Stratigraphy and palaeontology of the lower Miocene Kiel Sand Member (Berchem Formation) in temporary exposures in Antwerp (northern Belgium)

Abstract

The stratigraphic position of the lower Miocene Kiel Sand Member of the Berchem Formation in the Antwerp area (northern Belgium) is not well constrained and its depositional environments are poorly known. Due to a spatial limited decalcification front, the Kiel Sand Member is completely decalcified in southern Antwerp and gradually becomes fossiliferous to the north-east of the city. The stratigraphy and palaeontology of the fossiliferous sediments in three temporary exposures are presented. The dinoflagellate cyst analysis of fossiliferous horizons shows the relative progress of a transgression in the southern North Sea Basin during the early–middle Burdigalian, that probably initiated in the late Aquitanian. The Kiel Sand Member contains an important mollusc fauna, with several species reported for the first time from this member. The taphonomy and fauna of the shell beds indicate a shallow marine, high energetic depositional environment, strongly influenced by storms, currents, waves and a rather low sedimentation rate. The climate was warm-temperate to subtropical. In all studied sections, the Kiel Sand Member could be clearly distinguished from the Antwerpen Sand Member: similarities and differences are discussed. Moving to the north of Antwerp, the erosive base of the Antwerpen Sand Member cuts deeper into the Kiel Sand Member. The Early Miocene Unconformity (EMU) is suggested at this contact.

Distinguishing the Miocene Kiel and Antwerpen Members (Berchem Formation) and their characteristic horizons using cone penetration tests in Antwerp (northern Belgium)

“…A closer look at the correlation between the Argenta outcrop as described and drawn by De Schutter and Everaert (2020) and a nearby mechanical CPT. Everaert et al (2020) performed dinocyst analyses on samples of this outcrop and thereby established the biozones as defined by de Verteuil and Norris (1996), shown on the right‐hand side. For the location of the outcrop and CPT, see Figure 1 …”

“…(e) Illustration of the stronger abrasion of shells in the Kiel Member (lower shell) compared to the Antwerpen Member (upper shell). In addition, Glycymeris from the Kiel Member generally show a more symmetric morphology with less posterior elongation, probably adapted to rougher, more current swept sea bottoms (temporary Argenta outcrop, see Everaert et al, 2020)…”

“…A total of seven outcrops was selected along a more or less S‐N line to the east of the city of Antwerp. These outcrops include some older sections exposed in the 1960s during the construction of the Antwerp Ring Road (De Meuter et al, 1976; Berchem‐Grote Steenweg, Borgerhout‐Stenen Brug and Borgerhout‐Rivierenhof), and more recent temporary outcrops described by Louwye et al (2010; Posthofbrug), Everaert et al (2019; Post X), De Schutter and Everaert (2020; Argenta) and Everaert et al (2020; Tweelingenstraat and a synthesis of the Argenta and Post X sections).…”

“…This resulted in the correlation profile of Figure 5. Among the Post X, Argenta, and Tweelingenstraat outcrops, the correlations were based on those already performed by Everaert et al (2020). The latter were extended for this study towards the other outcrops.…”

“…In the central and northern Antwerp city area, the Kiel Member is covered by the fossiliferous Antwerpen Member. In several temporary outcrops in and around the city of Antwerp, the boundary between the Antwerpen and Kiel Members was described in great detail and illustrated by De Meuter et al (1976), Louwye, Marquet, Bosselaers, and Lambert (2010), Hoedemakers and Dufraing (2018), De Schutter and Everaert (2020) and Everaert et al (2019, 2020). The latter authors indicated that the Antwerpen Member appears finer grained and more clayey in the basal parts compared to the underlying Kiel Member.…”