Biocrystallization models and skeletal structure of Phanerozoic corals

1996 ◽  
Vol 1 ◽  
pp. 159-185 ◽  
Author(s):  
James E. Sorauf
Keyword(s):  
Crystal Growth ◽  
Organic Matrix ◽  
Structural Motif ◽  
Skeletal Structure ◽  
Low Magnesium ◽  
Stony Corals ◽  
Fossil Corals ◽  
Magnesium Calcite ◽  
Matrix Control ◽  
Diagenetic History

Modern understanding of skeletal microstructure in fossil corals builds on knowledge of structure and biomineralization in modern corals and diagenesis of carbonate skeletons. It is agreed that the skeleton of living stony corals, the Scleractinia, is made of fibrous aragonite, with growth of biocrystals generally according to rules of crystal growth as observed in inorganic aragonite, but here controlled by organic matrix. Fossil scleractinians all apparently fit the same model of biomineralization seen in living corals, although some early taxa (Triassic) lack septal trabeculae, rod-like framework structures typical of all living and most fossil septate corals.Paleozoic corals, both septate Rugosa and non-septate Tabulata, had a skeleton of calcite, most likely low-magnesium calcite, thus had diagenetic histories differing considerably from the aragonitic Scleractinia. Agreement is lacking as to whether a single structural motif can be defined for the calcitic corals, that is, whether the Rugosa and Tabulata originally had a calcitic skeleton built of fibrous biocrystals, analogous to the scleractinians, or whether some others originally had a non-fibrous, lamellar skeletal microstructure. The disagreement hinges on whether both of these basic configurations are biogenic, or whether the latter is sometimes or always diagenetic in origin. The presence of matrix control over biomineralization in Rugosa and Tabulata is yet to be proven, but will play an important role in models for biocrystallization in these older cnidarians. Details of diagenetic history and modification of structures in these calcitic corals likewise warrant investigation to improve our ability to interpret the Paleozoic corals.

Skeletal microstructure, geochemistry, and organic remnants in Cretaceous scleractinian corals: Santonian Gosau Beds of Gosau, Austria

1999 ◽  
Vol 73 (6) ◽  
pp. 1029-1041 ◽  
Author(s):  
James E. Sorauf
Keyword(s):  
Trace Elements ◽  
Electron Micrographs ◽  
Upper Cretaceous ◽  
Organic Matrix ◽  
Skeletal Structure ◽  
Biogenic Origin ◽  
Fossil Corals ◽  
Formed Part ◽  
First Time ◽  
Distribution Of Trace Elements

Extremely well-preserved specimens of the species Rennensismilia complanata and Aulosmilia cuneiformis occur in Santonian (Upper Cretaceous) strata of the Lower Gosau beds, near Gosau, Austria. Two of these, here reported, have aragonitic skeletal mineralogy and skeletal structures that are typical for their families, and, in addition, show distribution of trace elements (Sr and Mg above all) that confirm the biogenic origin of structures observed. R. complanata also has proteinaceous matrix preserved within its skeleton, which, seen here for the first time in electron micrographs of living or fossil corals, forms sheaths of organic matrix surrounding bundles of skeletal crystallites. Matrix is most abundant along the axial plane of septa, which also is the first-formed part of each septum. Although A. cuneiformis lacks observable organic matrix materials, its skeletal structure and its distribution and amount of trace elements are analogous to that seen in R. complanata and also in modern corals.

scholarly journals Palaeozoic stromatoporoid diagenesis: a synthesis

Facies ◽  
2021 ◽  
Vol 67 (3) ◽  
Author(s):  
Stephen Kershaw ◽  
Axel Munnecke ◽  
Emilia Jarochowska ◽  
Graham Young
Keyword(s):  
Sediment Surface ◽  
Pore Waters ◽  
Middle Ordovician ◽  
Low Magnesium ◽  
Magnesium Calcite ◽  
Stage 1 ◽  
Diagenetic History ◽  
Pressure Dissolution

