美国科德角半岛地貌

科德角(Cape Cod)是美国马萨诸塞州东南部的一个半岛,面对浩瀚的大西洋,著名的伍兹霍尔海洋研究所(Woods Hole Oceanographic Institution)位于这个半岛的西南角。整个半岛犹如一个巨人弯曲的臂膀,从马萨诸塞州东南部的新英格兰陆地上伸向大西洋(图1)。半岛上,山丘蜿蜒成弧,象一个巨大的花瓣;海滨沙嘴弯如月,沙坝长如刀;海蚀崖陡峭,砾石滩发育;滨海平原上一排排小     

海南岛鹿回头珊瑚礁与全新世高海平面

通过实地考察和资料分析,海南岛南部全新世以来以沉降活动为主要特征,鹿回头珊瑚礁能够反映全新世以来的海平面变化,鹿回头岸礁礁坪面上的原生珊瑚礁是全新世高海平面时期的产物。全新世以来南海北部至少存在过 4 期相对高海平面阶段:7300~6000、4800~4700、4300~4200和3100~2900cal.aBP。其中 7300~6000aBP 是整个全新世最高海平面时期,也是鹿回头珊瑚礁发育的繁盛期,基本形成了现代珊瑚礁的地貌格局,后来不同时期发育的珊瑚礁是在此时期形成的礁塘或礁坑等低洼地中形成,并在鹿回头半岛两侧向外发展,现代珊瑚礁则发育于全新世珊瑚礁的外礁坪和礁前斜坡带。另外,鹿回头珊瑚礁反映的南海北部全新世高海平面时间与南海其他地区高海平面时间可以衔接或对应,说明南海地区全新世高海平面具有全球背景,至少在南海是一致的,且与气候变暖紧密相联。     

山东半岛近岸海区全新世泥质沉积体研究现状

20世纪80年代以来,山东半岛近岸海区全新世泥质沉积体引起了地学界的关注,很多学者对其进行过研究并发表了众多相关论文。综合前人的研究成果认为,山东半岛全新世泥质沉积体受到黄海暖流和黄海沿岸流的共同作用,呈现出中间厚、向海向陆减薄的楔形,并沿山东半岛发育,其物质来源主要是黄河注入所带来的沉积物;在形成机制上,受到海平面上升、潮流和黄河入海口的迁移等多种因素的控制,成因复杂;在形成时间上,现今的研究成果普遍认为该泥楔形成于全新世冰后期海平面上升时期。对目前研究中仍存在的问题进行讨论,提出了山东泥楔的未来研究方向,指出应该建立多种水动力耦合作用下的泥沙输运与沉积模式,着重从海洋沉积动力学角度进行新的研究。     

东海西湖凹陷新生界沉积相的演化

西湖凹陷是东海陆架盆地重点生海气凹陷之一，它在新生代经历断陷，坳陷，区域抬升和区域沉降四个阶段，在纵向序列上表现为二次明显的海侵和一次海退，一次水进和一次水退。由于构造运动的不均匀性，沉积基地的起伏，多物源和水进水退多次旋回，在凹陷不同时期，不同部形成不同的沉答相，这一切与下油气的生成，聚集有着极为密切的关系。     

Sedimentary facies and paleoenvironmental interpretation of a Holocene marsh in the Gironde Estuary in France

1Introduction Since the last glacial maximum, the Holocenehas been marked by a rapid rise in sea level. After6 000 a BP, the present-day level was reached andthe rate of sea-level rise (SLR) decreased rapidly(Morzadec -Kerfourn, 1974; Kidson, 1986 ).These…     

Facies architecture of the mixed carbonate/siliciclastic inner continental shelf of west-central Florida: implications for Holocene barrier development

