However, it is well established that volcanic rocks e. The layers of sediment are up to meters thick and were supposedly laid down one layer at a time each year. Carbon has 3 isotopic forms: But then, these geologists put a happy face on the situation. Stratigraphic applications of the method have been demonstrated from both marine and non-marine sequences all over the world using a variety of carbonate fossil materials including mollusks, foraminifera, bone, ostrich egg shells, ostracodes, and tooth enamel. Carbon has a half-life of 5, years. It provides more accurate dating within sites than previous methods, which usually derived either from stratigraphy or from typologies e.
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Once produced, the 14 C quickly combines with the oxygen in the atmosphere to form carbon dioxide CO 2. The first number corresponds to the years before present. Once it dies, it ceases to acquire 14 C , but the 14 C within its biological material at that time will continue to decay, and so the ratio of 14 C to 12 C in its remains will gradually decrease. It is these highly consistent and reliable samples, rather than the tricky ones, that have to be falsified for "young Earth" theories to have any scientific plausibility, not to mention the need to falsify huge amounts of evidence from other techniques. The Himalayan mountains are said by most modern scientists to have started their uplift or orogeny some 50 million years ago.
No matter what the geologic situation, these basic principles reliably yield a reconstructed history of the sequence of events, both depositional, erosional, deformational, and others, for the geology of a region.
This reconstruction is tested and refined as new field information is collected, and can be and often is done completely independently of anything to do with other methods e.
The reconstructed history of events forms a "relative time scale", because it is possible to tell that event A occurred prior to event B, which occurred prior to event C, regardless of the actual duration of time between them.
Sometimes this study is referred to as "event stratigraphy", a term that applies regardless of the type of event that occurs biologic, sedimentologic, environmental, volcanic, magnetic, diagenetic, tectonic, etc. These simple techniques have widely and successfully applied since at least the early s, and by the early s, geologists had recognized that many obvious similarities existed in terms of the independently-reconstructed sequence of geologic events observed in different parts of the world.
One of the earliest relative time scales based upon this observation was the subdivision of the Earth's stratigraphy and therefore its history , into the "Primary", "Secondary", "Tertiary", and later "Quaternary" strata based mainly on characteristic rock types in Europe.
The latter two subdivisions, in an emended form, are still used today by geologists. The earliest, "Primary" is somewhat similar to the modern Paleozoic and Precambrian, and the "Secondary" is similar to the modern Mesozoic. Another observation was the similarity of the fossils observed within the succession of strata, which leads to the next topic. As geologists continued to reconstruct the Earth's geologic history in the s and early s, they quickly recognized that the distribution of fossils within this history was not random -- fossils occurred in a consistent order.
This was true at a regional, and even a global scale. Furthermore, fossil organisms were more unique than rock types, and much more varied, offering the potential for a much more precise subdivision of the stratigraphy and events within it. The recognition of the utility of fossils for more precise "relative dating" is often attributed to William Smith, a canal engineer who observed the fossil succession while digging through the rocks of southern England. But scientists like Albert Oppel hit upon the same principles at about about the same time or earlier.
In Smith's case, by using empirical observations of the fossil succession, he was able to propose a fine subdivision of the rocks and map out the formations of southern England in one of the earliest geological maps Other workers in the rest of Europe, and eventually the rest of the world, were able to compare directly to the same fossil succession in their areas, even when the rock types themselves varied at finer scale.
For example, everywhere in the world, trilobites were found lower in the stratigraphy than marine reptiles. Dinosaurs were found after the first occurrence of land plants, insects, and amphibians. Spore-bearing land plants like ferns were always found before the occurrence of flowering plants. The observation that fossils occur in a consistent succession is known as the "principle of faunal and floral succession". The study of the succession of fossils and its application to relative dating is known as "biostratigraphy".
