重庆地区末次冰期气候变化的石笋记录研究

对采自重庆金佛山梁天湾洞穴的1 根长达295 mm的石笋进行了高精度的TIMS-U系定年和碳氧同位素测试分析,建立了末次冰期晚期(31.90~15.21 ka B.P.)长江中游较高分辨率(平均为280 a/mm)的古气候变化序列。从石笋的氧同位素曲线中明显地检出Heinrich事件,并且氧同位素曲线与南京葫芦洞和贵州董歌洞的石笋记录有着良好的对比关系。但明显的差别是,重庆地区石笋的同位素记录表明,该地区末次冰期晚期古气候是受西南季风和东南季风双重影响的。     

末次冰期盛期中国热带的变迁

参照约６０个实例,探讨末次冰期盛期中国热带位置的纬度地带性和经度地带性变迁。当时,热带中部、热带北部、亚热带南部３个地带的北界分别南移５个、２个、６个纬距。经度地带性差异可分为５个区。其年均温下降幅度,台湾岛最大（５￣９℃）,两广及海南岛其次（３￣４℃）,闽南粤东较小（２￣３℃）,滇南最小（１￣２℃）。南海冬季水温降幅较大（２．４￣５．７℃）。除闽南、粤东、南海趋于冷干外,大部分地区环境趋于冷湿。     

末次冰期以来浑善达克沙地粒度组成的环境记录

浑善达克沙地周缘及腹地质量磁化率的测定和粒度分析表明：区域上粒度变化表现为东部较西部粗，腹地较周缘粗，南部较北部粗的规律，说明粒径的大小及土壤的成壤与源区及地表环境有关，同时也说明了浑善达克沙地的形成过程受东亚季风变化的影响；时间上，末次冰期晚期，浑善达克沙地全面扩张，主要表现为现代草场的位置都可找到古风成砂；冰后期，浑善达克沙地成壤作用较好，这个时期属于一个大的成壤期，即使在沙地的腹地也成壤；目前该地区处于成壤期，但成壤作用比冰后期差，粘土含量减少，地表粗化现象严重，表明了人类活动在沙漠化过程中的突出作用。     

中国热带红树林的发展及其地理背景

参照约３０个红树林孢粉分析实例，探讨中国南方晚第三纪以来红树林的发展。红树林开始出现于晚始新世；晚第三纪其分布比今偏北；第四纪冰期使红树林向南退缩至雷州半岛北部。末次间冰期４２ ０００～２５ ０００ ａ ＢＰ红树林扩展，以海桑属为代表的典型红树林的北界从现今的 １９°３０′扩展到２３°４０′Ｎ。末次冰期红树林衰落。早全新世９ ６００～７ ９００ ａ ＢＰ红树林复兴，中全新世达到繁盛，向北分布到闽江口（２６°Ｎ），与现今的北界一致，但是中全新世以来海桑属在１９°３０′Ｎ以北不再出现，奠定了现今红树林地带性分布的格局。     

青藏高原大湖期

青藏高原湖盆中古湖岸线分布广泛,从最高湖岸线的分布确定的大湖期湖泊面积,一般比现代湖泊面积大数倍至十多倍。据高原不同地区的十多个湖泊沉积测年数据分析,大湖期的年代大致相近,在４０￣２４ｋａ ＢＰ居多,有的可能延续至２０ｋａ ＢＰ,与深海氧同位素３阶段、末次冰期间冰段相当。时期高原环境特别湿润。大湖期的形成与该时期亚洲夏季风特别强盛有关。     

南京葫芦洞石笋生长速率及其气候意义讨论

一支连续发育4?000年纹层的末次盛冰期葫芦洞石笋的年际生长速率与高分辨率δ¹⁸O曲线对比分析表明,年际生长速率在不同时间尺度上对年均温和地表有效湿度的变化有着复杂的响应关系。对该洞内持续发育3~4万年的两支单体石笋实测了33个²³⁰Th年龄,其生长曲线显示MIS 2比MIS 3阶段平均生长速率增大了40%以上。以5000年为步长的同一洞穴17支石笋生长频率支持平均生长速率的研究结果,说明在轨道尺度上较大的石笋生长速率并不完全指示较暖湿的气候条件。作者认为,年际尺度的连续生长速率是决定石笋平均生长速率的关键因素。盛冰期条件下本区洞穴内外的温差效应导致了24~14ka B.P.年际尺度的石笋连续生长。     

