Baochun Huang

Assessment of heavy metal pollution from a Fe-smelting plant in urban river sediments using environmental magnetic and geochemical methods

Environmental magnetic proxies provide a rapid means of assessing the degree of industrial heavy metal pollution in soils and sediments. To test the efficiency of magnetic methods for detecting contaminates from a Fe-smelting plant in Loudi City, Hunan Province (China) we investigated river sediments from Lianshui River. Both magnetic and non-magnetic (microscopic, chemical and statistical) methods were used to characterize these sediments. Anthropogenic heavy metals coexist with coarse-grained magnetic spherules. It can be demonstrated that the Pollution Load Index of industrial heavy metals (Fe, V, Cr, Mo, Zn, Pb, Cd, Cu) and the logarithm of saturation isothermal remanent magnetization, a proxy for magnetic concentration, are significantly correlated. The distribution heavy metal pollution in the Lianshui River is controlled by surface water transport and deposition. Our findings demonstrate that magnetic methods have a useful and practical application for detecting and mapping pollution in and around modern industrial cities.

Late Cenozoic magnetochronology and paleoenvironmental changes in the northern foreland basin of the Tian Shan Mountains

[1] The folded Neogene deposits in the northern foreland basin of the Tian Shan Mountains provide important information about tectonic history and environmental changes of northwestern China. On the basis of lithostratigraphic and magnetostratigraphic evidence, we develop a new chronology for the previous studied Kuitun He section. Our palynological study on the late Miocene–Pliocene sediment of the Dushanzi section yields new information about vegetation and climate change during the period of 8.7–2.58 Ma. The results indicate that steppe taxa (Artemisia and Chenopodiaceae) were generally dominant in the studied areas between 8.7 and 2.58 Ma, implying that a dry climate has occurred in the inland basins of northwestern China at least since 8.7 Ma ago. Although the general climate pattern indicated by our palynological results displays to some extent of drought, a warm and humid phase occurred at 5.8–3.9 Ma ago. This climatic optimum is comparable with the other records from the Chinese Loess Plateau, central Japan, the Sub-Himalayan Zone, and the marine eustatic sea level rise, implying this seems to be, at least, a regional climatic optimum.

Biomonitoring of atmospheric particulate matter using magnetic properties of Salix matsudana tree ring cores

Magnetic properties of atmospheric particulate matter collected by both natural and artificial dust receptors are increasingly being used as proxy parameters for environmental analyses. This study reports the first investigation of the relationship between smelting factory activity and the impact on the environment as recorded by the magnetic signature in Salix matsudana tree rings. Magnetic techniques including low-temperature experiments, successive acquisition of isothermal remanent magnetisation (IRM), hysteresis loops and measurements of saturated IRM (SIRM) indicated that magnetic particles were omnipresent in tree bark and trunk wood, and that these particles were predominantly magnetite with multidomain properties. The magnetic properties of tree trunk and branch cores sampled from different directions and heights implied that the acquisition of magnetic particles by a tree depends on both orientation and height. The differences of SIRM values of tree ring cores indicated that pollution source-facing tree trunk wood contained significantly more magnetic particles than other faces. The results indicated that magnetic particles are most likely to be intercepted and collected by tree bark and then enter into tree xylem tissues during the growing season to become finally enclosed into the tree ring by lignification. There was a significant correlation between time-dependent SIRM values of tree ring cores and the annual iron production of the smelting factory. From the dependence of magnetic properties with sampling direction and height, it is argued that magnetic particles in the xylem cannot move between tree rings. Accordingly, the SIRM of tree ring cores from the source-facing side can contribute to historic studies of atmospheric particulate matter produced by heavy metal smelting activities.

Addendum to “Late Cenozoic magnetochronology and paleoenvironmental changes in the northern foreland basin of the Tian Shan Mountains” by Jimin Sun, Qinghai Xu, and Baochun Huang

[1] Sun et al. (2007) constructed a magnetostratigraphic record of the Kuitun River section (Xinjiang Province, China) and reinterpreted a magnetostratigraphic record from the same section previously published by Charreau et al. (2005). In this paper, we show that Sun et al. miscorrelated their column with respect to that of Charreau et al. A compatible correlation, recognized by both sides, is presented.

