SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES • NUMBER 15

Sands in the Alboran Sea:

A Model of Input in a

Deep Marine Basin

Daniel Jean Stanley, Gilbert Kelling,

Juan-Antonio Vera, and Harrison Sheng

SMITHSONIAN INSTITUTION PRESS

City of Washington

1975
ABSTRACT

Stanley, Daniel Jean, Gilbert Kelling, Juan-Antonio Vera, and Harrison Sheng.

Sands in the Alboran Sea: A Model of Input in a Deep Marine Basin. Smithsonian Contributions to the Earth Sciences, number 15, 51 pages, 23 figures,

8 tables, 1975.—The Alboran Sea, an almost totally land-enclosed, mountainbounded (Rif, Betic ranges) basin, lies east of Gilbraltar in the westernmost

Mediterranean. A petrologic study of the sand fraction in river, river mouth,

and beach samples collected on the coast of the Alboran Sea defines the composition and distribution of the principal light and heavy mineral groups along

its margins. The investigation details 20 mineralogical provinces on the southern

Iberian and northern Moroccan margins and the Strait of Gibraltar sector and

identifies the major source terrains and fluvial and marine point sources of

terrigenous sediment entering the basin.

Significant sample-to-sample changes in the proportion of mineralogical components are attributed to marine processes, particularly nearshore currents,

which move sands laterally along the coast and, while so doing, modify the

proportions of light and heavy mineral components. Lateral trends observed

within Moroccan and Spanish mineralogical provinces provide evidence on the

actual sense of nearshore sediment dispersal. Marine transport agents have a

more pronounced effect on the light mineral fraction, while even unstable heavy

mineral species appear to suffer less modification as a result of the transport in

the marine environment. The paths followed by the sands between source terrain and final depositional site in deepwater environments are complex ones.

A comparison of mineral assemblages in coastal sands and in sands in deep-sea

cores shows a provenance from the Serrania de Ronda complex in the Betic

range west of Malaga. After initial deposition on the coast, these river-borne

sediments are transported in a southwestward direction toward Gibraltar and

then eventually are funneled downslope in a southeastward direction toward

the Western Alboran Basin through the Gibraltar Canyon and submarine valley.

In geological terms, the Alboran Sea study can serve as a model for sedimentation in one type of elongate enclosed basin bounded by regions of high relief.

Although the geographic and geologic configuration of the Alboran Sea and

contiguous land conforms to a multisource basin model, the transport paths of

sediment since the late Quaternary have been essentially longitudinal. This

longitudinal input, with filling as a result of currents primarily from the Strait

of Gibraltar sector, is independent of a major delta source and is thus unlike

many elongate, deep-sea basins examined in present oceans and troughs (including fiysch) mapped in the ancient rock record.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 5251. SERIES COVER DESIGN:

Aerial view of Ulawun Volcano, New Britain.

Library of Congress Cataloging in Publication Data

Stanley, Daniel J.

Sands in the Alboran Sea.

(Smithsonian contributions to the earth sciences, no. 15)

Supt. of Docs, no.: SI 1.26:15

1. Sand—Alboran Sea. 2. Sedimentation and deposition. I. Kelling, Gilbert, joint author.

II. Vera, Juan-Antonio, joint author. III. Title. IV. Series: Smithsonian Institution. Smithsonian contributions to the earth sciences, no. 15.

QE1.S227 no. 15 [GC389] 550'.8s [551.4'62'1] 74-20880

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Price $1.20
Contents

Page

Introduction 1

General Considerations 2

Sampling and Methodology 3

Definition of Mineralogic Provinces 9

General 9

Spanish River Samples 12

Iberian Coast 13

Moroccan Margin 19

Strait of Gibraltar Region 23

Alboran Sea 26

Provenance of Sediments on Alboran Sea Margins 27

General 27

Origin of Selected Spanish River Sediments 28

Origin of Spanish Margin Sediments—Light Minerals 28

Origin of Spanish Margin Sediments—Heavy Minerals 29

Origin of Moroccan Margin Sediments—Light Minerals 30

Origin of Moroccan Margin Sediments—Heavy Minerals 31

Mineralogical Modification by Coastal Processes 32

Dispersal of Marginal Sands to the Western Alboran Basin 38

Summary 46

Appendix: Brief Summary of the Betic Cordillera Source Terrains 47

Literature Cited 49
Sands in the Alboran Sea:

A Model of Input in a

Deep Marine Basin

Daniel Jean Stanley, Gilbert Kelling,

Juan-Antonio Vera, and Harrison Sheng

Introduction

This investigation, an outgrowth of sedimentological and oceanographic surveys of the Alboran

Sea between Morocco and Spain, summarizes the

results of a mineralogic analysis of coastal samples

collected along the southern Spanish margin and

the northern coast of Morocco in the westernmost

Mediterranean Sea. The primary purpose of the

study was to identify the principal source terrains

of the sediments derived from the adjacent mountainous sectors into this almost totally enclosed sea

(Figure 1). To date, little is known concerning the

mineralogy and distribution of sediments along

the margins of the Alboran Sea. This study is intended to define the major point sources of terrigenous sands entering the Western Alboran Sea from

the Strait of Gibraltar and the Moroccan and Spanish sectors. In turn, this involves both determination of the predominant direction of sediment

movement along the coast and the identification of

the major transport paths from the coast seaward

into the deeper regions of the Western Alboran

Sea. The relative efficacy of heavy and light minDaniel Jean Stanley and Harrison Sheng, Division of Sedimentology, Smithsonian Institution, Washington, D.C. 20560.

Gilbert Kelling, Department of Geology and Oceanography,

University of Wales, Swansea, Great Britain. Juan-Antonio

Vera, Departamento de Estratigrafia, Universidad de Granada,

Granada, Spain.

erals in the context of provenance and dispersal

is also investigated.

Another purpose of this study was to better

evaluate the factors influencing provenance and

dispersal in analogous ancient marine basins whose

sediments are preserved in the fossil record. The

similarity between the sediments in the Western

Alboran Basin plain, a flat, deep (just over 1500

m) oval (24 by 37 km) basin, and some ancient

flysch deposits has been noted elsewhere (Stanley

et al., 1970; Stanley and Unrug, 1972). The mineralogical study in the Alboran Sea is of potential

value geologically because it enables the sand-sized

sediments, materials initially transported by rivers

to the coast and subsequently modified by marine

coastal agents, to be traced downslope to deeper

environments in an almost completely enclosed

system. Thus, the Alboran case can serve as a

model for a type of multisource dispersal system

possibly applicable to some ancient basins, including flysch troughs (Stanley and Unrug, 1972, figs.

37-40).

ACKNOWLEDGMENTS.—We are indebted to Mr. N.

Cano and Mr. F. de Castillejo, both of the Spanish

Institute of Oceanography, Malaga, and to Professor D. V. Ager and Dr. N. Fry, University of Wales,

Swansea, for their help in the collection of samples

along the Spanish margin. Particular thanks are

expressed to Mr. A. Giiven, University of Wales,

Swansea, for assistance with the mineralogic analy-
30'

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

4* 30' 3*

ALBORAN BE

CORE LOCATIONS

FIGURE 1.—Chart showing core localities and major geographic features in the Alboran Sea and

Strait of Gibraltar region. Details on cores available in Huang and Stanley (1972). (Geographic

names cited in the text are shown here and on Figures 2 and 3.)

sis, and to Professor J. F. Fontbote, University of

Granada, for providing us with valuable regional

data, maps, and references, and for his review of

the text. The 3.5 kHz subbottom records were collected on 1972 cruises of the USNS Lynch, and

aerial photographs were supplied by the Defense

Intelligence Agency, Washington, D. C. Dr. A.

Maldonado, University of Barcelona, also reviewed

the manuscript.

Funds for this study, part of the Mediterranean

Basin Project, including travel to Spain and Morocco and the collecting and processing of samples,

were provided to one of us (D. J. S.) by Smithsonian Research Foundation grants (FY 1971) 472350

and (FY 1972) 430035. Support was also provided

(G. K.) by the United Kingdom Natural Evironment Research Council and the Royal Society of

London.

General Considerations

The southern flank of the Betic Cordillera bordering the southern Spanish margin (elevations to

over 3000 m) and the northern flank of the Rif

(maximum elevations in excess of 2000 m) are cut

by numerous seasonally active rivers (or oueds)
NUMBER 15

and torrents capable of carrying material of mud

to boulder size directly to the coast. The study was

planned so that sand-size material collected in

these rivers and along the coast of both margins

eventually could be compared to sand collected

offshore in cores from the deeper Alboran Sea.

A review of the major geologic units that provide sedimentary material is necessary to properly

interpret the provenance of coastal samples. The

major stratigraphic-structural units mapped in the

Betic Cordillera and the Rif chains are depicted in

Figures 2 and 3. Each of these units can be distinguished on the basis of gross lithology and mineralogy, which permits the composition of river

mouth and coastal sands to be identified with outcrops of specific units.

The major stratotectonic units comprising the

Betic Cordillera source terrains (Figure 2) are

defined on the basis of investigations of many

workers. Among the more recently published regional studies pertinent to the Iberian margin, we

can cite the following: Kockel (1963), Mollat

(1965), Diirr (1967), Hernandez-Pacheco (1967),

Boulin (1968), Durand-Delga (1968), Hoppe

(1968), Aldaya (1969), Egeler and Simon (1969),

Jacquin (1970), Aldaya and Vera (1971), Fontbote (1971), Gonzalez-Donoso et al. (1971), Orozco

(1971), Puga (1971), and Loomis (1972). A summary of the major units providing sediments to the

Spanish coast is presented in the Appendix.

The general geology of the Moroccan margin

illustrated in Figure 3 is based on the published

maps of the Service G^ologique du Maroc, together

with more detailed discussions by Fallot (1937),

Fallot and Marin (1952), Milliard (1959), and

Durand-Delga and Kornprobst (1963).

Sampling and Methodology

Samples on the Iberian margin were collected

at the mouths of major rivers and on beaches between the Strait of Gibraltar and Adra (i.e., from

3° to 5°37'W longitude) in the region popularly

called the Costa del Sol. Sampling here is facilitated by the presence of a major coastal road

(Spanish highway no. 340) that follows the shoreline along much of this area. The spacing between

Spanish coastal samples ranges from 2 to 6 km;

the average distance between stations is 3 to 4 km

(position given in Table 1; see also Figure 2). The

major rivers, principal fluvial drainage basins, and

sample localities are shown in Figures 2 and 4. The

name of each drainage basin is derived from the

principal river. Several of the smaller morphological basins without major rivers bear no name.

It is useful to compare the mineralogy of riverborne material and that of sediment at the same

river mouths along the coast. In this respect, six

sample stations were occupied between the Calena

(near Marbella) and the Genal-Guadiaro rivers

west of Marbella. The rivers sampled include, from

east to west, the Calena, Guadaiza, Guadalmansa,

Padron, Enmedia, and Genal-Guadiaro (rivers between 7 and 4 on Figure 4); sampling stations were

made close to where Highway 340 crosses the

rivers. Two samples were collected about 100 m

apart at each of the six stations. The results are

listed in Tables 4 and 5 and illustrated in Figures

5 and 6.

In similar fashion, samples were collected in the

major rivers and river mouths and along the coast

on the Moroccan margin between Cap Spartel and

Al Hoceima (also known as Al Hucemas) from

4° 10' to 5°50'W longitude (Figure 3, Table 2).

However, the coastal area of northern Morocco

remains considerably less accessible than that of

Spain, and as a consequence the sampling is neither

as regular or as complete, although we believe that

it provides representative data.

The grain size of the 113 Spanish and 38 Moroccan river and littoral samples examined varies

from muddy sand to granule grade. Consequently,

only the 0.062 to 0.25 mm fraction (very fine to

fine sand) was selected for petrologic study in

order to minimize size-sorting problems and thus

to provide a better evaluation of regional changes

in mineralogy.

It is in this fraction that the heavy minerals,

sensitive indicators of provenance, are generally

concentrated. The granules and pebbles, common

in most of the samples, include a wide variety of

metamorphic as well as carbonate rock types; the

petrology of these coarse fractions is not examined

in the present study.

Heavy minerals were separated by the standard

heavy liquid method and their percent (by weight)

calculated. Light minerals were mounted on glass

slides, ground and stained according to the method

of Hayes and Klugman (1959), in order to identify
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES
NUMBER 15

FIGURE 2.—Geological map of the southern coast of Spain

between Adra and the Strait of Gibraltar showing the major

tectonic-stratigraphic (including lithologic) units in the

Betic Cordillera. The map is based on geologic maps published by the Instituto Geol6gico y Minero de Espana at a

scale of 1:200,000 and modified by J. M. Fontbote and J.-A.

Vera. Lithology of the different units are described in the

Appendix. Coastal and river sample localities are also shown

(see Table 1). [Broken line = Boundary between the major

Atlantic and Mediterranean drainage systems. Dotted line =

Boundary delineating the principal Mediterranean fluvial

basins in the study area; the basins are named after the

major rivers flowing southward toward the Mediterranean

Sea; those basins with rivers and torrents of only minor importance remain unnamed. Internal Zones: 1, Peridotite

(ultrabasic) Complex; 2, Nevado-Filabride Complex, metamorphic rocks; (3-7, Alpujarride Complex, eastern sector);

3, Paleozoic, with prevailing dolomite and marble; 4, Paleozoic, with prevailing micaschist and quartzite; 5, PermianWerfenian, phyllite and quartzite; 6, Middle and Upper

Triassic, limestone and/or dolomite; 7, Permo-Trias, undifferentiated (5) and (6); 8, Malaguide Complex, Pre-Cambrian

(?), miscaschist and gneiss; 9, Sierra Blanca Unit; 10, Casares

Unit (Alpujarride Complex, western sector); 11, Las Nieves

Unit; 12, Malaguide Complex, Paleozoic (also includes,

locally, a thin Mesozoic-Tertiary cover). External Zones: 13,

Triassic ("Germanic fades"); 14, Jurassic, limestone and

marly limestone; 15, Cretaceous-Paleogene-lower Miocene,

mainly marl and marly limestone; also sandstone and limestone. Posl-Orogenic Sequences: 16, Neogene-Quaternary,

mainly detrital sedimentary rocks and sediments.]
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Sediment sample localities on the southern Mediterranean coast of

Spain and vicinity of the Strait of Gibraltar, from west to east (see Figure 2)

Sample

Number

(On Fig. 2)

Dir ctio

General Description of Sample Locality on Southern Spanish Coast and Gibraltar (October 1970)

Dominant Beach

Lithology

Pebble

Sandy

Pebbly

Sand

Pebble

Pebbly

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Sand

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Sandy

Pebbly

Pebbly

s and larger

pebbly

s and larger

sand

sand

sand

sand

sand

sand

sand

cobble (>10 cm)

sand

sand

Pebbly sand

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Sand

Sand

Sand

Shelly

Shelly

Shelly

Sand

Pebbly

Shelly

Sand

Sand

Pebbly

Pebbly

Pebbly

Pebbly

Sandy

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Sandy

Sand

Sandy

Pebble

Pebbly

Pebbly

sand

sand

sand

sand

sand

pebbly sand

pebbly sand

sand

sand

pebbly sand

sand

sand

sand

sand

pebbly

sand

sand

sand

sand

sand

pebbly

pebbly

s and larger

Pebbly and coarser

Pebbly

Pebbly

Pebbly

Sandy

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Pebbly

Sandy

Sandy

Sandy ;

