Thomas Becker

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The unique Devonian of Immouzer-du-Kandar (Middle Atlas basement) – biostratigraphy, faunas, and facies development

Frontiers in Science and Engineering, 2020

Fig. 1: View (from the hill at Douar Ahmed-ben-Mellouk) on Devonian exposures of Immouzer-du-Kand... more Fig. 1: View (from the hill at Douar Ahmed-ben-Mellouk) on Devonian exposures of Immouzer-du-Kandar (hill rising from Chabat el Jenanet, Sections C2 and C3 of CYGAN et al. 1990), our Section C4, with outcrop of the lower Emsian conglomerate (Chabat Jenanet Formation) along and above the track, faulted upper Emsian to lower Givetian limestones in the lower slope (new Ahmed-ben-Mellouk Formation), the reef breccia forming a small terrace ca. 2/3 upwards, and the Famennian upper slope (new Chabat el Hallouf Formation, Section C5) towards the top. The slope to the left (NNE) is occupied by Triassic red beds. Section numbers are marked in circles.

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The Devonian and Viséan transgression in the Eastern Jebilet (Moroccan Meseta) – review and new data

Frontiers in Science and Engineering, Jul 5, 2021

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Analysis of ammonoid palaeobiogeography in relation to the global Hangenberg (terminal Devonian) and Lower Alum Shale (Middle Tournaisian) events

Annales de la Société géologique de Belgique, Jun 1, 1993

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Age and correlation of the transgressive<i>Gonioclymenia</i>Limestone (Famennian, Tafilalt, eastern Anti-Atlas, Morocco)

Geological Magazine, Nov 21, 2016

The widely quarried and commercially exploitedGonioclymeniaLimestone of the western and southern ... more The widely quarried and commercially exploitedGonioclymeniaLimestone of the western and southern Tafilalt Platform (Anti-Atlas, SE Morocco) represents a transgressive but strongly condensed and shallowing upwards unit that overlies conformably or unconformably Famennian to Lower Devonian deposits. It is characterized by abundant, giant-sizedGonioclymenia speciosa, which characterizes the Famennian V-B, and rareLeviclymenia ramulasp. nov. Associated conodont faunas fall in theBispathodus costatusSubzone of theB. aculeatus aculeatus(= Middleexpansa) Zone. A rare outcrop at Jebel Ihrs West proved thatKalloclymeniaand conodont faunas of theB. ultimus ultimus(= Upperexpansa) Zone occur in a separate, overlying unit of the lower part of Famennian VI. Consequently, joint occurrences ofGonioclymeniaandKalloclymeniaon large limestone slabs that are on offer in rock shops are artificial assemblages; there is no evidence for a regional co-occurrence of both genera. This is supported by correlation into thicker sections of the adjacent Maider and Tafilalt Basins. The TafilaltGonioclymeniaTransgression may represent the regional expression of a eustatic pulse in theB. costatusSubzone that is known on the Ardennes Shelf as the transgressive Epinette Event. The conodont faunas yieldedNeopolygnathus fibulasp. nov.,Pseudopolygnathus primus tafilensisssp. nov., new morphotypes ofB. spinulicostatusandPseudopolygnathus primus primus, the oldestSiphonodella (Eosiphonodella)and variable ‘siphonodelloids’ that are currently left in open nomenclature.

Refined conodont stratigraphy at Martenberg (Rhenish Massif, Germany) as base for a formal middle/upper Frasnian substage boundary

Palaeobiodiversity and Palaeoenvironments, Jul 15, 2022

The famous Martenberg section of the eastern Rhenish Massif, Germany, type-section of classical F... more The famous Martenberg section of the eastern Rhenish Massif, Germany, type-section of classical Frasnian goniatite and conodont zonations, has been restudied in order to document the microfacies development and to refine the conodont stratigraphy around the global semichatovae Event/Transgression, the proposed level to define a future upper Frasnian substage. More than 8.000 platform elements were identified and include new taxa. Palmatolepis jamieae is subdivided into the subspecies Pa . jamieae jamieae , Pa . jamieae savagei n. ssp., Pa. jamieae rosa n. ssp., and Pa. jamieae ssp. δ. Another new species, Pa . adorfensis n. sp., was previously partly identified as Pa. jamieae , while Pa. descendens n. sp. has previously been described in open nomenclature from Inner Mongolia. Morphotypes are defined in Icriodus symmetricus, Pa. ljaschenkoae , and Pa. proversa . A global literature survey shows that the eustatic semichatovae Event can be recognised in more than 20 regions of all cont...

