They can form via abiotic redox processes during wettingdrying cycles, as well as via biotic redox processes mediated by microorganisms (Jien etal., 2010b; Timofeeva etal., 2014; Zhang etal., 2014). A stepwise acquisition of IRM up to a field of 5T is carried out for concretions extracted from three depths70cm (Bz horizon), 80cm (BzC horizon), and 120cm (C1 horizon). Mozley, P. S., and Goodwin, L., 1995, Patterns of cementation along 539-542. Overturned, broken, and in part dissolved MIS 5 stalagmites inside passages with quite delicate schist flakes sticking out of the roof suggests dramatic, but very short-lasting, episodes of flushing and corrosion since then. Summary parameters from coercivity analysis by fitting IRM acquisition curves with cumulative Gaussian functions, using IRM-CLG1.0 software (Kruiver etal., 2001) for samples from concretions extracted from different depth intervals of the OK Planosol profile. They are most dense along parallel nerve tracts oriented at 90 to the gill filaments (Silverman et al., 1983; Steffens et al., 1985). concretions is the only way of understanding these early features. This rate is almost two orders of magnitude less than the ice-contact rates of Table 1. 617-632. al., 1995). The size of a fully developed nodule varies from a fraction of a millimeter to as much as 20cm with an average size between 5 and 10cm. Figure4.6.3. interior (Raiswell, 1971; Astin, 1986). 4.6.3, although all concretions are characterized by a magnetically soft component dominating the total IRM, a weak high coercivity component is present as well. Although the native Cu was affected by corrosion, the study showed that a significant proportion (30%80% of the original thickness) of the Cu sheets had been preserved in the saturated compacted clay environment for many millions of years, at least since the end of the Lower Jurassic (Milodowski et al., 2000, 2002, 2003). (cementation) in localized portions of the rock. Figure5.10.4. The hematitic concretions reflect formation in a complex and reactive Fe- and Mg-rich, acidic evaporite system. But the dividing force of phosphatogenesis is organic matter produced by the whole water mass from top to bottom. Concretions are hard masses of sedimentary and, more rarely, (usually composed of calcite, CaCO3) is cut by a radiating internal shrinkage of the concretion body (like the cracks found in At the same time, the intensity of the soft component in the concretions is about five times higher than in the soils (compare Tables5.10.4 and 5.9.1). or by oxidation of melanterite, which is a candidate highly soluble evaporite mineral, for example. Complex cementation textures and authigenic mineral assemblages in Table5.10.1. Its internal structure has no differentiated layers, but rather it is built up of soil particles incorporated into the nodule's matrix. To access this article, please, Access everything in the JPASS collection, Download up to 10 article PDFs to save and keep, Download up to 120 article PDFs to save and keep. The heating curve shows mineral transformations above 300C with the creation of a new strongly magnetic phase. 5.10.1) is 1.6mm in diameter and has an irregular shape. a Cenozoic normal fault: A record of paleoflow orientations: Geology, Sp.) Outwash-lag of calcareous concretions in glacial silt (Hhlenkrapfen) cemented on scalloped wall, Pikhaugene. McBride, E. F., Picard, M. D., and Folk, R. L., 1994, Oriented Such an inhomogeneity is a characteristic feature of most of the soil nodules (F. Liu etal., 2002; Cornuetal., 2005; Gasparatos, 2013). (1983), a fluctuating water table leads to an increased Fe2+ concentration in the soil pores and then, depending on the rate of oxidation, either hematite or maghemite precipitate, or a mixture of these. ground-water flow direction (McBride et al., 1994). The elemental composition data shown in Tables4.6.14.6.4 demonstrate enhanced Fe and Mn contents that are especially pronounced in the nodules from the PR Planosol. v. 23, pp. In an analysis of the contribution of individual variables, logistic regression showed that two features correlate with the presence of soft-tissue preservation in concretions: (1) fine-grained host lithology, and (2) relatively constant C values. As demonstrated in Fig. v. 152, pp. Specimen from the Early Cretaceous Romualdo Member, Santana Formation, NE Brazil. Salt accumulation and increased colloidal capacity likely lead to the creation of the above-described conditions for the formation of dense concretions with a nondifferentiated structure. Salthlene, N. Norway. 