Foraminifera and tidal notches: Dating neotectonic events at Korphos,Greece

Fossil assemblages of foraminifera and thecamoebians from three salt-marsh cores recovered at Korphos, Greece, provided evidence for five transgression events since the mid Holocene. Marsh accretion rates based on radiocarbon-dated peat and geomorphic evidence from a series of discrete, v-shaped, submerged tidal notches indicated that these transgression events were rapid and episodic. Correlation of the tidal notches with the transgression horizons in the salt-marsh stratigraphy revealed a stepwise pattern of relative sea-level change at Korphos, which is best explained by coseismic subsidence related to fault displacement (earthquakes) associated with the Hellenic subduction zone. A comparison between the Korphos data and a model of Holocene sea-level change for the Peloponnesus reinforces this interpretation as sea-level rose in a series of jumps by amounts greater than accounted for by eustatic and glacio-hydro-isostatic factors (up to ~ 2.0 m). This study illustrates that by combining microfossil, sedimentary and geomorphic records of past sea-level change, problems frequently encountered with each record individually (e.g. dating submerged notches and autocompaction of marsh sediments) may be overcome.     

Facies architecture of the mixed carbonate/siliciclastic inner continental shelf of west-central Florida: implications for Holocene barrier development

Sediment vibracores and surface samples were collected from the mixed carbonate/siliciclastic inner shelf of west–central Florida in an effort to determine the three-dimensional facies architecture and Holocene geologic development of the coastal barrier-island and adjacent shallow marine environments. The unconsolidated sediment veneer is thin (generally <3 m), with a patchy distribution. Nine facies are identified representing Miocene platform deposits (limestone gravel and blue–green clay facies), Pleistocene restricted marine deposits (lime mud facies), and Holocene back-barrier (organic muddy sand, olive-gray mud, and muddy sand facies) and open marine (well-sorted quartz sand, shelly sand, and black sand facies) deposits. Holocene back-barrier facies are separated from overlying open marine facies by a ravinement surface formed during the late Holocene rise in sea level. Facies associations are naturally divided into four discrete types. The pattern of distribution and ages of facies suggest that barrier islands developed approximately 8200 yr BP and in excess of 20 km seaward of the present coastline in the north, and more recently and nearer to their present position in the south. No barrier-island development prior to approximately 8200 yr BP is indicated. Initiation of barrier-island development is most likely due to a slowing in the Holocene sea-level rise ca. 8000 yr BP, coupled with the intersection of the coast with quartz sand deposits formed during Pleistocene sea-level highstands. This study is an example of a mixed carbonate/siliciclastic shallow marine depositional system that is tightly constrained in both time and sea-level position. It provides a useful analog for the study of other, similar depositional systems in both the modern and ancient rock record.     

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.     

Holocene sedimentation of a wave-dominated barrierisland shoreline: Cape Lookout, North Carolina

The sedimentary record of 130 km of microtidal (0.9 m tidal range) high wave energy (1.5 m average wave height) barrier island shoreline of the Cape Lookout cuspate foreland has been evaluated through examination of 3136 m of subsurface samples from closely spaced drill holes. Holocene sedimentation and coastal evolution has been a function of five major depositional processes: (1) eustatic sea-level rise and barrier-shoreline transgression; (2) lateral tidal inlet migration and reworking of barrier island deposits; (3) shoreface sedimentation and local barrier progradation; (4) storm washover deposition with infilling of shallow lagoons; and (5) flood-tidal delta sedimentation in back-barrier environments.

Twenty-five radiocarbon dates of subsurface peat and shell material from the Cape Lookout area are the basis for a late Holocene sea-level curve. From 9000 to 4000 B.P. eustatic sea level rose rapidly, resulting in landward migration of both barrier limbs of the cuspate foreland. A decline in the rate of sea-level rise since 4000 B.P. resulted in relative shoreline stabilization and deposition of contrasting coastal sedimentary sequences. The higher energy, storm-dominated northeast barrier limb (Core and Portsmouth Banks) has migrated landward producing a transgressive sequence of coarse-grained, horizontally bedded washover sands overlying burrowed to laminated back-barrier and lagoonal silty sands. Locally, ephemeral tidal inlets have reworked the transgressive barrier sequence depositing fining-upward spit platform and channel-fill sequences of cross-bedded, pebble gravel to fine sand and shell. Shoreface sedimentation along a portion of the lower energy, northwest barrier limb (Bogue Banks) has resulted in shoreline progradation and deposition of a coarsening-up sequence of burrowed to cross-bedded and laminated, fine-grained shoreface and foreshore sands. In contrast, the adjacent barrier island (Shackleford Banks) consists almost totally of inlet-fill sediments deposited by lateral tidal inlet migration. Holocene sediments in the shallow lagoons behind the barriers are 5–8 m thick fining-up sequences of interbedded burrowed, rooted and laminated flood-tidal delta, salt marsh, and washover sands, silts and clays.

