A. Sautkin - Mud volcanoes in the Alboran Sea: evidence from ...

Mud volcanoes in the Alboran Sea: evidence from micropaleontological and geophysical data

A. Sautkin a ; , A.R. Talukder b , M.C. Comas b , J.I. Soto b , A. Alekseev a

a Moscow State University, Geological Faculty and UNESCO Center of Marine Geology and Geophysics, Moscow, Russia b Instituto Andaluz de Ciencias de la Tierra (C.S.I.C. University of Granada), Campus Fuentenueva s/n, 18002 Granada, Spain

Received 5 June 2001; accepted 5 November 2002

Abstract During the BASACALB-TTR9 cruise of the R/V Professor Logachev (1999), two mud volcanoes (called

Marrakech and Granada) were discovered in the southern sector of the mud diapir province in the West Alboran Basin (WAB). This paper presents micropaleontological and geophysical data on these mud volcanoes from gravity core samples, sidescan sonar (OKEAN) images and high-resolution seismic lines. Mud breccia recovered from the Granada mud volcano is matrix-supported with well-consolidated clasts of limestone, marlstone, claystone, siltstone, sandstone and mudstone, whereas mud breccia from the Marrakech mud volcano contains unconsolidated clasts. The mud breccia matrix contains abundant Miocene calcareous nannofossils (CN), together with Pliocene^Pleistocene species and reworked late Cretaceous and Paleocene^Eocene species. CN dating indicates that clasts in the mud breccia derive from late Cretaceous, Paleocene, Eocene, and probable Miocene sediments. These data suggest that the mud diapirs and mud volcanoes in the WAB can be derived from the olistostromes of Unit VI, the basal stratigraphic sequence in the Alboran Sea basin. Unit VIconsists of lower Miocene sediments that incorporated late Cretaceous and Paleocene^Eocene materials and basement-derived rock fragments. The mud volcanic deposits are covered by a thin drape of pelagic marls, suggesting that these two volcanoes are currently inactive. Structures determined on high- resolution seismic profiles across mud volcanoes and surrounding diapirs correspond to the late-stage, Pliocene-to- Quaternary diapir development. This stage is thought to have developed during a compressional tectonic setting that produced folding and wrench tectonics throughout the basin. Mud ascent at that time resulted in active diapirism and mud volcanoes on the seafloor. < 2002 Elsevier Science B.V. All rights reserved.

Keywords: mud diapirs; mud volcanoes ; calcareous nannofossils ; Mediterranean; Alboran Sea

1. Introduction many other locations around the world (e.g. Iva- nov et al., 1996 ; Robertson et al., 1996 ; Robert-

Mud volcanism is widespread in the Mediterra- son and Kopf, 1998; Ivanov, 1999 ; Milkov, nean, Black Sea, and Atlantic Ocean, as well as in

2000 ). In mud volcanoes, plastic, clayey materials or matrix from deep source strata are extruded to the sea£oor by various driving forces (e.g. Akh-

* Corresponding author.

manov and Woodside, 1998; Robertson and

E-mail address: fu@msu.geol.ru (A. Sautkin).

Kopf, 1998; Kopf et al., 2000 ). During mud as-

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

cent through layers of di¡erent ages, it mechani- volcano area ( Fig. 1 ), two mud volcanoes named cally assimilates fragments of rocks surrounding

Granada and Marrakech were observed on the the feeder channel and transports them to the

sidescan images within the diapiric structures. sea£oor. These fragments of rocks can be partial-

Three gravity cores were taken from the top of ly disintegrated and become incorporated in the

the volcanoes, which gave us the opportunity to matrix. By this means mud volcanic deposits,

study the lowermost sediment units of the WAB, called mud breccia, usually consist of clay or

where the mud diapir province is considered to be silty-clay matrix with rock clasts that are hetero-

rooted (e.g. Comas et al., 1992, 1999 ; Chalouan et geneous in composition, shape and size ( Cita et

al., 1997 ; Pe¤rez-Belzuz et al., 1997 ). It was the al., 1981 ; Sta⁄ni et al., 1993 ). Mud volcanoes can

¢rst time that mud volcanoes were directly ob- root several kilometers below the sea£oor ( Hig-

served and sampled on the Alboran sea£oor. gins and Saunders, 1974 ; Fowler et al., 2000 ;

The main aim of this paper is to determine the Aslan et al., 2001 ) and can therefore be consid-

age of the material brought up by the mud volca- ered ‘windows’ in the sedimentary basins that al-

noes in the WAB. Special attention was paid to low the sampling of deep rocks.

the micropaleontological study of matrix and rock In the Alboran Sea basin, mud diapirism and

clasts from the mud breccia. As there exists a mud volcanism occurred in the West Alboran Ba-

close relationship, both spatial and genetic, be- sin (WAB), where major sedimentary depocenters

tween mud volcanoes and mud diapirs ( Silva et occurred (up to 7^8 km thick) ( Fig. 1 ). The sedi-

al., 1995 ), the age of the mud volcano samples mentary sequence in the WAB has been the sub-

would have important implications for the age ject of numerous papers based on seismic re£ec-

of the mobilized sediments and clasts in the mud tion interpretation tied to commercial well data

diapirs.

(e.g. Comas et al., 1992, 1999; Jurado and Co- mas, 1992; Watts et al., 1993 ; Soto et al., 1996 ; Chalouan et al., 1997 ; Pe¤rez-Belzuz et al., 1997 ).

2. Geological setting

Two commercial wells in the Spanish shelf (An- dalucia G1 and Alboran A1 ; Fig. 1 ), drilled

The Alboran Sea represents a basin of about through the complete sedimentary cover, provide

400 km long and 200 km wide with a maximum information on the lowermost units in major de-

water depth of 2 km. It has complex sea£oor pocenters. Ocean Drilling Program (ODP) Leg

morphology, with several ridges, seamounts, 161 ( Comas et al., 1996 ) drilled the sedimentary

troughs and three main sub-basins : the WAB, sequence in the WAB, sampling sediments from

the East Alboran Basin and the South Alboran the middle Miocene to Holocene on top of the

Basin ( Fig. 1 ). The Alboran Ridge is the most metamorphic basement at Site 976 ( Figs. 1 and

prominent NE^SW linear relief across the Albo-

2 ). According to seismic interpretation, it has ran Sea, and emerges locally forming the small been postulated that mud diapirs in the WAB

Alboran Island. The Xauen Bank is situated at have their origin in the lowermost sediments ( Ju-

the southern extremity of the WAB at the junc- rado and Comas, 1992 ; Chalouan et al., 1997 ;

tion with the Alboran Ridge. The bank is formed Pe¤rez-Belzuz et al., 1997 ) but no sedimentological

by close folds trending ENE^WSW ( Bourgois et or paleontological studies on diapiric materials

al., 1992 ; Comas et al., 1992, 1999 ). have been done yet to con¢rm this interpretation.

