The resolution of stratigraphic inconsistency in the luminescence ages of marine terrace sediments from Korea

Several sets of marine terraces are exposed along the southeastern coast of the Korean peninsula. The formation ages of these terraces have attracted considerable attention because they provide essential information on local crustal stability. Over the last few years considerable effort has been put into the determination of these ages using optically stimulated luminescence (OSL) dating of the marine sediments from which the terraces were built. For several sites, the results of dose recovery tests and other OSL characteristics, including the dependence of equivalent dose on heat treatment prior to stimulation, have been described in detail elsewhere (Quat. Sci. Rev. 22 (2003) 407). However, it has been found that the samples from one site exhibit various undesirable OSL characteristics, which result in stratigraphically inconsistent OSL ages. In this paper, we investigate these characteristics, and use luminescence component separation to resolve this inconsistency. The resolved OSL ages obtained as such are then used for the discussion on the local crustal stability of the southeastern coast of Korea during the Late Pleistocene.     

Luminescence dating of Late Quaternary sediments from East Greenland

Luminescence dating based on K-feldspars and using both TL and OSL methods have been performed on 94 sediment samples from East Greenland. The ages go back more than 380 ka, but are mainly from the last interglaciation and the subsequent period and include both shallow-marine/coastal-fluvial and ice proximal meltwater sediments. Independent age control indicates that the dates in the first group generally fall within ± 15% of the expected age, although a few samples show larger deviations. The ice proximal sediments, on the other hand, show a much larger spread and exaggerated ages, probably owing to incomplete bleaching. OSL may give better results than TL in these sediments.     

海洋沉积物测年方法综述

海洋沉积物是研究古气候变化、海平面升降、地球化学循环等重大科学问题的载体之一,精确的测年结果是上述研究的重要前提.随着海洋沉积物测年理论、技术设备不断突破,测年方法如210pb法、137Cs法、AMS14C测年、光释光法、古地磁定年、天文轨道调谐法、氧同位素曲线对比、电子自旋共振法、铀系法等层出不穷.文章总结了海洋地质...     

Luminescence dating of loessic sediments from the Loess plateau, China

Loess/palaeosol sequences from the Loess plateau in China were investigated by combined infrared optically stimulated luminescence (IRSL) and thermoluminescence (TL) dating techniques in order to study the luminescence properties of the loessic sediments and to provide a direct chronological link for correlation and position of the last interglacial soil in Central Asia and the Loess plateau in China. Sensitivity changes were found for all samples through artificial bleaching of the samples. The greatest sensitivity changes, of up to 50%, were found for very old loess samples designated to be older than the Matu-yama/Brunhes magnetic boundary and hence older than 788,000±1,800 years. The upper dating limit, as investigated by the very old loess samples, ranges from 250,000 to 300,000 years, if the TL additive dose method is applied. The chronological position of the last interglacial soil S1 at the section near Lanzhou indicates luminescence age estimates ranging from 82,000 to 75,000 years for the marine-isotope stage 5 to 4 transition. However, the loess from below S1 yielded luminescence age estimates between 153,200±14,200 and 110,100±20,100 years for TL and IRSL additive dose methods, respectively. Thus, a direct correlation between the S1 and the first intercalated pedocomplex PC1 in Central Asia is most likely. Received: 31 March 1998 / Accepted: 25 October 1998     

冰川沉积释光测年： 采样策略与测试选择

释光测年是可对冰川地貌进行直接定年的一种测年技术,已被广泛应用于冰川沉积测年中,推动了第四纪冰川研究的深入发展。但冰川沉积释光测年还没有达到标准化的程度,实际应用中仍有不少问题需要探究,其中最受关注的是冰川沉积物释光信号晒退不完全的问题,即样品在埋藏前因曝光机会有限导致信号没有归零或仅部分归零。冰川沉积释光信号晒退程度与地貌部位和沉积环境密切相关。冰川沉积释光采样需注意几个方面：（1）详细的地貌学和沉积学调查及对采样点的选择;（2）较适合释光测年的冰水沉积和冰缘风成沉积采集及其与冰川作用期次的联系;（3）冰碛夹层中的冰水砂透镜体的选取;（4）冰碛垄采样时垂直与水平方向上的考量;（5）岩石释光测年的发展使砾石成为当前第四纪冰川释光测年采样的一种选择。室内进行释光等效剂量测试时,也有几个关键的选择：（1）粗颗粒石英光释光测年是末次冰期以来冰川作用的首选方法;（2）如果样品年代老于石英测年上限,或者石英不适合测试,则可考虑钾长石后红外高温释光测年方法;（3）单颗粒、小测片和岩石释光埋藏测年技术可以鉴别样品的晒退情况,是目前最适合冰川沉积释光测年的几种选择;（4）如有条件,尝试用不同矿物、不同粒径、不同方法进行测试对比和交叉检验。要获得第四纪冰川释光测年的最佳年代学结果,地貌学、沉积学和年代学的结合是非常必要的。     

