Paleoclimatology Data

Sea caves are formed by the power of the ocean or in some cases, lakes attacking zones of weakness in coastal cliffs. The weak zone is usually a fault, or fractured zone formed during slippage. Another type of weak zone is formed where dissimilar types of rocks are interbedded and one is weaker than the other. Typically this is a dike, or intrusive vein of more easily eroded rock found within a stronger host rock. Yet a third instance is in sedimentary rocks where a layer of softer rock is interbedded between harder layers. The cave may begin as a very narrow crack into which waves can penetrate and exert tremendous force, cracking the rock from within by both the weight of the water and by compression of air. Sand and rock carried by waves produce additional erosive power on the cave’s walls. Sea caves rarely have formations like solution caves or lava tubes, so we’re just devoting one page to them here in The Virtual Cave.

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Exploring the wonders of geology in response to young-Earth claims Please read my guidelines and background posts before proceeding! Saturday, May 14, How to put the ‘paleo’ in paleoclimatology:

Th/U-dating of fossil corals and speleothems. 1 Introduction Palaeoclimate archives such as ice cores, deep sea sediments or speleothems provide important insights about natural climate.

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Speleothem

A number of studies in recent years, however, report cases of diagenetic alteration which compromises the use of U-series systematics in speleothems, resulting in inaccurate U-Th ages. Here we present the results of a high-resolution U-Th dating study of a stalagmite CC26 from Corchia Cave in Italy where we document a number of departures from an otherwise well-defined age-depth model, and explore potential causes for these outliers. Unlike examples illustrated in previous studies, CC26 contains no visible evidence of neomorphism, and appears, at least superficially, ideally suited to dating.

Good reproducibility obtained between multi-aliquot U-Th analyses removes any possibility of analytical issues contributing to these outliers. Furthermore, replicate analyses of samples from the same stratigraphic layer yielded ages in stratigraphic sequence, implying very localized open-system behavior.

Jan 01,  · variations of cave mineral deposits have been identified. [4] The vast majority of speleothems are calcareous, composed of calcium carbonate in the form of calcite or aragonite, or calcium sulfate in the form of eous speleothems form via carbonate dissolution reactions.

Paleogeografie[ bewerken ] Tijdens het Mioceen ging de Alpiene orogenese door. In de Alpen vond bijvoorbeeld tussen 10 en 5 miljoen jaar geleden een belangrijke fase van opheffing plaats, waardoor de zee definitief uit het Molassebekken in het noordelijke voorland zou verdwijnen. Ten noorden van de Alpiene gebergtegordels lag tijdens het Mioceen een grote binnenzee, de Paratethys , waarvan de tegenwoordige Zwarte Zee en Kaspische Zee restanten zijn.

Tijdens het Mioceen waren de Paratethys en de Middellandse Zee afwisselend wel of niet verbonden door zeestraten. Een geologisch gezien kortstondige, maar wel ingrijpende gebeurtenis was het zo goed als geheel droogvallen van de Middellandse Zee tijdens de Messinian salinity crisis rond 6 miljoen jaar geleden.

Ook dit werd veroorzaakt door de noordwaartse beweging van Afrika, die ervoor zorgde dat de voorlopers van de Straat van Gibraltar sloten. Hierdoor trok de zee, die in het Paleogeen nog de westelijke rand van Noord-Amerika bedekte, zich terug naar het westen. Deze bergketens ontstonden met het vulkanisme ten gevolge van de subductie van de Farallonplaat onder Noord-Amerika. Een gevolg van het omhoog komen van het Coloradoplateau rond 9 miljoen jaar geleden was de vorming van de Grand Canyon door inslijting van de rivier de Colorado.

Paleoklimaat[ bewerken ] Het vroege Mioceen had een warmer klimaat dan het voorafgaande Oligoceen. Rond 14,8 miljoen jaar geleden vond het Early Middle Miocene Climatic Optimum plaats en was het klimaat op zijn warmst. Daarna koelde het klimaat plotseling snel af. Er zijn meerdere hypotheses waarom het klimaat afkoelde.

speleothem

A “speleothem” is a secondary mineral deposit formed by a physico-chemical reaction from a primary mineral within the cave environment. The term speleothem refers to the mode of occurrence of a mineral and not to its composition. In this second edition, the classification of speleothems is based primarily on morphology i. Speleothems are divided into types, subtypes, and varieties and the rationalization for this three-fold division is explained.

Thirty-eight “official” speleothem types e.

Through continuing research and the need for ever more accurate and precise paleoclimate data, Victor has developed new techniques for dating speleothems and increased the resolution of climate studies using speleothems by a factor of

The paleomagnetism and U—Th dating of three Canadian speleothems: Ford, and , G. Pearce Canadian Journal of Earth Sciences, , 19 These cave deposits do not appear to show the kind of depositional effects on the recorded magnetic signal as is often the case with sediments. In addition the signal may be referred directly to geographic coordinates so that virtual geomagnetic pole plots may be constructed.

This in turn has allowed assessment of any possible bias of the paleofield. The U—Th activity ratios of two flowstones from the Crowsnest Pass area of British Columbia indicated ages greater than the ka dating limit of the dating method. One of the samples was reversely magnetized. Besides their use in the study of the ancient field, these samples have useful geomorphic applications.

A stalagmite from Vancouver Island was shown to have recorded clockwise loops of the field vector in the period 5. This implies a mainly westward drift of the paleofield for this period; the corresponding VGP’s were mostly far-sided and slightly left-handed.