Each increment of time in the stratigraphy could be characterized by a particular assemblage of fossil organisms, formally termed a biostratigraphic "zone" by the German paleontologists Friedrich Quenstedt and Albert Oppel. These zones could then be traced over large regions, and eventually globally. Groups of zones were used to establish larger intervals of stratigraphy, known as geologic "stages" and geologic "systems".
The time corresponding to most of these intervals of rock became known as geologic "ages" and "periods", respectively.
By the end of the s, most of the presently-used geologic periods had been established based on their fossil content and their observed relative position in the stratigraphy e. These terms were preceded by decades by other terms for various geologic subdivisions, and although there was subsequent debate over their exact boundaries e.
By the s, fossil succession had been studied to an increasing degree, such that the broad history of life on Earth was well understood, regardless of the debate over the names applied to portions of it, and where exactly to make the divisions. All paleontologists recognized unmistakable trends in morphology through time in the succession of fossil organisms. This observation led to attempts to explain the fossil succession by various mechanisms.
Perhaps the best known example is Darwin's theory of evolution by natural selection. Note that chronologically, fossil succession was well and independently established long before Darwin's evolutionary theory was proposed in Fossil succession and the geologic time scale are constrained by the observed order of the stratigraphy -- basically geometry -- not by evolutionary theory.
For almost the next years, geologists operated using relative dating methods, both using the basic principles of geology and fossil succession biostratigraphy. Various attempts were made as far back as the s to scientifically estimate the age of the Earth, and, later, to use this to calibrate the relative time scale to numeric values refer to "Changing views of the history of the Earth" by Richard Harter and Chris Stassen. Most of the early attempts were based on rates of deposition, erosion, and other geological processes, which yielded uncertain time estimates, but which clearly indicated Earth history was at least million or more years old.
A challenge to this interpretation came in the form of Lord Kelvin's William Thomson's calculations of the heat flow from the Earth, and the implication this had for the age -- rather than hundreds of millions of years, the Earth could be as young as tens of million of years old.
This evaluation was subsequently invalidated by the discovery of radioactivity in the last years of the 19th century, which was an unaccounted for source of heat in Kelvin's original calculations. With it factored in, the Earth could be vastly older. Estimates of the age of the Earth again returned to the prior methods.
The discovery of radioactivity also had another side effect, although it was several more decades before its additional significance to geology became apparent and the techniques became refined. Because of the chemistry of rocks, it was possible to calculate how much radioactive decay had occurred since an appropriate mineral had formed, and how much time had therefore expired, by looking at the ratio between the original radioactive isotope and its product, if the decay rate was known.
Many geological complications and measurement difficulties existed, but initial attempts at the method clearly demonstrated that the Earth was very old. In fact, the numbers that became available were significantly older than even some geologists were expecting -- rather than hundreds of millions of years, which was the minimum age expected, the Earth's history was clearly at least billions of years long.
Radiometric dating provides numerical values for the age of an appropriate rock, usually expressed in millions of years. Therefore, by dating a series of rocks in a vertical succession of strata previously recognized with basic geologic principles see Stratigraphic principles and relative time , it can provide a numerical calibration for what would otherwise be only an ordering of events -- i. The integration of relative dating and radiometric dating has resulted in a series of increasingly precise "absolute" i.
Given the background above, the information used for a geologic time scale can be related like this: A continuous vertical stratigraphic section will provide the order of occurrence of events column 1 of Figure 2.
These are summarized in terms of a "relative time scale" column 2 of Figure 2. Geologists can refer to intervals of time as being "pre-first appearance of species A" or "during the existence of species A", or "after volcanic eruption 1" at least six subdivisions are possible in the example in Figure 2.
For this type of "relative dating" to work it must be known that the succession of events is unique or at least that duplicate events are recognized -- e. Unique events can be biological e. Ideally, geologists are looking for events that are unmistakably unique, in a consistent order, and of global extent in order to construct a geological time scale with global significance.
Some of these events do exist. For example, the boundary between the Cretaceous and Tertiary periods is recognized on the basis of the extinction of a large number of organisms globally including ammonites, dinosaurs, and others , the first appearance of new types of organisms, the presence of geochemical anomalies notably iridium , and unusual types of minerals related to meteorite impact processes impact spherules and shocked quartz.
