Milankovitch cycles

The Early Turonian interval represents a unique confluence of climatic and oceanographic conditions including peak surface temperatures, high greenhouse-gas concentrations and maximum Phanerozoic sea level. The susceptibility of this climate mode to astronomical insolation forcing remains poorly understood partly due to a limited time control and unknown phasing of astronomical cycles in this interval. Here we offer a refined astrochronology of the Early Turonian based on laterally consistent precession signals preserved in offshore strata of the Bohemian Cretaceous Basin (central Europe). Pristine amplitude modulation verified through interference patterns in depth-frequency plots provides a robust indication of ~100-kyr and 405-kyr eccentricity phases (maxima and minima) that are pinned to ammonite biozones and new carbon-isotope data from two cores. The Early Turonian is estimated as 885 ±41 (2s) thousand years (kyr) in duration, with the Cenomanian/Turonian boundary predating the first Turonian 405-kyr maximum (no. 232 in the Geological Time Scale 2020) by 82 ±70 (2s) kyr. The results support a possible link of the recovery from Oceanic Anoxic Event II to increasing magnitude of seasonal insolation extremes due to rising eccentricity on 405-kyr and million-year (Myr) time scales. Superimposed upon this trend are small-scale carbon-isotope anomalies the pacing of which passes from ~110 kyr, resembling short eccentricity, to ~170-kyr, possibly related to obliquity modulation. This eccentricity-to-obliquity transition, paralleling the rising phase of Myr-scale eccentricity, suggests decoupling of the carbon-cycle perturbations from low-latitude seasonal insolation and involvement of mid- to high-latitude carbon reservoirs.  

The strong correlation of the eccentricity, obliquity and precession changes in the Earth's orbit (Milankovitch cycles) with the proxy temperature indicators (principally δ 18 O) in continuous cores of sediment and ice, accumulated during the last 1-2 Myr, has led to a conclusion that climatic change is entirely a result of the fluctuations in the amount and latitudinal distribution of solar energy reaching the Earth's upper atmosphere, i.e. they are a result of 'solar forcing'. While a very good correlations exists for some Milankovitch spectra, there are misfits that suggest that the observed correlations may not be fully causative, i.e. some other related process is also involved that may be even more important. Furthermore, the temperature changes at the top of the atmosphere are small, relative to those of climatic changes, and so must be amplified by secondary effects, principally albedo changes resulting from changing snow and/or cloud cover. Spectral analyses of geological and geophysical properties in the absence of such secondary albedo processes, such as during the Cretaceous, have shown all Milankovitch periodicities are present in both gravitational and climatically related properties. Identical spectral peaks and ratios are also present in geomagnetic properties and sea-floor spreading rates of the same age. No other spectra are identified, but all Milankovitch frequenies are recorded. Such old seqences suggests that the climatic changes of the last 2 Myr should be similarly controlled by the distance and angular relationship with the Sun and Earth. It is suggested that current attribution of all terrestrial climatic change to only Milankovitch cycles in the Earth's orbit neglects the effects that changing plantetary orbits will have on the activity of the Sun. It is proposeded that dominant 100 kyr climatic cycle during the last 1-2 Myr is due to Jupiter's gravitational influence on the amount and quality of solar radiation being generated. This radiation is then modulated by the Earth's orbital behaviour.

The current theory of axial precession of the earth relative to the distant stars resulting in continuous precession of the equinoxes and the corresponding pole shift in a circle around the zodiac in a cycle of approximately 26000 years is not recognized by the Indic Thought that proposes a short cycle of 7200 years consisting of forward and backward motion of the equinoxes and a corresponding limited number of pole stars spread across the span of the constellation of Ursa Minor, known as Shishumara in Puranas and Vedic texts. The decipherment of the 'difficult passage' of Siddhanta Shiromani reveals the cycle of eccentricity of the earth's orbit that differs from that of Milankovitch which suffers from '100 000 year problem'. The precession cycle of Milankovitch stands disputed by the Surya Siddhantic cycle and the 'Yuga of Ayana' of Munjāla and Vishnuchandra that consists of three cycles of equinoxes. The concept of obliquity of Milankovitch absent in Indic Thought is also non-existent in the emerging scientific revelation from lunar data and solar path-based movement that is mistaken as precession of the axial tilt. The three Indic cycles enumerated from Siddhantas and checked against the Milankovitch cycles are verified with paleocliamtic data. It is found that the sequence of glacial events since Last Glacial Maximum match with the mid-point of the Ayana cycle of equinoxes. The incidence of Dansgaard-Oeschger events that remain unexplained by any current theory are found to match with Ayana cycles, besides giving credence to the sinusoidal path of the sun that is observed as to and fro motion from the earth.

The relationship between climate change at the Pleistocene-Holocene Boundary (ca. 12,600-10,200 cal B.P.) and cultural responses to attendant shifts in the environment remains a vexing issue for archaeologists. This study compiles and analyzes glacial, palynological, faunal, and stratigraphic/geomorphological proxy datasets for climate change in the Pacific Northwest of North America and compares them to the coeval archaeological record. The primary purpose of this exercise is to consider the potential ways in which climate change at the Pleistocene-Holocene Boundary affected cultural development for Late Paleoindian-Early Archaic peoples in the Pacific Northwest. Results indicate that climatic and environmental change at this interval was rapid or abrupt, and of a magnitude that likely produced varying adaptational responses by peoples of different cultural traditions who appear across the region at this period. Transformations in tools and technology, shifts in dietary habits, migration and regionalization, and trade intensification are all elements of Late Paleoindian-Early Archaic cultural responses to rapid climate change.

