siderite concretions

Siderite concretions; indicators of early diagenesis in

Concretions in rapidly deposited sediments formed at shallow depths (<10 m), whereas siderite concretions in sediments that accumulated slowly formed at greater depths (>200 m), later in the burial history The Gammon served as both source rock and reservoir for accumulations of biogenic methane and, like the siderite concretions, the methane was generated during early diagenesis Both

Siderite concretions: indicators of early diagenesis in

Concretions that formed at shallow depths, early in the history of the sediment, contain a high percentage (7585%) of carbonate, preserve uncompacted structures and have oxygen isotopic ratios similar to that of seawater In contrast, concretions that formed later and/or at greater depths have lower carbonate content and lower 18O/16O ratios

Siderite concretions Big Chemical Encyclopedia

Siderite concretions Croal LR, Johnson CM, Beard BL, Newman DK (2004) Iron isotope fractionation by anoxygenic Fe(II)phototrophic bacteriaGeochim Cosmochim Acta 68 12271242 Curtis CD, Coleman ML, Love LG (1986) Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions Geochim Cosmochim Acta 50 23212334

Siderite Wikipedia

THE OCCURRENCE AND ORIGIN OF SIDERITE CONCRETIONS IN

01/01/1979· Siderite concretions in Francis Creek Shale in the working face of the H K Porter pit, near Ottawa, Illinois occur throughout the shale, although they are more abundant in some zones than others shale is 242 g/cc DEPOSITIONAL ENVIRONMENT OF THE FRANCIS CREEK SHALE The interpretations of the lithotopes, those containing the siderite concretions and those below and

Origin of Siderite Concretions In Microenvironments of

01/08/2012· They host siderite concretions with δ 13 C values ranging from −35 to 121‰ which show that sulfate reduction and methanogenesis contributed to the production of bicarbonate Fossils are found within each of the concretions, suggesting that the decay of these organic remains provided a catalyst for concretionary growth The pore water was freshened, which is indicated by the very negative δ

Siderite concretions Big Chemical Encyclopedia

Siderite concretions Croal LR, Johnson CM, Beard BL, Newman DK (2004) Iron isotope fractionation by anoxygenic Fe(II)phototrophic bacteriaGeochim Cosmochim Acta 68 12271242 Curtis CD, Coleman ML, Love LG (1986) Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions Geochim Cosmochim Acta 50 23212334

Magnesian siderite in carbonate concretions from

Chemical evidence indicates that, for one concretion at least, the phase of smaller cell dimensions is a magnesian siderite with around 25 mole % MgCOa Both abundances and compositions of the two phases vary between concretions whilst a single phase only is present in disseminated siderite It is thought unlikely that the two phases represent

The crystallographic fabric and texture of siderite in

21/12/2001· The siderite concretions from marine and nonmarine formations exhibit differences in fabric style, although both display increases in the degree of preferred siderite caxis orientation towards the concretion margins The Westphalian nonmarine siderites show a preferred orientation of siderite caxes in the bedding plane, whereas the Pliensbachian marine siderites have a preferred

(PDF) Origin of Siderite Concretions In Microenvironments

They host siderite concretions with d13C values ranging from 235 to 121% which show that sulfate reduction and methanogenesis contributed to the production of bicarbonate Fossils are found

(PDF) Siderite concretions from nonmarine shales

The concretions are composed of 50100 mu m, zoned crystallites, which exhibit no noticeable centertoedge variation within any individual concretion This indicates that siderite crystallites

Magnesian siderite in carbonate concretions from

Magnesian siderite in carbonate concretions from argillaceous sediments in the Westphalian of Yorkshire Volume 39 Issue 306

Siderite: The mineral Siderite information and pictures

Concretionary Siderite nodules are noted for containing a wide variety of flora and fauna fossils, especially in the openpit coal mining operations of eastern Illinois and western Indiana, where these concretions are common in the rock removed before the coal veins are exposed