These types of distinctive events provide confirmation that the Earth's stratigraphy is genuinely successional on a global scale. Even without that knowledge, it is still possible to construct local geologic time scales. Although the idea that unique physical and biotic events are synchronous might sound like an "assumption", it is not. It can, and has been, tested in innumerable ways since the 19th century, in some cases by physically tracing distinct units laterally for hundreds or thousands of kilometres and looking very carefully to see if the order of events changes.
Geologists do sometimes find events that are "diachronous" i. Because any newly-studied locality will have independent fossil, superpositional, or radiometric data that have not yet been incorporated into the global geological time scale, all data types serve as both an independent test of each other on a local scale , and of the global geological time scale itself.
The test is more than just a "right" or "wrong" assessment, because there is a certain level of uncertainty in all age determinations. For example, an inconsistency may indicate that a particular geological boundary occurred 76 million years ago, rather than 75 million years ago, which might be cause for revising the age estimate, but does not make the original estimate flagrantly "wrong".
It depends upon the exact situation, and how much data are present to test hypotheses e. Whatever the situation, the current global geological time scale makes predictions about relationships between relative and absolute age-dating at a local scale, and the input of new data means the global geologic time scale is continually refined and is known with increasing precision.
This trend can be seen by looking at the history of proposed geologic time scales described in the first chapter of [Harland et al, , p. The unfortunate part of the natural process of refinement of time scales is the appearance of circularity if people do not look at the source of the data carefully enough. Most commonly, this is characterised by oversimplified statements like:.
Even some geologists have stated this misconception in slightly different words in seemingly authoritative works e. When a geologist collects a rock sample for radiometric age dating, or collects a fossil, there are independent constraints on the relative and numerical age of the resulting data.
Stratigraphic position is an obvious one, but there are many others. There is no way for a geologist to choose what numerical value a radiometric date will yield, or what position a fossil will be found at in a stratigraphic section.
Every piece of data collected like this is an independent check of what has been previously studied. The data are determined by the rocks , not by preconceived notions about what will be found. Every time a rock is picked up it is a test of the predictions made by the current understanding of the geological time scale. The time scale is refined to reflect the relatively few and progressively smaller inconsistencies that are found.
This is not circularity, it is the normal scientific process of refining one's understanding with new data. It happens in all sciences. The percentage of 40 Ar is even less for younger rocks. For example, it would be about one part in million for rocks in the vicinity of million years old. However, to get just one part in 10 million of argon in a rock in a thousand years, we would only need to get one part in 10 billion entering the rock each year.
This would be less than one part in a trillion entering the rock each day, on the average. This would suffice to give a rock an average computed potassium-argon age of over a billion years. Some geochronologists believe that a possible cause of excess argon is that argon diffuses into certain minerals progressively with time and pressure.
Significant quantities of argon may be introduced into a mineral even at pressures as low as one bar. We can also consider the average abundance of argon in the crust.
This implies a radiometric age of over 4 billion years. So a rock can get a very old radiometric age just by having average amounts of potassium and argon. It seems reasonable to me that the large radiometric ages are simply a consequence of mixing, and not related to ages at all, at least not necessarily the ages of the rocks themselves.
It seems to me to be a certainty that water and gas will enter most, if not all, volcanic type rocks through tiny openings and invalidate almost all K-Ar ages. Rocks are not sealed off from the environment. This contamination would seem to be more and more of a problem the older the rock became.
Let me illustrate the circulation patterns of argon in the earth's crust. So argon is being produced throughout the earth's crust, and in the magma, all the time. In fact, it probably rises to the top of the magma, artificially increasing its concentration there.
