Organic Mud Research Articles

The Last Interglacial to Glacial Transition, Togiak Bay, Southwestern Alaska

An 18-m-high coastal bluff at Togiak Bay (northwestern Bristol Bay, southwestern Alaska) exposes marine, lacustrine, fluvial, glacial, volcanic, and organic deposits that record the ∼50,000-year-long transition from the peak of the last interglaciation to the early Wisconsin glaciation. The base of the section is dominated by stratified sand and silt extending up to 4.3 m above sea level; marine diatoms are present, and pollen assemblages are characterized by relatively high percentages of Picea, Alnus, and Betula and low percentages of Poaceae and Cyperaceae. The marine sediment was probably deposited during the peak of marine oxygen-isotope stage (OIS) 5e. An infrared stimulated luminescence (IRSL) age of 151,000±13,000 yr from near the base of the exposure is permissive of this correlation. The marine sand and silt are overlain by 0.8 m of peaty silt with diatoms that record a transition from marine to lacustrine conditions. During this interval, Poaceae and Cyperaceae dominate the pollen assemblages, and Picea and shrubs are nearly absent, suggesting that herb tundra occupied the landscape. This interval probably encompasses OIS 5d on the basis of the herb tundra and an IRSL age of 119,000±10,000 yr from 60 cm below the marine/lacustrine transition. The organic mud is overlain by 3.1 m of stratified sand and organic silt that apparently record shallowing of the lake; reappearance of spruce and shrubs (=OIS 5c?); and subsequent deepening of the lake (=OIS 5b?); followed by aggradation of a floodplain (=OIS 5a?), which was dry at the time basaltic lava buried the site. Thermoluminescence analyses on lava-baked sediment indicate that the eruption occurred 70,000±10,000 yr ago. Sometime thereafter, but prior to 53,600 14C yr B.P. an outlet of the Ahklun Mountains ice cap advanced over the site and deposited ∼7 m of bouldery ice-contact drift. The sedimentary sequence contains at least four tephra beds. Major- and trace-element chemistry provide a basis for correlating two of the tephras with tephra beds at nearby sites. The tephras, luminescence ages, and correlations with marine isotope stages provide the geochronological control to place the Togiak Bay section into a global context. The site serves as an important new reference section for late Pleistocene paleoenvironmental change in eastern Beringia.

A reconnaissance marine geophysical survey in Alexandria, Egypt, for the detection of ancient shipwrecks and other traces of human activity

A detailed marine geophysical survey was planned and carried out in the coastal zone of Alexandria (Egypt), by the Laboratory of Marine Geology and Physical Oceanography of the University of Patras in co-operation with the Hellenic Institute of Ancient and Medieval Alexandrian Studies. The survey aimed to the detailed mapping of the geomorphological and textural features of the seafloor and the detection and recognition of targets, which may to represent wrecks or man-made structures. The following equipment were used: (i) an EG&G260 corrected image side scan sonar, (ii) a Remote Operated Vehicle (R.O.V) Benthos MKII and (iii) a Trimble 4000 Differential Global Positioning System (DGPS). The study of the sonar data has shown that the seafloor is covered by rocky outcrops and loose sediments. The rocky outcrops are layered and cover about 75% of the surveyed zone. The rest of the seafloor is covered by sandy sediments. The sonar survey identified a large number of potentially interesting targets (e.g. shipwrecks) on the sandy seafloor. These targets are located in four isolated areas. The detection and the recognition of the targets is complicated by the presence of cohesionless organic mud of anthropogenic origin The sonar survey has shown the presence of elongated features, which are perpendicular to the Alexandria's shoreline and parallel to the Cape Lochias. These elongated features are detected on sandy seafloor in water depth of about 5 to 8 m, have a maximum depth of about 135 m and a width ranging from 5 to 20 m. At least at one site, two of these features cross each other at a water depth of about 6 m. The visual inspection of the elongated features reveals that consist of well-shaped limestone blocks. The areal extension, the size and the geometrical shape of the elongated features, support the suggestion that some of them may be related to manmade structures.

