渤海湾巨葛庄贝壳堤与下伏泥层有孔虫组合的海面变化意义

根据巨葛庄贝壳堤及下伏泥层的有孔虫研究,讨论了贝壳堤底板和下伏泥层各类沉积环境的海面意义,以此作为海面标志点重建的古海面误差范围为±0.225~±0.625m。结合该贝壳堤底板和下伏泥层顶板的年龄数据,重建了3900~3300cal BP时的海面高度为-2.955~-2.715m。     

珠江口盆地西部珠三坳陷珠江组沉积演化

为了加强珠三坳陷珠江组的油气勘探理论,笔者从层序格架、岩芯特征、有孔虫分布、岩石类型及岩性组合等方面,分析珠三坳陷及周缘珠江组三个层序的沉积特征及沉积演化规律:从S50--S60～S40--S41层序,岩芯特征呈现规律性变化,砂岩粒度减小、分选性增强,水动力条件从强-较强-弱转变;有孔虫丰度变化从零星中低值--连续中高值--连续中值,水深从浅-深-较深,神狐隆起从局部出露到完全沉没。古珠江三角洲及海南隆起—粤桂隆起物源三角洲是S50-S60及S41-S50层序的重点沉积体系。从S50-S60～S40-S41层序,古珠江三角洲规模从"大--中--小"依次演变,海南隆起—粤桂隆起物源三角洲呈"大-大-小/无"变化,浅海迅速扩张,仅半深海分布较稳定。     

渤海湾沿岸贝壳堤对潮滩有孔虫海面变化指示意义的影响

通过对渤海湾沿岸有贝壳堤发育和无贝壳堤发育的2类现代开放潮滩有孔虫组合的对比,研究了该2类潮滩环境沉积物中有孔虫的海面指示意义。5个有孔虫组合带被MHWST(平均大潮高潮位)、MHW(平均高潮位)、MHWNT(平均大潮低潮位)和MSL(平均海面)分隔,分别对应潮滩的高盐沼、低盐沼、潮间带上部、潮间带中上部和潮间带中下部5个不同亚环境。不同亚环境沉积物因其所含的有孔虫群的独特性,均可作为高精度海面标志物,误差为各亚带高差的1/2。沿岸贝壳堤可对潮滩有孔虫的属种组成产生影响,影响程度从高潮位向低潮位逐渐降低。在MHWNT潮位之下,有孔虫组合不再受到沿岸贝壳堤的影响。     

冲绳海槽北段表层沉积物中底栖有孔虫分布的研究

对1992年5月取自冲绳海槽北段（水深113-1156m，东经126°58.71'-129°9.06’，北纬28°41.75'-31°40.56'）92个表层沉积物中的底栖有孔虫数据进行R型因子分析。分析表明，黑潮流系有4个不同垂直水团的底栖有孔虫群落组合。其中Pseudorotaliaindopacifica,Bolovinarobusta,Cibicidesmargaritiferus,Textulariasaggitula,Cibicideslobatulus和Quinqueloculinaspp.代表黑潮流系的表层水;Hyalineabalthica，Caribeanelladepressa,Cibicidespraecinctus，Planulinawuellerstorfi和Melonisaffinis代表黑潮流系的次表层水;Globobuliminapacifica,Globocassidulinasubglobosa和Trifarinaspp.代表黑潮流系的中层水;Oridorsalistener,Martionottiellaokinawaensis,Pulleniaquinqueloba和Uvigerinadirupta代表黑潮流系的深层水。     

Age determination of marine sediments in the western North Pacific by as partic acid chronology

The ages of fossil planktonic foraminifera,Pulleniatina obliquiloculata, in sediments (core 3bPC) from the western North Pacific were determined by aspartic acid chronology, which uses the racemization reaction rate constant of aspartic acid (k_Asp). Aspartic acid racemization-based ages (Asp ages) ranged from 7,600 yrBP at the surface, to 307,000 yrBP at a depth of 352.9 cm in the sediments. This sediment core was also dated by the glacial-interglacial fluctuation of δ¹⁸O chronology, and the ages determined by both chronologies were compared. The ages derived from aspartic acid chronology and δ¹⁸O stratigraphy were more or less consistent, but there appeared to be some differences in age estimates between these two dating methods at some depths within the core. In the core top sediments, the likely cause for the age discrepancy could be the loss of the surface sediment during sampling of the core. At depths of 66.3 and 139 cm within the core, Asp ages indicated reduced sedimentation rates duringca. 60,000-80,000 yrBP andca. 140,000–190,000 yrBP. The maximum age differences in both chronologies are 33,000 yr and 46,600 yr during each of these periods. These anomalous reductions in sedimentation rates occurring during these periods could possibly be related to some geological events, such as an increased dissolution effect of the calcium carbonate in the western North Pacific. Another possible reason for these age differences could be the unreliability in δ¹⁸O ages of core 3bPC as they were estimated by δ¹⁸O ages of another core, 3aPC.     

