Deposition of laminated shale: A field and experimental study

Carey, Daniel L.; Roy, David C.

doi:10.1007/bf02629790

Cited by 8 publications

(7 citation statements)

References 5 publications

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“…The 10 to 50 mm thick fine-grained turbidite beds of the Phyllopod bed (table 1) would in their original loose state have been about 50 to 250 mm thick (compare Rieke and Chilingarian, 1974, p. 31-86). Each turbidite bed (consisting, when complete, of laminated siltstone followed by parallel-laminated siltstonemudstone that is itself followed by non-laminated mudstone) was deposited from a single decelerating turbidity current laden with silt and clay (compare Carey and Roy, 1985;Piper and Stow, 1991). The entrained animals, seaweeds, and cyanobacterial colonies were brought in by the turbidity current and dropped with the rest of the sediment.…”

Section: Nucleation and Growth Of Iron(ii)-rich Layer Silicates On Prmentioning

confidence: 99%

Mechanisms of fossilization of the soft-bodied and lightly armored faunas of the Burgess Shale and of some other classical localities

Petrovich¹

2001

American Journal of Science

126

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The splendid preservation of the Middle Cambrian Burgess Shale fauna, a fauna of exceptional importance for our understanding of the evolution of life, has not been adequately explained. Preservation of diagenetically altered remnants of the original organic tissues and formation of chlorite/illite coatings and cuticle replacements, both documented in the Burgess Shale fossils though not necessarily occurring together, can be understood as products of the same mechanism of fossilization of soft tissues. It is argued here that this mechanism consists of the following steps: (1) adsorption on structural biopolymers such as chitin, cellulose, and collagens of Fe 2؉ ions released during the oxidation of organic matter by iron(III)-reducing bacteria, (2) inhibition by the adsorbed Fe 2؉ ions of further bacterial decomposition of these biopolymers, which enables them to persist and later become kerogens; (3) in some microenvironments, nucleation of crystals of an iron(II)-rich clay mineral, a berthierine or a ferroan saponite, on the Fe 2؉ ions adsorbed on the preserved biopolymers and growth of such clay-mineral crystals to form a coating on the organic remains and/or to replace parts of the organism. The critical factors in the Burgess Shale-type preservation of Early and Middle Cambrian soft-bodied and lightly armored animals were probably: (1) rapid transport of live or freshly killed organisms into suboxic water, (2) extensive suboxic diagenesis in a sediment of high iron(III)/ (organic carbon) ratio, and (3) curtailment of the supply of sulfate ions shortly after the onset of pyritization. The proposed model of early diagenesis that results in Burgess Shale-type fossil preservation critically depends on the availability of steady suboxic depositional environments in open oceanic settings at depths of the order of 100 m in which iron(III)-rich fine-grained sediments, rapidly deposited with the entrained animals by turbidity currents, could accumulate without being disturbed by storm waves and deep currents. Evidence discussed in the present paper suggests that such conditions were common in the Early and Middle Cambrian.Adsorption of Fe 2؉ ions on structural biopolymers as a means of protecting organic fossil remains from decomposition by bacterial enzymes is a novel suggestion and needs to be demonstrated by direct experimentation. It is based on the following considerations. First, Fe 2؉ ions are strongly adsorbed on chitin under experimental conditions comparable to those in pore waters of suboxic iron-rich sediments, and while data on Fe 2؉ ion adsorption on collagen and cellulose seem to be lacking, other heavy-metal ions are strongly adsorbed on these biopolymers under appropriate conditions. Second, Fe 2؉ ions bonded with functional groups of chitin, collagen, or cellulose would prevent the very specific configuration and bonding which a biopolymer strand has to achieve within the active-site cleft of the appropriate bacterial enzyme to make enzymatic hydrolysis possible.Close examination of two other mecha...

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Section: Nucleation and Growth Of Iron(ii)-rich Layer Silicates On Prmentioning

confidence: 99%

Mechanisms of fossilization of the soft-bodied and lightly armored faunas of the Burgess Shale and of some other classical localities

Petrovich¹

2001

American Journal of Science

126

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“…Stow and Shanmugam (1980) recognized some 10 divisions in graded silt to mud turbidite beds, with individual beds commonly showing either base-or top-cut-out of many divisions. The origin of silt laminae in mud turbidites has been widely debated in the literature without any consensus emerging (Stow and Bowen, 1980;Hesse and Chough, 1980;Carey and Roy, 1985). Although Piper and Stow (1991) attempted a synthesis of scattered data from the literature, there is no well-established model of variation in finegrained turbidite facies with different deep-sea physiographic environments.…”

Section: Fine-grained Turbiditesmentioning

confidence: 99%

Fine-grained turbidites of the Amazon Fan: facies characterization and interpretation

