PYRENEES

MAURICE MATTAUER Laboratoire de G~ologie Structurale, Facult6 des Sciences, Place E. Bataillon, Montpellier 34, France

and

JACQUES HENRY Soci~t6 Nationale des P~troles d'Aquitaine, AII6es de Morlaas, (64) Pau, France

CONTENTS

A. General data on the segment 3

B. Subdivision of the segment 12

C. Data on individual structural zones 12 1. Northern Folded Foreland 12 2. North Pyrenean zone 14 3. Axial zone 16 4. South Pyrenean zone 17 5. Southern Folded Foreland 19

D. References 20

A. G E N E R A L D A T A ON T H E S E G M E N T

1. T H E SEGMENT STUDIED

The Pyrenees have a special interest at the present time in relation to interpretation of global structure, as one of the key areas in discussions on the relation of Europe and Africa. There is strong geophysical evi- dence that the Iberian peninsula has rotated relative to the rest of Europe; there is equally strong geological evidence, detailed in this chapter, that there has been neither pivoting movement nor late trans- current faulting in the Pyrenees. These lines of research must eventu- ally be reconciled, and a knowledge of all the critical evidence is basic to an informed analysis of the problem. Segment: this has a length, measured along strike, of 100 km (Fig. 1). Both north and south margins of the orogen are either broadly grada- tional (> 3 km) or are submarine. The belt has a width ranging from over 200 km in the east to 100 km, and averaging 180 km within the segment. Zones: the orogen is remarkably structurally symmetrical from north to south, although corresponding features are not quite contemporaneous. It is divided into five zones. The Northern Folded Foreland (zone 1) is characterized by open folds in a very thick Mesozoic-Tertiary sequence. The North Pyrenean zone (2) consists of northward thrust Mesozoic and older rocks, including volcanics. The Axial zone (3) contains thrust and imbricated sediments resting on intensely deformed pre- Permian rocks and metamorphics; the thrusts are outwardly directed. The South Pyrenean zone (4) is formed of a southward directed nappe of Tertiary and Cretaceous rocks on a d6collement surface of Triassic evaporites. The Southern Folded Foreland (5) shows normally folded Tertiary and Mesozoic rocks. History: the 'basement' rocks of the Pyrenees were deformed during the pre-Stephanian, Hercynian orogeny. In Stephanian and Permian times continental strata, including andesitic volcanics, accumulated. In early Triassic times the area formed a peneplaned, stable block, which through the rest of Triassic and Jurassic times was progressively sub- merged. During Cretaceous times the Pyrenean trend developed pro- gressively: uplift and subsidence, flysch sedimentation in troughs, normal faulting and submarine vulcanism all occurred.

Folding first occurred at the end of the Cretaceous in zone 2. Thick flysch sequences accumulated in Eocene times and in M. and/or U. Eocene times folding, thrusting and schistosity development (Pyrenean phase) occurred widely. Molasse sedimentation took place north and south of this Pyrenean chain in Oligocene to Miocene times, and folding occurred at the end of the Oligocene in zones 4 and 5. The present relief of the Pyrenees may be largely of Quaternary date.

2. SHAPE OF T H E O R O G E N IN PLAN

is Towards the west and east the belt runs into the Atlantic and the

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4 PYRENEES

Mediterranean. To the east in Provence, Pyrenean structures of Eocene age have been affected by Alpine structures of Miocene date.

24 General trend: the Pyrenees are rectilinear and 400 km in length. Secondary arcs are present in Languedoc (radius 100 km), north and south Pays Basque (radius in south, 50 km) and in the centre of zone 4.

3. SURFACE SHAPE OF T H E S E G M E N T IN E L E V A T I O N

30 Highest 5% of the ground: 2500 m. Average height of: 3t north margin of the belt, 200 m; 82 south margin of the belt, 500 m.

38 A geomorphological surface recognized from summit heights and approaching 2400 m in height, exists in the eastern Pyrenees, to the east of the segment. The surface cuts Palaeozoic rocks but there are no deposits overlying the surface. The surface may be of U. Miocene age because Pliocene strata occur in surrounding basins and the geo- morphological surfaces of neighbouring regions (Aquitaine, Ebro and Roussillon basins) are of U. Miocene age.

34 Two other surfaces occur at lower levels within the segment: at 1500 to 1800 m (zone 3) and 1100 m (in the north of zone 3) of ?Pontian age; at 1700 m (?Pontian) and 1000 m (U. Miocene to Pliocene?) in zone 4.

37 References: see Birot (1937), Taillefer (1951), Barrere (1969) and Viers (1960).

14 • ~ ' ~ + . . . . . .

4. GEOPHYSICAL DATA

38 Gravity data: see Fig. 2 and Cizancourt ((1948). 41 The segment is in approximate isostatic equilibrium and (42. 43) the general gravity field is parallel to the main tectonic and topographic trends.

45 Regional rnagnetk data: see Borgne & Mouel (1969). 47-s The anomalies are concordant with the main tectonic trend but are not concordant with the topographic trend.

67Palaeomagnetic data: see Girdler (1968), Schwarz (1962), and Dongen (1967).

5. PRESENT-DAY A C T I V I T Y IN T H E S E G M E N T

68 Seismic activity: see Fig. 3. See also Rothfi (1967) and Roth~ & Dechevoy (1954, 1967).

6. T I M E R E L A T I O N S

85 The oldest undeformed rocks in the segment are Pliocene in age on the north margin of belt (Crouzel 1956) and L. Miocene in age on the south margin (Crusafont et al. 1966).

s3 The youngest deformed strata in the segment belong to the Pou- dingue de Juran~on Fm (U. Miocene) on the north margin (Crouzel 1965), and to the Molasse (Oligocene) on the south margin of the belt.

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Figure 1. Structural zones of the Pyrenees (1 to 5) and the outline of the segment described here.

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P Y R E N E E S 5

Table 1

M E S O Z O I C - C E N O Z O I C PHASES OF M O B I L I T Y

91 Phase and Age locality 92 Nature 93 Maximum 94 Minimum 95 Evidence for age

8 Mainly in zones 4 and 5

7 Zones 4 and 5

6 Pyrenean phase, zones 1 to 4

5 Zones 1, 2 and 4

4 Zone 2

3 Zones 1, 2 and 4

2 Zones 2, 3 and 4

1 Zones 1, 2 and 4

Vertical move- ments responsible for the present- day relief

Plioc

Third phase of L. and M. Mioc folding Olig (Aquit)

Thick sedimenta- tion

Second phase of folding; folds, thrusts, schistosities

Very thick sedimentation

To the west of the segment M. Eoc M. Eoc (L. Lutet) (U. Lutet)

More to the east M. Eoc U. Eoc

L. Eoc U. Eoc

First phase of Palaeoc L. Eoc folding; with (slightly older outside schistosity the segment) development

General reversal Coniac Santon to of subsidence Campan

Vertical move- ments with fault- ing and tilting

Vertical move- ments and tilting

M. Alb M. Cenom

Berrias Haut to Barrem

Marine Plioc at >2000 m in Cerdagne (eastern Pyrenees)

Angular uncon- formity

Rapid thickening of series with 'intra- formational uncon- formities'

Angular uncon- formity

Angular uncon- formity and 'intra- formational unconformity'

Rapid thickening with local uncon- formity on the border of the basin

L. Eoc lies with angular or regional unconformity on U. Cretaceous; cleaved and metamorphosed U. Cretaceous rocks occur as pebbles in L. Eoc strata

Regional and locally angular uncon- formity of Senon on Cenom-Turon or L. Cretaceous

Rapid thickening and local uncon- formity on the border of basins

Regional or locally angular uncon- formity of L. Creta- ceous over Jurassic

87--9 In i t i a t ion of Mesozo ic -Ter t i a ry mobi l i ty is i n d i c a t e d in boreholes in the Pau region, w h i c h show Berr ias ian to V a l a n g i n i a n strata over- ly ing fo lded T i t h o n i a n rocks at an u n c o n f o r m i t y w h i c h is locally sharp.

I n fact a degree of 'mobi l i ty ' existed after the e n d of the H e r c y n i a n orogeny, i.e. d u r i n g the S t e p h a n i a n a n d par t i cu la r ly d u r i n g the Tr i - assic (which is ve ry var iab le in thickness) a n d Jurassic , bu t it was only in the L. Cre taceous tha t the mobi l e zones a d o p t e d an o r i en ta t ion para l le l w i th the chain , or a connec t ion w i t h it. ' P y r e n e a n ' mob i l i t y p rope r d id no t therefore start un t i l then.

76-8o Basemen t rocks w i th in the s egmen t r ange in age f r o m (?Pre- C a m b r i a n ) a n d O r d o v i c i a n to V i s 6 a n - N a m u r i a n (Mirouse 1966). Basemen t rocks of O r d o v i c i a n to N a m u r i a n age are k n o w n wi th in 100 k m to the n o r t h of the bel t f rom the ev idence of boreholes. W i t h i n 100 k m to the south of the belt , b a s e m e n t rocks of S i lur ian to D e v o n i a n age are known , aga in only f rom boreholes .

