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1.
N. O. Chistyakova E. V. Ivanova B. Risebrobakken E. A. Ovsepyan Ya. S. Ovsepyan 《Oceanology》2010,50(4):573-581
Environmental changes in the surface and bottom water layers of the Ingøydjupet Basin and the history of the Atlantic Water inflow to the southwestern Barents Sea during the last 16 ka are reconstructed based on planktic and benthic foraminiferal assemblages. The multiproxy study of sediment cores PSh-5159R and PSh-5159N, including AMS 14C dating, provides a time resolution of about 200 years for the deglaciation, 100 years for the Holocene, and 25–50 years for the last 400 years. Stable polar conditions with the sea ice at the surface were typical for the Early Deglaciation period. Unstable bottom settings and the onset of ice rafting marked the Oldest Dryas. The cold Atlantic Water inflow increased notably during the Bölling-Alleröd interstadial nearby the site location and then decreased during the Younger Dryas. The initial Holocene was characterized by abrupt warming in bottom and surface water layers, especially ～9.7–7.6 ka BP. Stable conditions prevailed during the Middle Holocene. Remarkable changes in the sea-surface temperature and bottom environments occurred during the last 2.5 cal. ka BP. 相似文献
2.
An oxygen minimum zone (OMZ) currently exists at intermediate water depths on the northern Japanese margin in the northwestern Pacific. The OMZ results largely from a combination of high surface–water productivity and poor ventilation of intermediate waters. We investigated the late Quaternary history (last 27 kyr) of the intensity of this OMZ using changes in benthic foraminiferal carbon isotopes and assemblages in a sediment core taken on the continental slope off Shimokita Peninsula, northern Japan, at a water depth of 975 m. The core was located well within the region of the present-day OMZ and high surface–water productivity. The benthic foraminiferal δ13C values, which indicate millennial-scale fluctuations of nutrient contents at the sediment–water interface, were 0.48‰ lower during the last glacial maximum (LGM) than during the late Holocene. These results do not indicate the formation of glacial intermediate waters of subarctic Pacific origin, but rather the large contribution of high-nutrient water masses such as the Antarctic Intermediate Water, implying that the regional circulation pattern during the LGM was similar to that of modern times. Benthic foraminiferal assemblages underwent major changes in response to changes in dissolved oxygen concentrations in ocean floor sediments. The lowest oxygen and highest nutrient conditions, marked by dysoxic taxa and negative values of benthic foraminiferal δ13C, occurred during the Bølling/Allerød (B/A) and Pre-Boreal warming events. Dysoxic conditions in this region during these intervals were possibly caused by high surface–water productivity at times of reduced intermediate–water ventilation in the northwestern Pacific. The benthic assemblages show dysoxic events on approx. 100- to 200-year cycles during the B/A, reflecting centennial-scale productivity changes related to freshwater cycles and surface–water circulation in the North Pacific. 相似文献
3.
A program of geophysical mapping and vibracoring was conducted to better understand the geologic evolution of Apalachicola
Bay. Analyses of the geophysical data and sediment cores along with age control provided by 34 AMS 14C dates on marine shells and wood reveal the following history. As sea level rose in the early Holocene, fluvial deposits
filled the Apalachicola River paleochannel, which extended southward under the central part of the bay and seaward across
the continental shelf. Sediments to either side of the paleochannel contain abundant wood fragments, with dates documenting
that those areas were forested at 8,000 14C years b.p. As sea level continued to rise, spits formed of headland prodelta deposits. Between ∼6,400 and ∼2,500 14C years b.p., an Apalachicola prodelta prograded and receded several times across the inner shelf that underlies the western part of
the bay. An eastern deltaic lobe was active for a shorter time, between ∼5,800 and 5,100 14C years b.p. Estuarine benthic foraminiferal assemblages occurred in the western bay as early as 6,400 14C years b.p., and indicate that there was some physical barrier to open-ocean circulation and shelf species established by that time.
It is considered that shoals formed in the region of the present barrier islands as the rising sea flooded an interstream
divide. Estuarine conditions were established very early in the post-glacial flooding of the bay. 相似文献
4.
