7 resultados para Tidal flats.
em Doria (National Library of Finland DSpace Services) - National Library of Finland, Finland
Resumo:
This thesis includes detailed sedimentological and ichnological studies on two geological units: the Pebas Formation, with a special focus in its informal upper member, and the Nauta Formation. Both formations were deposited during the Miocene in Northeastern Peruvian Amazonia, in the Amazon retroarc foreland basin. The Pebas and Nauta successions mainly consist of non-consolidated, clastic sedimentary deposits arranged into sand- to mud-dominated heterolithic successions, which can be upward-coarsening to upward-fining. Sediments in both the Pebas and Nauta successions range from mud to fine- to medium-grained sand. The main facies observed were 1) mud-dominated horizontal heterolithic couplets; 2) rooted brownish mud; 3) lenticular, mud-draped, cross-stratified sand; 4) mud- to sand-dominated, inclined heterolithic stratification; 5) sand-dominated horizontal heterolithic couplets; and 6) mud-draped, trough cross-stratified sand. Locally, tidal rhythmites were documented. The facies are interpreted as: 1) muddy, shallow, subaqueous flats/shoals; 2) palaeosols; 3) secondary tidal channels or run-off creeks; 4) tidally influenced point bars; 5) shoreface deposits; and 6) subtidal compound dunes. Thalassinoides-dominated Glossifungites ichnofacies, low-diversity expressions of the Skolithos ichnofacies and depauperate suites consisting of elements common to the Cruziana ichnofacies strongly indicate brackish-water conditions. However, continental trace fossil assemblages, with possible elements common to the Scoyenia ichnofacies, have also been identified. In addition to the palaeoenvironmental study, a local hydrogeochemical characterisation of the Pebas and Nauta formations was also conducted. The geochemistry of the groundwaters reflects the characteristics and the soil geochemistry of the geological formations studied. The Pebas formation has low hardness, acid to neutral waters, whereas the upper Pebas has high hardness, acid to neutral waters. In both units, the arsenic content is locally high. The Nauta formation has low hardness acid groundwaters. A regional review of the Pebas and Nauta formations placed the local observations into a continental perspective and suggests that the whole Pebas-Nauta system was a probably shallow (some tens of metres at maximum), brackish- to freshwater, tidally-influenced epicontinental embayment with a probable semi-diurnal to mixed tidal regime and a microtidal range, surrounded by continental environments such as forest floors, lagoons, rivers and their flood plains, and lakes.
Resumo:
Tutkimuksen päätavoitteena on selvittää hankintastrategian muutoksen vaikutusta käyttöpääoman sitoutumiseen. Tutkimus on kvalitatiivinen case-tutkimus. Siinä tutkitaan kohdeyrityksen nuorisomuotimyymälöiden käyttöpääoman kehitystä suhteessa liikevaihtoon viiden vuoden aikasarjalla. Tutkimuksen tiedot ovat kerätty POS-järjestelmästä kuukauden tarkkuudella. Tutkimuksessa seurataan käyttöpääoman trendin lisäksi sesonkivaihteluja. Tutkimusyrityksen uudessa hankintastrategiassa lisättiin sesongin aikaisia express- ja täydennysostojen osuutta. Toimintatavan muutos johti ennakko-ostojen vähenemiseen, mikä puolestaan lyhensi ostojen ja myyntisesongin välistä keskimääräistä aikaa. Lyhyemmät ennakkoajat vähentävät ennustusvirhettä, mikä parantaa varaston hallittavuutta. Parempi ennustettavuus vähentää varmuusvarastojen tarvetta ja joustavampi materiaalivirta tasaa varastonhuippuja. Molemmat tekijät vähentävät myymälöiden käyttöpääoman tarvetta. Tutkimuksen johtopäätöksenä todetaan, että nopeampi toimitusketju vähentää käyttöpääoman tarvetta kohdeyrityksessä. Johtopäätös on yhdenmukainen tutkimuksen teoreettisen viitekehyksen kanssa.
