Seasonal influences on weathering processes in Turkish Badlands: Laboratory-based climate experiments

The formation of badlands is commonly linked to the presence of dispersive deposits. Meanwhile, the sediments having more resistance to disintegration might also cause badlands formation given the time and adequate climate conditions. Although the notable influences of climate conditions have been highlighted on badlands morphologies so far, only a few attempts illustrated how materials weather in response to the diverse climate conditions. Supportingly, this research aims to learn about the primary weathering processes in various types of badland landforms (sharp-edged, rounded-edged, tower type, and calanchi mammellonari) in the Mediterranean arid, semi-arid, and humid climate of Turkey. For that purpose, we have used 11 badlands bedrock samples and determined climate conditions to simulate realistic weathering conditions in the laboratory condition. Bedrock samples were marl from the arid region, poorly sorted and packed sandstones from the Mediterranean region, highly consolidated sandstones from the humid region, pyroclastic sediments from the Cappadocia – semi-arid region. We have conducted four cycles representing each season during one water year to simulate precipitation and temperature variations. In this regard, we compiled the total amount and type of precipitation and insolation data for each season. Prior to the experiment, we have determined grain size, mineralogical composition, physico-chemical properties, the content of major elements of badland samples that enable us to discuss their morphological variety.

Regarding the temperature conditions, we simulated day spring/autumn (~20°C), mild winter (4-5°C), winter (-2°C), summer (~25 – 35°C) conditions considering fluctuation of temperature along the different seasons. After precipitation in each cycle, represented by either rain or snow, we collected leachates to quantify the variations between the seasons by measuring volume, pH, electrical conductivity (EC), concentrations of anion, and cations.

The laboratory experiments testing weathering processes under the different climate conditions and various types of badland materials show that the apparent differences in crust and desiccation crack emerged between the seasons. Although the obtained highest sediment flux in Mediterranean badlands having the deep crack systems, especially in autumn after high drying in summer, the ponds were formed relatively temporarily (a few hours) to long-lived (a few days) by filling the cracks with the sediments during spring seasons due to the scarcity in drying during the winter. The badland materials under arid climate conditions are highly likely to disintegrate because of their critical susceptibility to dispersivity; after one year of simulation (4^th cycle), they became highly unstable due to their higher content of clay swelling capacity. However, the humid badland materials subjected to harsh climate conditions -snow and freezing conditions appeared to be the most durable samples reason for which is the strong cementation of coarse-grain sandstone. Seasonal trends in sample leachates' properties were also obtained. We can conclude that drying and wetting are more effective than the cooling and thawing processes in weathering of the bedrock from sampled badlands.

This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329.