Lecture Notes ni Earth Sciences Edited by Somdev Bhattacharji, Gerald M. Friedman, Horst .J Neugebauer and Adolf Seilacher 51 Volker H. Jacobshagen ).dE( ehT System Atlas fo Morocco Studies on sti Geodynamic Evolution galreV-regnirpS Berlin Heidelberg NewYork London Paris oykoT Editor Prof. Dr Volker H. Jacobshagen Frele Unlversltat Berhn FB Geowissenschaften, Instltut fur Geologle Altensteinstrasse 34a, D-1000 Berhn 33, FRG ISBN 3-540-19086-4 Sprmger-Verlag Berhn Heidelberg New York ISBN 0-387-19086-4 Springer-Verlag New York Berlin Heidelberg yrarbtL Congress of nohachbuP-nt-gmgolataC system/ Atlas the of evoluhon Data Geodynamlc H Volker Morocco / Jacobshagen, ed p cm -(Lecture notes ni scrences, earth )51 the of "One the on conference a was book this of sources cJmanydoeg m organtzed system, Atlas the of aspects Berltn ni 1986" by Kontlnentalrander"-Pref akhver the Forschungsgruppe "Mobrhtat ISBN 0-387-19086-4 U( S ) 1 Geology-Morocco-Atlas Mountains 2 Geology-Morocco-Antt-Atlas Mountains 3 Geo- dynamics .I Volker Jacobshagen, II Senes QE339 MSG36 1988 556 4'4-dc 91 88-12329 srhT work si subject to copyright whole the whether reserved, are All rights or the of part material st concerned, the specifically rights of of re-use reprmtrng, translation, ,snottartsullJ recttatlon, reproduction on broadcasttng, smliforcrm or ni banks data m storage and ways, other no~tachpuD thereof or parts pubhcahen thrs of sr the permitted under only snoJstvorp the German Copynght of Law of September ,g 1965, ni June of versron its ,42 always fee copyright be a must and 1985, paid Violations fall the act prosecution under Copyrtght the of German Law Hetdelberg Spnnger-Veriag 1988 Berhn @ Pnnted nr Germany gnhmrP and binding. Beltz, Hemsbach/Bergstr Druckhaus 2132/3140-543210 ECAFERP ehT mia of this volume is to reflect the current state of geoscien- tific activity focused no the cimanydoeg evolution of the Atlas metsys dna to discuss wen results dna ideas. ehT volume provides a selection of papers no the geological history, structural development, dna geo- physical data of Morocco. It saw ton possible to cover all areas of geoscientific interest, however, ew hope to shed emos light no the major cimanydoeg problems. enO of the sources of this book saw a conference no the cimanydoeg aspects of the Atlas system, organized in Berlin in 6891 yb the For- schergruppe "Mobilit~t aktiver Kontinentalr~nder". ehT financial sup- port for this project is being provided yb the Deutsche -egsg~!:thcsroF meinschaft dna yb the Freie Universit~t dna the Technische Universi o t~t of Berlin (West). Furthermore ew are very glad to mention that ew evah received a great rebmun of publications yb authors from different countries ohw did not take part in the Berlin conference. It should eb noted that, at present, a lot of international geo- scientific activity is concerned with Morocco. This is not only eud to the fascinating complexity of naccoroM geology dna the beautiful outcroups, that yam provide the yek to ynam general problems, but also testifies to the liberal dna prescient science politics of the -coroM nac authorities, most of all the Ministery of Energy dna Mining in Rabat. Therefore, no behalf of all the authors from abroad, I take the opportunity to express our deepest gratitude to ruo host country, especially to the leaders of the Division ed la G~ologie, the general director .rD .M Bensaid dna the directors .M inamhaD dna .M .aduommaH sknahT are, furthermore, eud to Springer Verlag (Berlin-Heidelberg- weN York) for offering the opportunity to publish a evisneherpmoc emulov dna especially to .rD gnagfloW Engel for his patience dna help- ful advices. .V negahsbocaJ CONTENTS INTRODUCTION JACOBSHAGEN, V.: Geodynamic evolution of the Atlas System, Morocco: an introduction 3 ANTI-ATLAS 11 WALLBRECHER, E.: The Anti-Atlas system tan overview 31 WALLBRECHER, E.: A ductile shear zone in