Resumo:
Tutkimus on tehty tilaustyönä pienelle osakeyhtiölle, jonka varsinainen toiminta loppui vuoden 2007 lopussa. Yhtiö oli lopettaessaan toiminnan velaton ja omaisuus käsitti liiketilan, kaksi asuinhuoneistoa ja käteistä. Lisäksi yhtiöllä oli elinkeinoverolain alaisia tappioita, joita ei voitu käyttää ilman toimialan muuttamista. Tutkielman päätavoitteena oli selvittää edullisin tapa saada kiinteistöomaisuudesta tuotto, kun tutkittavan osakeyhtiön varsinainen toiminta on loppunut. Edullisinta tapaa mitataan yhtiön ja osakkaan maksamien verojen jälkeen jäävänä puhtaana tuottona osakkaalle. Tutkimuksen alussa on selvitetty eri toimintavaihtoehdot yhtiön varsinaisen toiminnan loppuessa. Päävaihtoehtoina on ollut toiminnan jatkaminen ennallaan osakeyhtiön muodossa, toimialan muuttaminen sijoitusyhtiöksi, yhtiön purkaminen ja osakekannan tai omaisuuden myyminen. Jokaisesta näistä vaihtoehdosta on tutkittu niiden veroseuraamukset yhtiön ja osakkaan kannalta sekä laskettu omistajan saama puhdas tuotto. Case-yhtiön omistajalle on kannattavinta vaihtaa yhtiön toimiala kiinteistösijoittamiseksi ja jatkaa toimintaa osakeyhtiönä, jolloin yhtiö saa käyttöönsä vanhat elinkeinoverolain alaiset tappionsa. Toimialan vaihtamisessa piilee verotuksellinen riski, jonka suuruuteen voidaan vaikuttaa. Yhtiön kannattaa jakaa joka vuosi yhtiön nettovarallisuudesta yhdeksän prosenttia osinkona, joka on osingonsaajalle verovapaata. Osinkona kannattaa pääsääntöisesti jakaa ensimmäisenä käteiset varat, seuraavana in natura –osinkona asuinhuoneistot ja viimeisenä liiketila. In natura –osinko kannattaa arvostaa alihintaan, jolloin yhtiö sekä omistaja säästävät veroissa.
Resumo:
This PhD study aims to exploit the rich archive provided by the Miocene mollusc fauna of the Pebas Formation and other inland Miocene Amazonian formations to reconstruct landscape evolution and biotic development in lowland Amazonia during the Neogene. Over 160 samples from more than 70 Pebas Formation outcrops mostly collected by the author were processed for this study. Additional samples were collected in Andean areas of Colombia and Venezuela and further material from other northwestern South American basins was studied in museums. Pebas Formation samples and well log data made available by Occidental Peru from three wells in the Marañon Basin in Peru were also investigated. During this study four genera and 74 species from the Pebas Formation have been described and a further 13 species have been introduced in open nomenclature, and several species were reported for the first time. The number of mollusc species attributed to the Pebas fauna has increased from around 50 to 156. The Pebas fauna is characterised as aquatic, endemic and extinct, and is a typical representative of a long-lived lake fauna. Fluvial taxa are not common, (marginal) marine taxa are rare. An additional molluscan fauna from the Miocene Solimões Formation of Brazil, containing 13 fresh water species was also described. The newly documented fauna was used to improve biostratigraphic framework of Miocene Amazonian deposits. Twelve mollusc zones were introduced, the upper eleven of which cover a time interval of approximately seven million years covered previously by only three pollen zones. An age model calculated for the borehole data indicates that the Pebas Formation was deposited between c. 24 and 11 Ma. The areal distribution of the outcropping mollusc zones uncovered a broad dome structure, termed here the Iquitos-Araracuara anteclise in the study area. The structure appears to have influenced river courses and also contributed to edaphic heterogeneity that may have been in part responsible for the current high biodiversity in the study area. The Pebas system was a huge system (> one million km2) dominated by relatively shallow lakes, but also containing swamps and rivers. The system was fed by rivers draining the emergent Andes in the west and lowlands and cratons to the east. The Pebas system was located at sea level