Environmental magnetism study of Lake Cadagno, Switzerland

2021 ◽  
Author(s):  
Artin Ali ◽  
Andrea Biedermann ◽  
Jasmine Berg ◽  
Mark Lever ◽  
Hendrik Vogel
Keyword(s):  
Grain Size ◽  
Sedimentary Environment ◽  
Environmental Magnetism ◽  
Late Glacial ◽  
Magnetic Minerals ◽  
Climate Conditions ◽  
Glacial Sediments ◽  
Depth Profiles ◽  
Magnetic Carriers ◽  
Lake Bottom

<p>Climate affects the mineralogy and grain size of sediments deposited in lakes. These properties are reflected in the sediment magnetic properties and can be characterized using magnetic methods. As part of the Cadagno-Project, which recovered several gravity and piston cores spanning the entire lake history from the deglacial to the present from the deepest part of permanently stratified Lake Cadagno, which is due to its peculiar water column chemistry considered an early Earth ocean analogue, our study aims to define changes in climate conditions during sedimentation. Here, we present a rock magnetic dataset (low-field magnetic susceptibility and its temperature dependence, anhysteretic and isothermal remanent magnetization (ARM, IRM), acquired in various fields, AF demagnetization, and hysteresis loops) that helps characterize the concentration, mineralogy, and grain size of magnetic carriers, and their variability with depth. Susceptibility, ARM, and IRM were measured on core sediments down to a depth of 886 cm below the lake bottom, providing a high-resolution record of the sedimentary environment of Lake Cadagno over the last 11,000 years. In addition to these depth profiles, detailed rock magnetic experiments were conducted at specific depths. The cores consist of pelagic sediments, flood turbidites, and late glacial sediments. In order to determine the characteristics of the background sedimentation, only turbidite-free intervals were included in this study. The depth profiles of susceptibility, ARM and IRM have approximately similar variations with depth. They show distinct peaks at the upper parts of the pelagic sediments (156-158 cm below the lake bottom,   ̴1280-1320 cal. Yr Bp) and of the late glacial sediments (826-844 cm below the lake bottom), which can be interpreted as increased concentration of ferromagnetic minerals or as a change in the magnetic mineralogy, in addition to decreasing trend in the background. Several intervals within the pelagic sediments are dominated by low-coercivity minerals (<10 mT), while higher coercivity grains (10–100 mT) contribute significantly at (150-170, 418-448 and 719-735 cm below the lake bottom). Magnetic grain size was analyzed using a Day plot, and shows that single domain magnetite dominates at (844 cm) below the lake bottom, indicating the presence of magnetotactic bacteria, which are believed to dwell mainly in the oxic–anoxic interface where chemical gradients are high. These results provide important constraints on the environmental conditions and climate change recorded by the magnetic minerals in Lake Cadagno.</p>

Holocene climate recorded by magnetic properties of lake sediments in the Northern Rocky Mountains, USA

The Holocene ◽  
2019 ◽  
Vol 30 (3) ◽  
pp. 479-484
Author(s):  
Daniel P Maxbauer ◽  
Mark D Shapley ◽  
Christoph E Geiss ◽  
Emi Ito
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Rocky Mountains ◽  
Future Research ◽  
Magnetic Minerals ◽  
Holocene Climate ◽  
Northern Rocky Mountains ◽  
The North ◽  
Lake Bottom ◽  
Northern Rockies

We present two hypotheses regarding the evolution of Holocene climate in the Northern Rocky Mountains that stem from a previously unpublished environmental magnetic record from Jones Lake, Montana. First, we link two distinct intervals of fining magnetic grain size (documented by an increasing ratio of anhysteretic to isothermal remanent magnetization) to the authigenic production of magnetic minerals in Jones Lake bottom waters. We propose that authigenesis in Jones Lake is limited by rates of groundwater recharge and ultimately regional hydroclimate. Second, at ~8.3 ka, magnetic grain size increases sharply, accompanied by a drop in concentration of magnetic minerals, suggesting a rapid termination of magnetic mineral authigenesis that is coeval with widespread effects of the 8.2 ka event in the North Atlantic. This association suggests a hydroclimatic response to the 8.2 ka event in the Northern Rockies that to our knowledge is not well documented. These preliminary hypotheses present compelling new ideas that we hope will both highlight the sensitivity of magnetic properties to record climate variability and attract more work by future research into aridity, hydrochemical response, and climate dynamics in the Northern Rockies.