Pebbly

sand

and coarser

and coarser

pebbly

and coarser

and coarser

and coarser

and coarser

and coarser

and coarser

pebbly

pebbly

pebbly

sand

Pebbly sand

S 1

S 2

S 7

S 8

S 9

S10

Sll

SI 2

SI 3

SI 4

S15

S16

G 4

G 2

G 5

S19

S20

S21

S22

S23

S24

S25

S26

S27

S28

S29

S30

S31

S32

S33

S34

S35

S36

S37

S38

S39

S40

S41

S42

S43

S44

S45

S46

S47

S48

S49

S50

S51

S52

S53

S54

S55

S56

S57

S58

S59

S60

S61

S62

S63

S64

S65

S66

S67

S68

S69

S70

S71

S72

S73

S74

S76

S78

S79

S80

S81

S82

S83

S84

Rocky beach east of Tarifa along rugged coastline; rocky offshore

Beach at base of mountainous coast near Arroyo Vifias about 4 km east o

Tarifa; rocky offshore

Coast near Punta del Carnero (a mountainous cape), near old destroyed

jetty

Ensenada de Getares, near mouth of Arroyo del Lobo, small delta

Just north of Punta de San Garcia, Algeciras Bay, same latitude

as Europa Point

Algeciras, south of jettys

Beach at base of hill, just north of Algeciras

Mouth of Palmones River, Algeciras Bay

Beach between Palmones and Guadarranque rivers, Algeciras Bay

Mouth of Guadarranque River, Algeciras Bay

Northern Algeciras Bay, near large petroleum refinery; near Arroyo de

los Lecheros

Northern Algeciras Bay near El Campamento; low coastal plain

Northeast Algeciras Bay near La Lfnea; low coastal plain

Camp Bay, southwest side of Gibraltar, northwest of Europa Point

Beach from Sandy Bay, east side of Gibraltar

Dune sand (Pleistocene?), just south of Catalan Bay, east side of

Gibraltar

Beach at southern end of Catalan Village Bay, east side of Gibraltar

Eastern Beach, east side of Gibraltar, south of La Lfnea

North of La Llnea, near Torre de Senales; dunes along coast

Beach at base of hills, Punta Carbonera

Dunes along coast just south, Guadiaro River

Mouth of Guadiaro River

Beach north of Guadiaro River; low deltaic coastal plain

Playa del Negro, north of Punta Chullera

Beach near mouth of Rio de Manilva; coastal plain below hills

West of Estepona, near Arroyo de Guadalobon

Estepona, near port

Narrow rocky beach west of Rfo del Padr6n

Mouth of Rfo del Padron; small water bodies present

Near Rfo del Castor; semi-desert physiography

San Pedro de Alcantara, east of Rio Guadalmansa

Arroyo de Dos Hermanas, west of Rio Guadalmina

Mouth of Rfo Guadalmina; river sediments form delta

Beach near Arroyo del Chopo

Beach near mouth of Rfo Verde, west of Marbella

On Ensenada de Marbella, west of Marbella; near Arroyo de Nagueles

Beach east of Marbella, near Rfo Real

Beach near Chalets Costa Bella

Beach near Punta Ladrones

Beach near Torre de Calahonda

Beach at Ensenada de Cala del Moral

Cabo de Calaburra, west of Rfo de Fuengirola

Beach at Fuengirola, west of Arroyo Real

Beach near Arroyo de Presas, Torre Blanca del Sol

Beach near Torre Benalmadena

Arroyo de la Miel, west of Torremolinos

Beach at Torremolinos, Playa de la Carihuela

Beach west of Guadalhorce River, on delta

Beach east of Guadalhorce River, on delta; west of Malaga (industrial

zone)

Beach west of Malaga, west of Guadalmedina River

Mouth of Guadalmedina River, Malaga

East of Malaga, Malaga Bay

Near El Palo, Malaga Bay, at mouth of dry torrent

Beach west of La Victoria, Malaga Bay

Beach near Cala del Moral, Malaga Bay

Beach at La Victoria, Malaga Bay

Beach near Estacion Benagalbin

Beach off plain, east of Torre Moya

Beach, west of Rio Velez

Mouth of Rfo Velez, on small delta west of Torre del Mar

Torre del Mar, east of Rfo Velez

Beach east of Torre del Mar and west of La Caleta

Narrow beach east of Rfo de Algarrobo

Beach west of Morche

Beach on delta, west of Rio de Torrox

Mouth of Rfo de Torrox, on small delta

Beach east of Rfo de Torrox

Beach east of Punta de Torrox

Mouth of Rfo Higuerdn, on small delta

Beach east of Nerja, south of Maro

Beach off rocky high terrain, east of Maro

Beach on rocky point west of La Herradura

Beach at La Herradura

Beach east of Punta de la Mona and west of Rio Verde

Beach east of Rfo Verde and Almunecar

Small river south of Taramay

Beach west of Salobrena and La Caleta

Beach on delta of Rio Guadalfeo, south of Salobrena

Beach at mouth of Rio Guadalfeo

Beach at mouth of Rio Guadalfeo, on delta

Beach on eastern part of Rfo Guadalfeo delta

130°

105°

125

95°

115°

130°

160°

150°

85°

110°

180°

180°

180°

170°

170°

175°

175°

130°

130°

130°

130°

160°

140°

130°

120°

140°

140°

150°

150°

125°

180°

190°

160°

175°

170°

170°

175°

120°

120°

110°

115°

150°

210°

190°

180°

170°

165°

190°

190°

200°

190°

190°

200°

220°

250°

230°

220°

220°

200°

210°

220°

240°

250°

150°

140°

140°

160°

155°

170°

165°

170°
NUMBER 15

TABLE 1.— (Continued)

Sample Locality Spanish Coast and Gibraltar

Direction

(October 1970) Lithology

S 85

S 86

S 87

S 88

S 89

S 90

S 91

S 93

S 94

S 95

S 96

S 97

S 98

S 99

SI 00

S101

S102

£103

S104

H at the Port of Motril

on Cabo Sacratif, near light house

on Cabo Sacratif, off flat plain

at Calahonda, at mouth of small river

east of Calahonda along rough coastlin

at Castell de Ferro, near Rambla Gualc

east of Castell de Ferro, along rough

i beach east of La Hamola

at La Rabita, at mouth of small river

beach east of El Pozuelo

;jes t of La Alcazaba

at Cainos Bajos

rfest of Adra, near small port

east of Adra

on delta, west of Rio Chico (R. Adra)

outh of Rfo Chico (R. Adra), on delta

145

155°

160°

180°

140°

125°

170°

120°

150°

120°

115°

150°

140°

130°

135°

160°

145°

140°

130°

Sandy pebblv

Sand

Sandy pebbly

Pebbly sand

Sandy pebbly

Pebbly and c

Pebbly and c

Pebbly and c

Sandy pebbly

Pebbly sand

Pebbly and c

Pebbly sand

Pebbly sand

Pebbly sand

Sandy pebbly

Pebbly and c

Pebbly sand

Pebbly sand

Sandy pebbly

STRAIT OF GIBRALTAR

TANGER

8

KILOMETERS

FIGURE 3.—Geological map of the northern margin of Morocco showing major stratigraphic

sequences (based on maps by Fallot, 1937; Fallot and Marin, 1952; and others). Coastal and

river sample localities also shown (see Table 2). Note that for clarity, the submarine outcrops

of basic/ultrabasic rocks around Cabo Negro deduced by Milliard (1959) and others are also

shown as occupying the peninsula.
GUADALQUIVIR BASIN

MEDITERRANEAN SEA

ALGECIRAS

1.

2.

3.

4.

5.

6.

7.

R. de las Canas

R. Guadarranque

R. Hozgarganta

R. Guadiaro

R. Genal

R. Guadalevin

R. Verde

8.

9.

10.

11.

12.

13.

14.

R. Fuengirola

R. Grande

R. Turon

R. Guadalhorce

R. de las Campanillas

R. Guadalmedina

R. Velez

15.

16.

17.

18.

19.

20.

2 1 .

R. Algarrobo

R. Torrox

R. Verde

R. Guadalfeo

R. Izbor

R. de Lanjaron

R. Poqeria

22.

23.

24.

25.

26.

27.

28.

R.

R.

R.

R.

R.

R.

R.

Yator

Ujijar

Bayarcal

Adra

Chi co

Andarax

Nacimento

FIGURE 4.—Map showing distribution of rivers on the southern Iberian margin. (Black triangles

denote stations occupied by the Centro de Estudios Hidrograficos (1966); river flow data listed

in Table 3.)

and distinguish different types of feldspar grains.

A total of about 300 light mineral grains and 200

transparent, heavy mineral grains were counted

and relative percentages calculated. Opaque minerals were also counted. Mica flakes occur in both

heavy and light mineral concentrations; in this

study, the micas have been assigned for quantitative purposes to the light mineral fraction.

A total of 23 mineral species were identified in

the heavy fractions, many of them occurring in

trace amounts or in only a few samples. Only the

dozen or so nonopaque mineral species which appear with reasonable consistency in a large number

of samples have been distinguished and plotted

in Figures 7 and 9. Moreover, for purposes of quantitative comparison the related mineral species

have been grouped together in a manner reflecting their provenance characteristics and assigned

to 10 categories (including opaque minerals and

"others"). Similarly, light minerals were assigned

to eight groups, together with two ratios (total

quartz to total feldspar, and igneous quartz to

metamorphic quartz). Certain categories of light

minerals, notable rock fragments and glauconite,

although locally common, are not sufficiently widespread in their occurrence to justify the erection

of additional compositional groups.

Inspection of the compositional data from individual samples (Figures 7 to 10) revealed significant geographic variations, which enabled the

Spanish and Moroccan samples to be assigned to

provinces (i.e., regions characterized by sands of

comparable composition). In most cases, the province boundaries can be drawn solely on the basis of

marked changes in the relative abundance of several of the heavy or light mineral groups. However, in a few instances, there is a more gradual

change in composition, and the province boundary

is then more arbitrarily defined, usually on the

basis of some geographic feature such as a major

river or prominent cape.

This original compositional data was subsequently compared with data previously obtained

from deep-sea samples in the Strait of Gibraltar
NUMBER 15

TABLE 2.—Sediment sample localities on the northern Mediterranean coast of Morocco, from west to

east (see Figure 3)

SAMPLE

NUMBER MOROCCAN SAMPLE LOCALITY

M 8 Mouth of Oued el Herradou, approx. 4 km west of Tangier town

M 1 Beach at mouth of Oued Chall, just east of Tangier

M 2 Oued approx. 4 km south of Cap Malabata on Route S7O4, about

2 km from coast

M 3 Beach at mouth of Oued Sfisifa, near Pointe Kankouch

M 4 Oued el Lgam, along Route S704, near Pointe Bou Maaza

M 5 Oued el Razor, at Ksar-es-Seghir, along Route S704

M 6 Beach at Benzou, about 10 km west of Ceuta

M 7 Beach about 6 km southwest of Ceuta, near junction of Routes

P28 and 8303

M 20 Small oued at Riffien, north of Oued Negron, Route P28

M 21 Mouth of Oued Negron, north of Restinga, Route P28

M 22 Dune sand in Restinga-Smir area, 16 km south of Ceuta,

Route P28

M 19 Near mouth of Oued Smir, along Route P28, 3 km north of M'Diq

M 23 Oued ed Siador, along Route P28, 3 km south of Cabo Negro

M 9 Rio Martin, just south of Tetouan

M 18 Oued just north of Cap Mazari, approx. 13 km southeast of

Tetouan, Route S608

M 17 Oued Emsa, south of Cap Mazari and west of Cap Timousourga,

Route S608

M 16 Oued on southeast flank of Cap Akaili, Route S608

M 15 Oued northwest (approx. 4 km) of Cap Menkal, Route S608

M 14 Oued Laou, near Es Sebt, Route S608

M 13 Oued Akheron, near El Arba, Route S608

M 12 Mouth of Oued Targa, at Targa, Route S608

M 11 Oued, near Asenli, approx. 5 km southeast of Targa, Route S608

M 10 Junction of Oued el Had and Oued Bouchia at town of Bou-Hamed,

Route S608

M 24 Mouth of Oued Ouringa, approx. 1 km west of Pointe des Pecheurs

M 25 Mouth of small Oued, Pointe des Pecheurs

M 28 Junction of Oued Mestasa and Oued Bi Chetouan, near village

of Mastassa

M 27 Mouth of Oued 0.5 km east of Cala Iris beach

M 26 Mouth of Oued Bou Frah, near Torres-de-Alcala

M 29 Oued Bades, north of Arba-Snada, on Route S610

M 30 Oued approx. 4 km east of El Hader Rouadi, on Route S610

M 31 Oued Merelia, west of Ait-Kamara, on Route S610

M 35 Mouth of Oued Boussikour, approx. 12 km west of Al Hoceima

M 36 Oued east of Pointe Boussikour, approx. 7 km west of

Al Hoceima

M 37 Small Oued approx. 3 km west of Al Hoceima, on Piste 8506

M 38 Beach below Mohammed V Hotel, Al Hoceima (no Oued)

M 34 Beach at Plage Espalmadero, 4.5 km southeast of Al Hoceima

on Route P39A

M 33 Oued Rhis, approx. 12 km southeast of Al Hoceima, on Route P39

M 32 Oued Nekor, approx. 6 km south of Al Hoceima Bay, on Piste S604

TABLE 3.—River flow data collected on the southern Iberian margin (see Figure 4); sample stations

occupied by the Centro de Estudios Hidrogrdficos

(1966)

RIVER

Guadarranque

Guadiaro

Guadalhorce

Guadalmina

Velez

Algarrobo

Guadalfeo

Adra

SAMPLE STATION

CODE (FIG. 4)

A

B

C

D

E

F

G

H,I,J,K

LITERS/SECOND

17.2

19.4

4.73

8.17

5.65

5.49

3.47

2.13

(average)

MONTHS DRY

July, August

July, August

None

July, August

July, August

(almost dry)

June, July,

August

August

July, August

(almost dry)

region and the western Alboran Basin (Kelling

and Stanley, 1972; Huang and Stanley, 1972), reassigned as far as possible to the same mineralogic

groupings (Table 8).

A survey of selected aerial photographs, collected

at altitudes of from 5,000 to 14,000 m, was made

in order to provide information on short- and

long-term coastal sedimentation and littoral drift

patterns on both the Moroccan and Spanish margins. Predominant near-shore current drift paths

(cf., Figures 12 to 14) are defined on the basis of

beach-groin patterns, delta shapes and river outflow, and suspended sediment lobe distribution.

Particular attention has also been paid to published data of river flow and rain data (cf., Figures

4 and 20) on the Spanish margin (Centro de

Estudios Hidrograficos, 1966, 1970) and to offshore

surface drift data in the Alboran Sea (GaibarPuertas, 1967; Lanoix, 1974).