7. S E D I M E N T A R Y R E L A T I O N S

Table 2

S U M M A R Y OF S T R A T A L DATA

Syn- and Post-orogenic sedimentation within 50 km outside the north

In the orogenic belt in the segment margin of the orogenic

Pre-orogenic Syn-orogenic Post-orogenic part of the segment

9~ Age span from Steph Berr Mioc Berr to Tith U. Olig Plioc Plioc

9s Maximum thick- 2500 to (At any one ?500 m ness 3500 m locality)

5000 m ~9 Estimated volume 15x 103 km 8 45x 103 km 3 1.5x I0 a km 3

per 100 km length of segment And probable 25% 25% 25% error in this estimate

x00 Dominant Triassic Marls Molasse Limestones facies evaporites

Percentage of the total volume occupied by-- and the error 101 Dominant facies 40-t- 10% 60-t-20% 50+ 10% 40_+20% 102 Volcanic rocks < 1% < 1% 0% 103 Sedimentary rocks 40+ 10% 10__+5% <1%

with over 90% carbonate

x04 Sedimentary rocks 1 __+0.5% <1% <1% with over 95% quartz

10~ Source area of Syn-orogenic sediments unknown;

post-orogenic-- the orogenic belt

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6 P Y R E N E E S

/.~ ~ ~ Auch / ~ oToulouse .~---------_J ~- - -~

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Bouguer . . . . " . .. " - ~ "eo

"-,. .......... "'--._:.-., . . . . . . . . . . . . , ......... a, .,% o ~ g

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Figure 2. Bouguer anomaly m a p of southernmost France.

~06 The effects of deformation have not been taken into account in assessing the stratal thicknesses 98. In zones 1 and 5 the influence of deformation is weak and elsewhere thicknesses are not known with much precision. lo8 Major erosion surfaces occur at the following levels: pre-Stephano- Permian; pre-Trias; local, intra-Cretaceous levels (in particular, pre- Cenomanian); end-Cretaceous or beginning of Eocene; locally U. Eocene to L. Oligocene; Mio-Pliocene.

8. S T R U C T U R A L RELATIONS

m-an Major faults: 1. The North Pyrenean frontal thrust lies at the zone 1/2 boundary and consists of folds and reverse faults directed northwards. Movements commenced in the Senonian to L. Eocene interval, probably in end-Cretaceous times and ceased in the M. Eocene to Miocene-Pliocene interval, probably in M. to U. Eocene or U. Oligocene times. Horizontal and vertical movements amount to c. 5 kin. 2. The North Pyrenean fault occurs at the zone 2/3 boundary. Two episodes of movement are inferred: (i) late Hercynian, dextral (?), transcurrent displacement may have attained several hundred kilometres. It occurred in the Vis6an to Permian interval, probably in Stephanian times. (ii) Very steep reverse faulting, involving vertical movements of >3 km and northward thrusting, occurred in the Senonian to U. Eocene interval. 3. The Gavarnie thrust at the zone 3/4 boundary is a low angle reverse fault thrust towards the south; dis- placement is > 10 km. Movement may have commenced in M. Eocene times but probably occurred in the U. Eocene. 4. The South Pyrenean frontal thrust forms the zone 4/5 boundary and consists of reverse faults (and folds) with movement towards the south; displacement is < 10 km? Movement occurred in two phases, probably in U. Eocene and U. Oligocene times.

n~ Type of evidence used to assess displacement: 1, borehole evidence; 2 (i), from general arguments (the shape of the Gulf of Gascony; fitting of Hercynian structures on opposite sides of the belt); 2(ii), observed displacement; 3, presence of a window; 4, general arguments within the segment (see Figs. 7 and 8), borehole evidence more to the west. n9-~4 Megatectonics: attempts have been made to establish the relative displacements on opposite sides of the whole belt using the offset of: the Hercynian orogenic belt on either side of the Pyrenees and the late Hercynian, North Pyrenean transcurrent fault (Mattauer 1968). Regional magnetic anomaly patterns in the Bay of Biscay (Matthews & Williams 1968) and palaeomagnetic data concerned with the rotation of Spain (Girdler 1968; Dongen 1967) suggest other relative displace- ments have taken place.

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Figure 3. Epicentres of earthquakes dur ing the pre-1931 period (asterisks) and for the 1931 to 1968 period (circles). Intensity: small circles, < 6 ; large circles, ~ 6 . The dashed line shows the axis of nor th Pyrenean seismic activity. Data supplied by

J . P. Roth~.

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PYRENEES 7

9. R E V I E W OF O R O G E N I C D E V E L O P M E N T

126 REGIONAL CHRONOLOGY AND CORRELATION

As many formations are rich in fossils, and especially in microfossils, regional chronology and correlations are generally based on palaeonto- logical evidence. Some series are difficult to date, however. (i) Firstly, the chronology and correlation of rocks older than Caradoc in the Axial zone are based solely on lithological analogies and local evidence of superposition. Absolute dating of the crystalline rocks has not yet been undertaken systematically. (ii) The L. Cretaceous is very poor in distinguishing fossils, is subject to rapid horizontal variations in thick- ness as well as facies, and is very uniform vertically. (iii) Precise correla- tion and subdivision of the late or post-tectonic continental formations remains difficult because of the rarity of fossils and rapid facies varia- tions.

127 MIGRATION OF TROUGHS OF SEDIMENTATION

From the point of view of its sedimentation history, the chain may be subdivided into a western part (the Pyrenean chain proper) and a rather different eastern part (Languedoc-Provence).

In the western part, the evolution of basins in which the thickness frequently exceeds 5 km is rather complex. The L. Cretaceous is char- acterized by a series of small troughs, each of which has a partly inde- pendent evolution. Uplifts and subsidences resulted in sedimentary sequences of varying ages (Neocomian, Aptian or Albian) from one basin to another, or even within a single basin. Starting in the Middle Albian, the dominant feature is a large flysch trough which occupies the North Pyrenean zone (sometimes known as the Cenomanian zone) and which no doubt connects with a larger basin in the Cantabrian area. In the Senonian a new arrangement accompanied a major trans- gression. The North Pyrenean flysch trough migrated towards the north to a position at the southern boundary of zone 1. It spread out largely in the west where it again covered part of the Axial zone and all of the Cantabrian area. A second trough developed more to the south.

After an end-Cretaceous regression, followed by an Eocene trans- gression, the North Pyrenean trough contracted rapidly and emergent regions appeared, at slightly different times from area to area. By contrast, the South Pyrenean zone, after the end-Cretaceous regression, became the site of an important episode of sedimentation which occu- pied the whole of the South Pyrenean zone. This basin may be divided into three units: in the east (Catalanian Pyrenees) a marine area with important deltaic influences; an intermediate area (Aragon) occupied by several thousands of metres of flysch (3 km) ; a western area (Basco- Cantabrian) of dominantly neritic sediments of much smaller thick- ness.

Finally, in the Oligocene, after the uplift of a large part of the chain a very marked displacement of basins took place towards the exterior of the chain, including to the north the 'Aquitaine basin' with a thin sedimentary sequence and to the south the 'Ebro basin' where the thickness of the molasse can exceed 3 km.

In conclusion, the complex story of mobile basins which did not end until the close of the Oligocene produced a quite simple result: the thickness of syn-orogenic sediments is demonstrably the same (about 5000 m) in all parts of the belt, but their age is distinctly different from place to place.

In the eastern part the evolution was rather different and was char- acterized by: (i) the emergence of the 'Durance isthmus' during the Albian-Aptian. This area was rich in bauxites and its existence inter- rupted communications between the Alpine sea and the Pyrenean troughs. (ii) The very important NE-SW faulted basins which formed during the Oligocene. These are post-tectonic and are oblique to the structures of the belt and contain sediment thicknesses as great as 5 km.

131 SOURCE OF THE SEDIMENTS

In the L. Cretaceous, two principal sources for the sediments can be seen. The most important is the Spanish meseta which supplied large quantities of detrital material to the Cantabrian basin and to the

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Figure 4. Palinspastic cross-section of the Mesozoic and Tertiary strata of the Pyrenees.

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8 P Y R E N E E S

western French Pyrenees. The second source, which is more difficult to localize (the Massif Central?, the Catalan Massif?, a Mediterranean continent?) supplied the sandy material to the eastern Pyrenees. In the Cenomanian, these sources still existed, but in the North Pyrenean trough material started to be transported longitudinally from east to west; at the same time uplifts marginal to this trough gave rise to breccia deposits. In the Senonian, all the material forming the flysch was transported from east to west in the North Pyrenean trough. The source of the material of the Cantabrian area is not known. In the Eocene, the South Pyrenean basin received deltaic material coming from the north-east in the eastern part and flysch, which consisted of material transported from east to west. Finally, at the beginning of the U. Eocene or in the Oligocene, the belt was uplifted and mountains (> 2000 m) formed; they gave rise to very thick continental or lacus- trine sedimentation which often buried the ancient hills. The depth of erosion since the end of the Eocene must be estimated at a minimum of 5 kin.

1~4 THE OVERALL EVOLUTION OF THE BELT

Pre-Orogenic history (Stephanian to U. Jurassic)

After the major Hercynian foldings, the Hercynian chain was deeply eroded and peneplaned. The Pyrenees then belonged to the conti- nental European block (including Spain). In Westphalian to Stephan- Jan times this block was affected by a brittle tectonic deformation which was essentially shown by large fault movements (well known in the French Massif Central) ; the 'North Pyrenean fault' is of this type and may possibly have a horizontal displacement of several hundred kilo- metres; other faults must also have resulted from this major episode. It is a remarkable fact that the E-W Pyrenean direction is precisely that of the North Pyrenean fault and it is only logical to consider that it is the late Hercynian fractures which are responsible for the orienta- tion of the Pyrenees.

In the Stephanian, then in the Permian, sedimentary basins were initiated; in them more than 2 km of continental strata accumulated; although slight unconformities can be seen they were not accompanied by any folding; it is even probable that, on the contrary, this was a tensional phase as the andesitic vulcanism indicates. The movements ceased in the L. Triassic, which overlies the Stephanian to Permian and the Hercynian substratum. The area formed a peneplaned, stable block. During the Trias sedimentary basins started to become apparent in this block. At first, a thick series of lagoonal evaporites accumulated, with, in the M. Trias, marine incursions. A major transgression started in the Jurassic which submerged the Triassic basins and a large area of the belt was covered by calcareous deposits. It is notable that the (facies) distribution of Jurassic does not yet seem to be influenced by the Pyrenean direction; and so the basins appear oblique to the belt.

