Geochemical investigation of the taphonomy, stratigraphy, and palaeoecology of the mammals from the Ouled Abdoun Basin (Paleocene-Eocene of Morocco) (original) (raw)
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Gondwana Research, 2014
first insight into the organic carbon isotope chemostratigraphy (δ 13 C org) of the Moroccan phosphate series and Available online 25 April 2013 a refined dating of its vertebrate-bearing levels. Four Paleocene-Eocene sections in the NE Ouled Abdoun quarries show consistent δ 13 C org long term evolutions, from the base to the top: 1) positive trend in phosphorite Handling Editor: P. Eriksson Bed IIa, beginning with the lower Bone Bed yielding mammals such as Eritherium, Ocepeia, Abdounodus, Lahimia, Keywords: of early Thanetian and Selandian age; 2) transitional negative trend in the Intercalary phosphorite Beds II/I that Ouled Abdoun Basin includes the Otodus obliquus and Phosphatherium escuilliei Bone Bed of earliest Ypresian age; 3) negative trend to Carbon isotopes the lowermost δ 13 C org values that are correlative to the early-middle Ypresian interval including ETM 2 and ETM Paleocene-Eocene phosphorites 3 hyperthermal events in the global record; 4) positive trend in chert-enriched facies containing the middle EECO Ypresian EECO global climatic event. Our chemostratigraphic study of the Ouled Abdoun phosphate series African mammals provides a new chronostratigraphic framework for calibrating the beginning of the evolution of placental mammals in Africa. The lower Bone Bed level from the Paleocene phosphorite Bed IIa yielding Eritherium is not younger than early Thanetian, and is most likely Selandian. The Phosphatherium Bone Bed in the Intercalary Beds II/I is earliest Ypresian. The phosphorite Bed 0, from which Daouitherium probably came, is early-middle Ypresian, just below the EECO. This suggests that the first large proboscideans evolved after the PETM, during mid-Ypresian warming events. The δ 13 C org study does not support the presence of Lutetian in the NE Ouled Abdoun phosphate series and suggests that a noticeable part of the upper Thanetian is absent.
International Journal of Earth Sciences, 2012
Fossil shark teeth and coprolites from three major phosphorite occurrences in the Gafsa Basin (southwestern Tunisia) were investigated for their geochemical compositions to improve local stratigraphy and to better assess paleoenvironmental conditions. 87 Sr/ 86 Sr isotope ratios of shark teeth from the Early Maastrichtian El Haria Formation and from the Early Eocene Métlaoui s.s. Formation yielded Sr isotope ages of 68 ± 1 and 47.9 ± 1.3 Ma, respectively, which accord with the expected stratigraphic positions of these sediments. Conversely, shark teeth from the Paleocene-Eocene Chouabine Formation have large variation in Sr isotope ratios even within individual layers. After statistical treatment and then elimination of certain outlier samples, three age-models are proposed and discussed. The most reasonable solution includes three subsequent Sr ages of 61.8 ± 2.2 Ma, 57.2 ± 1.8 and 54.6 ± 1.6 for layer IX, layers VIII-V and layers IV-0, respectively. Three scenarios are discussed for explanation of the presence of the outliers: (1) diagenesis, (2) reworking and (3) locally controlled seawater Sr isotope ratio. The most plausible account for the higher 87 Sr/ 86 Sr ratios relative to the global ocean in some fossils is enhanced intrabasinal reworking due to low sea level. Conversely, the sample with lower 87 Sr/ 86 Sr than the global seawater may link to diagenesis or to seawater influenced by weathering of Late Cretaceous marine carbonates, which latter is supported by model calculation as well. The e Nd values of these fossils are very similar to those reported for Paleogene and Late Cretaceous Tethyan seawater and are compatible with the above interpretations. The relatively low oxygen isotope values in shark teeth from the topmost phosphate bed of the Chouabine Formation, together with the Sr isotope results, point toward recovering better connections with the open sea. These d 18 O data reflect elevated ambient temperature, which may link to the Early Eocene Climatic Optimum.
