The organic and mineral matter contents in deposits infilling floodplain basins: Holocene alluviation record from the K艂odnica and Osob艂oga river valleys, southern Poland

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• 作者：K.J. Wó ; jcicki ; ^{krzysztof.wojcicki@us.edu.pl} ; L. Marynowski
• 关键词：TOC ; Denudation ; Soil erosion ; Fluvial processes ; Late Quaternary
• 刊名：Geomorphology
• 出版年：2012
• 期刊代码：31_0169555x
• 类别：soc
• 出版时间：15 July, 2012
• 卷：159-160
• 期：Complete
• 页码：15-29
• 文件大小：5495 K

摘要

The work examines the timing and environmental conditions of floodplain sedimentation in the valleys of the upland K艂odnica and piedmont Osob艂oga rivers in the Upper Odra River basin. A distribution of 52 ¹⁴C-ages shows relatively high floodplain sedimentation at the Late Glacial-Holocene transition, more stable floodplain environments since the Early (in the K艂odnica Valley) and Middle Holocene (in the Osob艂oga Valley) and a gradual increase in floodplain deposition in the Late Holocene (since < 3.4 kyr BP). Organic matter [OM] and mineral matter [MM] fluctuations were correlated with variables responsible for the activation of erosion (i.e. vegetation changes, human impact and hydrological events) as well as factors affecting the local record of sedimentation (i.e. valley morphology, hydrologic conditions and episodes of local erosion). A clear relationship is shown between an increase in alluviation and climate- or human-induced extension of unforested areas. The deposition of mineral-rich sediments increases rapidly during periods characterized by non-arboreal pollen values exceeding approximately 8%in pollen diagrams. On the other hand, the results obtained do not confirm significant interactions between Holocene changes in forest composition and alluviation. Despite the settlement of agrarian groups, the sedimentary record of human activity in the Osob艂oga catchment is very poor during the Neolithic and early Bronze Age. A large-scale alluviation of the Osob艂oga and K艂odnica valleys was initiated during the settlement of people of the Lusatian culture from the middle Bronze Age and escalated in the early Middle Ages and Modern Times. The deposition of products of soil erosion was limited to between ca. 1.9-1.2 kyr BP, probably due to demographic regression during the Migration Period. Comparison of OM/MM fluctuations with phases of increased fluvial activity does not show a relationship between Holocene wetter phases and catchment sediment yield. Sedimentary episodes in the Upper Odra basin also show a low degree of correlation with the probability density curve of the ¹⁴C-ages. The results obtained in the K艂odnica and Osob艂oga valleys indicate a strong to moderate correlation between the spatial distribution of the study sites and the origin of MM-rich deposits, but a weak correlation between the spatial distribution of the study sites and TOC content. Such a pattern suggests that OM/MM fluctuations relate predominantly to the changes in sediment yield, although morphological conditions have a significant impact on the capture potential of sedimentary basins during phases of alluviation. Additionally, high OM content is not a simple function of an increase in wetness of the sedimentary environment. On the other hand, hydrologically-conditioned hiatuses as well as erosion episodes impoverish the sedimentary record, complicating the consideration on the geochronology of deposits and making it difficult to calculate reliable accumulation rates. However, they do not reduce the value of OM/MM fluctuations as an indicator of alluviation events for a preserved series of sediments.