While barrier island sequences are generally 10 m in thickness, inlet-fill sequences may be as much as 25 m thick and comprise an average of 35% of the Holocene sedimentary deposits. Tidal inlet-fill, back-barrier (including flood-tidal delta) and shoreface deposits are the most highly preservable facies in the wave-dominated barrier-shoreline setting. In the Cape Lookout cuspate foreland, these three facies account for over 80% of the sedimentary deposits preserved beneath the barriers. Foreshore, spit platform and overwash facies account for the remaining 20%.     

日照近岸海域晚更新世以来地层结构及沉积环境演化

根据在日照近岸海域施工的地质钻孔和浅地层剖面测量资料,对比南黄海已有钻孔成果,系统地开展日照近岸海域晚更新世以来地层结构特征识别和沉积环境演化重建。结果表明:日照近岸海域沉积地层中见含有有孔虫化石的第二海相层,形成年代介于34.3~41.4 cal.ka B.P.,对应MIS3的暖湿阶段,该层位可能与古三角洲有关。沉积层从上往下分别为:滨海相细砂混杂泥质沉积层(命名为DU1沉积单元);河流-河口相粉砂质黏土夹粗砂、粉砂层(DU2沉积单元);浅海相粉砂质黏土夹粗砂层(DU3沉积单元);河流-湖泊相粗砂夹黏土层(DU4沉积单元)。晚更新世以来日照东部南黄海海域主要经历了2~3次显著的海侵和海退,各区域因条件不同表现有所差异:日照近岸浅水区主要表现为两次海侵和海退,东部深水区主要表现为三次海侵和海退,由于地势高低和侵蚀破坏等原因,总体表现为从离岸深水区域向近岸浅水区域海相地层厚度逐渐减少的趋势,部分地层出现尖灭消失。     

Mid-Holocene evolution and paleoenvironments of the shoreface–offshore transition, north-eastern Argentina: New evidence based on benthic microfauna

A sedimentary record spanning 5792–5511 cal yr BP and 3188–2854 cal yr BP was recovered at 36° 45′ 43″ S–56 ° 37′ 13″ W, south-west South Atlantic. The sedimentological features and micropaleontological (benthic foraminifera and ostracoda) content were analyzed in order to reconstruct paleoenvironmental conditions. Considerable environmental fluctuations are indicated by all these proxies. Five different stages were distinguished: Stage 1 (ca. 5800–5000 cal yr BP) consists of muddy sand with abundant microfossils. In this interval, species typical for inner marine shelf environments maintained a high abundance. Stage 2 consists of plastic light greenish grey clays barren of microfossils, and probably represents fluvial input from the de la Plata River to the shelf contemporaneous of a lowering of sea level. Stage 3 is composed of brownish yellow sandy silts, and represents increasing marine conditions in the area as reflected by higher faunal diversity and typical foraminifera of inner shelf environments. Stage 4 is made of homogeneous mud, barren of microfossil, which represents a new pulse of fluvial input to the shelf in consequence of a new fall in sea level. The final part of the core (Stage 5) is a coarsening upward sequence, grading from greeny brown clayey sandy silts to coarse shelly sands and represents the modern sedimentation in the area. This interpretation strengthens the stepped model of late-Holocene sea-level fall between 5511–5792 cal yr BP and 2854–3188 cal yr BP in Buenos Aires coast, and agrees with the relative sea-level history previously proposed by some authors from western South Atlantic coasts.     