Sediment vibracores and surface samples were collected from the mixed carbonate/siliciclastic inner shelf of west–central Florida in an effort to determine the three-dimensional facies architecture and Holocene geologic development of the coastal barrier-island and adjacent shallow marine environments. The unconsolidated sediment veneer is thin (generally <3 m), with a patchy distribution. Nine facies are identified representing Miocene platform deposits (limestone gravel and blue–green clay facies), Pleistocene restricted marine deposits (lime mud facies), and Holocene back-barrier (organic muddy sand, olive-gray mud, and muddy sand facies) and open marine (well-sorted quartz sand, shelly sand, and black sand facies) deposits. Holocene back-barrier facies are separated from overlying open marine facies by a ravinement surface formed during the late Holocene rise in sea level. Facies associations are naturally divided into four discrete types. The pattern of distribution and ages of facies suggest that barrier islands developed approximately 8200 yr BP and in excess of 20 km seaward of the present coastline in the north, and more recently and nearer to their present position in the south. No barrier-island development prior to approximately 8200 yr BP is indicated. Initiation of barrier-island development is most likely due to a slowing in the Holocene sea-level rise ca. 8000 yr BP, coupled with the intersection of the coast with quartz sand deposits formed during Pleistocene sea-level highstands. This study is an example of a mixed carbonate/siliciclastic shallow marine depositional system that is tightly constrained in both time and sea-level position. It provides a useful analog for the study of other, similar depositional systems in both the modern and ancient rock record.     

北部湾X1钻孔岩芯沉积物的Ⅹ射线衍射分析研究

X射线技术在结晶矿物学上已得到广泛的应用,它测量精度较高,快速简便,对样品无破坏作用,是地质研究中的重要手段之一,它还广泛地用于大陆架地区的沉积物研究(俞旭等,1982; Devine,1972)。本文将对北部湾东北部x1钻孔近百米的沉积物岩芯全样进行X射线衍射定量分析研究,并根据矿物组合特征,探讨北部湾沉积区的沉积环境及演化过程。     

台湾海峡两岸第四纪生物群特征及古地理演变

本文以大量古生物、古文化遗址及测年资料，分析台湾海峡两岸受新构造运动影响和自更新世以来的古地理演变，从而证明了台湾是中国神圣领土不可分割的一部分。     

南沙永暑礁表层珊瑚年代结构及其环境记录

南沙群岛永暑礁7个表层礁坪原生块状珊瑚的高精度TIMS U-Th和12个常规^14C测年结果表明,永暑礁表层礁坪形成于现代,与钻探研究结果吻合。全新世永暑礁系从约7300aBP开始,以现代礁坪面以下17m左右的晚更新世礁灰岩为基底连续发育至今,因此,与南海周边地区的珊瑚礁不同,南沙群岛珊瑚礁的表层块状珊瑚不能够提供全新世高海平面的证据。由于现代珊瑚礁的堆积速率大于地壳沉降速率,可能会形成更多的灰沙洲或灰沙岛。     

Sand ridges off Sarasota, Florida: A complex facies boundary on a low-energy inner shelf environment

The innermost shelf off Sarasota, Florida was mapped using sidescan-sonar imagery, seismic-reflection profiles, surface sediment samples, and short cores to define the transition between an onshore siliciclastic sand province and an offshore carbonate province and to identify the processes controlling the distribution of these distinctive facies. The transition between these facies is abrupt and closely tied to the morphology of the inner shelf. A series of low-relief nearly shore-normal ridges characterize the inner shelf. Stratigraphically, the ridges are separated from the underlying Pleistocene and Tertiary carbonate strata by the Holocene ravinement surface. While surficial sediment is fine to very-fine siliciclastic sand on the southeastern sides of the ridges and shell hash covers their northwestern sides, the cores of these Holocene deposits are a mixture of both of these facies. Along the southeastern edges of the ridges the facies boundary coincides with the discontinuity that separates the ridge deposits from the underlying strata. The transition from siliciclastic to carbonate sediment on the northwestern sides of the ridges is equally abrupt, but it falls along the crests of the ridges rather than at their edges. Here the facies transition lies within the Holocene deposit, and appears to be the result of sediment reworking by modern processes. This facies distribution primarily appears to result from south-flowing currents generated during winter storms that winnow the fine siliciclastic sediment from the troughs and steeper northwestern sides of the ridges. A coarse shell lag is left armoring the steeper northwestern sides of the ridges, and the fine sediment is deposited on the gentler southeastern sides of the ridges. This pronounced partitioning of the surficial sediment appears to be the result of the siliciclastic sand being winnowed and transported by these currents while the carbonate shell hash falls below the threshold of sediment movement and is left as a lag. The resulting facies boundaries on this low-energy, sediment-starved inner continental shelf are of two origins which both are tied to the remarkably subtle ridge morphology. Along the southeastern sides of the ridges the facies boundary coincides with a stratigraphic discontinuity that separates Holocene from the older deposits while the transition along the northwestern sides of the ridges is within the Holocene deposit and is the result of sediment redistribution by modern processes.