渤海湾西岸海岸带第四纪地质研究成果概述

本文简要介绍了天津地质调查中心海岸带与第四纪地质研究所(海岸带近现代地质环境变化研究小组)自1998年承担国土资源大调查任务以来,以滨海新区及渤海湾西岸海岸带为主要研究基地所取得的基本成果:(1)确立了泥质海岸带(沿海低地-潮间带-浅海区)地质环境变化(大致划分为(a)晚更新世以来-"小冰期"、(b)"小冰期"结束-现...     

A sedimentary facies model for stepped,fluvial tufa systems in the Iberian Range (Spain): the Quaternary Piedra and Mesa valleys

Stratigraphic and sedimentological analyses of the Quaternary tufa and associated deposits in the Piedra and Mesa river valleys allowed a number of stages of their sedimentary evolution to be characterized, and a depositional sedimentary model for this north‐central sector of the Iberian Range (Spain) to be established. The proposed sedimentary facies model may explain tufa arrangements in other medium to high gradient, stepped, fluvial tufa systems with narrow transverse profiles occurring in temperate, semi‐arid areas, in both recent and past scenarios. There are several tufa deposits within the Piedra and Mesa river valleys that, over a maximum thickness of about 90 m, record one or more stages of tufa deposition produced following the fluvial incision of the bedrock or previous tufa deposits. Each depositional stage begins with coarse detrital sedimentation. Six fundamental, vertical sequences of tufa facies with small amounts of detrital material reveal the sedimentary processes that occurred in different fluvial environments: channel areas with: (i) free‐flowing water; (ii) barrages and/or cascades; and (iii) dammed water and palustrine floodplains. The proposed sedimentary model involves narrow, stepped, fluvial valleys in which tufa cascades were common. Alternating intervals of bryophyte and stromatolite facies commonly formed at some cascades. Many of these represented barrage‐cascade structures that consisted of phytoclast rudstones, thick phytoherms of mosses and associated stromatolites, and curtain‐shaped phytoherms of stems. Upstream of these structures, dammed areas with bioclastic sands and silts developed and palustrine vegetation grew. The channel stretches between barrages and/or cascades were loci for extensive stromatolite growth in fast flowing water. The palustrine floodplain was home to pools and drainage channels. The model also explains the growth of some barrages in the River Piedra that surpassed the height of the divide, with the diffluence of the main channel into a secondary course forming other tufa deposits in the area. The distribution and abundance of certain types of tufa facies in fluvial basins may be an indicator of differences in their gradients. The facies studied in this work suggest that the gradient of the ancient River Piedra was steeper than that of the ancient River Mesa. Assuming similar scenarios for climate and hydrology, the depositional settings mentioned above and their dimensions would have been determined mainly by the gradient and width of the associated river valleys. This sedimentary model may also be useful for inferring variations in other river basin slopes, as well as accounting for the presence of tufas in areas that normally have no permanent water input.     

渤海湾泥质海岸带近现代地质环境变化研究(Ⅱ):成果与讨论

渤海湾泥质海岸带国土资源大调查以其特有的方法、手段和要求,获得了一批带有地质调查特点的、关于全新世地层与近现代地质环境变化的阶段性成果,主要包括:1)该地区海岸带全新世地层具有4种沉积类型:(A)远离海岸的传统的"三分"型;(B)海相层与陆(海陆过渡)相层的多次交替;(C)末次冰期后期未接受沉积,全新统半咸水的海陆过渡相直接覆于历时约10～20ka的沉积间断面上,向上,进一步发育为海相层;(D)沿海低洼地区在末次盛冰期后的晚更新世晚期即已进入海侵阶段,晚更新世晚期与全新世早期的海陆过渡相沉积是连续的,向上继续发育海相层.2)从以海水影响为主的开放潮坪(及浅海区)环境转变为(陆源影响逐渐加强的)湖-盐沼环境,是研究区中晚全新世地质环境转变的重要特征,建立了表征这两种不同环境的非正式地层单位("灰色单元"与"黄色单元").3)牡蛎礁与贝壳堤的对比方案,以牡蛎礁对应潮坪的贝类繁盛期,牡蛎礁中的水平再搬运夹层和/或上覆泥质盖层(往往形成"岭地")对应贝壳堤成堤.4)大比例尺区调地质点(浅孔)揭示了中晚全新世(近现代)地质环境变化,编绘出约4500calB.P.以来小于1ka时段的二维、假三维环境系列图.一个实例是Ⅱ贝壳堤向陆侧的洼地甚至早于该堤的形成,推测洼地边缘的NNW向的埋藏线性凸起可能受同一方向的新构造活动控制.5)渤海湾沿海平原线性砂坝(障壁岛)-湖/盐沼成因假说.作为堆积贝壳堤正地形的补偿,堤前因"簸选"贝壳导致的潮坪负地形,同样可发育湖沉积.6)210pb/137Cs测年研究提供了该地区现代沉积速率的初步结果(＜0.1cm/a或＞3cm/a不等),据此将海岸带划分为不同的沉积类型区.     

