A Hypothesis for the Sawlike Pattern of World Sea-Level Fluctuations

A theory of the world's sea-level fluctuations during late Pleistocene time, based on the analysis of the general equation of the mass balance between ocean water and inland water, suggests that the exchange of water masses between the ocean and the land, where at continental glaciation periods water is stored as ice, occurs only as a result of global climatic changes. The tectonic effect is considered insignificant for late Pleistocene time. The proposed theory explains the asymmetric character and the sawlike shape of the curve of the main cycles of sea-level fluctuations. The theory also makes it possible to construct a diagram of sea-level fluctuations from the last glacial maximum to the present time. This diagram is governed by two parameters, the amount of the average “effective” evaporation from the world's ocean surface (evaporation minus rainfall) and the rate of the sea-level rise at the present time. The resulting theoretical curve agrees well with known estimates of sea level within the time span being considered. The comparison of the theoretical curve with these estimates eliminates the apparent discrepancy between data obtained by different methods: measurements of old coastline and the isotopic composition of bottom sediments.

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Sedimentary conditioning of a rocky strait during the Holocene transgression: Ría de Ferrol (NW Spain)

10.5194/egusphere-egu2020-10493 ◽

2020 ◽

Author(s):

Soledad García-Gil ◽

Víctor Cartelle ◽

Castor Muñoz-Sobrino ◽

Natalia Martínez-Carreño ◽

Iria García-Moreiras

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Late Pleistocene ◽

Nw Spain ◽

The Holocene ◽

Incised Valley ◽

Sedimentary Evolution ◽

Holocene Transgression ◽

The Last Glacial Maximum ◽

The Last Glacial

Understanding coastal responses to relative sea level rise is key to be able to plan for future changes and develop a suitable managing strategy. The sedimentary record of the Late-Pleistocene and Holocene transgression provides a natural laboratory to study the long-term changes induced in coastal landscapes by the rapid sea level rise. As sea level rises, coastal morphology continually adapts towards equilibrium changing the landscape and reshaping the distribution of sedimentary environments. The R&#237;a de Ferrol is a confined tide-dominated incised valley located in the mesotidal passive Atlantic margin of western Galicia (NW Spain). &#160;A multidisciplinary approach was used to identify the elements of sedimentary architecture within its sedimentary record since the Last Glacial Maximum. The sedimentary evolution was reconstructed combining seismic and sedimentary facies analysis with radiocarbon, geochemical and pollen data. The R&#237;a de Ferrol is characterised by a particular morphology with a rock-incised narrow channel in the middle of the basin (the Ferrol Strait) connecting an inner shallower sector with an outer deeper sector. The inner sector is characterised by low energetic conditions and is where the main fluvial inputs occur. The outer sector is connected to the shelf. The main factor influencing the sedimentary evolution of the R&#237;a de Ferrol incised valley was Late Pleistocene and Holocene sea-level rise. However, this evolution was modulated by the antecedent morphology, particularly once the middle strait became flooded during the Holocene transgression. Three main phases of evolution are distinguished: a fluvial valley drained by a braided river system, a tide-dominated estuary and a shallow marine basin (ria). During the lowstand of the Last Glacial Maximum (ca 20 kyr BP), the ria was a fluvial valley whose sediments are mainly preserved in the inner sector. Sediments cores recovered sediments from ponds and stagnant areas, dated to be older than 10790-11170 cal yr BP. During the Holocene, the basin turned into a tide-dominated estuary whose facies distribution was conditioned by the strait. The strait acted as a rock-bounded tidal inlet enhancing tidal erosion and deposition at both ends, where an ebb-tidal delta and tidal sandbanks appear. At this time, extensive tidal flats occupied most of the inner sector, dissected by estuarine channels of varied dimensions. Radiocarbon data showed ages from 8610-8910 to 5760-5940 cal yr BP. An erosive episode is identified after 6 cal kyr BP with the formation of a ravinement surface. Wave and tidal energy were split by the middle strait. A wave ravinement surface is identified in the outer sector, while a coetaneous tidal ravinement surface occurs in the inner sector. Slow sea-level rise after ca 4 ka BP finally forced rivers to retreat to the present position, causing the dispersion of their energy and leading to the final evolution of the area into a fully marine system.

