scholarly journals Late Holocene Environmental Changes at Kuninaka Plain, Sado Island, Central Japan, Deduced from Sediment Facies and Diatom Assemblages.

2001 ◽  
Vol 40 (5) ◽  
pp. 355-371 ◽  
Author(s):  
Keiko Matsunaga ◽  
Yoko Ota
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Diatom Assemblages ◽  
Central Japan

Crustal subsidence inferred from reconstruction of the Pleistocene–Holocene palaeogeography in the northern Lake Inba area, central Japan

2019 ◽  
Vol 94 ◽  
pp. 61-79
Author(s):  
Takashi Chiba ◽  
Shigeo Sugihara ◽  
Yoshiaki Matsushima ◽  
Yusuke Arai ◽  
Kunihiko Endo
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Environmental Changes ◽  
Sea Level Changes ◽  
Diatom Assemblages ◽  
Central Japan ◽  
Lower Salinity ◽  
The Holocene ◽  
Holocene Transgression

ABSTRACTTo help characterise the palaeogeographic and lacustrine environmental changes that resulted from the Holocene transgression and residual subsidence in the eastern Kanto Plain of central Japan, we analysed four drill cores and reviewed other core data from the southern part of the Lake Inba area. Fossil diatom assemblages yielded evidence of centennial-scale palaeogeographic and salinity responses to sea-level changes since the late Pleistocene. We determined that the seawater incursion into the Lake Inba area during the Holocene transgression occurred at approximately 9000 yr. We also recognised a late Holocene regression event corresponding to the Yayoi regression, considered to have occurred from ca. 3000 to ca. 2000 yr, and a subsequent transgression. Our data clarify some of the palaeogeographic changes that occurred in the Lake Inba area and document an overall trend toward lower salinity in the lake during the regression. In particular, the environment in Lake Inba changed from brackish to freshwater no later than 1000 yr. From the detailed palaeogeographic and palaeo-sea-level reconstruction, we recognised that residual subsidence occurred during the Holocene in this area. Thus, comparison of sea-level reconstructions based on modelling and fossil diatom assemblages is effective in interpreting Holocene long-term subsidence.

scholarly journals Using Paleoecological Proxies to Determine Holocene Environmental Change: A Case Study at Onaero Beach, North Taranaki

2021 ◽  
Author(s):  
◽  
Rachel Skudder
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Marine Species ◽  
Loss On Ignition ◽  
Diatom Assemblages ◽  
Diatom Analysis ◽  
Global Context ◽  
Prevailing Wind Direction ◽  
Climatic Event

<p>A multi-proxy paleoecological and sedimentological record for the last ~8.3kyr is extracted from a 2.1m coastal seacliff at Onaero Beach, North Taranaki. This record is used to infer both local environmental changes including shoreline, coastal conditions, as well as regional changes in atmospheric circulation and climate wetness. Analysis of diatom and pollen populations, particle size, and loss on ignition provide the raw data from which inferences regarding salinity and vegetation are made. Changes are tied to a chronology determined through radiocarbon ages and tephrochronology.  Key objectives of this study are: (1) To characterize changes in salinity and relative shoreline position at Onaero Beach (2) To characterise changes in vegetation and relate these changes to overall state of the climate through the Holocene (3) Compare the results of this study with others from New Zealand and the wider south pacific to investigate how the Onaero Beach section fits in both a regional and global context.  Diatom analysis of the Onaero section revealed the dominance of brackish to marine species which suddenly at 7.3ka after which time diatom assemblages were dominated by fresh and salt intolerant species. The marine to freshwater transition represents a transition from a brackish to freshwater coastal lagoon.  Pollen analysis of the Onaero Beach section indicates the region was dominated by podocarp forest. The increasing dominance of Dacrydium and decline in other podocarps suggests an increase in overall climate wetness.  The disappearance of pollen in conjunction with the deposition of tephra at ~4.15ka is not conclusive proof of, but certainly fits with, the idea of a significant climatic event occurring at ~4.2ka resulting in a reversal of the current prevailing wind direction and supports the case for a formal Middle/Late Holocene boundary at this time.</p>

scholarly journals Using Paleoecological Proxies to Determine Holocene Environmental Change: A Case Study at Onaero Beach, North Taranaki

2021 ◽  
Author(s):  
◽  
Rachel Skudder
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Marine Species ◽  
Loss On Ignition ◽  
Diatom Assemblages ◽  
Diatom Analysis ◽  
Global Context ◽  
Prevailing Wind Direction ◽  
Climatic Event

<p>A multi-proxy paleoecological and sedimentological record for the last ~8.3kyr is extracted from a 2.1m coastal seacliff at Onaero Beach, North Taranaki. This record is used to infer both local environmental changes including shoreline, coastal conditions, as well as regional changes in atmospheric circulation and climate wetness. Analysis of diatom and pollen populations, particle size, and loss on ignition provide the raw data from which inferences regarding salinity and vegetation are made. Changes are tied to a chronology determined through radiocarbon ages and tephrochronology.  Key objectives of this study are: (1) To characterize changes in salinity and relative shoreline position at Onaero Beach (2) To characterise changes in vegetation and relate these changes to overall state of the climate through the Holocene (3) Compare the results of this study with others from New Zealand and the wider south pacific to investigate how the Onaero Beach section fits in both a regional and global context.  Diatom analysis of the Onaero section revealed the dominance of brackish to marine species which suddenly at 7.3ka after which time diatom assemblages were dominated by fresh and salt intolerant species. The marine to freshwater transition represents a transition from a brackish to freshwater coastal lagoon.  Pollen analysis of the Onaero Beach section indicates the region was dominated by podocarp forest. The increasing dominance of Dacrydium and decline in other podocarps suggests an increase in overall climate wetness.  The disappearance of pollen in conjunction with the deposition of tephra at ~4.15ka is not conclusive proof of, but certainly fits with, the idea of a significant climatic event occurring at ~4.2ka resulting in a reversal of the current prevailing wind direction and supports the case for a formal Middle/Late Holocene boundary at this time.</p>

