Oolitic Grains Research Articles

New data on Hirnantian (latest Ordovician) postglacial carbonate rocks and fossils in northern Guizhou, Southwest China

The Kuanyinchiao Formation (Hirnantian, Upper Ordovician), yielding the typical Hirnantia fauna, has commonly been accepted as representing cool-water sediments deposited during the glacial interval in the Hirnantian Global Boundary Stratotype Section and Point (GSSP) region of South China. Recent investigation reveals that the uppermost carbonate-dominated part of this formation yields a warm-water rugose coral fauna with Silurian affinities at many localities of northern Guizhou Province, which substantially differs from the underlying cool-water fauna. This suggests that these carbonates were probably postglacial warm-water sediments, rather than having formed during the Hirnantian glacial interval as previously thought. Such a conclusion is consistent with the evidence from the associated brachiopod fauna, i.e., the Dalmanella testudinaria – Dorytreta longicrura community, which is similarly distinct from the underlying typical Hirnantia fauna. The sedimentological data show warm-water features at the same level (e.g., the presence of oolitic grains), also supporting this new interpretation.

Bacterial community of oolitic carbonate sediments of the Bahamas Archipelago

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 485:9-24 (2013) - DOI: https://doi.org/10.3354/meps10359 Bacterial community of oolitic carbonate sediments of the Bahamas Archipelago Mara R. Diaz1,*, Alan M. Piggot2, Gregor P. Eberli2, James S. Klaus2,3 1Marine Biology and Fisheries, and 2Marine Geology and Geophysics, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida 33149, USA 3Department of Geological Sciences, University of Miami, Coral Gables, Florida 33146, USA *Email: mdiaz@rsmas.miami.edu ABSTRACT: The present study characterized bacterial communities associated with oolitic carbonate sediments from the Bahamas Archipelago, ranging from high-energy ‘active’ to lower energy ‘non-active’ and ‘mat-stabilized’ environments. Bacterial communities were analyzed using terminal restriction fragment length polymorphisms (TRFLP), clone analyses of the 16S rRNA gene, confocal laser scanning microscopy (CLSM) and the quantitative phenol-sulfuric acid assay for extracellular polymeric substances (EPS). Confocal imaging of oolitic grains stained with cyanine dye-conjugated lectin and EPS quantification demonstrated that all 3 environments harbored attached biofilm communities, but densities increased from the active to the mat-stabilized environment. Bacterial communities associated with all 3 settings were highly diverse and dominated by Proteobacteria (50 to 61%). Analysis of similarity (ANOSIM) and similarity percentages (SIMPER) revealed significant differences among the 3 environments in the relative abundance of Proteobacteria, Planctomycetes, Cyanobacteria, Chlorobi, and Deinococcus-Thermus. Bacterial primary production in the active shoal environment was associated with Rhodobacteraceae, Ectothiorhodospiraceae, and Chlorobi, whereas the lower energy environments appear to harbor a more complex consortium of aerobic photoautotrophs and anaerobic/aerobic anoxygenic phototrophs. The ubiquitousness of photosynthetizers, along with the presence of aerobic/anaerobic heterotrophic microbes (e.g. denitrifiers, sulfate-reducers, biofilm producers/degraders) and the gradient increase in biofilm production on ooid grains from active to mat-stabilized environments, support the potential involvement of these communities in biomineralization and carbonate precipitation. KEY WORDS: Ooids · Carbonate sediment · Carbonate precipitation · 16S rRNA diversity · Bacterial community · Biofilm Full text in pdf format Supplementary material PreviousNextCite this article as: Diaz MR, Piggot AM, Eberli GP, Klaus JS (2013) Bacterial community of oolitic carbonate sediments of the Bahamas Archipelago. Mar Ecol Prog Ser 485:9-24. https://doi.org/10.3354/meps10359 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 485. Online publication date: June 27, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Deposition of serpentine-bearing conglomerate and its implications for Early Cretaceous tectonics in northern Japan

