The Ordovician Magnetostratigraphy and Cyclostratigraphy:A Review

The study of magnetostratigraphy and cyclostratigraphy in the last two decades has provided a great deal of opportunities to improve the geologic time scale.The Cenozoic and Mesozoic geologic timescale have been well calibrated(Gradstein et al..2012;Ogg et al,2012;Cohen et al.,2018).However,for the Paleozoic era the uncertainty over boundary ages are still very large.

Cyclostratigraphy Study on Upper Cretaceous Eastern Tethys

The Cyclostratigraphy study is increasingly important in the precise dating of the marine strata, especially in the Tethyan realm.Compared with the Western Tethys,the Cyclostratigraphy study on the Eastern Tethys is relatively insufficient.Cretaceous marine sediments are cropped out widely in Southern Tibet,among them the late Cretaceous in the Gongzha section of Tingri area is rather continuous and integral.

Cyclostratigraphy Data as a Proxy for Geoelectrical Data Interpretation: Application to Phosphate Minerals Exploration in Matam (Senegal)

The vertical electrical soundings on the Matam region phosphates deposits are interpreted by inversion. To retrieve lithology from the obtained resistivities, mechanical drilling was performed to compare directly the lithologies and the geoelectrical resistivities. The obtained relation is not simple and is not sufficient to interpret all the VES. This situation motivated the collection of supplementary information from cyclostratigraphy. Geoelectrical and cyclostratigraphic?information is combined using fuzzy logic techniques to build a fuzzy inference system. The obtained results seem to be consistent with the stratigraphy of the investigated region and allow retrieving lithological succession. Further investigations are necessary for more accurate thickness determination.

The Upper Devonian orbital cyclostratigraphy and numerical dating conodont zones from Guangxi,South China

The hierarchically organized laminae, bundles, bundlesets and superbundlesets which correspond to a sub-Milankovitch, obliquity or precession, eccentricity and long eccentricity cyclothems, respectively, have been distinguished from the Upper Devonian Frasnian-Famennian (F-F) transitional carbonate successions deposited in the carbonate-basin and slope facies of Guangxi, South China. The durations of cyclothems are 8000-10000a, 16667a or 33333a, 100000a and 400000a, respectively. The ratio of eccentricity to precession, eccentricity to obliquity, and long eccentricity to eccentricity is 1:6,1:3 and 1 : 4 in the Devonian,respectively. Orbital cyclostratigraphical studies show that the durations of the conodont falsiovalis Zone, transitans Zone, punctata Zone, Lower hassi Zone, Upper hassi Zone, jamieae Zone,Lower rhenana Zone, Upper rhenana Zone,linguiformis Zone, Lower triangularis Zone, Middle triangularis Zone and Upper triangularis Zone are 0.4, 0.4, 0.4, 0.3, 0.4, 0.2, 0.8, 0.6, 0.8, 0.3, 0.3and 0.3 Ma from bottom to top, respectively, and the duration of the Frasnian is 4.3 Ma. The conodont is the normal marine organism of the latest mass extinction (the latest linguiformis Zone)and the first recovery (including the whole Lower triangularis and Middle triangularis Zone) in the F-F transition. The conodont mass extinction and recovery lasted 200000-100000a and 0.6 Ma,respectively. We consider that average durations of the fossil zones calculated by reported numerical ages divided by fossil zone numbers within a stage or series or system cannot discovery complications and non-uniformity of evolutionary organisms and environments.

Cyclostratigraphy of the Induan (Early Triassic) in West Pingdingshan Section,Chaohu,Anhui Province

The Induan sequence in the West Pingdingshan Section, Chaohu, Anhui Province, displays a series of superimposed mudstone/limestone cycles. The lithological character of the cycles, combined with power spectral and wavelet analysis of magnetic susceptibility readings, reveals 12 short eccentricity and 56 precession Milankovitch cycles - obliquity cycles are not apparent. The uniformity of cycle thicknesses indicates a stable depositional setting making this section ideal to perform various geo-logical studies. Accordingly, the Induan Stage is estimated to have lasted 1.1 Ma, and the depositional rate for this part of the section is about 3.7 cm/ka. This places the Induan-Olenekian boundary in the West Pingdingshan Section at about 251.5 Ma based on an age of 252.6 Ma for the Permian-Triassic boundary.

High-resolution cyclostratigraphy of geochemical records from Permo-Triassic boundary section of Dongpan,southwestern Guangxi,South China

Spectral analysis is applied to geochemical data from a deep-water Permian-Triassic Boundary (PTB) section across PTB in Dongpan, Guangxi for high-resolution cyclostratigraphic research. The characteristics of the Milankovitch Cycles have been well recorded in the strata of the Dongpan section. Spectrum on Ce/La records shows especially that the ratios among its three preponderant cycles in the section are 5:2:1, which well displays the phenomenon of the sedimentary cycles driven by orbital force. The Milankovitch theory is further confirmed by the Paleozoic records.

