Multi-proxy Records of Environmental Changes in a Freshwater Wetland in Louisiana during the Late Holocene

2019 ◽  
Vol 8 (3) ◽  
pp. 417-428
Author(s):  
Junghyung Ryu ◽  
Kam-biu Liu
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Freshwater Wetland ◽  
Proxy Records

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.

scholarly journals Eastern Andean environmental and climate synthesis for the last 2000 years BP from terrestrial pollen and charcoal records of Patagonia

2015 ◽  
Vol 11 (3) ◽  
pp. 2121-2157 ◽  
Author(s):  
G. D. Sottile ◽  
M. E. Echeverria ◽  
M. V. Mancini ◽  
M. M. Bianchi ◽  
M. A. Marcos ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Environmental Changes ◽  
Fire Regime ◽  
Ice Age ◽  
Circulation System ◽  
Forest Steppe ◽  
Proxy Records ◽  
The Andes ◽  
Precipitation Regimes ◽  
Southern Patagonia

Abstract. The Southern Hemisphere Westerly Winds (SWW) constitute an important zonal circulation system that dominates the dynamics of Southern Hemisphere mid-latitude climate. Little is known about climatic changes in the Southern South America in comparison to the Northern Hemisphere due to the low density of proxy records, and adequate chronology and sampling resolution to address environmental changes of the last 2000 years. Since 2009, new pollen and charcoal records from bog and lakes in northern and southern Patagonia at the east side of the Andes have been published with an adequate calibration of pollen assemblages related to modern vegetation and ecological behaviour. In this work we improve the chronological control of some eastern Andean previously published sequences and integrate pollen and charcoal dataset available east of the Andes to interpret possible environmental and SWW variability at centennial time scales. Through the analysis of modern and past hydric balance dynamics we compare these scenarios with other western Andean SWW sensitive proxy records for the last 2000 years. Due to the distinct precipitation regimes that exist between Northern (40–45° S) and Southern Patagonia (48–52° S) pollen sites locations, shifts on latitudinal and strength of the SWW results in large changes on hydric availability on forest and steppe communities. Therefore, we can interpret fossil pollen dataset as changes on paleohydric balance at every single site by the construction of paleohydric indices and comparison to charcoal records during the last 2000 cal yrs BP. Our composite pollen-based Northern and Southern Patagonia indices can be interpreted as changes in latitudinal variation and intensity of the SWW respectively. Dataset integration suggest poleward SWW between 2000 and 750 cal yrs BP and northward-weaker SWW during the Little Ice Age (750–200 cal yrs BP). These SWW variations are synchronous to Patagonian fire activity major shifts. We found an in phase fire regime (in terms of timing of biomass burning) between northern Patagonia Monte shrubland and Southern Patagonia steppe environments. Conversely, there is an antiphase fire regime between Northern and Southern Patagonia forest and forest-steppe ecotone environments. SWW variability may be associated to ENSO variability especially during the last millennia. For the last 200 cal yrs BP we can concluded that the SWW belt were more intense and poleward than the previous interval. Our composite pollen-based SWW indices show the potential of pollen dataset integration to improve the understanding of paleohydric variability especially for the last 2000 millennial in Patagonia.

scholarly journals Anthropogenic impacts on Late Holocene land-cover change and floristic biodiversity loss in tropical southeastern Asia

2021 ◽  
Vol 118 (40) ◽  
pp. e2022210118 ◽  
Author(s):  
Zhuo Zheng ◽  
Ting Ma ◽  
Patrick Roberts ◽  
Zhen Li ◽  
Yuanfu Yue ◽  
...  
Keyword(s):  
Late Holocene ◽  
Southern China ◽  
Anthropogenic Impacts ◽  
Biodiversity Loss ◽  
Freshwater Wetland ◽  
Social Changes ◽  
Rice Agriculture ◽  
Human Land Use ◽  
Key Species ◽  
The Face

Southern China and Southeast Asia witnessed some of their most significant economic and social changes relevant to human land use during the Late Holocene, including the intensification and spread of rice agriculture. Despite rice growth being associated with a number of earth systems impacts, how these changes transformed tropical vegetation in this region of immense endemic biodiversity remains poorly understood. Here, we compile a pollen dataset incorporating ∼150,000 identifications and 233 pollen taxa to examine past changes in floral biodiversity, together with a compilation of records of forest decline across the region using 14 pollen records spanning lowland to mountain sites. Our results demonstrate that the rise of intensive rice agriculture from approximately 2,000 y ago led not only to extensive deforestation but also to remarkable changes of vegetation composition and a reduction in arboreal diversity. Focusing specifically on the Tertiary relic tree species, the freshwater wetland conifer Glyptostrobus (Glyptostrobus pensilis), we demonstrate how key species that had survived changing environmental conditions across millions of years shrank in the face of paddy rice farming and human disturbance.