Definition of Mineralogic Provinces

GENERAL

Both heavy and light minerals are utilized in

denning the various mineralogic provinces in the

study area. The light mineral fraction in the very

fine to fine sand-size range accounts for the bulk

(usually 90 to 95% or more) of the total material

present. In most instances, approximately 2 to 11

samples comprise the regional mean.

Thirteen zones have been established on the

southern Iberian margin between Tarifa and Adra

and seven on the Moroccan coast from Cap Spartel

to the mouth of the Oued Nekor. In addition,

assemblages already established for the sublittoral

portions of the Strait of Gibraltar Submarine

Valley and the Western Alboran Basin (Kelling

and Stanley, 1972a, b; Huang and Stanley, 1972)

were reexamined in the light of this new data.

The abundance of individual light and heavy

mineral species may differ appreciably from sample

to sample (see Figures 7 to 10), but it is seldom

feasible to utilize the presence or absence of specific

minerals to define geographic associations. We have

found it more useful to assign the dominant heavy

mineral species to ten groups (cf., Tables 5, 7, and

8), which are defined primarily on the basis of probable provenance. Seven light mineral groups are

recognized in this study. In addition, two compositional ratios (igneous quartz/metamorphic

quartz and total quartz /feldspar) help define

mineralogic provinces.
10 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

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12 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 4.—Mineral provinces for Spanish coastal and river samples (see Figures

5 to 8)

Province

Designation Geographic Limits of Province Sample Numbers

COASTA L SAMPLE S

larifa to Punta San Garcfa (Algeciras

Bay)

Punta San Garcfa (north side) to Rfo

Guadarranque mouth

Rfo Guadarranque mouth to Europa Point,

Gibraltar

Europa Point, Gibraltar (east side) to

La Lfnea (eastern beach)

La Lfnea to Guadiaro River mouth

Guadiaro River mouth to Rfo Verde mouth

(Marbella)

Rfo Verde mouth to Torrente Calaburra

Torrente Calaburra to Rio Guadalhorce

mouth (Malaga)

Rfo Guadalhorce mouth to Rfo Velez mouth

Rfo Velez mouth to Rfo Higueron mouth

(Nerja)

Rfo Higuer6n mouth to Rfo Guadalfeo delta

Rfo Guadalfeo delta to Calahonda

Calahonda to Adra

SI,2,6,

S9-13

S14-16,

Gl,2,3,

S20-23

S24-36

S37-43

S44-50

S51-60

S61-70

S71-74,

S82-91,

S94-104

7,8

G4

5; S19

76,78-81

93

No heavy mineral

from sample S6

No heavy mineral

from samples S25,

No heavy mineral

from samples S62,

No heavy mineral

from samples S82,

No heavy mineral

from samples S96.

fractions

fractions

28, 30

fractions

67

fractions

90-93

fractions

101,104

RIVE R SAMPLE S

I

II

III

IV/V

VI

Rfo de Calena

Rfo Guadaiza

Rfo Guadalmansa

Rfo Padron and Rio Enmedia

Rfo Guadiaro-Genal

IA, IB

IIA, IIB

IIIA, IIIB

IVA, IVB, VA, VB

VIA, VIB

Province boundaries were established primarily

on the basis of marked changes in either qualitative or quantitative character of the mineral content of the samples, and were further denned in

light of geographic factors (presence of major

rivers, promontories and capes, etc.).

SPANISH RIVER SAMPLES

The river samples constitute five associations

which are distinguishable on both heavy and light

mineral components (Figures 5 and 6). These will

be discussed in sequence from west to east.

GUADIARO-GENAL ASSEMBLAGE (VI).—This heavy

mineral suite is characterized by moderate amounts

of orthopyroxene and clinopyroxene, together with

a relatively high proportion of metamorphic group

minerals (mainly andalusite) and opaque grains.

The content of ZTR (zircon, tourmaline, rutile)

is higher than in any other Spanish rivers. The

total quartz abundance also attains its highest

value in this river, while total feldspar is present

in minimal quantities.

ENMEDIA-PADRON ASSEMBLAGE (IV-V).—These

two rivers furnish closely similar, heavy mineral

assemblages which display the highest values of

orthopyroxenes, clinopyroxenes, and amphiboles

encountered in the Spanish rivers and exceeded by

only two coastal samples. Opaque grains and the

ZTR group are deficient. There is a more conspicuous difference between the two rivers in terms

of light minerals, the Enmedia being substantially

richer in quartz and poorer in feldspar content

than the Padron.

GUADALMANSA ASSEMBLAGE (III).—This assemblage is distinguished from the neighboring rivers

on the basis of its greatly enhanced garnet and

olivine plus spinel. The light mineral assemblage
NUMBER 15 13

is broadly similar to that of the Padron River.

GUADAIZA ASSEMBLAGE (II).—The heavy mineral

assemblage is distinguished by the highest proportions of metamorphic group minerals (mainly

staurolite), olivine and spinel, and contains the

lowest proportions of garnet. The light mineral

assemblage is characterized by a high quartz to

feldspar ratio, together with a greatly increased

content of mica.

Rio DE CALENA ASSEMBLAGE (I).—This assemblage is notably deficient in pyroxenes and amphiboles but relatively enriched in opaque minerals

and garnet. Carbonate minerals predominate in

the light mineral assemblage, but quartz substantially exceeds feldspars in abundance.

IBERIAN COAST

PROVINCE A.—This province extends from Tarifa

to Punta San Garcia, in the southwest part of

Algeciras Bay (Figures 7 and 8). No major rivers

traverse this rocky coast. The heavy assemblage is

dominated by the opaque minerals, although the

proportion of ZTR minerals reaches its maximum

for the Iberian coastal samples. The percentage

of opaque and ZTR minerals increases eastward,

whereas that of garnet, epidote, and olivine actually decreases. All other heavy mineral groups are

equally deficient. The total content of quartz is

comparable to values obtained in other samples

from the southern Iberian margin but considerably

lower than the immediately adjacent provinces.

However, the ratio of igneous to metamorphic

quartz is comparable to that measured in the neighboring regions. The total feldspar percentage for

this province readies a maximum for these Iberian

samples, and as a consequence the quartz/feldspar ratio is minimal.

PROVINCE B.—This province includes samples on

the west side of Algeciras Bay, from Algeciras to

the mouth of the Rio Guadarranque. The major

rivers are the Palmones and Guadarranque. The

heavy assemblage is characterized by a reduced

proportion of opaque minerals and a greatly enhanced content of pyroxenes. The opaque minerals

TABLE 5.—Mineralogic composition of Spanish coastal and river samplesprovince means (see Figures 5 and 6)

PROVINCE

Opaque Minerals

Zircon + Tourmaline

+ Rutile (ZTK)

Orthopyroxenes

Clinopyroxenes

Amphi boles

Metamorphic Group"

Garnets

Olivine + Spinel

Epidote Croup

Others'

Igneous Quartz5

Metamorphic Quartz4

Total Quartz

Quartz Ratio

Potash Feldspar

Plagioclase

Total Feldspar

Quartz/Feldspar

Ratio

Micas + Chlorite

Carbonates

Others6

NO. OF SAMPLES

79

2

2

0

1

1

5

0

3

2

12

19

31

0

1

56

57

0

0

4

5

A

.9

.3

.5

.5

.9

.0

.0

. 7

. 6

.6

. 1

.7

.8

.61

. 4

.0

.4

.55

.8

.4

.3

/ 37

B

25.6

1.3

34.2

4.8

5.0

5.1

4.7

3.7

12.5

3. 1

25.2

45.7

70.9

0.55

-

10.0

10.0

7.09

3.9

5. 7

9.2

5/1

C

21.6

1.5

27.8

8. 3

3.2

4.4

12.6

2.3

15.1

3.2

20.6

31.5

52.1

0.65

8.1

22.6

30.7

1.69

0.8

10.7

5.7

4/2

D

19.0

tr.5

38.6

6.5

2.4

4.8

15.6

1.5

9.7

1.6

29.6

33.3

62.9

0.88

0.6

21.2

21.8

2.88

2.7

7.0

5.6

5/4

E

33.9

tr.

18.4

8.9

8.7

5.1

7.3

2.6

11.4

3.3

8.1

41.5

49.6

0.19

1.4

30.1

31.5

1.57

1.1

4.5

13.0

4/1

F

17.1

0.5

26.9

10.3

3.9

2.7

9.7

7.5

16.7

4.7

2.8

31.7

34.5

0.08

2.6

34.1

36.7

0.94

1.3

9.6

17.6

10/2

G

27.0

1.4

20.0

3.2

7.4

3.2

11.5

5.6

14.9

5.8

2.4

28.5

30.9

0.08

1.2

37.9

38.1

0.81

0.8

12.2

17.7

111

H

30.

1.

12.

3.

7.

3.

22.

3.

12.

2.

4.

22.

27.

0.

tr

37.

37.

0.

-

14.

20.

3

3

7

8

5

0

8

1

8

7

2

8

0

18

0

3

72

6

0

7/1

I

42.6

0.6

10.5

0.6

9.4

5.0

9.9

1.2

17.4

2.8

10.9

21.3

32.2

0.51

1.0

43.0

44.0

0.73

1.5

6.9

14.6

10/5

J

30.0

1.0

9.1

5.6

8.3

9.0

11.5

1.1

22.6

1.8

7.8

25.4

33.2

0.30

0.8

28.8

29.6

1.12

5.5

8.1

24.0

8/2

K

29.9

0.9

8.9

1.6

18.0

7.9

6.4

1.0

22.5

1.9

14.2

15.0

29.2

0.94

1.1

38.2

39.3

0.74

11.8

3.5

16.1

9/1

L

39.7

1.1

1.1

0.6

4.1

1.0

40.6

2.0

8.9

0.9

10.8

20.0

30.8

0.54

1.5

29.2

30.7

1.00

1.7

18.5

18.0

7/2

M

43.4

0.8

0.7

0.5

3.2

0.9

38.6

1.0

8.1

2.8

9.7

30.3

40.0

0.32

tr.

28.0

28.4

1.40

1.5

7.9

22.0

8/2

I

46.5

1.7

10.9

5.8

5.8

3.2

13.8

8.7

1.8

1.8

24.5

8.5

2.88

3.0

64.0

2/2

II

20.4

tr.

33.4

4.5

7.1

7.7

0.8

10.1

4.7

0.9

62.0

9.5

6.53

26.5

2.0

2/2

III

11.

0.

32.

13.

7.

2.

16.

12.

2.

1.

60.

15.

4.

12.

3.

0

7

5

6

2

2

1

4

8

5

5

3

54

1

1

2/2

7

0

44

21

13

1

2

6

2

54

24

2

10

11

IV

.5

.7

.2

.1

.6

.1

.8

.7

.3

-

.6

.6

.22

.5

.0

2/2

10

45

19

12

2

2

4

1

1

79

8

9

8

4

V

.8

_

.5

.2

.8

.2

.8

.8

.4

.9

.5

.4

.46

.0

.0

111

VI

28.

2.

30.

5

3

0

12.8

5.

6.

7.

3.

1.

2.

85.

3.

24.

6.

4.

2

9

3

2

1

7

7

5

5

3

1

2/2

2. Mainly Apatite,

3. Simple, unstra:

4. Composite and f

te, Staurolite, Slllimanite, Andalusite and Chiastolite

Sphene, Anatase, Monazite, Corundum and Topaz

5.

6.

7.

tr.

Mai

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ond digit refers

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16 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES
NUMBER 1

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18 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

decrease northward paralleling the increase of pyroxenes. The light assemblage comprises the highest total quartz, the lowest amounts of feldspar, and

one of the higher proportions of micas encountered in the southern Iberian coastal samples.

PROVINCE C.—This province extends from northern Algeciras Bay near Arroyo de los Lecheros to

Europa Point on the southern tip of Gibraltar.

There are no major rivers in this region. The

heavy assemblage includes enhanced proportions

of garnet and clinopyroxene and slightly higher

epidote. The southernmost sample (G4) is somewhat anomalous in this group, displaying a considerably increased quantity of opaque and ZTR

minerals and a deficiency of ferromagnesian

minerals. There is a slight decrease in clinopyroxenes toward the south, whereas the orthopyroxenes

increase as far as La Linea. The light assemblage

is characterized by the highest proportion of

potash feldspar sampled anywhere on the Iberian

coast. The proportion of total quartz, although less

than adjacent provinces, is still relatively high,

and the igneous to metamorphic quartz ratio is

similar to that of provinces A and B. Mica content

is diminished.

PROVINCE D.—This province lies on the eastern

flank of Gibraltar from Sandy Bay to La Linea.

There are no rivers in this region. The heavy fraction is distinguished by the highest mean value of

orthopyroxene encountered in the coastal samples.

Epidotes show a regular decrease northward as far

as La Linea, and garnet increases northward to a

maximum near the Gibraltar airfield and then declines. Quartz dominates the light mineral assemblage with the second highest mean value of Iberian coastal samples measured. Metamorphic quartz

exceeds igneous quartz. The total amount of quartz

decreases rather steadily from this province eastward as far as Province H, while the total feldspar

content displays a corresponding increase.

PROVINCE E.—This province extends from north

of La Linea to the mouth of the Guadiaro River,

the only major river in this sector. The heavy

fraction in this province contains somewhat enriched opaque minerals, amphiboles, and metamorphics, together with diminished amounts of

orthopyroxenes. There is a notable increase in the

proportion of opaques northward, accompanied by

a decrease in clinopyroxenes. The proportion of

quartz with respect to feldspar is diminished, and

the igneous to metamorphic quartz ratio is substantially reduced compared to the previously

described provinces.

PROVINCE F.—This province extends from north

of the mouth of the Guadiaro River to near the

mouth of the Rio Verde west of Marbella. This

sector includes numerous other rivers, such as the

Manilva, Padron, Guadalmansa, Guadalmina, and

Guadaiza. The heavy assemblage is distinguished

by the highest mean values of clinopyroxene and

olivine with spinel and the lowest values of opaque

minerals. Amphiboles and metamorphic minerals

are somewhat diminished with respect to the adjacent provinces. There is a general increase in

opaque minerals toward the northeast. The highest value of olivine in the Iberian coastal samples

occurs at the mouth of Arroyo dos Hermanas

(sample 33). There is an irregular decrease northward in proportion of clinopyroxenes. The decline

in the total quartz content observed in Province E

is continued into Province F and is accompanied

by a corresponding increase in the total amount of

feldspar (largely plagioclase), which in fact slightly

predominates. Curiously, the ratio of igneous to

metamorphic quartz reaches a minimum value in

Provinces F and G.

PROVINCE G.—This province extends from 3 km

west of Marbella to the Torrente Calaburra. Rivers

include the Arroyo de Calena, Rio Real, Arroyo

de Siete Revueltas, and Arroyo de Cala del Moral.

The heavy fraction is distinguished by a slightly

enhanced proportion of opaque and ZTR minerals and a decreased amount of pyroxenes. There

is an irregular increase in garnet toward the east.

The light fraction is broadly similar to that in

Province F, but it has a slightly higher proportion

of feldspar to quartz and a higher proportion of

detrital carbonate.

