The objective of this study was to characterize the morphological and magnetic properties of Sari loess-paleosol section in northern Iran for paleopedologic and paleoenvironmental interpretation.The section consisted ...The objective of this study was to characterize the morphological and magnetic properties of Sari loess-paleosol section in northern Iran for paleopedologic and paleoenvironmental interpretation.The section consisted of a modern soil(MS)and three paleosols(PS1,PS2,PS3)separated by loess layers(LS1,LS2 and LS3).Based on particle size distribution,clay mineralogy,carbonates distribution and size of secondary carbonates,pedogenic development of the soils was in order of PS3>PS2>PS1=MS.Presence of redoximorphic features in PS3 was attributed to alternate stagnic saturation due to local water or high precipitation.Dominance of smectite and vermiculite as well as large carbonated dolls in PS3 indicated suitable environment and sufficient time for pedogenic development.Magnetic properties(χlf andχfd%)were distinctly higher in MS,PS1 and PS2 when compared to loess layers.The Lowest magnetic properties values were observed in PS3 which can be the result of ferrimagnetic minerals destruction under hydromorphic conditions.The highest Fed content occurred in PS3,however,lowχlf/Fed ratio indicated that majority of the iron minerals in PS3 are not magnetic.In conclusion,the particle size distribution,clay mineralogy and carbonates features were indicative of pedogenesis intensity,whereas,magnetic properties were useful to characterize the pedogenic environment.展开更多
Methodological problems of climatic reconstruction for different periods of Holocene are discussed on the basis of a multiple group biological analysis on peat-sapropel sediments. The possibility of biological analysi...Methodological problems of climatic reconstruction for different periods of Holocene are discussed on the basis of a multiple group biological analysis on peat-sapropel sediments. The possibility of biological analysis is exemplified by the paleoclimatic reconstruction for Carpathian and Altai Mountain ranges. For the ＂Skolevsky Beskidy＂ national park of Carpaty the paleoclimatic scenarios have been drown up aiming at the more precise definition of climatic conditions for the period of mass mountain slope terracing. The stability of terrace systems of various designs in the current climatic conditions has been assessed. It is shown that during periods of humid climate the terraces, whose designs have been focused on drainage, were built. In periods of dry and warm climate the terrace systems capable of accumulating water were built. Both these types of terrace systems are destroyed in nowadays. Only those terrace systems are stable which were adjusted by their builders to contrast variations of precipitation. For Western Altais the paleoclimatic scenario has been done to forecast the safety of the Bronze Age kurgans （burial earth mounds） with permafrost inside the construction. In the Altay region during the Holocene it has revealed two periods of sharp cooling, the peaks of which occurred in the intervals 4500- 4300 and 2500-2300 years pronounced climatic drying ago, and two periods of 4900-4700 and 130-70 years ago. Depletion of the algae composition in the layer corresponding to the last period of drying climate indicates a very sharp change in the parameters of moisture and turning the lake into a dry swamp. Periods of cold weather may have contributed to the formation of special ritual traditions of the Sakan tribes that require the frozen ground to bury the dead. The later climate fluctuations identified have not affected the safety of permafrost in burial mounds constructed in the V-III cc BC.展开更多