Role of climate in the rise and fall of Neolithic cultures on the Yangtze Delta

Climatic changes in the Yangtze Delta have played an important role in the emergence, persistence and collapse of civilization. Archaeological excavations in the region over many years have demonstrated that there are several layers of fine sand or organic mud that interrupt the consecutive culture strata in a number of Neolithic culture sites. Continuous biostratigraphical and sedimentological records from the Maqiao cultural site, Shanghai, suggest that the fine sand and organic mud units resulted from expansion of water bodies both by sea‐level fluctuations and from increased flooding during cold and humid episodes of Holocene climates. The absence of human settlement from 7240 BP to 5320 BP in the region was mainly caused by higher sea levels resulting from a warm and humid climate. The Neolithic cultures developed under conditions of lower and more stable sea level as well as warmer and dryer climates between about 4410 BP and 3250 BP. A flood‐induced lake expansion interrupted the civilization in the region at about 4200 BP. Later, higher water tables and expansion of lakes between 3250 BP and AD 618 under a cold and moist climate temporarily terminated settlement on the delta. Later, during the Tang Dynasty, beginning at about AD 618, the region again became suitable for human settlement under conditions of more favourable climate and lower water tables.

Early Holocene environments of the River Ure near Ripon, North Yorkshire, UK

SUMMARY A sequence of peat and calcareous organic mud from the floodplain of the River Ure near Ripon has yielded pollen, plant macrofossils, Mollusca, Coleoptera, and Ostracoda which allow the first recorded reconstruction of earliest Holocene valley-floor environments for this area. A conventional radiocarbon date on a bulk sample of peat yielded an age of 9710 ± 60 bp . The palaeontological evidence suggests that the sediments accumulated in a shallow, slow moving or stagnant water body, surrounded by marshy, damp, grassland, away from contemporary channel processes, probably of a single thread river system. The climate during deposition of the sediments was no warmer than the present, and possibly slightly colder.

Sedimentology, palaeoecology and geochronology of Last Interglacial deposits from Deeping St James, Lincolnshire, England

Pollen, plant macrofossil, molluscan and coleopteran data from organic muds below the low terrace of the River Welland at Deeping St James, Lincolnshire indicate deposition in the mixed oak forest phase of a Late Pleistocene interglacial. Coleopteran and molluscan data suggest summer temperatures up to 4°C warmer than at present in eastern England, and plant macrofossil material suggests a climate more continental than that of Britain in the Holocene. No direct analogue of this biota, however, exists currently in Europe. Biostratigraphical indications from the pollen coleoptera and Mollusca suggest an age in the Ipswichian Interglacial. Thermoluminescence dates between 120 ka and 75 ka and amino-acid ratios with a mean of 0.11 show that deposition of the sediments took place during Oxygen Isotope Stage 5. This accurate dating of a partial Ipswichian succession allows discussion of the ages of a number of other interglacial sites in eastern England of assumed Ipswichian age. Copyright © 1999 John Wiley & Sons, Ltd.

Tropical vegetational change in the late Pleistocene of New Caledonia

The south eastern plateau of New Caledonia (22°S) preserves remnants of a deep regolith of ultramafic soils which is extensively gullied or eroded to form large alluvial fans. Dated sediments from four closed basins on the Plaine des Lacs (ca. 220 m altitude) show that organic muds were accumulating prior to 30,000 yr B.P. Over the next 5000–14,000 years limonitic clays infilled two basins as a result of slope instability in their catchment. Resistant laterite and bog iron surfaces became exposed during the period 30,000–15,000 yr B.P. by erosional events that seem to have been of greater magnitude than any in the earlier Pleistocene. Two sites, Lake Emeric and Lake Suprin, were chosen for pollen analysis. During the phases of organic deposition of these lakes, Nothofagus forests collapsed several times and were replaced by Gymnostoma maquis, apparently as a result of fires. These Pleistocene fires were associated with some inorganic deposition, presumably due to the substantial loss of primary forest cover. Regeneration of forest usually followed after an estimated gap of several centuries. Thus, fire was able to cause forest retreats of the same order of magnitude as that caused by massive fires today. The low nutritional status of the soils or lateritic crusts means that, as now, forest had difficulty reclaiming sites. Human activity is unknown prior to 3000 years ago, so the major erosion is presumed to have had natural causes. Thus, many of the wide-ranging changes are the result of natural instability in the sub-tropics, and some may be much older than hitherto thought. Climate change towards periods of dry, fire-prone, conditions may have been an underlying cause. In the Holocene, some climatic factor, possibly cyclonic storms, seems to prevent organic sedimentation. Switching from cyclone-free to cyclone-prone at the end of the Pleistocene may reflect temperature change in sea surfaces in the region.

