Origin and paleoecology of Middle Jurassic hiatus concretions from Poland

Bored and encrusted carbonate concretions, termed hiatus concretions, coming from the Middle Jurassic (Upper Bajocian and Bathonian) siliciclastics of the Polish Jura, south-central Poland, have been subjected to detailed paleoecological investigation for the first time. The concretions possess variable morphology and bear distinct traces of bioerosion and encrustation as a result of exhumation on the sea floor during intervals of low sedimentation and/or erosion. The borings are dominated by Gastrochaenolites and Entobia. Epilithozoans, represented by at least 26 taxa, are dominated by sabellid/serpulid worm tubes and bryozoans, while sponges and corals are minor. No relationship between the concretion size and the number of encrusters has been found, suggesting that concretion size was not the primary factor controlling diversity. Stable isotope analyses and the presence of crustacean scratch marks and Rhizocorallium traces on many of the hiatus concretions indicate that they formed just below the sediment–water interface, within the sulfate reduction zone. Moreover, crustacean activities may have been a prelude to their origin, as shapes of many concretions closely resemble thalassinoidean burrow systems. It is also possible that crustacean activity around the concretions promoted their exhumation by loosening the surrounding soft sediment. The presence of borings and encrusters on different concretion surfaces, as well as truncated borings and a number of abraded epilithozoans, indicate that after the concretions were exhumed they were repeatedly overturned and moved on the sea floor, probably due to episodic storm-related bottom currents in shallow subtidal environment.     

Formation of large carbonate concretions in black cherts in the Gufeng Formation (Guadalupian) at Enshi,South China

The formation of carbonate concretions is a cementation process which passively infills the pore spaces within sediments. They record the original environments of deposition and diagenetic conditions of the host rocks. Little is known about the precise mechanisms responsible for the precipitation of carbonate concretions. The most common host rocks are mudstones/shales, sandstones, and limestones. This study presents an example of large carbonate concretions from an unusual host rock, the black bedded cherts of the Gufeng Formation (Guadalupian) at Enshi on the northern Yangtze Platform, South China. Petrographic observations (X‐ray diffraction, optical microscopy, scanning electron microscopy) and multiple geochemical analyses (pyrite‐ and carbonate‐associated‐sulfate (CAS)‐sulfur isotopes, carbon isotopes) indicate that (a) the studied carbonate concretion are mainly composed of micritic calcite with subordinate dolomite; (b) the concretions may have been mainly formed in the bacterial sulfate reduction (BSR) zone during very early diagenesis near the sediment–water surface; (c) the paleo‐bottom water overlying the sediments during formation of the concretions was mainly euxinic; and (d) the growth of the studied concretions proceeded via a pervasive model, where later cementation phase initiated in the lower part of the concretions and progressed upward.     

Role of Fungal Mycelium in the Formation of Carbonate Concretions in Growing Media—An Investigation by SEM and Synchrotron-Based X-Ray Tomographic Microscopy

Soil fungi can facilitate calcification. Mushroom Morchella sp . mycelium induced the formation of carbonate concretions on the surface of an organic-based growing media amended with sand and ground limestone. According to SEM observation and X-ray-tomographic microscopy a dense mycelial network induced calcification. The CaCO₃ content of concretions (?: 0.3–1.5 cm) was found to be at 30%. Microsparitic calcite cemented the pores between the sand grains forming a dense clogging microstructure. Besides water uptake by the mycelium, a high evaporation rate and a decrease in pCO₂ contributed to the formation of the concretions. Fungal mycelium in the concretions is surrounded by voids indicating that at the surface of the mycelium, calcification is counteracted most probably by the release of organic acids.     

Ultrastructural data on the scales of the dipnoan Protoptems annectens (Sarcopterygii, Osteichthyes)

The structure and the mineralization of the scales of the living dipnoan (lungfish) Protoptems annectens have been investigated by transmission electron microscopy (TEM). The thin and imbricated scales are composed of two layers: the squamulae and the basal plate. At the outer surface, the squamulae form isolated plates superficially ornamented with spines and concretions and made up of acellular bone. After demineralization, the squamulae show a heterogeneous organic matrix composed of thin randomly oriented collagen fibrils forming a loose network within which the concretions appear as electronlucent circular areas. Abundant and aggregated concretions are located within the spines. The crystallites are oriented by the collagen fibrils except in the concretions. Anchoring bundles composed of parallel collagen fibrils arise from the squamulae and connect the scales to the overlying dermis.
The basal plate, the most developed part of the scale, is made up of isopedine. Its main component consists of thick, closely packed collagen fibrils organized in a 'double twisted plywood-like structure'. Fibroblasts are present in the basal plate. Mineralization occurs only in few plies located beneath the squamulae. Mandl's corpuscles are found in front of the mineralization front. The mineral deposit is oriented by the collagen fibrils.
The scales of Protoptems annectens differ from the typical elasmoid scales of the teleosts by the peculiar structure of the squamulae, nevertheless they show enough structural characteristics to support the hypothesis that they can be considered as scales of the elasmoid grade, which have retained some plesiomorphic characteristics.     

