, and Al Enckstin reviewed the manuscript.872

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Southeastern Mediterranean Sea 873Spezia (from 1961-65). Tog ether this gro up hascollected over 300,000 km of cruise track and produced several geophysical charts on bathymetry,free-air gravity, Bouguer gravity, and total magnetic field (Allan and Morelli, 1971; Finetti andMo relh, 1973). M ore recently this grou p has started to obtain seismic-reflection profiles, five ofwhich cross our area (Finetti and Morelli , 1973;Morelli, 1975).

Shell Oil Company also has made some seismicprofiles in the eastern Mediterranean (locationsof tracks have not been published) to study theevolution of the area and the distribution of Miocene evaporites (Mulder, 1973; Mulder et al,1975). Ad dition al continu ous seismic profileshave been made in the area by Hersey, 1965;Wong and Zarudski, 1969; Ryan et al, 1970; andby D. Matthews and J . Woodside of Cambridge.England. The Israeli Geological Survey has extensive seismic coverage off their coast (Neev etal , 1973; Neev, 1975) which we have used to extend our results and interpretations eastward(Fig. 1).

Seismic-refraction studies in the eastern Mediterranean (Gaskell and Swallow, 1953; Ewingand Ewing, 1959; Moskalenko, 1965, 1966; Lort,1973; Malovitskiy et al, 1975) have shown crustalthickness of 27 km on the continental rise northof the Nile cone (Lort, 1973) and 24 km in theHerodotus abyssal plain (Malovitskiy et al, 1975).Recent syntheses of the geology and geophysicsof the entire Mediterranean include those ofRyan et al (1970), Allan and Morelli (1971), Stanley (1972), Dewey et al (1973), Finetti and Morelli(1973), Biju-Duval et al (1974), Malovitskiy et al(1975), and Morelli (1975). These authors had little continuous seismic-reflection data and thestudies and references generally summarize thepast information known about the eastern Mediterranean.METHODS

Our cruise track, during R/V Chain Cruise 119,was chosen for a representative coverage, to complement previous profiles, and to come close tooffshore wells (Fig. I). We usually terminated oursurvey hnes at water depths of about 60 to 100 m,where multiple returns generally obscured theseismic data.Soundings were obtained using 3.5- (first leg)and 12-kHz (second leg) echo-sounders, with thedepths recorded on a Precision Graphic Re

corder, usually at a 100- or 200-fm sweep. Wekept the ping length short for better resolutionand penetration. Depths generally were recordedat 5-minute intervals and at changes in slope. Thedigitized data were corrected for variations in

sound velocity using Matthew's (1939) tables andplotted relative to our navigation system with theaid of a computer. Navigation was mainly by satellite, supplemented by radar fixes and star sights.Depths at traverse crossings generally agreedwithin several meters. A bathymetric chart of thearea was compiled using data from both legs ofthe Chain cruise and previous data (Fig. 2).

The seismic source was a 300-cu-in. (4.9 1) airgun charged to between 1,300 to 1,500 psi andfired every 12 sec. The gu n was towed at a dep thof 8 m about 8 to 10 m behind the ship. Twolinear arrays of hydrophones each having 200PZT 5 cylindrical crystals were towed a bou t 10 mbelow the surface and about 100 m astern. Thereturning signals were summed, filtered.at between 15 to 160 Hz and recorded both on XY Zrecorders and on digital magnetic tape. The seismic data were analyzed by making line-drawingoverlays from the originals and reducing them,after correcting for variations in ship speed (usually between 11 to 14 km/hour).

Magnetic-field measurements were obtainedusing a Varian proton-precession magnetometertowed approximately 200 m astern of the ship.Values were digitized every 5 minutes and mergedwith the ship's navigation; anomalies were calculated by subtracting a reference field (lAGAComm. 2, Working Group 4, 1969) from the regional magnetic field.Twenty-seven successful oblique reflection-refraction profiles were made using expendable ra-dio-sonobuoys (Navy type An/SSQ4I) , and theair-gun sound source. Hydrophone depth was setat either 19 or 91 m depending on the sea stateand the water temperature-depth profile (determined by XBT prior to sonobuoy launching).We at tempted to deploy the hydrophone withinthe wave-mixed, uniform-temperature surfacelayer to facilitate the detection of the direct waterwave. Site locations were chosen for geologic significance, adequate seismic penetration, and uniformly sloping horizons. Prominent reflectionand refraction arrivals were picked and the datawere reduced using the techniques of Knott andHosk ins ( l 975 ) .GEOLOGIC SETTING

Nile SystemThe principal factors in molding the sedimentary framework of the Egyptian continental marginare the Nile River and the deposition of a se

quence of evaporites during the Messinian (lateMiocene). The present Nile River Valley is a recent geologic feature probably having been cutduring the late Miocene (Soliman and Fans,1963; Said, 1973) or middle Miocene (Salem,

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FIG. 1Position of seismic and 3.5-kHz profiles, and sonobuoy stations made during Chain cruise 119. Locations of selected profiles (Figs. 13-18) are shown bywiggly line. Also shown are DSDP sites, nearshore and offshore Egyptian wells (Said, 1962, 1973), seismic-refraction stations (Lort, 1973), and locations of other seismiclines and wells in eastern part of study area (Neev et al, 1973).

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FIG. 2Bathymetry of continental margin and adjacent deep sea. Map was compiled using data from R/V Chain cruise 119 (3.5, first leg, and 12 kHz , secon d leg,tracklines-are shown) supplemented by data from charts by Carter et al (1972). Contours in meters corrected for sound velocity using Matthews (1939) tables. CO

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876 David A. Ross and Elazar Uchupi1976). Eariicf river deposits such as the late Eocene-early Oligocene sequence in the Faiyum depression and the lower Miocene strata in the eastern tip of the Qattara depression are not relatedto the present river system. In the middle Miocene the northern part of the present delta (northof 3050'N) was an embayment bordered on thewest and south by chffs of Cretaceous and Eocene rocks rising more than 1,000 m above theMiocene sea (Said, 1973). The so uthern topo graphic high known as the South Delta block appears to have been fault controlled. Within theembayment itself thick middle Miocene depositsconsist of muddy marine facies intercalated withevaporites at the top of the section, which gradeeastward and westward into calcareous reefal facies (Said, 1973; El Shazley et al, 1975; Salem,1976).