Micromorphological studies show that a comparision of the loess-paleosol sequence ofthe Karamaydan section, Central Asia, with the upper part of the Luochuan section, China, clearlyindicates that for the Brunhes chron...Micromorphological studies show that a comparision of the loess-paleosol sequence ofthe Karamaydan section, Central Asia, with the upper part of the Luochuan section, China, clearlyindicates that for the Brunhes chron the sequence at Karamaydan is even more detailed than thecorresponding section at Luochuan. Single paleosols at Luochuan correspond to pedocomplexes atKaramaydan; some pedocomplexes at Luochuan are represented by more detailed successions atKaramaydan (fig. 1). The loess-paleosol sequence at Karamaydan should therefore be regarded asa key sequence for reconstructing the climatic history of the Brunhes epoch. Correlation with thedeep-sea oxygen isotope record of Bassinot et al. (1994), which includes an accurate astronomicaltime scale, allows a detailed chronostratigraphical subdivision of the loess-paleosol sequence inKaramaydan for the Brunhes chron. Mineralogical and clay mineralogical investigations show thatthere is little difference in the type and amount of pedogenic clay mineral formation between twoHolocene soils and the paleosols in the Brunhes chron at Karamaydan. These results indicate thatthe climates of the interglacials represented by the B or Bt horizons of the buried paleosols weresimilar to that of the Holocene. In view of these results the Paleopedology Commission shoulddevelop a uniform terminology of mono- and polygenetic paleosols and pedostratigraphic unitswhich can be used globally.展开更多
The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come fr...The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come from the Cretaceous paleosols of the Marília Formation(Bauru Basin,SE Brazil),in which the T.barretti ichnofabric and rhizoliths represent the biotic record.Beetle larvae are considered to be the most likely T.barretti tracemakers in these paleosols.The intensity and recurrence of bioturbation suggest that the windows of opportunity for beetle population growth were very short and controlled by the progressive substrate desiccation after flood cessation.The characteristics of the trace fossil assemblage suggest soil colonization by r-strategic organisms triggered by flooding events that provided the resource inputs necessary for their living during rainy seasons.The results also show that in fluvial systems with high discharge variations,the boundaries between a“pre-desiccation suite”and a“desiccation suite”in the Scoyenia ichnofacies can be diffuse due to the short duration of colonization windows and progressive terrestrialization of floodplains and channels.Therefore,the frequency of flooding events,the lowered water table,and the rapidity of substrate desiccation constrained colonization by other burrowers and may be considered as firstorder factors controlling the generation of a monotypic T.barretti ichnofabric.Thus,the monotypic Taenidium ichnofabric in the Scoyenia ichnofacies context is an ichnomarker of brief windows for colonization in highly seasonal environments.展开更多
基金Ferdowsi University of Mashhad Research Council for their financial support of this study (Grant: 3/31011:29/02/1393)
文摘The objective of this study was to characterize the morphological and magnetic properties of Sari loess-paleosol section in northern Iran for paleopedologic and paleoenvironmental interpretation.The section consisted of a modern soil(MS)and three paleosols(PS1,PS2,PS3)separated by loess layers(LS1,LS2 and LS3).Based on particle size distribution,clay mineralogy,carbonates distribution and size of secondary carbonates,pedogenic development of the soils was in order of PS3>PS2>PS1=MS.Presence of redoximorphic features in PS3 was attributed to alternate stagnic saturation due to local water or high precipitation.Dominance of smectite and vermiculite as well as large carbonated dolls in PS3 indicated suitable environment and sufficient time for pedogenic development.Magnetic properties(χlf andχfd%)were distinctly higher in MS,PS1 and PS2 when compared to loess layers.The Lowest magnetic properties values were observed in PS3 which can be the result of ferrimagnetic minerals destruction under hydromorphic conditions.The highest Fed content occurred in PS3,however,lowχlf/Fed ratio indicated that majority of the iron minerals in PS3 are not magnetic.In conclusion,the particle size distribution,clay mineralogy and carbonates features were indicative of pedogenesis intensity,whereas,magnetic properties were useful to characterize the pedogenic environment.