Holocene environmental history of a peatland in the Lena River valley, Siberia

A 3.86 m core of peat and organic lake mud from a polygonal peatland in the Lena River valley of Siberia was radiocarbon dated and analyzed for pollen, plant macrofossils, chrysophyte stomatocysts, stable isotopes, and charcoal. At around 7200 BP, a shallow lake or open-water wetland supported diverse aquatic macrophytes. The site had transformed initially into a richer fen with Carex, Comarum palustris, and Drepanocladus and later a poorer fen with Sphagnum which persisted until around 3000 BP. Fire may have been responsible for silt being blown onto the peatland, which changed the hydrological and geochemical conditions for development of the poor fen. Ice accretion led to an increase in the height of the centre of the polygon and expansion of Sphagnum peatland .18O values become progressively more enriched, which reflects more direct input of summer precipitation waters and less groundwater during this period. Finally, the peatland surface was elevated sufficiently to limit water and nutrient supply, thereby allowing Ericaceae and Betula to grow at the coring site. Fire burned the peatland surface and may have exaggerated the extremely slow rate of peat accumulation. Fire may also be a factor in maintaining the open Larix dahurica forest in the region today, while climate may be contributing to reducing postfire regeneration. Fire and climate together may be controlling the character and composition of forests near tree line in the Lena River valley of this part of Siberia.

A late Quaternary ostracod record from Wallywash Great Pond, a Jamaican marl lake

Two assemblages typify the ostracod fauna of a 9.23 meter core taken from Wallywash Great Pond, a small perennial freshwater marl lake in Jamaica. The first, dominated by Cypretta brevisaepta, lived in deep water, similar to present-day conditions. The second, dominated by Candonopsis sp., reflects the existence of a shallower lake. The core has a basal date of c. 125 kaBP. Four inferred deep-water phases occurred in the period 125–93.5 kaBP with periods of inferred shallower water in between. The lake was dry between 93.5 kaBP and c. 10 kaBP as suggested by the absence of ostracods or fossils of other aquatic organisms. Ostracod faunal evidence indicates that there have been three highstands and two lowstands of the lake during the Holocene, although ostracods are not preserved in the organic mud and lignite that formed under swampy conditions as the basin filled at the start of the Holocene and during part of the two subsequent lowstands of the lake. A major hydrological perturbation, associated with the flooding of the nearby Black River catchment around 1.2 kaBP, caused an increase in the ostracod species diversity of the Great Pond, although this was relatively short lived and the lake attained a faunal composition similar to present around 1 kaBP. Major variations in ostracod assemblages in the core thus represent lake-level changes and accord well with previously-published interpretations of water depth based on lithofacies variation and stable oxygen isotope ratios in authigenic carbonates.

