Institute of Geology and Geophysics

The Central Asian Orogenic Belt ( c . 1000–250 Ma) formed by accretion of island arcs, ophiolites, oceanic islands, seamounts, accretionary wedges, oceanic plateaux and microcontinents in a manner comparable with that of circum-Pacific Mesozoic–Cenozoic accretionary orogens. Palaeomagnetic and palaeofloral data indicate that early accretion (Vendian–Ordovician) took place when Baltica and Siberia were separated by a wide ocean. Island arcs and Precambrian microcontinents accreted to the active margins of the two continents or amalgamated in an oceanic setting (as in Kazakhstan) by roll-back and collision, forming a huge accretionary collage. The Palaeo-Asian Ocean closed in the Permian with formation of the Solonker suture. We evaluate contrasting tectonic models for the evolution of the orogenic belt. Current information provides little support for the main tenets of the one- or three-arc Kipchak model; current data suggest that an archipelago-type (Indonesian) model is more viable. Some diagnostic features of ridge–trench interaction are present in the Central Asian orogen (e.g. granites, adakites, boninites, near-trench magmatism, Alaskan-type mafic–ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, rhyolitic ash-fall tuffs). They offer a promising perspective for future investigations.

The Solonker suture records the termination of the central Asian Orogenic Belt (CAOB). However, tectonic development of the Solonker suture is poorly understood. We report new field data for the Ondor Sum melange in the Ulan valley, and present a new evaluation of the orogenic belt extending from the southern Mongolia cratonic boundary to the north China craton within the context of a new geological framework and tectonic model, which incorporates relevant data from the literature. The southern accretionary zone between the north China craton and the Solonker suture is characterized by the Mid‐Ordovician‐Early Silurian Ulan island arc‐Ondor Sum subduction‐accretion complex and the Bainaimiao arc. This zone was consolidated by the Carboniferous‐Permian when it evolved into an Andean‐type magmatic margin above a south dipping subduction zone. The northern accretionary zone north of the Solonker suture extends southward from a Devonian to Carboniferous active continental margin, through the Hegenshan ophiolite‐arc accretionary complex to the Late Carboniferous Baolidao arc associated with some accreted Precambrian blocks. This northern zone had consolidated by the Permian when it developed into an Andean‐type magmatic margin above a north dipping subduction zone. Final subduction of the central Asian ocean caused the two opposing active continental margins to collide, leading to formation of the Solonker suture in the end‐Permian. Predominant northward subduction during final formation of the suture gave rise in the upper northern plate to a large‐scale, postcollisional, south directed thrust and fold belt in the Triassic‐Jurassic. In summary, the CAOB underwent three final stages of tectonic development: early Japanese‐type accretion, Andean‐type magmatism, and Himalayan‐type collision.

The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth’s magnetic field.

Various zircons of Proterozoic to Oligocene ages (1060‐31 Ma) were analysed by laser ablation‐inductively coupled plasma‐mass spectrometry. Calibration was performed using Harvard reference zircon 91500 or Australian National University reference zircon TEMORA 1 as external calibrant. The results agree with those obtained by SIMS within 2s error. Twenty‐four trace and rare earth elements (P, Ti, Cr, Y, Nb, fourteen REE, Hf, Ta, Pb, Th and U) were analysed on four fragments of zircon 91500. NIST SRM 610 was used as the reference material and 29 Si was used as internal calibrant. Based on determinations of four fragments, this zircon shows significant intra‐and inter‐fragment variations in the range from 10% to 85% on a scale of 120 μm, with the variation of REE concentrations up to 38.7%, although the chondrite‐normalised REE distributions are very similar. In contrast, the determined age values for zircon 91500 agree with TIMS data and are homogeneous within 8.7 Ma (2 s ). A two‐stage ablation strategy was developed for optimising U‐Pb age determinations with satisfactory trace element and REE results. The first cycle of ablation was used to collect data for age determination only, which was followed by continuous ablation on the same spot to determine REE and trace element concentrations. Based on this procedure, it was possible to measure zircon ages as low as 30.37 0.39 Ma (MSWD = 1.4; 2 s ). Other examples for older zircons are also given.

