External Rif Research Articles

Middle Eocene dinoflagellate cysts from the Tsoul section, eastern External Rif, Morocco: biostratigraphy and paleoenvironmental interpretations

This palynological study is carried out on the Eocene sediments in the Tsoul section, which is located in the Taza region, Tsoul Unit, eastern External Rif, northeastern Morocco. It aims their age assessment and paleoenvironmental interpretations, based on palynological data. The palynological content is diverse, well preserved and rich in organic-walled dinoflagellate cysts (dinocysts), whereas spores and pollen are rare. We identified 117 dinocyst species (including some reworked species), among which 6 species and 1 acme are good biostratigraphic markers of the Bartonian (middle Eocene). The main dinocyst bioevents that are used to assign the studied section to the Bartonian include the lowest occurrences (LOs) of Glaphyrocysta semitecta, Impagidinium dispertitum, Lentinia serrata, Membranophoridium aspinatum and Operculodinium divergens, the highest occurrence (HO) of Castellodinium compactum and the acme of Polysphaeridium spp. Regarding the paleoenvironment, the studied section was deposited in a marine environment, characterized by a low productivity inferred from the scarcity of peridinioid cysts and by important environmental changes ranging from restricted inner neritic (lagoon) conditions, inferred from the dominance of Homotryblium and Polysphaeridium, to outer neritic open marine conditions inferred from the dominance of Spiniferites.

Bartonian to Priabonian dinoflagellate cyst biostratigraphy and paleoenvironments of the M'karcha section in the Southern Tethys margin (Rif Chain, Northern Morocco)

Abstract Palynological analyses were performed on the Eocene sediments of the M'karcha section, which is located in the Taza region, structural Tsoul Unit, eastern External Rif (northeastern Morocco). The palynological content of this section is composed essentially of well-preserved and diverse dinoflagellate cyst assemblages, allowing detailed taxonomic determinations, age assignments, biostratigraphic correlations and paleoenvironmental interpretations. Other palynomorphs, such as spores, pollen grains and foraminiferal linings, are rare and therefore, not taxonomically determined up to the genus level. 131 dinoflagellate cyst species were identified. Age assignments are based on dinocyst bioevents, considered previously as potential biostratigraphic markers of the Bartonian and Priabonian, including the lowest occurrences (LOs) of Glaphyrocysta semitecta, Impagidinium dispertitum, Rhombodinium perforatum, Cooksonidium capricornum, Stoveracysta ornata, Stoveracysta sp. 2 of Brinkhuis and Biffi (1993) and LO and highest occurrence (HO) of Schematophora speciosa. The quantitative palynological analyses, based mainly on dinoflagellate cysts through the M'karcha section revealed an inner neritic, generally lagoon, environment with a low productivity, alternated with short episodes of the open marine influence.

Detrital zircon U-Pb ages in the Rif Belt (northern Morocco): Paleogeographic implications

Detrital zircon U-Pb age distributions in Mesozoic and Cenozoic rocks from the External Rif and Maghrebian Flysch Complex (including the so-called Mauretanian internal flysch units) are very similar, strongly suggesting that the External Rif and the entire Maghrebian Flysch Complex were part of the same NW African paleomargin. These patterns include scarce Paleozoic zircon grains that show influence from the Sehoul Block. Neoproterozoic and Paleoproterozoic grains are abundant with a dominant Ediacaran zircon population at ca. 590 Ma, which could have been sourced from the Variscan Moroccan Mesetas, the northern components of the West African Craton, or from Triassic sediments from the Central High Atlas and Argana basins. Mesoproterozoic zircon ages between 1.1 and 1.6 Ga were also observed (15% in the combined age spectra), the nearest sources for these being in the central part of the West African Craton. Transport of the Mesoproterozoic grains to the NW African paleomargin requires northward-directed fluvial systems parallel to the Central Atlantic continental margin of Africa. In contrast, samples from the Internal Rif or Alborán Domain are different to those from the External Rif and Maghrebian Flysch Complex, especially in the scarcity of Mesoproterozoic zircons, suggesting that the Alborán Domain was not a source area for zircons found in the NW African paleomargin.

