Content uploaded by James R. Boles
Author content
All content in this area was uploaded by James R. Boles on Jan 24, 2019
Content may be subject to copyright.
The Moeraki Boulders--Anatomy of Some Septarian Concretions
Abstract
The Moeraki boulders are large (to 2m) calcite concretions with septarian veins of calcite and rare late-stage quartz and ferrous dolomite. The carbonate composition trends reflect interaction between the growing concretion and the enclosing mudstone pore-fluid system. The observed Fe, Mn, Mg depletion trends probably reflect depletion of elements released by short-time-scale diagenetic events of finite size. The growth time of the larger concretions is estimated at about 4 m.y. based on published diffusion growth models. Extrapolation of compositional trends versus growth time from these concretion bodies suggests that septarian veins form on a time scale of several million years.-from Authors
... Apatite data in the concretions are also shown in Table 1. The strongest peak due to ν 1 -PO 4 3− (symmetric stretching vibration) of apatites is divided into two groups ( Fig. 1B): Group N (narrow FWHM group), in which the ν 1 -PO 4 3− band appears at a higher wavenumber (~ 962 cm −1 ) and the FWHM is narrower (Fig. 1B(a)′, (b)′, (c)′), and Group W (wide FWHM group), in which the ν 1 -PO 4 3− band appears at a lower wavenumber (~ 954 cm −1 ) and the FWHM is wider (Fig. 1B(d)′, (e)′, (f)′). Figure 1B Other apatite peaks are observed at 585 cm −1 (ν 4 : bending) and 425 cm −1 (ν 2 : bending) 15 (Fig. 1A(d) and (f)). ...
... Apatite data in the concretions are also shown in Table 1. The strongest peak due to ν 1 -PO 4 3− (symmetric stretching vibration) of apatites is divided into two groups ( Fig. 1B): Group N (narrow FWHM group), in which the ν 1 -PO 4 3− band appears at a higher wavenumber (~ 962 cm −1 ) and the FWHM is narrower (Fig. 1B(a)′, (b)′, (c)′), and Group W (wide FWHM group), in which the ν 1 -PO 4 3− band appears at a lower wavenumber (~ 954 cm −1 ) and the FWHM is wider (Fig. 1B(d)′, (e)′, (f)′). Figure 1B Other apatite peaks are observed at 585 cm −1 (ν 4 : bending) and 425 cm −1 (ν 2 : bending) 15 (Fig. 1A(d) and (f)). ...
... Apatite data in the concretions are also shown in Table 1. The strongest peak due to ν 1 -PO 4 3− (symmetric stretching vibration) of apatites is divided into two groups ( Fig. 1B): Group N (narrow FWHM group), in which the ν 1 -PO 4 3− band appears at a higher wavenumber (~ 962 cm −1 ) and the FWHM is narrower (Fig. 1B(a)′, (b)′, (c)′), and Group W (wide FWHM group), in which the ν 1 -PO 4 3− band appears at a lower wavenumber (~ 954 cm −1 ) and the FWHM is wider (Fig. 1B(d)′, (e)′, (f)′). Figure 1B Other apatite peaks are observed at 585 cm −1 (ν 4 : bending) and 425 cm −1 (ν 2 : bending) 15 (Fig. 1A(d) and (f)). ...
Micro-Raman spectra of concretions with and without fossils were measured in a nondestructive manner. The band position and full width at half maximum height (FWHM) of ν1-PO4³⁻ of apatite in the concretions were analyzed to investigate the origin of apatite. The analyzed concretions were derived from the Kita-ama Formation of the Izumi Group, Japan. The micro-Raman analysis showed that the apatites in the concretions were divided into two groups: Group W (wide FWHM group) and Group N (narrow FWHM group). The apatite belonging to Group W is suggested to be biogenic apatite originating from the soft body tissues of organisms because the Sr content is high and the FWHM is similar to that of apatite in bones and teeth of present-day animals. The other apatite belonging to Group N is considered affected by the diagenetic process because of its narrow FWHM and F substitution. These features of both groups were observed regardless of the presence of fossils or absence of fossils in the concretions. This Raman spectroscopic study suggests that the apatite at the time of concretion formation belonged to Group W but was changed to Group N by the substitution of F during the diagenesis process.
