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Malcolm Richard Gent Mario Menéndez Alvarez Jesús José María García Iglesias Javier TaraÑo Álvarez 《Marine Georesources & Geotechnology》2013,31(1-2):39-59
ABSTRACT Results of offshore water-jet sediment sampling demonstrate the potential for interstadial placer deposits of industrial minerals in the shore-face to inner-shelf of Cape Ortegal, NW Spain. Placer deposition is interpreted to have occurred during glacial interstadials since the Last Glacial Maximum, and deposits sampled at 24 to 42 m. BSL were formed during the Younger Dryas, and subsequently preserved as a result of very rapid rising sea-levels. The sediments are almost entirely terrestrially derived with a particularly high heavy mineral content (Sp. Gr. >2.9), of more than 75% in all samples. Reworked garnet from earlier-sedimentary deposits constitutes an important fraction of the placer deposits identified but is generally absent in other sediments. Indications of the presence of +5 m-thick paleo-placer deposits with sections include:
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Placer garnet + spinel grades increase with depth in those sediments at 24 to 42 m BSL to the ocean-floor.
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The d50 of sediments with background grades decrease with depth while those of placer deposits do not display any significant trend.
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Garnets in non-mineralized sediments are almost entirely angular, whereas in placer enriched sediments they vary in form from well-rounded to angular. Some grains in the latter display surface morphologies typical of reworked sediment while none of the former do.
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河南省史前人类遗址的时空分布及其驱动因子 总被引：2，自引：1，他引：1
基于ArcGis10.0 平台分析了河南省史前时期的仰韶文化遗址和龙山文化遗址的空间分布、濒河性、空间集聚度等指标。结果显示,18.8%的仰韶期遗址分布在河流的1 km缓冲区内,而龙山期遗址只有16.5%,其濒河性呈减弱趋势。豫西山区、南阳盆地、颍河-淮河地区龙山期遗址的空间集聚度比仰韶期分别增加了0.006,0.016 和0.021,暗示龙山时期的自然条件逊色于仰韶期导致人类活动范围受到局限。遗址密度3-D分析表明,河南地区史前人类活动格局从仰韶期的“单核型”演化为龙山时期的“多核型”。这种空间格局的变化可能与5.4 kaBP降温事件相关,而且龙山期的气候特征与仰韶时期相比显得温凉、干燥,加之农业生产技术的进步和人口增加促使史前人类活动核心区从豫西山区向豫东平原和豫北平原地区扩散。同时4.0 ka BP前后河南地区的干旱、洪水、低温等自然灾害频发亦加速了人类活动范围的快速扩展,并且石家河、大汶口、关中等史前文化类型向河南地区的渗透,造成河南龙山文化类型的多元化和空间分布的复杂化。而全新世早期的裴李岗遗址和晚期的二里头遗址数目较少且均匀分布于嵩山两翼,初步推测环嵩山地区是河南史前文化的肇源地区。 相似文献
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The indices related to sedimentary pyrite are widely used in paleo-environmental studies;however its application principles and flaws have not been presented in detail so far , therefore it is necessary to review the controlling factors of them .In this study the authors described the application principles in detail , including py-rite morphology, C/S ratio, DOP, size distribution, sulfur isotope, and further discussed the C-S-Fe system in oil shale in Meihe Formation which indicates oxic or suboxic conditions during oil shale deposition .The concen-tration of TOC and S in the oil shale in Meihe Formation is more than that in background mudstone , and the py-rite formation is limited by sulfate .Therefore studying the indices related to pyrite proves to be of great impor-tance. 相似文献
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湖北松滋刘家场地区寒武系覃家庙组三段发育层状、不规则层状和柱状叠层石,三游洞组发育柱状和半球状叠层石。从层状、不规则层状、柱状到半球状叠层石,内部灰泥含量不断减少,纹层特征从明显到断续,反映了水动力条件加强的变化环境。从沉积岩石学角度与叠层石分类观点讨论得出,研究区不同沉积环境的叠层石组合类型有所差异,不同类型的叠层石主要沉积相带不同:潮上带主要分布层状(包括不规则层状)和柱状叠层石,潮间带主要分布柱状、半球状叠层石;层状叠层石主要分布于水动力条件较弱的潮上带,而柱状和半球状叠层石主要分布于水动力条件较强的潮间带下部。部分后生动物的大量灭绝导致叠层石微生物生长繁殖是松滋寒武系叠层石发育的主要原因。 相似文献