Global sea-level control on local parasequence architecture from the Holocene record of the Po Plain,Italy

Holocene deposits exhibit distinct, predictable and chronologically constrained facies patterns that are quite useful as appropriate modern analogs for interpreting the ancient record. In this study, we examined the sedimentary response of the Po Plain coastal system to short-term (millennial-scale) relative fluctuations of sea level through high-resolution sequence-stratigraphic analysis of the Holocene succession.Meters-thick parasequences form the building blocks of stratigraphic architecture. Above the Younger Dryas paleosol, a prominent stratigraphic marker that demarcates the transgressive surface, Early Holocene parasequences (#s 1–3) record alternating periods of rapid flooding and gradual shoaling, and are stacked in a retrogradational pattern that mostly reflects stepped, post-glacial eustatic rise. Conversely, Middle to Late Holocene parasequences (#s 4–8) record a complex, pattern of coastal progradation and delta upbuilding that took place following sea-level stabilization at highstand, starting at about 7 cal ky BP. The prominent transgressive surface at the base of parasequence 1 correlates with the period of rapid, global sea-level rise at the onset of the Holocene (MWP-1B), whereas flooding surfaces associated with parasequences 2 and 3 apparently reflect minor Early Holocene eustatic jumps reported in the literature. Changes in shoreline trajectory, parasequence architecture and lithofacies distribution during the following eustatic highstand had, instead, an overwhelming autogenic component, mostly driven by river avulsions, delta lobe switching, local subsidence and sediment compaction. We document a ∼1000-year delayed response of the coastal depositional system to marine incursion, farther inland from the maximum landward position of the shoreline. A dramatic reduction in sediment flux due to fluvial avulsion resulted in marine inundation in back-barrier position, whereas coastal progradation was simultaneously taking place basinwards.We demonstrate that the landward equivalents of marine flooding surfaces (parasequence boundaries) may be defined by brackish and freshwater fossil assemblages, and traced for tens of kilometers into the non-marine realm. This makes millennial-scale parasequences, whether auto- or allogenic in origin, much more powerful than systems tracts for mapping detailed extents and volumes of sediment bodies.The Holocene parasequences of the Po coastal plain, with strong age control and a detailed understanding of sea-level variation, may provide insight into the driving mechanisms and predictability of successions characterized by similar depositional styles, but with poor age constraint, resulting in more robust interpretations of the ancient record.     

Holocene environmental change and the accumulation–erosion balance of sheltered river-mouth sediments, Göteborg, SW Sweden

Holocene sedimentological change was investigated in 15 sediment piston cores (250 cm long) from the mouth of the Göta älv River, outside of Göteborg, which is sheltered by an archipelago. The main objective was to interpret recent, natural and human-induced influences upon the accumulation–erosion balance and the sedimentary environment from Holocene sediment units. The five main units are: consolidated glaciomarine clay (Facies gC) lowermost, consolidated estuarine clay (Facies dC), soft sub-recent sediment (Facies omC and Facies C) uppermost and dumped sediment (Facies D) in some parts of the study area. The sediment facies are divided by two major hiatuses: (a) the early Holocene hiatus between Facies gC and dC involves a time gap of at least 7000 years, ending at ca. 4000 BP and (b) the late Holocene hiatus between the consolidated clays (Facies gC and dC) and Facies omC spans 1000 years and ends ca. 50 BP (i.e. 100 years ago). Both hiatuses probably relate to the effects of isostatic land uplift. Surface sediments consist mainly of an organic-matter-rich clay facies, suggesting changes in the trophic state of the estuary during the last 100 years. Together with human-induced increased river erosion and loss of accommodation space in the estuary, this caused the onset of sedimentation in the estuary. The recent sediments are contaminated with heavy metals (Cu, Zn, Pb, Hg), with highest concentrations in the lower part of Facies omC.     

Yangtze offshore,China: highly laminated sediments from the transition zone between subaqueous delta and the continental shelf

This study examines the deposition of highly laminated muddy sediment in vibrocores recovered from a depth of 40–55 m of water and located 120 km east of the Yangtze River mouth. X-radiographs show numerous sharp-based sedimentary rhythmics with nearly parallel and undulated laminations, interbedded with silty lenses and interbeds. The laminated sediment varies from clayey silt to silty clay. AMS radiocarbon dates on well-preserved bivalves are primarily younger than 5500 y BP, indicating the formation of the laminated sediment under the present sea-level conditions. Macro- and microfossils in the sediments are consistent with the modern offshore sedimentary setting. The laminated sediment originated from the Yangtze estuary, but the sedimentation processes were not deltaic. The highly laminated sediment that lies below the normal wave base of 10 m was deposited on the seaward margin of the Yangtze subaqueous delta, closely associated with submarine tidal and storm-generated currents.     

