Microbial mediation in phosphatogenesis: new data from the Cretaceous phosphatic chalks of northern France

Lamboy, M.

doi:10.1144/gsl.sp.1990.052.01.11

Cited by 23 publications

(19 citation statements)

References 23 publications

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“…Phosphate matrix corresponding to apatite globules of about 1 μm diameter is also typical ( figure 4H). The globules resemble fossilized microbial cells reported by several workers (Rao and Nair 1988;Lamboy 1990). The crystalline faces of the globules may indicate transformation of initially formed structures.…”

Section: Petrology Of the Cretaceous Phosphoritessupporting

confidence: 75%

Origin of Cretaceous phosphorites from the onshore of Tamil Nadu, India

et al. 2007

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Cretaceous phosphorites from the onshore of Tamil Nadu have been investigated for their origin and compared with those in the offshore. Cretaceous phosphorites occur as light brown to yellowish brown or white nodules in Karai Shale of the Uttatur Group in the onshore Cauvery basin. Nodules exhibit phosphatic nucleus encrusted by a chalky shell of carbonate. The nucleus of the nodules consists of light and dark coloured laminae, phosphate peloids/coated grains and detrital particles interspersed between the laminae. Scanning electron microscope (SEM) studies reveal trapping and binding activity of microbial filaments. A mat structure with linearly arranged microbial filaments and hollow, cell-based coccoid cyanobacterial mat are present. Nodules contain abundant carbonate fluorapatite, followed by minor calcite, quartz and feldspar. The P 2 O 5 content of the phosphorites ranges from 18 to 26%. The CaO/P 2 O 5 , Sr and F contents are higher than that of pure carbonate fluorapatite. Concentrations of Si, Al, K, Fe, and Ti are low. We suggest that the nuclei of the nodules represent phosphate clasts related to phosphate stromatolites formed at intertidal conditions. At high energy levels the microbial mats were disintegrated into phosphate clasts, coated with carbonate and then reworked into Karai Shale. On the other hand, Quaternary phosphorites occur as irregular to rounded, grey coloured phosphate clasts at water depths between 180 and 320 m on the continental shelf of Tamil Nadu. They exhibit grain-supported texture. Despite Quaternary in age, they also resemble phosphate stromatolites of intertidal origin and reworked as phosphate clasts onto the shelf margin depressions. Benthic microbial mats probably supplied high phosphorus to the sediments. Availability of excess phosphorus seems to be a pre-requisite for the formation of phosphate stromatolites.

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Section: Petrology Of the Cretaceous Phosphoritessupporting

confidence: 75%

Origin of Cretaceous phosphorites from the onshore of Tamil Nadu, India

et al. 2007

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“…Krajewski 1984;Delamette 1988a;FOllmi 1989b;Lamboy 1990. The optimum in preservation of microbial mats is observed in distal areas of the belt of condensation and phosphogenesis, and was probably related to the proximity of the oxygenminimum zone (Fig.…”

Section: Current-induced Condensation and The Presence Of An Oxygen-mmentioning

confidence: 97%

Condensation and phosphogenesis: example of the Helvetic mid-Cretaceous (northern Tethyan margin)

Föllmi¹

1990

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The Aptian to Lower Ccnomanian condensed phosphatic beds, deposited in the Helvetic Shelf along the northern Tcthyan margin, consist of thin strata (generally <50 cm) of densely packed phosphatizcd partictcs and crudcly laminated crusts embedded in glauconitic sands, marls, and pclagic micritcs. The beds record very low net sedimentaccumulation rates (typically 2-20 cm Ma 1). The presences of complex internal and laterally rapidly changing microstratigraphies, multiple phosphate gcncrations, intimate mixtures of fossils from different biostratigraphical zones and ecological habitats, a proximal transition into bioturbatcd glauconitic sands, and a distal transition into aliochthonous sediments deposited in channel and fan systems, indicate that the condensed phosphatic beds formed along the axis of a stable westward-flowing current system contouring the northcrn Tethyan margin. Repetitive cycles of deposition, phosphogencsis, re-exposure and rcworking, and deposition (Baturin Cycles), caused by current-induced lateral migration of sand bodies, shaped the internal stratification and composition of the condensed phosphatic beds. Catastrophic burial of entire benthic communities was crucial to phosphogenesis. The sudden presence of large amounts of organic matter buried in siliciclasts created a reactive environment favourable for the concentration and precipitation of phosphates, probably with the help of physicochemical cycles of the Fe 3s -Fe e+ and Mn 4+-Mn 2+ redox pairs.Condensed phosphatic sediments form in marine environments, characterized both by lowered net sediment-accumulation rates and episodic sediment remobilization, and by (bio-) chemical conditions suitable for phosphogenesis. This exceptional combination of physical and chemical oceanographic circumstances limits the occurrence of condensed phosphatic beds to specific settings in space and time, and renders these sediments an unique value as palaeoceanographic marker beds.Although extensively studied over the last fifty years, condensed phosphatic beds remain enigmatic in many aspects (e.g., Heim

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“…However, the controversy still exists as whether the apatite is formed by direct precipitation or by replacement of calcium carbonate. Many workers have concluded that most phosphorite deposits have formed due to accumulation of carbonate fluorapatite formed by the post mortem alteration of phosphorus-rich bacterial cells (O'Brien, et al 1981;Riggs 1982;Prtvtt & Lucas 1986;Lamboy 1990;Lewy 1990). On this basis it can be suggested that microorganisms were responsible for the phosphatized stromatolites of the Jhamarkotra and other deposits, and that mineralization took place preferentially in subtidal areas, in part because here stromatolites only originally contained low-Mg calcite, which was easily transformed into apatite.…”

Section: Discussionmentioning

confidence: 99%

The influence of magnesium ions during the formation of stromatolitic phosphorites of Udaipur, Rajasthan, India

Sisodia

Chauhan

1990

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The stromatolites of the Precambrian Aravalli Supergroup outcropping around Udaipur City are composed of carbonate (dominantly dolomite) and/or phosphate (carbonate-fluorapatite). The phosphate present in these stromatolites occurs in varying proportions, from traces levels to a major constituent. Compositional variation is attributed to the differences in the original magnesium contents stromatolites which reflects their different of the depositional environments, Intertidal stromatolites had primary magnesium calcite mineralogies, while those deposited in subtidal areas were composed of aragonite and/or lower magnesium calcite. The Mg/Ca ratio in the stromatolites appears to have been controlled by microorganisms which, it is argued, also played an important role in the process of phosphate fixation. It is inferred that the high Mg content of intertidal stromatolites prevented extensive phosphatisation in this facies.

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Microbial mediation in phosphatogenesis: new data from the Cretaceous phosphatic chalks of northern France

Cited by 23 publications

References 23 publications

Origin of Cretaceous phosphorites from the onshore of Tamil Nadu, India

Origin of Cretaceous phosphorites from the onshore of Tamil Nadu, India

Condensation and phosphogenesis: example of the Helvetic mid-Cretaceous (northern Tethyan margin)

The influence of magnesium ions during the formation of stromatolitic phosphorites of Udaipur, Rajasthan, India

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