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Late Holocene sea-level change around Newfoundland /Daly, Julia F., January 2002 (has links)
Thesis (Ph. D.) in Geological Sciences--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 141-149).
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Late Quaternary sedimentation off the Queensland continental margin (northeast Australia) in response to sea level fluctuationsAlexander, Ian T. January 1996 (has links)
Drilling during ODP Leg 133 offshore Cairns, northeast Queensland, provided a unique opportunity to document carbonate production and facies development on a mixed carbonate-siliciclastic margin. Recent studies have shown that variations in the sedimentology of Late Quaternary and Pliocene periplatform sediments (Schlager and James, 1978), deposited on continental slopes and in deep basins surrounding shallow carbonate platforms, are linked to changes in sea-level (Droxler et al., 1993; Schlager et al., 1994). However, considerable debate has arisen to the timing of the production and export of shallow water carbonate material, with respect to sea level change. Two main hypotheses have been proposed to explain the response of shallow water carbonate platforms to variation in Late Quaternary sea level: I) 'highstand shedding' and 2) 'lowstand shedding'. Proponents of highstand shedding argue that depositional systems shed most of its carbonate sediments onto the platform slopes during highstands of sea level. Conversely, during lowstands of sea level bank top production and export of carbonate material is restricted, and platform slopes are largely starved of bank derived carbonate (Schlager, 1992; Schlager et al., 1994 ). Supporters of lowstand shedding maintain that significant carbonate production and export of shallow water carbonate material occurs during lowstands (and highstands) of sea level (Bosellini, 1989; Goldhammer and Harris. 1989; Grammer and Ginsburg. 1992). In order to investigate the response of mixed carbonate-siliciclastic systems to variations in Late Quaternary sea level and climate change, core material was collected from Ocean Drilling Program (ODP) Leg 133, Sites 819 and 823 (northeast Australian margin). These two sites form part of an eastward extending transect of drill localities, offshore Cairns, Queensland, from the outershelf/upper-slope of the Great Barrier Reef (Sites 821 /820/819), into the Queensland Trough (Site 823) and ultimately onto the flanks of the Queensland Plateau (Sites 824 and 811 /825). Pelagic to hemipelagic sediments collected from these two sites were examined for the downcore distribution of grain size, magnetic susceptibility, carbonate content, variations in carbonate mineralogy (XRD), and major and minor element (XRF) geochemistry. Using high resolution foraminiferal stable oxygen isotopes, coupled with biostratigraphic and magnetostratigraphic datums, well defined age models for Hole 819A and Hole 823A have been constructed, although it was not an easy task as hiatuses occur in these records. Age models for the sequences recovered from Hole 819A and Hole 823A have been further refined using correlation with existing isotopic stratigraphies in the Pacific Ocean (ODP Hole 677, Raymo et al., 1989), and comparison with high resolution sedimentologic records from other ODP Leg 133 marine sequences. Analysis of the mineralogical, sedimentological and geochemical records from Holes 819A and 823A indicate that, over the last 1.1 million years, highstands of sea level (and during the early regression) are characterized by increased shallow water carbonate production, and deposition on the upper slope. This pattern of carbonate deposition is consistent with the highstand carbonate shedding scenario outlined by Schlager et al. (1992), and Schlager et al. ( 1994 ). Lowstands of sea level (and particularly the early transgression) are characterized by increased deposition of non-carbonate (mainly terrigenous) material and/or were not diluted by shallow water carbonate platform material. During the lowstands of sea level the shallow water carbonate factories were switched off. Therefore, the sediments deposited during lowstands of sea level tend to record the greater influence of pelagic driven carbonate. Although the above mentioned scenario of highstand shedding applies to the entire record of 1.1 million years. mineralogical and geochemical data indicate that shallow burial diagenesis, and dissolution of solution sensitive carbonate, occurred in the lower part of the records. The diagenesis and dissolution, however, have played only a minor role in determining the composition of the Queensland margin sediments. Variations in the terrigenous input (Cr/Al and Ti/AI ratios) in Queensland margin sediments indicate that interglacial periods were generally wetter than corresponding glacials or lowstands of sea level, during the Late Quaternary.