Present-day sedimentation patterns of the Gulf of Cadiz northern shelf from heavy mineral analysis

The sedimentary processes on the northern shelf of the Gulf of Cadiz (SW Spain) are basically controlled by two factors: the different rates of fluvial supply between the northern and southern sectors and the dominant water flows toward the SE. The distribution of heavy minerals shows differences between the two sectors with predominance of ultrastable minerals in the southern sector, in relation to the different supply rates. This distribution is related to the sea-level change during the Holocene, fluvial supplies, and oceanographic factors. The application of statistical multivariate methods to heavy mineral data shows the principal heavy mineral association (epidote—garnet—rutile), which is very similar to that in neighboring terrestrial areas and offers the possibility of referring factors to source areas.     

Stratigraphic framework of sediment-starved sand ridges on a mixed siliciclastic/carbonate inner shelf; west-central Florida

Seismic reflection profiles and vibracores have revealed that an inner shelf, sand-ridge field has developed over the past few thousand years situated on an elevated, broad bedrock terrace. This terrace extends seaward of a major headland associated with the modern barrier-island coastline of west-central Florida. The overall geologic setting is a low-energy, sediment-starved, mixed siliciclastic/carbonate inner continental shelf supporting a thin sedimentary veneer. This veneer is arranged in a series of subparallel, shore-oblique, and to a minor extent, shore-parallel sand ridges. Seven major facies are present beneath the ridges, including a basal Neogene limestone gravel facies and a blue-green clay facies indicative of dominantly authigenic sedimentation. A major sequence boundary separates these older units from Holocene age, organic-rich mud facies (marsh), which grades upward into a muddy sand facies (lagoon or shallow open shelf/seagrass meadows). Cores reveal that the muddy shelf facies is either in sharp contact or grades upward into a shelly sand facies (ravinement or sudden termination of seagrass meadows). The shelly sand facies grades upward to a mixed siliciclastic/carbonate facies, which forms the sand ridges themselves. This mixed siliciclastic/carbonate facies differs from the sediment on the beach and shoreface, suggesting insignificant sediment exchange between the offshore ridges and the modern coastline. Additionally, the lack of early Holocene, pre-ridge facies in the troughs between the ridges suggests that the ridges themselves do not migrate laterally extensively. Radiocarbon dating has indicated that these sand ridges can form relatively quickly (1.3 ka) on relatively low-energy inner shelves once open-marine conditions are available, and that frequent, high-energy, storm-dominated conditions are not necessarily required. We suggest that the two inner shelf depositional models presented (open-shelf vs. migrating barrier-island) may have co-existed spatially and/or temporally to explain the distribution of facies and vertical facies contacts.     

Preliminary investigation of the surficial sediments in the Cap-Breton Canyon (southwest France) and the surrounding continental shelf

A total of 120 grab samples of the surficial sediments in the Cap-Breton submarine canyon and surrounding continental shelf were collected and analyzed by grain-size sieving. A Q-mode Factor Analysis was made on the grain-size data in order to define the most meaningful facies types. Four distinct lithological facies were found to exist: silt and clay, very fine sand, fine sand, and coarse sand. Comparison with previous work and a ¹⁴C date on the silt and clay facies showed that the facies are not contemporaneous. The sands and coarse sands on the shelf were emplaced during the pre-Würm and Würm regressions, and later probably reworked during the Holocene (Flandrian) transgression. The silty clays found in the canyon and on the shelf to the south are younger and represent sediments brought in as suspended load by the Adour and other nearby rivers during the Holocene (Flandrian) transgression.     

