The Monterey Event within the Central Mediterranean area: The shallow‐water record

Abstract

The middle Miocene is an important time to understand modern global climate evolution and its consequences on marine systems. The Mid-Miocene Climatic Optimum (between 17Á0 Ma and 13Á5 Ma) was the warmest time interval of the past 35 million years during which atmospheric CO 2 concentrations were lower than today. In the Mid-Miocene Climatic Optimum, a significant carbon cycle perturbation occurred, expressed as a last long-term positive carbon isotope shift, known in literature as the Monterey Carbon Isotope Excursion and recorded in open-ocean settings. In this work, the lower to middle Miocene carbon isotope records from three different domains of the Central Mediterranean are analysed with the aim of identifying the local carbonate platform response to the major global carbon cycle perturbation of the Monterey Event. Carbon and oxygen isotope ratios have been measured on samples belonging to three different stratigraphic sections, two of them are representative of shallow-water settings (Latium-Abruzzi and Apula platforms), and the latter of a hemipelagic setting (Umbria-Marche Basin). A well-defined Monterey Carbon Isotope Excursion is recorded also in these shallow-water sections. Despite their expected problematic stratigraphic constraints, a reliable age model is provided by calcareous nannofossil biostratigraphy and strontium isotope stratigraphy. In both of the carbonate platform successions examined, the Monterey Carbon Isotope Excursion coincides with a spread of bryozoans over other carbonateproducing biota. The high productivity of the bryozoan-dominated factory in the aphotic zone had an important control on the platform depositional profile. The high rates of sediment production in the deeper aphotic and oligophotic zones produced a depositional profile of a low-angle ramp.

Miocene Oceanographic Evolution Based on the Sr and Nd Isotope Record of the Central Mediterranean

“…Volcanism brings into the oceans a large input of the light 86 Sr isotope, lowering the seawater 87 Sr/ 86 Sr ratio, whereas the second raises the overall 87 Sr/ 86 Sr signature of the global ocean due to the weathering of old, continental crust (McArthur et al, ). Based on these assumptions, a global reference 87 Sr/ 86 Sr curve, calibrated with biostratigraphy and magnetostratigraphy, has been developed for the entire Phanerozoic (McArthur et al, , ) and has been used extensively to date and correlate carbonate successions (Brandano, Cornacchia, Raffi, et al, ; Brandano & Policicchio, ; Frijia & Parente, ; McArthur & Howarth, ). However, it has become increasingly evident that the Sr isotope signature of marginal basins may deviate from the global ocean signature due to salinity changes, runoff, and local volcanism, coupled with restricted conditions (Cornacchia et al, ; Ingram & Sloan, ; Kocsis et al, ; Schildgen et al, ).…”

Do drifts deposited adjacent to carbonate platforms record the signal of global carbon isotopic values?

“…A and B). While the Monterey Event has been recognized principally in pelagic settings, changes in the δ 13 C values have also been identified in locations in which the sediments are heavily influenced by shallower water calcareous organisms such as in the Central Apennines carbonate platforms (Brandano et al ., ). The Monterey Event occurs approximately at the same time as the Miocene Climate Optimum (MCO), one of several interruptions in the long‐term cooling over the past 50 Myr recorded in the oxygen isotope record (Holbourn et al ., ).…”

Mesozoic climates and oceans – a tribute to Hugh Jenkyns and Helmut Weissert

“…Similarly, comparisons and contrasts between OAEs and Cenozoic warming events, such as the Palaeocene–Eocene Thermal Maximum or the Miocene Monterey Event, has elucidated common processes and highlighted the extreme magnitude of the Earth system perturbations that have occurred in the earlier history of the planet (e.g. Jenkyns, , ; Cohen et al ., ; Brandano et al ., ). The widespread distribution of studied localities and overall larger datasets for Cenozoic events generally provides greater opportunity to comprehend the potential rapidity of environmental processes, and the timing of consequent environmental changes in the different reservoirs of the lithosphere, hydrosphere and biosphere, something that has not yet been achieved with any degree of confidence for the Mesozoic.…”