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1.
Bruce W. Hayward Hugh R. Grenfell Ashwaq T. Sabaa Margaret S. Morley 《Estuaries and Coasts》2008,31(5):941-959
The ecological impact from the establishment of dense intertidal beds of introduced Asian date mussels (Musculista senhousia) and cordgrass (Spartina alterniflora) in five northern New Zealand estuaries and harbours was documented in 2005–2006, using the fossil record of the shells of
foraminifera, ostracods and molluscs in paired sediment cores and surface samples taken from inside and outside selected beds.
The most significant changes in faunal composition in all, but the most saline sites, generally occurred in both cores in
each pair and could be attributed to the impact of decreased salinity and pH as a result of increased freshwater runoff following
clearance of the surrounding forest in the 19th century and urban development in the late 20th century. Establishment of Asian
date mussel beds had a greatest impact on the composition of ostracod faunas. At near oceanic salinity, the mussels had completely
replaced the native infaunal bivalve fauna, but had little impact on the foraminifera. At more brackish sites, the presence
of mussel shells appears to have buffered the calcareous foraminifera from the effects of lowered pH, which had dissolved
this component outside the beds. Establishment of cordgrass patches had no impact on ostracod faunas, and little on molluscs
except at Kaipara, where introduced Pacific oysters had colonised the cordgrass. Cordgrass had the most impact on the foraminifera.
At brackish sites, cordgrass patches had been colonised by agglutinated foraminiferal species different from those that dominate
outside. In cordgrass at more saline sites, agglutinated foraminifera have invaded and bloomed at the expense of calcareous
Ammonia spp., which dominated outside the patches. 相似文献
2.
A small, protected karstic feature exposed in a limestone quarry in Bermuda preserved abundant sedimentary and biogenic materials documenting a transgressive phase, still-stand, and regressive phase of a sea-level in excess of 21.3 m above present during Marine Isotope Stage (MIS) 11 (400 ka) as determined by U/Th dating and amino acid racemization. Cobbles and marine sediments deposited during the high-energy transgressive phase exhibit rim cements indicating a subsequent phreatic environment. This was succeeded stratigraphically by a still-stand deposition of fine calcareous lagoonal sediments containing bioclasts of red algae and benthic and planktonic foraminifera that was intensely burrowed by marine invertebrates, probably upogebiid shrimp, that could not be produced under any condition other than sustained marine submergence. Overlying this were pure carbonate beach sands of a low-energy regressive phase containing abundant remains of terrestrial and marine vertebrates and invertebrates. The considerable diversity of this fauna along with taphonomic evidence from seabird remains indicates deposition by high run-up waves over a minimum duration of months, if not years. The maximum duration has yet to be determined but probably did not exceed one or two thousand years. The most abundant snails in this fauna are two species indicative of brackish water and high-tide line showing that a Ghyben-Herzberg lens must have existed at > + 20 m. The nature of these sediments and fossil accumulation is incompatible with tsunami deposition and, given the absence of evidence for tectonic uplift of the Bermuda pedestal or platform, provide proof that sea-level during MIS 11 exceeded +20 m, a fact that has widespread ramifications for geologists, biogeographers, and human demographics along the world's coastlines. 相似文献
3.
MORTEN HALD TOR K. DANIELSEN STEIN LORENTZEN 《Boreas: An International Journal of Quaternary Research》1989,18(4):367-388
A benthic foraminiferal stratigraphy from the southwestern Barents Sea indicates that foraminifera were reworked and deposited in tills during the last glaciation. The deglaciation occurred in three main steps: (1) Presence of an Elphidium excavatum dominated assemblage > 13,300–12,000 B.P. (2), Nonion barleeanum dominated assemblage 12,000–10,000 B.P., and (3) establishment of a fauna similar to the modern one at 10,000 B.P. The transition from step 1 to step 2 indicates that the deglacial warming/incipient intrusion of Atlantic water was delayed in the southwestern Barents Sea compared with the western margin of the Norwegian shelf by approximately 1,000 years. Corrosive bottom water that formed during the last deglaciation causing carbonate dissolution may be due to poor ventilation or increased biogenic production accompanying the inferred oceanographic changes. 相似文献
4.