Improved method of bacterial enumeration in sandy and deposit-feeder gut sediments using the fluorescent stain 4,6-diamidino-2-phenylindole (DAPI)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 173:299-304 (1998) - doi:10.3354/meps173299 Improved method of bacterial enumeration in sandy and deposit-feeder gut sediments using the fluorescent stain 4,6-diamidino-2-phenylindole (DAPI) Sabrina N. Hymel1, Craig J. Plante2,* 1Graduate Program in Marine Biology, University of Charleston, 205 Fort Johnson Road, Charleston, South Carolina 29412, USA 2Department of Biology, Grice Marine Laboratory, University of Charleston, 205 Fort Johnson Road, Charleston, South Carolina 29412, USA *E-mail: plantec@cofc.edu ABSTRACT: A series of optimization experiments was carried out to improve visualization of DAPI-stained bacteria extracted from sandy sediments and midgut sediments of the deposit feeder Abarenicola pacifica. Treatments tested for the effects of fixative removal (prior to sonication) and removal of unbound DAPI (prior to filtration). Both quantitative (mean number of cells) and qualitative (cell fluorescence, background fluorescence, dispersion, cell counting rates) characteristics were examined. Removal of fixative and/or unbound stain did not significantly increase mean cell counts versus controls for sandy sediments, although variability (unbiased coefficient of variation) was reduced. Qualitative characteristics were not significantly improved by removing fixative, although visualization improved slightly and counting rates (cells s-1) increased with final removal of stain. In midgut sediments, removal of fixative and unbound stain resulted in increased cell counts as well as decreased variability. Significant improvements in contrast (i.e. increased cell fluorescence, decreased background fluorescence) were observed, as well as increased counting rate. These results indicate that both qualitative and quantitative aspects of direct counts may be improved by these methods for problematic sediments such as deposit-feeder gut and fecal samples or highly organic muds. KEY WORDS: Bacteria · Enumeration · Sediment · Epifluorescence · DAPI · Deposit-feeder Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 173. Publication date: November 12, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Holocene Fluctuations of a Meromictic Lake in Southern British Columbia

Holocene deposits of Mahoney Lake, a meromictic saline lake located in a closed basin in the semi-arid Okanagan Valley, contain evidence of frequent and marked changes in lake depth (up to >12 m/10014C yr) probably caused by short-term changes in effective precipitation. We studied a 5.45-m-long core comprising a basal layer of inorganic mud overlain by a succession of layers of calcareous laminated and nonlaminated organic mud, marl, and sand. We used Mazama tephra to adjust nine radiocarbon ages for the hardwater effect. Meromixis developed ca. 900014C yr B.P., and the lake has been episodically meromictic for about half the time since. Because of close linkages between sediments and depositional environments in meromictic and saline lakes, we infer that laminated sediments indicate meromictic conditions and high lake levels (>ca. 12 m water depth), whereas thick marl layers and nonlaminated sediments indicate nonmeromictic conditions and thus low lake levels (<ca. 8 m depth). Many of the inferred short-term climatic changes have not been identified in previous studies in northwestern North America, perhaps because of insensitive climatic proxies, inadequate temporal resolution, or discounting of anomalous findings.

Early Holocene pollen and molluscan records from Enfield Lock, Middlesex, UK

Pollen, molluscan data, and sediment analyses, are presented from Enfield Lock, Middlesex, UK. The pollen data, from organic muds, show similarities with Pre-boreal and Boreal pollen spectra at other sites in the Thames basin; an overlying non-polleniferous marl yielded a diverse molluscan fauna. Radiocarbon dates on organic sediments at the site confirm the pollen records are from the early Holocene, but the shelly marl is less easily dated; there are affinities with molluscan records of the early to mid Holocene from sites elsewhere in southeast England. The biological and sedimentological data chronicle the changing depositional environments of the floodplain of the River Lea during four millennia of the early to mid Holocene. Charcoal records imply that fire was, at times, a significant influence on early Holocene vegetation, but a lack of local human artefacts contrasts with evidence for Mesolithic sites elsewhere, and has implications for the interpretation of early Holocene pollen assemblages from charcoal-rich sediments.

The problem of vast numbers of cladodont shark denticles in the Pennsylvanian Excello Shale of Pike County, Indiana

