Loss of loess in the geological record due to poor preservation

Loess deposits are widespread in the Quaternary, but relatively rare in older geological records. This disparity is commonly linked to the unique climate conditions of the Quaternary, but those cannot fully explain the scarcity of loess in older records. Instead, we propose that the poor preservation of loess due to its windblown nature also plays an essential role. To test this hypothesis, we assess the preservation potential of loess by quantifying its modern-day distribution in active sedimentary basins. This analysis shows that on the global scale only 20% of loess occurs in basins of which the majority is in a foreland setting, possibly because of the proximity to silt-producing mountains and rain shadow aridity. The other 80% is ultimately either eroded or reworked and therefore poorly preserved in the long term. This conclusion implies that loess deposits may have been more common in pre-Quaternary periods, despite being less abundant in the geological record.