The Alboran Sea basin is located in the inner During the BASACALB cruise, leg 3 of the

part of the Gibraltar Arc, Betic Rif mountain Training Through Research (TTR) 9 cruise, on-

belt, and has formed by crustal extension in a board the R/V Professor Logachev, the mud dia-

setting of overall convergence since the late Creta- pir province was surveyed in the southern WAB

ceous (e.g. Dewey et al., 1989 ). The direction of to encounter mud volcanoes by means of high-

plate convergence was N^S between the middle resolution seismic, sidescan sonar (OKEAN),

Oligocene and the late Miocene and changed to and gravity coring. In this area, called the mud

NW^SE from the latest Tortonian (9^8 Ma) to

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Fig. 1. Structural map of the WAB and surrounding areas showing the diapir province, early Miocene to Holocene structures and main sedimentary depocenters (taken from Comas et al., 1999 ). AI= Alboran island; AR = Alboran Ridge; Alb-A1 = Alboran A1; EAS = East Alboran Basin; EJ = El Jebha; G1 = Andalucia G1; SAB = South Alboran Basin; SBB = South Balearic Basin; WAB = West Alboran Basin; XB = Xauen Bank; 976 = ODP Site 976. Bold box shows the location of the mud volcano area ( Figs. 3 and 7 ). Inset map shows simpli¢ed bathymetry of the westernmost Mediterranean (Alboran and South-Balearic seas).

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Western Alboran Basin (WAB)

Andalucia G-1

Site 976

Alboran A-1

Pleisto- cene Calabrian

UNIT-I

Plio- L Piacenzian

cene E Zanclean

UNIT 10.4 -IV

MIOCENE 2219 m

Langhian

16.3 -V UNIT Alb-A1

E Gibraltar

Diapir

21.5 WAB Province

Aquitanian ?

area Studied

MB

Fig. 2. Correlation between sedimentary sequences drilled at ODP Site 976, and commercial wells Andalucia G1 and Alboran A1. Seismic stratigraphic units (labeled VIto Ifrom bottom to top), metamorphic basement (MB) and major regional re£ectors are shown. R = re£ectors, correspond to major unconformities within sediments. M = Messinian unconformity. TB = Top of base- ment (from Comas et al., 1992 ). Inset map shows location of commercial wells and ODP Site 976.

the present day. The basin itself formed by late and consist of olistostromes containing polymictic orogenic extension and crustal thinning, coeval

rocks (olistoliths and rock breccia) embedded in with thrusting and shortening in the peripheral

an under-compacted shale matrix. Unit VIhas mountain belt. Extensional tectonics was active

been drilled only at the Alboran A1 well and from at least the early Miocene (about 22 Ma)

the precise age of this unit is still under debate. to the late Tortonian (about 9^8 Ma). Since

It consists of clays with interbedded sandy and then, contractional tectonics produced inversion

sandy-pebbly intervals. Low values for sonic ve- of previous normal faults, reverse and strike-slip

locity, density, and resistivity, shown by logging faults, and folding (see Comas et al., 1999 , for

data, are consistent with the occurrence of under- references).

compacted shales in Unit VI(Alboran A1 well) Six litho-seismic units (labeled VI^I from bot-

and also at the base of Unit V (Andalucia G1 tom to top ; Fig. 2 ), tied to the commercial wells

well) ( Jurado and Comas, 1992 ). The under-com- o¡ the Spanish coast, have been recognized within

pacted shales of Unit VIand probably from the the sedimentary record of the Alboran Sea basin

base of Unit V have been suggested as the source ( Comas et al., 1992 ; Chalouan et al., 1997 ). Ac-

layer for the mud diapirs and volcanoes in the cording to these data, the older deposits overlying

WAB ( Comas et al., 1992 ; Jurado and Comas, the basement (Unit VI) are marine sediments of

1992 ; Chalouan et al., 1997 ; Pe¤rez-Belzuz et al., probable latest Aquitanian ( ?)^Burdigalian age,

241 Granada mud volcano

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Marrakech mud volcano

120 0 35 ° 40'

TTR9 - 262G

TTR 259G

TTR 258G

80 0 b

cm a 0 TTR9 - 262G

TTR9 - 258G TTR9 - 259G

0 0 cm 0 0 50

cm

sample of pelagic marl

of matrix

of matrix

Legend

sample of muddy mixed

sediments

mud breccia

sample of carbonate clay (N 1)

Recovery: 119 cm

muddy mixed sediments

sample of carbonate clay (N 2)

sample of carbonate

sample of carbonate clay (N 3)

clay (N 4)

Recovery: 144 cm 200

marl

sample of crashed

carbonate clay rocks (N 5) Recovery: 210 cm

Fig. 3. Acoustic mosaic (OKEAN sidescan sonar images) of the sea£oor from the studied area. Core logs of gravity cores from the Granada (TTR9 258G and TTR9 259G) and Marrakech (TTR9 262G) mud volcanoes are shown. Arrows and numbers in core logs correspond to samples taken for CN studies. Bathymetric contour lines in the central sidescan ¢gure are in meters.

3. Mud volcano morphology nian) mainly consists of sand-silt-clay turbidite and turbiditic muds. Sediments from Unit III

Unit IV (middle Serravallian to lower Torto-

The surface expressions of mud volcanoes and (Tortonian) comprise sandstone intervals, with

diapir highs were analyzed on the sidescan sonar claystone and silty clay beds, also corresponding

mosaic, composed of seven OKEAN pro¢les (9.5 to turbidite facies. Unit II (Messinian deposits)

kHz) recorded during the BASACALB cruise consists of marine siliciclastic and shallow carbon-

(TTR-9, leg 3) in the mud volcano area ( Fig. 1 ). ate facies, with occasional gypsum and thin anhy-

The OKEAN pro¢les are 8 km wide and overlap drite intervals ( Jurado and Comas, 1992 ). Unit I

each other, giving a full coverage of an area of (Pliocene to Holocene sediments) was sampled in

about 1120 km 2 ( Fig. 3 ).

