Astronomical Cycles Research Articles

Orbital scale variation of primary productivity in the central equatorial Indian Ocean (Maldives) during the early Pliocene

We investigate the response of the central equatorial Indian Ocean (ODP Site 716, Maldives) upwelling system to orbital forcing between 3.64 and 4.19Ma. This time interval in the early Pliocene was characterized by global average temperatures considerably warmer than present and reduced zonal and meridional sea surface temperature gradients across the major oceans. Chlorin, a degradation product of chlorophyll and a potential indicator of primary productivity, was previously shown to record orbital scale variations at this site. To confirm that chlorin records primary productivity and to understand the mechanism controlling the orbital variations, we compare changes in the planktic foraminiferal assemblages with the chlorin content of the sediment. Cross wavelet analysis demonstrates the in-phase relationship between the abundance of thermocline species and chlorin content, indicating that upwelling and a shallower thermocline drive the productivity changes. The aragonite content in periplatform carbonates is known to reflect variations in sea-level and/or climate, with high values generally indicating sea-level highstands. The aragonite content in the studied interval shows precession and eccentricity astronomical cycles, whereas the primary productivity proxies show only precessional cycles. The negative correlation between aragonite content and the relative abundance of thermocline species on the precessional band implies that the primary productivity increased during sea-level lowstands. This phase coupling is consistent with Quaternary productivity records from the central Indian Ocean that were proposed to be controlled by orbital induced variations of the El Niño-Southern Oscillation (ENSO). We therefore propose that a similar mechanism was active in the early Pliocene despite major changes in the global boundary conditions.

Lunar recession encoded in tidal rhythmites: a selective overview with examples from Argentina

The study of tides from the sedimentary record of tidal rhythmites, applying fast Fourier transform analysis, contributes to the understanding of the surficial evolution of our highly dynamic planet, and of the astronomical cycles that influenced the ancient tidal systems. This overview of lunar retreat rates, which includes examples from Argentina, displays a generalized pattern of nonlinear, progressively extended lunar cycles up to the present day. The lunar retreat calculated at different stages of the Earth’s history identifies three time spans of extremely high recession rates, amounting to almost twice that of the present day: Archean–Paleoproterozoic (6.93 cm/year), Neoproterozoic I–Ediacaran (7.01 cm/year) and Ediacaran–early Cambrian (6.48 cm/year). Older comparable recession rates are difficult to recognize because of the lack of tidal rhythmic sequences. The maximum lunar retreat rate is registered after the Copernican meteor bombardment event on the Moon at ~900 Ma, and the time span coincides with the continental dispersal of Rodinia. Every acceleration of the lunar retreat rate coincides with two main processes: (1) meteorite impacts on the Earth or Moon, and (2) reconfiguration of landmasses accompanied by earthquakes that generated changes in the rotational axis of the Earth, inundation surfaces, and glaciation/deglaciation processes. The simultaneous occurrence of such processes makes it difficult to distinguish the causes and effects of each individual process, but its conjunction would have promoted the destabilization of the Earth–Moon system in terms of moment of inertia that was transferred to the Moon rotation.

High-precision time-space correlation through coupled apatite and zircon tephrochronology: An example from the Permian-Triassic boundary in South China

Abstract Accurate and precise dating of individual volcanogenic beds that spread across multiple sedimentary successions is a powerful tool to untangle stratigraphic age contradictions, since these horizons are deposited synchronously. In this study, we show that combining apatite chemistry with zircon age, Th/U ratio, and Hf isotope composition leads to reliable lateral correlation of volcanic horizons across sections representing disparate biological, chemical, and physical paleoenvironments. We correlate two volcanogenic horizons across six sedimentary sections straddling the Permian-Triassic boundary (PTB) in the Nanpanjiang Basin (South China), including the last Permian bed below the unconformity in shallow-water sections of the Luolou Platform. We place the PTB in our sections at the marked lithological change in order to avoid the difficulties that arise from the diachronism of the index conodont Hindeodus parvus, the first occurrence of which defines the PTB at the Global Stratotype Section and Point at Meishan. Our new data demonstrate that these volcanogenic beds are contemporaneous and cogenetic, allowing us to pool high-precision U-Pb zircon ages from the same horizon across several sections, and dating the last Permian volcanic event in this basin at 252.048 ± 0.033 Ma. We show that the mineral chemistry of apatite and zircon of intra- and interbasin-wide volcanogenic beds provides tie points against which biozones, carbon isotopes, astronomic cycles, and geomagnetic polarity time series can be stringently tested.

