Additional coralline algae from the Lower Miocene to Late Holocene sediments of the Porbandar Group,Gujarat

The Neogene-Quaternary sediments well exposed in the Porbandar Basin are characterized by coralline algae. The limestone, calc-arenites and marls are the dominant lithology of this sequence. The present paper documents ten species of coralline algae. Among these, the nongeniculate coralline algae are represented by four species and geniculate coralline algae include six species. The sediments yielding this algal flora range in age from the Lower Miocene to Late Holocene.     

Nongeniculate coralline algae from early middle Miocene offshore sequence of Kachchh basin,Western India: Paleoenvironmental significance

The present paper reports five nongeniculate coralline algal species, viz., Lithothamnion valens Foslie, Mesophyllum roveretoi Conti, Phymatolithon calcareum (Pallas) Adey and Mckibbin, Melobesioideae gen. et spec. indet. and Lithoporella melobesioides Foslie form the early middle Miocene Chhasra Formation of Offshore Sequence of Kachchh basin, western India. The present day depth distribution of Lithothamnion and Mesophyllum and growth forms of five nongeniculate coralline algal species points that the two cores belonging to the Chhasra Formation of offshore sequence of Kachchh basin were deposited in inner shelf environment at 60-100m depth in moderate-energy conditions.     

Geniculate coralline algae from the Neogene-Quaternary sediments in and around Porbandar,southwest coast of India

The present paper documents nine geniculate coralline algal species, namely Arthrocardia cretacica, Calliarthron antiquum, Corallina hayasaki, C. marshallensis, C. prisca, C. typica, Jania mengaudi, J. sripadaraoi and J. vetus from Neogene-Quaternary sediments of Porbandar area, Saurahtra, Gujarat. Out of nine species, six species namely Arthrocardia cretacica, Calliarthron antiquum, Corallina hayasaki, C. marshallensis, C. prisca and C. typica occur in the Dwarka Formation (lower-middle Miocene), one species Jania sripadaraoi occurs in the Adatiana Member of the Miliolite Formation (early middle-late Pleistocene) and two species namely, Jania mengaudi and J. vetus occur in the Porbandar Calcarenite Member of the Chaya Formation (late Pleistocene-late Holocene). These species indicate that the Dwarka Formation and the Adatiana Member of the Miliolite Formation were deposited in tropical marine environment with moderate to low energy conditions at depths ranging from intertidal to 60 m, and that the Porbandar Calcarenite Member of the Chaya Formation was deposited in a tropical marine environment under moderate to low energy conditions at depths ranging from 40 m to 60 m.     

山西晋中盆地晚新生代地层划分、沉积环境及其先秦以来气候和湖泊演化

【研究目的】晋中盆地位于汾渭断陷盆地带的中部,新生代最大沉积厚度超过3800 m,建立晋中盆地精确地层年代框架和高分辨率沉积层序对于理解汾渭断陷盆地带的演化、华北地区气候变化具有重要意义。【研究方法】本文对晋中盆地东北部晚新生代标准孔ZK01（钻孔深度870.5 m）岩心开展了年代学和沉积学研究。【研究结果】将ZK01孔揭示的松散沉积物分为6个岩性组。首次通过磁性地层学研究,划分出13个正极性时段和12个负极性时段,建立了ZK01孔地层年代框架。晋中盆地新生代沉积物底部最老年龄约8.1 Ma,将晋中盆地活动的起始时间从前人一般认为的上新世初期,确定为中新世晚期,提前了约3 Ma。区内晚新生代地层划分为新近系中新统灞河阶（N₁⁴）和保德阶（N₁⁵）,上新统高庄阶（N₂¹）和麻则沟阶（N₂²2）,第四系下更新统泥河湾阶（Qp¹）,中、上更新统和全新统。【结论】构造活动与气候变化是盆地沉积环境的主要控制因素,共同导致了上新世早期和早更新世中晚期的两次湖泊大规模发育。全新世时期,早中期即先秦（约2.5 ka以前）,盆地中仍是河湖共存阶段;晚期（2.5 ka以来）,出现湖消河长的局面,直至明、清时期湖泊全部消失,气候变化和人类活动影响是盆地中湖泊最终消失的主要原因。创新点：首次通过磁性地层学将晋中盆地发育时间确定为中新世晚期约8.1 Ma;盆地的湖泊发育早期主要受构造和气候控制,全新世以来气候变化和人类活动造成湖泊最终消亡。     

