Solar Flare Effect on Geological Thorium Radiometric Dating

Dating is very important in understanding our earth, its aeons, and the changes that have occurred throughout the many years of its existence. The age of one fossil layer is determined by comparing it to another, and for this purpose we must date layers and minerals [1]. Dating layers can also shed a great deal of light on evolution. There are various geological dating methods, among them relative dating, Fossil Index, absolute dating, and more. However, geologists favour radioactive dating, which is based on the decay rate of natural radioactive isotopes in nature. For a long time, traditional radioactive dating methods have been employed to determine and date the age of geological layers of materials such as organic substances, rocks, minerals, and other objects. To calculate and define the age of a layer, it is necessary to compare the abundance of the radioisotope “parent” with the products of its decay, “daughters,” while using a known decay rate constant [2]. Using this calculation, we can date all materials anywhere around the globe at sea level, under sea level, volcanos, rocks, and more. Several radioactive geological dating methods are used, such as the Uranium Chain, U-238, U-234, Th-232, and Th-230. This Uranium chain and its derivatives emit Alpha radiation. Our new findings reveal that the Neutrino flux interacts and affects the Alpha emitter, consequently affecting the half-life (T1/2). Therefore, the reliability and accuracy of these common dating methods must be questioned. Indeed, the solar activity raises the Neutrino flux and apparently changes Half-Life duration, which was until now considered a constant value [3].

In addition to the Uranium Chain method, which is called Uranium-Lead dating, there are also many other well-known radiometric dating methods such as Argon-Argon Dating and Potassium-Argon dating. All these can help to define the age of a layer. We can obtain a huge amount of data regarding fossil ages by using these Geological Radiometric dating methods. The above methods are considered accurate and useful, and each method is employed visa- vis a different material or location. In this article we will discuss Uranium-Thorium dating, known as Th-230 Radiometric dating method. This method was established during the 1960s and is used to determine the age of materials that contain calcium carbonate, such as coral. This dating method, which is based on the U-series, is highly sensitive because it derives into many chemicals and many isotope fractions or “daughters.” The decay of U-234 to Th- 230 is part of a very long decay chain of the Uranium-Lead decay chain that starts with U-238 and ends with Pb-206 [4]. It is very difficult to calculate an accurate or reliable age because the earth is constantly changing geologically, and simultaneously isotopic concentration changes occur. The initial radioactive isotopic ratio of Th-230/U-234 at the time the sample was formed must be known or calculated for Uranium-Thorium dating, because this will constitute part of the comparison rate. It should be noted that Th-230 is the parent of Ra-226 that decays to Rn-222. In our previous paper, we reported that the Rn-222 decay constant changes as well [5]. Once the radioactive isotopes start to decay, they will accumulate in the sample over time. The sample age can be calculated based on the difference between the initial amount rate of Th-230/U-234 and the accumulated rate of the sample, assuming that this occurs in a closed, unchanged system. The Uranium-Thorium method is used for sediment samples, carbon samples, and bone and teeth samples with an estimated age of 1000-300,000 years. When applying this Uranium-Thorium method to human fossil dating (bones and teeth), the closed system assumption is highly relevant. When we compare bones to fossils bones, the fossil can contain hundreds of times more Uranium, due to the high exposure to ground water. The fossil bone tends to behave like an absorbent sponge when it is buried in sediment, and it absorbs a great deal of Uranium-the “uptake” phenomenon. The Uranium can also leak out of the bonethe “leaching” phenomenon. Many articles and studies emphasize the difficulty in identifying the U-series (U-234-U-238) and (Th- 230-U-234) sources in sediments [6]. It is difficult to define coral ages older than 150,000-200,000 years [7]. Thorium is a naturally occurring radioactive material with some radioactive isotopes that are part of the uranium decay chain, and it is about three times more abundant than Uranium in nature. We find Thorium in sands and sediments because it is insoluble [8]. By contrast, we find Uranium in seawater because it is soluble. Thorium dating is a known, usable method that can employ both Thorium-232 and Thorium-230. Thorium-230, which is more radioactive, can be used for age dating in marine sediments. The half-life of Th-232 is 14.5 Giga years and the half-life of Thorium-230 is 75,200 years, making it useful for dating sediments of up to 400,000 years old when applying the Th- 232/Th-230 rate [8].