The Central Asian Orogenic Belt records the accretion and convergence of three collage systems that were finally rotated into two major oroclines. The Mongolia collage system was a long, N–S-oriented composite ribbon that was rotated to its current orientation when the Mongol-Okhotsk orocline was formed. The components of the Kazakhstan collage system were welded together into a long, single composite arc that was bent to form the Kazakhstan orocline. The cratons of Tarim and North China were united and sutured by the Beishan orogen, which terminated with formation of the Solonker suture in northern China. All components of the three collage systems were generated by the Neoproterozoic and were amalgamated in the Permo-Triassic. The Central Asian Orogenic Belt evolved by multiple convergence and accretion of many orogenic components during multiple phases of amalgamation, followed by two phases of orocline rotation.

Research Article| November 01, 2003 Adakites from continental collision zones: Melting of thickened lower crust beneath southern Tibet Sun-Lin Chung; Sun-Lin Chung 1Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Dunyi Liu; Dunyi Liu 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Jianqing Ji; Jianqing Ji 3School of Earth and Space Sciences, Peking University, Beijing, China Search for other works by this author on: GSW Google Scholar Mei-Fei Chu; Mei-Fei Chu 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Hao-Yang Lee; Hao-Yang Lee 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Da-Jen Wen; Da-Jen Wen 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Ching-Hua Lo; Ching-Hua Lo 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Tung-Yi Lee; Tung-Yi Lee 5Department of Earth Sciences, National Taiwan Normal University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Qing Qian; Qing Qian 6Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Qi Zhang Qi Zhang 6Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Geology (2003) 31 (11): 1021–1024. https://doi.org/10.1130/G19796.1 Article history received: 09 May 2003 rev-recd: 31 Jul 2003 accepted: 01 Aug 2003 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Sun-Lin Chung, Dunyi Liu, Jianqing Ji, Mei-Fei Chu, Hao-Yang Lee, Da-Jen Wen, Ching-Hua Lo, Tung-Yi Lee, Qing Qian, Qi Zhang; Adakites from continental collision zones: Melting of thickened lower crust beneath southern Tibet. Geology 2003;; 31 (11): 1021–1024. doi: https://doi.org/10.1130/G19796.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Adakites are geochemically distinct intermediate to felsic lavas found exclusively in subduction zones. Here we report the first example of such magmas from southern Tibet in an active continental collision environment. The Tibetan adakites were emplaced from ca. 26 to 10 Ma, and their overall geochemical characteristics suggest an origin by melting of eclogites and/or garnet amphibolites in the lower part (≥50 km) of thickened Tibetan crust. This lower-crustal melting required a significantly elevated geotherm, which we attribute to removal of the tectonically thickened lithospheric mantle in late Oligocene time. The identification of collision-type adakites from southern Tibet lends new constraints to not only the Himalayan-Tibetan orogenesis—how and when the Indian lithosphere started underthrusting Asia can be depicted—but also the growth of the early continental crust on Earth that consists dominantly of the tonalite-trondhjemite-granodiorite suites marked by adakitic geochemical affinities. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.

A record from Wanxiang Cave, China, characterizes Asian Monsoon (AM) history over the past 1810 years. The summer monsoon correlates with solar variability, Northern Hemisphere and Chinese temperature, Alpine glacial retreat, and Chinese cultural changes. It was generally strong during Europe's Medieval Warm Period and weak during Europe's Little Ice Age, as well as during the final decades of the Tang, Yuan, and Ming Dynasties, all times that were characterized by popular unrest. It was strong during the first several decades of the Northern Song Dynasty, a period of increased rice cultivation and dramatic population increase. The sign of the correlation between the AM and temperature switches around 1960, suggesting that anthropogenic forcing superseded natural forcing as the major driver of AM changes in the late 20th century.

