江苏南部滆湖成因演化的初步认识

借助高速公路勘察资料及前人研究成果,分析了江苏南部滆湖地区第四纪晚更新世土层空间的展布特征。据此认为,晚更新世晚期在常州西存在北东走向的古长江汊流河谷,滆湖是连接该河谷的古河道所在地。湖区钻探水下发现宽达300m的北东走向全新世古河道,进一步说明河道淤塞是形成现今滆湖的主要成因。     

辽宁沿海早、中期全新世海进中的一次海退事件探讨

通过分别对辽东半岛东侧大洋河平原中部的D65孔岩心做连续的硅藻分析,以及对辽东半岛西侧的长兴岛八岔沟古泻湖平原B3孔、下辽河平原的机械钻孔X33及手动钻孔X11和X21等钻孔岩心做连续的粘土混浊水电导率测定,得到各岩心的硅藻图谱/或粘土混浊水电导率图谱。显示出在这些海岸平原均有厚度在6m以上的海相层存在。表明全新世海侵时海水达到并长期占据这些海岸平原。同时还显示在这些海相地层的5～7m深处,普遍存在一层陆相或海陆交互相地层,通过对各地点已有的14C年代数据分析,推测这层陆相层或海陆交互相地层应该形成于全新世海面上升的早全新世—中全新世时期。表明全新世海进期当中,辽宁沿海普遍存在一次海退地质事件。从下辽河平原样品的14C测年数据,推测这次海退时期大致在9300～8000aB.P.(校正年)。     

A structural interpretation of magnetometer and seismic profiler records in the Bismarck Sea,Melanesian Archipelago

During a marine geophysical survey of the Bismarck Sea by the Australian Bureau of Mineral Resources in 1970, magnetic, gravity, and seismic reflection recordings were made along north‐south traverses with a spacing of 30 to 40 km. The magnetic data have been interpreted, first by visual inspection of magnetic and topographic trends and then by two‐dimensional computer modelling along typical profiles. The interpretation indicates that the Bismarck Sea is divided into two main tectonic provinces separated by a boundary which roughly coincides with a line joining Manus Island and the Willaumez Peninsula of New Britain. An area of apparently nonmagnetic basement about 10 km wide coincides with a well defined band of shallow earthquakes which runs east‐west across the centre of the Sea. A major boundary is present at the eastern end of the Sea along the west coast of the Gazelle Peninsula of New Britain; it continues along an offset in the band of earthquakes to New Hanover.     

河海交互作用与苏北平原成因*

苏北平原向海侧分布着大冈、上冈两列古贝壳堤以及依此而建的范公堤;西侧有低山丘陵环绕,江淮水系河流汇入平原内侧的湖泊群,发育了伸出型三角洲;兴化、里下河地区是平原的最低洼处。这一系列地貌组合与分布特点,启迪着探究平原的成因。146m深的宝应望直港钻孔,穿透了2.58Ma以来的第四纪地层。沉积相、微体古生物、古地磁测定与沉积层常量元素分析等综合研究,阐明了4次主要的海洋作用沉积环境,尤其是晚更新世3.9~2.6万年前的浅海环境沉积更为显著。河湖相泛滥平原沉积与潮滩浅海沉积交互成层,证实了苏北平原是第四纪时期由河-海交互作用,从古海湾发育堆积成宽大平原。进一步工作需探索相关时期的江-海分布变化及黄河和黄渤海通道与苏北平原发育的关系。     

Unravelling the conundrum of river response to rising sea‐level from laboratory to field. Part I: Laboratory experiments

The most recent deglaciation resulted in a global sea‐level rise of some 120 m over approximately 12 000 years. In this Part I of two parts, a moving boundary numerical model is developed to predict the response of rivers to this rise. The model was motivated by experiments at small scale, which have identified two modes describing the transgression of a river mouth: autoretreat without abandonment of the river delta (no sediment starvation at the topset–foreset break) and sediment‐starved autoretreat with abandonment of the delta. In the latter case, transgression is far more rapid and its effects are felt much further upstream of the river mouth. The moving boundary numerical model is checked against experiments. The generally favourable results of the check motivate adaptation of the model to describe the response of the much larger Fly‐Strickland River system, Papua New Guinea to Holocene sea‐level rise; this is done in the companion paper, Part II.     