... Analyses of C and O stable isotope and trace elements by different authors (Astin & Scotchman, 1988;Boles et al., 1985;Coleman & Raiswell, 1981;Loyd et al., 2014;Marshall, 1983;Scotchman, 1991) show that the first cements filling septarian cracks crystallised while the outermost parts of the concretion were growing. In the studied examples, geochemical mappings by microfluorescence indicate a clear geochemical differentiation between matrix and septarian crystals for main and trace elements. ...
This works analyses the Albian barite septarian concretions of the Fardes Formation located in the Geopark of Granada within the Subbetic (Betic Cordillera, SE Spain) from a stratigraphic, textural, mineralogical and geochemical point of view. The early diagenetic conditions that favoured the development of the concretions and their septaria are interpreted, taking into account the importance of the organic-rich clay facies (black shales) in which they are found as well as the interruptions in the sedimentation rate. The barite concretions formed in different stages: (1) Sedimentation of black shales containing Ba of organic origin and deposited in low oxygen environments; (2) diffusion of seawater interstitial solutions containing Ba ²⁺ mainly from organic matter and sulfate originating from the decomposition of organic matter by bacterial reduction; (3) crystallization of barite on nucleation sites and rapid growth of concretion at the water–sediment interface when the depth of the barite front stabilized at a few meters depth due to a very low or no sedimentation rate; (4) rapid growth of the concretions and sediment load favoured the formation of septarian cracks that were filled first with Sr-rich barite crystals and finally by calcite. The association of barite concretions and stratigraphic discontinuities can be very useful for the recognition of depositional hiatuses in thick monotonous clayey or marly sequences.
... , Martill, 1988;Seilacher, 2001;Potter et al., 2014;Mccoy et al., 2015aMccoy et al., , 2019Mccoy et al., , 2022Mccoy et al., , , 2016, 2021Yoshida et al., 2015, 2018aYoshida et al., 2015, 2018aYoshida et al., 2020, 2021, 2021, 2022, 2021Muramiya et al., 2020, 2023, , 2022 , Chan et al., 2004Yoshida et al., 2018b pH Sirono et al., 2021;Ormö et al., 2004, Potter et al., 2011Sirono et al., 2021Chan, 2022, 2023;, 2022;, 2023;, 2022 1 2 Large concretions containing whale fossils, Oga Peninsula, Akita Prefecture, Tohoku, Japan. McBride et al., 2003;Yoshida et al., 2018a;Wu et al., 2021 1 Allison andPye, 1994;, 2019, , Boles et al., 1985Fig. 1e 1 Plotnick, 1986Bishop and Williams, 20051960R.A.Berner 1968a, 19691970, Curtis et al., 1972Irwin et al., 1977;Hudson, 1978;Irwin, 1980;Coleman and Raiswell, 1981;Curtis et al., 1986;Scotchman, 1991;Mozley and Burns, 1993, Loyd et al., 2012, Astin, 1986Dix and Mullins, 1986;Astin and Scotchman, 1988;Desrochers and Al-Aasm, 1993;Hounslow, 1997 Concentric Model Bojanowski and Clarkson, 2012;Yoshida et al., 2018aPervasive Model , 1970, Raiswell, 1976, 1987Coleman, 1993;DeCraen et al., 1999;Mozley and Davis, 2005Coleman, 1993Mozley and Davis, 2005Berner, 1968bRaiswell, 1971;Willkinson and Dampier, 1990;Coleman and Raiswell, 1995 30 50 wt% 60 wt% Morad and Eshete, 1990Berner, 1980Berner, 1968b, 1980Yoshida et al., 2020 EA-IRMS δ 13 C vs PDB Scanning X-ray Analytical Microscope SXAM Yoshida et al., 2015Yoshida et al., , 2018aKatsuta et al., 2003Katsuta et al., 2000Katsuta et al., , 1987 , 1999 3 5 cm Fig Rep. Miyazaki Pref. ...