Liassic age of an oceanic gabbro of the External Rif (Morocco): Implications for the Jurassic continent–ocean boundary of Northwest Africa

This work concerns the northernmost limit of the West African Craton (WAC) and Variscan WAC-related terranes of NW Africa. Based on newly obtained radiometric age of an oceanic gabbro from the “Mesorif Suture Zone” of the External Rif Belt, we propose a revised interpretation of this puzzling lineament. We report on a 190±2 Ma LA–ICP–MS U–Pb zircon age of a trondhjemite vein cross-cutting the Bou Adel gabbro, which is one of the largest oceanic units of the quoted suture zone. We previously interpreted the arcuate MSZ in terms of transported, hyper-extended margin of the Alpine Tethys, based on a K–Ar 166±3 Ma age ascribed to the Bou Adel gabbro in the literature. The new, Early/Middle Liassic age coincides instead with the onset of oceanic floor formation in the Central Atlantic. We hypothesize that the Mesorif suture zone corresponds to the transported trace of the West African Atlantic margin surrounding the northwestern Moroccan Meseta promontory and connecting with the ENE-trending North African Transform North African transform. The latter zone sharply bounded the North Africa margin and connected the Central Atlantic with the Alpine Tethys. We propose that transported elements from the North African transform constitute the “Mesorif Basalt–Breccias” lineament parallel to and more external than the Mesorif suture zone. If correct, this new interpretation provides an opportunity to develop detailed field and laboratory studies of an exhumed segment of the up-to-now conceptual Jurassic North African transform.

Middle Eocene to early Oligocene dinoflagellate cyst biostratigraphy and paleoenvironmental interpretations of the Ben Attaya section at Taza, eastern External Rif, Morocco

The palynological study was carried out on middle Eocene to early Oligocene sediments from the Ben Aattaya section, located in the Taza region, eastern External Rif, northeastern Morocco. The palynological content is dominated by dinoflagellate cysts (dinocyst), while spores and pollen are rare. Very known dinocyst event markers were used for dating the Ben Attaya section. The first occurrences (FO) of Cerebrocysta bartonensis, Glaphyrocysta semitecta, Lentinia serrata, Operculodinium divergens indicate the Bartonian. The FOs of Deflandrea heterophlycta, Schematophora speciosa, Stoveracysta ornata were used to recognize the Priabonian. While the FOs of Chiropteridium lobospinosum and Wetzeliella gochtii, as well as the last occurrences (LO) of Achilleodinium biformoides, Charlesdowniea coleothrypta subsp. coleothrypta, Enneadocysta pectiniformis, Glaphyrocyst semitecta, Hemiplacophora semilunifera, Lentinia serrata, Operculodinium divergens, Rhombodinium perforatum, Schematophora speciosa and Stoverocysta ornata highlight the Rupelian. The changes in relative abundances of selected dinocyst groups and sporomorphs (pollen and spores) suggest a lagoonal to coastal inner neritic marine environment during the Bartonian and Priabonian, which was interrupted by a short phase of outer neritic conditions at the basal part of the section and ended by a marked decrease in the sea level, probably due to a regression during the Priabonian. The Rupelian deposits indicate a middle neritic marine environment marked by a progressive rise during the transgression.

Eocene to Oligocene dinoflagellate cysts from the Tattofte section, western External Rif, northwestern Morocco: Biostratigraphy, paleoenvironments and paleoclimate