Optimizing significance testing of astronomical forcing in cyclostratigraphy

AbstractThe recognition of astronomically forced (Milankovitch) climate cycles in geological archives marked a major advance in Earth science, revealing a heartbeat within the climate system of general importance and key utility. Power spectral analysis is the primary tool used to facilitate identification of astronomical cycles in stratigraphic data, but commonly employed methods for testing the statistical significance of relatively high narrow‐band variance of potential astronomical origin in spectra have been criticized for inadequately balancing the respective probabilities of type I (false positive) and type II (false negative) errors. This has led to suggestions that the importance of astronomical forcing in Earth history is overstated. It can be readily demonstrated, however, that the imperfect nature of the stratigraphic record and the quasiperiodicity of astronomical cycles sets an upper limit on the attainable significance of astronomical signals. Optimized significance testing is that which minimizes the combined probability of type I and type II errors. Numerical simulations of stratigraphically preserved astronomical signals suggest that optimum significance levels at which to reject a null hypothesis of no astronomical forcing are between 0.01 and 0.001 (i.e., 99–99.9% confidence level). This is lower than commonly employed in the literature (90–99% confidence levels). Nevertheless, in consonance with the emergent view from other scientific disciplines, fixed‐value null hypothesis significance testing of power spectra is implicitly ill suited to demonstrating astronomical forcing, and the use of spectral analysis remains a difficult and subjective endeavor in the absence of additional supporting evidence.

Orbital control on the timing of oceanic anoxia in the Late Cretaceous

Abstract. The oceans at the time of the Cenomanian–Turonian transition were abruptly perturbed by a period of bottom-water anoxia. This led to the brief but widespread deposition of black organic-rich shales, such as the Livello Bonarelli in the Umbria–Marche Basin (Italy). Despite intensive studies, the origin and exact timing of this event are still debated. In this study, we assess leading hypotheses about the inception of oceanic anoxia in the Late Cretaceous greenhouse world by providing a 6 Myr long astronomically tuned timescale across the Cenomanian–Turonian boundary. We procure insights into the relationship between orbital forcing and the Late Cretaceous carbon cycle by deciphering the imprint of astronomical cycles on lithologic, physical properties, and stable isotope records, obtained from the Bottaccione, Contessa and Furlo sections in the Umbria–Marche Basin. The deposition of black shales and cherts, as well as the onset of oceanic anoxia, is related to maxima in the 405 kyr cycle of eccentricity-modulated precession. Correlation to radioisotopic ages from the Western Interior (USA) provides unprecedented age control for the studied Italian successions. The most likely tuned age for the base of the Livello Bonarelli is 94.17 ± 0.15 Ma (tuning 1); however, a 405 kyr older age cannot be excluded (tuning 2) due to uncertainties in stratigraphic correlation, radioisotopic dating, and orbital configuration. Our cyclostratigraphic framework suggests that the exact timing of major carbon cycle perturbations during the Cretaceous may be linked to increased variability in seasonality (i.e. a 405 kyr eccentricity maximum) after the prolonged avoidance of seasonal extremes (i.e. a 2.4 Myr eccentricity minimum). Volcanism is probably the ultimate driver of oceanic anoxia, but orbital periodicities determine the exact timing of carbon cycle perturbations in the Late Cretaceous. This unites two leading hypotheses about the inception of oceanic anoxia in the Late Cretaceous greenhouse world.