Spherical concretions found in sedimentary rocks are fascinating natural objet trouvés because of their rounded shapes and distinct boundaries. They consist of several minerals, including carbonate minerals, silicate minerals, and iron oxides. Well-preserved fossils are often found in concretions, particularly those composed of calcium carbonate. Concretions are thought to form by diffusion and the development of a syn-depositional reaction front that travels rapidly from the center of the concretion toward its outer margins. Based on the examination of several hundred spherical calcium carbonate concretions, we developed a diffusion-based model to represent the generalized growth conditions of spherical concretions. This model shows that spherical concretions grow rapidly during the first few years of diagenesis. In particular, carbonate concretions consist mainly of CaCO3, and their permeability is greatly reduced by cementation and sealing by calcite. As a result, any fossils inside the concretion are well preserved, as water is prevented from penetrating the concretion after its formation. This sealing can provide strong resistance to weathering for more than a million years. Based on this model, we have developed synthetic concretion-forming solvents. To test the effectiveness of these solvents in sealing groundwater flow paths, we conducted an in situ experiment in an underground laboratory in Horonobe, Hokkaido. In the experiment, groundwater flow paths in the excavation damaged zone around an underground gallery were successfully sealed. The experiment showed a decrease in permeability by a factor of 1/100 to 1/1,000 over one year. Here we present a detailed model of the concretion formation process and our conclusions about the sealing process. This sealing process can be applied to activities that require long-term containment of material underground; for example, the geological disposal of nuclear waste and underground carbon dioxide storage. These applications will become increasingly important in the near future.
... Sizes and Shapes Concretions occur in many sizes, spanning three orders of magnitude: mm, cm, and m scales (Fig. 3). The largest concretions on the m-scale are generally carbonate, such as the Moeraki Boulders of New Zealand (Boles et al. 1985;Yoshida et al., 2020), although some m-scale iron oxide concretions are noted in the Cretaceous Baseline Sandstone of southern Nevada (Duncan and Chan, 2015) (Fig. 3D). Spheroidal forms are most common (Fig. 3), as an equilibrium shape dominated by diffusive processes under saturated conditions (Clifton, 1957;Berner, 1968Berner, , 1980Raiswell et al., 2000;Ortoleva, 1994;Chan et al., 2004Chan et al., , 2007Mozley and Davis, 2005). ...
There is an amazing array of concretions throughout the sedimentary record of Earth, and now iron oxide examples (“blueberries”) recognized in several regions of Mars. Two questions address the current state of knowledge on nodular cemented mineral masses as well as coloration patterns. Collectively the authigenic cements and patterns chronicle past diagenetic conditions, particularly in clastic rocks.
What do we know? Concretions are cemented mineral masses that occur in many sizes, spanning three orders of magnitude (mm, cm, and m scales). Spheroidal forms are most common, as an minimum free stage dominated by diffusive processes. There are multiple cement mineralogies, sometimes even within single concretions, reflecting different water compositions in open systems. Other concretionary geometries are affected by primary textures such as bedding, grain size, and porosity/permeability, or later textures such as fractures, joints, and faults. Iron cycling is readily apparent where visual coloration patterns indicate histories of early iron reddening, secondary bleaching (removal of iron), and iron replacement or reprecipitation. Interfingering colors may indicate a possible interface of immiscible fluids.
What are the remaining challenges? There are many aspects of concretion diagenesis that are still yet to be deciphered. Non-unique pathways or processes may produce similar-looking end products. Thus, it can be difficult to determine exact histories, as well as the fluid compositions and environmental conditions that initiate concretion formation, particularly if an obvious nucleus is lacking. Microbial life may enhance nucleation and precipitation, and geochemical gradients are potential places to search for biosignatures. Timing and events are mostly relative relationships in these open systems, but newer developments in U-Th/He dating may provide age constraints for iron oxide cements. Continued explorations, field studies, modeling approaches, analytical advances, and instrument precision will enlighten our understanding on the diagenetic histories of both Earth and Mars.