Zircon has long been recognized as the best geochronometer and the most important timekeeper in geosciences. Modern microbeam techniques such as SIMS and LA‐ICPMS have been successfully applied to in situ U‐Pb zircon age determinations, at spatial resolutions of 20–30 μ m or less. Matrix‐matched calibration by external standardization of well‐characterized natural zircon references is a principal requirement for precise microbeam U‐Pb zircon age determination due to fractionation effects between Pb and U, which usually result in an external age error exceeding 1%. Alternatively, zircons with a closed U‐Pb system can be directly dated by measurement of 207 Pb/ 206 Pb isotopic ratio without external standardization, which has been a common practice for zircons older than 1.0 Ga, but not for relatively young (<1.0 Ga and particularly Phanerozoic) ones because of limitations of analytical precision. We describe in this paper a method of 207 Pb/ 206 Pb measurement on Phanerozoic zircons using a new generation of large radius magnetic sector multicollector Cameca IMS‐1280 SIMS. In combination with multicollector mode, a Nuclear Magnetic Resonance (NMR) magnet controller and oxygen flooding techniques, we achieve precisions of 207 Pb/ 206 Pb ratio of <0.1% and 0.1 ∼ 0.2%, propagating to Pb/Pb age errors <0.4% and 1–3% (excluding U decay constant uncertainties), for zircons of latest Neoproterozoic and late Paleozoic to Mesozoic age, respectively. Therefore, the multicollector SIMS is capable of direct determination of zircon Pb/Pb ages as young as Mesozoic age with uncertainties of geological significance. This technique is useful for direct dating of zircons in thin sections. Moreover, it has significance for dating of some other U‐rich minerals (i.e., baddeleyite and zirconolite) that are not suitable for SIMS U‐Pb dating by external standardization.

We introduce a potential new working reference material – natural zircon megacrysts from an Early Pliocene alkaline basalt (from Penglai, northern Hainan Island, southern China) – for the microbeam determination of O and Hf isotopes, and U–Pb age dating. The Penglai zircon megacrysts were found to be fairly homogeneous in Hf and O isotopes based on large numbers of measurements by LA‐multiple collector (MC)‐ICP‐MS and SIMS, respectively. Precise determinations of O isotopes by isotope ratio mass spectrometry (IRMS) and Hf isotopes by solution MC‐ICP‐MS were in good agreement with the statistical mean of microbeam measurements. The mean δ 18 O value of 5.31 ± 0.10‰ (2 s ) by IRMS and the mean 176 Hf/ 177 Hf value of 0.282906 ± 0.0000010 (2 s ) by solution MC‐ICP‐MS are the best reference values for the Penglai zircons. SIMS and isotope dilution‐TIMS measurements yielded consistent 206 Pb/ 238 U ages within analytical uncertainties, and the preferred 206 Pb/ 238 U age was found to be 4.4 ± 0.1 Ma (95% confidence interval). The young age and variably high common Pb content make the Penglai zircons unsuitable as a primary U–Pb age reference material for calibration of unknown samples by microbeam analysis; however, they can be used as a secondary working reference material for quality control of U–Pb age determination for young (particularly < 10 Ma) zircon samples.