its entirety at ODP Site 976 ( Fig. 2 ). It mainly Most of the area is draped with uniform sedi- consists of pelagic marls, muddy turbidites, hemi-

mentation that provides a relatively uniform pelagic clays and rare silty-sand turbidites ( Comas

backscatter. In three places, high backscatter in- et al., 1996 ). Neogene calcareous nannofossils

tensity in comparison with the general level of (CN) in middle to upper Miocene and Pliocene

background backscatter is observed ( Fig. 3 ). sediments in the WAB were comprehensively de-

Two of these high backscatter features have scribed in samples from ODP Site 976 ( Siesser

been proved to correspond to mud volcano cra- and de Kaenel, 1999 ).

ters. The variation of backscatter intensity among

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

the di¡erent mud volcanoes is probably caused by

Table 1

variation in thickness of pelagic sediments over-

Lithology and age groups of the rock clasts from the Grana-

lying the mud breccia, which produces an acoustic da mud volcano attenuation of the sidescan sonar signal ( Volgin

and Woodside, 1996 ). The Granada mud volcano presents an elliptical feature de¢ned by an outer ring with moderate backscatter and an inner elliptical patch with high backscatter compared to the low uniform background backscatter intensity. The patch of high backscatter is o¡set towards the northeast of the outer circle and is about 1.8 km in diameter ( Fig. 3 ). The Marrakech mud volcano shows a circular feature with irregular boundaries. To the northwest of this mud volcano, the patch of high backscatter with very irregular boundaries is interpreted as a diapiric high with a positive mor- phologic expression. On the southeastern £ank of this diapiric high, a series of patches with moder- ate backscattering are observed, which can be in- terpreted as mud £ows on the £ank of the mud diapiric volcanic structure ( Fig. 3 ).

4. Nature of breccia and clasts The Granada mud volcano was sampled by

gravity cores 258G and 259G, taken from its cra- ter at water depths of 583 m and 580 m, respec- tively ( Fig. 3 ). Lithological studies of the cores from the Granada mud volcano indicate that the materials consist of matrix-supported mud breccia with sedimentary rock clasts. Core 258G recov- ered 144 cm of sediments, the uppermost being

er clasts (1^2 m) were observed at the crater of the

18 cm of brown pelagic marls, whereas the rest Granada mud volcano by the underwater TV sys- is a matrix-supported breccia with clasts of vary-

tem ( Comas et al., 2000a ). The rock clasts from ing lithology ( Fig. 3 ). Rock clasts were randomly

each core were classi¢ed according to their com- distributed throughout the core sections and make

position, color, grain size, structure, reaction with up approximately 5% by volume of the mud brec-

HCl and hardness ( Table 1 ). In the Granada mud cia deposits. The average size of the rock clasts is

volcano the more abundant clast lithologies are 2^3 cm. Core 259G recovered 119 cm of similar

limestones (15 clasts) and claystones (10 clasts), mud breccia with rock clasts ( Fig. 3 ). The upper

whereas marlstones (four clasts), sandstones part of the succession is characterized by intervals

(three clasts), siltstones (four clasts) and mud- with abundant sandy admixture. Larger rock

stones (three clasts) are less common ( Table 1 ). clasts are found at the top of this core (the largest

The recovered mud breccia was similar to that clast is formed of cemented siltstone, 10 cm in

described in the eastern Mediterranean ( Kopf et diameter) although their maximum size is limited

al., 2000 ; Sta⁄ni et al., 1993 ). by the diameter of the core (14.8 cm). Much larg-

The Marrakech mud volcano was sampled by a

243 Table 2

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Summary information on distribution of Upper Cretaceous CN

single gravity core (262G) taken from its slope at val is similar to the patchy/cloudy mud breccia

a water depth of 1086 m ( Fig. 3 ). The core recov- described by Sta⁄ni et al. (1993) in volcanoes ered 210 cm of sediments, which is composed of

from the eastern Mediterranean. pelagic marl (0^30 cm) ; gray, structureless muddy mixed sediments (30^150 cm) with numerous un- consolidated clasts of claystone (varying in size

5. CN biostratigraphy

from 0.05 to 1 mm) ; and patchy/cloudy clayey sediments (150^210 cm) ( Fig. 3 ). The clasts have

CN assemblages were carefully examined on

a similar consistency to the matrix. Samples of smear slides for all lithological varieties of the muddy mixed sediments, di¡erent-colored carbon-

rock clasts. Smear slides of matrix and pelagic ate clays observed in the patchy/cloudy interval,

marl from the Granada mud volcano and from and a crushed fragment of soft unconsolidated

the various types of sediments encountered in rocks pressed into the sediments were studied

the Marrakech mud volcano were prepared for ( Fig. 3 ). The muddy mixed sediments with numer-

CN identi¢cation. The smear slides were prepared ous millimetric and unconsolidated clasts might

by standard techniques ( Perch-Nielsen, 1985 ). No

be considered mud breccia. The lowermost inter- cleaning or concentration of the materials was

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Table 3 Age of Upper Cretaceous rock clasts

undertaken in order to retain original sediment composition and gather data on the biogenic

Table 4

and inorganic composition of the ¢ne fraction.

Summary information on distribution of Paleogene and Neo-

Smear slides were studied using an Olympus po-

gene CN

larizing light microscope with a magni¢cation of U1000. A semiquantitative method of investiga-

tions was performed on the smear slides ( Silva et al., 1995 ).

For a more precise analysis of CN, 19 rock clasts were studied under the scanning electron microscope (SEM). A settling technique described by Shumenko (1987) , which allows the elimina- tion of particles under 2 Wm and above 30 Wm, was used to prepare samples for SEM. This study provides additional data for CN biostratigraphy and SEM microphotographs of CN.

The abundance of individual species and the total abundance of CN species are indicated in Tables 2^8 as follows : RR: very rare : one speci- men in 2^20 ¢elds of view; R: rare : one or two specimens in 1^2 ¢elds of view ; C : common : 2^10 specimens in each ¢eld of view ; A: abundant: 10^

20 specimens in each ¢eld of view ; AA: very abundant: more than 20 specimens in each ¢eld of view.

The estimation of CN preservation is based on

245 Table 5

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Table 6

Age of Paleogene rock clasts Summary information on distribution of CN in pelagic marl (pm), matrix, muddy mixed sediments (mms) and in samples of carbonate clays

the comments of Siesser and de Kaenel (1999) and indicated in Table 2^8 as follows : P: poor pres- ervation : severe dissolution, fragmentation and/or secondary overgrowths destroying primary struc- ture. Most specimens cannot be identi¢ed to the species or generic level ; M: moderate preserva- tion : dissolution and/or secondary overgrowths alter primary morphological features. Most speci- mens can be identi¢ed to the generic level and often to species level ; G: good preservation : mi- nor evidence of dissolution and/or secondary overgrowths. Diagnostic features are fully pre- served and almost all specimens can be identi¢ed to species level.

