Petrology of green polished stone axes of the Jomon period from the Sannai-Maruyama site,Japan, investigating the origin of source rock

Numerous green polished stone axes have been excavated from the Sannai-Maruyama site, one of Japan's largest archeological sites in the Jomon period (5.9–4.2 cal kyr BP). The axes are composed of weakly metamorphosed fine-grained volcaniclastic rock having a peculiar texture that includes numerous acicular actinolites growing in random directions within a quartz and albite matrix. Cobbles of Aotora stone found along the Nukabira River, Biratori town, southern Hokkaido, are the most likely raw material for these stone axes. Aotora stones have alternate bands of a soft dark-green picritic layer and a hard SiO₂-rich pale-green layer. The pale-green layer has a texture similar to the stone axes. Basaltic and picritic volcanic rocks of the Sorachi-Yezo Belt occupy the area along the Shidoni River, a tributary of the Nukabira River. Volcaniclastic rocks similar in texture, mineralogy, and bulk rock compositions to the Aotora stone are exposed in the area. These rocks underwent metamorphism under the actinolite-pumpellyite facies conditions. Their protolith is submarine hyaloclastic rocks that are intercalated with laminated picrite detritus. The stone axes, pale-green layers of Aotora stone, and those of the volcaniclastic rocks of the Shidoni River area all have high SiO₂ (~ 55 wt%), Cr (~ 840 μg/g), and Ni (~ 370 μg/g). The rare earth element patterns with abundant light rare earth elements and depleted heavy rare earth elements of stone axes were also consistent with the pale-green layers of the outcrop. These pale-green layers, interleaved with dark-green layers of picritic detritus, were the likely source rock of the stone axes. The high SiO₂ content in the pale-green layer caused the crystallization of quartz and albite in the matrix, which resulted in high-quality raw material for making stone axes.     

一种绿色“斑马石”玉料的矿物组成研究

最近在江苏东海的水晶市场上出现了一种名为“斑马石一的玉石,该玉石总体颜色为墨绿色,其中有白色条纹呈带状分布并呈丝绢光泽。为了查明其组成,利用偏光显微镜、X射线粉末衍射仪、红外光谱仪、拉曼光谱仪以及激光诱导离解光谱仪等测试方法对该样品进行了测试分析。结果表明,该“斑马石”实际就是一种蛇纹石的集合体材料。其绿色部分的主要矿物组成为利蛇纹石,其次为绿泥石,白色部分由纤蛇纹石构成,含少量绿泥石,黑色包裹体为磁铁矿。这种材料不同于一般的蛇纹石玉,在于该玉石中含有一些定向的纤蛇纹石的平行纤维条带,正是这种纤维状平行排列的结构,导致了“斑马石”中呈丝绢光泽的条带。“斑马石”的折射率,相对密度及荧光特征与一般的蛇纹石玉无差异。     

Effect of the 2004 Asian tsunami in the sea cave of Tham Phaya Nak (Koh Phi Phi archipelago,Thailand) and possible evidence of a prehistoric event

Tsunamis may leave traces on the landscapes whose study provides a prehistorical approach and the analysis of possible recurrences. In karstic areas, caves and speleothems are good recorders for natural or anthropogenic events. They preserve traces of fragile remains as prehistoric paintings and they have been used for palaeoseismology studies. The effects of the 2004 Asian tsunami on the karstic shores have been studied in Western Thailand, close to Phuket. Limestone cliffs of Koh Phi Islands and the marine cave of Phi Phi Leh have been poorly affected, but a prehistoric-event has provoked the deposit of a layer of coral fragments into the cave. This damage could be attributed to a tsunami but a storm cannot be excluded.     