A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin, Northeastern China

A continuous terrestrial succession was recovered from the Songke-2(SK-2)borehole in the Songliao Basin,Northeastern China.This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period,following a series of achievements of the Songke-1(SK-1)core.In this study,thorium(Th)logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis.The Th series varies quasi-periodically;power spectra and evolutionary fast Fourier transformation(FFT)analysis reveal significant cycles in the Quantou(K2 q),Qingshankou(K2 qn),Yaojia(K2 y)and Nenjiang(K2 n)formations.The ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1,corresponding to long orbital eccentricity(405 kyr),short orbital eccentricity(100 kyr),obliquity(37 kyr),and precession cycles(22.5 kyr and 18.4 kyr).The durations of the K2 n,K2 y,K2 qn and K2 q are estimated as 6.97,1.83,5.30 and 4.52 Myr,respectively,based on the constructed^18.62 Myr"floating"astronomical time scale(ATS).Comparison of the durations between the SK-1 s and SK-2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2 qn and K2 y.Nevertheless,our ATS of K2 n supports the chronostratigraphic frame constructed by the CA-ID-TIMS data of the SK-1 s borehole.This new"floating"ATS provides precise numerical ages for stratigraphic boundaries,biozones and geological events in the Songliao Basin,and can serve as a basis for correlation of strata and events between marine and terrestrial systems.

Orbital control on cyclical organic matter accumulation in Early Silurian Longmaxi Formation shales

High resolution(939 samples)total organic carbon content(TOC)analyses were conducted on the Shuanghe Section of^152.6 m in the Changning area,Sichuan Basin.The sampling section was divided into two units considering the distinct-different deposit environment and sediments accumulation rate.The lower part(Unit 1)and the peer part(Unit 2)with high resolution sample spacing(0.08–0.4 m)enables the identification of the precession cycle in two sedimentary sequences with distinct different sedimentary accumulation rate.MTM Power spectral analyses on untuned TOC series reveals significant peaks exceeding above the 95%confidence level and shows that both Unit 1 and Unit 2 have recorded Milankovitch cycles of 405 kyr long eccentricity,short eccentricity,obliquity and precession.The floating astronomical time scale(ATS)was constructed on the Shuanghe Section in the Early Silurian(~439.673–444.681 Ma),and which was calibrated by 405 kyr long eccentricity cycles.The total duration of the Wufeng and Longmaxi shales is 5.01 Myr.The floating ATS used for estimating the duration of the graptolite zones and each stage in the study interval.Finally,we postulated two models that could verify the linkage between orbital cycle and organic accumulation.To make sure whether productivity or preservation is the main factor that under long eccentricity control,the phase correlation between the obtained filtered signal and the theoretical orbital solution should be made clear in the further research.

Cyclostratigraphic Calibration of the Upper Ordovician(Sandbian-Katian) Pagoda and Linhsiang Formations in the Yichang Area,South China

1 Introduction The Sandbian-Katian is a critical period for the transition from"hot-house"in the Lower Ordovician to"ice-house"in the end-Ordovician(Trotter et al.,2008).During this interval,the South China Block was located in the equatorial region(Torsvik and Cocks,2016),with the widespread accumulation of Pagoda and Linhsiang formations(Zhan and Jin,2007).

Review of the Variation of Astronomical Cycles and Its Influence on Geology

Cyclostratigraphy is more and more utilized in high-resolution dating in stratgraphy because of its characteristics of high resolution.It is based on the theory of orbital cycles,which are related to three Earth orbital parameters:eccentricity(e),obliquity (ε),and precession(e~*sinω).They affect the Earth periodically and then this information could be preserved in the sediments to be calibrated.However, in the geological time,the periodicities were changing,the reason of which is that it is caused by

Effects of astronomical orbital cycle and volcanic activity on organic carbon accumulation during Late Ordovician–Early Silurian in the Upper Yangtze area, South China

Based on field outcrop data,the effects of cyclic change of astronomical orbit and volcanic activity on organic carbon accumulation during the Late Ordovician-Early Silurian in the Upper Yangtze area were studied using cyclostratigraphic and geochemical methods.d13 C and chemical index of alteration(CIA)were used to filter the astronomical orbit parameters recorded in sediments.It is found that the climate change driven by orbital cycle controls the fluctuations of sea level at different scales,obliquity forcing climate changes drive thermohaline circulation(THC)of the ocean,and THC-induced bottom currents transport nutrient-laden water from high latitude regions to the surface water of low-latitude area.Hence,THC is the main dynamic mechanism of organic-carbon supply.The marine productivity indexes of Ba/Al and Ni/Al indicate that volcanic activities had limited effect on marine productivity but had great influences on organic carbon preservation efficiency in late Hirnantian(E4).Paleo-ocean redox environmental indicators Th/U,V/Cr and V/(V+Ni)show that there is a significant correlation between volcanism and oxygen content in Paleo-ocean,so it is inferred that volcanisms controlled the organic carbon preservation efficiency by regulating oxygen content in Paleo-ocean,and the difference in volcanism intensity in different areas is an important factor for the differential preservation efficiency of organic carbon.The organic carbon input driven by orbital cycle and the preservation efficiency affected by volcanisms worked together to control the enrichment of organic carbon in the Middle–Upper Yangtze region.