The Thorium dating method assumes that the initial Th-232/ Th-230 rate stays constant, without any changes, assuming a closed system during the period of sediment layer formation. In addition, this method also assumes that the Th-232/Th-230 rate of leaching, precipitation out to the sediment, stays constant. If these two assumptions are correct, this dating method can produce accurate and reliable results [8,9]. During evolutionary processes and changes in the earth, the sedimentation processes also undergo massive changes. Consequently, in a closed system, the classical U-238-U- 234-Th-230 dating system is not always sufficiently accurate and reliable. To make this method more accurate, calculations must use the initial rates of (U-234/U-238)0 and (Th-230/Th-232)0 and in so doing can achieve increased accuracy in determining the ages of corals and sediments. The sample data set demonstrates that the interpretation of U-Pb dates in terms of sediment deposition age is not necessarily straightforward. This requires a full control for any post-crystallization lead loss, which would result in a date younger than the previously supposed age. Post-crystallization Pb loss is therefore a serious problem that must be mitigated. Such effects may explain the 1Ma discrepancy of zircon 206Pb/238U dates of Ash Bed [10-14].

Previous studies indicated that alpha emitters were affected as the decay rate decreased due to neutrino flux change from the sun’s activity [3,5]. Our new findings question the reliability of these dating methods. Solar activity changes impact the half-life duration of the isotopes that are used for dating and as a result the determined layer age is probably not accurate. Solar X-ray flares occur when the sun’s activity intensifies during the active sun cycle, which is known to be around 11 years. During the active cycle there is a higher probability that solar flares will occur. The solar X-ray flare phenomenon produces an increased neutrino flux [3,15]. A series of GOES (Geostationary Operational Environmental Satellites) satellites operated by the Space Weather Prediction Center, National Oceanic and Atmospheric Administration provides daily measured solar X-ray flux data, which is reported in units of W/m2 for each minute. This daily x-ray flux data is classified as A, B, C, M, or X according to peak flux magnitude, where class A, the lowest flux, is less than 10-7W/m2, X is above 10-4W/m2, and the difference from class to class is 10-fold. Data concerning solar flares was collected for the years 2014-2020 for the purpose of analyzing its effects on radioactive sources. This seven years solar flares data represent a single branch of the 11-years recent periodical solar activity cycle. The database helped understand the changes in the radioactive material’s count rate, and how the characteristics of the solar flares (magnitude - size (B, C, M, X), frequency, and duration) affect the count rate. There are many solar flare events with different durations and magnitudes, however, solar flare events between 11 and 30 minutes occur at a high frequency. Data concerning the magnitude of solar flares was collected daily in the years 2015-2020. The magnitude of the solar flares is divided into 4 types, B,C,M, and X, and during those specific months with many events, there were more solar flares events as well as their magnitude was higher. As part of this study, we performed count rate measurements for radioactive sources from August 2018, and these are still ongoing [3,5]. The measurements were caried out in order to discover whether solar flares affect the decay of radioactive sources. We sought to discern whether this impacts the radioactive half-life of alpha emitters. Therefore, we checked the following radioactive sources: Am-241, Rn-222, and Th-232. Our measurements clearly demonstrate that count rates prior to the solar flares were relatively smooth and stable. Once a solar flare occurred, we detected significant decreases in the count rates of the radioactive sources.