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New upper Givetian to basal Frasnian conodont faunas from the Tafilalt (Anti-Atlas, Southern Morocco)

Geological Quarterly, Mar 27, 2010

Cono dont fau nas, mostly from pre vi ously unsampled sec tions of the Tafilalt (east ern Anti-At... more Cono dont fau nas, mostly from pre vi ously unsampled sec tions of the Tafilalt (east ern Anti-At las, Mo rocco) and span ning the up per Givetian to basal Frasnian, in clude first re cords of spe cies for the re gion and NW Gond wana as well as new taxa: "Ozarkodina" maroccanica n. sp., Polygnathus aequidivisus n. sp., Po. dengleri sagitta n. ssp., Po. jorfensis n. sp., Po. saevus n. sp., Po. tafilensis n. sp., and Schmidtognathus longicavus n. sp. The mor phol ogy of Tortodus subsymmetricus n. sp. sug gests re la tion ships of Tortodus with Frasnian ancyrognathids. Other taxa are de scribed in open no men cla ture: Po. cristatus n. ssp., Icriodus aff. I. symmetricus, Skeletognathus aff. Sk. norrisi, and enig matic sup posed Pb el e ments (Gen. et sp. indet.). Ctenopolygnathus lanei Kuzmin (1995) is emended and dis tinc tive morphotypes are rec og nized in Ct. angustidiscus and Po. collieri. Mesotaxis falsiovalis Sandberg et al. (1989) is a sub jec tive ju nior syn onym of the widely over looked M. guanwushanensis (Tian, 1988). The re vised re gional lithostratigraphy and cono dont se quences al low to re fine the up per Givetian zonation. The for mer Up per disparilis Zone is sub di vided into suc ces sive Po. dengleri sagitta and Po. dengleri dengleri subzones. The basalmost Frasnian Ancyrodella rotundiloba pristina Zone (= MN 1 Zone) is pre served as a thin, con densed lime stone just at one lo cal ity (Bine Jebilet). The over ly ing Frasnes Event Beds (Lower Styliolinites) seem to fall in the sub se quent Ad. rotundiloba soluta Zone (MN 2 Zone). Re cords of rare taxa, such as Po. paradecorosus, Po. pollocki Morphotype 1, old est Po. webbi, Ct. angustidiscus, and Ct. lanei may be help ful for cor re la tion into dis tant ar eas or shal lower fa cies.

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Bioclastic bottom‐current deposits of a Devonian contourite terrace: Facies variability and depositional architecture (Tafilalt Platform, Morocco)

Sedimentology

ABSTRACTThe study examines bioclastic carbonate contourites that arise from the broad spectrum of... more ABSTRACTThe study examines bioclastic carbonate contourites that arise from the broad spectrum of bottom‐current related sedimentary processes ranging from deposition to erosion. The result of the intermittent accumulation of sediment are thin and condensed successions with abundant hiatuses. Such bottom‐current deposits are poorly known, since the broadly accepted contourite‐facies model, the bi‐gradational sequence, characterizes environments of contourite depositional systems as a continuous accretion of fine‐grained siliciclastic sediments. To increase current understanding of the carbonate facies within hiatal contourite records, the Eifelian–Frasnian of the Tafilalt Platform in Morocco was investigated. The succession is divided into five facies associations that are interpreted to reflect pelagic sedimentation and deposition from bottom currents on a contourite terrace, a gently inclined section of the upper slope of Gondwana shaped by a water‐mass interface. Contourite depos...

Refined conodont stratigraphy at Martenberg (Rhenish Massif, Germany) as base for a formal middle/upper Frasnian substage boundary

Palaeobiodiversity and Palaeoenvironments

The famous Martenberg section of the eastern Rhenish Massif, Germany, type-section of classical F... more The famous Martenberg section of the eastern Rhenish Massif, Germany, type-section of classical Frasnian goniatite and conodont zonations, has been restudied in order to document the microfacies development and to refine the conodont stratigraphy around the global semichatovae Event/Transgression, the proposed level to define a future upper Frasnian substage. More than 8.000 platform elements were identified and include new taxa. Palmatolepis jamieae is subdivided into the subspecies Pa. jamieae jamieae, Pa. jamieae savagei n. ssp., Pa. jamieae rosa n. ssp., and Pa. jamieae ssp. δ. Another new species, Pa. adorfensis n. sp., was previously partly identified as Pa. jamieae, while Pa. descendens n. sp. has previously been described in open nomenclature from Inner Mongolia. Morphotypes are defined in Icriodus symmetricus, Pa. ljaschenkoae, and Pa. proversa. A global literature survey shows that the eustatic semichatovae Event can be recognised in more than 20 regions of all continents ...