Landslide Fens as a Sensitive Indicator of Paleoenvironmental Changes Since the Late Glacial: A Case Study of the Polish Western Carpathians

Radiocarbon ◽  
2018 ◽  
Vol 60 (4) ◽  
pp. 1199-1213 ◽  
Author(s):  
Włodzimierz Margielewski
Keyword(s):  
Grain Size ◽  
Human Activity ◽  
Sedimentary Environment ◽  
Late Glacial ◽  
Climatic Changes ◽  
Western Carpathians ◽  
Sensitive Indicator ◽  
Loss On Ignition ◽  
Paleoenvironmental Changes

AbstractIn the sequences of landslide fen (mire) deposits of the Polish Western Carpathians, Late Glacial-Holocene paleoenvironmental changes were recorded. Downpours and/or continuous rains cyclically repeated during phases of climate humidity growth, causing supplies of mineral material to the minerogenic mires. In effect, illuvial or mineral horizons were formed in landslide fen deposits, as well as mineral covers overly fens in some sites. Sedimentological records reflect various, overlapping factors, as climatic changes, human activity (e.g. accelerating erosion), as well the specificity of the sedimentary environment in each studied landslide fens. The reconstruction and interpretation of the paleoenvironmental changes recorded in landslide fen sediments must be supported by multiproxy analysis of the sequences using pollen, lithological (loss on ignition, grain size and petrography) analyses of samples accurately dated by numerous radiocarbon (14C) dates.

scholarly journals SEDIMENTOLOGICAL AND PALAEOENVIRONMENTAL CHARACTER OF LAKE KORONIA SEDIMENTS

2017 ◽  
Vol 50 (1) ◽  
pp. 295
Author(s):  
S. Doani ◽  
K. Albanakis ◽  
O. Koukousioura ◽  
K.K. Koliadimou
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
Environmental Conditions ◽  
Water Body ◽  
Fine Sand ◽  
Lake Bottom ◽  
Bottom Sampling ◽  
Palaeoenvironmental Conditions ◽  
Freshwater Ostracods ◽  
Ostracod Species

The aim of the present study is to investigate the sedimentological characteristics of Lake Koronia down to a depth of 3.5m below lake bottom. Sampling operations took advandage of a season that the lake bottom was exposed to subaerial conditions. The sedimentological analysis proved that sediments consist of mud to sandy mud, with 2 phases of very fine sand fractions. The proportion of dry organic matter contained into sediment, appears to be generally small while the rates of moisture and volatiles are relatively high. Furthermore, this study examines the distribution of ostracod populations in the sediments of the lake in relation to depth, grain size and other environmental conditions of this water body. Four ostracod species were identified: Candona neglecta, Darwinula stevensoni, Heterocypris spp. and Limnocythere inopinata. The study of freshwater ostracods provides information for the palaeoecological/palaeoenvironmental conditions during the sedimentation.

scholarly journals High-Resolution Petrographic Evidence Confirming Detrital and Biogenic Magnetites as Remanence Carriers for Zongpu Carbonates in the Gamba Area, South Tibet

2021 ◽  
Vol 9 ◽  
Author(s):  
Qian Zhao ◽  
Baochun Huang ◽  
Zhiyu Yi ◽  
Pengfei Xue
Keyword(s):  
High Resolution ◽  
Electron Backscatter Diffraction ◽  
Early Stage ◽  
Electron Microscopic Observation ◽  
Optical Microscope ◽  
Magnetic Minerals ◽  
Electron Microscopic ◽  
Magnetic Carriers ◽  
Magnetic Extraction ◽  
South Tibet

Paleocene carbonates from the Gamba area of South Tibet provide the largest paleomagnetic dataset for constraining the paleogeography of the India-Asia collision in the early stage. Previous studies argued that the characteristic remanences (ChRMs) obtained from this unit were remagnetized via orogenic fluids. This study carries out a high-resolution petrographic study on the Paleocene carbonates from Gamba aiming to test the nature of the ChRMs. Electron microscopic observation on magnetic extracts identified a large amount of detrital magnetite that are multi- to single domain in sizes and nanoscale biogenic magnetite. Minor framboidal iron oxides were also identified, which were previously interpreted as authigenic magnetite that substitutes pyrite. However, our scanning and transmission electron microscopic (SEM/TEM) observations, along with optical microscope and Raman spectrum investigations further suggest that these magnetic minerals are pigmentary hematite and goethite that are incapable of carrying a stable primary magnetization. We therefore argue that the ChRMs of the limestones from the Zongpu Formation in the Gamba area are carried by detrital and biogenic magnetites rather than authigenic magnetite. The paleomagnetic data from the Gamba area are interpreted as primary origin and can thus be used for tectonic reconstructions. We emphasize that magnetic extraction, integrated with advanced mineralogic studies (e.g., electron backscatter diffraction and electron diffraction) are effective approaches for investigating the origin of magnetic carriers in carbonate rocks.

scholarly journals <sup>10</sup>Be depth profiles in glacial sediments on the Swiss Plateau: deposition age, denudation and (pseudo-) inheritance

2017 ◽  
Vol 66 (2) ◽  
pp. 57-68 ◽  
Author(s):  
Lorenz Wüthrich ◽  
Claudio Brändli ◽  
Régis Braucher ◽  
Heinz Veit ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Radioactive Decay ◽  
Glacial Sediments ◽  
Depth Profiles ◽  
Denudation Rates ◽  
Last Glaciation ◽  
The Alps ◽  
Swiss Plateau ◽  
High Concentrations ◽  
Cosmogenic 10Be