The new Climate Timeline and Correlating Periods of Human and Earth History chart is revised, more detailed and improved.
These view of Earth's history over the last 20 million years addresses various interdisciplinary aspects of Earth's history and their interactivity, along with the emergence and development of human and human-like species. The new graph focuses on high-precision dating, so far possible, regarding the overall timing of the events.

A 19. század óta számos kutatót megihletett az éghajlatváltozás csillagászati okainak kutatása. A 20. század elején Milutin Milankovićnak sikerült matematikai formába önteni. A számításokat Bacsák György pontosította. A számítások főképp az utolsó jégkorszak idejére tehetők. Ezeket az eredményeket a matematikai számítások igazolták. Milankovic és Bacsák vizsgálatai igazolták, hogy ha a Föld jövőbeni éghajlatát akarjuk kiszámítani, akkor, ha nem is teljesen, de, döntő mértékben dinamikailag értenünk kell a múlt éghajlatát. Ezért elengedhetetlenek a paleoklimatológiai vizsgálatok, Milanković-Bacsák módszer segítségével. Kulcsszavak: Milanković-Bacsák-ciklus, extraterresztrikus okok, éghajlatváltozás, földtan Bevezetés A 20. század első felében -eltekintve az első világégéstől -töretlenül fejlődött a természettudományok ismerete, ugyanakkor a csillagászatra és a földtudományokra is jellemző volt e tendencia. E tudomány fejlődés lényegében érintette a tágabb értelemben vett Kárpát -medencét is, ahol egy szerb származású tudós (Milutin Milanković) csillagászati megfigyeléseket végzett, amelyből következtetéseket vont le az éghajlatváltozásra. Ezeket az eredményeket egy magyar tudós (Bacsák György) matematikailag kiegészített. E cikk szerzője 2013-ban a Magyar Tudomány 2. számában (Hágen A. 2013) kifejtette a Milanković által megfigyelt csillagászati paraméterek hatását a földtörténeti múlt rétegeiben. 1 Módosított közlés. Első közlés: Hágen A. 2013: Milanković-Bacsák-ciklus és a földtan. -Magyar Tudomány, 2013/2, 200-205.

Over periods of tens of thousands to millions of years, periodic changes of climate due to astronomically defined variations in the distribution of solar energy over the Earth are of influence upon the climate and upon oceanic circulation systems. This in turn may affect the production of carbonate and organic matter in marine surface waters and the oxidation and dissolution of these products in the deep ocean. Rhythmic variations in the flux of the resulting pelagic sediments are readily preserved in the deep oceanic record. However, similar reflections of regular, astronomically induced fluctuations of climate have been widely observed in other sedimentary environments, including glacial, lacustrine, fluvial, aeolian, deltaic, shallow marine, and submarine fan.

Periodic climatic and oceanographic changes and the resulting rhythmic sedimentation patterns can be preserved in the sedimentary record, providing that the sediment-supplying mechanisms (weathering and transport on the land, production of biogenic sediment in the ocean) as well as the relative sedimentary facies are sufficiently sensitive. Pelagic and lacustrine, and especially evaporitic, settings have proved to be sensitive to the influence of orbital forcing of climate. It is in such facies that, at the turn of the century, cyclicity in sedimentary sequences was recognized to be the result of orbital forcing (Gilbert, 1894; Bradley, 1929). Other sedimentary environments can be sensitive to such astronomically induced climatic variations in a similar way, but in many cases disturbing factors, such as variations in the rate of sedimentation and intermittent erosion, will obscure an otherwise clear record in the sedimentary column. Recognition of orbital cycles in environments other than the pelagic and lacustrine ones is of more recent date, but even coarse-grained alluvial fan and submarine fan environments can now be proven to bear the marks of orbitally induced climatic changes. Once demonstrated in the record, Milankovitch cycles have applications in assessing rates and durations of geological processes, and in the analysis of the palaeoclimate.

The Aptian/Albian oceanic anoxic event 1b contains the record of several perturbations in the global carbon cycle and multiple black shale levels, particularly in the Western Tethys. The local lithological expression of an oceanic anoxic event depends on palaeogeographical and depositional setting as well as on regional palaeoclimate. Marine sediments at a particular location may therefore be more or less organic-rich (or not at all) and they may consist of different lithologies. In most studies, however, much of the lithological variability associated with oceanic anoxic events is left unaccounted for and, thus, the exact processes leading to the enrichment of organic matter in these marine sediments and their subsequent preservation in the geological record are unknown. This study focuses on the local sedimentary processes behind the deposition of organic-rich sediments at Deep Sea Drilling Project Site 545 and Ocean Drilling Program Sites 1049 and 1276 in the North Atlantic during oceanic anoxic event 1b. Although specifically dealing with the sediments deposited during this particular event at these localities, it is expected that the same processes were responsible for determining the exact sedimentary products at localities in similar settings, as well as during other similar events in the Mesozoic. Here, it is shown that the deposition of organic-rich sediments during oceanic anoxic event 1b was a consequence of the enhanced productivity favoured by upwelling and by riverine nutrient input, or aeolian fertilization of the euphotic zone depending on geographical location. Slope instability processes resulted in the transfer of part of these organic-rich sediments from the shelf to deep sea depocentres as mud-laden organic-rich turbidites, especially in the northern North Atlantic. The so-called ‘black shales’ are much more varied than their name implies. The end product of sedimentation during an oceanic anoxic event at a particular location is commonly the result of several equifinal processes acting on a local scale rather than the direct result of basinal or even global mechanisms.

There are over 50 years of systematic, multidisciplinary research at Olduvai Gorge. This summary is a general view of some scientific results in the gorge, to get a picture of the landscape, ecosystem and climate evolution superimposed on the hominin evolution.