Occurrence and regional distribution of calcareous concretions in the rat pineal gland

Summary Serial sections of 90 Sprague-Dawley rat brains with the pineal in situ were scanned to determine the occurrence and regional distribution of calcareous concretions within the pineal gland and its surrounding leptomeningeal tissue. In 90 % of the cases examined concretions were found in varying number and appearance, predominantly lying in the dorsal region of the pineal gland and in the distal portion of the pineal stalk.Discussing the hypothesis advanced by Lukaszyk and Reiter (1975) that the origin of pineal concretions may be related to a neurosecretory process involving a pineal carrier protein, called neuroepiphysin, it is thought that, in view of the intra- and extra-pineal occurrence of concretions, processes other than secretion should be considered. Since in the pineal organ lymphatics are lacking it may well be that, due to a reduced drainage of tissue fluid, the coagulation of intercellular organic debris mingled with minerals increases with age.Supported by a grant (Vo 135/4) of the Deutsche Forschungsgemeinschaft within the Schwerpunktprogramm Neuroendokrinologie     

Microbial manganese oxidation and nitrification in relation to the occurrence of macrophyte roots in a lacustrine sediment

Aquatic macrophytes in the Concretion Cove area of Lake Charlotte, Nova Scotia, Canada appear to restrict microbial manganese oxidation to the production of dispersed, microscopic oxides within sediments. When macrophyte roots are not present in the sediments, large ferromanganese concretions are found at the sediment surface. Macrophyte roots and the manganese oxidizers may have also played a role in the restriction of nitrification to deeper in the sediments.     

Increase in number and size of kidney concretions as a result of PCP exposure in the freshwater snail Planorbarius corneus (Gastropoda, Pulmonata)

Molluscan kidneys are able to excrete solids in the urine in the form of concretions. It is thought that increased formation of these concretions occur under pollutant, environmentally or reproductive induced stress. This study examined the formation of concretions in the kidney of the freshwater snail Planorbarius corneus L. experimentally exposed to pentachlorophenol (PCP). Light microscopic histopathological analysis of the PCP-exposed P. corneus revealed significantly enhanced production of the kidney concretions when compared to the kidneys of control individuals. Measurements of the number of kidney concretions, the apparent area of the concretions, and the epithelial area filled with concretions indicated an increase in the number and size of concretions in all treated snails. Lipofuscin content of excretory cell concretions was detected.     

Study of a DC gas discharge with a copper cathode in a water flow

A dc gas discharge between copper electrodes in the current range of 5–20 А was studied experimentally. The discharge gap length was varied within 45–70 mm. The cathode was a 10-mm-diameter rod placed in the water flowing out from a dielectric tube. Three discharge configurations differing in the position of the cathode upper end with respect to the water surface were considered: (i) above water; (ii) flush with the water surface, and (iii) under water. The electric and optical characteristics of the discharge in the second configuration were studied in more detail. It is established that the discharge properties are similar to those of an electric arc. Considerable cathode erosion was observed in the third configuration. It is revealed that fine-dispersed copper grains form in the course of erosion.     

Reworked marine sandstone concretions: a record of high-frequency shallow burial to exhumation cycles

Concretions, with abundant calcite-dolomite cement-replacement textures originally hosted in shallow-marine sandstones, were reworked into Lower Cretaceous fluvio-deltaic conglomerates and shoreface sandstones (External Zones, Betic Cordillera). A cycle of host sand deposition, early diagenetic concretion formation and concretion reworking is documented: (1) Well-sorted shoreface sandstone deposited. (2) Spherical to ovoid, non-ferroan calcite-cemented concretions formed below flooding surfaces at shallow-burial depths during early eodiagenesis. Non-ferroan calcite cements were precipitated from the bicarbonate derived from seawater and from dissolution of marine bioclasts, as shown by isotope analyses. (3) Concretions were reworked and exposed on the seafloor in a high-energy setting as indicated by the presence of numerous bivalve borings (Entobia ichnofacies), laminated micritic microbial crusts around the concretions, and epilithobionts (oysters, barnacles and corals) on the concretion surface. Concretions also appear as erosional remnants on the floor of channels which were incised into the shoreline sandstone when sea-level fell. (4) The fluvio–deltaic channels were filled with sediment during flooding in the late lowstand of sea-level. (5) The concretions are partly dolomitized, and the presence of siderite, pyrite and barite in the outer part of the concretions precipitated before the dolomite, suggests that the latter formed during shallow burial.     

