Evidence Of Volcanic Activity Research Articles

Control of climate events caused by the volcano on organic matter enrichment in the lacustrine source rocks of the Ordos Basin, central China

We systematically analyze the geochemical characteristics of source rocks of the Yan Chang Formation in the Ordos Basin to reveal the influence mechanisms of the volcano on lacustrine organic matter enrichment. Organic matter enrichment is not synchronous with the volcanic eruption in time, but it has a “hysteresis” effect. The evidence of volcanic activity mainly includes two aspects: one is a large amount of volcanic ash in black shale, and the other is a negative shift of organic carbon isotopes of source rocks and finding that black shale was affected by climate events caused by the volcano. The climate event caused by the volcano has three effects on organic matter enrichment in black shale: (1) it brought nutrients for the growth of organisms and released a large amount of greenhouse gases, such as CO2, to accelerate photosynthesis and promote the growth of organisms; (2) a large amount of toxic gases, such as SO2 and H2S, were released and O2 was consumed and diluted in the air, forming a severe anoxic environment and accelerating the preservation of organic matter; and (3) it caused extremely hot weather, resulting in long-time surface runoff and other climate events, increasing input of terrestrial organic matter, and forming light components of hydrocarbons.

Molybdenum and sulfur incorporation as oxyanion substitutional impurities in calcium carbonate minerals: A computational investigation

Marked increases in sulfur and molybdenum concentration in stalagmites have been proposed as possible evidence of volcanic activity in the past. Thus, speleothems have great potential to deliver long and continuous records of volcanic activity. However, little is known about the chemical nature of these impurities in the calcium carbonate (CaCO3) phases forming stalagmites, which hinders the rationalization of the incorporation mechanisms. While sulfur is known to incorporate as a sulfate anion in CaCO3 polymorphs, the nature and stability of molybdenum incorporation in these minerals has not been investigated before. Here, we present a computer simulation study, based on density functional theory, comparing the thermodynamics of incorporation of sulfur and molybdenum as tetrahedral oxyanions [XO4]2− (X = S, Mo) in anion sites of CaCO3 polymorphs (calcite, aragonite, vaterite, monohydrocalcite and ikaite). Among the different polymorphs, vaterite incorporates [XO4]2− ions most favourably, which reflects the relatively low density of this carbonate phase. We show that molybdate anions are very unstable (more so than sulfate anions) in the bulk of all three anhydrous carbonate phases, with respect to the formation of naturally occurring competing phases. Most of the Mo impurities found in typical calcite/aragonite stalagmites is therefore likely to concentrate at surface/interface regions such as grain boundaries. Using the calcite (10.4) surface as a model, we show that the energies of substitution are indeed much lower at the surface than at the bulk. Our results suggest that factors affecting the crystallinity of CaCO3 in stalagmites, and therefore the specific surface area, will have a significant effect on the concentration of incorporated molybdenum, which should be a key consideration when interpreting data from Mo-based speleothem archives.

Evidence of volcanic activity in the growth rings of trees at the Tacaná volcano, Mexico–Guatemala border

Volcanic activity can have a significant effect on the growth and survival of trees. The objective of our research was to analyze the effects of the 1855–1856 eruption of the Tacaná volcano and the ashfall from the 1902 eruption of the Santa María volcano, Guatemala, on the radial growth of trees at Tacaná. Dendrochronological sampling was carried out on sites covered by Pinus hartwegii Lindl., and a ring-width chronology was built using 102 increment cores from 75 trees. The ring-width chronology shows two statistically significant suppression events. One of these events occurred from 1857 to 1868 and was potentially caused by the historic eruption of Tacaná (1855–1856). The second suppression event occurred from 1903 to 1908, during which tree growth was affected 1 year after the ashfall caused by the 1902 eruption of Santa María. The growth suppression did not have the same magnitude in all sampled trees and may be related to the thickness of the ash layer deposited around each tree. For the first time, we show that tree growth at Tacaná is reduced by ashfall from volcanic eruptions. Our results may contribute to the evaluation of risks associated with the volcanic activity of the Tacaná volcano.