In outcrops, shallow-water carbonates often form thick, vertically stacked, metre-scale, exposure-bounded depositional packages, here called carbonate cycles. Because the facies within carbonate cycles can be tied precisely to water depths, they are considered ideal for reconstructing past sea-level changes. There is, however, increasing evidence that these depositional cycles are unreliable recorders of both the frequency and the amplitude of orbitally driven sea-level fluctuations. Carbonate cycles record only a fraction of the amplitude of a sea-level cycle: a portion of the rise and nothing of the fall. Cores through the Pleistocene cycles on Great Bahama Bank illustrate this shortcoming. Although the amplitudes of the last nine sea-level changes are each a hundred metres or more, the thickness of the cycles varies from a few metres to ca 15 m. The lack of correlation between sea-level amplitude and cycle thickness is not eliminated for cycles deposited during times of lower sea-level amplitudes, for example, the Cretaceous. Upper Cretaceous cycles on the Maiella platform margin document the irregularly filled accommodation space and the resultant variability in cycle thickness and frequency. Uncertainties in assessing the frequencies of sea-level changes from shallow-water carbonate cycles are caused by 'missed beats' and metre-scale oscillations of sea-level within highstands that potentially produce cycles of very short duration. The random amplitude variability during the last 57 glacio-eustatic sea-level changes illustrates the difficulty of assessing 'missed beats', where a sea-level fluctuation is not recorded because the sea-level rise does not reach the platform top. 'Missed beats' are also produced by the depositional topography that is created by irregularly filled accommodation space. As a result, variable numbers of cycles are deposited across the platform. Further complicating orbital frequency analyses are decametre-scale oscillations of the sea-level during highstands. The amplitude of these suborbital sea-level oscillations (up to 17 m within the last interglacial, Marine Isotope Stage 5e) are sufficient to expose shallow platforms like Great Bahama Bank and subsequently produce an additional depositional cycle with similar facies successions. The combined effects of missed beats and oscillations within highstands are likely to produce cycles and hiatuses of variable duration that are difficult to extract from the rock record. Consequently, estimates of the orbital forcing mechanisms and frequencies from ancient shallowwater carbonate cycles carry large uncertainties.

Cyclical fluctuations in planktic foraminiferal assemblages have been recognized in the pre-evaporitic Messinian
in a marginal basin of the western Mediterranean. The fluctuations coincide with a dominantly precession-controlled
sedimentary cyclicity (sapropels). During sapropel deposition, high planktic foraminiferal diversities are indicative of
relatively stable marine conditions, while during homogeneous marl deposition low diversities seem to indicate the presence
of unfavourable, more saline surface water conditions. The dominance of a precession-related signal indicates that regional
climate oscillations rather than (obliquity-related) glacio-eustatically controlled influxes of Atlantic and=or Mediterranean
waters are responsible for the faunal fluctuations and sedimentary cyclicity. Our scenario links the persistence of normal
marine conditions during sapropel formation with increased rainfall and run-off along the western Mediterranean at times
that perihelion occurred in Northern Hemisphere summer. Less favourable, highly saline surface water conditions prevailed
during periods of drier climate induced by opposite precessional extremes. The cyclical oceanographic fluctuations could
also have governed periodic reef growth along the margins.

Orbital cycles are related to variations of Earth's orbit through time and exert profound control on glacial and interglacial climates due to changes in insolation. In this study, we aim to test whether orbital and millennial-scale climate cycles conditioned the deposition of rhythmites in the southern Gondwana during the Late Paleozoic Ice Age (LPIA). We present the first cyclostratigraphic study based on X-ray fluorescence records from a 27-m-thick interval of LPIA rhythmites in the southeastern border of the Paraná Basin, Brazil. TiO 2 and Fe 2 O 3 records display cycles in the Milankovitch and millennial bands. Among millennial-scale variability, there are strong signals suggesting cycles with periods similar to the~2.4-kyr Hallstatt heliomagnetic and the~1.5-kyr Dansgaard-Oeschger cycles. We estimated an average sediment accumulation rate of 5.94 cm/kyr, which suggests that the rhythmites were deposited in a relatively distal setting, during deglaciation episodes paced by millennial-scale climate cycles. We interpret variations in concentrations of the terrigenous components TiO 2 and Fe 2 O 3 as indicative of glacial-interglacial changes, reflected by advances and retreats of glaciers under drier and wetter climate conditions, respectively. Here we show that these high-latitude glacial-interglacial cycles were probably paced by short eccentricity, as previously suggested for Carboniferous cyclothems in low-latitude deposits, and highlight the importance of millennial-scale climate cycles at controlling glacially influenced deposition at high latitudes. Our results for the LPIA are similar to patterns seen in Pleistocene records. Plain Language Summary In this study, we investigate a geological record from the Late Paleozoic Ice Age (LPIA), one of the major glaciations that ever occurred in Earth's history and increasingly compared to the Pleistocene glaciation. With high-resolution profiles that reflect the chemical composition of the sediments, we were able to identify orbital and millennial-scale climate cycles that show similarities to Pleistocene glacial and interglacial climate variability. Assuming that changes in the concentrations of iron and titanium in the sediments reflect paleoclimatic characteristics, we suggest that major advances and retreats of high-latitude glaciers during the LPIA occurred about 100,000 years apart, under drier and wetter climate conditions, respectively. Our results suggest that the behavior of glaciers during the LPIA was comparable to Pleistocene glacial-interglacial cycles.