The palynological analysis of the Eocene–Oligocene succession from the Tattofte section in the western External Rif (northwestern Morocco) reveals the presence of well-preserved and diverse assemblage, rich in dinoflagellate cysts (dinocysts). Qualitative analyses, especially of the dinocysts, differentiate the individual stages of the deposits, while quantitative analyses permit paleoenvironmental and paleoclimatic interpretations. We assign the lower part of the Tattofte section to the Middle Eocene (Lutetian and Bartonian) and its upper part to the Upper Oligocene (Chattian), and define a hiatus spanning the Late Eocene (Priabonian) and Early Oligocene (Rupelian). The dinocyst marker events used for the biostratigraphic interpretations include the first and last occurrences of marker species, such as Batiacasphaera compta, Castellodinium compactum, Cerebrocysta bartonensis, Distatodinium biffii, Distatodinium paradoxum, Distatodinium ellipticum, Enneadocysta arcuata, Homotryblium floripes, Hystrichokolpoma bullatum, Impagidinium velorum, Lentinia serrata, Pentadinium imaginatum, Rhombodinium spinula, Saturnodinium perforatum and Ynezidinium brevisulcatum, as well as the Chiropteridium spp. acmes. And we equate the Chattian with the dinocyst Distatodinium biffii Zone of Brinkhuis et al. (1992).Changes in the relative abundances of selected dinocyst groups, spores and pollen lead to the distinction, from oldest to youngest, of four marine environments: 1) marginal marine to coastal inner neritic under relatively warm-water during the Middle Eocene; 2) outer neritic to oceanic during a transgressive regime in the early Chattian; 3) fluctuating restricted to open marine in the middle Chattian; and 4) shallow coastal to open marine due to sea-level fall at the top of the section in the latest Chattian, suggested by the Chiropteridium spp. acmes.The acmes of selected thermophilic dinocyst taxa, such as Polysphaeridium spp. and Homotryblium spp. suggest warm water marine conditions, which may be related to the Middle Eocene climatic optimum (MECO) and Late Oligocene warming.

Geochemistry of the Miocene Zoumi flysch thrust-top basin (External Rif, Morocco): new constraints on source area weathering, recycling processes, and paleoclimate conditions

This study focuses on the Lower-Middle Miocene syn-orogenic flysch deposits of the Zoumi basin to infer source area paleoclimatic conditions, the intensity of source rocks paleoweathering, and mechanical sorting and recycling effects. The mudrocks are enriched in Al2O3, Fe2O3, CaO, and TiO2 relative to PAAS and depleted in the other mobile major elements. There are high positive correlations between SiO2, Al2O3, and TiO2 and negative correlations between SiO2 and CaO. Geochemically, the mudstones are mainly classified as shales, Fe-shales, and wackes. Various discriminant diagrams were used to reveal the inferred tectonics, source paleoweathering intensity, and paleoclimatic conditions. Chemical index of alteration (CIA) and chemical index of weathering (CIW) values for Lower-Middle Miocene vary from 50 to 80% indicating low to moderate degree of source area weathering compatible with non-steady-state weathering under wet and humid paleoclimatic conditions. Locally (Zoumi mid-section) CIA values are higher (> 80) reflecting intense source area weathering, which may be attributed to high tectonic impulses and more humid conditions during deposition. The combination of ICV-CIA, Al2O3-Zr-TiO2, and Th/Sc-Zr/Sc values suggests the bulk rock is chemically immature and has experienced modest physical sorting and recycling reflecting little transportation until the final deposition.

The External Tanger Unit (Intrarif sub-Domain, External Rifian Zones, Morocco): an interdisciplinary study

The External Tanger Unit represents one of the most complete Cretaceous-Miocene successions in the central areas of the Internal Intrarif sub-Domain (External Rif Zones, Morocco). An interdisciplinary study has been carried out to propose a new characterization of this unit which would allow a better comprehension of the confused and complex relationships among different units of the same sub-domain. The results achieved can be summarized as follows: (1) redefinition of the stratigraphic (litho-, bio-, and chrono-) record and introduction of a new, informal lithostratigraphic terminology; (2) recognition of two main depositional sequences (lower-middle Eocene p.p. and lower Oligocene p.p.-lower Miocene p.p.) separated by extended gaps (latest Cretaceous-early Eocene p.p. and middle Eocene p.p.-early Oligocene p.p.); (3) reconstruction of the evolution of the sedimentary realm, and of the relationships between tectonics and sedimentation; and (4) comparison between the upper Cretaceous-Miocene stratigraphic record and tectonic events of the Intrarif, which is located in the western external portion of the Maghrebian Flysch Basin, and the equivalent sedimentary record of the eastern portion of this basin in the Tunisian Tell. More in general, our results allowed (i) a first reconstruction of the Cretaceous-Miocene main tectono-sedimentary events; (ii) a more detailed location of the sedimentary suite in the external African Margin in the context of a wider palaeogeographic framework; and (iii) the definition of the main stages of the geological evolution of the area.