Geological Magazine, 2017
New Palaeogene vertebrate localities were recently reported in the southern Dakhla area (southwestern Morocco). The Eocene sediment strata crops out on cliffs along the Atlantic Ocean coast. Vertebrate remains come from five conglomeratic sandstone beds and are principally represented by isolated teeth belonging to micromammals, selachians and bony fishes, a proboscidean assigned to ?Numidotherium sp. and many remains of archaeocete whales (Basilosauridae). From fieldwork five lithostratigraphic sections were described, essentially based on the lithological characteristic of sediments. Despite the lateral variations of facies, correlations between these five sections were possible on the basis of fossil-bearing beds (A1, B1, B2, C1 and C2) and five lithological units were identified. The lower part of the section consists of rhythmically bedded, chert-rich marine siltstones and marls with thin black phosphorite with organic matter at the base. The overlying units include coarse-grai...
PLOS ONE, 2019
Here we explore the carbon and oxygen isotope compositions of the co-existing carbonate and phosphate fractions of fish tooth enameloid as a tool to reconstruct past aquatic fish environments and harvesting grounds. The enameloid oxygen isotope compositions of the phosphate fraction (δ 18 O PO4) vary by as much as~4‰ for migratory marine fish such as gilthead seabream (Sparus aurata), predominantly reflecting the different saline habitats it occupies during its life cycle. The offset in enameloid Δ 18 O CO3-PO4 values of modern marine Sparidae and freshwater Cyprinidae from the Southeast Mediterranean region vary between 8.1 and 11.0‰, similar to values reported for modern sharks. The mean δ 13 C of modern adult S. aurata and Cyprinus carpio teeth of 0.1±0.4‰ and-6.1±0.7‰, respectively, mainly reflect the difference in δ 13 C of dissolved inorganic carbon (DIC) of the ambient water and dietary carbon sources. The enameloid Δ 18 O CO3-PO4 and δ 13 C values of ancient S. aurata (Holocene) and fossil Luciobarbus sp. (Cyprinidae; mid Pleistocene) teeth agree well with those of modern specimens, implying little diagenetic alteration of these tooth samples. Paired δ 18 O PO4-δ 13 C data from ancient S. aurata teeth indicate that hypersaline water bodies formed in the Levant region during the Late Holocene from typical Mediterranean coastal water with high evaporation rates and limited carbon input from terrestrial sources. Sparid tooth stable isotopes further suggest that coastal lagoons in the Eastern Mediterranean had already formed by the Early Holocene and were influenced by terrestrial carbon sources. Overall, combined enameloid oxygen and carbon isotope analysis of fish teeth is a powerful tool to infer the hydrologic evolution of aquatic environments and assess past fishing grounds of human populations in antiquity.
The Maastrichtian to Ypresian dated sediments of the Tahar Cut [1, 2], Western Outer Rif (Northwest Morocco), are studied here for paleoenvironmental and paleoclimatic reasons. The results of quantitative and qualitative analyses of dinoflagellate cysts and other palynomorphs of continental origin (spores and pollen) allowed the reconstruction, in ascending order, of twelve different marine depositional environments: (1) outer neritic without productivity and thus without continental influence at the base of the section (Th1-Th3: Upper Maastrichtian); (2) inner neritic without productivity (Th4: Upper Maastrichtian:); (3) shallow outer neritic with low productivity (Th5-Th7: Upper Maastrichtian); (4) inner neritic in a phase of marine regression and widespread cold climatic conditions at the end of the Maastrichtian (Th7a-Th7b': Upper Maastrichtian); (5) outer neritic of very low productivity marking thus a slight marine transgression (Th7c : Danian); (6) inner neritic, reflecting a relative decrease in sea level (Th7d: Danian); (7) outer neritic with very low biological productivity for interval G, reflecting a rise in sea level compared to the previous interval (Th7e-Th7f: Selandian-Thanetian); (8) indeterminate paleoenvironment due to the scarcity of palynomorphs in this interval (Th8: Selandian-Thanetian); (9) marine oceanic without productivity which would result in a marine transgression (Th8a: Selandian-Thanetian); (10) neritic external (Th9: Selandian-Thanetian); (11) neritic internal without productivity for the K interval with a drop in sea level, under relatively warm climatic conditions (Th9a: Ypresian); (12) outer neritic, which would result in a marine transgression (Th10-Th11: Ypresian). These variations in paleoenvironments coincide with global climate changes at the Cretaceous-Paleocene (K-Pg) and Paleocene-Eocene (P-E) boundaries.