Limnic Sediments Research Articles

Palaeoecology of two lake basins from Disko, West Greenland

AbstractThe macrofossils, lithology and chronology of two lake basins on Disko in central West Greenland have been investigated. Both lakes were isolated from the sea in the mid‐Holocene as a result of relative land uplift. A marine‐brackish‐limnic sequence was recovered from the Qivittut Lake. The marine fauna is unusually diverse, whereas the brackish water fauna consists only of few species. Immediately after isolation the lake passed through a short‐lived eutrophic phase, after which stable, mesotrophic conditions were established. From the second lake basin, the Fortunebay Lake, only limnic sediments were recovered. This lake record demonstrates that rather stable conditions have persisted since mid‐Holocene times. Both lakes show anomalously high accumulation rates.

Mineralogy and stratigraphy of three deep lateritic profiles of the Jos plateau (Central Nigeria)

The Fluviovolcanic Series (= FVS) of the Jos plateau, Central Nigeria are an upper Eocene to middle Miocene time-equivalent to the Continental Terminal of the surrounding basins. It can be divided into a lower part with mafic to intermediate and even felsic volcanic rocks (according to the Zr/TiO 2), fluvial or limnic sediments and an upper part of mafic volcanic rocks with intercalated transported pisoids and quartz grains. Palynomorphs of a limnic clay reflect a subtropical to montane tropical vegetation rich in plant species. The lower part of the FVS often shows distinct tilting as a result of neotectonic movement along a reactivated conservative plate boundary in continuation of the transatlantic Romanche fracture zone. The various rocks have been completely converted into deep (often > 80 m) polygenetic soils which consist of repetitive sequences of saprolite, mottled horizon and ferricrete. The ferricrete represents a paleosurface and protects the profiles against erosion. The mineralogy of 3 profiles consists essentially of kaolinite with various amounts of goethite and hematite; gibbsite appears in one confined horizon, whereas anatase and residual (weathered) ilmenite and quartz occur as accessories. The presence or absence of ilmenite, quartz and anatase in the various sections of the profiles were taken as an indicator for different parent rocks. The crystallinity of kaolinite (Hinckley index), the crystal size and Al substitution of goethite and hematite varied sectionwise indicating different weathering environments. For example, the goethite in laminar-massive ferricretes appearing at the base of all 3 profiles had lower Al substitution and somewhat larger crystals than that of the pisolitic-vermiform ferricretes and was associated with redoximorphic conditions. On the basis of mineralogical, paleontological, sedimentological and absolute K/Ar age of basalts, the profiles were placed into the transition from Paleogene to Neogene and stratigraphic correlation was suggested.

A view on microbial ecology

In the research areas referred to above the Department of General Microbiology in Copenhagen is involved directly or indirectly. Microbial ecology in Denmark is wider in its scope and other departments or groups are active in different research areas.Marine and limnic sediments have been studied with great success in the Department of Ecology and Genetics in Aarhus, and in recent years several microelectrodes for detailed studies of microbial processes have been developed.A new research group on rhizosphere studies has been established at the Agricultural University, Section for Microbiology. New detection systems are being developed for study of specific bacterial strains (Pseudomonas spp) and their functional role.All of these research areas are simultaneously being studied all over the world and often in cooperation between different research groups. Some of the important global themes are connected with: the microbial response to climate change; the production of toxins in food for man and animals; the dispersal, growth and survival of pathogenic organisms in the environment; the microorganisms in pollution control and bioremidiation; and microbiological control with pathogenic organisms.With the introduction of molecular methods in microbial ecology it seems as if a series of ecological themes will be addressed with appropriate methods. The stability of strains and of populations will be examined, the exchange of genetic material, the adaptation to changing environmental conditions will find new microbial ecology and also of interest for the use of microorganisms by society is expected. *** DIRECT SUPPORT *** AAK17001 00013.

Postsettlement changes in limnic sediments from southern Alberta, Canada

Analysis of lake sediment cores from nine water bodies in southern Alberta found relatively greater quantities of organic matter and an increased abundance of silt in post- relative to pre-European settlement sediments. These greater abundances are attributed to increased lake nutrient levels and increased wind erosion due to the development of agriculture in the region.