昆仑山垭口小南川末次冰期早期成层坡积的沉积特征和气候…

成层坡积结构构造特征、粒度、化学、电镜扫发描分析和测年资料揭示其形成于末次冰期间冰段。存在由湿冷向干冷的气候变化。成层坡积上覆的坡积黄土则代表末次冰期全盛及全部世环境以显著于冷为特征。     

末次冰期以来贵南沙地土地沙漠化与气候变化的关系

通过对青海贵南县凤凰山地层剖面的沉积相、磁化率曲线特征分析认为：（１）未次冰期以来，贵南沙地的土地沙漠化发展模式以正、逆过程相交替为基本特点；（２）贵南沙地的土地沙漠化正、逆过程与气候的干冷和暧湿变化所导致的水平生物气候带移动密切相关；（３）随着ＣＯ＿２等温室效应气体的增多，全球气候变暖，我国季风雨区扩大，本区降水量可能增加，土地沙漠化的发展趋势将是，正过程有所抑制，逆过程有所发展。     

巴丹吉林沙漠东南缘末次冰期沉积物地球化学特征及气候指示意义

沙漠古气候重建对于了解区域古气候演变具有重要意义。通过以巴丹吉林沙漠东南缘巴润宝日陶勒盖(BRBG)剖面为研究对象,进行全样地球化学、分组分分粒级元素地球化学及Sr同位素分析,重建该地区末次冰期期间(66.8~41.0 ka)的气候演化模式。研究表明:66.8~41.0 ka呈现残留组分高Sr/Ca值、酸溶组分及残留组分低Ba含量特征,指示化学风化增强及湖泊补给量增加,反映暖湿气候特征。微量元素变化特征指示沉积物细粒组分中的微量元素指标对气候的敏感度高于粗粒组分。Sr同位素结果显示酸溶组分中87Sr/86Sr值在66.8 ka附近达到最大值,可能与湖水盐度升高相关。此外,几乎所有指标均指示在41.0 ka前后存在一次气候突变事件,研究认为巴丹吉林沙漠东南缘41.0 ka前后从暖湿突变为干冷气候可能是该时期的西伯利亚高压系统增强所致。     

东亚沿海山地末次冰期冰川与环境

对东亚沿海山地末次冰期冰川发育的气候条件、构造背景、冰进时序、发育规模等研究表明,台湾山地保存着3期冰川作用遗迹,冰川的最大前进规模发生在MIS3b阶段,其规模大于MIS2阶段;日本山地冰期系列齐全,包含了末次冰期的早(MIS4)、中(MIS3)、晚(MIS2)3个阶段的冰进,其规模是MIS4/3阶段大于MIS2阶段;而长白山存在2期冰川作用的遗迹,即末次冰盛期(MIS2)和晚冰期.在相似的冬雨(雪)型季风影响区,冰川发育的时序与规模也有一定不同,反映出在大气候背景下的区域性差异,在东亚季风影响范围内,末次冰期的环流变化在各地也很不一致.最新推算的现代理论雪线自北(日本)向南(台湾)依次递增,范围是2750～4245 m,除日本北部的高纬地区雪线降低值400 m之外,末次冰盛期(LGM)的雪线降低值在800～1300 m之间,平均值1000 m左右.东亚沿海山地冰川发育与新构造运动密切相关,更新世山体的快速抬升为冰川发育的内因,如台湾山地在末次冰期的MIS3b阶段,山体的抬升量约为250 m,对山体的高度和雪线变化有很大影响.     