An attempt has been made to understand the Pleistocene bottom water history in response to the paleoclimatic changes in the
northern Indian Ocean employing quantitative analyses of deep sea benthic foraminifera at the DSDP sites 219 and 238. Among
the 150 benthic foraminifera recorded a few species show dominance with changing percent frequencies during most of the sequence.
The dominant benthic foraminiferal assemblages suggest that most of the Pleistocene bottom waters at site 219 and Early Pleistocene
bottom waters at site 238 are of North Indian Deep Water (NIDW) origin. However, Late Pleistocene assemblage at site 238 appears
to be closely associated with a water mass intermediate between North Indian Deep Water (NIDW) and Antarctic Bottom Water
(AABW).
Uvigerina proboscidea is the most dominant benthic foraminiferal species present during the Pleistocene at both the sites. A marked increase in
the relative abundance ofU. proboscidea along with less diverse and equitable fauna during Early Pleistocene suggests a relative cooling, an intensified oceanic
circulation and upwelling of nutrient rich bottom waters resulting in high surface productivity. At the same time, low sediment
accumulation rate during Early Pleistocene reveals increased winnowing of the sediments possibly due to more corrosive and
cold bottom waters. The Late Pleistocene in general, is marked by relatively warm and stable bottom waters as reflected by
low abundance ofU. proboscidea and more diverse and equitable benthic fauna.
The lower depth range for the occurrence ofBulimina aculeate in the Indian Ocean is around 2300 m, similar to that of many other areas.B. aculeata also shows marked increase in its abundance near the Pliocene/Pleistocene boundary while a sudden decrease in the relative
abundance ofStilostomella lepidula occurs close to the Early/Late Pleistocene boundary. 相似文献
5.
Several sections from the uppermost Eocene and Oligocene of northern Slovenia have been investigated with respect to sedimentary facies, foraminiferal assemblages, stable isotopes, carbonate microfacies, and palynology. The main objective was to reconstruct the paleoenvironmental history of the Paleogene Paratethys in this region of the eastern Alpine realm. The sediments exhibit a transgressive succession beginning with conglomerates, sandstones, and mudstones of fluvial and lacustrine origin followed by carbonates and muddy marls indicating marine conditions. The foraminiferal faunal changes from brackish to shallow marine to deeper marine assemblages and the distribution of the palynofloras corroborate the sedimentological results. Microfacies analysis of the limestones shows a wide variation of shallow water, generally mud-rich facies dominated by coralline algae, foraminifera, and corals. Microfaunas adapted to low-oxygen conditions indicate temporal sluggish bottom-water circulation which can be associated with high fresh-water fluxes. These results are discussed as reflecting both the global sea-level rise during the Early Oligocene and the regional tectonic and climatic evolution. 相似文献
6.
N. Malarkodi G. Keller P. J. Fayazudeen U. B. Mallikarjuna 《Journal of the Geological Society of India》2010,75(6):851-863
Intertrappean beds exposed between upper and lower traps of the Government and Sunnamrayalu quarries of Rajahmundry were analyzed
based on benthic and planktic foraminifera, ostracodes and algae observed in thin sections. Planktic foraminifera indicate
deposition occurred in the early Danian Parvularugoglobigerina eugubina (P1a) zone shortly after deposition of the lower trap flows. The most diverse planktic assemblages were deposited in limestones
of the middle intertrappean interval and indicate an upper P1a age, or subzone P1a(2), as marked by the co-occurrence of P. eugubina, Globoconusa daubjergensis, Parasubbotina pseudobulloides and Subbotina triloculinoides. Reworked late Maastrichtian planktic foraminifera are common in a limestone interval and suggest erosion of uplifted Cretaceous
sediments. Benthic foraminiferal assemblages indicate deposition occurred predominantly in shallow inner shelf to brackish
environments. Similarly, ostracodes indicate variable environments ranging from inner neritic to brackish with fresh water
influx, as also indicated by the presence of fresh water algae. These data confirm an overall deepening from restricted shallow
marine to estuarine, lagoonal and finally open marine conditions followed by abrupt emersion and paleosoil deposition prior
to the arrival of the upper trap flows at or near the base of C29n. 相似文献
7.