In the course of identi¢cation of CN we have adhered to the criteria presented by Perch-Nielsen (1985) for Mesozoic CN and for Cenozoic CN. In addition, the following publications were used : Young (1998) for Neogene CN, Varol (1998) for Paleogene CN, Burnett (1998) for Upper Creta- ceous CN, Albian to Pleistocene CN from the Western South Atlantic ( Perch-Nielsen, 1977 ), Neogene CN from the Mediterranean ( Muller,

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Table 7 Distribution of Upper Cretaceous CN

1978 ), Oligocene^Miocene CN biostratigraphy have been classi¢ed into three main groups ac- and paleoecology from Iberia abyssal plain ( De cording to age ( Table 1 ).

Kaenel and Villa, 1996 ), Eocene CN from Iberia abyssal plain ( Liu, 1996 ).

Group 1 (Cretaceous) :

Distribution of Paleogene and Neogene CN The CN content in this group, although rela- taxa has been re¢ned based on data from ODP

tively abundant, is badly to moderately preserved drilling results ( Muller, 1978 ; Liu, 1996 ; De Kae-

( Fig. 4 ), and has low diversity ( Table 2 ). The age nel and Villa, 1996 ; Siesser and de Kaenel, 1999 ).

of the studied samples is mainly late Cretaceous, The Cenozoic zonation of Martini (1971) and

but their biostratigraphic zone is often uncertain Cretaceous zonation of Sissingh (1977) , revised

due to the low diversity of CN and the lack of by Perch-Nielsen (1985) , were applied.

marker species. Only in some cases was a precise dating of clasts possible.

5.1. Granada mud volcano Samples : TTR9 258G Ic, 258G Ia, 258G IIc. The presence of Aspidolithus parcus expansus in-

5.1.1. Rock clasts dicates an age of early Campanian (zones CC18^ All clasts sampled in cores 258G and 259G

CC19) for these clasts ( Table 3 ).

247 Table 8

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Distribution of Paleogene and Neogene CN

248 A. Sautkin et al. / Marine Geology 195 (2003) 237^261

3 sample 259G 1s15

sample 259G 1s5 sample 259G 1s1

sample 258G VI 1 m

7 sample 259G 2s6 1 m

10 11 1 m 12

sample 258G V

sample 258G III a

sample 258G II

Fig. 4. SEM microphotographs of late Cretaceous species of CN found in rock clasts. 1. Gartnerago obliquum (sample 259G 1s15)

2. Prediscosphaera sp. (sample 259G 1s15) 3. Ei¡ellithus turrisei¡elii (sample 259G 1s15) 4. Cribrosphaerella ehrenbergii (sample 259G 1s5) 5. Arkhangelskiella sp. (sample 259G 1s5) 6. Tranolithus exiguus (sample 259G 1s1) 7. Lithraphidites carniolensis (sample 258 VI) 8. Micula decussata (sample 259G 2s6) 9. Rhagodiscus angustus (sample 258G II) 10. Arkhangelskiella cymbiformis (sample 258G V) 11. Arkhangelskiella sp.? (sample 258G IIIa) 12. Watznaueria barnesae (sample 258G II)

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Samples : TTR9 259G 1s16, 259G 2s10, 258G. set of Toweus eminens ( Fig. 6 ) in the late Paleo- IIb, 259G 1s5. The presence of Arkhangelskiella

cene ( Perch-Nielsen, 1985 ) and the upper age limit cymbiformis indicates that the age of these clasts

corresponds to the last occurrence of Ellipsolithus could be between late Santonian and late Maas-

macellus ( Fig. 5 ) in the early Ypresian (top of trichtian ( Table 3 ). But taking into consideration

NN11) ( Varol, 1998 )( Table 5 ). the last occurrence of specimens of A. cymbiformis

Sample TTR9 258G VII. The presence of Cru- var. NT with thin margin ( Fig. 5 ) in the upper

ciplacolithus frequens, Ellipsolithus bollii and Neo- Campanian ( Varol, 1989 ), we can assume that the

chiastozygus sp. ( Fig. 5 ) indicates that the age of age of these rocks is late Santonian^late Campa-

this rock is middle Paleocene^late Paleocene (Se- nian.

landian^Thanetian) ( Table 5 ). CN assemblages found in the other rock clasts

Paleocene^Eocene species were also observed in show less diversity ( Table 2 ). However, based on

the others clasts ( Table 4 ), but the preservation of these CN associations we can suggest ages for the

CN is somewhat worse.

rock clasts. For most of these rocks the lower age Sample TTR9 258G VIII. Based on the pres- limit is the onset of Arkhangelskiella cymbiformis

ence of Toweius spp., Toweius eminens (last occur- (CC17) ( Burnett, 1998 ) or Micula decussata

rence in early Eocene) ( Perch-Nielsen, 1985 ), and (CC14) ( Perch-Nielsen, 1985 ) and the upper limit

Reticulofenestra spp. (¢rst occurrence in early Eo- is extinction of late Cretaceous CN (Cretaceous^

cene) ( Perch-Nielsen, 1985; Varol, 1998 ), this Tertiary boundary) ( Table 3 ). The occurrence of

rock can be approximately dated as lower Eocene Tranolithus orionatus indicates that the upper age

(Ypresian).

limit is early Maastrichtian (CC23) ( Perch-Niel- Sample TTR9 259G 2s14. The presence of sen, 1985 ; Burnett, 1998 ). The last occurrence of

Campylosphaera dela (NN10^NN15) ( Perch-Niel- the large forms of Aspidolithus parcus groups near

sen, 1985 ) indicates that the age of this clast could the Campanian/Maastrichtian boundary ( Perch-

be early^middle Eocene (Ypresian^Lutetian) ( Ta- Nielsen, 1985 ), thus the presence of these forms

ble 5 ).

indicates an age older than Maastrichtian. Based Sample TTR9 259 1s6 can be approximately on these observations we can assume that most of

dated as middle Paleocene^early Paleocene based the rock clasts are Santonian^Campanian or San-

on the rare occurrence of Fasciculithus tympani- tonian^Maastrichtian in age ( Table 3 ). Clast

formis (NN5^NN9) ( Perch-Nielsen, 1985 )( Table 258G II and clast 259G 1s15 could be dated be-

tween middle Cenomanian, based on the ¢rst oc- currence of Gartnerago obliquum ( Burnett, 1998 )