4.6.3). shale host rock was eroded by wave action. Other varieties of nodules consist of more or less abundant microglobular isotropic phosphate or in part finely crystalline phosphate. This is to be expected, if diagenetic beds, also called sheet concretions (Pirrie and Marshall, 1991), result from the coalescence of concretions in concretion horizons during prolonged growth. As seen from Fig. 4.6.1cd from the OK Planosol profile and Integral Spectrum (Int. For the Cloridorme Formation, comparison with compaction curves from deep-sea drilling sites (Hesse et al., 2004; Rocker, 1974; Shephard et al., 1982) suggests that the measured maximum minus-cement porosities (87%) correspond to a burial depth of <1 mbsf, where concretion growth started. A comparison between the coercivities of the two components in the bulk soil and in the concretions from the depth of 42cm (the closest one to the soil sample analyzed, OK38Table4.4.1) shows that the IRM1 component is of higher coercivity in the bulk soil, while its intensity is much lower there and vice versa for the IRM2it has higher coercivity in the concretions compared with the soil. Independent evidence for substantial post-concretion compaction of the host sediment is obtained from the reduction of the distance between distinct depositional layers traced laterally from within a concretion into the not-carbonate cemented host rock between concretions (Fig. Figure5.10.1. Unlithified and lithified coprolites from 12 to 56cm in size, from fish and marine animals are present and they have a characteristic fibrous nature of many parts of them. <0.05%; 2. Commonly, when you break open concretions you will find that they have Similarly to the bulk soil samples, two coercivity components in the IRM are separated in the concretions (Table4.6.5)magnetically soft (IRM1) and magnetically hard (IRM2). hammer (yes, he lived to tell about it)! concretions. and other processes disrupt the original sediment. some concretions.) This gel-like phosphate fills the valves of recent diatoms and coats bones of Recent fishes. 4.6.3. Clay-fabric analyses of Carboniferous carbonate concretions from England (Oertel and Curtis, 1972) have shown that, in the centre of the concretions, clay-particle orientation is essentially random, as would be expected for a flocculated clay suspension with 8090% water content in which carbonate precipitation occurred. As also will be discussed in the Vertisols properties (Chapter 5), the layered concretions are thought to form in more loamy horizons with a frequent change in reductionoxidation conditions, while dense nodules missing an ordered internal structure form in heavy clayey illuvial horizons (Zhang and Karathanasis, 1997). Dense massive tannish-brown nodules irregular in shape and consisting chiefly of microgranular and finely crystalline phosphate. 535-540. Colored curves: dated 18Oc records. Siderite (FeCO3) concretions in the unit found in northwest New Mexico. Concentric-layered structure of two more concretions from OK profile is demonstrated in (c)as well. Cementation by micritic carbonate is not displacive, in contrast to slowly growing, low-nucleation rate cone-in-cone and related spherulitic calcite cements or calcium sulphates that create their own growth space and cannot be used for porosity estimates (e.g. Scallop relief approximately 5cm. The advantage of the magnetic methods to detect even a trace amount of strongly magnetic minerals (e.g., Oldfield, 1999; Evans and Heller, 2003) allows us to confirm the presence of magnetite-type mineral in the concretions from the salt-affected soil S. Sarah Jane Butterworth, Jonathan R. Lloyd, in The Microbiology of Nuclear Waste Disposal, 2021. Violet shade: Ice extent as a function of time, varying between the SwedishNorwegian water divide, via coastline of Norway to the continental shelf, data from Olsen et al. Cu waste containers will have a greater thickness than 12mm [reference canisters in Sweden have a Cu shell of 50mm (Andersson et al., 2004)] and would, therefore, be expected to show better performance. In summary, diagenetic hematitic concretions embedded within the outcrops appear to have formed relatively rapidly under stagnant to very slow fluid migration. An attempt was made to evaluate the absolute age of the most dense nodules (Baturin, 1982). Considerations concerning the diffusive communication length (Section 12.3.7) suggest a depth limit for active concretion growth of ~10 mbsf. 9.68). the concretions "freezes" the early sediment structure, Each plate consisted of composite stacks of individual thin Cu (>99.4%) sheets each 12mm thick. A comparison between the component analysis for soil samples (Table5.9.1) and the concretions evidences a much higher share of the high-coercivity component in the soil compared with concretions. The first component shows a low coercivitythe B1/2 parameter varies between 35 and 43mT, while the high-coercivity component is characterized by B1/2=280mT (Table5.10.4). However, the activities could not be commercialized due to excess availability of onshore nickel metal, anticipated ecological imbalance, and conservation of the natural resources for the future. (A)The greater variability in carbonate content of the beds compared to the concretions indicates a longer duration of the growth of the former, reflecting the coalescence of individual concretions in a concretion horizon. The Cu mineralization occurred before maximum compaction of the host rock and is older than 176Ma. Soft, unconsolidated, compacted or dense nodules usually occur together in the same dredge or core samples. One of the proteins is similar to vertebrate, calcium-binding calmodulin. The carbonate concentration of the Cloridorme concretions and diagenetic beds (Table 9.4) generally shows a systematic centre-to-margin decrease (Fig. 4.6.1e) and nodules (Fig. Black curve: Atmospheric CO2 content based on the Vostok ice core (Barnola et al., 1987). For terms and use, please refer to our Terms and Conditions 5.10.2 has a spherical shape with a 1.3-mm diameter, a well-established concentric structure, and characteristic outer shell. Studies on the mineralogy of soil concretions most often use spectroscopy methods and prove the presence of goethite and ferrihydrite (F. Liu etal., 2002; Cornu etal., 2005) butalso hematite and maghemite (Mitsuchi, 1976; Zhang and Karathanasis, 1997; Singh and Gilkes,1996). For example, siderite concretions from the East Coast continental rise off the United States may have formed at burial depths of 8001200m, well beyond the early-diagenetic stage, in accordance with their isotopic signatures (DSDP Leg 93: Von Rad and Botz, 1987). These evolved nodules must not be confounded with older ones observed in the deeper layers with ages over 1Ma. The patterns of interaction of the variables in the MCA revealed that the most important factors controlling exceptional preservation in concretions are related to (1) the potential for fossil preservation in the broader depositional setting (i.e., how likely fossils are to be preserved without concretions but in the same depositional environment) and (2) the rate of concretion growth. associated shrapnel, including some large unexploded shells (Al-Agha et Thus, it can be anticipated that in the more clayey Bt2 horizon, this situation is met and a higher amount of maghemite precipitates, while down in the Ck1 horizon, there is a larger amount of hematite but it is of a lower crystallinity. Diagenetic beds of the Cloridorme Formation show significantly larger variations in minus-cement porosities than the concretions (Fig. SEM images in the back-scattered electrons mode of the three concretions from the OK profile, extracted from the soil material from an 82- to 84-cm depth, and two nodules from the PR profile, extracted from a 62- to 64-cm depth, are shown in Fig. (2001a) and Mangerud (2004). The absolute age of the diatomaceous matrix determined by radiocarbon, ranges from contemporary to 6,600yrBP. Other deposits where 3D preservation occurs owing to concretions include a diverse biota from the Carboniferous Mazon Creek (Illinois, USA) in siderite concretions, and vertebrates and invertebrates from the Lower Cretaceous Santana Formation (NE Brazil) in carbonate concretions (Figure 6). The IRM acquisition curves are depicted in Fig. Carbonate content, 13C and 18O values across concretions and diagenetic beds of the Cloridorme and Levis Formations and the Cow Head Group. The high coercivity component may be related to hematite and shows higher B1/2 values for the soils than for concretions. Figure 5 - EDS spectra in selected spots of concretion S-2 shown in the SEM image in Fig. Although the samples were collected from traverses across several diagenetic beds, random sampling of the beds apparently resulted in different growth stages being captured. Stratigraphic top towards the right. No net corrosion has taken place after the sediments were deposited on the wall. They are 25% protein by dry weight. 11) emphasises the higher deposition of this element from 20 to 35 (Emelyanov, 1973). (C) The 18O-profiles display similar comet-shaped decreases from centre to the margins of the concretions and beds as the carbonate- and 13C-profiles reflecting decreases of the three parameters with increasing burial depth.