PROVINCE H.—This province extends from the

Rio Fuengirola to the Guadalhorce River, west of

Malaga, the major river in this sector. The heavy

fraction is distinguished by an enhanced proportion of garnet and diminished pyroxene and olivine content. There is an irregular decrease in

metamorphic minerals toward the northeast. The

total quartz reaches a minimal value for the coastal

samples, whereas the total feldspar content is comparable to that of Province G. The proportion of

detrital carbonate is again increased.

PROVINCE I.—This province extends from west of
NUMBER 15 19

Malaga to west of the Rio Velez. The Guadalmedina is the most important river in this sector.

The heavy fraction is distinguished by high mean

proportions of opaque minerals and epidotes and

decreased amounts of pyroxene (especially clinopyroxene) and garnet. Very high values of amphiboles are localized at the mouth of the Guadalmedina River and beach to the southwest (samples

52 and 51). There is an increase in epidote eastward toward Estacion Benagalbon. The light assemblage has the second highest total feldspar content and a somewhat enhanced proportion of

igneous quartz.

PROVINCE J.—This province extends from the

mouth of the Rio V^lez to the mouth of the Rio

Higueron. Important rivers include the V£lez,

Algarrobo, Torrox, and Chillar. The heavy fraction includes somewhat enhanced proportions of

clinopyroxene, metamorphic group minerals, and

epidote. There is a slight but regular decrease in

the opaque minerals eastward. There is also a

marked and regular decrease in amphiboles eastward from east of the Rio Velez delta, but a notable increase in amphibole is observed at the

mouth of the Rio Chillar. The total quartz content

and the ratio of igneous to metamorphic quartz

are similar to values encountered in Province I,

but the total feldspar content is substantially reduced. The percentage of micas and chlorite also

increases significantly with respect to Province I.

PROVINCE K.—This province extends from east of

Nerja to west of the mouth of the Rio Guadalfeo.

The Rio Verde is the most important river in

this sector. The heavies are characterized by a

marked increase in the amphibole content and

decrease in the clinopyroxene and garnet. The

proportions of amphiboles are substantially higher

in the samples west of the Rio Verde (nos. 72-76),

whereas the proportions of opaque minerals and

epidotes are substantially greater to the east of the

Rio Verde. In the light fraction, the total quartz

content remains relatively low, although it is noteworthy that the proportions of igneous and metamorphic quartz are nearly identical in sharp contrast to adjacent provinces. The highest values of

micas and chlorite in the Iberian coastal samples

occur in this province.

PROVINCE L.—This province extends from the

delta of the Rio Guadalfeo to west of Calahonda.

The Guadalfeo is the only major river in this sector. The heavy fraction is dominated by garnet,

and there is a decrease in almost all other mineral

groups except the opaques. The major break in

trend of proportion of garnet occurs on both sides

of the mouth of the Guadalfeo. The proportion of

epidote also decreases noticeably east of the mouth

of the Guadalfeo. It is noteworthy that in the

region of El Varadero (sample 86), there is a

dramatic change in the amphibole and epidote

content and a corresponding decrease in garnet.

The light assemblage is essentially similar to Province K except that the proportion of metamorphic

quartz is again higher, while the micas and chlorite

revert to a low value. The carbonate content is

also substantially higher than in the neighboring

provinces.

PROVINCE M.—This province extends from Castell

de Ferro to east of Adra. The major river is the

Chico (Rio Adra). The heavy assemblage is distinguished by garnet and opaques and a slightly

diminished olivine content. Garnet content increases toward the east from Punta Negra, and the

epidote decreases eastward from this point as well.

The major break in mineral trends is localized at

the delta of the Rio Chico, just west of its mouth,

where proportion of amphiboles and opaque minerals increase substantially, accompanied by a very

marked decrease in garnet content. The light fraction is marked by a substantial increase in total

quartz content and a slight decrease in total feldspar and micas. The proportion of detrital carbonates is also significantly reduced compared with

Province L.

MOROCCAN MARGIN

PROVINCE N.—The area included in this province

extends from Cap Spartel west of Tangier to west

of Ceuta along the south flank of the Strait of

Gibraltar (Figures 9 and 10). As in all seven Moroccan provinces, opaque grains comprise the most

abundant single group of the heavy minerals. The

ZTR group is dominant among the nonopaque

minerals, closely followed by garnet and the metamorphic group. The proportion of garnet increases toward the east, while zircon tends to decrease in the same direction. Significantly, orthopyroxene and olivine occur only in the beach samples from the western sector of the Strait. Andalusite is the dominant metamorphic mineral, but
20 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES
NUMBER 15 21

*o "5b

5? a

&

ISW)
22 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

staurolite also occurs in all samples. Dolomite

rhombs are abundant in samples M8 (west of

Tangier) and M6 (below Djebel Moussa near

Ceuta). Quartz dominates the light mineral assemblage with the igneous variety generally in excess

of metamorphic quartz. The average total feldspar content is the lowest observed in the Moroccan samples.

PROVINCE O.—This province extends from the

south side of Ceuta peninsula to Cap Mazari. The

major river in this sector is the Rio Martin. This

association contains substantially higher proporTABLE 6.—Mineral provinces for Moroccan coastal and river samples (see

Figures 5, 6, 9, 10)

Province

Designation

a

0

P

Q

R

S

T

Geographic Limits of Province

Cap Spartel to Ceuta (north side)

Ceuta (south side) to Cap Mazari

Cap Mazari (south side) to Targa

Targa to Bou Haned (Oued El Had)

Oued Ouringa mouth to Pointe des

Pecheurs

Oued Mestasa to Al Hoceima (western

side)

Al Hoceima (eastern side) to Oued

Nekor

Sample

Ml-6,8

M7,9,1

Ml 2-17

M10.11

M2U,25

M26-31

Numbe rs

8-23

, 35-37

, 38

Romarks

M1,3,6,8 are coastal

samples.

M7,19,20-22 are coastal

samples

M2U is a coastal sample

M35 is a coastal sample

M38 is a coastal sample

TABLE 7.—Mineralogic composition of Moroccan samples-province means (see

Figures 5 and 6)

PROVINCE

Opaque Minerals

Zircon + Tourmaline + Rutile (ZTR)

Orthopyroxenes

Clinopyroxenes

Amphiboles

Metamorphic Group

Garnets

Olivine + Spinel

Epidote Group

Others2

Igneous Quart z-^

Metamorphic Quartz

Total Quartz

Igneous/Metam. Quartz Ratio

Potash Feldspar

Plagioclase

Total Feldspar

Quartz/Feldspar Ratio

Micas + Chlorite

Carbonates

Others6

NO. OF SAMPLES

N

41.3

18.4

0.6

tr.5

tr.

13.8

17.2

tr.

3.9

3.9

43.4

22.6

66.1

1.92

1.8

23.2

25.0

2.64

tr.5

8.0

tr.

7

0

29.1

5.8

15.1

5.8

2.3

15.1

13.9

8.1

2.2

2.6

32.2

19.5

51.8

1.65

2.7

37.1

39.8

1.30

0.9

6.2

1.3

8

P

70.2

8.1

1.3

tr.

tr.

4.0

6.7

2.7

1.8

4.9

3.7

13.8

17.5

0.26

0.6

65.8

66.4

0.26

1.-2

4.4

9.5

6

Q

22.9

5.7

9.2

8.0

4.6

12.6

18.4

9.2

6.1

4.3

7.8

11.7

19.5

0.67

4.7

71.2

75.0

0.26

tr.

tr.

5.0

2

R

80.0

3.6

tr.

4.9

-

8.3

1.5

-

3.1

-

0.5

29.3

29.8

0.01

1.7

43.3

45.0

0.66

0.5

4.7

19.9

2

S

63.1

20.8

tr.

1.0

2.0

10.9

1.1

0.6

1.7

-

37.9

13.6

51.5

2.79

1.9

41.2

42.1

1.22

tr.

4.5

1.7

9

T

63.6

4.5

-

3.0

15.2

4.5

1.5

-

6.2

1.5

14.1

6.1

20.2

2.31

2.1

54.1

56.3

0.36

0.5

22.0

1.0

4

1. Comprises Kyanite, Staurolite, Sillimanite, Andalusite and Chiastolite

2. Mainly Apatite, Sphene, Anatase, Monazite, Corundum, Topaz

3. Simple, unstrained quartz

4. Composite and strained quartz

5. tr. = trace (< 0.5%)

6. Mainly rock-fragments and carbonaceous debris
NUMBER 15

tions of orthopyroxenes, clinopyroxenes, olivine,

spinel and amphibole, and diminished ZTR and

garnet. Amphiboles increase toward the south,

while the metamorphic species decrease toward the

south. A high proportion of dolomite rhombs occurs in sample M9 from the Rio Martin. Feldspar

increases in relation to quartz, and there is a slightly

higher proportion of metamorphic quartz.

PROVINCE P.—This province extends from the

south side of Cap Mazari to Targa. Important

rivers in this region include Oued Emsa and Oued

Laou. This region is characterized by an abundance of opaque and ZTR minerals. Both olivines

and pyroxenes increase in the southern samples.

High proportions of dolomite rhombs occur in

sample M16 (near Cap Akaili) and M14 (Oued

Laou). The total quartz content is minimal in

samples taken north of the Oued Laou, while

feldspar reaches a maximum value in the same

samples. The ratio of igneous to metamorphic

quartz increases substantially to the south of the

Oued Laou.

PROVINCE Q.—This province extends from Targa

to Bou Hamed and includes the Oued el Had.

The heavy mineral assemblage here is similar to

that of Province O, but it includes a slightly decreased proportion of orthopyroxene and increased

amount of garnet. Olivines and both pyroxenes

tend to increase northward. There is a dominance

of the metamorphic quartz variety, and the ratio

of quartz to feldspar is similar to that in Province

P.

PROVINCE R.—This province includes the region

adjacent to Pointe des Pecheurs and includes the

Oued Ouringa. The heavy mineral assemblage contains the highest proportion of opaque grains in

the Moroccan samples. The metamorphic minerals

(especially andalusite and kyanite) represent the

most abundant nonopaque group. Orthopyroxenes,

garnets, and olivines are notably deficient. Samples

24 and 25 contain high proportions of rhombic

dolomite. The ratio of igneous to metamorphic

quartz decreases considerably from that of Province

Q, and the ratio of quartz to feldspar increases as

a result of a significant diminution in the total

feldspar content as compared with Province Q.

PROVINCE S.—This province extends from Oued

Mastasa to just west of Al Hoceima (Al Hucemas).

The most important rivers include the Oued Mastasa, Oued Bou Frah, Oued Bades, and Oued

Boussikour. The dominant nonopaque heavy mineral group is the ZTR suite, which here attains

its maximum abundance for Moroccan samples,

especially in the Bou Frah-Mestasa drainage basin.

The metamorphic minerals are also important,

especially andalusite. Amphiboles are also present

and increase conspicuously in the eastern samples.

Dolomite rhombs are locally important, particularly in the Oued Bou Frah. The proportion of

igneous to metamorphic quartz in this region

reaches its highest level in the Moroccan samples,

and the proportion of quartz to feldspar continues

to increase.

PROVINCE T.—This province includes the west

side of Al Hoceima Bay and extends to the Oued

Nekor. The Rhis and Nekor comprise the two

main drainage systems. Amphiboles are the dominant, nonopaque mineral group and include substantial proportions of actinolite, rare elsewhere

in the Moroccan assemblages. The amphibole percentages decrease toward the west of Oued Nekor.

An increase in the proportion of epidote is accompanied by a decrease in metamorphic minerals.

Epidotes decrease eastward from Al Hoceima. Dolomite proportions are universally high and reach

a maximum value in sample M33 (Oued Rhis).

There is a notable decrease in the quartz to feldspar ratio as compared to Province S and R and a

slight decline in the ratio of igneous to metamorphic quartz.

STRAIT OF GIBRALTAR REGION

STRAIT CHANNEL, NORTH PROVINCE.—The material examined lies in the northern of the two deep

channels, passing through the Strait of Gibraltar

(Kelling and Stanley, 1972a, b). The heavy fraction is distinguished by relatively high values of

pyroxenes and garnet and low values of ZTR and

amphibole. The mean total quartz and potash

feldspar values are the highest noted in the Strait

region. There is a considerable excess of igneous

over metamorphic quartz, as in all the Strait provinces. Mica content is minimal.

STRAIT CHANNEL, SOUTH PROVINCE.—These samples were obtained in the South Channel sector

of the Strait proper. The heavy mineral assemblage is characterized by high values of opaque

minerals and the maximum ZTR and clinopyroxenes. Garnet, metamorphic minerals, and ortho-

cu

a

•3 8
26 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

pyroxenes are minimal. Garnets and orthopyroxenes

increase from west to east, while the clinopyroxenes,

epidotes, and amphiboles show a broad reverse

trend. The light fraction is distinguished by minimal values of total quartz and feldspar, together

with a low proportion of mica and chlorite. Carbonates (mainly shell debris) are the dominant

light component.

GIBRALTAR CANYON PROVINCE.—The samples were

obtained from the Gibraltar Canyon, both in the

axial region and on the adjacent flanks between

the northern portion of Algeciras Bay and the zone

of confluence at the eastern end of the Strait (see

Kelling and Stanley, 1972b, fig. 14). The heavy

fraction comprises the highest mean values of

metamorphic minerals and amphiboles, together

with a considerable amount of orthopyroxenes.

Opaque minerals occur in amounts similar to

those in the North Channel, while the mean clinopyroxene value is the lowest encountered in the

Strait region samples. The proportion of amphiboles broadly decreases down-canyon until the flat

east sector of the Strait and then increases slightly.

The light fraction is characterized by the highest

proportion of igneous to metamorphic quartz, total

feldspar and plagioclase, and mica in the Strait

region; the lowest values of carbonate (shell debris) are noted here.

CEUTA CANYON PROVINCE.—The samples were collected from the axial region of the Ceuta Canyon

to the southern flat region of confluence at the

eastern end of the Strait (Kelling and Stanley,

1972b, fig. 14). Heavy minerals in this region are

characterized by the highest mean value of garnet,

epidote, and olivine in the Strait region. Garnet

increases down-canyon, while orthopyroxenes decrease in the same direction. The light fraction is

distinguished by the highest quartz to feldspar

ratio in the Strait region.

ALBORAN SEA

GIBRALTAR VALLEY-MALAGA LOW PROVINCE.—

Samples in this province were derived from core

TABLE 8.—Mineralogic composition of Alboran deep-sea samples-province and

core means (see Figures 5 and 6)

PROVINCE OR CORE

Opaque Minerals

Zircon + Tourmaline +

Rutile (ZTR)

Orthopyroxenes

Clinopyroxenes

Amphiboles

Metamorphic Group1

Garnets

Olivine + Spinel

Epidote Group

Others2

Igneous Quartz

Metamorphic Quartz

Total Quartz

Igneous/Metamorphic

Quartz Ratio

Potash Feldspar

Plagioclase

Total Feldspar

Quartz/Feldspar Ratio

Micas + Chlorite

Carbonates

Others5

NO. OF SAMPLES

GC

11.4

7.0

28.4

3.4

6.7

18.6

16.7

3.2

2.2

2.4

34.0

10.6

44.6

3.21

0.8

7.0

7.8

6.56

5.4

25.4

16.8

5

CC

20.0

6.8

17.4

6.5

4.7

12.9

22.1

3.9

3.6

2.1

30.0

12.9

42.9

2.33

1.6

3.6

5.2

8.20

4.5

28.2

19.2

3

SS

27.8

7.3

15.9

12.3

5.6

10.1

11.6

3.8

3.5

2.1

21.1

8.3

29.4

2.54

2.6

1.5

4.1

7.17

1.6

57.8

7.1

4

SN

10.9

2.0

35.1

8.1

2.7

14.4

21.9

2.0

1.4

1.5

41.3

13.8

55.1

2.99

3.4

3.8

7.2

7.65

1.0

29.7

7.0 .