Detailed sedimentological, sequence stratigraphical and cyclostratigraphical analyses have been made from four lower Tithonian–lower Valanginian sections of the Vaca Muerta Formation, exposed in the southern Mendoza area of the Neuquén Basin, Argentina. The Vaca Muerta Formation is characterized by decimetre-scale rhythmic alternations of marls, shales and limestones, and consists of five facies associations, which reflect different paleoenvironmental conditions: basin to restricted outer ramp, outer ramp, and middle ramp. Vertical organization within the Vaca Muerta Formation shows a well-ordered hierarchy of cycles, where elementary cycles, bundles and superbundles with frequencies within the Milankovitch band have been recognized. According to biostratigraphic data, elementary cycles have a periodicity of ~ 20 ky, which correlates with the precession cycle of Earth's axis. Spectral analysis based on series of cycle thickness allows us to identify frequencies of about 400 ky and 90–120 ky, which we interpret as the modulation of the precessional cycle by the Earth's orbital eccentricity. Cycles are probably driven by variations in carbonate exportation, as fluctuations in shallow-water carbonate production involve modifications in carbonate basinward exportation. Cyclostratigraphic data allowed us to build a floating orbital scale for the Tithonian–lower Valanginian interval in the Neuquén Basin. Correlation between studied sections allowed us to recognize a discontinuity between the Substeueroceras koeneni and Argentiniceras noduliferum ammonite zones in the Malargüe Anticline area. Orbital calibration of these sections is consistent with Riccardi's biostratigraphic scheme, wich place the Jurassic-Cretaceous boundary within the Substeueroceras koeneni ammonite Zone. On the other hand, the base of the Vaca Muerta Formation (Virgatosphinctes mendozanus ammonite Zone) would be probably placed in the base of the middle Tithonian rather than the lower Tithonian, which is also consistent with our preliminary palaeomagnetic data.

Carbon sources and sinks are key components of the climate feedback system, yet their response to external forcing remains poorly constrained, particularly for past greenhouse climates. Carbon-isotope data indicate systematic, million-year-scale transfers of carbon between surface reservoirs during and immediately after the Late Cretaceous thermal maximum (peaking in the Cenomanian-Turonian, circa 97-91 million years, Myr, ago). Here we calibrate Albian to Campanian (108-72 Myr ago) high-resolution carbon isotope records with a refined chronology and demonstrate how net transfers between reservoirs are plausibly controlled by~1 Myr changes in the amplitude of axial obliquity. The amplitude-modulating terms are absent from the frequency domain representation of insolation series and require a nonlinear, cumulative mechanism to become expressed in power spectra of isotope time series. Mass balance modeling suggests that the residence time of carbon in the ocean-atmosphere system is-by itself-insufficient to explain the Myr-scale variability. It is proposed that the astronomical control was imparted by a transient storage of organic matter or methane in quasi-stable reservoirs (wetlands, soils, marginal zones of marine euxinic strata, and potentially permafrost) that responded nonlinearly to obliquity-driven changes in high-latitude insolation and/or meridional insolation gradients. While these reservoirs are probably underrepresented in the geological record due to their quasi-stable character, they might have provided an important control on the dynamics and stability of the greenhouse climate.

Alice M. Doughty, Joerg M. Schaefer, Aaron E. Putnam, George H. Denton, Michael R. Kaplan, David J.A.
Barrell, Bjørn G. Andersen, Samuel E. Kelley, Robert C. Finkel, and Roseanne Schwartz

Here we address a long-standing puzzle of ice-age climate called
the “fly in the ointment of the Milankovitch theory.” Using geomorphic mapping and 10Be surface-exposure dating, we show that five moraine belts were formed during maxima of the last ice age by the Pukaki glacier in New Zealand’s Southern Alps. They afford ages of 41.76 ± 1.09 ka, 35.50 ± 1.26 ka, 27.17 ± 0.68 ka, 20.27 ± 0.60 ka, and 18.29 ± 0.49 ka. These five maxima spanned an entire precessional cycle in summer insolation intensity at the latitude of the Southern Alps. A similar mismatch between summer insolation and glacier extent also characterized the Chilean Lake District in the mid-latitudes of South America. Thus, in apparent contrast to northern ice sheets linked by Milankovitch to summer insolation at 65°N latitude, the behavior of southern mid-latitude glaciers was not tied to local summer insolation intensity. Instead, glacier extent between 41.76 ka and 18.29 ka, as well as during the last termination, was aligned with Southern Ocean surface temperature and with atmospheric carbon dioxide.

The sedimentary record of orbitally-forced variations in climate has the potential to provide high-resolution dating to levels of a few hundred thousand years or less. Easily-measured, bed-to-bed variations in various components give the basic data for defining these rhythms. The Cretaceous is a particularly appropriate period for testing both the validity and the application of cyclostratigraphy.
Recommended specific short range objectives are: detailed comparative studies of time slices, in order to recognize the effect of orbital influences in different sedimentary environments, and to map the paleogeographic distributions of obliquitydominated patterns versus precession-eccentricity dominated ones. This approach should illuminate Cretaceous climates and oceanography, and the pathways along which sedimentary systems were forced.

Isotopic mass balance models are employed here to study the response of carbon isotope composition (δ 13 C) of the ocean-atmosphere system to amplitude-modulated perturbations on Milankovitch time scales. We identify a systematic phase distortion, which is inherent to a leakage of power from the carrier precessional signal to the modulating eccentricity terms in the global carbon cycle. The origin is partly analogous to the simple cumulative effect in sinusoidal signals, reflecting the residence time of carbon in the ocean-atmosphere reservoir. The details of origin and practical implications are, however, different. In amplitude-modulated signals, the deformation is manifested as a lag of the 405 kyr eccentricity cycle behind amplitude modulation (AM) of the short (~100 kyr) eccentricity cycle. Importantly, the phase of AM remains stable during the carbon cycle transfer, thus providing a reference framework against which to evaluate distortion of the 405 kyr term. The phase relationships can help to (1) identify depositional and diagenetic signatures in δ 13 C and (2) interpret the pathways of astronomical signal through the climate system. The approach is illustrated by case studies of Albian and Oligocene records using a new computational tool EPNOSE (Evaluation of Phase in uNcertain and nOisy SEries). Analogous phase distortions occur in other components of the carbon cycle including atmospheric CO 2 levels; hence, to fully understand the causal relationships on astronomical time scales, paleoclimate models may need to incorporate realistic, amplitude-modulated insolation instead of monochromatic sinusoidal approximations. Finally, detection of the lagged δ 13 C response can help to reduce uncertainties in astrochronological age models that are tuned to the 405 kyr cycle.