The role of the first of these can be tested experimentally. Scanning electron microscopy images of cross-sections of three concretions from the OK Planosol (ad) and two nodules from the PR Planosol (ef). The Silurian Herefordshire fauna (UK) has produced spectacular three-dimensionally preserved fossils, owing to early stiffening of decaying animals by volcanic ash, followed by calcite infilling of the void left by the decayed tissues, and precipitation of calcite nodules around the fossil. Blue curve: Marine isotope stages from benthic forams. The obtained acquisition curves are shown in Fig. The dense, irregularly shaped S-3 concretion (Fig. zone (Mozley and Goodwin, 1995). There is no unanimous view on the mode of occurrence of maghemite in concretionssome authors suppose that it is inherited from the parent rock (Mitsuchi, 1976), or it is a result of pedogenic precipitation (Singh and Gilkes, 1996), while others consider it to be as a result of the thermal alteration of the nonmagnetic nodules located at the top of the profile during severe bushfires (Lhr etal., 2013). Skoglund, in Treatise on Geomorphology, 2013.

The intensity, relative contribution (% from IRMtotal), median acquisition field (B1/2), and dispersion parameter (DP) for each coercivity component are shown. Field studies, however, provide evidence for concretion growth that has occurred at kilometre depth. 4.6.2). Polymetallic nodules occur in most oceans of the world with the greatest abundance at the vast abyssal floor at depths between 4000 and 6000m. Areas of economic interest have been identified in the north central Pacific Ocean, the Peru basin in the southeast Pacific, and the center of the north Indian Ocean. As discussed in Chan etal. Dense calcium phosphate [Ca3(PO4)2] concretions occur in unionoidean tissues. The Kvithola at Fauske; Northern Norway: an example of ice-contact speleogenesis. Sometimes, the nodules are coated with blue iron sulphides. The occurrence of native Cu within these rocks represents a natural analogue for the long-term behavior of Cu canisters sealed in compacted bentonite-based material in a deep geological repository. Preservation of the growth-related isotopic zonation of the concretions and diagenetic beds argues against recrystallisation (see also Section 12.3.5). Recent phosphate concretions are found in diatomaceous oozes in various facies representing a gradual transition from unconsolidated to lithified deposits (Baturin, 1982): Phosphatised soft aggregates of diatomaceous ooze from fraction of a millimetre to 14mm in size; their occurrence is variable: round, lenticular, tabular, and also encrusting or shapeless formations. Robert F. McMahon, Arthur E. Bogan, in Ecology and Classification of North American Freshwater Invertebrates (Second Edition), 2001. In some areas this is unfortunate, as the concretions to burial and compaction (Astin, 1986). With MEB examination, the nannostructures consist of fusiform crystals (~1mm long) and of aggregates of microglobules from one to several microns in diameter. Table5.10.2. Sites yielding exceptional fossils were distributed randomly through the 88 examples considered, suggesting that exceptional preservation can occur in almost any environment where concretions form. S.E. 45Ca tracer studies indicate that 90% of glochidial shell Ca was of maternal origin in P. grandis, the most likely source being gill concretions, with nonmineralized Ca accounting for only 8% of glochidial Ca in L. subrostrata (Silverman et al., 1987). Thus, gill concretion mass in brooding individuals of L. subrostrata and P. grandis was only 47 and 70% that of nonbrooding individuals, respectively (Silverman et al., 1985). 3). PALAIOS content emphasizes the impact of life on Earth's history. Boles. Some of these grains are phosphate casts of gastropod shells or fragments of phosphatic bones. Since at a lower pH (e.g., in the upper part of the Bt2 horizon) more Fe2+ will be present in the solution for a longer time, hematite precipitation will last the longest there and, according to Chan etal. provide a direct measurement of the past ground-water flow orientation 4.6.1a,b from the OK Planosol profile and Integral Spectrum (Int. The observed differences among the three concretions indicate the existence of different environmental settings during their formation and, therefore, their multistage genesis. As already discussed in other chapters, such thermomagnetic behavior is typical for maghemite, which is unstable on heating (Dunlop and zdemir, 1997). Therefore, a strong inhomogeneity in the chemical elements' distribution into different parts of the nodule is observed. Figure4.6.4. Figure 26. 