Speleothem

Recent progress on minimising sample sizes needed for U-Th dating makes it possible to date small amounts of carbonate taken from deposits in direct stratigraphic relationship with cave art to constrain the age of the painting itself. Our methods are published in detail in Quaternary Geochronology. Some of our results were published in Science. The article , which was also the cover story of the Science issue, was accompanied by a perspective article highlighting the importance and potential of U-series dating for cave art research.

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Zeitschrift für Geomorphologie main volume is a peer-reviewed international journal presenting original contributions of high scientific standard from all fields of geomorphology, encompassing basic research and applied studies.

Proceedings of the symposium in Bergen, Norway, August 1—4th Chemical Geology Isotope Geoscience. Sea level during the past , years. Physical Geography 17 5: Geochimica et Cosmochimica Acta A review of the existing models and a new approach.

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Speleothems formed from salt, sulfur and other minerals are also known. Speleothems made of pure calcium carbonate are a translucent white color, but often speleothems are colored by chemicals such as iron oxide , copper or manganese oxide , or may be brown because of mud and silt particulate inclusions. Chemistry[ edit ] Many factors impact the shape and color of speleothem formations including the rate and direction of water seepage, the amount of acid in the water, the temperature and humidity content of a cave, air currents, the above ground climate, the amount of annual rainfall and the density of the plant cover.

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According to a paper published Thursday in Science, that melting could come sooner, and be more widespread, than experts previously believed. If global average temperature were to rise another 2. It all depends on how quickly the permafrost melts, and how quickly bacteria convert the plant material into carbon dioxide and methane gas, and nobody knows the full answer to that. But since climate scientists already expect a wide range of negative consequences from rising temperatures, including higher sea level , more weather extremes and increasing risks to human health , anything that accelerates warming is a concern.

While the rate at which melting permafrost will add carbon to the atmosphere is largely unknown, a study released February 11 in Proceedings of the National Academy of Sciences at least begins to tackle the problem. To get an idea of what might be in store for the future, Vaks and his colleagues searched for evidence from the distant past — specifically, from stalagmites and stalactites formed over hundreds of thousands of years in underground Siberian caves.

These spiky mineral deposits, known collectively as speleothems, grow layer by layer as surface water percolates through the ground dissolving limestone as it goes, and finally forms droplets that hang from the ceiling of a cave. If the water evaporates before dropping to the floor, it leaves the limestone behind, and over the centuries those bits of limestone grow into a downward-pointing stalactite.

If it drops first, then evaporates, the limestone builds up from the floor, creating a stalagmite. In places without permafrost, this process happens year-in and year-out. So Vaks and his colleagues enlisted members of the Arabica Speleological Club in Irkutsk, Russia — amateur cave explorers — to help identify likely caves in a north-south line across Siberia. The scientists took their samples back to the lab, sliced them lengthwise, and exposed layers laid down over nearly , years.

The last time these northern speleothems showed any growth, in fact, was during an unusually warm period about , years ago.

Uranium series dating of speleothems and climate

Pike taking speleothems samples from a cave site in Spain for uranium-thorium U-Th dating. The study relies on the concept that mineral forming rock flows over the walls of the caves covered in paleolithic art work. In doing so, it forms a sort of time capsule, meaning that anything encased within the flowstone is older than the flowstone itself.

By comparing the ratio of atoms in the minerals deposited nearest the cave wall, the team was able to calculate the lower limit on the age of the art that lies just beneath.

Exploring the dating of “dirty” speleothems and cave sinters using radiocarbon dating of preserved organic matter. Quaternary Geochronology, Vol. 39, p.

Cave popcorn , or cave coral, are small, knobby clusters of calcite; Cave pearls are the result of water dripping from high above, causing small “seed” crystals to turn over so often that they form into near-perfect spheres of calcium carbonate; Snottites are colonies of predominantly sulfur oxidizing bacteria and have the consistency of “snot”, or mucus; [1] Speleothems may also occur in lava tubes.

Although sometimes similar in appearance to speleothems in caves formed by dissolution, these are formed by the cooling of residual lava within the lava tube. Speleothems formed from salt, sulfur and other minerals are also known. Speleothems made of pure calcium carbonate are a translucent white color, but often speleothems are colored by minerals such as iron , copper or manganese , or may be brown because of mud and silt particulate inclusions.

Chemistry Many factors impact the shape and color of speleothem formations including the rate and direction of water seepage, the amount of acid in the water, the temperature and humidity content of a cave, air currents, the above ground climate, the amount of annual rainfall and the density of the plant cover. Most cave chemistry revolves around calcite ; CaCO3, the primary mineral in limestone. It is a slightly soluble mineral whose solubility increases with the introduction of carbon dioxide , CO2.

It is paradoxical in that its solubility decreases as the temperature increases, unlike the vast majority of dissolved solids. This decrease is due to interactions with the carbon dioxide, whose solubility is diminished by elevated temperatures; as the carbon dioxide is released, the calcium carbonate is precipitated. Most other solution caves that are not composed of limestone or dolostone are composed of gypsum calcium sulfate , the solubility of which is positively correlated with temperature.

As climate proxies Samples can be taken from speleothems to be used like ice cores as a proxy record of past climate changes. Stalagmites are particularly useful for palaeoclimate applications because of their relatively simple geometry and because they contain several different climate records, such as oxygen and carbon isotopes and trace cations.

Absolute dating Main article: Absolute dating Another dating method using electron spin resonance ESR — also known as electron paramagnetic resonance EPR — is based on the measurement of electron-hole centers accumulated with time in the crystal lattice of CaCO3 exposed to natural radiations.

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