While studying X-ray films of new iniopterygians (Subterbranchialia, Chondrichthyes) in the Excello Shale from the Field Museum of Natural History's Bethel Quarry locality in southern Pike County, Indiana, a moderately dense spread of tiny cladodont shark denticles was noticed on the radiographs, confined to micro-horizons of shale about 7.5 mm thick, which also contained the iniopterygians.These denticle spreads, which are entirely unrelated to the iniopterygians, but are seen on X-ray films of most of the chondrichthyan skeletons collected from a sheet of Excello Shale of about 500 m2 in extent, and mostly from two very fossiliferous levels, have an average density of about nine denticles per 1 cm2. Because the chondrichthyan skeletons were collected from all parts of the quarry, it is probable that the denticle spreads in several micro-horizons extended over the entire quarry area and perhaps beyond. The number of denticles in each of the micro-horizons in 500 m2 of shale thus amounts to about 4.6 million.A discussion of the origin of these vast numbers of cladodont denticles, given a variety of taphonomic and depositional constraints, results in the conclusion that these large numbers of denticles could not have resulted from the two species of sharks, Denaea meccaensis and Stethacanthulus longipeniculus, that are members of the burial assemblage and bear dentition teeth indistinguishable from those in the areal spread. Evidence suggesting very rapid deposition of organic muds that produced the characteristic Mecca Quarry type carbonaceous, sheety shales rules out the possibility of accumulation of the denticle spreads over extended periods of time. Because sharks do not possess nearly enough dentition teeth to account for this occurrence, one must entertain the possibility that the denticles are not all dentition teeth, but perhaps for the most part mucous membrane (or even dermal) denticles, though none such are presently known to display cladodont design.

A Neoproterozoic multi-phase rift sequence: the Grampian and Appin groups of the southwestern Monadhliath Mountains of Scotland

The Grampian and Appin groups of the southwestern Monadhliath Mountains form the earliest known syn-rift sequences of the Scottish central Highlands. They were likely to have formed in an intracontinental setting and represent deposition of mixed clastic and carbonate shallow and deep marine strata. The Grampian Group of the southern Monadhliath Mountains was deposited during a period of initial basin rifting (NW–SE extension) followed by a phase of thermal subsidence. Syn-rift sediments comprise a 2.5–6 km thick turbidite system. Thermal subsidence brought about the basinward progradation of shallow marine shelf sediments resulting in the infilling of pre-existing basin topography. The overlying Appin Group commenced with deposition of a shallow marine sequence alternating between nearshore tidal sand and offshore mud deposition. This formed in response to renewed rifting and concomitant subsidence. Accelerated rifting resulted in localized footwall uplift and erosion while sedimentation continued in the hanging-wall areas. Resultant subsidence, perhaps partly thermally driven, caused gradual basin widening and produced an onlapping marine sequence. There followed a period of progressive clastic deprivation when carbonates were precipitated, and at the onset of anoxic conditions, deposition of organic muds. The fundamental structural elements responsible for the formation of the Grampian and Appin group basins were also influential in the orogenic evolution of the basin-fill. Half-graben fills were deformed to produce regionally extensive folds such as the Stob Ban–Craig a’ Chail Synform.

Tsunami deposits in a lacustrine sequence of the Sanriku coast, northeast Japan

Lacustrine deposits of the Pacific coast of northeast Japan, consisting mostly of black organic mud, contain intercalated thin beds of well-sorted medium sand. Examination of the deposits from a coastal site of Sanriku has revealed that sand grains are of marine origin and are fractions of deposits in marshy ponds, transported from the littoral environment by a great flooding of seawater. The mode of sedimentation shown in the thin beds of sand implies that they were deposited by tsunamis, each with a maximum rise of 1 m or more above sea level.

Preliminary environmental reconstructions from late Quaternary pollen and mollusc assemblages at Egg Lagoon, King Island, Bass Strait

Abstract A late Quaternary environmental record is currently being developed from Egg Lagoon, King Island, Bass Strait, a site which is geographically well situated to contribute towards a history of the Bass Strait region. Environmental reconstructions are based on a stratigraphic survey and pollen, charcoal and mollusc analyses of sediment core samples. The recorded stratigraphy includes five sedimentary units representing estuarine‐marine, freshwater lake and swamp depositional environments. Amino‐acid racemization analyses of marine shells indicate a greater than last interglacial age for the basal estuarine‐marine unit, while radiocarbon analyses of organic muds and wood suggest that a substantial section of the overlying freshwater lake and swamp facies is beyond the conventional limit for this technique. Local pollen assemblages represent freshwater lake and swamp plant communities that have varied presumably according to water level changes at the site. Regional pollen assemblages represent terrestrial herbaceous communities, believed to have existed under cooler and drier climates than today, and Eucalyptus‐ and Phyllocladus‐dom'maied forests and woodlands from periods with greater effective precipitation than at present. A sustained increase in charcoal representation dating from at least 39 000 years before the present may indicate an anthro‐pogenically induced change in the fire regime, consistent with the earliest dates for human occupation in mainland Tasmania.

