Sections with continuous sedimentation across the Devonian-Carboniferous (D-C) boundary in the Montagne Noire allow to build a virtual transect from shoreline to deep basin. Nearshore facies characterise the D-C boundary stratotype and neighbouring sections at La Serre in the Cabrières klippen domain and offshore facies are present at the Col de Tribes and Puech de la Suque sections in the Mont Peyroux nappe domain. Both domains exhibit equivalents of the Hangenberg Black Shale (HBS). At La Serre, an initial regressive trend is indicated by the presence of oculated trilobites in the topmost pre-HBS Wocklumeria Limestones. Above the HBS level, regressive depositional conditions characterise oolitic deposits that comprise lithic erosional flows with an admixture of transported shallow-water biotas. Maximum regression is recognised with the deposition of coarse breccias and local features of emergence prior to the first appearance of Protognathodus kockeli. The oolites are superseded by the transgression of outer shelf deposits. In the nappe domain, the HBS is intercalated in outer ramp nodular limestones, and it exhibits detrital elements pointing to its regressive nature. The regressive trend culminates than reverses when post-HBS carbonate sedimentation resumes. Protognathodus kockeli appears in the post HBS carbonates. Associated oculated trilobites indicate shallower bathymetric conditions than those of the pre-New Manuscript#1 Click here to access/download;Manuscript;Feist_D-C_MN_R#1.doc Click here to view linked References HBS Wocklumeria Limestones. Thereafter, replacement of sighted trilobites by blind ones and the protognathodid biofacies by facies dominated by siphonodellids indicate a deepening trend. The near-and off-shore sites of the D-C transition permit correlation of short-term bathymetric fluctuations with faunal turnovers and entries of biostratigraphic markers.
The widely quarried and commercially exploited Gonioclymenia Limestone 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-sized Gonioclymenia speciosa, which characterizes the Famennian V-B, and rare Leviclymenia ramula sp. nov. Associated conodont faunas fall in the Bispathodus costatus Subzone of the B. aculeatus aculeatus (= Middle expansa) Zone. A rare outcrop at Jebel Ihrs West proved that Kalloclymenia and conodont faunas of the B. ultimus ultimus (= Upper expansa) Zone occur in a separate, overlying unit of the lower part of Famennian VI. Consequently, joint occurrences of Gonioclymenia and Kalloclymenia on 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 Tafilalt Gonioclymenia Transgression may represent the regional expression of a eustatic pulse in the B. costatus Subzone that is known on the Ardennes Shelf as the transgressive Epinette Event. The conodont faunas yielded Neopolygnathus fibula sp. nov., Pseudopolygnathus primus tafilensis ssp. nov., new morphotypes of B. spinulicostatus and Pseudopolygnathus primus primus, the oldest Siphonodella (Eosiphonodella) and variable ‘siphonodelloids’ that are currently left in open nomenclature.
A review of the literature shows that the Famennian global Annulata Event(s) can be recognized as a transgressive, often hypoxic and eutrophic, interval that interrupts an overall regressive eustatic trend in more than 40 regions of North America, Europe, North Africa, Asia and Australia. According to differences in palaeogeography, sedimentology and biota, these occurrences are assigned to 10 event settings. The first detailed data on facies, ammonoid and conodont faunas are presented for the Rheris Basin of the eastern Anti-Atlas (southern Morocco) and compared with previously studied sections of the adjacent Tafilalt Platform, Tafilalt Basin and Maider Basin. The rather argillaceous succession at El Gara resembles the Tafilalt Basin (Hassi Nebech section) in its lack of black shales/limestones and similar ammonoid and conodont assemblages. However, the Sulcoclymenia sulcata Zone (Upper Devonian III-C2) below the Annulata Events contains ammonoid taxa that are unique for all of the Anti-Atlas and North Africa: Protornoceras ornatum Dybczynski, 1913, Genuclymenia aff. angelini (Wedekind, 1908), Protactoclymenia aff. implana (Czarnocki, 1989) and ?Pleuroclymenia sp. juv. The first regional record of the marker conodont Pseudopolygnathus granulosus Ziegler, 1962 also distinguishes the pre-event assemblage. As in many other regions, there is a major decline in ammonoids well before the Lower Annulata Event, which suggests an episode of extreme oligotrophy. Both Annulata Events at El Gara are whitish-weathered marly shales with only small specimens of Platyclymenia and Prionoceras (sensu lato), which are also typical for the annulata Zone (UD IV-A) of other Tafilalt sections, but benthonic organisms are nearly absent. This suggests local low-oxygen conditions, but only a moderate production of organic carbon, insufficient for black shale formation, unlike many German sections or in the Maider Basin (section Mrakib). The latter region represents a deeper shelf basin that had much higher productivity and a unique ‘Gundolficeras–Erfoudites–Protactoclymenia–Stenoclymenia–Guerichia biofacies’ of the Lower Annulata Shale. The upper part of the annulata Zone at El Gara is characterized by Platyclymenia (Platyclymenia) levata n. sp. Other new taxa of the same zone in the Anti-Atlas are Posttornoceras ascendens n. sp. and Stenoclymenia rectangula n. sp. Whilst the ammonoid faunal overturn between UD III-C and UD IV-A was severe, the strong reduction in conodont diversity with the two Annulata Events was mostly (apart from two taxa) a palaeoecologically triggered, only episodic, feature. The comparison of the various Anti-Atlas Annulata Event beds and assemblages enables the distinction of event biofacies types, which reflect local differences of bathymetry, trophic conditions and seafloor ventilation.
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