Abstract:

TheEjinabasin,locatedinthearidareainNWChina,underwentcomplicateddepositionalprocessesduringQuaternary. Basedoncharacteristicsofdifferentsedimentarystructures,a18mlongsedimentcorefromthecenteroftheEjinaBasincanbe divided into fluvial, aeolian, swamp and lacustrine sediments. The grain-size analysis shows that the depositional environment, transportdynamicsintheEjinabasincanbedistinguishedbycharacteristicofgrain-sizedistribution.Themajorgrain-sizecomponent offluvialsedimentwascoarsesandandYvaluewasgreaterthan1;themajorgrain-sizecomponentofaeoliansandwasfinesandandY valuewascloseto0;themajorgrain-sizecomponentofswampsedimentwasalsofinesandbutfinerthanaeoliansand,withanegative Yvalues;themajorgrain-sizecomponentoflacustrinesedimentwasfinesiltwhichwastransportedbysuspension,butdifferentwith settledowndepositinstandingwater,andYvalueswaslessthan-9.Theseresultsshowcharactersofgrainsizedistributioncanbe usedfordistinguishingdifferenttransportprocessesanddynamics,which,inturn,isabletoprovidecriticalinformationforaccurate interpretationofthedepositionalenvironmentchangeinthisarea.

Key words: Ejinabasin；depositionalenvironment；sedimentaryfacies；grain-sizedistribution