基于遥感技术的兖济滕矿区采煤沉陷区现状及动态变化特征

利用遥感技术,对兖济滕矿区2000-2010年的采煤沉陷区动态变化进行了研究,结果表明,2010年,兖济滕矿区累计沉陷面积为88．43km^2,占整个矿区面积的3．53％。10年来,沉陷区面积呈直线上升趋势,由2000年的57．37km^2,增加到2010年的88．43km^2,平均年增沉陷地面积约为3．45km^2。采用遥感手段,在大范围内,可以较直观、准确地确定采煤沉陷区的范围、面积、形态、动态变化等特征,可为沉陷区的综合治理提供科学依据。     

地下水与环境变化研究

环境变化研究是当前国际地球科学和环境科学界最为活跃的研究领域之一。作为全球水循环的重要环节,地下水是全球环境变化的受体和信息载体。地下水及其沉积物的物理、化学指标,诸如地下水水位、宏量组分、微量组分、同位素、惰性气体等可以用作不同时间尺度上环境变化的指示剂。从地下水及其沉积物中识别和提取高分辨率的环境变化信息,实现对环境变化的预警功能是地下水科学向环境科学延伸的重要方向;而随着全球淡水资源紧缺形势不断恶化,全球环境变化、特别是全球气候变化对地下水资源的影响成为水文地质研究的新课题。     

湘西北喀斯特山区耕地变化与经济发展的相关性——以张家界市永定区为例

根据张家界市永定区1989~2005年耕地资源及人均GDP的统计资料,分析了永定区耕地面积与经济发展的动态变化过程,建立了耕地减少量与人均GDP数据的定量相关模型,从而得出了该地区耕地面积减少与经济发展间的关系规律。研究结果表明,永定区耕地面积减少量最初随着人均GDP的增加而增加,当越过一个阈值后(2002年),就开始随着人均GDP的增长而降低。虽然这样的演化规律受当地的自然条件及其他相关因素的影响而有所波动,出现阶段性变化,但基本上仍吻合库兹尼茨曲线的一般特征。结合当前实际,对湘西北喀斯特地区如何实现经济增长与耕地保护的协调发展提出了相应的措施和建议。     

广东汕尾近40年以来气温的变化特征

根据汕尾地区汕尾、海丰、陆丰站1960—1999年的气温序列资料,采用线性趋势、累积距平、小波分析以及Mann-Kendall突变检验等方法对汕尾地区气温变化特征进行了分析,结果表明：40年来汕尾地区存在暖-冷-暖3个气候变化阶段。年季平均气温均呈上升趋势,尤其在1980年代中期以后升温更为明显;四季升温率以冬季最为显著。在不同冷、暖阶段,冷、暖年（季）出现的年数差异很大,其中异常冷年均出现在1980年前,异常暖年均出现在1990年后。年平均最高气温与最低气温同年平均气温一样均呈升高趋势。但不同站点的气温变化仍有一定差异。年平均气温汕尾站存在2—3a、6—7a、准12a周期,海丰站存在准7a与14—16a周期,陆丰存在准1．5a、准2．5a、5—7a、准16a周期,MK检验发现汕尾平均气温在1998年发生突变,其他两站的突变发生在1997年。     

略谈气候异变对中国上古农业转型的影响

结合考古资料,对气候异变与中国上古农业转型的关系进行了论述,认为在全新世时期中国发生过几次较大的降温事件,气候异变一方面给原始农业文化造成严重的损害,另一方面又激发了人们应对这种挑战的勇气和智慧,成为原始农业文化进化和转型的契机;中国上古农业发展中的两次重大转型——农业"边缘"地区游牧经济的形成和黄河中下游地区"沟洫农业"的出现,均与气候异变有关;人类科学地应对和适应气候异变,使中华文明的进程出现了新格局。历史经验表明,自然环境虽然能够对历史过程产生重大影响,但关键是人类如何去应对,人类自身才是历史发展更为重要的决定性因素。     

中国东部中新世风尘沉积的发现及其研究意义

黄土高原红粘土古气候与古环境研究取得巨大进展。已知最老的红粘土时代达到22 Ma，在亚洲晚新生代环境演变研究，特别是在指示亚洲内陆干旱荒漠化、高原隆升的环境效应等方面有重要意义。结合野外实地调查和室内粒度、磁化率、扫描电镜和地球化学实验分析结果，对南京附近灵岩山剖面的沉积特征与风尘沉积证据进行了探讨。在灵岩山剖面玄武岩下覆的松散沉积层中有厚度超过4 m的风尘沉积层，时代在12 Ma以前，为迄今中国东部发现的新生代最老的风尘沉积物，是中新世季风气候出现之后的产物，推测与秦安红土剖面记录的15～13 Ma快速强烈粉尘沉积阶段一致，并和南极冰盖15 Ma开始扩大造成的全球降温事件有关联。     

Sedimentary Features and Sea-Level Changes Reflected in Drill Holes in the Zhuhai Area

Experimental examinations and analyses have been made of the sediments from drill holes in the Zhuhai area, Guangdong Province. The studies show that there occurred four transgressions in this area over the historical times. The first transgression occurred at 7500 a B.P., with the maxium sea level up to about 1 m above the present level. The second transgression occurred at 5750 a B.P., with the sea level possibly 4 m higher than the present. The third and fourth transgressions took place at 4650 a B.P. and 2600 a B.P. respectively, which lasted for a long time with multiple fluctuations. The fifth transgression is in process. It could be predicted that the sea level at Zhuhai would rise by 15-20 cm in the coming 50 years.