Lateral Variabilities of Cycle Stacking Patterns in the Latemàr, Triassic, Italian Dolomites

Peterhänsel, Arndt; Egenhoff, Sven

doi:10.2110/pec.08.89.0217

Cited by 9 publications

(29 citation statements)

References 40 publications

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“…The teepees occur on an outer belt of the platform, which most probably represents the shallowest part of the lagoon (Marangon et al ., ). The centre was probably somewhat deeper and was only exposed during major sea‐level lowstands (Peterhänsel & Egenhoff, ). The conditions in the lagoon are considered to have been shallow subtidal with periodic eustatic shallowing and subaerial exposure during deposition of the dolomitic cycle caps (Egenhoff et al ., ).…”

Section: Dolomites In the Palaeoenvironmental And Diagenetic Contextmentioning

confidence: 97%

Dolomite formation in the shallow seas of the Alpine Triassic

Meister

McKenzie²,

Bernasconi³

et al. 2013

Sedimentology

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The Alpine Triassic units of Switzerland, Northern Italy and Western Austria offer an extensive geological archive, in which the enigmatic process of dolomite formation can be studied in a palaeoenvironmental context. Recent studies clearly demonstrate that large amounts of the Alpine Triassic dolomites are late diagenetic or hydrothermal. Nevertheless, as part of multiple generations of diagenetic overprint, some generations of fine‐crystalline, Ca‐rich dolomite appear strictly confined to their depositional facies and show signs of very early formation at surface temperatures in specific ancient depositional environments. In this review, three cases of Alpine Triassic dolomites are discussed, where dolomite rocks may have formed during or soon after sedimentation. The sedimentary facies indicate contrasting palaeoenvironmental conditions and, hence, document three different possible processes of dolomite formation: (i) In the Dolomite Mountains (Northern Italy), dolomite beds of the partly isolated Middle Triassic (Anisian/Ladinian) Latemar Platform are confined to the very top of shallowing‐upward lagoonal facies cycles. (ii) Dolomite beds of the San Giorgio Basin (Southern Switzerland), an intra‐platform basin that opened during the Anisian/Ladinian transition, are associated with organic carbon‐rich shales, which were deposited in a deeper water environment under anoxic conditions. (iii) In the entirely dolomitized platform facies of the Dolomia Principale (Hauptdolomit Formation), a very early generation of fine‐crystalline dolomite occurs in the shallowest part of evaporative peritidal cycles. This platform extended over thousands of square kilometres along the Tethys margin during the Late Triassic (Carnian and Norian) and large amounts of carbonate were deposited under hypersaline sabkha‐like conditions. Representing three distinct depositional environments, these three different Triassic systems show features in common with several dolomitization models developed from the study of modern dolomite‐forming environments; for example, the sabkha model, the evaporative lagoon/lake model, the organogenic model and the microbial model. Although these actualistic models may be applicable to reconstruct the palaeoenvironmental conditions during dolomite formation, dolomite‐forming processes during the Triassic were apparently quite different from the modern world in terms of distribution and scale. Recent developments in stable‐isotope geochemistry and high‐resolution geochemical probing offer the possibility to make better reconstructions of Triassic palaeoceanographic conditions and suggest a non‐actualistic approach to better understand dolomite formation during the Triassic.

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Section: Dolomites In the Palaeoenvironmental And Diagenetic Contextmentioning

confidence: 97%

Dolomite formation in the shallow seas of the Alpine Triassic

Meister

McKenzie²,

Bernasconi³

et al. 2013

Sedimentology

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“…Even in the absence of relative sea‐level oscillations, the autocyclic model advocates processes within a sedimentary system that develops cyclic feedback loops linking sediment production, transportation and deposition and under such auspices, shoreline progradation might be a cycle‐producing mechanism. While Pratt & James () and Satterley () provided outcrop data supporting autocyclicity, as does Strasser (), albeit at a limited scale, and the output of numeric forward models also backs the plausibility of autocyclicity (Burgess, , ; Burgess et al ., ; Burgess & Wright, ), platform‐scale evidence of the concept is scarce in the rock record and it remains challenging to tease apart cyclicity generated by factors internal to the sedimentary system versus those related to sea‐level oscillation (Schwarzacher, ; Peterhänsel & Egenhoff, ; Eberli, ).…”

