Aragonite preservation in late Quaternary sediment cores on the Brazilian Continental Slope: implications for intermediate water circulation

2000 ◽  
Vol 88 (4) ◽  
pp. 607-618 ◽  
Author(s):  
S. Gerhardt ◽  
H. Groth ◽  
C. Rühlemann ◽  
R. Henrich
Keyword(s):  
Continental Slope ◽  
Late Quaternary ◽  
Sediment Cores ◽  
Water Circulation ◽  
Intermediate Water ◽  
Quaternary Sediment

Control of sediment supply, palaeoceanography and morphology on late Quaternary sediment dynamics at the Galician continental slope

2012 ◽  
Vol 32 (4) ◽  
pp. 313-335 ◽  
Author(s):  
Vera B. Bender ◽  
Till J. J. Hanebuth ◽  
Anxo Mena ◽  
Karl-Heinz Baumann ◽  
Guillermo Francés ◽  
...  
Keyword(s):  
Continental Slope ◽  
Late Quaternary ◽  
Sediment Dynamics ◽  
Sediment Supply ◽  
Quaternary Sediment

Late-Quaternary Sediment Cores from Lakes on Bjørnøya

1968 ◽  
Vol 50 (4) ◽  
pp. 235 ◽  
Author(s):  
Hannu Hyvärinen ◽  
Hannu Hyvarinen
Keyword(s):  
Late Quaternary ◽  
Sediment Cores ◽  
Quaternary Sediment

scholarly journals SEDIMENT EXPORT DYNAMICS REFLECTING THE HOLOCENE HYDRODYNAMIC VARIABILITY OF A HIGH-ENERGY CONTINENTAL SHELF SYSTEM (SOUTHEASTERN SOUTH AMERICA)

2019 ◽  
Vol 4 (3) ◽  
pp. 312-331
Author(s):  
Till Jens Jörg Hanebuth ◽  
Vera Barbara Bender ◽  
Renata Hanae Nagai
Keyword(s):  
Continental Slope ◽  
Water Depth ◽  
Sediment Cores ◽  
High Energy ◽  
Silty Sand ◽  
Outer Shelf ◽  
Sandy Sediment ◽  
Intermediate Water ◽  
High Concentration ◽  
Sediment Distribution

This study reconstructs Holocene hydrodynamic changes on the outer shelf off Uruguay by examining deposits from a morphological terrace on the uppermost continental slope (250 m water depth). Seismo-acoustics, litho- and chronostratigraphy, granulometry, and Neodymium isotopy were applied to three sediment cores. The 9.5-m thick terrace sediment record, documenting the past 11.5 cal ka BP, provides exceptional insight into the transport and settling mechanisms of the sand injected from the shelf into the open ocean. The sandy outer shelf is identified as the principal sediment origin. Contouritic bottom currents do not significantly affect deposition on the terrace. Instead, the sandy sediment gets spilled over the shelf edge in the form of suspension clouds, spreading uniformly over the whole terrace. The suspended sand does not transform into high-concentration gravity-driven bottom flows but rains down onto the terrace as a quasi-permanent material supply. This observation suggests that the formation of turbidite beds, as frequently found at the deeper slope in this region, requires first a temporary storage of sediment at deposition-favoring locations on the uppermost continental slope (terraces, canyon heads), before a secondary and episodic process can mobilize the mass.An overall fining-upward trend in silty sand shelf export over Holocene times reflects the deglacial sea-level rise dynamics, leading to overall less effective material mobilization on and transfer across the shelf due to water deepening. The pronounced vertical hydrographic shelf front, as a shallow expression of the regional oceanic confluence zone, acted temporarily as main sediment exporting conveyer, before it shifted further north. The water depth of the terrace coincides with the transition zone between Central Water and Intermediate Water. The pronounced water density gradient might influence sediment distribution twofold, acting as a barrier for sand suspension cloud spreading as well as a medium for incoming internal waves bringing sediment remobilization. DINÂMICA DE EXPORTAÇÃO DE SEDIMENTOS EM FUNÇÃO DA VARIABILIDADE HIDRODINÂMICA DURANTE O HOLOCENO NUM SISTEMA DE PLATAFORMA CONTINENTAL DE ELEVADA ENERGIA (SE DA AMÉRICA DO SUL) ResumoEste estudo pretende ser uma contribuição para a reconstrução das alterações hidrodinâmicas Holocénicas, da plataforma continental externa do Uruguai, a partir de depósitos sedimentares de um terraço do talude continental superior (250 m de profundidade). Três testemunhos de sedimentos foram submetidos a análises geofísicas, lito e cronostratigráficas e granulométricas, tendo também sido obtidos resultados de isótopos de neodímio. O registro sedimentar com 9,5 m de espessura no terraço, documentando os últimos 11,5 ka cal BP, fornece importantes informações sobre os mecanismos de transporte e sedimentação da areia remobilizada da plataforma continental e transportada para o oceano profundo.Os dados obtidos na área de estudo revelaram que o substrato arenoso da plataforma continental externa foi a principal fonte de sedimento para o talude continental superior. As correntes de fundo de contorno não afetaram significativamente a deposição de sedimentos no referido terraço. Em vez disso, o sedimento arenoso remobilizado da plataforma formou nuvens de partículas em suspensão que se espalharam uniformemente por todo o terraço. A areia, uma vez em suspensão, não deu ludar a fluxos gravitacionais de fundo concentrados, mas “choveu” de modo quase continuo por todo o terraço. Esta constatação sugere que a formação de camadas turbidíticas, tais como as que freqüentemente são encontradas no talude continental inferior da região, requerem que primeiramente haja um armazenamento temporário de sedimentos em locais favoráveis à sua deposição na plataforma continental superior (terraços, cabeceiras de cânions), antes da ocorrência de um processo secundário e episódico poder mobilizar os materiais acumulados.Verifica-se, na área de estudo, uma tendência geral de redução da granulometria da areia siltosa ao longo do Holoceno devido à subida do nível do mar após a deglaciação; esta terá levado a uma menor remobilização e a uma transferência menos eficaz de sedimentos da plataforma continental para o talude devido ao aumento da profundidade da coluna de água.A pronunciada frente hidrográfica vertical da plataforma, expressão da zona de confluência oceânica regional, atuou temporariamente como principal processo de transporte e exportação de sedimentos, para norte. A profundidade da água do terraço coincide com a zona de transição entre a Água Central e a Água Intermediária. O pronunciado gradiente de densidade da água poderá ter influenciado de duas maneiras a distribuição de sedimentos, atuando como uma barreira para a propagação da nuvem de areia em suspensão e como meio de propagação de ondas internas que chegam, remobilizando e exportando sedimentos. Palavras-chave: Exportação de sedimentos de plataforma. Margem oceânica de elevada energia. Sudeste da América do Sul. Holoceno. 