Radiocarbon Dating of Limnic Sediments: A Comparative Analysis and Discussion

EcologyVolume 72, Issue 3 p. 1150-1155 Article Radiocarbon Dating of Limnic Sediments: A Comparative Analysis and Discussion G. M. MacDonald, G. M. MacDonaldSearch for more papers by this authorR. P. Beukens, R. P. BeukensSearch for more papers by this authorW. E. Kieser, W. E. KieserSearch for more papers by this author G. M. MacDonald, G. M. MacDonaldSearch for more papers by this authorR. P. Beukens, R. P. BeukensSearch for more papers by this authorW. E. Kieser, W. E. KieserSearch for more papers by this author First published: 01 June 1991 https://doi.org/10.2307/1940612Citations: 119AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume72, Issue3June 1991Pages 1150-1155 RelatedInformation

The fossil geothermal system of the Baden-Baden trough (northern Black Forest, F.R. Germany)

Limnic sediments of the Upper Carboniferous, Lower Permian and Triassic from the Baden-Baden trough were hydrothermally altered during the Jurassic. Concentric alteration halos, each having a characteristic mineral composition, were formed. From center to margin, zones of sericitization, albitization and weak alteration covering an area of > 100 km 2 are evident. These zones indicate decreasing hydrothermal influence, whereby the solutions must have risen in the center. The chemistry of mica, changing systematically from a muscovitic toward an illitic composition, also reflects this trend; the boron content increases from 75 to 205 ppm. The estimated maximum alteration temperature ranges between 240° and 290°C. These remarkable changes are obviously early manifestations of geothermal events related to the development of a continental rift (Rhine graben).

A Comparison of Sedimentation and Environmental Change in New Guinea Shallow Lakes

Contemporary mires in the equatorial rainforest of Malesia have evolved from shallow lakes. Often these occupy karstic basins in ultrabasic or volcanic rocks. There is a marked difference in the rate of infilling of the lakes, depending on the degree to which nutrient accession from allochthonous sediments has occurred. Some lakes have infilled slowly with no allochthonous input; these variations in the rate of sedimen- tation reflect the controls of climatic change and human modification of the catchment. Others have infilled very rapidly, and in these the role of tephra fall is crucial. The boost to nutrient levels afforded by periodic tephra fall is reflected in the changes recorded in limnic sediment and terrestrial pollen derived from the surrounding vegetation, An episodic decline in Nothofagus and other pollen reflects the increase in floristic and structural complexity of the rainforest vegetation in the absence of disturbance. Catchment instability, either from tephra fall or landslips, creates oppor- tunities for new generations of trees within a climatic regime which is variable but relatively unchanged through time.

Palaeogeobotanical evaluation of the Holocene profile from the Řežabinec fish-pond

Stratigraphic, pollen and macroscopic analyses of the Holocene limnic and peat sediments from the Řežabinec fish-pond (southern Bohemia, Czechoslovakia) are presented and evaluated. New information on the sedimentary processes (especially the middle Holocene stratigraphic anomaly), the development of aquatic and mire vegetation, the character of the forest cover and human activity in the Řežabinec area during the Preboreal, Boreal, Subboreal and Subatlantic has been obtained.

Biostratigraphic correlation of the Kärlich Interglacial, Northwestern Germany

Palaeobotanical investigations of limnic sediments in the Karlich clay pit (Middle Rhine area) in Northwestern Germany indicate that deposition took place during a middle Pleistocene interglacial, the initial part of which is absent at the site investigated. Of special biostratigraphic importance is the occurrence of taxa Azolla filiculoides, Pterocarya and Celtis auslralis. In the Carpinus‐Betula zone of this interglacial, early Palaeolithic artifacts are present. Remains of mammalian fauna have been found in the investigated layers. The interglacial has no clear palaeobotanic equivalent in Northwestern Europe, but the intermediate character of the palaeoflora suggests an intra‐Saalian age.

Age, palaeoenvironments, and climatic significance of late Pleistocene Konya lake, Turkey

The Konya Basin, a closed depression at the southern margin of the Anatolian Plateau, contained a shallow but extensive lake during the late Quaternary. Nearshore sands and gravels containing Dreissena shells form prominent depositional terraces around the basin edges at elevations between 1005 and 1020 m, and the highest has been dated at more than 30,000 yr B.P. The last major phase of limnic sedimentation occurred between 23,000 and 17,000 yr B.P., after which the lake fragmented into a number of subbasins or secondary depressions which evolved to become either marshes or playas. A final expansion of these residual lakes has been dated to ca. 11,000 yr B.P. in one secondary depression. Archaeological and other evidence indicate that only minor lake-level fluctuations occurred during the Holocene. The dominant sedimentary process over the last 10,000 years has been alluviation at the basin margin. The Konya sequence confirms that the most recent period of high-lake levels in the northern Near East was of the last glacial age. The palaeolakes of Anatolia and Iran were, however, more a product of reduced evaporation brought about by temperature depression than of changes in precipitation, and thus belie their often-used description as an indicator of “pluvial” climatic conditions.