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Sedimentary and faunal evidence for the Late Devonian Kellwasser and Annulata events in the Balkan Terrane (Bulgaria)

Geologica Balcanica

The global Upper Kellwasser (Frasnian–Famennian boundary interval) and Annulata Events (base of u... more The global Upper Kellwasser (Frasnian–Famennian boundary interval) and Annulata Events (base of upper Famennian, Upper Devonian IV-A) are recorded for the first time in deep marine sedimentary successions of western Bulgaria. Within the upper Parchar Formation of the Lyubash-Golo Bardo Unit, a distinctive black shale unit yielded frequent, partly still articulated bivalves (Guerichia) and a Platyclymenia-fauna, including the name-giving Pl. annulata, although smooth platyclymeniids are more common. This interval reflects within a thick Eovariscan flysch succession an episode of starved sedimentation, increased organic productivity, oxygen deficiency, and bloom of opportunistic specialists. The event biofacies agrees with a basinal setting far away from land and its nutrient input. The Upper Kellwasser interval is recognized within the thick flysch sequence of the Katina Formation in the Svoge Unit. It is characterized by an interruption of carbonate deposition, as it is typical for ...

Late Early Devonian ostracodes from the Torkoz area (SW Morocco) and the Emsian/Eifelian boundary

PalZ

A new rich and diversified ostracode fauna from the Torkoz area (section Hassi Mouf South, Morocc... more A new rich and diversified ostracode fauna from the Torkoz area (section Hassi Mouf South, Moroccan Anti-Atlas) is described and the ostracode distribution near the Early/Middle Devonian boundary is discussed. This ostracode fauna of a single limestone bed yields 32 taxa and is compared with the less-diversified ostracode fauna from an adjacent parallel section Hassi Mouf South as well as with a published conodont-bearing sample from section Torkoz. All three ostracode faunas are closely related, and therefore, the same latest Emsian age is postulated. Palynomorphs (acritarchs and prasinophytes) from section Torkoz support this late Early Devonian age and the scarce brachiopod fauna of the equivalent level from section Hassi Mouf South suggests a stratigraphical position very close to the Emsian/Eifelian boundary, probably latest Emsian. Zygobeyrichiasubcylindrica from a thin marly bed embedded in shales, slightly below the ostracode-rich sample from section Hassi Mouf South, and th...

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Devonian of the Benahmed region western Moroccan Meseta

Based on new field work, sampling for conodonts, ammonoids, and microfacies analysis, the Lower t... more Based on new field work, sampling for conodonts, ammonoids, and microfacies analysis, the Lower to Upper Devonian stratigraphy of the Benahmed region is refined. Fossiliferous neritic limestones of the Pragian/lower Emsian represent a continuation of the shallow carbonate platform of the Al Attamna region to the north (Units A/B of Sidi Ahmed Lemdoun Formation). More argillaceous upper Emsian/Eifelian strata are regionally still poorly known. In the southern Chaouїa or Beni Sekten region NW of Benahmed, Givetian deep neritic to shallow pelagic mud-wackestones of the new Oulad Amar Formation were partly reworked and re-sedimented together with crinoidal grainstones in conglomeratic debris flow beds. Peaks of Eovariscan block faulting and reworking occurred high in the middle (ansatus Zone) and at the top of the Givetian (norrisi Zone). Lower/middle Frasnian strata are still unknown in outcrop but limestones with corals of possible Givetian/Frasnian age have been reported from E/SE of...

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The Devonian of Jebel Ardouz (Mzoudia region, SW Moroccan Meseta) – new data on stratigraphy, facies, and palaeogeography

The long-known Devonian of the Jebel Ardouz west of Marrakesh, and just north of Mzoudia, is comp... more The long-known Devonian of the Jebel Ardouz west of Marrakesh, and just north of Mzoudia, is composed of an allochthonous stack of clastic and carbonate rocks that were thrusted onto each other from the northeast. New biostratigraphic data prove an age range of sedimentation from the lower Eifelian to ?upper Famennian. The lowest, western thrust unit is composed of reddish sandstones and conglomerates/breccias (new Ardouz Formation) deposited originally by rockfall and debris flows on the slope of a repeatedly active fault scarp. Limestone clasts yielded sandstones of unknown age, Eifelian, Givetian and lower/middle Frasnian conodonts, and encrusted reef corals. Re-sedimentation may have occurred in the upper Frasnian or post-dated the Famennian. The "red conglomerates" record a block that was strongly tilted by Eovariscan extensional tectonics, forming on the uplifted side a small island. Exhumation, erosion down into Eifelian carbonates, and a long phase of reworking (pe...

