Orbital Turning of the upper Albian from the site U1513D – Palaeoenvironmental implications
Résumé
An exceptional record of Cretaceous climate and carbon cycle perturbations was
recovered at Site U1513 in the Mentelle Basin, southwest of Australia at a paleolatitude
of 60°S, during IODP Expedition (Huber et al., 2019). However, sediments across the
Albian–Cenomanian transition (307.10 to 282.61 m) are barren of microfossils, and
this lack of biostratigraphic indicators limits our ability to study paleoenvironmental
change. Here we present results from cyclostratigraphic analyses, which provide new
age constraints for the Albian-Cenomanian boundary. Time series analysis of highresolution
(2 cm) elemental data obtained through XRF core-scanning and natural
gamma radiation confirm the influence of orbital forcing. Filtering the 3.5 m periodicity,
which likely corresponds to the short (100 kyr) component of eccentricity-modulated
precession, leads to a duration estimate of 64*100= 6.4 Myr for the interval covering
the Albian–Cenomanian transition (from 387m to 285.45 m). Independently derived
logging data of natural gamma radiation reveal a similar number of short eccentricity
cycles. The barren interval contain 23 cyles of short eccentricity suggesting a duration
of 23*100=2.3 Myr. The clear expression of short eccentricity cycles allows us to
estimate the duration of the barren interval at 2.3 Myr. This astronomical time scale
provides an age model to reconstruct the timing of changes in Cretaceous oceanography
and sedimentation in the Mentelle Basin, and highlights the sensitivity of southern high
latitude paleoclimate to eccentricity forcing.