The mid-Cretaceous was marked by emplacement of large igneous provinces (LIPs) that formed gigantic oceanic plateaus, affecting ecosystems on a global scale, with biota forced to face excess CO 2 resulting in climate and ocean perturbations. Volcanic phases of the Ontong Java Plateau (OJP) and the southern Kerguelen Plateau (SKP) are radiometrically dated and correlate with paleoenvironmental changes, suggesting causal links between LIPs and ecosystem responses. Aptian biocalcification crises and recoveries are broadly coeval with C, Pb, and Os isotopic anomalies, trace metal influxes, global anoxia, and climate changes. Early Aptian greenhouse or super-greenhouse conditions were followed by prolonged cooling during the late Aptian, when OJP and SKP developed, respectively. Massive volcanism occurring at equatorial versus high paleolatitudes and submarine versus subaerial settings triggered very different climate responses but similar disruptions in the marine carbonate system. Excess CO 2 arguably induced episodic ocean acidification that was detrimental to marine calcifiers, regardless of hot or cool conditions. Global anoxia was reached only under extreme warming, whereas cold conditions kept the oceans well oxygenated even at times of intensified fertility. The environmental disruptions attributed to the OJP did not trigger a mass extinction: rock-forming nannoconids and benthic communities underwent a significant decline during Oceanic Anoxic Event (OAE) 1a, but recovered when paroxysmal volcanism finished. Extinction of many planktonic foraminiferal and nannoplankton taxa, including most nannoconids, and most aragonitic rudists in latest Aptian time was likely triggered by severe ocean acidification. Upgraded dating of paleoceanographic events, improved radiometric ages of the OJP and SKP, and time-scale revision are needed to substantiate the links between magmatism and paleoenvironmental perturbations.

Abstract Geological interest in Earth’s orbital variations harks back to the discovery of the Pleistocene ice ages in the 1840 by Louis Agassiz, who convinced numerous prominent geologists that the “drift” that covered much of northern Europe was not a relict of the biblical deluge but of a great ice sheet ( Imbrie and Imbrie, 1979 ). What had caused this to happen?

Abstract This work presents a detailed 87 Sr/ 86 Sr isotope curve for the 7.5–9.8 Ma time interval obtained by analyzing isotope compositions of the Orbulina universa planktonic foraminifer species from the Mediterranean Gibliscemi section (southern Sicily). The available astronomical tuning of the section provided the opportunity to assess a direct control of the Milankovitch climate cyclicity on the seawater Sr isotope changes. Results of spectral analysis suggest a linear forcing of the 400 ky eccentricity component on the 87 Sr/ 86 Sr ratios of the Mediterranean seawater. The recorded amplitude of Sr isotope 400 ky cycles ranges between ± 5.5 × 10 -5 and ± 6 × 10 -5 around the long-term trend for the Tortonian at global scale. Such a ∆ 87 Sr is of the same order of magnitude of that measured by Capo and DePaolo (1990) and Dia et al. (1991) for the Pleistocene 100 ky glacial-interglacial cycles and about two times larger than that reported for site 758 by Clemens et al. (1993) for the same periodic oscillations. Mass-balance calculations applied to our dataset suggest that periodic changes of about 100–150%in the riverine inputs can account for the amplitude oscillations of 87 Sr/ 86 Sr ratios recorded in the Mediterranean during the Tortonian,thus emphasizing the high potential of this basin as good recorder of climate-induced seawater Sr isotope changes.

Abstract High-resolution cyclostratigraphy and calcareous plankton astrobiochronology have been obtained from the latest Langhian to the earliest Tortonian of the Mediterranean. The investigated areas (Malta, Tremiti, and Sicily) are located in different geological settings, and the three studied sections show different cyclicity. Direct correlation between the Laskar 90 (1.1) solution of the insolation curve and the sedimentary cycle pattern occurring in the investigated sections showed that all the sedimentary cycles are forced dominantly by Milankovitch periodicity. This forcing is also reflected in the climate-sensitive data (CaCO 3 content, and the relative abundance of the planktonic foraminifer Globigerinoides ) as shown by the application of spectral and filtering analyses. The calibration provided astronomical ages for all the sedimentary cycles and bioevents recorded in the sections. In particular, an age of 13.59 Ma was obtained for the extinction level of Sphenolithus heteromorphus , which is the best event approximating the Langhian-Serravallian boundary and an age of 10.55 Ma for the first regular occurrence of Neogloboquadrina acostaensis , the event that better approximates the Serravallian-Tortonian boundary in the Tortonian type section.