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Late Quaternary coastal landforms and associated sediments of west CornwallJames, H. C. L. January 1994 (has links)
No description available.
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A mtDNA study of aspects of the recent evolutionary history and phylogeographic structure of selected teleosts in coastal environments of south-western Australiarhoddell@central.murdoch.edu.au, Richard James Hoddell January 2003 (has links)
At present, there is a general lack of information regarding the spatial genetic
architecture and genetic diversity of estuarine and coastal freshwater fish in
Australia or about the interacting intrinsic, extrinsic and historical influences
responsible for sculpting these patterns. This thesis represented the first
investigation of the phylogeographic structure and recent evolutionary histories
of teleost fishes from the coastal and estuarine environments of south-western
Australia, using the resolution afforded by mtDNA sequence data. Available
evidence indicated that, to different degrees, these species have limited
potential for dispersal amongst local assemblages from different water bodies.
As this theoretically reduces the confounding effects of recent gene flow on
extant genetic structure, these fishes were well suited to studying the
influences of historical factors. Historical influences were expected to be
particularly profound, given that these coastal environments underwent
massive modifications during Late Quaternary eustatic fluctuations.
The thesis consists of four major components, which explored different
aspects of interspecific and intraspecific phylogeny and p hylogeograp hy of
three teleost species, based on mtDNA control region and cytochrome b
fragments. First, the relationship between the endemic, 'strictly estuarine'
Leptatherina wallacei (Atherinidae) and the more widespread, 'estuarine &
marine' 6. presbyteroides was examined, with a view to establishing whether
6. wallacei represents a monophyletic or polyphyletic lineage and whether this
species was derived recently (i.e. in Holocene estuaries). Second, the
phylogeographic structure and genetic diversity of L. wallacei were investigated and compared with data from L. presbyteroides, with a view to
using this information to interpret the recent evolutionary histories of each
congener. Third, the divergence between assemblages of L. wallacei
inhabiting two isolated coastal lakes was used to estimate a maximal
substitution rate for the control region, which was then used to infer general
time frames for the divergence between the two Leptatherina species and
between the major phylogeographic partitions within each species. Fourth,
investigations were initiated into phylogeographic patterns and levels of
genetic diversity within and among assemblages of Pseudogobius olorum
(Gobiidae) from several coastal lakes and an estuary.
Phylogenetic analyses indicated that the two Leptatherina species were
characterised by exclusive and reciprocally-monophyletic lineages of
haplotypes from both mtDNA regions, supporting the monophyletic origins of
L. wallacei. Both 6. wallacei and 6. presbyteroides exhibited high levels of
genetic diversity and extensive overall subdivision (e.g. Qsr = 0.691 & 0.644
respectively for control region data). There was a profound phylogeographic
break in both species between all conspecific assemblages from the lower
west coast (LWC phylogroup) and all those from the south coast (SC
phylogroup), which suggested the influences of shared extrinsic and/or
historical factors. There was limited genetic structuring within the two major
phylogroups of either Leptatherina species, apparently reflecting recent
connectivity amongst local assemblages, with subsequent fragmentation and
insufficient time for lineage sorting. However, two major phylogeographic
breaks distinguished monophyletic control region phylogroups of L. wallacei from the isolated coastal Lake Clifton and Lake Walyungup, consistent with
their independent evolution following lacustrine entrapment during the
Holocene.
The divergence between these two isolated lacustrine assemblages of
Leptatherina wallaceiformed the basis for an estimate of the maximal
substitution rate of the control region. While these data were unable to
provide a precise estimate of the actual rate of molecular evolution, all the
evidence suggested that it was proceeding very rapidly. The maximal rate
estimate of 172.3% lineage-' MY-' was among the fastest ever reported.
Based on this rate, the two Leptatherina species diverged at least 1 SKya, thus
rejecting a Holocene origin for L. wallacei. The divergence between the LWC
and SC phylogroups of L. wallacei has been ongoing for at least GKya, while
the equivalent divergence in L. presbyteroides has been ongoing for at least
11 Kya. As the time frames of these divergences were consistent with periods
of massive environmental modifications associated with the end-Pleistocene
fall in sea level and the HMT, it was likely that these factors have played
important roles in sculpting the species' divergence and intra-specific genetic
structure. Although useful in temporally scaling genetic divergences within
and between the two Leptatherina species, wider application of this rate
estimate to questions regarding other taxa was limited. For example, evident
rate heterogeneity between the genera precluded its use with even the
relatively closely-related atherinid Atherinosoma elongafa.
