Centennial-scale Asian monsoon variability during the mid-Younger Dryas from Qingtian Cave,central China

The regional climate correlation within the Northern Hemisphere in the cold/dry mid-Younger Dryas event (YD) remains elusive. A key to unraveling this issue is sufficient knowledge of the detailed climate variability at the low latitudes. Here we present a high-resolution (3-yr) δ¹⁸O record of an annually laminated stalagmite from central China that reveals a detailed Asian monsoon (AM) history from 13.36 to 10.99 ka. The YD in this record is expressed as three phases, characterized by gradual onsets but rapid ends. During the mid-YD, the AM variability exhibited an increasing trend superimposed by three centennial oscillations, well-correlated to changes in Greenland temperatures. These warming/wetting fluctuations show a periodicity of ~ 200 yr, generally in agreement with centennial changes in cosmogenic nuclides indicated by the ¹⁰Be flux from the Greenland ice. This relationship implies that centennial-scale climate changes during the mid-YD are probably caused by solar output and rapidly transported over broad regions through atmosphere reorganization.     

Summer Monsoon Rainfall Variability in Central China over the Past 4700 Years and Its Possible Link to Solar Activity

Based on 467 pairs of δ~(18) O and δ~(13) C records and 8 230 Th dates from a stalagmite(BF4) from Xiniu Cave, central China, we present a reconstruction of ~9-yr resolution monsoon rainfall record for the past 4700 years. Our δ~(18) O record shows good coherence with East Asian summer monsoon(EASM) rainfall proxies from adjacent regions during the overlapping intervals, suggesting that δ~(18) O signal in BF4 can be interpreted as a monsoon rainfall proxy. The δ~(13) C variations are related to changes in local processes at the cave site, and regional rainfall and temperature changes.Based on the δ~(18) O record, a series of dry periods can be identified at 4500–4200, 3500–3200, 2800–2500,1900–1600, 1400–1200, 700–500, and 400–200 yr BP, while a series of wet periods can be identified at 4200–3600,2400–2200, 3200–2800, 1100–900, 600–400, and 200–100 yr BP. Power spectrum analysis on our δ~(18) O record reveals significant cycles at ~470 and ~80 yr, coinciding with the typical solar periodic variations. This result suggests that changes in solar activity play a dominant role in driving centennial–decadal monsoon rainfall variation in central China. Due to minor changes in solar irradiance(less than 1.5 W m~(-2)) over the past 4700 years, our record was further compared to the El Ni?o–Southern Oscillation(ENSO) and Pacific Decadal Oscillation(PDO) proxies,confirming that solar forcing on monsoon rainfall changes might be amplified by the ENSO and PDO variations.From 600 to 150 yr BP(the Little Ice Age, LIA), a positive shift of ~2‰ can be revealed in both the δ~(18) O and δ~(13) C records, indicating a cold/dry climatic pattern. By comparing our δ~(18) O and δ~(13) C records with historical documents,we suggest that the climatic deteriorations between 450 and 250 yr BP may have caused serious social unrest at the end of the Ming Dynasty.     

神农架三宝洞倒数第二次冰期高分辨率石笋δ13C记录

基于神农架三宝洞两支石笋24个230Th年龄以及637个δ13C测试数据,建立了倒数第二次冰期191±1.8～133±0.6kaB.P.时段洞穴石笋高分辨率δ13C的时间序列.在冰期/间冰期尺度上,δ13C值振幅达4.5％,整体变化趋势与全球冰量曲线类似.在倒数第二次冰期,石笋δ13C记录揭示出一系列较大振荡幅度的千年...     