The Pretoria Saltpan: a 200,000 year Southern African lacustrine sequence

The Pretoria Saltpan is a circular crater 1130 m in diameter and is situated some 40 km N of Pretoria (lat. 25°34′30″/long. 28°04′59″E). A recent tube sampling and core drilling programme has revealed an infilling consisting of some 90 m of fine lacustrine sediments (chiefly organic muds, underlain below 30 m depth by micrites) which rest upon a further 61 m of coarse clastic debris. Granite bedrock was encountered at − 151 m. Broad sedimentary zones correspond with major phases in the evolution of the crater lake. Superimposed cyclical patterns of accumulation reflect environmental changes on millenial to seasonal timescales. 14C age determinations on algal debris from the upper 20 m of the core indicate a mean rate of sedimentation of about 1 m/2000 yr, suggesting that the lacustrine sequence may span almost 200,000 yr. Over this period major environmental changes are apparent from sedimentological, chemical, mineralogical and isotopic analyses of the core and studies of the pollen spectra and diatom assemblages present within it. This long continental sequence is therefore providing a high-resolution palaeoenvironmental record for southern mid-latitudes over much the same period as is covered by the Vostok ice-core in Antarctica.

Lake Bogoria, Kenya: soda, hot springs and about a million flamingoes

Lake Bogoria is a saline, alkaline, meromictic lake in a geothermally active part of the Kenya Rift Valley. Coring of the lake floor has shown two types of sedimentation – a shallow fan–deltaic clastic zone and a deeper zone with alternating organic muds and evaporites. The organic muds formed during periods of relatively high lake level and high microbial productivity, the evaporites during more arid phases. Analyses of the cores show many environmental fluctuations during the past 30000 years, related to regional climatic changes and to local tectonic and hydrological controls.

Late Quaternary palaeolimnology of a tropical marl lake: Wallywash Great Pond, Jamaica

Wallywash Great Pond (17° 57′ N, 77° 48 W, 7 m a.s.l.) is the largest perennial lake in Jamaica. It occupies a fault trough within the karstic White Limestone. The Great Pond is a hardwater lake with a pH of 8.2–8.6 and an alkalinity of 3.6–3.9 meq 1−1. Its chemistry is strongly influenced by the spring discharge from the limestone. The lake water is subject to degassing, evaporation and bicarbonate assimilation by submerged plants and algae, resulting in marl precipitation. A 9.23 m core (WGP2), taken from a water depth of 2.8 m, was analysed for magnetic susceptibility, loss-on-ignition, carbonate content, mole % MgCO3 in calcite, and stable isotopes in the fine carbonate fraction. The chronology is based on ten14C and four U/Th dates. Four main sediment types alternate in the core: marl; organic, calcareous mud; organic mud or peat; and earthy, brown, calcareous mud. The marls represent periods of wet/warm climate during sea-level highstands and the organic deposits, shallower, swampy conditions. In contrast, the brown, calcareous muds were laid down when the lake was dry or ephemeral. The last interglacial (120 000- 》 106 000 yr BP) is represented by three distinct marl units. After a dry interval, stable, wet/warm conditions set in from 106 000 to 93 000 yr BP. A dry/cool climate prevailed between 93 000 and at least 9500 yr BP. Three subsequent cycles of alternating wet and dry conditions culminated in flooding of the basin by the Black River during the late Holocene. These recent events cannot be accurately dated by14C due to significant and temporally-variable inputs of ‘dead’ carbon from the springs.