Phylogeographic analyses identified high levels of genetic diversity and
extensive genetic subdivision (e.g. st = 0.652 for control region) amongst an
estuarine and several lacustrine assemblages of Pseudogobius olorum,
although phylogeographic structure was shallower than in either Leptatherina
species. There was increased divergence between three assemblages from
the lower west coast and two from the south coast, consistent with the
profound break evident in the Leptatherina. One lacustrine assemblage
appeared to represent a distinct lineage and a preliminary maximal rate
estimate (~61.4% lineage-1 MY-1) was calculated based on the minimum
divergence of this assemblage from its nearest conspecifics. Although slower
than the rate calculated for L. wallacei, this was still high for teleost fishes.
Overall, this study indicated that historical environmental factors, especially
those related to Quaternary eustatic changes, have played important roles in
sculpting the phylogeography and evolution of three teleost species from
south-western Australia. Moreover, as these species have differential
dependencies on estuarine environments (is. 'strictly estuarine' vs 'estuarine
& marine') and represented two different taxonomic groups (i.e. Atherinoidei &
Gobioidei), historical environmental factors may have exerted similar
influences on other coastal species in the region.
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Παλαιογεωγραφική αναπαράσταση του ελληνικού αρχιπελάγους τα τελευταία 150.000 χρόνια με την χρήση του Arcgis / ArcviewΧρονόπουλος, Κωνσταντίνος 20 September 2010 (has links)
Η παρούσα εργασία μελετά την παλαιογεωγραφική αναπαράσταση του ελληνικού αρχιπελάγους τα τελευταία 150,000 χρόνια με την χρήση του ARCGIS και ARC VIEW. Σκοπός της παρούσας εργασίας είναι να αναπαρασταθεί η συνεχώς μεταβαλλόμενη έκταση της υφαλοκρηπίδας του ελληνικού αρχιπελάγους τα τελευταία 150.000 χρόνια εξαιτίας της μεταβολής της στάθμης της θάλασσας. Και συγκεκριμένα για τα εξής πέντε χρονικά διαστήματα:
1. Πριν από 100.000 χρόνια έως 60.000 χρόνια όταν η στάθμη της θάλασσας ήταν από 20m έως 60m χαμηλότερη από την σημερινή, επικεντρωμένο στα 70.000 χρόνια πριν όταν η στάθμη της θάλασσας ήταν στα -60 m από την σημερινή.
2. Πριν από 30.000 χρόνια όταν η στάθμη της θάλασσας ήταν 80m χαμηλότερη από την σημερινή.
3. Πριν από 22.000χρόνια έως 18.000 χρόνια όταν η στάθμη της θάλασσας ήταν 120m χαμηλότερη από την σημερινή.
4. Πριν από 10.000 χρόνια όταν η στάθμη της θάλασσας ήταν 50m χαμηλότερη από την σημερινή.
5. Πριν από 8.000 χρόνια όταν η στάθμη της θάλασσας ήταν 20m χαμηλότερη από την σημερινή
Με στόχο κατά κύριο λόγο την εκμάθηση χρήσης του GIS για την ανάδειξη χώρων που μπορεί να έχουν οικονομικό και πολιτιστικό ενδιαφέρον. Με την παρούσα εργασία θα παρουσιαστούν μια σειρά από χάρτες που θα δείχνουν τις μεταβολές της ακτογραμμής του ελληνικού αρχιπελάγους τα τελευταία 150.000 χρόνια ώστε να βοηθηθούν οι γεωλόγοι, βιολόγοι, αλιευτείς και αρχαιολόγοι ώστε να μπορούν να εστιάζουν τις έρευνες τους στις σωστές περιοχές για κοιτάσματα, αλιευτικών πεδίων καθώς επίσης και προϊστορικούς οικισμούς. Επιπλέων με την χρήση του GIS γίνεται: (1) αναπαράσταση των ακτογραμμών και του θαλάσσιου ανάγλυφου τα τελευταία 100.000 χρόνια για να εξετασθεί αν οι νήσοι Λευκάδα, Κεφαλληνία, Ιθάκη και Ζάκυνθος καθώς επίσης και οι Σποράδες παρέμειναν συνεχώς νησιά όλη αυτή την διάρκεια με σκοπό να διερευνηθεί πότε άρχισε η ναυσιπλοΐα στην Ελλάδα και (2) με την 3-D αναπαράσταση της γεωμετρίας των ακτογραμμών και του περιβάλλοντος ανάγλυφου για συγκεκριμένα χρονικά διαστήματα για να αποκτήσουμε μια εικόνα για το πώς αντιλαμβανόταν ο προϊστορικός άνθρωπος τον γύρω χώρο του. Καθώς επίσης και πως η αντίληψη αυτού του χώρου εντός στον οποίο κινιόταν τον ώθησε να αναπτύξει ναυσιπλοΐες ικανότητες για να επισκεφθεί τα νησιά.