Now, some rocks in the crust are believed not to hold their argon, so this argon will enter the spaces between the rocks. Leaching also occurs, releasing argon from rocks. Heating of rocks can also release argon. Argon is released from lava as it cools, and probably filters up into the crust from the magma below, along with helium and other radioactive decay products. All of this argon is being produced and entering the air and water in between the rocks, and gradually filtering up to the atmosphere.
So this argon that is being produced will leave some rocks and enter others. Different Dating Methods Agree. It is often said that a great many dating methods, used on a single specimen, will agree with each other, thus establishing the accuracy of the date given. In reality, the overwhelming majority of measurements on the fossil bearing geologic column are all done using one method, the K-Ar method Recall that both potassium and argon are water soluble, and argon a gas is mobile in rock.
Thus the agreement found between many dates does not necessarily reflect an agreement between different methods, but rather the agreement of the K-Ar method with itself Especially noting that Dalrymple suggested that only K-Ar dating methods were at all trust worthy. I have seen no good double-blinded research studies that say otherwise.
One would think that if this were a good science, then such studies would be done and published, but they are strangely lacking. Also, specific differences are known and have been known to exist between different dating methods.
For example, Isotopic studies of the Cardenas Basalt and associated Proterozoic diabase sills and dikes have produced a geologic mystery. Using the conventional assumptions of radioisotope dating, the Rb-Sr and K-Ar systems should give concordant "ages". However, it has been known for over 20 years that the two systems give discordant "ages", the K-Ar "age" being significantly younger than the Rb-Sr "age".
The "argon reset model" was the first explanation proposed for the discordance. A metamorphic event is supposed to have expelled significant argon from these rocks. The reset model is unable to reconcile the new data, leading to a metamorphic event which is excessively young and inconsistent with the conventional stratigraphic interpretation. The "argon leakage model" also attempts to explain why these rocks have about half the argon which seems to be required by the Rb-Sr system.
The leakage model supposes an incredible improbability. Both the old and new data imply that the rocks leaked argon in nearly exact proportion to the abundance of potassium producing a "leakage isochron", an explanation not supported by a quantity of an appropriate mineral or mesostasis phase.
Strong negative correlation between K-Ar model age and K 2 O in the upper portion of the Cardenas Basalt is not easily explained in a consistent manner. Furthermore, reset and leakage models have difficulty explaining the abundance of initial 36 Ar in the rocks, especially the abundance of 36 Ar in those rocks which supposedly leaked the most 40 Ar. Three alternatives are suggested to the two argon loss models. The "argon inheritance model" and "argon mixing model" simply propose that argon is positively correlated with potassium from its magma source or produced by a mixing process, and that the linear relationship on a plot of 40 Ar versus 40 K is an artifact of the magma, not produced by radioisotope decay within these rocks.
The inheritance of argon seems to be a better model than is the mixing model. All three explanations offered as alternatives to the argon loss models invalidate using the K-Ar system as conventional geochronology would assume. The word "isochron" basically means "same age". Isochron dating is based on the ability to draw a straight line between data points that are thought to have formed at the same time.
The slope of this line is used to calculate an age of the sample in isochron radiometric dating. The isochron method of dating is perhaps the most logically sound of all the dating methods - at first approximation.
This method seems to have internal measures to weed out those specimens that are not adequate for radiometric evaluation. Also, the various isochron dating systems seem to eliminate the problem of not knowing how much daughter element was present when the rock formed. Isochron dating is unique in that it goes beyond measurements of parent and daughter isotopes to calculate the age of the sample based on a simple ratio of parent to daughter isotopes and a decay rate constant - plus one other key measurement.
What is needed is a measurement of a second isotope of the same element as the daughter isotope. Also, several different measurements are needed from various locations and materials within the specimen. This is different from the normal single point test used with the other "generic" methods. To make the straight line needed for isochron dating each group of measurements parent - P, daughter - D, daughter isotope - Di is plotted as a data point on a graph.
The X-axis on the graph is the ratio of P to Di. For example, consider the following isochron graph: Obviously, if a line were drawn between these data points on the graph, there would be a very nice straight line with a positive slope. Such a straight line would seem to indicate a strong correlation between the amount of P in each sample and the extent to which the sample is enriched in D relative to Di.