Abstract Methodology of cyclostratigraphic analysis applied to benthic foraminifera is verified utilizing a faunal and geochemical dataset,from the Middle Miocene Ras il-Pellegrin composite section (Malta Island, central Mediterranean). Benthic data were elaborated by Q-mode varimax principal factor analysis. In this paper, spectral analysis is carried out only on two factors, which have a clear paleoecological significance: Factor 1 (loaded by Cibicidoides ungerianus and Siphonina reticulata ), indicative of oxic bottom waters, and Factor 2 (loaded by Bulimina elongata group), indicative of oxygen-stressed conditions. Results of these analyses show that Factor 1 and Factor 2 curves are,respectively, in and out of phase with maxima of the eccentricity (100 d 400 ky). We utilize the 3D paleocenographic model of Bellanca et al. (2002) as reference for the Middle Miocene Mediterranean circulation and focus our attention on the Mediterranean Intermediate water, characterized by hydrographic and hydrodynamic features similar to those presently recorded in the Levantine Intermediate Water (LIW). Consequently, we suppose that Middle Miocene Mediterranean Intermediate Water, here defined as proto-MIW, played a role similar to that of present Mediterranean Intermediate Water (MIW). Following this hypothesis, Factor 1, which is indicative of oxic bottom waters, is interpreted as a tracer of high production of proto-MIW, during periods of high eccentricity and, probably, precession minima, characterized by coldest winter seasons. These results point out a direct link between selected benthic species, long-term astronomical forcing, and deep-water response and provide a useful tool for astronomical calibration of geologic time and for paleoceanographic reconstructions.

Abstract The mid-Cretaceous (Albian) deep-water sediments (coccolith-globigerinacean marls) of the Umbria-Marche Apennines show complex rhythmic bedding. We integrated earlier work with a time-series study of a digitized and image-processed photographic log of the Piobbico core. A drab facies is viewed as recording normal stratified conditions, and a red facies as the product of downwelling warm saline (halothermal) waters. Both are pervaded by orbital (Milankovitch) rhythms. These reflect fluctuations in the composition and abundance of the calcareous plankton in the upper waters. The drab facies is overprinted by redox oscillations on the bottom, including episodic precessional anaerobic pulses (PAPs). Contrasts between the individual beds representing the alternate phases of the precessional rhythm rose and fell with orbital eccentricity, in the classical pattern of Berger’s climatic precession or precession index curve, varyingly complicated by the obliquity rhythm. We conclude that greenhouse oceans in general, and perhaps this area in particular, were very sensitive to orbital forcing. Our count of 29 406-ky eccentricity cycles yields an Albian duration of 11.8 ± 0.4 My.

Abstract Zircon dates and orbital interpretation of bedding rhythms have yielded very different estimates on the duration of Middle Triassi stages. Recently, a core was drilled in Middle Triassic basin sediments at Seceda (western Dolomites) to directly compare cyclostratigraphy with geochronologic data. Detailed study of facies, sediment sources, and transport mechanisms formed the basis of the statistical analysis of bedding rhythms that are based on a grayscale scan and a gamma-ray well log. Amplitude spectrograms reveal strong frequency components at f = 0.025 cycles/cm in the main nodular limestone interval (92–64 m core depth), corresponding to the dominant 40 cm bedding thickness. Significant spectral differences were found between the grayscale and gamma-ray bedding proxies, placing doubt on the appropriateness of the use of the latter as an effective tool in cyclostratigraphy. In the uppermost part of the succession (59–45 m core depth) calciturbidites constitute more than 50% of the rock volume. If turbidites and tuffs are removed from the rock column, the spectrogram in this interval becomes much smoother and significant peaks appear at higher frequencies. The signals of this pelagic background sedimentation were extracted by bandpass filtering and show strong similarities to Milankovitch cycles in the Quaternary. According to this cyclostrati-graphic interpretation, the dominant 40 cm bedding rhythm was produced by eccentricity, and the average sedimentation rate results in ~3.6 mm/ky. This estimate is in contrast to zircon data from volcaniclastic layers that bracket this core interval and suggest a sedimentation rate of 13.5 mm/ky. As it currently stands, neither of the two interpretations is yet fully satisfactory. Although the presence of orbital variations in the Triassic analogous to those predicted for the last 20 My remains questionable owing the presumed chaotic behavior of the planets, the zircon age data have uncertainties related to their origin that remain unaccounted for and require further investigation.

