Monsoon Variability Reconstructed from Sedimentological and Mineral Magnetic Studies from Vaghad Tank Deposits, Nashik District, Maharashtra

An attempt made to reconstruct the monsoon variability using sedimentological, geochemical and mineral magnetic studies from deposits in Vaghad Tank, Nashik district, Maharashtra (India). The ~140 years multi-proxy data of the 3.3 meter thick sedimentary section of the tank exhibits some minor changes in sediment characteristics up to the depth of ~150 cm. The grain-size analysis and mineral magnetic studies of 67 samples of sediment suggests that, the sediment dominated by clay. Overall, sedimentary profile does not exhibit any systematic trend in the sediment properties. Finally, the present study concludes no significant changes in the past monsoon conditions have been occurred during the last century but some minor changes in the hydrodynamic conditions have been noticed during the last few decades.

Application of environmental magnetism to trace sediment sources contributing to Kruger National Park reservoirs

Sediment source fingerprinting using environmental magnetism has successfully differentiated between sediment sources in different regions of South Africa. The method was applied in the natural landscape of the Kruger National Park to trace sediment sources delivered to four reservoirs (Hartbeesfontein, Marheya, Nhlanganzwani, Silolweni) whose contributing catchments were underlain by a range of igneous, metamorphic, and sedimentary rocks. This research attempted to evaluate the impact of vegetation, lithology, and particle size controls on the ability of magnetic signatures to discriminate between lithology-defined potential sources. Potential source samples were collected from each lithology present in all catchments, except for the Lugmag catchment where the lithology was uniform, but the vegetation type varied significantly between woodland and grassland. One sediment core was taken in each of the four catchment reservoirs where there was more than one lithology present in order to unmix and apportion contributing sediment sources. Sampling time in the field was often restricted to short periods, dependent on anti-poaching activities and movement of free-roaming wildlife across the Park. This occasionally led to the sub-optimal collection of enough source samples to capture source signature variability. Mineral magnetic parameters were unable to discriminate between vegetation-defined sediment sources in the Lugmag catchment (homogenous underlying lithology) but were able to discriminate between lithology-defined sediment sources (to varying degrees) in the other four catchments. The contributions of each lithology-defined sediment source were estimated using a straightforward statistical protocol frequently used in published literature that included a Mann-Whitney U or Kruskal-Wallis H test, mass conservation test, discriminant function analysis, and an (un)mixing model. A contribution from each lithology source to reservoir sediment was estimated. Connectivity was a significant factor in understanding erosion in each of the catchments. Both longitudinal (e.g., drainage density) and lateral connectivity (e.g., floodplain - river) were important. Travel distance of eroded sediment to reservoirs was also an essential element in two of the four catchments. There are no defined floodplains, so channel bank soils are very similar to the catchment soils. Therefore, channel bank storage potential would be similar to the storage potential within the catchment. Vegetation played a crucial role in protecting soils, by reducing ii erosion potential as well as trapping and storing sediment, thereby interrupting lateral connectivity. Underlying geology and soils are determining factors of vegetation type and density. A published study estimated catchment area-specific sediment yields for different KNP catchments, including the Hartbeesfontein, Marheya, Nhlanganzwani and Silolweni catchments. The published data was used in combination with the (un)mixing model source contribution estimates of this thesis to determine specific sediment yields by lithology, i.e., for each catchment source. The polymodal particle size characteristics of the sample material led to an investigation into particle size controls on the ability of magnetic signatures to discriminate between potential sources. Due to time constraints, only the Hartbeesfontein and Marheya catchments were tested for grain size differences. For each catchment, one bulk sample was created for each lithology source. This bulk sample was divided into 10 subsamples. The samples were then fractionated into four particle size fraction groups: coarse (250 – 500 μm), medium (125 – 250 μm), fine (63 – 125 μm), and very fine (<63 μm). Reservoir samples were also bulked to create 10 down-core samples for each reservoir, and the samples were also fractionated into the four fraction groups. The same statistical protocol was applied to the fractionated samples and contribution estimates were obtained by lithology for each particle size fraction group. The goodness of fit and uncertainty of the (un)mixing model varied in each catchment, with the two measures of accuracy often showing an inverse relationship. The fractionated modelling estimated the same primary source in the two catchments as in the unfractionated modelling. However, additional information on the secondary and tertiary sources was obtained. Connectivity remained a significant factor in interpreting the results of the fractionated analysis. Specific sediment yields were estimated for each catchment source per particle size fraction group. These sediment yields provided a deeper understanding of sediment transport through a catchment and which particle size groups are most important in catchment erosion. An original contribution to research was made by estimating source contribution estimates for the four reservoirs, quantifying sediment yields for each catchment lithology and then for each catchment lithology by particle size. Mineral magnetic tracing of the catchments was applied for the first time in this region of South Africa.

Mineral magnetic properties of loess–paleosol couplets of northern Serbia over the last 1.0 Ma

We conducted the first detailed mineral magnetic investigation of more than nine loess–paleosol couplets of the composite Titel-Stari Slankamen loess section in Serbia, which provides one of the longest and most complete terrestrial record of paleoclimatic changes in Europe since ~1.0 Ma. The results show that the ferrimagnetic mineral assemblage of the loess units is dominated by partially oxidized multidomain (MD) and pseudo-single domain (PSD) magnetite; however, with an increasing degree of pedogenesis, the eolian contribution is gradually masked by pedogenic superparamagnetic(SP) and single-domain (SD) ferrimagnets (mainly maghemite). The overall consistency of ferrimagnetic grain-size parameters indicates an absence of dissolution of the fine-grained ferrimagnetic fraction despite changes in climate regime over the past 1.0 Ma. The variations of normalized dJ/dT@120K and normalized χheating@530°C reflect a long-term stepwise increase in aridity during glacials with a major step at ~0.6–0.5 Ma, over the last 1.0 Ma. Overall, the results provide an improved basis for the future use of the magnetic properties of Serbian loess deposits for paleoclimatic reconstruction.

