NEW Research Project: The role of dust storms and aeolian dust deposition in the formation of Central European red clays and red paleosoils in loess sequences

New research project entitled "The role of dust storms and aeolian dust deposition in the formation of Central European red clays and red paleosoils in loess sequences" has started.

Project start: 01/09/2013
Closing date: 31/08/2016

Summary of the research and its aims for experts

The aim of the proposed research is the investigation of role of dust storms and aeolian dust sedimentation in the formation of red clays and red paleosoils of loess sequences. Almost half of the Carpathian Basin is covered by thick loess-paleosoil series, generally underlain by red clays. These deposits provide information on the paleoclimatic and paleoenvironmental changes of the last 3–3.5 million years. The Late and partly, the Middle Pleistocene loess deposits are intercalated by steppe, forest-steppe and brown forest soils, while the older pedogene horizons are different kinds; these are red, Mediterranean-type soils. The younger soils were formed from the underlying loess deposits, while according to preliminary data, dust deposition could have played more dominant role during the formation of the older ones; similarly to certain types of red clays.
In the course of the proposed research, red clay-loess-paleosoil samples from the Carpathian Basin and Saharan dust-derived “terra rossae” from the Mediterranean (e.g. Istria, Croatia) would be investigated by grain-size (granulometric profile for sedimentation type), magnetic susceptibility (environment, startigraphy), scanning electron microscopy (micromorphology, transportation), geochemical and clay-mineralogical (provenance, environment) analyses to get more information on the origin of the deposits, with respect to paleocirculation data. By using these various types of data and stratigraphic survey, I would like to refine the results of previous paleoenvironmental reconstructions (e.g. climofunctions, aeolian dust concentration), which have not taken into account the possibility of interglacial dust deposition.

What is the major research question?

In the course of the investigations, I would like to study the intensity of interglacial aeolian dust deposition, which could have been sufficient to syngentic, accretionary soil development even during the warm-moist periods. The similarities of Saharan dust-derived Mediterranean terra rossae and red paleosoils in the Carpathian Basin are also in the focus of this project.
I would like to determine the ratio of the two, distinct types of aeolian dust sedimentation mechanisms (discontinuous dust storms and almost persistent back-ground dust loads), which were identified during observations of recent dust depositional episodes in several samples. By mathematical-statistical partition of polymodal grain-size distribution curves and by the concrete separation of the sediment populations, the coarse particles from local sources transported by short suspension episodes and the fine-grained ones from large distances could be analysed separately, providing more information on the provenance. The question of detrital and secondary origin of clay and fine-silt sized particles can be answered by the comparison of sedimentary data of fine-grained populations from distinct sources and ages, and by the observations of recent dust intrusions.

What is the significance of the research?

The possibility of significant interglacial aeolian dust deposition is leading to several other questions. According to the classical assumption, the loess deposits have been formed from the depositing dust material, while the paleosoils developed from the underlying loess deposits by weak weathering processes. However, intensive interglacial dust accumulation claims a different kind of stratigraphic interpretation. In the first case, when the soils were formed from the underlying deposits, the last period of loess formation could not have been identified as loess in the sequence. In the second case, the soils form syngenetically from the falling dust, and all of the changes are represented in the stratigraphic column. From a paleocliamtic viewpoint, these glacial-interglacial shifts and abrupt warmings of glacial climax periods are one of the most interesting research topics.
The paleoprecipitation and paleotemperature data of the widely used geochemical climofunctions deserve also further reconsideration. The fine-grained populations of deposits are consisting of detrital and secondary particles; only the secondary ones provide relevant information on the environmental properties of the soil formation. By the assessment of the amount of detrital, windblown clay-minerals the result of these reconstructions could have be refined significantly.
Dust storms and related atmospheric mineral dust particles have been standing in the focus of environmental studies for the last two decades. Investigations confirmed that aeolian dust is an active component of the climate system, and can modify its elements via both direct (e.g. modifying the incoming solar irradiance and outgoing longwave radiation) and indirect (e.g. iron fertilization, cloud-formation); however our knowledge on these topics is still insufficient. In some periods of the Earth’s history the amount of atmospheric aeolian dust have increased by several orders of magnitude, compared to the present 1–2 billion of tons, and played substantial role in the climatic system.
By the comparison of reconstructed interglacial long-range dust transportation and recent observations, the anthropogenic responsibility for dust outbreaks can be evaluated.

Summary and aims of the research for the public

Almost half of the area of the Carpathian Basin is covered by thick loess deposits. The pale yellow material has been accumulated by intensive Pleistocene dust storms. The cold-dry climate was not suitable for pedogenic processes, however during the moist and warm interglacial periods the upper part of the loess has been formed to soil. These dark layers were buried by dust during the next glacial phase, and archived the warm interglacial period as paleosoil. (The most famous Hungarian loess-paleosoil sequences are situated along the River Danube; e.g. the high-bluffs of Dunaföldvár, Paks, Dunaszekcső.)
The warming periods were not uniform, during different periods different types of soils have been formed. The younger loess deposits are intercalated by steppe-like soils, while the older (more than 650 kyr old), red paleosoils have been formed under a Mediterranean-like climatic regime. These old paleosoils have some similar properties to the red clay deposits, which are underlying the lowermost, oldest loess deposits and have been formed under a warmer and moister climate.
According to the preliminary data, aeolian dust played important role in the sedimentation during the formation of red clays and red paleosoils. By using different sedimentary and stratigraphic methods, the transportation-type and origin of soil’s material, and also the environment of their formation can be determined.

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