华北晚古生代陆表海盆地海侵事件微观沉积特征及成煤探讨

采用沉积学、煤地质学、古生物学、地层学及地球化学等多技术手段,结合比较分析法的思路,分析了事件型海侵的特点和海侵事件沉积组合特征,研究发现:海侵事件沉积组合为区域对比性强、具沉积时间连续性与相序间断性的暴露沉积-煤层-灰岩组合,其关键沉积学特征是煤层底板的暴露沉积.海侵事件组合灰岩的古生化石个体小、破碎强烈等特征表现为高能量水体运动等环境,孢粉表现为低含量的单缝孢和裸子植物及高含量的三缝孢.地球化学分析表明暴露沉积为陆相环境,煤层中的微量元素表现为海相主要原因是由于泥炭沼泽覆于深水后受海水影响所致.海侵事件成煤与海侵过程成煤差异体现在两个方面:第一,盆地属性差异,即海侵事件成煤形成于陆表海盆地之中,而海侵过程成煤则形成于具有缓坡的边缘海盆地,第二,成煤原理存在着差异,海侵事件成煤强调的是成煤前海侵未发生前的碎屑体系废弃而发育大量泥炭沼泽且被后期突发性海侵终止,而海侵过程成煤则强调的是泥炭沼泽发育于滨海的活动碎屑体系并终止于后期的缓慢海平面上升.     

天津—河北沿海钻孔地层中的末次盛冰期下切河谷

文章回顾了1965年李四光先生追寻末次冰期对环境影响的讲话,以及40余年来在天津-河北沿海钻孔地层中、末次盛冰期下切河谷的发现过程。在源到汇过程中,起码自晚更新世以来,研究区已经是古黄河沉积区,多处发现的末次盛冰期下切河谷底板多位于30~32 m深度,低于全新统底板一般在20 m的深度;与长江口地区钻孔末次盛冰期下切河谷深62 m相比,研究区下切河谷规模不如前者,也没有一个统一的大河口。末次盛冰期下切河谷最远地点,是距现代海岸约80 km的河北省孟村回族自治县县城北侧,即西汉黄河亚三角洲叶瓣顶部。众多钻孔见早全新世快速沉积,只能是黄河支流有这样充足的泥沙供给,在局部顶托了早全新世海侵作用发生。     

陆相盐湖层序地层学研究简述

陆相盐湖盐源复杂多样,主要有陆源、海源和地壳深部三大类。前两类主要通过蒸发成盐,气候起着关键作用,形成的陆相盐湖低水位和高水位体系域中盐岩发育,湖侵体系域中盐岩相对不发育;第三类主要通过兑卤成盐,作为深层卤水通道的深大断裂的活动期次控制了盐岩的发育,盐岩主要发育在湖侵体系域,高水位体系域次之,低水位体系域中盐岩一般不发育。     

Basin‐scale fluvial correlation and response to the Tethyan marine transgression: An example from the Triassic of central Spain

The relationships between large‐scale depositional processes and the stratigraphic record of alluvial systems, e.g. the origin and distribution of channel stacking patterns, changing architecture and correlation of strata, are still relatively poorly understood, in contrast to marine systems. We present a study of the Castillian Branch of the Permo‐Triassic Central Iberian Basin, north‐eastern Spain, using chemostratigraphy and a detailed sedimentological analysis to correlate the synrift Triassic fluvial sandstones for ~80 km along the south‐eastern basin margin. This study investigates the effects of Middle Triassic (Ladinian) Tethyan marine transgression on fluvial facies and architecture. Chemostratigraphy identifies a major, single axially flowing fluvial system lasting from the Early to Middle Triassic (~10 Ma). The fluvial architecture comprises basal conglomerates, followed by amalgamated sandstones and topped by floodplain‐isolated single‐ or multi‐storey amalgamated sandstone complexes with a total thickness up to ~1 km. The Tethyan marine transgression advanced into the basin with a rate of 0.04–0.02 m/year, and is recorded by a transition from the fluvial succession to a series of maximum flooding surfaces characterised by marginal marine clastic sediments and sabkha evaporites. The continued, transgression led to widespread thick carbonate deposition infilling the basin and recording the final stage of synrift to early‐post‐rift deposition. We identify the nonmarine to marine transition characterised by significant changes in the Buntsandstein succession with a transition from a predominantly tectonic‐ to a climatically driven fluvial system. The results have important implications for the temporal and spatial prediction of fluvial architecture and their transition during a marine transgression.     

东海陆架南部海域及周边陆域白垩纪海侵标志及地质意义

东海陆架盆地南部在新生界有诸多油气发现,其下很可能发育了巨厚的、规模巨大的中生界,但对古地理背景的认识尚不清楚,制约了对其进一步开展工作。利用少量钻井及前人关于周边陆域白垩系的零星资料,从多因素入手,综合分析了白垩纪岩相古地理背景,结果表明,在东海陆架盆地南部及周边陆域广泛发育了岩石、化石、生物标志物等各类海侵标识,且其特征和分布具有区域规律性：从花东海盆的放射虫—台湾的菊石、瓣腮类—东海陆架盆地的海绿石—沿海石浦地区的灰岩—浙东付鲚鱼—武夷山及邻区的红藻、褐藻及线叶植物,对应指示的沉积环境自SE至NW依次为深海、浅海、海陆过渡、陆地的总趋势,推测古海侵方向为自SE往NW向。而海侵事件控制了早白垩世东海南部周边邻域的岩相古地理背景,也塑造了如茶湾组这样的有利烃源岩层。