The origin of the rotations detected paleomagnetically in the Central Andes is controversial. Tectonic models proposed to explain it involve Late Cenozoic oroclinal bending (the Bolivian Orocline), and/or small‐block rotations driven by oblique subduction. In this paper, we report paleomagnetic data from upper Miocene ignimbrites from the Puna, in the presumed southern limb of the orocline. These rocks showed high unblocking temperature and high coercivity magnetization. The resulting pole position (latitude 85.7°S, longitude 80.5°E, A95 = 7.9°, K = 22, N = 17) indicates that the study area has not been significantly affected by vertical‐axis rotation since late Miocene onward. This implies that the whole Puna has not undergone significant regional rigid‐body rotation during the same time span. A farther analysis based on Neogene paleomagnetic data from 31 Andean localities distributed from 11°S to 31°S shows the presence of rotated and unrotated areas. Systematic counterclockwise rotations in Perü and northern Bolivia are observed, whereas clockwise rotations are present in southern Bolivia, northern Chile, and perhaps northwestern Argentina. No systematic rotations are found farther south. The overall time‐spatial distributions of these Neogene paleomagnetic data suggest that if orogenic bending occurred, it must have taken place before the middle Miocene. Thus the oroclinal hypothesis cannot explain the rotations observed in middle Miocene rocks or younger ones, which also show orocline‐like declination anomalies. We suggest that small‐block rotations driven by distributed shear may be a single process that can account for the whole rotations in the Central Andes. It is hypothesized that horizontal shear in the Andean crust could be controlled by ancient structures.

This international investigation was designed to determine if, and under what circumstances experiences at science centers, significantly correlated with a range of adult general public science and technology literacy measures. Given the complex and cumulative nature of science and technology learning, and the highly variable and free‐choice nature of science center experiences, an epidemiological research approach was used. Quantitative surveys were administered to 6,089 adults living in 17 communities located in 13 countries; all with active science centers. Data collection and analysis protocols ensured a representative sampling based on age, education, and income from each of the 17 participating communities. Results showed that individuals who used science centers had significantly higher understanding, interest and curiosity, participation in free‐choice leisure activities, and identity relative to science and technology than did individuals who did not visit; even when potential self‐selection biases such as income, education level, and prior interest were taken into consideration. These findings significantly strengthen the argument that the presence of one or more healthy and active science centers within a community, region, or country represents a vital investment for fostering and maintaining a scientifically and technologically informed, engaged, and literate public.

Abstract. Paleomagnetic studies in the southern Central Andes have shown the widespread presence of clockwise vertical-axis rotations. Rock units sampled in these studies, however, are heterogeneously distributed in stratigraphic age with most palcomagnetic data from northern Chile being from Mesozoic and lower Tertiary rocks, whereas most data in the southern Altiplano, Puna, and Cordillera Oriental are from upper Tertiary rocks. In this paper we present the results of a palcomagnetic study on upper Miocene sedimentary rocks and ignimbrites from the Precordillera of northern Chile (at 22øS). These rocks are coeval with the initiation of crustal shortening in the eastern foreland fold-thnmt belt which some teetome models relate to oroclinal rotation of northern Chile. Primary magnetizations in rocks from widely distributed sites in two ignimbrites indicate that no relative rotations have occurred between sites, suggesting the study area has acted as a single coherent block with respect to vertical-axis rotational deformation. Although minor inadequate sampling of palcosecular variation can affect our data set, its time-averaged palcomagnetic direction is indistinguishable from the expected late Miocene reference direction indicating no palcomagnetically significant rotation of the study area since circa 11 Ma. This suggests that late Miocene-R•nt oroclmal rotation of the northern Chilean forearc, if present, must be either very low or nonuniform. A direct implication of this restfit is that much of the unquestionable teetome rotations detected from upper Miocene rocks in the southern Central Andes is of local origin. Available structural data permit us to relate several of these rotations with shear in dextral transfer zones in the foreland thrust belt on the east side of the Andes.

No abstract

No abstract

No abstract

No abstract

Late Cenozoic volcanic rocks outcrop in the northern Patagonia Extrandina. Lava flows, characterized as olivine and alkaline basalts, belong to intraplate volcanism. We report paleomagnetic and rock-magnetic studies carried out on Late Cenozoic basalts belonging to the Cráter, Mojón and Moreniyeu Formations. The paleomagnetic sampling comprised 75 sites in lava flows and dikes from the Cráter Formation, three sites in a lava flow from the Mojón Formation and three sites in a lava flow from the Moreniyeu Formation. Alternating field (AF) and thermal detailed demagnetization techniques were used. Most of the samples have a viscous component. The AF procedure was more effective than thermal demagnetization in destroying viscous components and in defining the characteristic remanent magnetizations. Demagnetization curves and rock-magnetic studies suggest that the main remanence carrier is Ti-poor magnetite. Radiometric K-Ar ages were performed on these basalts. The radiometric ages are 0.8±0