Group 3 (Neogene) :

and upper Maastrichtian ( Table 3 ). Samples This group includes only two clasts containing TTR9 258G VIand 259G 1s2 can be approxi-

poorly preserved and di⁄cult to identify CN ( Fig. mately dated as Cretaceous ( Table 3 ), based on

the presence of Lithraphidites carniolensis (Berri- Samples TTR9 259G 2s11, 259G2s12. Very asian^Maastrichtian) and Predicosphaera spp.

similar assemblages of CN are encountered in (lower Albian^Maastrichtian) ( Perch-Nielsen, 1985 ).

these two clasts ( Table 4 , Fig. 6 ). The presence of Coccolithus miopelagicus indicates that the

Group 2 (Paleogene) : age of these clasts could be between late Oligo- This group represents the smaller proportion of

cene and Miocene.

the collected clasts. CN are abundant and moder- The ¢ve samples TTR9 259G 2s8, 259G 2s7, ately well preserved ( Fig. 5 ), but have relatively

258G IIa, 259G 1s18, 258G Ib ( Table 1 ) are bar- low diversity ( Table 4 ). The following samples

ren of CN.

contained well-preserved CN. Sample TTR9 258G III. This clast can be dated

5.1.2. Mud breccia matrix

as upper Paleocene^lower Eocene (Thanetian^ The matrix of mud breccia has been analyzed in Ypresian). The lower limit corresponds to the on-

two cores ( Fig. 3 ). Abundant Miocene to Pliocene

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

and rare pre-Miocene CN are found. Upper Cre- ble 7 ). Paleocene^Eocene CN are rare and badly taceous CN are rare and moderately preserved

preserved ( Table 6 ). The matrix also contains spe- ( Table 6 ). Together with widely distributed taxa

cies common during the late Eocene, Oligocene ( Table 7 ), the marker species of late Campanian^

and early Miocene ( Tables 6 and 8 ). Maastrichtian Quadrum tri¢dum (CC22^CC23)

Miocene to Pliocene CN are well preserved ( Ta- and Arkhangelskiella cymbiformis are found ( Ta-

bles 6 and 8 ). The ages determined are early Mio-

sample 258G III

11 1 m sample 258G VII

1 m 10 1 m

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

1 m 3 sample 259G 2s11

7 sample 259G 2s12

Fig. 6. SEM microphotographs of Neogene species of CN found in rock clasts. 1. Helicosphaera sp. (sample 259 2s11)

2. Discoaster sp. (sample 259G 2s11) 3. Pontosphaera multipora (sample 259G 2s11) 4. Reticulofenestra sp. (sample 259G 2s12) 5. Discoaster sp. (sample 259G 2s12)

6, 7. Discoaster cf. de£andrei (sample 259G 2s12)

cene (Burdigalian) (Discoaster druggii, Sphenoli-

5.1.3. Pelagic marl

thus belemnos), and middle Miocene^middle Plio- One sample of pelagic marl overlying mud brec- cene (Reticulofenestra pseudoumbilicus, Discoaster

cia in core 258G ( Fig. 3 ) was examined. CN are intercalaris). The most common species are Reti-

very abundant in this sample. The large share of culofenestra minuta and Reticulofenestra minutula,

Emiliania huxleyi ( Table 6 ) in the assemblage in- which are widespread from the Miocene to the

dicates the Emiliania huxleyi acme zone, thus this late Pliocene. At the same time, Gephyrocapsa

pelagic marl can be dated as the late Pleistocene^ spp., typical for Pliocene sediments, are less com-

Holocene.

mon in the matrix.

Fig. 5. SEM microphotographs of Paleogene species of CN found in rock clasts. 1. Chiasmolithus cf. bidens (sample 258G III)

2. Chiasmolithus solitus (sample 258G III) 3. Ericsonia subpertusa (sample 258G III)

4, 7. Discoasteroides cf. bramlettei (sample 258G III) 5. Toweius eminens (sample 258G III) 6. Ellipsolithus macellus (sample 258G III) 8. Ellipsolithus bollii (sample 258G VII) 9. Neochiastozygus sp. (sample 258G VII) 10. Neochiastozygus cf. perfectus (sample 258G VII) 11. Cruciplacolithus frequens (sample 258G VII)

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

5.2. Marrakech mud volcano crushed fragment of soft rock sampled in the core ( Fig. 3 ) containing poorly or moderately pre-

In the muddy mixed sediments from this core, served, low-diversity CN assemblage. The most CN are abundant or common and their preserva-

common are upper Cretaceous taxa ( Table 6 ). tion varies from rather poor for older species to

The presence of Lithraphidites quadratus indicates good for Miocene to recent forms ( Table 6 ).

a late Maastrichtian age (zones CC25 and CC26). Upper Cretaceous CN are rare in this sample

Miocene taxa, including early Miocene Triquetro- ( Table 6 ). In association with widely distributed

rhabdulus carinatus (NN1^NN2), were also en- taxa ( Table 7 ) marker species of Maastrichtian

countered in this sample ( Table 6 ). age, Lithraphidites quadratus (zones CC25^ CC26) and late Campanian^Maastrichtian ages, Quadrum tri¢dum (zones CC22^CC23), are en-

6. Structures associated with mud diapirs and countered ( Table 7 ). Paleocene^Eocene and Oli-

volcanoes

gocene CN are very rare in this sample ( Tables

6 and 8 ). In the mud volcano area ( Fig. 1 ), 70 km of Miocene^Pliocene CN are common ( Table 6 ).

high-resolution seismic lines recorded during the Triquetrorhabdulus carinatus is a marker species

BASACALB cruise (TTR9, leg 3) were used to for earliest Miocene (Aquitanian^Burdigalian)

study the recent mud diapirism and volcanism age (NN1^NN2), the presence of Cyclicargolithus

( Fig. 7 ). Multichannel seismic re£ection lines £oridanus, common Cyclicargolithus abisectus and

crossing the area were used to correlate the dis- Discoaster de£andrei is also indicative for early

tinguished litho-seismic units. Miocene age ( Table 7 ). Discoaster pseudovariabilis

On the high-resolution seismic pro¢les, mud di- is characteristic for middle Miocene, Discoaster

apirs are imaged as transparent to semitranspar- pansus for early Pliocene age. Many species with

ent seismic facies with a chaotic facies at their

a relatively wide distribution were observed in the nucleus. Seismic pro¢ling only crossed the Marra- sample ( Table 8 ).

kech mud volcano, although the seismic tracking Pleistocene CN are abundant ( Table 6 ). The

was o¡ center. This mud volcano developed on most abundant are small Gephyrocapsa sp. ( 6 3

the £ank of a diapir with a chaotic seismic facies, Wm), Gephyrocapsa caribbeanica and Emiliania

and has a negative sea£oor expression ( Figs. 3 huxleyi.

and 8 ).