地质历史时期曾发过许多对生命的演化进程造成过重大影响与制约的全球性地质事件,白垩纪—古近纪就是一个重大地质事件频发的时期。随着冈瓦纳大陆在中生代时期的解体,全球海陆格局发生了根本的变化,地球的表层和岩石圈层均发生了重大的改变,由此引发了构造运动空前活跃,发生过诸如大洋缺氧事件(OAE)、大洋富氧事件(CORBs)、白垩纪/古近纪(K/Pg)生物大灭绝事件、古新世—始新世极热(PETM)事件、印度-亚洲板块碰撞、新特提斯洋的演化及最终消亡等一系列的全球性重大地质事件。对这些重大地质事件的研究,有助于加深我们对古海洋、古地理、古环境的认识。尝试追踪和捕捉这些重大地质事件,恢复和重建古地理,其基础是建立精确的年代地层格架。西藏南部保存了中国最为完整的海相白垩纪—古近纪沉积,完整地记录了上述的全球性重大地质事件,通过对札达、岗巴、定日、亚东、江孜、萨嘎和吉隆等地区高分辨率浮游和底栖有孔虫、介形虫、钙质超微化石和放射虫生物地层学研究,可直接约束全球性重大地质事件发生的时间,并为重建新特提斯洋古海洋环境和古地理提供证据。此外,在重大地质环境突变期间生物的演化过程,也可为探明极端环境变化发生时期气候-环境-生物之间的协同演化关系提供证据。本文系统总结了课题组为主的近年来对藏南白垩纪—古近纪海相地层中微体古生物学的研究成果及重要进展,并对未来研究提出展望。 相似文献
8.
Anna Stepanova Ekaterina Taldenkova Henning A. Bauch 《Boreas: An International Journal of Quaternary Research》2012,41(4):557-577
Fossil ostracod assemblages were investigated in five AMS 14 C‐dated cores from various water depths of the Laptev and Kara seas ranging from the upper continental slope (270 m) to the present‐day shelf depth (40 m). Six fossil assemblages were distinguished. These represent the varying environmental conditions at the North Siberian continental margin since about 18 ka. In the cores from the shelf the ostracod assemblages reflect the gradual transition from an estuarine brackish‐water environment to modern marine conditions since 12.3 ka, as induced by the regional early Holocene transgression. The core from the upper continental slope dates back to c. 17.6 ka and contains assemblages that are absent in the shelf cores. The assemblage older than 10 ka stands out as a specific community dominated by relatively deep‐water Arctic and North Atlantic species that also contains euryhaline species. Such an assemblage provides evidence for past inflows of Atlantic‐derived waters from as early as c. 17.2 ka, probably facilitated by upwelling in coastal polynyas, and a considerable riverine freshwater influence with enhanced surface water stratification owing to the proximity of the palaeocoastline until early Holocene times. In all studied cores, relative increases in euryhaline species dominant in the inner‐shelf regions are recorded in the mid–late Holocene sediments (<7 ka), which otherwise already contain modern‐like ostracod assemblages with relatively deep‐water species. This observation suggests euryhaline species to be largely sea‐ice‐ and/or iceberg‐rafted and therefore may provide evidence for a climate cooling trend. 相似文献
9.
A. Cearreta 《International Journal of Earth Sciences》1993,82(2):234-240
The main sedimentary features of the northern coast of the Iberian Peninsula during the Holocene transgression are characterized by the formation of estuaries, the deposition of sand bars and sand beaches, and the accumulation of aeolian dunes. These coastal deposits are very favourable for identifying Quaternary sea-level changes as they contain great volumes of well preserved sediments including marine, brackish and freshwater beds. The micropalaeontological analysis (benthic foraminifera) of diverse littoral sequences has allowed different microfaunal assemblages to be recognised and their corresponding depositional environments determined. Two recurrent phases of sediment build-up as the sea level rose have been distinguished. They have been interpreted as the consequence of two different marine advances in this region: one dated at around 8 000 years BP and the second around 2 500 years BP. 相似文献
10.