Rinded iron‐oxide concretions: hallmarks of altered

In all three deposits, rinded concretions formed when preexisting, sideritecemented concretions were oxidized within a sand matrix Unlike fluvial examples, siderite in the Navajo Sandstone was autochthonous and of late diagenetic origin, having precipitated from carbon dioxide and methaneenriched waters moving through folded and jointed strata Ironrich rinds formed in all these strata

Concretion Wikipedia

A concretion is a hard, Some of the most unusual concretion nuclei are World War II military shells, bombs, and shrapnel, which are found inside siderite concretions found in an English coastal salt marsh Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth In concentric growth, the

Siderite concretions Big Chemical Encyclopedia

Siderite concretions Croal LR, Johnson CM, Beard BL, Newman DK (2004) Iron isotope fractionation by anoxygenic Fe(II)phototrophic bacteriaGeochim Cosmochim Acta 68 12271242 Curtis CD, Coleman ML, Love LG (1986) Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions Geochim Cosmochim Acta 50 23212334

Siderite concretions: indicators of early diagenesis in

The Gammon member of the Pierre shale of the northern Great Plains, USA, contains abundant siderite concretions The relative depth and time of siderite precipitation can be inferred from the structure, mineralogy and isotopic composition of these concretions Concretions that formed at shallow depths, early in the history of the sediment, contain a high percentage (7585%) of carbonate

THE OCCURRENCE AND ORIGIN OF SIDERITE CONCRETIONS IN

Siderite concretions are well known from the Francis Creek Shale because of their extensive fossils The excellent fossil preservation requires that concretions began to form early during diagenesis Conditions for siderite formation are very restricted; ΣaS must be low, PCO 2 (or ΣaCO 3 = ) relatively high (much higher than for water in equilibrium with the atmosphere), a Fe ++ much higher

(PDF) Origin of Siderite Concretions In Microenvironments

They host siderite concretions with d13C values ranging from 235 to 121% which show that sulfate reduction and methanogenesis contributed to the production of bicarbonate Fossils are found

(PDF) Siderite concretions from nonmarine shales

The concretions are composed of 50100 mu m, zoned crystallites, which exhibit no noticeable centertoedge variation within any individual concretion This indicates that siderite crystallites

SIDERITE CONCRETIONS IN THE COPAN CRINOID LAGERSTÄTTE

A thin interval of bioturbated, fossiliferous mudstone within the middle portion of the Upper Pennsylvanian Barnsdall Formation crops out near Copan, northeastern Oklahoma Representing slow background sedimentation in an oxygenated distal shelf setting, this exposure has yielded an exceptionally diverse and wellpreserved crinoid fauna consisting of over 1200 articulated or partially

Siderite: The mineral Siderite information and pictures

Concretionary Siderite nodules are noted for containing a wide variety of flora and fauna fossils, especially in the openpit coal mining operations of eastern Illinois and western Indiana, where these concretions are common in the rock removed before the coal veins are exposed

Origin and timing of siderite and calcite concretions in

Siderite concretions in materials (Fig 51, often in a serial fashion be the Glen Afton Claystone are rarely larger than tween their centre and margin Standard petro 40 cm across, finergrained, and develop a graphic thinsections were prepared for all sam yellowbrown goethite coating upon weathering ples and the chemical composition of the carbon Septarian siderite concretions in the

Concretion Wikipedia

Some of the most unusual concretion nuclei are World War II military shells, bombs, and shrapnel, which are found inside siderite concretions found in an English coastal salt marsh Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth In concentric growth, the concretion grows as successive layers

Concretions, nodules and weathering features of the

Concretions, nodules and weathering features of the Carmelo Formation The features that characterize a sedimentary rock can form at diverse times and under very different conditions Geologists divide these features into four classes Depositional features form while the sediment is accumulating They can tell a much about the ancient environment of deposition and include many examples in the