Upper Miocene anhydri te beds and stromatolite carbonate structures signal a regression duringwhich the northern part of the present Nile deltaarea dried up. This evaporitic sequence probablycorrelates with the evaporites deposited in theMediterranean during the Messinian when thedrainage changed from northwest to north in theearly Miocene, probably because of an eastwardtilting of the land. Concomitant with this tilting,the present Nile Valley was carved by a riverwhich Said called the Eonile.During the flooding of the desiccated Mediterranean in the early Pliocene the sea transgressedthe Nile Valley as far south as Aswan (24 N ;Chu mak ov, 1973; Said, 1973). W ith the exceptionof this narrow estuary the early Pliocene sea apparently did not overlap much of the presentcoast. Near the end of the early Pliocene the seathat filled the estuary began to retreat northward.During this regression fluvial sediments depositedby a river named the Paleonile by Said (1973)slowly filled the estuary. Said (1973) suggestedthat m ost (60%) of the Nile cone was dep osited by

the Paleonile system and that the Nile delta wasinitiated at this time and took form by the beginning of the Pleistocene.During the early Pleistocene from 1.8 to 0.70m.y.B.P. Egypt was converted to a desert and theriver (Paleonile) itself stopped flowing into Egypt.This period also is marked by tectonism whichresulted in the severing of the connec tion betwe enthe Paleonile and some of its southern sourcesand the lowering of the western part of the NileValley. This lowered segment became the path forthe Protonile which broke into Egypt about 660,000 B.P. This Protonile interval was rather short,being contemporaneous with Pleistocene glacia-tion of 700,000 to 600,000 B.P. The next interval,the Prenile extende d from 600,000 to 125,000 B.P.

and was characterized by an arid climate and bytectonic disturbances that severed the connectionof the river from its subequatoria! African sourcesand led to the capture of the Atbara and BlueNile sources. The Prenile river was the largest andmost effective one in outlining the modern valley,the delta, and the coastline with a delta twice thesurface area of the modern delta. Prenile sediments have been recognized as far seaward as thebase of the Nile cone (D SD P Leg 13, hole 130;Ryan et al, 1973; see Fig. 1).

The Prenile/Neonile interval extended fromthe waning of the Prenile 125,000 B.P. to thebreakthrough of the Neonile at 30,000 B.P. andwas characterized initially by a pluvial periodduring which large quantities of gravel derivedfrom the Eastern Desert were brought down tothe Mediterranean and deposi ted unconformablyatop the Prenile sands and silts. During the following arid period the valley and lands wereeroded by wind and cyclonic rains to nearly theirpresent form. The Neonile with a regime similarto the modern one broke into Egypt 30,000 years^go, and the regime of the present river was es-tabhshed about 9,000 years ago. Initially the distributaries of the delta were numerous extendingas far eastward as the old Pelusiac branch, whichemptied into the Bay of Tineh (east of Port Said)and seven branches were known in historicaltimesfive of which since have silted up. Onlytwo, Damietta and Rosetta, are active at present,but with limited flow because of the building ofthe Aswan dam.General Tectonism

Tectonism appears to have played a greaterrole in molding the sedimentary fabric of the Sinai and Israel coastal region than it did in Egypt.Much of this tectonism is related to the openingof the Red Sea and its extensions into the Gulf ofSuez and the Gulf of Aqaba/Dead Sea/JordanValley rift (Neev et al, 1973; Ginsburg et al,1975). The major folding in the region occurredfrom Late Cretaceous to Eocene as a consequence of the splitting of the Arabo-Nubianshield and the initial opening of the Red Sea.Faulting during the Oligocene is associated withthe opening of the Dead Sea/Jordan Valley riftsystem and the uplift of the Judean anticlinorium.

The middle Miocene also was a time of upliftand faulting, and as sea level dropped as a consequence of this uplift the coastal region underwentconsiderable erosion. The topographic lows laterwere filled during a subsequent middle to lateMiocene transgression. During the Messinian regression anhydrite, gypsum, and halite were deposi ted in coastal lagoons and s abkha s. W hen the

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Southeastern Mediterranean Sea 877Mediterranean again was connected with the Atlantic at the beginning of the Pliocene the seatransgressed rapidly across this region. In Pliocene/Pleistocene time there was a general westward tilting of the entire region with renewedmovement along the major fault zones.RESULTS: PHYSIOGRAPHY

Coa.stal RegionHistorically Egypt has been divided from westto east into the following morphologic provinces:the Western or Libyan Desert, the Nile Valleyand delta, the Eastern or Arabian Desert, and theSinai Plateau or Peninsula (Fig. 3). The WesternDesert extending from the Nile Valley on the eastto the border of Libya occupies more than two-thirds of Egypt and is essentially a plateau whosegeomorphic features are primarily due to windact ion.The most conspicuous physiographic featuresof Egypt are the Nile Valley and delta. About 20km north of Cairo the Nile divides into twobranches which meander across the Nile delta before entering into the Mediterranean at Rosettaand Damietta. The delta, covering an area of 22,000 sq km, measures 175 km from the apex to thebase and 200 km along its base (Sohman and Far-is, 1963). The western terminus of the delta is inthe vicinity of Alexandria and its eastern termi

nus is jus t east of th e Suez Can al a t the B ay ofTineh where the now abandoned Pelusiac branchentered the Mediterranean.Seafloor

Topographically the seafloor can be divided(Fig. 3) into the following physiographic provinces: cont inental shelf, continental slope, continental rise including the Nile cone and Levantplatform, Eratosthenes Seamount , Herodotus andEratosthenes abyssal plains, the MediterraneanRidge, and the Hellenic arc. The surface reflectivity characteristics of these provinces are shown onFigure 4.