NaI(Tl) gamma radiation detector system for count-rate measurements is used for each radioactive source (the system is described in our previous publication [3]. The NaI(Tl) detector faced a Th-232 source, 50g of Th(NO3)4.5H2O, and total counts were scored every 15 minutes. The detector showed a significant change (with a delay of 9 days) in its count rate once medium solar flare events occurred. In solar flare events the neutrino flux increased by 3-4 orders of magnitude. The detailed solar flare neutrino production process is reported by Ryazhskaya et al. [16]. A radioactive nucleus that captures a free neutrino into its system may possess it for a certain period until it will affect the count rate alteration [3,5]. We found that in the alpha emitter radioactive sources, the half-life altered due to changes in neutrino flux from the sun. Due to our novel findings, all the radiometric dating methods need to be re-evaluated and re-calculated.

Experimental results

In (Table 1) the measured count rate changes for Th-232 as scored in our system are summarized. Figure 1 presents the Th-232 count rates during the measurement period since January 2021. The changes due to solar flares are indicated. To verify the signal dip of our measurements for Th-232, if the count rate is below or above its mean value, we used the method ‘limits-of-detectability’ as described by Knoll (chapter 3 section VI) [17]. The Critical Level (LC) was calculated from the measured data counts of 12-Mar-2021 22:45 to 17-Mar-2021 3:00. The obtained LC was used to inspect the dips using the neighboring count rate moments. Then, the counts at the dip were compared to the LC (in percentage) that is equal to 2.326 times standard deviation by definition (“a 95% probability that a random sample will lie below the mean plus 1.645σ “). When the presented dip counts were below the LC value, then a reliable signal was detected. The calculations for the statistical significance were done as the following:

Figure 1: Gamma radiation count-rates of Th-232 (in 15-min intervals) during 2021. SF type and intensities are indicated.

According to this calculation, if a change in the count rate is more significant than |0.11|%, it can be ascertained that the signal exceeded the critical level.

Model development

To implement the relationship between the solar flare characteristics and the effect on the radioactive source decay, we developed a new formula. The change in the radioactive Th-232 decay constant occurs due to solar flares and their intensity, causing the count rate to decrease. The decay constant can only decrease.

Where:

λchange - Modified Decay Constant caused by solar flares

λ - Decay Constant from the literature

Δi - Random variable to match between dip distribution to solar Flare Types

Δduration - Solar flare duration dependency (currently Δduration=1 was used)

Δi dependency was obtained corresponding to the dip range: for Type B the range was set to (-0.79%) - (-0.28%), and for Type C, Type M the range was set to (-1.1%) - (-0.6%). These ranges were obtained from a set of measured dip responses of Th-232, as presented in Table 1. The solar flare duration influence on the count rate change is yet to be investigated and analysed, therefore we set this parameter as equal to 1. A Monte Carlo simulation was applied to this formula for estimations of Th-232 dating in a geological time scale. The decay constant change can only decrease, hence increasing the apparent half-life. For example, if a geological layer has been sampled and the date obtained was 200Ma, due to our methodical assessment calculations, the real age of this layer is 130Ma or even younger.

Table 1: Th-232 count rate responses to Solar Flares (SF) during 2021: Left to right: Solar flare occurrence date; SF type (letter and size in nW.m-2; Dip in count rate reading date, and the percentage of count rate change).

Radioactive materials that are used for dating are influenced and impacted by the change in neutrino flux due to solar flares. The Th-232 count-rate measurements showed several counting dips, indicating that the radioactive nuclide could be affected by neutrino flux change from the sun [3,5]. In (Table 1), we presented several relatively strong solar flare events and their responses, as collected in our database, and the dip size distribution is based on Th-232 count-rates changes, as shown in Figure 1. In this study we developed a new formula that enables us to simulate the radiometric aging corrections. Considering the dip size of the readings, we can calculate the overall decay constant changes that indicate the implications of solar flare on radioactive source decay. Based on the simulation we conducted with our new formula, we found that there is a significant delta change in time, a change of millions of years between the measured age and the real age of radioactive matter.

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