Modelling East Asian Calendars in an Open Source Authority Database

This paper discusses issues concerning the creation of conversion tables for East Asian (Chinese, Japanese, Korean) and European calendars and describes the development of an open source calendar database as part of the history of converting East Asian calendars. East Asian calendars encode both astronomical and political cycles. As a result, date conversion must in practice rely on complex look-up tables and cannot be done merely algorithmically. We provide a detailed overview of the history of such conversion tables and find that the modelling of these tables into the digital follows a trend of increasingly detailed computation of chronological time. The Buddhist Studies Time Authority Database was designed to allow computational conversion of the Chinese, the Japanese and the Korean Calendar, between each other, as well as with the Gregorian, proleptic Gregorian and Julian calendar. It relies on the Julian Day Number (JDN) as common referent for all conversions.

Astronomical cycles of Middle Permian Maokou Formation in South China and their implications for sequence stratigraphy and paleoclimate

High-resolution (930 samples) magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) analyses were conducted on the ~49m thick Middle Permian Maokou Formation at Dukou, South China. Spectral analysis of covariant MS and ARM series reveal Milankovitch cycles with eccentricity, obliquity, and precession. A 5.7myr floating 405kyr eccentricity cycle-calibrated astronomical time scale was constructed and used as a geochronometer for estimating the durations of the conodont zones. The results indicate that the durations of the Jinogondolella postserrata, J. altudaensis, J. prexuanhanensis, and J. xuanhanensis conodont zones were 490kyr, 560kyr, 820kyr, and 750kyr, respectively. The 405kyr-calibrated MS and ARM series also show prominent ~1myr cyclicity, which may correspond to the secular frequencies of Earth and Mars, s4–s3, in the Middle Permian. The early Capitanian time interval was synchronous with the Kamura cooling event, and the accentuated obliquity cycling may signal ice-sheet expansion. The modulations of the obliquity have a close relationship with third-order eustatic sequences of the Wordian and Capitanian stages, suggesting a glacioeustatic origin during the Middle Permian.

Reply to the comment on “Geologic evidence for chaotic behavior of the planets and its constraints on the third-order eustatic sequences at the end of the Late Paleozoic Ice Age” by Qiang Fang, Huaichun Wu, Linda A. Hinnov, Xiuchun Jing, Xunlian Wang, and Qingchun Jiang [Palaeogeography Palaeoclimatology Palaeoecology 400 (2015) 848–859

In their comment, Smith et al. (2016) discount the astronomical cycle identifications made from Middle Permian cyclostratigraphy in our recent paper (Fang et al. 2015), declaring that we presented defective null models and improper hypothesis tests, and greatly overestimated the statistical significance of cycles. Here we respond in detail to clarify the decisions that were made in our work, and to correct errors and omissions and other misunderstandings arising in their comment. We also discuss the advent of objective methodologies that promise to improve research in cyclostratigraphy in the near future.

Životna sredina - opasnosti i pravna zaštita / Human Environment ‒ Risks and Legal Protection

The most relevant factors that affect climate are astronomic cycles ant their effects on planet Earth and Earth’s orbit around the Sun. They have impact on the occurrence of glacial and interglacial periods at generally 100.000-year frequencies, which were affected by orbital shape variations and effects of greenhouse gases.The youngest geological epoch of the geological history of Earth is Holocene (started with warming) that began approximately 11.000 years BP. In that epoch, the shape of Earth’s orbit around the Sun was nearly circular, close to a perfect circle, and the seasonal contrast was less severe, due to decreased tilt of Earth’s axis from the plane of its orbit around the Sun. However, most scientists are arguing that the causes of rapid climate change are rooted in human activity, and not in its internal orbital variations. The main causes of global warming are increased level of carbon dioxide, but also of methane and chlorofluorocarbons in the atmosphere. These gases are responsible for the greenhouse effect, ozone layer depletion in stratosphere and rapid global warming. In order to set up the legal framework of environmental protection, the United Nations Conference on the Human Environment has adopted Stockholm Declaration in June 16, 1972. About twenty industrial states have ratified in 1987 the Montreal Protocol on Substances that Deplete the Ozone Layer, which has undergone many revisions by London Convention (1990), Copenhagen Accord (1992), Vienna Convention (1995), Kyoto Protocol (1997) and the Paris Agreement ‒ an international universal agreement on climate adopted at the 2015 Paris Climate Conference (COP21). Environmental protection in the European Union is provided for by its primary and secondary law, and the most EU environmental regulations were implemented in the Serbian legislation.