A rapid assessment of Scleractinian and non-Scleractinian coral growth forms along the Saudi Arabian coast,Red Sea

In this study we assessed the current status of coral reefs along the Saudi Arabian coast of the Red Sea. Among the three growth forms of Acroporid corals, the branching forms were found to dominate in the Farassan Islands(44.55%±11.10% cover) followed by tabular forms in the Doga Islands(ranging between 18%±6.47% and 18.30%±9.47% cover). Digitate forms were rarely found along the coast except at Maqna. Among the five growth forms of non-Acroporid corals, we observed maximum cover of branching forms in the Yanbu offshore area(58.89%±15.11% cover) followed by the Jeddah coast(24.76%±14.04% cover). The Millepora spp., a non-Scleractinian coral, was abundant at all the near-shore sites, such as Jeddah(10.70%±8.21%) and Al-Wajh(9.81%±6.69%). The live coral cover(including both Scleractinian and non-Scleractinian corals) of Saudi Red Sea coast was seen to be higher in the north and gradually decrease towards the south. Principal Component analysis showed that the contribution of Acroporid corals was greater in the southern region than in the northern and middle regions, but vice-versa in the case of non-Acroporid corals. Bray-Curtis cluster analysis categorized all the study sites into two major clusters with 60% similarity. Among them, one cluster-forming sites from Maqna to Masturah(Northern region) and the second one comprised the middle and southern regions(Jeddah to Farassan Islands), and one outlier Rabigh.     

Construction and analysis of a coral reef trophic network for Qilianyu Islands,Xisha Islands

Qilianyu Islands coral reefs (QICR), located in the northeastern part of the South China Sea, has been affected by human activities and natural disturbance. To characterize the trophic structure, ecosystem properties and keystone species of this region, a food-web model for the QICR is developed using methods involving a mass-balance approach with Ecopath with Ecosim software. Trophic levels range from 1.00 for detritus and primary producers to 3.80 for chondrichthyes. The mean trophic transfer efficiency for the entire ecosystem is 13.15%, with 55% of total energy flow originating from primary producers. A mixed trophic impact analysis indicates that coral strongly impacts most components of this ecosystem. A comparison of our QICR model with that for other coral reef ecosystems suggests that the QICR ecosystem is immature and/or is degraded.     

大亚湾及大鹏半岛沿岸造礁石珊瑚现状与生态脆弱性评价

本研究于2020年7月在大亚湾及大鹏半岛沿岸开展造礁石珊瑚的分布、覆盖率、死亡率、硬珊瑚补充量和物种多样性调查。结果表明：24个站位共发现造礁石珊瑚9科17属44种以及5个未定种,其中裸肋珊瑚科的种类最多,有7属27种,其次为鹿角珊瑚科和滨珊瑚科,均有2属6种;中央列岛沿岸造礁石珊瑚平均覆盖率为12.0%,三门岛沿岸平均覆盖率为12.9%,大鹏半岛沿岸平均覆盖率为5.2%;以坚实滨珊瑚（Porites solida）、翼形蔷薇珊瑚（Montipora peltiformis）、五边角蜂巢珊瑚（Favites pentagona）和多孔同星珊瑚（Plesiastrea versipora）等为优势种;造礁石珊瑚物种多样性较高。与历史数据相比,大亚湾及大鹏半岛沿岸造礁石珊瑚退化严重,活珊瑚覆盖率锐减,优势种由分支状珊瑚逐步转变为皮壳状或亚团块状珊瑚。此外,本研究构建了近岸造礁石珊瑚生态脆弱性评价体系,并对目前大亚湾及大鹏半岛沿岸造礁石珊瑚进行了生态脆弱性评价。结果显示,中央列岛、三门岛和大鹏半岛东侧海域造礁石珊瑚处于低或中脆弱状态;较场尾、杨梅坑、西冲和大鹏半岛西侧海域造礁石珊瑚处于高或很高脆弱状态,在环境压力影响下其受损可能性较高。在海水养殖、渔业捕捞、滨海旅游和船舶航行等日益频繁的人类活动下,大亚湾及大鹏半岛沿岸造礁石珊瑚整体处于中高脆弱状态,建议加强珊瑚礁监测,并采取相应的保护措施。     

降雨对土层标与基岩标影响的差异性分析

通过对南京地震台短水准测量中的基岩标志和土层标石的抗干扰分析,发现:温度、气压的影响可以通过改变观测时间段来尽量减小,使其对两类观测点观测资料没有明显影响;降雨量大小对基岩点的影响很弱,对土石点影响较大,则没办法消除.表明,在选择好的观测场地的同时,也要根据观测资料的需要埋设合理的测点标志类型.     