@n-Orogenic history (L. Cretaceous-U. Oligocene)

The appearance of a Pyrenean region did not actually start until the Cretaceous, which was a period of tension characterized by: (i) important positive and negative vertical movements (sometimes > 5 km). (ii) Thick sedimentation, often of flysch facies (up to 5 km thick) occurring in troughs which may be narrow and fault-bounded. (iii) The existence of normal faults contemporaneous with the sedimentation, which often produced very rapid variations of thickness and facies and which often caused relief resulting in the formation of breccias. (iv) Sudden reversals of subsidence, which often uplifted by more than 2 km a zone which had previously undergone an equivalent subsidence; cordilleras then formed. (v) Local submarine volcanic eruptions and perhaps intrusions of basic rock.

Cretaceous strata also show very variable thicknesses and facies. It could be said that during the Cretaceous the Pyrenean trend developed progressively; changes were slight in the L. Cretaceous, but became very rapid in the Senonian, for a relatively narrow North Pyrenean trough, which extended for close to 600 km from the Atlantic as far as Provence, developed then. It should, however, be noted that the Languedoc-Provence zone, palaeogeographically midway between the Alpine and Pyrenean areas, underwent a different evolution character- ized in particular by the emergence of the Bauxites Durance isthmus.

It is not until the end of the Cretaceous that the first compressional phase occurred which did not, however, affect more than part of the chain and which, furthermore, does not always seem to be of exactly the same age. In the Languedoc-Provence zone, this phase affected a very large area, but the folding was not intense; the age is clearly end-Cre- taceous. In the Pyrenees proper, there occurred a very important tectonic episode accompanied by schistosity development and meta- morphism but the area affected is remarkably narrow and is clearly con- netted with the North Pyrenean fault; as for the age, whilst in the east it is still Cretaceous, in the west it seems to be post-Palaeocene and pre- Ypresian. Whilst these foldings were being produced, the sedimentation continued to the north and south without interruption.

In the Eocene, predominantly vertical movements continued; thick series were deposited. In the South Pyrenean trough where a flysch facies accumulated, 5 km of strata were deposited. At the beginning of the M. Eocene, the affects of the Pyrenean compression phase were felt, little by little. In the South Pyrenean trough, folds formed whilst marly or flysch sedimentation continued; elsewhere olistostromes slid into the sea; in the western part of the North Pyrenean trough (gliding?) nappes were already moving into place during the Lutetian; in the continental areas breccias formed at the foot of slopes. Then, in the U. Eocene but perhaps at slightly different times in different areas, an important phase of compression with strong deformation took place and resulted in the emergence of the Pyrenean area over a distance of about 100 kin. The strong relief so formed was severely attacked by erosion at the end of the Eocene and in the Oligocene.

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P Y R E N E E S 9

A new series of vertical movements started then and continued during most of the Oligocene; thick molasse sediments accumulated in the Northern and, especially, the Southern Pyrenean basins. But at the beginning of the M. Oligocene, the evolution of the Pyrenees proper is quite different from that of the eastern part of the chain, now partially hidden beneath the Mediterranean; there, NE-SW post-tectonic fault troughs were developed oblique to the chain, so that the Pyrenean phase is the last tectonic phase. In contrast, more to the west and principally on the southern slope of the Pyrenees, a new folding phase occurred at the end of the Oligocene which moderately folded the internal area of basins. On the north slope some weak folds were produced even in the Miocene.

Post- Tectonic history

The post-tectonic period started at different times in different places: in M. Oligocene in the east, at the end of the Oligocene or at the beginning of the Miocene on the southern slope, and at the end of the Miocene in certain areas on the northern slope.

Furthermore, here also the Pyrenees proper characterized by their strong relief, must be separated from those parts of the chain which have sunk beneath the Mediterranean or the Atlantic. The relief of the Pyrenees seems to have been formed very recently and is probably in large part of Quaternary age. In the eastern Pyrenees, Pliocene features are found as high as nearly 2000 m; this recent uplift fits with present-

Cr@lac@ inf~rieur ~ \ ~ FRANCE ~ ~ ' ~ , ~

ESPAGNE ~ q ~o Km

C~nomanien ~/~ \\'~ FRANCE ,( A\\\,

- -_-222_ -. -. .... _---

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Figure 5. Palaeogeographical maps of the Pyrenean region. Present-day zone boundaries are shown by dashed lines. Vertical lines: European and Iberian blocks. Oblique shading: sea. Dense oblique shading: basins with thick, marine sedimentation. Circles: regions of continental sedimentation. Arrows: directions of sediment transport.

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10 P Y R E N E E S

n

M~tamorphisme pyr~n~en ' ' l t l [ y ~ooK~

J

Figure 6. The regions affected by 'Pyrenean' metamorphism. Black (main region): metamorphism of essentially end-Cretaceous age. Black (isolated, smaller, western region): age doubtful--either end-Cretaceous or Eocene. Crosses: Eocene meta-

morphism.

day seismic activity. In contrast to the Pyrenees, that part of the chain which is beneath the Mediterranean, has undergone a considerable de- pression; in the Gulf of Lions the base of the post-tectonic strata reaches, in effect, depths as great as 5 km. This downward movement continued until recently, for in the same area 1 km of Pliocene strata can be found today and the continental Villafranchian is beneath sea-level.

The history of that part of the Pyrenees which lies beneath the At- lantic still remains very poorly understood.

135 (i) THE NATURE OF THE PYRENEAN METAMORPHISM

Pyrenean metamorphism appears in two distinct areas (Fig. 6). (a) The metamorphism of the northern area (shown in black on Fig.

6) affects a narrow band of Mesozoic rocks (Triassic to Senonian in- elusive), the essential characters of which are as follows: (i) The area of Pyrenean metamorphism appears linear, at the scale of the chain. In effect it always affects a narrow zone; sometimes this is reduced to less than 5 km and continues, although irregularly, for close on 300 km. On the north slope of the chain there appears evidence that the meta- morphism is aligned along the 'North Pyrenean fault', that is to say along a very important discontinuity, which, it is known, started moving at the close of the Hercynian orogeny. Here therefore is an obvious relationship between the metamorphism and a deep fault, affecting the whole crust. (On the southern slope, the metamorphism of the Basque area does not appear to be connected with a deep fault.) (ii) The tran- sition from metamorphic to non-metamorphic areas is usually rapid or sharp, occasionally even, the two are separated by a post-metamorphic fault. This metamorphism is therefore characterized by a very steep

thermal gradient; and it is possible that the isograds have been, origin- ally, very steep. (iii) Intrusions of lherzolites in the Pyrenees only occur in the regions affected by the Pyrenean metamorphism. There is therefore a correlation between metamorphism and the ultrabasic rocks of the upper mantle. This correlation is not simple, however; the lherzolites are not responsible for the metamorphism because they have not developed any contact metamorphism; they seem to be emplaced in a solid state (accomplished by gas emissions) during a first stage in the tectonic and metamorphic evolution (Lallemant). (iv) Like most metamorphisms, the Pyrenean metamorphism has been found to be of syn-tectonic and post-tectonic date; the post-tectonic metamorphism is frequently the only one to have been observed. Therefore it can no longer be considered, as it once was (Ravier 1959), that this metamor- phism was accomplished in the sedimentary troughs at the same time as the sedimentationtook place and before any folding. (v) Detailed study of the facies and types of metamorphism remains to be done in the Pyrenees. In a local study Lallemant (1968) has shown that the para- genesis is ofgreenschist type but also ofalbite-epidote hornfels or locally of amphibolite facies which leads him to suggest this is a low pressure type (Abukuma). It is possible that the Pyrenean metamorphism is, in fact, subdivisible into several episodes; the first, for example, being of greenschist facies and the second of much higher grade and lower pressure accomplished during a late phase. (vi) The Pyrenean meta- morphism is associated with the end-Cretaceous tectonic phase; it is no more considered to be connected, as it was for a long time, to the pre- Cenomanian tectonic phase. The Pyrenean tectonic phase, of U. Eocene age, has deformed the metamorphic region. Because of this the isograds are irregular and are often difficult to reconstruct.

(b) The metamorphism of the southern area (marked with crosses on Fig. 6) only appears in a few outcrops of Permo-Triassic and of Cretaceous rocks in the southern part of the Hercynian axial zone. In the region of Gavarnie and of Bielsa the metamorphism is weak (seri- cite, chlorite, muscovite) ; around Aneto, limestones, considered to be of Permo-Triassic age by Mey (1968) and of Cretaceous age by M. Seguret (personal communication), contain scapolites and phlogopite. As throughout the zone the Eocene was deposited conformably on the Cretaceous, this metamorphism cannot be of late Cretaceous age. As furthermore the metamorphism seems to be syn-tectonic and the de- formation of the region is late Eocene in age, it is evident that the meta- morphism is of the same age.

In summary, in the Pyrenees there were two metamorphic episodes. Until now only the northern episode, which has now been established as late Cretaceous, has been studied.