In the present paper, the Holocene sea level changes and coastline shifts in Zhejiang, China are discussed, based on the ancient coastline evidence related with sea level changes and 21 14C dat-ings of shell, peat or mud and wood samples along the Zhejiang coast. The development of Zhejiang coastline during the Holocene period can be divided into four stages. A lot of data of historical period and modern times have shown that tracing coastline shifts back to its source, we have to consider tremendous effects of man's activities besides natural factors, such as elevation and subsidence of the earth crust, sea level changes, supply of sediment, and littoral hydrodynamics. 相似文献
5.
The study of foraminifers from sediments accumulated during the last 30 ky revealed their similar distribution in the central
and marginal parts of the Deryugin Basin, which implies similar environmental changes throughout this morphological structure.
The lack or extreme taxonomical impoverishment of the benthic foraminiferal assemblages during the Last Glacial Maximum indicates
a combination of several factors: the significant deterioration of the parameters controlling their bioproductivity in response
to the general cooling; the development of anoxic bottom conditions; and, probably, the unfavorable influence of cold barite-methane
seeps on the geochemical parameters of the bottom waters. The weaker activity of these seeps in the central part of the basin
during the Holocene is evident from some deviations in the structure of the benthic foraminiferal assemblages against the
background of their general taxonomic similarity. 相似文献
6.
M. S. Barash T. A. Khusid A. G. Matul M. P. Chekhovskaya N. Biebow D. Nürnberg R. Tiedemann 《Oceanology》2008,48(1):105-113
Benthic foraminifera are investigated in sediment core LV28-34-2 (53°51.971′N, 146°47.499′E, sea depth 1431 m, core length 965 cm). The distribution of foraminifera is studied in coarse-grained (>0.125 mm) sediment fractions of 191 samples taken with a step of 5 cm. The core covers the interval from oxygen isotope stage (OIS) 6 up to the Holocene. The foraminiferal assemblages of the penultimate (OIS 6) and last (OIS 5d-2) glaciations are characterized by low abundances and prevalence of Uvigerina auberiana. The specific structure of the OIS 6 assemblages differs from the last glaciation ones by the mass presence of Cassidulina teretis, which characterizes low temperatures and a high influx of organic matter to the sea floor. The major factor responsible for the weak development of benthic foraminifers during the glacial time is the deficiency of food resources. The foraminiferal assemblage of the interglacial optimum (OIS 5e) is composed of both calcareous and agglutinated species (Martinottiella communis).The inflow of Pacific waters was probably more intensive, the bioproductivity was higher, and the critical carbonate compensation depth was shallower at that time than during the glaciations. During the deglaciation, the quantity and structure of the foraminiferal assemblages reflected two pulses of warming (terminations 1B and 1A) with an intervenient cooling event (Younger Dryassic). The assemblages of warm periods were characterized by exclusively high foraminiferal abundances, which sharply decreased during the Younger Dryassic cooling. The specific structure of the foraminiferal assemblage during deglaciation was relatively uniform, being composed of only calcareous taxa typical of highly productive areas of the ocean. The paleoenvironmental conditions were similar to the conditions of the interglacial optimum (OIS 5e), although the preservation of calcareous tests is better. In the Holocene sediments, the concentration of benthic foraminifera is substantially lower than during the deglaciation, which is explainable by their dilution in the sediments by diatoms; the composition of the foraminiferal assemblages is similar to that of their glacial counterparts. 相似文献
7.
8.
《Marine Geology》1999,153(1-4):253-274
The planktic foraminiferal distribution identified in 60 cores collected in different basins of the Mediterranean Sea allowed to establish an ecostratigraphical scheme which provides a very important tool for the biochronological subdivision of the uppermost Quaternary. We identified a succession of ten ecozones during the last 23 ka in the Tyrrhenian basin and eight ecozones in the Adriatic Sea during the last 15 ka. The ecozones boundaries have been calibrated by 14C AMS radiometric data and by the stable oxygen isotope record. The chronological framework defined by the successive bioevents shows a very high resolution (millenary scale) and evidences that the changes in the planktic microfauna occurred more or less synchronously throughout the central Mediterranean Sea. Differences due to different oceanographic settings of the basins do not affect the general distributional pattern of planktic foraminifera. 相似文献
9.