Luminescence dating of fluvial and coastal red sediments in the SE coast,India, and implications for paleoenvironmental changes and dune reddening

The Holocene and late Pleistocene environmental history of the teri (‘sandy waste’ in local parlance) red sands in the southeast coastal Tamil Nadu was examined using remote sensing, stratigraphy, and optically stimulated luminescence (OSL) dating. Geomorphological surveys enabled the classification of the teri red sands as, 1) inland fluvial teri, 2) coastal teri and, 3) near-coastal teri dunes. The inland teri sediments have higher clay and silty-sand component than the coastal and near-coastal teri, suggesting that these sediments were deposited by the fluvial process during a stronger winter monsoon around > 15 ka. The coastal teri dunes were deposited prior to 11.4 ± 0.9 ka, and the near-coastal dunes aggraded at around 5.6 ± 0.4 ka. We interpret that the coastal dunes were formed during a period of lower relative sea level and the near-coastal dunes formed during a period of higher sea level. Dune reddening is post deposition occurred after 11.4 ± 0.9 ka for the coastal teri dunes and after 5.6 ± 0.4 ka for the near-coastal teri dunes. Presence of microlithic sites associated with the coastal dunes suggest that the cultures existed in the region during 11.4 ± 0.9 ka and 5.6 ± 0.4 ka.     

The lignin geochemistry of marine sediments from the southern Washington coast

Lignin oxidation products and stable carbon isotope distributions are used to investigate the sources, transport, and chemical stability of land-derived organic matter in dated cores of modern sediment from the southern Washington State continental shelf and slope. There is no evidence for significant chemical alteration of lignin compounds in these sediments for time periods of up to 400 yr. Gymnosperm woods and nonwoody angiosperm tissues account for most of the land-derived organic matter in the deposits. These land plant remains have an average δ¹³C of approximately ?25.5% and are concentrated in a narrow band of silty sediment which extends northward from the Columbia River mouth along the mid-shelf. Marine organic matter having an approximate δ¹³C of ?21.5%, strongly predominates in most other shelf and slope environments. Net fluxes of land-derived organic matter into the surface 5 cm of the cores vary directly with sediment accumulation rates. Net fluxes of marine organic material into the surface sediments are highest in environments which favor the preservation of organic matter, but correspond to less than 1% of the primary productivity in the overlying waters.     

Luminescence dating of Holocene playa sediments of the Egyptian Plateau Western Desert,Egypt

This study is part of a multidisciplinary project dealing with the investigation of geoarchaeological sites on the Egyptian Plateau. With the aim of reconstructing the palaeoecological background, providing age assessment which put the various results in an age frame that is of special interest. Here, results of one particular section have been selected because of a discrepancy in age determination based on different approaches. Radiocarbon ages were inconsistent with the age range provided by the archaeological context in this area. The underestimation observed is inferred to be caused by poor ¹⁴C-sample quality. An attempt to overcome this problem was the determination of the depositional ages of the non-organic sediments by using optically stimulated luminescence (OSL). Equivalent doses of four sediment samples were estimated from OSL measurements carried out on sand-sized quartz grains using the single-aliquot regenerative-dose (SAR) protocol. Dose rates were calculated from neutron activation analysis results. From the OSL ages obtained, we conclude that the sediment sequence exposing an alternation of lacustrine and eolian layers was deposited in a short period of time during the mid-Holocene (mean of OSL ages ∼7.8 ka). Compared to the ¹⁴C ages, the luminescence ages fit better into the archaeological context confirmed by surface dating.     