The formation of short-lived backswamps along the Carmel coast of Israel coincides with the rapid global sea-level rise during the late Pleistocene-early Holocene transition. The current study shows that the wetland phenomena originated around 10,000 yr ago and dried up shortly before the local Pre-Pottery Neolithic humans settled on the wetland dark clay sediments 9430 cal yr BP. Palaeontological and stable-isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the Carmel coastal plain. The water body contained typical brackish calcareous fauna, with variable numerical abundance and low species richness of ostracods and foraminifera. The δ18O and δ13C of the ostracod Cyprideis torosa show close similarity to the present Pleistocene coastal aquifer isotopic values. This study therefore concludes that the wetlands were shallow-water bodies fed by groundwater, with no evidence of sea-water mixing. It seems that they developed as the result of high groundwater levels, transportation of sediments landward, and deposition of sand bars at the paleo-river mouths. It is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr. 相似文献
11.
S. C. Khosla M. L. Nagori S. R. Jakhar A. S. Rathore 《Journal of the Geological Society of India》2009,73(5):724-732
Except for the east coast of Andhra Pradesh, the Deccan Inter-trappean sedimentary beds of Peninsular India have been long
known to yield non-marine microfauna, mainly ostracods. These have been extensively described from different localities of
Madhya Pradesh, Maharashtra, Karnataka, Andhra Pradesh, Gujarat and Rajasthan states. Occurrence of mixed microfaunal association
of marine, brackish water and non-marine foraminifers and ostracods is being recorded from these beds from Jhilmili, Chhindwara
district, Madhya Pradesh. It comprises at least two or more planktonic foraminifer species, and one brackish water and 17
non-marine ostracod species. The brackish water ostracod, Neocyprideis raoi (Jain, 1978) has been previously recorded in great profusion from the Inter-trappean beds of Duddukuru, West Godavari District,
Andhra Pradesh, which have been assigned Early Palaeocene age (Khosla and Nagori, 2002). Presence of molt stages of the bulk
of non-marine and brackish water ostracods in the Inter-trappean beds of Jhilmili is suggestive that they were inhabitants
of low mesohaline inland pool/lake. The planktonic foraminifers were carried to this pool/lake by a marine transgression probably
from the east coast of India through the Trans Deccan Straits. 相似文献
12.
Western Amazonia's landscape and biota were shaped by an enormous wetland during the Miocene epoch. Among the most discussed topics of this ecosystem range the question on the transitory influx of marine waters. Inter alia the occurrence of typically brackish water associated ostracods is repeatedly consulted to infer elevated salinities or even marine ingressions. The taxonomical investigation of ostracod faunas derived from the upper part of the Solimões Formation (Eirunepé; W-Brazil) documents a moderately diverse assemblage (19 species). A wealth of freshwater ostracods (mainly Cytheridella, Penthesilenula) was found co-occurring with taxa (chiefly Cyprideis) usually related to marginal marine settings today. The observed faunal compositions as well as constantly very light δ18O- and δ13C-values obtained by measuring both, the freshwater and brackish water ostracod group, refer to entirely freshwater conditions. These results corroborate with previous sedimentological and palaeontological observations, which proposed a fluvial depositional system for this part of western Amazonia during the Late Miocene. We demonstrate that some endemic, “brackish” water ostracods (i.e., Cyprideis) have been effectively adapted to freshwater conditions. Thus, their occurrence is no univocal evidence for the influence of brackish or marine waters in western Amazonia during the Miocene. 相似文献
13.