Stratigraphy and Petrography of Mafic Rocks from the Western Part of the Mesorif Sub-Domain (External Rif, Morocco)

The Rif-Betic Cordillera is atightly arcuate, oroclinal mountain belt along the western edge of the Alpine Peri-Mediterranean Orogen, it extends for ~2000 km from the Strait of Gibraltar in the West to Calabria and the Southern Apennines in the East. It developed as a result of the convergence andcollision between the Eurasian and African plates in the Miocene. The recent discovery of a suture zone with oceanic rocks in its central and eastern parts suggests that the external zone of the Rif Belt (Mesorif and Prerif Units) may include ophioliticunits. In this paper, we shed light for the first time on petrographic and stratigraphic characteristics of the mafic rocks that appear in the western part of the Mesorif suture zone as well as the Prerif sub-domain. These latter are represented by gabbro with a sub-ophitic to ophitic texture showing simple mineralogy made up of abundant euhedral to subhedral plagioclase, subhedral to anhedralclinopyroxene crystals that can be very altered and totally replaced by chlorite epidote and opaques, and less abundant olivine. Alteration phases include chlorite epidote and tremolites.

Retraction: Oceanic Crustal Rocks in the External Rif (Morocco) with High K-Boninitic Affinities: Subduction Initiation Record for the Ligurian- Maghrebian Ocean Basin?

Acta Geologica Sinica - English EditionVolume 91, Issue 1 p. e1-e1 Retraction Retraction: Oceanic Crustal Rocks in the External Rif (Morocco) with High K-Boninitic Affinities: Subduction Initiation Record for the Ligurian– Maghrebian Ocean Basin? Retraction(s) for this article Retracted: Oceanic Crustal Rocks in the External Rif (Morocco) with High K-Boninitic Affinities: Subduction Initiation Record for the Ligurian – Maghrebian Ocean Basin? F. HAISSEN, M.N. ZAGHLOUL, Y. DILEK, A. RIFAI, L. FEDELE, L. MAACHA, A. MICHARD, S. VITALE, Volume 90Issue s1Acta Geologica Sinica - English Edition pages: 212-214 First Published online: October 31, 2016 First published: 09 March 2017 https://doi.org/10.1111/1755-6724.13101AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract The above abstract from Acta Geologica Sinica - English Edition, published online on 31 October 2016 in Wiley Online Library (http://wileyonlinelibrary.com), has been retracted by agreement between the authors, the Journal Editor-in-Chief, Degan Shu and John Wiley & Sons Australia, Ltd. The retraction has been agreed as the abstract was submitted without agreement of all co-authors. Volume91, Issue1February 2017Pages e1-e1 RelatedInformation

A historical overview of Moroccan magmatic events along northwest edge of the West African Craton

