Terrestrial Sediments of the Earth: Development of a Global Unconsolidated Sediments Map Database (GUM)
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Abstract Mapped unconsolidated sediments cover half of the global land surface. They are of considerable importance for many Earth surface processes like weathering, hydrological fluxes or biogeochemical cycles. Ignoring their characteristics or spatial extent may lead to misinterpretations in Earth System studies. Therefore, a new Global Unconsolidated Sediments Map database (GUM) was compiled, using regional maps specifically representing unconsolidated and quaternary sediments. The new GUM database provides insights into the regional distribution of unconsolidated sediments and their properties. The GUM comprises 911,551 polygons and describes not only sediment types and subtypes, but also parameters like grain size, mineralogy, age and thickness where available. Previous global lithological maps or databases lacked detail for reported unconsolidated sediment areas or missed large areas, and reported a global coverage of 25 to 30%, considering the ice‐free land area. Here, alluvial sediments cover about 23% of the mapped total ice‐free area, followed by aeolian sediments (∼21%), glacial sediments (∼20%), and colluvial sediments (∼16%). A specific focus during the creation of the database was on the distribution of loess deposits, since loess is highly reactive and relevant to understand geochemical cycles related to dust deposition and weathering processes. An additional layer compiling pyroclastic sediment is added, which merges consolidated and unconsolidated pyroclastic sediments. The compilation shows latitudinal abundances of sediment types related to climate of the past. The GUM database is available at the PANGAEA database ( https://doi.org/10.1594/PANGAEA.884822 ).Keywords:
Deposition
Pangaea
Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to be a terrestrial equivalent to the foraminiferal oxygen isotope record in deep-sea sediments (Fig. 2). Loess is also a direct record of atmospheric circulation, and identification of loess paleowinds in the geologic record can test atmospheric...
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Silt
Deposition
Sand dune stabilization
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A Review of the Study on the Origin of Xiashu Loess in the Middle and Lower Reaches of Yangtze River
Main resultes of the researches on the origin of Xiashu Loess since 1930s are reviewed in order to further recognize the origin of Xiashu Loess and its significance for the environmental evolution in the eastern part of China. The contents discussed and reviewed mainly include the aeolian origin, the water-transporting origin and multiple origins of Xiashu Loess. To sum up, the origin of Xiashu Loess is complicated, mainly includes the aeolian origin, the water-transporting origin, and remnant and slope accumulating origin. However, in terms of the sequence and importance of the transporting forces, aeolian origin is first. In order to get a correct result when using the environmental information containing in Xiashu loess to derive environmental changes in the eastern part of China , the study section of Xiashu Loess should be selected carefully.
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ABSTRACT Petrographic characteristics and field relationships of Dutch and of Mississippi Valley, United States, loess deposits are described. The evidence indicates that the loess of both regions is eolian in origin.
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Optically stimulated luminescence
Sequence (biology)
Optical dating
Thermoluminescence dating
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Chemical weathering of the Xiashu Loess at three localities in the lower r eaches of the Changjiang River is studied in detail on basis of eleme ntal contents,K 2 O /Na 2 O,K 2 O /CaO ,Al 2 O 3 /Na 2 O,CIA and A 2 CN 2 K dia-gram.The results show that chemical weathering underwent by the Xiashu L oess is much stronger than that by the typical loess in Northwest China,an d Ca,Sr,Na and Mg are much leached out .Chemical weathering indexes prove that not only carbonates in the Xiashu Loess underwent rapid weathering,but also silicate minerals,su ch as plagioclase,experienced obvious weathering with much leach of Ca and Na ,whereas K-feldspar went through we ak weathering and K was less leached.We athering trends of the Xiashu Loess a nd the loess in NW China are very similar,reflecting close chemical compositions of their weathering mo ther materials.Strong chemical weathering underwent by the Xiashu loess might be related to strong monsoon climate i n the lower reaches of the Changjiang River.
Soil production function
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