The discovery of serpentinite-bearing conglomerate including detrital blue amphibole grains in Cretaceous forearc basin sediments in the northern part of Japan supports large tectonic movement in the forearc basin during the Early Cretaceous. Conglomerate and sandstone are intercalated in the Lower Cretaceous offshore mudstone sequence and contain serpentinite clasts, chromian spinels, blue amphiboles, and oolitic grains with chromian spinel nuclei. The conglomerate and sandstones were deposited as a debris flow consisting of an admixture of siliciclastic terrigenous sediments and calcareous biogenic material with serpentinite-derived sediments. The sandstones consist of feldspathic–lithic arenites and wackes, and their composition suggests that most of the terrigenous material was derived from the Cretaceous volcanic terrane and the Jurassic accretionary complex located to the west of the depositional basin. However, the serpentinite body correlated with the provenance of the sediments is not distributed in these terranes. Because the oolitic grains in the matrix of the conglomerate include only angular chromian spinels and serpentine clasts without quartz and feldspar grains, most of the serpentinite-derived sediments are considered to have been supplied primarily from a serpentinite body exposed along the shallow marine environments near the sedimentary basin. Therefore, the serpentine-derived sediments and feldspathic and lithic materials have essentially different sources. Thus, we may infer that the examined sediments are due to large slope failure affecting a relatively wide area of shallow coast involving the place where the serpentine body was emplaced and the place where river-fed terrigenous siliciclastic sediments accumulated. The stratigraphic range of the serpentinite-derived sediments, which are sporadically distributed in the Cretaceous forearc basin of northern Japan, suggests that the serpentinite-derived material was actively supplied to the forearc basin in Albian times. Recent tectono-stratigraphy of the Late Mesozoic accretionary complex in Japan reveals a strike–slip movement in the subduction zone around northeastern Asia. Large earthquakes affected by active strike–slip motion of the oceanic plate are inferred to be the trigger of tectonic movement, such as large slope failure following serpentine intrusion in the forearc region. Another possibility is that subduction of a large number of seamount on the oceanic plate might also cause a large change in basin morphology, bringing about large slope failure.

Internal Deformation of Thrust Sheets, Sawtooth Range, Northwest Montana

A popular conception in the geological community is that sedimentary rocks of the Cordilleran foreland fold-and-thrust belt are unmetamorphosed and lack significant internal deformation. This idea has been incorporated by many workers into regionally balanced cross sections and palinspastic restorations that yield approximately 50% shortening. This amount of shortening is based entirely on plane strain, rigid body translations, and rotations of strata above a regional decollement that becomes structurally and stratigraphically deeper to the west. Detailed field studies in the Sawtooth Range (Disturbed belt) of northwestern Montana challenge the popular model of thrust belt internal deformation and shortening. A variety of deformation fabrics exist at the microscopic and mesoscopic scales, including pervasive axial-planar pressure-solution cleavage, boudinage, pencil structures, deformed oolitic and pelletal carbonate grains, distributed shear zones, and a host of extension and shear fractures. These features demonstrate that these rocks have experiences substantial internal finite strains. The internal strains are primarily the result of layer-parallel longitudinal shortening, coupled with pure and simple shear. These observations are important for the following reasons. (1) The amount of total shortening across the fold-and-thrust belt has been traditionally underestimated, producing errors in palinspastic facies maps. (2) Internal deformational fabrics are important controls onmore » reservoir heterogeneity and permeability. (3) Recognition of internal deformation requires the reevaluation of dynamic and thermochemical models for foreland thrust belt formation.« less

Problematical Petrophysical Characteristics of Smackover at Bayou Middle Fork Field, Claiborne Parish, Louisiana: ABSTRACT

ABSTRACT Values of irreducible water saturation calculated from conventional electric and porosity logs at Bayou Middle Fork Field are often greater than 60 percent. Mercury injection curves reveal that the true water saturation averages about 40 percent. Scanning electron micrographs show oolitic grains that have been recrystallized and have rough irregular surfaces as well as intercrystalline porosity within the particles. Water adheres to these grain surfaces and occupies some of the intercrystalline porosity in productive zones, causing the calculated water saturations to read too high. Application of the Archie equation, the Guillotte et al. technique, and the Rocky Mountain technique each provide a different suite of water saturations. Archie water saturations average about 75 percent when density-neutron porosity values are used. Density-neutron porosity values tend to read about 2 porosity units low when compared with core porosity values throughout the field. When core-correlated porosity is used, the Archie saturation averages about 60 percent. The Guillotte et al. technique employs a variable textural parameter "w" which is dependent on porosity and permeability. Mean water saturation with this method averages about 49 percent, which is in better agreement with the mercury injection data. The Rocky Mountain ratio yields water saturations that are too high until the porosity balance technique is applied. Since Rt is assumed to read too low due to the excess immobile water, the Rocky Mountain derived porosities are too low. When Rt is increased to balance the porosity the water saturation averages about 43 percent, using z = .025. When the Rocky Mountain Rta is used in the Archie equation, water saturations more consistent with the mercury injection data result. In addition the difference between the observed Rt and the Rocky Mountain derived Rta can be plotted as a function of porosity.