Luminescence dating of anthropogenically reset canal sediments from Angkor Borei,Mekong Delta,Cambodia

This paper presents a case study in the analysis of anthropogenically reset sedimentary materials, through work undertaken to identify and date sediments in an ancient canal in the Mekong Delta, Cambodia. The emergence of rice cultivating communities, utilising canals for both hydraulic management and transport, represents an important stage in the social evolution of southeast Asia. The emergence of complex polities in the region, which may have depended on both international trade and intensified agriculture, led ultimately to the formation of the famous Khmer empires which dominated the region on several occasions through the 1st and 2nd millennia AD. French colonial scholars identified possibly ancient canals in the region that may have played roles in trade, agriculture, or both. This series of ancient canal features near Angkor Borei has been the subject of recent investigations in a collaboration between the Universities of Glasgow and Hawaii. Luminescence profiling measurements were used to identify the canal bed, by exploiting the contrast between a regional substrate of some 50 ka depositional age and more recent archaeological sediments. In this manner it has been possible to identify the sedimentary substrate, undisturbed canal sediments, and redeposited material. Ages have been estimated for substrate and canal infill sediments. The work represents the first convincing demonstration of luminescence dating of one of these important regional features, and indeed the first confirmation of the presumed antiquity of the canal system around Angkor Borei.     

Heavy metal pollution assessment in marine sediments in the Northwest coast of Sabah,Malaysia

Heavy metal contents along the Northwest coast of Sabah were determined to interpret the pollution level in the marine sediment. The metal abundance is regulated by the physico-chemical properties such as the average sediment pH(7.82, 9.00 and 8.99), organic matter(0.62%, 1.60%, and 2.27%), moisture content(25.00%, 29.70%, and 15.00%) and sandy texture in Kota Belud, Kudat and Mantanani Island,respectively. The major elements show Ca>Fe>Mg>Al>Mn for all study sites, while the heavy m...     

Thermoluminescence dating of sediments

The potential for using the thermoluminescence behaviour of sediments for dating them was first recognized by Soviet scientists G.V. Morozov and V.N. Shelkoplyas, and for over a decade their TL dates, obtained from a variety of sediments, have appeared in the Soviet literature. Since 1977 TL sediment dates have been published by six additional groups using a variety of methods.In this review we describe the principles of TL dating, the various methods used, and contrast TL dating of sediments with the now well-accepted TL dating of pottery. We conclude that while TL dating has the potential to solve many sedimentary problems, more fundamental research needs to be carried out before such dates should be accepted. A set of criteria for acceptable dates is proposed.     

Geochemical behavior of Pt and Pd in coastal marine sediments,southeastern margin of the Japan Sea

Eighty-one argillaceous marine sediments collected from the southeastern coastal margin of the Japan Sea were analyzed for Pt and Pd by atomic absorption spectrometry using a graphite furnace atomizer after solvent extraction separation. The average Pt (1.2 ± 0.5 ppb) and Pd(1.6 ± 0.9 ppb) contents are generally similar to those of the published crustal abundances. The Pt or Pd is generally enriched in the fine sediment fraction, and positively correlated with Cu, Pb and water depth. The inverse correlation between the Pt or Pd content and redox potential of the sediment suggests that significant amounts of Pt and Pd are supplied in their dissolved forms, and reduced to their metallic states. It is concluded that the Pt and Pd distributions in the coastal marine sediments are controlled by the geological characteristics of the studied area, grain size and redox potential of sediments, water depths, and dissolved O₂ concentration of sea water.     

Luminescence dating of protohistoric pottery from the Great Basin

Luminescence analyses of several protohistoric brownware ceramics from the Great Basin have produced dates ranging from the 15th to 19th centuries. These begin to add detail to the chronology of these ceramics, which up until now has been poorly known despite their potential importance for understanding Numic population movement in the area. Use of the “slide method” for determining equivalent dose has circumvented problems due to nonlinearity in the relationship between dose and luminescence and has provided much higher precision than traditional methods of dating. Disequilibrium detected in the U-series radioisotope decay chain and some contribution to the dose from nuclear fallout products have created some uncertainty in the dose rate, but less than the overall analytical error. © 1998 John Wiley & Sons, Inc.     