Obviously one would expect an increase in the ratio of D as compared with Di over time because P is constantly decaying into D, but not into Di. So, Di stays the same while D increases over time. But, what if the original rock was homogenous when it was made? What if all the minerals were evenly distributed throughout, atom for atom?
What would an isochron of this rock look like? It would look like a single dot on the graph. Because, any testing of any portion of the object would give the same results.
The funny thing is, as rocks cool, different minerals within the rock attract certain atoms more than others. Because of this, certain mineral crystals within a rock will incorporate different elements into their structure based on their chemical differences. However, since isotopes of the same element have the same chemical properties, there will be no preference in the inclusion of any one isotope over any other in any particular crystalline mineral as it forms.
So, when put on an isochron graph, each mineral will have the same Y-value. Since a perfectly horizontal line is likely obtained from a rock as soon as it solidifies, such a horizontal line is consistent with a "zero age.
Time might still be able to be determined based on changes in the slope of this horizontal line. As time passes, P decays into D in each sample. That means that P decreases while D increases. This results in a movement of the data points. Each data point moves to the left decrease in P and upwards increase in D. Since radioactive decay proceeds in a proportional manner, the data points with the most P will move the most in a given amount of time. Thus, the data points maintain their linear arrangement over time as the slope between them increases.
The degree of slope can then be used to calculate the time since the line was horizontal or "newly formed". The slope created by these points is the age and the intercept is the initial daughter ratio. The scheme is mathematically sound. The nice thing about isochrons is that they would seem to be able to detect any sort of contamination of the specimen over time. If any data point became contaminated by outside material, it would no longer find itself in such a nice linear pattern.
Thus, isochrons do indeed seem to contain somewhat of an internal indicator or control for contamination that indicates the general suitability or unsuitability of a specimen for dating. So, it is starting to look like isochron dating has solved some of the major problems of other dating methods. However, isochron dating is still based on certain assumptions. All areas of a given specimen formed at the same time. The specimen was entirely homogenous when it formed not layered or incompletely mixed.
Limited Contamination contamination can form straight lines that are misleading. Isochrons that are based on intra-specimen crystals can be extrapolated to date the whole specimen. Given these assumptions and the above discussion on isochron dating, some interesting problems arise as one considers certain published isochron dates.
So, what exactly is a whole-rock isochron? Whole-rock isochrons are isochrons that are based, not on intra-rock crystals, but on variations in the non-crystalline portions of a given rock. In other words, sample variations in P are found in different parts of the same rock without being involved with crystalline matrix uptake. This is a problem because the basis of isochron dating is founded on the assumption of original homogeny. If the rock, when it formed, was originally homogenous, then the P element would be equally distributed throughout.
Over time, this homogeny would not change. Thus, any such whole-rock variations in P at some later time would mean that the original rock was never homogenous when it formed.
Because of this problem, whole-rock isochrons are invalid, representing the original incomplete mixing of two or more sources. Interestingly enough, whole rock isochrons can be used as a test to see if the sample shows evidence of mixing. If there is a variation in the P values of a whole rock isochron, then any isochron obtained via crystal based studies will be automatically invalid.
The P values of various whole-rock samples must all be the same, falling on a single point on the graph. If such whole-rock samples are identical as far as their P values, mixing would still not be ruled out completely, but at least all available tests to detect mixing would have been satisfied. And yet, such whole-rock isochrons are commonly published. For example, many isochrons used to date meteorites are most probably the result of mixing since they are based on whole-rock analysis, not on crystalline analysis.
There are also methods used to detect the presence of mixing with crystalline isochron analysis. If a certain correlation is present, the isochron may be caused by a mixing. However, even if the correlation is present, it does not mean the isochron is caused by a mixing, and even if the correlation is absent, the isochron could still be caused by a more complex mixing Woodmorappe, , pp.