and was open to marine settings through a northern portal running through the Llanos Basin and East Venezuela Basin towards the Caribbean. Cyclical baselevel changes possibly related to Mylankhovitch cycles, have been documented in depositional sequences of the Pebas Formation. The composition of the Pebasian mollusc fauna implies that the system was mostly a fresh water system. Such an interpretation is matched by strontium isotope ratios as well as very negative δ18O ratios found in the shells, but is at odds with oligohaline and mesohaline ichnofacies found in the same strata. The mollusc fauna of the Pebas Formation diversified through most of the existence of the lake system. The diversification was mostly the result of in-situ cladogenesis. The success of some of the Pebasian endemic clades is explained by adaptation to fresh water, low oxygen, common unconsolidated lake bottoms (soup grounds) as well as high predation intensity. Maximum diversity was reached at the base of the late Middle to early Late Miocene Grimsdalea pollen zone, some 13 Ma. At the time some 85 species co-occurred, 67 of which are considered as Pebasian endemics. A subsequent drop in species richness coincides with indications of elevated salinities, although a causal relation still needs to be established. Apparently the Pebas fauna went (almost) entirely extinct with the replacement of the lake system into a fluvio-tidal system during the Early Late Miocene, some 11 Ma.
Resumo:
Connectivity depends on rates of dispersal between communities. For marine soft-sediment communities continued small-scale dispersal as post-larvae and as adults can be equally important in maintaining community composition, as initial recruitment of substrate by pelagic larvae. In this thesis post-larval dispersal strategies of benthic invertebrates, as well as mechanisms by which communities are connected were investigated. Such knowledge on dispersal is scarce, due to the difficulties in actually measuring dispersal directly in nature, and dispersal has not previously been quantified in the Baltic Sea. Different trap-types were used underwater to capture dispersing invertebrates at different sites, while in parallel measuring waves and currents. Local community composition was found to change predictably under varying rates of dispersal and physical connectivity (waves and currents). This response was, however, dependent on dispersal-related traits of taxa. Actively dispersing taxa will be relatively better at maintaining their position, as they are not as dependent on hydrodynamic conditions for dispersal and will be less prone to be passively transported by currents. Taxa also dispersed in relative proportions that were distinctly different from resident community composition and a significant proportion (40 %) of taxa were found to lack a planktonic larval life-stage. Community assembly was re-started in a large-scale manipulative field experiment over one year across several sites, which revealed how patterns of community composition (α-, β- and λ-diversity) change depending on rates of dispersal. Results also demonstrated that in response to small-scale disturbance, initial recruitment was by nearby-dominant species after which other species arrived from successively further away. At later assembly time, the number of coexisting species increased beyond what was expected purely by local niche requirements (species sorting), transferring regional differences in community composition (β-diversity) to the local scale (α-diversity, mass effect). Findings of this thesis complement more theoretical studies in metacommunity ecology by demonstrating that understanding how and when individuals disperse relative to underlying environmental heterogeneity is key to interpreting how patterns of diversity change across different spatial scales. Such information from nature is critical when predicting responses to, for example, different types of disturbances or management actions in conservation.
