Challenging asymmetric cements as indicators of vadose diagenesis: “pseudo-gravitational” cements from the lower Pliensbachian of the Traras Mountains in NW Algeria

Belkhedim, Salim; Munnecke, Axel; Benhamou, Miloud; Nemra, Abdelkrim; Sadji, Radouane

doi:10.1007/s10347-019-0554-7

Cited by 8 publications

(2 citation statements)

References 51 publications

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“…Particularly irregular overgrowths and eccentric development, localized dissolution embayments and meniscus formation seem diagnostic of subaerial–vadose processes (Figs 9K to O and 10, stage i); features that can be discerned by detailed petrographic observations (e.g. Scholle & Ulmer‐Scholle 2003; Belkhedim et al ., 2019). Vadose features (Fig.…”

Section: Environmental Processes Controlling Ooid Diversity In the Ya...mentioning

confidence: 99%

Atypical ooid diversity in the Upper Cretaceous Yacoraite Formation, Argentina

2022

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This study reports on ooid diversity from different lithotypes of the Yacoraite Formation (Salta Group basin) in the Central Andes of north‐west Argentina. The ooids display a variety of internal and external morphologies that may be deployed as proxies for seawater chemistry and hydrodynamic processes. A short review of nomenclature problems is first discussed, followed by presentation of a two‐fold quantitative and qualitative methodology. Our proposed classification addresses internal and external ooid characters in order to understand growth in response to various environmental processes at an individual particle level. This classification allows discrimination between a variety of morphologies, but also evaluation of the complexity of the processes involved in ooid formation as seen in the fossil record. This study evaluates whether the ooids present within the Yacoraite Formation share similarities with ooids formed in marine versus marine lagoon and/or lacustrine environments. A possible lacustrine interpretation finds its origin in the diverse assemblage of ooid morphotypes present, which exceeds the variations described for marine ooids. However, growth paths and occurrence of various compound morphologies point to intense marine recycling, suggesting little accommodation. Together with other sedimentological characteristics, for example, bi‐directional cross‐bedding, tidal shoals, hummocky cross‐stratification and exposure surfaces, these features suggest that marine processes had an impact on the sediments. Therefore, the ooid assemblage of the Cretaceous Yacoraite Formation was most likely formed in a shallow coastal lagoon in the framework of an epicontinental sea that at times experienced marine flooding events. A detailed evaluation of processes involved in oolite formation is needed in order to improve the stratigraphic and palaeoenvironmental understanding of ooid formation through time. This includes examining alternating constructive and destructive stages, early binding and cementation, reworking, recycling and averaging processes.

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Section: Environmental Processes Controlling Ooid Diversity In the Ya...mentioning

confidence: 99%

Atypical ooid diversity in the Upper Cretaceous Yacoraite Formation, Argentina

2022

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“…33-34). Recent publications document limestones exhibiting similar features from Italy (AMADIO et al, 2018) with "dendritic shrub-like fabric" and Algeria (BELKHEDIM et al, 2019) with "asymmetric fibrous cements (AFC)". In the present author's view, all these structures, being partly of a microbial nature, should not be considered as "cements" (i.e., a word the use of which should be restricted to crystals resulting of the purely chemical precipitation from a brine in voids) but as microbial crusts growing in cavities, i.e., "endostromatolites", as shown through the following simple and naturalistic approach.…”

Section: Introductionmentioning

confidence: 99%

The biosignature of sparite permits the distinction between gravitational cement and endostromatolites

Granier¹

2020

Carnets

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Following a brief summary of some fundamentals in carbonate sedimentology (sedimentary petrography) that highlights the significance of organic matter, some examples of biocrystals in carbonate grains/particles, such as bioclasts or ooids, are provided as an introductory chapter to a discussion on gravitational cements versus endostromatolites. The gravitational cements, either marine (fibrous) or continental (dog-tooth), are made of hyaline (i.e., translucent) sparitic crystals whereas endostromatolites are made of colored sparitic crystals and/or micrite. Gravitational cements forms in the vadose zone whereas endostromatolites grow in small rock cavities in the marine phreatic zone. As such the latter can grow centripetally in all directions (not only downward).

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