A record of astronomically forced climate change in a late Ordovician (Sandbian) deep marine sequence, Ordos Basin, North China

The late Ordovician Pingliang Formation on the southwestern margin of the Ordos Basin, North China, consists of rhythmic alternations of shale, limestone, and siliceous beds. To explore the possible astronomical forcing preserved in this lithological record, continuous lithological rank and magnetic susceptibility (MS) stratigraphic series were obtained from a ~34m thick section of the Pingliang Formation at Guanzhuang. Power spectral analysis of the MS and rank series reveal 85.5cm to 124cm, 23cm to 38cm, and 15cm to 27cm thick sedimentary cycles that in ratio match that of late Ordovician short eccentricity, obliquity and precession astronomical cycles. The power spectrum of the MS time series, calibrated to interpreted short orbital eccentricity cycles, aligns with spectral peaks to astronomical parameters, including 95kyr short orbital eccentricity, 35.3kyr and 30.6kyr obliquity, and 19.6kyr and 16.3kyr precession cycles. The 15cm to 27cm thick limestone–shale couplets mainly represent precession cycles, and siliceous bed deposition may be related to both precession and obliquity forcing. We propose that precession-forced sea-level fluctuations mainly controlled production of lime mud in a shallow marine environment, and transport to the basin. Precession and obliquity controlled biogenic silica productivity, and temperature-dependent preservation of silica may have been influenced by obliquity forcing.

Frequency modulation reveals the phasing of orbital eccentricity during Cretaceous Oceanic Anoxic Event II and the Eocene hyperthermals

Abstract Major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods, amplitudes and phases of the ‘Milankovitch cycles’ of precession, obliquity and eccentricity. While numerous quantitative approaches exist for the identification of these astronomical cycles in stratigraphic data, limitations in radioisotopic dating, and instability of the theoretical astronomical solutions beyond ∼50 Myr ago, can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies. Here we demonstrate that interference patterns accompanying frequency modulation (FM) of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data. One- and two-dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the FM method, and indicate that pristine eccentricity FM can be readily distinguished in paleo-records. Apart from paleoclimatic implications, the FM approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions, and for refining chronologies for the deep past. We present two case studies that use the FM approach to evaluate major carbon-cycle perturbations of the Eocene and Late Cretaceous. Interference patterns in the short-eccentricity band reveal that Eocene hyperthermals ETM2 (‘Elmo’), H2, I1 and ETM3 (X; ∼52–54 Myr ago) were associated with maxima in the 405-kyr cycle of orbital eccentricity. The same eccentricity configuration favored regional anoxic episodes in the Mediterranean during the Middle and Late Cenomanian (∼94.5–97 Myr ago). The initial phase of the global Oceanic Anoxic Event II (OAE II; ∼93.9–94.5 Myr ago) coincides with maximum and falling 405-kyr eccentricity, and the recovery phase occurs during minimum and rising 405-kyr eccentricity. On a Myr scale, the event overlaps with a node in eccentricity amplitudes. Both studies underscore the importance of seasonality in pacing major climatic perturbations during greenhouse times.