Located along the northwestern edge of the West African Craton, Morocco exhibits a wide variety of magmatic events from Archean to Quaternary. The oldest magmatic rocks belong to the Archean Reguibat Shield outcrops in the Moroccan Sahara. Paleoproterozoic magmatism, known as the Anti-Atlas granitoids, is related to the Eburnean orogeny and initial cratonization of the WAC. Mesoproterozoic magmatism is represented by a small number of mafic dykes known henceforth as the Taghdout mafic volcanism. Massive Neoproterozoic magmatic activity, related to the Pan-African cycle, consists of rift-related Tonian magmatism associated with the Rodinia breakup, an Early Cryogenian convergent margin event (760–700 Ma), syn-collisional Bou-Azzer magmatism (680–640 Ma), followed by widespread Ediacaran magmatism (620–555 Ma). Each magmatic episode corresponded to a different geodynamic environment and produced different types of magma.Phanerozoic magmatism began with Early Cambrian basaltic (rift?) volcanism, which persisted during the Middle Cambrian, and into the Early Ordovician. This was succeeded by massive Late Devonian and Carboniferous, pre-Variscan tholeiitic and calc-alkaline (Central Morocco) volcanic flows in basins of the Moroccan Meseta. North of the Atlas Paleozoic Transform Zone, the Late Carboniferous Variscan event was accompanied by the emplacement of 330–300 Ma calc-alkaline granitoids in upper crustal shear zones. Post-Variscan alkaline magmatism was associated with the opening of the Permian basins.Mesozoic magmatism began with the huge volumes of magma emplaced around 200 Ma in the Central Atlantic Magmatic Province (CAMP) which was associated with the fragmentation of Pangea and the subsequent rifting of Central Atlantic. CAMP volcanism occurs in all structural domains of Morocco, from the Anti-Atlas to the External Rif domain with a peak activity around 199 Ma. A second Mesozoic magmatic event is represented by mafic lava flows and gabbroic intrusions in the Internal Maghrebian flysch nappes as well as in the external Mesorif. This event consists of Middle-Upper Jurassic MORB tholeiites emplaced during opening of the Alpine Tethys ocean. The Central High Atlas also records Early Cretaceous alpine Tethys magmatism associated with the aborted Atlas rift, or perhaps linked to plume activity on the edge of the WAC.Cenozoic magmatism is associated with Tertiary and Quaternary circum-Mediterranean alkaline provinces, and is characterized by an intermittent activity over 50 Ma from the Anti-Atlas to the Rif Mountain along a SW–NE volcanic lineament which underlines a thinned continental lithosphere.

Retracted: Oceanic Crustal Rocks in the External Rif (Morocco) with High K‐Boninitic Affinities: Subduction Initiation Record for the Ligurian – Maghrebian Ocean Basin?

<i>Retracted</i>: Oceanic Crustal Rocks in the External Rif (Morocco) with High K‐Boninitic Affinities: Subduction Initiation Record for the Ligurian – Maghrebian Ocean Basin?

Tholeitic basalts and ophiolitic complexes of the Mesorif Zone (External Rif, Morocco) at the Jurassic-Cretaceous boundary and the importance of the Ouerrha Accident in the palaeogeographic and geodynamic evolution of the Rif Mountains

The stratigraphical series around the Jurassic-Cretaceous boundary of the External Rif Mountains, in particular those in the Mesorif Zone, exhibits many outcrops with volcanic materials spread westwards over 200 km. These materials show diverse aspects: basalt lithoclasts reworked into calcareous breccia beds or in marly matrix breccia, interstratified lava flows and volcanoclastic complexes incorporated within the Berriasian marls. In the Central Rif, several magmatic blocks outcrop, usually regarded as granite scales from the Paleozoic basement or as intrusive gabbros of Barremian age. Actually these magmatic massifs display typical ophiolitic sequences and they are overlaid by mega-olistoliths of Jurassic materials and locally by radiolarite layers. Geochemical analysis of several basalt and gabbro samples belonging to the Mesorif Zone evidenced that both display a typical E-MORB magma indicating at least partial oceanization of the Mesorif basement. Concerning geodynamics, the Mesorif Zone had undergone, at the Jurassic-Cretaceous boundary interval, two successive palaeogeographic phases: an uplift, close to emersion during the Kimmeridgian-Early Tithonian interval, stressed by important submarine volcanic activities and intense brecciation of the carbonate formations, followed by a general collapse at the Late Tithonian, underlined by lava flows, slumping as mega-olistoliths and the formation of an oceanic crust, at least in the Central Rif. These magmatic materials, distributed on both sides of the Ouerrha Valley, evidence that this westwards extending valley (the Nekor Accident), may correspond in the Central Rif, to two palaeo-subduction planes which become two major overlapping thrusts in the western part of the Rif Mountains.