Τα συμπεράσματα που βγαίνουν μελετώντας όλους τους χάρτες και παρατηρώντας την μεταβολή της στάθμης της θάλασσας σε κάθε μια από τις πέντε χρονικές περιόδους στο παρελθόν παρατηρούμε πολλές διαφορές στην μορφολογία τόσο της ηπειρωτικής περιοχής όσο και της νησιωτικής περιοχής. Η παράκτια μορφολογία του Αιγαίου και του Ιονίου ποικίλει αλλά συνήθως αποτελείται από απότομους βράχους και στενή παράκτια ζώνη. Οι περισσότερο εκτενείς περιοχές υφαλοκρηπίδας υπάρχουν στο βόρειο Αιγαίο και, σε μικρότερο βαθμό, στο Ιόνιο και στο ανατολικό Αιγαίο. / The present work studies the palaiogeographic representation of Greek archipelago the last 150,000 years with the use of ARCGIS and ARC VIEW. Aim of present work is to show the continuously altered extent of shelf of Greek sea the last 150.000 years because of the change of level of sea. And concretely for the following five chronicles spaces:
1. Before 100.000 years until 60.000 years when the level of sea was from 20m until 60m lower than current, focused in the 70.000 years before when the level of sea was in the -60 m from current.
2. Before 30.000 years when the level of sea was 80m lower than current.
3. Before 22.000 years until 18.000 years when the level of sea was 120m lower than current.
4. Before 10.000 years when the level of sea was 50m lower than current.
5. Before 8.000 years when the level of sea was 20m lower than current
Amining in the first place the learning of use of GIS for the appointment of spaces that can have economic and cultural interest. With the present work will be presented a line from charts that will show the changes of coast line Greek archipelago the last 150.000 years so that will be helped the geologists, biologists, are fished also archaelogists so that they can focus their researches in the correct regions for layers, piscatorial fields as well as prehistoric settlements. Floating with the use of GIS it becomes: (1) representation of the coast line and of the marine bas-relief the last 100.000 years in order to be examined the islands Lefkada, Kefallinia, Ithaca and Zante as well as Sporades remained continuously these islands with a full view to investigate the start of the navigation in Greece and (2) with the 3-D representation of the geometry of the coast line and environment of bas-relief for concrete time spaces in order to acquire a picture for how the prehistoric person conceived his around space. As well as how the perception of this space into in which he was living prompted him to develop navigations faculties in order to visit the islands.
The conclusions that come out, studying the all charts and observing the change of level of sea in each of five time periods in the past. It is observed a lot of differences in the morphology of the continental region and of the islander region. The coastal morphology of Aegean and Ionian varies but usually is constituted by abrupt rocks and narrow coastal area. The most extensive regions of shelf exist in northern Aegean and, in smaller degree, in Ionian and in Eastern Aegean.