4.6.1f) are present. In their modeling work, Tosca et al. The name septarian 1. The occurrence of concentric layers in the spherical soil concretions is usually related to their formation during separate stages of alternating dry and moist periods (Gasparatos etal., 2005; Cornu etal., 2005; Gasparatos, 2013). The worldwide resource has been estimated at 500 billiontonnes. Nevertheless, it supplied indirect proof that microbially influenced corrosion (MIC) was not an important process despite saturated and generally oxidizing conditions, suggesting that microbial activity must have been curtailed in this compacted smectitic environment in which the Cu sheets were embedded for many millions of years. PALAIOS is the journal of choice for publishing innovative research involving all aspects of past and present life from which geological, biological, chemical, and atmospheric processes can be deciphered and applied to finding solutions to past and future geological and paleontological problems. Nodules and concretions are also abundant in the three Planosols from Bulgaria (see the profiles' descriptions). On the other hand, in the heavy clayey impermeable soil horizons, the periods of water saturation are significantly longer and the cycles of water-logging more frequent, which provokes more intense reductive dissolution of Fe and Mn and formation of dense concretions (Zhang and Karathanasis, 1997). 5.10.3 and integral spectrum (Int. obtained for the whole diametric surface of the concretion. Through its network of international members, the Society is dedicated to the dissemination of scientific information on sedimentology, stratigraphy, paleontology, environmental sciences, marine geology, hydrogeology, and many additional related specialties. They are thought to form from flowing ground The host-sediment was originally carbonate-free. These various phosphatised concretions have been deposited on the middle or inner shelf, at depths of 60120m only during the last transgression. Bradley L. Jolliff, Ralf Gellert, in Volatiles in the Martian Crust, 2019. The S-2 soil concretion shown in Fig. 5.10.15.10.3. The second feature, a relatively constant C trend, suggests that certain patterns of concretion growth, pervasive growth or concentric growth with one growth layer, are more conducive to fossilization than others. 4.6.1. Raiswell, R., 1971, The growth of Cambrian and Liassic Figure 3 - Swapan Kumar Haldar, in Mineral Exploration (Second Edition), 2018. The native Cu occurred as thin plates, up to 160mm in diameter. The diagenesis of the concretions, which postdates the deposition of the host sediment, commonly date (U-series) to 3070kyr. has been cut on a rock saw to reveal septarian fractures filled with

WINTER, 1995. (a) Scanning electron microscopy (SEM) images (in a back-scattered electrons mode) of a nodule S-1 extracted from the salt-affected soil S. EDS spectra were taken at the two spots indicated by squares and labels Sp1 and Sp2. More detailed images of these two areas are shown in (b)and (c)together with the spots of the EDS analyses taken. 4.6.4. 4.6.1e from the PR Planosol profile, Table4.6.4. Paleoporosities estimated from minus-cement porosities may be converted to burial depths using compaction curves for appropriate tectonic environments. referring to the raised cracks on the outside of some septarian Astin, T. R., 1986, Septarian crack formation in carbonate term "little walled," referring to the raised cracks in the outside of The concretions formed 5.10.3b,c). Among the different layers in the shell, soil particles are caught up as well. originates from the Latin word saeptum (enclosure or wall), Concretions account for up to 60% of gill dry weight in some species (Silverman et al., 1985). Other observations to determine the state of compaction at the time of cement precipitation include (1) the degree of preservation of the original shape of fossils and fecal pellets, and (2) the degree of preferred orientation of clay particles. 5.10.3a). such as burrows, fossils, and sedimentary layering - that cannot be seen Top Red dots: 14C dates of Hhlenkrpafen carbonate (Olsen et al., 2001b). In other cases, massive, MIS 5 flowstones are corroded in situ (e.g., Skoglund and Lauritzen, 2010, Figure 12). 2015 SEPM Society for Sedimentary Geology SEM images of polished cross-sections as well as details of the three concretions are shown in Figs. several generations of coursely crystalline calcite cement. Figure4.6.2. EDS spectra in selected spots of concretion 1 shown in the SEM image in Fig. Dolomite concretion from the 6-member of the Cloridorme Formation, wave-cut platform at Grande Valle, Quebec, in a host sediment of black slate with intercalated centimetre-thin calcisiltite turbidites. A British geologist studying these concretions realized this The gel-like and unconsolidated phosphate clots are analogous in all characteristics to the enclosing ooze. concretions have even been found in faults cutting the Santa Fe Group, rest of the rock. Sample numbers in ascending order across vertical traverses. Concretions extracted from several depth levels from the S profile are used for magnetic measurements. The likelihood of such processes has been largely confirmed by subsequent modeling (Sefton-Nash and Catling, 2008) and experimental (Tosca et al., 2008b; Zhao and McLennan, 2013) results. because they have a strikingly different color and/or hardness than the This demonstrates that native Cu can remain stable in a saturated and compacted clay environment on the geological timescales that are considered in performance assessments of geological repositories. EDS spectra in a spot of the nodule shown in the SEM image in Fig. A more-detailed image of the layered structure of the concretion from the OK profile displayed in (a)is shown in (b). concretions: Sedimentology, v. 17, pp. For example, native, unusual sheet-like Cu concretions have been found in compacted smectitic mudstones and siltstones of the Permian Littleham Mudstone formation at Littleham Cove, south Devon, England.