2

91

17.7

5.1

35.86

2.5

5.1

9.4

tr.7

20.8

3.2

17.8

0.8

44.5

20.5

51.4

9.5

2

92

22.5

5.4

35.1

3.6

6.4

16.3

-

9.9

0.8

52.2

2.0

26.1

18.2

26.9

0.7

3

93

20.9

3.7

40.6

2.5

4.8

10.8

tr.

15.8

-

35.0

0.5

70.0

14.8

51.8

-

2

97

27.0

2.9

41.3

2.2

3.6

4.4

tr.

12.9

5.7

24.9

tr.

-

18.4

48.9

7.8

2

98

28.0

1.8

43.3

4.3

4.9

4.9

-

10.4

2.4

31.3

1.9

15.6

14.1

40.6

12.1

2

101

28.8

2.2

39.3

2.6

3.3

4.0

-

15.7

4.1

28.8

1.4

20.6

11.5

54.3

4.0

3

107

15.6

6.2

38.5

7.5

4.2

11.7

-

13.8

2.5

44.0

2.2

20.0

9.7

39.1

5.0

5

108

12.9

5.2

42.0

4.6

9.7

9.3

-

12.7

3.6

51.3

2.2

23.3

10.4

33.0

3.1

3

1-4. (as on other tables)

5. Mainly rock-fragments and carbonac

6. Total pyroxenes, undifferentiated

7. tr. = trace (< 0.5%)

GC = Gibraltar Canyon; CC = Ceu

SS = Strait of Gibraltar, southe

SN = Strait of Gibraltar, northe
NUMBER 15 27

108 in the Gibraltar Submarine Valley and core

107 from the Malaga Low, north of the Western

Alboran Basin (Figures 1, 5, and 6). One graded

sand layer in core 108 and two in core 107 were

analyzed (Huang and Stanley, 1972). The heavy

mineral assemblage is characterized by substantial

amounts of pyroxenes, amphiboles, and ZTR and

relatively low values of opaque minerals and

garnet. Olivine was not encountered. The light

fraction has a very low proportion of feldspar, and

quartz accounts for approximately half of the light

assemblage. The high carbonate values are largely

attributable to concentrations of foraminifera.

WESTERN ALBORAN BASIN PROVINCE.—Samples

were collected from the same sand layer (Lower

sand-and-silt layer) from six cores in cores 91, 92,

93, 97, 98, and 101 (Huang and Stanley, 1972, figs.

7, 8) in the flat plain of the Western Alboran

Basin. An average grouping of all sample data

examined shows a heavy mineral assemblage, which

is dominated by pyroxenes and epidote with high

values of ZTR. Quartz accounts for about onethird of the light fraction, and the carbonates

(mainly planktonic foraminifera) constitute about

the same proportion. Feldspars are notably deficient. A subtle regional trend can be discovered

on both sides of an east-west line bisecting the

basin plain. Samples to the south (cores 91, 92, 93)

contain somewhat higher values of ZTR, garnet,

epidote, total quartz, and mica, whereas those to

the north (cores 97, 98, 101) contain slightly enhanced amounts of opaque minerals, pyroxenes,

and carbonates.

Provenance of Sediments on Alboran Sea Margins

GENERAL

The regional distribution of mineral groups on

the southern Iberian and Moroccan margins is defined in terms of 20 light and heavy mineral provinces as described in the previous sections. The

position of these mineral provinces (Figures 5 and

6) is broadly concordant with the seaward limits

of the major drainage basins (Figures 2 and 3).

This emphasizes the close relationship which exists

between the varied lithology of the mountainous

margins of the Iberian Peninsula and North Africa

and the mineralogical composition of sediments

along the adjacent coast. The following section

details the manner in which the composition of

coastal and fluvial samples can be related to specific

source terrains in the Betic Cordillera and the Rif.

Essentially, two major mineralogical sectors are

recognized on the Spanish margin: one to the east,

extending from Velez-Malaga toward Adra, influenced by the Nevado-Filabride and Alpujarride

complexes, and the other, west of Malaga, draining

the ultrabasic rocks of the Peridotite Complex.

In the former region, the Adra and Guadalfeo

rivers, as well as smaller intervening rivers, carry,

among others, the following minerals: sodic plagioclase (albite, oligoclase), quartz, carbonates,

mica, garnet (very abundant), epidote, amphibole,

orthopyroxene, and opaque minerals.

In the western region, peridotites are among the

significant lithologies that crop out in basins of

the Guadalhorce, Fuengirola, and Verde rivers

and smaller basins between Malaga and Estepona.

These rivers carry the following: calcic plagioclase

(or calco-sodic varieties), mica, olivine, amphibole,

orthopyroxene, clinopyroxene, garnet, epidote,

and opaque minerals.

On the Moroccan margin, two major mineralogical sectors are also recognized: one to the east,

extending from the Beni Bouchera ultrabasic complex, influenced essentially by Paleozoic, Mesozoic,

and Tertiary sediments, and the other, north and

west of the ultrabasic complex, draining Paleozoic

sediments, metamorphic rocks, and basic or ultrabasic intrusives.

In the former, rivers such as the Nekor and

Ouringa convey sodic plagioclase, both igneous and

metamorphic quartz, carbonates, and opaque

heavy minerals (very abundant). In the northwestern region, rivers such as the Oued Laou and

Martin carry more calcic plagioclase and a high

proportion of metamorphic quartz, together with

garnet, orthopyroxene, and olivine.

A study of minerals in coastal sediments from

the Spanish margin east of Malaga by P£rezMateos et al. (1973) provides results which differ

in some major respects from those of this investigation. These authors show substantially higher

values of minerals such as andalusite, staurolite,

and quartz and much lower values of pyroxene,

epidote, and feldspar than analyzed here. Furthermore, they recognize three provinces (I, II, III)

between Malaga and the Cabo de Gata as compared to five defined by us along the same sector
28 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

(Provinces I to M). A point of resemblance, however, is that the dramatic increase in the proportion of garnet to the east of Motril (Rio Guadalfeo) (Figure 7) is also recorded by Perez-Mateos

and others (1973).

ORIGIN OF SELECTED SPANISH RIVER SEDIMENTS

Two samples from each of six rivers in the

western sector of the Iberian margin (west of Marbella) were examined: Calena (I), Guadaiza (II),

Guadalmansa (III), Padron (IV), Enmedia (V),

and the Genal-Guadiaro (VI). These rivers fall

within the coastal mineral provinces G, F, and E,

from east to west respectively.

At each of the river localities the sample pairs

show similar heavy mineral associations, and consequently an average value is supplied for each

river (Table 5). Each river sample closely reflects

the lithology of the terrain traversed. Thus, the

main variations from river to river are most readily

ascribed to differences in lithology of the terrains

cut by the six rivers (cf., Figure 2). The notable

increase in quartz and mica and orthopyroxene,

amphibole, olivine, and metamorphic minerals and

the concurrent decrease of carbonate, garnet and

opaque minerals, from the Calena to the neighboring Guadaiza river, are explained by the fact that

the first river cuts carbonate-rich rocks, while the

second (Guadaiza) cuts across peridotites as well

as metamorphic terrains. The westernmost river,

the Genal-Guadiaro, carries an assemblage that is

more similar to that of the Guadaiza River than

the intervening rivers. The headwaters of the

Genal-Guadiaro also erode peridotites and metamorphic lithologies.

The percentage of total quartz increases substantially to the west, reflecting the westward predominance of source terrains of Cretaceous, Paleogene, and Miocene sediments.

Samples collected from these rivers are broadly

comparable in composition to the samples collected on the coast adjacent to the appropriate

river mouth. However, with the exception of epidote, which appears to be consistently more common in the coastal samples, there is little change

downstream. As a general rule, coastal samples contain higher values of opaque minerals and lower

values of orthopyroxenes. Moreover, the river

samples in aggregate generally contain more quartz

and mica and less feldspar than most of the coastal

sands (Table 5, Figure 6).

These differences in composition between fluvial

and coastal samples may be partly a function of

the relative efficacy of the differing hydraulic processes affecting these two environments, but the influence of grain-size factor cannot be excluded

(despite the restrictions of analyses to the same

grades, as indicated earlier, page 3).

ORIGIN OF SPANISH MARGIN SEDIMENTS—

LIGHT MINERALS

Quartz is marginally the most abundant mineral, ranging from 29% to 71% of the total light

mineral fraction (the average content approximates 40%). Metamorphic quartz is more abundant than quartz of igneous origin. The former

originates in metamorphic terrains that abound

in the study area. Quartz of igneous origin is derived from several sources: the acid volcanics of

the Cabo de Gata region, hydrothermal veins in

the different complexes, and reworked older sands

and sandstones, particularly those in the External

Zone. Plagioclase generally constitutes between

10% and 56% of the light mineral fraction, averaging about 35%. Both sodic and calcic plagioclases display distinct regional distributions. Sodic

plagioclase (albite and oligoclase) is predominant

east of Malaga; calcic species abound between

Estepona and Malaga. As would be expected, the

relation between plagioclase assemblages and river

supply is a direct one. For instance, sodic plagioclases are common in the rocks of the NevadoFilabride and Alpujarride complexes, i.e., sequences

that crop out in the fluvial basins east of Malaga.

An important source of calcic feldspars, on the

other hand, is the Peridotite Complex that crops

out in basins between Malaga and Estepona. Between Estepona and Tarifa, farther to the west,

both sodic and calcic varieties occur.

The lower relative percentages of potassic feldspars (generally less than 2%) in all coastal samples examined can be related to their generally

low abundance in most rock types of the different

stratigraphic-tectonic units cropping out in the

various drainage basins. An exception is Province

C, on the eastern side of Algeciras Bay, where the

increased quantity (to 8%) may reflect the importance of sedimentary sources conveyed into
NUMBER 15 29

the northern part of the Bay from the Rio

Guadarranque.

Carbonate, including dolomite rhombs, and

lithic fragments are commonly present and in

many cases can be related to specific carbonate rock

types cropping out in the drainage basins. The

highest percentages occur in Province L, which is

bounded by cliffs of Middle to Upper Triassic

shaly limestones and dolomites. High values are

also encountered in Provinces G and H and appear

to represent fluvial supply from the Sierra Blanca

unit, which includes marbles and gneisses.

Glauconite, essentially of detrital origin, is observed in some samples. Most of the detrital glauconite originates in the sandstones of Cretaceous,

Paleogene, and lower Miocene age in the External

Zone and in sands and sandstones of postorogenic

sequences (especially the Miocene).

The percentage of mica is variable, but is generally quite low (less than 2%). Muscovite and particularly biotite abound in most of the metamorphic sequences of the Internal Zone. The highest

mica values (12%) occur in Province K east of

Nerja, west of Motril, where Paleozoic micaschists

and quartzites crop out in the coastal ranges. Certain other coastal samples contain a notably high

percentage of mica. An example in point are those

in the Bay of Algeciras which, interestingly enough,

are fed by rivers that cut metamorphic units not

particularly rich in mica. This suggests that enriched mica content may also be related to factors

other than provenance (see following section).

ORIGIN OF SPANISH MARGIN SEDIMENTS—

HEAVY MINERALS

Garnets occur at all sample stations along the

Spanish margin (Figure 7), and a large fraction

of these undoubtedly are derived from the NevadoFilabride Complex. In addition, garnets are supplied from certain Alpujarride Complex sequences,

from basal units of the Malaguide Complex, and

from the Casares Unit. The highest percentages of

garnet occur in samples from the sector between

the mouths of the Adra and Gualdalfeo rivers.

These rivers traverse extensive outcrops of the

Nevado-Filabride Complex (Figure 2). Other areas

where high amounts of garnet occur include

coastal sections near the mouths of the Guadalhorce and Fuengirola rivers, where garnetiferous

sequences of the Malaguide Complex crop out.

High values of epidote occur along the coast,

and the highest concentrations are found in the

region between Malaga and Motril, and in some

sectors to the west of Adra. This mineral has different possible origins that include the NevadoFilabride and Alpujarride Complexes as well as

certain sequences of the Malaguide Complex.

Pyroxenes are abundant west of Motril. Percentages of orthopyroxenes are higher than those

of clinopyroxenes except in certain isolated cases

(sample stations 2, 20, 35 and 74). Provenance of

pyroxenes (ortho- as well as clinopyroxenes) is

closely related to the Peridotite Complex. Some

clinopyroxenes are derived from the amphibolites

of the Alpujarride Complex that are intercalated

in the Paleozoic dolomites exposed west of Motril.

Amphiboles are present in all samples in variable amounts. In some sectors, such as near Nerja,

it is the most important mineral in the heavy fraction in some samples. Here, its origin lies in the

amphibolites of the Paleozoic sequences of the

Alpujarride Complex that crop out extensively

north of the coast between Nerja and Motril.

Olivine is derived in large part from the Peridotite Complex, and the highest percentages observed

in coastal samples occur between Estepona and

Marbella, where rivers eroding this complex reach

the sea. Olivine is abundant from Algeciras to

Malaga; this in part explained by the load carried

by the various rivers (Guadalhorce, Fuengirola,

Verde) cutting this complex and is also due to

coastal currents carrying olivine-bearing sediments

toward the west (see next chapter). At the mouth

of the Guadalfeo River there is an anomalously

high percentage of olivine; this can be interpreted

as originating in the "rocas verdes" (altered basic

igneous rocks) facies of the Nevado-Filabride and

Alpujarride complex that crop out in the drainage

basin of this river.

Significant percentages of apatite occur only in

samples collected in the vicinity of the Strait of

Gibraltar. Apatite, derived in large part from

igneous rocks, is transported by currents from

source terrains that are exposed along this coastal

sector. There is no primary source for this mineral

in the fluvial basins north of this area. The presence of very rounded grains does suggest that

apatite is reworked, at least in part, from older

apatite-bearing sandstones.
30 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Tourmaline is derived from the NevadoFilabride Complex, phyllites of the Alpujarride

Complex and the Casares Unit, and the amphibolites of diverse units. The total ZTR content

ranges up to 2.3% and is more abundant in the

coastal samples from the Strait of Gibraltar region, tending to decrease eastward from this area.

This change results from the diminished importance of sedimentary terrains east of Gibraltar.

Kyanite is associated with certain lithologic sections (micaschists) of the Nevado-Filabride Complex. Sillimanite originates in rocks, including

micaschists, of possible pre-Cambrian age in the

Malaguide Complex and the Sierra Blanca Unit.