东海北部陆架柱样中底栖有孔虫组合及其古环境研究 总被引：1，自引：0，他引：1
东海北部陆架区D-46C和D-74C柱样底栖有孔虫分析结果表明,D-46C柱样自下而上为压扁卷转虫(Am-moniacompressiuscula)组合,并可以进一步划分出压扁卷转虫—花朵虫(A.compressiuscula-Florilusspp.)亚组合、压扁卷转虫—叶状串珠虫(A.compressiuscula-Textularia foliacea)亚组合和压扁卷转虫—强壮箭头虫(A.compressiuscula-Bolivina robusta)亚组合;D-74C柱样自下而上可以划分出三个组合:叶状串珠虫—压扁卷转虫(Textularia foliacea-Ammonia compressiuscula)组合、大西洋花朵虫—异地希望虫(Florilus atlanticus-Elphidium advenum)组合和大西洋花朵虫—结缘寺卷转虫(Florilus atlanticus-Ammonia ketienziensis)组合。两个柱样中底栖有孔虫组合垂向变化明显,结合AMS14C测年结果,初步认为两个柱样均为全新世以来的沉积。其中,D-74C柱样为全新世中期(相当于亚北方期)以来的沉积,在全新世晚期一直受到陆地冲淡水的强烈影响;D-46C柱样为全新世早期(相当于前北方期和北方期)以来的沉积,受到陆地冲淡水流的影响较D-74C柱样小。 相似文献
10.
Indian summer monsoon variability during the holocene as recorded in sediments of the Arabian Sea: Timing and implications 总被引：1，自引：0，他引：1
Meloth Thamban Hodaka Kawahata Venigalla Purnachandra Rao 《Journal of Oceanography》2007,63(6):1009-1020
Indian monsoon precipitation fluctuated significantly during the Holocene and a reliable reconstruction of the timing of the
events and their implications is of great benefit to our understanding of the effect and response of low latitude climate
systems to the forcing factors. We have carried out high-resolution terrigenous proxy studies on a laminated sediment core
from the Oxygen Minimum Zone of the eastern Arabian Sea margin to reconstruct the summer monsoon-controlled precipitation
changes during the Holocene. The temporal variation in the terrigenous proxy indicators of this core, in combination with
other high-quality cores from the Arabian Sea, suggests several abrupt events in monsoon precipitation throughout the Holocene.
The early Holocene monsoon intensification occurred in two abrupt steps at 9500 and 9100 years BP and weakened gradually thereafter,
starting at 8500 years BP. A weakening in precipitation recorded at ∼7000 years BP, synchronous with similar conditions in
India. One of the most significant weak monsoon periods recorded in our studies lies between 6000 and 5500 years BP. Spectral
analysis of the precipitation records reveals statistically significant periodicities at 2200, 1350, 950, 750, 470, 320, 220,
156, 126, 113, 104 and 92 years. Most of these millennial-to-centennial cycles exist in various monsoon records as well as
the tree ring Δ14C data and/or other solar proxy records. We suggest that throughout the Holocene, externally, small changes in solar activity
controlled the Indian monsoon to a large extent, whereas internally, non-solar causes could have influenced the amplitude
of decadal-to-centennial oscillations. 相似文献
11.