Holocene diatom assemblages from Dunderbukhta sediments, West Svalbard

2019 ◽  
pp. 242-245
Author(s):  
Ksenya V. Poleshchuk ◽  
Zinaida V. Pushina ◽  
Sergey R. Verkulich
Keyword(s):  
Environmental Changes ◽  
Ecological Groups ◽  
Diatom Assemblages ◽  
Diatom Analysis ◽  
Diatom Flora ◽  
Sediment Samples ◽  
Ecological Zones ◽  
Middle Holocene ◽  
Temperature Trends

The diatom analysis results of sediment samples from Dunderbukta area (Wedel Jarlsberg Land, West Svalbard) are presented in this paper. The diatom flora consists of four ecological groups, which ratio indicates three ecological zones. These zones show environmental changes of the area in early–middle Holocene that is demonstrating periods of regression and temperature trends.

An Assessment of Environmental Changes in Three Lakes from King's County (Nova Scotia, Canada) Using Diatom-Based Paleolimnological Techniques

2008 ◽  
Vol 43 (2-3) ◽  
pp. 85-98 ◽  
Author(s):  
Joshua R. Thienpont ◽  
Brian K. Ginn ◽  
Brian F. Cumming ◽  
John P. Smol
Keyword(s):  
Nova Scotia ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Lake Management ◽  
River System ◽  
210Pb Dating ◽  
Hydroelectric Power ◽  
Diatom Assemblages ◽  
Shoreline Development ◽  
Before And After

Abstract Paleolimnological approaches using sedimentary diatom assemblages were used to assess water quality changes over the last approximately 200 years in three lakes from King's County, Nova Scotia. In particular, the role of recent shoreline development in accelerating eutrophication in these systems was assessed. Sediment cores collected from each lake were analyzed for their diatom assemblages at approximately 5-year intervals, as determined by 210Pb dating. Analyses showed that each system has changed, but tracked different ecosystem changes. Tupper and George lakes recorded shifts, which are likely primarily related to climatic warming, with diatom assemblages changing from a preindustrial dominance by Aulacoseira spp. to present-day dominance by Cyclotella stelligera. In addition to the recent climatic-related changes, further diatom changes in the Tupper Lake core between approximately 1820 and 1970 were coincident with watershed disturbances (farming, forestry, and construction of hydroelectric power infrastructure). Black River Lake has recorded an increase in diatom-inferred total phosphorus since about 1950, likely due to impoundment of the Black River system for hydroelectric generation and subsequent changes in land runoff. Before-and-after (i.e., top-bottom) sediment analyses of six other lakes from King's County provided further evidence that the region is being influenced by climatic change (decreases in Aulacoseira spp., increases in planktonic diatom taxa), as well as showing other environmental stressors (e.g., acidification). However, we recorded no marked increase in diatom-inferred nutrient levels coincident with shoreline cottage development in any of the nine study lakes. Paleolimnological studies such as these allow lake managers to place the current limnological conditions into a long-term context, and thereby provide important background data for effective lake management.

scholarly journals Late-Holocene landscape evolution and human presence in the northern Danube delta (Chilia distributary lobes)

The Holocene ◽  
2021 ◽  
pp. 095968362110191
Author(s):  
Luminița Preoteasa ◽  
Alfred Vespremeanu-Stroe ◽  
Anca Dan ◽  
Laurențiu Țuțuianu ◽  
Cristian Panaiotu ◽  
...  
Keyword(s):  
Middle Ages ◽  
Economic History ◽  
Late Holocene ◽  
Environmental Changes ◽  
Land Use Changes ◽  
Sedimentary Facies ◽  
The Black Sea ◽  
Danube Delta ◽  
Human Presence ◽  
Historical Texts

This paper documents the Late-Holocene environmental changes and human presence in the northern Danube delta using a multidisciplinary approach that combines geoscientific data with archaeological findings, historical texts, and maps. It follows the formation and progression of the Chilia distributary and the reconfiguration of socioeconomic activities. Sedimentary facies identified on five new cores by changes in texture properties, magnetic susceptibility, geochemistry, and macro- and microfauna composition together with the newly obtained chronology constrain the complex evolution of the Chilia branch as filling in a long-lasting bay and then of a giant lagoon (Thiagola) which covered most of the northern delta since the Old Danube lobe inception (ca. 7500 yrs BP) till modern Chilia development. It initiated during the Greek Antiquity (ca. 2500 yrs ar BP) at the delta apex, while in Roman times (ca. 1800 yrs BP) it pursued its slow flowing into the vast Thiagola Lagoon. The most dramatic transformations occurred in the last 800 years when the river passed east of the Chilia promontory, rapidly went through the present-day Matița-Merhei basin (several decades), and created its first open-sea outlet. Solid discharge increased in two distinct periods, once in the Middle Ages (ca. 750 yrs BP) and then in the Modern Period (ca. 150 yrs BP) due to human-induced land-use changes in the Danube watershed. The chronology of the cultural remains on the pre-deltaic Chilia promontory and the multiproxy analysis of a sediment core retrieved nearby downstream suggest the terrestrial connection of the island with the mainland in ancient times. The hitherto contended issue of the old Thiagola Lagoon and its location are redefined here, as are the original identifications of ancient and medieval toponyms and hydronyms, especially for Chilia-Licostomo, Byzantine, Genoese, Moldavian, Ottoman, and Russian trading point of great importance in the political and economic history of the Black Sea and neighboring regions.

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