Abstract. During the Pleistocene, glaciers advanced repeatedly from the Alps onto the Swiss Plateau. Numeric age control for the last glaciation is good and thus the area is well suited to test a method which has so far not been applied to till in Switzerland. In this study, we apply in situ produced cosmogenic 10Be depth profile dating to several till deposits. Three sites lie inside the assumed Last Glacial Maximum (LGM) extent of the Rhône and Aare glaciers (Bern, Deisswil, Steinhof) and two lie outside (Niederbuchsiten, St. Urban). All sites are strongly affected by denudation, and all sites have reached steady state, i.e., the 10Be production is in equilibrium with radioactive decay and denudational losses. Deposition ages can therefore not be well constrained. Assuming constant denudation rates of 5 cm kyr−1, total denudation on the order of 100 cm for sites within the extent of the LGM and up to tens of meters for older moraines are calculated. Denudation events, for example related to periglacial conditions during the LGM, mitigate the need to invoke such massive denudation and could help to explain high 10Be concentrations at great depths, which we here dub pseudo-inheritance. This term should be used to distinguish conceptionally from true inheritance, i.e., high concentrations derived from the catchment.

Multi-proxy studies of the Late Glacial fluvio-aeolian succession in the type site Mierzyn, central Poland 

2021 ◽  
Author(s):  
Moska Piotr ◽  
Sokołowski Robert ◽  
Jary Zdzisław ◽  
Zieliński Paweł ◽  
Raczyk Jerzy ◽  
...  
Keyword(s):  
Western Europe ◽  
Late Glacial ◽  
Luminescence Dating ◽  
Climate Conditions ◽  
Central Poland ◽  
Depositional Processes ◽  
Dating Methods ◽  
Absolute Dating ◽  
Absolute Age ◽  
Pedogenic Processes

&lt;p&gt;Multi-proxy studies (including sedimentological, pedological, radiocarbon and optically stimulated luminescence dating methods) were used to establish origin and chronology of depositional processes in the type section Mierzyn, central Poland. The investigated key site is located in the extraglacial zone of the Last Glaciation, ca. 130 km to the south from the Last Glacial Maximum in the Luci&amp;#261;&amp;#380;a river valley area. In the studied profile (16 m thick) two lithofacial complexes were identified. The lower, fluvio-aeolian complex consists of silty-sandy sediments (1.6 m) deposited. The final phase of fluvio-aeolian deposition is expressed by initial pedogenic processes. Above is located aeolian complex (13 m of thickness). Three aeolian units are separated by two palaeosols.&lt;/p&gt;&lt;p&gt;To establish stratigraphic framework of depositional and pedogenic processes, four samples for radiocarbon dating from palaeosols and twelve samples for OSL dating from sandy units were collected. The obtained results reveal very good agreement of both absolute dating methods. It led to reconstruct chronology of main palaeoenvironmental changes. The fluvio-aeolian complex and the lowermost part of aeolian complex (below the lower palaeosol) were deposited in the Oldest Dryas in relatively cool and dry climate conditions. The amelioration of climate in the B&amp;#248;lling interstadial caused development of pedogenic processes expressed by 0.3 m thick palaeosol. Main part of aeolian complex (10 m of thickness) was deposited in the Older Dryas. The upper palaeosol developed in the Aller&amp;#248;d interstadial as a result of the next amelioration of the climate. During the Younger Dryas was deposited the uppermost part of aeolian complex.&lt;/p&gt;&lt;p&gt;Classic development of fluvial to- aeolian succession in the Mierzyn site as well as detailed chronology based on two independent absolute age methods reveal that it can be treated as stratotype for the Late Glacial and correlated with other type sections in the Central and Western Europe.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Ackowledgments&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Presented results were obtained with support of Polish National Science Centre, contract number 2018/30/E/ST10/00616.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Sedimentary environment prediction of grain-size data based on machine learning approach

2020 ◽  
Vol 8 (3) ◽  
pp. SL71-SL78
Author(s):  
Qiao Su ◽  
Yanhui Zhu ◽  
Fang Hu ◽  
Xingyong Xu
Keyword(s):  
Machine Learning ◽  
Grain Size ◽  
Prediction Model ◽  
Sedimentary Environment ◽  
Machine Learning Algorithms ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Data Set ◽  
Sedimentary Environments ◽  
Size Data

Grain size is one of the most important records for sedimentary environment, and researchers have made remarkable progress in the interpretation of sedimentary environments by grain size analysis in the past few decades. However, these advances often depend on the personal experience of the scholars and combination with other methods used together. Here, we constructed a prediction model using the K-nearest neighbors algorithm, one of the machine learning methods, which can predict the sedimentary environments of one core through a known core. Compared to the results of other studies based on the comprehensive data set of grain size and four other indicators, this model achieved a high precision value only using the grain size data. We have also compared our prediction model with other mainstream machine learning algorithms, and the experimental results of six evaluation metrics shed light on that this prediction model can achieve the higher precision. The main errors of the model reflect the length of the conversation area of sedimentary environment, which is controlled by the sedimentary dynamics. This model can provide a quick comparison method of the cores in a similar environment; thus, it may point out the preliminary guidance for further study.

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