Continental shelfThe continental shelf is widest (48 to 64 km) between the Rosetta Branch andthe Bardawil Lagoon (Fig. 2). West of Alexandriait narrows to less than 20 km and off rocky headlan ds to less tha n 10 km . Off the Sinai the shelf is50 to 42 km wide, and off Israel it ranges from 26km at the south to 10 km at the north .West of Alexandria the shelf's edge is 75 to 90m deep, and between the Roset ta and Damiet tabranc hes it dee pen s to between 150 and 265 m.Downwarping of the shelf by the weight of theNile delta probably is responsible for the deepening of the shelf's edge in this area. North of theSinai Peninsula the shelf 's edge ranges in depth

from 90 to 128 m, and off Israel from 125 m atthe south ti' 85 m off Mount Carmel at the north.Emery and Bentor (1960) attributed the southward deepening of the shelf's edge off Israel tothe downwarping of the region by the Nile delta.However, our study indicates that such downwarping has affected only the region immediatelynorth of the delta.

Continental slopeThe maximum relief of theco ntin ent al slope off Egypt is west of 28E wherethe 34 to 56 km-wide slope descends from theshelf's edge (75 to 90 m) to a depth of 2,000 to2,400 m. The topography here is very irregular, asthe slope is entrenched deeply by gullies. Acoustically the surface is a strong reflector and no sub-bottom penetration was observed on any of the3.5-kHz records from this region (Fig. 4). Off theNile delta between Alexandria and the BardawilLagoon the continental slope is only about 20 kmwide, is smooth, and has little relief as its baseranges in depth from 300 to 600 m. At the westernend this smooth-slope segment is entrenched byAlexandria Canyon which extends from the edgeof the shelf to the upper rise. The 3.5-kHz recordsshow that this smooth slope has well-developedstratification that is broken by many closelyspaced normal faults with the downthrown blockson the seaward side (Fig. 4). Depths along thebase of the continental slope off Israel are intermediate to those seaward of the Nile delta and offwestern Egypt.Continental Rise, Nile cone, Levant platform, andEratosthenes SeamountThe area seaward of thecontinental slope is a broad sedimentary apronthat, on a morphologic basis, can be divided intotwo main provinces: a humm ocky to gently un dulating terrain and a region with considerable relief. The more subdued surface is the continentalrise and the more irregular one, the Levant platform (F ig. 3). W est of 27 E long, the co ntin en talrise is narrow, being 12 to 38 km wide and termi

nating on the seaward side at a depth of 2,800 to3,000 m. The rise is developed best off the Niledelta. This segment of the rise, known as the Nilecone, is 230 km wide and extends to the Mediterranean Ridge. Much of the surface of the cone ishummocky to gently undulating and acousticallya poor reflector (Fig. 4). The Nile cone's surfacedisplays very little relief except at its base wheresalt intrusion (see structure section) has deformedthe strata resulting in a valley-ridge type of topography. This irregular terrain extends from thewestern end of Herodotus abyssal plain to Eratosthenes Seamount (Fig. 3).The continental rise also is well developed inthe Cyprus basin extending from the eastern edgeof the Levant platform to the continental slope

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28 29 30 31 32FIG . 3Physiographic provinces of coastal region and adjacent seafloor.

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27 28 * 29 " 3 0 ' 31" 32"' 33F I G . 4Morphologic character istic s of seafloor as determined from 3.5-kHz records .

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880 David A. Ross and Elazar Uchupioff Israel. Southeast of Eratosthenes Seamountthe surface of this rise is characterized by gentleundulations (Fig. 4). As suggested in the following, these features could be a result of gravitysliding along Horizon M, the top of the Messinianevaporites that underlie much of this region. Therise in the Cyprus basin is nearly separated fromthe rise north of the Levant platform by Eratosthenes Seamount, a northeast-trending high thatrises more than 1.000 above the surroundingseafloor.

In contrast to the Nile cone, the sedimentaryapron north of Port Said is irregular. This roughterrain extends from the base of the continentalslope off the Sinai northwestward for a distanceof 356 km. On the east it is flanked by the Nilecone, on the north and west by the continentalrise, and on the northeast it is separated from Eratosthenes Seamount by a narrow channel . Thename Levant platform is suggested for this feature. This name previously was used by Neev et al(1973) for the southern part of the Cyprus basin,but appears more appropriate for the uplifted anddeformed rise west of the basin.

The Levant platform terminates on its northernedge at a 100 to 400 m-high escarpment that descends onto the continental rise. (Dn the west thetransition from the Levant platform to the Nilecone ranges from a recognizable slope severalhundred meters high to a change from a relativelysmooth bot tom on the cone to an undulat ing oneon the platform. The contact between the platform and the rise in the Cyprus basin is similar tothat between the platform and the Nile cone. Emery et al (1966), who first noted the topographicuniqueness of this region, described it as a northeast oval-shaped area of abyssal hills which divided the Nile cone into two parts which they termedthe Rosetta and Damietta fans. The presentstudy, however, indicates that the cone consists ofone single province separated from the rise in theCyprus basin by the Levant platform.Recently Carter et al (1972) suggested that theroughness of the Levant platform area resultedfrom a series of northwest-trending ridges andvalleys which probably were controlled structurally. Using long-range side-scan sonar and seismic-reflection profiles Kenyon et al (1975) suggested that the topographic irregularities weredue to east-northeast grabens and to a lessernumber of narrower structural lows extendingdownslope in a northwest direction. They alsopointed out that, although the topographic grainis northwest, the main relief has an east-northeastto northeast trend. Kenyon et al (1975) ascribedthis rough terrain to diapirism and mass down-slope movement, or possibly to the north-north