Basin to mid-ramp cyclic facies of the Tithonian Vaca Muerta Formation are exposed in the Loncoche creek section of the Neuquén Basin, Mendoza province, Argentina. This unit is characterized by a decimetre-scale rhythmic alternation of marls/shales and limestones, and extends from the early Tithonian to late Berriasian. Cyclostratigraphic studies based on a detailed facies analysis allowed the identification of cyclic patterns with frequencies within the Milankovitch band. According to biostratigraphic data, the dominant cycle in the studied section has a period of 20 ky, which correlates with the Earth’s axis precession element. Spectral analysis based on series of compacted and decompacted cycle thickness identified a subordinate frequency of about 90-120 ky, which we interpret as the modulation of the precessional cycle caused by the Earth’s orbital eccentricity. The strength of the precession signal together with the absence of a well-defined cyclicity attributable to the obliquity orbital cycle (i.e. ~ 40 ky) is in agreement with previous data from the Northern Hemisphere.

Astronomical forcing is one of the main drivers of climate change, and astronomical cyclicity recorded in sediments provides a clue to understand the dynamics of the global climate system. Bedded cherts consist of rhythmic alternations of chert and shale beds. Although previous studies have hypothesized that the origin of bedded chert is related to astronomical cycles (e.g. Fischer, 1976; Hori et al., 1993), conclusive proof remains elusive. To explore this possibility, we established a continuous, high-resolution lithostratigraphy of middle Triassic bedded chert in Central Japan. The average duration of each chert-shale couplet is 20 kyr, similar to that of the precession cycle. Spectral analysis of a bed number series of thickness variations in chert beds was performed assuming that each chert-shale couplet represents a 20-kyr precession cycle. The results reveal cycles involving approximately 200, 20, 5, and 2-3 beds, corresponding to periodicities of approximately 4000, 400, 100, and 40-60 kyr, respectively. By further assuming that the 20-bed cycle represents a 405-kyr eccentricity cycle of constant and stable periodicity, we converted the bed number series to a time series. Spectral analysis of the time series revealed distinct periodicities of 3600, 117, 97, and 38 kyr, in addition to 405 kyr. Besides 3600 kyr, these periodicities agree well with the 120, 95, and 37 kyr periodicities for eccentricity cycles and the obliquity cycle during the Triassic. Moreover, we detected amplitude modulation of the approximately 100-kyr cycle of thickness variations in chert beds with a 405kyr periodicity, which may correspond to amplitude modulation of 100-kyr climatic precession cycle with the 405-kyr periodicity. The approximately 3600-kyr periodicity described above and 1800-kyr periodicity manifested as the amplitude modulation of the 405-kyr cycle are correlated to present-day long-term eccentricity cycles of 2400 and 4800 kyr evolved by chaotic behavior of solar planets. Collectively, these similarities in the periodicities of dominant cycles, their hierarchy, and the nature of amplitude modulation of cycles in chert bed thickness with those of astronomical cycles strongly support the hypothesis that the sedimentary rhythm of bedded chert is paced by astronomical cycles, thereby indicating the potential of bedded chert as a template for a Mesozoic cyclostratigraphy.

In my first article on paleoclimatology, I discussed a theory called the Milankovitch Ice Age Theory which explained why and how often ice ages occurred. In this article, I explore the Last Glacial Maximum (LGM) during the Wisconsin Ice Age in North America.

In the austral summer of 2006/7 the ANDRILL MIS (ANtarctic geological DRILLing-McMurdo Ice Shelf) project recovered a 1285m sediment core from beneath the Ross Ice Shelf near Ross Island, Antarctica in a flexural moat associated with volcanic loading. The upper ~600m of this core contain sediments recording 38 glacial/interglacial cycles of Early Pliocene to Pleistocene time, including 13 discrete diatomite

The Aptian/Albian oceanic anoxic event 1b contains the record of several perturbations in the global carbon cycle and multiple black shale levels, particularly in the Western Tethys. The local lithological expression of an oceanic anoxic event depends on palaeogeographical and depositional setting as well as on regional palaeoclimate. Marine sediments at a particular location may therefore be more or less organic-rich (or not at all) and they may consist of different lithologies. In most studies, however, much of the lithological variability associated with oceanic anoxic events is left unaccounted for and, thus, the exact processes leading to the enrichment of organic matter in these marine sediments and their subsequent preservation in the geological record are unknown. This study focuses on the local sedimentary processes behind the deposition of organic-rich sediments at Deep Sea Drilling Project Site 545 and Ocean Drilling Program Sites 1049 and 1276 in the North Atlantic during oceanic anoxic event 1b. Although specifically dealing with the sediments deposited during this particular event at these localities, it is expected that the same processes were responsible for determining the exact sedimentary products at localities in similar settings, as well as during other similar events in the Mesozoic. Here, it is shown that the deposition of organic-rich sediments during oceanic anoxic event 1b was a consequence of the enhanced productivity favoured by upwelling and by riverine nutrient input, or aeolian fertilization of the euphotic zone depending on geographical location. Slope instability processes resulted in the transfer of part of these organic-rich sediments from the shelf to deep sea depocentres as mud-laden organic-rich turbidites, especially in the northern North Atlantic. The so-called ‘black shales’ are much more varied than their name implies. The end product of sedimentation during an oceanic anoxic event at a particular location is commonly the result of several equifinal processes acting on a local scale rather than the direct result of basinal or even global mechanisms.