基金supported by the Russian Foundation for Basic Research (Grant No 08-05-92223)
文摘Methodological problems of climatic reconstruction for different periods of Holocene are discussed on the basis of a multiple group biological analysis on peat-sapropel sediments. The possibility of biological analysis is exemplified by the paleoclimatic reconstruction for Carpathian and Altai Mountain ranges. For the ＂Skolevsky Beskidy＂ national park of Carpaty the paleoclimatic scenarios have been drown up aiming at the more precise definition of climatic conditions for the period of mass mountain slope terracing. The stability of terrace systems of various designs in the current climatic conditions has been assessed. It is shown that during periods of humid climate the terraces, whose designs have been focused on drainage, were built. In periods of dry and warm climate the terrace systems capable of accumulating water were built. Both these types of terrace systems are destroyed in nowadays. Only those terrace systems are stable which were adjusted by their builders to contrast variations of precipitation. For Western Altais the paleoclimatic scenario has been done to forecast the safety of the Bronze Age kurgans （burial earth mounds） with permafrost inside the construction. In the Altay region during the Holocene it has revealed two periods of sharp cooling, the peaks of which occurred in the intervals 4500- 4300 and 2500-2300 years pronounced climatic drying ago, and two periods of 4900-4700 and 130-70 years ago. Depletion of the algae composition in the layer corresponding to the last period of drying climate indicates a very sharp change in the parameters of moisture and turning the lake into a dry swamp. Periods of cold weather may have contributed to the formation of special ritual traditions of the Sakan tribes that require the frozen ground to bury the dead. The later climate fluctuations identified have not affected the safety of permafrost in burial mounds constructed in the V-III cc BC.
文摘Micromorphological studies show that a comparision of the loess-paleosol sequence ofthe Karamaydan section, Central Asia, with the upper part of the Luochuan section, China, clearlyindicates that for the Brunhes chron the sequence at Karamaydan is even more detailed than thecorresponding section at Luochuan. Single paleosols at Luochuan correspond to pedocomplexes atKaramaydan; some pedocomplexes at Luochuan are represented by more detailed successions atKaramaydan (fig. 1). The loess-paleosol sequence at Karamaydan should therefore be regarded asa key sequence for reconstructing the climatic history of the Brunhes epoch. Correlation with thedeep-sea oxygen isotope record of Bassinot et al. (1994), which includes an accurate astronomicaltime scale, allows a detailed chronostratigraphical subdivision of the loess-paleosol sequence inKaramaydan for the Brunhes chron. Mineralogical and clay mineralogical investigations show thatthere is little difference in the type and amount of pedogenic clay mineral formation between twoHolocene soils and the paleosols in the Brunhes chron at Karamaydan. These results indicate thatthe climates of the interglacials represented by the B or Bt horizons of the buried paleosols weresimilar to that of the Holocene. In view of these results the Paleopedology Commission shoulddevelop a uniform terminology of mono- and polygenetic paleosols and pedostratigraphic unitswhich can be used globally.
基金the Sao Paulo Research Foundation(FAPESP)for supporting and funding this work(grant 2015/17632-5)The Brazilian National Council for Scientific and Technological Development(CNPq)is also thanked for the Ph.D.grant provided to DLN(140807/2017-9)+3 种基金the post-doctoral fellowship grant to DS(159548/2018-7)the research grants to AB(310734/2020-7)RGN(310377/2019-6)FSBL(307951/2018-9,303977/2021-3).
文摘The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial systems.The data come from the Cretaceous paleosols of the Marília Formation(Bauru Basin,SE Brazil),in which the T.barretti ichnofabric and rhizoliths represent the biotic record.Beetle larvae are considered to be the most likely T.barretti tracemakers in these paleosols.The intensity and recurrence of bioturbation suggest that the windows of opportunity for beetle population growth were very short and controlled by the progressive substrate desiccation after flood cessation.The characteristics of the trace fossil assemblage suggest soil colonization by r-strategic organisms triggered by flooding events that provided the resource inputs necessary for their living during rainy seasons.The results also show that in fluvial systems with high discharge variations,the boundaries between a“pre-desiccation suite”and a“desiccation suite”in the Scoyenia ichnofacies can be diffuse due to the short duration of colonization windows and progressive terrestrialization of floodplains and channels.Therefore,the frequency of flooding events,the lowered water table,and the rapidity of substrate desiccation constrained colonization by other burrowers and may be considered as firstorder factors controlling the generation of a monotypic T.barretti ichnofabric.Thus,the monotypic Taenidium ichnofabric in the Scoyenia ichnofacies context is an ichnomarker of brief windows for colonization in highly seasonal environments.