Reconstructing the Climate Variability During the Last 5000 Years From the Banni Plains, Kachchh, Western India

The climatic conditions during the beginning of the last 5,000 years have been discussed, debated, and documented from various parts of the Indian subcontinent, due to the human–climate interrelationship. In the present study, we report a multi-proxy dataset encompassing the widely used ∼ geochemical and mineral magnetic proxies supported by radiocarbon and optical chronologies from the Banni Plains of the Rann of Kachchh, western India. Our results support the earlier observations of the prolonged wetter climatic condition synchronous with the mature phase of Harappan era which witnessed a short and intense arid condition at the terminal part of the mature Harappan phase. The climate system dramatically fluctuated during the last five millennia from pulsating between relatively arid (4,800–4,400 years BP, 3,300–3,000 years BP, and at 2,400 years BP) and relatively humid phases (&gt;4,800 years BP, 4,000–3,300 years BP, 1900–1,400 years BP, and 900–550 years BP). The multi-proxy dataset shows a gradual strengthening of the monsoonal conditions from the Banni Plains during the late Harappan phase. Apart from this, the high sedimentation rate (&gt;1 mm/yr) recorded from the Banni Plains suggests it can be tapped as a robust archive to reconstruct multi-decadal to centennial climatic events spanning the Holocene epoch.

Fired clay from Neolithic houses – the role of past environment revealed in mineral magnetic properties

&lt;p&gt;Human behavior and especially the use of fire increasingly influence our environment during the Anthropocene epoch. Balkan Peninsula is on the road of the ancient human dispersal during the Neolithic period. Burnt Neolithic remains are often related to ancient houses which ended their existence as a result of extensive fire. Materials from burnt clay remains from house destructions originating from 18 Neolithic sites from Bulgaria were studied using rock magnetism. Mineral magnetic studies and equivalent firing temperature estimates were carried out. The aim of the study was to explore the magnetic signature of fired clay materials in relation to the most important environmental factors. The main magnetic minerals identified were magnetite, maghemite and hematite, in several cases also epsilon-Fe&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;. Magnetic susceptibility enhancement is dependent on the raw clay mineralogy and the firing intensity, being higher for sites developed on loess materials. Sites located in river valleys from South Bulgaria show lower susceptibility enhancement. Magnetic susceptibility&amp;#160; and percent frequency dependent magnetic susceptibility at site level were considered in relation to the climatic conditions during the Neolithic as revealed by anthracological studies already published for the study region. Firing temperature estimates, comprising 198 single determinations in total, vary in the range 580 &amp;#8211; 1050&amp;#176;C across the sites. Estimated average firing temperatures at site&amp;#8217;s level showed higher values in Early Neolithic sites (Tfire average=815&amp;#176;C) as compared to Late Neolithic ones (Tfire average = 746&amp;#176;C and 713&amp;#176;C). Several possible hypotheses for the trend observed are considered: difference in climate regimes across the territory leading to different &amp;#8220;fire weather&amp;#8221;; difference in the vegetation fuel used in house construction; and intentional burning of Early Neolithic houses. This study is financially supported by the project KP-06-COST/2, funded by the Bulgarian National Science Fund.&lt;/p&gt;

A new reference loess-paleosol archive spanning the last 850 kyrs near Pleven (Bulgaria) – first results

&lt;p&gt;Loess-paleosol sequences (LPSs) are proven valuable archives for continental paleoclimatic reconstructions. However, studied LPSs worldwide, spanning multiple glacial-interglacial cycles, are seldomly sampled and analyzed at a continuous high resolution. Exceptionally, in a quarry setting near the city of Pleven (Bulgaria), a new LPS, with a thickness of 27 m, was continuously sampled at a 2 cm resolution resulting in 1340 bulk-samples. We present herein first rock magnetic results suggesting that the site archives aeolian deposition and soil formation over the last 850 kyrs. &amp;#160;Room temperature bulk mineral magnetic parameters including magnetic susceptibility, hysteresis loop derived parameters, IRM, and ARM (underway) were acquired on all samples. Variations in mineral magnetic data clearly show the alternation of strongly developed paleosols overlying loess units indicative of interglacial and glacial climate cycles. We created a correlative age model by comparing X&lt;sub&gt;ferri&lt;/sub&gt;/M&lt;sub&gt;s&lt;/sub&gt; to inverted LR04 benthic oxygen isotope ratios and adjustments undertaken by the Imbrie &amp; Imbrie ice model. This initial correlative age model leads to an assumed continuous dust accumulation for the last 850 kyrs, from MIS 19 to present. In addition to the regionally widely observed L2-tephra, which is observed outcropping along the Pleven LPS, several other sharp spikes in concentration dependent magnetic characteristics suggest that the sedimentary record had preserved also other tephra layers, clearly identified in the magnetic record due to the accomplished high-resolution sampling design. Additional geochemical and mineralogical data are however necessary for an unequivocal source (age) identification of these events. A tentative scheme of a possible correspondence with well dated tephra layers from sedimentary core at Fucino Basin is established. It implies the occurrence of westerly wind directions during the last 850 kyrs in SE Europe. In summary, the Pleven LPS provides new insights into late-Pleistocene climatic regimes, prevailing wind directions and preservation of tephra layers, essential for further correlative terrestrial-aeolian-coupled age models, regional stratigraphic correlations and paleoclimate reconstructions.&lt;/p&gt;