east movemtnt of the Smai Peninsula. Our present more detailed study of the region indicatesthat topographic irregularities are due to verticaland horizontal flow of evaporites and collapse ofthe crests of some of the diapirs (see section onstructu re a nd Figs. 18, 20).Northeast of the Levant platform is Eratosthenes Seam ount, a 110 by 70-km topograp hic highthat rises I km above the continental rise and isseparated from the Levant platform by a 50-kmwide channel. A topographic low surrounds theseamount on both its southern and eastern flanks(Fig. 2). Profile 21 (Fig. II) which crosses thisfeature shows blocky topography, probably faultcontrolled, on the crest. As indicated by this profile, Eratosthenes Seamount is asymmetric incross section with the northwest flank of the seamount being steepest.Abyssal plainsAlong the northern fringes ofthe con tinental rise-N ile cone wedge are twoabyssal plains, Herodotus on the west and Eratosthenes on the east (Fig. 3). Emery et al (1966)suggested that these plains connect to form a continuous feature along the base of the Mediterranean Ridge. Our study shows that they are notconnected, but are separated by the Nile conewhich extends to the Mediterranean Ridge. TheHerodotus abyssal plain slopes gently westwardfrom a depth of 3,070 m at its eastern end to 3,100

m at its western end. Depths within the Eratosthenes abyssal plain are about 2.600 m with maximum depths at the center of the plain. Acoustically, both abyssal plains are characterized by astrongly reflecting bottom, and the 3.5-kHz records show little to no penetration (Fig. 4).Mediterranean Ridge and Hellenic arcRising700 m above the abyssal plains and the Nile coneis the Mediterranean Ridge, a 185 to 120 km-wide. east-northeast-trending rise that terminatesagainst Cyprus (Emery et al, 1966; Ryan et al,1970). North of and parallel \yith the ridge is a

series of linear ridges and depressions with depthsin excess of 4,000 m, forming the Hellenic arc.These have been studied in detail by Ryan et al(1970) and were not emphasized in our program.RESULTS: STRUCTURE

MagneticsMagnetic anomalies generally are negative overthe entire area, and their pattern is relativelysmooth (Fig. 5). There are two broad areas wherevalues are more negative than 200 gammas.The largest extends from the Herodotus abyssalplain eastward to the western part of the Nilecone . The second extends north eastwa rd from thewestern part of the Levant platform across theouter part of the continental rise to the Eratosth-
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FIG. 5Magnetic anomalies of Egyptian continental margin and adjacent deep sea. Anomalies calculated by removal of reference f ield ( lAGA Comm. 2, WorkingGro up 4, 1969) from total- intensity f ield. Areas having values more negative than -2 0 0 gam mas are dashe d. 0 00 0

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882 David A. Ross and Elazar Uchupi

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FIG. 6Line drawing of seismic profiles 5, 7, 9 from western part of study area. See Figure I for location ofprofiles. Travel time is two-way. Stronger reflectors are indicated by thicker lines; different reflectors are discussedin text; 5 followed by number indicates location of sonobuoy station; numbers under sonobuoy station are measured seismic velocities in kilometers/second; L followed by number indicates where profile is crossed by anotherone; F indicates fault. Main physiographic provinces (Fig. 3) are indicated in upper part of figures. Verticalexaggeration (based on water velocity of 1,5(X) m/sec) of these and other profiles is about 27 times.

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Southeastern Mediterranean Sea 883

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FIG. 7Line drawings of seismic profiles I, i, 28, 29 off Alexandria on western part of Nile cone. See caption forFigure 6 for explanation of symbols.

enes abyssal plain; this low flanks the westernpart of the Eratosthenes Seamount. A positiveanomaly is present on the southern flank of theEratosthenes Seamount and the outer parts of theLevant platform. This anomaly has values morethan 200 gammas and is the only positive areaobserved. A similar southerly offset of a positiveanomaly from the Eratosthenes Seamount hasbeen noted by Ben-Avraham et al (1975). An ex

amination of magnetic anomalies and physiographic provinces generally showed little correlation between them except over Eratosthenes Seamount .Sonobuoy

The sonobuoy data (see Figs. 6-12) show threerelatively distinct velocity units. The uppermostunit has interval-reflection velocities ranging

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from 1.6 km/sec to about 2.2 km/sec, and usuallygives several good reflections^ The second unit ischaracterized by layers having interval-reflectionvelocities of 2.4 km/sec to about 2.8 km/sec.Both these units undoubtedly are relatively unconsolidated sediments. At many stations, a faster, deeper third unit is present having an interval-reflection velocity ranging from 3.2 km/sec to4.07 km/sec. Several refraction velocities of 4.5km/sec or more were received from this unit. Thethird unit appears to represent at least two different faciesevaporite and limestone; this point isdiscussed later. The average depth (27 sono-

buoys) of the deepest resolvable reflector wasabout 1,350 m beneath the seafloor. Refractionreturns from interfaces were observed from 22 so-nobuoys, one as deep as 2,800 m beneath theseafloor (so nob uoy 18). N o arrivals from crystalline rock were detected, probably because of themodest size of the energy source and the largesediment thickness.Seismic Profiles

Line drawings of the seismic profiles are shownin Figures 6 to 12; they have been arranged in awest-to-east series of generally north-south sec-

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Sou theastern Me diterranean Sea 885

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FIG. 10Line drawings of seismic profiles 19, 24, }1 east of Nile cone and on Levant platform. Seecaption for Figure 6 for explanation of symbols.

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gesting tilting of the upper parts of the continental margin. In general there is a surprising lack ofchannels or canyons on the continental slope; theexception is at the base of the slope on profile 28(Fig. 7). Possibly the orientation and spacing ofour lines may have missed some channel or canyons. Some topographic highs on the continentalslope may represent old reefs (Fig. 6, profiles 7,5) .

Two strong subsurface reflectors are presentunder parts of the continental slope and deeperareas. The shallower one, reflector Q, is restrictedto the western part of the study area (Fig. 6) andtends to obscure deeper penetration, its relativeshallowness indicates that it is within the Pliocene-Pleistocene section.Reflector P is the deeper reflector and one ofthe most distinctive features from our records(Fig. 13). As discussed later we feel that this re

flector is Miocene in age (probably late Miocene)and represents either a carbonate platformformed at that time or an erosional surface truncating pre-Messinian strata. It is not clear if reflector P is correlative with reflector M commonto our records from deep water, which marks thetop of the Messinian evaporite sequence.A deep broad anticlinal feature underlies theouter shelf and upper slope off Egypt and possibly the Sinai. It appears to merge into the southern boundary of the Levant platform (profile 17,Fig. 9) where it may becom e the Bardawil Esca rpment noted by Neev et al, 1973.