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Dynamique de la végétation alluviale côtière dans le Sud-Est de la France (bassins versants du Loup et de la Cagne, Alpes-Maritimes) au cours de la première moitié de l' Holocène / Vegetation dynamics in the Mediterranean coastal plains (Loup and Cagne basin, Southeastern France) during the early to mid HoloceneGuillon, Sebastien 14 March 2014 (has links)
Au cours de la première moitié de l’Holocène les conditions climatiques, eustatiques et anthropiques connaissent de nombreuses et importantes modifications. Parmi celles-ci, les données. Parmi celles-ci, les données régionales relatives au quart nord-ouest du bassin méditerranéen révèlent plusieurs variations pluriscalaires et significatives des conditions d’humidité ainsi que des températures. Parallèlement, la hausse du niveau marin enregistre des vitesses très élevées et la région de l’arc Liguro-Provençal voit l’installation des premières communautés agro-pastorales de la culture « Impressa », en l’occurrence dès le début du 6ème millénaire cal. BCE. Afin de qualifier la réponse de la végétation alluviale côtière, entre la fin du 8ème et le 5ème millénaire, face à l’évolution de ces conditions, l’analyse pollinique à haute résolution de deux séquences sédimentaires alluviales (bassin du Loup et de la Cagne) à été réalisée. Grâce à une approche pluridisciplinaire (carpologie, ostracologie, sédimentologie…) et méthodologique inédite (analyse du transport pollinique fluviatile) les résultats montrent une évolution précise des écosystèmes végétaux côtiers et alluviaux. Au sein de cette évolution, la remontée du niveau marin joue un rôle fondamental comme en témoigne l’expansion littorale des aulnaies marécageuses. Le forçage climatique joue également un rôle important. Les étés plus humides du 6ème millénaire participe à la diffusion du sapin à basse altitude, alors que l’augmentation de la fréquence des sécheresses estivales enregistrées à partir du 5ème millénaire favorise le développement d’une végétation sclérophylle à bruyère arborescente. La néolithisation de la région participe également au façonnage des paysages littoraux. La récurrence du type pollinique Cerealia (gr. Hordeum) dès les premières décennies du 6ème millénaire atteste de l’importance des plaines alluviales côtières dans l’économie de production des premiers groupes néolithiques. / This study investigates the impact of climate and sea level changes and the anthropogenic perturbations on the alluvial vegetation in the Mediterranean French coastal plains during the early to mid Holocene. Between 7000 and 3700 BCE, the combination of different type of regional proxy records reveal significant changes in the humid conditions and temperatures. These records also reveal rapid sea level changes and the first Neolithic settlement (5800 caL. BCE) in Southeastern France (« Impressed ware culture »). High resolution pollen data from two cores sampled in the alluvial plains of the Cagne and the Loup Rivers enable to study the vegetation responses to these changes. Thisstudy employed a pluridisciplinary approach (carpology, study of ostracods, sedimentology…) and developed a new ethodology for the assessment of the fluvial pollen transport. The results reveal a significant connection between the vegetation structure from the coastal area and the sea level changes. This relationship explains the alder expansion in the swamp area. Moreover the results also reveal the effects of the humid summer conditions on the vegetation dynamics and explain the spruce expansion during the sixth millennium BCE as well as the expansion of the sclerophyllous vegetationduring the fifth millennium BCE. The impact of the Neolithic agriculture on the alluvial land cover started with the first ecades of the sixth millennium BCE. Thanks to the frequencies of the pollen grains of cereals (Hordeum gr.) and the pollen vidence of forest decline between 6000 and 3700 BCE, the results show the significance of the Mediterranean coastal area in the Neolithic economy.