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基于现代黄河水下三角洲浅地层剖面资料和GYDY钻孔的岩性、磁性、地层年代与古生物数据,将研究区26.2m以浅地层自上而下划分为6个沉积单元,分别对应DU 1～6.在高分辨率粒度测试的基础上,根据沉积物粒径组分、粒度参数、粒度资料图解和结构散点图等分析手段,分析了各沉积单元的粒度分布规律及对应的动力沉积环境,并探讨了研究区晚更新世末期(约36.2cal.ka B.P.)以来的动力环境演化.结果表明:DU 6沉积单元为献县海侵层,形成于浅海陆架沉积环境,水动力环境强度弱,沉积作用以静水悬浮沉积为主;DU5沉积单元形成于末次盛冰期,动力强度大,动力环境变化复杂,粒度图解显示其整段或局部可能接收风营力改造,接受风成沉积物补给的可能性较大;DU4沉积单元冰后期约13.3～ 8.5ka B.P.,为河口沉积层,以中等到弱沉积动力为主,动力环境变化复杂;DU3沉积单元为狭义黄骅海侵层,形成于受多种营力作用的滨海环境,沉积环境较稳定;DU 1和DU 2沉积单元属现代黄河三角洲沉积层,形成于较弱到中等动力强度三角洲环境,其中DU 2沉积单元可能受到黄河1855年铜瓦厢改道入渤初期尾闾大幅度摆动的影响,粒度特征变化复杂.各沉积单元的粒度特征的变化规律与海侵-海退层序基本一致,是冰期-间冰期旋回海陆变迁过程中多营力共同作用的结果.研究区古气候变化仅在本区暴露于陆的末次盛冰期与冰后期早期对相应沉积单元粒度分布有一定影响. 相似文献
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湖南花垣县杨二洞化石点位于沅江上游,动物群种类包括有6目26种,动物群时代为晚更新世末期。杨二洞小型哺乳动物化石材料较多。有些小型哺乳动物在我国更新世时期首次发现,如大爪长尾鼩、大黑伏翼、大齿鼠等。杨二洞动物群在我国西南地区更新世末期的材料之中,具有较为突出的森林性特征,反映出湘西北更新世末期具有南亚热带森林古环境。动物群综合研究发现,小家鼠、褐家鼠在中更新世晚期分别产生于中国东北和长江下游,其中小家鼠在更新世晚期经华北向长江流域及其以南扩散,褐家鼠在更新世较晚时期分别向华北和岭南扩散。晚更新世以来,有较多小哺乳动物出现了从低海拔向高海拔山区进行生境转移的现象,这种生境转移对认识大熊猫生态演变有重要参考。杨二洞堆积物特征反映,沅江上游晚更新世末期时河床侵蚀性下切明显,地貌变化显著。 相似文献
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本文根据孢粉分析,推测古石灰华沉积时期的植被,是以蒿、藜为主的山地草原,散布有柳、栎、榆、桦等组成的落叶阔叶林块;古气候比现今温暖湿润,年平均气温约10—13℃,属暖温带半干旱气候,当时的海拔高度约1500—2000m。 相似文献
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Effect of Miocene basaltic volcanism in Shanwang (Shandong Province, China) on environmental changes
Miocene(16―10 Ma) basalts,together with significantly well-preserved fossils(including animal and plant fossils) in the contemporaneously tephra-rich Maar sediments,are located in Shanwang volcanic region,Shandong Province,China.Distribution area of the basaltic eruption products is about 240 km2.Detailed field observations indicate that most of basaltic rocks are fissure eruptive products and some are central eruptives constrained by linear faults.The well-preserved fossils in the lacustrine deposits have been considered to be a result of mass mortalities.Based on physically volcanologic modeling results,eruption column of the basaltic fissure activities in the Shanwang volcanic region is estimated to have entered the stratosphere.Petrographic observations indicate that the basalts have porphyritic textures with phenocrysts of olivine,pyroxene,plagioclase feldspar and alkali feldspar setting in groundmass of plagioclase feldspar,alkali feldspar,quartz,apatite and glass.Based on observations of tephra,tuff and tuffites collected in the Maar sediments of the Shanwang area,we determined major element oxide concentrations and volatile composition of melt inclusions in phenocrysts and matrix glasses by electron microprobe analysis.Volatile(including S,Cl,F and H2O) concentrations erupted into the stratosphere were estimated by comparing pre-and post-eruptive volatile concentrations.Our determination results show that contents of S,Cl,F and H2O emitted into the stratosphere were 0.18%― 0.24%,0.03%―0.05%,0.03%―0.05% and 0.4%―0.6%,respectively,which was characterized by high-S contents erupted.Amounts of volatiles emitted in the Shanwang volcanic region are much higher than those in eruptions which had a substantial effect on climate and environment.According to the com-positions and amounts of the volatiles erupted from the Miocene basaltic volcanism in Shanwang,we propose a hypothesis that volatile-rich basaltic volcanism could result in the mass mortalities by in-jecting volatiles(e.g.,SO2,H2S,HCl,HF and H2O) into the stratosphere that would have triggered abrupt environmental changes(including formation of acid rain,temperature decline,ozone depletion,etc.) and altered lake chemistry,and subsequently volcanic ash fall buried and covered the dead animals and plants,forming well-preserved fossils in Shanwang Maar sediments. 相似文献
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根据我国的地理位置和第四纪地层的特色分析,海陆结合是我国海洋第四纪研究的优势所在.半世纪以来,中国海洋地质的研究经历了从调查到研究、从海岸到浅海再到深海、从晚第四纪到晚新生代、从低分辨率到高分辨率以及从定性到定量的进展过程,取得了重要进展,但仍有很大的差距.新世纪初期,应当从国际、国内第四纪研究的关键问题着眼选题,以西太平洋边缘海与暖池作为主战场,和陆地工作、和现代过程相结合展开研究.文章对我国海洋第四纪研究的方向、措施进行了讨论. 相似文献