Continental rise, Nile cone, and Levant plat-form The con tinen tal rise west of the delta area(Fig. 6) has relatively little sediment thicknessand an irregular surface. Subsurface penetrationin part is obscured by reflector Q, although onprofile 7 reflector P was detec ted at 1.5 sec below

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FIG. 12Line drawings of seismic profiles 10, 30, 32 made in east-west direction across study are a. See caption forFigure 6 for explanation of symbols.

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FIG . 14Part of continu ous seismic profile 5 showing contact of Nile cone and M editerrane an Ridge. Note diapir ic appearan ce of reflector M near left side of figure.See Figure 1 for location of p rofile.

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S o u t h e a s t e r n M e d i t e r r a n e a n S e a 8 9 1the surface. Reflecting horizons in this area aicnot very continuous and small faults and subsurface channeling (Fig. 6, profile 5| arc present.Profile 29 (Fig. 7) trending obliquely across therise also shows irregular subsurface layering.

Sediment reflectors from the Nile cone are generally irregular but become less so eastward.Faulting (down basin) and folding are fairly common although again these decrease eastward. TheNile cone generally extends out onto the Mediterranean Ridge, in some places even being incorporated in it (Fig. 14). In these areas, either saltmovement or crustal deformation folded even themost recently deposited sediments (see, for example. Fig. 8, profiles 11, 13: Fig. 15).

In the area off the eastern part of the delta(Figs. 9, 10) the Nile cone ends in a series of faultsthat lead to the more irregular, somewhat shallower and flatter Levan t platform (Fig . 16). Sed iments on the Levant platform (above reflector M)are generally thinner than on the Nile cone andmore deformed. Much of the deformation is dueto salt flow which in many places forms diapirs oractually outcrops (Figs. 17, 19). In some areas thediapirs have undergone solution, forming collapsestructu res (see, for exa mp le, Fig. 10, profile 24;Fig. 18). In one area, southwest of the Eratosthenes Seamount a 100-km long wall of evaporitescrops out forming a salt ridge (Fig. 9, profile 26;Fig. 10, profiles 19, 24; F ig. 11, profile 21 ; Figs.17, 20). Structurally, the Levant platform, with itssalt front along the northern edge, the intense deformation of its sediment cover by diapirs. andfaulted southern slope, resembles the continentalmargin in the western Gulf of Mexico. As in thegulf, structures in the eastern Mediterranean appear to result from the vertical and lateral plasticflow of evaporites. The salt ridge, faults, and collapse structures separate the Levant platformfrom a more typical continental rise toward thenorth and northeast. On the north the sedimentsare highly deformed by recent movements alongthe Mediterranean Ridge.

In the eastern part of the area the continentalrise is relatively smoothly layered with little folding or faulting (Fig. 11, profile 23).The contrast between the structure of the Nilecone, the Levant platform, and MediterraneanRidge can be seen clearly from a series of west-east profiles (Fig. 12). Although the Nile is thesediment source for all the areas, the behavior ofthe underlying sediments (as characterized byeither reflector M or P) has determ ined the degreeof folding or faulting in the different areas.Eratosthenes SeamountProfiles near the Eratosthenes Seamount show layer M cropping outas a salt ridge on the seamount's southern flank(Fig. I I, profile 21 ). A deeper reflector (reflector

B) cuiiKs ncai ihc Mirfacc at llie lop and no rthe rnHank of I he seamount. and is covered bv a thinlayer of st-dinienl. On a southeasterlv crossing, re-'Icclitr B ,s dippinji sieepK and disap pea rs b elowthe sediments of the C'sprus basin (I'ig. I I. profile22). Faillicr south another reflector, possibly M.appears although it is uncharacteristically smooth(Fig. II. profile 23). Near the Levant platformreflector M definitely appears with its typical dia-piric stru ctu re (Fig. I I. profile 23).

Abyssal plains Profiles across the Herodotusabyssal plain (Fig. 6. profiles 5. 7. 9) and the Eratosth ene s abys sal plain (F ig. 10. profile 19) showrelatively horizontally layered sediments. Deeperreflectors also are undisturbed. Both abyssalplains are between the highly deformed M editerranean Ridge on the north and disturbed parts ofthe continental rise.Mediterranean /^/liije--Seismic profiles fromthe Mediterranean Ridge show a high degree offolding, which in many instances obscures the recor d (F ig. 6. profiles 5, 7; F ig. 7, profiles 1, 3; F ig.8, profiles I I. 13; Fig. 9, profiles 15. 17, 18; Fig.10, profile 19; Figs. 14, 15). A profile pa rallel w iththe ridge also shows the intense folding (Fig. 12,profile 10). The folding app aren tly is due to eitherthe movement of reflector M or crustal deformation or a combination of both. This deformationhas been so recent as to affect even the upper

most sediment reflectors. Sediments now are accumulating at a greater rate in the valleys than onthe troughs of this folded area.DISCUSSION

The major factors controlling the recent structural and sedimentary evolution of the continental margin and adjacent deep-sea floor north ofEgypt are: (I) the deposition of the cone and delta sediments by the Nile River, (2) the evaporitedeposition during the Messinian regression andits subsequent deformation, and (3) the tectonismassociated with the Mediterranean Ridge. In middle Miocene time the northern part of the presentNile delta was an embayment. a site of terrigenous deposition. East and west of the embayment , carbonate materials were the dominantsediment type. Near the end of the Miocene thecarbonate banks of the Western Desert prograd-ed eastward over the embayment. This carbonateprogradation occurred during the Messinian regression which affected the entire Mediterranean.Restricted access of the region to the open seaappears related to late Miocene-early Pliocenetectonic events that increased the subdivision ofthe Miocene depositional area. This isolation during the late Miocene regressive phase led to thedeposition of evaporites throughout much of theMediterranean. The top of this evaporitic se-

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FIG. 17- -Part of seismic profile 19 across outer part of Levant platform showing near outcroppmg of reflector M ( top of upper Miocene evaporite sequence!This area was crossed several times and ou tcro p covers con sidera ble area (see Fig. 19). See Figure 1 for location of pro file.

