Preprints
https://doi.org/10.5194/cp-2021-181
https://doi.org/10.5194/cp-2021-181

  20 Dec 2021

20 Dec 2021

Review status: this preprint is currently under review for the journal CP.

Development of longitudinal dunes under Pangaean atmospheric circulation

Hiroki Shozaki1,2, and Hitoshi Hasegawa3, Hiroki Shozaki and Hitoshi Hasegawa
  • 1Deptartment of Earth and Planetary Science, Tokyo Institute of Technology, Tokyo, 152-8550, Japan
  • 2Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550, Japan
  • 3Faculty of Science and Technology, Kochi University, Kochi 780-8520, Japan
  • These authors contributed equally to this work.

Abstract. As a result of the large difference in heat capacity between land and ocean, global climate and atmospheric circulation patterns in the supercontinent Pangaea were significantly different from today. Modelling experiments have suggested the seasonal overturning of cross-equatorial Hadley circulation; however, there are large discrepancies between model-generated surface wind patterns and the reported palaeo-wind directions from aeolian dune records. Here, we present the results of measurements of spatial distribution of dune slip-face azimuths recorded in Lower Jurassic aeolian sandstones over a wide area of the western United States (palaeolatitude: ~19°–27° N). The azimuth data of dune slip-faces reveal a bi-directional and oblique angular pattern that resembles the internal structures of modern longitudinal dunes. Based on the spatial pattern of slip-face directions and outcrop evidences, we suggest most of Lower Jurassic aeolian sandstones to be NNE–SSW- to NNW–SSE- oriented longitudinal dunes, which likely formed as the result of a combination of westerly, northwesterly, and northeasterly palaeo-winds. The reconstructed palaeo-wind pattern at ~19°–27° N appears to be consistent with the model-generated surface wind pattern and its seasonal turnover. The reconstructed palaeo-wind patterns also suggest an influence of orbitally induced changes in atmospheric pressure configuration in Pangaea.

Hiroki Shozaki and Hitoshi Hasegawa

Status: open (until 14 Feb 2022)

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Hiroki Shozaki and Hitoshi Hasegawa

Hiroki Shozaki and Hitoshi Hasegawa

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Short summary
Atmospheric circulations in the supercontinent Pangaea is thought to be significantly different from today. We present the spatial distribution of palaeo-wind directions recorded in Lower Jurassic aeolian sandstones in the western US. The result reveals development of longitudinal dunes, formed by combination of westerly, northwesterly, and northeasterly palaeo-winds. The reconstructed palaeo-wind pattern at ~19°–27° N are consistent with the model-generated surface wind pattern in Pangaea.