_________________________________________ O_C_E_AN_O __ LO_G __ 'C_A_A_C_T_A_,_'_9_8 '_,_N_O_S_P-1~--------

Subduction and tectonicso Subduction Teclonics

Ac tive mllrgins IPOO

Discussion on the results Subduclion Tectonique:

Marges a.ct ives IPOO

of the IPOD program o

active ln

ABSTRACT

RÉSUMÉ

o

marglns

J . Aubouin", R. Blanchetb

a Département de Géoteclonique. Université Pierre el Marie Curie. 4, place Jussieu. 75230 Paris Cedex OS, et Labor:uoire Associé nO 215 du CN RS. b Département des SCÎences de la Terre . Université de Bretagne Occidentale, 6. avenue Le Gorgeu, 29283 Brcst Cedex. et Groupement dïntérêl Sdenlifique 120009 ; Océanologie et Géodynamique.

Sinec the adve"1 of pla te leclonÎcs the active margins of the oceans have been studied according 10 a model whose basis is a piling up of imbrications of O\;eanic material units, in fronl of the upper plate. forming a gre,11 teetonic accrelionary prism. This model is broadly the SHme for ait the authors ; it has been largely used for a lpine·type or paleo.oceanic mountain chain , ail around the world. After more than a year of deep driltings on active margins, the IPOO program has given fund amental data making it necessary to reconsider previous models and Iheir appl ication to mountain chains. T he authon have directly taken part in the dr ill ings o n western and eastern P<lcific active margins (Legs 60 and 67) and Ihey have worked on the teclonics of a lpine (paleo-ocea nic) chains of the peri ·rnediterranean. peri·caribbean. and perip<icific bel ls. They compare the geologicll i d<itll accumul<ited (rom these IWO direct sources. T he teelonic constra ints regime is speeified and the conseque nces of the Subd~lion are looked for . The notions of coll ision and obduction are diseussed in relation to subduction and tectonics. Finally, an an<ilysis of the temporal evolution of :lcti ve margins l'lnd of chains, shows the necess ity of thinking in terms of superimposed tectonics.

Octlltlol. At·w. 1981 . Proceedings 26'h International Geological Congress. Geology of continenlal margins symposium , Paris, July 7-17, 1980, 283-294.

Subduction el tectonique. Réflexions à partir des ré sultats d u programme IPOO sur les marges actives,

Depuis J'avè nement de la tectonique des plaques, les marges actives des océn ns sont trai tées se lon un mod~le dont la base, à quelques variantes près selon les auteurs, est un empilement d'imbrications d 'unité s à matériel océanique . au front de la plaque supérieure , en un important prisme d 'accrétion tectonique. Ce modèle li été abondummenl appliqué aux chaînes de montagnes de type alpin, ou paléo-océanique, tout autour du globe. Après plus d'un an de forages profonds sur les marges actives, le programme IPOD li apporlé des données essentielles qui obligent li recons idérer, au moins en par tie, les modèles antérieurs et leurs applications aux chaînes de montagnes. Les auteurs ayant, d'une part partic ipé directement ;lUX forages sur les marges act ives Ouest et Est Pacifique (Legs 60 et 67), d 'autre part tr~l vll il1é sur ln tectonique des chaînes .. a lpines" (paléo-océaniques) périméditerranéennes, péricaraïbes, péripacifiques, confrontent les fa its

283

J . AUBOUIN, A. BLANCHET

géologiques accumulés par ces deux sources directes. Le régime des contraintes tec to niques est précisé e t les con5équences de la subduction sont recherchées. Les notions de collis ion et d 'obduction sont di scutées par rapport à la subduction et à la tectonique . Enfin. une analyse de révol ution dans le temps des marges actives comme des chaînes, montre la nécess ité de raisonner en terme de tectoniques superposées.

O eta/lOI. A c ta. 1981. Actes 26" Congrès International de Géologie. Colloque GéOlogie de~ marges continentales, Paris, 7-17 juil. 1980, 283-294.

INTRODUCTION

Since the bi rth of plate tectonics the active margins of the oceans have been deal t with from a quite simple model : the subduction of an oceanic lithosphere under another lithos­phere determines oceanic materials uni ts which pile up in the front of the upper plate forming an accretionary prism made of tectonic imbrications which lift up the margin and build up a range during the lime of subduction.

This model resulls, on the one hand , from the theoretical cons traints irnposed by the general kinematics of the plates, and on the other hand , f rom the Interpretation of marine data: bathymetry. seismic profiles, gravimetry (S ugimura , Vyeda, 1973 ; Karig, 1974 ; Karig, Sharrnan. 1975 : Biju Du val et al., 1979 : Dickinson. Seely , 1979. etc.) . The model of the accretionary prism was soon applied to mounlain belts : western-american range. California, Oregon, Alaska (Ernst. 1970: Scholl, Marlow, 1974 : Blake , Jones, 1974: Rangin, 1978, etc.). Alpine chains (Ernst , 1975 : Boccaleni el al .. 1971), Caribbean chains, we stern Pacifie belts, etc . (Dewey, Bird , 1970). The bibliography using now dassic models ili very large and the dtcd rcfcrcnccs arc ju~ t an introduction. A complete bibliography can be found in the various artides of this vol ume.

Active margins only recently have been explored in a direct way by deep drilling in the framework of IPOD program (1977-1979). Unexpected results have been obtained and new problems have come up.

We propose to assemble the principal fa cts brought 10 the fore by the IPQD drillings ca rried out up to now. Then we shall compare the notions of subduction in the Oceans with

284

the teClOnies in the mounlain s, before trying to differentiale thei r roles in the evolution of oroge nie belts. We shall base our investigations on data collectcd on carth - in the perimediterranean and peric:lribbean ranges and the wes­tern-american Cordilleras _ and on data coltected al sea , having taken part in the Leg 60 (R. B., Mariana transect) and Leg 67 (J. A. Middle America Trench. Guatemalan transect). We shall s tress the new problems and the diffieul­lies of classic mode!s more than on generally accepted condusions.

IPOD DRILLINGS IN ACTI VE MARG INS: UPDATED CONCE PTIONS; THE URGENT NEED TO KNOW MORE

Thanks to Ihe IPOD/DSDP prognlm , direct data obtained by deep drillings are available for the aClive margins of Japa n (Legs 56 and 57). of the Shikoku basin (Leg 58), of the Phil ippine sea and the Marianas (Legs 59 and 60) and of Centrul America [Legs 66 und 67 (Fig. 1)].

Moreover , direct observations - in submersible - ha ve been done by the HEAT group (Hcllenic Arc and Trench) in the Hellenic Trench in the Eastern Mediterranean (Le Pichon et al .. 1979 a and /J. a nd this vol ume).

Finally , detailed surveys - carried out by Scabeam (CNEXO, RlV jean Charcot) _ have recently given a very precise bathymetry pcrmilting a morpho-structural analysis of certain areas of the Middle Americ,l Trench <l nd of the Hellenic Trench.

Figure 1

L/Jcm iO/r mup of tht /1'O/J dril, lill).l in Puâf/(- u,·ti,·t ",u'iiills (I_tg mmr/;ltr). Carte de localisation des campa­gnes de forage 11'01> ~u r les marges aClive~ du Pacifique (numéro du I.eg).

What are the broadoutlines which arise after these studies (Fig. 2.7)"

The present subduction in the Oceans is 11 fundamental geodynamlc proccss, jus te like the expansion of oceanic f1oor. lt is the tectonic superpos ition. on the dimension of the lilhosphere, of two plates along an act ive teclonic contac t : the subd uction zone is marked out by earth­quakes, in a double-layered structure (Wadati·Benioff zones). The associated magmalism is s ignificant in magni­tude and its geochemistry , ilS petrography. its deposilS, ils mineralisat io ns are quite typical.

However , one can notice that, up 10 the present day. the greal tectonic contact of subduction areas has not yet been dr illed : it is a major objective 10 be reached as soon as possible (for example al the level of the Middle America Trench fer. Leg 67 . Von Huene el 01., 1980 (Fig. 7) or al the fool of the Antillean Arc. objeclive of Leg 78A]. Direct dala are required about Ihe contact , the s late of the constraints, the nalure and the composition of the down·going plaie. the possible modifications of the upper plaie.