Post-collisional deformation of the Anatolides and motion of the Arabian indenter: A paleomagnetic analysis

In the Anatolides of Turkey the neotectonic (post collisional) phase of deformation embraces the period since final closure of the southern arm of Neotethys in mid-Miocene times. The Arabian Shield indenter has continued to deform into the weak Anatolian accretionary collage resulting from subduction of this ocean by a combination of differential movement relative to the African Plate and counterclockwise (CCW) rotation. Much of resulting deformation has been accommodated by slip along major transforms comprising the North Anatolian Fault Zone (NAFZ), the East Anatolian Fault Zone (EAFZ) and the northward extension of the Dead Sea Fault Zone (DSFZ) but has also been distributed as differential block rotations through the zone of weak crust in between. Facets of this deformation comprise crustal thickening and uplift to produce the Anatolian Plateau, establishment of transform faults and tectonic escape as Arabia has continued to impinge into the Anatolian collage. Paleomagnetic analysis of this deformation is facilitated by the widespread distribution of neotectonic volcanism and graben infills, and rotations relative to the Eurasian reference frame are recognised on two scales. Rapid rotation (up to 5°/10,000 years) of small fault blocks is identified between master faults along the intracontinental transforms but deformation does not extend away from these zones and shows that seismogenic upper crust is decoupled from a lower continental lithosphere undergoing continuum deformation. The broad area of weak accreted crust between the transforms is dissected into large fault blocks which exhibit much lower rotation rates (mostly < 1°/100,000 years) that vary systematically across the Anatolides. Large CCW rotations near the Arabian indenter diminish westwards to become zero then CW near the limit of tectonic escape in western Turkey. The view that the collage has rotated anticlockwise as a single plate, either uniformly or episodically, during the Neotectonic era is refuted. Instead, deformation has been distributed and differential as the collage has adapted to changing tectonic regimes. Crustal extrusion to the west and south has expanded the curvature of the Tauride Arc and combined with retreat of the Hellenic Arc to produce the extensional horst and graben province in western Turkey. A challenge of present work is to resolve the temporal framework of tectonic rotation. Evidence from the Cappadocian volcanic province and Sivas Basin in central Anatolia indicates that rotation has been concentrated within the last 2–3 million years of the neotectonic era and therefore correlates with establishment of the intracontinental transform framework. Thus we recognise two phases to the evolution of this sector of the orogen: the first embraces crustal thickening and uplift with initiation defined specifically by transition from marine to terrestrial deposition in the Serravallian at ~12 Ma, and the second embraces crustal extrusion to the west motivated by continuing northward movement of Arabia and roll back on the Hellenic Arc since late Pliocene times. Latitudinal motions detected by paleomagnetism are close to confidence limits and consistent with small northward motion of the Anatolides since Eocene times including up to a few hundred km of closure linked to crustal thickening since the demise of NeoTethys. The driving motion from the Arabian indenter can be partially resolved from the widespread basaltic volcanism that occurred along the periphery of the Arabian Shield at 12–18 Ma during final stages of collision along the Bitlis Suture. This defines CCW rotation of 13–21° with respect to Eurasia. An average CCW rotation of 0.9°/Myr since closure of the Bitlis Suture in mid-Miocene times is unlikely to have been uniform because it has been linked to three adjoining interactions namely episodic opening of the Red Sea, a transition from crustal thickening to tectonic escape in the Anatolian collage and variable rates of strike slip motion on the DSFZ.

Comment on “Remagnetization of the Paleogene Tibetan Himalayan carbonate rocks in the Gamba area: Implications for reconstructing the lower plate in the India-Asia collision” by Huang et al.: Remagnetization of the Zongpu Limestones

The recent publication of “Remagnetization of the Paleogene Tibetan Himalayan carbonate rocks in the Gamba area: Implications for reconstructing the lower plate in the India-Asia collision” by Huang et al. [J. Geophys. Res. Solid Earth, 122, doi:10.1002/2016JB013662] argued for a complete chemical remagnetization on the characteristic remanence of carbonate rocks from the Zongpu Formation (Fm) at Gamba, southern Tibet, and discussed its implications for the reconstruction of India-Asia collision. To support their conclusion, the authors performed nonparametric fold tests on the paleomagnetic data obtained from the Zongpuxi section, we previously published in Yi et al. [Earth Planet. Sci. Lett., 2011, 309 (1-2):153-165] and argued for a synfolding or postfolding origin. In this comment, we demonstrate that their reinterpretation of the fold tests is invalid, and a prefolding origin of the ChRMs from the Zongpu Fm is still supported by the data. We agree that the new rock magnetic and SEM results are robust evidence for a secondary origin of the magnetite fraction in the Zongpu Fm; however, the associated secondary remanence was most likely acquired shortly after deposition of the carbonates, or even in an early diagenetic stage. We conclude that the paleomagnetic results from Gamba area can still be used for reconstructing the pre-collisional extent of Greater India.