Late Pleistocene-Holocene Paleoceanography and Ventilation of the Gulf of California 总被引：1，自引：0，他引：1
Lloyd D. Keigwin 《Journal of Oceanography》2002,58(2):421-432
Sediment cores collected in 1990 from the Gulf of California have been studied using stable isotope and radiocarbon techniques
to reconstruct the climate and ventilation histories since the last glacial maximum. Benthic foraminiferal δ18O from core tops in a water depth range of 145 to 1442 m increases by about 2% with increasing depth. This is consistent with
a composite temperature profile constructed from several hydrocasts in the various gulf basins. However, the δ18O water/salinity relationship is not sufficiently linear in gulf locations or in nearby open Pacific Geochemical Ocean Sections
Study (GEOSECS) stations to be useful in solving paleotemperature equations. Of the most common benthic foraminifera, only
Planulina ariminensis has δ13C that is consistent with the measured δ13C of ΣCO2. Several cores in the depth range 500 to 900 m have the laminated Holocene and Bolling/Allerod sediments, and the nonlaminated
glacial age and Younger Dryas sediments that are typical of the gulf and other locations such as Santa Barbara Basin. The
best of those, Jumbo Piston Core (JPC) 56 from 818 m water depth on the western margin of Guaymas Basin, was sampled for intensive
study. Oxygen isotope ratios in benthic and planktonic foraminifera show little evidence for deglacial temperature oscillations.
Carbon isotope ratios are generally lower during warm epochs, but the most striking result is strongly lowered benthic and
planktonic δ13C about 9500 years ago. This may reflect water column oxidation of locally released methane. Neither benthic δ13C in depth section nor paired benthic and planktonic 14C data in JPC56 are consistent with increased intermediate water ventilation during the glacial maximum and Younger Dryas.
Likewise, 14C data from 5 pairs of foraminifera from the Okhotsk Sea fail to support better ventilation in that basin during the last
glacial maximum.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
Claudia Gutterres Vilela 《Geo-Marine Letters》1995,15(3-4):199-203
The distribution of benthic foraminiferal microfauna recovered from two offshore transects on the Amazon shelf was studied. Eight box-core samples were collected along the inner, middle, and outer parts of the continental shelf. Each box-core sample was divided into 10 subsamples, of 1- to 5-cm intervals, in order to investigate the foraminiferal microhabitat preferences. The variations of salinity, oxygen, lithology, and sediment accumulation rates were used to evaluate ecological patterns. Four benthic foraminiferal assemblages identified in the study area characterize a record of oceanographic changes from early Holocene to the present. An abundant assemblage, with opportunistic species, was found near the river mouth. Two assemblages were identified northwest of the river mouth, with dominant epifaunal and infaunal species, respectively. A relict assemblage was encountered northwest of the river mouth. 相似文献
13.
Late Quaternary carbonate sedimentation at the Sierra Leone Rise (eastern equatorial Atlantic Ocean)
In the eastern equatorial Atlantic Ocean, changes in the concentration of carbonate in Late Quaternary sediments resulted from reduced production of carbonate in surface waters and increased dilution with non-carbonate sediments during glacial maxima. During glacial stages, production of carbonate in surface water (measured as its accumulation rate in shallow, undissolved cores) decreased by one half. The glacial accumulation rate of non-carbonate components increased 1.5 to 4 times over Holocene values; the greatest increases occurred in the deepest cores.
Carbonate dissolution during stages 2, 3 and 4 increased the proportion of foraminiferal fragments and decreased the accumulation rate of susceptible species in the deep sites. In shallow sites, slightly increased dissolution can be detected during stage 3 while greatly increased dissolution occurred during stage 4. Bathymetric profiles of foraminiferal fragmentation and accumulation document a shoaling of the foraminiferal lysocline by 1000 m during glacial isotopic stages. We present a mass balance model of sediment accumulation for carbonate and insoluble components and from this model we estimate the rate of downslope transport and dissolution of carbonate at the Sierra Leone Rise. Our results show that during stage 4 the rate of carbonate loss to dissolution was greater than the rate observed today or during other interglacial stages. The calculated rates of dissolution for stages 2 and 3 are not significantly different from those calculated for stage 1. 相似文献
14.