scholarly journals Time-integrated 3D approach of late Quaternary sediment-depocenter migration in the Tagus depositional system: From river valley to abyssal plain

2016 ◽  
Vol 153 ◽  
pp. 192-211 ◽  
Author(s):  
Geert-Jan Vis ◽  
Cornelis Kasse ◽  
Dick Kroon ◽  
Jef Vandenberghe ◽  
Simon Jung ◽  
...  
Keyword(s):  
Late Quaternary ◽  
River Valley ◽  
Abyssal Plain ◽  
Quaternary Sediment ◽  
Depositional System

scholarly journals Late Quaternary paleoenvironment of the Ross Sea continental shelf, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 275-280 ◽  
Author(s):  
Akira Nishimura ◽  
Toru Nakasone ◽  
Chikara Hiramatsu ◽  
Manabu Tanahashi
Keyword(s):  
Organic Carbon ◽  
Marine Environment ◽  
Environmental Changes ◽  
Ross Sea ◽  
Late Quaternary ◽  
Sedimentary Environment ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Accelerator Mass Spectrometer

Based on sedimenlological and micropaleontological work on three sediment cores collected at about 167° Ε in the western Ross Sea, Antarctica, and accelerator mass spectrometer l4C ages of organic carbon, we have reconstructed environmental changes in the area during the late Quaternary. Since 38 ka BP at latest, this area was a marine environment with low productivity. A grounded ice sheet advanced and loaded the sediments before about 30-25 ka BP. After 25 ka BP, the southernmost site (76°46'S) was covered by floating ice (shelf ice), preventing deposition of coarse terrigenous materials and maintaining a supply of diatom tests and organic carbon until 20 ka BP. The northernmost site (74°33'S) was in a marine environment with a moderate productivity influenced by shelf ice/ice sheet after about 20 ka BP. Since about 10 ka BP, a sedimentary environment similar to the present-day one has prevailed over this area.

scholarly journals Cryostratigraphy, sedimentology, and the late Quaternary evolution of the Zackenberg River delta, northeast Greenland

2017 ◽  
Vol 11 (3) ◽  
pp. 1265-1282 ◽  
Author(s):  
Graham L. Gilbert ◽  
Stefanie Cable ◽  
Christine Thiel ◽  
Hanne H. Christiansen ◽  
Bo Elberling
Keyword(s):  
Late Quaternary ◽  
Sediment Cores ◽  
River Delta ◽  
Optically Stimulated Luminescence ◽  
Delta Plain ◽  
Valley Fill ◽  
Subaerial Exposure ◽  
Facies Associations ◽  
Delta Progradation ◽  
Ice Content

Abstract. The Zackenberg River delta is located in northeast Greenland (74°30′ N, 20°30′ E) at the outlet of the Zackenberg fjord valley. The fjord-valley fill consists of a series of terraced deltaic deposits (ca. 2 km2) formed during relative sea-level (RSL) fall. We investigated the deposits using sedimentological and cryostratigraphic techniques together with optically stimulated luminescence (OSL) dating. We identify four facies associations in sections (4 to 22 m in height) exposed along the modern Zackenberg River and coast. Facies associations relate to (I) overriding glaciers, (II) retreating glaciers and quiescent glaciomarine conditions, (III) delta progradation in a fjord valley, and (IV) fluvial activity and niveo-aeolian processes. Pore, layered, and suspended cryofacies are identified in two 20 m deep ice-bonded sediment cores. The cryofacies distribution, together with low overall ground-ice content, indicates that permafrost is predominately epigenetic in these deposits. Fourteen OSL ages constrain the deposition of the cored deposits to between approximately 13 and 11 ka, immediately following deglaciation. The timing of permafrost aggradation was closely related to delta progradation and began following the subaerial exposure of the delta plain (ca. 11 ka). Our results reveal information concerning the interplay between deglaciation, RSL change, sedimentation, permafrost aggradation, and the timing of these events. These findings have implications for the timing and mode of permafrost aggradation in other fjord valleys in northeast Greenland.

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