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1.
Theoretical constraints and chronological evidence of Holocene coastal development in central and southern New South Wales, Australia 总被引：3，自引：0，他引：3
Holocene coastal evolution in New South Wales has been interpreted essentially as the unfolding of the impact of marine transgression. Sea level on this coast supposedly reached its present height at 6–6.5 ka, and varied < 1 m since then. The early Holocene rise of the sea has been considered the key factor (“forcing function”) in dune migration, coastal sand barrier development, and the evolution of estuaries. Episodic storminess during the late Holocene has been seen as an important, though secondary, factor in beach erosion and dune mobilisation. An alternate interpretation presented here challenges the concept of the marine transgression as the primary “forcing function”. It (a) attributes early Holocene dune mobilisation to climate rather than the rising sea; (b) shows that the sea reached its present level by 7 ka and rose to at least + 2 m until 1.5 ka; (c) links late Holocene dune activity to local disruption of vegetation rather than to regional episodic storminess; (d) demonstrates a fall of 2°C in sea surface temperature after 3 ka that coincides with the onset of barrier erosion; (e) recognises the imprint of at least three tsunamis in the coastal sedimentary record. 相似文献
2.
Three radiocarbon dates on marine organic material from southernmost Spitsbergen are presented, making it possible to compare the Holocene shoreline displacement in this area with that of other areas of Svalbard. The most distinct raised beach feature is the large beach ridge terrace about 10 m above sea level which most probably is the result of a marine transgression ca. 6500 years ago. Dating of 2700-year-old laminaria from about 2 m above sea level demonstrates a small rising of the land during the youngest Holocene. 相似文献
3.
渤海湾西北岸全新世海侵问题的初步探讨 总被引：12，自引：0，他引：12
渤海湾西北岸的全新世海侵问题,已往对它缺乏系统研究。本文从全新世地层特征及其所含植物孢粉和微体古生物等方面,证实了本区在中全新世期间遭受过海侵,并根据海相生物分布和微地貌差异等进行综合分析,划出了这次海侵的范围。最后从河流—海洋水文动力条件,解释了渤海湾西北岸与西岸各自发育了牡蛎礁和贝壳堤的原因。 相似文献
4.
通过对珠江口岛屿小型海湾如珠海淇澳岛和澳门黑沙滩一级阶地上的古沙坝/沙丘进行光释光（OSL）年代测定、粒度分析,结果表明,全新世潮间带砂体沉积的底部年代根据光释光测年结果和沉积速率推算,超过9 ka。海岸带形成的古沙坝或风成砂质沉积的光释光测年结果大部分老于新石器文化堆积的器物年代,表明全新世高海面期砂质滨海相沉积的形成先于新石器人类活动遗迹。潮间带砂质滨海相沉积的上覆地层常在6.5 ka左右快速转变为潮上带的风成沉积-人类活动混合堆积,导致文化层中沉积物粒度分选变差,参数波动较大。淇澳岛小沙澳湾9―4.3 ka的滨海相砂质沉积的顶部目前位于海拔＋4.8 m,这一高程可能与构造抬升运动有关。 相似文献
5.
长江河口地区第四纪古地理古环境变迁 总被引：21，自引：4，他引：17
通过对钻孔样品的粒度、层理揭片、矿物、微体古生物、孢粉、地球化学元素及古地磁等项目的实验室分析,着重探讨长江河口地区第四纪古地理、古环境变迁特征和长江三角洲的发育过程。 相似文献
6.