Preservation of overmature,ancient, sedimentary organic matter in carbonate concretions during outcrop weathering

Concretions are preferentially cemented zones within sediments and sedimentary rocks. Cementation can result from relatively early diagenetic processes that include degradation of sedimentary organic compounds or methane as indicated by significantly ¹³C‐depleted or enriched carbon isotope compositions. As minerals fill pore space, reduced permeability may promote preservation of sediment components from degradation during subsequent diagenesis, burial heating and outcrop weathering. Discrete and macroscopic organic remains, macro and microfossils, magnetic grains, and sedimentary structures can be preferentially preserved within concretions. Here, Cretaceous carbonate concretions of the Holz Shale are shown to contain relatively high carbonate‐free total organic carbon (TOC) contents (up to ~18.5 wt%) compared to the surrounding host rock (with <2.1 wt%). TOC increases with total inorganic carbon (TIC) content, a metric of the degree of cementation. Pyrite contents within concretions generally correlate with organic carbon contents. Concretion carbonate carbon isotope compositions (δ¹³C_carb) range from ?22.5 to ?3.4‰ (VPDB) and do not correlate strongly with TOC. Organic carbon isotope compositions (δ¹³C_org) of concretions and host rock are similar. Thermal maturity data indicate that both host and concretion organic matter are overmature and have evolved beyond the oil window maturity stage. Although the organic matter in general has experienced significant oxidative weathering, concretion interiors exhibit lower oxygen indices relative to the host. These results suggest that carbonate concretions can preferentially preserve overmature, ancient, sedimentary organic matter during outcrop weathering, despite evidence for organic matter degradation genetic mechanisms. As a result, concretions may provide an optimal proxy target for characterization of more primary organic carbon concentrations and chemical compositions. In addition, these findings indicate that concretions can promote delayed oxidative weathering of organic carbon in outcrop and therefore impact local chemical cycling.     

Fine structure and X-ray microanalysis of mineralized concretions in the Malpighian tubules of the housefly, Musca domestica

The epithelium and the lumen of the Malpighian tubules of the housefly contains mineralized dense bodies called concretions. The morphological characteristics, mode of origin, nature of the sequestered elements and the age-associated changes in the distribution of concretions are reported. There are three types of concretions in the cytoplasm, which have been designated as type A, type B, and type C. Type A concretions are membrane-bound spherical structures which may arise by the gradual intravacuolar accumulation of dense material. Type B concretions appear to be related to multivesicular bodies. Type C concretions are heteromorphic and morphologically resemble the residual bodies. They show a positive localization of acid phosphatase reaction product. X-ray microanalysis of intracytoplasmic and intraluminal concretions revealed the presence of phosphorus, sulphur, chlorine, calcium, iron, zinc and copper. There was no evidence suggesting the extrusion of the intracytoplasmic concretions into the lumen of the Malpighian tubules. There is an age-associated increase in the distribution of type C concretions. It is hypothesized that the sequestration of metal ions within the concretions may provide a means for the effective excretion of these elements.     

The interplay between event and background sedimentation and the origin of fossil‐rich carbonate concretions: a case study in Permian rocks of the Paraná Basin,Brazil

The Permian Serra Alta Formation was generated under transgressive conditions within a large, calm epeiric sea. A monotonous succession of ‘barren’, massive mudstones deposited under oxygen‐deficient conditions (mainly below storm wave base) is the main lithofacies of this unit. Fossils are generally rare and diluted in the matrix, but certain intervals contain shell‐rich concentrations with well‐preserved, closed articulated bivalves, mixed with shells and comminuted debris with variable quality of preservation, all encased in carbonate concretions. Two main scenarios may account for the origin of these bivalve‐rich concretions (i.e. unique events in sea‐water chemistry or unique burial‐starvation couplets). Sedimentological and taphonomic information indicates that the final deposition of the original shell‐rich mudstone intervals was probably tied to episodic influx of fine‐grained sediments in distal settings. Moderate bioturbation is also recorded suggesting low rates of sedimentation prior to early diagenesis. Hence, the fossil concentrations in concretions were formed due to the interplay of event and background sedimentation. These are internally simple concentrations with complex depositional histories. The concretion‐bearing beds are not randomly distributed in the Serra Alta Formation. Rather, they are found in the sparsely fossiliferous offshore deposits of the basal to intermediate portions of the unit. Thus, the concretionary mudstone beds and associated deposits are preserved in particular intervals and can be tracked for kilometres. This indicates that the conditions essential for concretion development existed only at particular stratigraphical intervals. Finally, our study strongly corroborates the idea that concretions are critical sources of sedimentological, taphonomic and stratigraphical information.     

