Parent Limestone Research Articles

Early-Middle Devonian paleosols and palustrine beds of NW Canada in the context of land plant evolution and global spreads of anoxia

Dozens of subaerial exposure surfaces are assessed in cores from cyclic peritidal carbonates of the Emsian–Eifelian (~410–385 Ma) age. These surfaces range from incipient erosional surfaces to paleokarst profiles and thick (>1 m) calcretic-clayey paleosols. Palustrine carbonates intervening at multiple levels in same strata are the earliest known occurrence of a typical palustrine facies in a coastal carbonate plain environment. None of paleokarst and paleosol profiles contain traces of vascular-plant root penetration, and only palustrine facies exhibit swarms of thin rhizoliths. These findings are within the context of Devonian paleosols on marine carbonate substrates where root traces and laminar calcretes are extremely rare (only 2 reports), and no instances of root penetrations are trackable from unconformities in pre-Givetian carbonate successions. The δ13C and δ18O signatures indicate variable diagenetic reset of isotopic composition. Modest δ13Cvpdb offset towards lighter values is preserved in two thicker paleosols (−3.4 to −8.0‰ in calcretic matrix vs. -1.35 to −6.5‰ in parent limestone). Such offsets are very rare in pre-Late Devonian pedogenic carbonates, and their attribution to plant-derived CO2 is dubious. It is inferred that the land surface in calcimagnesian landscapes remained a regolith or primary desert (i.e., was never colonized by tracheophytes) long after the spread of vascular plants in more favorable wetland settings. Furthermore, the advent of seed reproductive strategy in the latest Devonian and plant adaptations to aridic habitats manifesting in fossil floras only since Pennsylvanian indicate that much of land surface remained within the realm of primary desert long after the afforestation of wetlands. The direct (plant roots, shoots and spores) and indirect (sedimentary features) fossil records of land greening during the Paleozoic are not corroborating the hypothesis holding the primordial embryophytic cover on land accountable for the Late Ordovician atmospheric oxygenation-decarbonization event. It is further argued that the evolution of root systems and plant stature could hardly trigger anoxic events and biotic crises in the Devonian marine realm.

Geological Exploration of Marble Deposits in Toto Area, Nasarawa State, Nigeria

Geological mapping as well as chemical analysis for marble deposit in the Muro-Obugu-Panda area of Toto Local Government, Nasarawa State, Nigeria, was carried out. The objectives of the study are to first map out the extent of the deposit and then evaluate its chemical characteristics. The geology of the area forms part of the Upper Proterozoic low-grade (green schist facies) schist belts of Central Nigeria, and consists of schists, banded iron, quartzite, and marble. Geological mapping revealed that the marble deposit stretches in a NE-SW direction, from Muro in the north to Kolo in the south, covering about 28 km2. This deposit consists mainly of silicified gray and white varieties of marble. The mapping also identified three (3) exploration targets A—Panda, B—Obugu, and C— Soka. Chemical analysis of eight (8) selected samples shows that CaO content varies from 3.72 to 53.12 wt%. Other impurities are Fe2O3, Al2O3, MgO and SiO2. Plot of Na2O + K2O vs. SiO2 shows a positive correlation while that of CaO and MgO exhibits a well defined negative correlation with SiO2 and this reflects the introduction of chert during the deposition of the parent limestone of the marble body. The variation plot of CaO vs. MgO shows an inverse relationship. This is reflected in the inverse relationship in the proportion of calcite to dolomite in the marble. All these results correlate with those found in the adjacent area by previous workers and this indicates the same extension of marble in these areas. The Muro marble can be used economically as raw materials for a variety of products such as fillers, glass, papers, lime, pesticide and sewage treatment, decorative construction, monuments, paint making and most of all very suitable for cement production.

CO2 capture by calcium aluminate pellets in a small fluidized bed

Synthetic pellets made using calcium aluminate cement and quicklime have been examined in a small fluidized bed reactor to determine their performance in cyclic CO2 capture for up to 20 calcination/capture cycles. Two batches were examined one a “fresh” batch, and the second an “aged” batch of pellets and their performance was compared with the original parent limestone. Carbonation was carried out at 650°C and calcination at 900°C, both with 15% CO2, balance N2, as a synthetic flue gas. Experiments were also performed with and without steam in the flue gas and showed that steam always improved capture performance. In addition, there was no major attrition associated with the pellets, and pellets tended to perform better in terms of carbon capture than the parent limestone.