Middle to late Holocene environmental changes in western Ireland inferred from fluctuations in preservation of biological variables in lake sediment

2012 ◽  
Vol 48 (2) ◽  
pp. 433-448 ◽  
Author(s):  
S. Murnaghan ◽  
D. Taylor ◽  
E. Jennings ◽  
C. Dalton ◽  
K. Olaya-Bosch ◽  
...  
Keyword(s):  
Lake Sediment ◽  
Late Holocene ◽  
Environmental Changes ◽  
Biological Variables ◽  
Western Ireland

scholarly journals Correction to: Late Holocene palaeovegetational and environmental changes inferred from organic geochemical proxies in sediments from Pookot Lake, southern India

2019 ◽  
Vol 12 (24) ◽  
Author(s):  
Sandeep Kizhur ◽  
Rajasekhariah Shankar ◽  
Anish Kumar Warrier ◽  
Madhusudan G. Yadava ◽  
Rengaswamy Ramesh ◽  
...  
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Southern India ◽  
Geochemical Proxies

scholarly journals Radiocarbon Analysis Confirms the Annual Nature of Sagebrush Growth Rings

Radiocarbon ◽  
2007 ◽  
Vol 49 (3) ◽  
pp. 1231-1240 ◽  
Author(s):  
Franco Biondi ◽  
Scotty D J Strachan ◽  
Scott Mensing ◽  
Gianluca Piovesan
Keyword(s):  
Great Basin ◽  
Cross Sections ◽  
Environmental Changes ◽  
Spatially Explicit ◽  
Growth Rings ◽  
Ams Radiocarbon Dating ◽  
Big Sagebrush ◽  
Proxy Records ◽  
Annual Resolution ◽  
Wildfire Regimes

In the Great Basin of North America, big sagebrush (Artemisia tridentata Nutt.) growth rings can be used to reconstruct environmental changes with annual resolution in areas where there is otherwise little such information available. We tested the annual nature of big sagebrush wood layers using accelerator mass spectrometry (AMS) radiocarbon dating. Four cross-sections from 3 sagebrush plants were collected near Ely, Nevada, USA, and analyzed using dendrochronological methods. Ten 14C measurements were then used to trace the location of the 1963–64 “bomb spike.” Although the number of rings on each section did not exceed 60, crossdating was possible within a section and between sections. Years assigned to individual wood layers by means of crossdating aligned with their expected 14C values, matching the location of the 14C peak. This result confirmed the annual nature of growth rings formed by big sagebrush, and will facilitate the development of spatially explicit, well-replicated proxy records of environmental change, such as wildfire regimes, in Great Basin valleys.

Holocene climatic and palaeoenvironmental changes in the South-Eastern Barents Sea – new insights from palaeomagnetic and geochemical stratigraphy

2020 ◽  
Author(s):  
Martin Klug ◽  
Karl Fabian ◽  
Jochen Knies ◽  
Valérie Bellec ◽  
Leif Rise
Keyword(s):  
North Atlantic ◽  
Remanent Magnetization ◽  
Late Holocene ◽  
Environmental Changes ◽  
Barents Sea ◽  
Marine Ecosystem ◽  
Planetary Science ◽  
Coastal Current ◽  
The South ◽  
South Eastern

<p>Holocene climate variability and environmental changes have been studied using a sediment record from the Barents Sea with focus on the spatio-temporal evolution of bio-productivity and terrestrial sediment deposition in response to changes of climate and regional oceanography. From a 3 m long sediment core recovered in the South-Eastern Barents Sea at 72.5°N 32.5°E u-channels were extracted and stepwise demagnetized and measured for their natural remanent magnetization (NRM) and anhysteretic remanent magnetization (ARM) at the cryogenic magnetometer facility at the Geological Survey of Norway. The u-channel measurements at 3 mm resolution allow the reconstruction of palaeoinclination, relative declination and relative palaeointensity. Comparison of these parameters to FENNOSTACK (Snowball et al., 2007) and EGLACOM-SVAIS (Sagnotti et al., 2011) establishes a robust age model for the sediment sequence which otherwise contains little datable material. We applied statistical factor analysis as centred logratio (clr) transformation to reduce dimensionality of the XRF data and compare changes in high-resolution magnetic susceptibility, wet bulk density and XRF elemental composition with changes of climate proxies in other North Atlantic sedimentary records.</p><p>Based on the new chronostratigraphic framework changes of inorganic and organic proxies at long-term and sub-millennial scale resolve the temperature variability throughout the Holocene. Calcium content changes are related to regional bio-productivity changes in response to surface temperature changes with a pronounced deterioration at the beginning of the Neoglaciation and gradual enhancement during the late Holocene. Besides palaeoclimatic responses, the results offer the opportunity to study sediment transport and deposition during the regional deglaciation and mid-Holocene glacier growth in northwestern Fennoscandia. The temporal changes of the regional oceanography and the variability of marine palaeoproductivity in the South-Eastern Barents Sea indicate an active interplay between the North Atlantic Current (NAC) and the Norwegian Coastal Current (NCC) during the early Holocene, a predominance of the NCC during middle Holocene and a re-amplification of the NAC during the late Holocene. Comparison to other records from the Nordic Seas enables the reconstruction of responses and the vulnerability of this arctic marine ecosystem to past climate variations and may help to estimate upcoming responses to recent and future climate changes.</p><p> </p><p>References:</p><p>Snowball, I., L. Zillén, A. Ojala, T. Saarinen, and P. Sandgren (2007), FENNOSTACK and FENNORPIS: Varve dated Holocene palaeomagnetic secular variation and relative palaeointensity stacks for Fennoscandia, Earth and Planetary Science Letters, 255, (1-2), 106–116</p><p>Sagnotti, L., P. Macrì, R. Lucchi, M. Rebesco, and A. Camerlenghi (2011), A Holocene paleosecular variation record from the northwestern Barents Sea continental margin, Geochemistry, Geophysics, Geosystems, 12, (11)</p>

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