' n the near future. we can hope 10 drill Ihi s major conlact where it just slips under the upper plate. The Glomar C hallenger can do il in sorne particular places and it is, a fortiori. within the capabili ty of a ship like the Glomar Explorer.

However, is seems Ihat only in Ihe distant future will it be possible to dr ill deep enough to reach the subduction conlac t , where one expects the thermodynamic conditions 10 generate Ihe blue schists facies metamorphis (30 km of depth correspond with a lilhostatic pressure of 30 kilobars !), Unless, taking into account that tec tonic overpressures may reduce the depth required by the mere considerat ion of Ihe lithos talic pression, So, if most of the characleristics of the subd uction have been observed -and .'10. demonstrated - or if they will be soon observed , on Ihe contrary, the relal ionship between 'blue schists' and sub­duction will s lill remain a postulate for a long lime ... And wc know Ihe prominent role il plays in the interpretalion of ranges.

- _. ........ -Figure 2 Leg 57: Japan luneh Iranseel (afrer Von Huene el al .• 1978). Di08rommatic history of Neogene .wbsidence on Ihe inner slope of the Japan rrem;h, bused on Leg 57 sampling and lPDC mullich(.mnel record.~. K ,. Creta. ceous ; ECt ,. eorly Cenozo;c (Poleogell/!) : LCz .... Lau Cenowic (Neogene). Lell 57: Coupe de la Fosse du Japon (d'après Von Huene el al.. 1978). Schéma illustrant la subsidence néogène du mur interne de III Fosse du Japon. basé sur les résultats du Leg 57 et sur les enregistre· ments sismiques mullitraces du lPDC. K - Crétacé; ECz ,. Terti:lire inférieur (Paléogène): Lez ,.. Tertiaire supérieur (Néogène).

285

SUBDUCTION AND TECTONICS

The plunging occanlc plaie beurs 115 own 1~lonic history

Recent s tudies (drillings, Seabeam surveys have enabled us 10 assess the oceanic nature of the c rus t entering the subd uction zone, 10 check the age of this crust, to s tudy its sedimentary coyer. to set up Ihe main Slructures il takes on.

So, in front of the Middle America Trench (Fig. 4), the detailed Seabeam survey (Aubouin et ai., 1980: Renard el ai" 1980) shows a system of eXlensional fau l t~ and flexures determining a series of rectilinear N 130 to N 140 oriented spurs on the Cocos plate. These highs are oblique to the trench. but clearly parallel to magnelÎC anomalies in Ihe site of Leg 66 (Fig. 5·6). Renard el (Ii. (1980) think that this struc turation is probably prime val : it looks like the s truc tu­ration on the Eas te rn Pacific Rise (Francheteau et al., 1979 ; Cyamex Scienlific Team , 1980). The down bending and the subsidence of the subducled plate preferenlially brings about the rejuvenal ion of inherited fault s.

ln fron l of the Mariana Treneh, the oeeanic lilhosphere is a lso CUI by fauhs, oblique to the trench (Fig. 3): it is covered bya thin manlle of deep oceanic sedimenls marked by the great hiatus (from Upper Cretaceous to Pleistocene) which eharacterizes the sedimentary Cenozoic history of the Weslern Pacifie (H ussong el oi" 1978: Blanchet , 1979 ; Blanchet et ai. , 1979).

The nalure , Ihe structure, the sedimenlary coyer of the subducted oceanic plate characterize the geoJogical evol u· lion of the oceanic area which is concerned .

The Middle America Treneh has been drilled down to ilS oceanic substratum which hold s up a sedimentiITY series of the same nature and age as the Cocos pla te series (Aubouin el 01. , 1979 ; Von Huene el ai. , 1980). The structures o f the Cocos pla te, examined with Ihe Seabeam, plunge under the axis of the trench wHhoul contacting the inner slope of the trench and without modifying the struc ture of this s lope (Fig. 5, 6). This confirms Heezen and Rawson's opinion (1977): Ihey thought that the ac ti ve SUbduclion area was nOie the foot of the slope but he ax is of the treneh.

Bes ides. al the level of Leg 66. a s lighl topographie feature revealed by the Seabeam survey, parallel to the axis of the

'"' ........ " ..... _., .. ~ .. -

J . AUBOUlN, R. BLANCHET

C"l" C]~ ••. •• "".",,·1,.1 Cl r .. ,·. ,. ".H ........ 1 i:.... c ..... , 1.,., ......... .1

r.:o ~ ....... 1 ... ' ·/ ... 1

Figure J l .tS 6(): Marillua /rau ste / (a//u Hl/ssoliS t/ al .. 1978). Ph )"siographic diasrl/III alld crll s/al SlrIIl"llffl! (J eross Ihe Mariana Irtllch olld un:. und /ht Morianu /r(/URh. ll'i/II Lell 60 sile loco/ions shown. Lei 60 ; Coupe des Mlir iannes (d'après Hussong 1'/ ul .. 1978). Schéma ù'organisil tion el struclure de la croÎue le long d'une coupe de la fosse de l'arc el du bassin des Mariannes : la posilion des SileS de forage du Leg 60 e ~ 1 indiquée.

Figure" SIfI/t' l ur(J1 di(JIJf(J/li 0/ M iddlt Am"ri,·u Trend. «(J/tu RtII(J rd 1'/

al .. 1980). 1 ;

Cadre 51ructural de la Fosse d 'Amérique cenlrale (d'après Renard et 01., 19!IO).

.. ,

.. •

;,

t ." .... " .. ,.,"'',,

"~,.,,, """ "' .... ", .. ... ~""'."". ,,, , .. . •• .. ...

:.. ,'~ 1

f~ ....... -- " •

" ........... " ... ' :::':~'''-\--''' .. '.-... e,. __ •

,-

" "rlf' Q Ul \ , ' •.

" " \

Figure j

" • , •. ,. --

" .,.

LtR 66 - Vil/JlfUmmUlic S"ubt(J11I nlUP und ugi/}Ilal II/llg"l.'fi,· ulUJ/II/II,ts (u/,u Rl,'lIurd 1'1 ul .. 1980).

286

Leg 66 : Carte Seabeam schématique el anomalic~ magnêtiquc~ rêgionlllc~ (d'après Renllrd 1'1 al .. 1980).

., ... " ,",*

,,~

+

Figure 6

Leg 67 - Diagramma/ic Seabeam map and regional magne/ie anomalies (alter Renard el tll., 1980). Carte Seabcam sch6matique ct anomalies magn6tiques r6gionale, (d 'aprh Renard el al. . 1980).

'- I~"_~ ... + ., .. " ... ~ D;:'~'.::' ..

ISI t::: 'o:'oo

+

french (and nOllo Ihe s lructura tion fo the oUler slope) could be the mark of the subduction ilse lf.

So, the trench looks like a series of loze nge-shaped basins separated by small ridges whieh correspond to the beginning of the horsts of the Cocos plaie.

Finatly , we must note Ihat - up 10 the fool of the inner s lope - no compressive derormation was observed.

The Inner wall of the Irenehes and the arC-Irench realm have been drilled off Japan (Von Huene e/ al., 1978 ; Fig. 2). off Marianas (Hussong el al .. 1978 a nd this volume; Fig. 3). Mexico (Moore el al., 1979. a nd Watkins el al., Ihis volume ; Fig . 4-5), and Guatemala (Von Huene el al.. 1980 a nd Ihis volume ; Fig. 4. 6 , 7) ; Ihey have been observed in submersible in the Hellenîc trench (Le Picho n el al., Ihis volume).

The drillings have reached the Upper Cre taceous off Guatemala and Ihe Middle Eocene off the Maria nas and various levels of the Tertiary to upper Creataceous in the lapan trench after hilving gone through complele seq uences in which the normill and continuous sira tigraphie succession ca n he described with the very precis ion of nannofossils.