文安斜坡东营组沉积相研究

从岩心相,测井相,沉积展布几个方面对文安斜坡东营组的总体沉积特征进行了论述,并将研究区的沉积相类型定义为河流相。通过对研究区岩心相的详细分析,认为东营组主要发育有边滩微相、天然堤微相和泛滥平原微相。在岩心相分析的基础上发现了对沉积相响应较好的三类测井曲线,得出了研究区的测井相模式。根据对该区东营组沉积相的平面展布特征的研究表明,研究区以河流沉积和泛滥平原沉积为主,河道类型主要为曲流河至网状河,总体上呈由东向西方向展布,由早期的河道向下侵蚀作用为主到中晚期的河道侧向侵蚀作用为主,向湖盆方向河道变宽变浅直至消失,呈泛滥平原化,并在此基础上分析得出了泛滥平原化河流相的相模式。     

四川盆地中南部地区中三叠统雷口坡组沉积相研究

川中南部地区中三叠统雷口坡组划分为3个相（开阔台地相、局限台地相、蒸发台地相）、4个亚相（潮下、泻湖、潮阃坪、潮上坪）和17个微相。沉积相横向上总体变化不大，岩性较统一，蒸发岩较发育，纵向上沉积相变化具有同步性。利用单因素法和优势相法，并结合层序地层学研究成果，把雷口坡组分为7个作图单元，较精确地展示了雷口坡纽不同层段的沉积相展布和演化。研究区内雷口坡期的相对海平面升降变化和台地次级洼隆相间的古地貌共同控制着沉积相带展布和演化。雷口坡组以局限台地相为主，主要发育在雷一段1亚段的台内滩微相，为储集体有利的发育相带，多发育于潮间高处与泻湖的过渡区附近相对高能带。     

末次冰盛期后黄河三角洲沉积物的磁性特征及其沉积环境

On the basis of measuring the magnetic parameters of sediment in Core YDZ1, combined with a grain size analysis and Carbon-14 dating, the magnetic properties of sediment and sedimentary environment in the Huanghe(Yellow River) Delta area after the last glacial maximum have been studied. The results show that the ferrimagnetic minerals of a pseudo single domain and multi domain particles dominate the magnetic properties of sediment in Core YDZ1. The imperfect anti ferrimagnetic minerals have more contribution on sediment in a depth of 24.0–22.1 m, and more stable-single domain and pseudo single domain particles exist. The susceptibility of anhysteretic remanent magnetization and the ratio of the susceptibility of anhysteretic remanent magnetization to saturation isothermal remanent magnetization show a decrease trend below depth of 24 m, a marked increase trend in a depth of 24.0–13.5 m, and a rapid decrease at depth of 13.5 m, then a fluctuation trend upward. The above two magnetic parameters and the ratio of the susceptibility of anhysteretic remanent magnetization to the mass susceptibility can be regarded as the proxy indicators for the content of clay(4 μm)and the fine-grained size(32 μm). The sedimentary environment after the last glacial maximum in the Huanghe Delta area has experienced the fluvial facies, the tidal flat facies, the neritic facies, the pro delta facies, the delta front facies and the floodplain facies. Thickness of the Holocene transgression layer is 10.5 m and the depth of substrate is about 24 m according to the YDZ1 core. The sedimentary dynamic has a variation trend with strongweak-strong, which has been proved by the Flemming triangular schema.     

全新世以来珠江三角洲海鸥沙形成过程的地貌动力学分析

海鸥沙是珠江三角洲一个极富特色的沉积砂体。本文基于钻孔资料并结合长周期“动力-沉积-形态”模型, 从沉积学和地貌动力学角度对全新世以来海鸥沙的形成演变过程进行了探讨。海欧沙在全新世的沉积层序自下而上分别为河流相、河口湾浅海相和三角洲相。全新世海侵盛期以来, 虎门涨潮射流和东北—西南向涨落潮流是影响海鸥沙形成演变的主要动力。6000—2500a BP, 受东北—西南向涨落潮流的影响, 海鸥沙中北部地区一直处于冲刷无沉积状态, 由虎门涨潮射流带来的泥沙主要在海鸥沙南部沉积, 沉积速率约为0.67mm·a ^-1; 2500—1700a BP, 随着番禺平原的发育, 东北—西南向涨落潮流逐渐消弱, 海鸥沙进入一个快速沉积期, 平均沉积速率约为15mm·a ^-1, 沉积由两端向中间发展; 1700—600a BP, 随着沙湾水道的形成, 海鸥沙中部迅速发展, 至600a BP左右, 海鸥沙基本形成并出露水面。     