Magnetic field hyperactivity during the early Neoproterozoic: A paleomagnetic and cyclostratigraphic study of the Katav Formation, southern Urals, Russia

We present a detailed magnetostratigraphic and cyclostratigraphic profile through the Riphean(Tonian)Katav Formation in the southern Urals.The study confirms the primary nature of the magnetization in these rocks.The cyclostratigraphic study identified several orbital periods including the 405 ka long eccentricity.This allows us to quantify the reversal frequency in the Katav and our estimates range of 7–12 reversals per million years.Based on our study,we identify an interval of magnetic field reversal hyperactivity in the Neoproterozoic interval.Age estimates for the Katav are contentious and range somewhere between 800 Ma and 900 Ma based on carbonate Pb-Pb ages and stable isotope correlations.The paleomagnetic poles obtained in this study of the Katav(and overlying Inzer)Formation do not fit anywhere on the Baltica apparent polar wander path between 1100 Ma and 900 Ma.Furthermore,they lie 90away from the 900 Ma segment of the path.We tentatively estimate their age to be closer to 800 Ma and perhaps confirm a previously hypothesized pulse of rapid true polar wander between 825 Ma and 790 Ma.

A case study on how astronomical cycles affect the organic carbon accumulation

The paleoclimate change impacts the sedimentary environment and process,which in turn control the accumulation of organic carbon.Numerous studies have shown that the paleoclimate is controlled by astronomical cycles.Hence,understanding how these cycles impact the accumulation of organic carbon is a critical question that requires in-depth discussion.Previous studies have shown that Milankovitch cycle can be revealed from the sediments of the 7^(th)Oil Member(Chang 7 Member for short)of the Triassic Yanchang Formation in the southern Ordos Basin,suggesting that the deposition was controlled by astronomically-forced climate changes.Building on previous research,this study collected natural gamma(GR)data of Chang 7 Member from the N36 Well to further analyze astronomical cycles,combined with X-ray fluorescence(XRF)analysis and total organic carbon(TOC)tests,to reconstruct the paleoenvironment and analyze the organic matter enrichment characteristics.The results of this contribution show that,paleoclimate,paleo-redox conditions,paleo-water level,paleo-productivity and sediment accumulation rate(SAR)collectively controlled the enrichment of organic matter.Notably,this study identified the presence of eccentricity,obliquity,precession,and the 1.2 Myr long obliquity cycle in the Chang 7 Member.These cycles controlled the paleoenvironmental changes at different timescales and influenced the enrichment of organic matter,which has implications for subsequent energy exploration.

Cretaceous integrative stratigraphy and timescale of China

Cretaceous strata are widely distributed across China and record a variety of depositional settings. The sedimentary facies consist primarily of terrestrial, marine and interbedded marine-terrestrial deposits, of which marine and interbedded facies are relatively limited. Based a thorough review of the subdivisions and correlations of Cretaceous strata in China, we provide an up-to-date integrated chronostratigraphy and geochronologic framework of the Cretaceous system and its deposits in China.Cretaceous marine and interbedded marine-terrestrial sediments occur in southern Tibet, Karakorum, the western Tarim Basin,eastern Heilongjiang and Taiwan. Among these, the Himalayan area has the most complete marine deposits, the foraminiferal and ammonite biozonation of which can be correlated directly to the international standard biozones. Terrestrial deposits in central and western China consist predominantly of red, lacustrine-fluvial, clastic deposits, whereas eastern China, a volcanically active zone, contains clastic rocks in association with intermediate to acidic igneous rocks and features the most complete stratigraphic successions in northern Hebei, western Liaoning and the Songliao Basin. Here, we synthesise multiple stratigraphic concepts and charts from southern Tibet, northern Hebei to western Liaoning and the Songliao Basin to produce a comprehensive chronostratigraphic chart. Marine and terrestrial deposits are integrated, and this aids in the establishment of a comprehensive Cretaceous chronostratigraphy and temporal framework of China. Further research into the Cretaceous of China will likely focus on terrestrial deposits and mutual authentication techniques(e.g., biostratigraphy, chronostratigraphy, magnetostratigraphy and cyclostratigraphy). This study provides a more reliable temporal framework both for studying Cretaceous geological events and exploring mineral resources in China.