A mixture of CN of di¡erent ages was observed The host rocks (Pliocene to Recent sediments) in the carbonate clays sampled from the lower-

consist of continuous re£ections in a parallel-to- most interval ( Table 6 ). Upper Cretaceous CN,

divergent and convergent, generally aggrading poorly or moderately preserved, are rare in these

strata pattern. Litho-seismic units generally have samples ( Table 6 ). Paleocene^Eocene CN are

a wedge-shaped geometry, achieving their maxi- rarer than upper Cretaceous ones and only a

mum thickness between two diapiric highs or at few poorly preserved specimens were encountered

the border of the diapirs ( Figs. 8 and 9 ). When ( Table 6 ).

maximum thickness is attained at the diapir £ank, The most abundant species in these samples are

it can be deduced that the diapir rise occurred well preserved and diversi¢ed Miocene^Pliocene

through pre-existing faults ( Fig. 9 ). The contacts CN ( Table 6 ). Among them species indicative

between diapirs and host rocks are in some cases for late Miocene to late Pliocene age are encoun-

sharp, being characterized by high-angle or sub- tered ( Table 8 ).

vertical faults. Near the diapirs, angular uncon- Finely preserved and abundant Pleistocene CN

formities with onlap and/or toplap geometry are were also identi¢ed in the samples ( Table 6 ), with

observed, passing laterally to become conform- common forms being Emiliania huxleyi and small

ities. Based on the occurrence of local unconform- Gephyrocapsa spp. ( 6 3 Wm).

ity, the Pliocene to Quaternary sedimentary in¢ll Among the samples of particular interest is a

can be divided into four seismic units (labeled,

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Marrakech mud volcano

Fig. 8

262G

258G 259G

Granada mud volcano

Conrad 828

Morocco

single channel seismic lines seismic lines presented in figures

MCS lines mud volcanoes sampled by gravity coring

Fig. 7. Location map of high-resolution seismic (Ps lines), multichannel seismic (MCS) pro¢les and gravity cores studied in the mud volcano area (see location in Fig. 1 ). Bathymetry contour lines are in meters.

from top to bottom, Q1 to Q3, for the Quater-

7. Discussion

nary ; and P1 and P2 for the Pliocene ; Figs. 8 and

9 ). Subunit Q2 presents the maximum thickness Lithological and CN data from the studied variation. Folds observed in the studied area are

samples indicate the nature of the materials trans- mainly related to the distribution of diapiric

ported to the sea£oor by the mud volcanoes. The highs, so that the anticlines and synclines coincide

abundance of Miocene CN in the matrix from the with the diapiric highs and marginal troughs, re-

Granada mud volcano ( Table 6 ) suggests that the spectively.

principal sources forming the mud volcano are

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

TWTT(msec)

Marrakech mud volcano

Q2

Diapir high

P1+Q3

P2

TWTT(msec)

Fig. 8. High-resolution seismic line Ps 174 across a mud diapir and interpretation. This line crosses the Marrakech mud volcano o¡ center. Note that this mud volcano developed on the £ank of a diapiric high, following a probable fault. Q1 to Q3, P1 and P2: seismic subunits distinguished in the Plio^Quaternary sediments (Unit I; Fig. 2 ). Location of seismic line is shown in Fig. 7 .

sediments of Miocene age. The presence of the pierced overlying strata during the ascent of the early Miocene (Burdigalian) marker species indi-

mud volcano.

cates that the sediments belonging to the lower The upper Cretaceous (Santonian^Maastricht- Miocene unit (olistostrome Unit VI) were the

ian), Paleocene and Eocene CN observed in the source layer. At the same time, the presence of

matrix are interpreted as reworked material. The late Miocene and Pliocene CN indicates that

relatively common occurrence of these CN in the younger sediments were incorporated from the

matrix ( Table 6 ) results from the redeposition of

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Fig. 9. High-resolution seismic line Ps 172 across mud diapirs and interpretation. Note the sharp contact between diapir and

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Table 9

derived from Paleocene, Eocene and Miocene

A comparison between upper Cretaceous CN contents from

sediments are less common ( Table 1 ). The mixing

rock clasts, matrix and muddy mixed sediments

of rock clasts of di¡erent ages is interpreted as derived from material belonging to the basal olis- tostrome Unit VI, drilled by the commercial well Alboran A1 in the WAB. The variety and abun- dance of Miocene CN in the matrix and the scar- city of Miocene rocks in the mud breccia indicate that the Miocene rocks were most probably to- tally disintegrated into muddy lithologies, whereas the older, and more consolidated rocks (Creta- ceous to Eocene) were better preserved as clasts in the mud breccia.

The most common CN assemblage in the Mar- rakech mud volcano deposits is Miocene^Pliocene and Pleistocene in age. The lower Miocene taxa (Aquitanian^Burdigalian) are encountered in this assemblage, so it seems possible that the Marra- kech mud volcano could have the same source as the Granada mud volcano (olistostrome unit VI). However, the common presence of the middle Miocene to early Pliocene species would seem to indicate that younger sediments were extensively involved in the activity of this mud volcano. The presence of reworked upper Cretaceous (Santo- nian^Maastrichtian) and Paleogene CN was also determined in the Marrakech mud volcano. The set of upper Cretaceous CN encountered in the muddy mixed sediments, very similar to that of those from the rock clasts and matrix from the Granada mud volcano ( Table 9 ), implies that these materials could be reworked from the same source. The crushed fragments of rock (sam- ple N5) with upper Cretaceous and lower Mio- cene CN ( Table 6 ) is evidence for the disintegra- tion of upper Cretaceous rocks into a muddy lithology.

