New insights on the Late Paleocene − Early Eocene dinoflagellate cyst zonation for the Paris and Dieppe basins

Alina I Iakovleva,Christian Dupuis,Florence Quesnel

doi:10.1051/bsgf/2021035

Abstract

The Anglo-Belgo-Paris Basin, historical cradle of the Paleogene stratigraphy since the 19th century, is known by the presence of very specific so-called “Sparnacian” deposits (very diverse and laterally highly variable, predominantly lagoonal to terrestrial facies), which encompass the short stratigraphic interval of the Paleocene-Eocene Thermal Maximum (PETM). Due to the insufficient nature of the paleontological record, the “Sparnacian” succession of the Paris and Dieppe-Hampshire basins still needs to be robustly chronostratigraphically correlated with other Paleogene records worldwide. In order to refine the stratigraphy of the Thanetian-Lower Ypresian succession in northern France a number of cores and outcrop sections have been investigated palynologically. As a result, an updated version of the dinoflagellate cyst zonation for the Paris and Dieppe basins is proposed and contains six new or revised biozones for this stratigraphical interval:Alisocysta margarita,Apectodinium hyperacanthum,Apectodinium-acme,Biconidinium longissimum-acme,Dracodinium astra, andAxiodinium lunare/Stenodinium meckelfeldense. Based on combined bio-, litho- and chemostratigraphic data, it appears that the dinocyst assemblages, corresponding to the PETM event interval (“Sparnacian” deposits, Soissonnais and upper Mortemer formations), are characterized by an acme ofApectodiniumspp. (70–98%) in both basins, sometimes alternating with an acme of a few gonyaulacoid groups in the Dieppe Basin. Dinocyst assemblages from the PETM interval contain a significant number of atypical, longer specimens ofApectodinium parvum, which could represent an ecological onshore substitute forAxiodinium augustumin the Paris and Dieppe-Hampshire basins. The establishment of a newBiconidinium longissimum-acme Zone suggests that the stratigraphic hiatus previously inferred within this sequence in the Paris Basin does not exist.

Highlights

The Paris Basin is where the Paleocene Epoch and the “Sparnacian Stage” were originally defined and introduced in the 19th century (Dollfus, 1880; Schimper, 1874)
The establishment of a new Biconidinium longissimum-acme Zone suggests that the stratigraphic hiatus previously inferred within this sequence in the Paris Basin does not exist
Our updated version of dinoflagellate cyst zonation of the Late Paleocene-Early Eocene interval for northern France is based on the study of ∼600 palynological samples, investigated during the last 13 years under the scope of the BRGM PaleoScene and “Paléosurface éocène-Paleocene-Eocene Thermal Maximum (PETM)” research projects from more than 35 new or already well-known PaleoceneLower Eocene key localities and boreholes (Fig. 3)

Summary

Introduction

The Paris Basin is where the Paleocene Epoch and the “Sparnacian Stage” were originally defined and introduced in the 19th century (Dollfus, 1880; Schimper, 1874). Broadly referred to the Paleocene “Sables de Bracheux” and the Eocene “Sables de Cuise”, bracket a poorly understood lithologic body composed by terrestrial and brackish clays, limestones, sands and lignites (mostly containing organic matter) and widely referred to as “Argiles à Lignites” This lithologic complex of littoral to terrestrial deposits with particular facies and faunas, sandwiched between marine Thanetian and “Cuisian” sands, was considered in the 19th century sufficiently distinctive as to erect a new, Sparnacian stage by Dollfus (1880). The “Sparnacian” deposits, diachronous across the Paris and Dieppe basins and represented by diverse and laterally highly variable, predominantly lagoonal and non-marine facies, are still insufficiently documented and chronostratigraphic correlation with other Paleogene records worldwide needs to be updated

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