辽东湾晚第四纪层序地层

通过对辽东湾高分辨率浅地层剖面声学地层与典型钻孔沉积地层的对比分析,揭示了研究区晚第四纪MIS5以来的地层层序。辽东湾高分辨率浅地层剖面自下而上划定的6个声学地层单元(SU5、SU4、SU3、SU2、SU12、SU11)与钻孔岩芯划分的6个沉积地层单元(DU5、DU4、DU3、DU2、DU12、DU11)具有良好的对应关系。分别与MIS4期、MIS2期低海面时期的沉积间断密切相关的两个层序界面R5、R3,将辽东湾识别出的地层单元自下而上划分为3个层序(SQ3、SQ2、SQ1)。其中SQ3仅识别出上部的海侵体系域与高水位体系域,对应MIS5期海平面相对较高时期的滨浅海相沉积(DU5);SQ2自下而上由低水位体系域(MIS4期的河流相与河道充填相沉积(DU4))与海侵体系域(MIS3期早中期滨海相沉积(DU3))组成;SQ1自下而上包括低水位体系域(MIS2期的河流相与河道充填相沉积(DU2))、海侵体系域(全新世早中期滨海相沉积(DU12))高水位体系域(全新世高海面以来的浅海相沉积(DU11))。研究区的海侵体系域厚度较薄且变化较小,分布广泛,而低水位体系域厚度与横向分布均变化较大。     

Implication of salt marsh foraminiferal assemblages in Suncheon Bay,South Korea

Analyses of the compositions of benthic foraminifera and sediment, observations of tidal level and salinity, and a geographic survey of the tidal salt marsh in Suncheon Bay were conducted to examine the vertical distribution of foraminifera and evaluate their potential use for sea level studies. The salt marsh is composed mainly of fine-grained silty clay sediment and its salinity is below approximately 11 psu. The tidal current flows in the southwest-tonortheast direction with an average velocity of 26.57 cm/s. A total of 33 species of foraminifera (17 agglutinated and 16 calcareoushyaline) belonging to 24 genera was identified. The species diversity (1.1 on average) was relatively low. Dominant species were Ammonia beccarii, Miliammina fusca, Haplophragmoides wilberti, and Jadammina macrescens. Calcareous foraminifera (29.5%) were dominantly represented by the Ammonia beccarii assemblage, which characterized the region between mean tide level and mean low high water (MLHW). Agglutinated species (70.5%) were represented mostly by Miliammina fusca, Miliammina fusca-Haplophragmoides wilberti, and Haplophragmoides wilberti assemblages, which characterized the MLHW–mean high water (MHW), MHW–mean highest high water (MHHW), and MHHW–Approx. highest high water tide levels, respectively. In particular, the Haplophragmoides wilberti assemblage is believed to represent the highest elevation zone of foraminifera in the salt marshes of Suncheon Bay and is considered to be a reliable indicator of sea level as a result of its narrow vertical range.     

杭州湾地区末次冰盛期第一硬质黏土层粒度特征及其环境意义

对于沉积物粒度分布特征的研究是衡量沉积介质能量,判别沉积地理环境和水动力条件的最基本方法之一。对杭州湾地区河姆渡钻孔的末次冰盛期第一硬质黏土层样品进行系统的粒度分析,并与典型黄土、古土壤、下蜀土及河流相、湖相样品进行对比后发现,该层位样品所显示的粒度分布特征与湖相沉积物极为相似,而与下蜀土及河流相沉积物有所差别。从粒度分布的角度推断,该区第一硬质黏土层的沉积环境为河湖相。     

广东台山淤泥质海岸高分辨率地震资料解释

根据广东台山广海湾150km高分辨率地震资料,研究岬湾型海岸起伏多变的基底和上覆的第四纪沉积层序、沉积演化以及复杂的新构造作用。该区晚第四纪自下而上发育有5个层序：（1）滨海相杂色粘土,下部为河道充填;（2）河道冲积砂;（3）内大陆架粉砂质粘土;（4）滨海相潮坪沉积;（5）河口湾淤泥质沉积。研究区基底形态起伏较大,主要为黑云母花岗岩风化壳及少量变质岩。NNE和NEE向两组断裂系统最为发育,它们控制了盆地发展并经历了两期活动。