Mineralogical composition of the Lower and Upper Kazanian (Mid-Permian) rocks and facies distribution at the Petchischi region (Eastern Russian Platform)

The mineral composition proportions of carbonate rocks of Kazanian (Mid-Permian) age in the Petchischi region (eastern part of the Russian Platform) was identified by X-ray powder diffraction, ICP-MS and optical microscopy. The Lower Kazanian deposits are presented predominantly by bio-dolomicrites with changing terrigenous component and the lack of gypsum-bearing layers in the succession. Dolomicrites are prevalent in the Upper Kazanian succession, which is composed of alternation of gypsum-bearing dolomites, clayey dolomites and pure dolomites. The discovered bentonite-bearing component in marls and bentonite clays are proposed as evidence of volcanic activity in the Urals in the Kazanian stage. Two marine facies on the Eastern Russian Platform in the Kazanian: peritidal shallow flat and coastal sabkha agree well with the trends of δ18O and δ13C ratios.

The expanded population of Amphistegina lobifera at Üç Adalar and Beş Adalar (Antalya, Turkey)

The foraminiferal test is one of the principal sources of CaCO3 in oceans. The principal habitats of Amphistegina include the Indo-Pacific islands and the Caribbean Sea. Although quite rare in the Aegean Sea Amphistegina lobifera is typical of various regions throughout the eastern Mediterranean and has also been reported from the middle and north Aegean Sea. But, on the south-western coast of Turkey it is found in extensive amounts, to such an extent that, it forms a 50 cm thick layer of sand and changes the benthic structure, as well as the ecology. Our results are based upon 12 samples from Uc Adalar (Antalya), and 13 samples from Bes Adalar (Antalya) collected from 4–30 m of depth. Each sample contains a high proportion of A. lobifera within the sediment. The exaggerated proportion of the A. lobifera test on the benthos points to certain conditions. Other benthic foraminiferans are not only scarce in genus and species number, but they are also found in very small populations. Even though there is no evidence of volcanic activity from west of the Gulf of Antalya, tectonic activity is present, resulting in formation of submarine springs which are located on the active faults. The presence of limestones with karstic characteristics in the Taurus Mountains combined with submarine springs cause salinity and temperature variations, as well as an increase in CaCO3 in the seawater. So alterations in the chemical and physical conditions of seawater may be responsible for this enormous expansion of the A. lobifera population.

Petrography and geochemistry of Paleocene–Eocene limestones in the Ching-dar syncline, eastern Iran

The Ching-dar syncline is located to the west of the city of Birjand, in the east of Iran. The ca. 500 m thick studied section at the eastern flank of the syncline contains a sequence of almost continuous shallow-marine limestones that exhibit no major sedimentary breaks or evidence for volcanic activity. Skeletal grains consist of large benthic foraminifera and green algae whereas non-skeletal grains are mostly peloids and intraclasts. They were deposited on a shallow-marine carbonate ramp. The limestones have undergone extensive diagenetic processes with varying intensities, the most important of which are micritization, cementation, compaction (chemical and mechanical), internal filling and stylolitization. Chemical analysis of the limestone samples revealed high calcium and low magnesium content. Major and minor element values were used to determine the original carbonate mineralogy of these limestones. Petrographic evidence and elemental values indicate that calcite was the original carbonate mineral in the limestones of the Ching-dar syncline. The elemental composition of the Ching-dar carbonates also demonstrates that they have stabilized in a meteoric phreatic environment. Variation of Sr/Ca vs. Mn values suggests that diagenetic alteration occurred in an open geochemical system.

