Ichnology, sedimentology, and orbital cycles in the hemipelagic Early Jurassic Laurasian Seaway (Pliensbachian, Cardigan Bay Basin, UK)

A 20‐million‐year Early Jurassic cyclostratigraphic record and its implications for the chaotic inner Solar System and sea‐level changes

“…The minimal and maximal durations for the combined Jamesoni-Ibex zones are assessed at ~3.91 and ~6.24 Myr. These durations are different from those published from the Mochras borehole, who reported a duration between ~4.2 and ~4.8 Myr, respectively, for the combined Jamesoni-Ibex zones (Ruhl et al, 2016;Storm et al, 2020;Pieńkowski et al, 2021) (Table 2). This difference in terms of durations between cores (~3.91 vs ~4.2) may be explained by the large uncertainties in the definition of the boundaries of biohorizons and/or by the presence of hiatuses in the interval spanning the Sinemurian/Pliensbachian boundary (Peti et al, 2017).…”

“…The minimal duration of the Davoie zone obtained in this study (~0.51 Myr) is close to that proposed by Ruhl et al (2016) Ruhl et al, 2016;~2.7 Myr, Storm et al, 2020). However, our duration estimate of the Margaritatus zone (~2.67 to ~2.78 Myr) is much longer than that inferred from ichnological cyclostratigraphy (~2.33 Myr; Pieńkowski et al, 2021). Our estimation is also consistent with that of McArthur et al (2000) (~2.75 Myr) based on an independent approach (isotopic trends in 87 Sr/ 86 Sr).…”

“…The minimal duration is somewhat close to the ~1.4 Myr estimate at Mochras (Ruhl et al, 2016;Storm et al, 2020). However, it is longer than the ~0.8 Myr and ~1.21 Myr durations proposed by Pieńkowski et al (2021) and McArthur et al (2000), respectively (Table 2).…”

“…Our estimation is also consistent with that of McArthur et al (2000) (~2.75 Myr) based on an independent approach (isotopic trends in 87 Sr/ 86 Sr). Interestingly, the duration of the Jamesoni-Margaritatus interval at Sancerre (~7.2 Myr) is very close to the ~7.3 Myr estimate from Mochras using Ca and δ 13 C TOC cyclostratigraphies (Ruhl et al, 2016;Storm et al, 2020) but shorter than that inferred from ichnological cyclostratigraphy (~7.6 Myr; Pieńkowski et al, 2021). Finally, the minimal duration of the Spinatum zone at Sancerre is assessed at ~1.54 Myr (minimal) and ~1.87 Myr (maximal).…”

“…The ~8.74 Myr minimal duration is close to the ~8.7 to ~8.8 Myr duration estimated on the basis of a cyclostratigraphic study (on XRF elemental Ca content, δ 13 C TOC ) from the Mochras borehole (Wales, UK) (Ruhl et al, 2016;Storm et al, 2020) (Table 2). However, this duration is longer than the more recent estimate of ~8.4 Myr inferred from cyclostratigraphy of ichnological data in the same Mochras borehole (Pieńkowski et al, 2021). Additionally, using the 405 kyr timescale we provide durations for the standard ammonite biozones (Table 2).…”