Andalusite is derived from several units: micaschist

of the Alpujarride Complex, lower sequences of

the Paleozoic Malaguide Unit, the Casares Unit,

and the Sierra Blanca Unit. The percentages are

noteworthy along the coast from Nerja toward the

west.

Opaque minerals are present, generally in high

percentages. Particularly significant are coastal

samples containing large amounts of opaques

(45% to 60%) between Malaga and the MotrilAdra sector and the Strait of Gibraltar sector. Of

these minerals, magnetite is very abundant in the

fine sands of this coast (beaches such as the Playa

de Carchuna near Motril). Magnetite has several

possible origins and can be found in diverse stratigraphic sections of sedimentary and metamorphic

as well as ultrabasic rocks.

ORIGIN OF MOROCCAN MARGIN SEDIMENTS—

LIGHT MINERALS

Feldspar, particularly plagioclase, is the most

abundant mineral, ranging from 25% to 75% of

the total light mineral fraction (the average content approximates 43%). Plagioclase generally constitutes between 27 and 71%, and calcic varieties

predominate, particularly in the central sectors

(Provinces O, P, Q, and R). High values of calcic

plagioclase in the sediments of Provinces P and Q

reflect a source terrain which includes bodies of

ultrabasic rock (Beni Bouchera). Individual coastal

samples from the vicinity of Cabo Negro in Province O also contain enhanced proportions of

calcic plagioclase, probably derived from the peridotite bodies intruded into the Paleozoic metamorphic rocks of this region (Figure 3). High

values of more sodic plagioclase are encountered

in the sediments of Province T and probably derive, directly or indirectly, from isolated outcrops

of Paleozoic metamorphic rocks in the drainage

basin of the Oued Nekor.

Total quartz, ranging from 17% to 66%, is most

abundant in the western sectors (Provinces N and

O) and also in Province S, west of Al Hoceima (to

52%). These areas drain essentially sedimentary

terrains. The igneous quartz variety predominates

over the metamorphic type in those provinces cited

above which contain abundant total quartz of

presumably sedimentary origin, whereas the metamorphic quartz is dominant in Provinces such as

P, Q, and R, receiving material largely from Paleozoic metamorphic sources. The dominance of

igneous quartz in Province T probably reflects

the derivation of material from acid and intermediate volcanic rocks of late Mesozoic and Tertiary age including the Cap Quilates Complex.

Carbonate content generally ranges between 4%

and 8%, but reaches the exceptionally high mean

value of 22% in Province T east of Al Hoceima.

Dolomite rhombs constitute an important part of

the carbonate fraction and reach their peak abundance in samples from the Oued Nekor drainage

basin. Such carbonate components derive largely

from Mesozoic limestone and dolomite sequences,

particularly those of Triassic and early Jurassic

age, most commonly exposed in the eastern part of

the study area. High values of carbonate in individual samples (Figure 6) which occur in Provinces N, O, and P may be ascribed to a similar

provenance, although some may also be derived

from smaller bodies of marble developed in the

Paleozoic terrains between Ceuta and Bouhamed.

Glauconite is generally rare in the Moroccan

samples except in a sample (no. 3) east of Tangier

in the Strait of Gibraltar (Figure 10), whose origin

lies in the adjacent terrain of Cretaceous/Tertiary

sandstones.

Rock fragments account for only a minor proportion of the light fraction except in sample 6

just west of Cueta, where they consist mainly of

slate.

Mica percentages are generally low and consist

predominantly of biotite. The highest values, encountered in Province P, are attributable to the

adjacent Paleozoic sediments.
NUMBER 15 31

ORIGIN OF MOROCCAN MARGIN SEDIMENTS—

HEAVY MINERALS

In general, garnets account for the highest percentage of transparent heavy mineral fraction but

vary considerably in abundance (1.1% to 18.4%).

The highest values occur in river sediment samples

from the Province Q (Bouhamed) region and in

coastal samples from the Strait of Gibraltar and

the region south of Ceuta (Provinces N and O).

Paleozoic metamorphic rocks represent the primary source of this mineral and account for its

abundance in the Bouhamed region. However, the

abundance of garnet in the coastal sediments may

be attributed either to reworking of younger sedimentary rocks or to preferential concentration by

littoral processes.

The ZTR group is generally an important constituent of most of the Moroccan heavy fraction

(4% to 18% mean values), and varieties of zircon

tend to dominate the group. Exceptionally high

values of ZTR occur in samples from Province S

(west of Al Hoceima) and from the Strait of Gibraltar region. These enhanced proportions clearly

indicate the increased importance of sedimentary

rocks in the source terrains.

Minerals assigned to the metamorphic group

(andalusite, kyanite, staurolite, and sillimanite)

are also abundant in the heavy mineral assemblages from the Moroccan margin, ranging from

4% to 15% mean values. This group attains its

maximum abundance in the region south of

Ceuta (Province O), although high mean values

also occur in the Bouhamed area (Province Q)

adjacent to extensive outcrops of metamorphosed

Paleozoic rocks. High values in the Strait of Gibraltar (Province N) are mainly observed in the

littoral samples and probably reflect the increased

resistance of certain members of this group, notably staurolite. Staurolite constitutes 12.2% of the

nonopaque fraction in individual samples but is

almost confined to Provinces N and O in the

western portion of the study area. This mineral

recurs in lesser abundance in the samples from the

Bouhamed metamorphic area (Province Q, Figure

5). Andalusite is common, but exceptionally large

values are noted in individual samples from Provinces R, S, and T near Al Hoceima. They are

evidently reworked from Mesozoic and Tertiary

sediments, an origin confirmed by the well-rounded

character of these grains. Large relative values of

kyanite are also noted in the same samples. However, angular grains of kyanite are consistently

abundant in samples from Provinces O and Q

(south of Ceuta and Bouhamed) where such grains

may be more confidently attributed to the surrounding metamorphic rocks.

Orthopyroxenes are highly variable in abundance (up to 24% in individual samples) and are

almost confined to Provinces O and Q. The enhanced content of the orthopyroxene in these regions reflects the presence of ultrabasic bodies

occurring in the vicinity. Clinopyroxene is more

widespread than the orthopyroxene but is almost

always lower in value. The highest percentages of

clinopyroxene are found in Provinces O and Q.

Somewhat enhanced proportions of clinopyroxene

occur in coastal samples from the Pointe de

Pecheurs area (Province R) and here may be derived from the basic or ultrabasic intrusives nearby. A sample from the Oued Nekor provides the

highest individual value of clinopyroxene, which

probably originates from igneous or metamorphic

rocks that crop out in small areas near the source

of this river.

Province T, in the Oued Nekor drainage basin,

also provides the consistently highest content of

amphibole minerals, including substantial amounts

of actinolite, which is typical of the amphibolite

metamorphic facies. The minor amounts of amphibole encountered in the more westerly regions

(especially Province Q) are dominated by brown

and green hornblende, together with some glaucophane. These minerals probably originated in

the Paleozoic metasediments.

Olivine and spinel (mainly picotite) are considered together because these minerals are derived largely from basic and ultrabasic rocks in

which these two species are intimately associated.

The distribution of olivine and spinel closely

parallels the distribution of orthopyroxene, confirming the basic or ultrabasic provenance of these

minerals. The maximum values for this group

occur in the region between Pointe Targa and

Bouhamed, reflecting the influence of the Beni

Bouchera igneous mass.

Epidote attains maximum abundance in Provinces Q and T, areas rich in metamorphic source

terrains.

Apatite is relatively uncommon on the Moroccan
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

margin but attains appreciable abundance (up to

4.7%) in individual samples from the Strait of

Gibraltar beaches. Grains are well rounded and,

in part, may be reworked from older sedimentary

terrains.

Opaque minerals comprise the most important

component of the heavy mineral fraction, with

mean values ranging from 23% to 80% and averaging approximately 45%. The highest mean

values occur in rivers and beaches in the more

easterly provinces (R, S and T), together with

Province P (Cap Mazari area). Opaques are probably derived from sedimentary and metasedimentary rocks, although this provenance is diverse and

subsequent concentration by both fluvial and

coastal processes has also occurred.

Mineralogical Modification by Coastal Processes

Although the similarity of heavy and light mineral assemblages in river and adjacent coastal samples attests to the virtually direct transport of sediment from source to sea on all margins of the

Alboran Sea, several features indicate that some

modification of mineralogy does occur while material is held in the littoral and nearshore zone. The

nature of these modifications may be used to interpret the effects of coastal processes and the consequent dispersal pattern on both Iberian and Moroccan margins.

The most compelling evidence for modification

by coastal processes derives from the nonconcordance in detail of mineral province boundaries

30'

30'

FIGURE 11.—Predominant movement of coastal and nearshore currents based primarily on aerial

photographic analysis (cf. Figures 12-14).
NUMBER 15 33

/.-•

CURRENT PATTERN

SAMPLE LOCALITY

FI'GURE 12.—Aerial photographic coverage of selected portions of the southern Iberian margin

(arrows denote major current pattern). Upper: Malaga Bay (altitude approximately 7000 m;

R. Ghor = Rio Guadalhorce; R. Gmed = Rio Guadalmedina; Mai = Malaga; El P = El Palo;

Vic = La Victoria). Lower: Strait of Gibraltar (altitude approximately 7000 m; R. Ve — Rio

de la Vega; Tar = Tarifa).

with the adjacent drainage basin boundaries, despite the broad parallelism already noted. Important and abrupt variations in the mineralogy of

the coastal sands are related to the supply at a

river mouth or to the presence of coastal outcrops

directly supplying material to the adjacent beach.

However, where examined in detail (see previous

section), the mineralogical variation from river

to river is greater than that observed along the

intervening stretch of coast near the river mouths.

An example of this effect is shown by the comparison of coastal and fluvial materials on the

Spanish margin between the Calena and GenalGuadiaro rivers. Here, coastal stations 27 to 30

(Figure 2) display a greater increase in the percentage of garnet than is observed between the

supplying rivers (Enmedia and Padron).' Stations

22 to 29 contain appreciably enhanced proportions

of olivine as compared to adjacent rivers, and

both clinopyroxene and amphibole are less abundant in samples from the corresponding rivers

than in the sands from coastal stations 27 to 36.

There is, in addition, a much higher content of

orthopyroxene observed in all the coastal samples

as compared with the fluvial sediments. Thus, river

samples, as would be expected, reflect more directly

the mineralogy of the terrains crossed by the fluvial flow, while the greater sample-to-sample similarity along the coast indicates that at least some

mixing and dilution of individual river supply
34 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FK.I'KK 13.—Aerial photographic coverage of Algeciras Bay. (Altitude

approximately 7000 in; PSG = Punta tie San Garcia: Alg = Algeciras;

RPa = Rio Palinones; RGuad = Rio Guadarran(|iie: (Jib = Gibraltar; EP —• Europa Point; La I.i = La Linea. Allows denote major

current pattern.)
NUMBER 15 35

FICURE 14.—Aerial photographic coverage of selected portions of the Spanish margin east of

Malaga (altitude approximately 5000 m; arrows denote major current pattern). Upper: area

near Castell de Ferro (= Ca Fe; RaGua = Rio Gualchos). Lower: area near Calahonda ( =

Cal; Fa = Faro, light house; B.R. = beach ridges).

has occurred at the coast as a result of wave and

longshore current transport.

This example demonstrates that the coastal

modification processes are not solely concerned

with enhancement of the more stable or resistant

mineral species. For example, the increased proportions of pyroxenes in the coastal sands west of

Marbella (Figure 7) indicate some increment in

these relatively unstable minerals from sources

other than the adjacent rivers, presumably through

littoral drift from more distant fluvial or coastal

sources.

Evidence concerning the actual sense of nearshore sediment transport is provided by the lateral trends observed within both Moroccan and

Spanish coastal mineral provinces. Such trends

involve distinct, regular diminution or augmentation of the relative proportions of certain mineral

species, which may be assigned to supply from a

given river or coastal outcrop. For example, in

the region of Malaga, samples 48 to 52 show a

steady southward decrease in the abundance of

amphibole and a concurrent increase in the proportion of garnet and olivine (Figure 7). The

implication of this trend is that this stretch of

coast is subject to an essentially southwestward

longshore movement of sediment by coastal currents. This conclusion is substantiated by an independent appraisal of coastal current motion and

long-term sediment drift patterns observed from
36 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

aerial photographs and large-scale charts (Figures

11 and 12).

The coastal current map suggests a predominance of westerly trending transport along the

Spanish coast from Malaga to the Strait of Gibraltar. Surface drift surveys (Gaibar-Puertas, 1967)

also reveal a similar pattern. Such transport would

help account for the observation that the highest

percentage of the main mineral species generally

occurs in samples taken immediately west of the

river delivering it to the sea (note changes on

heavy mineral bar graphs, Figure 7). This southwestward transport is further attested by the remarkably high concentrations of orthopyroxene,

amphibole, and olivine in the region of the Strait

of Gibraltar, a region isolated from direct fluvial

or coastal supply of these minerals.

The distribution of minerals in the coastal sand

of the Bay of Algeciras poses some problems in

that the mineral assemblages are rich in metamorphic species, pyroxenes and olivine, although the

rivers that flow into the Bay do not cross metamorphic or ultrabasic terrains. It is significant,

therefore, that the Bay assemblage is similar to

assemblages outside of the Bay and east of Gibraltar (Kelling and Stanley, 1972a). There are several possible interpretations: (a) currents from

the east, moving around the peninsula of Gibraltar, enter the Bay carrying with them sediments

from La Li'nea and farther east; (b) the sands are

eroded from Tertiary-Quaternary sediments that

bear this particular suite of minerals and that are

exposed near the Bay; (c) or the present peninsula

forming the "rock" of Gibraltar was an island

4«- - "••-'••-

•si

FIGURE 15.—Photographs showing strong coastal currents in the Strait of Gibraltar region.

Upper left: ship heading west across Algeciras Bay toward Algeciras. Lower left: view from the

Rock of Gibraltar across Algeciras Bay toward the Strait (to the southwest). Right: view showing

east side of the Rock and coastline north of Gibraltar. (Note current patterns parallel to the

straight coastline off La Linea-Gibraltar region. Large structure in foreground is a water catchment above Catalan Bay.)

\
NUMBER 15 37

FICURE 16.—Photographs showing evidence of strong coastal currents. Upper: currents oft Morocco

between Cap Mazari and Cabo Negro. Lower: view east toward the plain of Carchuna from

Cape Sacratif (southeast of Motril, Spain).
38 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

during the recent past, and the coast line along

which minerals moved originally lay north of the

"rock" (i.e., in the low area close to the Gibraltar

air strip and the Gibraltar-Spanish border); (d)

or, still, a fourth possibility is that the Guadiaro

River in the past occupied the present lower valley

of the Guadarranque River; subsequently, the

Guadiaro River was captured and occupied its

present position east of Gibraltar. Thus, if hypotheses (b), (c), or (d) are valid, some of the

Algeciras Bay coastal sands would be essentially

relict in origin.

In any event, the present distribution of minerals in the Bay sediments conforms closely to the

predicted counterclockwise transport path (Figures 13 and 15). Note for example the southward

diminution of pyroxene in the western part of

the Bay (samples 13 to 8) and the northward decrease in orthopyroxene from Europa Point toward

La Linea on the eastern side of the Bay.