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quence is reflector M, a prominent horizon thatwas mapped in much of the offshore region.The opening of the Strait of Gibraltar duringearly Pliocene time led to a marine transgressionduring which marine waters extended over 3,000km into the present Nile Valley. During the remainder of the Pliocene this estuary slowly became filled with terrigenous sediments forcing thesea to retreat slowly northward. During this regression most of the Nile cone was deposited inthe Messinian subsiding basin and the Nile deltawas initiated, taking form by the beginning of thePleistocene. As the Nile cone sediments depositedatop the Messinian evaporites increased in thickness, they eventually caused mobiUty of the evaporites that in turn subsequently deformed the overlying Pliocene-Quaternary sediment cover. Onthe Levant platform, deformation due to intrusion by the evaporites has been most intense, resulting in the elevation of the platform slightlyabove the rest of the Nile cone. The evaporiticsequence appears to have moved not only vertically but also seaward with the Levant platform'snorthern slope marking the front of this advancing salt wedge (see Fig. 19). Further structuralcomplexities have resulted from the collapse bysolution of evaporites from the crest of some ofthe diapirs (Figs. 18, 19). Sediment deformation,facilitated by the plastic flow of the Messinianevaporites, also has taken place farther seawardas a consequence of the interaction between theEurasian, African, and Arabian plates. Thesouthern flank of the Mediterranean Ridge consists of uplifted and deformed sediments that

were deposited on the northern edge of a previously more extensive Nile cone and fringing abyssal plains.However, all the tectonic features of the Egyptian margin are not related to salt or plate tecton-ism. For example, the numerous small faults onthe slope north of the Nile delta are probably dueto sediment instability caused by rapid sedimentation which affects the whole sediment sectionand acoustic basement. Other examples includethe major faults on the upper Nile cone off Alexand ria and the subsurface ridge on reflector Pj us tnorth of the Nile delta.

Acoustic basementThe deep reflectors forming the acoustic basement of the Egyptian marginand adjacent deep sea can be classified into twomorphologic types; one displays considerable relief (M, B), the other is more subdued (P; Fig. 19).Reflector B is an irregular horizon that forms thefoundation of the northeast-trending Eratosthenes Seamount (Fig. 11). Beneath most of the inner Egyptian margin is a much smoother reflector, P. The rest of the margin, adjacent abyssalplains, and the Mediterranean Ridge are underlain by reflector M. In places reflectors P and Mare in fault contact and in other localities thetransition from one to the other is marked by agradual increase in the relief of acoustic basement. Several nearshore wells appear to havepenetrated P; however, its age is not conclusive.Compressive refraction velocities obtained fromthe strata beneath reflector P (along profile 5, Fig.6, where values of 4.2 and 5.0 km/sec were recorded) are suggestive of carbonate rocks. Incor-

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Southeastern Mediterranean Sea 8 9 7porating this with the well data indicates that reflector P may delineate the top of a carbonatesequence of middle to late Miocene age, that pro-graded eastward from the Western Desert (Said.1973; Salem, 1976) during the Messinian regression. An alternative explanation is that reflector Pis an erosional surface carved atop pre-MessinianMiocene marls and marly limestones that werefaulted and uplifted during late Miocene tectonicmovements that fragmented the much larger earlier Miocene basins (Mulder, 1973; Mulder et al,1975).

The irregular topography of reflector M beneath the outer margin, Levant platform, abyssalplains, and the southern flank of the Mediterranean Ridge we believe is due to the plastic flow ofevaporites and the solution of these deposits onthe crests of some of the diapirs. Reflector M iscommon to much of the Mediterranean. Sediments below this reflector have a compressional-wave velocity of 3.5 km/sec or more. DSDP drillings in the study area and other Mediterraneanlocalities where reflector M has been detectedshow that the reflector marks the top of an upperMiocene (Messinian) evaporite sequence (Ryan etal, 1973). On sho re an d offshore of Israel, reflectorM has been identified in boreholes and on seismic-reflection profiles as an evaporitic sequence,mainly anh ydrite (Ginzb urg et al, 1975). The relatively low velocity associated with the evaporitesequence probably results from the unit actuallybeing a mixture of several sediment types including pelagic and terrigenous material. However,salt must be fairly common in the sequence asevidenced by the numerous flowage features.

Reflector B, forming the foundation of Eratosthenes Seamount , can be t raced beneath reflector M along line 21 (Fig. 11) and thus it isprobably pre-Messinian in age. As we only detected this reflector in the vicinity of the sea-mount we are not able to determine the relationbetween this horizon and reflector P. Mulder(1973) has interpreted the seam ount as a large stable block of pre-Messinian age so possibly reflector B actually represents that base me nt. If ou rinterpretation as to the ages of horizons P and Mare correct then the structure map on Figure 20shows the depth of what essentially is the top ofthe Miocene and the isopach map on Figure 21displays the thickness of the Pliocene-Quaternarysediment cover.