the Panafrican basement on the northwestern margin of the West-Afri- can craton (Sirwa dome, central Anti-Atlas) 91 BASSIAS, Y., WALLBRECHER, E. and WILLGALLIS, A.: Tectono- thermal evolution of the Late Panafrican orogeny in the Central Anti-Atlas (Southern Morocco) 43 BRABERS, P.M.: A plate tectonic model for the Panafrican orogeny in the Anti-Atlas, Morocco 16 BUGGISCH, .W and FLOGEL, E.: The Precambrian/Cambrian boundary in the Anti-Atlas (Morocco). Discussion ~nd new results 18 SDZUY, K. and GEYER, G.: The base of the Cambrian in Morocco 19 BUGGISCH, .W and SIEGERT, R,: Paleogeography and facies of thed~r~s terminaux'~(uppermost Lower Cambrian, Anti-Atl as/Morocco) 107 BUGGISCH, W.: Diagenesis and very low-grade metamor- phism of the Lower Cambrian rocks in the Anti-Atlas (~4orocco) 123 HIGH DNA MIDDLE ATLAS 129 SCHAER, J.-P.: Deformation of igneous dikes in and around the Tichka granite, High Atlas - Morocco 131 LORENZ, J.C.: Synthesis of Late Paleozoic and Trias- sic redbed sedimentation in Morocco 139 EMRAW J.E.: Jurassic carbonate facies of the Central and Eastern High Atlas rift, Morocco 169 BRECHBQHLER, Y.A., BERNASCONI, R. and SCHAER,J.-P.: Jurassic sediments of the Central High Atlas of Morocco: Deposition, burial and erosion history 201 FROITZHEIM, N., STETS, J. and WURSTER, P.: Aspects of !qestern High Atlas tectonics 219 ,I~,EGAHSBOCAJ V , BREDE, R , HAUPTMA~IH, M HEINITZ,W and 7YLKA, R : Structure and post-Palaeozoic evo- lution of the central High Atlas 245 lV FRAISSINET, C., ZOUINE, E.M., MOREL,J.-L., POISSON, A., ANDRIEUX, J. dna FAURE-MURET, A.: Structural evolution of the southern and northern Central High Atlas in Paleogene and Mio-Pliocene times 273 ,YANSERD .R du: Recent data no the geology of the Middle- Atlas (Moro, cco) 392 HERBIG, H.-G.: Synsedimentary tectonics in the Northern Middle Atlas (Morocco) during the Late Cretaceous dna Tertiary 123 ,ZRA/,!HCS .G dna WIGGER,P.J. Geophysical studies of the earth's crust and upper mantle in the Atlas system of Morocco 933 CIOZONEC BASINS 953 G~RLER, K., ,HCADMLEH F.-F., ,SREMEAG P., HEISSIG, K., HINSCH, W., =RELD#M K., ,SNAHZRAWHCS .I~ dna ZUCHT, .M The uplift of the central High Atlas as deduced from Neogene continental sediments of the Ouarzazate pro- vince, Morocco 163 ,HCADMLEH F.-F.: ehT ostracode fauna of the Ait Kandoula region: systematic description 504 ST~BLEIN, G.: Geomorphological aspects of the Quaternary evolution of the Ouarzazate basin, Southern Morocco 334 SCHMIDT, K.-H.: Rates of scarp-retreat: a means of dating neotectonic activity 544 SESEHTNYS 463 ,AGLED-DNARUD .M and OLIVIER,Ph.: Evolution of the Aiboran block margin from Early Mesozoic to Early Miocene time 465 ,NEGAHSBOCAJ V., G~RLER, K. dna GIESE, P.: Geodynamic evo- lution of the Atlas System (Morocco) in post-Palaeozoic times 184 Introduction CIMANYDOEG NOITULOVE FO EHT SALTA ,METSYS :OCCOROM NONIATCUDORTNI Volker negahsbocaJ Institut fur Geologie, Freie Universit~t Berlin, Altensteinstr. 43 ,A 0OOl-D Berlin 33 ehT Atlas metsyS ehT northwestern margin of Africa, neewteb eht Atlantic naecO dna eht Lesser Syrtis, is characterized yb high mountain ranges, eht ele- vation of which stnuomrus 000.3 m in the western part. Jbel lakbuoT (4.165 )m in eht High Atlas is eht highest mountain of North Africa. esehT ranges have neeb synchronously uplifted since eht Miocene. yehT differ, however, both in structure dna geological history. ehT -erhgaM bides consisting of eht Rif dna Tell Atlas along eht Mediterranean coast era a typical Alpidic negoro with xelpmoc eppan structures. ehT segnar in their southern foreland, called eht Middle dna High Atlas, era anorogenic intracratonic mountain belts separated yb elevated pla- teaus. ehT eastern prolongation of eht High Atlas is formed yb the -aS narah dna Tunisian Atlas. ehT Anti-Atlas, which however, lies south of eht High Atlas in ,occoroM originated yb simple gnimodpu of