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Devonian and the Carboniferous transgression in the Skoura region, Sub-Meseta Zone, Morocco

The Sub-Meseta Zone forms the transition between the southern Meseta of the main Variscides and t... more The Sub-Meseta Zone forms the transition between the southern Meseta of the main Variscides and the Anti-Atlas realm. The Skoura region at the southern foot of the High Atlas includes a west-east, discontinuous sequence of Devonian and Lower Carboniferous outcrops, from Tizi-n´Tichka East in the NW of Ouarzazate to Asserhmo in the NE. Based on detailed logging, microfacies, conodont and macrofauna sampling, especially at Taliouine and Tizi n-Ouourti, the regional Devonian litho, bio- and event stratigraphy and facies development is revised. The Lochkovian is marked by a change from unfossiliferous black shales (Lower Member of new Tizi-n-Tichka Formation) to condensed, discontinuous, black, detrital Orthocone Limestones (Upper Member, middle Lochkovian) deposited under strong bottom current influence (contourites). Slumps and a subsequent erosional disconformity mark the regional tectonic episode Sk-TP-1a, followed by a distinctive "Antevariscan" conglomerate and reworking...

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Givetian (Middle Devonian) brachiopod–goniatite–correlation

Abstract: The Givetian pelagic and dysoxic outer shelf facies of the Dra Valley (SW Morocco) yiel... more Abstract: The Givetian pelagic and dysoxic outer shelf facies of the Dra Valley (SW Morocco) yielded as minor benthic faunal elements a number of stringocephalid and uncitid brachiopods that allow a precise correlation of these marker brachiopods with the regional, detailed goniatite zona-tion. In a reverse situation, the predominant neritic shallow-water succession of the Bergisch Glad-bach area (Rhenish Massif, Germany), which is characterized by a detailed succession of stringocephalids and Uncites, has yielded rare and new Middle Givetian goniatite species. These findings allow, with some help of conodont data, neritic–pelagic correlations within and between widely separated basins. New species are Tornoceras n. sp. from the Büchel Formation (with coloration remains), ‘Trevoneites ’ paffrathensis n. sp. from the Lower Plattenkalk For-mation, and Maenioceras heinorum n. sp. from the Hornstein Member. New material of stringo-cephalids and Uncites is described from the Dra Valley....

Late Early Carboniferous conodonts from a supposed Middle Devonian reef limestone of the Marrakech region (Morocco)

Stratigraphy, 2017

Comparison of Frasnian (Upper Devonian) Conodont Zonations

Previously it has no t been possible to correlate the thirteen-fold Frasnian conodont zonation fi... more Previously it has no t been possible to correlate the thirteen-fold Frasnian conodont zonation first developed in the Montagne No ire, southern France, with the nine-fold standard zonation of the Frasnian. The impasse has been due to the Jact that the taxonomies underlying the two zonations are so disparate that comparisons offounallists and range charts lead to substantial misalignments. We propose here an alignment of the two zonations, based on our sampling of the Martenberg reference section of the standard zonation in the Rfienish Siate Mountains of Germany, combined with application oj the taxonomic concepts underlying the Montagne Noire zonation to the conodonts recovered. RIASSUNTO-[Confronto tra le biozonacure a conodomi del Frasniano (Devoniano sup.)] -Per molto tempo non è stato possibile correlare le tredici biozone della biozonatura a conodonti del Frasniano, basata sulle sequenze della Montagna Nera, con le nove della Biozonatura Standard del Frasniano. Questo era dovuto principalmente al fotto che i criteri tassonomici alla base delle due biozonature erano talmente diversi che il confronto di elenchi di faune e tabelle di distribuzione provocava notevoli errori nei tentativi di correlazione. Una correlazione tra le due biozonature viene qui proposta, sulla base di una nuova campionatura della sezione di Martenberg {sezione di riferimento della biozonatura standard, nelle Montagne del Reno, in Germania), alla quale sono stati applicati i criteri tassonomici che stanno alla base della biozonatura della Montagna Nera.