Sediment ThicknessThe top of the Miocene dips gently seawardfrom Cairo reaching a depth of about 3 sec alongthe Egyptian coast (Fig. 20). Near the outer edgeof the shelf the continuity of this seaward-slopingsurface is disrupted by a shallowing of the top of

the Miocene to form a ridge, an uplift that affectsnot only its surface but the sediment cover on it(Figs, 8, 9). Seaward of this high the topographyof the top of the Miocene is complex as it descends tc a depth in excess of 5 sec below sealevel. In this region the Miocene surface is brokeninto a series of northeast-trending highs paralleling the southern flank of the MediterraneanRidge. The topography of the top of the Mioceneis even more irregular on the Levant platformwhere it is more than 3.5 sec thick (Fig. 21). Seaward of this depositional center, the Nile conesediments generally thin except along the cone'seastern margin against the western edge of theLevant platform where they are more than 2 secthick. This north-trending trough along the eastern end of the Nile cone appears to be fault controlled along its eastern edge. The sediment coveron the northern part of the Levant platform isvery patchy because of the vertical migration ofthe Messinian evaporites, and ranges from lessthan 0.1 sec thick on the crests of the diapirs andon the salt front forming the northern slope of theplatform to more than 2 sec thick on the structu ral lows between the diapirs. From the lower Nilecone to the base of the Mediterranean Ridge thesedim ent co ver ranges from less than 1 sec alongthe crest of the easterly trending highs to morethan 2 sec thick on structural lows. Within theMediterranean Ridge proper the sediments andthe acoustic basement are folded so tightly that itis impossible to determine sediment thickness.Total post-Messinian sediment volume (abovereflectors P and M) for the study area is about387,000 cu km (assuming an average sediment velocity of 2 km/sec). This calculates to an averagethickness of 1.89 km for the area, and an averagesediment rate of 37 cm/1,000 years. This averagesedimentation rate is similar to that determinedfrom surface sediment studies (Parker, 1958;Olausson, 1961; Emery et al, 1966; Ryan et al,

1970; McCoy, 1974).Lort (1973) has reported on a series of seismic-refraction and reflection profiles from the easternMediterranean. The six profiles within the area ofour study (F ig. 1) generally show ed a surface-sediment layer (velocity between 2.0 and 3.1 km/sec)underlain by a 3.6 to 4.1 km/sec layer. The latteris interpreted to be evaporitesa conclusion consistent with our work. Lort 's data show as muchas 6 sec (two-way reflection time) of evaporiticsediments underlying the outer part of the Nilecone or about 11 km. Whether this is actually theaverage thickness or represents an area of salt tectonics and flow is debatable, but an averagethickness of 11 km seems highly improbable, especially because her profile R4 on the flank of theM editerra nean Ridge about 100 mi (160 km )

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FIG. 21Isopach map of sedimentary deposits (Pliocene-Quaternary) above acoustic basement ( two-way travel time). Based on data obtained during present studvsupplemented by data from Neev et al (1973) and Ginsburg et al (1975).00

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away (but in a similar area) only has about 0.2 sec(about 700 m) of evaporites.Underlying the evaporites (based on Lort,1973, data) is a 4.5 to 5.1 km/sec unit overlying a5.4 to 6.5 km /se c se quence. On o ne profile east ofthe Levant platform a mantle velocity of 8.4 km/sec was obta ined from a depth of abo ut 13 sec.Finetti and MorelU (1973) made a wide-angleseismic station on the Nile cone (about 3330'N,3130'E) that showed 1.5 km of pre-evaporitic

sediment, about 2.5 km of evaporite (4.6 km/sec),abo ut 8 km of 6.1-km /sec m aterial (Hmestone?),and ab ou t 10 to 11 km of abo ut 6-km /sec ma terial overlying mantle (8.25 km/sec) at about 25 km.They interpret material in the 5.0 to 6.7-km/secrange as being part of a granitic layer that is present over much of the eastern Mediterranean.The upper parts of these refraction and reflection data are similar to our sonobuoy results, inthat we also note a variable post-evaporite thick-

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Southeastern Mediterranean Sea 901ness (see Fig. 21). This variability is related clearly to deltaic deposition on the Nile cone andprobably turbidity-current deposition (of Nilesediment) on the abyssal plains and Mediterranean Ridges.

Plate TectonicsIt is generally accepted th at the M editerra neanSea occupies a part of a former sea known as theTethys which extended from the Atlantic to Asiaand the Indian Ocean. Recent studies based onplate-tectonic considerations indicate that theevolution of the Mediterranean area was extremely complex, involving an almost constantlychanging mosaic of small and large plates producing ridges, trenches,, back -arc basins, islandarcs, etc. (see, for example, Dewey et al, 1973).The most recent movement in the eastern Mediterranean (Fig. 22) appears to result from compression between the large and relatively stableAfrican, Arabian, and Eurasian plates, whichhave caused varying motion in the small micro-plates caught between Africa and Europe (Mc-Kenzie, 1970). One proposed microplate, calledthe Levantine plate, is bounded by the Hellenicarc-Mediterranean Ridge, the Gulf of Aqaba-Dead Sea rift , the Sinai and, supposedly, a faultzone exten ding up the Gulf of Suez no rth-n orth westerly to the M editerrane an Ridge. This lastboundary was not detected from our study, although the southwestern part of the Levant platform that might contain this bou nda ry comm onlyis faulted. In actuahty there does not seem to beany necessity to include a Levantine plate between the present Arabian and Eurasian plates.Neev et al (1973) and Neev (1975) have suggested that the Pelusium hne (see Fig. 19) is thewestern boundary of a "Central plate" which hasbeen wedged between surrounding plates andthus caused northeast- t rending compressionalfeatures and northwest-trending tensional fea

tures in much of the Middle East area. Our data,mainly west of this proposed plate boundary, offer little support for the existence of this plateother than showing a dramatic change in thecharacter of reflector M near Eratosthenes Sea-mount. A deep reflector (apparently M) is essentially horizontal in the immediate area east andsou thea st of the sea m ou nt (Fig. 11, profiles 22,23) but clearly becomes diapiric landward nearthe eastern slope of the Levant platform and underlying ita pattern essentially reversed fromthat proposed by the Neev model. We believe thenearshore geology of the Middle East is not amenable to a simple solution based on plate tectonics. However, the offshore region (at least the areawe have studied) seems fairly simple so far as

