The fossil oribatid mite fauna (Acari: Oribatida) in late-glacial and early-Holocene sediments in Kråkenes Lake, western Norway

The oribatid mite assemblages found in late-glacial and early-Holocene sediments in Kråkenes Lake, western Norway, consist of 38 species within 24 genera. In accordance with known present habitat distribution we distinguish 4 true aquatic species, 6 species associated with wetland, 2 with mesic grassland, 12 with dry grassland and heathland, 3 with saxicolous and arboricolous lichens, 7 widely distributed species, and 4 with uncertainly known habitat preferences. The sediments from the pioneer phase (12,300-11,700 ¹⁴C BP) contain 7 species, among them the 2 typical pioneer species Limnozetes ciliatus and Tectocepheus velatus.The sediments of the warmer Allerød interstadial (11,700-10,900 BP) contain 18 species, the cold Younger Dryas (10,900-10,000 BP) 9 species, and the early Holocene (10,000-9,000 BP) 36 species.The oribatid fossils of the pioneer phase indicate habitats and climate similar to the mid-alpine zone in western Norway today, the Allerod interstadial that of the low- to mid-alpine zone. L. ciliatus is the aquatic pioneer species in the Allerod. In the Younger Dryas the climate was more arctic, 60-70% of the species had presumably disappeared, and no aquatic species were found. In the early Holocene, 4 true aquatic species colonised the lake and showed a high productivity. The terrestrial oribatid fauna in this period contained a high diversity of more boreal species, while the alpine species declined or became extinct.     

金沙江支流硕曲河中更新世红土层的发现及地质意义

金沙江支流硕曲河V级及以上阶地阶面和两级带状剥夷面上发现中更新世红土层。根据ESR、     

西太平洋DSDP451孔晚中新世—第四纪的微体化石群及其古海洋学意义

西太平洋 DSDP45 1孔 (18°0 0 .88′N、143°16 .5 7′E,水深 2 0 6 0 m)的微体化石群和底栖有孔虫的同位素变化揭示了研究区中新世晚期以来的古海洋学演变及其重大事件。介形类化石群由晚中新世—早上新世 (超微化石 NN11- 13/ 14带 )的 Cytheropteron组合向早上新世—第四纪 (NN15～ 2 1带 )的 K rithe组合转变及 K rithe丰度的连续上升 ,很可能指示了西马里亚纳海岭自中新世以来下沉幅度达千米左右 ,水团由早期的中层水逐渐被深层水替代。底栖有孔虫 Cibicidoides wuellerstorfiδ1 8O在 NN11带晚期至 NN12带早期急剧变轻 ,反映了中新世末期碳偏移的全球事件。在 NN12带晚期至 NN16带早期 ,δ1 8O比其现代值轻 0 .5 5‰ ,推测早—中上新世暖期时底层水温要比现代高约 2℃左右 ;介形类的新生速率大于灭绝速率指示当时为有利底栖生物的时期。 δ1 8O最急剧的转变发生在 NN16和 NN17的过渡带 (距今约 2 .5 Ma) ,增值达 1.0‰ ,并在此后保持高值 ,标记北极冰盖的形成和北半球冰期气候的开始     

A 14.7 Ka record of earth surface processes from the arid‐monsoon transitional zone of China

The stability of Earth's critical zone is intimately linked with erosion, weathering and vegetation type and density. Therefore, it affects global biogeochemical processes which in turn affect the global climate by absorbing and reflecting solar radiation, and by altering fluxes of heat, water vapour, carbon dioxide and other trace gases through various feedback mechanisms. However, there is a lack of knowledge about how Earth's critical zone processes have changed over time and their link with past monsoon variability, especially in Asia. The study of lake sediments, which contain a suite of inorganic elemental and isotopic proxies, may facilitate the understanding of the Earth's critical zone processes on millennial timescales. Here we reconstruct the history of erosion–weathering–vegetation interactions since ~14.7 ka using geochemical records from a radiocarbon‐dated sediment core from Lake Gonghai in the monsoon‐arid transitional zone of north China. Detrital (Al, Ti, K, Rb) and authigenic (Ca, Sr) elemental records reveal distinct, millennial‐scale, late deglacial‐Holocene erosion and weathering patterns and transitions with the former (latter) elements showing higher (lower) values in warm intervals and vice versa. Chemical Index of Alteration (CIA) molar, a humidity proxy, suggests low humidity during the late deglacial ~11.5–14.7 ka, high humidity during the early‐mid Holocene ~11.5–3.2 ka, and intermediate humidity during the late Holocene interval since ~3.2 ka. The results of cross‐spectral analysis and comparison of our records with other climate reconstructions also suggest a pattern of orbitally‐phased humidity changes in north China. Overall, our results provide evidence for the solar‐forcing of Earth's surface processes in mid‐latitude China under natural climatic conditions. Copyright © 2017 John Wiley & Sons, Ltd.     