Understanding what drove Northern Hemisphere ice sheet melt during the last deglaciation (21-7 ka) can help constrain how sensitive contemporary ice sheets are to greenhouse gas (GHGs) changes. The roles of orbital forcing and GHGs in the deglaciation have previously been modelled, but not yet quantified. Here, for the first time we calculate the relative effect of these forcings on the North American deglaciation by driving a dynamical ice sheet model (GLIMMER-CISM) with a set of un-accelerated transient deglacial simulations with a full primitive equation based ocean atmosphere general circulation model (FAMOUS). We find that by 9 ka, orbital forcing has caused 50% of the deglaciation, GHG 30% and the interaction between the two 20%. Orbital forcing starts affecting the ice volume at 19 ka, 2,000 years before CO2 starts increasing in our experiments, a delay which partly controls their relative effect.

An evaluation of the global synchronicity and duration of “3rd-order” sea-level fluctuations during the Cretaceous greenhouse has been hampered by poor constraints on potential climatic and tectonic drivers, and limitations of geochronology and chronostratigraphic correlation. To provide insight into the nature of such sea-level fluctuations, here we present a new Late Cretaceous record from the Jordanian Levant Platform, comprising a detailed physical-, bio-, chemo- and sequence stratigraphy. Carbonate content of these strata reflects overall sequence stratigraphic development, and demonstrates a dramatic 3rd-order-scale cycle that is also apparent in the δ13C record. Updated radioisotopic constraints and astrochronologic testing provide support for the inference of an ~ 1 million year long sea-level oscillation associated with this 3rd-order cycle, which likely reflects a long-period obliquity (1.2 Myr) control on eustasy and stratigraphic sequence development, linked to the global carbon cycle. The observation of cyclic sea-level fluctuations on this time scale suggests sustained global modulation of continental fresh-water-storage. The hypothesized link between astronomical forcing and sea-level forms a baseline approach in the global correlation of sequence boundaries.

Variations in the first Euler angle known as Earth precession phenomenon which is described as a change in the Earth's orbit; found to have strong impact on the climate of Earth. These observations of climate changes were connected with the behavior of the global ice sheets, including their advancing and retreating movements which have been recorded. In fact, Earth's climate depends essentially on the cycle of glaciers' growth and reduction. The alternative glacial periods and the interglacial periods coincide with the variations in Earth's orbit known as "Milankovitch cycles", which affect the insolation, and the sunlight exposure of different regions of the world and thus ultimately the behavior of ice formation. This paper aims to document the variations of the Earth's axis orientation and to discuss how these changes have affected to the sea-level fluctuation of the South Asian Region during late Pleistocene. Experiment methodology consists of compelling a standardized dataset of the sea-level index (Data SET 01-Radiocarbon Journal, Katupotha. J, Data SET 02-SEAMIS database and selected 35 number of carbon dating values recorded and published in the literature of the South Asian Region) and then compare it with the data of Milankovitch Cycles. The discussed results show that the sealevel variations occurred mainly between 12,500 ± 1,500 YBP to 11,000± 1,500 YBP, indicating that 25m ± 5m recorded to be the lower sea level documented than the current sea level found around the South Asian region. This has been resulted by a quick glacier transition that happened in the Late Pleistocene.

This research paper has the main purpose to discuss the relationship between mathematics and astronomy. The topics that are covered start with the history of astronomy and end on the Milankovitch Cycles. In particular, I will cover how ancient civilizations looked at astronomy and defined it; how scientists of the Renaissance period developed these doctrines; how several of these doctrines apply to the Milankovitch Cycles.

Deep marine successions of early Campanian age from DSDP (Deep Sea Drilling Project) site 516F drilled at low paleolatitudes in the South Atlantic reveal distinct sub-Milankovitch variability in addition to precession, obliquity and eccentricity-related variations. Elemental abundance ratios point to a similar climatic origin for these variations and exclude a quadripartite structure as an explanation for the inferred semi-precession cyclicity in the magnetic susceptibility (MS) signal as observed in the Mediterranean Neogene for precession-related cycles. However, semi-precession cycles as suggested by previous work are likely an artifact reflecting the first harmonic of the precession signal. The sub-Milankovitch variability, especially in MS, is best approximated by a ∼ 7 kyr cycle as shown by spectral analysis and bandpass filtering. The presence of sub-Milankovitch cycles with a period similar to that of Heinrich events of the last glacial cycle is consistent with linking the latter to low-latitude climate change caused by a non-linear response to precession-induced variations in insolation between the tropics.

While in the present icehouse episode sea level apparently is controlled dominantly by the waxing and waning of polar ice caps, this controlling factor is controversial when it comes to sea level fluctuation during the Cretaceous greenhouse episode. Controversy exists because ice played a much smaller role and was only temporarily present on just one pole. Yet global sea level kept fluctuating at rates comparable to the icehouse mode. The amount of water in the global oceans in fact seems to have alternated following a consistent cyclic beat regardless of which mode, icehouse or greenhouse. So, what could have controlled sea level during the greenhouse mode? Here we follow this question by examining cyclic global stable isotope data that are correlated to sea level cycles deposited during the Cenomanian-Turonian peak greenhouse period. A sedimentary succession from Jordan that represents a Cretaceous shelf environment was analyzed. Mineralogical cycles in this section are associated with the cycles of fluctuating global sea level and suggest a cyclic pattern in continental weathering. Given the potential of water storage on land in groundwater aquifers, the observed signal could explain sea level changes due to a process that doesn’t require ice caps for water storage.