AbstractPalaeozoic stromatoporoids, throughout their 100-million + year history (Middle Ordovician to Late Devonian and rare Carboniferous), are better preserved than originally aragonite molluscs, but less well-preserved than low magnesium-calcite brachiopods, bryozoans, trilobites and corals. However, the original mineralogy of stromatoporoids remains unresolved, and details of their diagenesis are patchy. This study of approximately 2000 stromatoporoids and the literature recognises three diagenetic stages, applicable throughout their geological history. Timing of processes may vary in and between stages; some components are not always present. Stage 1, on or just below sediment surface, comprises the following: micrite filling of upper gallery space after death, then filling of any remaining space by non-ferroan then ferroan calcite in decreasing oxygen of pore-waters; partial lithification of associated sediment from which stromatoporoids may be exhumed and redeposited, evidence of general early lithification of middle Palaeozoic shallow-marine carbonates; microdolomite formation, with the Mg interpreted to have been derived from original high-Mg calcite (HMC) mineralogy (likely overlaps Stage 2). Stage 2, short distance below sediment surface, comprising the following: fabric-retentive recrystallisation (FRR) of stromatoporoid skeletons forming fabric-retentive irregular calcite (FRIC), mostly orientated normal to growth layers, best seen in cross-polarised light. FRIC stops at stromatoporoid margins in contact with sediment and bioclasts. FRIC geometry varies, indicating some taxonomic control. Evidence that FRIC formed early in diagenetic history includes syntaxial continuation of FRIC into some sub-stromatoporoid cavities (Type 1 cement), although others were pre-occupied by early cement fills (Type 2 cement) formed before FRR, preventing syntaxial continuation of FRIC into cavities. Likely contemporaneous with FRIC formation, stromatoporoids in argillaceous micrites drew carbonate from adjacent sediment during reorganisation of argillaceous micrite into limestone–marl rhythms that are also early diagenetic. Stage 3, largely shallow burial, comprises the following: dissolution and silicification, but these may have occurred earlier in stromatoporoid diagenetic histories (more data required); burial pressure dissolution forming stylolites.

scholarly journals Fossil Corals With Various Degrees of Preservation Can Retain Information About Biomineralization-Related Organic Material

2021 ◽  
Vol 9 ◽  
Author(s):  
Jeana L. Drake ◽  
Maxence Guillermic ◽  
Robert A. Eagle ◽  
David K. Jacobs
Keyword(s):  
Trace Element ◽  
Organic Matrix ◽  
Trace Element Composition ◽  
Element Composition ◽  
Living Tissue ◽  
Coral Skeletons ◽  
Meaningful Information ◽  
Biomineralization Process ◽  
Fossil Corals ◽  
Molecular Components

Scleractinian corals typically form a robust calcium carbonate skeleton beneath their living tissue. This skeleton, through its trace element composition and isotope ratios, may record environmental conditions of water surrounding the coral animal. While bulk unrecrystallized aragonite coral skeletons can be used to reconstruct past ocean conditions, corals that have undergone significant diagenesis have altered geochemical signatures and are typically assumed to retain insufficient meaningful information for bulk or macrostructural analysis. However, partially recrystallized skeletons may retain organic molecular components of the skeletal organic matrix (SOM), which is secreted by the animal and directs aspects of the biomineralization process. Some SOM proteins can be retained in fossil corals and can potentially provide past oceanographic, ecological, and indirect genetic information. Here, we describe a dataset of scleractinian coral skeletons, aged from modern to Cretaceous plus a Carboniferous rugosan, characterized for their crystallography, trace element composition, and amino acid compositions. We show that some specimens that are partially recrystallized to calcite yield potentially useful biochemical information whereas complete recrystalization or silicification leads to significant alteration or loss of the SOM fraction. Our analysis is informative to biochemical-paleoceanographers as it suggests that previously discounted partially recrystallized coral skeletons may indeed still be useful at the microstructural level.