Alignment of stone‐pavement clasts by unconcentrated overland flow – implications of numerical and physical modelling

The crucial role of stone pavements in arid environments for aeolian or alluvial processes and as numerical dating tools is increasingly acknowledged. This role is based on the assumption that stone pavements are stable landforms, formed gradually over time and predominantly by vertical processes. However, this is challenged by evidence of stone‐pavement clast reworking or burial. Bimodal, mostly slope aspect‐symmetrical clast orientation is a frequent phenomenon in various study areas. It implies that stone pavements may be influenced by unidirectional lateral processes besides vertical ones. Here, the finding of lateral processes contributing to stone‐pavement evolution is supported by numerical modelling and physical experiments. These unequivocally show that unconcentrated overland flow can transport clasts to form a closely packed stone mosaic with characteristics similar to those of natural stone pavements. The commonly observed length‐axes orientation angle of 40 ± 14° for natural stone‐pavement clasts is consistently reproduced by angle‐dependent force equilibrium. Monte Carlo runs confirm the natural scatter and allow characterization of the control parameters of clast orientation. The model explains up to 70% of the natural variance. It is further validated by flume experiments, which confirm model predictions of single object orientation angles. Experiments with multiple objects yield artificial stone pavements with properties similar to those found in the field. The unidirectional lateral process acting on natural stone pavements requires the presence of a vesicular horizon. This underlines the tight genetic coupling of this common epipedon feature and the clast cover. The presented findings highlight the role of stone pavements as process and environment proxies. However, stone pavements represent information since the last surface disturbance only. This has to be considered when using them as age indicators. Copyright © 2013 John Wiley & Sons, Ltd.     

近45年涠洲岛5次珊瑚热白化的海洋站SST指标变化趋势分析

根据涠洲岛珊瑚礁普查(Reef Check)历史资料和涠洲岛海洋站实测海表温度(SST)历史资料,采用对比分析与相关分析方法,分析1966―2010年该岛珊瑚热白化的SST指标变化特征,结果显示:1)涠洲岛珊瑚热白化的最热周平均SST值为31.6℃或最热日平均SST值为32℃;2)1966―2010年涠洲岛的逐年最热月月均SST、最热日日均SST、年极端最高SST及最热周平均SST呈准同步变化,彼此间的相关系数为0.71~0.89,4种珊瑚热白化SST指标没有显著上升趋势;3)最热月月均SST和最热周平均SST的变化趋势与全球变暖在统计上存在显著相关关系。     

浙江自然地理环境与采石文化的关系

浙江是石材大省,采石文化源远流长,近年来陆续发现多个古代采石遗迹。浙江采石文化是在浙江特有的地质、地貌、水系、气候等自然地理要素的综合作用下产生和发展起来的。浙江的地质条件是区域采石文化发生和发展的前提条件。“七山一水二分田”的地貌格局对采石文化的产生和发展具有重要影响。山地丘陵本身就是潜在的采石场所,蕴藏着丰富的石材资源,平原中的孤丘、平原与山地丘陵过渡地带以及盆地边缘地带常常分布有采石场,而特殊的河口地貌、漫长曲折的海岸线和数量众多的岛屿都会在一定程度上对采石文化产生影响。纵横交错的水系为石材的运输提供了便捷,有利于采石文化的传播,而河流水利工程的建设也会对采石文化产生一定的影响。特殊的沿海气候条件也会对采石文化产生一定的影响。采石文化对自然地理环境会产生一定的反作用,影响并且改变当地的地貌、水文、植被等自然地理环境要素。人类的采石活动对自然地理环境的改变主要是通过采石场景观的形成和石材的使用两条途径来实现的。