广东黄圃镇海蚀遗址的形成年代及古地理环境 总被引：1，自引：0，他引：1
广东中山市黄圃镇海蚀遗址是广东沿海至今为止所发现最大规模的海蚀遗址之一,古海蚀地貌延伸范围超过200米,海蚀洞、海蚀崖、海蚀平台等海蚀地貌仍保持得较为完好。根据地形特征、地层（钻孔）资料、海侵范围、史料记载进行综合确定了古海蚀遗址的形成年代和古地理环境。古海蚀崖所在的尖峰山由白垩系陆相红色碎屑岩系构成。黄圃附近地区在晚更新世末期第一次海侵前已经是一隆起地块,在晚更新世和全新世两次海侵时都处在较高的位置,出露的白垩系地层（尖峰山）为蚀余的低矮山地。这些残余山地在全新世海侵大部分时段内为珠江口古海湾中的岛屿,黄圃镇作为大陆岸线的时间很短,海蚀地形主要形成于晚全新世前海侵时（距今约6100～1600年）的岛屿时期。 相似文献
7.
下辽河平原和辽东半岛海岸带晚更新世以来的海侵 总被引：12，自引：2，他引：10
本文根据钻孔资料、14C测年数据、微体古生物及孢粉组合特征,讨论了研究区晚更新世以来海侵的次数、规模、时间以及岸线变化。 相似文献
8.
为了深入探讨珠江三角洲的沉积古环境和古气候历史,在三水市区获取了2个高取芯率的钻孔岩芯,进行了12个AMS 14C测年,并结合孢粉、硅藻等分析结果探讨三水地区全新世的海平面与河流水动力变化,以及古植被演替过程。结果表明：钻孔所在区域全新世沉积总体从9 000 cal. a B.P.左右开始,呈现河流相―河湾相―河口湾相―潮坪相―河口湾相―河漫滩相的演变过程。三水区的早全新世沉积阶段年代最早为9 000 cal. a B.P.左右,表现为河口湾相的淤泥质粉砂沉积,硅藻以淡水种类为主,最高沉积速率为1.6 cm/a。海侵初始时间为8 700 cal. a B.P.左右,最高海平面时间为7 600 cal. a B.P.左右,此时海岸带发育红树林,丘陵山地发育较茂盛的亚常绿热带常绿阔叶林;中―晚全新世阶段（6 500―2 200 cal. a B.P.）,以泥炭粉砂沉积为主,沉积速率为0.2~0.5 cm/a,河口区高潮线附近及河流弯道低洼滩地在5 000 cal. a B.P.前后形成淡水沼泽、河口三角洲边缘区洼地水松林发育。在晚全新世（2 200 cal. a B.P.左右）以来,陆相黏土质沉积指示河口泥沙快速堆积,三角洲平原迅速扩大,沉积速率高达1.7 cm/a。孢粉结果显示次生的芒箕孢子剧增,陆地植被稀疏,人类活动显著增强。 相似文献
9.
F. García-Rodríguez D. Metzeltin P. Sprechmann R. Trettin G. Stams L.F. Beltrán-Morales 《Journal of Paleolimnology》2004,32(2):117-135
Paleolimnological data are presented on trophic development in relation to sea level variation in Rocha Lagoon, a 72 km2 coastal lagoon in southern Uruguay. Using sediment cores that extended to ∼20,000 yr BP, analyses of grain size, organic matter, carbonate, total carbon, nutrients, and diatoms allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene relative sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regressions progressed. Diatom Association Zones (DAZ) were identified in both cores. Those DAZ corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter and nutrient values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and both organic matter and nutrients. Although the lagoon formed after the first Holocene marine transgression, our data indicate the existence of a marine/brackish aquatic system during upper Pleistocene (i.e., before 15,000 yr BP), but by ∼20,000 yr BP, the system was still likely to be a semi-arid terrestrial system. 相似文献
10.
H. Inda F. García-Rodríguez L. del Puerto V. Acevedo D. Metzeltin C. Castiñeira R. Bracco J. B. Adams 《Journal of Paleolimnology》2006,35(4):699-713
Paleolimnological data are presented on trophic development, climatic change and sea level variations in Rocha Lagoon, a 72 km2 coastal lagoon in southern Uruguay. Using a sediment core that extended from 7000 to about 3700 yr BP, analyses of organic
matter, carbonate, diatoms and chrysophyte cysts were used to track the early Holocene paleolimnological conditions of Rocha
Lagoon. Opal phytoliths were also counted and identified, both temperature and humidity indices were calculated, and Opal
Phytolith Association Zones (OPAZ) were identified by performing Principal Coordinates Analysis (PCO). Diatom Association
Zones (DAZ) corresponding to marine/brackish and brackish/freshwater episodes were closely related to changes in trophic state.