断陷湖盆滩坝砂体成因与成藏:以东营凹陷沙四上亚段为例

滩坝砂是一种发育在滨浅湖高能环境的薄互层沉积,是以往未被重视的、认识程度较低的碎屑岩储集体。围绕滩坝砂成因与成藏的难点,研究了东营凹陷沙四上亚段滩坝砂沉积特征和分布规律,明确了滩坝砂成藏要素与富集规律。提出了滩坝砂沉积受古地貌、古水动力(波浪、湖流)和古基准面控制的"三古控砂"机制和油气成藏受断裂裂隙、有效储层、烃源岩超压控制的"三元控藏"认识,指出断陷盆地中长期基准面持续上升,短期基准面频繁震荡形成了大面积分布的滨浅湖滩坝砂沉积,烃源岩生烃增压与成岩过程中耗水降压共同作用下的"压-吸充注"是滩坝砂岩大面积含油的主要原因。     

南京直立人的U/Th和U/Pa年代

中国直立人化石的准确定年对于研究人类演化有着极为重要的意义。1993～1994年在南京汤山葫芦洞发现的两个直立人头盖骨化石和一枚牙化石被称为“南京直立人”。其中1号头盖骨化石之上的方解石钙板的U/Th年龄为53.3_(-1.2)~(+1.5)万年;但考虑到定年的准确性,则为53.3_(-3.0)~(+3.5)万年。其~(231)Pa/~(235)U活度比值为0.998±0.006。这表明“南京直立人”的年代应该大于50万年。与”南京直立人”伴生的动物牙化石U/Th年代为18.5～29.0万年;U/Pa年代为13.7～17.2万年。此外,对于同一颗牙化石,牙釉的年龄小于牙本质的年龄。同一样品的U/Pa年龄也显著小于其U/Th年龄。因此,牙化石的U摄取过程并不符合U早期摄取模式。多数牙化石分析点在~(234)U/~(238)U-~(230)Th/~(238)U图上落在位于U早期摄取和线性摄取模式曲线之间,指示牙化石的U摄取过程很可能介于上述两种模式之间。如果这一假设成立,那么牙化石的U/Th和U/Pa线性摄取模式年龄则为其年代的上限。因为不受U摄取过程~(234)U/~(238)U变化的影响,U/Pa线性摄取模式年龄比U/Th较为可靠。最小的U/Pa线性摄取模式年龄为1Ma,这是”南京直立人”上限年龄的估计。从定年结果看,”南京直立人”可能生活在海洋同位素(MIS)16阶段,但这不是最终结论。     

Response of groundwater chemistry to water deliveries in the lower reaches of Tarim River,Northwest China

In this paper, we analysed the monitored data from nine groundwater-monitoring transects in the lower reaches of Tarim River during the five times of stream water deliveries to the river transect where the stream flow ceased. The results showed that the groundwater depth in the lower reaches of Tarim River rose from −9.30 m before the conveyances to −8.17 and −6.50 m after the first and second conveyances, −5.81 and −6.00 m after the third and fourth the conveyance, and −4.73 m after the fifth. The horizontal extent of groundwater recharge was gradually enlarged along both sides of the channel of conveyance, i.e., from 250 m in width after the first conveyance to 1,050 m away from the channel after the fourth delivery. With the rising groundwater level, the concentrations of major anions Cl⁻, SO₄²⁻ and cations Ca²⁺, Mg²⁺, Na⁺, as well as total dissolved solids (TDS) in groundwater underwent a significant change. The spatial variations in groundwater chemistry indicated that the groundwater chemistry at the transect near Daxihaizi Reservoir changed earlier than that farther from it. In the same transect, the chemical variations were earlier in the monitoring well close to watercourse than that farther away from the stream. In general, the concentration of the major ions and TDS at each monitoring well increased remarkably when the water delivery started, and decreased with the continued water delivery, and then increased once again at the end of the study period. Hence, the whole study period may be divided into three stages: the initial stage, the intermediate stage and the later stage. According to the three stages of groundwater chemistry reaction to water delivery and the relationships between groundwater chemical properties and groundwater depths, we educe that under the situation of water delivery, the optimum groundwater depth in the lower reaches of the Tarim River should be −5 m.     