Abstract Potassic volcanism has been widespread and semi-continuous on the Tibetan plateau since ∼13 Ma, post-dating the orogenic thickening of the India-Asia collision. Volcanism may have commenced slightly earlier (∼16–20 Ma) in the southern portion of the plateau and then ceased around 10 Ma. The dominant lavas are pyroxené- and plagioclase-phyric shoshonites with subordinate occurrences of dacites and rhyolites. Their mineralogy reflects crystallization from high-temperature (≦1100°C) magmas which had elevated oxygen and water fugacities. Geochemically, they are characterized by relatively low TiO2, Al2O3 and Fe2O3, and high Na2O, coupled with variable abundances of compatible trace elements and very high contents of incompatible trace elements. Normalized incompatible element patterns have marked negative Nb, Ta and Ti anomalies whereas K2O appears to be buffered at ∼4% over a wide range of SiO2. Isotope data show a relatively broad and enriched range of 87Sr/86 Sr (0.7076–0.7106) at more restricted ENd (−5.2 to −8.1). Pb isotopes are characterized by a range of 207Pb/204 Pb (15.51–15.72) and 208 Pb/204Pb (38.67–39. 30) at very uniform 206Pb/204 Pb (18.39–18.83), leading to vertical arrays. Volcanics from the southern parts of the plateau have more primitive isotopic compositions: 87Sr/86 Sr 0.7048–0.7080, εNd 1.4 to −3.3, 206Pb/204 Pb 18.48–18.67, 207Pb/204 Pb 15.59–15.68 and 208Pb/204 Pb 38. 73–38.98. In general, the geochemical and isotopic data most closely approximate partial melting arrays, although fractionation processes have clearly operated. The isotopic ratios and the enrichment of incompatible elements and LREE/HREE cannot be derived from a depleted mantle source via a single-stage melting process. Instead, a metasomatized, garnet peridotite source containing ∼6% phlogopite is required and this is inferred to lie within the lithospheric mantle. The enrichment in incompatible elements in this source must have been sufficiently ancient to generate the observed isotopic ratios, and Nd depleted mantle model ages suggest this was Proterozoic in age (∼1.2 Ga), whereas Pb model ages record an Archaean event, suggesting the source had a multi-stage enrichment history. The negative Ta, Nb and Ti anomalies and low Rb/Ba suggest that metasomatism may have occurred during an ancient subduction episode. The high 208Pb/204Pb, 207Pb/204 Pb and low Nb/U, Ce/Pb of the Tibetan shoshonites are distinct from ocean island basalts. Thus, if convectively removed lithospheric mantle provides a source for ocean island basalts, it must differ significantly from the source of the Tibetan shoshonites. A lithospheric mantle source for the volcanism places important constraints on geodynamic models for the evolution of the Tibetan plateau and the India-Asia collision. For likely thermal structures beneath the plateau, the temperatures required to trigger melting within the lithospheric mantle can only be plausibly obtained if the lower parts of the lithospheric mantle were removed by convective thinning. This is consistent with recent models which invoke the same process to explain the current elevation and extensional deformation of the plateau. The age data suggest this occurred at ∼13 Ma and the duration of volcanism may be explained by continued conductive heating since that time. Poorly sampled but slightly older volcanics from the southern portions of the plateau may indicate that convective thinning began in the south and migrated northwards. Rapid uplift of the plateau may have resulted in increased rates of chemical weathering, which led to global cooling, as indicated by oxygen isotope data from Atlantic sediments.

A new regional compilation of the drainage history in southeastern Tibet suggests that the modern rivers draining the plateau margin were once tributaries to a single, southward flowing system which drained into the South China Sea. Disruption of the paleo‐drainage occurred by river capture and reversal prior to or coeval with the initiation of Miocene (?) uplift in eastern Tibet, including ∼2000 m of surface uplift of the lower plateau margin since reversal of the flow direction of the Yangtze River. Despite lateral changes in course due to capture and reversal, the superposition of eastward and southward draining rivers that cross the southeastern plateau margin suggests that uplift has occurred over long wavelengths (>1000 km), mimicking the present low‐gradient topographic slope. Thus reorganization of drainage lines by capture and reversal events explains most of the peculiar patterns of the eastern plateau rivers, without having to appeal to large‐magnitude tectonic shear.

This paper deals with the various tectonic units in the Chinese Eastern Tianshan orogenic collage in the Central Asian Orogenic Belt, and discusses the Paleozoic geological history of the several periods of accretion and collision of archipelago systems lying between the Tarim and southern Angaran continental margins. The Late Ordovician-Silurian to Early Devonian Eastern Tianshan archipelago was characterized by (a) the Harlik-Dananhu subduction system with a S-dipping polarity in the north; (b) a southerly N-dipping subduction system beneath the Central Tianshan arc in the middle; and (c) the South Tianshan ocean against Tarim in the south. During the Devonian to Early Carboniferous, N-dipping subduction led to the Harlik-Dananhu arc and the Kanggurtag forearc basin/accretionary complex. In the Early to Mid-Carboniferous, the magmatic front associated with the N-dipping subduction beneath the Dananhu-Harlik arc migrated southwards, forming the Yamansu arc constructed upon the Kanggurtag accretionary forearc. By the Late Carboniferous the Dananhu-Harlik arc was attached northwards to the Angaran margin, resulting in lateral enlargement of the Angaran continent. In the latest Carboniferous to Early Permian a multiple soft collision left wide suture zones in the south that include the ophiolite-strewn Aqikkuduk-Shaquanzi and Kumishi accretion-collision complexes, which were stitched by Early Permian post-collisional plutons. By re-defining and re-interpreting the various tectonic terranes, this paper presents a new, improved model for the Paleozoic evolution of this part of Central Asia.