Generic distinguishing characteristics and stratigraphic ranges of fossil corallines: An update

Corallines or coralline algae are carbonate secreting and strongly calcified red algae of the order Corallinales of division Rhodophyta. Architecturally, the corallines have two groups, the nongeniculate and geniculate coralline forms. Corallines are used as a potential tool for paleoecology, paleoenvironments and paleobathymetry. Coralline algae are builder of porous and permeable carbonate reservoir rocks for hydrocarbon and reefs rich in hydrocarbon. The old approach, ca. prior to 1977, of taxonomy of fossil coralline genera has been replaced by the modern approach that established during the last decade using certain distinguishing features such as arrangement of basal filaments, cell fusions, conceptacle perforations and orientation of filaments around conceptacles of living corallines. The earliest confirmed fossil record of coralline algae is from the Hauterivian (Early Cretaceous) and from the Hauterivian to the Pleistocene 9 nongeniculate coralline genera, namely Distichoplax, Lithophyllum, Lithoporella, Lithothamnion, Mesophyllum, Neogoniolithon, Phymatolithon, Spongites and Sporolithon and 7 geniculate genera, viz. Amphiroa, Arthrocardia, Calliarthron, Corallina, Jania, Metagoniolithon and Subterraniphyllum having different stratigraphic ranges are unequivocally known as fossils. After 1977, we do not have a comprehensive publication giving the generic distinguishing characteristics and stratigraphic ranges of both nongeniculate and geniculate corallines. The present paper gives an update of distinguishing characteristics of fossil coralline algal genera and their stratigraphic ranges.     

新生代西昆仑隆升的地层学和沉积学记录

西昆仑北坡的新生代沉积在很大程度上良好地记录了新生代西昆仑的隆升过程。区域性不整合面和沉积界面记录了隆升的阶段性；沉积环境变化反映了山体和盆地在格局上的变化；沉积物厚度、粒度变化显示了隆升的幅度和速率。就西昆仑的情况看，海相环境（塔里木海湾）由晚白垩世持续到渐新世，尽管此时海湾已退缩到西部。在此期间，形成了石膏层、瓣鳃类介壳灰岩和杂色砂泥质沉积。中新世全面出现了陆相沉积。中新世2000－3000m的沉积厚度表明了相对较高的隆升速率。从中新世后期开始的厚达2000－3000m的磨拉石沉积，其粒度向上加大，显示从中新世后期到早更新世隆升速率高而且是加速的。磨拉石沉积被早更新世的一次强烈的构造脉动所打断，它使磨拉石沉积和较老的沉积在许多地方高角度向盆地方向倾斜甚至直立、倒转。水平盖在磨拉石和更老地层之上的中－晚更新世河流和冲积扇机粗粒沉积是重新隆升的标志，亦可视为磨拉石沉积的继续。由昆仑山流向塔里木盆地的河流将中－上更新统及更老沉积切割50－100m以上，表明全新世以来的隆升速率是相当高的。     