E. A. Gusev N. Yu. Anikina L. G. Derevyanko T. S. Klyuvitkina L. V. Polyak E. I. Polyakova P. V. Rekant A. Yu. Stepanova 《Oceanology》2014,54(4):465-477
The molluscan shells from three drill and two piston cores obtained in the southern Russian sector of the Chukchi Sea are dated by the AMS 14C measurement method back to 0.8–3.5 and 9.2–10.5 ka. The period of 9–10 ka was marked by increased sedimentation rates related to the transgression onset. The fossils in the lower Holocene section exhibit the successive upward replacement of brackish-water organisms by their marine counterparts. After the opening of the Bering Strait in the middle Holocene, the sedimentation was under influence of the increased bioproductivity of the waters. The climatic optimum in the Chukotka region corresponds to the early Holocene, while the late Holocene was characterized by the wider development of the ice cover on the shelf. 相似文献
15.
I. F. Gablina L. L. Demina O. B. Dmitrenko N. S. Os’kina E. A. Popova T. A. Khusid V. V. Shilov 《Oceanology》2011,51(3):476-490
The first thorough analysis of microfossils from ore-bearing sediments of the Ashadze-1 hydrothermal field in the Mid-Atlantic
Ridge sampled during cruise 26 of the R/V Professor Logachev in 2005 revealed the substantial influence of hydrothermal processes on the preservation of planktonic calcareous organisms,
as well as on the preservation and composition of the benthic foraminifers. From the lateral and vertical distribution patterns
and the secondary alterations of the microfossils, it is inferred that the main phase of the hydrothermal mineralization occurred
in the Holocene. Heavy metals (Cu, Co, Cr, and Ag) were accumulated by foraminiferal tests and in their enveloping Fe-Mn crusts.
The distribution of authigenic minerals replacing foraminiferal tests demonstrates local zoning related to the hydrothermal
activity. There are three mineral-geochemical zones defined: the sulfide zone, the zone with an elevated Mg content, and zone
of Fe-Mn crusts. 相似文献
16.
Paleoenvironmental records from the northern South China Sea since the Last Glacial Maximum 总被引：1，自引：0，他引：1
Core ZHS-176 contains the paleoenvironmental records from the northern South China Sea (NSCS) since the Last Glacial Maximum (LGM). A coupled approach based on clay mineral assemblages, planktonic foraminiferal oxygen and carbon isotopes, and calcium carbonate content is used to trace the sources of the fine-grained sediment and to investigate the paleoenviornmental evolution in this area. Clay mineral assemblages are dominated by illite (average about 39%) and chlorite (about 27%), which comes mainly from Taiwan and the East China Sea. Kaolinite, which accounts for about 13%, comes mainly from the Zhujiang (Pearl) River, and Luzon Island is the main source for smectite (about 21%). The planktonic foraminiferal oxygen isotopic oscillations during the last glacial period are coeval with climate variations recorded in the Greenland ice core and Western Pacific sediment. These variations include the LGM, Heinrich event 1, Bφlling-Allerφd (B/A), and Younger Dryas. For the Holocene, three periods of strong precipitation (S1-S3) and three periods of weak precipitation (W1-W3) are identified. The oxygen isotopic record exhibits corre-lation with climate records from distant regions, including the high-latitude Northern Hemisphere, providing evidence for global tele-connection among regional climate. A brief, negative planktonic foraminiferal carbon isotopic excursion during B/A reflects increased methane released from marine gas hydrate due to the rapid warming of the water. By comparing calcium carbonate content curves of the core ZHS-176 with these of other five boreholes lying above the lysocline, a remarkable low calcium carbonate event is found during the early Holocene in NSCS. 相似文献
17.
Marine isotope stage (MIS) 9 is one of the least investigated Pleistocene interglaciations. The present study describes reconstructions
of deep-water conditions during this time interval based on benthic foraminiferal assemblages from sediment core M23414 (Rockall
Plateau, North Atlantic). The results of faunal analysis were supported by planktic δ18O, sea surface temperature reconstructions based on planktic foraminiferal assemblages and content of ice rafted debris. Statistical
data processing using principal component analysis revealed five climate-related benthic foraminiferal associations that changed
in response to alterations of deep-water circulation. 相似文献
18.