A red deer (Cervus elaphus L.) skeleton from seamer carrs, Cleveland, England: Provenance of the skeleton and palaeoecology of the site

Abstract A Red deer, Cervus elaphus L., skeleton from Seamer Carrs was excavated and the collagen fraction of one of the bones dated to 4330 ± 100 bp (Birm. 977). The bones were embedded in a limnic sediment that was dated to 7360 ± 120bp(Birm.882). This date was confirmed by the pollen assemblage, which indicated a Flandrian I/II chronozone age. The date of the Cervus bone is explained by its movement vertically downwards in the limnic sediment. Attention is drawn to the number of large mammalian skeletons that have been recovered from Seamer Carrs during drainage operations and subsequently, and to the mesolithic and neolithic artifacts recovered from the slopes around the Carrs.

Accumulative phases for heavy metals in limnic sediments

Accumulative phases for heavy metals in limnic sediments

Accumulative phases for heavy metals in limnic sediments

Accumulative phases for heavy metals in limnic sediments

Das Vorkommen einiger Chlorokokkalalgen in böhmischen Spätglazial und Postglazial

During the pollen analyses of Bohemian peat and limnic sediments numerous empty cell walls of some chlorococcal algae, particulary, of the genusPediastrum, were found. This material was taxonomically determined and the ecology of different taxa was reconstructed and compared with the present one. The greatest difference was found inPediastrum integrum andP. kauraiskyi occurring commonly in Central Europe in the lakes during the Late-Glacial and Postglaciial Periods but very rarely at present. Our results were compared with some data given in the literature.

Late Quaternary paleoenvironments of the Morley Flats and Kananaskis Valley of southwestern Alberta

A 3.1 m section of limnic sediment and peat from a bog on the Morley Flats and a 2.8 m section of limnic sediment from Wedge Lake in the Kananaskis Valley have yielded the first comprehensive late Quaternary biostratigraphic record from south-western Alberta. Both sections were analyzed for subfossil pollen, molluscs, and several sedimentary indices. Two distinct pollen zones were recognised. The basal zone, characterized by high relative abundancy of Artemisia–Salix–Juniperus, suggests that the Morley Flats were dominated by a sparse vegetation composed of aggressive pioneer species following deglaciation until prior to approximately 10 000 BP. Similarly, the mollusc fauna from this zone is dominated by northern ranging species. The second zone is typified by a predominance of Pinus and Picea. This reflects the expansion of coniferous forest into the region. Both the relative abundance of southern ranging mollusc species and the total carbonate concentration in the sediment increase in this zone. The vegetation of the region has remained generally stable since at least 9395 BP. However, increases in the abundance of Pinus relative to Picea and Abies in the mid-Holocene suggest that this period experienced an increase in fire frequency, possibly generated by climatic amelioration.

Bridge River tephra: revised distribution and significance for detecting old carbon errors in radiocarbon dates of limnic sediments in southern British Columbia

Ash-grade Bridge River tephra, identified as such on the basis of shard habit, modal mineralogy, and composition of ilmenite, occurs in sedimentary cores from three lakes located to the south of the previously documented plume and necessitates a significant enlargement of the fallout area of that tephra in southwestern British Columbia.These new, more southerly occurrences are probably equivalent to the ~2350 year old Bridge River tephra, although it can be argued from the evidence at hand that the 14C dates and biotite-rich nature support relationship to a slightly earlier Bridge River event.Large differences exist in the 14C age of sediments immediately adjacent to the Bridge River tephra at these three lake sites; maximum ages of 3950 ± 170 years BP (GX-5549) and 3750 ± 210 years BP (I-10041) were obtained at Phair and Fishblue lakes, respectively, whereas the corresponding age at Horseshoe Lake is only 2685 ± 180 years BP (GX-5757). The two older dates are considered to be significantly affected by old carbon contamination for the bedrock locally consists of calcareous sedimentary rocks and the lacustrine sediments are very calcareous. The 14C date from Horseshoe Lake, which occurs in an area of igneous rocks, appears to be only slightly too old relative to the ~2350 year old Bridge River tephra.Well-dated tephra beds, therefore, can be very useful in assessing the magnitude of old carbon errors associated with radiocarbon dates based on limnic sediments. Calcareous gyttja deposits beneath Bridge River tephra within the study area exhibit old carbon errors of the order of 1350–1550 years.

Glacial history of western Norway 15,000–10,000 B.P.