Resumo:
Tavoitteena tässä diplomityössä oli selvittää puuelementtien teollisen tuotannon mahdollisuuksia ja kehityksen tilaa. Millaiset valmiudet puuelementtien valmistajilla on valmistaa rakennuttajien ja rakentajien edellyttämiä suur- ja tilaelementtejä puukerrostaloja varten, millaista tuotekehitystä ja tuotantoinvestointeja tarvitaan kaiken tämän mahdollistamiseksi, mikä on yritysten halukkuus ja resurssit investoida uuteen teknologiaan sekä kuinka voidaan parantaa tuotannon tehokkuutta. Ensin diplomityössä luotiin katsaus puukerrostalorakentamisen historiaan, nykytilaan, kerrostalojärjestelmiin, palomääräyksiin ja ruotsalaiseen puuelementtien valmistamisen kehityksen tilaan. Puuelementtien valmistukseen tutustumisen jälkeen laadittiin kyselylomake tutkimusta varten, joka lähettiin 64:lle puuelementtien valmistajalle. Tutkimukseen vastasi kaikkiaan 20 puuelementtien valmistajaa. Vastausprosentiksi muodostui 31 %. Tutkimuksen perusteella voidaan todeta puuelementtien valmistajien olevan pieniä ja keskisuuria pk-yrityksiä jotka valmistavat puuelementtejä pääasiassa pientaloteollisuudelle. Suomalaisten valmistajien automaation taso ja tekninen osaaminen ei juuri eroa ruotsalaisesta puuelementtien valmistuksesta. Suomessa puuelementtien valmistus puukerrostaloja varten ei ole vielä vakiintunutta samalla tavalla kuten Ruotsissa. Suomessa Puukerrostalokohteita lähtee liikkeelle tällä hetkellä vielä aivan liian vähän. Kilpailukyky ja tehokkuus tulevat kehittymään nopeasti kun teollinen valmistus saadaan riittävän korkealle tasolle.
Resumo:
Highly dynamic systems, often considered as resilient systems, are characterised by abiotic and biotic processes under continuous and strong changes in space and time. Because of this variability, the detection of overlapping anthropogenic stress is challenging. Coastal areas harbour dynamic ecosystems in the form of open sandy beaches, which cover the vast majority of the world’s ice-free coastline. These ecosystems are currently threatened by increasing human-induced pressure, among which mass-development of opportunistic macroalgae (mainly composed of Chlorophyta, so called green tides), resulting from the eutrophication of coastal waters. The ecological impact of opportunistic macroalgal blooms (green tides, and blooms formed by other opportunistic taxa), has long been evaluated within sheltered and non-tidal ecosystems. Little is known, however, on how more dynamic ecosystems, such as open macrotidal sandy beaches, respond to such stress. This thesis assesses the effects of anthropogenic stress on the structure and the functioning of highly dynamic ecosystems using sandy beaches impacted by green tides as a study case. The thesis is based on four field studies, which analyse natural sandy sediment benthic community dynamics over several temporal (from month to multi-year) and spatial (from local to regional) scales. In this thesis, I report long-lasting responses of sandy beach benthic invertebrate communities to green tides, across thousands of kilometres and over seven years; and highlight more pronounced responses of zoobenthos living in exposed sandy beaches compared to semi-exposed sands. Within exposed sandy sediments, and across a vertical scale (from inshore to nearshore sandy habitats), I also demonstrate that the effects of the presence of algal mats on intertidal benthic invertebrate communities is more pronounced than that on subtidal benthic invertebrate assemblages, but also than on flatfish communities. Focussing on small-scale variations in the most affected faunal group (i.e. benthic invertebrates living at low shore), this thesis reveals a decrease in overall beta-diversity along a eutrophication-gradient manifested in the form of green tides, as well as the increasing importance of biological variables in explaining ecological variability of sandy beach macrobenthic assemblages along the same gradient. To illustrate the processes associated with the structural shifts observed where green tides occurred, I investigated the effects of high biomasses of opportunistic macroalgae (Ulva spp.) on the trophic structure and functioning of sandy beaches. This work reveals a progressive simplification of sandy beach food web structure and a modification of energy pathways over time, through direct and indirect effects of Ulva mats on several trophic levels. Through this thesis I demonstrate that highly dynamic systems respond differently (e.g. shift in δ13C, not in δ15N) and more subtly (e.g. no mass-mortality in benthos was found) to anthropogenic stress compared to what has been previously shown within more sheltered and non-tidal systems. Obtaining these results would not have been possible without the approach used through this work; I thus present a framework coupling field investigations with analytical approaches to describe shifts in highly variable ecosystems under human-induced stress.