Abstract

Linear dunes, which are widespread on Earth and on some other planets, are generally considered to have a depositional origin and to form by loose sand under a bidirectional wind regime or by stabilized sand under a unidirectional wind regime, while the wind-rift (erosional origin) model has commonly been rejected due largely to lack of sufficient evidence and difficulty in morphodynamic interpretations. The linear dunes in the Qaidam Basin have been proposed to form as self-extending lee dunes under a unidirectional wind regime owing to a high level of total silt, clay, and salt (TSCS) content or cohesiveness of sediments, and they have undergone southward lateral migration at rates of up to 3 m/yr. We present herein results from studies of the sediments, internal structures, and optically stimulated luminescence (OSL) ages to show that: (1) the linear dunes in the Qaidam Basin are most likely of erosional origin similar to yardangs with orientations controlled by strikes of joints; (2) TSCS content or related sediment cohesion is unlikely to be an important factor determining the formation of these linear dunes; and (3) the linear dunes consist of 0.81–3.21 ka cross-strata with small lateral migration rates of 0.02–0.04 m/yr. Our findings evidently suggest that linear dunes can be of erosional origin. We therefore propose that the possibility of erosional origin should not be ruled out for linear dunes in some other dune fields on Earth as well as on Titan. If the control of tectonic structures on the orientation of wind-eroded ridges is taken into account, morphodynamic interpretations for the wind-rift model may become much simpler.

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