T he fact s, observed by dri llings and in submers ible diner s lightly [rom Ihe pred ic tion of standard model s. They arc described in deta il e lsewhere in this volume.

We mention thal as for the cited act ive margins :

- up to now, no tec tonic repctit ions in the sequences

267

,,~

+

SUBDUCTION AND TECTONICS

t U TM!II ITRI! SU·l tAli

(, ..... , ............. .-.. . ' _ .. 1

UOIIAUEI liAi . ni QUI. ! ( iIQIIAI U .... • ...... K.J.M' ,"""oft.,"'.

l,",. , .. ".' •• 110 ~.""". I

corresponding 10 imbrication of tec lonic units of a prism were observed :

- the sequences , drilled a t Ihe foo t of the inner wall off Gu.uemala (Leg 67) , a re much older (Upper Cretaceous) than the sedime nts which cover Ihe oceanic crust in the nearby t rench : this contradicts the progressive accretion of more and more recenl terra ins;

- the tectonic regime is a generalized a nd active extension, 1 and not a compressio n (al least si nce the Neoge ne). T his can be observed wit h submersible in the Hellenic trench (Le Pichon el al., 1979 a and b) in the drill ings (especially Leg 60), in the Seabeam surveys (Middle America). in Ihe seismic profi les (Leg 60), so Ihis can be observed al several scales (Blanchet , 1979) ;

- a differentia l aclive subs ide nce and not an uplifting - is revealed in the l apan trench . in the Mariana and the Guatemala Irenches. It gocs wilh an uplift ing of the island arcs (The Mariana arc, Guam, Ti nian , the Egean Arc -Crete) : Ih is also contradic ts the idea of progressive accre­lion ;

- the eruptive baseme nl , when it is reached (Legs 57. 60, 67) is not from oceanic Iype , even in the so-called ' intra­oceanic' system of the Marianas wich is set up on a basement of cale-alcali ne lavas and of arc-tholeii les (bro n­zite-a ndes iles, "boninites"). Everything occurs as if the arrangement of active margins, which is observed now , was born in Neoge ne and superposed on prior lectonic evolu­tio ns. paleogene and older but having their own logic.

J. AU BOUI N. R. BLANCHET

·-1.f ~ '·

..!. .., SSW

. 1· '-.

--.•. ..

T he problem of Ihe leclonic accretlonsry prlsm , crealed by subduct ion arises

Il is also the problem of its premanency. postuiated in the models in order to structure a nd uplift the mountain chains.

l n the examples studied until now. when subduction undoubtedly works in its present position (that is to say s ince the Neogene) no rectonic repetit ions have been observed. T here is no compression but extension. the inner walls of the Irenches are not uplifted but subsided and the fOOI of the inner wall is much older. ils nature is not the same as the nature of the sediments which arrive into the Irench. Moreover, on the transect of Legs 57.60.67 there is no suffi cienl room for an accretionary prism which would have the volume predicted by the models. though the subduction could have been significan! (10 cm/yeur. 100 km/M. Y .. in the place of Leg 67 in the Middle America Trench).

ln the Middle America trench (Leg 66). sorne of the reflectors deeping eastward on the seismic profile s were

NNE

_ .

--....1!.!!.... , .. " .. ,., .. " ... " Figure 7

288

• (after Aubouin fi II I .• 1980) . A . I-4COlion of Ihe Leg 67 Iron~ec/ ; 8 . UTMI Mulrichallel seismic profile (Ladd ct al.. 1978); dn"/ll'd sile locations are illdic:ated : C. Geolagital inlerprelulion of Ihe B profile; D. CO/lceplUal diagrum for Ll'g 67 /T(l/IseCI.

(d'après Aubouin el al .. 1980). A. Situat ion du Leg 67. B. Profi l sismique muhilrace (Ladd el al .. 1978) ; la situation des sites fo r~ s l'SI indiquée . C. Interprétat ion géologique du profil B. D. Schéma interprétatif pour la coupe du Leg 67.

interpreted as the overthrusting planes of an accretionary prism. before the leg have been gone through by the IPOD drillings : in fac t , these arc coarse sa nd layers in a more silty sequence. T his stresses the fact Ihal indirect geophysic data must be cautiously interpreted a nd that il Îs necessary to have a direc t geological control as for the oceanic bedrocks just as fo r the emerged outcrops on land .

' n the same part of Middle America trench. the grading of coarse terrigenous facies - from Neogene - (these facie s being încreasingly older when going up the slope) was considered as an indirec t argument in favor of the exislence of an accret ionary prism (Moore el al .. 1979. and Watkin s el al .. this volume); every CO<lTSe level is sedimented in the tre nc h. then it is accreted and uplifted . But . no tec tonic contact has been gone through a nd e verything i~ based on the faet that the depos ît of al! the coarse turbidites occurs in the trench.

T he Seabeam surve ys in the Middle America Trench (Renard et al., 1980) show sedime nta ry basins. terraced along the inner wall ; a branche of submarine canyon opens

into every basin. So. terrigenous sediments Clin seille directly on the le rraced bas ins jus i like it was predkted (Karis el tll ., 1978). Th is limits, nllthe more. the indirec t in terpretat ion bllsed on the dis tr ibution of lerr isenous fa cies. Moreover. Ihe fiTst indicatio lls deducted from the repartit ion of glauconite _ a good indic 'llor of shallow sedimenlHlio n - suggesb .1 sUDsidence o f Ihe Mexica n continenta l margin s ince - flnd while - the Neogene , 'Ind nOI li n uplihing. But we mus t s trongl y underline Ihal ac ti ve margins are jusl heginning 10 be Sludied by direc t methods and Ihat the observed facls are necessaril y limited 10 Ihe explored regions. Whlllaboul the Caribbean (the Antillean Arc - Ihe Uarbados Ridge) in the Aleulian . in Indones ia . where Ihe interpretatio n of indirec t data ~eem s 10 indicatc a weil s tructurcd accre tionary prism ? Time will tell and we muSI consider that an accretion:uy prism may occur in sorne trenches . depcnd ing on various parameters : dceping of the RenioH zone . age of the subducting plate con vergence rate. sedimentary thickness . tectonk framework ...

Sf'~eral rcmarks can bc made as hypothesis fOf new scîenti· fic works :

a ) the presenl framework observed :11 the level of subduc­tion zones seems young or very young : the s tructural morphology seem s to take place or to bccome more m'lrked in the Mio-Plio-Quatcrnary. The Middle America trench wa~ probably born in the beginning o f Pliocene. During this evolulion Ihe teclOnic regime is lens ional with s trong .. ys tems of normal faults going with 11 subs idence ch:lrac leri­l cd e verywhcre in the studied liTe<l ;

h ) this neolec tonit: regime creates the present arrangement ~md is superposed on 10 an is land arc or li continental border wh ich has been s truc tured ail a long prior lec tonic phase) thm C'ln he seen on land : the Miocene. P'lleogene. Upper Cre tllceous (Lammian), Middle Cretaceous. Upper Jurassic (Nevadian) phases.

This neolec tonic regime may have no connection with prior struc tures. l n ilS norlhern half Ihe Middle America Trench CUI S southern Mex ican s tructures with a 45~ angle. The Japan Trench is Obl ique to Hokkaïdo Is land struc tures which \Ire bllck up to il (the Ho kkaïdo nappes are thru sled we~twnrd , lowllrds Asia). The neotectonics of present trenc hes has not necessarely genclic rela tio nship which Ihe lec to nic of the mounta in chains or of the Cordilleras edged by these trenches :

c) Ihe inner wall of the trench (whose s truc tural morpho­logy is neotectonic) is composed of the superposed lec to­nics of Ihe continent orof the lIrc along which il runs. These leClonÎç:. ha ve thcir own structures. fold :" overlhursts, nappes. The mosl recent of Ihese lec tonic Jeformations can be conlemporary wi th the subduction .

50 . it is necess'lry to care(ully dis tinguish the supcrposed tec tonics al the level of act ive margins before trying to determine the re lat ions of cause and dfeCI between subduc­tio n and struc tures.