Modified lime-based pellet sorbents for high-temperature CO2 capture: Reactivity and attrition behavior

Modified lime-based pellets have been developed as potential regenerable high-temperature CO2 sorbents using calcium aluminate cement binders to enhance pellet strength. A mechanical pelletizer was used for granulation of the powdered materials, namely quick lime and hydrated lime, produced from Graymont limestone with the addition of spray water. The CO2 carrying capacity of both the pellet sorbents and the parent limestone was tested in a thermogravimetric analyzer (TGA) at 800°C with repeated calcination/carbonation cycles. It was found that the CO2 carrying capacity of the pelletized sorbent was higher than that of the parent limestone, and the stability over multiple cycles was improved when cement was added to the pellets. The attrition resistance of these pellets was examined using a bubbling fluidized bed (50mm ID). The particle size distribution (PSD) of both the calcined pellets and limestone was determined before and after 2h attrition tests which were performed using air as the fluidizing gas at room temperature and at 800°C. The results of attrition tests showed that after fluidization for 2h, particle size distribution changed such that the average particle diameter (d50) of the sample always decreased, but for the pellet sorbents, high-temperature fluidization did not result in significantly more pronounced attrition.

Preparation of heterogeneous catalysts from limestone for transesterification of vegetable oils—Effects of binder addition

A limestone from the South of Thailand was utilized as a source for preparation of heterogeneous base catalysts for transesterification of various vegetable oils with methanol and ethanol has been investigated. Series of CMA catalysts were prepared through a wet mixing of ground limestone with different divalent and trivalent metal precursors, as binders, followed by drying and calcination. Effects of preparation conditions, including types of wetting media and metal precursors, metal compositions, and thermal treatment temperatures for the parent limestone and the mixed catalyst precursors, on the structural properties and the transesterification activity of the resultant catalysts, and on the catalyst formulation were studied. The catalytic test under batch conditions at 60 °C indicated an enhancement of the methyl ester formation over the catalysts prepared due to the presence of new active phase generated in situ upon the calcination of the mixed catalyst precursors at high temperatures. The metal precursors also acted as good binders in the catalyst shaping. Using the sodium salt of Al as a precursor remarkably improved the mechanical strength of the catalyst extrudates. The CMA catalysts can be regenerated and reused without a severe drop of the methyl ester yield. Moreover, the transesterification in a continuous-flow fixed bed reactor indicated a good activity and stability of the catalyst extrudates prepared.

Skarn development from limestone adjacent to the Glenrock Granodiorite, Marulan Batholith, New South Wales, Australia

Skarns are developed over two temperature‐time intervals in calcite limestone adjacent to the southern extension of the Glenrock Granodiorite, a pluton of the Marulan Batholith, Southern Highlands, New South Wales. The initial volumetrically‐dominant prograde phase of skarn formation produced a suite comprising bimetasomatic skarn, including pyroxene endoskarn, potassic endoskarn and wollastonite‐bearing exoskarn, together with mineralogically‐zoned vein skarn, massive garnet‐pyroxene skarn and calcite‐vesuvianite skarn. Retrograde replacement is manifested by the development of hydrous silicate minerals, carbonate and cross‐cutting sulphide veinlets. A genetic model is proposed to account for the development of bimetasomatic skarn in the deposit. Exoskarn geochemistry indicates addition of many components relative to an essentially pure limestone precursor, including Si, Al, Fe, Zr, Zn, S, Mn and Cu, negligible transfer of K, Na and Rb and loss of CO2. Strontium and Ca loss from the parent limestone is i...

Calciustolls in Central Texas: II. Genesis of Calcic and Petrocalcic Horizons

AbstractSoils on hillslopes in the Grand Prairie and eastern Edwards Plateau regions of Texas are developed from multiple facies of interbedded weakly to strongly indurated Cretaceous limestones. Most contain either calcic or petrocalcic horizons. Stable C isotope analysis of the carbonate‐enriched horizons from seven pedons sampled in this area permitted quantification of the amount of pedogenic carbonates. Features indicative of carbonate translocation and accumulation were observed in the soils. However, reconstruction analysis indicated that none of the calcic horizons and few of the petrocalcic horizons contained more carbonates than the parent limestone. Microfabric development in calcic horizons supports loss of carbonates as a major process in these horizons. The pedogenic nature of most of the carbonates in calcic horizons is attributed to in situ recrystallization of the parent limestone. Petrocalcic horizons commonly had areas of strongly indurated limestone in matrix interiors, and micromorphic observations indicated that much of the pedogenic carbonates in these horizons was also the result of in situ recrystallization of the limestone. Petrocalcic horizons occurred on all landscape positions. Their occurrence and position in the profile appears to be related to an indurated limestone bed within the normal depth of wetting. The development of calcic and petrocalcic horizons primarily by recrystallization rather than translocation and accumulation of carbonates contrasts with the commonly accepted model for formation of these horizons.

