scholarly journals Post-glacial Foraminifera of the incised Yangtze paleo-valley and paleoenvironmental implications

2017 ◽  
Vol 91 (6) ◽  
pp. 1102-1122 ◽  
Author(s):  
Xue Ke ◽  
Baohua Li ◽  
Zongyan Zhang ◽  
Yi Wei ◽  
Fei Hu ◽  
...  
Keyword(s):  
Sea Level ◽  
Middle Part ◽  
The Other ◽  
Glacial Deposit ◽  
Benthic Foraminifers ◽  
The Holocene ◽  
Middle Holocene ◽  
Sea Level Fluctuations ◽  
The Core ◽  
Abundance And Diversity

AbstractThree gravity cores (LZK1, ZKA4, and CSJA6) from the incised Yangtze paleo-valley comprise a thick sequence of the post-glacial deposit. Nineteen genera (26 species) of the benthic foraminifers are described from these cores, with detailed down-core foraminiferal variations to investigate their paleoenvironmental implications. Three foraminiferal assemblages are recognized for the lower, middle, and upper parts of the cores respectively. The lower part is dominated byAmmonia beccariivar. andFlorilus decoruswith lower abundance and diversity. In the middle part, the foraminifers are abundant and diverse, dominated by bothAmmonia beccariivar. andElphidium advenum.Cavarotalia annectens,Pararotalia nipponica, and porcellaneous benthic foraminiferal forms are always present, sometimes abundant. The upper part is characterized by theAmmonia beccarii-Elphidium magellanicumassemblage, except for the Core ZKA4, which is barren of foraminifers in this interval. AMS14C dates and foraminiferal assemblages both confirm that the transgression-regression sequence in these cores belongs to the “Ammoniatransgression” during the Holocene. In addition to documenting the post-glacial sea-level fluctuations, the benthic foraminifers also reflect a warmer climate during the early–middle Holocene. The foraminiferal differences among the three cores can be used to interpret the influence of seawater during the post-glacial sea-level fluctuations. The area in the vicinity of Core ZKA4 was affected by marine water only during the middle Holocene, which was much shorter than the areas of the other cores.

scholarly journals Sedimentary archives of climate and sea-level changes during the Holocene in the Rhône prodelta (NW Mediterranean Sea)

2016 ◽  
Vol 12 (12) ◽  
pp. 2161-2179 ◽  
Author(s):  
Anne-Sophie Fanget ◽  
Maria-Angela Bassetti ◽  
Christophe Fontanier ◽  
Alina Tudryn ◽  
Serge Berné
Keyword(s):  
Sea Level ◽  
Water Depth ◽  
Late Holocene ◽  
Sea Level Changes ◽  
The Holocene ◽  
Middle Holocene ◽  
The Core ◽  
Condensed Section ◽  
Core Site ◽  
Nw Mediterranean

Abstract. A 7.38 m long sediment core was collected from the eastern section of the Rhône prodelta (NW Mediterranean) at 67 m water depth. A multi-proxy study (including sedimentary facies, benthic foraminifera, ostracods, and clay mineralogy) provides a multi-decadal to century-scale record of climate and sea-level changes during the Holocene. The early Holocene is marked by alternative silt and clay layers interpreted as distal tempestites deposited in a context of rising sea level. This interval contains shallow infra-littoral benthic meiofauna (e.g., Pontocythere elongata, Elphidium spp., Quinqueloculina lata) and formed between ca. 20 and 50 m water depth. The middle Holocene (ca. 8.3 to 4.5 ka cal. BP) is characterized, at the core site, by a period of sediment starvation (accumulation rate of ca. 0.01 cm yr−1) resulting from the maximum landward shift of the shoreline and the Rhône outlet(s). From a sequence stratigraphic point of view, this condensed section, about 35 cm thick, can be identified on seismic profiles as a maximum flooding surface that marks the transition between delta retrogradation and delta progradation. The transition between the early Holocene deposits and the middle Holocene condensed section is marked by a gradual change in all proxy records. Following the stabilization of sea level at a global scale, the late Holocene is marked by the establishment of prodeltaic conditions at the core site, as shown by the lithofacies and by the presence of benthic meiofauna typical of the modern Rhône prodelta (e.g., Valvulineria bradyana, Cassidulina carinata, Bulimina marginata). Several periods of increased fluvial discharge are also emphasized by the presence of species commonly found in brackish and shallow-water environments (e.g., Leptocythere spp.). Some of these periods correspond to the multi-decadal to centennial late Holocene humid periods recognized in Europe (i.e., the 2.8 ka event and the Little Ice Age). Two other periods of increased runoffs at ca. 1.3 and 1.1 ka cal. BP are recognized, which are likely to reflect periods of regional climate deterioration that are observed in the Rhône watershed. Conversely, the Migration Period Cooling (ca. 1.4 ka cal. BP) and the Medieval Climate Anomaly (ca. AD 950–1250) correspond locally to periods of increased dryness.