It is possible thOiI !>Orne fea tures on the seismic profils <Ire struclures or teclonic contOiCIS (overthrust) older th:ln subduction. 50, this I<llter h,IS not originated them . Thus. a future submersio n of the Californian r:lnge would give a margin wilh as many potenti:IJ eHs lwllrd-deeping refleClors as pre-Uppcr-Eocene o verthrusting contac ts. which can bc observed on IHnd (Roure. 1979). Thus, 10!llorrow," submer­s ion of Crete would show a profil of accretionary prism­type discontinuities Iruncated by norm'II neogene faul ts.

289

SUBDUCTION AND TECTONICS

The present aspect summarizes ail the tec tonic marks of the pas to

Like in the Middle America Trench. the Cos ta Rican tec tonic bel t (N icoya-Sa nta Elena) gO in the inner wall (LeK 67) , al the foo l of which li sedimentary sequence s imilnr in logie and age h<ls bee n drilled . A s trong pos itive magnelic anomOily on the continent'II shelf lines up on to NicoY'1 PeninsuJa structures which are pre-Camp:lnian in age (Ladd tl al .. 1978). Are Ihe eas tward -deeping seismic rdlectors thc pre-Neogene o verthrus ting planes of the chain whic h oUlcrop on land ? or. are Ihese refiectoTS the great lithologic break of ilS sequence ? The same remark can be made llbout Oregon and Alas ka profiles : samples of Upper Cretaceous age have been collectcd there by dredgings (Von Huene el lIl .. 1978).

On the contrary one can note thm many compressive struclures marki ng the l'lio-Quaternary have no connection with a chnracterized subduction context : Ihe Los Angeles bas in . the Northern-ens tern marKin of Venezuela or. even more . in a coll ision conlext , in Ira n. India ... ;

d) subduction and compression , subduct ion and accretio­nary prism may not be sys tematically connected. On the contrary. il is necessary to wonder welher on bath sides of the major lithospheric o verlhrust shown by the Benioff zone the IWO plates. yet s truc turcd by their prior own e vol ution, essentially react in an ellOtens ive regime, the down going plate falling into the subduction zone while the upper pla tc follows this dipping by tensional faulting and subs i­dençe ;

r.) but it is poss ible thatlln accretionary prism might he built up by subduction in now unexplored regions. To be certain of that we mus t basc our investigations on direct dala -suc h as drillings and submersible observations - analyzing the superposed tec lonics of thcse regions. Any other approach would leave doubts : the s truc tures (rold and overlhru~ ling) of an inner wall are not necessari ly ge nentted by the subduction in the trench. Intra-plates tectonic deformalions can occur there or e lsewhere. and only the knowledge of regional Icc tonics can guide the interpreta­tion.

PR ES ENT AND OLD ACT IVE MARGINS : (PALEO) SUBDUCTION AND TECTONICS IN MOUNTAI N C HAINS

Since 1%8. the plate· teClOnic Iheory has becn creating new concepts about the mountain building . A s ignificanl number of modeJs has been published about ail the chllins in the world to make the goedynarnic e yolution visible by USillg platc-tectonics.

This profusio n of conceptions hllS been generally positive : but the wrong s ide of this success is Ihat unavoidable supposit io ns and has t y s implifications concealthe complex relility : and when only indirec t Inrge-scale data are taken inlO :account . il lead s very often to an explanation for a geological problem po~d in nnothcr dimension.

Considering that : ophioli tes charac terize old oceanic c rust ;

- subduction builds up a tectonic accretion;ITY pris!Il ; - subduction carries lithosphere mliteriliis down 10 s ignifi-ca nt depth, it can be inferred thal the c hains with ophiolites ( << paleo-oceanic ,.) firs t take the shltpe or tectonic accretio­nary prism ; if the process s tops then . they a re genemlly

J . AUBOUIN, A. BLANCHET

ç'l lled • subduccion chains _. if Ihe process ends wich the coll is ion bclween IWO continents , chey are generall)' calJed .. collision chil ins _. In both cases. subduction is Iho ught 10 have cenrated the blue schist facies (high pressure metamor­phi ... m ) .

TorJ;IY. to Ile accumte . onl! can o nly use cleatl)' de monslm ­ted da ta for present subduclÎon 10 explain old subductions. 50. we know precisel )' the seismie c harac teri ... tics of present subd UCIÎOI1S : Che e vidence of a major tectonie contact :tl lhe foo t o f Ihe treneh has bee n demonstra ted b)' the Sreat diffe rence of the se r ies in the tre nch ,Ind in thc continenta l mars in (Leg 67); the spat ial connection with andesit ic volcanism is obvious whc n one studies the loca tio n ... of vokanis rn in the western parts of America s , wi th the break fro m Middle America to Oregon a t the Icvcl of the Ira n ... -form zone of California . We can even hope. in the near future. the dr ill ing of the subd uction co nlac t (see lI oove . p.21'l.5).

Ilui . in the near fu ture. wc will probably he unable of drillins ;nlo the depth'i where blue schis is formation is suppo ... ed to take place : this la 11er is connected 10 subd uc­t ion lIccordi ng 10 the interpretMÎon of p'ileosubd uction zone .... Thcre il' no actual is tic refere nçe to high pressure melamorphi ... m : ib connecl io n with paleosubdu\,: l ion s is based on a pure geoloSic argumenlation.

So. present ... ubduction markers which can he u ... ed to think aboul Ihe pas t are only Ihe s trong caJcalcaline magmatism lInd Ihe lec lonic COnlact of a vulcanized lInd gr:lOitized continental margin overthrUsled upon oceanic ~ed imenls Iying on oceanie c rust. But. calcalca line magmatis rn ;mu a lso the conlinenl-oce;m contac t Clin he ro und in o ther conte XIS (whieh a rc not p.aleosubduct ion).

W c ca n sum up h)' li quick overview o n sorne ex'Jlllples or c hain~ :

Figure ~ Cm u SI'Cl iQ II of /III! Ditillfides 111.11 Ba /kali II/pilll' c lra ilu (a/ rer Allbol/ lu (1977)).

Cuupe dt: 1:, chaîne (,Jpmc Jc~ l)mllTlde~ au:\. OaJla n~ (t.I ·a prè ~ Aubouin . 1977 ).

••

• , -,~<~~ .. ~.: .. '.:' //. ~ '. ' .

~~ '. ' . - . -, l 'w Ir

1 /

o -." ...

10 Che Ml'diCl' rrarwan IIlpine domaio

T eclOnic bel l;; re .. ult rrom collision. a~ Ihe me re chronolos)' show), (Fil:. 8). So. we mu~ 1 look for subduction in older s tages or their his lory (c .g. JUnlssic). The tec tonie f rame­work . reveab thal Ihe major colli~ion with contine ntal blac ks occ urs in Ihe late Jurassic in the Hellcnides and Ihe Dinarides (Aubouin f t (11 •• 1970 ; Aubouin. 1976 : Blanchet. 1974) and ma)' be in o thers parts of the Alpi ne bell. The paleosubd u\,: lion is older than Ihe coll ision (Fig. ':1 ).

ln the loc,ltions (such as the Ege~tn Arc) where a subduct ion is ac t;ve today, rlil the struc tures. prior to the neotec to nic. result rrom the collision wil h li continental block in Mc~o-

1:oic and car l)' ccnozoic ti me : a t Ihe bas is of the pile of nappes rcsultin!; from the collis ion Ihere a re se ries wi th contine ntal "a~eme nl (A ubouin. 1977). Ever)'where in the domain born of the Tcth)'s. the collis ions play the e~sential role ; Ihe ~ ubd uc t ions precede or follow them. Il is nOI in the Tcth )'a n domtlin thlll the tcc tonie role of Subd uclio n will he casil)' and co nvincingl)' uetcrmined .

Til(' C~Hrurnia n domnln . appltrentl)' more favour..t ble. docs not sugges l bener conclus ions: Ihere is an carl y coll is io n with contine nta l fraSments. these collis io ns being associa· led or nul with Ihe s rea t tr:lns lalio ns revealed b)' pa ieollla­gnetism (J one~ et (II .• 1977).

