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Posted by: Gomi Posted on: 09.06.2020

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Studies of Cave Sediments pp Cite as. Carbonate speleothems that contain ppb-ppm levels of uranium can be dated by the U- U- Th and U- Pa disequilibrium techniques. Accurate ages are possible if the initial concentrations of Th and Pa are well constrained and if the system has remained closed to post-depositional exchange of uranium, thorium, and protactinium. For many speleothems, particularly those composed of nearly pure calcite, initial Th may be trivial. Because Pa is more soluble than Th, Th is a poor analog for Pa.

Those soda straws that continue to grow as narrow tubes eventually break under their own weight. One of the longest known soda straws is in Kartchner Caverns in Arizona. It is 23 feet long, still growing, and only as wide as a drop of water and hollow. Stalagmites tend to be much broader, flatter and more round than stalactites because the drop will disperse when it hits the floor. This spreads the carbonic acid over a much greater area.

Often, only a stalagmite will be found because the flow is always too great to allow formation of a stalactite. Helictites are finger-like growths of calcite that look like clusters of spaghetti, branching and twisting without regard for what is up or down. They are formed by water that seeps into the cave in amounts so small that it moves by capillary forces, rather than by gravity. Water covers the growing helictites in a thin film, depositing most of its dissolved calcite on bulges and outward projections, where carbon dioxide is rapidly lost to the cave air.

Any bumps on the original helictite grow in this irregular manner, lengthening into branches. Most helictites have microscopic tubes running through their centers which supply moisture from the bedrock to the growing tips. They form when the calcite is deposited around tiny pebbles or sand grains. If the drop of acid falls from a great distance, the grains may roll around and remain unattached. As they grow, the grains become more rounded until they look just like pearls.

Speleothems have many different ages and grow at different rates.

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The growth rate depends on several conditions including 1 the temperature both inside and outside the cave, 2 the amount of precipitation, 3 the amount of water moving through the cave rivers, flooding, etc. All these factors affect the amount of dissolved calcite carried into the cave. Another point is if you are looking at relative annual variations, then in most cases it is reasonable to treat each ring as an annual ring, and most of the time you will be right.

You may even be able to distinguish where a ring is missing. So it needs work to figure out how to use the speleothem data, but it has good potential.

Some speleothems can be dated by measuring tiny amounts of unstable or radioactive elements present within the calcite. But if the formation is too old (>,), there will be too little datable material. Also, to date a speleothem, it is necessary to destroy part of it. This dating is done only when it is absolutely necessary. The dating method of choice for speleothems, known as the uranium-thorium (U-Th), or Th method, belongs to the family of uranium-series methods and was first applied to speleothems in the early s, although its physical principles were known since the beginning of the 20th mcauctionservicellc.com by: 7.

Other chemical traces or isotopic variations may provide more useful climatological data than the width of speleothem rings. It is a field worth keeping you eye on. More on this later.

Speleothem Sampling - Cool Climate Change Work!

I suppose the easiest thing to do would be to say interesting and ignore it, or to trash the paper completely, but I will try to do a fair evaluation. One of the main considerations is a difference in mind set between two different groups of scientists. One group are geologists the other tree-ring researches.

Of course the rings in the stalagmite do not correspond 1 to 1 with the calendar years and hence will not correlate 1 to 1 with tree ring dates.

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These features form in the Vadose zone- the area above the water table. So it has little to do with the level of the water table, although periods of dry weather may affect features in the vadose zone as well as drop the water table at the same time.

During dry periods over seasons or months or even years there may not be enough water to flow down all of the possible water paths from the surface to the cave chamber in which the speleothems form. Thus while some speleothems may grow during a dry period because they are along a preferred flow path, others will dry up. If the the normal wet season is particularly dry then some speleothems will not receive any water at all.

I could see this on Isla de Mona, Puerto Rico. During most of the times I have visited the island most of the spel3othems in the caves, and the caves were reasonably well decorated, looked dry and desiccated, and were dusty to the touch.

However during a large rain event all of these speleothems became active and wet. For those whose drip water feeding them was saturated with caco3, they only would grow and could only potentially add rings during periods when it was very wet.

Others received water on a more continuous basis and would have the potential for more rings. As a caveat probably only those with nearly continuous flow would be good candidates for developing the concentric rings demonstrated by the stalagmites in question, but periods of several years of hiatus in which growth did not take pace is not out of the question. The key would be to see if there was some way to identify these hiatuses in the cross section of the stal.

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The other possibilities for missing rings include maybe the technique was not sensitive enough or set at a sufficient resolution to detect thin rings, or that two adjacent growth periods may have had a virtually identical coloration and were not distinguished in the analysis.