南海神狐海域水合物钻探区钙质超微化石生物地层与沉积速率

2007年我国首次在南海北部陆坡神狐海域实施了天然气水合物钻探, 并钻取水合物实物样品.为了解钻区地层、水合物产出带(the zone of gas hydrate occurrence)或水合物储层的地层时代以及沉积速率特征, 对其中4口钻孔(SH1B、SH2B、SH5C和SH7B)岩心沉积物进行钙质超微化石年代地层学和沉积速率变化的研究.本次工作识别出17个新近纪钙质超微化石事件, 确定了神狐钻探所钻达最老地层为新近系上中新统; 水合物产出带的地层为上中新统-上新统.这4个钻井地层沉积速率的变化特征因站位和时期而异.中新世以来各地质时期沉积速率差异较大, 全新世最高(20~34.16 cm/ka之间), 其次为更新世和晚中新世(3.14~5.74 cm/ka), 上新世最低(1.88~3.27 cm/ka).此外, 水合物产出带地层的沉积速率在各钻孔也有差异, SH2B孔为4.18 cm/ka, SH7B孔为1.88 m/ka.表明南海水合物产出层位沉积速率差异较大, 沉积速率与水合物成藏的关系可能比前期的认识更为复杂.      

Geoarchaeological investigations of henson creek: A low-order tributary in Central Texas

A complex late Quaternary alluvial history was documented along Henson Creek, a low order tributary on the Fort Hood Military Reservation in central Texas. Three Quaternary alluvial landforms were recognized: terrace 2 (T2), terrace 1 (T1), and the modern floodplain (T0). The late Pleistocene T2 terrace may contain an array of sites spanning the entire known cultural record, while T1 may have sites spanning the last 5000 years only. Five fluvial units, three colluvial facies, two alluvial fan facies, and two buried paleosols were also recognized. Fluvial deposition was occurring approximately 15,000 yr B.P., 10,000-8000 yr B.P., 7000–4800 yr B.P., 1650-600 yr B.P., and during the last 400 years. Colluvial deposition was ongoing mainly in the early and middle Holocene, while alluvial fan aggradation was proceeding primarily in the middle Holocene. Because of erosional unconformities, there is minimal potential for recovering buried sites dating to intervals between depositional eposides for most of the drainage basin. Preservation potentials for buried sites are greatest in fine-grained fluvial deposits dating to the late Pleistocene, early Holocene, and parts of the late Holocene, and in fine-grained colluvial deposits dating to the early and middle Holocene. This investigation demonstrates that within the study area, and perhaps throughout much of central Texas, a greater continuum of sediments and preservation potentials exists in late Quaternary alluvial deposits of rivers than in low-order tributaries.     

甘肃广河地区中中新世哺乳动物化石的发现及其地层学意义

本文记述了采自甘肃广河石那奴中中新世地层的哺乳动物化石6目10科12属16种类（以小化石为主）,其中新种两个:Alloptox guangheensis sp. nov., Pseudaelurus guangheensis sp. nov.。通过对动物群性质的研究及与其它地区的详细对比,认为下化石层的时代应为中中新世早期,上化石层应为中中新世晚期。二者分别与山旺期、通古尔期大体相当。 广河地区中中新世早期车头沟组和中中新世晚期咸水河组的建立,表示该地区存在着中中新世两个时期的不同环境沉积。     

Palaeoecological implications of corallinacean red algae and halimedacean green algae from the prang formation of south shillong plateau, meghalaya

The southwestern part of south Shillong plateau (Meghalaya, N-E India), designated as Sylhet Limestone Group is sub-divided into three lithounits i.e., Lakadong, Umlatdoh and Prang formations in ascending order. The Prang Formation is the youngest lithostratigraphic unit of the Sylhet Limestone Group and has been dated as Middle to early Upper Eocene based on the benthic foraminifera studies. Thin section analysis of carbonate rocks from Prang Formation, exposed in the Bholaganj limestone quarry yielded a rich assemblage of calcareous algae. The coralline algal assemblage comprises both non-geniculate and geniculate forms. The green algae are represented by species of Halimeda belonging to the family Halimedaceae. Palaeoecological interpretation based on diversity, growth-form analysis and taphonomic aspects of the algal assemblage indicate that in all probabilities the deposition of Prang Formation occurred in shallow, warm, shelf environment of normal salinity within the transgressive phase.     