The chain . as it can he observed in California (Bailey et al .. 1970) a~ it eX le nds sout hward in sout hern California (J oncs. et ' II .. 1976 ; Gastill et al .. 1975 : Rangin. 1971'l) and in Ihe North in OreSon (Roure . 19KO) re ~uhs fro m many superpo­sed tcclonks SÎnce the J urassie. the most rece nt C VCIlI

rewnrking ail the rreviou~ s iruel lires .

. .. L~" " .,

"-/ 1 oZ::'"

" ,." , .......... ~·"'"·.·c· ,'--------i',:, ::-. IJ.I0\

11~ ... rc 'J

A pultoJ..x·"ul lO/-:rllphic modtl for l itt Dîllarir Alps (afltr 8/llIIchel . 1977).

" \, ff ,-,.. ~.

" •• - • .......,...,. ',-=-•• "

. .... 'i,'-,.. •...

290

, Modële p"Jéo-océanollrll phiquc pour un )CClc ur uc~ Alpe, 1)1R:lTlque~ (d 'a pr,,~ Blanchct. 1977).

The major compressive phases (oCten with overthrusting and nappes) are Upper Jurassic (as shown by the disconfor­mit y of the Lower Cretaceous in Baja-Calîfornia a nd the age, about 150 m .y., of the blue sc hists reworked as exotic blocks in the mélange in California); Lower to Middle Cre taceous (as shown by the disconformity of Campanian Maeslrichtian in Oregon) Upper Cretaceous - Lower Eocene or even younger (as proved by the age of youngeSI unit of the western most Fr;tncisea n).

Today. the basal contacts o f the westward overthrust nappes are late contacts: in no way they can rcprescnt the simple primeval contllCts of an accretioOluy prism. Th is is the case of high pressure facies unit s which a re overthrus ted on sedimentary units much younger than the age o f thcir metamorphism : whatevcr the point of vicw from whieh the COntact is looked at mlly be, it cannot be li subduction.

When the supcrposed tectonics have been made out, one can propose fi geodynamic model such as in southern California (Ra ngin, 1978) where one can recognize (Fig. 10) :

- a paleo-oceanic evol ut ion frolll Upper Triassic toJuras­sic . A smalt oceanic basin (ophiolites. ntdiolarites) is bordered. to the East, by an act ive island arc whose oUlcroping volcanic materials and volcanodetritic sed imen­tary consequences are known . ln such an epoch an ellStd ip­ping suhductio n might expla in this magmatism ;

- a period of collisio n beginning in Upper Jurassic: H.P. metamorphism dates back to Lower Cretaceous (so it is diachronous with the subduction) :

- from the Middle Cretaceous, hypen;ollis ion generates overthrusting which form most of the Cont,lCts which C,m be seen today :

- a neogene cutting up into horsts and grabens and the Plio-Qualernary opening of Ihe Baja California Gulf arc superimposed 10 prior lectonics,

Thus, this example enables 10 diffcrcnciatc (palco)­subduction (Upper Trias, Jurassic) and tectonics (polypha­sed from Upper Jurassic to Paleogene) before the reworking of the whole structure by a neotectonic phenomenon.

Figure 10

SUBDUCTION AND TECTONICS

The Carlbbean domaln whcrc the conditions fo r a pure collision do not seem to be realized today was nevenheless Ihe area where collis ion took place in the Upper J urassie when. for the fifst lime ophiolitic nappes were set up (beforc bcing reworked laler).

The geodynamic mode!. recently proposed (Beck et ,II .. 1979: S téphan et al .. 1980: Bell izzia el tll., 1980) emphasi­zes the paleo-ocelomÎC and tec tonic s tages of evolution .

Taking into account the present a rrangement of the chain. il has been necessary to backlrack the lectonie framework (Fig. 11) and to replace the tec tonic. magmalic and meta­morphic events since Jurassic, according to a timing impo­sed by the fa çlS.

Thc pareo-oceanographie stage is Lower to Middle Jurassic and there is no clear evidence of subduction. Suture. obduction and coll ision took place in an early phase during Upper Jurassic - Eocre taeeous. H.P. melamorphism is considered 10 be Eocretaceous and, seems 10 be conlempo· raneous with olxluclion and collision. rather than with subduction.

Many hype rcoll ision phases took place in Upper Cretaceous and in Terliary ; additionally there were tensional periods and megafolding.

Tecto nies. from abduction lmd suture (U pper Jurass ic) until present day is permanent: the role of subduction at the moment of the oceanie spreading is not yet fixcd. Once more, the tec tonic contacts cannot represent the simple prime val contacts lied with a subduction .

EVOLUTION : FROM OCEANS TO MOUNTA INS. AND T HEN TO THE OPEN ING OF NEW OC EANS

One can make out the superpos ition of many tempotll l s lages in the building up of a palco-oceanic cha in between its continental edges.

DeMy/ramie; model for ,l,e jurlJ,fsic-creluceouS e\'o/ulion uf 8«j«·Ca/ifurnia (u/ler RI"'!;in , 1978). Modtle géodynamique pour l'évolution jurassique CI crétacée de la Basse C:difornie. Mexique (tl 'après Rangin . 1978).

P 1'1 n ~' ''''' · ~L~'~

~,*.,~

~~iw

291

J. AUBOUIN. A. BLANCHET

",f , ..... "t"

The st~l.oe of the oce~nk (paleo-oceank) basin

Fo r Alpine chai os the oceanic hislOry is as old as Tria:.sico­Jurassic (200-140 m.y.). T he markers arc ophioli tes which may represent the former oeeanic crust (Allègre CI al .. 1973; Coleman. 1977 and Rocd. 1980). Sometime~ thert is .. large ocean, sometimes there are small Ot:canic ba~in~. marginal basins. with continenlal margins. passive and active.

The sc tt ing up and the evolulion of paleosubductions mu:.t he looked for in such l' stage. The mOlrkers arc calcalcaline magmatism on continental margins or arc. and voka noclas· tic sequences in sed imentary series. They can be S1udied ma inly in the chains where inner zones and back-Iands out-crop (c:. lifornill. Dinaro-HellcniJes. Southern Asia). If an accretionary prism is buil! up by ~ubJuction. it musi bc looked for in such a stage, as weil. But ~u(;h a pri.:.m has problably not las ted until now wilhout changing. Thi.:.. becau:.e of :.uperpo:.cd tectonics, because of ~uperpn~ed metamorphisms and of hypcrcullis iun processcs characteri­zing inner zones.

Moreover. is not there fi funJamental Jiffercnce betwecn the great ocean subductions (whieh are in faet particular ca~es of opening having succ.ecdcd ) lLnd .:.mal! oce,mi.' baMn :.ubductiun)? We think IhlL! marginal b •• ~ins and ~mall

oeeanic basin ... could be Ihe rcal mode!:. wc can apply lU Ihe palen-oceanic zone~ of the chain:. {Blanchet. ]977 : Le Pichon. l.ilanchet. 1978). They ,Ire the uni y une~ whit:h (;an gencrate a pift: uf nappe, (i ncJuding eleillenb ,)f \KeanÎç cru't) hy collision between a cOlllin<:nt ltnd an i"land ar~' which lirni!" the"e hlock:.. Wherea~ the f~Lle of the large ocean is probably to disappear in the permanent ~ubduction. like in Ihc Andes Cordi ller" (,tpproximatdy "in..:c:::!O m.y. Le Pichon. Blanchet. 1978).

Thus Ihe Pacific is a key domain for understanding the chains wilh its twO Iypes of arrangement :

- in Ihe western PacifÎ\; the overthrusts :lrc towards the contÎnent like in the periaustralian ophiolitic çrown (Aubouin el ul .. 1977 a) : in Ihe continuation of the Tethys they mighl provide a model for the Alpine ch(\in~ derived from the Tethys. This type can also he found from

292

""".