Again, that is something that could be looked at if you had the original stal to examine. Ed Frank dbhg- comcast. There is plenty to review or at least comment on for drought records in the American SW. I would guess the authors of the tree-rings vs speleothems felt snubbed by the lack of acknowledgement in the review of New Mexico drought history; like the speleothems trumped the tree-rings.

When reviewing a subject in the scientific literature, it is proper and instructive to point out similarities and differences with other studies in the region. I haven't looked at the paper in a long time, but I do not think that the two records even agreed upon the major historical drought events. So, it begged the question, "what is the coherency between these records?

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Ideally, we should be able to use each in concert to better understand the Earth system. I wouldn't say the comparison was silly and pointless. These types of comparisons are necessary because they will teach us what parts of the the Earth climate system each proxy is reflecting and what more we need to learn. The Earth system is complex. We need all the proxies in our current tool kit and we need to know what each proxy is saying.

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With perhaps a period of delay before 'percolating' down to the cave environment? It would be very uncommon to find delays greater than that. If you want to find rings then you need drips with a short retention time for the water otherwise any variations would be smoothed out.

I doubt that the large stalagmites in Carlsbad's Big Room at feet have a delay of more than a few weeks if that. I don't know that the subject has been studied in detail. So yes the rings would show a big blip associated with nuclear weapons use, particularly in c14 incorporated into the calcite.

Particles are another question. If the flow is direct enough to carry particles through, then the saturation index of the calcite may not be high enough to precipitate calcite upon entering the cave atmosphere. Some transport does take place, and some stal is dirtier than others, but these are not ideal for speleothem research because of the detrital material present. I have searched a number of websites, but all have assumed the reader is up on these things.

For the one uninformed ENTS member, could someone throw me a bone here. There are dozens of different speleothems with differing shapes, and compositions.

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The most common and the ones relevant here are those made of calcite or aragonite a pseudomorph with the same composition. The three most common speleothems are stalactites which look like icicles hanging from the ceiling, stalagmites which grow like fat posts from the ground and flowstone, which forms waterfall-like deposits on the surfaces of cave wall. Stalactites Cling tight to the ceiling Stalagmites Grow mighty from the ground Many speleothems are variants of these basic features or combinations of them.

A column is formed when a stalactite and stalagmite grow together.

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Rain falls from the sky. Generally it hold dissolved CO2 at atmospheric concentrations and pressure. When it hits the ground it sinks into the soil. Soil concentrations of CO2 are much higher. The water picks up more co2 and this forms a weak carbonic acid solution. This solution is aggressive meaning it has the potential to dissolve to calcite.

If the rock below is limestone, made up of calcite mineral, the water with the increased co2 will try to dissolve it. The water moves down through the limestone along cracks and fractures. This is called secondary permeability. Primary permeability allows water to pass through the matrix of the rock itself between particles. Limestone has virtually no primary permeability, so movement is virtually entirely along cracks and fractures.

As it flows, this aggressive water dissolves calcite from the surfaces of the cracks. These cracks may be large in size or microscopic. If it flows far enough it will eventually become saturated with dissolved calcite.

If the flow path of the water then intersects a cave, an open area in the subsurface, then things change. The atmosphere of the cave is generally almost the same as the surface atmosphere with respect to co2 concentration. Caves breath and air passes in and out with wind and pressure changes.

The water will form a drop on the ceiling of the cave. The water contains dissolved co2 at a higher partial pressure than the cave atmosphere, so it degasses. With the loss of co2, the droplet is able to hold less dissolved calcite, so the calcite precipitates from the droplet.

Depending on the situation this precipitation may take place on the cave ceiling forming a ring of precipitated calcite, and eventually a stalactite.

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In other situations the drop will fall before the calcite precipitates. When it hits the ground the droplet splatters into many smaller droplets. With greater surface area these droplets de-gas faster, lose some of their dissolved co2 and precipitate calcite from solution eventually forming a stalagmite.

On the ceiling these little rings will add layer upon layer, ring upon ring, and slowly lengthen to form a narrow hollow tube. These are called soda straws, because of their similarity in size to soda straws, and because they are hollow.

Water flows down the inside of the tube and deposits a new ring at the base of the tube where it first encounters the cave atmosphere. These soda straws can grow to many feet in length until their own weigh or disturbance will cause them to fracture. Generally before they reach great length they will plug up.

Then the water flows along the outside of the tube forming the common carrot shaped stalactite. The deposition is concentric. Calcite is first deposited in one place, then as that point is now higher, the next drop flows somewhere else, and deposits its load of calcite, etc. It is a self regulating system that assures that calcite is evenly deposited around the perimeter of the stalactite.