135 (ii) ON THE AMOUNT OF SHORTENING AND ITS CONSEQUENCES: THE PROBLEM OF STRIKE-SLIP FAULTS

Along the whole belt, the amount of shortening seems slight and pretty near constant; with a reasonable approximation, it is always 50 :t: 20

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PYRENEES 11

$ 4 2

S

Avant pays pliss~ Sud

Zone Sud- pyr6n(~enne

Chevauchement frontal I Sud pyr6n6en

Zone axiale

Chevauchement

l et Nappe de Gavarnie

Zone I

nard. ] Avant pays pyr~n~enne

I Chevauchement frontal

Nard pyr~n6en Faille I

Nard pyr~n(~enne

pliss6 Nard

Flexure aquffaine

Odo

. . . . .

Molasse

Eocene

Cr~tac6 { sup~rieur inf6rieur

Jurassique Trias

N f l \~, \~ \~ .. _ Hercynien

t ~ [ I0

i ! I

Figure 7. Outline geological profile across the Pyrenees within the selected segment.

km. Because of this, it is positively not possible to admit, like most geophysicists, that Spain has undergone, in relation to Europe, an anti- clockwise rotation of 30 ° resulting in the opening of the Bay of Biscay.

In effect, if such a rotation had taken place, it would have been about an axis situated somewhere in the eastern end of the Gulf of Gascony; under these conditions the amount of shortening in the Pyrenees has to increase progressively from west to east, and should attain, in the eastern part of the belt, values of more than 300 kin, which is certainly not the case.

One might ask whether the modest amount of shortening of the Pyrenees is accompanied by displacement parallel to the chain; the shape of the Gulf of Gascony does in effect suggest the existence of a major transcurrent fault. In fact if such a fault had been produced at the same time as the folding one should find in the belt one or more large faults of E -W strike, showing horizontal fault-slickensides and associ- ated with en dchelon folds; but, laying aside some local faults of little importance, there are never any such in the belt. There is no indication therefore of any important transcurrent movement contemporaneous with the formation of the chain (on the contrary, there are several argu- ments which suggest that important faults of this type were produced at the end of the Hercynian orogenesis). On a continental scale then, the relative movements of Spain and Europe remain very modest. This is a hypothesis of which future theories on the origin of the Atlantic Ocean and the Mediterranean should take account. (See new data in IFP & CNEXO, 1971.)

x35 (iii) THE NATURE OF DEFORMATIONS CONTEMPORANEOUS WITH THE SEDIMENTATION

The vertical movements which occurred in the Pyrenean area during a large part of the Mesozoic resulted in deformations which were occa- sionally important and which often give the appearance of true fold- ings. In fact, the results of boreholes have shown (especially in zone I) that these 'structures' were generally caused by the displacement of regions of subsidence, accompanied by the erosion of emerging zones. Those beds affected by local disturbances have therefore acquired dips of more than 30 °, normal faults can appear and local discordances be produced in neutral zones; the result therefore is to produce basins in which the total thickness of strata remains almost constant but where a given level may vary considerably (e.g. 0-400 m) in thickness and this over very short distances.

The basin appears then as if folded, and faulted (if syn-sedimentary faults exist), when in fact it is not possible to distinguish any true folding phases. It should be stressed that all these syn-sedimentary deformations have often strongly influenced the style of the true folding which suc- ceeds them. The thick series do not react in the same way as the thin ones; the syn-sedimentary normal faults are often re-activated and transformed into reverse faults and therefore structures are sometimes produced which at first sight have a totally misleading geometry. On the south side of the Pyrenees, M. and U. Eocene sedimentation is oc- casionally quite clearly contemporaneous with the folding, resulting in thickness and facies variations, as well as emergence.

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12 PYRENEES

B. S U B D I V I S I O N OF T H E S E G M E N T

I , ¢ " ~ ' C h e v a u c h e m e n t et fail le inverse

I ~_~-~ Di rect ion g~ndrale du plissement

Anticlinal ~,~ Synclinal

2B

G

Oligo not)

Plisse"

\ \ t #

50kin

Oligoc~ne plisse"

I Trias diapir

Terrain hercynien 4- granite

• ° ° . ° , , , , °

:ONE 5 ::'.'.'. .'::.'...::: :~'.-'.'.::.

Figure 8. Outline geology of the selected segment.

Table 3 2ol ZONES AND ELEMENTS IN THE SEGMENT

Zones

Element

1 2 3 4 5 Northern Worth South Southern Folded Pyrenean Axial Pyrenean Folded Foreland zone zone zone Foreland

a

Molasse X X X X

b Eocene X X X

C U. Cretaceous X X X X X

d L. Cretaceous X X X

e

Triassic to Jurassic x

f Stephanian to Permian

X X X

X X X X

g Basement x x x x

~o2 Basis for the correlat ion of elements between zones: a, rare fossils-- (vertebrates, continental gastropods, charophytes) ; b, numerous mar ine fossils, rich microfauna; c, rich microfauna; d, a few fossils; e, fossils (with microfauna) and lithology; f, plants in the Stephanian; g, fossils, and lithology in pre-Caradoc rocks.

C. D A T A ON I N D I V I D U A L S T R U C T U R A L Z O N E S

Z O N E 1. N O R T H E R N F O L D E D F O R E L A N D

302-4 Zone margins: the nor thern margin is broadly gradat ional ( > 3 kin) and the southern margin is sharply defined ( < ½ km). The whole zone is occupied by the outcrop of sedimentary rocks. For convenience of description, two sub-zones may be recognized: 1A the Platform

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PYRENEES 13

(north) and 1B the Trough (south). The line of division between these sub-zones corresponds to the position of an impor tan t syn-sedimentary flexure, which separates a region of L. Cretaceous subsidence in the north from an area of U. Cretaceous subsidence in the south.

312--14 Elements: in sub-zone 1A the following elements occur - Molasse strata (element a) are slightly tilted and rest unconformably on older rocks. Eocene (b) and U. Cretaceous (c) strata are affected by broad folds and are separated locally by an unconformity. Lower Cretaceous strata (d) are separated from the U. Cretaceous strata by a local un- conformity; they have been tilted due to subsidence and have been af- fected by syn-sedimentary faults. Local unconformities or an incomplete sequence separate the L. Cretaceous strata from under ly ing Triassic to Jurassic strata (element e). The latter have been strongly tilted and rest with regional unconformity on the little known rocks of elements f and g. Triassic strata exhibit diapirism. Element a has been affected by the formation of a shallow basin and elements b to e have suffered slight shortening due to the gentle folding.

SSW NNE . , S i l l o n -[ . . . . P l o t e f o r m e

"~ Molasse

f/

F~gure 9. Profile of zone 1. (Section A, Fig. 8.)

Sub-zone 1B contains the following e lements- -Molasse strata (ele- ment a) are locally tilted and are unconformable on older rocks. Eocene strata (b) rest conformably on U. Cretaceous strata (c) ; both are folded. L. Cretaceous strata (d) are tilted and folded and affected by reverse faults; their upper and lower contacts are both unconformities. Triassic to Jurassic strata (e) are folded and reverse faulted and overlie the little known rocks of elements f and g unconformably. Triassic evaporites exhibi t diapir ism. Element a has been affected by the formation of a shallow basin in the north and a rise in the south. Elements b - e exhibi t less than 5% of shortening due to folding.

315--16 Outcrop areas o f the elements: element a outcrops over the whole of sub-zone 1A ( m a x i m u m area 100 x 40 kin) ; elements a and b outcrop in sub-zone 1B over m a x i m u m areas of 100 x 20 km and 30 x 5 km respectively. All other elements in both sub-zones are known only from sub-surface data.

Table 4

S T R A T I G R A P H Y IN ZONE 1

a19 Unit

320 3~ Thickness m

Age and evidence for Maxi- Mini- Aver- age 33t Lithology m u m m u m age

a,a E l e m e n t

in which these rocks o ¢ ¢ u r

Molasse

Eocene

M. to U. Eoc Conglomer- to Plioc; ares, sand- correlation stones, clays, with marine lacustrine strata and limestones stratigraphic position

Dan to L. Sub-zone 1A: Eoc marls, lime- (Ypresian) ; stones microfauna sub-zone 1B:

flysch

U. U. Alb to 1A: lime- Cretaceous Maestr; stones, marls;

macro- and 1B: flysch micro-fossils

L. Valang to Marls, bio- Cretaceous M. Alb; genie

microfauna limestones

Jurassic Tith to Hett; Dolomites, lithology limestones

1500 0 500

1000 100 500

1800 0 1500

1000 100 400

6000 100 5000

{ o oo o

o ooJ

1500 0 1000

a

(1A and 1B)

e

(1A and 1B)

Trias L. Trias to Clays, > 1000 20 - - L. Hett; evaporites, lithology sandstones,

conglomerates

Palaeozoic Carboni- Limestones f ferous and and slates Devonian; microfauna

Palaeozoic Cambro- Metamorphic g Ordovician; schists lithology

e

(1A and 1B)

326--32 Igneous activity: Hercyn ian igneous activity p robably occurred here (see zones 2 and 3). Basic igneous rocks of later date occur in ele- ment e throughout the zone. Sills in t rude Triassic shales and are prob- ably contemporaneous with tufts which occur in He t tang ian strata. The total volume for these basic rocks throughout the zone is c. 500 km 3.

335-42 Metamorphism : a long the southern border of the zone rocks show the beginnings of low grade me tamorph i sm ( ' anch imetamorph isme ' , Kub le r 1967) at depths of 4 to 5 km.

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14 PYRENEES

344-8 Deformation: Phase 1--the rocks of elements c-g were affected by the development of very broad folds in the Palaeocene to Ypres- ian interval. The evidence is the local unconformity between ele- ments b and c. Phase 2--folding, generally of simple type except in Triassic rocks, affected elements b-g in the M. to U. Eocene interval: rocks as young as M. Eocene are affected and are unconformably over- lain by U. Eocene strata (Pyrenean phase). Phase 3--tilting or very weak folding affected all the elements, probably in the U. Oligocene or Miocene for Molasse strata are affected but are unconformably over- lain by unaffected Pliocene strata.