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Végétation, climat et changement du niveau marin durant le quaternaire récent dans la province de Fuzhuo, sud-est de la Chine / Late Quaternary vegetation, climate and sea-level changes in coastal Fujian Province, southeastern ChinaYue, Yuanfu 07 June 2012 (has links)
RésuméUne série de sondages continentaux (FZ4, FZ5, et SZY) ont été collectés dans la plaine de Fuzhou et dans la montagne de Ningde. Les trois enregistrements ont permis de reconstituer et ainsi de comprendre l'évolution de la végétation ainsi que d'évaluer l'impact de la mousson est-asiatique et les changements du niveau marin sur les environnements du quaternaire récent. Ma thèse donne un aperçu de la végétation passée et des changements paléoclimatiques au cours des 50000 dernières années. Pour les derniers millénaires je me suis aussi intéressé aux activités humaines préhistoriques et leur relation avec les changements de l'environnement local durant l'Holocène. Dans cette thèse, j'ai utilisé une approche multidisciplinaire incluant principalement la palynologie, la sédimentologie, le paléomagnétisme et la micropaléontologie pour reconstituer les environnements passés.L'enregistrement palynologique SZY issu d'une tourbière subalpine couvre les 50000 dernières années en continu. Les diversité de la flore et des changements forestiers au cours des 50 dernières millénaires permettent de reconstituer l'évolution de la mousson régionale dans le sud-est de la Chine. Les changements climatiques estimés par un indice de mousson saisonnier, la température et les précipitations mensuelles ont été quantitativement reconstruits.Les assemblages polliniques pendant la période entre ca. 50 et 30,4 ka cal BP, correspondant au stade isotopique marin (MIS) 3, sont caractérisés par une forte abondance de pollen arboricole, principalement subtropicaux Quercus, Castanopsis/Lithocarpus avec des taxons tempérés de montagne à feuillage caduque tels que Fagus et Alnus et accompagné de quelques conifères mésiques de montagne telles que les Taxodiaceae et Tsuga. Une telle composition de l'écosystème suggère que le MIS 3 était plutôt humide avec une forte mousson d'été. L'insolation d'été élevée peut avoir entraîné une intensification de la mousson au cours de cette période et a donc contribué au maintien d'un tel écosystème subtropical. Une expansion progressive des taxons arborés feuillus, qui a remplacé les taxons subtropicaux à feuillage persistant pendant la période du dernier maximum glaciaire (LGM) (de ca. 30,4 à 11,8 environ cal ka BP), indique que le climat est devenu beaucoup plus frais que lors du MIS 3. Cet intervalle froid se produit entre ca. 21 et 17 cal ka BP lorsque la savane arbustive a augmenté et la forêt de feuillus a diminué rapidement. Cet événement est également marqué par la concentration de pollen qui montre des valeurs faibles au cours du dernier maximum glaciaire. Ceci est probablement lié à un paysage ouvert ou semi-ouvert sous un climat plus sec et plus froid que durant le MIS 3. En comparaison avec les études des isotopes de l'oxygène (δ18O/δ16O) issues de spéléothèmes et ses carottes de glace du Groenland, plusieurs événements climatiques rapides pourraient être reconnues tels que le Dryas récent et l'interstade Bølling-Allerød qui ont marqué la fin de la dernière période glaciaire. Au cours de l'Holocène, la forêt sempervirente est restaurée rapidement. Le groupe arboré à feuillage persistant est devenu plus élevé que celui à feuilles caduques à environ 8000 cal BP. Ceci reflète un renforcement de la mousson d'été. Deux événements rapides semble être enregistré à ca. 8,2 cal ka BP et 5 cal ka BP, probablement causé par des événements de refroidissement au cours de l'Holocène. Dans le tronçon inférieur de la rivière Min, l'étude interdisciplinaire de deux enregistrements révèlent que l'environnement sédimentaire dans la plaine de Fuzhou a connu des cycles de sédimentation à plusieurs reprises au cours de l'Holocène. La première transgression marine dans a eu lieu aux alentours de ca. 9000 cal yr BP, et a atteint son plus haut niveau entre ca. 7000 et 4000 cal yr BP. La granulométrie et l'analyse des diatomées ainsi que les datations 14C AMS permettent de décrire la transgression marine et / AbstractA series of sediment cores (FZ4, FZ5, and SZY) were collected in Fuzhou plain and Ningde mountain area. The three cores, located respectively in the near coast basins and mountains, are well suited for understanding the evolution of vegetation and the impact of the East Asian monsoon and sea level changes on the Quaternary environments. My thesis provides insight into regional palaeovegetation and palaeoclimatic changes over the last 50000 years, as well as an investigation of the prehistoric human activities and their relationship with local environmental change during the Holocene. In this thesis, I have used a multidisciplinary approach including