Was the Devonian geomagnetic field dipolar or multipolar? Palaeointensity studies of Devonian igneous rocks from the Minusa Basin (Siberia) and the Kola Peninsula dykes, Russia

Defining variations in the behaviour of the geomagnetic field through geological time is critical to understanding the dynamics of Earth's core and its response to mantle convection and planetary evolution. Furthermore, the question of whether the axial dipole dominance of the recent palaeomagnetic field persists through the whole of Earth's history is fundamental to determining the reliability of palaeogeographic reconstructions and the efficacy of the magnetosphere in shielding Earth from solar wind radiation. Previous palaeomagnetic directional studies have suggested that the palaeofield had a complex configuration in the Devonian period (419–359 Ma). Here we present new high-quality palaeointensity determinations from rocks aged between 408 and 375 Ma from the Minusa Basin (southern Siberia), and the Kola Peninsula that enable the first reliable investigation of the strength of the field during this enigmatic period. Palaeointensity experiments were performed using the thermal Thellier, microwave Thellier and Wilson methods on 165 specimens from 25 sites. Six out of eight successful sites from the Minusa Basin and all four successful sites from the Kola Peninsula produced extremely low palaeointensities (<10 μT). These findings challenge the uniformitarian view of the palaeomagnetic field: field intensities of nearly an order of magnitude lower than Neogene values (except during relatively rare geomagnetic excursions and reversals) together with the widespread appearance of strange directions found in the Devonian suggest that the Earth's field during this time may have had a dominantly multipolar geometry. A persistent, low intensity multipolar magnetic field and associated diminished magnetosphere would increase the impact of solar particles on the Earth's magnetosphere, ionosphere and atmosphere with potential major implications for Earth's climate and biosphere

Changes to the Fossil Record of Insects through Fifteen Years of Discovery

The first and last occurrences of hexapod families in the fossil record are compiled from publications up to end-2009. The major features of these data are compared with those of previous datasets (1993 and 1994). About a third of families (>400) are new to the fossil record since 1994, over half of the earlier, existing families have experienced changes in their known stratigraphic range and only about ten percent have unchanged ranges. Despite these significant additions to knowledge, the broad pattern of described richness through time remains similar, with described richness increasing steadily through geological history and a shift in dominant taxa, from Palaeoptera and Polyneoptera to Paraneoptera and Holometabola, after the Palaeozoic. However, after detrending, described richness is not well correlated with the earlier datasets, indicating significant changes in shorter-term patterns. There is reduced Palaeozoic richness, peaking at a different time, and a less pronounced Permian decline. A pronounced Triassic peak and decline is shown, and the plateau from the mid Early Cretaceous to the end of the period remains, albeit at substantially higher richness compared to earlier datasets. Origination and extinction rates are broadly similar to before, with a broad decline in both through time but episodic peaks, including end-Permian turnover. Origination more consistently exceeds extinction compared to previous datasets and exceptions are mainly in the Palaeozoic. These changes suggest that some inferences about causal mechanisms in insect macroevolution are likely to differ as well

Approaches to the Algorithm of Analyzing the Results of Laboratory Testing of Micro- and Macronutrient Content of Bakery Products: Part 1

Introduction: Data on the chemical composition of food products are important for solving many problems in medical and social spheres. The development of mechanisms for updating existing databases of the chemical composition of foodstuffs, including the need to change approaches to obtaining primary data and develop algorithms of their processing, is in demand. Objective: To develop an algorithm of obtaining statistically correct values of average concentrations and variability of the main micro– and macronutrients in bakery products. Materials and methods: To develop and test the algorithm, we used the results of testing bakery products obtained in 2020 within the Federal Project on Public Health Strengthening by the laboratories of the Russian Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing (Rospotrebnadzor). Results: A good separating power was demonstrated by k-means clustering into two groups by the fat content. An algorithm for generalization of data obtained from different laboratories is proposed due to impossibility to assess the whole aggregate of potential errors related to testing, laboratory personnel, data entry, etc. To assess the effectiveness of each stage and the algorithm as a whole, we used the value of the deviation of the resulting variability from the initial one. As a result of processing, this indicator ranged from 5 % for the carbohydrate content to 72 % for the fat content. For the contents of carbohydrates, ash, dietary fiber, vitamin B1, sodium and moisture in both clusters, statistically significant differences were obtained between the processed and original data. This result and the comparability of the obtained values of the mean and variability with the reference ones may indicate the correctness of the algorithm. There were no statistically significant differences between the obtained values of fat and protein content, but the consistency of the order of values with the reference ones was also recorded. Conclusion: The developed algorithm made it possible to obtain up-to-date information about the chemical composition of bakery products. Further research should be aimed at testing and, if necessary, adjusting the algorithm for all major food groups.</jats:p

New palaeodirections and palaeointensity data from extensive profiles through the Ediacaran section of the Volyn Basalt Province (NW-Ukraine)

Summary Changes of the geomagnetic field over geologic time scales can be used to study the evolution and processes of its sources in Earth's deep interior. As a stark contrast to the geomagnetic field behaviour of the recent past, the field in the late Neoproterozoic is defined by ambiguous polar wander paths, ultra-low field strengths and a period of extreme reversal hyperactivity. Palaeointensity data from this time are still scarce and conclusions made from these data suffer from large uncertainties brought by a low sampling density. In this study, we present new palaeomagnetic and palaeointensity data from quarry outcrops and five deep drill cores, covering the longest and most complete profiles through the Ediacaran units in the Volyn Basalt Province (NW-Ukraine) to date. Palaeodirectional analysis of thermal and alternating field demagnetisation experiments reveal at least six reversals in the profile as well as four palaeopoles that agree with previously published poles. Whole-rock palaeointensity estimates are derived from a multi-method approach that utilises thermal and microwave Thellier experiments in Coe- and IZZI-protocol as well as Wilson and double-heating-Shaw experiments. These produce instantaneous site-mean palaeointensity estimates in the range of 2.1±0.4 µT - 11.1±3.5 µT and virtual dipole moments in the range of 0.31±0.06 ×1022Am2 - 1.67±0.53 ×1022Am2. Small-scale variations of palaeointensities throughout the profile not only show extremely weak field strengths around polarity changes but could also suggest that the field strength never fully recovered between reversals. These new results increase the density of intensity data coverage for Baltica in the Late Ediacaran and, in combination with previously published Ediacaran dipole moments, support an extremely weak field that seems to increase in strength towards the Ediacaran-Cambrian transition.</jats:p