Ooids: A review

Ooids are spherical or subspherical carbonate grains characterized by an internal concentric structure and average dimensions ranging mainly from 0.25 to 1.00 mm. In Recent, unaltered ooids it is possible to distinguish a variable nucleus (mud aggregate, bioclastic grains, quartz grains, etc.) and an external cortex formed by concentric envelopes of variable thickness and number. Chemically ooids are formed almost completely of CaCO3 and may be distinguished as (a) concentric ooids with cortical envelopes in which the individual crystals are randomly or tangentially arranged, and (b) radialfibrous ooids with cortical envelopes in which the individual crystals have a radial arrangement. While the former ooids always appear to be aragonitic, the latter may be formed by aragonite as well as by high-Mg calcite. These oolitic structures were formerly considered in general as the typical products of shoal environments, but in recent years a more complex view has developed and different environmental conditions are envisaged for different ooids. Ooids are known in the geological past from the Precambrian onward, but they are now always calcitic. Generally they show a complex structure where concentric and radial structures coexist. This combination has for a long time been interpreted as a result of diagenetic transformation of oolitic grains with original tangential substructure. Recent works tend to recognize close analogies between ancient radial-fibrous ooids and Recent unaltered structures with similar crystalline arrangement.

Recent Sediments of Hypersaline Estuarine Bay: ABSTRACT

Cayo del Grullo is a hypersaline estuarine bay on the south Texas Gulf Coast. Most surficial sediment is mud, with sand predominating around the periphery of the bay. Influx of sediment is small and distribution of the several lithofacies and biofacies within the bay is related directly to the prevailing energy conditions. The mud comes from several sources, from Laguna Madre, from erosion of surrounding Pleistocene bluffs, and from intermittent streams during heavy rains. Organic content of bottom sediments is inversely proportional to grain size. Oolitic aragonitic sands are present in the bay and are more extensive than previously reported. Oolitic grains are precipitated and deposited in the high-energy swash zone. Other carbonate material End_Page 2205------------------------------ in the sediments is primarily pelecypod shell fragments. Concentration of carbonate material is a function of currents and wave activity. A few species of Foraminifera and Ostracoda which can tolerate severe fluctuations of salinity comprise the microfauna. End_of_Article - Last_Page 2206------------

The Gravels of Little Hayes, and the Age of the Crouch Valley, South-East Essex

The rarity of drifts in the Crouch Valley has been often remarked. The only river gravel marked in it on the Geological Survey Map, sheet I N.E., is a small patch at Little Hayes, a couple of hundred yards north of the Crouch, and 1¼ miles S.S.W. from Woodham Ferrers railway station. In the Evolution of the Essex Rivers (1922, p. 47), an analysis of the five chief constituents, based on a collection made by Mr. H. J. Nicholson, recorded some Jurassic sandstones which I regarded as probably derived from the boulder clay on hills about three miles north and north-west. A visit to the pit last year in order to obtain larger specimens of the Jurassic material yielded various cherts; one is a typical Rhaxella chert, which has not been previously recorded so far to the south-east. A thin bedded oolitic chert, which was different to any that I knew, was submitted to Mr. H. C. Sargent with the inquiry whether it might be one of the Carboniferous cherts of the Midlands. Mr. Sargent identified some of the inclusions as silicified oolitic grains, and rejected the rock as Midland Carboniferous. The specimens and slides were also kindly examined by Professor Boswell, who showed them to Mr. E. T. Dumble for comparison with the Rhaxella chert found by him in the Crag; they also did not know any similar rock. The specimens were then sent to Dr. Morley Davies, who confirmed the identity of the one specimen with the ordinary Oxford-Buckingham Rhaxella chert, and has, in the previous note, described the other as a Rhaxella chert in which the spicules are the nuclei of oolitic grains.