Although some workers (Perez-Mateos et al.,

1973), using size parameters, have deduced a

predominant eastward transport of the coastal

sediments in the region east of Malaga, the mineralogic trends between Malaga and Adra observed

in this study are generally less regular in sense

or in degree. This variability may be partly a function of the increased contributions from coastal

outcrops and partly attributable to the less constant coastal drift patterns revealed by independent

analysis of the aerial photographs (Figures 11 and

14)\

Similar effects of nearshore transport have been

identified on the Moroccan margin. Coastal samples from the western part of the Moroccan shore

of the Strait of Gibraltar contain substantial

quantities of minerals, such as orthopyroxene and

olivine, which are virtually absent from the adjacent river sediments. The source of these minerals

lies in ultrabasic intrusives exposed on the coast

around Ceuta, and their presence in this western

region implies a net westward transport of detritus

along this portion of the Strait (Figure 11).

As in the region west of Malaga, the predominant nearshore sediment drift, as revealed by

aerial photo survey, is essentially toward west and

north, in the region from Melilla to Cap Negro

(Figures 11 and 16). The region between Cap

Negro and Ceuta appears to be one of converging

flow (to the south from Ceuta, and to the north

from Cap Negro). The mineral distribution in

this coastal region is significant (samples 7, 19-22,

Figures 9 and 10). Here, the orthopyroxene derived respectively from ultrabasic bodies outcropping at Ceuta and at Cap Negro (Milliard, 1959)

decreases away from these sources to a minimum

in the central region near the mouth of the Oued

Negron. These decreasing trends parallel the current convergence (Figure 11).

Two other factors, in addition to nearshore

currents, influence the distribution of mineral

assemblages. These are (a) coastal morphology

(i.e., embayments and sheltered areas that serve

to trap selected minerals such as micas versus long,

open straight coastlines that are prone to more

intense wave attack with resulting concentration

of heavy mineral lag deposits; the orientation of

beaches that may be more or less prone to erosion

by wave and coastal currents, etc.) and (b) meteorological conditions including rainfall, snow-melt,

water, and wind patterns that vary seasonally. A

case in point is the region of Gibraltar where

highly contrasted coastal regimes occur on either

side of the Rock. East of Gibraltar, the long

straight beaches are exposed to strong attack by

waves as well as longshore currents, with the consequence that these eastern sands contain very high

proportions of heavy minerals (up to 71% in samples from Eastern Beach near La Linea). On the

other hand, the Bay of Algeciras, west of Gibraltar,

is a region of lower energy where deposition prevails, resulting in the enhanced proportions of

mica.

It is apparent, therefore, that the abundance of

individual mineral species is not solely dependent

on provenance but is subject to modification by

processes active in the coastal zone. Such processes

operate chiefly to concentrate or dissipate specific

minerals of differing size, density, or physical

durability.

Dispersal of Marginal Sands to the

Western Alboran Basin

The evidence cited in the previous section demonstrates that sediment transported by rivers from

both the Iberian and Moroccan highlands maintain, at least in a general manner, their mineralogical integrity along well-defined coastal sectors. This
NUMBER 15 39

fact should enable the provenance of sands in more

offshore environments to be identified.

Earlier studies have shown that sand is actively

being conveyed into deeper marine environments

both to the west and east of the Strait of Gibraltar

(Heezen and Johnson, 1969; Kelling and Stanley,

1972a, b). These investigations indicated that

coarse sediment is principally being transferred

from the Ceuta-Cabo Negro and the GibraltarAlgeciras regions to the eastern end of the Strait

through two major canyons, Ceuta and Gibraltar

canyons. From the canyons, this material is transported to a zone of canyon confluence in a relatively flat sector at the eastern end of the Strait

(Figure 17) and subsequently is shifted predominantly in a westward direction under the

influence of the strong deep Mediterranean undercurrent (Kelling and Stanley, 1972b, figs. 15, 16).

The results of the present study provide independent evidence for this westward transport, since

coastal and fluvial samples from both the Spanish

and Moroccan borders of the Strait show little

mineralogical resemblance to samples from the

adjacent deep floor of the Strait (Figures 5 and 6).

Significantly, the latter bear a closer mineralogical

resemblance to coastal samples obtained farther

to the east.

However, there is some evidence that part of

the canyon-fed sediment load reaching the zone

of confluence is conveyed eastward and may reach

the Western Alboran Basin plain via the large

Gibraltar Submarine Valley (Figure 18; cf., Kelling and Stanley, 1972b:518). This eastward transport of sand is substantiated by the results of a

detailed high-resolution subbottom survey (Stanley

et al., 1970; Bartolini et al., 1972) showing the

distribution of sand layers in the Western Alboran

Basin. The number and thickness of these sand

layers provide a means of determining the gross

dispersal pattern of late Pleistocene-Holocene

elastics within the Basin. These earlier surveys

showed that sands were primarily transported from

the west and north.

Further confirmation of this mode of filling has

EAST

FIGURE 17.—Two east-west high resolution subbottom profiles (3.5 kHz) at the eastern end of

the Strait of Gilbraltar showing the zone of confluence, a flat area between Gibraltar and Ceuta.

Profiles cross Ceuta Ridge bounding the eastern margin of Ceuta Canyon (see Figure 1). (Spacing between horizontal lines is 20 fm (37 m).)
40 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

been provided by compositional studies of the sand

layers in numerous cores from the western Alboran

Basin plain and surrounding area (Bartolini et al.,

1972; Huang and Stanley, 1972). Material from

several turbidites was attributed to a source area

in the region of the Serrania de Ronda west of

Malaga and at the eastern end of the Strait of

Gibraltar.

A closer evaluation enables us to identify more

precisely the immediate and ultimate sources of

the late Quaternary and Holocene sands in the

deep-sea cores. It is evident that the heavy mineral

assemblages are more valuable for this purpose

than the light fraction, partly because of the addition of biogenic carbonate (largely planktonic

foraminifera and some shell debris) and mica, and

partly because of size-sorting effects. The data of

Huang and Stanley (1972, table 5) pertaining to

the Upper sand turbidite layer (dated at about

10,000 years B.P.) and to the Lower sand turbidite

layer (emplaced subsequently to about 12*500

years B.P.) in six cores (91, 92, 93, 97, 98, and 101)

was re-expressed in order to achieve mineral proportions compatible with those of the shallower

regions.

The Western Alboran Basin heavy mineral suite

is consistent from core to core and is dominated by

pyroxenes and opaque minerals, with substantial

proportions of epidote, garnet, and ZTR. On the

basis of the mean values of the heavy minerals,

the deep-sea sands most closely resemble those of

coastal sands in the vicinity of Gibraltar (Provinces

B, C, and D). The high proportion of pyroxene

precludes derivation of the Alboran Basin sands

from coastal areas east of Marbella on the Spanish

margin. No assemblage resembling these deep-sea

sands occurs on the Moroccan margin (low pyroxene and low epidote).

The ultimate derivation of the Lower sand

layer may lie in the Serrania de Ronda as suggested by Bartolini et al. (1972) on the basis of

abundant enstatite and also indicated by river

NORTHWEST

IcEUTA RIDGE

600 fm

SOUTHEAST

FIGURE 18.—High resolution subbottom profile (3.5 kHz) extending from the Ceuta Ridge near

the Strait of Gibraltar downslope across the Alboran Basin. Traverse cuts diagonally across

Gibraltar Submarine Valley, Malaga Low, and Alboran Trough (see Figure 1). (Spacing between

horizontal lines is 20 fm (37 m).)
NUMBER 15 41

samples from this region. Tenuous evidence of

more direct derivation from the north (region of

Malaga-Marbella) is provided by the sands of core

107 collected south of Malaga in the Malaga Low

(north of the Western Alboran Basin). The sands

in this core display mineralogic attributes closely

comparable to those in rivers draining the region

north of coastal provinces F and G (Figure 5). It

34"N

3"W

FIGURE 19.—General geology of region surrounding the

Alboran Sea-Strait of Gibraltar region. Note general symmetric distribution of stratigraphic terrains around the Alboran Basin, including position of ultramafic rocks (Ronda

and Beni Bouchera) on opposite margins. (1, Predominantly

Paleozoic sedimentary, granitic, and metamorphic terrain of

the Meseta. 2, Mesozoic and Tertiary zones of transitional

depth clastic and carbonate deposition. 3, Mesozoic subbetic

deep water carbonate, marl, and volcanic rocks; intrarif sandy

flysch. 4, Spanish Rondaides and Moroccan Chaine CalcaireMesozoic carbonate rocks with Alpine-type facies in the

Triassic. 5, Cretaceous and Tertiary sandy flysch. 6, Spanish

Betic and Moroccan Paleozoic zones; Paleozoic geosynclinal

clastic and thin Mesozoic carbonate rocks. 7, Andalusitesillimanite low-pressure metamorphic sequences. 8, Ultramafic

rock, including an outcrop near Ceuta. High-pressure metamorphic rock with kyanite is exposed in the Sierra Nevada

uplift. Figure and legend after Loomis, 1972, fig. 1.)

is conceivable that these sands may have been conveyed directly offshore to this locale during periods

of eustatic low sea level stands in the late Quaternary (Huang et al., 1972).

However, our analysis of the modern coastal

sands demonstrates that a predominant transport

from the Serrania de Ronda complex and adjacent

regions directly to the deep sea is unlikely. Our

evidence favors the transfer of Serrania de Ronda

detritus southwestward toward Gibraltar and subsequent funneling to the Western Alboran Basin

through the Gibraltar Canyon and Submarine

Valley (Figure 23), a hypothesis suggested earlier

by Huang and Stanley (1972). The trace of this

transport path is recorded by sands of core 108

(lying 28 km southeast of Europa Point close to

the Gibraltar Submarine Valley) that bear a

marked mineralogic resemblance to the Alboran

Basin sands on the one hand and the coastal sands

of Province D (eastern shore of Gibraltar) on

the other (Figure 5).

It should be noted that other source terrains

and dispersal paths cannot be excluded for the

older, deeper Western Alboran Basin sands. Thus,

derivation from the north African margin and

from the region east of Malaga during earlier

geological periods remains a possibility which

would require further examination and could now

be identified on the basis of mineralogy. We can,

however, exclude as a possible source area the Moroccan margin south of the NE-SW trending

morphological barrier created by the XauenTofino-Alboran Ridge (Milliman et al., 1972).

In the broader context, the asymmetry of provenance of recent sands of the Western Alboran

Basin plain indicated in this survey is a feature

which at first sight would have been difficult to

predict in view of the marked similarity of the

opposite margins. The relief (Houston, 1964) as

well as the geology of both margins are comparable and in certain respects mirror one another

(Figure 19). Both areas are drained by relatively

short, steep rivers flowing seasonally, and the spacing of these streams is similar on both the Spanish

and Moroccan borders. Climatic conditions are

comparable with rain concentrated during the

winter months with 300 to 1400 mm per year on

the Iberian margin (Figure 20) and 400 to 1400

mm per year on the Moroccan side (Jackson,

1961). Rainfall on both margins decreases toward
42 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

GUADALQUIVIR BASIN

MEDITERRANEAN SEA

FIGURE 20.—Map showing rainfall distribution on the southern Spanish margin (contour interval, 100 mm/year). Maximum rainfall (1400 mm/year) occurs in the Sierra de Grazalema

(headwater of the Guadiaro River) and in the Sierra Nevada (1000 mm/year). (Data after

Centro de Estudios Hidrograficos, 1970.)

the east and in zones of lower elevations. It appears

that intensity or river flow, at least on the Iberian

margin, increases substantially toward the west,

suggesting increased fluvial input of sediment in

this sector. Although some major rivers are perennial, the majority are dry during much of the

year (Figure 21). Snow melt derived from mountainous regions of the Sierra Nevada and the Rif

may provide additional increments of sediment

during the late winter and spring. Winds also are

seasonally variable in both intensity and direction,

but the strongest and most persistent aeolian transport is to be anticipated from the Sirocco, which

is known to convey particles up to sand size (Figure 22) well offshore from the Moroccan coast

(Ericksson, 1961).

The morphological symmetry of both margins

of this part of the Mediterranean is further reflected in the submarine topography; narrow

shelves (approximately 10 km wide to the 200 m

isobath) leading to relatively smooth slopes of

comparable gradients (less than 6°). Coastal currents also reflect this symmetry, showing a predominant westerly trend along both Moroccan and

Iberian coasts* (Figure 11).

Despite these resemblances, this mineralogical

study has enabled us to define the source and complex dispersal path of a deep-sea turbidite sand

deposited in the intervening basin. The geometry

of this and older sand bodies in the Western Alboran Basin plain, as determined by high-resolution

subbottom surveys, had previously been defined

(Bartolini et al., 1972) and a general input from

the northwest postulated (Stanley et al., 1970).

Moreover, a plausible source terrain of these sands,

the Serrania de Ronda lying to the northwest, has

* It is noteworthy that predominant nearshore currents

trend toward the west in the Western Alboran Sea in spite

of the fact that the main direction of surface flow is to the

east. This less saline surface and near-surface water mass,

originating in the Atlantic, apparently produces large-scale

jetlike eddies as it enters the Mediterranean east of Gibraltar

(Gaibar-Puertas, 1967; Lucayo, 1969; Lanoix, 1974). Our

study suggests that these eddies entrain a clockwise flow of

water along the Moroccan margin and a counterclockwise

movement along the Spanish coast.
NUMBER 15 43

FIGURE 21.—Photographs showing typical river beds which are dry during most of the year.

Upper: Rambla de Albunol, north of la Rabita and Punta Negra on the Spanish margin.

Lower: mouth of Oued Ouringa, at Pointe des Pecheurs on the Moroccan coast. (Note coarse

bed load moved during flood stage.)
44 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

been identified on mineralogical ground (Bartolini

et al., 1972; Huang and Stanley, 1972). The present

study has refined these earlier surveys by enabling

the complex transport path from source terrain to

coast, through the nearshore zone and thence to

the deep basin, to be defined by means of sediment

composition.

Most previous heavy mineral studies of modern

sediments in enclosed marine basins have been

concerned either with relatively shallow areas, in

which depositional processes differ greatly from

those operative in the Alboran Sea (van Andel

and Postma, 1954), or with deeper basins differing

in important morphological respects from the

present study area. Certain of the latter category

differ in possessing bordering areas of low relief

(Baak, 1936; Hsu, 1960; Davies and Moore, 1970),

while others, although bordered by mountainous

regions, receive an important part of their filling

sediment from one end of the elongate trough,

usually from a major deltaic source (van Andel,

1964; Pigorini, 1968).

Our study suggests that there exists yet another

type of elongate basin bounded by regions of high

relief which a priori could supply material of varied

source directly to the adjacent deeps, thus conforming to a multisource basin model (Pettijohn, 1957;

Pettijohn et al., 1973). However, the evidence presented above suggests that during the recent geological past, the dispersal patterns within this

basin have been essentially longitudinal, i.e., input

from the western termination. In view of the possible reversal of currents on the Strait of Gibraltar

(with eastward flowing bottom currents below a

westward surface outflow), it is probable that this

longitudinal transport pattern was reinforced during glacial lowstands of the Pleistocent (Huang et

al., 1972).

