[1] A global data set of archeomagnetic and paleomagnetic data covering the past 7000 years has been compiled. It consists of 16,085 results of inclination, 13,080 of declination, and 3188 of intensity for the time span 5000 BC to 1950 AD. Declination and inclination data come partly from existing databases and partly from original literature. A new global compilation of intensity data for the millennial scale is included. Data and dating uncertainties are discussed as we attempted to obtain an internally coherent data set. The global distribution of the data is very inhomogeneous in both time and space. All the data are compared to predictions from the previous 3000 year global model, CALS3K.1. This collection of data will be useful for global secular variation studies and geomagnetic field modeling, although southern hemisphere data are still underrepresented. In particular, we will use it in a further study to update and extend the existing global model, CALS3K.1. The huge increase in data compared to the previous compilation will result in significant changes from current models. As we might have missed some suitable data, we encourage the reader to notify us about any data that have not been included yet and might fit in, as improving our global millennial scale models remains our aim for the future. The data files described in this paper are available from the EarthRef Digital Archive (ERDA) at http://earthref.org/cgi-bin/erda.cgi?n=331.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004GC000800

Continuous geomagnetic field models for the past 7 millennia: 1. A new global data compilation

Effect of high temperature on physical and mechanical properties of Jalore granite

Many centuries ago, humans used to build their houses using wood, but due to natural hazards such as fire, humans have now shifted to the concept of building their houses and monuments using rock materials such as concrete, sandstone, bricks, etc. Managing fires or extinguishing them in time, the change in the physical properties of stone building materials at elevated temperature, and the variation in the strength and deformation of stone building materials with change in temperature remain debatable issues. Understanding the effect of fire on stone building materials such as sandstones would be helpful to evaluate whether fire-damaged monuments can be strengthened or should be demolished, or whether damaged parts should be replaced. For centuries, sandstone has been used not only in India but all over the world for several purposes. Widescale application of sandstone can be seen in different monuments, temples, and buildings in India, i.e., the Red Forts of Delhi and Agra, places and buildings in Fatehpur Sikri, Kota, Jaipur, Jodhpur, Buddhist Rameswaram temples in south India, the Indian parliament house, the presidential house, the supreme court building, etc. Globally, the White House in the USA is made of Aquia Sandstone, and Ayres rock (Uluru) in Australia, the world’s largest monolithic sacred site, is made of kosic sandstone (Allison and Bristow 1999; Allison and Goudie 1994; BRE 1945; Hajpal 1999, 2002a, b; Chakrabarti 1993; Chakrabarti et al. 1996; Dorn 2003; Fitzner et al. 2003; Goudie et al. 1992; Alm 1985). In particular, India has witnessed several fire incidents recently (Gorton Castle, Shimla 2014; Connaught Place, Delhi 2014; Surat, Gujarat 2014). Hence, the effect of temperature on the strength and deformation behavior of stone building materials such as sandstones needs to be studied in detail before construction of any monuments using these materials. Under the influence of high temperatures but below the melting point of sandstone, its microstructure rearranges, new microcracks develop, and preexisting ones become widespread and widen. Meanwhile, various physical and mineralogical changes take place in the rock matrix. After cooling down to air-dried temperature, thermally induced changes become permanent in some of the sandstone matrix. The effect of temperature on the physical and mechanical properties of rock has become an important area of study in the rock mechanics field. Over the last few years, various investigations have been carried out in this field to determine the complex behavior of rock under thermomechanical (TM) coupling (Alshayea et al. 2000; Hudson et al. 2005; Cheng and Arson 2014; Heuze 1983; Jaeger et al. 2007; Tian et al. 2012). That work measured the variation of physicomechanical parameters such as the modulus of rock deformation, Poisson ratio, tensile strength, compressive strength, cohesion, internal friction angle, viscosity, thermal expansion coefficients, etc. with temperature (Brede 1993; Xu et al. 2008; Somerton 1992; Dwivedi et al. 2008). & P. K. Gautam pgautam.embedded@gmail.com; neurogeneticamit@gmail.com

Thermomechanical Analysis of Different Types of Sandstone at Elevated Temperature

https://www.ipgp.fr/~legoff/Download-PDF/Archeomag/GalletLegoff_EPSLSyrie-2006.pdf

High-temperature archeointensity measurements from Mesopotamia

A paleomagnetic study has been undertaken on two late Quaternary volcanic sequences from the Piton de la Fournaise volcano (island of La Reunion) in order to provide absolute paleointensities of the Earth's magnetic field from a site in the southern hemisphere. The pattern of secular variation recorded by both sequences clearly indicates that the extrusion rate of the lava flows was not constant with time. A detailed investigation of the magnetic properties of the samples was carried out in parallel with paleointensity experiments which were performed with the Thellier method. Samples with minimum overprint, composed by single-domain or pseudo-single-domain magnetite showing good thermal stability and a narrow blocking temperature spectrum were the most successful during Thellier's experiments. Values of the paleofield strength from 19 to 55 mT have been obtained on 23 flows among the 30 which were sampled. Few variations (7.5–9.9×1022 A m2) are observed in the virtual dipole moments (VDMs) determined on the youngest sequence (5–12 ka). Those values are within the range of fluctuations of the worldwide variations of VDMs for this period. On the other hand, data from the oldest sequence (82–98 ka) are the first paleointensity values obtained in that time period, and the observed VDMs extend from 4.1 to 8.8×1022 A m2. These results suggest that for this time interval, the field did not depart from its average behavior.

K. Ramaswamy

Papers

Archaeomagnetic determination of the ancient intensity of the geomagnetic field in Tamilnadu, India

Archaeomagnetic studies on some archaeological sites in Tamil Nadu, India

Cooling rate dependence of thermoremanent magnetization of some archaeological samples

Mo¨ssbauer study of some archaeological materials in Tamilnadu (India)

Palaeomagnetic study of some charnockites of the Palni Hills