If it is correct that the source of mud volcano materials is the olistostrome unit in the WAB (Unit VI), known in the commercial well (Albo- ran A1) o¡ the Spanish coast, then we can spec-

Upper Cretaceous and Paleogene materials. The ulate that this unit is distributed throughout the existence of the same set of upper Cretaceous taxa

WAB and ¢lled the main depressions on both the in the matrix as well as in the rock clasts ( Table 9 )

Spanish and Moroccan margins. Based on our suggests a common sediment source. Most of the

micropaleontological data, we can also demon- rock clasts encountered in the Granada mud vol-

strate that this olistostrome unit includes upper cano are from upper Cretaceous sediments,

Cretaceous and Paleogene blocks. mainly Santonian^Maastrichtian, whereas clasts

Gravity cores TTR9 262, taken from Marra-

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

kech mud volcano, and TTR9 258G, taken from 1992 ; Comas et al., 1992, 1999 ). High-angle Granada mud volcano, were found generally cov-

faults, folds and sharp contacts in relation to ered by a drape of pelagic marls. The local ab-

mud diapirs, together with the geological situation sence of a pelagic blanket (core TTR9 259G) may

of the mud volcano area, suggest that mud volca-

be due to erosion of the uppermost sediments by nism developed in a general compressional setting surface currents. Study of the CN assemblage

during the Pliocene to Quaternary. from these sediments (recovered on the Granada

Our CN dating of the mud volcano material mud volcano) enables dating of this marl as late

demonstrates for the ¢rst time that the source Pleistocene^Holocene. On the Granada mud vol-

layer of the mud volcanoes and mud diapirs in cano there was no evidence of £uid escape seen on

the WAB is lower Miocene sediments with em- underwater TV system during the BASACALB

bedded Paleogene and Upper Cretaceous clasts. cruise ( Comas et al., 2000b ). The existence of

The mud volcanoes seem to be rooted in olistos- these pelagic marl blankets, together with the ab-

tromic Unit VI, so our data con¢rm the early sence of £uid escape and the relatively uniform

Miocene age of this unit, and also indicate that backscatter intensity across the area, suggests

the olistostrome contains Paleogene and Creta- that the two mud volcanoes are probably cur-

ceous materials.

rently inactive. The Pliocene-to-Quaternary diapiric rise, occur- ring during sedimentation, created local uplift and

8. Conclusions

subsequent erosion and thinning of the litho-seis- mic units producing lateral pinchout and onlap

(1) Mud volcanoes encountered in the WAB are towards the diapiric highs, and therefore inducing

formed by matrix-supported mud breccia. Based local unconformities in the sedimentary sequence

on the presence of lower Miocene CN along with ( Figs. 8 and 9 ). The angular unconformities at the

the mixing of diversi¢ed rock clasts in the mud base of subunits Q1 and Q2 and the highly vari-

breccia, we determined that the mud volcanoes able thickness of subunit Q2 suggest that there

are likely rooted in olistostromic Unit VI, which were at least two major pulses of diapiric rise

should therefore be early Miocene in age, forming (pre- and post-Q2) during the late Pliocene and

the lowermost sedimentary sequence in the WAB. Quaternary in the studied sector ( Figs. 8 and 9 ).

(2) The occurrence of upper Cretaceous to Eo- The Marrakech mud volcano developed on the

cene clasts in the mud volcano sediments suggests £ank of a diapiric high following a fault ( Fig. 8 ),

that olistostromic Unit VIcontains, among other indicating that it was probably formed by £uid

materials, upper Cretaceous and Paleogene migration through the body of the diapir. The

blocks.

Granada mud volcano, on the other hand, shows (3) Drapes of pelagic marl on mud volcanic no direct relationship with any visible diapir. The

deposits indicate that the studied mud volcanoes existence of larger and abundant clasts on the

are currently inactive.

crater of this volcano (seen on the underwater (4) The Marrakech mud volcano is interpreted TV system during the cruise) and the surrounding

as resulting from £uid migration along the sea- moderate backscatter intensity suggest that it was

£oor-piercing mud diapiric body. The Granada probably the result of the rise of £uidized sedi-

mud volcano is probably formed from the rise ments through faults from probably deeper dia-

of £uidized mud breccia along a fault on the £ank pirs. Thus, we suggest that these mud volcanoes

of a deeper diapir.

can be the result of diapirism (as diapir extrusion) (5) High-angle faults in the border of the mud primarily driven upward by buoyancy forces (e.g.

diapirs, together with anticline folds coinciding Brown, 1990; Kopf et al., 1998 ; Milkov, 2000 ).

with diapir highs, suggest that mud volcanism The mud volcano area developed at the north-

and diapirism developed during the Pliocene and ern £ank of Xauen Bank, which is formed by

Pleistocene in a general compressional tectonic post-Messinian close folds ( Bourgois et al.,

setting.

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Acknowledgements Markalius inversus (De£andre in De£andre and Fert, 1954) Bramlette and Martini (1964) We are grateful to M.K. Ivanov, of the TTR

Markalius spp.

program, for his all-encompassing help. More- Manivitella pemmatoidea De£andre over, we wish to express our gratitude to the BA-

Microrhabdulus decoratus De£andre SACALB TTR9 scienti¢c party. We thank refer-

Micula concava (Stradner in Martini and Strad- ees J.A. Flores, E. De Kaenel, A. Kopf and N.

ner, 1960) Verbeek (1976)

Kenyon for their thoughtful comments and de- Micula decussata Vekshina (1959) tailed criticism, which helped to clarify the manu-

Placozygus sigmoides (Bramlette and Sullivan, script. We also thank C. Laurin for her careful

1961) Romein (1979)

and detailed linguistic revision. Funding for the Predicosphaera grandis Perch-Nilsen (1979) BASACALB Cruise and this work was provided

Predicosphaera cretacea (Arkhangelsky, 1912) by Project REN2001-3868-C03 (MCYT, Spain).

Gartner (1968)

Predicosphaera spinosa (Bramlette and Martini, 1964), Gartner (1968)

Appendix. Calcareous nannofossils identi¢ed in

Predicosphaera spp.

this paper Quadrum tri¢dum (Stradner in Stradner and Papp, 1961) Prins and Perch-Nilsen in Manivit Group 1. Cretaceous CN listed alphabetically

et al. (1977)

by generic epithet. Rhagodiscus angustus Stradner (1963) Ahmuellerella octoradiata (Gorka, 1957) Rein-

Rhagodiscus spp.

hardt (1966) Retecapsa crenulata (Bramlette and Martini, Arkhangelskiella cymbiformis Vekshina (1959)

1964) Noel (1970)

Arkhangelskiella specillata Vekshina (1959) Tetrapodorhabdus decorus (De£andre in De£an- Arkhangelskiella cf. A. specillata

dre and Fert, 1954) Wind and Wise (1977) Arkhangelskiella spp.

Thiersteinia cf. T. ecclesiactica Aspidolithus parcus (Stradner, 1963)

Thoracosphaera spp.

