Заява Спілки Археологів України щодо проекту Закону України “Про відродження унікального Символу православ’я — церкви Богородиці (Десятинної) в місті Києві” (№ 9196)

The Milankovitch theory of climate change is widely accepted, but the registration of the climate changes in the stratigraphic record and their use in building high-resolution astronomically tuned timescales has been disputed due to the complex and fragmentary nature of the stratigraphic record. However, results of time series analysis and consistency with independent magnetobiostratigraphic and/or radio-isotopic age models show that Milankovitch cycles are recorded not only in deep marine and lacustrine successions, but also in ice cores and speleothems, and in eolian and fluvial successions. Integrated stratigraphic studies further provide evidence for continuous sedimentation at Milankovitch time scales (10^4 years up to 10^6 years). This combined approach also shows that strict application of statistical confidence limits in spectral analysis to verify astronomical forcing in climate proxy records is not fully justified and may lead to false negatives. This is in contrast to recent claims that failure to apply strict statistical standards can lead to false positives in the search for periodic signals. Finally, and contrary to the argument that changes in insolation are too small to effect significant climate change, seasonal insolation variations resulting from orbital extremes can be significant (20% and more) and, as shown by climate modelling, generate large climate changes that can be expected to leave a marked imprint in the stratigraphic record. The tuning of long and continuous cyclic successions now underlies the standard geological time scale for much of the Cenozoic and also for extended intervals of the Mesozoic. Such successions have to be taken into account to fully comprehend the (cyclic) nature of the stratigraphic record

The Tortonian reference section at Monte dei Corvi (Ilaty): evidence for early acquired NRM of greigite-bearing sediments

International audienc

Spectral colour data (400-700nm) from Monte dei Corvi, near Ancona, Italy

Orbital tuning and understanding climate response to astronomical forcing in the Miocene require detailed knowledge of the effect of tidal dissipation (Td) and dynamical ellipticity (dE) on astronomical solutions used to compute insolation and orbital target curves for paleoclimatic studies. These Earth parameters affect precession and obliquity; the determination of their effect is of fundamental importance, as phase relations between astronomical forcing and climate response can only be accurately calculated when the relative phasing between precession and obliquity is known. This determination can be achieved through comparison of solutions having different values for Td and/or dE with well‐understood paleoclimate data. In this paper we use quantitative color records of precession‐obliquity interference recorded in two successive 2.4 Myr eccentricity minima (9–9.6 and 11.5–12.1 Ma) in the Monte dei Corvi section in northern Italy to constrain the effect of Td, using the assumption of a direct response of sapropels to insolation. This quantitative approach results in a minimum uncertainty of astronomically tuned age models of ± 0.8 kyr and Td values 0.95 and 1.05 for the 9–9.6 Ma interval and of +4/−1 kyr (Td values between 0.95 and 1.15) for the 11.5–12.1 Ma interval. This (un)certainty not only limits the precision of determining phase relations but also improves our understanding of the limitations of tuned time scales and determining phase relations in the Miocene

High-precision zircon U–Pb geochronology of astronomically dated volcanic ash beds from the Mediterranean Miocene

Several orbitally tuned Miocene sedimentary sequences around the Mediterranean contain abundant intercalated volcanic ash beds. These sequences provide the rare opportunity to directly compare radioisotopic dating methods with independent and accurate deposition ages derived from astrochronology. We present a large data set (N=16N=16, n=166n=166) of zircon U–Pb dates obtained by chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) techniques for ash beds from an almost continuous orbitally tuned Messinian to Langhian (6.2–15.4 Ma) sedimentary sequence exposed along the Adriatic coast south of Ancona, Italy. We use this unique data set to evaluate (1) the accuracy of zircon U–Pb dates, (2) the significance of initial intermediate daughter product disequilibria for zircon U–Pb geochronology of young rocks, (3) the effect of prolonged pre-eruption zircon crystallization and zircon recycling on U–Pb derived ash bed deposition ages, and (4) discuss the implications for the intercalibration of radioisotope geochronometers and the calibration of the Geologic Time Scale