The formation of type-I concretions in Drosophila Malpighian tubules studied by electron microscopy and X-ray microanalysis

There are two types of concretions in Drosophila Malpighian tubules: Type-I concretions originate in the distal segments of the anterior tubules, type-II concretions in the adjacent transitional segment between the apical microvilli. Type-I concretions are formed with the aid of carbonic anhydrase within intracellular vesicles, which migrate to the apical cell membrane where they are discharged into the lumen by exocytosis. The carbonic anhydrase inhibitors acetazolamide or hydrochlorothiazide prevent the formation of concretions by interruption of bicarbonate supply. In addition, the formation of concretions can be reduced by feeding with sodium cellulose phosphate.     

Origin,structure, composition and age-dependence of mineralized dense bodies (concretions) in the midgut epithelium of the adult housefly, Musca domestica

The epithelial cells of the midgut in 1–40 day old adult female houseflies were examined by electron microscopic, X-ray microanalytic and histochemical techniques in order to study the mode of genesis, chemical nature and age-associated distribution of dense bodies. Dense bodies contain high concentrations of phosphorus, sulphur, chlorine, calcium, iron and copper; they are therefore termed concretions. Concretionary material is initially deposited within Golgi vesicles, lamellar bodies and residual bodies. The average size of the concretion granules and the concentration of the sequestered material increases with age, while new concretions are continually formed throughout life. With advancing age, concretions accumulate in the epithelial cells and occupy a considerable proportion of the cytoplasm in old flies. It is postulated that the concretions sequester superfluous minerals and may play an important role in the excretory system of the adult housefly.     

A new model of the formation of Pennsylvanian iron carbonate concretions hosting exceptional soft‐bodied fossils in Mazon Creek,Illinois

Preservation of Pennsylvanian‐aged (307 Ma) soft‐bodied fossils from Mazon Creek, Illinois, USA, is attributed to the formation of siderite concretions, which encapsulate the remains of terrestrial, freshwater, and marine flora and fauna. The narrow range of positive δ³⁴S values from pyrite in individual concretions suggests microenvironmentally limited ambient sulfate, which may have been rapidly exhausted by sulfate‐reducing bacteria. Tissue of the decaying carcass was rapidly encased by early diagenetic pyrite and siderite produced within the sulfate reduction and methanogenic zones of the sediment, with continuation of the latter resulting in concretion cementation. Cross‐sectional isotopic analyses (δ¹³C and δ¹⁸O) and mineralogical characterization of the concretions point to initiation of preservation in high porosity proto‐concretions during the early phases of microbially induced decay. The proto‐concretion was cemented prior to compaction of the sediments by siderite as a result of methanogenic production of ¹³C‐rich bicarbonate—which varies both between Essex and Braidwood concretions and between fossiliferous and unfossiliferous concretions. This work provides the first detailed geochemical study of the Mazon Creek siderite concretions and identifies the range of conditions allowing for exceptional soft‐tissue fossil formation as seen at Mazon Creek.     

Fluorescence microscopy of pollen and spores: a tool for investigating environmental change

Fluorescence microscopy of fossil pollen and spores has only been exploited by palynologists for geological time scales. A reconstruction of ecological change, blanket peat erosion and consequent sediment flux within an area of moorland in the north of England during the late Holocene has provided an opportunity to evaluate whether fluorescence microscopy of pollen and spores can be used as a tool for reconstructing environmental change at shorter and more recent timescales.The fluorescence properties of pollen and spores in samples of blanket peat (sediment source) and reservoir sediments (sediment sink) were assessed during routine pollen counts. Fluorescence varied with taxon. Bog surface processes such as moorland fire and dessication were observed to have no visible effect on fluorescence, but air pollution deposition (indicated by Pb) did have an effect, although exactly which pollutant(s) is responsible is unclear.The effect on fluorescence of the physical processes associated with peat erosion and re-sedimentation in reservoirs was examined. Spores of lower plants found in reservoir sediment samples with a high content of eroded peat were well preserved (fluorescing at blue-green wavelengths), suggesting that the eroded peat was transported from the bog surface to the reservoir as peat fragments containing pollen and spores. There is a direct correlation between the proportions of pollen and spores with extinguished fluorescence (very poor preservation state) in sediment samples, and sediment accumulation rate. This relationship is probably not applicable for quantitatively estimating sedimentation rate at other sites due to the effect of local factors. However, the relationship can provide the basis for a simple, quick and relatively inexpensive method of examining qualitative shifts in sediment flux, which can be conducted during routine pollen counts.     

