Chemostratigraphy and stratigraphic distribution of keeled planktonic foraminifera in the Cenomanian of the North German Basin

Abstract

The record of keeled planktonic foraminifera during the Cenomanian in boreal epicontinental basins is discontinuous. Micropalaeontologic and bulk carbonate carbon and oxygen isotope investigations from two cores in the center of the North German Basin (NGB, Wunstorf, Lower Saxony) showed keeled praeglobotruncanids and rotaliporids to exclusively appear during three stratigraphic intervals of varying duration in the lower and middle Cenomanian. Our new high-resolution carbon isotope (δ 13 Ccarb) composite curve shows that keeled foraminifera are absent during the Mid Cenomanian Event (MCE) I. In the aftermath of MCE I, keeled planktonic foraminifera are present throughout. The data are correlated to previously published sequence stratigraphic models for the NGB. The presence/absence of keeled planktonic foraminifera in the epicontinental NGB is believed to be controlled by sea level and according environmental conditions in the epicontinental basin. KurzfassungIn den Cenoman-zeitlichen Abfolgen der epikontinentalen Becken der borealen Kreide lassen sich gekielte planktonische Foraminiferen nicht durchgehend nachweisen. Neue Untersuchungen an zwei Bohrungen aus dem Norddeutschen Becken bei Wunstorf in Niedersachsen zeigen, dass sich die Vorkommen von gekielten Praeglobotruncanen und Rotaliporiden auf drei stratigraphisch klar abtrennbare Intervalle des Untercenomaniums und Mittelcenomaniums beschränken. Die hier präsentierte neue und hochauflösende Kohlenstoffisotopenkurve (δ 13 Ccarb) belegt außerdem, ein Fehlen gekielter planktonischer Foraminiferen während der positiven C-Isotopen-Exkursion des Mid Cenomanian Event (MCE) I. Oberhalb des MCE I ist das Vorkommen gekielter planktonischer Foraminiferen kontinuierlich. Die Korrelation unserer Daten mit etablierten sequenzstratigraphischen Untergliederungen für das Cenomanium Norddeutschlands weist auf einen Zusammenhang zwischen Meeresspiegelschwankungen und dem Vorkommen gekielter Formen hin. Offensichtlich ermöglichten die Umweltbedingungen während hoher Meeresspiegelstände das Leben gekielter Formen in den Randbecken.

Albian to Turonian agglutinated foraminiferal assemblages of the Lower Saxony Cretaceous sub-basins – implications for sequence stratigraphy and paleoenvironmental interpretation

“…The recorded thickness is surprisingly low compared to other studies (e.g. Erbacher et al, 2007;Voigt et al, 2008b). About 12 m of Turonian strata is completely missing, likely induced by a prominent fault at 68 m core depth (Fig.…”

“…9). This likely links to the prominent early Cenomanian transgression belonging to the Depositional Sequence Albian-Cenomanian 1, DS Al-Ce 1, which are described in detail at sections of the Lower Saxony Basin by Niebuhr et al (1999Niebuhr et al ( , 2001, Wilmsen (2003, Bornemann et al (2007), and Erbacher et al (2020). A minimum of relative abundances of M4b in the Wunstorf Wu2010/1 core at a depth of 49.05 m (Fig.…”

“…5) core comprises 3 m of limestone of the Brochterbeck Formation (86-83 m core depth), 20 m of black shale-marlstone alternations of the Hesseltal Formation (83-63 m core depth), and 27 m limestones of the Söhlde Formation (63-36 m core depth). The detailed stratigraphical framework mainly based on stable isotope, event, and sequence stratigraphy and biostratigraphy applied to the quarry section and three drill cores is derived from Meyer (1990), Wilmsen (2003, Erbacher et al (2007), Voigt et al (2008b), Seibertz (2013), and Erbacher et al (2020).…”

Planktonic foraminifera document palaeoceanographic changes across the middle Cenomanian carbon-isotope excursion MCE 1: new evidence from the UK chalk

“…Moreover, the assemblage is characterized by the relatively high abundance of the eutrophic-mesotrophic Praeglobotruncana and Muricohedbergella. Interestingly, M. portsdownensis, a species also documented as occurring in the middle Cenomanian record of the North German Basin at Wünstorf (Erbacher et al 2020), shows a stratigraphic distribution limited to the carbon isotope excursion identifying the MCE 1 at Folkestone. The species first appears in the C. arlesiensis Bed at the same level of the occurrence of Boreal macrofossils species and coincident with a positive δ 18 O shift of 1 ‰ and disappears slightly after the termination of the MCE 1 at the level (37.80 m) that records the increase in % P and the appearance of the intermediate forms between R. montsalvensis and R. cushmani (Fig.…”

“…In the present study, the appearance of R. cushmani is recorded at 38.80 m whereas it was first observed by Paul et al (1994) above this level at c. 40.5 m. The difference is minor and is probably related to the different sampling resolution (1 m in Paul et al 1994 compared to 50 cm in this study), to the preservation of the specimens and to the rarity of the first representatives of R. cushmani. In fact, R. cushmani evolved from R. montsalvensis (González-Donoso et al 2007;Petrizzo & Gilardoni, 2020) and occurs together with common specimens that are morphologically transitional with its ancestor, making the identification of the first R. cushmani sometimes difficult to detect (Ando et al 2015;Erbacher et al 2020).…”