Pasteurella multocida is a highly versatile pathogen that infects a wide range of animals, including goats, causing pneumonia and hemorrhagic septicemia. Circular RNA (circRNA) is a type of non-coding RNA that plays an important role in regulating cellular metabolism. However, whether and how circRNA is involved in regulating immune responses in the goat lung has not been reported. Thus, this study was designed to examine the function of circRNA in goats infected with Pasteurella multocida. Goats were assigned into one of two groups: an uninfected control group (CK) and an infected group challenged with P. multocida. Compared with the CK group, which remained healthy, the infected goats showed clinical signs of infection, including depression, cough, nasal discharge, and dyspnea, along with elevated body temperature and lesions in the lung. Whole-transcriptome sequencing and small RNA sequencing were then performed using lung samples from goats from each group. A total of 138 circRNA, 56 microRNAs (miRNA), and 2,673 messenger RNA (mRNA) molecules were significantly differentially expressed in the P. multocida-infected group compared with the CK group. Randomly selected differentially expressed circRNA, miRNA, and mRNA molecules (n = 5 per group) were then validated by quantitative reverse-transcriptase polymerase chain reaction analysis. Gene ontology (GO) analysis of the source genes indicated that six immune-related terms were enriched among the differentially expressed cirRNA molecules, including inflammatory response, immune effector process, cell activation involved in immune response, cytokine-mediated signaling pathway, response to endogenous stimulus, and immune response. The corresponding circRNA molecules were then selected for construction of a competitive endogenous RNA network to identify networks that may be involved in the immune response to P. multocida infection. The results indicated that P. multocida HN01 may cause pneumonia and stimulate an immune response in goats via regulation of circRNA expression. This study presents the first comprehensive circRNA profile in response to P. multocida infection in goats, thus, providing a basis for understanding the function of circRNA in the host immune response to P. multocida infection.

ABSTRACT A section from the Ultrahelvetic units of Upper Austria comprises the transition from light-gray, upper-bathyal to middlebathyal carbonates of Early Turonian age towards red-colored carbonates of the Middle Turonian. The total-organic-carbon content is very low throughout the section, but benthic foraminifera associations, especially high abundance of Tappanina laciniosa, indicate repeated phases of enhanced organic-matter flux and decreased oxygen concentrations at the seafloor. The overlying reddish layers are enriched in iron oxides and hydroxides and pyrite and may represent paleo–redox fronts that were related to periods of well oxygenated bottom waters, reduced sedimentation rates, and degradation of organic matter in the underlying sediments. Cyclic sedimentary packages consist of four marlstone–limestone couplets with upward-increasing bedding thickness, red carbonates at the base, and a gray limestone bed at the top. Based on carbon isotope stratigraphy, these packages reflect the 400 kyr eccentricity cycle, with the four marlstone–limestone couplets representing the 100 kyr cycle. Three 400-kyr-cycle boundaries are preceded by horizons with high T. laciniosa abundance and are followed by a paleo-redox front and red-bed deposition. Thus, there is indication of the temporary presence of a local oxygen-minimum zone during enhanced production at the end of each 400 kyr cycle, possibly linked to sea-level fluctuations. Organic-carbon fluxes seem to have decreased immediately above the cycle boundaries. Recycling of organic carbon could be responsible for the distinct carbon-isotope minima at the base of each cycle. Accumulation rates based on our orbital model suggest a switch from relatively uniform sedimentation rates in the Early Turonian to cyclic fluctuations of sedimentation rates in the Middle Turonian. The occurrence of three 400 kyr cycles between the main carbon-isotope excursions points to a 1.2 Myr periodicity, which may reflect the Earth’s long obliquity cycle. A long-term increase in bottom-water aeration from the Early to the Middle Turonian is evident from the increasing dominance of red sediments.

The 720-m-thick succession of the Middle Triassic Latemàr Massif (Dolomites, Italy) was used to reconstruct the lagoonal facies architecture of a small atoll-like carbonate platform. Facies analysis of the lagoonal sediments yields a bathymetric interpretation of the lateral facies variations, which reflect a syndepositional palaeorelief. Based on tracing of lagoonal flooding surfaces, the metre-scale shallowing-upward cycles are interpreted to be of allocyclic origin. Short-term sea-level changes led to subaerial exposure of wide parts of the marginal zone, resulting in the development of a tepee belt of varying width. Occasional emergence of the entire lagoon produced lagoon-wide decimetre-thick red exposure horizons. The supratidal tepee belt in the backreef area represented the zone of maximum elevation, which circumscribed the sub- to peritidal lagoonal interior during most of the platform’s development. This tepee rim, the subtidal reef and a sub- to peritidal transition zone ...

The basal section of the lower Albian Barra Nova Group in the onshore portion of the Regência Platform, a central-eastern geological province of the Espírito Santo Basin, Brazil, comprises a mixed succession characterized by the cyclic alternation of dominant fluvial to shallow marine, siliciclastic rocks and marine carbonate strata. Spectral analysis of gamma-ray logs of four wells has shown consistent evidence of a short eccentricity orbital frequency (100 ka) influence on sedimentation. The spectral analysis points to a time span from 2.95 to 3 Ma (depending on the method employed) for the deposition of the interval studied in the most complete section (Well 1), and from 1.84 to 2.1 Ma in the least complete section (Well 4), owing to partial erosion. These figures are consistent with the palynological dating of the section (2 Ma), hence showing that cyclostratigraphy can play an important role in assigning a time span for high-frequency cycles (4th and 5th orders). Climatic factors not necessarily linked to eustasy, such as the alternation of dry (carbonate deposition) and mild humid (increased siliciclastic input) climate, are supposed to have controlled the cyclical stratigraphic arrangement. Accommodation as a result of diastrophism, loading and eustatic sea-level rise would not explain such a high mean accumulation rate (29.1 cm/ka) estimated through cyclostratigraphy. Therefore, based on these assumptions and seismic data, the high preservation potential, and resulting well-preserved cyclicity, is herein assigned to halokinesis. Several pieces of evidence obtained from the analysis of seismic data, core description, stratigraphic correlation, palaeontology and spectral data have shown the importance of halokinesis to increasing accommodation, and then the excellent preservation of the cyclical nature of the geological record. This is unusual in sedimentary environments subject to recurrent erosive events such as those related to shallow-marine settings.

