Paleosols are the product of ancient physical, chemical, and biological processes on the Earth's surface and, as such, may record information that can be used to reconstruct the paleoatmospheric and paleoenvironmental conditions under which they formed. In Brazilian continental sedimentary successions, few studies using ancient soils have focused on the relationship between paleopedogenesis and paleoclimate. The Marilia Formation is a 160-m-thick section of the Bauru Basin in which ∼ 66% of the deposits show some evidence of pedogenic modification as paleosols. In this paper, paleosol profiles in the Marilia Formation containing thick calcrete intervals are described and attributed to three pedotypes: Avencas, Monte Alto, and Garça. Macro and microscopic pedogenic features of each pedotype are described in detail. Moreover, the analysis of clay mineralogy, whole-rock geochemistry, and stable-isotope composition are used to define pedogenic processes, paleoclimate proxies, and atmospheric pCO2 estimates. The Avencas pedotype is composed of six polygenetic profiles with different phases of carbonate precipitation, clay illuviation, and biogenic actions. The Monte Alto pedotype is moderately developed and composed of calcic horizons formed mainly by rhizoliths, with higher degrees of calcification and oxidation compared to Avencas profiles. The Garça pedotype is well developed with five polygenetic profiles presenting high carbonate content and low accumulation of clay minerals (CIA-K) and leaching. Estimates of paleoprecipitation and paleotemperature from the studied paleosols using climofunctions of molar ratio of base to alumina, depth of carbonate accumulation, salinization, oxygen composition, and paleosol weathering index proxy (PWI) show values ranging from 242 to 718 mm/yr and 11° to 14°, respectively. Climofunction values suggest a paleoclimate of semiarid to subhumid during deposition of the Marília Formation. The climate data also suggests that during the Maastrichtian, the Bauru Basin was geographically within the Southern Hot Arid Belt zone, though showing strong influence of the lower latitudinal Equatorial Humid belt. Furthermore, atmospheric pCO2 values calculated from pedogenic carbonates may correlate with a cooling interval during the latest Maastrichtian (68.5–66.25 My).

中文翻译：

---

马斯特里赫特大气 pCO2 和 Marília 组碳酸盐古土壤的气候重建（巴西东南部）

古土壤是地球表面古代物理、化学和生物过程的产物，因此可以记录可用于重建它们形成的古大气和古环境条件的信息。在巴西大陆沉积演替中，很少有使用古土壤的研究关注古成土作用与古气候之间的关系。Marilia 组是 Bauru 盆地的一个 160 米厚的部分，其中约 66% 的沉积物显示出一些成土改变为古土壤的证据。在本文中，包含厚钙质层段的 Marilia 组古土壤剖面被描述并归因于三种土壤类型：Avencas、Monte Alto 和 Garça。详细描述了每种 pedotype 的宏观和微观 pedogenic 特征。而且，粘土矿物学、全岩地球化学和稳定同位素组成的分析用于定义成土过程、古气候代理和大气 pCO2 估计。Avencas pedotype 由六个多基因谱组成，具有不同阶段的碳酸盐沉淀、粘土浸蚀和生物成因作用。Monte Alto 土壤类型适度发育，由主要由根石形成的钙化层组成，与 Avencas 剖面相比，钙化和氧化程度更高。Garça 土壤类型发育良好，具有五个多成因剖面，显示出高碳酸盐含量和低粘土矿物 (CIA-K) 积累和浸出。使用碱与氧化铝的摩尔比、碳酸盐堆积深度、盐碱化、氧成分和古土壤风化指数 (PWI) 的值分别为 242 至 718 毫米/年和 11° 至 14°。气候函数值表明在 Marília 组沉积期间的古气候为半干旱至半湿润。气候数据还表明，在马斯特里赫特期间，包鲁盆地在地理上位于南部热干旱带内，尽管显示出低纬度赤道湿润带的强烈影响。此外，从土壤碳酸盐计算的大气 pCO2 值可能与最近马斯特里赫特（68.5-66.25 My）期间的冷却间隔相关。气候函数值表明在 Marília 组沉积期间的古气候为半干旱至半湿润。气候数据还表明，在马斯特里赫特期间，包鲁盆地在地理上位于南部热干旱带内，尽管显示出低纬度赤道湿润带的强烈影响。此外，从土壤碳酸盐计算的大气 pCO2 值可能与最近马斯特里赫特（68.5-66.25 My）期间的冷却间隔相关。气候函数值表明在 Marília 组沉积期间的古气候为半干旱至半湿润。气候数据还表明，在马斯特里赫特期间，包鲁盆地在地理上位于南部热干旱带内，尽管显示出低纬度赤道湿润带的强烈影响。此外，从土壤碳酸盐计算的大气 pCO2 值可能与最近马斯特里赫特（68.5-66.25 My）期间的冷却间隔相关。