Millennial-scale climate changes manifest Milankovitch combination tones and Hallstatt solar cycles in the Devonian greenhouse world: COMMENT

Smith, David G.

doi:10.1130/g46475c.1

Cited by 5 publications

(4 citation statements)

References 6 publications

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“…A recently described process which more clearly unfolded how laminae are quickly produced and able to cover large areas, is a combination of high fluid shear and sediment concentration (Al-Mufti & Arnott, 2023). In conclusion, there are many indications that presumed varves in pre-Pleistocene outcrops have been deposited much more quickly than on a yearly basis, which may be discovered by detailed studies (Matys Grygar, 2019;Smith, 2019Smith, , 2023 reinterpreting 60 recently published papers on this subject; Kochhann et al, 2020;Isbell et al, 2021;Molén, 2021).…”

Section: Laminated Sedimentsmentioning

confidence: 89%

Patterns, processes and models - an analytical review of current ambiguous interpretations of the evidence for pre-Pleistocene glaciations

Molén

2023

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Models (paradigms) and former interpretations have often been presupposed when conducting field research. In the 19th century diamictites were for the first time interpreted to have originated from ancient glaciations. These interpretations have to a large part prevailed in the geological community, although there has been much progress in the areas of sedimentology, glaciology and physical geography. The present work is an effort to find criteria which most clearly discriminate between geological features produced by different processes, mainly glaciation and mass flow, the latter predominantly sediment gravity flows. Geological features which have been interpreted to have formed by glaciation throughout pre-Pleistocene Earth history are compared to similar-appearing geological features formed by mass flow and tectonics, so as to uncover variations in the appearance between features resulting from these different processes. The starting point for this comparison is documentation of the appearance of Quaternary products of erosion and deposition, in order to discern the origin of older formations. It is shown that the appearance and origin of pavements, dropstones, valleys, small-scale landforms, surface microtextures and most other geological features may in some cases be equivocal, but in others the details are indicative of the process which generated the feature. Detailed geological field data which have been compiled by geologists from outcrops of pre-Pleistocene strata, more often than is considered in most papers, commonly point to a mass flow origin, mainly a sediment gravity flow origin, rather than a glaciogenic origin. A process of multiple working hypotheses or interpretations is therefore advocated, based mainly on a comparison of the appearance of features formed by different geological processes documented from different research disciplines. Instead of starting with current interpretations or models, this multiple working hypothesis or methodology helps to avoid confirmation bias and jumping to conclusions.

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Section: Laminated Sedimentsmentioning

confidence: 89%

Patterns, processes and models - an analytical review of current ambiguous interpretations of the evidence for pre-Pleistocene glaciations

Molén

2023

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“…ATNTS2012 (Astronomically Tuned Neogene Time Scale; Hilgen et al 2012), has not been astronomically tuned in the pre-MCO and early MCO periods of time. Simultaneously, cyclostratigraphy still requires refinement of mathematical and statistical tools and the development of robust criteria for its users (Vaughan et al 2011, Smith 2019, in particular due to inevitable stratigraphic distortion and 'contamination' of the orbital signal by non-climatic factors in real sedimentary records (Meyers 2019, Matys Grygar 2019. Statistical tests might be insufficient to confirm the existence of orbital signatures.…”

Section: Sw Nementioning

confidence: 99%

Beginning of the Miocene Climatic Optimum in Central Europe in sediment archive of the Most Basin, Czech Republic

Grygar¹,

Mach²,

Koubová³

et al. 2021

Bull. Geosci.

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The Miocene Climatic Optimum (MCO; ca. 17 to 15 Ma) represents a time of global warming within the persistent Cenozoic cooling (Zachos et al. 2001). The MCO brought thermophilic vertebrate species into central Europe (Böhme 2003), and was terminated by an abrupt return to global cooling. In spite of considerable research efforts, climate evolution in the pre-MCO and early MCO periods has not been fully understood. The southern polar ice cap (Antarctic Ice Sheet, AIS) was considerably reduced during the MCO (Gasson et al. 2016, Levy et al. 2016), perhaps due to a coincidence of particular paleogeographic (Gasson et al. 2016) and orbital settings (De Vleeschouwer et al. 2017), and possibly acting in coincidence with long carbon cycles (Liebrand et al. 2016, Valero et al. 2016). The global pre-MCO climate could also have responded to some specific, yet unidentified trigger(s). A volcanic hypothesis was proposed (Courtillot & Renne 2003), tested, rejected based on a critical discussion on Ar-Ar dating precision (Barry et al. 2010, Armstrong McKay et al. 2015), and finally revoked after new dating and upon addressing all uncertainties of the Miocene time scales (Kasbohm & Schoene 2018). An increase in atmospheric CO 2 was assumed to have been the MCO trigger; evidence for this was searched for in

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“…The intent of these analyses was to confirm the presence of Milankovitch signals in the data rather than to establish the formal statistical significance of the results (e.g. as discussed in Da Silva et al, 2018; Da Silva et al., 2019; Hinnov, 2018; Hinnov, Wu, & Fang, 2016; Smith, 2019).…”

Section: Estimation Of Sedimentation Ratementioning

confidence: 99%

Interplay of eustatic, tectonic and autogenic controls on a Late Devonian carbonate platform, northern Canning Basin, Australia

et al. 2020

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Frasnian reef complexes along the northern margin of the Canning Basin in northwestern Australia evolved during rifting of the Fitzroy Trough. Geological investigations of the Frasnian Hull platform, which developed on an active tilted fault‐block, reveal significant lateral and vertical facies variations superimposed on prominent metre‐scale cyclicity. This study uses numerical analyses of facies and magnetic susceptibility data from three measured sections along the Hull platform to test whether a tectonic signal can be distinguished from eustatic and other signals. Geostatistical analysis of facies variations reveals an exponential distribution of thin (<3 m) facies, characteristic of stochastic depositional processes. Thick subtidal facies predominate in the Guppy Hills (GH) and southeastern Hull Range (SHR) sections near the hangingwall margin, and thick shallow‐subtidal to intertidal facies dominate the Horse Springs drillcore (HD 14) section near the footwall margin. Power and wavelet spectral analyses indicate a strong periodic component; Average Spectral Misfit and spectral optimisation methods confirm the presence of Milankovitch eccentricity signals and suggest the presence of obliquity and precession signals. However, the results also expose strong temporal and spatial variation providing evidence for tectonic control. Spectral analyses show strongest periodicity is recorded in short intervals that are not correlated across the platform and provide evidence of variations in sedimentation rate and hiatuses. Time series for the neighbouring GH and SHR sections show no overall statistical correlation, and Markov analysis indicates weakly ordered vertical facies transitions that do not correlate across the platform. Subtidal to intertidal facies data from HD 14 core suggest that at least 35% of the section is absent, almost obscuring the Milankovitch signal. The results indicate a complex set of controls on deposition on the Hull platform with local tectonic effects having produced spatio‐temporal moderation of the underlying eustatic signals and autogenic processes adding a localised stochastic response.

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Millennial-scale climate changes manifest Milankovitch combination tones and Hallstatt solar cycles in the Devonian greenhouse world: COMMENT

Cited by 5 publications

References 6 publications

Patterns, processes and models - an analytical review of current ambiguous interpretations of the evidence for pre-Pleistocene glaciations

Patterns, processes and models - an analytical review of current ambiguous interpretations of the evidence for pre-Pleistocene glaciations

Beginning of the Miocene Climatic Optimum in Central Europe in sediment archive of the Most Basin, Czech Republic

Interplay of eustatic, tectonic and autogenic controls on a Late Devonian carbonate platform, northern Canning Basin, Australia

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