Prior to phase 1, large scale 'structures' formed during the Creta- ceous. They did not result from compression but were due to subsidence of varying intensity at different times and in different places.

350-5 Fold tructures: Phases 1 and 2 have produced folds in elements a to d which have amplitudes of > 1000 m and wavelengths of 2 to 10 km. On average two such folds occur in any one cross-section of the zone. Axial surfaces strike at 080 ° to 120 ° and dip at 90 ° to 70 ° towards the south. In element e folds are of complicated shape due to the presence of shales and evaporites. Phase 3 has produced one fold which has an amplitude > 1000 m and wavelength > 10 km.

356 Fold styles: Phase 2 folds which belong to categories 2B, 2C and 1D are known.

35v Maps of folds: see SNPA (1:200 000, Western Pyrenees).

3n6-73 Minor faults: syn-sedimentary faults defining zones of sedimenta- tion appear to have existed since Triassic or Jurassic times. A system oriented 020 ° to 040 ° is quite well known from subsurface data. Like- wise a second system oriented 100 ° to 120 ° has also probably been active. Vertical displacements of many hundreds of metres seem to have been attained by the end of the Jurassic. In the L. Cretaceous faults or syn- sedimentary flexures became much more active; those trending 100 ° to 120 ° were much more active than those trending 0200-040 °. Cumu- lative movements on these structures at the end of this epoch amounted to thousands of metres. The most important of these structures, which may be either a fault or a major flexure, delimits sub-zone 1A (plat- form) from sub-zone 1B (trough). The North Pyrenean frontal struc- ture, which forms the southern boundary of zone 1, likewise has a large movement.

During the U. Cretaceous, the most important structures were those on the north and south margins of sub-zone lB.

In the Tertiary two types of structures which made use of the earlier structures appeared. The structures trending 100 ° to 120 ° became transformed into reverse faults and the structures trending 020 ° to 040 ° (and perhaps 160°-180 ° ) moved as strike-slip faults.

2. N O R T H PYRENEAN ZONE

~o2 Zone margins: both north and south margins are sharply defined ( < ½ km). 3°8-1°Approximate areas of the zone occupied by the outcrop

of rock types: volcanic < 1% ; plutonic 3% ; sedimentary 95% ; meta- morphic 2%. For convenience of description the zone can be sub- divided in three sub-zones: 2A Cenomanian sub-zone; 2B Limestone ranges; 2C North Pyrenean massifs. 313-14 Elements: in sub-zone 2A the following elements occur - Molasse strata (element a) are post-tectonic, have low dips and rest unconform- ably on older rocks. U. Cretaceous strata (c) are folded on the scale of metres, are schistose and have suffered important shortening; they rest unconformably on element g. Basement rocks (g) consist of lime- stones, schists and granites (Hercynian) ; they are intensely folded and schistose and have suffered important but poorly known shortening.

Sub-zone 2B contains elements d and e. L. Cretaceous strata (d) are folded on the scale ofkilometres, are schistose, show steep reverse faults, have suffered important shortening and rest with local unconformity or incomplete sequence on element e. Triassic to Jurassic strata (e) are also folded on the scale of kilometres, show steep reverse faults and have suffered important shortening.

Sub-zone 2C contains elements c-e (see 2A and 2B), f a n d g (see 2A).

Sud

• t 6 Km

Faille nord pyr~n~enne /

Z o n e [ Z o n e 2 [ Z o n e t

5 ~ I~ 2 B 2A . • ~ , < , , . . _ ~ / / / Nord

o ~ , ~ , ~ ~ ~ v ~ . ~ . o o o, o

6 4 ~ ~ ~ ~- -~ ' - - - -: 6 4 Krn

! 0 5 10 Km I i I

2E

2A ~\~, 2C ,. 2B. ,. C~nomonien I

\ ~ 71 11 7/ I / o ¢.

6 6

Figure 10. Profiles of zone 2. (Sections B, C, D, Fig. 8.)

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P Y R E N E E S 15

Element f (Stephanian to Permian strata) exhibits large folds. Elements c-e rest with angular regional unconformity on element f, which rests unconformably on element g. The sub-zone consists of faulted anti- clines or horsts with margins marked by reverse faults. zis-zn Outcrop areas of the sub-zones: 2A, maximum area 100 x 10 kin; 2B, 100 x 15 km; 2C, 40 × 6 kin.

Table 5

S T R A T I G R A P H Y I N Z O N E 2

a~2 Thickness m a2a E lemen t

320 Age and in which evidence for Maxi - Mini- Aver- these rocks

s19 Unit age a2x Lithology mum mum age occur

Molasse Mioc to Conglomer- 250 0 a Plioc; ates fossils

Flysch Senon to Flysch 3000 0 ?2000 c U. Alb; microfauna

L. Valang to Marls, 2000 0 1800 d Cretaceous M. Alb; biogenic

microfauna limestones and ammonites

Jurassic Ti th to Hett ; Dolomites, 1200 0 1000 e microfauna limestones

Trias Bunter to Clays, (Not known >250 e L. Hett ; evaporites, due to com- lithology conglomer- plicated

ates, tectonics) sandstones

Stephanian Age from Shales, sand- 2000 and local flora stones and red Permian and lithology conglomer-

ates

0 -- f

Carboni- Vis~an ; Shales, ? 1000 ferous goniatites sandstones

Devonian Goniatites, Shales, pteropods limestones,

dolomites

400 300 300 g

'Schistes Silurian and Black shales Carbur6s' basal with lime-

Devonian; stones graptolites

Cambro- Cambro- Shales, Ordovician Ordovician; quartzites

lithology

?1000

?200

8~s-32 Igneous activity: Episode 1--acid dykes and major intrusions occur in element g and are of pre-Permian age (Hercynian). Approxi- mate volume--50 km 3. Episode 2--basic lavas and tufts occur inter- bedded in fossiliferous U. Triassic to Hettangian strata. Approximate volume--?0"5 km 3. Episode 3--basic, submarine lavas and tufts occur interbedded in strata whose age, as indicated by superposition and cor- relation, is Albian to Senonian. Approximate volume--10 km 3. Episode 4---in end-Cretaceous times, dolerite, theralite and nepheline syenite dykes and sills and lherzolite intrusions were emplaced in elements c-g. Some intrusions post-date the folds but in other cases the relations are not clear. Approximate volume--5 km 3.

ass-49. Metamorphism: the rocks of element g have been affected by Hercynian metamorphism (maximum age: Visfan; minimum: Per- mian; probable: Westphalian, see zone 3). Pelitic rocks show musco- vite-biotite-chlorite, muscovite-cordierite-staurolite (4-andalusite) and muscovite-cordierite-sillimanite assemblages, indicating greenschist and amphibolite facies metamorphism of low to intermediate pressure type.

'Pyrenean' metamorphism locally affects the rocks of elements c, d and e (and g in the eastern Pyrenees), especially in sub-zone 2A. The metamorphism has a maximum age of Senonian, and probably oc- curred at the end of the Cretaceous/beginning of the Eocene; in the east of the Pyrenees fragments of metamorphic rocks occur in L. Eocene strata. Calcareous rocks contain scapolite, albite and muscovite; pelitic rocks contain quartz, sericite and chlorite. Outside the segment calcar- eous rocks contain: scapolite, orthoclase, tremolite, diopside, chlorite, sphene, phlogopite, apatite, tourmaline; pelitic rocks contain: plagio- clase, scapolite, biotite, tremolite, hornblende, garnet, tourmaline, sphene and epidote. East of the segment the metamorphism is of green- schist, hornfels and amphibolite facies and of low-pressure type. Iso- grads are difficult to determine, for they have been affected by the Pyrenean deformation. See Zwart (1968) and Ravier (1959).

344-s Deformation: Phase 1--Hercynian folding and metamorphism affected element g. See zone 3 for details. Phase 2--folding with schisto- sity development and metamorphism occurred in several subphases af- fecting elements c-g in end-Cretaceous times. The maximum age of the movements is Senonian and they probably occurred in end-Cretaceous to earliest Eocene times: pebbles of metamorphosed Triassic rock occur in the Ypresian of zone 1 and, to the east of the segment, pebbles occur in L. Eocene strata. Phase 3--folding, reverse faulting and thrusting affected elements c-g in the L. Eocene to Miocene interval, probably in M. to U. Eocene times (Pyrenean phase). For evidence of age see z14 and 890; to the east of the segment the phase is post-M. Eocene, pre-end Eocene in age.

Prior to phase 2, large-scale 'structures' formed during the Creta- ceous. They did not result from compression but were due to subsidence of varying intensity at different times and in different places. In parti- cular, a pre-Cenomanian phase of tilting is well developed.

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16 PYRENEES

85o-5 Fold structures: due to the absence of post-Cretaceous strata, it is very difficult to distinguish the effects of phases 2 and 3. Phase 2 is probably responsible for most schistose structures, but a schistosity due to phase 3 may exist. Phase 3 is usually of a much more brittle nature; it is only obvious in the northern part of zone 2.

Phase 1 produced folds on all scales, see zone 3 for details. Phases 2 and/or 3 produced the following structures in each of the sub-zones. Sub-zone 2A: folds with amplitudes and wavelengths both ranging from > 1000 m to < 1 cm; two folds larger than 1000 m occur in any cross-section of the sub-zone. Sub-zone 2B: folds (> 1000 m to 1 cm) and faults; three folds larger than 1000 m. Sub-zone 2C: folds ( > 1000 m to 100 m) and faults; one fold larger than 1000 m. The average direction of axial surfaces is E-W. Folds are arranged in a fan structure with axial planes dipping both north (commonest) and south.

