Astronomical calibration of the Ocean Anoxic Event 1b and its
implications for the cause of mid-Cretaceous events: a multiproxy record
Abstract
Cyclostratigraphic analyses were performed on magnetic susceptibility
(MS), and elemental Ti and Fe series along the upper Aptian-lower Albian
interval of the Poggio le Guaine (PLG) core, a Cretaceous pelagic
succession in the Umbria-Marche Basin (central Italy). This interval
represents one the most detailed and complete sedimentary archives and
records oceanic perturbations associated with Oceanic Anoxic Event (OAE)
1b. The MS, Ti and Fe orbital control indicates a timespan of 2.68 Myr
for OAE 1b event (114.10 to 111.34 Ma) and short eccentricity cycles
played a key role, in controlling the amount of detrital input from
weathering during monsoonal periods. Our chronostratigraphic study also
provides age of 114.09 Ma for 113/Jacob, 113.25 Ma for Kilian, 112.67 Ma
as a central age of the Monte Nerone cluster, 111.70 Ma for Urbino and
111.37 Ma for Leenhardt subevents, and a timespan of ~20
kyr for 113/Jacob, 70 kyr for Kilian, 670 kyr for Monte Nerone cluster,
60 kyr for Urbino and 60 kyr for Leenhardt levels. This study provides
compelling evidence of the enormous potential C-isotope stratigraphy as
tie points for cyclostratigraphic studies and as a valuable way to
evaluate diachronism of bioevents. The organic-rich levels encompassing
OAE 1b event has particular characteristics resulting from the
combination of warm climate triggered by volcanic CO2 input, heavy
precipitation, intense weathering and rapid marine transgressions, which
leads the oceanic-atmospheric perturbations, acting as amplifiers of
orbital forcings paleoclimate changes, resulting in deoxygenation and
carbon burial during OAE 1b.