史上有过一个案例,我们发现什么似乎是一个史前化石,但没有办法约会吗?- 江南体育网页版- - - - -地球科学堆江南电子竞技平台栈交换 最近30从www.hoelymoley.com 2023 - 07 - 07 - t21:35:28z //www.hoelymoley.com/feeds/question/19439 https://creativecommons.org/licenses/by-sa/4.0/rdf //www.hoelymoley.com/q/19439 6 史上有过一个案例,我们发现什么似乎是一个史前化石,但没有办法约会吗? 香农 //www.hoelymoley.com/users/19121 2020 - 03 - 11 - t16:25:41z 2022 - 07 - 22 - t15:20:10z < p >我发现,当我学一个新的化石,化石总是说提到的时代。这个困扰我鉴于直觉罕见迄今似乎有放射性物质的形成。我知道,古生物学家也使用其他化石形成日期新化石然而肯定有情况下,我们发现新化石,我们没有办法知道年龄吗? < / p > //www.hoelymoley.com/questions/19439/-/19440 # 19440 0 回答由Michael Walsby史上有过一个案例,我们发现什么似乎是一个史前化石,但没有办法约会吗? 迈克尔Walsby //www.hoelymoley.com/users/17166 2020 - 03 - 11 - t19:45:48z 2020 - 03 - 11 - t19:45:48z < p >总有一些约会的化石。这个问题与其说是在寻求一种方式找到一个准确的方法。实验室通常要处理非常少量的材料。比如钾-氩法。< / p > < p >火山凝灰岩不会纯钾,它只会包含一个痕迹。一千年只有一个钾原子放射性钾40(半衰期1、3000、000000年)。因此只有有用的约会数百万年旧的东西,不适合约会尼安德特人化石,例如。困难并没有结束。只有11%的K40非常不同寻常的方式成为Ar40衰变,衰变的其余部分正常的β衰变成为钙40。< / p > < p >你可以看到程序非常微妙和敏感,因为微量科学家一起工作,这是一个不知道他们得到了有用的结果。 Such dating is often contentious as not surprisingly, like all radiometric dating, it is subject to error. Similar problems exist with regard to carbon 14, which is suited to more recent fossils like Neanderthal man.

For dating fossils as far back as the late Precambrian a new dating method called the rhenium - osmium method has recently been used, and is much more accurate for that period than previous methods, being capable of reliably dating fossils a billion years old. Previous inaccurate datings were rendered obsolete.

Fossils found in limestone cave accretions such as Raymond Dart's Taung child (a gracile australopithecine from S. Africa) are notoriously difficult to date because of the lack of stratigraphy and suitable radioactive elements.

//www.hoelymoley.com/questions/19439/-/19445 # 19445 9 答案由Inkenbrandt史上有过一个案例,我们发现了什么似乎是一个史前化石,但没有办法约会吗? Inkenbrandt //www.hoelymoley.com/users/510 2020 - 03 - 12 - t15:00:14z 2020 - 03 - 12 - t16:46:44z < p >简短的回答是否定的,因为我们总是有一些旧东西的约束。有时我们与大化石日期误差,通常我们不知道多久,物种的存在。大日期范围限制在某些情况下,像考古一样,不可能是有用的。如果标本取自没有注意的位置,然后我们迄今没有上下文,这是一个很大的理由不掠夺古生物网站。< / p > < p >约会化石、岩石的上下文层,其他化石,横切机组和位置是关键。地质学家必须使用绝对和相对年龄测定技术的结合。地质学家研究岩层的化石被发现和比较其他岩层层段关联。他们使用基本的相对年龄测定方法,包括:< / p > < ul > <李>叠加原理:老层底部,年轻的层上李< / > <李>横切关系的原则:如果一个特性(如火成岩侵入和错误)穿过一层,那么以下的特性是层< /李> <李>原始水平状态:原理层沉积以水平方式< /李> <李>横向连续性原则:横向层一般沉积在一个连续的方式,直到他们捏;如果你看到一个峡谷两侧和类似的层,你可以假设它以前连续峡谷是年轻。李李< / > < >动物区系演替原理:化石的存在与否团体可以使用的时间李< / > < / ul > < p >有各种各样的绝对年代测定技术,每个都有自己的时间和介质的限制。同位素年龄测定、裂变径迹的约会和古地磁的方法通常局限于火成岩。 For radiometric dating, only a small quantity of isotopes are needed for a measurable date. Igneous rocks contain usable quantities of minerals like zircon that are good at holding atoms of uranium and other elements useful in for the absolute age-dating technique. Geologists use absolute dates of rocks that can be dated in combination with relative dating techniques to constrain the age of a rock layer that cannot be dated with absolute techniques.