Those DAZ representing marine/brackish stages exhibited a lower trophic state than those DAZ dominated by brackish and freshwater
diatoms. This highlights that during the first Holocene marine transgression, Rocha Lagoon did not continuously exhibit marine/brackish
conditions as reported in previous papers. Instead, three brackish/freshwater episodes related to sea level variation and
changes in humidity were identified. The first episode, by ~6000 yr BP, was related to sea level change as no significant
changes in either temperature or humidity indices were observed. The second episode, between 5000 and 4400 yr BP, was related
to both a sea level decrease and an increase in humidity, as a transition from humid to very humid climate was inferred. Concomitant
decreases in salinity and increases in trophic state were also observed. The third episode, after ~4000 yr BP, was related
to the end of the first Holocene regressive phase when sea level was slightly below present levels. Further decreases in salinity
and increases in trophic state were detected. The paleoclimatic trends inferred in this study were in close agreement with
other regional studies on climatic change, as cool temperatures were inferred. However, major changes in humidity were also
detected. A humid to very humid climate was inferred for ~7000–4500 yr BP, but the occurrence of a semiarid/arid climate was
inferred for ~4500–3700 yr BP. Our data suggest that during transgressive and regressive events there might be higher frequency
and lower amplitude sea level oscillations that might lead to changes in salinity and trophic state of coastal aquatic systems.
Such oscillations could only be tracked by high resolution analyses of sedimentary records and could be best interpreted with
complementary data on paleoclimate. In addition, microfossils such as diatoms and opal phytoliths were shown to be very sensitive
to such paleoenvironmental changes. 相似文献
11.
An emergence curve based on nine radiocarbon dated samples of mosses, shells, whale bones and driftwood has been constructed for Agardhbukta. Beach sediments and delta deposits were found up to c. 50 m above sea level, and the oldest date goes back to about 10, 000 yrs BP. However, the possibility of a higher marine limit cannot be excluded. The Agardhbukta curve shows a nearly linear uplift during the entire Holocene. It differs from the western Spitsbergen curves, where a transgression occurs, and is more similar to curves from areas further east in the Svalbard archipelago. 相似文献
12.
莱州湾南岸咸水入侵区晚更新世以来的古环境演变 总被引：8，自引：0，他引：8
莱州湾南岸是我国典型的咸水入侵区,古环境变化构成了现代咸水入侵发生的背景。本文通过对潍河下游地区A1、A5孔岩芯系统的孢粉、有孔虫、粒度、14C及热释光测年资料的分析,结合100余个钻孔的沉积特征,论述了莱州湾南岸地区晚更新世以来的古环境演化特征。本区经历了三次明显的冷暖气候波动,三次显著的暖湿期为85～76kaBP、50～24kaBP、10～4kaBP,为海陆过渡相沉积环境,这三个时期分别与晚更新以来的三次海侵相对应,与相邻区域相比,全新世海侵开始早、结束晚;两次冷干期为76～50kaBP、24～10kaBP,分别对应于早大理冰期、晚大理冰期,为陆相沉积环境。 相似文献
13.
全新世以来里下河地区古地理演变 总被引：12，自引：2，他引：12
里下河地区是苏北平原的重要组成部分，全新世以来，本区古地理环境经历了巨大的变化。据作者研究，大致可分为三个阶段：早全新世，本区受海侵影响，7－6kaB.P．左右海侵达到高峰，整个里下河地区成为一个大的浅水海湾；中全新世，海面相对稳定，长江、淮河等河流挟带大量泥沙入海，古海湾被岸外砂堤所包围，形成泻湖；晚全新世，海岸东迁，古泻湖演变为湖泊沼泽，在人类活动与黄河夺淮的影响下，本区逐渐演变为里下河平原。 相似文献
14.