Origin of Oils in “Subtle pools” in the Dongying Depression, Bohai Bay Basin, China

Subtle traps or oil pools have become an important exploration play in the Dongying Depression, Bohai Bay Basin, east China. Despite recent successes in exploration, the formation mechanisms of subtle traps are still not well understood. The majority of subtle oil pools in the Dongying Depression are developed in the middle interval of the Es3 Member of the Paleogene Shahejie Formation with the subtle traps being primarily of lenticular basin-floor turbidite sands encompassed in mudstones. Oil in the subtle traps was previously thought to have migrated directly from the surrounding source rocks of the same formation （Es3）. Detailed geochemical investigation of 41 oils and 41 rock samples from the depression now indicates that the oils from the subtle traps cannot be correlated well with the surrounding Es3 source rocks, which are characterized by high Pr/ Ph （〉1）, low Gammacerane/C30hopane, representing a freshwater lacustrine setting. In contrast the oils features low Pr/Ph （〈1） and relatively high Gammacerane content, showing a genetic affinity with the underlying Es4 source rocks, which also have the same qualities, indicating a brackish lacustrine setting. Oils in the Es3 subtle traps are probably derived from mixed sources with the contribution from the upper Es4 source rocks predominating. Therefore unconventional oil migration and accumulation mechanisms need to be invoked to explain the pooling of oils from the ES4 source rocks, which probably came through a thick low interval of the Es3 source rocks with no apparent structural or stratigraphic pathways. We suggest that the subtle oil migration pathway probably plays an important role here. This finding may have significant implications for future exploration and the remaining resource evaluation in the Dongying Depression.     

东亚季风“2.8ka”事件高分辨率的石笋记录

据湖北省神农架永兴洞一支石笋的8个230Th年龄、648个δ18O数据,建立了晚全新世4.40～ 1.75ka B.P.时段平均分辨率为4a的东亚夏季风演化序列,其中在2.92～ 2.74ka B.P.期间,δ18O发生显著正偏,幅度达2.5‰,指示一个显著的弱季风事件(这里称之“2.8ka”事件).该事件以夏季风缓慢减弱开始,迅速增强结束,事件内部有两个次一级的振荡旋回(两峰三谷结构),在内部细节与转型特征上类似湖北和尚洞石笋δ18O记录的“8.2ka”事件,暗示发生在全新世这两个冷事件的驱动机制基本一致.这两个弱季风事件都发生在太阳活动明显减弱时期,并分别与北大西洋Bond 2和Bond 5冰漂碎屑事件同步,表明百年尺度的东亚季风环流的演化由太阳活动和北高纬气候共同驱动.     

新疆北部扎河坝坳陷上二叠统沉积环境

扎河坝坳陷位于阿尔泰造山带与准噶尔盆地之间,属于中亚造山带的一部分,自早古生代以来经历了准噶尔洋盆的打开和闭合等阶段,富含煤炭和金属矿产,也具有一定的油气勘探前景。研究区火山岩和含煤层系发育,地表风化剥蚀严重,对研究其地层发育特征和沉积环境起到了一定的制约。对扎河坝坳陷新富地1井岩芯样品开展沉积岩微量元素测试,分析结果表明,扎河坝坳陷上二叠统为温暖湿润的淡水沉积环境,表明扎河坝坳陷晚二叠世经历了火山活动和陆相淡水沉积2个阶段,印证了准噶尔洋由俯冲消减向陆内阶段转换的过程。该研究对恢复研究区构造演化及沉积古地理特征具有重要意义。     

水下光通信技术的研究与展望

水下光通信（Underwater Optical Wireless Communication,UOWC）是一种新型的水下通信技术,具有保密性好、可靠性高等优点,对于构建全光立体通信网络以及6G空天海地一体化全方位通信有重要的意义。分析了水下光通信相较于其他传统水下通信方式的优点,对水下光通信发展历程与进展进行了综述,对比了水下光通信2种主流光源：激光光源和LED光源。针对现阶段水下光通信面临的难题,提出了一种完善的水下光通信系统框图,并研制出相应的硬件系统,完成了水下通信调试。水下光通信是一种切实可行的新型通信方式,兼具灵活、保密、高速率等特点,在未来的6G时代中将会得到进一步的发展和应用。