Abstract Detailed sedimentological and carbon-isotope data have allowed us to propose a high-resolution regional correlation between four Lower Cretaceous carbonate-platform successions, Early Aptian to Early Albian in age, cropping out in the southern Apennines. These successions, formed in open to restricted lagoonal and peritidal-supratidal settings, reveal a high-frequency cyclic recurrence of depositional and early meteoric (karstic and/or pedogenetic) features. The latter are normally superimposed on subtidal deposits, suggesting that the above cyclicity may be linked to sea-level changes. In the studied sections, elementary cycles are grouped into bundles, which in turn are grouped into superbundles. Although bundles and superbundles appear to be related to the Earth’s orbital short-eccentricity and long-eccentricity signal, respectively, elementary cycles seem to record either the precession or a combination of the precession and obliquity periodicity. Moreover, the stacking pattern of the orbitally controlled cycles suggests that they are superimposed on lower-frequency sea-level fluctuations (transgressive-regressive facies trends). The δC curves, established throughout the sections, show the same carbon-isotope pattern as the time-equivalent pelagic strata (two positive carbon-isotope episodes separated by an interval with lower carbon-isotope values). On the basis of this correspondence, and integrating the cyclostratigraphy and the carbon-isotope stratigraphy with the sequence stratigraphy, we propose a high-precision regional correlation and a chronostratigraphic chart and suggest a duration of 7.8 My for the studied interval. Moreover, on the basis of sequence stratigraphy and isotope geochemical criteria, and using our orbital chronostratigraphy as a reference frame, a correlation with current global scales is here proposed.

Abstract A detailed carbon-isotope stratigraphy has been generated from Barremian to Lower Aptian shallow-water carbonate sections in the Campania Apennines (Monte Raggeto, southern Italy). The new isotope curve is correlated with the magnetostratigraphically and biostratigraphically dated pelagic carbon-isotope stratigraphy from the Cismon locality (Southern Alps, northern Italy). All the major positive and negative carbon-isotope excursions that characterize the Barremian and Early Aptian carbon-isotope stratigraphy can be recognized in the shallow-water curve. Cyclostratigraphy, which was established earlier at the Monte Raggeto section, is used as an age calibration tool for the Barremian and Early Aptian isotope stratigraphy. The duration of the isotopically calibrated stratigraphic interval between the top of Chron M3 and the base of Chron M0 is estimated as 4 My. These time calculations are in good agreement with cyclostratigraphic data from the Cismon locality but differ from estimates based on a magnetic anomaly block model for the interval between M3 and M0 that yield only 3 My. We have also calculated that the Selli Level Equivalent (SLE) at the Monte Raggetto locality was deposited within 1.2 My. Our results demonstrate that the combination of chemostratigraphic and cyclostratigraphic studies can contribute significantly to the calibration of the Mesozoic time scale.

Abstract The Berriasian Pierre-Châtel Formation in the Swiss and French Jura Mountains is dominated by shallow-marine carbonates tha overlie lacustrine and marginal-marine sediments with a major transgressive surface. Detailed facies analysis of five sections allows the definition of elementary and small-scale depositional sequences, which commonlexhibit deepening-shallowing trends. Benthic foraminifera and rare ammonites on the platform, as well as a sequence-stratigraphic correlation with a well-dated deeper-water section,furnish the biostratigraphic framework. Thus, the large-scale sequence boundaries below and at the top of the Pierre-Châtel Formation can be correlated with dated boundaries in other European basins. This time constraint and the hie archical stacking pattern on the platform as well as in thebasin suggest that the sea-level fluctuations influencing the formation of the depositional sequences were controlled,at least partly, by Milankovitch cycles. The elementary sequences correspond to the 20 ky precession cycle, and the small-scale sequences to the 100 ky eccentricity cycle. Uncertainties in the definition of sequences exist if facies contrasts are too low to develop clearly marked sequence boundaries or maximum-flooding intervals. Nevertheless, a best-fit solution for the correlation of the small-scale sequences between the studied sections can be proposed. Thelowermost three small-scale sequences of the Pierre-Châtel Formation are analyzed in detail. They are decompacted and correlated on the level of the elementary sequences. Within this relatively precise time frame, the flooding of the Jura platform (following the early Berriasian sea-level lowstand) can be monitored. It is seen that the transgression occurred stepwise: every 20 ky, atransgressive pulse established marine facies farther towards the platform interior. This study demonstrates that the cyclostratigraphical approach makes it possible to construct a narrow time frame, within which the rates of sedimentary, ecological, and diagenetic processes can be evaluated, phases of differential subsidence identified, and the durations of stratigraphic gaps estimated. The complex and dynamic evolution of an ancient carbonate platform can thus be studied with a time resolution of 20 to 100 ky.