Geology, biostratigraphy and carbon isotope chemostratigraphy of the Palaeogene fossil-bearing Dakhla sections, southwestern Moroccan Sahara

MOULOUD BENAMMI, SYLVAIN ADNET, LAURENT MARIVAUX, JOHAN YANS, CORENTIN NOIRET, RODOLPHE TABUCE, JÉRÔME SURAULT, IMAD EL KATI, SÉBASTIEN ENAULT, LAHSSEN BAIDDER, OMAR SADDIQI, MOHAMED BENAMMI

Research output: Contribution to journalReview article

Abstract

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-grained to microconglomeratic sandstones interbedded with silts, indicating deposition in a shallow-marine environment with fluvial influence. The natural remanence magnetization of a total of 50 samples was measured; the intensity of most of the samples is too weak however, before or after the first step of demagnetization. The palaeomagnetic data from the samples are very unstable, except for eight from three similar sandstone levels which show a normal polarity. Matched with biostratigraphic data on rodents, primates, the selachian, sirenian and cetacean faunas, the new carbon isotope chemostratigraphy on organics (1) refines the age of the uppermost C2 fossil-bearing bed to earliest Oligocene time and (2) confirms the Priabonian age of the B1 to C1 levels.
Original languageEnglish
Pages (from-to)117-132
Number of pages16
JournalGeological Magazine
Volume156
Issue number1
DOIs
Publication statusPublished - 2019

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chemostratigraphy
biostratigraphy
Paleogene
carbon isotope
geology
sandstone
fossil
vertebrate
sirenian
phosphorite
cetacean
demagnetization
chert
siltstone
whale
cliff
magnetization
primate
sediment
rodent

Keywords

  • Oligocene rodents
  • southwestern Morocco
  • magnetostratigraphy
  • chemostratigraphy
  • biostratigraphy

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BENAMMI, MOULOUD ; ADNET, SYLVAIN ; MARIVAUX, LAURENT ; YANS, JOHAN ; NOIRET, CORENTIN ; TABUCE, RODOLPHE ; SURAULT, JÉRÔME ; EL KATI, IMAD ; ENAULT, SÉBASTIEN ; BAIDDER, LAHSSEN ; SADDIQI, OMAR ; BENAMMI, MOHAMED. / Geology, biostratigraphy and carbon isotope chemostratigraphy of the Palaeogene fossil-bearing Dakhla sections, southwestern Moroccan Sahara. In: Geological Magazine. 2019 ; Vol. 156, No. 1. pp. 117-132.
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abstract = "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-grained to microconglomeratic sandstones interbedded with silts, indicating deposition in a shallow-marine environment with fluvial influence. The natural remanence magnetization of a total of 50 samples was measured; the intensity of most of the samples is too weak however, before or after the first step of demagnetization. The palaeomagnetic data from the samples are very unstable, except for eight from three similar sandstone levels which show a normal polarity. Matched with biostratigraphic data on rodents, primates, the selachian, sirenian and cetacean faunas, the new carbon isotope chemostratigraphy on organics (1) refines the age of the uppermost C2 fossil-bearing bed to earliest Oligocene time and (2) confirms the Priabonian age of the B1 to C1 levels.",
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author = "MOULOUD BENAMMI and SYLVAIN ADNET and LAURENT MARIVAUX and JOHAN YANS and CORENTIN NOIRET and RODOLPHE TABUCE and J{\'E}R{\^O}ME SURAULT and {EL KATI}, IMAD and S{\'E}BASTIEN ENAULT and LAHSSEN BAIDDER and OMAR SADDIQI and MOHAMED BENAMMI",
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BENAMMI, MOULOUD, ADNET, SYLVAIN, MARIVAUX, LAURENT, YANS, JOHAN, NOIRET, CORENTIN, TABUCE, RODOLPHE, SURAULT, JÉRÔME, EL KATI, IMAD, ENAULT, SÉBASTIEN, BAIDDER, LAHSSEN, SADDIQI, OMAR & BENAMMI, MOHAMED 2019, 'Geology, biostratigraphy and carbon isotope chemostratigraphy of the Palaeogene fossil-bearing Dakhla sections, southwestern Moroccan Sahara', Geological Magazine, vol. 156, no. 1, pp. 117-132. https://doi.org/10.1017/S0016756817000851

Geology, biostratigraphy and carbon isotope chemostratigraphy of the Palaeogene fossil-bearing Dakhla sections, southwestern Moroccan Sahara. / BENAMMI, MOULOUD; ADNET, SYLVAIN; MARIVAUX, LAURENT; YANS, JOHAN; NOIRET, CORENTIN; TABUCE, RODOLPHE; SURAULT, JÉRÔME; EL KATI, IMAD; ENAULT, SÉBASTIEN; BAIDDER, LAHSSEN; SADDIQI, OMAR; BENAMMI, MOHAMED.

In: Geological Magazine, Vol. 156, No. 1, 2019, p. 117-132.

Research output: Contribution to journalReview article

TY - JOUR

T1 - Geology, biostratigraphy and carbon isotope chemostratigraphy of the Palaeogene fossil-bearing Dakhla sections, southwestern Moroccan Sahara

AU - BENAMMI, MOULOUD

AU - ADNET, SYLVAIN

AU - MARIVAUX, LAURENT

AU - YANS, JOHAN

AU - NOIRET, CORENTIN

AU - TABUCE, RODOLPHE

AU - SURAULT, JÉRÔME

AU - EL KATI, IMAD

AU - ENAULT, SÉBASTIEN

AU - BAIDDER, LAHSSEN

AU - SADDIQI, OMAR

AU - BENAMMI, MOHAMED

PY - 2019

Y1 - 2019

N2 - 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-grained to microconglomeratic sandstones interbedded with silts, indicating deposition in a shallow-marine environment with fluvial influence. The natural remanence magnetization of a total of 50 samples was measured; the intensity of most of the samples is too weak however, before or after the first step of demagnetization. The palaeomagnetic data from the samples are very unstable, except for eight from three similar sandstone levels which show a normal polarity. Matched with biostratigraphic data on rodents, primates, the selachian, sirenian and cetacean faunas, the new carbon isotope chemostratigraphy on organics (1) refines the age of the uppermost C2 fossil-bearing bed to earliest Oligocene time and (2) confirms the Priabonian age of the B1 to C1 levels.

AB - 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-grained to microconglomeratic sandstones interbedded with silts, indicating deposition in a shallow-marine environment with fluvial influence. The natural remanence magnetization of a total of 50 samples was measured; the intensity of most of the samples is too weak however, before or after the first step of demagnetization. The palaeomagnetic data from the samples are very unstable, except for eight from three similar sandstone levels which show a normal polarity. Matched with biostratigraphic data on rodents, primates, the selachian, sirenian and cetacean faunas, the new carbon isotope chemostratigraphy on organics (1) refines the age of the uppermost C2 fossil-bearing bed to earliest Oligocene time and (2) confirms the Priabonian age of the B1 to C1 levels.

KW - Oligocene rodents

KW - southwestern Morocco

KW - magnetostratigraphy

KW - chemostratigraphy

KW - biostratigraphy

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U2 - 10.1017/S0016756817000851

DO - 10.1017/S0016756817000851

M3 - Review article

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SN - 0016-7568

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