Paleosols Capping Regressive Carbonate Cycles in the Pennsylvanian Black Prince Limestone, Arizona

ABSTRACT The lower Pennsylvanian (Morrowan to early Derryan) Black Prince Limestone, exposed in southeastern Arizona, consists of shallowing-upward (regressive) carbonate cycles that accumulated on a shallow-shelf platform. A typical complete cycle from the base upward consists of the following fades: mixed skeletal mudstones to grainstones(subtidal shelf, open circulation), mixed skeletal to nonskeletal packstones and grainstones (restricted shelf-lagoon), nonskeletal fenestral mudstones to grainstones (intertidal), nonskeletal cryptalgally laminated, brecciated mudstones to wackestones (supratidal), and paleosol horizons (terrestrial). Two paleosol types occur, calcrete and terra rossa. Calcrete occurs as thin (< 5-10 cm) profiles consisting of laminar micrite, coated grains, aggregate grains, and vadose diagenetic features. Terra rossa paleosols consist of subspherical nodules derived from pedogenic alteration of parent limestones, separated by a reddish, insoluble accumulation ofclays, iron oxides, calcite skeletal debris, and quartz silt. The terra rossa paleosols occur as in situ preserved C horizons and as reworked soil residuum. The first occurrence is marked by parent limestone in completely brecciated into nodules, whereas reworked paleosols consist of nodules enveloped in red matrix. Both calcrete and terra rossa paleosols record subaerial exposure, although the terra rossa paleosols suggest that signi icant amounts of limestone were removed during pedogenesis. The terra rossa paleosols also favor an extrinsic versus anintrinsic mechanism for the origin of the cycles.

Rubification of Terrae Rossae in Slovakia: A Mössbauer Effect Study

AbstractMineralogical and 57Fe Mössbauer spectroscopic analyses were made on seven terrae rossae and two terrae fuscae samples of Pliocene to Early Pleistocene age from Slovakia and limestone residues from their parent materials. In most of the samples, no mineral weathering or clay mineral formation could be detected by optical or X-ray powder diffraction investigation, compared with their parent limestone residues; only one terra rossa showed a strong weathering of primary feldspar and phyllosilicates and a high rate of clay formation, especially kaolinite. Mössbauer measurements between 5° and 300°K showed that hematite and goethite are the dominant color pigments in the rubified terrae rossae and their corresponding limestone residues. The mean particle size of hematite and goethite was estimated from Mössbauer effects and X-ray powder diffraction data to be 95 and 250 Å, respectively. Reduced values of the hyperfine fields at 5°K of the soil iron oxides, as compared with those of the pure oxides, indicate a partial substitution of Fe(III) by Al. The hematite content correlates with the Munsell color notation of 5 of the 7 terrae rossae samples and their corresponding limestone residues. All terrae rossae samples showed higher hematite contents than their corresponding limestone residues, indicating that the rubification of such materials is independent of the degree of weathering.

Clay Minerals in a Limestone Soil Profile

AbstractThe clay minerals in a soil developed from Lenoir limestone (Ordovician) in Augusta County, Va., are kaolinite and chlorite. The Lenoir limestone contains clay partings consisting of hydrous mica, and the clay in the soil is considered to be residual from that in the parent limestone and modified by soil-forming processes (podzolic). X-ray diffraction patterns of the clay fraction (&lt;2μ) from samples from different positions in the profile show a reduction in hydrous mica and an increase in kaolinite and chlorite content as the A horizon is reached. Partial chemical analyses of the whole soil and of the clay fractions are given, as well as pH and ion-exchange capacity determinations. The silica-alumina ratios are similar to those characteristic of podzolic soils, and excess silica in the A horizon accumulates as recrystallized quartz together with chert which is considered to be residual from the limestone. Mechanical analyses by the standard pipette method show that the quantity of clay in the soil varies from 17 percent at the surface to 61 percent at 26 inches (C horizon).