Chronology of the Upper Pleistocene loess sequence of Havrincourt (France) and associated Palaeolithic occupations: A Bayesian approach from pedostratigraphy,OSL, radiocarbon,TL and ESR/U-series data

In connection with the future Seine-North Europe Canal (Seine-Scheldt), a large-scale rescue archaeological survey was conducted at Havrincourt (northern France) between 2008 and 2011. The discovery of several levels of Palaeolithic flint artefacts embedded in a relatively thick loess sequence (ca 6–7 m) preserved on a gentle slope facing North-East, resulted in a 6000 m² excavation. This opened the opportunity for a detailed pedosedimentary and interdisciplinary geochronological survey (¹⁴C, optically stimulated luminescence, thermoluminescence, ESR/U-series) that has allowed us date the sequence reliably. On the basis of these results we propose this sequence as a new pedostratigraphic and archaeological reference sequence for northern France. We present here the optical dating of the sequence performed on fine (4–11 μm) quartz grains extracted from 17 samples. The luminescence characteristics of these extracts indicate that the single-aliquot regenerative dose optically stimulated luminescence (SAR-OSL) procedure that was applied is well suited. A consistent set of optical ages was obtained for the loess deposited up to around 70 ka ago. Independent age control (pedostratigraphy, ¹⁴C, ESR/U-series dates) allowed us to apply a Bayesian approach to build a chronometric model. This in turn enabled a regional chronostratigraphic framework to be built, to constrain the correlations with neighboring regions (northern France and Belgium) and to calculate a precise age for the four Palaeolithic levels discovered, including a unique occupation related to the early Upper Palaeolithic which was previously unknown in the area.     

LATE QUATERNARY ACTIVITY AND PALEOSEISMIC RUPTURE BEHAVIOR FOR THE SOUTHEAST SECTION OF THE GANZI-YUSHU FAULT

The Ganzi-Yushu Fault, the boundary of Bayan Har active tectonic block, Qiantang active tectonic block and Sichuan-Yunan active tectonic block, is a sinistral strike-slip fault zone with intensive Holocene activity. Thus, the study of activity characteristics and rupture behavior of paleoearthquakes in the late Quaternary on the Ganzi-Yushu Fault is of fundamental importance for understanding the future seismic risk of this fault. The southeast section of Ganzi-Yushu Fault is made up of three segments of Ganzi, Manigange and Dengke, where a M_S7.3 earthquake in 1866, a M_S7.7 earthquake in 1854 and a M_S7.3 in 1896 occurred, respectively. There is still lack of in-depth study on the active features and the cascading rupture possibility of these segments, which hindered the evaluation of seismic risk for the southeast section of Ganzi-Yushu Fault. By the means of field geological survey and micro topography measurement, this paper studied the geological and geomorphological features of the southeast section of the Ganzi-Yushu Fault. The results show that the Ganzi and Dengke segments show obvious extension movement, in addition to the left-lateral movement. For Manigange segment, the characteristics of the movement are mainly left-lateral strike-slip and thrusting, and the maximum vertical displacement of the Holocene strata is greater than 2m. In part areas, the movement is normal faulting, which perhaps relates to the left stepping zone in the local stress environment. Therefore, combining the research results such as the fracture distribution in different motion characteristics, rupture behavior of paleoearthquakes, and the distribution of historical earthquake surface ruptures, we divide the southeast section of Ganzi Yushu Fault into Ganzi, Manigange and Dengke segment, and consider the Yakou and the Dengke Basin as the stepovers and the segments' boundaries. As the small scale of impermanent barriers including Dengke Basin and the ridge near Yakou, of which the width is about 1~2km, they may be broken through in great earthquake rupture in future. A trench was excavated in Zhuqing township to investigate the paleoearthquakes on the Manigange segment, radiocarbon dating was employed and 3 paleoseismic events were revealed in the Zhuqing trench, which are the seismic events occurring respectively at 3875~3455BC, after 775BC, and the latest one that ruptured the surface. Compared with the previous results of paleoseismology in the southeast section of Ganzi-Yushu Fault, it is found that the paleoseismic events in the Manigange segment are obviously different with that in Ganzi segment and Dengke segment. Due to the lack of sufficient data on the southeast section of the Ganzi-Yushu Fault, it still needs further discussion whether the cascade-rupturing between these segments exists.     

A discontinuity in the late Pleistocene alluvial deposits,Hwacheon‐ri,Gyeongju, Korea: Occurrences and paleoenvironmental implication

