30 million years of orbitally influenced sedimentation across the Jurassic—Cretaceous boundary and Early Cretaceous period

Abstract

A continuous sedimentary succession spanning the Early Cretaceous through the Latest Jurassic was retrieved from the Lingshan Island Scientific Borehole 1 (LS-1), located on Eastern Asia southwest of Qingdao. Spectral analysis of different intervals in the data reveals a hierarchy of meter-to decameter-scale cyclicity. The ratios of the cycles in several stratigraphic units are ∼20:5:2:1, corresponding to those of Milankovitch cycle periods of 405 kyr (long orbital eccentricity), 100 kyr (short orbital eccentricity), 40 kyr (obliquity), and 20 kyr (precession), indicating astronomical control on sedimentation. From interpreted 405 kyr long orbital eccentricity cycles along the magnetic susceptibility, uranium, and gamma ray stratigraphic series, a floating astronomical time scale with a duration of ∼30 Myr is established. This ATS provides numerical ages for stratigraphic boundaries and geological events, and serves as the basis for correlation of strata and events between marine and terrestrial systems. The ATS is anchored to a rather imprecise U-Pb determined age of 125 Ma for the K1l (Laiyang Formation of Early Cretaceous)-K1q (Qingshan Formation of Early Cretaceous) boundary from the Lingshan Island outcrops. The anchored time scale places the location of the Jurassic/Cretaceous (J-K) boundary at 677-674 m (∼144.6 Ma). The Purbeckian marine regression at the J/K boundary impacts the Milankovitch signals around the J/K boundary. Distinct spectral peaks with periods of ∼11-Myr are observed in the power spectra of the proxy time series, indicating a possible tectonic imprint. This ∼11-Myr cycle may be attributed to the subduction of the paleo-Pacific plate under Eurasia during the Late Mesozoic, which is being recorded in the ∼30 Ma here investigated sedimentary record. The interplay between the ∼11-Myr tectonic cycle and the ∼2.4-Myr orbital eccentricity cycle appears to jointly control the variation in depositional rates and environments.