Although Quaternary deposits within the Ganyanchi (Salt Lake) pull-apart basin along the eastern Haiyuan fault preserve a record of both the paleoenvironmental and tectonic evolution of the northeastern Tibetan Plateau, this sedimentary archive has yet to be dated. Here we report a paleomagnetic study of a 328-m-long sediment core drilled near the modern depocenter of the basin, and use this record to both date the onset of sedimentation and reconstruct the depositional history of the basin. The observed magnetic polarity sequence comprises 13 normal and 12 reversed polarity zones, and we explore two possible correlations to the geomagnetic polarity time scale. Our preferred correlation minimizes changes in sedimentation rate and extends from the Brunhes normal polarity chron to the Gauss normal polarity chron. This correlation indicates that the Ganyanchi Basin began to develop by at least ca. 2.76 ± 0.03 Ma. Sediment accumulation rates (SAR) were elevated in two intervals, from ca. 1.92 to 1.78 Ma, when they were ~130.3 m/m.y., and from ca. 0.77 Ma to present, when they were ~234.6 m/m.y. We attribute these enhanced depositional episodes to both Northern Hemisphere cooling and local tectonic effects, with SAR values increasing as the regional climate has shifted toward overall drier and cooler conditions.

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