856 Fold styles: Phase 2 folds in element c have styles of 3D-E and 4D-E. Phase 2 folds in element d have styles of 3D-E and 4D. Phase 2 folds in element e have styles of 3D-E. Phase 3 folds in elements d and c have styles of 2D-F and 1E.

85~, 8~4 M a p s o f fo lds and faul ts : see SNPA (1:200 000, Western Pyrenees) and Choukroune (1969).

85~-6s Planar and linear structures: see zone 3 for details of phase 1 struc- tures. Phase 2 has produced flow and fracture cleavages and stretch- ing and intersection lineations. Phase 3 may have produced fracture cleavage (see 850-55). See Choukroune (1969).

366-~ Minor fau l t s : normal faults trending E -W and ?N-S affected elements c-g in Cretaceous times. At the end of the Cretaceous, reverse faults (with folds) developed. They trend E-W, are partly along rejuvenated normal faults and, throughout the zone, have effected short- ening of 30% to 50%. In M. to U. Miocene times, reverse faults devel- oped which trend E-W and are partly, rejuvenated earlier faults; they produced renewed shortening. Total shortening in the zone is probably over 50%.

3. AXIAL ZONE

302.3o4 Zone margins: the northern margin is sharply defined (< ½ km) and the south margin is in part narrowly gradational (½ to 3 km) and in part broadly gradational (>3 km), z°S-nApproximate areas of the zone occupied by the outcrop of rock types: volcanic < 1% ; plutonic 15% ; sedimentary 75% ; metamorphic 10%.

812-14 Elements: U. Cretaceous strata (element c) are recumbently folded in the south, are overthrusted and have an imbricate structure in the north; they rest unconformably on older rocks. Triassic to Jurassic strata (e) are locally affected by reverse faults and show important shortening; they rest unconformably on older rocks. Stephanian to Permian strata (f) are affected by folds, which are overturned south- wards in the south of the zone; they rest with major unconformity on the intensely deformed basement rocks (g).

315-16 Outcrop areas o f the elements: element g is present over the whole area of the zone (length 100 km; width 30 to 55 km). Elements c, e and f occur in a few isolated outcrops.

Z o n e 5 S Base St~phano Chevauchement des Base N

crOac~ Partaken Eaux .Chaudes • secondalre , \ ,"'-=~-~. / - CrOac~[ / l

•

J ~

? 5 'OiKm 7 / /~ /

Figure 1I. Profile of zone 3. (Section E, Fig. 8.)

Table 6

STRATIGRAPHY IN ZONE 3

3sz Thickness m 3~o Age and

evidence for Maxi- Mini- Aver- 319 Unit age 831 Lithology mum mum age

8~a Element in which these rocks o c c u r

Flysch Campan to Sandstones, 250 0 Maestr; marls microfauna

Calcaires Cenom to Limestones, 700 0 des Cations Santon; sandy

Rudists and limestones mierofauna

Triassic- Age based on Jurassic lithology

Stephanian Age based on to lithology Permian and flora

Carboni- Vis6an to ferous L. Westphal;

fossils

Devonian Fossils

'Schistes Gothlandian; Carburfs' graptolites

Caradoc; fossils

Ordovician Lithology

?Cambro- Stratigraphic Ordovician position to Pre- Cambrian?

Evaporites, 500 0 limestones

Shales, 2000 sandstones, conglomer- ates, volcanics

Limestones, ? 1000 shales, sandstones

Limestones, dolomites, shales

Shales, rare limestones

Shales, quartzites

Shales, quartzites Micaschists, gneiss

700 500

300

150

>600

600

0 e

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PYRENEES 17

32~-3~. Igneous activity: migmatizafion and acid major intrusions and dykes of late Hercynian date (post-Vis6an, pre-Stephanian) affect element g; they have an approximate volume of 500 km 3 within the segment. Lavas and tufts occur in Stephanian to Permian strata; they are of intermediate composition, have associated dykes and an approxi- mate total volume of 10 km 3. Basic, sills, lavas and tufts occur very locally in U. Triassic to Hettangian strata; their approximate volume is 0"5 km 3 (see zones 1 and 2).

335--42 Metamorphism: the rocks of element g have been affected by very complex Hercynian metamorphism (maximum age: Namur to L. Westphal; minimum age: U. Westphal; probable age: Westphal). Pelitic rocks show the same assemblages as in zone 2, plus cordierite- sillimanite-K-feldspar, indicating greenschist to amphibolite facies of low to intermediate pressure type.

'Pyrenean' metamorphism affects the rocks of element c at Eaux Chaudes and Gavarnie. The metamorphism has a maximum age of U. Cretaceous and probably occurred in M. to U. Eocene times at Gavarnie, and may be earlier at Eaux Chaudes; it is syntectonic with the Pyrenean deformation. Calcareous rocks contain scapolite, asbestos, phlogopite; pelitic rocks contain sericite, chlorite, muscovite. The metamorphism is probably of greenschist facies and low-pressure type. See Zwart (1968) and Debar (1965).

344--8 Deformation: 1. Hercynian deformation affected element g in the Vis6an to Namurian to Stephanian interval, as evidenced by the un- conformity between elements g and f. There were many phases of intense folding, with schistosity development and metamorphism. 2. Thrusting and folding with cleavage development, possibly in two subphases, affected elements c, e, f and g in the M. Eocene to L. Oligocene interval, probably in M. to U. Eocene times: see zone 4 for the age evidence.

350-5 F o l d structures: deformation phase 1 produced folds with amplitudes and wavelengths ranging from > 1000 m to < 1 cm; five folds larger than 1000 m occur on average in a cross-section of the zone; the orien- tation of the folds varies with each phase, but in the most prominent phase axial planes trend E or NW and dip south. Phase 2 produced folds with amplitudes and wavelengths ranging from > 1000 m to < 1 cm; there are too few outcrops to determine the number of folds larger than 1000 m in a cross-section of the zone, but there are prob- ably more than three; axial surfaces trend approximately E -W and are south-dipping.

aSO Fold styles: Phase 1 folds have styles of 2D-E, 3C-E, 4B-E and 5B-E. Phase folds have styles of 1D-E, 2G-E and 3D-E.

3s7 Maps of folds: see Mey (1968), Wennekers (1968), Wensink (1962), Mirouse (1966) and Carte G~ologique de la France (1 : 80 000, Luz and Bagn~res de Luchon).

359-e~. Planar and linear structures: flow and fracture cleavages are fre- quently developed in element g due to Hercynian movements (Zwart 1963). The Pyrenean phase has produced flow and fracture cleavages in elements c and e and, locally, new cleavages in element g (Choukroune et al. 1968).

366--73 Faulting: Hercynian faults, especially reverse faults, affect element g. They are oriented parallel to the folds, dip at 20 ° to 80 ° and have resulted in important contraction of the zone. Reverse and thrust faults developed during the M. to U. Eocene Pyrenean phase; one major thrust is known at Eaux Chaudes. These faults trend E - W and dip at 450-80 ° north and 00--45 ° south. The shortening caused by them is difficult to estimate due to the rarity of outcrops of element c; it is probably of the order of 50%.

Z o n e 4 ] Z o n e 3 Base cr~tac~

S Base Eocene _ ~ J~_. -- ~- , ¢ ~ ' ~ ~ ~ N

Trios - - - " / ) / ' / . , - - o 5 to Km I I I

Figure 12. Profile of zones 3 and 4. (Section F, Fig. 8.)

4. S O U T H PYRENEAN ZONE

3o2. 8o6 Zone margin: the southern margin is in part sharply defined (<½ km) and in part indefinite because of lack of exposure.

3o8-~1o Approximate areas of the zone occupied by the outcrop of rock types: volcanic < 1% ; sedimentary 100%. For convenience of description the zone may be subdivided into two sub-zones, the eastern basin (4A) and the western basin (4B). The roughly N-S boundary between the two is marked by N-S folds and corresponds to an old palaeogeographical feature (?Stephanian, Jurassic). It separates an eastern, Senonian flysch basin from a western, Eocene flysch basin.

3zg-z4 Elements: in sub-zone 4A the following elements occur. Molasse conglomerates (element a) are sub-horizontal in the north and rest unconformably on older rocks. Eocene marls, sandstones and conglom- erates (b) rest conformably on U. Cretaceous limestones and flysch (c). The latter rest with local unconformity or an incomplete sequence on L. Cretaceous limestones, marls and sandstones (d). Triassic to Jurassic strata (element e: limestones, dolomites, evaporites) are sepa- rated from the Stephanian to Permian (f) by a level of d~collement.

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18 PYRENEES

Elements b -e have suffered d6collement on the Trias and have been displaced as far as 40 km. In the north, thrust folds towards the south affect elements f to b; the thrusts are re-folded a n d dip south; the dis- placements d iminish towards the south. See Seguret (1971).

Sub-zone 4B contains elements a, b, c and e. The conglomerates, marls and sandstones of the Molasse (element a) are folded with dips of up to 90 °. They rest unconformably on older rocks. Eocene flysch (b), U. Cretaceous limestones (c) and Triassic to Jurassic evaporites (e) have undergone similar deformation here to that in sub-zone 4A.

315-16 Outcrop areas o f the elements: m a x i m u m dimens ions- -a , 70 x 20 km; b, c, d, e, 100 x 60 km; f, 10 x 2 km.