Figure Il Geodyuumi(' Mode/for Il.e Smllh CUfibbeuu bell i" Ve"e~"f/u (ufler Hel/i:~i(l el a/ .. 1980). 1. JIlfl/SSir (l''O .... (r 10 Midd/e): (>ce/mi< ope",'ns of Ihl' Tellly.t. 2. Uppa lt'fIUSh" - Ln ... ·l'm".))1 ('reta­reolls : SlIllIr e. ubd.lt'I;on. (·O/liS;OIl . J. A/bitm 10 TUfOtLiau." Ope,IÎnll uf Ih f caribvfall bl ... ·i"..... Paleo-IJn'<IItf18rupl,i(' reorgallÎSmÎQlr . 4. Un ... 'f S<,uouia'i ." Comprnsil)/l. 5. Upper Semll1iull ." E.rlt,uiUlI ; ("ulco/ca· fj/!(. lIIagmmism. (,. l'u/eocellf _ Eoel"ll': Comprl'ssiQ'I '­V\·alh",sls. 7. Upper EtJ{"(",e - 10 P,esrlll : < 'omfl,e~-510lls (md e.~lrllsiO/I$ : Il''I/s/;'I[.I. II/r[.lafu­Id;'18. !Ulllliuil. 8. Diugramlllalic cross sU' lilm lib (9). 9. Sm"'/urILI diagfllm !rum Ihe SI/it/h Car ibbe/lll (afur SU/Jlrw, el al., 1978). Modèle géodynamique pour la chaîne Sud Caraïbe au Vénhuéla (<J'upri:~ Oelli!.!.iu el III .. 1980).

Hokkaïdo 10 S;lk h"line in the Nurth-West and in Taïw;1Il in the Centre.

- in the North Eastern PlKific. the ovcrthruslS - at least Ihe recenl ones - arc IOward the I)acific like in Ba ja Cal ifornia. C<tlifornia and Oregon.

We can nOie that the continental ffleing :.y~ten1s afe siluated in the close vieÎnily of the contÎnental masse~. ur separetcd from them by seas originated from pure o!xlen~iun (like Tasman !!Iea. for cxamplc) and always limited on the oceanic s ide by olher mar,!: inal ba:.ins and not the subduc tion of the Pacif ie: the Pacifie ibo!!f b never ùriflcd towards the conti nent.

What are. for example. the temporal evolulion of south China Se .. :Ind of the Manila Trench '! What i5 the ~pati al lransition from the South China ~ea-Ma nila Trench­Phil ippine ~y:.tem to Taïwan ,lOd Ryu-Kyu 'J Thi ~ i~ a key-area in the globe to beuer under:.tanding Ihe forOl~Ltion of chains (R. UI 'mchet. 1'J77).

The end of the Ol'tan ÎC t' \'olution

The fir~t lectonics take pla~'e when the whole ~y~tem get ,( compressivc rcgimc : the oceanic crust is sliced up in large unit ~ which arc overthru:'lcd on the continental margin (Iethian or alpine-type collisiun~). or on bland arcs with continental ba~ement (Cal ifurni,m Iype eolli ~iun) ; the O\'er­Ihr ust of ophiolites is, a t li chaine-scale. the grer.t carly tcclunic phase which generate~ in the basÎn ~, sedimentary sequence:. w;lh bluck:. (mélanges. olistoliths, .. séries 11 bloc~") by reworking Ihe ophiulile sequences of thc o ver­thrusled Unil ~ (diabase-radiularile:. form'H Îon. in the Dinari· des-Hellcnides. mélange in California. ~ome uf the" :.çhi~­te~ lu~trés" unit:. in the Alps, :.cries wit h blocks in the Caribbe,tn chain). Thi~ overlh ru:.t of Ophiolite!> WH) called obd uclion (Coleman. 1'J71). I f we wallt to u~e the word "ubduction", it i~ to mean an oceanÎC overthrust or charriage due 10 the (;ollbiun of a continent wilh a block that have slopped a previou~ ~ubdudiun . thi!> word can .. Iso be u~cd ~Imply tu 111<,,(11 "Icrlhru,t "1 d l.Jrrt,'gc •• t ophIO­lite,.

Aller the suturlltion ( Ihe oceanic SUl unll ion can occur as m:l ny times as the num ber of oceanic spaces to bc sutured) the collision gocs on, and by many compressive phases , sl ices up the oceanÊc series. the margins (theÎr basins and their floors) into units overthrusted twiee, three times or more, and pilcd up by fiaI shcaring or by" décollemenl ".

A fl a t crustal shearing of great magnÎ tude gencralJy rcworks the bclt during hypercoll ision. generating Ihe mosi apparent horizontal contacts . The mos t spcctacular hypercoll is ion resuh is the Himlilaya (Mattlluer. 1975) : the eaSlern Alps arc another example. But Ihis phenomenon is quite general (Aubouin et (,1 .. 1977 b: Auboui n . 19KO).

Finall y. wide fold s or swells set up in Ihe late phase , frequently generating the most cvidcnt Ch:H;lctcristie fealU­res of Ihe chains: it is the ct,se in the Alpine chaines originated from the Tethys where - except in the Himalaya d. supra - the highesi summils arc always situaled o n such swell ings .

The chain may be reworked by tensional lec tonies crealing basins. crus tal thinning (Basin ~ I nd Range. pannonie Basi n, eircum alpine fault SYSlem). Sorne o f them ma y succede p ~, rt ic ula r ly weil and generale new small oceanic basins (the Gulf of California. Ihe weSlern Med iterranean). Such an e vol ution may have happened in various epochs : Ihus. Ihe se!l ing up of the C[,ribbean bas in in Middle Cre taceous ( .. bout 110 m. y. BP), after the subductio ns and collisions of the late Jurass ic and of the Lower Cretaceous. has certa in s imilarities wit h the fo rml.tion of Ihe Mediterranean sel!.

CONCL USION

T he 11>00 program has e nabled us to gel direc t dalll o n ac tive murgins, for the firs t lime . The drill ings have provided new fa c ts wh ich are yet parti y obscure but thm mus t be I<Lkcn into accoun t before any general isalion. If the fe is .1 tectonie accretion;lry prism on the d rilled margins it is necessarily more limi ted than on the classic model s. Ii seems thal on these drilled margins the general regime resul ting from subduction is ex tens ion and not compression. subsidence and not uplifting. The Subduclion ~cem~ to be the fundamental gcodynamie phenomena . al the dime nsion of the lithosphere. marked by the overthrustingof one plate on :mother one. Secondary phenomcna resull from subduc­tion : such as the subs idence of the margin in exte nsive regime . making the tre nch look like a graben. According to our present knowlcdge. the formation of an aecrct ionary

REFERENCES

The biblio~r .. phy on Ihe subjecl h very lar~e. l'he clle<.l referell(:e~ ,t re ju~t an inlroouction. A mure complete bibliol;f'tphy ean be round in Ihe v:trious "rliclcs of this \"olume.

Allèll:r~ C. J ., Montigny R., BoWnJ.:a V .. 1973. Curtèllc uphiolitique ct eorte~e océ;oniquc. géoch imie "urnpar":c ct flUx.lC <.le J;enèse. IJul/. 50,'. Ciol. Fr .. 7. I.S . 461 -477. Aubouln J .. 1976. Alpine tectonÎcs and plaIe leclunic~ : though., about the (Eastern) Mcdilcrranean in : E,/rutl .. j",,,, C ru )'/ /0 ClIf ... edited by D. V. Ager and M. Brouks. Lum.!on. Witey, 145·158.

293

SUBDUCTION AND TECTONICS

prism does not seem compatible with these data, in the dril1ed areas : each plate has its own deformations. ilS superposed tec tonics and ilS geologic evolulion. When studying act ive margins we must systematically carry out reseurch in regiomll lectonies on the a rcs and at the same time on the continental borders.

As regards mountain belts . chains such as California , the Alps. the Caribbcan. for example. were saon eompared with acerc tionary prism model (precise ly taken up in the Pacific). When analyzi ng superposed lectonies. we eun determine the role of each tecronie phase in the forma tion of the belt bcfore Ihe role of paleosubduclions can be cons idered . The observed tectonic contac ts a re generally laie and. thus. Ihey eannot be compared with the possible carly contac ts of accrelionary prisms resulting (rom subduction. Il is more and more admited tha t bluesch isls arc in several chains, synehronous with leelonie ph:lses, neeessari ly younger than the possible paleosubductions. So. wc e:lI1nol take the teetonie accretionary prisms of the chains as a referencc: to just ify thelr exis tence in the oceans.