palynology, sedimentology, paleomagnetism and micropaleontology to reconstruct the past environments. The SZY pollen record from a subalpine peat bog covers the past 50,000 years continuously. The diverse flora and forest changes during the last 50 ka indicate regional monsoon evolution in subtropical southeastern China. The climate proxies such as seasonal monsoon index, monthly temperature and precipitation were quantitatively reconstructed.The pollen assemblage during the period ca. 50-30.4 cal ka BP, roughly corresponding to Marine Isotope Stage (MIS) 3, was characterized by high abundance of arboreal pollen, mainly subtropical evergreen Quercus, Castanopsis/Lithocarpus mixed with temperate mountain deciduous broad-leaved trees such as Fagus, Alnus and accompanied with some mountain mesic conifers such as Taxodiaceae and Tsuga. Such ecosystem composition suggests that MIS 3 was rather wet with strong summer monsoon. The high summer insolation may have caused an intensification of the summer monsoon during this period and thus helped maintaining such subtropical ecosystem.A gradual expansion of deciduous broad-leaved taxa which replaced the subtropical evergreen ones during the Last Glacial Maximum (LGM) period (ca. 30.4-11.8 cal ka BP), indicates that climate became much cooler than during MIS 3. The coldest interval occurs during the interval ca. 21-17 cal ka BP, when the shrubby savanna increased and the broadleaved forest rapidly declined. This event is marked also in the pollen concentration which show low values during the LGM. This is probably related to an open or semi-open landscape under a colder and dryer climate than during MIS 3. In comparison with regional oxygen isotope data (δ18O/δ16O) from speleothems and Greenland ice cores, several rapid climate events could be recognized, for instance the Younger Dryas and the Bølling-Allerød interstadial that marked the final stages of the last glacial period. During the Holocene, the evergreen forest restored rapidly. The evergreen pollen group became higher than the deciduous one at around 8000 cal yr BP, reflecting the strengthening of the Summer Monsoon. Two sharp events occurred at ca. 8.2 cal ka BP and ca. 5 cal ka BP, probably caused by cooling events during the Holocene.In the lower reach of Min River, the interdisciplinary study of two cores reveal that the sedimentary environment in Fuzhou Plain experienced several sedimentation cycles during the Holocene. The marine transgression into Fuzhou basin took place in around ca. 9000 cal BP, and reached its highest sea level at 7000-4000 cal BP. Grain-size and diatom analysis and AMS dating allow to depict the marine transgression and reconstruct its timing. Pollen analyses support the warm subtropical climate during the Mid-Holocene with dense forest dominated with evergreen broadleaved taxa. The optimal climate and the formation of marine estuary during the high-stand of the sea level were in favor of the development of the Neolithic culture (mainly Tanshishan Culture between ca. 6800-4500 cal yr BP) where the fishing and hunting were the main economic lifestyles.The sedimentological results show that the retreat of the coastline took place during the late Holocene. This is indicated by a layer of tidal peat dated around ca.1900 cal yr
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Aspectos biogeográficos e paleogeográficos de costões rochosos de Ubatuba - São Paulo / Biogeographic and paleogeographic aspect of Ubatuba\'s rocky coast (São Paulo)Vilano, Wagner Ferreira 18 November 2013 (has links)
Dentre os ecossistemas presentes na região entre-marés e habitats da zona costeira, os costões rochosos são considerados um dos mais importantes por conter uma alta riqueza de espécies de grande importância ecológica e econômica. Desta forma estudos biogeográficos e paleogeograficos são importantes ferramentas para o entendimento dos padrões de distribuição da biota: o espaço (área geográfica de ocorrência dos organismos), o tempo (eventos históricos que influenciaram os padrões atuais de ocorrência) e a forma dos grupos de organismos. Este estudo teve como objetivo principal abordar a distribuição da biota relacionando-a com a geologia e a morfologia dos costões rochosos alem de caracterizar a presença de indicadores de paleoníveis marinhos de três costões rochosos localizados nas Baías do Flamengo e da Fortaleza, em Ubatuba (SP). Os resultados desse estudo indicam que as distribuição da fauna foi muito homogênea sendo encontrado em todos os costões estudados as cracas do genêro Chtamalus, Balanus e Tetraclita, moluscos do genêro Thais, Littorina (mais abundantes), alem de colonias de Phragmatopoma e extensas bancos de algas do gênero Sargassum que estiveram presentes durante toda amostragem. A ocupação das zonas pela biota vai depender mais do declive da rocha do que da composição mineralógica, juntamente com o regime de ondas atuante no local, que