Fossil morphology must also be considered to determine if you are really looking at a new species or just a special case of a previously identified species. Sometimes, evolutionary approaches can be applied to help place the specimen into a timeline.

Figuring out the temporal extent of a species takes more time and multiple discoveries of samples of that species to better constrain that extent.

A combination of approaches and techniques can help paleontologists be detectives in determining the age of specimen. Like other sciences, geology is social in the sense that it relies on the culmination of the work of many, with multiple lines of complementary pieces of information, to come to a conclusive age.

Here are some great articles related to your question:

Here is an example of an "undatable" fossil, where the age could "only" be constrained by 2 million years:

//www.hoelymoley.com/questions/19439/-/22635 # 22635 5 回答约翰史上有过一个案例,我们发现什么似乎是一个史前化石,但没有办法约会吗? 约翰 //www.hoelymoley.com/users/7080 2021 - 07 - 31 - t15:13:26z 2022 - 07 - 22 - t15:20:10z < h2 >是的它发生,我们知道什么时候和为什么会发生。< / h2 > < ol > <李> < p > <强>糟糕的集合。< / >强最常见的原因是由于糟糕的收集方法。有时非专业人员收集化石没有记录,或当他们收集,在这些情况下化石没有普罗维登斯,为科学分析通常是无用的。只要你知道岩层化石来自一个窗口的时间从何而来。顺便说下这是为什么一些古生物学家绝对厌恶私人收藏家,因为经常导致这些无用的化石。而通常你至少可以得到一个粗略的想法通过比较类似的化石,但有时化石是严重受损甚至这样做。李李< / p > < / > < > < p > <强> < /强>带来坏的运气。偶尔化石收集正确,因为不寻常的情况下(比如一个博物馆被轰炸战争)收集数据丢失和化石再次变得毫无用处,因为它没有普罗维登斯,这是一个原因鼓励收集详细记录在多个位置。这经常发生,古生物化石收集在早期时记录往往是低质量。李李< / p > < / > < > < p > <强>坏演员< /强>。有时一位私人收藏家从事彻头彻尾的欺诈,这通常发生在私人收藏家谁想要更畅销的化石。通常这发展坚持从不同的地层矿物在岩石或多个不同的化石组合到一个欺诈。 this is another reason many paleontologist dislike private collecting as it can encourage sellers to purposefully destroy a fossils providence. It is usually fairly easy for an experience paleontologist to spot such frauds but private buyers often cannot.

  • Bad Luck again. There is one other circumstance, rarely you have reworked material, that is fossils that where exposed by erosion in the distance past then reburied, This is exceedingly rare, and always leaves its mark on the fossil, in that case we know the fossil is in the wrong place but may not know exactly where and thus when it comes from originally. Usually you can identify by finding similar fossils, but rarely the fossil so badly degraded identification is impossible.

  • http://preparation.paleo.amnh.org/35/techniques-in-the-field

    https://www.nature.com/articles/512371c

    //www.hoelymoley.com/questions/19439/-/22658 # 22658 2 把手抓扒者回答的史上有过一个案例,我们发现什么似乎是一个史前化石,但没有办法约会吗? 旋钮刮子 //www.hoelymoley.com/users/7333 2021 - 08 - 06 - t00:23:31z 2021 - 08 - 06 - t00:23:31z

    To answer your question, "...surely there have been cases where we have found new fossils that we have no way of knowing the age?", the short answer is yes.

    Prior to modern radiometric dating in the early 1900s, which placed firm constraints on age, you could say that all fossils found until that point were of unknown age. Sure, you could establish depositional constraints: this fossil is older because it lies under that one, but no one knew how old, relative to the age of the earth, it was, or how old relative to each other they were.

    For a long time, at least throughout Europe, the Bible was the chief source of all information and natural philosophers assumed fossils were victims of The Great Flood. If you spent all of your time studying the bible for clues for when God created everything, you'd back-calculate that nothing on earth could be older than about 4,000 years old. They were derided as "Antediluvialists" by later generations of thinkers for whom the concept of deep time was a very real possibility. Even Lord Kelvin, the smartest man in the world at the time, couldn't understand why fossils needed to be so old.

    Discounting Tinder, it's impossible to find an undatable fossil, even those that have survived metamorphism.

    An analogous situation existed for European history. Prior to carbon dating, it was believed that all of European culture was derived from the Greeks, as it was (by circular reasoning) the "oldest" that anyone could find because all artifacts found throughout Europe had to be derivations.

    When carbon dating revealed European cultures pre-dating the Greeks by thousands of years, an entire school of thought that lasted centuries, vanished literally overnight.

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