Present and Late Pleistocene equilibrium line altitudes in Changbai Mountains, Northeast China

According to the glacial landforms and deposits with the optically stimulated luminescence (OSL) dating results, two glacial stages of the last glacial cycle (LGC) and Late Glacial were identified. The Late Glacial stage (Meteorological Station glacier advance) took place about 11 ka (11.3±1.2 ka), and the last glacial maximum (LGM), named Black Wind Mouth glacier advance, occurred at 20 ka (20.0±2.1 ka). Based on the Ohmura’s formula in which there is a relationship between summer (JJA) atmospheric temperature (T) and the annual precipitation (P) at ELA, the present theoretical equilibrium line altitude (ELAt) in Changbai Mountains was 3380±100 m. Six methods of accumulation–area ratio (AAR), maximum elevation of lateral moraines (MELM), toe–to headwall altitude ratios (THAR), the terminal to summit altitudinal (TSAM), the altitude of cirque floor (CF), and the terminal to average elevation of the catchment area (Hofer) were used for calculation of the former ELAs in different stages. These methods provided the ELA for a range of 2250–2383 m with an average value of 2320±20 m during the LGM, which is 200 m higher than the value of previous investigation. The snowlines during the Late Glacial are 2490 m on northern slope, and 2440 m on western slope. The results show that the snowline on northern slope is 50 m higher than that on western slope during the Late Glacial, and the average snowline is 2465m. The ELA △ values were more than 1000 m during the LGM, and about 920 m lower than now during the Late Glacial stage respectively. Compared with Taiwanese and Japanese mountains in East Asia during the LGM, the effect of the uplift on ELA in Changbai Mountains during the glaciations (i.e. 20 m uplift in the LGM and 11 m in the Late Glacial) is not obvious.     

云南东北部拱王山末次冰期

1 Introduction The Gongwang mountains constitute one of the few high m ountains of irrefutable late Pleistocene glaciation in eastern China. This area is one of the m ost extensively studied Quaternary geologicallocationsin eastern China and the interpret…     

OSL dating of glacier extent during the Last Glacial and the Kanas Lake basin formation in Kanas River valley, Altai Mountains, China

The Kanas River originates on the southern slope of Youyi Peak, the largest center of modern glaciers in Altai Mountains, China. Three sets of moraines and associated glacial sediments are well preserved near the Kanas Lake outlet, recording a complex history and landscape evolution during the Last Glacial. Dating the moraines allows the temporal and spatial glacier shift and climate during the Last Glacial to be determined, and then constrains when and how the Kanas Lake basin was formed. Dating of the glacial tills was undertaken by utilizing the optically stimulated luminescence (OSL) method. Results date four samples from the three sets of moraines to 28.0, 34.4, 38.1, and 49.9 ka and one sample from outwash sediment to 6.8 ka. The Kanas Lake basin is a downfaulted basin and was eroded by glacier before 28.0 ka, and the glacial moraines blocked the glacier-melt water after the glacier retreat, which made the present-day Kanas Lake eventually form at least before 6.8 ka BP. In Altai Mountains, the glacier advance was more extensive in Marine Isotope Stage (MIS) 3 than MIS 2, probably because the mid-latitude westerlies shifted northward and/or intensified during the MIS 3, resulting in a more positive glacier mass balance. Nevertheless, the Siberian High dominated the Altai Mountains in MIS 2, resulting in a relative decrease in precipitation.     

青藏高原东部当子沟末次冰期冰川演化光释光测年

青藏高原东部横断山脉沙鲁里山北支雀儿山北麓的当子沟, 保留了4 组末次冰期冰碛垄, 每组冰碛垄由若干道小冰碛垄组成, 是末次冰期多次冰川波动的理想地貌证据。为恢复该地末次冰期冰川演化历史, 从这4 组冰碛垄中采集了7 个光释光测年样品进行年代测定。等效剂量采用单片再生法(SAR)和标准生长曲线法(SGC)进行测试。年代结果显示:第1~3 组冰碛垄形成于22.4-16.5 ka BP, 属深海氧同位素2 阶段(MIS-2), 大致与全球末次盛冰期(LGM)相当。第4 组冰碛垄形成于MIS-3。MIS-3 冰川规模大于MIS-2。第1~3 组9 道次一级小冰碛垄表明, 约在22.4-16.5 ka BP期间当子沟冰川经历了9 次小波动。冰川在稍早于22.4 ka BP达到MIS-2 的最大范围, 此后规模在波动中逐渐萎缩, 可能是冰川对MIS-2 后期太阳辐射增强、气温回升的响应。最里侧冰碛垄形成于16.5 kaBP, 可能标志着该地冰消期的开始。此后, 当子沟冰川大幅快速退缩。冰川融水在最里侧冰碛垄里侧低洼谷地汇集并被阻塞形成当子错。     