塔里木盆地东北部新生代介形类与沉积环境 总被引：8，自引：2，他引：6
塔里木盆地东北部库车以东地区下第三系化石罕见。该地区主要为红色含膏盐的粗碎屑岩沉积。中新世以来 ,由于喜马拉雅运动的影响 ,天山不断隆升 ,导致本区加速沉降 ,出现滨浅湖沉积环境 ,介形类逐渐繁盛。中新世中晚期半咸水介形类 Cyprideis爆发 ,广泛出现Cyprideis占绝对优势的半咸水浅湖环境含膏砂泥岩沉积 ,与东邻柴达木盆地阿尔金山以南地区相似。上新世以来 ,本区沉降速率猛增 ,堆积速率更快 ,基本上处于超补偿沉积 ,湖泊大规模萎缩 ,介形类数量锐减。由于喜马拉雅运动晚期的影响 ,天山山脉库车—库尔勒一线以北的山峰不断隆升 ,本区第四纪湖区规模比上新世大大扩展 ,湖泊范围比中新世显著向南迁移 ,Cyprideis再度繁盛并占优势 ,早更新世晚期距今大约不足百万年 ,本区尤其是库南 1井地区 ,除继续出现丰富的 Cyprideis外 ,突然出现淡水 -微咸水介形类 ,形成一个属种多样的高分异度介形类动物群 ,与柴达木盆地南部昆仑山北麓的介形类组合类似 ,主要有 Candona torosa,Candoniella lactea,Candona neglecta,Candona arcina,Cypridopsis vidua,Limnocythereinopinata,Cypris subglobosa,Ilyocypris gibba,Ilyocpyrisbiplicata,Eucyprisinflata,Candoniellaalbicans,Darwinula sp.,Stenocypris sp.等。 相似文献
14.
南海北部陆架中全新世沉积记录及古环境意义 总被引：2，自引：1，他引：1
通过分析珠江口外陆架C069孔沉积柱样的粒度、黏土矿物、主量元素及底栖有孔虫,来研究南海北部中全新世晚期古环境演化。4.2 ka前为全新世大暖期后期,气候湿润,珠江口外陆架受大量的珠江淡水影响,导致C069孔位置的水动力条件较强,形成下段粒度较粗的碎屑沉积物,高岭石含量较高,低的MgO/Al2O3比值,以及受冲淡水影响形成的底栖有孔虫。由于受4.2 ka的极冷事件的影响,C069孔上段的沉积环境受珠江冲淡水影响减小,水动力条件减弱,沉积物粒度变细,高岭石含量降低,MgO/Al2O3比值增大,形成正常浅水环境的底栖有孔虫。4.2 ka以后,台湾来源物质的贡献增多,导致沉积物中伊利石和绿泥石的含量增多,伊利石结晶度和化学指数值都明显变小。 相似文献
15.
In the latest Early to Middle Miocene section of the Kingfish 8 well, offshore Gippsland Basin, the characteristically deep‐marine ostracod genus Zabythocypris is a conspicuous component of ostracod assemblages dominated by species of the genera Argilloecia, Krithe and Parakrithe. The taphonomy and taxonomic composition of the assemblages suggests that they accumulated in an upper bathyal environment (500–1000 m water depth) occurring in a lower continental slope setting. Supporting evidence for these deep‐marine ostracod assemblages occurring near the upper limit of their palaeobathymetrical range is the broadly coincident occurrence of the deep‐marine taxa Legitimocythere sp. and Neonesidea whatleyi Warne, in what would otherwise be considered an outer‐shelf (120–160 m) ostracod fauna at Fossil Beach, Mornington. Ostracod occurrences indicative of dysaerobic sea‐floor conditions in the Kingfish 8 well and Fossil Beach sections, when considered together, appear to record a shallowing of the oceanic oxygen‐minimum zone during the latest Early Miocene to earliest Middle Miocene transgressive phase of southeast Australia. 相似文献
16.
Like most sill fjords, Gullmar Fjord on the Swedish west coast, is subject to periods of stagnation. Deep water is usually renewed annually, but since the late 1970s several low-oxygen events have been documented in the deepest part of the fjord. These events occurred during a time when the North Atlantic Oscillation (NAO) was in a highly positive phase. We investigated how the benthic environment, in the deepest part of the fjord, has varied during the 20th century, using benthic foraminifera and an extensive history of instrumental hydrographic data. The foraminifera have undergone one major faunal change and two minor modifications during this time. The major faunal change occurred in the late 1970s to early 1980s, when the common Skagerrak-Kattegat fauna was replaced by one dominated by the opportunistic, low-oxygen-tolerant species,Stainforthia fusiformis. This major faunal change appears to be related to the severe low-oxygen event in 1979–1980. In the latter part of the 1990s the fauna changed again; the concentration ofS. fusiformis was still high, but other low-oxygen-tolerant species also became important. This minor faunal modification occurred in connection with the 2-yr stagnation period between 1996 and 1998 when a low-oxygenevent evolved, the most severe recorded in Gullmar Fjord. Between 1930 and 1980, there was little faunal variation, and a stable fjord environment is indicated. During this time, negative NAO indexes dominated and climate was more continental, with an increase in winds from the northeast and east. In connection with a climate transition indicated by the NAO index switching from positive to negative, a minor faunal change occurred in the late 1920s to early 1930s: the concentration of the Skagerrak-Kattegat fauna increased markedly in the fjord. The fauna characterizing the positive NAO phase between 1900 and the late 1920s is very different from the present positive NAO fauna. The foraminiferal record laid down between approximately 1914 and 2001 indicates that between 1930 and 1980 Gullmar Fjord was a stable fjord environment. During the last 20 yr, it experienced conditions that were more fluctuating and changing. For the most part, changes in the foraminiferal fauna are caused by changes in the deep-water renewal, their extent and frequency, which in turn are caused by climatic oscillations. 相似文献
17.
