Our understanding of long-term organic matter preservation comes mostly from studies in aquatic systems. In contrast, taphonomic processes in extremely dry environments are relatively understudied and are poorly understood. We investigated the accumulation and preservation of lipid biomarkers in hyperarid soils in the Yungay region of the Atacama Desert. Lipids from seven soil horizons in a 2.5 m vertical profile were extracted and analyzed using GC-MS and LC-MS. Diagnostic functionalized lipids and geolipids were detected and increased in abundance and diversity with depth. Deeper clay units contain fossil organic matter (radiocarbon dead) that has been protected from rainwater since the onset of hyperaridity. We show that these clay units contain lipids in an excellent state of structural preservation with functional groups and unsaturated bonds in carbon chains. This indicates that minimal degradation of lipids has occurred in these soils since the time of their deposition between >40,000 and 2 million years ago. The exceptional structural preservation of biomarkers is likely due to the long-term hyperaridity that has minimized microbial and enzymatic activity, a taphonomic process we term xeropreservation (i.e. preservation by drying). The degree of biomarker preservation allowed us to reconstruct major changes in ecology in the Yungay region that reflect a shift in hydrological regime from wet to dry since the early Quaternary. Our results suggest that hyperarid environments, which comprise 7.5% of the continental landmass, could represent a rich and relatively unexplored source of paleobiological information on Earth.

中文翻译：

---

阿塔卡马沙漠超干旱土壤中功能化脂质生物标志物的异种保存

我们对长期有机物质保存的理解主要来自对水生系统的研究。相比之下，极端干燥环境中的土壤埋藏过程研究相对不足，并且知之甚少。我们调查了阿塔卡马沙漠云盖地区超干旱土壤中脂质生物标志物的积累和保存。使用 GC-MS 和 LC-MS 提取和分析 2.5 m 垂直剖面中七个土壤层的脂质。检测到诊断功能化脂质和土工脂质，其丰度和多样性随着深度的增加而增加。更深的粘土单元包含化石有机物质（放射性碳死亡），自极度干旱开始以来，这些物质就一直受到雨水的保护。我们表明，这些粘土单元包含具有良好结构保存状态的脂质，在碳链中具有官能团和不饱和键。这表明，自 40,000 至 200 万年前沉积以来，这些土壤中脂质的降解很少。生物标志物的特殊结构保存可能是由于长期的极度干旱使微生物和酶活性最小化，我们称之为 xeropreservation（即通过干燥保存）的土埋过程。生物标志物的保存程度使我们能够重建 Yungay 地区生态的重大变化，这些变化反映了自第四纪早期以来水文状况从潮湿到干燥的转变。我们的结果表明，占大陆陆地 7.5% 的超干旱环境，