The deglaciation patterns of the Bergen and Nordfjord‐Sunnmøre areas in western Norway are described and correlated. In the Bergen area the coast was first deglaciated at 12,600 B.P., with a succeeding re‐advance into the North Sea around 12,200 B.P. Later, during the Allerød, the inland ice retreated at least 50 km, but nearly reached the sea again during the Younger Dryas re‐advance, ending at 10,000 B.P. Sunnmøre was ice‐free during an interstadial 28,000–38,000 B.P. Later the inland ice reached the sea. The final deglaciation is poorly dated in Sunnmøre, while further south in Nordfjord, it started slightly before 12,300 B.P., followed by a major retreat. No large re‐advance of the inland ice occurred during the Younger Dryas. However, in the Sunnmøre‐Nordfjord area many local glaciers formed outside the inland ice during the Younger Dryas. Limnic sediments outside one such cirque glacier have been cored and dated, proving that the glacier did not exist at 12,300‐11,000 B.P., and that it was formed and disappeared in the time interval 11,000–10,000 B.P. (Younger Dryas). The erosion rate of the cirque glacier was 0.9 mm/year.

The deglaciation of southern Sweden 13,500‐10,000 B.P.

Because of its well‐developed ice‐marginal zones, SW Sweden is an important reference area for the study of deglaciation, chronology and palaeoclimate 13,500‐10,000 B.P. The ice‐marginal zones are described and defined. Earlier research and opinions concerning the deglaciation are summarized. Based on radiocarbon dates from shells, vertebrate bones and limnic sediments, a revised deglaciation chronology is presented. This chronology is supported by biostratigraphic transects of time‐space diagrams. The radiocarbon and varve chronologies are compared. Some ice‐marginal zones are supposed to be 400 to 900 years older than expected from the varve chronology. The deglaciation chronology is correlated within the southern margin of the Scandinavian inland ice. Various consequences for the interpretation of glacial dynamics, shoreline displacement, and the biological environment are mentioned.

Late Quaternary Deposits from Southeast Scotland. II. The Diatom Assemblage of a Marl Core

Analysis of the diatom content of limnic sediments from Linton Loch, Roxboroughshire, allowed a subdivision of the sequence into six diatom assemblage zones. Palynological evidence from the same core has been used to relate the sequence to the Late Quaternary chronozones of Din Moss. Fragilaria spp. are the dominant pioneer taxa in the basal clays of Late Devensian age, when a minerogenic environment persisted. With the onset of the Flandrian, biogenic precipitation of marl commenced and a planktonic community developed, together with an epiphytic flora dominated by Epithemia spp. Productivity, as indicated by diatom concentrations, remained low throughout the period of marl deposition, though the rate of accumulation was in excess of that for other Late Quaternary sediments in Britain. Consequent on anthropogenic disturbance in the catchment, productivity increased as muds and finally peat were deposited in the basin with a diatom flora dominated by Fragilaria spp. Possible reasons for the apparent competition between Epithemia spp. and Fragilaria spp. are discussed. The persistence of an alkaliphilous/alkalibiontic diatom flora suggests the maintenance of waters of high base-status throughout the Late Quaternary. The limited application of Centrales:Pennales and Araphidineae:Centrales ratios in a marl deposit and in a palaeoenvironmental context are discussed. The Linton Loch diatoms are compared with other sites. There are unique characteristics, which appear to relate to the existence of a marl environment, and do not conform with general trends of Late Quaternary lake evolution in Britain.

Late Quaternary Deposits from Linton Loch, Southeast Scotland I. Absolute and Relative Pollen Analyses of Limnic Sediments

Stratigraphic investigations at Linton Loch in Roxboroughshire, Scotland, revealed the presence of a U-shaped central trough and a littoral shelf. Limnic clays, marl, muds and peat accumulated sequentially during the Late Devensian and Flandrian. Absolute and relative pollen analyses have permitted subdivision of the sequence into three pollen assemblage zones which represent the Flandrian period. These assemblage zones and their subdivisions are described in detail, and their ecological implications are discussed in terms of vegetational history. During zone LLI, forest species became established at the expense of herbaceous species. Of particular interest is the spread of Corylus on to a Betula-dominated landscape, but not at the expense of Betula. In zone LL2, the mixed oak forest component dominates. Zone LL3 begins as the values of Ulmus pollen fall, and man's influence on the vegetation pattern becomes clear. The pollen assemblage zones of Linton Loch have been related to the chrono- zones of Din Moss, and have been compared with evidence for the Late Quater- nary environment from sites elsewhere in Britain.