云南千湖山第四纪冰川发育特点与环境变化

千湖山(4249 m) 是横断山脉中段保存确切第四纪冰川遗迹的山地,受西南季风影响强烈。对于研究青藏高原边缘山地冰川发育与气候和构造之间的耦合关系具有十分重要的科学意义。在千湖山海拔3500 m以上保存着古冰川侵蚀与堆积地貌,冰川发育依托海拔4000~4200 m的夷平面及其支谷地形。冰川形态类型为小型的冰帽以及由冰帽边缘溢流进入山谷的山谷冰川。应用相对地貌法,光释光(OSL) 年代测试,本文确定千湖山地区的冰进系列:末次冰盛期(LGM,22.2±1.9 ka BP)、末次冰期中期(MIS3b,37.3±3.7 ka BP、45.6±4.3 ka BP45.6±4.3 ka BP)、末次冰期早期(MIS4)。千湖山冰川前进规模是MIS3b 阶段大于末次冰盛期,主要原因是末次冰期中期(MIS3b) 时本区气候相对湿润,而在末次冰盛期(MIS2) 时气候条件比较干燥。在总体相似的气候背景下,与横断山其它存在多期次冰川作用的山地相比,千湖山只发育末次冰期的冰川作用,其差异性说明该地区冰川发育主要受山体构造抬升控制。     

GLACIATION OF MT ALLEN, STEWART ISLAND (RAKIURA): THE SOUTHERN MARGIN OF LGM GLACIATION IN NEW ZEALAND

The origin of two ridges on the eastern slopes of Mt Allen, southern Stewart Island, has remained equivocal, with differences of opinion over the exact process-mechanisms of formation. A variety of approaches was used to test a number of possible hypotheses about the origin of the ridges. These include topographic and spatial positioning, geomorphology, sedimentology and palaeoclimatological extrapolations to reconstruct two small former cirque glaciers with equilibrium line altitudes (ELAs) of c. 600 m. It would appear the two ridges reflect a glacial origin, the glaciers interpreted as forming during the Last Glacial Maximum (LGM) in New Zealand. Whilst glaciation during this time (18–19 ka) was extensive in the Southern Alps, the restricted nature of glaciation on Mt Allen suggests the low altitude restricted glaciation to niche sites on the lee side of upland areas.     

Late Pleistocene glaciation of the Hulifang Massif of Gongwang mountains in Yunnan Province

Late Pleistocene glaciation was restricted to only a few high mountains in eastern China. The Gongwang mountains constitute one of the typical places once glaciated. Geomorphic mapping of the area and the TL dating provides evidence for at least four distinct glaciations. YJT-I glacial advance occurred about 100 ka BP and two TL absolute ages (101,100 ±7780 a BP; 104,000±8300 a BP) indicate this advance happened during the Penultimale Glaciation. The early stage glacial advance (YJT-II advance) during the last glaciation occurred about 40,920±3400 a BP. The last glacial maximum advance (YJT-III advance) about 18-25 ka BP, which sustained by two TL ages (18,230 ±1420 a BP; 25,420 ±2110 a BP). The Penultimale and the early stage glaciations were more extensive and the last glacial maximum (LGM) and the late-glacial period (YJT-IV advance, 10 ka BP) were progressively less extensive. Correlated with the other mountains in eastern China, these glacial advances in the Gongwang mountains just like the advances in the western part such as Diancang mountains, Yulong mountains of Yunnan Province and the glacier series are more complete than the adjacent mid-latitude regions such as Taibai mountain and Taiwan mountains and are roughly representative of climate changes during the last glacial cycle in Yunnan Province.     