Biostratigraphie des kystes de dinoflagellés et paléoenvironnements dans l’Eocène de la coupe d’Ibn Batouta, région de Tanger, Rif Externe occidental, Maroc

Palynological investigations of Eocene sediments from the Ibn Batouta section, located in the external Tangier Unit (western External Rif, northwestern Morocco), revealed the presence of well-preserved figured organic matter, rich in dinoflagellate cysts. Qualitative and quantitative analysis of palynological content, mainly dinoflagellate cysts, allowed a biostratigraphic subdivision and a paleoenvironmental reconstruction of these deposits. The dinoflagellate cyst events used for the characterization of the Middle Eocene (Lutetian and Bartonian) in the lower part of the Ibn Batouta section are: the first and last appearances of Castellodinium compactum, Distatodinium craterum, Distatodinium ellipticum, Distatodinium pilosum, Hystrichokolpoma salacia, Phthanoperidinium geminatum, Polysphaeridium biformum, Rhombodinium spinula, Ynezidinium brevisulcatum, the first appearance of Homotryblium floripes and the last appearance of Hystrichokolpoma bullatum. The disappearance of most of these species and the last appearance of Deflandrea phosphoritica are used for deduction of an Upper Eocene–Lower Oligocene age for the upper part of the section. Relative abundance changes of selected dinoflagellate cyst groups and continental palynomorphs (spores and pollen) allowed to highlight, in ascending order, five different marine environments: (1) neritic coastal with important nutrient availability at the base of the section; (2) outer neritic at the beginning of a transgressive phase in the Lutetian; (3) deeper outer neritic to oceanic in full transgressive phase in the Bartonian; (4) probably shallower outer neritic at the beginning of a regressive phase in the upper Bartonian; (5) coastal, probably estuarine in full regressive phase in the Upper Eocene–Lower Oligocene interval. These paleoenvironmental changes coincide with the global climate changes of the Middle Eocene Climatic Optimum (MECO).

Campanian to Eocene dinoflagellate cyst biostratigraphy from the Tahar and Sekada sections at Arba Ayacha, western External Rif, Morocco

Our detailed palynological study of the Upper Cretaceous–Lower Eocene marly succession from the Sekada and Tahar sections in southern Arba Ayacha, westernmost External Rif Chain (northwestern Morocco), has provided precise age determinations based on dinoflagellate cyst biostratigraphy. Dinoflagellate cysts (dinocysts), which are the dominant palynomorphs, allowed us to recognize the following ages: Late Campanian, Early and Late Maastrichtian, Danian, Selandian, Thanetian and Early Ypresien. Published studies on the western External Rif based on lithostratigraphy, show conflicting ages of Late Cretaceous (Senonian) and Early Eocene. Our age determinations are based on dinocyst events, which are more reliable. We recognize the Late Campanian on the First Occurrence (FO) and Last Occurrence (LO) of Exochosphaeridium? masureae, and the FO of Cerodinium spp., and the LOs of Cribroperidinium wilsonii subsp. wilsonii, Odontochitina porifera and Trithyrodinium suspectum. The Early Maastrichtian is denoted by the FOs of Alterbidinium varium and Palaeocystodinium golzowense and the LO of Alterbidinium acutulum. We define the Late Maastrichtian on the FOs of Disphaerogena carposphaeropsis and Glaphyrocysta perforata, and the LOs of Alisogymnium euclaense, Dinogymnium spp., Isabelidinium cooksoniae, and Pterodinium cretaceum, plus the worldwide latest Maastrichtian acme of Manumiella seelandica. Marking the Danian is the overall range of Senoniasphaera inornata, the FOs of Carpatella cornuta, Damassadinium californicum and Membranilarnacia? tenella. Species having LOs in the Selandian incude Cerodinium diebelii, Manumiella seelandica, Senoniasphaera inornata, Palaeocystodinium australinum and Cerodinium speciosum. We recognize the Thanetian mainly on the FO of Homotryblium tenuispinosum and based the worldwide terminal Thanetian acme of Apectodinium spp. The Early Ypresian is characterized by the FO of Deflandrea phosphoritica and a high abundance of Apectodinium spp. and Kenleyia spp. Thus, we now know that the rocks outcropping in the Sekada and Tahar sections are Late Campanian to Early Ypresian in age.