scholarly journals KECEPATAN PENGANGKATAN PULAU BUTON DAN JEJAK PERUBAHANMUKA AIR LAUT DI ZAMAN KUARTER

2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Prijantono Astjario ◽  
D.A. Siregar
Keyword(s):  
Sea Level ◽  
Radiocarbon Dating ◽  
Active Fault ◽  
Present Situation ◽  
Tectonic Uplift ◽  
The Other ◽  
Uplift Rate ◽  
Sea Level Fluctuations ◽  
Astronomical Theory ◽  
Reef Platform

Beberapa indikasi menunjukan adanya jejak muka laut cukup tinggi di zaman Kuarter, ketinggiannya mencapai ±250 meter diatas muka laut masa kini, ditemukan pada kawasan pantai Tira hingga Tanjung Labokeh, Buton bagian selatan. Jejak tersebut terrekam pada permukaan terumbu karang yang membentuk undak laut di kawasan pantai Buton Selatan. Tujuh buah hasil pentarikhkan Radiokarbon memberikan tiga contoh berumur 1500 hingga 3000 tahun dan contoh terumbu karang lainnya berumur lebih tua dari 40.000 tahun sebelum saat ini. Runtunan data Radiokarbon secara garis besar menunjukan kesesuaian dengan perubahan muka laut pada zaman Kuarter yang telah di prakirakan oleh teori astronomi perubahan cuaca masa lalu. Jika dibandingkan data Radiokarvbon dengan data urutan undak laut menunjukan bahwa rata-rata aktivitas tektonik pengangkatan dikawasan pantai Tira hingga Tanjung Labokeh adalah 0,7 = 0,8 mm/tahun. Pengangkatan rata-rata Pulau Buton tampak lebih cepat dari Pulau Muna akibat adanya sesar aktiv diantara kedua pulau tersebut. Several indicators of a slightly higher Quaternary sea-level, reaching about ± 250 meters above the present situation have been found along the coastas of Tira to Cape Labokeh. South Buton. They are corrals in growth position on the surface of reef platform of South Buton. Seven Radiocarbbon datings have provided ages of three samplewsa are 1500 to 3000 and the other four samples are more older than 40.000 years BP. The Radiochronological data are thus broadly consistent with the timing of sea-level fluctuations predicted by the astronomical theory of paleoclimates. Comparision with the data from terraces sequences and from Radiocarbon dating records indicates that the average tectonic uplift rate at Tira and Cape Labokeh, South Buton is on the order of 0,7 – 0.8 mm / years. The uplift rate of Buton is more faster than Muna because of the active fault in between.

ACCUMULATIVE COASTS AS RELIABLE INDICATORS OF THE KINEMATICS OF THE SEA LEVEL DURING THE HOLOCENE

2017 ◽  
Author(s):  
Nikolay Dunaev ◽  
Nikolay Dunaev ◽  
Tatiana Repkina ◽  
Tatiana Repkina
Keyword(s):  
Sea Level ◽  
Coastal Zone ◽  
Synoptic Scale ◽  
The Holocene ◽  
Single View ◽  
Sea Level Fluctuations ◽  
Current State ◽  
Geological Section ◽  
Global Sea Level ◽  
Different Parts

