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.

Late holocene environmental changes in the Southwestern Chukchi Sea inferred from diatom analysis

2017 ◽  
Vol 43 (4) ◽  
pp. 276-285 ◽  
Author(s):  
I. B. Tsoy ◽  
M. S. Obrezkova ◽  
K. I. Aksentov ◽  
A. N. Kolesnik ◽  
V. S. Panov
Keyword(s):  
Late Holocene ◽  
Environmental Changes ◽  
Chukchi Sea ◽  
Diatom Analysis

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 Biostratigraphy, shoreline changes and origin of the Limnea Sea lagoons in northern Estonia: a case study of Lake Harku

Baltica ◽  
2014 ◽  
Vol 27 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Ieva Grudzinska ◽  
Leili Saarse ◽  
Jüri Vassiljev ◽  
Atko Heinsalu
Keyword(s):  
Magnetic Susceptibility ◽  
Loss On Ignition ◽  
Diatom Assemblages ◽  
Depositional History ◽  
Shoreline Changes ◽  
Basin Development ◽  
Radiocarbon Data ◽  
Closed Lake

The paper presents diatom, loss-on-ignition, magnetic susceptibility, and radiocarbon data to reconstruct the depositional history and evolution of Lake Harku, a former Limnea Sea lagoon. Harku is one of the youngest isolated lakes that has been studied bio- and chronostratigraphically in Estonia to date. Based on changes in diatom assemblages, four evolutionary stages in basin development have been recognized (lagoon, semi-enclosed lagoon, transitional and closed lake). Shoreline positions at 2000, 1500, 1000 and 800 cal BP have been reconstructed and displayed on 3D palaeogeographic maps. Lake Harku became isolated from the Limnea Sea at ~800 cal BP, followed by occasional seawater incursions over the next 300 years. Plain landscape, low-lying sill threshold, and proximity to the sea contributed to extended basin isolation.

scholarly journals Diatom analysis of Edku Lake sediments to assess the Late Holocene environmental changes in northern Egypt

2017 ◽  
Vol 38 (2) ◽  
pp. 234-247
Author(s):  
Abdelfattah A. Zalat ◽  
Hamza M. Khalil ◽  
Ali S. Ali ◽  
Seham A. El Nagar
Keyword(s):  
Lake Sediments ◽  
Late Holocene ◽  
Environmental Changes ◽  
Diatom Analysis ◽  
Northern Egypt
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