Hidetaka Nomaki Naohiko Ohkouchi Petra Heinz Hisami Suga Yoshito Chikaraishi Nanako O. Ogawa Kouhei Matsumoto Hiroshi Kitazato 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(9):1488-1503
We conducted an in situ feeding experiment using 13C-labeled unicellular algae in Sagami Bay, Japan (water depth, 1450 m), in order to understand the fate of lipid compounds in phytodetritus at the deep-sea floor. We examined the incorporation of excess 13C into lipid compounds extracted from bulk sediments and benthic foraminiferal cells. 13C-enriched fatty acids derived from 13C-labeled algae were exponentially degraded during 6 days of incubation in the sediment. Subsequent enrichments in 13C in sedimentary n-C15, anteiso-C17, and C17 fatty acids indicated the microbial degradation of algal material and production of bacterial biomass in the sediment. We observed the incorporation of 13C-labeled algal phytol and fatty acids into foraminiferal cells. The compositions of 13C-labeled algal lipids in foraminiferal cells were different from those in the bulk sediments, indicating that foraminiferal feeding and digestion influenced the lipid distribution in the sediments. Furthermore, some sterols in Globobulimina affinis (e.g., 24-ethylcholesta-5,22-dien-3β-ol, 24-ethylcholest-5-en-3β-ol, and 23,24-dimethylcholesta-5,22E-dien-3β-ol) were newly produced via the modification of dietary algal sterols within 4–6 days. In addition to the effects of bacteria, feeding by benthic foraminifera can result in a significant reorganization of the composition of organic matter and influence benthic food webs and carbon cycling at the deep-sea floor. 相似文献
19.
通过对安达曼海重力柱ADM-C1的浮游有孔虫群落分析, 探讨了该区全新世以来的海洋环境演化。研究发现, 该区浮游有孔虫群落总体以热带暖水种Globigerinoides ruber、Globigerinoides sacculifer、Neogloboquadrina dutertrei和Pulleniatina obliquiloculata等为主。其中G. ruber的相对丰度从早全新世至今呈逐渐降低的趋势, G. sacculifer则呈大致相反的变化趋势。N. dutertrei的相对丰度从11—7.9ka BP较高, 到7.9—3.8ka BP偏低, 3.8ka BP以来又逐渐升高。而P. obliquiloculata的变化趋势则与N. dutertrei大致相反。研究认为, 安达曼海不存在与冲绳海槽类似的晚全新世普林虫低值事件。浮游有孔虫群落Q型因子显示全新世海洋环境呈现三个明显的阶段变化: 早全新世 11—7.9ka BP期间, 浮游有孔虫群落以G. ruber、N. dutertrei与G. bulloides为主, 反映了该阶段较强的夏季风降水会导致表层水体盐度较低, 同时冬季风的影响相对较强; 7.9—3.8ka BP期间, 以G. ruber、P. obliquiloculata和Globigerinella aequilateralis为主, 指示水体盐度仍然较低, 同时次表层属种显著增多, 对应了该阶段强盛的印度夏季风, 上层海水混合强烈; 3.8—0ka BP期间, 以G. sacculifer、N. dutertrei和P. obliquiloculata为主要特征属种, 而G. ruber相对丰度明显下降, 表明该时期表层海水的盐度有显著上升, 对应了印度夏季风降水的明显减弱。安达曼海浮游有孔虫群落所呈现的全新世海洋环境阶段性变化和陆地夏季风记录有很好的一致性, 也与该孔敏感粒级组分所反映的印度季风的强度变化一致, 表明热带边缘海区的有孔虫群落组合可以很好地响应区域海洋环境变化。 相似文献
20.
盐城上岗全新世有孔虫组合的环境意义 总被引：1，自引：0，他引：1
对盐城上岗全新世柱状剖面中的有孔虫进行研究，划分出7个有孔虫组合类型。依据组合特征确定盐城地区全新世为潮滩环境，经历了由5次小规模的海水进退构成的海退过程。并且发现潮滩环境下的风暴沉积有孔虫组合中外海分子增多、壳体破损严重，显示出与河口环境的风暴潮有孔虫组合特点的差异。 相似文献