Currently, there is no single view of the Holocene global sea level kinematics. At the same time, the question of a possibility of it exceeding the current sea level by several meters is be-ing debated. The accumulative coasts of nearly tide-free seas, in areas where the vertical di-rection of coastal movement remained unchanged are the most convenient objects for study-ing this major paleogeographic issue. Effects of the sea level fluctuations are revealed in the resulting geomorphological structure and in the nature of sediment areas of the coastal zone developing in an accumulative mode. If the Holocene sea level exceeds its modern marks, then ladders of accumulative terraces would have formed over different parts of the coast. The heights of the terrace ladders would correspond to the amplitudes of these exceedances. The lower sediment levels should reflect the transgressive character of their formation in the structure of geological section, while the higher levels would reflect the regressions. The coast of the Thatcher Peninsula, located in the Bay of Cumberland microcontinent of the South Georgia (Antarctic) was the focus of our research. It was established that the Holo-cene sea level in the region reached its current state no later than about one thousand years ago and did not exceed it, being subjected to only minor fluctuations of the synoptic scale. The accumulative terraces are located in fragments. The differences in their absolute eleva-tions are related to their correspondence to different tectonic units experiencing differenti-ated uplift.

ACCUMULATIVE COASTS AS RELIABLE INDICATORS OF THE KINEMATICS OF THE SEA LEVEL DURING THE HOLOCENE

2017 ◽  
Author(s):  
Nikolay Dunaev ◽  
Nikolay Dunaev ◽  
Tatiana Repkina ◽  
Tatiana Repkina
Keyword(s):  
Sea Level ◽  
Coastal Zone ◽  
Synoptic Scale ◽  
The Holocene ◽  
Single View ◽  
Sea Level Fluctuations ◽  
Current State ◽  
Geological Section ◽  
Global Sea Level ◽  
Different Parts

Currently, there is no single view of the Holocene global sea level kinematics. At the same time, the question of a possibility of it exceeding the current sea level by several meters is be-ing debated. The accumulative coasts of nearly tide-free seas, in areas where the vertical di-rection of coastal movement remained unchanged are the most convenient objects for study-ing this major paleogeographic issue. Effects of the sea level fluctuations are revealed in the resulting geomorphological structure and in the nature of sediment areas of the coastal zone developing in an accumulative mode. If the Holocene sea level exceeds its modern marks, then ladders of accumulative terraces would have formed over different parts of the coast. The heights of the terrace ladders would correspond to the amplitudes of these exceedances. The lower sediment levels should reflect the transgressive character of their formation in the structure of geological section, while the higher levels would reflect the regressions. The coast of the Thatcher Peninsula, located in the Bay of Cumberland microcontinent of the South Georgia (Antarctic) was the focus of our research. It was established that the Holo-cene sea level in the region reached its current state no later than about one thousand years ago and did not exceed it, being subjected to only minor fluctuations of the synoptic scale. The accumulative terraces are located in fragments. The differences in their absolute eleva-tions are related to their correspondence to different tectonic units experiencing differenti-ated uplift.

scholarly journals Sedimentary archives of climate and sea-level changes during the Holocene in the Rhone prodelta (NW Mediterranean Sea)

2016 ◽  
Author(s):  
Anne-Sophie Fanget ◽  
Maria-Angela Bassetti ◽  
Christophe Fontanier ◽  
Alina Tudryn ◽  
Serge Berné
Keyword(s):  
Sea Level ◽  
Water Depth ◽  
Late Holocene ◽  
Ice Age ◽  
Sea Level Changes ◽  
The Holocene ◽  
The Core ◽  
Core Site ◽  
Nw Mediterranean ◽  
And Sea Level

Abstract. A 7.38 m-long sediment core was collected from the eastern part of the Rhone prodelta (NW Mediterranean) at 67 m water depth. A multi-proxy study (sedimentary facies, benthic foraminifera and ostracods, clay mineralogy, and major elements from XRF) provides a multi-decadal to century-scale record of climate and sea-level changes during the Holocene. The early Holocene is marked by alternative silt and clay layers interpreted as distal tempestites deposited in a context of rising sea level. This interval contains shallow infra-littoral benthic meiofauna (e.g. Pontocythere elongata, Elphidium spp., Quinqueloculina lata) and formed between ca. 20 and 50 m water depth. The middle Holocene (ca. 8.3 to 4.5 ka cal. BP), is characterized, at the core site, by a period of sediment starvation (accumulation rate of ca. 0.01 cm yr−1) resulting from the maximum landward shift of the shoreline and the Rhone outlet(s). From a sequence stratigraphic point of view, this condensed interval, about 35 cm-thick, is a Maximum Flooding Surface that can be identified on seismic profiles as the transition between delta retrogradation and delta progradation. It is marked by very distinct changes in all proxy records. Following the stabilization of the global sea level, the late Holocene is marked by the establishment of prodeltaic conditions at the core site, as shown by the lithofacies and by the presence of benthic meiofauna typical of the modern Rhone prodelta (e.g. Valvulineria bradyana, Cassidulina carinata, Bulimina marginata). Several periods of increased fluvial discharge are also emphasized by the presence of species commonly found in brackish and shallow water environments (e.g. Leptocythere). Some of these periods correspond to the multi-decadal to centennial late Holocene humid periods recognized in Europe (i.e. the 2.8 ka event and the Little Ice Age). Two other periods of increased runoffs at ca. 1.3 and 1.1 ka cal. BP are recognized, and are likely to reflect periods of regional climate deterioration that are observed in the Rhone watershed.