Polyphase deformation of the Dorsale Calcaire Complex and the Maghrebian Flysch Basin Units in the Jebha area (Central Rif, Morocco): New insights into the Miocene tectonic evolution of the Central Rif belt

In order to better understand the orogenic evolution of the Rif chain in the Eocene-Miocene interval, we provide new structural and kinematic data for the Jebha area, a key-sector of the Central Rif. Here the thrust sheet superposition occurs along the well-known Jebha-Chrafate lineament, widely considered as a major left-lateral transfer fault that enabled the Miocene westward migration of the internal thrust front. Our structural analysis was mainly focused on (i) the internal deformation of stacked nappes and (ii) the kinematics of the main thrust faults. Five main deformation stages were recognized for the Eocene-Miocene tectonic evolution of this area. The first orogenic pulse (D1), which occurred in the Eocene-Oligocene interval, was responsible for the tectonic stacking of the Ghomaride Nappes. Subsequently between the late Aquitanian and the late Burdigalian, imbrication (stage D2) occurred for some Internal Dorsale Calcaire thrust sheets within a dominant regional ENE-WSW shortening. At the Rif scale, different displacements of the WSW-migrating thrust front were accommodated by transfer structures including the Jebha-Chrafate fault. The following late Burdigalian-Langhian stage (D3) was defined, on the contrary, by a prevalence of the radial thrust front migration. In the Jebha area the early thrusting (stage D3a) was characterized by a main SE-vergence. In this phase the External Dorsale Calcaire and the Maghrebian Flysch Basin Units were included in the accretionary wedge. Two late D3 regional deformation phases were probably related to the buttressing effect that followed the collision of the thrust sheet pile against the crustal ramp of the External Rif domain. The first stage (D3b) consisted of an out-of-sequence thrusting recorded in the western sector of the Jebha area with the superposition of the Ghomaride Unit onto the External Dorsale Calcaire Unit, and in the eastern sector with the stacking of the Internal Dorsale Calcaire Unit directly onto the Predorsalian Unit. The second stage (D3c) included a late back-thrusting affecting the whole orogenic chain and deforming all the tectonic contacts. The fourth stage (D4) was characterized by strike-slip faulting and SW-verging folding. This latter mostly affected the successions located to the East of the Jebha village and was partially synchronous with the D3 stage. It was most probably related to the SW-migration of the internal thrust-front of the Bokkoya Dorsale Calcaire Complex and a renewed activity of the Jebha-Chrafate fault zone. The last tectonic stage (D5) included a radial extension expressed by high and low-angle normal faults.

Intérêt des kystes de dinoflagellés calcaires et du biomicrofaciès pélagique dans la datation des terrains du sommet du Jurassique et de la base du Berriasien dans le domaine téthysien occidental