Astronomical tuning of the La Vedova section between 16.3 and 15.0 Ma. Implications for the origin of megabeds and the Langhian GSSP

The early-middle Miocene, marked by the Middle Miocene Climatic Optimum (MMCO) followed by the Middle Miocene Climate Transition (MMCT) towards cooler temperatures, represents a crucial period in Earth's climate evolution. To understand this episode and reconstruct its origin and the regional impact of the observed global changes, it is critical that high-resolution astronomical age models are developed for climate sensitive regions around the world. One of these areas undoubtedly is the Mediterranean, but so far no such an age model has been established for the interval of the MMCO. Nevertheless, this interval is well exposed in the coastal cliffs along the Adriatic Sea near Ancona (Italy), where it is characterized by the occurrence of 7 conspicuous limestone beds, termed megabeds, alternating with marl intervals. Here, we use the Lower La Vedova Beach section to construct an astronomical time scale for the younger part of the MMCO in the Mediterranean. The tuning to ~ 100-kyr eccentricity seems robust, but is less certain for precession in some intervals, as a consequence of the less clearly developed internal structure of the basic precession related cycles and uncertainties in the phase relation with climatic precession and insolation and in the astronomical solution in terms of tidal dissipation and dynamical ellipticity values. The tuning nevertheless provides astronomical ages for calcareous plankton events and magnetic reversals for the interval between 16.3 and 15.0 Ma. Individual megabeds are related to the ~ 100-kyr eccentricity cycle corresponding to eccentricity minima and the megabed interval itself is partly controlled by the 405-kyr cycle, as it marks two successive minima and the maximum in between. However, no relation with very long period eccentricity cycles (2.4 and 1 myr) is evident, and a link to regional tectonic processes (a major orogenic phase at the base of the Langhian and the likely associated Langhian transgression) seems more plausible. The higher sedimentation rate in the megabeds can be explained by the additional preservation of biogenic silica, which may also account for the diluted planktonic foraminiferal assemblages. With the integrated magnetobiostratigraphy and the tuning to eccentricity and to precession/insolation, the Lower La Vedova Beach section meets key requirements for defining the Langhian GSSP

Magnetostratigraphy of the hominin-bearing Hadar Formation (Middle Ledi Region, Ethiopia) and regional evidences for environmental changes at ca. 3.2 Ma

International audienc

Accuracy and precision of the late eocene-early oligocene geomagnetic polarity time scale

An accurate and precise geomagnetic polarity time scale is crucial to the development of a chronologic framework in which to test paleoclimatic and paleoenvironmental interpretations of marine and terrestrial records of the Eocene-Oligocene transition (EOT). The magnetic polarity patterns of relatively continuous marine and terrestrial records of the EOT have been dated using both radioisotopic techniques and astronomical tuning, both of which can achieve a precision approaching ±30 k.y. for much of the Paleogene. However, the age of magnetic reversals between chrons C12n and C16n.2n has proved difficult to calibrate, with discrepancies of up to 250 k.y. between radio-isotopically dated and astronomically tuned marine successions, rising to 600 k.y. for comparisons with the 206Pb/238U-dated terrestrial record of the White River Group in North America. In this study, we reevaluate the magnetic polarity pattern of the Flagstaff Rim and Toadstool Geologic Park records of the White River Group (C12n-C16n.2n). Our interpretation of the Flagstaff Rim polarity record differs significantly from earlier studies, identifying a previously unreported normal polarity zone correlated to C15n, which eliminates discrepancies between the WRG and the 206Pb/238-dated marine record of the Rupelian Global Stratotype Section and Point in the Italian Umbria-Marche basin. However, residual discrepancies persist between U-Pb- dated and astronomically tuned records of the EOT even when stratigraphic and systematic uncertainties associated with each locality and dating method are taken into account, which suggests that the uncertainties associated with astronomically tuned records of the EOT may have been underestimated