Piper¹,

Deptuck²

1997

Proceedings of the Ocean Drilling Program, 155 Scientific Results

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Much of the sediment thickness found on Amazon Fan levees is attributed to mud with silt laminae. The distribution of sharp-based graded beds and the distribution of bioturbation, diagenetic fronts, and nannofossils demonstrates that many of the beds were deposited rapidly and episodically. The total thickness of mud decreases sharply away from active channels. These observations suggest that most of the levees are built of fine-grained turbidites. Twelve facies of fine-grained turbidites are distinguished from visual core description, X-radiography, and grain-size analysis. Some facies appear diagnostic of particular fan settings. Modal grain size of both muds and thin silt laminae decreases downfan. Facies distribution is consistent with the progressive spillover of a turbidity current as it moves down the channel system.

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“…Kemp (1996), Dean et al (2002), and Potter et al (2005) interpreted that silty laminae were deposited in relatively low-energy hydrodynamic conditions in reducing environments. The studies on sedimentary textures and structures and depositional environments of silty laminae by O'Brien (1990O'Brien ( , 1996, Shieber (1990Shieber ( , 1991, and Anderson (1996) and the physical experiment of Carey and Roy (1985) recognized several processes in the deposition of silty laminae, including eolian, colloidal, sediment gravity flow, and reworking by weak bottom flows.…”

Section: Introductionmentioning

confidence: 98%

“…Silty laminae in shales were subdivided into several types, such as thick or thin silty-clayey couplets, wavy-lenticular silty or parallel laminae, massive shale beds, etc. (Carey and Roy, 1985;Schieber, 1990Schieber, , 1991. Kemp (1996), Dean et al (2002), and Potter et al (2005) interpreted that silty laminae were deposited in relatively low-energy hydrodynamic conditions in reducing environments.…”

Section: Introductionmentioning

confidence: 98%

“…Textural heterogeneity of shales (Davies et al, 1991;O'Brien, 1996;Bustin et al, 2008;Aplin and Macquaker, 2011) and the occurrence of silty laminae and their depositional environments (Kemp, 1996), hydrodynamic conditions (Schieber, 1990;O'Brien, 1996), origin of silty laminae (Carey and Roy, 1985;Schieber, 1990Schieber, , 1991Anderson, 1996;O'Brien, 1996;Reineck and Singh, 2006), and provenance (Dean et al, 2002) have been studied. Silty laminae in shales were subdivided into several types, such as thick or thin silty-clayey couplets, wavy-lenticular silty or parallel laminae, massive shale beds, etc.…”

Section: Introductionmentioning

confidence: 99%

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Characteristics of silty laminae in Zhangjiatan Shale of southeastern Ordos Basin, China: Implications for shale gas formation

et al. 2015

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Shale oil and gas have been discovered in the lacustrine organicrich Zhangjiatan Shale of the Upper Triassic Yanchang Formation, Ordos Basin, China. Core observations indicate abundant silty laminae in the producing shales. This study documents the stratigraphic distribution of silty laminae and their relationship with interlaminated clay laminae. The type, structure, and characteristics of pores and mineral composition of silty laminae were observed and analyzed through thin section and scanning electron microscopy, X-ray diffraction, low-pressure CO 2 and N 2 adsorption, mercury porosimetry, and helium pycnometry. Results from silty laminae are compared with those of clayey laminae. The frequency and thickness of silty laminae vary over a wide range. The thickness ranges from 0.2 to 4 mm and is 1.5 mm on average; the frequency ranges from 4 to 32 laminae/m and is 23 laminae/m on average. The thickness percentage of silty laminae in the measured segments ranges from 6% to 17%. Silty laminae consist of quartz, feldspar, mixed-layer montmorillonite, and chlorite. In comparison to clayey laminae, non-clay detrital grains are larger, quartz and feldspar are more common, and clay minerals are less abundant. Pores in silty laminae are primary interparticle, dissolutional, intercrystalline, and microfracture types. Mesopores (2-50 nm in diameter) and macropores (50 nm-1 μm) are common, whereas, micropores ð<2 nmÞ are rare; the distribution of pore diameters is multimodal. However, microscopic pores with a diameter commonly smaller than 100 nm are common in

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Deposition of laminated shale: A field and experimental study

Cited by 8 publications

References 5 publications

Mechanisms of fossilization of the soft-bodied and lightly armored faunas of the Burgess Shale and of some other classical localities

Mechanisms of fossilization of the soft-bodied and lightly armored faunas of the Burgess Shale and of some other classical localities

Fine-grained turbidites of the Amazon Fan: facies characterization and interpretation

Characteristics of silty laminae in Zhangjiatan Shale of southeastern Ordos Basin, China: Implications for shale gas formation

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