And , vice versa. this paper can be ft program for further researeh. nOI an eSlablishcd conclusion. We must develop rcsellr" h ln present day oceans, o n active margins. espe· ciall y on Ihe IlIrgc areas which arc not yet drilled and in the more eomplex small oceanic basins {marginal bas ins in the wcsle rn l':u: if ic and in Ihe e:lstern Mcditerranea n).

Acknowledgcmenrs

The above remarks are based on many works fu nded by various organisms. We partic ularly thank :

- the Ins titut National d'A stronomie el de Géophysique ( INAG) which . by the ATP " Géodynamique ". has enabled us la seil le the progrllm .. Americlm Cordilleras" :

- the Cenlre National de la Recherche Scientifique (CN RS) which look over (ATP/IPOO. RCP American Cord illeras) :

- the Centre Na tional pour I"Exploitation des Oeé:m s (CNEXO) lmd parl ic ularl y the Centre Océanologique de Brelagne (CO B) whieh have granled the work on active margins and on Caribbe ~m :

- the Ins tit ut françai s du Pétrole (IFP), Geological Dcpar­tment. for fru it fuI discussions.

Finally. many d i scu~s ions with the ,lUt hors of this volume, section ac ti ve margins. ha ve enabled us 10 oblain Ihis defini tive le xl.

Aubouin J .. 1977. MédÎterranée oricutale et Méditerr~née oceiuen­talc: esquisse d 'une eomparai~un o..Iu caure alpin , Hull . Soc . Gi ol. Fr .. 7. 3. 19. 421-435 . Auhouin J ., 19HO. Oc h, lectonique ues plaljues à la genèse des ch:tÎnes de montagnes . Livre jubilaire de la Sociélé de Géologie de France. 1830·1980 . Mi",. Il .• )'':'. Sm:. Ciol. Fr .. 10. 163-180. Aubouin J .. M:ollauo:r M .. AII,,\:ro: C.J. , 1977 u. La coumnne "flh,,,IoIl<,U,' [l'" '.""1 ... ,10""'1<' . un ..:h •• rTl.,~" "..:c"n'qu~ r~prc'''nt:Ollf des stades précoces de I"é\"olution :tlpine . C. R. At·I,d. Sei. P;,ris. sir. D . 285. 953-956.

J. AUBDUIN. R. BLANCHET

Aubouln J., Blanchel R., I.abes.w H .. Wozniak J .• 1977 b. Alpes ocçidenta1cs e l Alpes oriemales: la zone du Canave~e e,\btc+ elle? C. R. Summ. SQ<". Géol. Fr . . J. 15$-1511.

Auoouin J .. Auma, J .• RelUlrd V .. Slcllhan J . F .• 1980. La fo~~ ... d 'Amérique: centra le: données tec loniques nouvelle~ is~ue, de~ forage.~ lPOI) et d ' un le,·e r du Jean·Charcot au sondeur muliifai~ ­.:eaullO (Seabeam), C. R. SOIllIll . . ttH:. Giol. Fr .. 5, 186-190.

Auoouln J . • Hlanch~1 R .• Cadel J . P., Criel p " Chan~1 J .. Cl>oro­... k?; J .. Cousin M .• RampnouJ; J . p .. 1970. E)!>i$i )ur la l>~oIOl!iedes Dinarides. Bull. 50<". Cioi. Fr .. 7, 12 . 1060-1093.

Aubouln J .. \ 'on H~nf R. , Az~ma J ., Coulbourn W. T .• Co .. ·an D. S., Curiale J . A .. Dengo C. A .. Faas R. W .. Harrison W .. lIaw R .• Ladd J . W .. Muzil« N •• Shikl T., Thompson P. R .. Wf:!i1herll J .. 1979. Premiers résul tats des forage s pr"fond) dans le P. .. ci fique au niveau de la fosse du Guatemala (fosse d 'Amérique centrale). Le i: 67 d u Deep Sea Drilling Prolec!. m<li·juin 1979. c.r. Ilc(ld. Sei. Parb . Sir. D .• 189. 1215-1220.

R~lIey F.. Il .. 81ake M. C. Jr. Jones 1) . L .. 1970. On-land mesozoic oceank c rus t in California Co.1St mnlle). US Geul. Surv .. Prof. l'a/'l .. 700c. c70-cgl.

lk.ock C •• Iklliaia A .. Blanchel R •• Siephan J . •..• 1979. The Caribbean chain from the Paçifie to the Atlan tic. 4/h I~/II.-AIII. Geol. Con~r .. Trinidad lIod Tooogo. 7-15 Jtdy 1979. in press.

8ellluia A., Blanchct R .. Reet C .. St~plulll J . .... 1980. La chaine cllrllibe du Mésoloique il factuel : TeetoGenèse et modèle d ·holu· tion lléodyn.amique. If riunion AIIII . Sâ. Tuu . Marseille. 34.

lJiju-Ouvlll IJ .. LtlOuuy J ., Montardel L .. 1979. Variety uf margÎn~ and deep ba~ins in Ihe Meditcrranean. in : Geological and Geophy. sical in"e)tig:lIion uf contÎntnUlI m:lrgins. edited by J . [). Watkins. L. Montadert and P. W. I)id;er~on. A /\PG. M em .• 19. 293·318.

BlAke 1\1 . t:. Jr . J olWS U. L. , \974. Drigin of franciscan me\ange~ in northern California. in : Modern II n(] tllleient geosynclina l se(]imen. t<l tion. editcd by r. h . jr [)Olt and R . D. Shllver . SEPM SpiC. Publ .. 19. 345·357.

llIanchet ~ .• 1974. De l'Adriatique au Ha_sin Pannonique. E~ ..... i d 'un modèle de chaine alpine. M tm. Soc. Giol. Fr .. UO. 1-172.

IJlalK'hel R .. 1977. Bassins m!lrginaull e l Télhy~ alpine: de la marb'e cont inen",-Ie au domaine océllnique dans les Dinarides. in : J,, /emlJ' IW,u.1 Symt><>ûlJm "" rh .. nrtu; IU",1 "iUQr}' of rh .. M"li,.., m""", bluins. Splil ( YugosIOI·ia). 2'-29 OCI. 1976. edited by B. 8iÎu ·Ou ~al !lnd 1.. Muntader!. Ed . Technip. Paris. 47-72.

IJlaDchel R .. 1919. Océans actuels ct océllns ancien~. 8ul/. s..,c. Giol. Fr .. 7. 21. '15-663.

Ulanchel 1( ., Il usson!; D .. U,etta S. ~1 1'fqul l)f scientifique du LeI: 6(l OS!) ... . 1979, Un profil complc t d 'une marge act ive de I"Oue~ t Pacifique: le système de~ Mari<lnncs. LeI.! 60 (DSt)P). Hull. Sor. Giol. Fr .. 7. 21. 529·532.

Boo;-ca lelll M .• Ellcr l' .• Guau.onc Il .• 1971 . Plate tectonic models for the dc'clopment of thc We<oh:rn IIlp~ .. nd Norlh<:m Apcnmne •. NIJ/. Pllys. Sei.. 234. 108-111.

Cukman R. G .. 1971 . Plate teelonic emplacement o f upper mantle peridotile along continental !:dges. J. Grophys. Rn .. 76. 1212·1222.

Coleman R. G .• 19n . Oph/n/ius. Sprin"er Veria". Btrlin-New York. 229 p.

C,-amtll Sc:itntilic Tcam. 19i10. I"irs t mllnned . ubmcnible divts on thc Ea~t Pacifi c Rise : gencral rc~ults. M ur. Gtvpltys. Rf's. (in pre,,).

Ik .. '~y J . F .. Bird J . M .. 1970. Mountain bdl) and the new tllob<11 lec!onks. J. Gl'up llys. Rn. 75. 2625-2(,47.