Therefore such tests are of questionable value. Interestingly, mainstream scientists are also starting to question the validity of isochron dating. The determination of accurate and precise isochron ages for igneous rocks requires that the initial isotope ratios of the analyzed minerals are identical at the time of eruption or emplacement. Studies of young volcanic rocks at the mineral scale have shown this assumption to be invalid in many instances.
Variations in initial isotope ratios can result in erroneous or imprecise ages. Nevertheless, it is possible for initial isotope ratio variation to be obscured in a statistically acceptable isochron. Independent age determinations and critical appraisal of petrography are needed to evaluate isotope data.
If initial isotope ratio variability can be demonstrated, however, it can be used to constrain petrogenetic pathways. But then,] The cooling history will depend on the volume of magma involved and its starting temperature, which in turn is a function of its composition. If the initial variation is systematic e. In short, isochron dating is not the independent dating method that it was once thought. As with the other dating methods discussed already, isochron dating is also dependent upon "independent age determinations".
Isochrons have been touted by the uniformitarians as a fail-safe method for dating rocks, because the data points are supposed to be self-checking Kenneth Miller used this argument in a debate against Henry Morris years ago. Now, these geologists, publishing in the premiere geological journal in the world, are telling us that isochrons can look perfect on paper yet give meaningless ages, by orders of magnitude, if the initial conditions are not known, or if the rocks were open systems at some time in the past?!
That sounds like what young earth creationists have been complaining about all along. But then, these geologists put a happy face on the situation. The problem is that it is starting to get really difficult to find a truly independent dating method out of all the various dating methods available.
Furthermore, because most upper crustal rocks cooled below annealing temperatures long after their formation, early formed lead rich in Pb is locked in annealed sites so that the leachable component is enriched in recently formed Pb The isotopic composition of the leachable lead component then depends more on the cooling history and annealing temperatures of each host mineral than on their geological age; and the axiom that Pb isotopes cannot be fractionated in the natural environment, is invalid.
Although these experiments are based on a strong Hf attack on zircons, we believe, given the widespread U anomalies of several hundred percent observed in groundwater Osmond and Cowart , that they apply to the differential mobility of radiogenic Pb isotopes on a local and global scale. Also, consider the following excerpt concerning ancient zirons from the Gabbro-Peridotite Complex of the Mar: Zircon age calculations on the base of Upb systematics have been complicated by high share of common Pb and uncertainty of its isotope composition.
Common lead was captured in the process of zircon crystallization, perhaps, by mineral and fluid inclusions. But there is a small share of inherited zircon substance with the age of 3.
Thus, the discordia itself obtained by us is interpreted as a result of mixture of newly formed young zircon with some share of Archean zircon presented in each studied crystal. Also, if errors for individual zircon tests are too large, these values are simply discarded. This enhances the mobility of U and especially Pb. So, how confident can one be in zircon dates who's published Pb levels range from very high to very low?
It seems to me that quite often published U-Pb and Pb-Pb dates do in fact involve fairly significant Pb levels. Of course, if the level of Pb is too high, the data obtained is not calibrated, but is simply discarded.
Doesn't this mess up the idea that all lead in zircons must be the result of radioactive decay? It is also of interest in regard to radiometric dating that Robert Gentry claims to have found "squashed" polonium haloes as well as embryonic uranium radiohaloes in coal deposits from many geological layers claimed to be hundreds of millions of years old.
These haloes represent particles of polonium and uranium, which penetrated into the coal at some point and produced a halo by radioactive decay. The fact that they are squashed indicates that part of the decay process began before the material was compressed, so the polonium had to be present before compression.
Since coal is relatively incompressible, Gentry concludes that these particles of uranium and polonium must have entered the deposit before it turned to coal. However, there is only a very small amount of lead with the uranium; if the uranium had entered hundreds of millions of years ago, then there should be much more lead. However, it's just hard to believe, according to conventional geological time scales, that this coal was compressed any time within the past several thousand or even hundred million years.
