Vertebrate Assemblages from the Early Late Cretaceous of Southeastern Morocco: an Overview
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Journal of African Earth Sciences 57 (2010) 391–412 Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci Geological Society of Africa Presidential Review No. 16 Vertebrate assemblages from the early Late Cretaceous of southeastern Morocco: An overview L. Cavin a,*, H. Tong b, L. Boudad c, C. Meister a, A. Piuz a, J. Tabouelle d, M. Aarab c, R. Amiot e, E. Buffetaut b, G. Dyke f, S. Hua g, J. Le Loeuff f a Dpt. de Géologie et Paléontologie, Muséum de Genève, CP 6434, 1211 Genève 6, Switzerland b CNRS, UMR 8538, Laboratoire de Géologie de l’Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France c Faculté des Sciences et Techniques, BP, 509, Boutalamine, Errachidia, Morocco d Musée Municipal, 76500 Elbeuf-sur-Seine, France e IVPP, Chinese Academy of Sciences, 142 XiZhiMenWai DaJie, Beijing 100044, China f School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland g Musée des Dinosaures, 11260 Espéraza, France article info abstract Article history: Fossils of vertebrates have been found in great abundance in the continental and marine early Late Cre- Received 16 June 2009 taceous sediments of Southeastern Morocco for more than 50 years. About 80 vertebrate taxa have so far Received in revised form 9 December 2009 been recorded from this region, many of which were recognised and diagnosed for the first time based on Accepted 11 December 2009 specimens recovered from these sediments. In this paper, we use published data together with new field Available online 23 December 2009 data to present an updated overview of Moroccan early Late Cretaceous vertebrate assemblages. The Cre- taceous series we have studied encompasses three Formations, the Ifezouane and Aoufous Formations, Keywords: which are continental and deltaic in origin and are often grouped under the name ‘‘Kem Kem beds”, Africa and the Akrabou Formation which is marine in origin. New field observations allow us to place four Mesozoic Vertebrata recognised vertebrate clusters, corresponding to one compound assemblage and three assemblages, Palaeoecology within a general temporal framework. In particular, two ammonite bioevents characterise the lower part Palaeogeography of the Upper Cenomanian (Calycoceras guerangeri Zone) at the base of the Akrabou Formation and the upper part of the Lower Turonian (Mammites nodosoides Zone), that may extend into the Middle Turonian within the Akrabou Formation, and allow for more accurate dating of the marine sequence in the study area. We are not yet able to distinguish a specific assemblage that characterises the Ifezouane Formation when compared to the similar Aoufous Formation, and as a result we regard the oldest of the four ver- tebrate ‘‘assemblages” in this region to be the compound assemblage of the ‘‘Kem Kem beds”. This well-known vertebrate assemblage comprises a mixture of terrestrial (and aerial), freshwater and brack- ish vertebrates. The archosaur component of this fauna appears to show an intriguingly high proportion of large-bodied carnivorous taxa, which may indicate a peculiar trophic chain, although collecting biases alter this palaeontological signal. A small and restricted assemblage, the OT1 assemblage, possibly corre- sponds to a specific, localised ecosystem within the Kem Kem beds compound assemblage. Microfossils and facies from the Aoufous Formation, corresponding to the top of the compound assemblage, provide evidence of extremely abiotic conditions (hypersalinity), and thus of great environmental instability. At the base of the Akrabou Formation the first ammonite bioevent, Neolobites, corresponds to the onset of the marine transgression in the early Late Cenomanian while the Agoult assemblage (Late Cenomanian?) contains a variety of small fish species that have Central Tethyan affinities. Finally, the youngest Mam- mites bioevent in the late Early Turonian corresponds to a deepening of the marine environment: this sequence is isochronous with the Goulmima assemblage, a diverse collection of fish and other marine taxa, and shows affinities with taxa from the South Atlantic, the Central Tethys and the Western Interior seaway of North America, and further highlights the biogeographical importance of these North African Late Cretaceous assemblages. Ó 2009 Elsevier Ltd. All rights reserved. * Corresponding author. Fax: +41 22 4186301. E-mail address: [email protected] (L. Cavin). 1464-343X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jafrearsci.2009.12.007 392 L. Cavin et al. / Journal of African Earth Sciences 57 (2010) 391–412 Contents 1. Introduction ......................................................................................................... 