塔克拉玛干沙漠腹地第四纪地层划分与环境变迁

通过塔中地区KT1孔和KT2孔井下第四纪地质测试研究，首次揭示出：塔克拉玛干沙漠腹地在深度653.80m以上，沉积物可划分42层，基本属于第四系。第四系下限初步定在761.17m深处。第四纪以来的气候演化大体有过3次大的气候波动和13个较大气候波动旋回。沉积环境早更新世为河湖相泛滥平原；中更新世以洼地湖泊相沉积为主，同时明显加入了风沙环境堆积，沙漠开始形成；从中更新世晚期开始，经晚更新世到新世，沙漠大规模形成，并逐步发展成今日的大沙漠景观。     

洞庭盆地澧县凹陷第四纪沉积特征与古地理演化

澧县凹陷内第四系厚度达200m左右,由早更新世-中更新世中期沉积和全新统组成。早更新世-中更新世中期沉积除顶部为粘土外,主体为砾石层,在凹陷中央夹粉砂、细砂和少量粘土。全新统分布于凹陷南部,为湖冲积粘土。早更新世澧县凹陷区断陷沉降,于河道和冲积扇环境下接受沉积;中更新世凹陷逐渐扩张,沉积范围扩展至凹陷外缘,凹陷主体部位自边缘向中央依次为冲积扇和扇前浅湖环境。中更新世中后期因盆地扩张,自凹陷中央至边缘地带均为静水湖泊环境。中更新世晚期至晚更新世,凹陷及周缘因构造抬升而遭受剥蚀而缺失沉积。全新世凹陷南部受澧水及区域湖面上升影响而发育湖冲积沉积。     

西太平洋782A钻孔新生代的有孔虫

大洋钻探工程” 1 2 5航次的 782 A钻孔位于西太平洋菲律宾海东北部 ,井深 4 76.8m。基底为安山岩 ,上覆盖层为中始新统—更新统的沉积层 ,其中保存有低丰度的有孔虫。自下而上可划分出 8个浮游有孔虫带。由于出现 Catapsydrax dissimilis,C.stainforthi为 N5 、N6 带的带化石 ,表明本钻孔存在早中新世的地层。同时由于缺失浮游有孔虫带 P1 5 — P1 6 下部 ,N3上部—N4,N7—N1 1 带的带化石 ,说明在中始新世与晚始新世之间、晚渐新世与早中新世之间、早中新世与中中新世之间存在 3个沉积间断。钻孔中的有孔虫标志本区当时处于温暖亚热带环境。根据不同时期温度的变化 ,可划分出 5个阶段 ,包括 3个偏暖时期和 2个温凉时期。     

中新世以来吕梁山及邻区构造——沉积演化

裂变径迹研究显示中新世早期(23±3Ma)现今吕梁山及周缘地区发生了一次整体性快速隆升。中新世晚期(约8Ma前),吕梁山前、鄂尔多斯盆地及东部宁武—沁水盆地结束了长期剥蚀历史,开始广泛接受新生代沉积。沉积物的垂向叠置关系及横向展布特征显示:8.35～6.7Ma为吕梁山快速差异隆升期,在山前(东西两侧)堆积了冲积扇相芦子沟组砾岩层,暗示了吕梁山已经地貌上成山;与此同时地势相对平坦且摆脱地表水流影响的鄂尔多斯盆地广泛堆积了风尘堆积—红黏土(保德组)。中新世晚期—早更新世早期(6.7～1.8Ma),吕梁山西部山前及鄂尔多斯地区整体缓慢隆升,堆积了新近纪保德组上部、静乐组红黏土及早更新世午城组黄土—古土壤序列。受西部六盘山快速抬升作用影响,鄂尔多斯西部抬升速率略高于东部,于早更新世中期(1.8～1.4Ma)形成现今西高东低的地势格局和南北向晋陕谷地,进而黄河及其支流顺流而下。中更新世以来,鄂尔多斯地区沉积与抬升并重,最终形成现今黄土高原。吕梁山以东的沁水盆地中新世演化史与西部相似,上新世起盆地开始断陷,汾河地堑开始形成。断陷一直持续到早更新世,自下而上依次沉积了下土河组、小白组、大沟组、木瓜组湖相地层,盆地边缘则持续抬升堆积了静乐组和午城组风成堆积。中更新世以来,断陷结束,盆地整体抬升。     

