Astrochronology of the Valanginian Stage from reference sections (Vocontian Basin, France) and palaeoenvironmental implications for the Weissert Event

Martínez, Mathieu; Deconinck, Jean‐François; Pellenard, Pierre; Reboulet, Stéphane; Riquier, Laurent

doi:10.1016/j.palaeo.2013.02.021

Cited by 65 publications

(72 citation statements)

References 65 publications

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“…Changes in mineralogical and faunal changes (ratio of pelagic organisms) between limestone beds and marlstone interbeds (DARMEDRU et al, 1982) indicated environmental changes possibly under astronomical control due to frequencies close to those of the terrestrial orbit (RIO et al, 1989), following the MILANLOVITCH theory of climate changes in the Quaternary. Later, the development of FOURRIER transform analysis on such limestone-marl successions led to the emergence of a way to calibrate geological time (BOULILA et al, 2008(BOULILA et al, , 2010CHARBONNIER et al, 2013;MARTINEZ et al, 2013). In this respect, the VT is a good candidate, given that most of its Jurassic to Lower Cretaceous stratigraphic column presents this primary alternating pattern.…”

Section: Figmentioning

confidence: 99%

Some key Lower Cretaceous sites in Drôme (SE France)

Granier¹

2017

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Section: Figmentioning

confidence: 99%

Some key Lower Cretaceous sites in Drôme (SE France)

Granier¹

2017

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“…A total of 555 gamma-ray spectrometry measurements were performed in situ on the La Charce section (Department of Drôme, SE France; Martinez et al, 2013. The section is composed of marl-limestone alternations that were deposited in a hemipelagic environment during the Valanginian and Hauterivian stages (∼ 134-132 Ma, Early Cretaceous; .…”

Section: The Geological Datasetsmentioning

confidence: 99%

“…Before each measurement, rock surfaces were first cleaned to remove reworked material and flattened to prevent any border effects that could affect the measurement value. Each measurement was performed using a SatisGeo GS-512 spectrometer, with a constant acquisition time of 60 s (more details are provided in Martinez et al, 2013).…”

Section: The Geological Datasetsmentioning

confidence: 99%

“…The La Charce section, one of the datasets treated here, has been measured multiple times in different publications. The thickness of the studied section was assessed at 106, 109 and 116 m (Bulot et al, 1992;Martinez et al, 2013;Reboulet and Atrops, 1999) with an average of 110.3 ± 5.1 m, which represents a relative uncertainty of 4.6 % in the total thickness of the series. In the field, the distance between two successive samples was measured independently of the construction of the log, providing an independent assessment of the distribution of the actual distance between two successive samples.…”

Section: The Geological Datasetsmentioning

confidence: 99%

“…Although uncertainties exist regarding the actual position of samples, few case studies document their effect on (e) Distribution of sample distances in the case of the La Charce series as published in Martinez et al (2013).…”

Section: Introductionmentioning

confidence: 99%

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Testing the impact of stratigraphic uncertainty on spectral analyses of sedimentary series

et al. 2016

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Abstract. Spectral analysis is a key tool for identifying periodic patterns in sedimentary sequences, including astronomically related orbital signals. While most spectral analysis methods require equally spaced samples, this condition is rarely achieved either in the field or when sampling sediment core. Here, we propose a method to assess the impact of the uncertainty or error made in the measurement of the sample stratigraphic position on the resulting power spectra. We apply a Monte Carlo procedure to randomise the sample steps of depth series using a gamma distribution. Such a distribution preserves the stratigraphic order of samples and allows controlling the average and the variance of the distribution of sample distances after randomisation. We apply the Monte Carlo procedure on two geological datasets and find that gamma distribution of sample distances completely smooths the spectrum at high frequencies and decreases the power and significance levels of the spectral peaks in an important proportion of the spectrum. At 5 % of stratigraphic uncertainty, a small portion of the spectrum is completely smoothed. Taking at least three samples per thinnest cycle of interest should allow this cycle to be still observed in the spectrum, while taking at least four samples per thinnest cycle of interest should allow its significance levels to be preserved in the spectrum. At 10 and 15 % uncertainty, these thresholds increase, and taking at least four samples per thinnest cycle of interest should allow the targeted cycles to be still observed in the spectrum. In addition, taking at least 10 samples per thinnest cycle of interest should allow their significance levels to be preserved. For robust applications of the power spectrum in further studies, we suggest providing a strong control of the measurement of the sample position. A density of 10 samples per putative precession cycle is a safe sampling density for preserving spectral power and significance level in the Milankovitch band. For lower sampling density, the use of gamma-law simulations should help in assessing the impact of stratigraphic uncertainty in the power spectrum in the Milankovitch band. Gamma-law simulations can also model the distortions of the Milankovitch record in sedimentary series due to variations in the sedimentation rate.

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Orbital Signals in Carbon Isotopes: Phase Distortion as a Signature of the Carbon Cycle

2017

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Isotopic mass balance models are employed here to study the response of carbon isotope composition (δ13C) 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 δ13C 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 CO2 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 δ13C response can help to reduce uncertainties in astrochronological age models that are tuned to the 405 kyr cycle.

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Astrochronology of the Valanginian Stage from reference sections (Vocontian Basin, France) and palaeoenvironmental implications for the Weissert Event

Cited by 65 publications

References 65 publications

Some key Lower Cretaceous sites in Drôme (SE France)

Some key Lower Cretaceous sites in Drôme (SE France)

Testing the impact of stratigraphic uncertainty on spectral analyses of sedimentary series

Orbital Signals in Carbon Isotopes: Phase Distortion as a Signature of the Carbon Cycle

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