汉江上游二级阶地光释光测年研究

汉江上游地处亚热带季风气候区北部边缘地带, 对气候变化非常敏感, 该地区发育有多级河流阶地, 其上堆积有厚层黄土, 是研究阶地形成年代及气候演化的良好材料。以往对汉江上游阶地形成年代的研究主要集中于一级阶地, 二级阶地形成年代框架还未系统建立, 其主要原因是受限于测年技术和合适的地质载体。文章通过对汉江上游汉中盆地、安康盆地、郧县盆地二级阶地上覆黄土-古土壤层、河漫滩相砂层样品的光释光测年, 利用常规SAR法、TT-OSL法对石英矿物进行等效剂量的测定。结果表明: 汉江上游二级阶地上覆黄土-古土壤的地层序列自下而上依次为黄土L₂→古土壤S₁→黄土L₁。汉中盆地、安康盆地、郧县盆地二级阶地河漫滩相砂层顶部石英TT-OSL测年得到的年龄分别为206.17±18.04 ka、215.14±9.99 ka和212.04±8.68 ka, 河漫滩相砂层之上的砂黄土层/黄土层底部年龄分别为184.16±12.78 ka、198.09±9.65 ka和178.18±9.48 ka。结合地层的光释光年龄数据及相邻区域同一时期的气候变化和构造活动, 确定汉江上游二级阶地在距今220 ka左右开始出现, 最晚于180 ka左右形成, 在随后的构造稳定时段(180~46 ka), 阶地面上堆积厚层风成黄土, 是构造运动和气候变化共同作用的结果。

     

怒江峡谷构造地貌的演化: 阶地宇宙成因核素定年的初步结果

地貌产生于构造活动和各种地表营力驱动的侵蚀夷平和堆积过程,如在构造抬升活跃的地区,河流强烈的侵蚀作用往往造就深切的峡谷地貌。对于这样的地区河流下切速率往往被用来衡量构造抬升速率[1,2]。然而河流下切速率的变化不仅与构造抬升有关,而且与气候变化有关。因此,正确理解     

Potassium-argon dating of polyhalite in southeastern New Mexico

Polyhalite, K₂Ca₂Mg (SO₄)₄-2H₂O, is an important mineral in many evaporites. Although its use for K-Ar dating has never been investigated, our results indicate that it is a very useful mineral for dating events ranging from the time of potash mineralization to any younger events which may have affected the evaporite. Five K-Ar dates on pure polyhalite, including two from included material and from beds distorted by the formation of a rubble chimney, yield dates between 198 and 216 Myp, in good agreement with Rb-Sr dates and the diagenetic age of the potash deposits from the same rocks. Two polyhalites mixed with sylvite gave lower dates (154 and 174 Myr) which is to be expected because of radiogenic ⁴⁰Ar loss from the sylvite phase. One polyhalite, formed after the intrusion of a 31 Myr lamprophyre dike, yielded 21 Myr. Collectively our results indicate that pure polyhalite is satisfactory for K-Ar dating and may provide critical age information in studies of the geologic history of the evaporite sequences.     

Luminescence dating of neotectonic activity on the southwestern coastal plain,Taiwan

The southwestern coastal plain of Taiwan is heavily urbanised, with a population of more than 6 million. The area is known to be subsiding, and the resulting basin is filled with thick fluvial deposits, of at least 200 m thickness. In the past century, three large earthquakes have occurred in the area; two caused surface ruptures, and resulted in large property loss and more than 2000 casualties. There is an urgent need for an understanding of the dynamics and recurrence intervals of this neotectonic activity, but little is known of the chronology of the late Pleistocene deposits. Recently more than 20 cores longer than 250 m were taken from the coastal plain as part of a large hydrogeological investigation, and basic data on lithology, hydrogeology and palaeobiology were collected. The base of these cores is beyond the ¹⁴C age limit, and so the application of luminescence dating to these sediments has been investigated.Optically stimulated luminescence methods have been applied to quartz sand-sized grains extracted from 29 samples. Dosimetry based on gamma spectrometry is also compared with ICP-MS and XRF analyses. In the age range up to ∼40 ka, radiocarbon ages are compared with the luminescence results, to give confidence that the initial bleaching of these sediments was sufficient. The luminescence ages are then discussed and differential rates of basin subsidence are deduced. It is clear from these data that the study area is tectonically active, and it may be that regions of similar subsidence rate correlate with identifiable geological structures.