Coral assemblages of the Serpukhovian–Bashkirian transition from Adarouch (Morocco)

Sergio Rodríguez,Ismail Said,Ian D Somerville,Pedro Cózar,Ismael Coronado

doi:10.1007/s12542-021-00586-3

Abstract

The Carboniferous outcrops from Adarouch (central Morocco) are composed of siliciclastic and carbonate rocks, and the latter have yielded abundant fossils. The upper part of the marine succession in the Idmarrach Formation and its laterally equivalent Tirhela Formation belong to the Bashkirian. More recent investigations of poorly preserved coral assemblages from the upper part of Idmarrach 2 section and the upper part of the Tirhela Formation are here described. The assemblage from the upper Idmarrach Formation comprises several typical Mississippian taxa, such as Aulophyllum fungites, Dibunophyllum bipartitum, Koninckophyllum interruptum, Siphonodendron scaleberense and Lithostrotion decipiens, and some highly evolved forms previously undescribed of Mississippian genera such as Haplolasma sp., Arachnolasma sp., Siphonodendron sp., Diphyphyllum sp., Solenodendron sp., Clisiophyllum sp. and a new species Corwenia tirhelensis sp. nov. In addition, an undetermined petalaxid has been also recorded. Similarly, the assemblage from near the top of the Tirhela Formation yielded some species regarded usually as Mississippian, such as Palaeosmilia murchisoni and Lithostrotion decipiens. We also identified the long-ranging tabulate Syringopora sp., Corwenia tirhelensis sp. nov., and a single species of the fasciculate rugosan, Siphonodendron tindoufense, previously described from Bashkirian rocks in the Tindouf Basin (southern Morocco). The presence of the latter taxon in both the Idmarrach and Tirhela sections implies a communication between the Adarouch region and the Saharan basins. The occurrence of S. tindoufense at the approximately same stratigraphic level in Tindouf, Taoudenni, Reggan-Ahnet and Adarouch, demonstrates its important regional stratigraphic value in North Africa.

Highlights

The Carboniferous stratigraphic successions from Adarouch, in the Moroccan Central Meseta (Fig. 1), are composed both of siliciclastic and carbonate rocks, with the latter rich in diverse fossil groups such as foraminifers, algae, brachiopods, conodonts, bryozoans, crinoids and corals. Termier (1936) first described the stratigraphy of the Palaeozoic1 3 Vol.:(0123456789)from the Moroccan Meseta
As the Bashkirian age of those rocks is well established using foraminifers and conodonts, it implies that some of the species are being recorded for the first time in the Bashkirian: Lithostrotion decipiens, Aulophyllum fungites, Koninckophyllum interruptum, Diphyphyllum fasciculatum, Siphonodendron scaleberense, Solenodendron furcatum and the genus Clisiophyllum extending their stratigraphical distribution to the lower Bashkirian
Some other species and genera typically recorded in the Mississippian (Palaeosmilia murchisoni, Dibunophyllum bipartitum, Arachnolasma sp.) were previously recorded in the lower Bashkirian from the Tindouf Basin (Rodríguez et al 2013; Cózar et al 2014b) and their Bashkirian distribution is confirmed here

Summary

Introduction

The Carboniferous stratigraphic successions from Adarouch, in the Moroccan Central Meseta (Fig. 1), are composed both of siliciclastic and carbonate rocks, with the latter rich in diverse fossil groups such as foraminifers, algae, brachiopods, conodonts, bryozoans, crinoids and corals. Termier (1936) first described the stratigraphy of the Palaeozoic. Clisiophyllum sp., specimen IDM2/9–26, transverse section 1 cm scale bar, same for all pictures, except Fig. 4:13 (1 mm scale bar) two Bashkirian species (S. tindoufense and S. ouarkzizense), recorded in the Tindouf Basin (Rodríguez et al 2013) and share with them the main diagnostic features, mostly flat tabulae and discontinuous axial columella. Siphonodendron scaleberense Nudds and Somerville, 1987 (Fig. 5:8)—Only one branching fragment of a fasciculate colony has been recorded in a debris bed (unit 9) It is smaller in size than the type material (9 mm in tabularium diameter), the number of major septa (36) is the same. The other two specimens show slightly larger measurements (19–20 major septa and 3–3.5 mm in tabularium diameter) but are included in the same species

Siphonodendron scaleberense

Discussion

Conclusions