The Paleocene/Eocene boundary intervals were studied in three outcrops along the Nile Valley: Gabal Taramsa, Gabal Qreiya, and Gabal Nag El Quda in Qena and Esna regions. The planktonic and benthic foraminifera have been examined. The qualitative study of planktonic foraminifera distinguishes eight planktonic biozones from (P4 and P5) Paleocene age to (E1, E2, E3, E4, E5, and E6) Early Eocene age. The analysis of quantitative distribution patterns of benthic foraminifera allows the reconstruction of the paleoenvironmental settings in the studied area. The disappearance or scarce appearance of deeper-water benthic foraminifera (Angulogavelinella avnimelechi and Gavelinella rubiginosus) and increasing dominance of shallow-marine taxa (Buliminides, Loxostomoides applinae) indicate deposition in shallow water environments. The benthic foraminiferal assemblages which dominated by Loxostomoides applinae, Buliminids, and Lenticulina indicate Dysoxic conditions and maximum food levels. The species of mid-way type fauna dominate the assemblages of the studied area; the species of Velasco-type fauna are very rare. 相似文献
18.
19.
Benthic foraminifera is the first kind of eukaryotes reported to carry on denitrification, which breaks the understanding of the eukaryotic metabolic way. Numerous studies have demonstrated that the contribution of benthic foraminifera to sedimentary denitrification exceeds the prokaryotes. Furthermore, benthic foraminifera stores large amount of nitrate intracellularly, which far exceeds the amount of nitrate in pore water. These findings challenge our understanding of the nitrogen cycle in sediments. The study of foraminiferal intracellular nitrate storage and denitrification is significant to figure out the metabolic way of eukaryote in anoxic environment and to quantify the balance of nitrogen in marine environment. The history of foraminiferal intracellular nitrate storage and denitrification study was discussed. In addition, the distribution of foraminiferal intracellular nitrate and denitrification rates in marine environment was also discussed. The latest research progresses about the related mechanism were also summarized. Finally, the problems and challenges in present and future studies were discussed. 相似文献
20.
依据ＧｅｒｔａＫｅｌｅｒ和Ｇａｓｐｅｒｉ，Ｋｅｎｎｅｔｔ有关中新世印度洋和太平洋浅层水、中层水和深层水浮游有孔虫深度分层组合的划分模式，对南海琼东南盆地崖１９－１－１井晚第三纪浮游有孔虫作了定量研究，并分析了陆架海区浮游有孔虫不同深度分层组合含量的变化与古地理环境变迁的关系。崖１９－１－１井以浅层水、中层水组合为主，深层水组合不发育，反映本区温跃层不发育，不利深层水浮游有孔虫的生存。滨海区，浮游有孔虫仅为少数几个浅层水的优势种，中层水浮游有孔虫不发育；内浅海区，浅层水浮游有孔虫占绝对优势，中层水浮游有孔虫处于次要地位，所含比例相对较小；外浅海区及陆坡半深海区，浅层水和中层水浮游有孔虫均较发育，中层水浮游有孔虫百分含量相对较高。崖１９－１－１井在上新世早中期曾出现外浅海至陆坡半深海区，为古水深最大时期 相似文献