Table 7

STRATIGRAPHY IN ZONE 4

322 Thickness m 32o Age and

evidence Maxi- Mini- Aver- 3t9 Unit for age 32x Lithology mum mum age

823 Element in which these rocks OCCUr

Flat lying U. Eoc to Conglomer- conglomer- L. Olig; ates, ates U. Olig to breccias

Mioc; fossils

2500 0

8x, Unit

Senonian Flysch

U. Creta- ceous

L. Creta- ceous

s22 Thickness m s2o Age and

evidence Maxi- Mini- Aver- for age 3~x Lithology mum mum age

4A: Campan Flysch 2000 0 to Maestr; microfauna 4A: Cenom~ to Santon; ] Limestones, 4B : Cenom~ sandy 2000 500 to Maestr; [ limestones microfossils ]

4A: Apt to Limestones, 1000 0 Alb; marls, microfossils sandstones

s~s Element in which these rocks o c c u r

1500 c

1000 c

Jurassic 4A: Rhaet Limestones, 1500 0 e to Kimm; dolomites fossils

Trias 4A, B; L. Evaporites, ?1500 0 1000 e Trias to sandstones, Keuper; conglomer- lithology and ates microfossils in Keuper

Folded Olig (?L.) ; Marls, Molasse Charophytes sandstones, (phase 2) conglomer-

ates

3000 Stephanian See zone 3 to Permian

Folded M. to U. Marls, Molasse Eoc; sandstones, (phase 1) vertebrates conglomer-

ates

Marly Eocene

4A: Ypresian

~ ° t e t i a n | 4 B : U. | E o c ; ~ microfossils

Flysch 4B: Eocene Ypresian to

L. Lutetlan; fossils

Alveolina limestone

4A ) Palaeoc;

~microfauna

1000 0

2000 0 1500

Blue marls >2000 500 1800

Flysch 6000 0 4000

Limestones, 1000 100 dolomites

326--32 Igneous activity: basic sills, lavas and tufts occur in U. Triassic to Het tangian strata, but see zones 1-3 for details.

844-8 Deformat ion: Phase 1 - - the Pyrenean phase affected elements b - f and produced d6collement, thrusting and folding, with cleavage develop- ment in the north. The m a x i m u m age of the movements is M. Eocene (sub-zone 4A) or U. Eocene (sub-zone 4B) a n d the m i n i m u m age is end Eocene; see 31~ and 320 for the age evidence. Movements p robab ly oc- curred in two sub-phases. Phase 2- - fo ld ing and local thrust ing affected all the elements dur ing the L. Oligocene to Aqu i t an ian interval , prob- ably in U. Oligocene times; for the age evidence see zone 5.

350-5 Fo ld structures: Phase 1 has produced folds with average ampli tudes and wavelengths from > 1000 m to 10 m. Folds in the nor th of the zone are complicated by the development of cleavage and thrusts, a n d by the development of thrusts in the south of the zone; s imple basins occupy the centre of the zone. Phase 2 has produced E - W t rending folds which range in size from 1000 m to 100 m.

356Fold styles: Phase 1 folds in e lement b have styles of 1D-E, 2E-F , and 3E. Phase 1 folds in elements c and d have styles of 1D--E and 3D. Phase 2 folds in e lement a have styles of 1 D - E and 2B--C.

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P Y R E N E E S 19

Z o n e 5 ~ ~ [ Z o n e 4 .~, S :~ E°c2ne

rcalceire rnernes" Discordance N . . . . . . Cr~loc~ su,p. | I Oligoc~ne pyr~n~enne .go - M~ocene • / ,} / ~

1 0-" " .., . , ._ , , . . . . 0

o o o o o "

2 2

4 4

6 6

Figure 13. Profile of zones 4 and 5. (Section G, Fig. 8.)

35~. 37, Map of folds and faults: Mapa geol6gico de Espafia (1:200 000, L~rida 1947 and Huesca 1957), Seguret (1971).

35~-~9 Planar and linear structures: flow and fracture cleavage are developed in elements b and c especially in the north of the zone. They are related to sub-phase 2 of the Pyrenean deformation.

3ee-73 Faulting: reverse faults, flat thrusts, and the d6collement structure on the Trias all developed during the Pyrenean phase of deformation. These faults trend E--W to NW-SE and dip at 0 ° to 60°; many thrusts are undulatory, or even folded. Reverse faults of post-Oligocene date affect element a; they trend ENE, dip at 45 ° and have produced only slight overall displacement.

ZONE 5. S O U T H E R N FOLDED FORELAND

304,306 Zone margin: the southern margin of the zone is in part broadly gradational ( > 3 km) and in part indefinite because of lack of exposure. Sedimentary rocks outcrop over the whole zone.

312-14 Elements: Molasse strata are symmetrically folded locally (element al) or are unfolded (a2). The simple folds have been influenced by the presence of gypsum. The Molasse rocks rest unconformably on older strata. Eocene limestones (b) and U. Cretaceous marls and limestones (c), each a few metres thick, are known from boreholes. Triassic and Jurassic strata (e) form diapirs of varying complexity; they are un- conformable on the basement rocks (g), which consist of limestones, shales and sandstones strongly folded during the Hercynian orogeny.

S I Z o n e 5 Z o n e 4 N

1 Oligoc~ne durossique Eocene Gypse t ~ ~ . [ Cr~tac~ ~ '~L

o ,, ~ ~ " ' ' ' . . o . - . ~ - ' ~ ~ " ~ ~-1o

Figure 14. Profile of zones 4 and 5. (Section H, Fig. 8.)

315--16 Out6rop areas of the elements: a outcrops over almost the whole zone (over 100 x 10 km); e outcrops very locally.

Table 8

S T R A T I G R A P H Y IN Z O N E 5

822 T h i c k n e s s m 333 Element 320 Age and in which

evidence for Maxi- Mini- Aver- these rocks 319 Unit age 321 Lithology m u m m u m age occur

Upper Mioc (Aqui- Conglomer- 1000 0 750 a2 Molasse tanian) ; ates, clays,

vertebrates breccias, sandstones

Lower L. and M. Conglomer- 2000 1000 1500 al Molasse Olig; Charo- ates, clays,

phytes and sandstones, vertebrates gypsum, (east of lacustrine segment) limestone

Trias L. Trias to Clays with > 1200 ?500 e Keuper evaporites;

sandstones, conglomer- ates

344-SDeformation: deformation has affected element a (L. Molasse), producing simple folds and diapirism of the gypsum beds. The un- conformably overlying U. Molasse is unaffected and so the deformation has a maximum age of M. Oligocene and a minimum age of Aquitan- i an .

35o-5 Fold structures: one or two E - W to ESE-WNW folds with am- plitudes and wavelengths > 1000 m affect element a. Numerous small folds occur in the gypsum formations.

35e Fold styles: the folds have styles of 2A and 2B.

857. 374 Maps of folds and faults: see Mapa geol6gico de Espafia (1 : 200 000, L6rida 1947 and Huesca 1957).

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20 P Y R E N E E S

ACKNOWLEDGEMENTS

The authors wish to thank P. Barr+re, M. Choukroune, M. Seguret and

J . L . R e i l l e for ass is tance .

D. R E F E R E N C E S

ALASTRUE, E., ALMELA, A. & Rtos, J. M. 1957. Explicacign al mapa geolggico de la provincia de Huesca. Escala 1/200 000. Madrid (Instituto Geol. y Min.).

AUBOUIN, J. & M~NNES~V.R, G. 1962. Essai sur la structure de la Provence. Livre P. Fallot, Soc. Gdol. France, 2, 45-98.

BARRAB~, L. 1952. Les roches intrusives ~ hornblende brune des Pyrdn&s. Int. geol. Congr. 19, 6, 9-21.

BARR~.R~, P. 1969. Le relief des Pyrgn(es centralesfranco-espagnoles. Bordeaux (unpublished thesis).

BVRTR~'~D, L. 1940. Sur la structure g6ologique du versant nord des Pyrdn&s. Bull. Serv. Carte g~ol. Fr. no. 204, 205-83.

BmOT, P. 1937. Recherches sur la morphologie des Pyrdnges orientales franco-espagnoles. Paris (Baillare).

BORGNE, E. LE & MOUEL, J. 1969. Carte magn&ique de France (anomalies du champ total). C.N.R.S. Orldans (B.R.G.M.).

CAPDECOMME, H., DELOFFRE, R., I"IENRY, J. & VILLANOVA, M. Sdries stratigraphiques et pal6og6ographie du Cr&ac6 supdrieur dam la r6gion de Lourdes. Bull. Soc. g~ol. Fr. (7), 7, 392-8.

CARTE O~OLOOI~U~ D~ LA FRANCE. Geological maps at 1:80 000 and 1:320 000. Serv. Carte g3ol. Fr.

CHEVILLY, F. DE, COLO, G., HENRY, G., NICOLAI, A., QUOl, J. & WINNOCK, E. 1969. Le champ de gaz de Meillon-Rousse et la structure profonde de l'anticlinal de Pau. Revue Inst. Jr. Pdtrole, 24, 564-78.

CHOUKROUN~, P. 1969. Sur la prdsence, le style et l'fige des tectoniques superposfies dans le Cr&ac~ nord-pyrfin6en de la rdgion de Lourdes. Bull. Bur. Rech. gdol. min., Paris, 2, no. 2, 11-20.

CHOUKROUNE, P., MARTINEZ, CL., SEGURET, M. & MATTAUER, M. 1968. Sur l'exten- sion, le style et l'~ge de raise en place de la nappe de Gavarnie (Pyrdn6es centrales). C.r. hebd. Sdanc. Acad. Sci., Paris, 266, 1360-3.

CIZ~,'~COURT, H. DE. 1948. Essai d'interpr&ation de la tectonique profonde des Pyr6n6es. Bull. Soc. ggol. Fr. (5), 18, 271-84.

