Detecting initial aragonite and calcite variations in limestone–marl alternations

Nohl, Theresa; Steinbauer, Manuel J.; Sinnesael, Matthias; Jarochowska, Emilia

doi:10.1111/sed.12885

Cited by 15 publications

(9 citation statements)

References 50 publications

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“…The different TiO2/Al2O3 ratios in limestones, marls, and clays in the studied section point to a primary signal that can be attributed to environmental changes, regardless of subsequent differential diagenesis (Fig. C6, see also Nohl et al, 2021). K 2 O/Al 2 O 3 is interpreted as a chemical weathering signal.…”

Section: Selection and Interpretation Of Elemental Ratio Proxiesmentioning

confidence: 82%

“…Furthermore, by using a ratio of detrital elements such as TiO 2 /Al 2 O 3, we avoid tracking distortions that arose from early differential diagenesis (Munnecke and Samtleben, 1996). Detrital elements bound to clay minerals are not mobilised during early diagenetic carbonate dissolution and reprecipitation (Nohl et al, 2021). By using a ratio, changes due to enrichment or dilution as a result of this carbonate dissolution and reprecipitation are accounted for (Westphal et al, 2010;Nohl et al, 2021).…”

Section: Selection and Interpretation Of Elemental Ratio Proxiesmentioning

confidence: 99%

“…Detrital elements bound to clay minerals are not mobilised during early diagenetic carbonate dissolution and reprecipitation (Nohl et al, 2021). By using a ratio, changes due to enrichment or dilution as a result of this carbonate dissolution and reprecipitation are accounted for (Westphal et al, 2010;Nohl et al, 2021). This is especially important in cyclostratigraphic studies, as differential diagenesis can produce limestone-marl alternations that can look similar to astronomically forced cyclic successions (Westphal, 2006;Nohl et al, 2020).…”

Section: Selection and Interpretation Of Elemental Ratio Proxiesmentioning

confidence: 99%

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Astronomically-paced climate and carbon-cycle feedbacks in the lead-up to the Late Devonian Kellwasser Crisis

Wichern¹,

Bialik²,

Nohl³

et al. 2023

Preprint

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Abstract. Repeated carbon isotope excursions and widespread organic-rich shale deposition mark the Middle and Late Devonian series. Various explanations such as extensive volcanism and land plant evolution have been given for these perturbations and the general sensitivity of the Devonian to oceanic anoxia, but their repeated nature suggests that astronomical forcing may have controlled their timing. Here, a cyclostratigraphic study of the Kellwasser Crisis at the Frasnian-Famennian stage boundary (ca. 372 Ma) is carried out. The Kellwasser Crisis was one of the most ecologically impactful of the Devonian perturbations and is ranked among the ‘Big Five’ Phanerozoic mass extinctions. The studied site is the Winsenberg Road Cut section in the Rhenish Massif, Germany, which represents a quiet tropical shelf basin setting. Centimetre-scale elemental records, generated by portable X-Ray scanning, allow for testing of the hypothesis that a 2.4 Myr eccentricity node preceded the Upper Kellwasser event. The study’s results are supportive of this hypothesis. We find enhanced chemical weathering (K2O/Al2O3) during the period leading up to the Upper Kellwasser, and a peak in distal detrital input (SiO2/CaO) and riverine runoff (TiO2/Al2O3) just prior to the start of the Upper Kellwasser. We interpret this pattern as the long-term eccentricity minimum facilitating excessive regolith build-up in the absence of strong seasonal contrasts. The Earth’s system coming out of this node would have rapidly intensified the hydrological cycle, causing these nutrient-rich regoliths to be eroded and washed away to the oceans where they resulted in eutrophication and anoxia. An astronomical control on regional climate is observed beyond this single crisis. Wet-dry cycles were paced by 405-kyr eccentricity, with both the Lower and Upper Kellwasser events taking place during comparatively drier times. A precessional-forced monsoonal climate system prevailed on shorter timescales. Intensification of this monsoonal system following the node may have caused the widespread regolith erosion. We estimate the total duration of the Kellwasser Crisis at ca. 900 kyr, with the individual events lasting for ca. 250 and 100 kyr, respectively. If astronomical control indeed operated via regolith build up in monsoonal climates, land plants may have played an important role. Not by certain evolutionary steps triggering specific perturbations, but by permanently strengthening the climatic response to orbital forcing via soil development – creating soils thick enough to meaningfully respond to orbital forcing – and intensifying the hydrological cycle.

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Section: Selection and Interpretation Of Elemental Ratio Proxiesmentioning

confidence: 82%

Section: Selection and Interpretation Of Elemental Ratio Proxiesmentioning

confidence: 99%

Section: Selection and Interpretation Of Elemental Ratio Proxiesmentioning

confidence: 99%

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Astronomically-paced climate and carbon-cycle feedbacks in the lead-up to the Late Devonian Kellwasser Crisis

Wichern¹,

Bialik²,

Nohl³

et al. 2023

Preprint

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“…On the other hand, the boundary between both lithologies crosscuts obliquely the time lines, thus merging diachronous deposits into one single limestone or marl layer, a phenomenon previously indicated by Nohl & Munnecke (2019) in the Silurian rhythmic series of Sweden (See also : Biernacka et al, 2005;Gani, 2017;Nohl et al, 2021).…”