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UPPER QUATERNARY SEA LEVEL FLUCTUATIONS AND STILLSTANDS ON THE CONTINENTAL SHELF OF SÃO PAULO STATE, BRAZIL: A SUMMARY

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v31i5.388 ◽

2013 ◽

Vol 31 (5) ◽

pp. 43 ◽

Cited By ~ 2

Author(s):

Valdenir Veronese Furtado

Keyword(s):

Continental Shelf ◽

Sea Level ◽

Bottom Topography ◽

Sao Paulo ◽

São Paulo ◽

Sea Level Fluctuations ◽

Sea Level Variation ◽

Variation Curve ◽

The Last Glacial Maximum ◽

The Last Glacial

ABSTRACT. Sea level ﬂuctuations are mainly related to glacial and deglacial events. São Paulo (Brazil) continental shelf shows many features, like terraces and sedimentary scarps, associated to older periods of sea level stillstands and drowned valleys, related to regressive and transgressive events. Although these features show well deﬁned spatial position obtained through bathymetric analysis; they lack isotopic dating, which prevents from obtaining more accurate space-temporal positions. However, correlations with similar depths along the Brazilian continental shelf and the dating of a feature in the area enabled us to elaborate an estimated sea level variation curve for São Paulo continental shelf and coastal areas, since the Last Glacial Maximum. Keywords: sea level ﬂuctuations, bottom topography, sedimentary features, São Paulo continental shelf. RESUMO. As ﬂutuações relativas do nível do mar, de caráter global, estão associadas a eventos climáticos de glaciação e degelo. Embora não tenham ocorrido glaciações no hemisfério sul, durante o Quaternário, exceto na Antártica, a plataforma continental de São Paulo apresenta feições morfológicas ligadas à última glaciação e ao período pós-glacial subsequente. Caracterizam-se por terraços e escarpas sedimentares, associados a períodos de estabilizações do nível do mar e paleo- canais ﬂuviais afogados, relativos ao Último Máximo Glacial e à posterior transgressão marinha. Essas feições, embora com posições espaciais bem deﬁnidas, através de análises batimétricas, apresentam lacunas de datação isotópica que não permitem o estabelecimento de posições espaço-temporais mais precisas. No entanto, correlações com profundidades similares ao longo da plataforma continental brasileira e datação de uma feição na área, permitiram a elaboração de uma curva tentativa de variação do nível do mar, desde o Último Máximo Glacial, para a plataforma continental de São Paulo e áreas costeiras. Palavras-chave: ﬂutuações relativas do nível do mar, topograﬁa de fundo, feições sedimentares, plataforma continental de São Paulo.

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Paleoproductivity changes during the Late Quaternary in the southeastern Brazilian upper continental margin of the Southwestern Atlantic

Brazilian Journal of Oceanography ◽

10.1590/s1679-87592010000500004 ◽

2010 ◽

Vol 58 (spe1) ◽

pp. 31-41 ◽

Cited By ~ 9

Author(s):

Renata Hanae Nagai ◽

Silvia Helena de Mello e Sousa ◽

Rafael André Lourenço ◽

Márcia Caruso Bícego ◽

Michel Michaelovitch de Mahiques

Keyword(s):

Sea Level ◽

Continental Margin ◽

Late Quaternary ◽

Climatic Conditions ◽

Continental Margins ◽

The Holocene ◽

Sea Level Fluctuations ◽

Brazil Current ◽

The Last Glacial Maximum ◽

The Last Glacial

Changes in the Brazilian continental margins oceanic productivity and circulation over the last 27,000 years were reconstructed based on sedimentological and microfaunal analyses. Our results suggest that oceanic paleoproductivity and the supply of terrigenous sediments to the Brazilian continental margin were higher during the Last Glacial Maximum (LGM) than during the Holocene. These changes may have been primarily influenced by significant sea level fluctuations that have occurred since the late Pleistocene. During the LGM, the lower sea level, higher productivity and lower sea-surface paleotemperatures may have been the result of the offshore displacement of the main flow of the Brazil Current. However, during the Holocene, the warm waters of the Brazil Current were displaced toward the coast. This displacement contributed to the increase in water temperature and prevented an increase in oceanic productivity. The decrease in terrigenous supply since the LGM could be related to the increase of the extension of the continental shelf and/or drier climatic conditions.