A sedimentary discontinuity is present in the late Pleistocene alluvial deposits exposed along the cliff in stream side, Gyeongju, Korea. Sedimentological study, Optically Stimulated Luminescence (OSL) age dating, and X‐ray diffraction (XRD), and X‐ray fluorescence spectrometer (XRF) analyses were conducted in order to interpret the origin of the discontinuity surface. Based on the sedimentological study, these deposits can be divided into three distinct stages, in ascending order: (Stage 1) development of a braided stream flowing from south to north and deposition by debris flows from the mountain aside the stream during and/or after deposition of the braided stream; (Stage 2) deposition by intermittent events during a state of stagnation after the abandonment or migration of the previously existed braided stream; and (Stage 3) deposition of gravels from debris flows from the mountain aside the stream. Hornfelsic gravels are common in Stage 1, whereas andesitic gravels are predominant in Stage 3, suggesting the provenance change from Stage 1 to Stage 3. The discontinuity surface is laterally extensive and marked by a distinct carbonaceous dark grey horizon between Stage 2 and Stage 3. It is characteristic that rootlets mineralized by vivianite are present, and iron‐oxide crusts are cutting across irregularly below the discontinuity surface. It is thus interpreted that the shift of depositional environment from an alluvial plain (Stage 2) (125 ka) to an alluvial fan (Stage 3) (94–55 ka) was an alluvial response to sea level change from the interglacial to the glacial. The development of iron‐oxide crusts and diagenetic vivianite in the discontinuity surface suggests humid condition persisted during the paleoclimatic shift from the last interglacial to the last glacial stages.     

广丰—绍兴断裂及其对晚白垩世沉积盆地的控制作用

本文讨论了广丰—绍兴断裂的位置和沿断裂分布的晚白垩世盆地。广丰—绍兴断裂位于浙赣铁路附近，它呈北东向展布，并被北西和东西向断层切割。晚白垩世沉积盆地的发育受广丰—绍兴断裂控制。由于盆地内地壳厚度变薄，上白垩统厚度大，高热流值等原因，故这些盆地定为伸展性盆地。     

RESEARCH PROGRESS ON LUMINESCENCE DATING OF ROCK SURFACES AND ITS APPLICATION

There are many examples of exposed or buried rock surfaces whose age is of interest to geologists and archaeologists. Luminescence dating is a well-established method of absolute chronology which has been successfully applied to a wide range of fine-grained sediments from hundreds of years to several hundred thousand years. Optical stimulated luminescence (OSL) has been recently proposed as a new method to date these rock surfaces (Laskariset al., 2011; Sohbatiet al., 2012a; Chapotet al., 2012; Pedersonet al., 2014; Sohbatiet al., 2015; Freieslebenet al., 2015). The basic principle is that luminescence signal of rock surface will soon decay when the rock is exposed to sunlight. When the rock surface is turned to be buried side, the OSL signal begins to accumulate again. With the variation of residual luminescence with depth, it is possible to estimate exposure and burial history of the rock. This article describes briefly the different luminescence dating methods for rock surfaces, its progress, application examples and present problems. For instance, Sohbatiet al. (2011) studied the depth dependence of the bleaching of the IRSL signal from granitic rocks, Laskaris and Liritzis (2011) proposed a mathematical function to describe the attenuation of daylight into rock surfaces, Sohbatiet al. (2012a) developed their model to include the environmental dose rate, Sohbatiet al. (2012b) overcame the problem of parameter estimation by using a known-age road-cut sample for calibration, Sohbatiet al. (2012c) further developed the OSL surface exposure dating model by including the simultaneous effect of daylight bleaching and environmental dose rate, and so on. These studies indicate that OSL dating method for rock surface can be applied widely to studies of geological and geomorphological evolution, archeology and Quaternary tectonic activity.     

THE NEW ACTIVITY OF TAN-LU FAULT ZONE IN SEGMENT OF DAHONGSHAN SINCE LATE QUATERNARY

The relationship between the latest activity of active fault and seismic events is of the utmost importance. The Tan-lu fault zone in eastern China is a major fault zone, of which the active characteristics of the segments in Jiangsu, Shandong and Anhui has been the focus of research. This study takes the Dahongshan segment of the Tanlu Fault in Sihong County as the main research area. We carried out a detailed geological survey and excavated two trenches across the steep slope on the southwest side of the Dahongshan. Each trench shows fault clearly. Combining the comparative analysis of previous work, we identified and cataloged the late Quaternary deformation events and prehistoric earthquake relics, and analyzed the activity stages and behavior of this segment. Fault gonge observed in the trench profiles shows that multiple earthquake events occurred in the fault. The faulting dislocated the Neogene sandstone, black gravel layer and gray clay layer. Brown clay layer is not broken. According to the relations of dislocated stratums, corresponding ¹⁴C and OSL samples were collected and dated. The result indicates that the Dahongshan segment of the Tanlu Fault has experienced strong earthquakes since the late Quaternary. Thrust fault, normal fault and strike-slip fault are found in the trenches. The microscopic analysis of slices from fault shows that there are many stick-creep events taking place in the area during the late Quaternary. Comprehensive analysis shows that there have been many paleoearthquakes in this region since the late Quaternary, the recent active time is the late Pleistocene, and the most recent earthquake event occurred in(12~2.5ka BP). The neotectonic activity is relatively weak in the Anhui segment(south of the Huaihe River)of Tanlu fault zone. There are difficulties in the study of late Quaternary activity. For example, uneven distribution of the Quaternary, complex geological structure, larger man-made transformation of surface and so on. The progressive research may be able to promote the study on the activity of the Anhui segment of Tanlu fault zone.