392 2. Geological setting. ......................................................................................... 393 3. Vertebrate assemblages . ......................................................................................... 394 3.1. The compound assemblage of the Kem Kem beds . ............................................................ 394 3.1.1. Faunal list . ................................................................................. 395 3.1.2. Age, palaeoenvironment and palaeogeography . .............................................. 399 3.2. The OT1 assemblage . ............................................................................ 402 3.2.1. Faunal list . ................................................................................. 402 3.2.2. Age, palaeoenvironment and palaeogeography . .............................................. 402 3.3. The marine transgression or Neolobites bioevent . ............................................................ 402 3.4. The Agoult assemblage . ............................................................................ 402 3.4.1. Faunal list . ................................................................................. 405 3.4.2. Age, palaeoenvironment and palaeogeography . .............................................. 405 3.5. The Goulmima assemblage . ............................................................................ 405 3.5.1. Faunal list . ................................................................................. 405 3.5.2. Age, palaeoenvironment and palaeogeography . .............................................. 405 4. Discussion and conclusions . ......................................................................................... 408 Acknowledgments . ......................................................................................... 409 References . ......................................................................................................... 409 1. Introduction in 1952. In the late 1940s and early 1950s, Lavocat (1948, 1949, 1951, 1954a,b) published a series of notes on his palaeontological The Cretaceous deposits surrounding the northern, eastern and discoveries in this area of Morocco, with special emphasis on his southern borders of the Palaeozoic Tafilalt and Mader basins in dinosaur finds. In 1954, he published a geological synthesis of Morocco have yielded numerous vertebrate remains for more than the Kem Kem area (Lavocat, 1954b) which is still one of the best 50 years. The first discoveries of fossil vertebrates in the ‘Grès accounts of the local geology. The first record of marine fish frag- Infracénomaniens’ of the Kem Kem region were made by French ments in the Turonian of the High-Atlas and Midelt area had been geologists, including Choubert who found tooth plates of lungfish made slightly earlier by Dubar (1949) and over the following dec- and ganoid scales south of Taouz in 1938 (Choubert, 1948; Chou- ades only a few vertebrate remains from the ‘mid’ Cretaceous of bert et al., 1952). Indeed, the first illustrations of vertebrate fossils this area of Morocco were described, including isolated fish frag- from the Kem Kem beds were published by Choubert et al. (Fig. 1A) ments described by Tabaste (1963). In 1971, a German team from Fig. 1. Plates from Choubert et al. (1952): (A) the first illustrations of vertebrate fossils from the Kem Kem beds. Fig. 2 shows a theropod tooth referable to Carcharodontosaurus (not Megalosaurus) saharicus. Fig. 3, labelled as Crocodilus sp., is probably a Spinosaurus tooth; (B) invertebrates from the Cenomanian including Neolobites vibrayeanus (Fig. 3). L. Cavin et al. / Journal of African Earth Sciences 57 (2010) 391–412 393 the University of Göttingen discovered vertebrate fossils in the 2009). In the Early Cretaceous, North Africa was extensively cov- Taouz area, including fish (Wenz, 1980, 1981) and dinosaurs ered with deltaic and brackish deposits, which were first referred (Buffetaut, 1989); over the last 20 years, local people in this part to as the ‘Continental Intercalaire’ by Kilian (1931). As a package, of Morocco have engaged in very active excavation work to collect this series of sediments has proved difficult to date because of Cretaceous fossils for commercial purposes (while Palaeozoic the absence of marine incursions, but recent attempts to do so invertebrates from the Tafilalt and Mader basins are also being ex- based on vertebrate assemblages indicate that Nigeran outcrops tracted and sold). Because of such commercial activity, beautifully of the ‘Continental Intercalaire’ [which does not comprise a Palae- preserved fossil specimens have been discovered in both the Kem ozoic component in this country, the so-called