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East Asian monsoon and sea-level controls on clay mineral variations in the southern South China Sea since the Last Glacial Maximum

Quaternary International ◽

10.1016/j.quaint.2021.04.033 ◽

2021 ◽

Author(s):

Thanakorn Jiwarungrueangkul ◽

Zhifei Liu

Keyword(s):

South China Sea ◽

Sea Level ◽

Clay Mineral ◽

South China ◽

Asian Monsoon ◽

East Asian Monsoon ◽

East Asian ◽

Southern South China Sea ◽

The Last Glacial Maximum ◽

The Last Glacial

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Sea-level evolution of the Laptev Sea and the East Siberian Sea since the last glacial maximum

arktos ◽

10.1007/s41063-015-0004-x ◽

2015 ◽

Vol 1 (1) ◽

Cited By ~ 14

Author(s):

Volker Klemann ◽

Birgit Heim ◽

Henning A. Bauch ◽

Sebastian Wetterich ◽

Thomas Opel

Keyword(s):

Sea Level ◽

Last Glacial Maximum ◽

Glacial Maximum ◽

Laptev Sea ◽

Last Glacial ◽

East Siberian Sea ◽

The Last Glacial Maximum ◽

The Laptev Sea ◽

The Last Glacial

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Reappraisal of sea-level lowstand during the Last Glacial Maximum observed in the Bonaparte Gulf sediments, northwestern Australia

Quaternary International ◽

10.1016/j.quaint.2015.03.032 ◽

2016 ◽

Vol 397 ◽

pp. 373-379 ◽

Cited By ~ 17

Author(s):

Takeshige Ishiwa ◽

Yusuke Yokoyama ◽

Yosuke Miyairi ◽

Stephen Obrochta ◽

Takenori Sasaki ◽

...

Keyword(s):

Sea Level ◽

Last Glacial Maximum ◽

Glacial Maximum ◽

Last Glacial ◽

Northwestern Australia ◽

The Last Glacial Maximum ◽

The Last Glacial

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Comparing a new paleomap of European loess landscapes to an atmospheric dust circulation model

10.5194/egusphere-egu21-4345 ◽

2021 ◽

Author(s):

Janina J. (Bösken) Nett ◽

Frank Lehmkuhl ◽

Erik J. Schaffernicht ◽

Stephan Pötter ◽

Philipp Schulte ◽

...

Keyword(s):

Last Glacial Maximum ◽

Late Pleistocene ◽

Circulation Model ◽

Glacial Maximum ◽

Source Areas ◽

Last Glacial ◽

Potential Source ◽

Aeolian Sediments ◽

The Last Glacial Maximum ◽

The Last Glacial

Loess is an important archive of environmental change covering approximately 10% of the Earth&#8217;s terrestrial surface. Numerous studies have analyzed loess deposits and in particular loess-paleosol sequences. To analyze these sequences, it is important to know the spatial distribution of aeolian sediments, their location relative to potential source areas, and the geomorphology of the sink area. We investigated these aspects by compiling a new map of aeolian sediments in Europe using highly resolved geodata from 27 countries (Lehmkuhl et al., in press). To determine the most relevant factors for the European loess distribution, we further mapped potential source areas and divided the map into different facies domains. We analyzed the geomorphological and paleoenvironmental effects on the deposition and preservation of Late Pleistocene loess. Finally, the geodata-based results were compared with results obtained from high-resolved regional numerical climate-dust experiments for the Last Glacial Maximum (LGM) in Europe, which were performed with the LGM-adapted Weather Research and Forecasting model coupled with Chemistry (WRF-Chem-LGM; Schaffernicht et al., 2020). &#160;Complementing the mapping-based findings with the WRF-Chem-LGM experiments results in an improved understanding of the Late Pleistocene loess landscape in Europe.&#160;References:Lehmkuhl, F., Nett, J.J., P&#246;tter, S., Schulte, P., Sprafke, T., Jary, Z., Antoine, P., Wacha, L., Wolf, D., Zerboni, A., Ho&#353;ek, J., Markovi&#263;, S.B., Obreht, I., S&#252;megi, P., Veres, D., Zeeden, C., Boemke, B., Schaubert, V., Viehweger, J., Hambach, U. (in press). Loess landscapes of Europe &#8211; Mapping, geomorphology, and zonal differentiation. Earth-Science Reviews. Doi: https://doi.org/10.1016/j.earscirev.2020.103496Schaffernicht, E.J., Ludwig, P., Shao, Y., 2020. Linkage between dust cycle and loess of the last Glacial Maximum in Europe. Atmospheric Chemistry and Physics 20, 4969&#8211;4986. Doi:10.5194/acp-20-4969-2020.

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