The evaluation of eccentricity-related amplitude modulation and bundling in paleoclimate data: An inverse approach for astrochronologic testing and time scale optimization

Cyclostratigraphic analysis has produced fundamental advancements in our understanding of climate change, paleoceanography, celestial mechanics, geochronology, and chronostratigraphy. Of central importance to this success has been the development of astrochronologic testing methods for the evaluation of astronomical-climate influence on sedimentation. Most pre-Pleistocene astrochronologic testing methods fall into one of two categories: (1) those that test for expected amplitude or frequency modulation imposed by an astronomical signal or (2) those that test for bedding hierarchies (frequency ratios or bundling) that are predicted by the dominant astronomical periods. In this study, a statistical methodology for combining these complementary approaches is developed, which identifies the time scale that simultaneously optimizes eccentricity amplitude modulation of the precession band, and the concentration of power at precession (carrier) and eccentricity (modulator) frequencies. The technique is demonstrated to have high statistical power—it is capable of identifying astronomical cycles when present—under a wide range of conditions, and its application to synthetic models illuminates a range of potential pitfalls that are encountered when more conventional nonoptimization approaches are used. The method is also independent from the interpretation of power spectrum peak significance, resolving previous concerns regarding appropriate confidence level assessment and “multiple testing.” As two case studies, the algorithm is applied to Miocene strata of Ocean Drilling Program (ODP) Site 926B, and the Paleocene-Eocene Thermal Maximum-Eocene Thermal Maximum 2 interval at ODP Site 1262. The results verify published cyclostratigraphic interpretations and support the theoretical astronomical solutions. This new astrochronologic testing approach can be used to evaluate cyclostratigraphic records spanning the Phanerozoic and potentially beyond.

New evidence of the age of the lower Maeotian substage of the Eastern Paratethys based on astronomical cycles

The lower Maeotian sedimentary rocks of the Popov Kamen section (Russia, Taman Region, Eastern Paratethys) were investigated by cyclostratigraphy methods based on magnetic susceptibility measurements. Time series analysis (Lomb–Scargle and REDFIT periodograms, wavelets, Gaussian filters) revealed statistically significant signals with 5.2–6.0m wavelength corresponding most likely to the 41,000-year obliquity cycle. These new data imply a duration of the early Maeotian regional substage of 0.9Myr, and this sets the age of the Sarmatian–Maeotian boundary to about ~7.6Ma. These astronomically tuned lower Maeotian sediments of the Popov Kamen section result in an average sedimentation rate of about 11–12cm/kyr (=90.9–83.3yr/cm) for the whole section. In the relatively deep-water setting of the lower Maeotian Popov Kamen section, no major hiatuses were detected, with the exception of an insignificant gap in the upper part of the successions. The marine transgression in the Eastern Paratethys at the beginning of Maeotian was probably caused by the opening and consequent deepening of Rifian Corridor. At the end of the Tortonian (~7.6Ma), this tectonic event terminated the restricted conditions in the Mediterranean and re-established the connection between the Mediterranean Sea and Paratethys. Therefore, the Tortonian–Messinian transition in the Mediterranean probably corresponds to the clays of the lower part of the lower Maeotian record in Paratethys, which is located above the first bryozoan build-ups and below the 1.8m thick diatomite bed in the Popov Kamen section. Our astronomically calculated age for the beginning of the Maeotian at ~7.6Ma strengthens the connection between these two transgressive events.

Milankovitch Period Uncertainties and Their Impact On Cyclostratigraphy

Abstract Astronomically calibrated cyclostratigraphy relies on correct matching of observed sedimentary cycles to predicted astronomical drivers such as eccentricity, obliquity, and climate precession. However, the periods of these astronomical cycles, in the past, are not perfectly known because: (i) they drift through time; (ii) they overlap; and (iii) they are affected by the poorly constrained recession history of the Moon. This paper estimates the resulting uncertainties in ancient Milankovitch cycle periods and shows that they lead to: (i) problems with using Milankovitch cycles for accurate measurement of durations (potential errors are around 25% by the start of the Phanerozoic); (ii) problems with correctly identifying the Milankovitch cycles responsible for observed period ratios (e.g., the ratio for long-eccentricity/short-eccentricity overlaps, within error, with the ratio for short-eccentricity/precession); and (iii) problems with verifying that observed cycles are Milankovitch driven at all (the probability of a random period ratio matching a predicted Milankovitch ratio, within error, is 20–70% in the Phanerozoic). Milankovitch-derived ages and durations should therefore be treated with caution unless supported by additional information such as radiometric constraints.