Functional analyses of chitinolytic enzymes in the formation of calcite prisms inPinctada fucata

2019 ◽  
Author(s):  
Hiroyuki Kintsu ◽  
Alberto Pérez-Huerta ◽  
Shigeru Ohtsuka ◽  
Taiga Okumura ◽  
Shinsuke Ifuku ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Crystal Growth ◽  
Calcium Carbonate ◽  
Small Angle ◽  
Organic Matrix ◽  
Pinctada Fucata ◽  
Prismatic Layer ◽  
Chitinolytic Enzymes ◽  
Organic Matrices

Abstract Background: The mollusk shells present distinctive microstructures that are formed by small amounts of organic matrices controlling the crystal growth of calcium carbonate. These microstructures show superior mechanical properties such as strength or flexibility. The shell of Pinctada fucata has the prismatic layer consisting of prisms of single calcite crystals. These crystals contain small-angle grain boundaries caused by a dense intracrystalline organic matrix network to improve mechanical strength. Previously, we identified chitin and chitinolytic enzymes as components of this intracrystalline organic matrix. In this study, we analyzed the function of those organic matrices in calcium carbonate crystallization by in vitro and in vivo experiments.Results: We analyzed calcites synthesized in chitin gel with or without chitinolytic enzymes by using transmission electron microscope (TEM) and atom probe tomography (APT). TEM observations showed that grain boundary was more induced as concentration of chitinolytic enzymes increased and thus, chitin became thinner. In an optimal concentration of chitinolytic enzymes, small-angle grain boundaries were observed. APT analysis showed that ion clusters derived from chitin were detected. In order to clarify the importance of chitinolytic enzymes on the formation of the prismatic layer in vivo , we performed the experiment in which chitinase inhibitor was injected into a living Pinctada fucata and then analyzed the change of mechanical properties of the prismatic layer. The hardness and elastic modulus increased after injection of chitinase inhibitor. Electron back scattered diffraction (EBSD) mapping data showed that the spread of crystal orientations in whole single crystal also increased by the effect of inhibitor injections.Conclusion: Our results suggested that chitinolytic enzymes may function cooperatively with chitin to regulate the crystal growth and mechanical properties of the prismatic layer, and chitinolytic enzymes are essential for the formation of the normal prismatic layer of P. fucata.

Effect of sulfate on magnesium incorporation in low-magnesium calcite

2019 ◽  
Vol 265 ◽  
pp. 505-519 ◽  
Author(s):  
Katja E. Goetschl ◽  
Bettina Purgstaller ◽  
Martin Dietzel ◽  
Vasileios Mavromatis
Keyword(s):  
Low Magnesium ◽  
Magnesium Calcite

Controlled Crystallization and Transformation of Carbonate Minerals with Dumbbell-like Morphologies on Bacterial Cell Templates

2020 ◽  
Vol 26 (2) ◽  
pp. 275-286 ◽  
Author(s):  
Chonghong Zhang ◽  
Fuchun Li ◽  
Jun Sun ◽  
Jiejie Lv
Keyword(s):  
Crystal Growth ◽  
Composite Materials ◽  
Formation Mechanism ◽  
Bacterial Cell ◽  
Industrial Applications ◽  
Industrial Engineering ◽  
Potential Significance ◽  
Magnesium Calcite ◽  
Controlled Crystallization ◽  
Template Region

AbstractResearch on the biogenic-specific polymorphism and morphology of carbonate has been gaining momentum in the fields of biomineralization and industrial engineering in recent years. We report the nucleation of carbonate particles on bacterial cell templates to produce a novel dumbbell-like morphology which was assembled by needle-like crystals of magnesium calcite or aragonite radiating out from both ends of the template bacterium. Mature dumbbell-like structures had a tendency to break apart in the central template region, which was made up mostly of weak amorphous carbonate. Further crystal growth, especially at the template region, transformed the broken pieces into spherulites. Rod-like cell templates were essential for the formation of dumbbell-like morphologies, and we propose a possible formation mechanism of the dumbbell-like morphology. Our findings provide new perspectives on the morphological formation mechanism in biomineralization systems and may have a potential significance in assembling composite materials suitable for industrial applications.