The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the "present" is defined as the year AD 1950). Our record reveals a gradually intensifying monsoon from 14.7-7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8-5.3 ka, and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5-8.5 ka, and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM, and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change.

The origin of millet from Neolithic China has generally been accepted, but it remains unknown whether common millet (Panicum miliaceum) or foxtail millet (Setaria italica) was the first species domesticated. Nor do we know the timing of their domestication and their routes of dispersal. Here, we report the discovery of husk phytoliths and biomolecular components identifiable solely as common millet from newly excavated storage pits at the Neolithic Cishan site, China, dated to between ca. 10,300 and ca. 8,700 calibrated years before present (cal yr BP). After ca. 8,700 cal yr BP, the grain crops began to contain a small quantity of foxtail millet. Our research reveals that the common millet was the earliest dry farming crop in East Asia, which is probably attributed to its excellent resistance to drought.

Research Article| February 01, 1990 Paleozoic accretion and Cenozoic redeformation of the Chinese Tien Shan Range, central Asia B. F. Windley; B. F. Windley 1Department of Geology, University of Leicester, Leicester LE1 7RH, England Search for other works by this author on: GSW Google Scholar M. B. Allen; M. B. Allen 1Department of Geology, University of Leicester, Leicester LE1 7RH, England Search for other works by this author on: GSW Google Scholar C. Zhang; C. Zhang 2Institute of Geology, Academica Sinica, P.O. Box 634, Beijing, People's Republic of China Search for other works by this author on: GSW Google Scholar Z-Y Zhao; Z-Y Zhao 2Institute of Geology, Academica Sinica, P.O. Box 634, Beijing, People's Republic of China Search for other works by this author on: GSW Google Scholar G-R Wang G-R Wang 3Institute of Geology, Xinjiang Resource and Geological Bureau, Urumqi, Xinjiang, People's Republic of China Search for other works by this author on: GSW Google Scholar Author and Article Information B. F. Windley 1Department of Geology, University of Leicester, Leicester LE1 7RH, England M. B. Allen 1Department of Geology, University of Leicester, Leicester LE1 7RH, England C. Zhang 2Institute of Geology, Academica Sinica, P.O. Box 634, Beijing, People's Republic of China Z-Y Zhao 2Institute of Geology, Academica Sinica, P.O. Box 634, Beijing, People's Republic of China G-R Wang 3Institute of Geology, Xinjiang Resource and Geological Bureau, Urumqi, Xinjiang, People's Republic of China Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1990) 18 (2): 128–131. https://doi.org/10.1130/0091-7613(1990)018<0128:PAACRO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation B. F. Windley, M. B. Allen, C. Zhang, Z-Y Zhao, G-R Wang; Paleozoic accretion and Cenozoic redeformation of the Chinese Tien Shan Range, central Asia. Geology 1990;; 18 (2): 128–131. doi: https://doi.org/10.1130/0091-7613(1990)018<0128:PAACRO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Tien Shan Range in central Asia contains two late Paleozoic sutures. The older, southern suture marks the collision of a passive margin at the north of the Tarim block and an active continental margin; subduction under the latter was to the north. The younger, northern suture separates a northern Carboniferous island arc from an active continental margin developed over a south-dipping subduction zone. The subduction direction under the island arc is unknown. Mesozoic elastics were deposited over the doubly sutured orogen. Rate and energy of sedimentation waned until deposition of Oligocene conglomerates above a regional unconformity-interpreted as marking the onset of deformation induced by the India-Asia collision. Molasse deposition accelerated in Pliocene and Quaternary time, and deposition continues today as active thrusts generate relief. Paleozoic structures control the gross divergence of Cenozoic thrusts across the orogen. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The geologic map pattern of the Qiangtang terrane in central Tibet defines a &gt;600-km-long and up to 270-km-wide east-plunging structural culmination. It is characterized by early Mesozoic blueschist-bearing mélange and upper Paleozoic strata in the core

Subfossil pollen and plant macrofossil data derived from 14C-dated sediment profiles can provide quantitative information on glacial and interglacial climates. The data allow climate variables related to growing-season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate reconstructions and their uncertainties, obtained using modern-analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on surface-pollen assemblages are shown to be accurate and unbiased. Reconstructed LGM and MH climate anomaly patterns are coherent, consistent between variables, and robust with respect to the choice of technique. They support a conceptual model of the controls of Late Quaternary climate change whereby the first-order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance.

