Integrated stratigraphy of the Upper Barremian–Aptian sediments from the south-eastern Crimea

Abstract

Previous studies made in different parts of the world have shown that Barremian–Aptian times imply many difficulties in deciphering the biostratigraphy, microfossil evolution and correlation of bioevents. In an attempt to improve our knowledge of this period in a particular area of the Tethyan realm, we present the first integrated study of microbiota (including planktonic foraminifera, calcareous nannofossils, ostracods and palynomorphs) and magnetostratigraphy of the upper Barremian–Aptian sediments from south-eastern Crimea. The nannofossils display the classical Tethyan chain of bioevents in this interval, while the planktonic foraminifera demonstrate an incomplete succession of stratigraphically important taxa. Our study enabled the recognition of a series of biostratigraphic units by means of four groups of microfossils correlated to polarity chrons. The detailed analysis of the microfossil distribution led to a biostratigraphic characterization of the Barremian/Aptian transition and brought to light an interval, which may correspond to the OAE1a.

Age of the Barremian–Aptian boundary and onset of the Cretaceous Normal Superchron

“…Establishing a more accurate numerical age for the Barremian-Aptian boundaryand the base of chron M0ris of fundamental importance for several applications in the geosciences. First, linking the biostratigraphic and magnetostratigraphic record with numerical ages provides a reference for correlating the fossil record and magnetic reversals across the world (e.g., Karpuk et al, 2018). Although this is generally important for all stage boundaries that lack a GSSP, the Barremian-Aptian boundary remains one of the most poorly constrained stage boundaries after the breakup of Pangea.…”

Frequent Polarity Reversals in the Cretaceous Normal Superchron

“…In addition, despite the disputes on whether these observed reversals were polarity events, their occurrence times and frequencies are also a subject of considerable debate due to uncertain paleomagnetic records and age models (Cronin et al., 2001). Therefore, elucidating these issues may help to improve the statistical structure of geomagnetic reversal chrons (Tarduno, 1990) and would have significant implications not only for better understanding the relationship between the geodynamo energy regime and the nature of the geomagnetic field during the superchron (Glatzmaier et al., 1999; Olson et al., 2012), but also for understanding the correlations of global polarity (Courtillot & Besse, 1987; Irving & Couillard, 1973), tectonic (Granot et al., 2012; Larson & Olson, 1991; Torsvik et al., 1998; Zhao, 2005), paleoclimatic (Larson, 1991; Larson & Erba, 1999), biologic (Courtillot, 1990; Courtillot & Olson, 2007; Karpuk et al., 2018), and paleo‐oceanographic events (He et al., 2012; Olierook et al., 2019).…”