Cyclostratigraphy of the Cenomanian-Turonian boundary in Jordan

The timescale of the Cenomanian-Turonian interval (Late Cretaceous, ∼94 million years ago) and associated environmental changes remain debated. In particular, the duration of the positive carbon isotope excursion (CIE), marking Oceanic Anoxic Event 2 (OAE2), is subject to controversies. This study presents an astronomical timescale for the Cenomanian-Turonian boundary in the Zarqa section of northern Jordan. Cyclostratigraphic analysis of magnetic susceptibility data and stable carbon isotope data (δ¹³Ccarbonate) reveals an averaged optimal sediment accumulation rate of 1.82 cm per thousand years. The high-resolution astronomical timescale suggests that the positive CIE, marked by positive δ¹³C spikes a-d, lasted about 0.88 Myr and can be correlated to eccentricity cycles E231 and E233. A hiatus of about 240 kyr occurs at the top of the δ¹³C spike d. The data indicate that the C/T transition correlates to an eccentricity minima node (2.4 myr g4-g3) of the La10c astronomical solution, as supported by amplitude and frequency modulation that are evident in the data. The expression of distinct orbital parameters in the analytical data suggest that during the Cenomanian-Turonian transition changes in Earth solar orbit directly impacted carbon cycling and environmental conditions.