scholarly journals INVESTIGATION OF THE INTERNAL STRUCTURE AND EVOLUTION OF THE HOLOCENE BARRIER OF MARICÁ (RIO DE JANEIRO, BRAZIL)

2015 ◽  
Vol 33 (3) ◽  
pp. 461
Author(s):  
Carolina Pereira Silvestre ◽  
André Luiz Carvalho da Silva ◽  
Maria Augusta Martins da Silva ◽  
Amilsom Rangel Rodrigues
Keyword(s):  
Internal Structure ◽  
Sea Level ◽  
Ground Penetrating Radar ◽  
Rio De Janeiro ◽  
Depositional Environments ◽  
Sea Level Changes ◽  
The Holocene ◽  
Sea Level Fluctuations ◽  
Sedimentary Architecture ◽  
Ground Penetrating

ABSTRACT. The objective of this study is the identification of the internal structure of the Holocene barrier of the Maricá coastal plain (Rio de Janeiro, Brazil) for the understanding of the evolution of this coast. The regional geomorphology is characterized by the large Maricá lagoon and by two sandy barriers which confines a series of small near-dry lagoons. Geophysical data obtained from ground-penetrating radar (GPR) images, with 400 and 200 MHz shielded antennae and borehole samples, both reaching down to about 10 meters in depth, provided information about the sedimentary architecture and geological and oceanographical processes responsible for the evolution of this area in the Holocene. The results show that the barrier internal structure is formed by a set of strata presenting different geometries, dip directions and organization, relative to the following depositional environments: dunes, washover fans, beach and tidal channels. It was possible to determine the importance of the sea level changes, longshore currents and overwash processes for the barrier development. Strong reflectors representing eolian strata dipping towards the continent point out to a phase of barrier retrogradation; afterwards, a succession of very well preserved beach paleoscarps, located south of the previous barrier, shows a phase of barrier progradation. Such evidences indicate that the barrier evolved according to the Holocene sea level fluctuations recognized for the Brazilian coast.Keywords: ground-penetrating radar, barrier-lagoon system, Holocene, Maricá coast. RESUMO. O presente estudo objetivou identificar a estrutura interna da barreira holocênica buscando compreender a evolução da planície costeira de Maricá (Rio de Janeiro). A geomorfologia regional é caracterizada pela Lagoa de Maricá e duas barreiras arenosas, separadas por pequenas lagunas colmatadas. Dados geofísicos obtidos com um georadar, com antenas de 400 e 200 MHz, e amostras de sondagem geológica, ambos até a profundidade média de 10 metros, forneceram informações sobre a arquitetura sedimentar e os processos geológicos e oceanográficos responsáveis pela evolução desta área no Holoceno. Os resultados mostram que a estrutura interna da barreira é formada por um conjunto de estratos de diferentes geometrias, direções de mergulho e modos de organização relacionados aos seguintes ambientes deposicionais: dunas, leques de arrombamento, praias e canais de maré. Essas características permitiram o entendimento da dinâmica costeira responsável pelo desenvolvimento da barreira, com destaque para as variações do nível do mar, correntes de deriva litorânea e mecanismos de sobrelavagem. Refletores marcantes representando estratos eólicos inclinados para o continente indicam uma fase de retrogradação da barreira; a esse episódio se seguiu um período marcado por sucessivas paleoescarpas de tempestade, localizadas mais ao sul, indicando uma fase de progradação. Essas evidências mostram que a barreira evoluiu de acordo com as fases de transgressão e regressão marinha do Holoceno reconhecidas para o litoral brasileiro.Palavras-chave: georadar, sistema barreira-laguna, Holoceno, litoral de Maricá.

