Wyniki wyszukiwania - Biblioteka Nauki

1

Rapid sea-level rise during the first phase of the Littorina transgression in the western Baltic Sea

100%

Stattegger K. , Leszczyńska K.

Oceanologia

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2023

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tom Vol. 65 (1)

202--210

EN

Glacio-isostatic adjustment (GIA) corrected limiting non-marine and marine sea-level data from the western Baltic Sea indicate a rapid relative sea-level (RSL) rise of 18 m for the first phase of the Littorina transgression using a linear age-elevation model. This accelerated RSL rise occurred in the time period 8.57 to 8.0 ka before present (BP) with an RSL rise rate of 31.5 mm/year. RSL rose from 28 m to 10 m below the mean relative sea level (bmrsl) during the time period of less than 600 years. The first phase of Littorina transgression documents the last big meltwater pulse (MWP), which has been reported also from various other regions in the world as a consequence of the final decay of the Laurentide ice sheet and additional meltwater sources from Antarctica.

2

Mineralogy of deep-sea sediments around Reunion Island (Western Indian Ocean)

80%

Duczmal-Czernikiewicz A. , Lorenc S. , Stattegger K.

Geologos

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2003

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tom Vol. 6

9--56

EN

Detailed petrographic and mineralogical analyses were performed in order to determine and classify ocean sediments in the vicinity of Reunion Island. Surface sediments from the ocean floor and samples from cores of thickness down to 560 cm were classified as hemipelagic muds of volcanogenic origin, pelagic calcareous oozes and basaltic breccia. Heavy, light and pelitic fractions were investigated separately. Basaltic breccia consists of rock fragments and glass shards. Hemipelagic muds consist mostly of basaltic fragments, plagioclases, pyroxenes and olivines, basaltic glass shards, zeolites, and clay minerals. Moreover, various amounts of carbonate and siliceous bioclasts also occur. Pelagic oozes (nannoplankton and foraminifera) are composed mainly of carbonate bioclasts and micrite. The mineral composition of the sediments and the relationship between pelagic and volcanogenic components were determined referring to the depth and distance from the Reunion Island. The sediments from the southernmost profile are different than others taken at a smaller distance from the island not only with respect to the fossil assemblage but also with respect to the occurrence of concretions (and quartz, staurolite and apatite) and greater degree of glass alteration. These sediments were formed under the conditions of pelagic sedimentation, and so the slow sedimentation rate facilitated the formation of concretions. The mineral composition of the sediments differs according to the distance from the volcanic Reunion Island and the depth from which the sediment was sampled.

PL

Przedmiotem badań była charakterystyka osadów z rejonu wyspy Reunion na podstawie szczegółowej analizy petrograficznej i mineralogicznej. Osady z dna oceanu oraz rdzenie o długości do 560 cm (150 próbek) zostały zaklasyfikowane jako: hemipelagiczne muły wulkanogeniczne, pelagiczne muły węglanowe (nannoplanktonowe i otwornicowe) oraz wulkanogeniczna brekcja bazaltowa. Brekcję bazaltową tworzą okruchy skal bazaltowych i szkliwa wulkanicznego. Muły wulkanogeniczne składają się głównie z fragmentów skał bazaltowych, minerałów pochodzenia wulkanicznego (plagioklazów, piroksenów i oliwinów), okruchów szkliwa wulkanicznego, zeolitów oraz minerałów ilastych. Ponadto występują w zmiennych ilościach bioklasty węglanowe i podrzędnie krzemionkowe. Muły pelagiczne są utworzone głównie z bioklastów węglanowych oraz mikrytu. Skład mineralny oraz wzajemne relacje składników pelagicznych i wulkanogenicznych osadu są zdeterminowane głębokością i położeniem punktów badawczych względem wyspy. Osady z profilu położonego najbardziej na SE różnią się od innych położonych bliżej wyspy nie tylko zespołem skamieniałości, ale również występowaniem konkrecji (także kwarcu, staurolitu i apatytu) oraz większym stopniem przeobrażenia szkliwa wulkanicznego. Osady te powstawały w warunkach sedymentacji pelagicznej oraz powolnym tempem sedymentacji wyznaczonym przez formowanie się konkrecji. Skład mineralny osadów zależy od odległości od wulkanicznej wyspy Reunion oraz od głębokości, z której osad był pobrany.

3

Sediment discharge and storage over the last deglacial highstand period on the central Vietnam shelf off Nha Trang

51%

Dung B. V. , Stattegger K. , Kieu N. V. , Thanh N. T. , Thong B. X. , Vu P. N. H. , Man H. Q. , Trang P. H.

Geological Quarterly

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2019

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tom Vol. 63, No. 2

395--406

EN

A sediment budget for the central Vietnam shelf off Nha Trang over the last deglacial Holocene highstand period has been investigated on the basis of shallow seismic and sediment core data and empirical equations. The annual suspended sediment discharge to the Nha Trang shelf ranges from: 4.3 to 5.4 Mt/year. Estimates based on published empirical equations suggest that the sediment discharge by three main local mountainous rivers (the Cai, Dinh and Van Phong rivers) that enter the Nha Trang shelf ranges between 1.7 and 4 Mt/year, which implies that the local rivers discharge approximately 75% of the total annual sediment input to the shelf. The annual sediment supply of the Cai River is approximately 2 and 6 times higher than that of the Dinh and Van Phong rivers, respectively. The highstand sediment depocentre of the Nha Trang shelf is mostly attached to the local river outflows, indicating their importance as the principal sediment supply sources to the shelf. Additional sources of sediment supply to the Nha Trang shelf can probably be related to along-shore transport from the nearby shelves. Calculations based on seismic and sediment core data indicate that the net sediment volume storage on the Nha Trang shelf is approximately 2.15 Mt/year. Approximately 50% of the total sediment yield supplied to the shelf is probably transported along-shore to the south. The sediment budget model for highstand deposits on the Nha Trang shelf is typical for a small mountainous river basin, which is significantly different from that of the large river delta systems in Vietnam such as the Mekong and Red rivers where 90% of the river sediments are captured on the delta plain/subaqueous part and only 10% of the river sediments are transported to the nearby shelf. In contrast, most of the sediments supplied by small mountainous rivers off Nha Trang are transported to the mid-shelf, forming a shore-parallel mud depocentre.