The Campanian Ignimbrite/Y5 tephra layer – A regional stratigraphic marker for Isotope Stage 3 deposits in the Lower Danube region, Romania

A number of volcanic ash layers embedded in Pleistocene loess and fluvial deposits of the lower Jiu and Olt valleys in south-western Romania have been analyzed for glass chemical compositions and general chronological relations. The WDS-EPMA chemical analyses document remarkably similar major and minor element compositions at the four investigated sites, and total alkali–silica diagrams ascribe these volcanic ashes a phonolite to trachyte affinity. A comparison with the Quaternary Carpathian volcanism chemical data refutes this volcanic field as the primary source, even though earlier works have tentatively taken some of these volcanic ashes as evidence of volcanic activity in this particular field. Instead, the chemical data suggest an origin in the Campi Flegrei volcanic province in Italy, and a comparison with chemical data from proximal and distal outcrops of the Campanian Ignimbrite/Y5 tephra confirm that the ash layers presented here are distal occurrences of this widespread tephra layer. The Campanian Ignimbrite/Y5 tephra is the product of one of the largest late Quaternary explosive events in the Mediterranean, and is consistently dated elsewhere to about 39–40 ka. It is one of the most important chronologic/stratigraphic markers of western Eurasia that provide an independent basis for establishing age–depth relationships for the embedding deposits. Optical luminescence age estimates obtained at two of the investigated sites further confirm that these volcanic ash occurrences represent a regionally synchronous depositional event, around 40 ka. These results highlight the important role that the Campanian Ignimbrite/Y5 tephra could play as marker horizon at sub-continental scale, providing that more potential tephra locations such as these from the Pleistocene sedimentary deposits in the Lower Danube region are chemically and chronologically constrained.

The Goli d’Aget Member: Early Permian volcanoclastic and volcanic rocks within the Briançonnais Grand St-Bernard Nappe (Valais, Switzerland)

The well-preserved sedimentary structures of the Goli d’Aget Member (Early Permian) allow to distinguish four successive environments of deposition: 1) An alluvial plain with important channeling and evidence of volcanic activity; 2) A shallow lacustrine environment with a low water level, deposition of massive carbonates and an increasing contribution of volcanic materials; 3) A fluviatile plain with the deposition of volcanic tuffs; 4) A deltaic to lacustrine environment occasionally covered by pyroclastic flows. An ignimbritic rhyolite from the upper part of the Goli d’Aget Member has an age of 267-282 Ma (U-Pb on zircon). Major and trace elements, as well as zircon typology point to a calc-alkaline and volcanic-arc affinity for that high-silica rhyolite. The Goli d’Aget Member may be the best-preserved unit among the Permian units from the Swiss Penninic Western Alps. This series provides an important point of comparison with other local Permian units (Dent de Nendaz and Cleuson Members) and with similar series in the Western Alps including the Melogno porphyroids in the Ligurian Alps and the Rochachille Series near Briancon (France).

ABSTRACT: Evidence of Volcanic Activity during the Late Cretaceous Sunniland Formation of Southwestern Florida: A New Oil Exploration Play

ABSTRACT: Evidence of Volcanic Activity during the Late Cretaceous Sunniland Formation of Southwestern Florida: A New Oil Exploration Play

Mise en évidence de corps d'origine cosmique probable au sein de la formation de Carnot (République Centrafricaine)

Two independent investigations, made on the Mesozoic fluvial Carnot Formation, yielded magnetic microspherules in borehole residues and a localized (270 m long) magnetic anomaly profile. The spherules are ferrous with sometimes traces of Al, Ti and Mn; their morphology is similar to the morphology of cosmic spherules (with mosaic, octahedral, spongy or with “Astrakhan coat”-like fabrics). The magnetic anomaly is related to a body buried at approximately 30–40 metres, i.e., in the Cretaceous Carnot Formation. This body could be modelled by a sphere or by an assemblage of dimensional polygons, with strong remanent magnetization. This indicates that the anomaly source has undergone a fusion and cooling process under the Cretaceous geomagnetic field. As there is no evidence of volcanic activity, this process is considered to be related to meteoritic falling. The magnetic spherules and the source of magnetic anomaly correspond to micrometeorites and meteorites which fell in the west of Central African Republic between Albian and Maastrichtian times. However, without geochronological data, it is not possible to indicate if the two perturbations are the result of the same extraterrestrial event or of two different events.