vai ditar a amplitude das faixas de ocupação dos organismos, essa inclinação da rocha pode diretamente interferir nos padrões de distribuição, alterando a taxa de substituição das espécies. Um grupo de moluscos gastrópodes vermetideos do gênero Petaloconchus merece especial destaque, pois, foi registrada a primeira ocorrência deste grupo no Estado de São Paulo, além disso seu remanescentes fósseis são importantes indicadores de paleoníveis marinhos. As estimativas de variações de nível do mar foram mais eficientes com a utilização de vermetídeos e paleotocas de ouriços somada as medições de campo dos vermetideos vivos e sua localização geográfica, permite determinar paleoníveis mais precisos, foram registrados níveis mais elevados no período de 3810 ± 30 Cal. anos AP, atingindo o máximo de 3,87m ± 0,5 m e o menor em 1340 ± 30 Cal. anos AP, registrando 1,00m ± 0,5 m. / Among the ecosystems in the region and intertidal habitats of the coastal zone, the rocky shores are considered one of the most important because it contains a high number of species of great ecological and economic importance. Thus paleogeographic and biogeographic studies are important tools for understanding the distribution patterns of biota: space (geographical area of occurrence of organisms), time (historical events that influenced the patterns of occurrence) and the form of groups of organisms.The present study aimed to approach the distribution of biota relating it to the geology and morphology of rocky coasts in addition to characterize the presence of indicators of marine paleolevels three rocky shores located in Bays Flamengo and Fortaleza, Ubatuba (SP) . The results indicate that the distribution of the fauna was very homogeneous being found in all the studied shores, barnacles of the genus Chtamalus, Balanus and Tetraclita, clams genus Thais, Littorina (most abundant), in addition to extensive colonies Phragmatopoma and banks Sargassum algae that were present during the whole sampling. The occupation of areas for biota will depend more on the slope of the rock that the mineralogical composition, together with the active wave regime in place that will dictate the extent of occupancy ranges of organisms, the inclination of the rock can directly interfere with the patterns distribution changing the rate of substitution of species. A group of gastropod mollusks vermetids of the genus Petaloconchus deserves special mention because it was the first recorded occurrence of this group in the State of São Paulo, besides its fossil remains are important indicators of marine paleolevels. Estimates of changes in sea level were more efficient with the use of vermetid and paleotocas urchins added field measurements of vermetid alive and their geographic location, to determine paleolevels most accurate, highest levels were recorded in the period 3810 ± 30 Cal. years BP, reaching a maximum of 3.87 m ± 0.5 m lower in 1340 ± 30 Cal. years BP, registering 1.00 m ± 0.5 m.
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Estudo comparativo dos sambaquis Caipora, Lageado e Jaboticabeira I: interpretações acerca da mudança de material construtivo ao longo do tempo / Comparative Study of Capiora, Lageado and Jaboticabeira I sambaquis: interpretations about the change of constructive material along time.Oliveira, Tânia Ferraz de 26 March 2010 (has links)
O presente trabalho apresenta o estudo das camadas estratigráficas de três sambaquis situados nos municípios de Jaguaruna e Treze de Maio, Santa Catarina, Brasil. Partimos do princípio de que eles são estruturas erigidas intencionalmente por uma população que habitou a região por aproximadamente 6000 anos, e que para a construção de seus cemitérios se apropriavam do material malacológico disponível na região. O desmembramento dos componentes de cada camada nos forneceu informações a respeito do material construtivo dos sítios, e a partir destes resultados foi possível testar algumas hipóteses sobre a mudança da matriz construtiva verificada nos sambaquis. / This work presents the study of stratigraphical layers of three sambaquis located on Jaguaruna and Treze de Maio, Santa Catarina, Brazil. We assume that such structures were intentionally built by a population that inhabited the region for over 6000 years, and that for the pilling up of their burial grounds they gathered malacological material available within the area. The breakdown of the elements of each layer provided us information regarding the construction material of the sites, and based on these results it was possible to test some hypothesis regarding a change on the constructive matrix recorded on the sambaquis.
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Late Quaternary vegetation, climate and ocean dynamics inferred from marine sediment cores off southeastern South AmericaGu, Fang 08 February 2018 (has links)
No description available.
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