the Pre- nairbmac tnemesab of eht arahaS craton. sA all these ranges era -oeg graphical andgeological related to hcae other they have neeb deman eht Atlas system yb .M RETHCIR (1970). ,suhT ew find a mobile zone in eht southern foreland of eht -erhgaM bide orogen, which in southern occoroM extends pu to 005 mk into the African plate. sA eht southern border of this enoz diverges erom dna erom from eht sediberhgaM to eht southwest, ew yam emussa that its -oeg logical evolution cannot eb solely decuded from eht Mediterranean oro- ,seseneg tub smees to eb erom .xelpmoc Geotectonic subdivision of occoroM ehT Moroccan segment of the Atlas system is relatively well known. For na overview, the publications of DRAHCIM (1976), TREBUOHC and TERUM-ERUAF (1962, 1971, 1973) and TERUM-ERUAF and TREBUOHC (1971) are recommended. The geotectonic subdivision of the Moroccan Atlas system is nwohs in fig. 1 dna is briefly described here: SEA 0 0 0 \ ,,x o on o o o o ~ o re=l o ~ I • :~$~Z1 acI((cib~$o£ ii;iC~i~ ~~ '~' SETUAH XUAETALP "v ,,x "t" *OOZ ~!iiiiiiii!!iiiiy ' .... [3 ,°=tnoou-.R ...... ~ c=zoea=e tsoP n- oinycroH :revoc [~ reppU ciozoretorP r,ppU ci0zn,eC se0,,n0tav f--I pi,te,u, nairbmacerP [~ reppU cioznoeC snisab (~ hgiH dne elddiM seltk Fig. I: Geotectonic sketch-map of the Atlas system of Morocco, based no DRAHCIM (1976) ehT narrow arc of the Rif orogen in the north is overthrust towards the S no na Upper Cenozoic marginal trough. oT the ,WS the orogenic belt is bordered yb the hills dna plains of the naccoroM Meseta. Its Variscan tnemesab is exposed in large areas from under a cover of flat-lying Mesozoic dna Palaeogene sediments. oT the ,ES the ateseM dna the Rif are bordered yb the High dna the Middle Atlas. Both ranges developed from early Mesozoic rift grabens which originated in cor- relation to the opening of the Western Tethys dna of the North Atlan- tic .naecO Rifting saw deinapmocca yb mafic volcanism, which culminated in the reppU Triassic/Liassic dna in the Dogger. emoS intrusions, however, are of Cretaceous dna even Palaeogene age. ehT structure of the High dna Middle Atlas generally correspond to each other, both gniwohs a base- tnem of Palaeozoic or Precambrian rocks that is covered yb thick Trias- sic dna Jurassic sediments. Prevailing structures era steep faults, -om noclines dna strike-slip faults. In places, especially in the central dna eastern High Atlas, overthrusts, xob folds dna even overturned folds exist. However, essential criteria of orogens such as: ophiolites, nappes, flysches, regional msihpromatem dna granitoids are not devel- oped. Both ranges are deinapmocca yb a wef small Cenozoic basins. ehT Middle Atlas forks off from High Atlas in a northeastern direction, -ne closing the so-called High Plateaus of Oran. ehT Variscan tnemesab of these plateaus is covered yb Mesozoic sediments, which are in the southwest overlain yb the Cenozoic of the Haute .ayuoluoM ehT High Atlas is separated from the Anti-Atlas yb the ssuoS dna the Ouarzazate basins ("sillon pr~africaine"). sA suggested yb OSSUR dna OSSUR (1934), ynam geologists believe that the High Atlas is bor- dered to the S yb na important fault zone, nwonk sa the South Atlas Marginal Fault zone ("accident sud-atlasien"). Although several authors doubt that this fault really exists, others have already introduced it to plate tectonic concepts. emoS of meht even believe it to eb the northwestern boundary of the African plate (e.g. YEWED etal., 1973). ehT Anti-Atlas saw formed yb wide-spanned gnimodpu of marginal parts of the Sahara craton. Precambrian rocks form the core of major semod ("boutonnieres") in the axial zone of the range. Normally, this base- tnem is covered yb poorly deformed sediments of tsomreppU Proterozoic or Lower Palaeozoic age. In the Tafilalt region (Southeast Morocco), the Anti-Atlas dips to the E beneath demrofednu Cretaceous stnemides of the Sahara platform.