Pure calcite is clear. Impurities and gas bubbles give it some color. In speleothems the major source of color are organic dyes, like tannin, etc that give them some color. The production of these organic dyes is related to activity on the surface, plant growth, decay, autumn, rainfall. These activities are seasonal. Therefore as calcite incorporating these dyes is deposited in the speleothems, there is a color variation in the stalactites and stalagmites that is also seasonal.

Since they deposit the calcite uniformly around the exterior of the stalactite and stalagmite These seasonal color variations are deposited in concentric bands or rings around the stalactite. These are the rings the posts are talking about. These bands can form in some cases in a single major rainfall event. It is possible that two rings may form if there are two wet periods and two growth seasons on the surface.

Rings may be missing if the stalactite did not get water in a particular season, or if there was insufficient difference in the color to distinguish a color difference. Most stalactites have rings, but they are not prominent in every case.

Only a few are good candidates for trying to find annual or near annual rings.

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Given these limitations, speleothem rings have enormous potential for environmental interpretations as some may contain records for hundreds of thousands of years. Ed, if it isn't too much of a job, could you go a step farther and give a layperson definition for various common cave formations?

We'd all appreciate it immensely. Thanks in advance. I promised to put my money where my mouth is and tell all of you how I would approach the problem. I have been thinking about it for some time, but just sat down and wrote this out this evening.

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I am sure I could polish it more, but If any of you want to offer me a graduate assistantship or research position to pursue this, I would not be adverse to the offer. Can you distinguish areas with missing rings? Do these areas correspond to particular characteristic of tree rings chronology?

Dealing with missing data Surveying analogy Cyclical pattern to infer duration of missing area?

is suggesting that the stalagmite can be dated by simply counting the. rings. In the case of these stalagmites or stalactites, especially in. hanging dates beyond the tree ring chronology, the resolution of the. actual age of the speleothem can not be greater than the resolution of. the dating technique. Carbonate speleothems that contain ppb-ppm levels of uranium can be dated by the UUTh and UPa disequilibrium techniques. Accurate ages are possible if Cited by: Speleothems, despite their uniform mineralogy (calcite, less commonly aragonite), occur in a great variety of forms, dimensions, and colors, and any of these can be dated by U-series methods provided their age is within the dating limit of the particular method. Still, with some exceptions, the majority of scientific studies have so far relied on stalagmites rather than stalactites, flowstones, or .

Is missing data important for the purpose you are using it for? Other types of climatic data Pollen Stable Isotopes Fluid Inclusions Conclusions Statement of Problem: Tree rings provide a useful analog for climatic data over the duration of the tree chronology of a few thousand years.

Speleothems also have annual rings.

Dating speleothems

Speleothem rings potentially can establish a chronology over many thousands to hundreds of thousands of years. The problem is that rings are often missing from a particular speleothem and it is unclear that the thickness of the rings has any meaningful relationship to overall climatic conditions.

Can tree ring data be used to calibrate speleothem data so that it can be used for meaningful annual climatic interpretations, and can the problem of missing rings be dealt with so that the resulting annual interpretations can be used for climatic interpretations over the longer time span of the speleothem record beyond that available to tree ring records.

Literature Review: The literature of dendrochronology is extensive.

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A literature review would be conducted to provide a background understanding of dendrochronology, its strengths and weaknesses, and implied assumptions used in making the correlation climatic interpretations. Specifically literature related to the establishment of a tree ring chronology in the area of the study would be reviewed in detail.

The literature relating to speleothem rings is much less extensive. A review of most of the speleothem literature would be feasible. Literature discussing the relationships between tree rings and speleothem rings is limited and an attempt should be made to review virtually all of this material. Several specimens from different areas could be selected to allow the comparison of results between the samples.

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In general actually having the speleothem sample is critical because the suggested protocol requires a reevaluation of the sample as problem areas are identified by making correlations with tree ring chronologies. Some samples are clearly better than others. In most caves there are speleothems already broken by previous visitors.

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Using these specimens for the analysis not only promotes cave conservation by not damaging other speleothems, but allows the collector to visually inspect the broken surface of the speleothem for rings prior to collection. Also specimens that have undergone extensive recrystalization can be avoided prior to collection. Specimens with dark, heavy rings are not good because they suggest a large amount of non-calcitic material may have been incorporated into the speleothem, a potential cause for age dating irregularities.

Good sized specimens, light in color, with faint but distinguishable rings, with no signs of recrystalization or inclusions, are best are the best. Detection of rings: a number of techniques have been used to distinguish rings in speleothems. The literature review would help determine the optimum methodology for ring detection.

At the moment the best method seems to be done using an optical scanner.



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