Terrace remnants close to the marine limit as well as two separate moraine ridges are observed in front of the glacier Albrechtbreen. The stacking of marine sediments from an original elevation of ca. 60–80 m a.s.l. into the Little Ice Age Moraine gives evidence for a considerably smaller glacier following the early Holocene deglaciation compared to that of the present. The outer moraine is composed of glacial diamicton. Radiocarbon datings of whale ribs, shell fragments and a log taken from sediment in front of Albrechtbreen indicate that the initial deglaciation occurred before 9, 400 B.P. and that the outer moraine was formed during a younger Holocene glacial advance. Lithological differences between the two moraine ridges suggest that the first ice advance occurred during a period with limited permafrost, whereas permafrost was more extensive during the Little Ice Age. 相似文献
15.
Fossil phytolith assemblages from a 154.5 m longdrillcore from the Lower Taieri Plain, Otago, New Zealand are presented. Transferfunctions, based on modern phytolith assemblages from sites within the sameregion, were applied to the fossil phytolith data set, and validated usingModern Analogue Technique (MAT) assemblage matching. Analogues for much of theHolocene and some of the Last Interglacial (provisionally Oxygen Isotope Stage5c) were obtained. Late Glacial/Holocene precipitation and pH estimates areconsistent with other paleoclimate records from the Otago region. Thephytolith-based precipitation and pH estimates may act as a combined proxy forsoil weathering. The precipitation estimates may also act as a useful index ofEffective Precipitation (EP). Temperature estimates derived have limited usefor paleoclimate interpretation. Estimates produced for the mid-Holoceneindicate a wetter environment than the present (50–100 mmgreater EP) with increased soil weathering (high precipitation/low pH). Soilconductivity estimates were below estuarine levels during a diatom inferredmarine transgression. This lack of phytolith response to conductivity changesis put down to a probable delayed development of suitable habitats forsaltmarsh plant species during the rapid transgression. The Last Interglacialestimates indicate conditions somewhat drier (200 mm less EP) thanthe Holocene. Consistently low log conductivity (below 0.7 µScm) estimates from the Last Interglacial contrast with the estuarineenvironments of the Holocene, indicating freshwater conditions in the Plainduring at least part of the Last Interglaciation. 相似文献
16.
The Late Weichselian and Holocene shoreline displacement on the west-central coast of Svalbard 总被引：1，自引：0，他引：1
Three well-developed raised marine shorelines along Nordenskioldkysten have been studied and correlated with the shoreline displacement since the last deglaciation. The marine limit of 64 m in the area is of Late Weichselian age and has been dated to 10, 900- 11, 000 years B.P. An intermediate level at 50 m is estimated to be 10, 600-10, 000 years old and demonstrates a sea level stagnation probably caused by a glacier readvance in eastern Svalbard during the Younger Dryas. A Holocene transgression culminating shortly after 6, 000 years B.P. has been stratigraphically demonstrated, and it probably correlates with the Tapes transgression of Scandinavia. No pre-Late Weichselian marine levels are found, and the large rebound can be attributed only to a Late Weichselian glaciation. 相似文献
17.