The discovery of elevated concentrations of the cosmogenic radionuclide 3 He in deep-sea sediments from Ocean Drilling Program (ODP) Site 926 (Atlantic Ocean) and ODP Site 757 (Indian Ocean) points toward accretion of extraterrestrial matter, probably as a result of the catastrophic disruption of a large asteroid that produced the Veritas family of asteroids at ca. 8.3 ± 0.5 Ma, and which may have had important effects on the global climatic and ecologic systems. Here, we investigated the signatures possibly related to the Veritas event by performing a high-resolution multiproxy stratigraphic analysis through the late Tortonian-early Messinian Monte dei Corvi section near Ancona, Italy. Closely spaced bulk-rock samples through a 36-m-thick section, approximately spanning from ca. 9.9 Ma to ca. 6.4 Ma, show an ~5-fold 3 He anomaly starting at ca. 8.5 Ma and returning to background values at ca. 6.9 Ma, confirming the global nature of the event. We then analyzed, at 5 cm intervals, bulk-rock samples for sedimentary and environmental proxies such as magnetic susceptibility, calcium carbonate content, total organic carbon, and bulk carbonate d 18 O and d 13 C, through a 21-m-thick section encompassing the 3 He anomaly. Available high-resolution sea-surface temperature data (via alkenone analyses) for this site show a temperature GSA decrease starting exactly at the inception of the 3 He anomaly. Cyclostratigraphic fast-Fourier-transform spectral analyses of the proxies indicate an age of 8.47 ± 0.05 Ma for the inception of the 3 He anomaly. A search for impact ejecta (analogous to what is present in the late Eocene, where both a 3 He anomaly and large-scale impact events are recorded) was not successful. Detailed cy-clostratigraphic analyses of our data suggest that the changes in the stable isotope series and environmental proxy series through this late Tortonian time interval had a common forcing agent, and that perturbations of or-bitally forced climate cycles are present exactly through the interval with the enhanced influx of extraterrestrial 3 He. Thus, the che-mostratigraphic evidence for a collisional event that created the Veritas family of asteroids , coinciding with climate perturbations on Earth, suggests yet another form of interaction between Earth and the solar system.

This study reports on a ß 150 m thick macrofossil-barren sequence of siliciclastic sediments from a Burdigalian age (Early Miocene) freshwater lake. The lake was located within an incipient rift system of the Most Basin in the Ohře (Eger) Graben, which was part of the European Cenozoic Rift System, and had an original area of 1000 km 2 . Sediments from the HK591 core that cover the entire thickness of the lake deposits and some of the adjacent stratigraphic units were analysed by X-ray fluorescence spectroscopy (a proxy for element composition) and magnetic polarity measurement. The element proxies were subjected to frequency analysis, which provided estimated sedimentation rates, and allowed for sediment dating by magnetostratigraphy and orbital tuning of the age model. Based on the resulting age model and the known biostratigraphy, the lake was present between 17.4 and 16.6 Ma, which includes the onset of the Miocene Climatic Optimum in the latest Early Miocene. The identification of orbital forcing (precession, obliquity and short eccentricity cycles) confirms the stability of the sedimentary environment of the perennial lake in an underfilled basin. The dating allowed the sediment record to be interpreted in the context of the current knowledge of the European climate during that period. The stability of the sedimentary environment confirms that precipitation was relatively stable over the period recorded by the sediments.

Cyclic fluctuations in global sea level during epochs of warm greenhouse climate have remained enigmatic, because absence or subordinate presence of polar ice during these periods precludes an explanation by glacioeustatic forcing. An alternative concept suggests that the water-bearing potential of groundwater aquifers is equal to that of ice caps and that changes in the dynamic balance of aquifer charge versus discharge, as a function of the temperature-related intensity of the hydrological cycle, may have driven eustasy during warm climates. However, this idea has long been neglected for two reasons: 1) the large storage potential of subsurface aquifers
was confused with the much smaller capacity of rivers and lakes and 2) empirical data were missing that document past variations in the hydrological cycle in relation to eustasy.
In the present study we present the first empirical evidence for changes in precipitation, continental weathering intensity and evaporation that correlate with astronomically (long obliquity) forced sea-level cycles during the warmest period of the Cretaceous (Cenomanian–Turonian). We compare sequence-stratigraphic data with changes in the terrigenous mineral assemblage in a low-latitude marine sedimentary sequence from the equatorial humid belt at the South-Tethyan margin (Levant carbonate platform, Jordan), thereby avoiding uncertainties from land–ocean correlations. Our data indicate covariance between cycles in weathering and sea level: predominantly chemical weathering under wet climate conditions is reflected by dominance of weathering products (clays) in deposits that represent sea-level fall (aquifer charge N discharge). Conversely, preservation of weathering-sensitive minerals (feldspars, epidote and pyroxenes) in transgressive sediments reflects decreased continentalweathering due to dryer climate (aquifer discharge N charge). Based on our results
we suggest that aquifer-eustasy represents a viable alternative to glacio-eustasy as a driver of cyclic 3rd-order sea-level fluctuations during the middle Cretaceous greenhouse climate, and it may have been a pervasive process throughout Earth history.