The pineal gland of the gerbil,Meriones unguiculatus

Summary Electron microscopy was employed in a study of the pineal gland of the Mongolian gerbil (Meriones unguiculatus). It was determined that the gerbil pineal gland contains pinealocytes and glial cells with the pinealocytes being the predominant cell type. The pinealocytes contain numerous organelles traditionally considered as being either synthetic or secretory in function such as an extensive Golgi region, smooth (SER) and rough (RER) endoplasmic reticulum, secretory vesicles and microtubules. Other cytoplasmic components are also present in the pinealocytes (synaptic ribbons, subsurface cisternae) for which no function has been assigned. Dense-cored vesicles are rare. Vacuolated pinealocytes are present and appear to be intimately associated with the formation of the pineal concertions. Evidence presented supports the proposal that the concretions form within the vacuoles. Once the concretions reach an enlarged state, the vacuolated pinealocytes break down and the concretions are thus extruded into the extracellular space where they apparently continue to increase in size. The morphology of the glial cells was interpreted as indicative of a high synthetic activity. The glial cells contain predominantly the rough variety of endoplasmic reticulum and form an expansion around the wide perivascular area.Supported by NSF grant PCM 77-05734     

Posthodiplostomum minimum: Examination of cyst wall and metacercaria containing calcarious concretions with scanning electron microscopy and X-ray microanalysis

Scanning electron micrographs show a smoothly fibrous structure of the cyst wall of the trematode Posthodiplostomum minimum, whereas the enclosed metacercaria posses a porous and papillate surface with occasional spines. Numerous excretory concretions fill the body of the metacercaria. The concretions appear layered from a central core and show an abundance of calcium, and, in some cases, magnesium.     

Phosphorylation of serine residues is fundamental for the calcium-binding ability of Orchestin,a soluble matrix protein from crustacean calcium storage structures

Orchestia cavimana is a terrestrial crustacean, which cyclically stores calcium in diverticula of the midgut, in the form of calcified amorphous concretions. These concretions are associated with a proteinaceous matrix, the main constituent of the soluble matrix is Orchestin, an acidic calcium-binding protein [Testenière et al., Biochem. J. 361 (2002) 327-335]. In the present paper, we clearly demonstrate that Orchestin is phosphorylated on serine and tyrosine residues, but that calcium binding only occurs via the phosphoserine residues. To our knowledge, this is the first example of an invertebrate mineralization for which a post-translational modification is clearly related to an important function of a calcifying protein.     

Paleontological evidence of a brief global sea-level event during the last interglacial

A gently undulating to flat erosion surface with shallow-water borings and burrows is present in the midst of a Sangamonian (Eemian; marine oxygen isotope substage 5e) reefal facies on the islands of San Salvador and Great Inagua, Bahamas. Precise U/Th dating of corals above and below this surface show that it formed around 125-124 ka, and that the sea-level regressive-transgressive cycle which produced it lasted for 1500 years or less. The surface occurs on entirely carbonate rocks and has a low relief punctuated by erosional channels and karstic caves formed during the sea-level lowstand. A terra rossa paleosol, developed during that lowstand, partially fills a set of large lithophagid bivalve borings ( Gastrochaenolites torpedo ), showing that they were excavated during the regression. Rhizomorphs formed by plant roots occur on the erosion surface at Great Inagua. Extensive boring of the upward-facing surfaces occurred during the ensuing transgression, including a smaller G. torpedo and a clionid sponge boring ( Entobia ovula ). The bored surface is encrusted by a variety of shallow-water corals and, eventually, the re-established bank-barrier coral reefs. A sparse assemblage of serpulid worm and vermicularid gastropod tubes encrusted the channel and cave walls. Robust Ophiomorpha burrow systems occur within pockets of sediment in the coral facies both below and above the erosion surface. The channels and caves are filled with transgressive calcarenitic sediments in which occur numerous Ophiomorpha and Skolithos burrows. The ichnofossils on, below, and above this erosion surface are prominent indicators of a short-lived but significant global sea-level event.