Some have argued that "radon that results from uranium decay is an inert gas and may have escaped, resulting in little lead being deposited. This would make the observed haloes consistent with an old age for the coal. In addition, not all of the radon would be on the surface of the particles of uranium.
That which was inside or bordering on coal would likely not be able to escape. Since radon has a half-life of about 4 days, it would not have much time to escape, in any event. What happens when something is dated as being very old, but shows little or no physical signs of relative aging? This basalt group is rather large covering an area of , square kilometers and fills a volume of , cubic kilometers. The vast extent and sheer volume of such individual flows are orders of magnitude larger than anything ever recorded in known human history.
Within this group are around individual lava flows each of rather uniform thickness over many kilometers with several extending up to kilometers from their origin. Now, the problem with the idea that these flows span a period of over 11 million years of deposition is that there is significant physical evidence that the CRBG flows were deposited relatively rapidly with respect to each other and with themselves.
The average time between each flow works out to around 36, years, but where is the erosion to the individual layers of basalt that one would expect to see after 36, years of exposure? The very fact that these flows cover such great distances indicate that the individual flows traveled at a high rate of speed in order to avoid solidification before they covered such huge areas as they did. Also, there are several examples where two or three different flows within the CRBG mix with each other.
This suggests that some of the individual flows did not have enough time to solidify before the next flow s occurred. If some 36, years of time are supposed to separate each of the individual flows where is the evidence of erosion in the form of valleys or gullies cutting into the individual lava flows to be filled in by the next lava flow?
There are no beds of basalt boulders that would would expect to be formed over such spans of time between individual flows. However, a recent real time study by Riebe et. Over the course of 36, years this works out to between 6 to 7 meters 19 to 23 feet of vertical erosion. This is significant erosion and there should be evidence of this sort of erosion if the time gap between flow was really 36, years.
So, where is this evidence? For several other such flows in the United States and elsewhere around the world the time intervals between flows are thought to be even longer - and yet still there is little evidence of the erosion that would be expected after such passages of time. For example, the Lincoln Porphyry of Colorado was originally thought to be a single unit because of the geographic proximity of the outcrops and the mineralogical and chemical similarities throughout the formation.
Later, this idea was revised after radiometric dating placed various layers of the Lincoln Porphyry almost 30 million years apart in time.
But how can such layers which show little if any evidence of interim erosion have been laid down thousands much less millions of years apart in time? Other examples, such as the Garrawilla Lavas of New South Wales, Australia, are found between the Upper Triassic and Jurassic layers and yet these lavas, over a very large area, grade imperceptibly into lavas which overlie Lower Tertiary sedimentary rock supposedly laid down over million years later.
The Napperby depositional sequence represents the upper limit of the Gunnedah Basin sequence, with a regional unconformity existing between the Triassic and overlying Jurassic sediments of the Surat Basin north of the Liverpool Ranges. The Gunnedah Basin sequence includes a number of basic intrusions of Mesozoic and Tertiary rocks.
These are associated with massive extrusions of the Garrawilla Volcanic complex and the Liverpool, Warrumbungle and Nandewar Ranges. Also, throughout the CRBG and elsewhere are found "pillow lava" and palagonite formations - especially near the periphery of the lava flows. There are a few outcrops where tens of meters of vertical outcrop and hundreds of meters of horizontal outcrop consist entirely of pillow structures.
Also, palagonite, with a greenish-yellow appearance produced via the reaction of hot lava coming in contact with water, is found throughout. These features are suggestive of lava flow formation in a very wet or even underwater environment.
Certainly pillow lavas indicate underwater deposition, but note that lavas can be extruded subaqeously without the production of pillow structures.
The potential to form pillow lava decreases as the volume of extruded lava increases. Thus, the effective contact area between lava and water where pillow formations can potentially form becomes proportionately smaller as the volume of lava extruded becomes larger. Other evidences of underwater formation include the finding of fresh water fossils such as sponge spicules, diatoms, and dinoflagellates between individual lava flows.