长江口区晚新生代沉积物粒度特征和沉积地貌环境演变

对长江河口区的三个晚新生代钻孔作了地层对比和粒度分析,据此探讨晚新生代长江河口的沉积地貌环境演变过程。结果表明,SG6和J18A孔上新世厚层含砾砂质沉积物粒度特征,反映了洪积扇和冲积扇相沉积环境,沉积物搬运距离短;而SG13孔缺失上新世沉积,反映古地势较高,以剥蚀为主。因此上新世长江三角洲地区古地势高差较大,侵蚀区和沉积区共存。早更新世,本区继承了上新世的冲、洪积扇沉积环境,但SG6孔泥质沉积明显变厚,J18A孔此时则以厚层含砾砂沉积为主,SG13孔也开始接受泥质沉积,反映在构造沉降作用下,冲、洪积扇体向西、南部迁移,沉积盆地范围扩大。中更新世,沉积物普遍变细且以悬浮沉积为主,显示了曲流河或曲流河冲积平原的沉积环境。晚更新世初,本区又发育含砾砂层,特别是SG13孔出现厚层含砾砂,但是粒径显著小于上新世和早更新世沉积物,反映本区再次发生显著构造沉积,河流地貌广泛发育。晚更新世中晚期和全新世沉积物以粘土和粉砂质粘土为主,悬浮沉积占优,说明本区已演变为滨、浅海沉积环境。因此在构造沉降、剥蚀和沉积的共同作用下,本区的地貌演变经历了自上新世至中更新世和自晚更新世至全新世的两次准平原化过程。     

Neogen und jungtertiäre Entwicklung der Insel Kos (Ägäis,Griechenland)

The geology of the central portion of Kos island (Greece) is described. A geological map shows the distribution of the Neogene Konstantinos, Gurniati, Stefanena und Tafi formations and of the Pleistocene Plateau-tuff in the vicinity of the Dikeos mountain chain. The Neogene and Pleistocene sedimentary formations of Kos are reviewed, and a detailed sketch of the history of the island from the Miocene till now is given. The deposition of marine sediments of lower to middle Miocene age was followed by tectonic movements and accumulation of lacustrine sedimentary rocks in the upper Miocene. During that time, Kos was part of a land mass including Anatolia, the Aegean Sea and the Greek mainland. Sediments, which can be assigned to the lower Pliocene with certainty, are not known from Kos until now. From the middle Pliocene to lower Pleistocene a continuous sequence of sediments was deposited. In the lowermost lithologic units (Gurniati and Stefanena formations in central Kos, Phoka and Sefto formations in east Kos) continental sediments predominate. In central Kos, about eight marine intercalations can be traced, but the sea did not reach the eastern area. The Tafi formation (central Kos, uppermost Pliocene to lower Pleistocene) was mainly accumulated in marine environments. During the same time, in east Kos in a lake of varying size the Kos up to the Elia formations were deposited. Its endemic gastropods include some of the best examples of evolutionary lineages. When by the beginning of the Pleistocene the sea invaded this basin, the endemic fauna was destroyed. After tectonic displacement of the Plio-Pleistocene sediments, what began during accumulation of the lower Tafi formation, and after their elevation above sea-level, the area of Kos and surrounding islands was covered by the Pleistocene Plateau tuff. At about the same time, Kos became separated from the Anatolian Datça peninsula and was transformed into an island. During periods of glacial sea-level fall, however, it was more than once united with the Anatolian mainland via a northern connection. The gradual phyletic change of the freshwater snail,Melanopsis sporadum into M.gorceixi is described. The evolutionary rate was influenced by marine transgressions causing a reduction of the population size.     