Oickinsun W. R .. Seely 1). R .. 1'J7,) . St ruc ture and ~tmtii:r .. phy of lore:lrc regions. AAPG 8,,1/ .. 63, 2·31.

Ernsl W. G .. 1')70. Tectonk Clmlac t betwecn the Frand)l,'an mclange and lhe Greai Valley Sequence. CruMal e:o:prehion of li laie MeSOloic Benioff lone. J. Gtophys. Ru .. 75. 886-901

Ernst W. G .• 1975. SystemlUic of large-.cale lectonics and age progressions in alpine and circumpacific blue schbt bell§. TtrIOIIO' physÎcs. 2:6. 229·246. Fr~nrhete.u J. , Julcau T " RanKln C .• 1979. Ba..al ti c pillars in the collllpsed lava·pool~ on the deep·oeean floor . No.wrt.181 . 5678. 209-2 11. (:astill G .. Phmp~ R . ... " Ailison F. . C .• 1975. Reconnais5.1nce geolol:Y uf Ihe state of Baja üllifurnia. Gcol. Soc. Am. Mrm .. I40. 170 p.

294

H"-,un IJ . C .. R,,"'sun ;\1 .. 1977. Vi~eua l obsen'alinns of the sell . rloor .uboJuction line in the Middle America Trellch. Seitllrf'. 196. 423·426.

HUMang 1)" Uycda S. And the I.eK 60 Sc:lcnlilk Party, 19711 . LCI! (,0 ends in Guam. GeOlimu. 10. 19-22. J UTM!!; U. L .. üluke M. C. Jr , K" nlltn C .. 1976. Thc four lurll)~k bc lt ~ of Northern Clliiforni" and their significance to the lIeuluay of the SoUlhcrn California borderlaod. in : AsptclS n/ IlIr 1If()/o~ic hislvry vf litt Colifurniu co",in~nlul b<lfdl'rl(.IOd. editcd by O. G . Howell. AA I'G. Pacific Secl . . Mi~c. l'ub!. , 343-362.

Jones D. L. , SlIlwrllnl N. J .• lllilhouse J. W .. 1977. Wl"lIngellia li displaced ternlne in north western North America . (il/! . J. Eurtll. Sr; .. 14. 2565-2577. "'a r llot D. E .• 1<;174. E\'olufion of arc systems in the western l'acinc. Ann. Re ... EOrlh /"fontl. Sei .• 2. 51-75. "'arlll 1>. E .. Sharman G. F. III. 1975 . Sudduclion and acc re tion in trenchcs. Geol. s..,c. Am . bll/l . . 86. 377-389. KarlK D. E .. Card,,"cll K. K .. Moore G. F .• Moorc D. G .• 1918. Late CenOlOÎc subduct ion and continental mar!!:i n lruncation alonl: Ihe nmthem Middle America Trench. Cf'ol. SIIC. (lm. hlll/ . • 91, 421.432.

LlIdd J . W .• Ibrahim A. K., McM ill~n K . J . , La tham f: . V .. Vun HIlfIK' R. E .. Watklns J . S .• Moore J . C .. Wonel J . I.. , 1979. Tectonic5 of the Middle America Tranch. orrshore Gualemlila. l n/cr. symp. 0/ CII(l/f'nrUIIl. ElJrlhqllukf' o.nd Rtcnnsl . Pmrf'ss .• GIIQ/tmala Cily.

lA Pichon X .• 81ancllf t R .. l m. Whcre lire the panive m<lrllins of the weSlern Te lhys Oce-an 1. Gro/u~y. 6. 597-600. f...,e Plcbun X . • AnJ,'flkr J . • Aubouin J .• Lylwris N •• MunIIS .• Remlrd V .. Got J .. Hsü K .. Mari Y •• Mastle J .• MaUIIf .. ·s 1) .. Mitrupoulos D .. T.so llias P .• C hronls G .• 1979 Il. From subduction to transform molion: a Seabellnl )urve-y of the hdlenic trench ~y)Iem. Eurtl, P/(IfI('I. Sei. Ln/ .. +1. 44\.450.

Lt Pichon X .. Angellcr J. , Boulin J .• Burcau 1)., Clldtl J. l' .. I)(>rwurt J .. Ghlcun G .• Gut J .. Kllrla; D .• Lyberls N., MllS<le J .. Rlcou 1. • • : •• Th ~haull .... 197'i h. Tectonique ac tive dans le fossé de subduction hellénique : observations par submersible. C. R. AC:/Jd. Sei. Pnris. ~'ir. D. 289. 122~·1228 .

Mall lluu .\1.. 1975. Sur le nlécllni~me de la formation de 101 ",·histo~ilé dan) l'Il imlilaya. Eu"h. /"fllnll. Sei. LtI/ .. 28. 144· 154. Moore J . C .. Watklns J . S . and Lcg 66 Sclenlille Pa rty, l'iN. progress;'·e lIccretion in the Middle America Trench. Southern me .~ico. Nil/urI'. 181. 638-642. Rliogin C .• 197H. Spcc ulalh·e model of MesOlOi" geodyrtllmics. centra l BaÎa California 10 North-ells lern Sono,.1 (Me"ico). edi ted by D. G. Ho .... ell <lnd K. A. Mac,Juull,,11. So(". EnJ/l. PIlIt'lJfllfJ/. Millcr .. Meso1.Oic Sympo~illm. 115·106. Rt' nard V .. Aubouin J .. Lunsdale J'., Stephlln J ..... 1990. "'renllcrs résult <l ts d'une é tude de 1<1 fu.~e y'Amérique cen"<l le <lU Mmdeur mult ifaisceaux 1Se;lbeam). C H. Arod. Sei. Pari~ . ~ér. 1). 291. 13 7-14~ .

Roo;-cl G .. 19!ro. Ophiolite~ 110 : une formation géologique éle .. ee au rang de marqueur géodynamique. Livre jubilaire Société de Géolo­gie de- Fr .. nce. Mim . h.·sir. Suc. 0101. Fr .. 10. 39·50. Ruure F .• 1919. Un profil géologIque dans k~ chailK~ de f'UueM américain (Californie CI Sud-OUCM Oregon) : dis.cu~)i<ln d'un modèle de paleo..ubduction. Thist dt lp«ilJ/i/i. Paris. 1979. 193 P Kuure .... 1980. Un profil tléolQgique dans les c haines de l'Oue.t ambic:lin. ](1 Cu,,~r. III/I'r. Clol . . Paris. abstmct. vol . 1. 31'14 . Sc:holl 1>. W .. Marlow M. S., 1<;174. Wohal teetonk, :wd th~ sediments of modern nnd lwdcnltrenches. Sorne diHerent interpre· t<l t ions. in : PI3te lcctunics. assessmenlS and reOlssessments. edi ted by C. F . Kahle. AAI'G Mf'III .. 23. 255·272. Stephlln J. F .. 1kck C .• Ikllitill A " IJlllochel ~., 1980. La chaine Caraïbe du Pacifique il l'At lOlntiquc. ]fI Cong,. (II/f'r. Giol .. colloque CS. Mim. HRGill . 115 . 38-59.

Sugimur'll A •• U,-cda S .. 1973. hlaod Arc • . lapan and ih environs. in : DfI"clopmf'nls in IItOIfClonlrs. V. 3. Elsevier. 247 p.

'·on II I.>fIK' K .. NlISu N. CI al .. 1979. Japan Treneh trlln..eeted . Gf'l/Iimf'$. 23. 4 . 16-20.

"un III1fM R .• Moore G. W .. Moore J . C .• 1979. Cru~~ ~ecl ion of Alaska Penin~ula-Kodl.,k hland.Aleuti;!n T rench. Geo/. SIIl' . Am . . Map and Ch3Tts. Seric, MC-2I1A. sc;!le 1 : 250.000.

'·On lIuenc R .• Aubouln J . liai .. 1980. !ci: 67: the Otep Sea Orilling Project Mid-Americu Trench trlln,ect off GU;l!emala. Geol . Sor. Am .. l'art 1. 91. 421·432 .