Experimental techniques to determine paleomagnetic field intensity are based on a theoretical framework that is valid only for single-domain (SD) ferromagnetic particles. Yet, most of the available materials exhibit distinctly non-SD properties. Designing the optimal paleointensity methodology for non-SD is, therefore, a fundamental challenge in paleomagnetism. The objective of this study is to experimentally test the IZZI Thellier absolute paleointensity method on small MD recorders. The test has two purposes: 1) to describe the characteristic non-SD patterns occurring in Arai plots, and 2) to identify the optimal approach in interpreting non-SD behavior. We carried out paleointensity experiments on 40 specimens from 4 synthetic re-melted slag samples with identical magnetic properties (mineralogy, texture, and non-SD state) produced under different field intensities. We ran three batches of IZZI experiments using different conditions that allow for a detailed characterization of the non-SD behavior. We find that the curvature of the Arai plot is systematically dependent on the angle and the proportion between the field used in the paleointensity experiment (B-TRM) and the field in which the NRM was acquired (B-NRM). Straight-line Arai plot occur when the two fields are parallel and equal, and seems to always give the 'true' slope. Convex curves occur when B-TRM is parallel and significantly stronger than B-NRM. Concave curves occur in all the other cases and yield two end-case slopes that are always different than the 'true' slope. In addition, zigzagged patterns increase with the angle the proportion between B-TRM and B-NRM. We test the accuracy of the 'best fitting' line approach and conclude that 'best fitting' line in curved plots cannot provide robust paleointensity estimates. Yet, the two 'end-case' slopes in concave curves provide adequate constraints for the true value. We introduce a new procedure to calculate a 95% confidence interval of the paleointensity from curved plots using bootstrap statistics. We substantiate the new procedure by conducting two independent tests. The first uses synthetic re-melted slag produced under known field intensities - 3 SD samples and 4 non-SD samples. The second compares paleointensity determinations from archeological slag samples of the same age - 34 SD samples and 10 non-SD samples. The two tests demonstrate that the bootstrap technique may be the optimal approach for non-ideal dataset. (C) 2011 Elsevier BM. All rights reserved.

In order to determine the nature of remanence carriers of the layered gabbro of the Troodos ophiolite, Cyprus, we report optical and electron microscopic observations, together with rock magnetic and paleomagnetic experiments. Above all, the study aims to understand and clarify the time of magnetic acquisition relative to the brittle deformation of the oceanic crust manifested by the ridge-transform intersection (Solea graben and the Arakapas transform). Petrographic examination of pyroxene grains revealed isolated magnetite inclusions ranging in size from single-domain (SD) to multi-domain (MD) and in addition, MD pyrrhotite inclusions residing in veins and cracks. Thermal demagnetization and thermomagnetic procedures indicate two components, low and high temperature. We argue that the low temperature component, <350 degrees C, and the high component, <580 degrees C, are the contribution of the pyrrhotite and magnetite, respectively. The SD magnetite inclusions exsolved in pyroxene are the dominant carriers of magnetic remanence in Troodos Gabbro. The initial formation of these inclusions occurred via exsolution reaction at temperatures between 520 and 850 degrees C, above the Curie temperature of pure magnetite during the solidification of the magma. Therefore, acquisition of remanent magnetization of the Troodos gabbro took place during the earliest stages of crustal accretion, before any brittle deformation associated with the spreading ridge and the transform fault occurred. (C) 2010 Elsevier B.V. All rights reserved.

