Geochemical investigation of the taphonomy, stratigraphy, and palaeoecology of the mammals from the Ouled Abdoun Basin (Paleocene-Eocene of Morocco)

• Published in: Palaeogeography, palaeoclimatology, palaeoecology Vol. 577; pp. 110523 - 17
• Main Authors: Kocsis, László, Ulianov, Alex, Mouflih, Mustapha, Khaldoune, Fatima, Gheerbrant, Emmanuel
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2021; Elsevier
• Subjects: Bioapatite; Biodiversity; Earth Sciences; Life Sciences; Paleontology; Phosphorite; Populations and Evolution; Rare earth elements; Sciences of the Universe; Stable isotopes; Strontium isotopes; Systematics, Phylogenetics and taxonomy; Bioapatite; Rare earth elements; Stable isotopes; Strontium isotopes; Phosphorite; stable isotopes; phosphorite; bioapatite; strontium isotopes; rare earth elements
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2021.110523

We performed different geochemical analyses of Paleogene terrestrial mammal remains to establish their taphonomy, stratigraphic provenance, and palaeoenvironmental conditions. Rare earth element (REE) results indicate a similar diagenetic history to that of previously investigated marine taxa from these beds. Therefore, the mammal remains were initially deposited in a marine setting, and probably not long after the death of the animals their bodies were washed into the sea. The Ce/Ce* and Pr/Pr* ratios for the mammal fossils were compared with the background dataset from the phosphate mines, which varies with time. This allowed us to characterize the stratigraphic levels bearing the fossils. The provenances of fossils with known origins were confirmed, while remains with unknown origins could be assigned to certain stratigraphic horizons that are compatible with previously proposed phylogenic relationships.
Marine diagenesis affected the various skeletal tissues differently, with the largest alteration in the bone and the least or none in the enamel. This is mostly demonstrated by the high F concentration, high Ca/P, and seawater related 87Sr/86Sr in the bone/dentine samples. Enamel shows the opposite, and retained the most pristine terrestrial values. The δ18OPO4 and δ13C results from mammal enamel revealed warm (>20 °C mean annual temperature-MAT) and dry (<500 mm mean annual precipitation) conditions for Paleocene-Eocene period in the region. From the early to mid-Ypresian about +5 °C ΔMAT is recorded that might be linked to the Early Eocene Climatic Optimum.
Furthermore, the 87Sr/86Sr ratios derived from shark tooth enameloid fit the global open ocean Sr-isotope record during the latest Paleocene and early Eocene providing further evidence for the age of these phosphate beds in the Ouled Abdoun Basin. However, older marine fossils yielded higher ratios than the global Sr-isotope curve, reflecting an alteration and/or somewhat restricted conditions in the Moroccan coastal basins, possibly triggered by global sea-level changes.
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•Rare earth element (REE) chemistry of fossil bones traces stratigraphic origin.•Marine diagenesis of terrestrial remains indicated by REE, Ca/P and 87Sr/86Sr.•The δ18OPO4 and δ13C of mammal enamel are linked to climatic conditions.•Warm and dry terrestrial biotope recognized for the Paleocene-Eocene period.•87Sr/86Sr ratios of marine fossils confirmed latest Paleocene and early Eocene age.