FIGURE 22.—Sirocco blowing silt and sand seaward on the Moroccan coast near Pointe des

Pecheurs (April 1973).
NUMBER 15 45

Elongate deep marine basins with predominant

longitudinal transport patterns are common in

the geological record. Various interpretations of

the dispersal systems in such troughs, including

elongate flysch basins, have been proposed

(Kuenen, 1958; Pryor, 1961). In geological terms,

our study demonstrates the importance of the

mineralogic changes produced by coastal processes

and the further modification, largely due to sizesorting, which ensues from downslope transport

to the final site of deposition. Changes induced by

marine transportation appear to have a more pronounced effect on the light mineral fraction, while

even relatively unstable heavy mineral species

(such as orthopyroxene) apparently suffer less

modification. This conclusion must be qualified

for geological purposes by the observation that

many heavy mineral species are susceptible to diagenetic alteration and removal (van Andel, 1959).

A further geological implication of our study is

ALBQRA N SE A

PROVENANCE OF

LOWER TURBIDITE SAND

-3d"

-3d1

Contour Interval- 50fm

3O* 5

FIGURE 23.—Summary diagram showing provenance and complex dispersal path of sands that

were deposited as the Lower sand-and-silt layer (Huang and Stanley, 1972) in the Western

Alboran Basin (dark pattern shows extent of this layer in the basin plain—after Bartolini et al.,

1972) at the end of the Pleistocene. These sediments, eroded from the Serrania de Ronda region,

were transported by rivers to the coast between Estepona and Marbella. The sands were

subsequently reworked to the southwest by coastal currents to the Strait of Gibraltar region,

and then downslope toward the southeast by turbidity current through the Gibraltar Submarine

Valley.
46 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

that the path taken by detritus from source terrain

to the final site of deposition may be highly complex and is largely governed by processes active in

the coastal zone, a region seldom preserved in

ancient mobile belts.

Summary

1. This study defines the composition and regional distribution of the major sand-sized light and

heavy mineral groups on the Iberian and Moroccan margins of the Alboran Sea, an almost totally

land-enclosed, mountain-bounded basin in the

western Mediterranean.

2. Twenty light and heavy mineral provinces are

identified along the basin margins and these are

broadly concordant with the limits of the major

drainage basins. The concordance emphasizes the

close relationship which exists between the varied

lithology of the mountainous Moroccan Rif and

the southern Iberian Betic margins, and the mineral ogical composition of sediments on the adjacent coast.

3. Sands in the coastal and fluvial samples can

be related to specific source terrains. Two major

mineralogical sectors (comprising 13 mineralogical

provinces) are recognized on the Spanish margin:

one between Velez-Malaga and Adra, influenced

by the Nevado-Filabride and Alpujarride complexes; the other west of Malaga draining the

ultrabasic rocks of the Peridotite complex. Two

major mineralogical sectors (comprising 7 mineralogical provinces) are also recognized on the Moroccan margin: one from the Bteni Bouchera

ultrabasic complex to the east, influenced by

Paleozoic, Mesozoic, and Tertiary sediments; the

other north and west of the ultrabasic complex,

draining Paleozoic sediments, metamorphic rocks,

and basic or ultrabasic intrusives.

4. A special study of samples from six rivers in

the western sector of the Iberian margin west of

Marbella shows that river samples closely reflect

the lithology of the terrain traversed. River samples and samples collected on the coast adjacent

to the appropriate river mouth are broadly comparable in composition, attesting to the virtual

direct transport of sediment from source to sea on

aJ] margins oi the Alboran Sea. Differences between

fluvial and coastal samples may be a function of

differing hydraulic processes and also possibly

grain-size factors.

5. That modification of the mineralogy occurs

while the sediment is held in the littoral and nearshore zone is demonstrated by the nonconcordance

in detail of mineral province boundaries with adjacent drainage basin boundaries. The mineralogical

variation from river to river is greater than along

the intervening stretch of coast near the river

mouths. The greater sample-to-sample similarity

along the coast indicates that at least some mixing

and dilution of river supply has occurred at the

coast as a result of longshore current transport.

6. The lateral trends observed within Moroccan

and Spanish coastal mineralogical provinces provide evidence on the actual sense of nearshore

sediment transport. The mineralogical trends suggesting predominant nearshore transport directions (movement largely to the west along extensive sectors of both the western Spanish and Moroccan margins) are substantiated by independent

evaluation of coastal current motion and longterm sediment drift patterns observed from aerial

photographs.

7. Lateral variations in mineralogical trends may

also be partly a function of the increased contribution from coastal outcrops and partly to less

constant coastal drift patterns (area east of Malaga

for example). Furthermore, local coastal morphological factors and meteorological conditions that

vary seasonally influence the distribution of mineral assemblages. These factors, as well as nearshore currents, operate to concentrate or dissipate

specific minerals of differing size, density, or physical durability.

8. Several possible interpretations are provided

for the origin of the mineral suites in the coastal

sands of the Bay of Algeciras. However, the present

mineralogic distribution within the Bay conforms

closely to predicted counterclockwise transport

paths.

9. This mineralogical study enables us to define

the source and dispersal of sands to the intervening

deep basin in spite of the geological and geographic similarities that characterize the opposite

margins of the Alboran Sea. A comparison of sands

collected in cores in the Western Alboran Basin

with sands on the Alboran coastal margins serves

to identify the ultimate source oi late Quaternary

and Holocene sands in the deep basin plain.
NUMBER 15 47

Sources east of Marbella on the Spanish margin

as well as on the Moroccan margin can be precluded. Heavy minerals indicate that the ultimate

derivation lies in the Serrania de Ronda complex

in the western Betic chain as postulated in earlier

studies.

10. The dispersal path of sands between the

Serrania de Ronda source to deep basin is a complex one. We suggest that detritus was first transferred southwestward toward Gibraltar by coastal

agents and then subsequently was funneled to the

Western Alboran Basin through the Gibraltar Canyon and submarine valley.

11. It appears that mineralogical changes produced during dispersal by marine processes

have a more pronounced effect on the light

mineral fraction, while even relatively unstable

heavy mineral species apparently suffer less modification. The implication of this study is that

there is a marked mineralogical evolution of detritus moving between source and deep basin, and

that these changes are largely governed by processes active in the coastal zone, a region seldom

preserved in ancient mobile belts.

12. In geological terms, the Alboran Sea can

serve as one type of model for sedimentaion in an

elongate, enclosed basin bounded by regions of

high relief. Although this region, a priori, would

conform to a multisource basin model, we show

that the dispersal pattern within the basin has

been essentially longitudinal. Unlike some elongate

basins in the geological record, filling from one

end has been from currents (input at the Strait of

Gibraltar) and not from a major delta point

source.

Appendix

Brief Summary of the Betic Cordillera Source Terrains

The Betic Cordillera, a highly complex mountain chain, can be discussed most readily in terms

of major stratigraphic-structural units. Two major

zones are recognized, i.e., an Internal Zone and

an External Zone. The major units described in

the following sections are depicted in Figure 2.

Internal Zone

The major stratigraphic-tectonic units in the

Internal Zone include the Nevado-Fildbride Complex (unit 2, Figure 2), Alpujdrride Complex,

eastern sector (units 3-7), Casares Unit, Alpujarride, western sector (unit 10). The Maldguide

Complex (units 8 and 12)> Peridotite Complex

(unit 1), and two other units—Sierra Blanca Unit

(unit 9) and Las Nieves Unit (unit 11)—whose

attribution to a specific complex is not clear—are

also included in the Internal Zone.

Nevado-Fildbride Complex.—Rocks of this unit

crop out extensively in the Sierra Nevada and its

prolongation toward the east. It comprises three

tectonic-lithological units.

The Sierra Nevada Series.—Composed largely of

graphite-bearing micaschists (in large part garnetiferous) with intercalations of quartzites. Quartz,

sodic plagioclase, garnet, white micas, biotite, tourmaline, zircon, rutile, and opaque minerals form

the predominant mineral assemblage. Locally,

amphibolites are present and these contain hornblende, actinolite, epidote, quartz, mica, and

tourmaline.

The Fildbride Series.—The Filabride Series,

more varied in composition than the one described

above, include micaschist, quartzite, marble, gneiss,

and amphibolite. The micaschists contain the same

minerals as in the Sierra Nevada Series as well as

staurolite, epidote, kyanite, and muscovite. Gneiss

includes quartz, albite, oligoclase, biotite, epidote,

garnet, and chlorite. Amphibolite contains various

amphibole minerals, chlorite, epidote, quartz, mica,

and clinopyroxene.

The Caldera Unit.—This unit contains similar

mineralogical assemblages as those in the Filabride sequence listed above.

Alpujdrride Complex.—This complex includes

strata of Paleozoic and Triassic age. Four major

lithostratigraphic units are recognized.

The Paleozoic formations include micaschist

and quartzite (depicted as unit 3 on Figure 2);

these, in their lower part and toward the west,

change facies and become dolomitic marble with

lenses of amphibolite (unit 4). The micaschist

includes quartz, sodic plagioclase (albite-oligo-
48 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

cla.se), white micas, biotite, and locally (in some

stratigraphic-tectonic nappe units) andalusite,

staurolite, chlorite, chloritoid, garnet, and epidote

(pistacite and zoisite). Dolomitic marble as well

as dolomite include calcic amphiboles (tremolite

and actinolite), feldspars (albite, oligoclase), biotite, muscovite, and phlogopite. Amphibolites,

which appear related to the recrystallized dolomites, include minerals of the type found in the

amphibolites of the Nevado-Filabride Complex

(see above).

The Permo-Werfenian Formations (unit 5) include lower grade metamorphic phyllites and

quartzites. Quartz, albite, muscovite, chlorite,

tourmaline, and zircon are the most common

minerals.

The Middle and Upper Triassic formations

(limestone and dolomite, partly recrystallized but

without the metamorphic mineral suite (unit 6))

contain metallic sulfides and oxides related to

sedimentary or hydrothermal processes, or both.

Quartz, calcite, fluorite, epidote, and hematite

occur in hydrothermal veins.

Maldguide Complex.—Two lithostratigraphic

units are recognized: a lower one, distinctly metamorphic of possible pre-Cambrian age, and an

upper one, consisting of Paleozoic strata (locally,

with a poorly developed Mesozoic-Tertiary cover),

which is essentially sedimentary. The base of the

Pre-Cambrian (?) rocks consists of gneiss and

micaschist. Gneisses dominate the base of the sequence; they are leucocratic, containing quartz,

plagioclase, microperthite, microcline, and also

sillimanite, garnet, and low amounts of cordierite.

Above these are found micaschist and micaceous

gneiss with garnet, sillimanite, staurolite, plagioclase, and microcline.

The Paleozoic rocks (unit 12, Figure 2), regionally, are lithologically extremely variable. Rocks

displaying low-grade metamorphism (phyllites and

micaschists with quartz, white mica, biotite, garnet

and andalusite) occur at the base of the section.

The bulk of the unit comprises sedimentary series,

including flysch-type sequences that have undergone considerable diagenesis, but without the formation of metamorphic minerals; interbedded

carbonates are also common. The Permian-MesozoicTertiary cover, which is only locally preserved,

includes limestone and sandstone.

Peridotite {ultrabasic) Complex.—Ultrabasic

plutonic rocks crop out extensively west of Malaga

and form the Peridotite Complex of the Serrania

de Ronda. In this region are found dunite and

harzburgite and, less frequently, pyroxenite, norite,

gabbro, lherzolite, and websterite. In many places,

these rock types have been partially, or totally,

serpentinized. Dominant minerals are olivine,

orthopyroxene, clinopyroxene, calcic and calcosodic plagioclase, apatite, spinel, and opaque

minerals.

Sierra Blanca Unit.—This group of rock types

(unit 9) has been affected by medium to highgrade metamorphism and is in part similar to the

Casares Unit described below. Marble and gneiss

are dominant, and amphibolites are also locally

present. Marbles are to a large degree totally, or

partially, dolomitized. The biotite gneiss contains

sillimanite, cordierite, and/or andalusite, depending upon the locality.

Casares Unit.—This group of rock types (unit

10) of the Alpujarride Complex (western sector)

comprises essentially Paleozoic metamorphics

overlain by limestone and dolomite, marbleized,

of Triassic age. The base of this metamorphic

sequence is related to the Peridotite Complex,

their mutual contact being intrusive. From older

to younger, the following types occur: gneiss, rich

in feldspar, cordierite and, locally, garnet; micaschist with andalusite, which in its lowest parts contains garnet, staurolite and biotite; phyllite and

quartzite, with similar minerals as those in the

Permo-Werfenian rocks of the Alpujarride Complex (eastern sector); limestone and/or dolomite,

marbleized, similar to the Middle and Upper Triassic of the Alpujarride Complex (eastern sector).

Nieves Unit.—Carbonates of the Upper Triassic

and Lias (unit 11) are assigned to the Internal

Zone by some authors and to the External Zone

by others. Limestone, partially dolomitized, is the

dominant lithology; abundant chert nodules are

present locally.

External Zone

A number of units including the Campo de

Gibraltar, "Flysch" de Colmenar, and the Subbetic

Zone are included in the External Zone. Each of

these sequences can be characterized by specific

lithological criteria; the age of each unit has also

been determined. Three major groups are differ-
NUMBER 15 49

entiated: a detrital red bed fades of Triassic age,

a Jurassic limestone-dominated facies, and a marlrich Cretaceous-Paleogene-Lower Miocene sequence.

Triassic Units.—The sediments comprising this

group (unit 13, Figure 2), very different from the

Triassic of the Internal Zone, display a "Germanic

facies" aspect. The predominant lithologies include variegated clay, marl, and sandstone. Locally

dolomite and ophite are exposed as well as evaporite (in particular gypsum and salt). These crop

out in numerous areas and are easily eroded.

Jurassic Units.—Sedimentary rocks of this group

(unit 14) include a highly variable suite of sediments, and show a great variability in thickness

(Gonzalez-Donoso et al., 1971). The dominant

lithologies include limestone of highly variable

texture and marls and petrologic transitions between the two. Very locally, there are notable outcrops of radiolarites and submarine basic volcanics

(pillow lava) intercalated in the Jurassic series.

Cretaceous-Paleogene-Lower Miocene Units.—

This suite of sedimentary rocks (unit 15) includes,

for the most part, marl and marly limestone facies.

There are recognizable lithologic variations that

are related to differences in age, outcrop locality,

and tectonic grouping. A flyschoid facies with

sandstone (includes rocks of different ages) dominates toward the west; toward the east, on the other

hand, marl and limestone intercalations

are

common.

Post-Orogenic Sequences

The extensive outcrops of sediments of NeogeneQuaternary age that fill postorogenic depressions

and recent alluvial basins are designated as PostOrogenic Sequences on the map (unit 16). The

most common lithologies of Neogene age are

conglomerates, sandstones, shales, and evaporites.

Limestone and bioclastic rocks also crop out locally. Quaternary sediments include large volumes

of detrital material of medium to coarse grain size.

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