Time-scale uncertainty of abrupt events in the geologic record arising from unsteady sedimentation

Defining the time scale of abrupt events in the stratigraphic record is a primary goal of high-resolution paleoclimate analysis. A significant hurdle in this endeavor is that abrupt, i.e., millennial and submillennial, events in deep time can rarely be temporally constrained accurately owing to the typical absence of high-precision age control at the scale of the events. Instead, the duration of abrupt events is commonly estimated via the linear partitioning of time between age control points (e.g., defined using astronomical cycles or radiometric dates) that bracket the event and span longer time intervals. The flaw with this approach is that sedimentation is an unsteady process and does not proceed linearly with time. Here a numerical model, parameterized by geologic data, is used to quantify theoretical time-scale uncertainties that result from unsteady sedimentation. This work demonstrates that the duration of assumed millennial events estimated via a linear partitioning approach may be significantly in error, even in complete, astronomically calibrated and unbioturbated successions best suited to the study of abrupt paleoclimate change. The uncertainties established in this study are largely a function of the precise statistical properties of the sedimentation process, properties that are difficult to constrain empirically, particularly over short time spans. Nevertheless, this study illustrates how unsteady sedimentation sets an important limit on the attainable temporal resolution of the stratigraphic record, with consequent implications for defining accurately the rates and durations of rapid events in Earth history.

Self‐organization of the Earth's climate system versus Milankovitch‐Berger astronomical cycles

AbstractThe Late Pleistocene Antarctic temperature variation curve is decomposed into two components: “cyclic” and “high frequency, stochastic.” For each of these components, a mathematical model is developed which shows that the cyclic and stochastic temperature variations are distinct, but interconnected, processes with their own self‐organization. To model the cyclic component, a system of ordinary differential equations is written which represent an auto‐oscillating, self‐organized process with constant period. It is also shown that these equations can be used to model more realistic variations in temperature with changing cycle length. For the stochastic component, the multifractal spectrum is calculated and compared to the multifractal spectrum of a critical sine‐circle map. A physical interpretation of relevant mathematical models and discussion of future climate development within the context of this work is given.

Decoupling of ground level pressures observed in Italian volcanoes: are they driven by space weather geo-effectiveness?

<p>Investigations on correlation drops between near-ground atmospheric pressures measured at sea level and at higher altitudes on Italian volcanoes have been carried out. We looked for perturbations of the atmospheric pressure field driven by volcanic activity, but not excluding possible external triggers for the observed anomalies. Decorrelations between atmospheric pressures measured at Stromboli Island in stations located at different altitudes (years 2002-10) have been analysed and compared with data from other volcanic (Vesuvius) and non volcanic (Mt. Soro) orographic structures. We investigated as their possible triggers volcanic, meteorological and space weather parameters, with particular attention to Total Solar Irradiance (TSI), Kp index and Forbush decreases. Pressure decorrelations seems to be driven by astronomic cycles, with maxima in summer and minima in winter. A further contribution was found, seemingly assignable to TSI anomalies, with correlation minima occurring 12 hours after these but only during phases of high Sun activity. Moreover, during the same phases a main periodicity of about 27 days in pressure decorrelations was revealed by FFT analysis. This period is the same of the Sun Carrington rotation, expressing the periodic reappearance of sunspot groups on Sun’s surface. The strong similarity between recurrences of sunspot number and atmospheric pressure anomalies further supports the role of the former as a possible trigger for the latter.</p>

Effects of Karoo–Ferrar volcanism and astronomical cycles on the Toarcian Oceanic Anoxic Events (Early Jurassic)