南海陆坡中新世以来沉积物特性与气体水合物分布初探

通过对南海陆坡地区中新世以来沉积物的一些属性和特征的研究,获得了下面的初步认识：（1）南海陆坡有几个沉积速率较高的地区, 如东沙一带、西沙海槽、中建南地区,以及南沙西南部和西北部（曾母、万安盆地）;（2）大洋钻探钻井资料的研究表明,中新世与早上新世为高碳酸盐比值的低速堆积期,而近200万a以来为低碳酸盐比值的高速堆积期,上新世晚期至全新世沉积物以粘土质粉砂和粉砂质粘土为最主要成分;（3）南海不同时期的沉积速率不同,全新世为沉积速率最高的时期,其次为更新世;上新世和中新世为沉积速率较低的时期。南海利于气体水合物存藏的沉积可能为全新世和更新世的沉积;（4）对南海晚第四纪以来沉积物的综合研究表明南海陆坡的A区（东沙附近）、B区（西沙海槽）、D区（南海西部、越南以东）等地区可能利于气体水合物的形成和分布;而E区（南沙西南部）、F区（南沙中上部）和G区(南沙海槽)则是气体水合物调查值得关注的地区。     

长江三角洲地区晚新生代沉积物岩石磁学特征及其物源指示意义

对长江三角洲地区7个晚新生代钻孔沉积物的岩石地层和磁化率特征进行详细对比,并进一步选择浦东机场孔（PD孔）进行了详细的岩石磁学测试,讨论了该地区的晚新生代沉积物物源的演变。结果显示沉积物磁性的4次显著变化：  1）各钻孔上新世磁性强弱差异明显;   2）早更新世早期本区普遍表现出弱磁性;   3）从早更新世中晚期至全新世,磁性强度一般随粒度粗细变化波动,即砂质沉积磁性强,泥质沉积磁性弱;   4）晚更新世晚期以来,细颗粒沉积物的磁性较明显增强。磁性参数分析显示上新世和早更新世早期磁性矿物晶体颗粒较细,早更新世中晚期-晚更新世以粗晶粒磁性矿物为主,全新世细晶粒磁铁矿再次占主导。我们认为上述磁性变化反映构造沉降控制下现代长江三角洲地区物源区的不断扩大。     

四川攀西地区晚新生代构造变形历史与隆升过程初步研究

基于TM遥感图像解译和野外调研，分析了攀西地区大渡河、安宁河深切河谷地貌特征和断裂带构造变形特征，建立了安宁河断裂带晚新生代5阶段变形历史。研究表明，中新世晚期—上新世早期，安宁河断裂以挤压走滑活动为主；上新世晚期至早更新世时期，断裂以斜张走滑活动为主，活动强度较弱；早中更新世之间发生的元谋运动使昔格达组湖相地层褶皱变形；中晚更新世时期发生断陷作用，形成安宁河两堑夹—垒的构造格局；晚更新世—全新世时期又以左旋走滑活动为主。综合安宁河、大渡河河谷地貌和晚新生代地层记录和变形特征，提出了攀西高原晚新生代4阶段隆升模式：中新世早中期(12Ma之前)以缓慢隆升与区域夷平化作用为主，中新世晚期—上新世早期(12～3．4Ma)是高原快速隆升与河流强烈下切的时期，上新世晚期—早更新世(3．4～1.1Ma)为昔格达湖盆发育时期，中晚更新世—全新世(1．1Ma以来)是高原快速隆升与河谷阶地发育时期。最后指出，至上新世晚期(3．4Ma以前)，攀西高原海拔高度可能超过了3000m。     

冈底斯山脉中段麦嘎古湖的形成演化发展与消亡

麦嘎盆地属典型的山间断陷盆地,其形成演化发展又受制于盆周的断层构造活动。麦嘎古湖的形成演化发展及消亡与麦嘎盆地的发展演化紧密相连。笔者从构造和湖积物特征人手,对麦嘎古湖的形成演化发展消亡作了深入探讨,认为其受到新构造活动、古气候、河流侵蚀等自然外力的综合作用,麦嘎盆地先后经历了河流→湖沼→河流→湖沼→湖泊→湖沼→湖泊→河流的演化过程。