Late Pleistocene climate inferred from the reconstruction of the Taylor River glacier complex, southern Sawatch Range, Colorado

Ice surface topography of a late Pleistocene glacier complex, herein named the Taylor River Glacier Complex (TRGC), was reconstructed on the basis of detailed mapping of glacial landforms combined with analyses of aerial photos and topographic maps. During the last glacial maximum (LGM), the TRGC covered an area of 215 km² and consisted of five valley or outlet glaciers that were nourished by accumulation in cirques basins and/or upland ice fields.Equilibrium-line altitudes (ELAs) for the glaciers of the TRGC were estimated using the accumulation-area ratio method, assuming that ratio to be 0.65 ± 0.05. ELAs thus derived ranged from about 3275 to 3400 m, with a mean of 3340 ± 60 m. A degree-day model (DDM) was used to infer the climatic significance of the LGM ELA. With no appreciable differences in precipitation with respect to modern climate, the ELA implies that mean summer temperatures during the LGM were 7.6 °C cooler than today. The DDM was also used to determine the temperatures required to maintain steady-state mass balances for each of the reconstructed glaciers. The required reductions in summer temperature vary little about a mean of 7.1 °C. The sensitivity of these results to slight (± 25%) changes assumed for LGM precipitation are less than ± 0.5 °C. Even under an LGM climate in which precipitation is assumed to be substantially different (± 50%) than the present, mean summer temperatures must be on the order of 7.0 to 8.5 °C lower to depress equilibrium lines to LGM altitudes. The greater sensitivity of the ELA to changes in temperature suggests that glaciation in the region was driven more by decreases in summer temperature rather than increases in precipitation.     

天山阿特奥依纳克河流域冰川沉积序列

阿特奥依纳克河位于我国天山的最西段,最大现代冰川作用中心托木尔峰的南麓。在第四纪冰期与间冰期的气候旋回中,该处留下了形态较为完整的6套冰川沉积。应用ESR测年技术 (辅以OSL测年技术) 对冰碛物及其相应的冰水沉积物进行了定年,测得6套冰碛年龄分别为7.3±0.8ka BP (OSL,冰水沙);12.3±1.2ka BP (OSL) 与15~29ka BP;46~54ka BP;56~65ka BP;155.8±15.6ka BP与234.8±23.5ka BP;453.0±45.3ka BP,测年结果表明它们分别形成于新冰期、海洋同位素阶段(MIS)2、3b、4、6、12。第三套冰碛测年结果表明该处MIS3b冰进规模较大,其规模基本上与末次盛冰期 (MIS2) 的规模相当。此处最老冰碛测年结果与我国中段天山乌鲁木齐河源高望峰冰碛的测年结果 (459.7±46ka BP与477.1ka BP) 遥相呼应,老冰碛的年龄显示我国天山西段与中段至少于MIS12进入了冰冻圈,开始发育冰川。     

四川螺髻山清水沟冰川槽谷演化及其影响因素

螺髻山地处青藏高原东南缘,是确切存在第四纪古冰川遗迹的典型山地之一,该区冰川地貌演化对于研究环境变化具有重要的科学意义。螺髻山东坡清水沟保存两套古冰川槽谷,分别为上槽谷和下槽谷,其中下槽谷保存完整,而上槽谷在3450~3600 m的阴坡部分出现缺失。采用野外地貌调查与模型分析相结合的方法,对冰川槽谷地貌进行分析,结果表明:清水沟槽谷的抛物线模型中,|A|值在1.3101~15.2064 之间变动,B 值变化于0.9695~3.2965 之间,且随着海拔由高到低,都存在着先变小后变大的规律,A、B值同时反映出在海拔3450~3600 m处冰川槽谷的演化不符合常态。分析认为岩性差异和河流溯源侵蚀是影响上槽谷形态的主要原因。对保存在清水沟上下槽谷内的高、低侧碛进行ESR年代测定,结果显示:高侧碛形成于58-84 ka BP左右的末次冰期早期,对应深海氧同位素4 阶段(MIS4);低侧碛形成于13-17 ka BP,属于于全球末次冰盛期晚期的产物。两次冰川作用分别塑造出两套冰川槽谷,即在末次冰期早期冰川作用形成上槽谷,末次冰期晚期形成下槽谷。