Environmental evolution of gucheng lake for the past 4000 years revealed by a short core

对固城湖6.2m深的现代沉积物柱状岩芯进行了放射性同位素、粒度、有机质含量、有机质σ¹³C和孢粉分析。沉积记录巾各项环境指标的变化表明, 4ka以来固城湖经历了高湖面—低湖面—高湖面的显著变化。气候变化是影响湖泊环境演化的重要自然因素, 但2.5ka以来人类活动对湖泊演化的影响显得更为明显。特别是2.5ka和1.1ka两次人类对湖泊水系的改造是引起湖泊环境两次突变的主要因素。;The sediment from a columnar core with a depth of 6. 2 min Gucheng Lake was analyzed with regard to radioisotope, grain size, organic matter content, δ¹³C of organic matter and pollen. ¹⁴C dating of 3630+230a was obtained from the organic mud sample 6. 1 m below the core top. The average sedimentary rate of recent sediments is 0. 71mm/a resulting from ²¹⁰Pb dating technique. According co the lithology and various environmental m ar kers of the sediment five lithoiogical beds and five correspondins stages of environmental evolution may be divided from the core profile:(1)5.1-6.2m , green-greymud and siltymud.Clay content(CL), organic matter conent(LOI)and δ¹³C values are all higher(77.5 , 5.6 and - 25.36‰ PDB respectively ) in th interva1. High-lake level was reflected during the period .(2) 3 .5- 5· 1n1, grey silty m ud. CL, LOI and δ¹³C va]ues are reduced slightly (62.2% , 5.0% , and-25.98%0 respectively). Lake-level was also higher in the period .(3) 1.2- 3.5m , grey muddy fine grained sand and sir. CL .LOI an d 6 C are all at their low est values in the profile (13.3 .3.7 and 26.31‰ respectively).Thelake—level was verylow in thetime. (4) 0.3- 1.2m. grey sandY an d silty mud. CL , LOI, and 6 C values are risen again to some extent(41.2% , 7.8 and -25.`` respectively ).The lake was expan ded during the t[nle. (5) 0 0.3m , dark—grey silty mud. CL , LOI and δ¹³C values are all quite high (70.3-10.6 and - 22.1 4‰ respectively).The Inke-level was probably higher during the period-According to the pollen forms and contents in the core profile, eight palynological assemblage zones are divided as follows;(I)Quercus-Casta~ea zone, (Ⅱ)Pinus-Quercus- Polypodiaceae zone, (Ⅲ )Quercus-Graminca- Typha zone, (IV)Graminea-Arteinsria-Quercus zone, (V ) Quercus-Graminca- Typha zone, (VI) Gram inea Pigza-Quercu zone, (Ⅶ) Qercus-Pinus-Castanea zone an d (Ⅷ )P inus-Graminea-Ariternaisira-Qzone. Com par ison of climatic change sequence resulting from pollen an alysk to the lake—level evolution m ay lead to the discovery that the clim ate change was coincident w ith lake—level change before 2.5 ka B.P.(6.2— 3.5m in the core)and the climate waS the main controlling factor for the lake expansion. But the regularitlos of lake—level fluctuation ar e not conformable to the clim atic change s.nce 2.5 ka B.P.(0- 3.5m in the core). Obviously the lake environm ent change was not controlled dom inantly by clim ate factor during the time. On the contrar y, human activities were the leading factor that affected lake environment evolution. In the historical records, the Xux[River channaled at caused Gucheng Lake water our eastwards an d also caused the lake to shrink intensely.As a result, the lake was converted into Taihu Lake drainage bas in. U P to 893 A .D. as five bars were built along the Xuxi River.the lake water flowing eas twards was CUt off resultin g in an expansion of lake ar ea and the lake beca me the Changjan g River drainage bas in again. Therefore, it is inferred that the twice abrupt changes of lake environment at 3.5m and 1.2m of the core are resulted from hum an’g tras form atinn on the lake water system in historical time.

住民の環境意識および音環境 （その２） 「ＵＴＳＵＲＯ」によるヘドロの浄化について

Now we are facing to the age for earth environment.The bottom of Tokyo Bay or Osaka Bay is covered by thick deposit of organic mud.Although it has caused water pollution and much affected to the echological and fishery environment, the solution has not been obtained neither from the viewpoint of study nor from that of administration.In this report, we present about our new findings of the application of the idea of marine hollow “UTSURO” to the purification of organic mud.In “UTSURO”, water is purified by natural energy such as waves or tides, which enables the solar ray to reach the sea bottom and decompose the organic mud.