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Frasnian-Famennian extinction events in the Devonian at Coumiac, southern France

Details are given of the succession of conodonts, goniatites and trilobites across the Frasnian-F... more Details are given of the succession of conodonts, goniatites and trilobites across the Frasnian-Famennian boundary, documenting extinction and appearance levels of the Kellwasser Events at Coumiac, north of Cessenon (Herault). The sequence may be considered as a potentially global stratotype boundary section for the definition of this boundary. -Authors

Unter-karbonische Trilobiten aus dem Anti-Atlas (S-Marokko) Lower Carboniferous trilobites from the Anti-Atlas (Morocco) 13 Abbildungen, 2 Tabellen und 3 Tafeln

Unter-karbonische Trilobiten aus dem Anti-Atlas (Marokko). – Geologica et Palaeontologica 44: 37 ... more Unter-karbonische Trilobiten aus dem Anti-Atlas (Marokko). – Geologica et Palaeontologica 44: 37 -74, 13 Abb., 2 Tab., 3 Taf.; Marburg, 31. 3. 2012. Neue Trilobiten-Funde aus dem Unter-Karbon (Mississippium) des Anti-Atlas in Marokko werden beschrieben. Sie stammen von einem Fund-Punkt in W-Marokko (Dra-Tal) und 10 Fund-Punkten in E-Marokko (Maíder, Tafilalt). Die Fund-Stellen und ihre stratigraphische Stellung werden diskutiert. Ihre stratigraphische Reichweite erstreckt sich vom höchsten Ober-Devon bis in das Ober-Viseum, mit einem Schwerpunkt im Unter-Tournaisium. Vorhanden sind 14 Trilobiten-Taxa, von denen 6 Arten und 2 Unterarten neu sind: Cyrtoproetus (Crassibole) acrops n. sp., Chlupacula (Chlupacula) erfoudensis n. sp., Diacoryphe (Archaeocoryphe) maiderensis n. sp., Dechenelloides tazoultensis n. sp., Pudoproetus zhorae n. sp., Archegonus (Phillibole) nehdenensis africanus n. ssp. und Reediella mitchelli tafilaltensis n. ssp. Die biogeographischen Beziehungen der Trilobite...

Geochemical evidence for major environmental change at the Devonian–Carboniferous boundary in the Carnic Alps and the Rhenish Massif

Palaeogeography, Palaeoclimatology, Palaeoecology, 2006

A positive carbon isotope excursion is reported for the global Hangenberg Event near the Devonian... more A positive carbon isotope excursion is reported for the global Hangenberg Event near the Devonian-Carboniferous boundary, one of the most significant Phanerozoic mass extinction events. The δ 13 C excursion occurs both in micritic limestones and in sedimentary organic matter of black shales and limestones from different palaeogeographical regions, which were precisely correlated by conodont biostratigraphy. The excursion indicates global change in the isotopic composition of marine dissolved inorganic carbon and atmospheric CO 2 . This resulted from the increased burial of organic matter by globally widespread deposition of black shales. The δ 18 O values of conodont apatite indicate that globally widespread black shale deposition was preceded by increasing temperature, probably with a thermal gradient between equatorial and higher latitudes (∼ 20 °S). The main regressive interval of the event, correlated previously with a short-lived glacial episode in Gondwana, yielded no material for geochemical analyses, but low temperatures are recorded in overlying beds and increase again during the terminal Devonian. Early Carboniferous sea-surface temperatures were similar to those of the Late Devonian. This pattern of increased organic carbon burial, and changes in climate and sea level, is similar to that of several other extinction events of the Phanerozoic. It supports the hypothesis that increased organic carbon burial and oceanic anoxia can trigger mass extinctions, glaciations and eustatic sea-level change.

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The global Taghanic Biocrisis (Givetian) in the eastern Anti-Atlas, Morocco

Palaeogeography, Palaeoclimatology, Palaeoecology, 2011

In the Tafilalt of the eastern Anti-Atlas, Morocco, the impact of the polyphase global Taghanic C... more In the Tafilalt of the eastern Anti-Atlas, Morocco, the impact of the polyphase global Taghanic Crisis (upper part of Middle Givetian) on facies and faunas was studied in more than twenty successions of a strongly condensed hemipelagic platform (northern and central Tafilalt), of a more neritic to biostromal area with interspersed shale basins (southern Tafilalt, Amessoui Syncline), and in a

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