Consider some interesting conclusions about these findings by Barnett and Fisk in a paper published in the journal, Northwest Science: The Palouse Falls palynoflora reflects reasonably well the regional climatic conditions as evidence by the related floras of the Columbia Plateau. The presence of planktonic forms, aquatic macrophytes, and marsh plants indicates that deposition of the sediments took place in a body of water, probably a pond or lake.
This interpretation is supported by the presence of abundant diatoms. The general decrease in aquatic plants and increase in forest elements upward in the section suggest a shallowing or infilling of the pond or lake, perhaps due to increased volcanic activity and erosion of ash from the surrounding region.
Supporting this view is the presence of thin bands of lignite near the top of the section, with a cm coal layer just underlying the capping basalt. Now, what is interesting here is that these "forest elements" to include large lenses of fossilized wood are widely divergent in the type of preserved wood found. It is interesting that hundreds of species are found all mixed up together ranging from temperate birch and spruce to subtropical Eucalyptus and bald cypress. The petrified logs have been stripped of limbs and bark and are generally found in the pillow complexes of the basaltic flows, implying that water preserved the wood from being completely destroyed by the intense heat of the lava as it buried them.
For Barnett and Fisk to suggest that the finding of such fossil remains suggest the presence of a small pond or lake being filled in by successive flows just doesn't seem to add up. How are such ecologically divergent trees going to get concentrated around an infilling pond or lake?
Also, how is a 10cm layer of coal going to be able to form under the "capping basalt"? It is supposed to take very long periods of time, great pressure, heat, and moisture to produce coal. How did this very thin layer of coal form and then be preserved without evidence of any sort of uneven erosion by a relatively thin layer of capping basalt? Also, numerous well-rounded quartzite gravel, cobbles, and boulders locally interbedded within and above the basalt flows.
Does this make any sense? Therefore, radiocarbon dates need to be calibrated with other dating techniques to ensure accuracy. Plants are not the only organism that can process Carbon from the air. Since plankton is the foundation of the marine food chain, Carbon is spread throughout aquatic life.
In recognition of this problem archaeologists have developed regional reservoir correction rates based on ocean bottom topography, water temperature, coastline shape and paired samples of terrestrial and marine objects found together in an archaeological feature such as a hearth.
Long tree-ring sequences have been developed throughout the world and can be used to check and calibrate radiocarbon dates. An extensive tree-ring sequence from the present to BC was developed in Arizona using California bristlecone pine Pinus aristata , some of which are years old, making them the oldest living things on earth.
Additional sequences have been developed for oak species in Ireland and Germany, ice core samples, and coral reefs from Caribbean islands. These sequences have helped to calibrate radiocarbon dates to calendar years, thus making them more accurate. Normally after 12, BP, the coral dating is used. The first number corresponds to the years before present. The second number is the standard deviation or error for the date. It creates a date range of - years before present that the sample can fall under.
An Introduction , 3rd edition, Philadelphia: University of Pennsylvania Press.
Images: dating methods of fossils
Silicate rocks, like quartz, are particularly good at trapping electrons. This carbon combines with oxygen to form carbon dioxide and is taken in by plants and then animals. I have seen no good double-blinded research studies that say otherwise.
A few principles were recognized and specified later. A straightforward reading of the Bible shows that the earth was created in six days about 6, years ago. Like gas counters, liquid scintillation counters require shielding and anticoincidence counters.
The observation that fossils occur in a consistent succession is known as the "principle of faunal and floral dating methods of fossils. The human element is also important dating age range rule. The Pleistocene methoss a geological epoch that began about nethods. This was true at a regional, and even a global scale. The average time between each flow works out to around 36, years, but where is the erosion to the individual layers of basalt that one would expect to see after 36, dating methods of fossils of exposure? By comparing the proportion of K to Ar in a sample of volcanic rock, and knowing the decay rate of K, the date that the rock formed can be determined.
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