... Similarly, the large basins with jagged rims associated with the Moeraki and Katiki concretionary boulders developed and preserved on the southern coast of South Island, New Zealand (e.g. Brunsden 1969;Boles et al. 1985) are altogether larger than the forms discussed here. Some coastal rock doughnuts also appear to grade into cones with crestal basins and into fonts (the benetiers of Coude Gaussen 1979; Twidale and Campbell 1998) in zones of granite different in composition and texture from the main body of the rock, and more resistant on that account. ...
Rock doughnuts are annular rims developed around rock basins that intermittently carry pools of water. They are developed in granitic rocks, and in arenaceous and calcareous sediments and in coastal as well as interior settings. Rock levees are found adjacent to gutters but are of a similar nature and origin. Both doughnuts and levees can be attributed to the development of protective coatings or veneers by biota, and of silica, iron oxides, and carbonates by overflowing pool waters. Contrasts in drainage from regolithic covers, weathering at sheltered interfaces and variations in runoff can also be cited at causative factors and situations.
... Another major difference is that, during the period of growth, the former may result in a much higher calcite concentration in the center of the sediment zone occupied by the present-day concretion, but zero calcite in the outer layer, while in the latter the calcite concentration is more or less uniform throughout the entire zone occupied by the present-day concretion. Both growth patterns may coexist in the formation process of a concretion, though one usually dominates over the other (Boles et al., 1985;Huggett, 1994;Raiswell and Fisher, 2000). ...
A comprehensive study is presented of the characteristics of calcareous concretions in the Connecticut Valley varved clay (CVVC), a glacial lake sediment, probed by an array of investigations, including compositional analyses via X-ray powder diffraction and energy-dispersive X-ray spectroscopy, mechanical property mapping by nanoindentation, selective dissolution, microstructure examination by optical and electron microscopy, and stable isotope analyses, with an objective to resolve some long-standing questions on their origin and growth mechanisms. Results show that these concretions are of a biogenic origin and consist of ~40 wt% primary host sediments and ~ 60 wt% secondary calcite post-depositionally precipitated as pore infills and inter-particle cement. The highly consistent layering and dry density between the carbonate-free host sediments in the concretions and in-situ varved sediments manifest that the precipitated calcite causes no disturbance to the original stratification and structure of the varved sediments. Moreover, both the mechanical properties (i.e., Young's modulus and hardness) and calcite concentration in concretions exhibit a radially decreasing pattern slightly disturbed by the sediments' layered textures. Further supported by the radial distribution patterns of stable carbon and oxygen isotopes, the CVVC concretions grow in a concentric pattern. A conceptual ion transport model is proposed to further interpret the growth mechanisms. These concretions grow radially in a nearly closed sediment system with diffusion-controlled transport of HCO3⁻ from decaying organic matter and Ca²⁺ from porewater at direction-dependent rates dominated by the pore characteristics of the local host sediments. The diverse concretion morphologies are attributed to the different growth rates in different directions affected by the heterogeneous layering and pore sizes of the host sediments.
... In outcrops the tusk-shells are seen to lie almost horizontally in the compacted muddy to clayey matrix and the fine layers around the concretions are bent due to compaction after concretion formation (Figs. 1b and 2b). The other one, Moeraki boulders are distributed in the Paleocence Moeraki Formation (40 Ma) (Boles et al., 1985;Thyne and Boles, 1989) and have sizes up to 1.5 m. They are all quite spherical and also buried in the muddy to silty fine sediments. ...
