A vague record of astronomical forcing across the Jurassic/Cretaceous transition: an evidence for diachronous timing of biozones in the pelagic successions of the Torre de’ Busi (Southern Alps, Italy) and Lókút (Transdanubian Range, Hungary) sections?

Herein are presented the results of cyclostratigraphic investigations performed in the Tithonian–lower Berriasian pelagic carbonates of the Torre de’ Busi (Southern Alps, Italy) and Lókút (Transdanubian Range, Hungary) sections. Precise bio- and magnetostratigraphic calibration of both successions provided a temporal framework and constraints on sedimentation rates. Although the studied sections are characterized by generally low and decreasing terrigenous input, magnetic susceptibility (MS) (Torre de’ Busi, Lókút) and anhysteretic remanent magnetization (ARM) (Lókút) series suggest the presence of 100-kyr short eccentricity cycles. Accordingly, 37 cycles were documented within the M20r–M18r magnetic chrons interval of the Torre de’ Busi section, whereas another 37 cycles were interpreted within M21n–M19n interval of the Lókút section. The number of cycles within given magnetozones correlates between the studied sections and roughly agrees with the geomagnetic polarity time scale (GPTS), which indicates a duration of ∼2.74 Ma for the M20n–M18r interval and ∼3.95 Ma for the M21n–M19n. Long eccentricity cycles are poorly expressed, and only within the lower Tithonian beds some traces of 405-kyr forcing can be observed. Unclear character of astronomical record within the studied sections is thought to result from a combination of their distal paleogeographic setting and the general arid climate during the latest Jurassic–earliest Cretaceous, which both effectively restricted clastic delivery to studied areas. Ultimately, the results of this study highlight the diachronic character of some bioevents, i.e., base of the Calpionella alpina calpionellid Subzone and the NJT17 calcareous nannofossil Zone, which are likely shifted between the two sections for ca. 300–400 kyr.