CALCIC VERTISOLS IN THE UPPER DAPTOCEPHALUS ASSEMBLAGE ZONE, BALFOUR FORMATION, KAROO BASIN, SOUTH AFRICA: IMPLICATIONS FOR LATE PERMIAN CLIMATE
CALCIC VERTISOLS IN THE UPPER DAPTOCEPHALUS ASSEMBLAGE ZONE, BALFOUR FORMATION, KAROO BASIN, SOUTH AFRICA: IMPLICATIONS FOR LATE PERMIAN CLIMATE
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DOI：
10.2110/jsr.2020.32
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发表时间：
2020-06-01
影响因子：
2
通讯作者：
Neveling, Johann
中科院分区：
文献类型：
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作者：
Gastaldo, Robert A.;Kus, Kaci;Neveling, Johann
南非卡鲁盆地的博福特群的全大陆演替已被用于开发环境模型，该环境模型建议用于跨越Daptocephalus到Lystrosaurus组合带之间接触的间隔，一些工作者将其与二叠纪末灭绝事件联系起来。干旱化的趋势被广泛接受，但地球化学数据表明，在这段时间内遇到的大部分原位古土壤在浸水环境中发展。到目前为止，在二叠纪末的钙质古土壤的存在只能推断出存在的方解石胶结成壤结核集中在河流通道滞后沉积。在这里，我们报告的第一个经验证据，发现在上Duptocephalus组合区附近的老Wapadsberg通行证，八个经典的地方之一，其中脊椎动物营业额报告在卡鲁盆地。在一个非常有限的横向范围内暴露的七个不连续的钙质变性土间隔，出现在与25米地层间隔类似的反。通过对一个古土壤的地球化学测量，计算了年平均温度和年平均降水量，这些估计表明成土作用时期的主要气候是季节性的寒冷和潮湿。与相邻地层剖面的相关性表明，晚二叠世景观经历了排水不良和排水较好的阶段，解释为反映气候之间的变化，偶尔干燥和偶尔潮湿。相反，在Wapadsberg通行证地区的地层单向干旱化的古环境重建，这项研究提供了新的证据，润湿趋势的Daptocephalus-Lystrosaurus组合区边界。
The fully continental succession of the Beaufort Group, Karoo Basin, South Africa, has been used in the development of environmental models proposed for the interval that spans the contact between the Daptocephalus to Lystrosaurus Assemblage Zones, associated by some workers with the end-Permian extinction event. An aridification trend is widely accepted, yet geochemical data indicate that the majority of in situ paleosols encountered in this interval developed in waterlogged environments. To date, the presence of calcic paleosols in the latest Permian can be inferred only from the presence of calcite-cemented pedogenic nodules concentrated in fluvial channel-lag deposits. Here, we report on the first empirical evidence of in situ calcic Vertisols found in the upper Duptocephalus Assemblage Zone near Old Wapadsberg Pass, one of eight classic localities in which the vertebrate turnover is reported in the Karoo Basin. Seven discrete intervals of calcic Vertisols, exposed over a very limited lateral extent, occur in anti similar to 25 m stratigraphic interval. Estimates of mean annual temperature and mean annual precipitation arc calculated from geochemical measurements of one paleosol, and these estimates indicate that the prevailing climate at the time of pedogenesis was seasonally cold and humid. Correlation with adjacent stratigraphic sections indicates that the late Permian landscape experienced poorly drained and better-drained phases, interpreted to reflect a climate that varied between episodically dry and episodically wet. In contrast to a paleoenvironmental reconstruction of unidirectional aridification from strata in the Wapadsberg Pass region, this study provides new evidence for a wetting trend towards the Daptocephalus-Lystrosaurus Assemblage-Zone boundary.