Origin of the vertically orientated clasts in brecciated shallow‐marine limestones of the Chaomidian Formation (Furongian, Shandong Province, China)

Loon, A.J. van; Han, Zuozhen; Han, Yu

doi:10.1111/sed.12018

Cited by 32 publications

(27 citation statements)

References 24 publications

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“…The lime mudstone clasts are usually flat or undulatory, discoidal or platy pebbles to cobbles with subangular to subrounded corners (Figures 1(c), (d)). Clasts are, in many cases, disorganized, but sometimes show certain fabric: horizontal/intact in the lower part of the conglomerate bed, subhorizontal/subvertical in the middle, and vertical in the upper part (Chen et al, 2009a;Van Loon et al, 2013). Diagenetic conglomerates beds are commonly associated with ribbon rocks (often showing various soft-sediment deformation structures such as "boudin structures" and intrastratal cracks) with gradational lower boundaries (Chen et al, 2010).…”

Section: An Overview Of the Cambrian Limestone Brecciasmentioning

confidence: 97%

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confidence: 98%

“…All clasts are parallel to each other in a specific cluster, while the various clusters may show different orientations of the clasts) in a few exposures, Van Loon et al (2013) proposed that these features resulted from numerous simultaneous "fountains" on the paleo-seafloor, which were originated from upward-directed fluidized flows and uplifted clasts to the then sedimentary surface or (possibly) penetrating the overlying sediment. Indeed, both Chen et al (2009a) and Van Loon et al (2013) claimed that the abundant, platy (sub) vertical clasts in the limestone breccias resulted from upward escape of liquefied and fluidized sediment during deformation. However, Chen et al (2009a) illustrated that the liquidized sediment was originated from the susceptible sediment (mostly argillaceous sediment) that was interbedded with the limestone layers that were later brecciated (see also Lee, 2013), whereas Van Loon et al (2013) postulated that it was sourced from the sediment underlying the layer of brecciated limestones (intraclasts), despite a lack of liquidization evidence in the underlying sediment.…”

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confidence: 98%

“…Most of these studies proposed a depositional origin, but without explaining specific transportation mechanisms of the clasts and how the clasts were preserved in vertical positions during deposition and burial. Van Loon et al (2013) provided a sound argument against the genesis of these limestone breccias by primary processes such as currents, waves, sediment gravity flows, and slumps, and illustrated in detail the deformation conditions and processes for the formation of abundant vertical clasts, which is based primarily on a previous study by Chen et al (2009a).…”

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confidence: 98%

“…I believe that science can profit only from further discussions. Therefore, in this paper, I intend to briefly review the characteristics of the limestone breccias with vertically orientated clasts in the Furongian Chaomidian Formation of the North China Platform and discuss particularly the origin of the limestone breccias proposed by Van Loon et al (2013).…”

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Origin of the Furongian limestone breccias in the North China Platform

Chen

2015

Sci. China Earth Sci.

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Limestone breccias are a common phenomenon in the Cambrian successions worldwide. They bear important geological implications that have attracted geologists for several decades. There are, however, still controversies on their origins, especially those of the breccias with abundant vertically orientated clasts. The Furongian (upper Cambrian) Chaomidian Formation of the North China Platform contains numerous levels of limestone breccias and conglomerates that provide an excellent example to look into their formative processes. These breccias and conglomerates have been the focus of study and discussion since the 1980s, but yet there is still no consensus with respect to their geneses. Recently, Van Loon and others argued that the vertically orientated clasts of the breccias developed by a number of simultaneous "fountains" on the paleo-seafloor; the "fountains" formed by upward-directed fluidized flows originated from the sediment underlying the brecciated limestones. While the novel "fountain" hypothesis is not impossible, based on field evidences and theoretical considerations, however, it is most likely that the vertically orientated clasts resulted from their re-orientation by upward flow of thixotropically liquidized, uncemented argillaceous sediment that was interbedded with brecciated limestone fragments. Besides, the deformation processes most likely took place under shallow burial. limestone breccia, flat-pebble conglomerate, soft-sediment deformation, early diagenesis, Cambrian Citation:Chen J T. 2015.

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Section: An Overview Of the Cambrian Limestone Brecciasmentioning

confidence: 97%

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confidence: 98%

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confidence: 98%

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confidence: 98%

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confidence: 99%

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Origin of the Furongian limestone breccias in the North China Platform

Chen

2015

Sci. China Earth Sci.

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Flat pebbles and their edge‐wise fabric in relation to 2‐D microbial mat

et al. 2018

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Flat pebbles and edge‐wise fabric in the Mesoproterozoic Rohtas Limestone Formation (RLF) and the Chikkshelikere Limestone Member (CLM), India, generate a new insight into their formation. Simple stacks of alternating dark micritic and light‐coloured microsparite planar layers in the targeted sedimentary successions manifest a low‐energy depositional background, disturbed only occasionally by weak storms. While the dark layers are homogeneous, light‐coloured layers are generally planar, wavy ripple laminated, and bear frequent load casts. The dark layers often display varieties of 2‐D microbial mat structures little known from carbonate formations. In compliance with their identity, they are comparatively enriched in carbon, a large part of which is organic and kerogen. The said structures with their intrinsic deformations indicate delayed cementation. Notwithstanding delayed cementation, the flat clasts in these formations are readily traceable to the dark laminae possibly because of early acquisition of their selective cohesiveness. Resultant stress led to brittle deformation in the mat layers, while the light‐coloured layers underwent ductile deformation. All the studied breccias bodies are in situ, but this fact does not preclude either the possibility of reworking of the clasts while exposed to high‐energy current or generation of intraclasts by high‐energy currents eroding the depositional surface.

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