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Paleomagnetic, rock magnetic, or geomagnetic data found in the MagIC data repository from a paper titled: Absolute Paleointensity Experiments on Aged Thermoremanent Magnetization: Assessment of Reliability of the Tsunakawa‐Shaw and Other Methods With Implications for “Fragile” Curvature 

This commentary paper addresses the outdated and misleading terminology used to categorize termites into “higher” and “lower”. These terms perpetuate a linear progression view of evolution, which is both inaccurate and detrimental to our understanding of the diversity of life. We trace the historical origins of these terms and highlight their flawed interpretation of evolutionary relationships. We advocate for the adoption of Termitidae (or termitid), rather than “higher termites”. As for the paraphyletic group of “lower termites”, we recommend refraining from grouping them together, unless specifically referring to their symbionts. In such cases, we propose “protist-dependent termites” or “non-Termitidae termites”. 

Abstract Absolute paleointensity (API) of the geomagnetic field can be estimated from volcanic rocks by comparing the natural remanent magnetization (NRM) to a laboratory‐induced thermoremanent magnetization (Lab‐TRM). Plots of NRM unblocking versus Lab‐TRM blocking from API experiments often exhibit nonideal curvature, which can result in biased estimates. Previous work showed that curvature can increase with age; however, selection criteria designed to eliminate such behavior yielded accurate estimates for two‐year‐aged specimens (70.3 ± 3.8 μT;N = 96 specimens out of 120 experiments). API can also be estimated in coercivity space. Here, we use the Tsunakawa‐Shaw (TS) method applied to 20 specimens aged in the laboratory field of 70.0 μT for 4 years, after acquisition of zero‐age (fresh) Lab‐TRM in the same field. Selection criteria for the TS experiment also yielded accurate results (68.5 ± 4.5 μT;N = 17 specimens). In thermal API experiments, curvature is related to internal structure with more single domain‐like behavior having the least curvature. Here we show that the fraction of anhysteretic remanent magnetization demagnetized by low‐temperature treatment was larger for samples with larger thermal curvatures suggesting a magnetocrystalline anisotropy source. We also tested experimental remedies that have been proposed to improve the accuracy of paleointensity estimates. In particular, we test the efficacy of the multi‐specimen approach and a strategy pretreating specimens with low field alternating field demagnetization prior to the paleointensity experiment. Neither yielded accurate results. 

Abstract The theory for recording of thermally blocked remanences predicts a quasilinear relationship between low fields like the Earth's in which rocks cool and acquire a magnetization. This serves as the foundation for estimating ancient magnetic field strengths. Addressing long‐standing questions concerning Earth's magnetic field requires a global paleointensity data set, but recovering the ancient field strength is complicated because the theory only pertains to uniformly magnetized particles. A key requirement of a paleointensity experiment is that a magnetization blocked at a given temperature should be unblocked by zero‐field reheating to the same temperature. However, failure of this requirement occurs frequently and the causes and consequences of failure are understood incompletely. Recent experiments demonstrate that the remanence in many samples typical of those used in paleointensity experiments is unstable, exhibiting an “aging” effect in which the (un)blocking temperature spectra can change over only a few years resulting in nonideal experimental behavior. While a fresh remanence may conform to the requirement of equality of blocking and unblocking temperatures, aged remanences may not. Blocking temperature spectra can be unstable (fragile), which precludes reproduction of the conditions under which the original magnetization was acquired. This limits our ability to acquire accurate and precise ancient magnetic field strength estimates because differences between known and estimated fields can be significant for individual specimens, with a low field bias. Fragility of unblocking temperature spectra may be related to grain sizes with lower energy barriers and may be detected by features observed in first‐order reversal curves.