This shrinkage perhaps is related to dehydration or 4.6.1ad) with a clearly seen core (commonly formed by a large soil particle) and numerous well-laminated layers around it. Simultaneously, the coercivity of the hard component decreases from the top of Bt2 toward Ck1, where, however, it has a higher intensity (Fig. Figure4.6.1. CORE), Table4.6.2. This could indicate smaller hematite grains in the soil and low crystalline hematite in concretions. Figure 5. Concretions are usually very noticeable features, In shales, concretions often preserve features of the original sediment -

This reflects the increasing effect of burial compaction on the host sediment during continuing concretion growth. including disks, grape-like aggregates, and complex shapes that defy For a variety of reasons, this nucleus created a more favorable They are commonly Although this natural analogue was studied in detail mineralogically and petrologically, no microbial analyses have been reported. obtained for the whole diametric surface of the concretion. Elongate As far as the timing of complete filling of the pore space by authigenic cement is concerned, the model of overlapping cementation shells provides insight into the problem (see Section 12.4). Lens cap for scale. EDS spectra in two selected spots of concretion shown in the SEM image in Fig. The major soil-forming elements such as Al, Mg, Si, Ti, and Ca are also present in the concretions, as well as Ba. direction: Journal of Sedimentary Research, v. A64, pp. suggested that they originate as tensile fractures produced in response have attracted the unwanted attention of local graffiti artists. H, horizontal traverse. Recent phosphorite formation in the Atlantic is localised in narrow north-south oriented zones along the coast of southwestern Africa. From: Evolution of Fossil Ecosystems (Second Edition), 2012, Reinhard Hesse, Ulrike Schacht, in Developments in Sedimentology, 2011. Table5.10.3. Fig. Table4.6.5. 9.67A). Those parts of the beds originally located between concretions that have not yet coalesced become cemented much later and consequently have lower minus-cement porosities. Septarian concretions are the most common type of concretion The mantle contains high concentrations of the enzyme, carbonic anhydrase which may be bound to the concretions (Istin and Girard, 1970b). Horizontal bars: growth periods as recorded in all available speleothems dates. Complex elongate concretions in the Zia Formation (Miocene), Table 9.4. SEPM (Society for Sedimentary Geology) is an international not-for-profit Society headquartered in Tulsa, Oklahoma. Formation of hematite by breakdown of jarosite during basin recharge by relatively dilute groundwater (Tosca et al., 2005) or oxidation of ferrous sulfates, such as melanterite, provide plausible mechanisms for their formation. Distribution of phosphorous in the uppermost (05cm) sediment layers off Namibia. 5.10.3d). Pale green horizontal bars: Cap mud of the Ursus horizon in Kjpsvik, dated by U-series (Nese and Lauritzen, 1996). In thin-sections, non-ferroan calcite grains, like detrital silt-sized quartz, are on average twice as large as the authigenic sucrose ferroan dolomite crystals with a diameter of 1015m. EDS spectra in two selected spots (Sp1 and Sp2) of nodule S-3 shown in the SEM image in Fig. The soil reaction pH sharply increases with increasing depth and thus the hematite's crystallinity would decrease, leading to a low B1/2.