The Middle-Eastern copper slag is a promising new material for studying intensity variations in the geomagnetic field with high resolution and precision. The purpose of this study is to test the accuracy of archaeointensity estimates determined using copper slag by addressing two questions: 1) "Does slag material display the magnetic properties required for valid Thellier experiments?" and 2) "What is the accuracy of the archaeointensity estimates derived from Thellier-style experiments on optimal samples?" We address the first question through a comprehensive microscopic and magnetic study of representative archaeological slag samples in order to identify the properties responsible for optimal behavior in Thellier experiments. To address the second question, we reproduced slag samples in the laboratory under controlled magnetic fields and analyzed them using the same 1721 paleointensity technique used for the ancient slag. Microscopic analyses of the archaeological slag show that ferromagnetic phases occur as three-dimensional dendritic structures whose branches consist of submicronelongated particles. Magnetic analyses show that these dendrites behave as an assemblage of shape-controlled, single-domain-like particles and that their magnetization is thermoremanent. We conclude that slag material can be magnetically suitable for valid Thellier experiments. The laboratory-produced slag material demonstrated similar magnetic and mineralogical properties as the archaeological slag. IZZI experiments showed that nonlinear TRM acquisition, even at field strengths similar to Earth's, and TRM anisotropy are important factors to monitor during paleointensity studies of slag material. Anisotropy and non-linearity are probably related to the dendritic shape of the oxide grains. Intensity estimates derived from three laboratory-produced slag samples demonstrated accuracy to within similar to 5% after applying the required corrections. (C) 2009 Elsevier B.V. All rights reserved.

We investigate a kilometer-scale steep relay ramp structure in the Galilee, northern Israel. The data indicate an asymmetric fold above the buried tip of the southern boundary fault as well as at the lower part of the ramp. Structural analysis suggests that the buried tip of the bounding fault is only a few hundred meters below the surface. A sequence of colluvial wedges, exposed at the base of the southern flank of the relay ramp over the blind tip of the boundary fault, presents successively decreasing angles from 67 at the bottom to 30 at the top. The lower three wedges rest at angles greater than the angle of repose, suggesting tilting during and after deposition. We suggest that the increasing angle of the wedges is the result of the development of the monocline over the buried tip of the boundary fault, which in turn reflects the development of the entire relay ramp structure. Paleomagnetic measurements test this hypothesis. Samples from three of the four lower wedges and the carbonate fill in the fractured bedrock yield northerly declination and positive inclination. Inclination anomalies are 19.4 +/- 3.3 and 11.3 +/- 1.8 for the fractured bedrock and the wedges, respectively. These anomalies reflect part of the tilt. Paleomagnetic measurements and optically stimulated luminescence (OSL) constrain the time of initial deformation of the monocline above the southern boundary fault between 780 ka and 461 +/- 75 ka (OSL age of wedge 1) and the termination of deformation to 176 +/- 22 ka (OSL age of wedge 5). These bounding ages suggest tilting rates that range between 1 degrees/16 kyr and 1 degrees/8 kyr. Termination of tilting along the southern flank of the relay ramp and the fact that the tip of the buried normal fault is only a few hundreds of meters below the surface suggest that the relay ramp may be close to being breached by a connecting fault. Citation: Matmon, A., O. Katz, R. Shaar, H. Ron, N. Porat, and A. Agnon (2010), Timing of relay ramp growth and normal fault linkage, Upper Galilee, northern Israel, Tectonics, 29, TC2016, doi: 10.1029/2009TC002510.

In paleomagnetism, periods of high field intensity have been largely ignored in favor of the more spectacular directional changes associated with low field intensity periods of excursions and reversals. Hence, questions such as how strong the field can get and how fast changes occur are still open. In this paper we report on data obtained from an archaeometallurgical excavation in the Middle East, designed specifically for archaeomagnetic sampling. We measured 342 specimens from 72 samples collected from a 6.1 m mound of well stratified copper production debris at the early Iron Age (12th-9th centuries BCE) site of Khirbat en-Nahas in Southern Jordan. Seventeen samples spanning 200 yr yielded excellent archaeointensity results that demonstrate rapid changes in field intensity in a period of overall high field values. The results display a remarkable spike in field strength, with sample mean values of over 120 mu T (compared to the current field strength of 44 mu T). A suite of 13 radiocarbon dates intimately associated with our samples, tight control of sample location and relative stratigraphy provide tight constraints on the rate and magnitude of changes in archaeomagnetic field intensities. (C) 2009 Elsevier B.V. All rights reserved.