I.—The Mineral Condition of the Calcium Carbonate in Fossil Shells

A recent paper by Mr. A. R. Horwood on “Aragonite in the y Middle Lias” raises again the question of the condition of the calcium carbonate in fossil shells. Mr. Horwood speaks (p. 176) of Jurassic shells as being “preserved in aragonite”, and quotes Dr. Sorby as being of the same opinion. But is Mr. Horwood sure that his shells are still in the aragonite condition? Sorby, when he writes of “aragonite shells”, means as a rule shells that were formed of aragonite at the time of the death of the originating animal; but he describes how, in many of our fossiliferous rocks, such shells are represented either by hollow spaces or by pseudomorphs in granular caleite. He points out that oolitic grains, originally consisting of aragonite, have similarly been changed into calcite, the more stable form of calcium carbonate. Some oolitic grains, however, were thought by him to have consisted of calcite from the outset. Doelter, after summing up Linck's researches on calcite and aragonite, states that calcareous oolites now consist of calcite; and we have no doubt that the “recrystallized aragonite concretions”, quoted by Mr. Horwood from Sorby, were held by Sorby to be at the time of examination in the calcite state.

Societies and Academies

Societies and Academies

Note on the occurrence of Brookite in the Cleveland ironstone

The references to the occurrence of the titanium dioxide minerals as rock constituents have been so recently summarized in the ‘Mineralogical Magazine, that it is unnecessary to repeat them, except to refer again to Mr. J. J. H. Teall's record of anatase in the Cleveland ironstone.Wishing to procure some of these crystals, a pound of ore from the Main Seam at Upleatham mines was treated by the usual processes of solution, washing by decantation, and separation by heavy solution. The residue obtained was equal to 0.16 per cent. of the material taken, and consisted mainly of anatase, mostly in sharply developed pyramidal crystals, with some pyrites in nodular concretions, possibly in replacement of some of the oolitic grains, together with other minerals of derived origin, among which futile and tourmaline were the most prominent.

V. Petrological Notes

Rocks from the Neighbourhood of Buta. Specimen No. 48.—This is a fine-grained, chocolate-coloured,laminated mudstone containing minute flakes of mica. There is no trace of any fossil, unless one or two microscopic pellets may be taken to represent coprolites. No. 42, Rubi River.—From large blocks apparently embedded in the clayey alluvium of the river. It is a compact cream-coloured rock, with well-marked oolitic structure. In the thin slice, opaque, dull, spherical grains are seen in a fairly-large amount of granular crystalline calcite, which forms the matrix. The grains are fairly uniform in size, and all possess a well-defined concentric structure; there is no trace of any radial structure, and the material is too dusty in character to give a cross in polarized light. The centres of the grains are usually filled with more or less clear granular calcite, and no organic or clastic bodies have been noticed in them. There are several compound grains, one large grain enclosing one or two smaller ones. (See P1. XLIV, fig. 2.) The rock is suggestive of an oolite formed from a calcareous spring, but there is nothing to show that organisms have taken any part in its formation. In places the rock includes small pellets of grey clay [52], and where this is present the limestone tends to assume a stylolitic structure. No. 51.—This specimen, said to be from the same locality as the preceding, is a compact rock of slightly-redder colour; in the hand-specimen it shows the spherical oolitic grains weathering more readily

The Formation of Oolite

If a thin section of oolite be mounted in Canada balsam and examined under a microscope, it is seen to be made up of a number of granules associated with fragmental remains of calcareous organisms, and the interstitial spaces are filled in with calcite. Looked at with a 2-inch object-glass these oolitic granules show, for the most part, a series of concentric strata or laminæ of calcium carbonate around a nucleus. There are also other secondary structures, the principal of which are dark striæ and patches, the former placed more or less at right angles to the nucleus. At the Bath meeting of the British Association in 1888 Prof. H. G. Seeley read a paper ‘On the Origin of Oolitic Texture in Limestone Rocks.’ In this communication the author stated that he ‘believed that oolitic texture might originate in many ways……’ He also drew attention to the ‘close resemblance of the internodal grains of the nullipores to grains of oolite as furnishing a further explanation of oolitic texture. These grains show a concentric structure as well as a radiated tubular structure, which would favour the recrystallization such as commonly occurs.’ Generally speaking, up to the year 1889 the concentric layers were supposed to be chemically deposited calcium carbonate. Thus Dr. Sorby, F.R.S., in his most able and memorable address to the Geological Society in 1879, describes the formation of normal Jurassic oolitic grains in the following words : They are ‘ composed of more or less well-defined layers of small