Middle to basal Upper Givetian facies development, faunal blooms, sea-level changes (including new depophase subdivisions) and extinctions (+ 1 to + 4 ) in the central (Mdoura-East to Ouidane Chebbi), southern (Amessoui Syncline), and southeastern Tafilalt (Hassi Nebech).

Contexts in source publication

Context 1

... L. mucronatus and Po. varcus. Subordinate Po. ovatinodosus and T. aff. weddigei (Aboussalam, 2003, pl. 28, Figs. 23-24) indicate that the upper part of the ansatus Zone has been reached. In the SE Tafilalt (Hassi Nebech) the Maenioceras Marl has changed into a sequence of hypoxic shales, variably with poor or rich goethitic/ haematitic faunas (Fig. 6), and alternating with thin siltstone or nodular interbeds (Fig. 5). As on the platform, the rotund Maenioceras n. sp. II (Figs. 8.3-4) is dominant and associated with some Afromaenioceras sulcatostriatum, Sobolewia, Agoniatites, and tornoceratids, especially in Beds 4 to 6. At the southern limb of the Amessoui Syncline (Jebel ...

Context 2

... lower contact (Figs. 7.4-5) that represents a disconformity and regressive phase. The name-giving Sellagoniatites waldschmidt occurs occasionally but other macrofaunal elements (some phacopids and gastropods) are rare. Agoniatites costulatus, Wedekindella, and Holzapfeloceras have regionally become extinct at its base (Fig. 3, Extinction 1 in Fig. 6) but Wedekindella ranges higher in the Dra Valley of Morocco ( ). The bed consists of three distinctive subunits (e.g., Figs. 5 and 7.5) that are separated by shallowing upwards successions (e.g., Figs. 10.3-4) and bioturbated discontinuity surfaces. The lower subunit, a styliolinid wackestone, has conodont faunas with dominant L. ...

Context 3

... weddigei (Bou Tchrafine) and of T. aff. caelatus (Mdoura-East, Figs. 9.9-10). The upper subunit tends to be much thinner than the lower two subunits or is reduced to a ferrugineous crust. Shallowing upwards is further indicated by the incoming of tabulate corals, the lack of fine matrix, and by an intraclastic level at Seheb-el-Rhassal (noted in Fig. 6). The intraclasts consist of mudstones that must have been reworked from older ...

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... but otherwise unfossiliferous sandstone, consisting of angular quartz grains. At Section 1b there is a more expanded interval of nodular limestone (poorly fossiliferous mudstone) and siltstone, with a high content of fine and evenly dispersed sand at the top. The combined evidence suggests a pre-crisis regression throughout the Tafilalt (Fig. 6), as a prelude to the main Taghanic Crisis. The sedimentation may have been most complete at Oum el Jerane, where thick and poorly fossiliferous Maenioceras Shales are only locally interrupted by tempestite lenses. Extinction 2 (Fig. 6) refers to a turnover in rugose corals faunas that needs to be studied in more ...

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... evenly dispersed sand at the top. The combined evidence suggests a pre-crisis regression throughout the Tafilalt (Fig. 6), as a prelude to the main Taghanic Crisis. The sedimentation may have been most complete at Oum el Jerane, where thick and poorly fossiliferous Maenioceras Shales are only locally interrupted by tempestite lenses. Extinction 2 (Fig. 6) refers to a turnover in rugose corals faunas that needs to be studied in more ...

Context 6

... at Seheb-el-Rhassal) although L. linguiformis, L. weddigei, L. klapperi, Po. ansatus and Po. varcus dominate. Po. timorensis, Po. xylus xylus, and Po. ovatinodosus are moderately common. New records from Mdoura-East (Table 1) include T. weddigei ( Fig. 9.12), T. aff. weddigei, T. variabilis sardinia ( Fig. 9.11), and T. variabilis variabilis ( Fig. 9.6). Fig. 9.5), I. brevis brevis, and Prioniodina ...

Context 7

... and fourth), others (first and third) thick and distinctive; the trace fossil bed is the top of Cycle 6 and the top of the ansatus Zone. Regressive trends are indicated by reworked mudstone clasts at the base of thin higher-energy sediments, such as the laminated styliolinid packstones (e.g., top of Cycle 1 at Hassi Nebech, Section 1, Fig. 10.2). Fig. 6 is based on the final disappearance of various conodonts (Fig. 2) and of the goniatite genera Agoniatites, Sobolewia, and "Trevoneites" (Fig. ...

Context 8

... possibly a new species ancestral to "Po." collieri sensu its holotype; 9.7) and T. aff. weddigei (Aboussalam, 2003, pl. 28, figs. 14-15) may continue the crisis bloom of the genus (Fig. 2). At the top of the bed the long-time dominant L. linguiformis declines in all platform sections and L. weddigei and L. klapperi become extinct (Extinction 4 in Fig. 6). The faunal change in conodonts is less severe than in ammonoids. At Mdoura-East (Table 1) the semialternans Zone limestones yielded a well-preserved Lat. latericriodus latericriodus ( Fig. 9.21), which was regionally only known from around the Upper pumilio Event. The taxon, however, is widespread in the Upper Tully Limestone and ...

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... conodont fauna with L. linguiformis, Po. ansatus, and Po. varcus; so far there is no local Oz. semialternans record. An overlying marl unit includes a final thin styliolinite (recrystallized styliolinid packstone with tentaculites, trilobites and ostracodes) and supports the idea of a second depositional subcycle in the upper crisis interval (Fig. 6). The same upper marl is rich in haematite at Section 2 (Bed 10b, Fig. 5) and yielded rare Afromaenioceras sulcatostriatum as the last representative of its family, as well as some phacopids. A subsequent grey nodular marl, the shallowing phase of the upper subcycle, contains Pharciceras aff. amplexum and phacopids. Oz. semialternans ...

Context 10

... with the post-crisis transgression at the base of the hermanni Zone. Evolutionary innovation took place contemporaneously in different lineages (Polygnathus s. str., Po. limitaris Group, Oz. sannemanni Group, Schmidtognathus). 11. The Taghanic Crisis caused a change of biostrome palaeoecology in the southern Tafilalt (Extinctions 2 and 4 in Fig. 6). Post-crisis coral limestones have fewer alveolitids and more thamnoporids and phillipsastreids. The taxonomic composition of biostromes from below, within, and above the crisis interval has not yet been investigated in detail. Therefore, it is currently difficult to estimate the coral extinction rate. Stromatoporoids have not yet ...