Abstract Dryland alluvial successions across interior South Africa are a focus of pedosedimentary research because they provide insights into past hydrogeomorphic changes and improve our understanding of allogenic and autogenic controls on fluvial system behaviour. This paper focuses on an alluvial succession preserved within the Wilgerbosch River, on the Great Escarpment, South Africa. The pedosedimentary architecture of a calcretized palaeosol formed within an abandoned MIS 3 (51–39 ka) floodplain was investigated using grain size, micromorphological, XRD and mineral magnetic analyses. The primary controls on pedogenesis are inferred and the impacts of their products on subsequent landscape development outlined. The biologically-dominated calcrete micromorphology is consistent with the rhizogenic calcrete variety, which together with XRD, grain size and soil magnetic data provides evidence for a palustrine palaeowetland system. Palustrine wetland systems have been documented across interior South Africa, but the formation of rhizogenic calcretes in association with these systems has, to our knowledge, not been reported previously. We interpret these palaeowetlands to have resulted from basin-wide hydrogeomorphic adjustments, rather than localised discontinuous channel and floodout processes. Magnetic enhancement of the soil column overlying the calcrete compared to the overlying floodplain deposits is indicative of moister climate conditions at ~51 ka relative to ~39 ka. We hypothesise that the longevity of geomorphic quiescence, coupled with relatively moist climate conditions in early MIS 3 resulted in enhanced soil CaCO3 accumulation. The resultant cementation of this abandoned floodplain deposit accounts for an alluvial record that is dominated by older rather than younger (e.g. Holocene) deposits, despite the narrow valley context (

中文翻译：

---

MIS 3 interstadial 期间的沼泽湿地形成：对南非卡鲁保存的冲积记录的影响

摘要 南非内陆的旱地冲积层序是土壤沉积研究的重点，因为它们提供了对过去水文地貌变化的见解，并提高了我们对河流系统行为的同种异体和自体控制的理解。本文重点介绍南非大悬崖上维尔格博斯河内保存的冲积层序。使用粒度、微形态、XRD 和矿物磁分析研究了在废弃的 MIS 3 (51-39 ka) 漫滩内形成的钙化古土壤的沉积结构。推断出对成土作用的主要控制，并概述了它们的产品对随后的景观发展的影响。以生物为主的钙质微形态与生根钙质品种一致，结合 XRD，粒度和土壤磁性数据为沼泽古湿地系统提供了证据。Palustrine 湿地系统在整个南非内陆都有记载，但据我们所知，与这些系统相关的发根钙质的形成以前没有报道过。我们将这些古湿地解释为流域范围内的水文地貌调整的结果，而不是局部不连续的河道和洪水过程。与上覆的漫滩沉积物相比，覆盖在钙质混凝土上的土柱的磁性增强表明 ~51 ka 相对于 ~39 ka 的气候条件更潮湿。我们假设地貌静止的寿命，加上早期 MIS 3 中相对潮湿的气候条件导致土壤 CaCO3 积累增加。