New constraints on the formation of hydrocarbon-derived low magnesium calcite at brine seeps in the Gulf of Mexico

2020 ◽  
Vol 398 ◽  
pp. 105572 ◽  
Author(s):  
Huiwen Huang ◽  
Xudong Wang ◽  
Shanggui Gong ◽  
Nicola Krake ◽  
Meng Jin ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Low Magnesium ◽  
Magnesium Calcite

scholarly journals STUDIES ON SHELL FORMATION

1961 ◽  
Vol 9 (4) ◽  
pp. 761-771 ◽  
Author(s):  
Norimitsu Watabe ◽  
Karl M. Wilbur
Keyword(s):  
Crystal Growth ◽  
Dendritic Growth ◽  
Three Dimensional ◽  
Outer Part ◽  
Organic Matrix ◽  
Transitional Zone ◽  
Homogeneous State ◽  
Concentration Gradients ◽  
Strong Concentration ◽  
Small Crystals

Details of crystal growth in the calcitostracum of Crassostrea virginica have been studied with the purpose of analyzing the formation of the overlapping rows of oriented tabular crystals characteristic of this part of the shell. Crystal elongation, orientation, and dendritic growth suggest the presence of strong concentration gradients in a thin layer of solution in which crystallization occurs. Formation of the overlapping rows can be explained by three processes observed in the shell: a two-dimensional tree-like dendritic growth in which one set of crystal branchings creeps over an adjacent set of branchings; three-dimensional dendritic growth; and growth by dislocation of crystal surfaces. Multilayers of crystals may thus be formed at one time. This is favored by infrequent secretion of a covering organic matrix which would inhibit crystal growth. The transitional zone covering the outer part of the calcitostracum and the inner part of the prismatic region is generally characterized by aggregates of small crystals with definite orientation. Growth in this zone appears to take place in a relatively homogeneous state of solution without strong concentration gradients. Thin membranes and bands of organic matrix were commonly observed in the transitional zone bordering the prismatic region. The membrane showed a very fine oriented network pattern.

Geochemistry and time-series analyses of orbitally forced Upper Cretaceous marl–limestone rhythmites (Lehrte West Syncline, northern Germany)

2005 ◽  
Vol 142 (1) ◽  
pp. 31-55 ◽  
Author(s):  
BIRGIT NIEBUHR
Keyword(s):  
Clay Minerals ◽  
Low Frequency ◽  
Geochemical Data ◽  
Carbonate Content ◽  
Element Geochemistry ◽  
Low Magnesium ◽  
Magnesium Calcite ◽  
High Carbonate ◽  
Time Series Analyses ◽  
End Members

A cyclic marl–limestone succession of Middle–Late Campanian age has been investigated with respect to a Milankovitch-controlled origin of geochemical data. In general, the major element geochemistry of the marl–limestone rhythmites can be explained by a simple two-component mixing model with the end-members calcium carbonate and ‘average shale’-like material. Carbonate content varies from 55 to 90%. Non-carbonate components are clay minerals (illite, smectite) and biogenic silica from sponge spicules, as well as authigenically formed zeolites (strontian heulandite) and quartz. The redox potential suggests oxidizing conditions throughout the section. Trace element and stable isotopic data as well as SEM investigations show that the carbonate mud is mostly composed of low-magnesium calcitic tests of planktic coccolithophorids and calcareous dinoflagellate cysts (calcispheres). Diagenetic overprint results in a decrease of 2% δ18O and an increase in Mn of up to 250 ppm. However, the sediment seems to preserve most of its high Sr content compared to the primary low-magnesium calcite of co-occurring belemnite rostra. The periodicity of geochemical cycles is dominated by 413 ka and weak signals between 51 and 22.5 ka, attributable to orbital forcing. Accumulation rates within these cycles vary between 40 and 50 m/Ma. The resulting cyclic sedimentary sequence is the product of (a) changes in primary production of low-magnesium calcitic biogenic material in surface waters within the long eccentricity and the precession, demonstrated by the CaCO3 content and the Mg/Al, Mn/Al and Sr/Al ratios, and (b) fluctuations in climate and continental weathering, which changed the quality of supplied clay minerals (the illite/smectite ratio), demonstrated by the K/Al ratio. High carbonate productivity correlates with smectite-favouring weathering (semi-arid conditions, conspicuously dry and moist seasonal changes in warmer climates). Ti as the proxy indicator for the detrital terrigenous influx, as well as Rb, Si, Zr and Na, shows only low frequency signals, indicating nearly constant rates of supply throughout the more or less pure pelagic carbonate deposition of the long-lasting third-order Middle–Upper Campanian sedimentary cycle.

Sign in / Sign up

Export Citation Format

Share Document