scholarly journals Pleistocene-Holocene sedimentation of Solimões-Amazon fluvial system between the tributaries Negro and Madeira, Central Amazon

2016 ◽  
Vol 46 (2) ◽  
pp. 167-180 ◽  
Author(s):  
Eliezer Senna Gonçalves Júnior ◽  
Emílio Alberto Amaral Soares ◽  
Sonia Hatsue Tatumi ◽  
Marcio Yee ◽  
Juan Carlos Ramirez Mittani
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Main Channel ◽  
The Other ◽  
Asymmetric Distribution ◽  
Fluvial System ◽  
The Holocene ◽  
Fluvial Terraces ◽  
Point Bars ◽  
Solimões River

ABSTRACT: In the scope of Solimões-Amazon fluvial system between the Negro and Madeira tributaries, three levels of Quaternary fluvial terraces overlie the Alter do Chão and Novo Remanso formations further than 100 km southward its current main channel. Smooth undulated topography presenting low drainages density formed by sparse secondary plain channels and rounded lakes characterizes these deposits. Internally, they show point bars morphology constituted by intercalated layers of mud (silt and clay) and sand forming an inclined heterolithic stratification. The asymmetric distribution of fluvial terraces allied to the records of old scroll-bars features and paleochannels in many extensions of the Solimões River suggests the predominance of a meander pattern between 240 to 6 kyears. On the other hand, the development of the current anabranching pattern took place in the last six kyears due to the Holocene sea-level rise, besides the action of neotectonics and rainforest establishment related to the increase of humidity in Amazonia.

Middle-Holocene sea-level fluctuations interrupted the developing Hemudu culture in the lower Yangtze River, China

2018 ◽  
Vol 188 ◽  
pp. 90-103 ◽  
Author(s):  
Keyang He ◽  
Houyuan Lu ◽  
Yunfei Zheng ◽  
Jianping Zhang ◽  
Deke Xu ◽  
...  
Keyword(s):  
Sea Level ◽  
Yangtze River ◽  
Middle Holocene ◽  
Sea Level Fluctuations ◽  
Lower Yangtze ◽  
Holocene Sea Level

scholarly journals Response of the Apodi-Mossoró estuary-incised valley system (NE Brazil) to sea-level fluctuations

2010 ◽  
Vol 58 (spe2) ◽  
pp. 13-24 ◽  
Author(s):  
Helenice Vital ◽  
Samia F.Lima Furtado ◽  
Moab Praxedes Gomes
Keyword(s):  
Sea Level ◽  
Satellite Image ◽  
Image Data ◽  
Northeastern Brazil ◽  
Sea Level Changes ◽  
Seismic Profiles ◽  
The Holocene ◽  
Incised Valley ◽  
Sea Level Fluctuations ◽  
Base Level

This study focuses on the Quaternary sea level changes in the Apodi-Mossoró Estuary and adjacent shelf, Northeastern Brazil, based on the analysis of high-resolution seismic profiles, integrated with echosounder, SRTM and satellite image data. We use these data to develop a relative stratigraphy. An incised-valley extending from the Apodi-Mossoró Estuary onto the shelf dominates the investigated area. In very shallow waters (down to 10 m depth) the channel lies mainly in a NW-SE direction, changing to NE-SW in waters below10 m, in the form of a J-shaped valley. The southern flank of the shallow channel presents an abrupt morphology, probably determined by a residual scarp due to neotectonic reactivation of a pre-existing fault. This incised-valley can be correlated with a former river valley formed during the late Pleistocene fall in sea-level. The base-level change related to this drop in sea level can be regionally expressed on seismic lines as a laterally-continuous stratigraphic surface named Horizon I, interpreted as representing the sub-aerial exposure of the continental shelf. Many incised valleys were excavated on this exposed shelf, including that of the Apodi-Mossoró Estuary and its incised valley system. This incised valley has lain buried since the Holocene transgression. The Holocene sediments present sub-horizontal layers, or they have filled the incised valley with oblique features.

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