One of the most profound environmental changes in the Mesozoic took place during Pliensbachian–Toarcian (Early Jurassic), including oceanic anoxia (Toarcian Oceanic Anoxic Event; T-OAE). The T-OAE is thought to have been caused by increased atmospheric CO2 triggered by Karoo–Ferrar volcanism. This idea, however, remains debated, primarily due to uncertainties in their age constraints of the relevant sedimentary sequences. To examine their temporal relationships, herein, we provide the astronomical time scale of the Lower Jurassic deep-sea bedded chert sequences from the pelagic Panthalassa superocean, which are exposed in the Inuyama area, central Japan. A 405-kyr tuned astrochronology, anchored to the end-Triassic extinction as 201.4±0.2Ma (Ikeda and Tada, 2013), allows us to constrain the ages of two black bedded cherts (T-OAE1 and T-OAE2). The ages of these T-OAEs overlap U–Pb ages of Karoo volcanic rocks. T-OAE in the European region is also synchronous with the Karoo–Ferrar volcanism, based on radiolarian and ammonite biostratigraphic correlation. These temporal relationships support the potential impact of Karoo–Ferrar volcanism on T-OAEs on a global scale. On the other hand, the onset of T-OAEs occur at the maxima of ~40kyr, ~100kyr, and 405kyr cycles of chert thickness variation. The termination of T-OAEs and the recovery to oxic conditions in pelagic ocean coincide with the minima of ~40kyr, ~100kyr, and 405kyr cycles of chert thickness. Moreover, the termination of final black chert and grey chert deposition coincide with the minima of ~1800kyr cycles of chert thickness. These temporal relationships imply that orbital-scale productivity cycles were important in controlling the onset and termination of T-OAEs through the carbon cycle dynamics, which have been already amplified by Karoo–Ferrar volcanism.

EVOLUTIONARY SEARCH FOR OPTIMIZED LNA COMPONENTS GEOMETRY

In this paper, an optimized design procedure based on genetic algorithm (GA) for automatic synthesis of dual-band concurrent fully integrated low-noise amplifiers (LNA) targeted to 802.16d @ 3.5 GHz and 802.11b, g @ 2.4 GHz standards is discussed. The algorithm delivers the circuit elements geometry, rather than their values, and bias levels to secure the best level of LNA gain, input matching, output matching and power consumption. Working on the components geometry level aims at considering the elements parasitic effects. The basic cascode and a current reuse folded cascode LNA's are tried. GA as an optimization engine is programmed in MATLAB and performance evaluation in 0.18 μm RF CMOS TSMC technology is ceded to HSPICE. Results indicate that the automated scheme well computes the desired circuit in an acceptable time span; otherwise, it may be explored by either tremendous manual trial and error or astronomical cycles of an exhaustive search. This is not accomplished without imposing certain approximate search space constraints.

Long period astronomical cycles from the Triassic to Jurassic bedded chert sequence (Inuyama, Japan); Geologic evidences for the chaotic behavior of solar planets

Astronomical theory predicts that ~2 Myr eccentricity cycle have changed its periodicity and amplitude through time because of the chaotic behavior of solar planets, especially Earth-Mars secular resonance. Although the ~2 Myr eccentricity cycle has been occasionally recognized in geological records, their frequency transitions have never been reported. To explore the frequency evolution of ~2 Myr eccentricity cycle, we used the bedded chert sequence in Inuyama, Japan, of which rhythms were proven to be of astronomical origin, covering the ~30 Myr long spanning from the Triassic to Jurassic. The frequency modulation of ~2 Myr cycle between ~1.6 and ~1.8 Myr periodicity detected from wavelet analysis of chert bed thickness variation are the first geologic record of chaotic transition of Earth-Mars secular resonance. The frequency modulation of ~2 Myr cycle will provide new constraints for the orbital models. Additionally, ~8 Myr cycle detected as chert bed thickness variation and its amplitude modulation of ~2 Myr cycle may be related to the amplitude modulation of ~2 Myr eccentricity cycle through non-linear process(es) of Earth system dynamics, suggesting possible impact of the chaotic behavior of Solar planets on climate change.