Section: Introductionmentioning

confidence: 99%

Unravelling the influence of water depth and wave energy on the facies diversity of shelf carbonates

2014

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Carbonate sequence stratigraphy is founded on the principle that changes in relative sea-level are recorded in the rock record by the accumulation of sediment with relative water depth-dependent attributes. While at the scale of a shelf to basin transect, facies clearly arrange by water depth, the relation blurs for depths <40 m, the most vigorous zone of carbonate production. The reason for this change in behaviour is two-fold. Firstly, in shallow water, the intrinsic processes of storm and wave reworking influence the seabed through submarine erosion and sediment redistribution. Secondly, facies diversity tends to be greater in shallow water than deep water because of a greater diversity in grain producers. Remote sensing imagery, field observations and hydrodynamic models for two reef-rimmed shore-attached carbonate platforms in the Red Sea show neither water depth nor energy regime to be reliable indicators of facies type when considered in isolation. Considered together, however, the predictive power of the two variables rises significantly. The results demonstrate it to be an oversimplification to assume a direct link between palaeo-water depth and depositional diversity of subtidal lithofacies, while highlighting the importance of hydrodynamics in directing the accumulation of carbonate sediments in the shallow photic zone. While the size distributions of facies extents in the two focus areas follow power laws, no direct relation between the lateral continuity of the facies belts and water depth or wave height is reported. The work is relevant for the interpretation of metre-scale subtidal carbonate cycles throughout the geological record by demonstrating how caution must be applied when inferring palaeowater depths from depositional facies.

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“…However, few studies describe sequences in different parts of the platform with the aim of performing facies modelling. Here, the dataset of Peterhänsel and Egenhoff (2008) (upper cyclic Facies stratigraphic interval) is used to evaluate and model asymmetrical (upward-shallowing) facies cycles and facies rhythmicity near the topographically high platform margin (Cimon Latemar) and in deeper lagoonal deposits of the platform interior (Cimon Forcellone). Peterhänsel and Egenhoff (2008) describe five microfacies based on thin sections: peloidal Fig.…”

Section: Case Study: the Latemar Carbonate Platform Northern Italymentioning

confidence: 99%

Geostatistical modelling of cyclic and rhythmic facies architectures

Blévec

Dubrule

John

et al. 2017

Preprint

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A Pluri-Gaussian method is developed for facies variables in three dimensions to model vertical cyclicity related to facies ordering and rhythmicity. Cyclicity is generally characterised by shallowing-upward or deepening-upward sequences and rhythmicity by the repetition of facies at constant intervals along sequences. Both of these aspects are commonly observed in shallow-marine carbonate successions, especially in the vertical direction. A grid-free spectral simulation approach is developed, with a separable covariance allowing a dampened hole-effect to capture rhythmicity in the vertical direction and a different covariance in the lateral plane along strata, as in space-time models. In addition, facies ordering is created by using a spatial shift between two latent Gaussian functions in the Pluri-Gaussian approach. Rapid conditioning to data is performed via Gibbs sampling and kriging using the screening properties of separable covariances. The resulting facies transiograms can show complex patterns of cyclicity and rhythmicity. Finally, a three dimensional case study of shallow-marine carbonate deposits at outcrop shows the applicability of the modelling method.

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Lateral Variabilities of Cycle Stacking Patterns in the Latemàr, Triassic, Italian Dolomites

Cited by 9 publications

References 40 publications

Dolomite formation in the shallow seas of the Alpine Triassic

Dolomite formation in the shallow seas of the Alpine Triassic

Unravelling the influence of water depth and wave energy on the facies diversity of shelf carbonates

Geostatistical modelling of cyclic and rhythmic facies architectures

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