Last week's specimen was a Lower Carboniferous fossiliferous siderite concretion from an unknown location, but likely from the Wooster area. It was donated to the department by Emeritus Geology Professor Sam Root. The concretion has beautiful crinoids preserved in it, including several stems of at ...
A concretion is a hard, ... Septaria usually contain crystals, often calcite, that precipitated from circulating solutions. Siderite or pyrite coatings are also occasionally observed on the wall of the cavities present in the septaria, giving rise respectively to a panoply of bright reddish and golden colors.
Concretions cemented mainly by siderite, Mg-calcite and iron monosulphide are common in late Holocene marsh and sandflat sediments on parts of the north Norfolk coast. Field experiments have shown that the concretions are actively forming in reduced sediments in which sulphate-reducing bacteria are active. ...
Concretions are hard bodies that form in sediments before they become sedimentary rocks. Slow chemical changes, perhaps related to microbial activity, cause minerals to come out of the groundwater and seal the sediment together. Most often the cementing mineral is calcite, but the brown, iron ...
Magnesian siderite in carbonate concretions from argillaceous sediments in the Westphalian of Yorkshire M. J. PEARSON Department of Geology and Mineralogy, The University, Marischal College, Aberdeen, AB9 IAS SUMMARY. Lattice parameters have been determined for two coexisting siderite …
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.
Jan 19, 2013· I have some siderite concretions that had been sitting open in the elements when found. They have some fine, light-colored material lodged in gaps in the fossil and on the broken nodule surface.
Small siderite concretions are abundant in the Woodbury in the northern part of the outcrop belt. Unconsolidated > Fine-detrital > Silt lay-silt, dark-gray; weathers brown and orange pink. Iron oxides fill fractures or form layers in the most weathered beds.
Rinded iron-oxide concretions: hallmarks of altered siderite masses of both early and late diagenetic origin ... concretions in the aeolian Navajo Sandstone of Utah. In all three deposits, rinded concretions formed when pre-existing, siderite-cemented concretions were oxidized within a sand matrix. Unlike ﬂuvial examples, siderite in the ...
REE in the concretions decrease from top to bottom concretions, concomitant with a decrease in the amounts of siderite. REE appear independent of clay amounts, suggesting they were incorporated in the carbonate-crystal structure, rather than in the clay fraction of the concretions.
The member consists of coals, claystones and siltstones rich in siderite concretions, and three to four levels of sandstone, each 2-10 m thick. From Cambridge English Corpus. Vivianite concretions are found in the basal part of the outcrop. From Cambridge English Corpus.
WELL-ORDERED KAOLINITE IN SIDERITE CONCRETIONS FROM THE BRAZIL FORMATION, WESTERN INDIANA Key Words--Concretion, Crystallinity, Kaolinite, Ordering, Siderite. Contact Supplier Concretions and Nodules in North Dakota .
Concretions often form early in diagenesis, shortly after compaction. Evidence for this is seen in the lack of compaction in layers and fossils preserved within the concretion relative to the layers outside of the concretion. Siderite and Pyrite. siderite (Fe2CO3) and pyrite (FeS2)
They host siderite concretions with δ 13 C values ranging from −3.5 to 12.1‰ 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.
Models of iron oxide concretion formation: ﬁeld, numerical, ... Calcite and siderite studies show a complex range of macroscopic and microscopic textures that suggest con-centric to pervasive growth as well as growth in different hydrologic environments (e.g. Mozley & Davis 2005).
alteration of siderite concretions in Mississippian shales, Scotland ... the concretions, particularly the timing of their formation and the source of ﬂuids. The content and nature of car- ... fractionation factor between siderite- and phosphoric acid-extracted CO 2 given by Rosenbaum and Sheppard (1986).
Siderite concretions that formed at shallow depths in the sediment column contain a large volume percent carbonate (75-85%), preserve uncompacted sediment textures, and have oxygen isotope ratios similar to those of carbonates precipitated in equilibrium with seawater (18 O e 0 to -2, PDB).
The concretions are composed of 50-100 m, zoned crystallites, which exhibit no noticeable center-to-edge variation within any individual concretion. This indicates that siderite crystallites nucleated at virtually the same time across the entire concretion and that the concretions did not grow by radial addition of siderite layers around a ...
WELL-ORDERED KAOLINITE IN SIDERITE CONCRETIONS FROM THE BRAZIL FORMATION, WESTERN INDIANA Key Words--Concretion, Crystallinity, Kaolinite, Ordering, Siderite. ... the siderite concretion is 680~ considerably higher than the dehydroxylation endotherm of most reference
North Dakota, especially in the wondrously sculpted badland areas of the west, has a fantastic variety of concretions and nodules. Some are the size and shape of petrified logs, while others, perched atop pedestals of softer sediments that they shield from erosion, have lens or disk shapes.
Siderite is commonly found in hydrothermal veins, and is associated with barite, fluorite, galena, and others. It is also a common diagenetic mineral in shales and sandstones, where it sometimes forms concretions, which can encase three-dimensionally preserved fossils . 
Abstract: A carbonate concretion from the shale bed overlying the No. 5 coal of Pennsylvanian age in Tuscarawas County is composed of siderite and contains pyrite, barite, sphalerite and traces of calcite in its interior and in fractures. The siderite has 8I 3C= +0.65%o, Sr=289 ppm and 87Sr/86Sr=0 ...
Siderite is a common mineral although excellent, attractive crystal specimens are sometimes hard to find. But many crystals, when colorfully iridescent, make a wonderful, colorful, satiny, shimmering mineral specimen.
Most fossils are found in concretions (siderite nodules) along the Mazon River area of the Illinois counties of Grundy, Will, Kankakee, Livingston and LaSalle, and are recovered from formation exposures along the river and nearby streams, roadcuts and within waste piles of abandoned and active coal mines.
Concretionary Siderite nodules are noted for containing a wide variety of flora and fauna fossils, especially in the open-pit coal mining operations of eastern Illinois and western Indiana, where these concretions are common in the rock removed before the coal veins are exposed.
The siderite concretions occur only in the lower 3–5 m (c. 10–15 ft) of the member, and only where the shale is more than 15 m (c. 50 ft) thick. The shale is coarser and bears sandstones near its top.
The host concretions are most commonly calcite, dolomite or siderite dominated, although rare occurrences have been interpreted from silica concretions. Septarian concretions are predominantly a pre-Pleistocene phenomenon, although a potential "proto" version has been described from the late Pleistocene ( Duck, 1995 ).
The diagenetic history of siderite concretions in Mesozoic sedimentary rocks on the island of Bornholm has been investigated using stable isotope-, AAS- and XRD-analysis and determination of …