Palaeogene volcanism: the sedimentary record in Denmark

Summary Approximately 200 volcanic ash layers are known from Palaeocene and Eocene marine clays in Denmark. The oldest layers are present in the upper part of the Upper Palaeocene and are sporadic, thin and acidic in composition. The main volcanic phase took place at the Palaeocene-Eocene transition. During the main phase, a supply from the N to NE is indicated, while a few layers probably had a source to the NW or W. A later volcanic phase is represented by thin and more sporadic ashes in the Lower to Middle Eocene. These are almost totally transformed to smectite. In the Upper Palaeocene, and partly in the Lower Eocene, smectite is a highly dominant clay mineral in the interbedded clays. Zeolites of the heulandite-clinoptilolite type are also present, while cristobalite is sporadically present in the lower part. A major supply of smectite from the N Atlantic may be indicated. Below the ash-bearing sequence the only evidence for volcanic activity is the presence of very smectite-rich, zeolitic clays with scattered opal-CT and slightly silicified horizons. Calculated chemical compositions of smectites from both ash layers and clay layers between ash layers and below the ash-bearing sequence are almost identical, indicating a volcanic source for the smectite.

Are oceanic fracture zones locked and strong or weak?: New evidence for volcanic activity and weakness

Traditionally, oceanic fracture zones and other lithospheric and crustal faults have been viewed as zones of weakness that are vulnerable to seismic and volcanic activity. This notion has recently been questioned on the basis of evidence showing that initial depth offsets (scarp height) across some Pacific fracture zones are preserved even after ∼100 m.y. of differential subsidence. This evidence suggests that some parts of oceanic fracture zones are locked shortly) after they drift away from ridge-transform intersections. Because the fracture zones seem to be strong welds, differential cooling stresses cause flexure in the lithosphere on both sides of the fracture. In this paper we briefly review the seemingly contradictory evidence for the thermomechanical characteristics of oceanic fracture zones (locked and strong vs. slipped and weak) and present new evidence indicating that parts of some fracture zones are volcanically active. Volcanism is an indication of relative weakness because strain and failure are required to open volcanic conduits. This and other evidence for the inherent weakness of fracture zones can be reconciled with evidence for strength if different segments of fracture zones exhibit contrasting thermomechanical behavior. More data are needed to determine whether this is so and whether there are systematic patterns of distribution for weak and strong parts of individual fracture zones.

Igneous Activity, Metamorphism, and Heart Mountain Faulting at White Mountain, Northwestern Wyoming: Reply

The spire of brown volcanic rock at White Mountain, long regarded as a filled volcanic conduit associated with eruption of the Eocene Wapiti Formation, is actually an erosional remnant of volcaniclastic sedimentary rocks of the Eocene Cathedral Cliffs Formation that has been transported 10 to 15 mi southeastward as part of a Heart Mountain detachment fault block. Prevolcanic Paleozoic carbonate rocks, which comprise the western part of this block, are metamorphosed and strongly folded, in contrast to the rocks of other Heart Mountain fault blocks. This metamorphism ends abruptly downward at the Heart Mountain fault plane. Rounded fragments of metamorphosed carbonate rock in Heart Mountain fault breccia and in related clastic dikes show that the metamorphism occurred before the faulting, presumably as a result of the Cathedral Cliffs igneous activity. Igneous rock fragments in the Heart Mountain fault breccia at White Mountain seem to have been derived from allochthonous sills and dikes that predate the Heart Mountain fault. Therefore these fragments are not evidence for volcanic activity during Heart Mountain faulting, nor for introduction of volcanic gases along the fault plane as suggested by Hughes (1970a). A fault plate would have to be large and coherent to be buoyed up by volcanic gas or other fluids. The present widespread distribution of the remnants of the upper plate indicates that the upper plate broke up to form a number of fault blocks very soon after the Heart Mountain faulting began.