CLAN, M., KOCH% H. DE LA, LELONO, F. & POLY, B. 1963. Nouvelles observations sur le massif granitique du Lys-Caillaouas. Sciences Terre, 9, 149-74.

C.N.R.S.--I .P.G. 1969. Carte magn&ique de France, I/I.000.000 (anomalies du champ total). (Centre National de la Recherche Scientifique, Insfitut de Phy- sique du Globe.)

CROUZEL, F. 1956. Le Miocene du bassin d'Aquitaine. Bull. Servs Carte gdol. Fr. no. 248.

C~USAVONT, M., RIBA, O. & VmL~A, J. 1966. Nota preliminar sobre un nuevo yacimiento de vertebrados aquitanienses en Santa Cilia. Notas Comun. Inst. geol. min. Esp. no. 83, 7-14.

CRUSAVONT, M., VmLALTA, J. F. & TRUYOLS, S. 1956. Caraeterisaci6n del Eocene continental en la cuenca de Tremp y edad de la orogdnesis pirimfica. Aetes du 2 ~ cong. Inst. d't~,t. Pyr. Toulouse, 2 (1), 39-53.

DALLOm, M. 1910. ~tudes g6ologiques des Pyrdn6es de l'Aragon. Annls Fac. Sci. MarseiUe, 19.

DEBAT, P. 1965. Les formations m6tamorphiques des vall&s de Gavarnie etd' H6ds (Htes-Pyrdndes). Bull. Soc. Hist. nat. Toulouse, 100, 137-73.

D~LOFVRE, R. 1966. t~tude gdologique du flysch crgtacg supdrieur entre les valldes de l'Ouzom et du Gave de Maulgon (Basses-Pyrdndes). Bordeaux (Bi~re).

DONG~N, P. G. VAN. 1967. The rotation of Spain: paleomagnetic evidence from the eastern Pyrenees. Palaeogeogr. Palaeodim. Palaeoecol. 3, 417-32.

GIRDLER, R. W. 1968. A paleomagnetic investigation of some late Triassic and early Jurassic volcanic rocks from the northern Pyrenees. Annls G~ophys. 24, 1-14.

HENRY, J. 1966. Le probl6me des &ages tectoniques dans la zone nord-pyr6n&nne occidentale. In l~tages tectoniques. Neuch~tel (Inst. G6ol. Univ.), pp. 253-67.

IFP & CNEXO 1971 HistoireStructurale du Golfe du Gascogne. (Symposium) Paris (Editions Technip), 2 vols.

KUBLER, B. 1967. La cristallinit6 de l'illite et les zones tout ~t fait sup6rieures du m6tamorphisme. In l~tages tectoniques. Neuchettel (Inst. G6ol. Univ.), pp. 105-23.

LALLFMANT, H. G. A. 1968. Structural and petrofabric analysis of an alpine type peridotite: the lherzolite of the French Pyrenees. I2id. geol. Meded. 42, 1-57.

MANGIN, J. P. 1960. Le nummulitique sud-pyrdnden d l'Ouest de l'Aragon. Zaragoza (Inst. Est. Pyrdn.), pp. 1-619.

MANCXN, J. P. & RAT, P. 1962. L'6volution post-hercynienne entre Asturies et Aragon. Livre P. Fallot, Gdol. Soc. France, 1, 333-49.

lk'f_APA GEOL6OICO DE ESPA~A (ScAI~: 1:200 000). Madrid (Instituto Geol6gico y Minero de Espafia).

MATTAUER, M. 1968. Les traits structuraux essentiels de la chalne des Pyr~n&s. Revue G3ogr. phys. Gdol. dyn. 10, 3-12.

MATTAUER, M. & PROUST, F. 1967. L'&olution structurale de la pattie est du domaine pyr6n6o-proven~al au Cr&ac6 et au Pal6og~ne. C.R. sur la Biog6ographie du Crdtac&l~oc6ne de la France m6ridionale. Tray. Lab. de G3ochimie de la Biosphere, pp. 9-20.

MATTE, P. 1968. La structure de la virgation hercynienne de Galice (Espagne). Revue Gdol. Alp. 44, 5-128.

MATTHV.WS, D. H. & WXLLma~S, C. A. 1968. Linear magnetic anomalies in the Bay of Biscay: a qualitative interpretation. Earth andplanet Sci. Lett. 4, 315.

Mmc, P. H. 1967. Evolution of the Pyrenean Basin during the late palaeozoic. Int. Syrup. Devonian System (Calgary). 2, 1157-66.

1968 A. The geoiogy of the upper Ribargorzana and Baliera valleys. B, Geology of the upper Ribagorzana and Tot valleys. Leid. geol. Meded. 41, 152- 220, 229-94.

MmovsE, R. 1966. Recherches g6ologiques dam la partie occidentale de la zone primaire axiale des Pyrdn6es. Mgm. Serv. Carte g3ol. dgt. Fr.

MXSCH, P. 1934. Der Bau der mittleren Sfidpyren~ien. Wachr. Ges. Wiss. G6ttingen, I I I , H. 12, 168 pp.

- - - - 1948. Publ. extranjeras sobre geol. de Espa~a; vol. IV, pp. 1-178, Madrid, 1948. RAVXFR, J. 1959. Le m&amorphisme des terrains seeondaires des Pyr6n&s. M3rn. Soc.

g3ol. Fr. no. 8. Rvvrv , J. L. 1967. Subdivisions stradgraphiques et phases de plissement dans le

Pal6og~ne continental sud-pyr6n6en. C.r. hebd. Sganc. Acad. Sci., Paris, 265, 852-4. - - 1971. Les relations entre orogen~se et sddimentation sur le versant sud des

Pyrdndes, d'apr~s l'&ude des formations tertiaires essentiellement continentales. Presses Univ. Sci. Technol. Languedoc, Montpellier. (In press.)

RICHERT, J. P. 1968. Analyse structurale de la zone charni~re entre le B~arn et le pays basque. Bull. Serv. Carte ggol. Als.-Lorr. 21, 3, 137-64.

ROTH~, J. P. 1967. Cartes de sdismicitd de la France. Annls Inst. Phys. Globe Univ. Strasbourg (Ggophys.), 8, 3-10 (see also, Seismicity maps of France, 3rd Wld Conf. Earthq. Engng, Wellington, 1965, 1 (3), 205-16).

ROTH~, J. P. & D~CHEVOY, N. 1954. La s6ismicit6 de la France de 1940 ~ 1950. Annls Inst. Phys. Globe Univ. Strasbourg (Ggophys.), 7, 24432.

ROTH~, J. P. & DECHEVOY, N. 1967. La sfiismicitd de la France de 1951 ~ 1960. Annls Inst. Phys. Globe Univ. Strasbourg (Ggophys.), 8, 19-84.

SCHWARZ, 1962. Geology and paleomagnetism of the valley of the rio Aragon sub- ordan north and east of Oza. Estudios geol. Inst. Invest. geol. Lucas Mallada, 18, 193-240.

SEOUR~T, M. 1969. Contribution ~ l '&ude de la tectonique sud-pyrfin&nne: sur le style et l 'importance des ddplacements vers le sud des s~ries secondaires et tertiaires de la partie centrale du versant sud des Pyr6n&s. C.r. hebd. Sganc. Acad. Sci., Paris, 268, 907-10.

by guest on January 28, 2022http://sp.lyellcollection.org/Downloaded from

P Y R E N E E S 21

SEGURET, M. 1971. i~tude tectonique du versant sud des Pyr6n6es centrales: nappes et sdries ddcolldes, r61e du serrage et de la gravit6. Presses Univ. Sci. Technol. Languedo¢, Montpellier.

SELZER, G. 1934. Geologic der sfidpyren~iischen Sierren in Oberaragonien. Neues oTb. Miner. Geol. Pal~'ont. BeilBd. 71, B, 370-406.

SITTER, L. U. DE 1956. A cross section through the central Pyrenees. Geol. Rdsch. 45, 214-33.

SOUQUET, P. 1967. Le Crdtacg supdrieur sud-pyrgngen en Gatalogne, Aragon et Navarre, Toulouse (Editions privat, Toulouse), 530 pp.

S.N.P.A. (Soci6t6 Nationale des P6troles d'Aquitaine). Geological maps at 1 : 50 000 (can be seen at the Geological Society of France): Saint-Vincent-de-Tyrosse, Bayonne, Espelette, Dax, Harparren, Iholdy, Saint-Jean-Pied-de-Port, Orthez, Maul6on, Tardets-Sorholus, Carrau, Pau, Oloron-Ste-Marie, Laruns, Somport, Lourdes, Argel6s-Gazost.

Geological maps at 1 : 200 000 of the Western Pyrenees. Sheets I and 2. TAILLEFER, F. 1951. Le Pigmont des Pjrgndesfran~aises. Toulouse (privately printed),

383 pp. VIERS, G. 1960. Le relief des Pyrgnges occidentales et leur pigmont. Toulouse (privately

printed), 604 pp. WENNEKERS, J. H. N. 1968. The.geology of the Esera Valley and the Lys-Caillauas

Massif. Leid. geol. Meded. 41,221-67. WENSlNK, H. 1962. Palaeozoic of the upper Gallego and Ara valleys, Huesca province,

Spanish Pyrenees. Estudios geol. Inst. Invest. geol. Lucas Mallada, 18, 1-73. ZWART, H. J. 1963. The structural evolution of the Paleozoic of the Pyrenees. Geol.

Rdsch. 53, 170-205. 1968. The paleozoic crystalline rocks of the Pyrenees in their structural setting.

Ifrystalinikum, 6, 125-40.

by guest on January 28, 2022http://sp.lyellcollection.org/Downloaded from