The (mis)conception of average Quaternary conditions

Spagnolo, Matteo, Rea, Brice R and Barr, Iestyn ORCID: https://orcid.org/0000-0002-9066-8738 (2022) The (mis)conception of average Quaternary conditions. Quaternary Research, 105. pp. 235-240. ISSN 0033-5894

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Abstract

The concept of Quaternary average conditions has gained popularity over the past few decades, especially with studies of long-term landscape evolution. In this paper, we critically assess this concept by analyzing the marine isotope record (LR04 δ<jats:sup>18</jats:sup>O stack) relative to the Quaternary. This shows that the frequency and amplitude of climate glacial-interglacial cycles are not constant throughout the Quaternary, with a clear change during the Middle Pleistocene Transition (MPT), and that many minor oscillations exist within each cycle. For this reason, the identification of pre- and post-MPT most-frequent and, cumulatively, longest-lasting (rather than average) conditions is recommended. The most-frequent pre-MPT δ<jats:sup>18</jats:sup>O value of 3.725 ± 0.025‰ last occurred during 11.31–11.47 ka, while the most-frequent post-MPT δ<jats:sup>18</jats:sup>O value of 4.475 ± 0.025‰ last occurred during 14.81–15.04 ka. However, many other δ<jats:sup>18</jats:sup>O values were almost as frequent throughout the Quaternary and we present geomorphological reasons as to why it is unlikely that the present-day landscape reflects Quaternary average or, indeed, most-frequent conditions. Collectively, our results indicate that extreme caution should be taken when attempting to infer long-term landscape evolution processes (including the buzzsaw hypothesis) based on average Quaternary conditions.