Different stratigraphic sequences of Late Quaternary sediments present in a vertically exposed 29 m deep river cliff were used as a model system to understand geochemical relationships with potential microbial activity in semiarid alluvial sediments. Microbial activities involved in carbon (C) and phosphorus (P) cycling were measured by dehydrogenase, alkaline phosphatase, and microbial respiration activities. We did not observe patterns in microbial activities that could be explained by sample depth. An extensive analysis of the physical and geochemical characteristics of exposed sediments was conducted along with multivariate statistical analysis to determine the influence of geochemical variables on potential microbial activity. Principal component analysis (PCA) and canonical correlation analysis (CCA) together with Pearson correlation analysis indicated that sediment organic carbon, moisture content, palynofacies components (acid-resistant particulate organic matter) such as fungal spores, brown carbon, structured carbon, and concentrations of Al₂O₃, FeO, MgO, MnO, and Zr were associated significantly with microbial activities in river cliff sediment deposits. These findings highlight drivers of microbial activity with consequences for C and P biogeochemical cycles in semiarid alluvial soils/sediments of river floodplains.

在垂直暴露的 29 m 深河崖中存在的晚第四纪沉积物的不同地层序列被用作模型系统，以了解与半干旱冲积沉积物中潜在微生物活动的地球化学关系。参与碳 (C) 和磷 (P) 循环的微生物活动通过脱氢酶、碱性磷酸酶和微生物呼吸活动进行测量。我们没有观察到可以用样品深度解释的微生物活动模式。对暴露沉积物的物理和地球化学特征进行了广泛的分析，并进行了多变量统计分析，以确定地球化学变量对潜在微生物活动的影响。₂ O ₃、FeO、MgO、MnO和Zr与河崖沉积物中的微生物活动显着相关。这些发现突出了微生物活动的驱动因素，对河流泛滥平原的半干旱冲积土壤/沉积物中的 C 和 P 生物地球化学循环产生影响。