Abstract
Fluvial sediments are valuable paleoenvironmental archives of the Quaternary. Since besides environmental factors they are also affected by local tectonics or intrinsic processes, large instead of small catchments should be studied. In drylands covering ca. 45% of the global terrestrial surface large river systems are generally missing, and most river systems are small rivers originating from mountain ranges. Their sediments are potentially interesting paleoenvironmental archives, but are often affected by intensive tectonics. During this study, to obtain a robust regional paleoenvironmental signal a small river system in the southwestern Binaloud Mountains in semi-arid NE Iran was exemplarily studied with a combined approach that encompassed both alluvial fan and catchment. By using geomorphological mapping and numerical dating, fluvial aggradation followed by incision was independently identified in larger areas or in different parts of the river system ca. 95–88 ka, 40 ka, 20 ka, around/after the Pleistocene/Holocene transition and possibly ca. 2.6 ka. These could be linked with regional and over-regional paleoenvironmental data. Furthermore, large boulders on the alluvial fan suggest anthropogenic destabilisation of the catchment during the last decades. Despite strong local tectonics the fluvial dynamics was mostly controlled by paleoenvironmental changes and human activity. This indicates that despite their small size, such river systems form valuable paleoenvironmental archives in drylands where other archive types are largely missing.
Highlights
Fluvial sediments are valuable archives of Quaternary landscape evolution and paleoenvironmental changes [1,2,3,4,5,6,7,8,9,10,11]
During this study we independently investigated the fluvial geomorphology in three different parts of the Kalshur river system: (i) the well-developed terrace levels in lower and central catchment, (ii) the terrace levels at the fan apex, and (iii) different surface generations of the present-day alluvial fan. (i) and (ii) mostly represent older fluvial phases that were protected from subsequent fluvial erosion by their elevated topographic position
In this study, using a combined approach, we exemplarily investigated the Late Pleistocene and Holocene dynamics of the small Kalshur river system with a catchment of some square kilometers at the southwestern margin of the Binaloud Mountain Range in the drylands of northeastern Iran
Summary
Fluvial sediments are valuable archives of Quaternary landscape evolution and paleoenvironmental changes [1,2,3,4,5,6,7,8,9,10,11]. 45% of the global land surface [15] If they exist these are either exotic streams that originate from more humid regions and, mostly display the hydrological dynamics of the latter [16], or they are currently paleovalleys that originate from former more humid periods but are not sensitive to smaller-scale hydrological variations during drier phases [17]. Most dryland river systems are small rivers with catchments of some square kilometers that originate from more humid mountain ranges. Their sediments are potentially interesting paleoenvironmental archives and store smaller-scale regional paleoenvironmental variations. The transitions between mountain ranges and forelands where they are located generally show high tectonic activity [18] They were regularly affected by tectonic movements and seismic events during the late Quaternary
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