Benthic foraminifera of the Holocene transgressive west-central Florida inner shelf: paleoenvironmental implications

The sedimentology, stratigraphic position, and benthic foraminiferal biostratigraphy of early- to mid-Holocene deposits from the west-central Florida shelf suggest that barrier islands developed along this coast as early as 8.3 ka, in an environment that was more arid than today. Predominant foraminifera of three paralic sedimentary facies deposited between 5.3 and 8.3 ka include miliolids, Elphidium spp., and Ammonia spp., all of which are common in back-barrier environments. Foraminiferal assemblages also suggest that early back-barrier sediments were deposited in a hypersaline environment, similar to that of the arid Laguna Madre of the western Gulf of Mexico. Modern back-barrier foraminifera in the Tampa Bay region are indicative of the humid subtropical climate of today. Thus, the climate of west-central Florida at approximately 8 ka was more arid than today, which is consistent with recent studies showing that climate in the Gulf of Mexico was dryer and cooler during this time period.     

南极长城湾全新世有孔虫研究

南极长城湾９３Ｉ（６２°１７．７４′Ｓ，５８°４９．９１′Ｗ）柱样含有较丰富的有孔虫动物群，计鉴定统计５１９００个体，归属于８６种，有孔虫总丰度以柱样中段较低，浮游类含量较低（〈５％）钙质类底栖有孔虫成占优势，全柱底栖有孔虫分异度变化范围不大，底栖有孔虫五个优势种的优势度占决量的８３．３％，优势种及其组合变化显著一定的古海洋学意义，探讨了长城湾海区晚第四纪环境变迁，为南大洋晚第四纪环境与全球变化关     

南海深海沉积中的更新统/上新统界线及与意大利Vrica层型剖面的对比

应用浮游有孔虫定量统计、底栖有孔虫氧同位素和磁性地层学等资料来确定南海ODP1148站深海沉积中的上新统／更新统(P／P)界线。氧同位素期(MIS)64和65之间的P／P界线在1148站位于井深112．75m处，计算年龄为1．805Ma，在地层对比上与Vrica层型剖面的P／P界线一致。浮游有孔虫Pulleniatina obliquiloculata在MIS62出现以右旋壳为主的转变，计算年龄为1．76Ma，此事件和Olduvai极性亚时顶界看来是最接近P／P界线的可靠时间面。除此以外，在1148站P／P界线及其附近没有发现重大的地层学和环境变化事件。相比之下，1148站底栖δ^18O值在3．05～2．53Ma期间快速变重，冬季表层海水温度下降了5℃，指示了北半球冰盖的形成。     

我国苏北建川潮汐盐沼有孔虫垂直分带的发现和特征

通过三个断面加密有孔虫表层采样和精确高程测量,发现建川开敞型盐沼存在特征性盐沼有孔虫组合,这些组合与盐沼植被带相应,受高程控制,有明显的垂直分带,垂直带顶面即最高高潮位以上有孔虫突然消失.这个有孔虫垂直分布模式可高精度地恢复古海面(精度最高可达±5cm).该研究为我国高分辨恢复古海面提供了一个地区性的现代有孔虫标尺,同时该工作也填补了国外仅局限于研究隐蔽型海岸盐沼有孔虫垂直分带的不足.     

Micropalaeontological record of Holocene estuarine and marine stages in the Corgo do Porto rivulet (Mira River, SW Portugal)

The Corgo do Porto is a small tributary of the Mira River, outleting 3.5 km upstream of its mouth. The valley is flat-floored due to terrigenous siltation and forms an alluvial plain reclaimed for agriculture/aquaculture. These conditions were quite distinct in the recent past because of extensive marine flooding of this area during the high-rate positive eustatism that followed the Last Glacial Maximum. The Holocene sedimentary column registers changes imposed by several forcing factors, mainly the climate-driven sea-level rise. As part of a multidisciplinary study, the sedimentological and micropalaeontological (benthic foraminifera and calcareous nannofossils) contents of a core taken from this infill were analyzed, and five different stages were distinguished within its environmental evolution: Stage A (prior to 10,000 cal yrs BP) consists of muddy, matrix-supported sand with abundant pebbles, barren of microfossils, and free of carbonates and organic matter that represents a fluvial environment contemporaneous of a low sea level. Between 10,000 and circa 4000 cal yrs BP the sediment is made of homogeneous mud, with bioclasts and organic matter. However, the assemblages of foraminifera and calcareous nannoplankton allowed the identification of several environmental stages, defining a cycle of increasing–decreasing marine influence inside the valley: brackish and brackish-marine sedimentation (Stage B), full-marine sedimentation (Stage C) and a return to brackish-marine sedimentation (Stage D). The final part of the core is barren of microfossils (Stage E) and it represents the modern sedimentation in the area with an accreting alluvial plain. This Holocene sedimentary sequence reflects an evolutionary succession that closely agrees with the palaeoenvironmental model previously presented by the authors elsewhere for the south-western Portuguese coast, where a change in the rate of sea-level rise has been recorded at around 5500 cal yrs BP when a very effective sandy barrier formed and isolated restricted brackish to fresh-water lagoonal environments from the open sea.