Spherical carbonate concretions are commonly observed in marine clayey sedimentary strata and often contain well preserved fossils. Previous studies revealed that the spherical concretions are formed by the very rapid reaction with decomposed organic matter from inside and Ca²⁺ ion of seawater. However, the detailed mass transport process during concretion formation has not been completely understood. Here two different size of spherical concretions, cm size of tusk-shell concretions and metre size of Moeraki boulders, are re-examined to understand the diffusion oriented formation process. Field observations, and detailed mineralogical (XRD) and geochemical analyses (SXAM, XRF, δ¹³C) revealed diffusive transport of HCO3⁻ from decaying organic matter and Ca²⁺ from surrounding pore-water of marine origin led to solid carbonate precipitation reactions that progressed from the margin of a concretion. Based on the compositional gradients across the concretions, a diffusion based diagram has been applied to estimate the growth rates of the different size of spherical concretions. The process and rate estimation indicate that even gigantic spherical concretions can form quite rapidly in the muddy matrices under a diffusion-controlled transport regime.
... Spherical carbonate (e.g., CaCO 3 ) concretions are observed in sedimentary strata of different geological ages worldwide (e.g., Sass and Kolodny, 1972;Baird et al., 1986;Pirrie and Marshall, 1991;Coleman, 1993;El Albani et al., 2001). Such concretions are common in fine marine sandstone to mudstone, with diameters ranging from a few centimeters to over 2 m (Boles et al., 1985;Coleman, 1993;Yoshida et al., 2018). Sedimentary structures in and around these concretions indicate frequent formation prior to substantial compaction of sediments (Sass and Kolodny, 1972;Pirrie and Marshall, 1991). ...
Spherical carbonate concretions are present in sedimentary strata of varying geological ages worldwide. Recent studies reveal that calcium carbonate concretions form very rapidly around dead organisms after burial in the seabed. However, the formation mechanism of spherical dolomite concretions in marine sediments, particularly the carbon source and the reason for their spherical shape, are still moderately known. This study aims to elucidate their formation process and diagenetic evolution through the characterization of the structure, mineralogical composition, and geochemistry in and around a concretion. Here, detailed studies were conducted on a gigantic dolomite concretion approximately 170 cm in diameter, which formed in tuffaceous fine sandstone of the Morozaki Group in Chita Peninsula, Japan. The Ca and Mg distributions in and around the concretion show that it rapidly formed by outward diffusion of bicarbonate from the carbon source in its center. The δ¹³C values ranging from +4.4‰ to +7.5‰ and large volume of dolomite cement indicate that the dolomite concretion formed at shallow depth from methanogenic organic matter decomposition during rapid sedimentation. Heulandite occurred only in the surrounding rock matrix comprising altered volcanic glasses because of high temperature during deep burial up to 2–4 km depth. This gigantic dolomite concretion properly preserves its evolution and changes in the superimposed post-depositional environment. This study shows that gaining a better understanding of spherical dolomite concretions can potentially help reveal the burial process of sediments during early diagenesis.
Diagenetische Reaktionen verlangen die Anwesenheit von Wasser als Porenlösung. Das Vorhandensein von Wasser im Porenraum ist Voraussetzung für die bei der Versenkungsdiagenese auftretenden mineralchemischen Reaktionen. Wo statt Wasser andere Porenfüller wie Öl, Gas oder mineralische Zemente die Poren besetzen, wird der Ablauf advektiv oder diffusiv beherrschter diagenetischer Prozesse unterbunden oder stark gehemmt.
Significance
We live on and among the by-products of fragmentation, from nanoparticles to rock falls to glaciers to continents. Understanding and taming fragmentation is central to assessing natural hazards and extracting resources, and even for landing probes safely on other planetary bodies. In this study, we draw inspiration from an unlikely and ancient source: Plato, who proposed that the element Earth is made of cubes because they may be tightly packed together. We demonstrate that this idea is essentially correct: Appropriately averaged properties of most natural 3D fragments reproduce the topological cube. We use mechanical and geometric models to explain the ubiquity of Plato’s cube in fragmentation and to uniquely map distinct fragment patterns to their formative stress conditions.
ResearchGate has not been able to resolve any references for this publication.