Igneous Activity, Metamorphism, and Heart Mountain Faulting at White Mountain, Northwestern Wyoming

The spire of brown volcanic rock at White Mountain, long regarded as a filled volcanic conduit associated with eruption of the Eocene Wapiti Formation, is actually an erosional remnant of volcaniclastic sedimentary rocks of the Eocene Cathedral Cliffs Formation that has been transported 10 to 15 mi southeastward as part of a Heart Mountain detachment fault block. Prevolcanic Paleozoic carbonate rocks, which comprise the western part of this block, are metamorphosed and strongly folded, in contrast to the rocks of other Heart Mountain fault blocks. This metamorphism ends abruptly downward at the Heart Mountain fault plane. Rounded fragments of metamorphosed carbonate rock in Heart Mountain fault breccia and in related clastic dikes show that the metamorphism occurred before the faulting, presumably as a result of the Cathedral Cliffs igneous activity. Igneous rock fragments in the Heart Mountain fault breccia at White Mountain seem to have been derived from allochthonous sills and dikes that predate the Heart Mountain fault. Therefore these fragments are not evidence for volcanic activity during Heart Mountain faulting, nor for introduction of volcanic gases along the fault plane as suggested by Hughes (1970a). A fault plate would have to be large and coherent to be buoyed up by volcanic gas or other fluids. The present widespread distribution of the remnants of the upper plate indicates that the upper plate broke up to form a number of fault blocks very soon after the Heart Mountain faulting began.

Claiborne Group of Central Texas: Record of Middle Eocene Marine and Coastal Plain Deposition: ABSTRACT

Sediments of the Claiborne Group in central Texas were deposited in a variety of nearshore-marine and coastal-plain environments. Fluctuations of the shoreline during middle Eocene time resulted in vertical stacking of 2,600 ft of sediments from contrasting depositional environments. Shoreline fluctuations probably did not result from simultaneous eustatic changes of sea level. They were caused by migrations of large fluvial, fluvio-deltaic, and interdeltaic complexes on the margins of a gently and perhaps uniformly subsiding basin. As a result of migrations of major sediment depocenters, the Claiborne rock record is characterized by high lateral and vertical variability. Each formation of the Claiborne Group commonly is considered to be the product of a single depositional environment which extended laterally for hundreds of miles. For example, the basal formation of the Claiborne, the Carrizo Sandstone, is generally accepted as having been deposited under fluvial conditions close to the shoreline. This assumption is not borne out by detailed field work. An examination of the Carrizo Formation from Bastrop to Freestone Counties reveals that Carrizo sediments were deposited in fluvial, deltaic, and marine environments. In a single outcrop the Carrizo Sandstone may be shown as having been deposited in both barrier bars and delta distributary channels. Such variability also holds true for sediments from each formation comprising the Claiborne Group. Petrographic analysis indicates that the sediment source remained constant during deposition of the Claiborne Group. The presence of phyllite and schist fragments together with the heavy minerals kyanite, staurolite, garnet, and zircon indicates that the source terrane was dominantly metamorphic. Evidence for volcanic activity is particularly strong in the Carrizo Formation and the uppermost Claiborne Yegua Formation. Volcanic minerals in these formations include bipyramidal quartz, euhedral apatite, and bentonite, indicating that the Claiborne coastline periodically was subjected to wind-transported detritus. End_of_Article - Last_Page 1693------------

On the Discovery of Two Crater Lakes and other Evidence of Volcanic Activity in the Neighbourhood of Ban Ban, near Gayndah.

On the Discovery of Two Crater Lakes and other Evidence of Volcanic Activity in the Neighbourhood of Ban Ban, near Gayndah.