Section: Diagenetic Aspectsmentioning

confidence: 87%

Stratigraphy and Biochronostratigraphy of the Lower Pliensbachian (Jurassic) from the Asturian basin (Northern Spain)

et al. 2023

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A stratigraphic study of the carbonate deposits from the interval between the uppermost Sinemurian and the base of the Upper Pliensbachian is presented herein. For this purpose, four expanded sections of the Asturian Basin, in Northern Spain, were sampled. The sections are located between Rodiles E section (Villaviciosa municipality) and Playa de Vega section (Ribadesella municipality). The ammonites recorded in over 100 successive levels of this sector enabled the substantial improvement of the biochronostratigraphic scale of reference; making it comparable with those defined for other basins of the Iberian Peninsula and other areas of the western Tethys. The lower boundary of the Pliensbachian is indicated by the first appearance of Gemmellaroceras aff. aenigmaticum (Gemmellaro) below the first appearance of the genus Apoderoceras. The upper boundary is defined by the first record of the Protogrammoceras. (Matteiceras) subgenus which in some levels is associated with Amaltheus stokesi (Sowerby). The boundaries between the zones and subzones were able to be established accurately in most cases. The ammonite assemblages are similar to those established for the NW European Province. Some intervals, however, include species typical of the Mediterranean Province. Among these, the Taylori Subchronozone (Gemmellaroceras) and the transition between the Jamesoni Subchronozone and the Valdani Subchronozone (Tropidoceras) can be highlighted. Additionally, taking into consideration the succession between of ammonite genera and species, 27 horizons were identified, 24 of which correspond to the Lower Pliensbachian, and the other 3 to the uppermost Sinemurian and the lowermost part of the Upper Pliensbachian. Moreover, the identification of 3 of the Lower Pliensbachian horizons were based upon the evolution of the Mediterranean Tropidoceras.

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“…Although some studies suggested a diagenetic origin for these limestone-marls cycles (e.g. Munnecke et al 2001;Nohl et al 2021), the dominant hypothesis is that these alternations result from primary rhythmic sedimentation patterns driven by the so-called "orbital" climatic cycles (Gilbert 1895;Milankovitch 1941). This climatic variability is driven by the sinusoidal fluctuations of the Earth's orbital parameters around the Sun, that control the climate through the seasonal repartition of insolation (e.g.…”

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confidence: 99%

Are marl-limestone alternations mainly driven by CaCO3 variations at the astronomical timescale? New insights from extraterrestrial 3He

Blard¹,

SUCHERAS-MARX²,

SUAN³

et al. 2023

Preprint

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Marl-limestone alternations are rhythmical inter-bedded deposits that commonly occur in many sedimentological environments. It is quite well established that these lithological variations originate from astronomically-driven climatic variations paced by the Milankovitch cycles of main periods 19, 23, 41, 100 and 405 ka. However, the sedimentological mechanisms involved are not clear: some models attribute these alternations to cyclic changes in the carbonate flux, while terrigenous siliciclastic input remained relatively constant. On the opposite, other models suggest that the carbonate flux was constant while the siliciclastic flux changed cyclically, or that both fluxes varied in antiphase. To disentangle these different scenarios, we collected marlstone and limestone samples from two sedimentary hemipelagic marl-limestone successions of Bajocian, Middle Jurassic (3 marl-limestone couplets over 3.4 m) and Valanginian, Lower Cretaceous (1 marl-limestone couplet over 0.9 m) from the Southern French Alps (Barles). We measured their concentrations in calcium carbonate, organic carbon, nannofossil, as well as in extraterrestrial 3He (3HeET). Carbonate contents range from 45% in marls to 86% in limestones. Importantly, the measured 3HeET concentrations of all samples remained nearly constant in the siliciclastic fractions, within uncertainties (< 20%). Hence, our results indicate that, at the astronomical timescale, sedimentation rates were mainly controlled by large changes in the CaCO3 net fluxes, leading to variable dilution of the terrigenous input. Nannofossil counting shows that pelagic CaCO3 fluxes of coccolithophores are inversely correlated to the total carbonate content along the marl-limestone alternations and represent less than 7% of the total carbonate content. Hence, in this setting, these marl-limestone alternations were driven by fluctuations in micritic CaCO3 supply from the nearby carbonate platform that variably diluted nannofossil and organic carbon particles. Finally, assuming a constant 3HeET flux of 100 pcc.cm-2.Ma-1, total 3HeET-derived sedimentation rates range from 20 to 30 m/Ma in the marl strata, while they reach up to 80 to 100 m/Ma in the limestone layers. These sedimentation rates are broadly compatible with local average rates estimated for the whole Bajocian and Valanginian stages by biostratigraphy.

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Detecting initial aragonite and calcite variations in limestone–marl alternations

Cited by 15 publications

References 50 publications

Astronomically-paced climate and carbon-cycle feedbacks in the lead-up to the Late Devonian Kellwasser Crisis

Astronomically-paced climate and carbon-cycle feedbacks in the lead-up to the Late Devonian Kellwasser Crisis

Stratigraphy and Biochronostratigraphy of the Lower Pliensbachian (Jurassic) from the Asturian basin (Northern Spain)

Are marl-limestone alternations mainly driven by CaCO3 variations at the astronomical timescale? New insights from extraterrestrial 3He

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