F. García-Rodríguez P. Sprechmann D. Metzeltin L. Scafati D.L. Melendi W. Volkheimer N. Mazzeo A. Hiller W. von Tümpling F. Scasso 《Journal of Paleolimnology》2004,31(1):99-115
Paleolimnological data are presented relating trophic development to sea level variation in Lake Blanca, a small (0.6 km2), coastal fresh waterbody in southern Uruguay. Using a sediment core that extended to 7300 years BP, analyses of grain size, thin sections, organic matter, carbonate, total carbon, nutrients, diatoms and palynomorphs, allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regression progressed. Four diatom association zones (DAZ) were identified in the sediment core. The basal core section pre-dated the first Holocene marine transgression, contained no diatoms, chrysophyte cysts or non-siliceous microalgae, and showed C/N ratios values higher than 20. Thus, it is likely that the system exhibited terrestrial characteristics. In the second section (6500–2200 years BP, following the first Holocene transgression), there was dominance of marine/brackish diatom species. The lowest trophic states of the core were observed in this section. The third section (2200–1100 years BP), represented the system as it became separate from the Atlantic Ocean, and showed a dominance of brackish/freshwater species and increases in trophic state were observed. In the last section (after 1100 years BP), the system became fully freshwater as no marine or brackish diatom species were found, but a trend to oligotrophication was observed, probably due to nutrient depletion. However, after 1967 AD, eutrophication intensified because of forestry and soil fertilization in the catchment. Pollen association zones (PAZ) allowed us to identify four sections. Below 250 cm (2200 years BP), the core contained no pollen grains as redox potential and pH values were not conducive for pollen preservation. After 2200 years BP (when the system started to separate from the ocean), xerophilic taxa typical of coastal dunes colonized the catchment. Only after 1100 years BP (after fully freshwater conditions established) pollen grains of trees were observed. 相似文献
18.
全新世海侵痕迹遥感信息特征提取方法研究* 总被引：5，自引：0，他引：5
本文应用TM、MSS、NOAA等多平台、多波段、多时相遥感信息,并结合地貌、水文地质、岩相、历史考古等地学信息进行综合分析,研究华北平原全新世海侵痕迹信息的特征提取方法。研究中特别注重利用与海侵有着直接成因关系的地下咸水体及水化学特征变化所传递的信息。这些信息涉及到水、热、盐、土、植被等环境因子。通过多种图象处理方法,突出古海岸线两侧环境因子的综合差异,识别和勾绘古岸线。 相似文献
19.
黄河三角洲利津超级叶瓣时空范围的再认识 总被引：1，自引：0，他引：1
黄河三角洲是世界著名的河流三角洲之一。自有学者首次系统地提出黄河三角洲全新世10期超级叶瓣的时空分布范围后,这一观点近30年来未见明显的改进。借助渤海湾南岸研究区获得的4个20～30 m钻孔地层资料和相应的AMS14C测年数据,以及前人部分钻孔的研究成果,本文对黄河三角洲利津超级叶瓣的沉积演化框架和时空分布特征进行了重新厘定:研究区全新世沉积环境由早期的河道和泛滥平原沉积,逐渐向海侵过程中盐沼、潮坪和浅海相演化。海平面上升速率减缓之后三角洲开始发育并逐步成陆,直至最后被陆相沉积所覆盖。黄河下游古河道在9000-8000 cal a BP左右可能在黄骅南部入海;大约8000 cal a BP之后,黄河主河道南迁到滨州—惠民一带,并在7000-5500 cal a BP之间发育利津超级叶瓣;利津超级叶瓣的北界可能在马山子和阳信一界,而南界在郭井子和弥河之间;约5500 cal a BP之后,黄河下游古河道可能重新过黄骅入海,于5500-3500 cal a BP左右形成黄骅超级叶瓣;约3500 cal a BP之后,黄河古河道北迁至天津,直至～700 BC左右主流河道入海口再次南迁至河北岐口附近。 相似文献
20.
We report a study of the Holocene coastal sediments of the Hai Phong area of the Bac Bo Plain (also known as the Red River Delta) in northern Vietnam. This is the first attempt to interpret the region's coastal depositional environments in the light of a geological model of Holocene environmental change recognising the interacting roles of Holocene sea-level change, alluvial responses to sea-level fluctuation, and tidal environment sedimentation. The coastal sediments overlie a Pleistocene land surface, and represent the Holocene marine transgression and regression. Prior to c .6000 bp , the sea rose to around or above its present elevation, converting the Pleistocene terrestrial landscape to a Holocene tidal landscape of tidal flat, channel and mangrove environments. Sea-level lowering by c .4000 bp triggered a switch in dominant sedimentary processes, allowing floodplain sediments to be deposited increasingly seawards. 相似文献