Braarudosphaera bigelowii (Gran and Braarud, Tranolithus exiguus Stover (1977) 1935) De£andre (1947)

Tranolithus gabalus Stover (1966) Calculites obscurus (De£andre, 1959) Prins and

Tranolithus orionatus Reinhardt (1966) Sissingh in Sissingh (1977)

Tranolithus spp.

Chiastozygus litterarius (Gorka, 1957) Manivit Watznaueria barnesae Black in Black and (1971)

Barnes (1959)

Cribrosphaerella ehrenbergii (Arkhangelsky, Zigodiscus cf. Z. variatus 1912) De£andre in Piveteau (1952)

Group 2. Cenozoic CN listed alphabetically by Ei¡ellithus turrisei¡elii (De£andre in De£andre

generic epithet.

and Fert, 1954) Reinhardt (1965)

Biscutum spp.

Gartnerago obliquum (Stradner, 1963) Noel Calcidiscus leptoporus (Murray and Blackman, (1970)

1898) Loeblich and Tappan (1978) Glaukolithus diplogrammus (De£andre in De-

Calcidiscus macintyrei (Murray and Blackman, £andre and Fert, 1954) Reinhardt (1964)

1989) Loeblich and Tappan (1978) Kamptnerius magni¢cus De£andre (1959)

Camylosphaera dela (Bramlette and Sulivan, Lithraphidites carniolensis De£andre (1963)

1961) Hay and Mohler (1967) Lithraphidites alatus Thierstein in Roth and

Ceratolithus spp.

Thierstein (1972) Chiasmolithus bidens Bramlette and Sullivan Lithraphidites praequadratus Roth (1978)

Lithraphidites quadratus Bramlette and Martini Chiasmolithus solitus (Bramlette and Sullivan, (1964)

1961) Locker (1968)

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Chiasmolithus consuetus (Bramlette and Sulli- Ellipsolithus macellus (Bramlette and Sullivan van, 1961) Gartner (1970)

1961) Sullivan 1964

Chiasmolithus spp. Emiliania huxleyi (Lohmann, 1902) Hay and Coccolithus eopelagicus (Bramlette and Riedel,

Mohler (1967)

1954) Bramlette and Sullivan (1961) Ericsonia subpertusa Hay and Mohler (1967) Coccolithus miopelagicus Burky (1971)

Fasciculithus tympaniformis Hay and Mohler Coccolithus pelagicus (Wallich, 1877) Schiller

(1930) Geminilithella bramlettei (Hay and Towe, 1962) Coronocyclus nitescens (Kamptner, 1963) Brem-

Varol (1989)

lette and Wilcoxon (1967) Gephyrocapsa oceanica Kamptner (1943) Cruciplacolithus tenuis Hay and Mohler (1967)

Gephyrocapsa caribbeanica Boudereaux and Cruciplacolithus frequens (Perch-Nielsen, 1977)

Hay (1967)

Romein, 1979

Gephyrocapsa spp.

Cruciplacolithus spp. Helicosphaera carteri (Wallich, 1877) Kamptner Cyclicargolithus abisectus (Muller, 1970) Wise

(1973) Helicosphaera mediterranea Muller, 1981 Cyclicargolithus £oridanus (Roth and Hay,

Helicosphaera euphratis Haq, 1966 1967) Bukry (1971)

Helicosphaera lophota Bramlette and Sullivan, Dictiococcites perplexa Burns (1975)

Dictiococcites productus Backman (1980)

Helicosphaera spp.

Dictiococcites bisectus (Hay, Mohler and Wade, Lanternithus minutus Stradner (1962) 1966) Bramlette and Sullivan (1961)

Nanotetrina spp.

Discoaster barbadiensis Tan (1927) Neochiastozygus cf. N. perfectus Discoaster bollii Martini and Bramlette (1963)

Neochiastozygus spp.

Discoaster brouweri (Tan, 1927) Bramlette and Pontoshpaera multipora (Kamptner) Roth Riedel (1954)

Discoaster de£andrei Bramlette and Riedel

Pontoshpaera spp.

(1954) Reticulofenestra haqii Backman (1978) Discoaster druggii Bramlette and Wilcoxon

Reticulofenestra hillae Bukry and Percival (1967)

Discoaster hamatus Martini and Bramlette Reticulofenestra minuta Roth (1970) (1963)

Reticulofenestra minutula (Gartner, 1967) Haq Discoaster intercalaris Bukry (1971)

and Berggren (1978)

Discoaster multiradiatus Bramlette and Riedel Reticulofenestra pseudoumbilicus Gartner (1969) (1954)

Reticulofenestra umbilicus (Levin, 1965) Martini Discoaster neorectus Bukry (1971)

and Ritzkowski (1968)

Discoaster pansus (Bukry and Percival, 1971) Rhabdosphaera procera Martini (1969) Bukry (1973)

Rhabdosphaera clavigera Murray and Blackman Discoaster pentaradiatus (Tan, 1927) Bramlette

and Riedel (1954) Scapholithus fossilis De£andre in De£andre and Discoaster pseudovariabilis Martini and Worsley

Fert (1954)

Scapholithus spp.

Discoaster variabilis Martini and Bramlette Sphenolithus belemnos Bramlette and Wilcoxon (1963)

Discoaster cf. D. de£andrei Sphenolithus elongatus Bramlette and Wilcoxon Discoaster spp.

Discoasteroides cf. D. bramlettei Sphenolithus moriformis (Bronnimann and Ellipsolithus bollii Perch-Nielsen (1979)

Stradner, 1961) Bramlette and Wilcoxon (1967)

A. Sautkin et al. / Marine Geology 195 (2003) 237^261

Sphenolithus radians De£andre in Grasse (1952)

(TTR-9 Post-Cruise Conference), Granada, Spain. IOC

Toweius eminens Bramlette and Sullivan (1961)

Workshop Report 168, pp. 29^30.

Toweius spp. De Kaenel, E., Villa, G., 1996. Oligocene^Miocene calcareous

nannofossil biostratigraphy and paleoecology from the Ibe-

Triquetrorhadulus carinatus Martini (1965)

ria abyssal plain. In: Whitmarsh, R.B., Sawyer, D.S., Klaus,

Umbilicosphaera sibogae (Weber van Bosse)

A., Masson, D.G. (Eds.), Proc. ODP Sci. Results 149, 79^

Gaarde (1970)

105. Dewey, J.F., Helman, M.L., Turco, E., Hutton, D.H.W., Knott, S.D., 1989. Kinematics of the Western Mediterra- nean. In: Coward, M.P., Dietrich, D., Park, R.G. (Eds.),

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