plate tectonics is involved. Earthquake activity isrestricted primarily to the Mediterranean Ridgearea, and subduction apparently is occurringalong the Hellenic arc-Mediterranean Ridge areawhere shallow-focus earthquakes have been detected (Barazang i and Do rman , 1969). Seismicdata from the Hellenic arc area indicate a northward-dipping fault suggesting thrusting of theNile cone under the Mediterranean Ridge (Papa-zochos and Comninakis, 1971; Papazochos, 1973,1974). The results of this movement were not directly observed from our seismic profiles, whichcrossed only the southern flank of the Mediterranean Ridge, whereas the subduction would be occurring on the northern flank. However, the intense folding seen from our records from the areacan be due, at least in part, to this subductionactivity. In all likelihood, the motion betweenArabia and Europe is not confined to a singlefault area, but rather to a series of such localitiesbetween the Mediterranean Ridge and Turkey.REFERENCES CITEDAllan, T. D., and C. Morelli, 1971, A geophysical studyof the Mediterranean: Boll. Geofisica Teor. ed Appl.,V. 13, no. 50, p . 99-142.Barazangi, M., and J. Dorman, 1969, World seismicitymap of ESSA Coast and Geodetic Survey epicenterdata for 1961-1967: Seismol. Soc. America Bull., v.

59, p. 369-380.Ben-Avraham, Z., Y. Shoam, and A. Ginzburg, 1975,Magnetic study of the Eratosthenes Seamount (abs.);EOS, V. 56, p. 163,Biju-Duval, B., et al, 1974, Geology of the Mediterranean Sea basins, in C. A. Burke and C. L. Drake, eds.,The geology of continental margins: New York,Springer-Verlag, p. 695-721.Carter, T. G., et al, 1972, A new bathymetric chart andphysiography of the Mediterranean Sea, in D. J. Stanley, ed., The Mediterranean Sea: Stroudsburg, Pa.,Dowden, Hutchinson and Ross, p. 1-23.Chumakov, I. S., 1973, Pliocene and Pleistocene deposits of the Nile Valley in Nubia and upper Egypt: Initial Kept. Deep Sea Drilling Project, v. 13, pt. 2, p.1242-1243.Dewey, J. F., et al, 1973, Plate tectonics and evolutionof the Alpine system: Geol. Soc. America Bull., v. 84,p. 3137-3180.El Shazley, E. M., et al, 1975, Geological and groundwater potential studies of El Ismailiya master planstudy area, in The remote sensing research project:Egypt, Acad. Sci. Research and Technology, 24 p.Emery, K. O., and Y. K. Bentor, 1960, The continentalshelf of Israel: Israel Geol. Survey Bull., v. 26, p. 25-41.

B. C. Heezen. and T. D. Allan, 1966, Bathymetry of the eastern Mediterranean Sea: Deep-Sea Research, V. 13, p. 173-192.Ewing, J., and M. Ewing, 1959, Seismic refraction measurements m the Atlantic Ocean basins, in the Medi-

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902 David A. Ross and Elazar Uchupiterranean Sea. on the Mid-.Atlantic Ridge, and in theNorwegian Sea: Geol. Soc. America Bull., v. 70. p.291-318.Fin elti. 1., and C . Morelli. 1973, Ge oph ysica l ex ploration of the Mediterranean Sea: Boll. Geofisica Teor.ed Appl.. V. 15. p. 263-340.

Gaskell, T. F., and J. C. Swallow, 1953. Seismic refraction experiments in the Indian Ocean and the Mediterranean Sea: Nature, v. 172, p. 535-537.Ginzbu rg, A., et al, 1975. Geology of Me diterran eanshelf of Israel: AAPG Bull., v. 59, p. 2142-2160.Hersey, J. B., 1965, Sedimentary basins of the Mediterranean Sea, in Submarine geology and geophysics(Colston Research Soc. 17th Symp. Proc): London,Butterworth, p. 75-91.lAGA Commission 2, Working Group 4. 1969, International geomagnetic reference field 1965.0: Jour. Geo-phys. Research, v. 74. p. 4407-4408.Ke nyo n, N . H.. A". H . Stride, and R. H.- Belders on,1975, Plan views of active faults and other features onthe lower Nile cone: Geol. Soc. America Bull., v. 86,p. 1733-1739.Kn ott. S. T., and H. H oskins, 1975, Collection an d analysis of seismic wide angle reflection and refractiondata using radio sonobuoys: Woods Hole Oceanog.Inst. Tech. Rept. 75-3, 86 p.Lort, J. M., 1973. Summary of seismic studies in theeastern Mediterranean, in Selection of papers on theeastern Mediterranean region (23d Cong. CIESM,Athens, 1972): Geol. Soc. Greece Bull., v. 10, p. 99-108.M alovitskiy, Y a. P., et al, 1975, Geo logical stru ctu re ofthe Mediterranean sea floor (based on geological-geophysical data) : M arine Geology, v. 18, p. 231-261.M atthew s, D. H., 1939, Tab les of velocity of sou nd inpure water and sea water: London, Admiral ty Hyd-rog. Dept., 32 p.McCoy, F. W., Jr., 1974, Late Quaternary sedimentation in the eastern Mediterranean Sea: PhD thesis,Harvard Univ. , 132 p.McKenzie, D. P., 1970, Plate tectonics of the Mediterranean region: Nature, v. 226, p. 239-243.Mikhay lov, O. V,, 1965, The rehef of the M editerra neanSea bottom , in L. M. Fomin, ed., Basic features of thegeological structure of the hydrological regime andbiology of the Mediterranean Sea: Moscow, Science,p. 14-33.Morelli, C , 1975, Geop hysics of the M editer ran ean :Cooperative Invest. Mediterranean Newsletter, Spec.I s s ue? , p . 27-111.Moskalenko, V. N., 1965, Study of the sedimentary series of the Mediterranean Sea by seismic methods, inL. M. Fomin, ed., Basic features of the geologicalstructure of the hydrological regime and biology ofthe Mediterranean Sea: Moscow, Science, p. 60-72.1966, New data on the structure of the sedimentary strata and basement in the Levant Sea: Oceanol-ogiya, v. 6, p. 828-836.

Mulder, C. J., 1973, Tectonic framework and distribution of Miocene evaporites in the Mediterranean, in

C W. Dro

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