The study of several hundreds of thin sections from dozen outcrops in three different paleogeographic basins: the External Rif Range (Morocco), the Vocontian Basin (Southeastern France) and the northern Tunisia, has confirmed the importance of pelagic microfaunal associations to date the Upper Jurassic deposits. Among those palaeontological groups, crinoid saccocomids, which appear in the Middle Oxfordian, are thriving noticeably in the three basins at the base of the lower Tithonian substage (Hybonotum ammonite zone). Calcareous dinoflagellate cysts (two new species) were also used to characterize 10 biozones, 7 at least have a general value in the Tethyan realm. Protoglobigerines, abundant in the Upper Oxfordian and at the base of the Kimmeridgian (Platynota zone), are rare or absent in younger strata. In the external Rif and in northern Tunisia, microfilaments show two levels of abundance, respectively in the Divisum and the Beckeri zones. They disappear at the top of the latter zone. Chitinoidellids were used to characterize the Lower Tithonian (Ponti zone)-Upper Tithonian (zone Microcanthum) boundary. Calpionellids, appearing at the top of the Microcanthum zone, are still abundant within the Durangites zone. Globochaete, often present, are really abundant only from the base of the Lower Tithonian and higher up throughout the Tithonian. Radiolarians show random stratigraphic distributions. Combining all these various fossil groups and their abundance, we define 13 biozones of concurrent range, which are well-correlated with ammonite zones. It corresponds respectively to the Upper Oxfordian-basal Kimmeridgian (Platynota zone), the Hypselocyclum zone, the Divisum zone, the Acanthicum-Eudoxus zones, the Beckeri zone, the Hybonotum zone, the Darwini-Semiforme zones, the Fallauxi zone, the Ponti zone, the Microcanthum pro parte zone, the upper part of the Microcanthum zone-lower part of the Durangites zone, the upper part of the Durangites zone and the lower part of the Euxinus zone. The present work aims to contribute towards to a better and more practical biostratigraphical zonation of the Upper Jurassic-lowermost Berriasian deposits in the western tethyan basins.

Description et biozonation des sections de crinoïdes saccocomidés du Jurassique supérieur (Oxfordien-Tithonien) du domaine téthysien occidental

The study of several hundreds of thin sections, from dozens of outcrops in three different palaeogeographic domains: the External Rif Chain (Morocco), the Vocontian Basin (Southeastern France) and the Northern Tunisia, has helped better to characterize the stratigraphic distribution of the pelagic crinoids, roveacrinid saccocomids. The saccocomids, appearing in the Middle Oxfordian, are thriving noticeably in the three studied basins at the base of the Early Tithonian substage (Hybonotum ammonite zone) and dominate the pelagic microfauna up to the relative disappearance of the group at the top of the Late Tithonian, at the limit of the A2 and A3 subzones of calpionellids. Careful examination of the respective skeletal elements of this fossil group in thin sections lead to define 47 types of skeletal sections, divided into 6 different groups. These skeletal sections are described and named on the base of their geometric forms. Most of these sections have typical geometric shapes and occur in coeval stratigraphic levels in the three investigated basins. Several of these sections are characteristic of a specific stratigraphic interval, either by their geometric shape or by their relative frequency. The stratigraphic distribution of the investigated skeletal sections, previously considered as of limited stratigraphical value, allowed to define 7 association and relative frequency biozones for the Late Oxfordian-Late Tithonian interval. These biozones are correlated with the ammonite zones.

Comment on “Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin: The Tanger-Ketama Unit (external Rif, northern Morocco)” by Vázquez et al., Geologica Acta 11 (2013), 277-293

Comment on “Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin: The Tanger-Ketama Unit (external Rif, northern Morocco)” by Vázquez et al., Geologica Acta 11 (2013), 277-293

Reply to the comment by Michard et al. on "Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin: The Tanger-Ketama Unit (External Rif, northern Morocco) by Vázquez et al., Geologica Acta 11 (2013), 277-293"

Michard et al. (this issue) commented on certain aspects of the Alpine metamorphism and structural evolution of the Rif belt (Morocco) that were briefly noted in Vazquez et al. (2013). In particular, they criticize our interpretation of an extensional setting during the main metamorphic recrystallization of the Tanger-Ketama Unit that we considered related to slaty cleavage (S1) parallel to the lithological layering generated during the Cretaceous. Michard et al. (this issue) interpret the S1 syn-metamorphic foliation as being related to compressional folds, and the peak metamorphism temperatures, in the Lower Cretaceous sediments, as ranging between 200–300°C. Therefore, they conclude that recrystallization of the Ketama Unit occurred during Miocene thrust nappe tectonics. We explain our view in the following sections.