Research Article| September 01, 1988 Pleistocene climates in China dated by magnetic susceptibility George Kukla; George Kukla 1Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar Friedrich Heller; Friedrich Heller 2Geophysical Institute, ETH-Honggerberg, CH-8093, Zurich, Switzerland Search for other works by this author on: GSW Google Scholar Liu Xiu Ming; Liu Xiu Ming 3Institute of Geology, Academia Sinica, Beijing, China Search for other works by this author on: GSW Google Scholar Xu Tong Chun; Xu Tong Chun 4Institute of Geophysics, State Seismological Bureau, Beijing, China Search for other works by this author on: GSW Google Scholar Liu Tung Sheng; Liu Tung Sheng 5Xian Laboratory of Loess and Quaternary Geology, Academia Sinica, Xian Shaanxi Province, China Search for other works by this author on: GSW Google Scholar An Zhi Sheng An Zhi Sheng 5Xian Laboratory of Loess and Quaternary Geology, Academia Sinica, Xian Shaanxi Province, China Search for other works by this author on: GSW Google Scholar Author and Article Information George Kukla 1Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 Friedrich Heller 2Geophysical Institute, ETH-Honggerberg, CH-8093, Zurich, Switzerland Liu Xiu Ming 3Institute of Geology, Academia Sinica, Beijing, China Xu Tong Chun 4Institute of Geophysics, State Seismological Bureau, Beijing, China Liu Tung Sheng 5Xian Laboratory of Loess and Quaternary Geology, Academia Sinica, Xian Shaanxi Province, China An Zhi Sheng 5Xian Laboratory of Loess and Quaternary Geology, Academia Sinica, Xian Shaanxi Province, China Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1988) 16 (9): 811–814. https://doi.org/10.1130/0091-7613(1988)016<0811:PCICDB>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation George Kukla, Friedrich Heller, Liu Xiu Ming, Xu Tong Chun, Liu Tung Sheng, An Zhi Sheng; Pleistocene climates in China dated by magnetic susceptibility. Geology 1988;; 16 (9): 811–814. doi: https://doi.org/10.1130/0091-7613(1988)016<0811:PCICDB>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The magnetic susceptibility of loess and interbedded soils in central China varies with the degree of pedogenesis and serves as a proxy measure of climate. The concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the Brunhes epoch. Susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology. On this scale, the susceptibility record closely parallels the oxygen-isotope fluctuations in deep-sea sediments, suggesting a close interdependence of the Chinese dust falls, the volume of land-based ice, and global climate. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

In environmental magnetism, rock and mineral magnetic techniques are used to investigate the formation, transportation, deposition, and postdepositional alterations of magnetic minerals under the influences of a wide range of environmental processes. All materials respond in some way to an applied magnetic field, and iron‐bearing minerals are sensitive to a range of environmental processes, which makes magnetic measurements extremely useful for detecting signals associated with environmental processes. Environmental magnetism has grown considerably since the mid 1970s and now contributes to research in the geosciences and in branches of physics, chemistry, and biology and environmental science, including research on climate change, pollution, iron biomineralization, and depositional and diagenetic processes in sediments to name a few applications. Magnetic parameters are used to routinely scan sediments, but interpretation is often difficult and requires understanding of the underlying physics and chemistry. Thorough examination of magnetic properties and of the environmental processes that give rise to the measured magnetic signal is needed to avoid ambiguities, complexities, and limitations to interpretations. In this review, we evaluate environmental magnetic parameters based on theory and empirical results. We describe how ambiguities can be resolved by use of combined techniques and demonstrate the power of environmental magnetism in enabling quantitative environmental interpretations. We also review recent developments that demonstrate the mutual benefit of environmental magnetism from close collaborations with biology, chemistry, and physics. Finally, we discuss directions in which environmental magnetism is likely to develop in the future.